Search references:
| 21. | Hu, Neng; Wang, Weijia; Lei, Lin; Fan, Huiqing; Tan, Yeqiang; Yuan, Hua; Mao, Zhengwei; Müller-Buschbaum, Peter; Zhong, Qi: A hydrogen evolution system based on hybrid nanogel films with capabilities of spontaneous moisture collection and high light harvesting. In: Green Chemistry, 23 (22), pp. 8969–8978, 2021. (Type: Journal Article | Links | BibTeX) @article{Hu_2021, title = {A hydrogen evolution system based on hybrid nanogel films with capabilities of spontaneous moisture collection and high light harvesting}, author = {Neng Hu and Weijia Wang and Lin Lei and Huiqing Fan and Yeqiang Tan and Hua Yuan and Zhengwei Mao and Peter Müller-Buschbaum and Qi Zhong}, doi = {https://doi.org/10.1039/D1GC03322K}, year = {2021}, date = {2021-01-01}, journal = {Green Chemistry}, volume = {23}, number = {22}, pages = {8969--8978}, publisher = {Royal Society of Chemistry (RSC)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 22. | Lei, Lin; Wang, Weijia; Xie, Zhengfeng; Wu, Xiaobo; Yadav, Arun Kumar; Müller-Buschbaum, Peter; Fan, Huiqing: A graphitic carbon nitride metal-free visible light photocatalyst with controllable carbon self-doping towards efficient hydrogen evolution. In: Sustainable Energy & Fuels, 5 (20), pp. 5227–5235, 2021. (Type: Journal Article | Links | BibTeX) @article{Lei_2021, title = {A graphitic carbon nitride metal-free visible light photocatalyst with controllable carbon self-doping towards efficient hydrogen evolution}, author = {Lin Lei and Weijia Wang and Zhengfeng Xie and Xiaobo Wu and Arun Kumar Yadav and Peter Müller-Buschbaum and Huiqing Fan}, doi = {https://doi.org/10.1039/D1SE01244D}, year = {2021}, date = {2021-01-01}, journal = {Sustainable Energy & Fuels}, volume = {5}, number = {20}, pages = {5227--5235}, publisher = {Royal Society of Chemistry (RSC)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 23. | Li, Nian; Chen, Wei; Song, Lin; Guo, Renjun; Scheel, Manuel A; Yang, Dan; Körstgens, Volker; Schwartzkopf, Matthias; Roth, Stephan V; Müller-Buschbaum, Peter: In Situ Study of Order Formation in Mesoporous Titania Thin Films Templated by a Diblock Copolymer during Slot-Die Printing. In: ACS Appl. Mater. Interfaces, 12 (51), pp. 57627–57637, 2020, ISSN: 1944-8244. (Type: Journal Article | Abstract | Links | BibTeX) @article{Li2020a, title = {In Situ Study of Order Formation in Mesoporous Titania Thin Films Templated by a Diblock Copolymer during Slot-Die Printing}, author = {Nian Li and Wei Chen and Lin Song and Renjun Guo and Manuel A Scheel and Dan Yang and Volker Körstgens and Matthias Schwartzkopf and Stephan V Roth and Peter Müller-Buschbaum}, url = {https://doi.org/10.1021/acsami.0c18851}, doi = {10.1021/acsami.0c18851}, issn = {1944-8244}, year = {2020}, date = {2020-12-01}, journal = {ACS Appl. Mater. Interfaces}, volume = {12}, number = {51}, pages = {57627--57637}, publisher = {American Chemical Society}, abstract = {Slot-die printing, a large-scale deposition technique, is applied to fabricate mesoporous titania films. Printing is interesting, for example, for scaling up solar cells where titania films with an interconnected mesoporous network and a large surface-to-volume ratio are desired as photoanodes. A fundamental understanding of the structure evolution during printing is of high significance in tailoring these films. In this work, we provide important insights into the self-assembly of the slot-die-printed titania/polystyrene-block-poly(ethylene oxide) (PS-b-PEO) micelles into ordered hybrid structures in real time via in situ grazing-incidence small-angle X-ray scattering (GISAXS). GISAXS allows for tracking both vertical and lateral structure development of the film formation process. In the hybrid film, a face-centered cubic (FCC) structure is preferentially formed at the interfaces with air and with the substrate, while a defect-rich mixed FCC and body-centered cubic (BCC) structure forms in the bulk. After calcination, the surface and inner morphologies of the obtained nanostructured titania films are compared with the spin-coated analogues. In the printed films, the initially formed nanoscale structure of the hybrid film is preserved, and the resulting mesoporous titania film shows a superior order as compared with the spin-coated thin films which can be beneficial for future applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Slot-die printing, a large-scale deposition technique, is applied to fabricate mesoporous titania films. Printing is interesting, for example, for scaling up solar cells where titania films with an interconnected mesoporous network and a large surface-to-volume ratio are desired as photoanodes. A fundamental understanding of the structure evolution during printing is of high significance in tailoring these films. In this work, we provide important insights into the self-assembly of the slot-die-printed titania/polystyrene-block-poly(ethylene oxide) (PS-b-PEO) micelles into ordered hybrid structures in real time via in situ grazing-incidence small-angle X-ray scattering (GISAXS). GISAXS allows for tracking both vertical and lateral structure development of the film formation process. In the hybrid film, a face-centered cubic (FCC) structure is preferentially formed at the interfaces with air and with the substrate, while a defect-rich mixed FCC and body-centered cubic (BCC) structure forms in the bulk. After calcination, the surface and inner morphologies of the obtained nanostructured titania films are compared with the spin-coated analogues. In the printed films, the initially formed nanoscale structure of the hybrid film is preserved, and the resulting mesoporous titania film shows a superior order as compared with the spin-coated thin films which can be beneficial for future applications. |
| 24. | Pratap, Shambhavi; Schlipf, Johannes; Bießmann, Lorenz; Müller-Buschbaum, Peter: Hierarchical Structures from Nanocrystalline Colloidal Precursors within Hybrid Perovskite Thin Films: Implications for Photovoltaics. In: ACS Appl. Nano Mater., 3 (12), pp. 11701–11708, 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{Pratap2020, title = {Hierarchical Structures from Nanocrystalline Colloidal Precursors within Hybrid Perovskite Thin Films: Implications for Photovoltaics}, author = {Shambhavi Pratap and Johannes Schlipf and Lorenz Bießmann and Peter Müller-Buschbaum}, url = {https://doi.org/10.1021/acsanm.0c03000}, doi = {10.1021/acsanm.0c03000}, year = {2020}, date = {2020-12-01}, journal = {ACS Appl. Nano Mater.}, volume = {3}, number = {12}, pages = {11701--11708}, publisher = {American Chemical Society}, abstract = {Originating from stochastic nanocrystalline colloidal precursors with differential chemical compositions, crystalline thin films exhibit hierarchical structures originating at the crystallographic level and scaling up to mesoscale structures, manifested within their nanocrystalline morphology and mesoscale topology. We interlink morphogenetic signatures within thin films to differential precursor chemistry and explain the cooperative impact of structure-defining inorganic and organic counterparts on perovskite hybrids. Understanding the effect of chemical species on the structural characteristics of thin films and leveraging complex assembly processes present facile routes to tuning multiscale morphologies in thin films, pertinent for engineering functional performance metrics within thin-film perovskite photovoltaics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Originating from stochastic nanocrystalline colloidal precursors with differential chemical compositions, crystalline thin films exhibit hierarchical structures originating at the crystallographic level and scaling up to mesoscale structures, manifested within their nanocrystalline morphology and mesoscale topology. We interlink morphogenetic signatures within thin films to differential precursor chemistry and explain the cooperative impact of structure-defining inorganic and organic counterparts on perovskite hybrids. Understanding the effect of chemical species on the structural characteristics of thin films and leveraging complex assembly processes present facile routes to tuning multiscale morphologies in thin films, pertinent for engineering functional performance metrics within thin-film perovskite photovoltaics. |
| 25. | Wallach, Christoph; Geitner, Felix S; Karttunen, Antti J; Fässler, Thomas F: Boranyl-Functionalized [Ge 9 ] Clusters: Providing the Idea of Intramolecular Ge/B Frustrated Lewis Pairs. In: Angewandte Chemie, 133 (5), pp. 2680–2685, 2020. (Type: Journal Article | Links | BibTeX) @article{Wallach_2020, title = {Boranyl-Functionalized [Ge 9 ] Clusters: Providing the Idea of Intramolecular Ge/B Frustrated Lewis Pairs}, author = {Christoph Wallach and Felix S Geitner and Antti J Karttunen and Thomas F Fässler}, url = {https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202012336}, doi = {DOI: 10.1002/ange.202012336}, year = {2020}, date = {2020-12-01}, journal = {Angewandte Chemie}, volume = {133}, number = {5}, pages = {2680--2685}, publisher = {Wiley}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 26. | Pritzl, Stefanie D; Urban, Patrick; Prasselsperger, Alexander; Konrad, David B; Frank, James A; Trauner, Dirk; Lohmüller, Theobald: Photolipid Bilayer Permeability is Controlled by Transient Pore Formation. In: Langmuir, 36 (45), pp. 13509–13515, 2020, ISSN: 0743-7463. (Type: Journal Article | Abstract | Links | BibTeX) @article{Pritzl2020, title = {Photolipid Bilayer Permeability is Controlled by Transient Pore Formation}, author = {Stefanie D Pritzl and Patrick Urban and Alexander Prasselsperger and David B Konrad and James A Frank and Dirk Trauner and Theobald Lohmüller}, url = {https://doi.org/10.1021/acs.langmuir.0c02229}, doi = {10.1021/acs.langmuir.0c02229}, issn = {0743-7463}, year = {2020}, date = {2020-11-01}, journal = {Langmuir}, volume = {36}, number = {45}, pages = {13509--13515}, publisher = {American Chemical Society}, abstract = {Controlling the release or uptake of (bio-) molecules and drugs from liposomes is critically important for a range of applications in bioengineering, synthetic biology, and drug delivery. In this paper, we report how the reversible photoswitching of synthetic lipid bilayer membranes made from azobenzene-containing phosphatidylcholine (azo-PC) molecules (photolipids) leads to increased membrane permeability. We show that cell-sized, giant unilamellar vesicles (GUVs) prepared from photolipids display leakage of fluorescent dyes after irradiation with UV-A and visible light. Langmuir-Blodgett and patch-clamp measurements show that the permeability is the result of transient pore formation. By comparing the trans-to-cis and cis-to-trans isomerization process, we find that this pore formation is the result of area fluctuations and a change of the area cross-section between both photolipid isomers.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Controlling the release or uptake of (bio-) molecules and drugs from liposomes is critically important for a range of applications in bioengineering, synthetic biology, and drug delivery. In this paper, we report how the reversible photoswitching of synthetic lipid bilayer membranes made from azobenzene-containing phosphatidylcholine (azo-PC) molecules (photolipids) leads to increased membrane permeability. We show that cell-sized, giant unilamellar vesicles (GUVs) prepared from photolipids display leakage of fluorescent dyes after irradiation with UV-A and visible light. Langmuir-Blodgett and patch-clamp measurements show that the permeability is the result of transient pore formation. By comparing the trans-to-cis and cis-to-trans isomerization process, we find that this pore formation is the result of area fluctuations and a change of the area cross-section between both photolipid isomers. |
| 27. | Restle, Tassilo M F; Dums, Jasmin V; Raudaschl-Sieber, Gabriele; Klein, Wilhelm; Fässler, Thomas F: Na7TaP4: A Ternary Sodium Phosphidotantalate Containing [TaP4]7– Tetrahedra. In: Inorganic Chemistry, 59 (24), pp. 18420–18426, 2020. (Type: Journal Article | Links | BibTeX) @article{Restle_2020, title = {Na7TaP4: A Ternary Sodium Phosphidotantalate Containing [TaP4]7– Tetrahedra}, author = {Tassilo M F Restle and Jasmin V Dums and Gabriele Raudaschl-Sieber and Wilhelm Klein and Thomas F Fässler}, url = {https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.0c03021}, doi = {DOI: 10.1021/acs.inorgchem.0c03021}, year = {2020}, date = {2020-11-01}, journal = {Inorganic Chemistry}, volume = {59}, number = {24}, pages = {18420--18426}, publisher = {American Chemical Society (ACS)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 28. | Eickhoff, Henrik; Hlukhyy, Viktor; Fässler, Thomas F: Na 2 Ge 3 P 3 and Na 5 Ge 7 P 5 Comprising Heteroatomic Polyanions Mimicking the Structure of Fibrous Red Phosphorus. In: Zeitschrift für anorganische und allgemeine Chemie, 646 (22), pp. 1834–1838, 2020. (Type: Journal Article | Links | BibTeX) @article{Eickhoff_2020, title = {Na 2 Ge 3 P 3 and Na 5 Ge 7 P 5 Comprising Heteroatomic Polyanions Mimicking the Structure of Fibrous Red Phosphorus}, author = {Henrik Eickhoff and Viktor Hlukhyy and Thomas F Fässler}, url = {https://onlinelibrary.wiley.com/doi/full/10.1002/zaac.202000316}, doi = {DOI: 10.1002/zaac.202000316}, year = {2020}, date = {2020-11-01}, journal = {Zeitschrift für anorganische und allgemeine Chemie}, volume = {646}, number = {22}, pages = {1834--1838}, publisher = {Wiley}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 29. | Sanchez-Naya, Roberto; Stepanenko, Vladimir; Mandel, Karl; Beuerle, Florian: Modulation of Crystallinity and Optical Properties in Composite Materials Combining Iron Oxide Nanoparticles and Dye-Containing Covalent Organic Frameworks. In: 2020. (Type: Journal Article | Links | BibTeX) @article{SanchezNaya2020, title = {Modulation of Crystallinity and Optical Properties in Composite Materials Combining Iron Oxide Nanoparticles and Dye-Containing Covalent Organic Frameworks}, author = {Roberto Sanchez-Naya and Vladimir Stepanenko and Karl Mandel and Florian Beuerle}, doi = {10.26434/chemrxiv.13194635.v1}, year = {2020}, date = {2020-11-01}, publisher = {American Chemical Society (ACS)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 30. | Sirtl, Maximilian T; Armer, Melina; Reb, Lennart K; Hooijer, Rik; Dörflinger, Patrick; Scheel, Manuel A; Tvingstedt, Kristofer; Rieder, Philipp; Glück, Nadja; Pandit, Pallavi; Roth, Stephan V; Müller-Buschbaum, Peter; Dyakonov, Vladimir; Bein, Thomas: Optoelectronic Properties of Cs2AgBiBr6 Thin Films: The Influence of Precursor Stoichiometry. In: ACS Applied Energy Materials, 3 (12), pp. 11597–11609, 2020. (Type: Journal Article | Links | BibTeX) @article{Sirtl2020b, title = {Optoelectronic Properties of Cs2AgBiBr6 Thin Films: The Influence of Precursor Stoichiometry}, author = {Maximilian T Sirtl and Melina Armer and Lennart K Reb and Rik Hooijer and Patrick Dörflinger and Manuel A Scheel and Kristofer Tvingstedt and Philipp Rieder and Nadja Glück and Pallavi Pandit and Stephan V Roth and Peter Müller-Buschbaum and Vladimir Dyakonov and Thomas Bein}, doi = {10.1021/acsaem.0c01308}, year = {2020}, date = {2020-11-01}, journal = {ACS Applied Energy Materials}, volume = {3}, number = {12}, pages = {11597--11609}, publisher = {American Chemical Society (ACS)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 31. | Hammer, Sebastian; Zeiser, Clemens; Deutsch, Marian; Engels, Bernd; Broch, Katharina; Pflaum, Jens: Spatial Anisotropy of Charge Transfer at Perfluoropentacene–Pentacene (001) Single-Crystal Interfaces and its Relevance for Thin Film Devices. In: ACS Applied Materials & Interfaces, 12 (47), pp. 53547–53556, 2020. (Type: Journal Article | Links | BibTeX) @article{Hammer2020, title = {Spatial Anisotropy of Charge Transfer at Perfluoropentacene–Pentacene (001) Single-Crystal Interfaces and its Relevance for Thin Film Devices}, author = {Sebastian Hammer and Clemens Zeiser and Marian Deutsch and Bernd Engels and Katharina Broch and Jens Pflaum}, doi = {10.1021/acsami.0c17152}, year = {2020}, date = {2020-11-01}, journal = {ACS Applied Materials & Interfaces}, volume = {12}, number = {47}, pages = {53547--53556}, publisher = {American Chemical Society (ACS)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 32. | Wang, Yue; Chao, Lingfeng; Niu, Tingting; Li, Deli; Wei, Qi; Wu, Hui; Qiu, Jian; Lu, Hui; Ran, Chenxin; Zhong, Qi; Song, Lin; Xing, Guichuan; Xia, Yingdong; Chen, Yonghua; Müller-Buschbaum, Peter; Huang, Wei: Efficient and Stable Perovskite Solar Cells by Fluorinated Ionic Liquid–Induced Component Interaction. In: Solar RRL, 5 (1), pp. 2000582, 2020. (Type: Journal Article | Links | BibTeX) @article{Wang2020, title = {Efficient and Stable Perovskite Solar Cells by Fluorinated Ionic Liquid–Induced Component Interaction}, author = {Yue Wang and Lingfeng Chao and Tingting Niu and Deli Li and Qi Wei and Hui Wu and Jian Qiu and Hui Lu and Chenxin Ran and Qi Zhong and Lin Song and Guichuan Xing and Yingdong Xia and Yonghua Chen and Peter Müller-Buschbaum and Wei Huang}, doi = {10.1002/solr.202000582}, year = {2020}, date = {2020-11-01}, journal = {Solar RRL}, volume = {5}, number = {1}, pages = {2000582}, publisher = {Wiley}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 33. | Salman, Munir; Bick, Christian; Krischer, Katharina: Collective oscillations of globally coupled bistable, nonresonant components. In: Phys. Rev. Research, 2 , pp. 043125, 2020. (Type: Journal Article | Links | BibTeX) @article{Salman2020, title = {Collective oscillations of globally coupled bistable, nonresonant components}, author = {Munir Salman and Christian Bick and Katharina Krischer}, url = {https://link.aps.org/doi/10.1103/PhysRevResearch.2.043125}, doi = {10.1103/PhysRevResearch.2.043125}, year = {2020}, date = {2020-10-01}, journal = {Phys. Rev. Research}, volume = {2}, pages = {043125}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 34. | Kick, Matthias; Scheurer, Christoph; Oberhofer, Harald: Formation and stability of small polarons at the lithium-terminated Li4Ti5O12 (LTO) (111) surface. In: The Journal of Chemical Physics, 153 (14), pp. 144701, 2020. (Type: Journal Article | Links | BibTeX) @article{Kick_2020, title = {Formation and stability of small polarons at the lithium-terminated Li4Ti5O12 (LTO) (111) surface}, author = {Matthias Kick and Christoph Scheurer and Harald Oberhofer}, url = {https://doi.org/10.1063/5.0021443}, doi = {10.1063/5.0021443}, year = {2020}, date = {2020-10-01}, journal = {The Journal of Chemical Physics}, volume = {153}, number = {14}, pages = {144701}, publisher = {AIP Publishing}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 35. | Tian, Ya-Ming; Guo, Xiao-Ning; Krummenacher, Ivo; Wu, Zhu; Nitsch, Jörn; Braunschweig, Holger; Radius, Udo; Marder, Todd B: Visible-Light-Induced Ni-Catalyzed Radical Borylation of Chloroarenes. In: Journal of the American Chemical Society, 142 (42), pp. 18231–18242, 2020. (Type: Journal Article | Links | BibTeX) @article{Tian2020, title = {Visible-Light-Induced Ni-Catalyzed Radical Borylation of Chloroarenes}, author = {Ya-Ming Tian and Xiao-Ning Guo and Ivo Krummenacher and Zhu Wu and Jörn Nitsch and Holger Braunschweig and Udo Radius and Todd B Marder}, doi = {10.1021/jacs.0c08834}, year = {2020}, date = {2020-10-01}, journal = {Journal of the American Chemical Society}, volume = {142}, number = {42}, pages = {18231--18242}, publisher = {American Chemical Society (ACS)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 36. | Geitner, Felix S; Fässler, Thomas F: Cluster Expansion versus Complex Formation: Coinage Metal Coordination to Silylated [Ge9] Cages. In: Inorganic Chemistry, 59 (20), pp. 15218–15227, 2020. (Type: Journal Article | Links | BibTeX) @article{Geitner2020, title = {Cluster Expansion versus Complex Formation: Coinage Metal Coordination to Silylated [Ge9] Cages}, author = {Felix S Geitner and Thomas F Fässler}, doi = {10.1021/acs.inorgchem.0c02190}, year = {2020}, date = {2020-10-01}, journal = {Inorganic Chemistry}, volume = {59}, number = {20}, pages = {15218--15227}, publisher = {American Chemical Society (ACS)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 37. | Hohn, Nuri; Wang, Xiaoyan; Giebel, Michael A; Yin, Shanshan; Müller, David; Hetzenecker, Andreas E; ß, Lorenz Bie; Kreuzer, Lucas P; Möhl, Gilles E; Yu, Haoyang; Veinot, Jonathan G C; Fässler, Thomas F; Cheng, Ya-Jun; Müller-Buschbaum, Peter: Mesoporous GeOx/Ge/C as a Highly Reversible Anode Material with High Specific Capacity for Lithium-Ion Batteries. In: ACS Applied Materials & Interfaces, 12 (41), pp. 47002–47009, 2020. (Type: Journal Article | Links | BibTeX) @article{Hohn_2020, title = {Mesoporous GeOx/Ge/C as a Highly Reversible Anode Material with High Specific Capacity for Lithium-Ion Batteries}, author = {Nuri Hohn and Xiaoyan Wang and Michael A Giebel and Shanshan Yin and David Müller and Andreas E Hetzenecker and Lorenz Bie ß and Lucas P Kreuzer and Gilles E Möhl and Haoyang Yu and Jonathan G C Veinot and Thomas F Fässler and Ya-Jun Cheng and Peter Müller-Buschbaum}, url = {https://pubs.acs.org/doi/abs/10.1021/acsami.0c13560}, doi = {DOI: 10.1021/acsami.0c13560}, year = {2020}, date = {2020-09-01}, journal = {ACS Applied Materials & Interfaces}, volume = {12}, number = {41}, pages = {47002--47009}, publisher = {American Chemical Society (ACS)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 38. | Selby, Joshua; Holzapfel, Marco; Lombe, Blaise Kimbadi; Schmidt, David; Krause, Ana-Maria; Würthner, Frank; Bringmann, Gerhard; Lambert, Christoph: Chiroptical Properties of Indolenine Squaraines with a Stereogenic Center at Close Proximity. In: The Journal of Organic Chemistry, 85 (19), pp. 12227–12242, 2020. (Type: Journal Article | Links | BibTeX) @article{Selby2020, title = {Chiroptical Properties of Indolenine Squaraines with a Stereogenic Center at Close Proximity}, author = {Joshua Selby and Marco Holzapfel and Blaise Kimbadi Lombe and David Schmidt and Ana-Maria Krause and Frank Würthner and Gerhard Bringmann and Christoph Lambert}, doi = {10.1021/acs.joc.0c01422}, year = {2020}, date = {2020-09-01}, journal = {The Journal of Organic Chemistry}, volume = {85}, number = {19}, pages = {12227--12242}, publisher = {American Chemical Society (ACS)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 39. | Rauch, Florian; Fuchs, Sonja; Friedrich, Alexandra; Sieh, Daniel; Krummenacher, Ivo; Braunschweig, Holger; Finze, Maik; Marder, Todd B: Highly Stable, Readily Reducible, Fluorescent, Trifluoromethylated 9-Borafluorenes. In: Chemistry – A European Journal, 26 (56), pp. 12794–12808, 2020. (Type: Journal Article | Links | BibTeX) @article{Rauch2020a, title = {Highly Stable, Readily Reducible, Fluorescent, Trifluoromethylated 9-Borafluorenes}, author = {Florian Rauch and Sonja Fuchs and Alexandra Friedrich and Daniel Sieh and Ivo Krummenacher and Holger Braunschweig and Maik Finze and Todd B Marder}, doi = {10.1002/chem.201905559}, year = {2020}, date = {2020-09-01}, journal = {Chemistry – A European Journal}, volume = {26}, number = {56}, pages = {12794--12808}, publisher = {Wiley}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 40. | Rauch, Florian; Endres, Peter; Friedrich, Alexandra; Sieh, Daniel; Hähnel, Martin; Krummenacher, Ivo; Braunschweig, Holger; Finze, Maik; Ji, Lei; Marder, Todd B: An Iterative Divergent Approach to Conjugated Starburst Borane Dendrimers. In: Chemistry – A European Journal, 26 (57), pp. 12951–12963, 2020. (Type: Journal Article | Links | BibTeX) @article{Rauch2020b, title = {An Iterative Divergent Approach to Conjugated Starburst Borane Dendrimers}, author = {Florian Rauch and Peter Endres and Alexandra Friedrich and Daniel Sieh and Martin Hähnel and Ivo Krummenacher and Holger Braunschweig and Maik Finze and Lei Ji and Todd B Marder}, doi = {10.1002/chem.202001985}, year = {2020}, date = {2020-09-01}, journal = {Chemistry – A European Journal}, volume = {26}, number = {57}, pages = {12951--12963}, publisher = {Wiley}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
References (last update: Dec 16, 2019):
2020 |
Stegmaier, Saskia; Hlukhyy, Viktor; Fässler, Thomas F The Intermetallic Type-I Clathrate Na 8 Zn 4 Ge 42 Journal Article Zeitschrift für anorganische und allgemeine Chemie, 646 (14), pp. 1073–1078, 2020. @article{Stegmaier_2020, title = {The Intermetallic Type-I Clathrate Na 8 Zn 4 Ge 42}, author = {Saskia Stegmaier and Viktor Hlukhyy and Thomas F Fässler}, url = {https://onlinelibrary.wiley.com/doi/full/10.1002/zaac.201900253}, doi = {DOI: 10.1002/zaac.201900253}, year = {2020}, date = {2020-05-01}, journal = {Zeitschrift für anorganische und allgemeine Chemie}, volume = {646}, number = {14}, pages = {1073--1078}, publisher = {Wiley}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Corp, Kathryn L; Rabe, Emily J; Huang, Xiang; Ehrmaier, Johannes; Kaiser, Mitchell E; Sobolewski, Andrzej L; Domcke, Wolfgang; Schlenker, Cody W J. Phys. Chem. C, 124 (17), pp. 9151–9160, 2020, ISSN: 1932-7447. Abstract | Links | BibTeX | Tags: @article{Corp2020, title = {Control of Excited-State Proton-Coupled Electron Transfer by Ultrafast Pump-Push-Probe Spectroscopy in Heptazine-Phenol Complexes: Implications for Photochemical Water Oxidation}, author = {Kathryn L Corp and Emily J Rabe and Xiang Huang and Johannes Ehrmaier and Mitchell E Kaiser and Andrzej L Sobolewski and Wolfgang Domcke and Cody W Schlenker}, url = {https://doi.org/10.1021/acs.jpcc.0c00415}, doi = {10.1021/acs.jpcc.0c00415}, issn = {1932-7447}, year = {2020}, date = {2020-04-01}, journal = {J. Phys. Chem. C}, volume = {124}, number = {17}, pages = {9151--9160}, publisher = {American Chemical Society}, abstract = {We demonstrate chemical tuning and laser-driven control of intermolecular H atom abstraction from protic solvent molecules. Using multipulse ultrafast pump-push-probe transient absorption (TA) spectroscopy, we monitor hydrogen abstraction by a functionalized heptazine (Hz) from substituted phenols in condensed-phase hydrogen-bonded complexes. Hz is the monomer unit of the ubiquitous organic polymeric photocatalyst graphitic carbon nitride (g-C3N4). Previously, we reported that the Hz derivative 2,5,8-tris(4-methoxyphenyl)-1,3,5,6,7,9,9b-heptaazaphenalene (TAHz) can photochemically abstract H atoms from water, in addition to exhibiting photocatalytic activity for H2 evolution matching that of g-C3N4 in aqueous suspensions. In the present work, we combine ultrafast multipulse TA spectroscopy with predictive wave function-based ab initio electronic-structure calculations to explore the role of mixed nπ*/ππ* upper excited states in directing H atom abstraction from hydroxylic compounds. We use an ultraviolet (365 nm) laser pulse to photoexcite TAHz to a bright upper excited state, and, after a relaxation period of roughly 6 ps, we use a near-infrared (NIR) (1150 nm) pulse to “push” the chromophore from the long-lived S1 state to a higher-lying excited state. When phenol is present, the NIR push induces a persistent decrease (ΔΔOD) in the S1 TA signal magnitude, indicating an impulsively driven change in photochemical branching ratios. In the presence of substituted phenols with electron-donating moieties, the magnitude of ΔΔOD diminishes markedly due to the increased excited-state reactivity of these complexes that accompanies the cathodic shift in phenol oxidation potential. In the latter case, H atom abstraction proceeds unaided by additional energy from the push pulse. These results reveal new insight into branching mechanisms among unreactive locally excited states and reactive intermolecular charge-transfer states. They also suggest molecular design strategies for functionalizing aza-aromatics to drive important photoreactions, such as H atom abstraction from water. More generally, this study demonstrates an avidly desired achievement in the field of photochemistry, rationally redirecting excited-state reactivity with light.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We demonstrate chemical tuning and laser-driven control of intermolecular H atom abstraction from protic solvent molecules. Using multipulse ultrafast pump-push-probe transient absorption (TA) spectroscopy, we monitor hydrogen abstraction by a functionalized heptazine (Hz) from substituted phenols in condensed-phase hydrogen-bonded complexes. Hz is the monomer unit of the ubiquitous organic polymeric photocatalyst graphitic carbon nitride (g-C3N4). Previously, we reported that the Hz derivative 2,5,8-tris(4-methoxyphenyl)-1,3,5,6,7,9,9b-heptaazaphenalene (TAHz) can photochemically abstract H atoms from water, in addition to exhibiting photocatalytic activity for H2 evolution matching that of g-C3N4 in aqueous suspensions. In the present work, we combine ultrafast multipulse TA spectroscopy with predictive wave function-based ab initio electronic-structure calculations to explore the role of mixed nπ*/ππ* upper excited states in directing H atom abstraction from hydroxylic compounds. We use an ultraviolet (365 nm) laser pulse to photoexcite TAHz to a bright upper excited state, and, after a relaxation period of roughly 6 ps, we use a near-infrared (NIR) (1150 nm) pulse to “push” the chromophore from the long-lived S1 state to a higher-lying excited state. When phenol is present, the NIR push induces a persistent decrease (ΔΔOD) in the S1 TA signal magnitude, indicating an impulsively driven change in photochemical branching ratios. In the presence of substituted phenols with electron-donating moieties, the magnitude of ΔΔOD diminishes markedly due to the increased excited-state reactivity of these complexes that accompanies the cathodic shift in phenol oxidation potential. In the latter case, H atom abstraction proceeds unaided by additional energy from the push pulse. These results reveal new insight into branching mechanisms among unreactive locally excited states and reactive intermolecular charge-transfer states. They also suggest molecular design strategies for functionalizing aza-aromatics to drive important photoreactions, such as H atom abstraction from water. More generally, this study demonstrates an avidly desired achievement in the field of photochemistry, rationally redirecting excited-state reactivity with light. |
Kick, Matthias; Grosu, Cristina; Schuderer, Markus; Scheurer, Christoph; Oberhofer, Harald Mobile Small Polarons Qualitatively Explain Conductivity in Lithium Titanium Oxide Battery Electrodes Journal Article J. Phys. Chem. Lett., 11 (7), pp. 2535–2540, 2020. Abstract | Links | BibTeX | Tags: @article{Kick2020, title = {Mobile Small Polarons Qualitatively Explain Conductivity in Lithium Titanium Oxide Battery Electrodes}, author = {Matthias Kick and Cristina Grosu and Markus Schuderer and Christoph Scheurer and Harald Oberhofer}, url = {https://doi.org/10.1021/acs.jpclett.0c00568}, doi = {10.1021/acs.jpclett.0c00568}, year = {2020}, date = {2020-04-01}, journal = {J. Phys. Chem. Lett.}, volume = {11}, number = {7}, pages = {2535--2540}, publisher = {American Chemical Society}, abstract = {Lithium titanium oxide Li4Ti5O12 is an intriguing anode material promising particularly long-life batteries, due to its remarkable phase stability during (dis)charging of the cell. However, its usage is limited by its low intrinsic electronic conductivity. Introducing oxygen vacancies can be one method for overcoming this drawback, possibly by altering the charge carrier transport mechanism. We use Hubbard corrected density functional theory to show that polaronic states in combination with a possible hopping mechanism can play a crucial role in the experimentally observed increase in electronic conductivity. To gauge polaronic charge mobility, we compute the relative stabilities of different localization patterns and estimate polaron hopping barrier heights.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Lithium titanium oxide Li4Ti5O12 is an intriguing anode material promising particularly long-life batteries, due to its remarkable phase stability during (dis)charging of the cell. However, its usage is limited by its low intrinsic electronic conductivity. Introducing oxygen vacancies can be one method for overcoming this drawback, possibly by altering the charge carrier transport mechanism. We use Hubbard corrected density functional theory to show that polaronic states in combination with a possible hopping mechanism can play a crucial role in the experimentally observed increase in electronic conductivity. To gauge polaronic charge mobility, we compute the relative stabilities of different localization patterns and estimate polaron hopping barrier heights. |
Restle, Tassilo M F; Dums, Jasmin V; Raudaschl-Sieber, Gabriele; Fässler, Thomas F Synthesis, Structure, Solid-State NMR Spectroscopy, and Electronic Structures of the Phosphidotrielates Li 3 AlP 2 and Li 3 GaP 2 Journal Article Chemistry – A European Journal, 26 (30), pp. 6812–6819, 2020. @article{Restle_2020b, title = {Synthesis, Structure, Solid-State NMR Spectroscopy, and Electronic Structures of the Phosphidotrielates Li 3 AlP 2 and Li 3 GaP 2}, author = {Tassilo M F Restle and Jasmin V Dums and Gabriele Raudaschl-Sieber and Thomas F Fässler}, url = {https://chemistry-europe.onlinelibrary.wiley.com/doi/full/10.1002/chem.202000482}, doi = {DOI: 10.1002/chem.202000482}, year = {2020}, date = {2020-04-01}, journal = {Chemistry – A European Journal}, volume = {26}, number = {30}, pages = {6812--6819}, publisher = {Wiley}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Mayer, Kerstin; Dums, Jasmin V; Benda, Christian B; Klein, Wilhelm; Fässler, Thomas F Angewandte Chemie, 132 (17), pp. 6866–6871, 2020. @article{Mayer_2020, title = {Lösemittel-induzierter Halbleiter-Metall-Übergang: Planare [Bi1-]-Zickzack-Ketten im metallischen KBi$cdot$NH3im Vergleich zu [Bi1-]-Helices im halbleitenden KBi}, author = {Kerstin Mayer and Jasmin V Dums and Christian B Benda and Wilhelm Klein and Thomas F Fässler}, url = {https://onlinelibrary.wiley.com/doi/full/10.1002/ange.201915735}, doi = {DOI: 10.1002/ange.201915735}, year = {2020}, date = {2020-04-01}, journal = {Angewandte Chemie}, volume = {132}, number = {17}, pages = {6866--6871}, publisher = {Wiley}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Xu, Yucheng; Zheng, Jiaxin; Lindner, Joachim O; Wen, Xinbo; Jiang, Nianqiang; Hu, Zhicheng; Liu, Linlin; Huang, Fei; Würthner, Frank; Xie, Zengqi Consecutive Charging of a Perylene Bisimide Dye by Multistep Low-Energy Solar-Light-Induced Electron Transfer Towards H 2 Evolution Journal Article Angewandte Chemie International Edition, 59 (26), pp. 10363–10367, 2020. @article{Xu2020, title = {Consecutive Charging of a Perylene Bisimide Dye by Multistep Low-Energy Solar-Light-Induced Electron Transfer Towards H 2 Evolution}, author = {Yucheng Xu and Jiaxin Zheng and Joachim O Lindner and Xinbo Wen and Nianqiang Jiang and Zhicheng Hu and Linlin Liu and Fei Huang and Frank Würthner and Zengqi Xie}, doi = {10.1002/anie.202001231}, year = {2020}, date = {2020-04-01}, journal = {Angewandte Chemie International Edition}, volume = {59}, number = {26}, pages = {10363--10367}, publisher = {Wiley}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Gernert, Markus; Balles-Wolf, Lukas; Kerner, Florian; Müller, Ulrich; Schmiedel, Alexander; Holzapfel, Marco; Marian, Christel M; Pflaum, Jens; Lambert, Christoph; Steffen, Andreas Cyclic (Amino)(aryl)carbenes Enter the Field of Chromophore Ligands: Expanded $uppi$ System Leads to Unusually Deep Red Emitting CuI Compounds Journal Article Journal of the American Chemical Society, 142 (19), pp. 8897–8909, 2020. @article{Gernert2020, title = {Cyclic (Amino)(aryl)carbenes Enter the Field of Chromophore Ligands: Expanded $uppi$ System Leads to Unusually Deep Red Emitting CuI Compounds}, author = {Markus Gernert and Lukas Balles-Wolf and Florian Kerner and Ulrich Müller and Alexander Schmiedel and Marco Holzapfel and Christel M Marian and Jens Pflaum and Christoph Lambert and Andreas Steffen}, doi = {10.1021/jacs.0c02234}, year = {2020}, date = {2020-04-01}, journal = {Journal of the American Chemical Society}, volume = {142}, number = {19}, pages = {8897--8909}, publisher = {American Chemical Society (ACS)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Giesbrecht, Nadja; Weis, Andreas; Bein, Thomas Formation of stable 2D methylammonium antimony iodide phase for lead-free perovskite-like solar cellsast Journal Article Journal of Physics: Energy, 2 (2), pp. 024007, 2020. Abstract | Links | BibTeX | Tags: @article{Giesbrecht2020, title = {Formation of stable 2D methylammonium antimony iodide phase for lead-free perovskite-like solar cellsast}, author = {Nadja Giesbrecht and Andreas Weis and Thomas Bein}, url = {https://doi.org/10.1088%2F2515-7655%2Fab78ef}, doi = {10.1088/2515-7655/ab78ef}, year = {2020}, date = {2020-03-01}, journal = {Journal of Physics: Energy}, volume = {2}, number = {2}, pages = {024007}, publisher = {IOP Publishing}, abstract = {The presence of lead in novel hybrid perovskite-based solar cells remains a significant issue regarding commercial applications. Therefore, antimony-based perovskite-like A3M2X9 structures are promising new candidates for low toxicity photovoltaic applications. So far, MA3Sb2I9 was reported to only crystallize in the ‘zero-dimensional’ (0D) dimer structure with wide indirect bandgap properties. However, the formation of the 2D layered polymorph is more suitable for solar cell applications due to its expected direct and narrow bandgap. Here, we demonstrate the first synthesis of phase pure 2D layered MA3Sb2I9, based on antimony acetate dissolved in alcoholic solvents. Using in situ XRD methods, we confirm the stability of the layered phase towards high temperature, but the exposure to 75% relative humidity for several hours leads to a rearrangement of the phase with partial formation of the 0D structure. We investigated the electronic band structure and confirmed experimentally the presence of a semi-direct bandgap at around 2.1 eV. Our work shows that careful control of nucleation via processing conditions can provide access to promising perovskite-like phases for photovoltaic applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The presence of lead in novel hybrid perovskite-based solar cells remains a significant issue regarding commercial applications. Therefore, antimony-based perovskite-like A3M2X9 structures are promising new candidates for low toxicity photovoltaic applications. So far, MA3Sb2I9 was reported to only crystallize in the ‘zero-dimensional’ (0D) dimer structure with wide indirect bandgap properties. However, the formation of the 2D layered polymorph is more suitable for solar cell applications due to its expected direct and narrow bandgap. Here, we demonstrate the first synthesis of phase pure 2D layered MA3Sb2I9, based on antimony acetate dissolved in alcoholic solvents. Using in situ XRD methods, we confirm the stability of the layered phase towards high temperature, but the exposure to 75% relative humidity for several hours leads to a rearrangement of the phase with partial formation of the 0D structure. We investigated the electronic band structure and confirmed experimentally the presence of a semi-direct bandgap at around 2.1 eV. Our work shows that careful control of nucleation via processing conditions can provide access to promising perovskite-like phases for photovoltaic applications. |
Charles, Bethan; Weller, Mark T; Rieger, Sebastian; Hatcher, Lauren E; Henry, Paul F; Feldmann, Jochen; Wolverson, Daniel; Wilson, Chick C Phase Behavior and Substitution Limit of Mixed Cesium-Formamidinium Lead Triiodide Perovskites Journal Article Chem. Mater., 32 (6), pp. 2282–2291, 2020, ISSN: 0897-4756. Abstract | Links | BibTeX | Tags: @article{Charles2020, title = {Phase Behavior and Substitution Limit of Mixed Cesium-Formamidinium Lead Triiodide Perovskites}, author = {Bethan Charles and Mark T Weller and Sebastian Rieger and Lauren E Hatcher and Paul F Henry and Jochen Feldmann and Daniel Wolverson and Chick C Wilson}, url = {https://doi.org/10.1021/acs.chemmater.9b04032}, doi = {10.1021/acs.chemmater.9b04032}, issn = {0897-4756}, year = {2020}, date = {2020-03-01}, journal = {Chem. Mater.}, volume = {32}, number = {6}, pages = {2282--2291}, publisher = {American Chemical Society}, abstract = {The mixed cation lead iodide perovskite photovoltaics show improved stability following site substitution of cesium ions (Cs+) onto the formamidinium cation sites (FA+) of (CH(NH2)2PbI3 (FAPbI3) and increased resistance to formation of the undesirable ∂-phase. The structural phase behavior of Cs0.1FA0.9PbI3 has been investigated by neutron powder diffraction (NPD), complemented by single crystal and power X-ray diffraction and photoluminescence spectroscopy. The Cs-substitution limit has been determined to be less than 15%, and the cubic α-phase, Cs0.1FA0.9PbI3, is shown to be synthesizable in bulk and stable at 300 K. On cooling the cubic Cs0.1FA0.9PbI3, a slow, second-order cubic to tetragonal transition is observed close to 290 K, with variable temperature NPD indicating the presence of the tetragonal β-phase, adopting the space group P4/mbm between 290 and 180 K. An orthorhombic phase or twinned tetragonal phase is formed below 180 K, and the temperature for further transition to a disordered state is lowered to 125 K compared to that seen in phase pure α-FAPbI3 (140 K). These results demonstrate the importance of understanding the effect of cation site substitution on structure-property relationships in perovskite materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The mixed cation lead iodide perovskite photovoltaics show improved stability following site substitution of cesium ions (Cs+) onto the formamidinium cation sites (FA+) of (CH(NH2)2PbI3 (FAPbI3) and increased resistance to formation of the undesirable ∂-phase. The structural phase behavior of Cs0.1FA0.9PbI3 has been investigated by neutron powder diffraction (NPD), complemented by single crystal and power X-ray diffraction and photoluminescence spectroscopy. The Cs-substitution limit has been determined to be less than 15%, and the cubic α-phase, Cs0.1FA0.9PbI3, is shown to be synthesizable in bulk and stable at 300 K. On cooling the cubic Cs0.1FA0.9PbI3, a slow, second-order cubic to tetragonal transition is observed close to 290 K, with variable temperature NPD indicating the presence of the tetragonal β-phase, adopting the space group P4/mbm between 290 and 180 K. An orthorhombic phase or twinned tetragonal phase is formed below 180 K, and the temperature for further transition to a disordered state is lowered to 125 K compared to that seen in phase pure α-FAPbI3 (140 K). These results demonstrate the importance of understanding the effect of cation site substitution on structure-property relationships in perovskite materials. |
Urban, Patrick; Pritzl, Stefanie D; Ober, Martina F; Dirscherl, Christina F; Pernpeintner, Carla; Konrad, David B; Frank, James A; Trauner, Dirk; Nickel, Bert; Lohmueller, Theobald A Lipid Photoswitch Controls Fluidity in Supported Bilayer Membranes Journal Article Langmuir, 36 (10), pp. 2629–2634, 2020, ISSN: 0743-7463. Abstract | Links | BibTeX | Tags: @article{Urban2020, title = {A Lipid Photoswitch Controls Fluidity in Supported Bilayer Membranes}, author = {Patrick Urban and Stefanie D Pritzl and Martina F Ober and Christina F Dirscherl and Carla Pernpeintner and David B Konrad and James A Frank and Dirk Trauner and Bert Nickel and Theobald Lohmueller}, url = {https://doi.org/10.1021/acs.langmuir.9b02942}, doi = {10.1021/acs.langmuir.9b02942}, issn = {0743-7463}, year = {2020}, date = {2020-03-01}, journal = {Langmuir}, volume = {36}, number = {10}, pages = {2629--2634}, publisher = {American Chemical Society}, abstract = {Supported lipid bilayer (SLB) membranes are key elements to mimic membrane interfaces on a planar surface. Here, we demonstrate that azobenzene photolipids (azo-PC) form fluid, homogeneous SLBs. Diffusion properties of azo-PC within SLBs were probed by fluorescence microscopy and fluorescence recovery after photobleaching. At ambient conditions, we find that the trans-to-cis isomerization causes an increase of the diffusion constant by a factor of two. Simultaneous excitation with two wavelengths and variable intensities furthermore allows to adjust the diffusion constant D continuously. X-ray reflectometry and small-angle scattering measurements reveal that membrane photoisomerization results in a bilayer thickness reduction of ∼0.4 nm (or 10%). While thermally induced back-switching is not observed, we find that the trans bilayer fluidity is increasing with higher temperatures. This change in diffusion constant is accompanied by a red-shift in the absorption spectra. Based on these results, we suggest that the reduced diffusivity of trans-azo-PC is controlled by intermolecular interactions that also give rise to H-aggregate formation in bilayer membranes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Supported lipid bilayer (SLB) membranes are key elements to mimic membrane interfaces on a planar surface. Here, we demonstrate that azobenzene photolipids (azo-PC) form fluid, homogeneous SLBs. Diffusion properties of azo-PC within SLBs were probed by fluorescence microscopy and fluorescence recovery after photobleaching. At ambient conditions, we find that the trans-to-cis isomerization causes an increase of the diffusion constant by a factor of two. Simultaneous excitation with two wavelengths and variable intensities furthermore allows to adjust the diffusion constant D continuously. X-ray reflectometry and small-angle scattering measurements reveal that membrane photoisomerization results in a bilayer thickness reduction of ∼0.4 nm (or 10%). While thermally induced back-switching is not observed, we find that the trans bilayer fluidity is increasing with higher temperatures. This change in diffusion constant is accompanied by a red-shift in the absorption spectra. Based on these results, we suggest that the reduced diffusivity of trans-azo-PC is controlled by intermolecular interactions that also give rise to H-aggregate formation in bilayer membranes. |
Geiger, Michael; Acharya, Rachana; Reutter, Eric; Ferschke, Thomas; Zschieschang, Ute; Weis, Jürgen; Pflaum, Jens; Klauk, Hagen; Weitz, Ralf Thomas Effect of the Degree of the Gate-Dielectric Surface Roughness on the Performance of Bottom-Gate Organic Thin-Film Transistors Journal Article Advanced Materials Interfaces, 7 (10), pp. 1902145, 2020. @article{Geiger2020, title = {Effect of the Degree of the Gate-Dielectric Surface Roughness on the Performance of Bottom-Gate Organic Thin-Film Transistors}, author = {Michael Geiger and Rachana Acharya and Eric Reutter and Thomas Ferschke and Ute Zschieschang and Jürgen Weis and Jens Pflaum and Hagen Klauk and Ralf Thomas Weitz}, doi = {10.1002/admi.201902145}, year = {2020}, date = {2020-03-01}, journal = {Advanced Materials Interfaces}, volume = {7}, number = {10}, pages = {1902145}, publisher = {Wiley}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Silva, Barbara P G; Tosco, Bruna; de Florio, Daniel Z; Stepanenko, Vladimir; Würthner, Frank; é, Jos; Brochsztain, Sergio Efficient Electronic Coupling in Perylenediimide Multilayered Films on Indium Tin Oxide Journal Article The Journal of Physical Chemistry C, 124 (10), pp. 5541–5551, 2020. @article{Silva2020, title = {Efficient Electronic Coupling in Perylenediimide Multilayered Films on Indium Tin Oxide}, author = {Barbara P G Silva and Bruna Tosco and Daniel Z de Florio and Vladimir Stepanenko and Frank Würthner and Jos é and Sergio Brochsztain}, doi = {10.1021/acs.jpcc.9b11373}, year = {2020}, date = {2020-02-01}, journal = {The Journal of Physical Chemistry C}, volume = {124}, number = {10}, pages = {5541--5551}, publisher = {American Chemical Society (ACS)}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Biewald, Alexander; Giesbrecht, Nadja; Bein, Thomas; Docampo, Pablo; Hartschuh, Achim; Ciesielski, Richard Local Disorder at the Phase Transition Interrupts Ambipolar Charge Carrier Transport in Large Crystal Methylammonium Lead Iodide Thin Films Journal Article The Journal of Physical Chemistry C, 124 (38), pp. 20757-20764, 2020. Abstract | Links | BibTeX | Tags: @article{Biewald2020, title = {Local Disorder at the Phase Transition Interrupts Ambipolar Charge Carrier Transport in Large Crystal Methylammonium Lead Iodide Thin Films}, author = {Alexander Biewald and Nadja Giesbrecht and Thomas Bein and Pablo Docampo and Achim Hartschuh and Richard Ciesielski}, url = {https://doi.org/10.1021/acs.jpcc.0c06240}, doi = {10.1021/acs.jpcc.0c06240}, year = {2020}, date = {2020-01-01}, journal = {The Journal of Physical Chemistry C}, volume = {124}, number = {38}, pages = {20757-20764}, abstract = {The low-temperature transition from a tetragonal to an orthorhombic crystal phase in methylammonium lead iodide (MAPI) is accompanied by drastic changes in the charge carrier mobility around a critical temperature of approximately 164 K. This transition is studied here using photoluminescence (PL) microscopy on large crystal MAPI thin films, which is extremely sensitive to modifications of the charge carrier dynamics and can resolve physical properties on a single-grain level. The key observation is that ambipolar charge carrier diffusion suddenly stops when the temperature falls below the phase transition temperature. From coexisting PL bands and their spatial distribution, it is concluded that the temperature range from just below the phase transition until about 150 K is determined by a mixed phase where small orthorhombic and tetragonal domains coexist. This results in local disorder, which hinders ambipolar charge carrier diffusion.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The low-temperature transition from a tetragonal to an orthorhombic crystal phase in methylammonium lead iodide (MAPI) is accompanied by drastic changes in the charge carrier mobility around a critical temperature of approximately 164 K. This transition is studied here using photoluminescence (PL) microscopy on large crystal MAPI thin films, which is extremely sensitive to modifications of the charge carrier dynamics and can resolve physical properties on a single-grain level. The key observation is that ambipolar charge carrier diffusion suddenly stops when the temperature falls below the phase transition temperature. From coexisting PL bands and their spatial distribution, it is concluded that the temperature range from just below the phase transition until about 150 K is determined by a mixed phase where small orthorhombic and tetragonal domains coexist. This results in local disorder, which hinders ambipolar charge carrier diffusion. |
Kampmann, Jonathan; Betzler, Sophia; Hajiyani, Hamidreza; Häringer, Sebastian; Beetz, Michael; Harzer, Tristan; Kraus, Jürgen; Lotsch, Bettina V; Scheu, Christina; Pentcheva, Rossitza; Fattakhova-Rohlfing, Dina; Bein, Thomas How photocorrosion can trick you: a detailed study on low-bandgap Li doped CuO photocathodes for solar hydrogen production Journal Article Nanoscale, 12 , pp. 7766-7775, 2020. Abstract | Links | BibTeX | Tags: @article{Kampmann2020, title = {How photocorrosion can trick you: a detailed study on low-bandgap Li doped CuO photocathodes for solar hydrogen production}, author = {Jonathan Kampmann and Sophia Betzler and Hamidreza Hajiyani and Sebastian Häringer and Michael Beetz and Tristan Harzer and Jürgen Kraus and Bettina V Lotsch and Christina Scheu and Rossitza Pentcheva and Dina Fattakhova-Rohlfing and Thomas Bein}, url = {http://dx.doi.org/10.1039/C9NR10250G}, doi = {10.1039/C9NR10250G}, year = {2020}, date = {2020-01-01}, journal = {Nanoscale}, volume = {12}, pages = {7766-7775}, publisher = {The Royal Society of Chemistry}, abstract = {The efficiency of photoelectrochemical tandem cells is still limited by the availability of stable low band gap electrodes. In this work, we report a photocathode based on lithium doped copper(ii) oxide, a black p-type semiconductor. Density functional theory calculations with a Hubbard U term show that low concentrations of Li (Li0.03Cu0.97O) lead to an upward shift of the valence band maximum that crosses the Fermi level and results in a p-type semiconductor. Therefore, Li doping emerged as a suitable approach to manipulate the electronic structure of copper oxide based photocathodes. As this material class suffers from instability in water under operating conditions, the recorded photocurrents are repeatedly misinterpreted as hydrogen evolution evidence. We investigated the photocorrosion behavior of LixCu1−xO cathodes in detail and give the first mechanistic study of the fundamental physical process. The reduced copper oxide species were localized by electron energy loss spectroscopy mapping. Cu2O grows as distinct crystallites on the surface of LixCu1−xO instead of forming a dense layer. Additionally, there is no obvious Cu2O gradient inside the films, as Cu2O seems to form on all LixCu1−xO nanocrystals exposed to water. The application of a thin Ti0.8Nb0.2Ox coating by atomic layer deposition and the deposition of a platinum co-catalyst increased the stability of LixCu1−xO against decomposition. These devices showed a stable hydrogen evolution for 15 minutes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The efficiency of photoelectrochemical tandem cells is still limited by the availability of stable low band gap electrodes. In this work, we report a photocathode based on lithium doped copper(ii) oxide, a black p-type semiconductor. Density functional theory calculations with a Hubbard U term show that low concentrations of Li (Li0.03Cu0.97O) lead to an upward shift of the valence band maximum that crosses the Fermi level and results in a p-type semiconductor. Therefore, Li doping emerged as a suitable approach to manipulate the electronic structure of copper oxide based photocathodes. As this material class suffers from instability in water under operating conditions, the recorded photocurrents are repeatedly misinterpreted as hydrogen evolution evidence. We investigated the photocorrosion behavior of LixCu1−xO cathodes in detail and give the first mechanistic study of the fundamental physical process. The reduced copper oxide species were localized by electron energy loss spectroscopy mapping. Cu2O grows as distinct crystallites on the surface of LixCu1−xO instead of forming a dense layer. Additionally, there is no obvious Cu2O gradient inside the films, as Cu2O seems to form on all LixCu1−xO nanocrystals exposed to water. The application of a thin Ti0.8Nb0.2Ox coating by atomic layer deposition and the deposition of a platinum co-catalyst increased the stability of LixCu1−xO against decomposition. These devices showed a stable hydrogen evolution for 15 minutes. |
Zehetmaier, Peter M; Zoller, Florian; Beetz, Michael; Plaß, Maximilian A; Häringer, Sebastian; Böller, Bernhard; Döblinger, Markus; Bein, Thomas; Fattakhova-Rohlfing, Dina ChemNanoMat, 6 (4), pp. 618-628, 2020. Abstract | Links | BibTeX | Tags: battery cathode materials, lithium nickel cobalt manganese oxide, nanoparticles, nanoscale-stabilized metastable phases @article{Zehetmaier2020, title = {Nanocellulose-Mediated Transition of Lithium-Rich Pseudo-Quaternary Metal Oxide Nanoparticles into Lithium Nickel Cobalt Manganese Oxide (NCM) Nanostructures}, author = {Peter M Zehetmaier and Florian Zoller and Michael Beetz and Maximilian A Plaß and Sebastian Häringer and Bernhard Böller and Markus Döblinger and Thomas Bein and Dina Fattakhova-Rohlfing}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/cnma.201900748}, doi = {https://doi.org/10.1002/cnma.201900748}, year = {2020}, date = {2020-01-01}, journal = {ChemNanoMat}, volume = {6}, number = {4}, pages = {618-628}, abstract = {Abstract We report the syntheses of various compounds within the pseudo-quaternary system of the type LiwNixCoyMnzOδ (δ≤1) (pre-NCMs). Four different compositions of this compound were realized as ultrasmall crystalline nanoparticles of 1–4 nm diameter using low-temperature solvothermal reaction conditions in tert-butanol at only 170 °C. All of the pre-NCMs crystallize in the rock-salt structure and their lithium content is between 20% and 30% with respect to the complete metal content. By adjusting the lithium content to 105% stoichiometry in the solvothermal reaction, the pre-NCMs can easily react to the respective Li(NixCoyMnz)O2 (NCM) nanoparticles. Furthermore, nanosized desert-rose structured NCMs were obtained after addition of nanocellulose during the synthesis. By using the mixed metal monoxides as precursor for the NCMs, cation mixing between lithium and nickel is favored and gets more pronounced with increasing nickel content. The cation mixing effect compromises good electrochemical capacity retention, but the desert-rose structure nevertheless enables enhanced stability at high power conditions, especially for NCM333.}, keywords = {battery cathode materials, lithium nickel cobalt manganese oxide, nanoparticles, nanoscale-stabilized metastable phases}, pubstate = {published}, tppubtype = {article} } Abstract We report the syntheses of various compounds within the pseudo-quaternary system of the type LiwNixCoyMnzOδ (δ≤1) (pre-NCMs). Four different compositions of this compound were realized as ultrasmall crystalline nanoparticles of 1–4 nm diameter using low-temperature solvothermal reaction conditions in tert-butanol at only 170 °C. All of the pre-NCMs crystallize in the rock-salt structure and their lithium content is between 20% and 30% with respect to the complete metal content. By adjusting the lithium content to 105% stoichiometry in the solvothermal reaction, the pre-NCMs can easily react to the respective Li(NixCoyMnz)O2 (NCM) nanoparticles. Furthermore, nanosized desert-rose structured NCMs were obtained after addition of nanocellulose during the synthesis. By using the mixed metal monoxides as precursor for the NCMs, cation mixing between lithium and nickel is favored and gets more pronounced with increasing nickel content. The cation mixing effect compromises good electrochemical capacity retention, but the desert-rose structure nevertheless enables enhanced stability at high power conditions, especially for NCM333. |
Fang, Jiawen; Debnath, Tushar; Bhattacharyya, Santanu; Döblinger, Markus; Feldmann, Jochen; Stolarczyk, Jacek K Photobase effect for just-in-time delivery in photocatalytic hydrogen generation Journal Article Nature Communications, 11 (1), pp. 5179, 2020, ISSN: 2041-1723. Abstract | Links | BibTeX | Tags: @article{Fang2020, title = {Photobase effect for just-in-time delivery in photocatalytic hydrogen generation}, author = {Jiawen Fang and Tushar Debnath and Santanu Bhattacharyya and Markus Döblinger and Jochen Feldmann and Jacek K Stolarczyk}, url = {https://doi.org/10.1038/s41467-020-18583-6}, doi = {10.1038/s41467-020-18583-6}, issn = {2041-1723}, year = {2020}, date = {2020-01-01}, journal = {Nature Communications}, volume = {11}, number = {1}, pages = {5179}, abstract = {Carbon dots (CDs) are a promising nanomaterial for photocatalytic applications. However, the mechanism of the photocatalytic processes remains the subject of a debate due to the complex internal structure of the CDs, comprising crystalline and molecular units embedded in an amorphous matrix, rendering the analysis of the charge and energy transfer pathways between the constituent parts very challenging. Here we propose that the photobasic effect, that is the abstraction of a proton from water upon excitation by light, facilitates the photoexcited electron transfer to the proton. We show that the controlled inclusion in CDs of a model photobase, acridine, resembling the molecular moieties found in photocatalytically active CDs, strongly increases hydrogen generation. Ultrafast spectroscopy measurements reveal proton transfer within 30 ps of the excitation. This way, we use a model system to show that the photobasic effect may be contributing to the photocatalytic H2 generation of carbon nanomaterials and suggest that it may be tuned to achieve further improvements. The study demonstrates the critical role of the understanding the dynamics of the CDs in the design of next generation photocatalysts.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Carbon dots (CDs) are a promising nanomaterial for photocatalytic applications. However, the mechanism of the photocatalytic processes remains the subject of a debate due to the complex internal structure of the CDs, comprising crystalline and molecular units embedded in an amorphous matrix, rendering the analysis of the charge and energy transfer pathways between the constituent parts very challenging. Here we propose that the photobasic effect, that is the abstraction of a proton from water upon excitation by light, facilitates the photoexcited electron transfer to the proton. We show that the controlled inclusion in CDs of a model photobase, acridine, resembling the molecular moieties found in photocatalytically active CDs, strongly increases hydrogen generation. Ultrafast spectroscopy measurements reveal proton transfer within 30 ps of the excitation. This way, we use a model system to show that the photobasic effect may be contributing to the photocatalytic H2 generation of carbon nanomaterials and suggest that it may be tuned to achieve further improvements. The study demonstrates the critical role of the understanding the dynamics of the CDs in the design of next generation photocatalysts. |
Huang, He; Feil, Maximilian W; Fuchs, Simon; Debnath, Tushar; Richter, Alexander F; Tong, Yu; Wu, Linzhong; Wang, Yiou; Döblinger, Markus; Nickel, Bert Growth of Perovskite CsPbBr3 Nanocrystals and Their Formed Superstructures Revealed by In Situ Spectroscopy Journal Article Chemistry of Materials, 32 (20), pp. 8877-8884, 2020. Abstract | Links | BibTeX | Tags: @article{Huang2020, title = {Growth of Perovskite CsPbBr3 Nanocrystals and Their Formed Superstructures Revealed by In Situ Spectroscopy}, author = {He Huang and Maximilian W Feil and Simon Fuchs and Tushar Debnath and Alexander F Richter and Yu Tong and Linzhong Wu and Yiou Wang and Markus Döblinger and Bert Nickel}, url = {https://doi.org/10.1021/acs.chemmater.0c02467}, doi = {10.1021/acs.chemmater.0c02467}, year = {2020}, date = {2020-01-01}, journal = {Chemistry of Materials}, volume = {32}, number = {20}, pages = {8877-8884}, abstract = {Metal halide perovskites have attracted substantial interest because of their promising properties for optoelectronic applications. Despite much progress made in the field, the exact growth mechanism of perovskite nanocrystals (e.g., CsPbBr3) remains elusive and further improvement of their controllable synthesis is challenging. Herein, we point out different phenomena during the processes of growth, cooling, and purification of high-quality CsPbBr3 nanocrystals using in situ photoluminescence spectroscopy. The as-synthesized materials have been further characterized by time-resolved transient differential transmission and photoluminescence spectroscopies. Using X-ray scattering, we confirm that nanocrystals form superstructures during the process of cooling already in dispersion, which is frequently ignored. The purification process is explained using a proposed model based on the self-size-selection. On the one hand, such superstructures pave a potential pathway to the fabrication of high-quality devices such as light-emitting devices. On the other hand, the approach to reveal their formation process benefits the comparison and understanding of the difference between nanocrystals and supercrystals. The fact that superstructures form already during synthesis may also apply to the different perovskite systems and thus help to improve the quality of the as-prepared nanocrystals.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Metal halide perovskites have attracted substantial interest because of their promising properties for optoelectronic applications. Despite much progress made in the field, the exact growth mechanism of perovskite nanocrystals (e.g., CsPbBr3) remains elusive and further improvement of their controllable synthesis is challenging. Herein, we point out different phenomena during the processes of growth, cooling, and purification of high-quality CsPbBr3 nanocrystals using in situ photoluminescence spectroscopy. The as-synthesized materials have been further characterized by time-resolved transient differential transmission and photoluminescence spectroscopies. Using X-ray scattering, we confirm that nanocrystals form superstructures during the process of cooling already in dispersion, which is frequently ignored. The purification process is explained using a proposed model based on the self-size-selection. On the one hand, such superstructures pave a potential pathway to the fabrication of high-quality devices such as light-emitting devices. On the other hand, the approach to reveal their formation process benefits the comparison and understanding of the difference between nanocrystals and supercrystals. The fact that superstructures form already during synthesis may also apply to the different perovskite systems and thus help to improve the quality of the as-prepared nanocrystals. |
Vila-Liarte, David; Feil, Maximilian W; Manzi, Aurora; Garcia-Pomar, Juan Luis; Huang, He; Döblinger, Markus; Liz-Marzán, Luis M; Feldmann, Jochen; Polavarapu, Lakshminarayana; Mihi, Agustín Templated-Assembly of CsPbBr3 Perovskite Nanocrystals into 2D Photonic Supercrystals with Amplified Spontaneous Emission Journal Article Angewandte Chemie International Edition, 59 (40), pp. 17750-17756, 2020. Abstract | Links | BibTeX | Tags: 2D photonic crystals, amplified spontaneous emission (ASE), PDMS template, perovskite nanocrystals, self-assembly @article{VilaLiarte2020, title = {Templated-Assembly of CsPbBr3 Perovskite Nanocrystals into 2D Photonic Supercrystals with Amplified Spontaneous Emission}, author = {David Vila-Liarte and Maximilian W Feil and Aurora Manzi and Juan Luis Garcia-Pomar and He Huang and Markus Döblinger and Luis M Liz-Marzán and Jochen Feldmann and Lakshminarayana Polavarapu and Agustín Mihi}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202006152}, doi = {https://doi.org/10.1002/anie.202006152}, year = {2020}, date = {2020-01-01}, journal = {Angewandte Chemie International Edition}, volume = {59}, number = {40}, pages = {17750-17756}, abstract = {Abstract Perovskite nanocrystals (NCs) have revolutionized optoelectronic devices because of their versatile optical properties. However, controlling and extending these functionalities often requires a light-management strategy involving additional processing steps. Herein, we introduce a simple approach to shape perovskite nanocrystals (NC) into photonic architectures that provide light management by directly shaping the active material. Pre-patterned polydimethylsiloxane (PDMS) templates are used for the template-induced self-assembly of 10 nm CsPbBr3 perovskite NC colloids into large area (1 cm2) 2D photonic crystals with tunable lattice spacing, ranging from 400 nm up to several microns. The photonic crystal arrangement facilitates efficient light coupling to the nanocrystal layer, thereby increasing the electric field intensity within the perovskite film. As a result, CsPbBr3 2D photonic crystals show amplified spontaneous emission (ASE) under lower optical excitation fluences in the near-IR, in contrast to equivalent flat NC films prepared using the same colloidal ink. This improvement is attributed to the enhanced multi-photon absorption caused by light trapping in the photonic crystal.}, keywords = {2D photonic crystals, amplified spontaneous emission (ASE), PDMS template, perovskite nanocrystals, self-assembly}, pubstate = {published}, tppubtype = {article} } Abstract Perovskite nanocrystals (NCs) have revolutionized optoelectronic devices because of their versatile optical properties. However, controlling and extending these functionalities often requires a light-management strategy involving additional processing steps. Herein, we introduce a simple approach to shape perovskite nanocrystals (NC) into photonic architectures that provide light management by directly shaping the active material. Pre-patterned polydimethylsiloxane (PDMS) templates are used for the template-induced self-assembly of 10 nm CsPbBr3 perovskite NC colloids into large area (1 cm2) 2D photonic crystals with tunable lattice spacing, ranging from 400 nm up to several microns. The photonic crystal arrangement facilitates efficient light coupling to the nanocrystal layer, thereby increasing the electric field intensity within the perovskite film. As a result, CsPbBr3 2D photonic crystals show amplified spontaneous emission (ASE) under lower optical excitation fluences in the near-IR, in contrast to equivalent flat NC films prepared using the same colloidal ink. This improvement is attributed to the enhanced multi-photon absorption caused by light trapping in the photonic crystal. |
Gramlich, Moritz; Bohn, Bernhard J; Tong, Yu; Polavarapu, Lakshminarayana; Feldmann, Jochen; Urban, Alexander S Thickness-Dependence of Exciton–Exciton Annihilation in Halide Perovskite Nanoplatelets Journal Article The Journal of Physical Chemistry Letters, 11 (13), pp. 5361-5366, 2020, (PMID: 32536167). Abstract | Links | BibTeX | Tags: @article{Gramlich2020, title = {Thickness-Dependence of Exciton–Exciton Annihilation in Halide Perovskite Nanoplatelets}, author = {Moritz Gramlich and Bernhard J Bohn and Yu Tong and Lakshminarayana Polavarapu and Jochen Feldmann and Alexander S Urban}, url = {https://doi.org/10.1021/acs.jpclett.0c01291}, doi = {10.1021/acs.jpclett.0c01291}, year = {2020}, date = {2020-01-01}, journal = {The Journal of Physical Chemistry Letters}, volume = {11}, number = {13}, pages = {5361-5366}, abstract = {Exciton–exciton annihilation (EEA) and Auger recombination are detrimental processes occurring in semiconductor optoelectronic devices at high carrier densities. Despite constituting one of the main obstacles for realizing lasing in semiconductor nanocrystals (NCs), the dependencies on NC size are not fully understood, especially for those with both weakly and strongly confined dimensions. Here, we use differential transmission spectroscopy to investigate the dependence of EEA on the physical dimensions of thickness-controlled 2D halide perovskite nanoplatelets (NPls). We find the EEA lifetimes to be extremely short on the order of 7–60 ps. Moreover, they are strongly determined by the NPl thickness with a power law dependence according to τ2 ∝ d5.3. Additional measurements show that the EEA lifetimes also increase for NPls with larger lateral dimensions. These results show that a precise control of the physical dimensions is critical for deciphering the fundamental laws governing the process especially in 1D and 2D NCs.}, note = {PMID: 32536167}, keywords = {}, pubstate = {published}, tppubtype = {article} } Exciton–exciton annihilation (EEA) and Auger recombination are detrimental processes occurring in semiconductor optoelectronic devices at high carrier densities. Despite constituting one of the main obstacles for realizing lasing in semiconductor nanocrystals (NCs), the dependencies on NC size are not fully understood, especially for those with both weakly and strongly confined dimensions. Here, we use differential transmission spectroscopy to investigate the dependence of EEA on the physical dimensions of thickness-controlled 2D halide perovskite nanoplatelets (NPls). We find the EEA lifetimes to be extremely short on the order of 7–60 ps. Moreover, they are strongly determined by the NPl thickness with a power law dependence according to τ2 ∝ d5.3. Additional measurements show that the EEA lifetimes also increase for NPls with larger lateral dimensions. These results show that a precise control of the physical dimensions is critical for deciphering the fundamental laws governing the process especially in 1D and 2D NCs. |
Strohmair, Simone; Dey, Amrita; Tong, Yu; Polavarapu, Lakshminarayana; Bohn, Bernhard J; Feldmann, Jochen Spin Polarization Dynamics of Free Charge Carriers in CsPbI3 Nanocrystals Journal Article Nano Letters, 20 (7), pp. 4724-4730, 2020, (PMID: 32453960). Abstract | Links | BibTeX | Tags: @article{Strohmair2020, title = {Spin Polarization Dynamics of Free Charge Carriers in CsPbI3 Nanocrystals}, author = {Simone Strohmair and Amrita Dey and Yu Tong and Lakshminarayana Polavarapu and Bernhard J Bohn and Jochen Feldmann}, url = {https://doi.org/10.1021/acs.nanolett.9b05325}, doi = {10.1021/acs.nanolett.9b05325}, year = {2020}, date = {2020-01-01}, journal = {Nano Letters}, volume = {20}, number = {7}, pages = {4724-4730}, abstract = {Lead halide perovskites (LHPs) exhibit large spin–orbit coupling (SOC), leading to only twofold-degenerate valence and conduction bands and therefore allowing for efficient optical orientation. This makes them ideal materials to study charge carrier spins. With this study we elucidate the spin dynamics of photoexcited charge carriers and the underlying spin relaxation mechanisms in CsPbI3 nanocrystals by employing time-resolved differential transmission spectroscopy (DTS). We find that the photoinduced spin polarization significantly diminishes during thermalization and cooling toward the energetically favorable band edge. Temperature-dependent DTS reveals a decay in spin polarization that is more than 1 order of magnitude faster at room temperature (3 ps) than at cryogenic temperatures (32 ps). We propose that spin relaxation of free charge carriers in large-SOC materials like LHPs occurs as a result of carrier–phonon scattering, as described by the Elliott–Yafet mechanism.}, note = {PMID: 32453960}, keywords = {}, pubstate = {published}, tppubtype = {article} } Lead halide perovskites (LHPs) exhibit large spin–orbit coupling (SOC), leading to only twofold-degenerate valence and conduction bands and therefore allowing for efficient optical orientation. This makes them ideal materials to study charge carrier spins. With this study we elucidate the spin dynamics of photoexcited charge carriers and the underlying spin relaxation mechanisms in CsPbI3 nanocrystals by employing time-resolved differential transmission spectroscopy (DTS). We find that the photoinduced spin polarization significantly diminishes during thermalization and cooling toward the energetically favorable band edge. Temperature-dependent DTS reveals a decay in spin polarization that is more than 1 order of magnitude faster at room temperature (3 ps) than at cryogenic temperatures (32 ps). We propose that spin relaxation of free charge carriers in large-SOC materials like LHPs occurs as a result of carrier–phonon scattering, as described by the Elliott–Yafet mechanism. |
Dey, Amrita; Richter, Alexander F; Debnath, Tushar; Huang, He; Polavarapu, Lakshminarayana; Feldmann, Jochen Transfer of Direct to Indirect Bound Excitons by Electron Intervalley Scattering in Cs2AgBiBr6 Double Perovskite Nanocrystals Journal Article ACS Nano, 14 (5), pp. 5855-5861, 2020, (PMID: 32298081). Abstract | Links | BibTeX | Tags: @article{Dey2020, title = {Transfer of Direct to Indirect Bound Excitons by Electron Intervalley Scattering in Cs2AgBiBr6 Double Perovskite Nanocrystals}, author = {Amrita Dey and Alexander F Richter and Tushar Debnath and He Huang and Lakshminarayana Polavarapu and Jochen Feldmann}, url = {https://doi.org/10.1021/acsnano.0c00997}, doi = {10.1021/acsnano.0c00997}, year = {2020}, date = {2020-01-01}, journal = {ACS Nano}, volume = {14}, number = {5}, pages = {5855-5861}, abstract = {Lead-free halide double perovskites have emerged as a nontoxic alternative to the heavily researched lead-based halide perovskites. However, their optical properties and the initial charge carrier relaxation processes are under debate. In this study, we apply time-resolved photoluminescence and differential transmission spectroscopy to investigate the photoexcited charge carrier dynamics within the indirect band structure of Cs2AgBiBr6 nanocrystals. Interestingly, we observe a high energetic emission stemming from the direct band gap, besides the previously reported emission from the indirect band gap transition. We attribute this emission to the radiative recombination of direct bound excitons. This emission maximum redshifts nearly 1 eV within 10 ps due to electron intervalley scattering, which leads to a transfer of direct to indirect bound excitons. We conclude that these direct bound excitons possess a giant oscillator strength causing not only a pronounced absorption peak at the optical band gap energy but also luminescence to occur at the direct band gap transition in spite of the prevailing intervalley scattering process. These results expand the understanding of the optical properties and the charge carrier relaxation in double perovskites, thus, facilitating the further development of optoelectronic devices harnessing lead-free perovskites.}, note = {PMID: 32298081}, keywords = {}, pubstate = {published}, tppubtype = {article} } Lead-free halide double perovskites have emerged as a nontoxic alternative to the heavily researched lead-based halide perovskites. However, their optical properties and the initial charge carrier relaxation processes are under debate. In this study, we apply time-resolved photoluminescence and differential transmission spectroscopy to investigate the photoexcited charge carrier dynamics within the indirect band structure of Cs2AgBiBr6 nanocrystals. Interestingly, we observe a high energetic emission stemming from the direct band gap, besides the previously reported emission from the indirect band gap transition. We attribute this emission to the radiative recombination of direct bound excitons. This emission maximum redshifts nearly 1 eV within 10 ps due to electron intervalley scattering, which leads to a transfer of direct to indirect bound excitons. We conclude that these direct bound excitons possess a giant oscillator strength causing not only a pronounced absorption peak at the optical band gap energy but also luminescence to occur at the direct band gap transition in spite of the prevailing intervalley scattering process. These results expand the understanding of the optical properties and the charge carrier relaxation in double perovskites, thus, facilitating the further development of optoelectronic devices harnessing lead-free perovskites. |
Paul, Sharmistha; Bladt, Eva; Richter, Alexander F; Döblinger, Markus; Tong, Yu; Huang, He; Dey, Amrita; Bals, Sara; Debnath, Tushar; Polavarapu, Lakshminarayana; Feldmann, Jochen Manganese-Doping-Induced Quantum Confinement within Host Perovskite Nanocrystals through Ruddlesden–Popper Defects Journal Article Angewandte Chemie International Edition, 59 (17), pp. 6794-6799, 2020. Abstract | Links | BibTeX | Tags: CsPbX3 nanocrystals, exciton properties, manganese-doped perovskite nanocrystals, quantum confinement, Ruddlesden–Popper defects @article{Paul2020, title = {Manganese-Doping-Induced Quantum Confinement within Host Perovskite Nanocrystals through Ruddlesden–Popper Defects}, author = {Sharmistha Paul and Eva Bladt and Alexander F Richter and Markus Döblinger and Yu Tong and He Huang and Amrita Dey and Sara Bals and Tushar Debnath and Lakshminarayana Polavarapu and Jochen Feldmann}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201914473}, doi = {https://doi.org/10.1002/anie.201914473}, year = {2020}, date = {2020-01-01}, journal = {Angewandte Chemie International Edition}, volume = {59}, number = {17}, pages = {6794-6799}, abstract = {Abstract The concept of doping Mn2+ ions into II–VI semiconductor nanocrystals (NCs) was recently extended to perovskite NCs. To date, most studies on Mn2+ doped NCs focus on enhancing the emission related to the Mn2+ dopant via an energy transfer mechanism. Herein, we found that the doping of Mn2+ ions into CsPbCl3 NCs not only results in a Mn2+-related orange emission, but also strongly influences the excitonic properties of the host NCs. We observe for the first time that Mn2+ doping leads to the formation of Ruddlesden–Popper (R.P.) defects and thus induces quantum confinement within the host NCs. We find that a slight doping with Mn2+ ions improves the size distribution of the NCs, which results in a prominent excitonic peak. However, with increasing the Mn2+ concentration, the number of R.P. planes increases leading to smaller single-crystal domains. The thus enhanced confinement and crystal inhomogeneity cause a gradual blue shift and broadening of the excitonic transition, respectively.}, keywords = {CsPbX3 nanocrystals, exciton properties, manganese-doped perovskite nanocrystals, quantum confinement, Ruddlesden–Popper defects}, pubstate = {published}, tppubtype = {article} } Abstract The concept of doping Mn2+ ions into II–VI semiconductor nanocrystals (NCs) was recently extended to perovskite NCs. To date, most studies on Mn2+ doped NCs focus on enhancing the emission related to the Mn2+ dopant via an energy transfer mechanism. Herein, we found that the doping of Mn2+ ions into CsPbCl3 NCs not only results in a Mn2+-related orange emission, but also strongly influences the excitonic properties of the host NCs. We observe for the first time that Mn2+ doping leads to the formation of Ruddlesden–Popper (R.P.) defects and thus induces quantum confinement within the host NCs. We find that a slight doping with Mn2+ ions improves the size distribution of the NCs, which results in a prominent excitonic peak. However, with increasing the Mn2+ concentration, the number of R.P. planes increases leading to smaller single-crystal domains. The thus enhanced confinement and crystal inhomogeneity cause a gradual blue shift and broadening of the excitonic transition, respectively. |
Huang, He; Wu, Linzhong; Wang, Yiou; Richter, Alexander F; Döblinger, Markus; Feldmann, Jochen Facile Synthesis of FAPbI3 Nanorods Journal Article Nanomaterials, 10 (1), 2020, ISSN: 2079-4991. Abstract | Links | BibTeX | Tags: @article{Huang2020a, title = {Facile Synthesis of FAPbI3 Nanorods}, author = {He Huang and Linzhong Wu and Yiou Wang and Alexander F Richter and Markus Döblinger and Jochen Feldmann}, url = {https://www.mdpi.com/2079-4991/10/1/72}, doi = {10.3390/nano10010072}, issn = {2079-4991}, year = {2020}, date = {2020-01-01}, journal = {Nanomaterials}, volume = {10}, number = {1}, abstract = {Metal halide perovskites are promising materials for a range of applications. The synthesis of light-emitting perovskite nanorods has become popular recently. Thus far, the facile synthesis of perovskite nanorods remains elusive. In this work, we have developed a facile synthesis to fabricate FAPbI3 nanorods for the first time, demonstrating a high photoluminescence quantum yield of 35–42%. The fabrication of the nanorods has been made possible by carefully tuning the concentration of formamidine-oleate as well as the amount of oleic acid with pre-dissolved PbI2 in toluene with oleic acid/oleylamine.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Metal halide perovskites are promising materials for a range of applications. The synthesis of light-emitting perovskite nanorods has become popular recently. Thus far, the facile synthesis of perovskite nanorods remains elusive. In this work, we have developed a facile synthesis to fabricate FAPbI3 nanorods for the first time, demonstrating a high photoluminescence quantum yield of 35–42%. The fabrication of the nanorods has been made possible by carefully tuning the concentration of formamidine-oleate as well as the amount of oleic acid with pre-dissolved PbI2 in toluene with oleic acid/oleylamine. |
Chen, Wei; Liang, Suzhe; Löhrer, Franziska C; Schaper, Simon J; Li, Nian; Cao, Wei; Kreuzer, Lucas P; Liu, Haochen; Tang, Haodong; Körstgens, Volker; Schwartzkopf, Matthias; Wang, Kai; Sun, Xiao Wei; Roth, Stephan V; Müller-Buschbaum, Peter In situ Grazing-Incidence Small-Angle X-ray Scattering Observation of Gold Sputter Deposition on a PbS Quantum Dot Solid Journal Article ACS Applied Materials & Interfaces, 12 (41), pp. 46942-46952, 2020, (PMID: 32941012). Abstract | Links | BibTeX | Tags: @article{Chen2020, title = {In situ Grazing-Incidence Small-Angle X-ray Scattering Observation of Gold Sputter Deposition on a PbS Quantum Dot Solid}, author = {Wei Chen and Suzhe Liang and Franziska C Löhrer and Simon J Schaper and Nian Li and Wei Cao and Lucas P Kreuzer and Haochen Liu and Haodong Tang and Volker Körstgens and Matthias Schwartzkopf and Kai Wang and Xiao Wei Sun and Stephan V Roth and Peter Müller-Buschbaum}, url = {https://doi.org/10.1021/acsami.0c12732}, doi = {10.1021/acsami.0c12732}, year = {2020}, date = {2020-01-01}, journal = {ACS Applied Materials & Interfaces}, volume = {12}, number = {41}, pages = {46942-46952}, abstract = {For PbS quantum dot (QD)-based optoelectronic devices, gold is the most frequently used electrode material. In most device architectures, gold is in direct contact with the QD solid. To better understand the formation of the interface between gold and a close-packed QD layer at an early stage, in situ grazing-incidence small-angle X-ray scattering is used to observe the gold sputter deposition on a 1,2-ethanedithiol (EDT)-treated PbS QD solid. In the kinetics of gold layer growth, the forming and merging of small gold clusters (radius less than 1.6 nm) are observed at the early stages. The thereby formed medium gold clusters (radius between 1.9–2.4 nm) are influenced by the QDs’ templating effect. Furthermore, simulations suggest that the medium gold clusters grow preferably along the QDs’ boundaries rather than as a top coating of the QDs. When the thickness of the sputtered gold layer reaches 6.25 nm, larger gold clusters with a radius of 5.3 nm form. Simultaneously, a percolation layer with a thickness of 2.5 nm is established underneath the gold clusters. This fundamental understanding of the QD–gold interface formation will help to control the implementation of sputtered gold electrodes on close-packed QD solids in device manufacturing processes.}, note = {PMID: 32941012}, keywords = {}, pubstate = {published}, tppubtype = {article} } For PbS quantum dot (QD)-based optoelectronic devices, gold is the most frequently used electrode material. In most device architectures, gold is in direct contact with the QD solid. To better understand the formation of the interface between gold and a close-packed QD layer at an early stage, in situ grazing-incidence small-angle X-ray scattering is used to observe the gold sputter deposition on a 1,2-ethanedithiol (EDT)-treated PbS QD solid. In the kinetics of gold layer growth, the forming and merging of small gold clusters (radius less than 1.6 nm) are observed at the early stages. The thereby formed medium gold clusters (radius between 1.9–2.4 nm) are influenced by the QDs’ templating effect. Furthermore, simulations suggest that the medium gold clusters grow preferably along the QDs’ boundaries rather than as a top coating of the QDs. When the thickness of the sputtered gold layer reaches 6.25 nm, larger gold clusters with a radius of 5.3 nm form. Simultaneously, a percolation layer with a thickness of 2.5 nm is established underneath the gold clusters. This fundamental understanding of the QD–gold interface formation will help to control the implementation of sputtered gold electrodes on close-packed QD solids in device manufacturing processes. |
Hohn, Nuri; Wang, Xiaoyan; Giebel, Michael A; Yin, Shanshan; Müller, David; Hetzenecker, Andreas E; Bießmann, Lorenz; Kreuzer, Lucas P; Möhl, Gilles E; Yu, Haoyang; Veinot, Jonathan G C; Fässler, Thomas F; Cheng, Ya-Jun; Müller-Buschbaum, Peter Mesoporous GeOx/Ge/C as a Highly Reversible Anode Material with High Specific Capacity for Lithium-Ion Batteries Journal Article ACS Applied Materials & Interfaces, 12 (41), pp. 47002-47009, 2020, (PMID: 32955236). Abstract | Links | BibTeX | Tags: @article{Hohn2020, title = {Mesoporous GeOx/Ge/C as a Highly Reversible Anode Material with High Specific Capacity for Lithium-Ion Batteries}, author = {Nuri Hohn and Xiaoyan Wang and Michael A Giebel and Shanshan Yin and David Müller and Andreas E Hetzenecker and Lorenz Bießmann and Lucas P Kreuzer and Gilles E Möhl and Haoyang Yu and Jonathan G C Veinot and Thomas F Fässler and Ya-Jun Cheng and Peter Müller-Buschbaum}, url = {https://doi.org/10.1021/acsami.0c13560}, doi = {10.1021/acsami.0c13560}, year = {2020}, date = {2020-01-01}, journal = {ACS Applied Materials & Interfaces}, volume = {12}, number = {41}, pages = {47002-47009}, abstract = {Nanostructured Ge is considered a highly promising material for Li-ion battery applications as Ge offers high specific capacity and Li-ion diffusivity, while inherent mesoporous nanostructures can contribute resistance against capacity fading as typically induced by high volume expansion in bulk Ge films. Mesoporous GeOx/Ge/C films are synthesized using K4Ge9 Zintl clusters as a Ge precursor and the amphiphilic diblock copolymer polystyrene-block-polyethylene oxide as a templating tool. As compared to a reference sample without post-treatment, enhanced surface-to-volume ratios are achieved through post-treatment with a poor-good azeotrope solvent mixture. High capacities of over 2000 mA h g–1 are obtained with good stability over 300 cycles. Information from morphological and compositional characterization for both reference and post-treated sample suggests that the good electrochemical performance originates from reversible GeO2 conversion reactions.}, note = {PMID: 32955236}, keywords = {}, pubstate = {published}, tppubtype = {article} } Nanostructured Ge is considered a highly promising material for Li-ion battery applications as Ge offers high specific capacity and Li-ion diffusivity, while inherent mesoporous nanostructures can contribute resistance against capacity fading as typically induced by high volume expansion in bulk Ge films. Mesoporous GeOx/Ge/C films are synthesized using K4Ge9 Zintl clusters as a Ge precursor and the amphiphilic diblock copolymer polystyrene-block-polyethylene oxide as a templating tool. As compared to a reference sample without post-treatment, enhanced surface-to-volume ratios are achieved through post-treatment with a poor-good azeotrope solvent mixture. High capacities of over 2000 mA h g–1 are obtained with good stability over 300 cycles. Information from morphological and compositional characterization for both reference and post-treated sample suggests that the good electrochemical performance originates from reversible GeO2 conversion reactions. |
Zhao, Heng; Naveed, Hafiz Bilal; Lin, Baojun; Zhou, Xiaobo; Yuan, Jian; Zhou, Ke; Wu, Hongbo; Guo, Renjun; Scheel, Manuel A; Chumakov, Andrei; Roth, Stephan V; Tang, Zheng; Müller-Buschbaum, Peter; Ma, Wei Hot Hydrocarbon-Solvent Slot-Die Coating Enables High-Efficiency Organic Solar Cells with Temperature-Dependent Aggregation Behavior Journal Article Advanced Materials, 32 (39), pp. 2002302, 2020. Abstract | Links | BibTeX | Tags: hot slot-die coating, hydrocarbon solvents, organic solar cells, temperature-dependent aggregation @article{Zhao2020, title = {Hot Hydrocarbon-Solvent Slot-Die Coating Enables High-Efficiency Organic Solar Cells with Temperature-Dependent Aggregation Behavior}, author = {Heng Zhao and Hafiz Bilal Naveed and Baojun Lin and Xiaobo Zhou and Jian Yuan and Ke Zhou and Hongbo Wu and Renjun Guo and Manuel A Scheel and Andrei Chumakov and Stephan V Roth and Zheng Tang and Peter Müller-Buschbaum and Wei Ma}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.202002302}, doi = {https://doi.org/10.1002/adma.202002302}, year = {2020}, date = {2020-01-01}, journal = {Advanced Materials}, volume = {32}, number = {39}, pages = {2002302}, abstract = {Abstract Organic solar cells (OSCs) have made rapid progress in terms of their development as a sustainable energy source. However, record-breaking devices have not shown compatibility with large-scale production via solution processing in particular due to the use of halogenated environment-threatening solvents. Here, slot-die fabrication with processing involving hydrocarbon-based solvents is used to realize highly efficient and environmentally friendly OSCs. Highly compatible slot-die coating with roll-to-roll processing using halogenated (chlorobenzene (CB)) and hydrocarbon solvents (1,2,4-trimethylbenzene (TMB) and ortho-xylene (o-XY)) is used to fabricate photoactive films. Controlled solution and substrate temperatures enable similar aggregation states in the solution and similar kinetics processes during film formation. The optimized blend film nanostructures for different solvents in the highly efficient PM6:Y6 blend is adopted to show a similar morphology, which results in device efficiencies of 15.2%, 15.4%, and 15.6% for CB, TMB, and o-XY solvents. This approach is successfully extended to other donor–acceptor combinations to demonstrate the excellent universality of this method. The results combine a method to optimize the aggregation state and film formation kinetics with the fabrication of OSCs with environmentally friendly solvents by slot-die coating, which is a critical finding for the future development of OSCs in terms of their scalable production and high-performance.}, keywords = {hot slot-die coating, hydrocarbon solvents, organic solar cells, temperature-dependent aggregation}, pubstate = {published}, tppubtype = {article} } Abstract Organic solar cells (OSCs) have made rapid progress in terms of their development as a sustainable energy source. However, record-breaking devices have not shown compatibility with large-scale production via solution processing in particular due to the use of halogenated environment-threatening solvents. Here, slot-die fabrication with processing involving hydrocarbon-based solvents is used to realize highly efficient and environmentally friendly OSCs. Highly compatible slot-die coating with roll-to-roll processing using halogenated (chlorobenzene (CB)) and hydrocarbon solvents (1,2,4-trimethylbenzene (TMB) and ortho-xylene (o-XY)) is used to fabricate photoactive films. Controlled solution and substrate temperatures enable similar aggregation states in the solution and similar kinetics processes during film formation. The optimized blend film nanostructures for different solvents in the highly efficient PM6:Y6 blend is adopted to show a similar morphology, which results in device efficiencies of 15.2%, 15.4%, and 15.6% for CB, TMB, and o-XY solvents. This approach is successfully extended to other donor–acceptor combinations to demonstrate the excellent universality of this method. The results combine a method to optimize the aggregation state and film formation kinetics with the fabrication of OSCs with environmentally friendly solvents by slot-die coating, which is a critical finding for the future development of OSCs in terms of their scalable production and high-performance. |
Yin, Shanshan; Tian, Ting; Wienhold, Kerstin S; Weindl, Christian L; Guo, Renjun; Schwartzkopf, Matthias; Roth, Stephan V; Müller-Buschbaum, Peter Key Factor Study for Amphiphilic Block Copolymer-Templated Mesoporous SnO2 Thin Film Synthesis: Influence of Solvent and Catalyst Journal Article Advanced Materials Interfaces, 7 (18), pp. 2001002, 2020. Abstract | Links | BibTeX | Tags: mesoporous structures, morphology, PS-b-PEO, SnO2, thin films @article{Yin2020, title = {Key Factor Study for Amphiphilic Block Copolymer-Templated Mesoporous SnO2 Thin Film Synthesis: Influence of Solvent and Catalyst}, author = {Shanshan Yin and Ting Tian and Kerstin S Wienhold and Christian L Weindl and Renjun Guo and Matthias Schwartzkopf and Stephan V Roth and Peter Müller-Buschbaum}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.202001002}, doi = {https://doi.org/10.1002/admi.202001002}, year = {2020}, date = {2020-01-01}, journal = {Advanced Materials Interfaces}, volume = {7}, number = {18}, pages = {2001002}, abstract = {Abstract As a crucial material in the field of energy storage, SnO2 thin films are widely applied in daily life and have been in the focus of scientific research. Compared to the planar counterpart, mesoporous SnO2 thin films with high specific surface area possess more attractive physical and chemical properties. In the present work, a novel amphiphilic block copolymer-assisted sol–gel chemistry is utilized for the synthesis of porous tin oxide (SnO2). Two key factors for the sol–gel stock solution preparation, the solvent category and the catalyst content, are systematically varied to tune the thin film morphologies. A calcination process is performed to remove the polymer template at 500 °C in ambient conditions. The surface morphology and the buried inner structure are probed with scanning electron microscope and grazing-incidence small-angle X-ray scattering. Crystallinity is characterized by X-ray diffraction. The multi-dimensional characterization results suggest that cassiterite SnO2 with spherical, cylindrical, and vesicular pore structures are obtained. The variation of the film morphology is governed by the preferential affinity of the utilized solvent mixture and the hydrogen bond interaction between the employed cycloether and H2O molecules in the solution.}, keywords = {mesoporous structures, morphology, PS-b-PEO, SnO2, thin films}, pubstate = {published}, tppubtype = {article} } Abstract As a crucial material in the field of energy storage, SnO2 thin films are widely applied in daily life and have been in the focus of scientific research. Compared to the planar counterpart, mesoporous SnO2 thin films with high specific surface area possess more attractive physical and chemical properties. In the present work, a novel amphiphilic block copolymer-assisted sol–gel chemistry is utilized for the synthesis of porous tin oxide (SnO2). Two key factors for the sol–gel stock solution preparation, the solvent category and the catalyst content, are systematically varied to tune the thin film morphologies. A calcination process is performed to remove the polymer template at 500 °C in ambient conditions. The surface morphology and the buried inner structure are probed with scanning electron microscope and grazing-incidence small-angle X-ray scattering. Crystallinity is characterized by X-ray diffraction. The multi-dimensional characterization results suggest that cassiterite SnO2 with spherical, cylindrical, and vesicular pore structures are obtained. The variation of the film morphology is governed by the preferential affinity of the utilized solvent mixture and the hydrogen bond interaction between the employed cycloether and H2O molecules in the solution. |
Chen, Wei; Tang, Haodong; Chen, Yulong; Heger, Julian E; Li, Nian; Kreuzer, Lucas P; Xie, Yue; Li, Depeng; Anthony, Carl; Pikramenou, Zoe; Ng, Kar Wei; Sun, Xiao Wei; Wang, Kai; Müller-Buschbaum, Peter Spray-deposited PbS colloidal quantum dot solid for near-infrared photodetectors Journal Article Nano Energy, 78 , pp. 105254, 2020, ISSN: 2211-2855. Abstract | Links | BibTeX | Tags: GISAXS, Near-infrared photodetector, PbS quantum Dots, Spray deposition @article{Chen2020a, title = {Spray-deposited PbS colloidal quantum dot solid for near-infrared photodetectors}, author = {Wei Chen and Haodong Tang and Yulong Chen and Julian E Heger and Nian Li and Lucas P Kreuzer and Yue Xie and Depeng Li and Carl Anthony and Zoe Pikramenou and Kar Wei Ng and Xiao Wei Sun and Kai Wang and Peter Müller-Buschbaum}, url = {http://www.sciencedirect.com/science/article/pii/S2211285520308326}, doi = {https://doi.org/10.1016/j.nanoen.2020.105254}, issn = {2211-2855}, year = {2020}, date = {2020-01-01}, journal = {Nano Energy}, volume = {78}, pages = {105254}, abstract = {Colloidal PbS quantum dots (QDs) are promising candidates for various optoelectronic applications based on solution-processed thin-film techniques. In this work, a versatile layer-by-layer (LBL) spray deposition of the QDs is introduced aiming for a future large-scale fabrication process of optoelectronic devices. As compared to spin-coated QD solids, a smaller inter-dot distance and a better-ordered superlattice stacking behavior of the QDs are found in the spray-deposited QD solids as confirmed by grazing-incidence small-angle X-ray scattering (GISAXS). The spectral mapping combined time-resolved photoluminescence analysis indicates a longer charge carrier lifetime and better order of the energy state distribution of the spray-deposited QD solid comparing with the spin-coated one. Thus, photodetectors based on spray deposition of QD solids demonstrate an excellent device performance, with the responsivity achieving 365.1 A/W and the detectivity reaching up to 1.4 × 1012 Jones under an illumination power of 63.5 μW/cm2 at a wavelength of 1250 nm. The spray-deposited device performances indicate a great potential of spray deposition of large sized QDs in large-scale fabrications for optoelectronics using longer wavelengths.}, keywords = {GISAXS, Near-infrared photodetector, PbS quantum Dots, Spray deposition}, pubstate = {published}, tppubtype = {article} } Colloidal PbS quantum dots (QDs) are promising candidates for various optoelectronic applications based on solution-processed thin-film techniques. In this work, a versatile layer-by-layer (LBL) spray deposition of the QDs is introduced aiming for a future large-scale fabrication process of optoelectronic devices. As compared to spin-coated QD solids, a smaller inter-dot distance and a better-ordered superlattice stacking behavior of the QDs are found in the spray-deposited QD solids as confirmed by grazing-incidence small-angle X-ray scattering (GISAXS). The spectral mapping combined time-resolved photoluminescence analysis indicates a longer charge carrier lifetime and better order of the energy state distribution of the spray-deposited QD solid comparing with the spin-coated one. Thus, photodetectors based on spray deposition of QD solids demonstrate an excellent device performance, with the responsivity achieving 365.1 A/W and the detectivity reaching up to 1.4 × 1012 Jones under an illumination power of 63.5 μW/cm2 at a wavelength of 1250 nm. The spray-deposited device performances indicate a great potential of spray deposition of large sized QDs in large-scale fabrications for optoelectronics using longer wavelengths. |
Wienhold, Kerstin S; Weindl, Christian L; Yin, Shanshan; Tian, Ting; Schwartzkopf, Matthias; Rothkirch, André; Roth, Stephan V; Müller-Buschbaum, Peter ACS Applied Materials & Interfaces, 12 (36), pp. 40381-40392, 2020, (PMID: 32805887). Abstract | Links | BibTeX | Tags: @article{Wienhold2020, title = {Following In Situ the Evolution of Morphology and Optical Properties during Printing of Thin Films for Application in Non-Fullerene Acceptor Based Organic Solar Cells}, author = {Kerstin S Wienhold and Christian L Weindl and Shanshan Yin and Ting Tian and Matthias Schwartzkopf and André Rothkirch and Stephan V Roth and Peter Müller-Buschbaum}, url = {https://doi.org/10.1021/acsami.0c12390}, doi = {10.1021/acsami.0c12390}, year = {2020}, date = {2020-01-01}, journal = {ACS Applied Materials & Interfaces}, volume = {12}, number = {36}, pages = {40381-40392}, abstract = {In situ printing gives insight into the evolution of morphology and optical properties during slot-die coating of active layers for application in organic solar cells and enables an upscaling and optimization of the thin film deposition process and the photovoltaic performance. Active layers based on the conjugated polymer donor with benzodithiophene units PBDB-T-2Cl and the non-fullerene small-molecule acceptor IT-4F are printed with a slot-die coating technique and probed in situ with grazing incidence small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and ultraviolet/visible light spectroscopy. The formation of the morphology is followed from the liquid state to the final dry film for different printing conditions (at 25 and 35 °C), and five regimes of film formation are determined. The morphological changes are correlated to changing optical properties. During the film formation, crystallization of the non-fullerene small-molecule acceptor takes place and polymer domains with sizes of some tens of nanometers emerge. A red shift of the optical band gap and a broadening of the absorbance spectrum occurs, which allow for exploiting the sun spectrum more efficiently and are expected to have a favorable effect on the solar cell performance.}, note = {PMID: 32805887}, keywords = {}, pubstate = {published}, tppubtype = {article} } In situ printing gives insight into the evolution of morphology and optical properties during slot-die coating of active layers for application in organic solar cells and enables an upscaling and optimization of the thin film deposition process and the photovoltaic performance. Active layers based on the conjugated polymer donor with benzodithiophene units PBDB-T-2Cl and the non-fullerene small-molecule acceptor IT-4F are printed with a slot-die coating technique and probed in situ with grazing incidence small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and ultraviolet/visible light spectroscopy. The formation of the morphology is followed from the liquid state to the final dry film for different printing conditions (at 25 and 35 °C), and five regimes of film formation are determined. The morphological changes are correlated to changing optical properties. During the film formation, crystallization of the non-fullerene small-molecule acceptor takes place and polymer domains with sizes of some tens of nanometers emerge. A red shift of the optical band gap and a broadening of the absorbance spectrum occurs, which allow for exploiting the sun spectrum more efficiently and are expected to have a favorable effect on the solar cell performance. |
Yang, Dan; Grott, Sebastian; Jiang, Xinyu; Wienhold, Kerstin S; Schwartzkopf, Matthias; Roth, Stephan V; Müller-Buschbaum, Peter In Situ Studies of Solvent Additive Effects on the Morphology Development during Printing of Bulk Heterojunction Films for Organic Solar Cells Journal Article Small Methods, 4 (9), pp. 2000418, 2020. Abstract | Links | BibTeX | Tags: crystallinity, morphology, PPDT2FBT:PC71BM films, printing, solvent additive @article{Yang2020, title = {In Situ Studies of Solvent Additive Effects on the Morphology Development during Printing of Bulk Heterojunction Films for Organic Solar Cells}, author = {Dan Yang and Sebastian Grott and Xinyu Jiang and Kerstin S Wienhold and Matthias Schwartzkopf and Stephan V Roth and Peter Müller-Buschbaum}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/smtd.202000418}, doi = {https://doi.org/10.1002/smtd.202000418}, year = {2020}, date = {2020-01-01}, journal = {Small Methods}, volume = {4}, number = {9}, pages = {2000418}, abstract = {Abstract The development of polymer morphology and crystallinity of printed bulk heterojunction (BHJ) films doped with the different solvent additives 1,8-diiodooctane (DIO) or diphenyl ether (DPE) is investigated with in situ grazing-incidence small/wide-angle X-ray scattering. The solvent additives, having different boiling points, lead to a different film drying behavior and morphology growth states in the BHJ films of the benzothiadiazole-based polymer (PPDT2FBT) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The phase demixing in the printed films is changing over time along with solvent evaporation. Polymer domains start aggregating to form larger domains in the liquid–liquid phase, while phase separation mainly occurs in the liquid–solid phase. The present work provides a profound insight into the morphology development of printed BHJ films doped with different solvent additives, which is particularly important for the large-scale fabrication of organic photovoltaics.}, keywords = {crystallinity, morphology, PPDT2FBT:PC71BM films, printing, solvent additive}, pubstate = {published}, tppubtype = {article} } Abstract The development of polymer morphology and crystallinity of printed bulk heterojunction (BHJ) films doped with the different solvent additives 1,8-diiodooctane (DIO) or diphenyl ether (DPE) is investigated with in situ grazing-incidence small/wide-angle X-ray scattering. The solvent additives, having different boiling points, lead to a different film drying behavior and morphology growth states in the BHJ films of the benzothiadiazole-based polymer (PPDT2FBT) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The phase demixing in the printed films is changing over time along with solvent evaporation. Polymer domains start aggregating to form larger domains in the liquid–liquid phase, while phase separation mainly occurs in the liquid–solid phase. The present work provides a profound insight into the morphology development of printed BHJ films doped with different solvent additives, which is particularly important for the large-scale fabrication of organic photovoltaics. |
Wienhold, Kerstin S; Chen, Wei; Yin, Shanshan; Guo, Renjun; Schwartzkopf, Matthias; Roth, Stephan V; Müller-Buschbaum, Peter Following in Operando the Structure Evolution-Induced Degradation in Printed Organic Solar Cells with Nonfullerene Small Molecule Acceptor Journal Article Solar RRL, 4 (9), pp. 2000251, 2020. Abstract | Links | BibTeX | Tags: degradation mechanisms, meniscus-guided slot-die coatings, organic solar cells, short-circuit currents @article{Wienhold2020a, title = {Following in Operando the Structure Evolution-Induced Degradation in Printed Organic Solar Cells with Nonfullerene Small Molecule Acceptor}, author = {Kerstin S Wienhold and Wei Chen and Shanshan Yin and Renjun Guo and Matthias Schwartzkopf and Stephan V Roth and Peter Müller-Buschbaum}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/solr.202000251}, doi = {https://doi.org/10.1002/solr.202000251}, year = {2020}, date = {2020-01-01}, journal = {Solar RRL}, volume = {4}, number = {9}, pages = {2000251}, abstract = {Understanding the degradation mechanisms of printed bulk-heterojunction (BHJ) organic solar cells during operation is essential to achieve long-term stability and realize real-world applications of organic photovoltaics. Herein, the degradation of printed organic solar cells based on the conjugated benzodithiophene polymer PBDB-T-SF and the nonfullerene small molecule acceptor IT-4F with 0.25 vol% 1,8-diiodooctane (DIO) solvent additive is studied in operando for two different donor:acceptor ratios. The inner nano-morphology is analyzed with grazing incidence small angle X-ray scattering (GISAXS), and current–voltage (I–V) characteristics are probed simultaneously. Irrespective of the mixing ratio, degradation occurs by the same degradation mechanism. A decrease in the short-circuit current density (JSC) is identified to be the determining factor for the decline of the power conversion efficiency. The decrease in JSC is induced by a reduction of the relative interface area between the conjugated polymer and the small molecule acceptor in the BHJ structure, resembling the morphological degradation of the active layer.}, keywords = {degradation mechanisms, meniscus-guided slot-die coatings, organic solar cells, short-circuit currents}, pubstate = {published}, tppubtype = {article} } Understanding the degradation mechanisms of printed bulk-heterojunction (BHJ) organic solar cells during operation is essential to achieve long-term stability and realize real-world applications of organic photovoltaics. Herein, the degradation of printed organic solar cells based on the conjugated benzodithiophene polymer PBDB-T-SF and the nonfullerene small molecule acceptor IT-4F with 0.25 vol% 1,8-diiodooctane (DIO) solvent additive is studied in operando for two different donor:acceptor ratios. The inner nano-morphology is analyzed with grazing incidence small angle X-ray scattering (GISAXS), and current–voltage (I–V) characteristics are probed simultaneously. Irrespective of the mixing ratio, degradation occurs by the same degradation mechanism. A decrease in the short-circuit current density (JSC) is identified to be the determining factor for the decline of the power conversion efficiency. The decrease in JSC is induced by a reduction of the relative interface area between the conjugated polymer and the small molecule acceptor in the BHJ structure, resembling the morphological degradation of the active layer. |
Yang, Dan; Löhrer, Franziska C; Körstgens, Volker; Schreiber, Armin; Cao, Bing; Bernstorff, Sigrid; Müller-Buschbaum, Peter In Operando GISAXS and GIWAXS Stability Study of Organic Solar Cells Based on PffBT4T-2OD:PC71BM with and without Solvent Additive Journal Article Advanced Science, 7 (16), pp. 2001117, 2020. Abstract | Links | BibTeX | Tags: crystallinity, degradation, in operando, organic photovoltaics, solvent additives @article{Yang2020a, title = {In Operando GISAXS and GIWAXS Stability Study of Organic Solar Cells Based on PffBT4T-2OD:PC71BM with and without Solvent Additive}, author = {Dan Yang and Franziska C Löhrer and Volker Körstgens and Armin Schreiber and Bing Cao and Sigrid Bernstorff and Peter Müller-Buschbaum}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/advs.202001117}, doi = {https://doi.org/10.1002/advs.202001117}, year = {2020}, date = {2020-01-01}, journal = {Advanced Science}, volume = {7}, number = {16}, pages = {2001117}, abstract = {Abstract Solvent additives are known to modify the morphology of bulk heterojunction active layers to achieve high efficiency organic solar cells. However, the knowledge about the influence of solvent additives on the morphology degradation is limited. Hence, in operando grazing-incidence small and wide angle X-ray scattering (GISAXS and GIWAXS) measurements are applied on a series of PffBT4T-2OD:PC71BM-based solar cells prepared without and with solvent additives. The solar cells fabricated without a solvent additive, with 1,8-diiodoctane (DIO), and with o-chlorobenzaldehyde (CBA) additive show differences in the device degradation and changes in the morphology and crystallinity of the active layers. The mesoscale morphology changes are correlated with the decay of the short-circuit current Jsc and the evolution of crystalline grain sizes is codependent with the decay of open-circuit voltage Voc. Without additive, the loss in Jsc dominates the degradation, whereas with solvent additive (DIO and CBA) the loss in Voc rules the degradation. CBA addition increases the overall device stability as compared to DIO or absence of additive.}, keywords = {crystallinity, degradation, in operando, organic photovoltaics, solvent additives}, pubstate = {published}, tppubtype = {article} } Abstract Solvent additives are known to modify the morphology of bulk heterojunction active layers to achieve high efficiency organic solar cells. However, the knowledge about the influence of solvent additives on the morphology degradation is limited. Hence, in operando grazing-incidence small and wide angle X-ray scattering (GISAXS and GIWAXS) measurements are applied on a series of PffBT4T-2OD:PC71BM-based solar cells prepared without and with solvent additives. The solar cells fabricated without a solvent additive, with 1,8-diiodoctane (DIO), and with o-chlorobenzaldehyde (CBA) additive show differences in the device degradation and changes in the morphology and crystallinity of the active layers. The mesoscale morphology changes are correlated with the decay of the short-circuit current Jsc and the evolution of crystalline grain sizes is codependent with the decay of open-circuit voltage Voc. Without additive, the loss in Jsc dominates the degradation, whereas with solvent additive (DIO and CBA) the loss in Voc rules the degradation. CBA addition increases the overall device stability as compared to DIO or absence of additive. |
Reb, Lennart K; Böhmer, Michael; Predeschly, Benjamin; Grott, Sebastian; Weindl, Christian L; Ivandekic, Goran I; Guo, Renjun; Dreißigacker, Christoph; Gernhäuser, Roman; Meyer, Andreas; Müller-Buschbaum, Peter Perovskite and Organic Solar Cells on a Rocket Flight Journal Article Joule, 4 (9), pp. 1880 - 1892, 2020, ISSN: 2542-4351. Abstract | Links | BibTeX | Tags: organic solar cell, perovskite solar cell, rocket flight, space, specific power @article{Reb2020, title = {Perovskite and Organic Solar Cells on a Rocket Flight}, author = {Lennart K Reb and Michael Böhmer and Benjamin Predeschly and Sebastian Grott and Christian L Weindl and Goran I Ivandekic and Renjun Guo and Christoph Dreißigacker and Roman Gernhäuser and Andreas Meyer and Peter Müller-Buschbaum}, url = {http://www.sciencedirect.com/science/article/pii/S2542435120303226}, doi = {https://doi.org/10.1016/j.joule.2020.07.004}, issn = {2542-4351}, year = {2020}, date = {2020-01-01}, journal = {Joule}, volume = {4}, number = {9}, pages = {1880 - 1892}, abstract = {Summary Perovskite and organic solar cells possess a revolutionary potential for space applications. The thin-film solar cells can be processed onto thin polymer foils that enable an exceptional specific power, i.e., obtainable electric power per mass, being superior to their inorganic counterparts. However, research toward space applications was mainly restricted to terrestrial conditions so far. Here, we report the launch of perovskite and organic solar cells of different architectures on a suborbital rocket flight. This is an in situ demonstration of their functionality and power generation under space conditions. We measured solar cell current-voltage characteristics in variable illumination states due to different rocket orientations during flight. Under strong solar irradiance, the solar cells perform efficiently, and they even produce power with weak diffuse light reflected from Earth’s surface. These results highlight both the suitability for near-Earth applications as well as the potential for deep-space missions for these innovative technologies.}, keywords = {organic solar cell, perovskite solar cell, rocket flight, space, specific power}, pubstate = {published}, tppubtype = {article} } Summary Perovskite and organic solar cells possess a revolutionary potential for space applications. The thin-film solar cells can be processed onto thin polymer foils that enable an exceptional specific power, i.e., obtainable electric power per mass, being superior to their inorganic counterparts. However, research toward space applications was mainly restricted to terrestrial conditions so far. Here, we report the launch of perovskite and organic solar cells of different architectures on a suborbital rocket flight. This is an in situ demonstration of their functionality and power generation under space conditions. We measured solar cell current-voltage characteristics in variable illumination states due to different rocket orientations during flight. Under strong solar irradiance, the solar cells perform efficiently, and they even produce power with weak diffuse light reflected from Earth’s surface. These results highlight both the suitability for near-Earth applications as well as the potential for deep-space missions for these innovative technologies. |
Wienhold, Kerstin S; Körstgens, Volker; Grott, Sebastian; Jiang, Xinyu; Schwartzkopf, Matthias; Roth, Stephan V; Müller-Buschbaum, Peter Solar RRL, 4 (7), pp. 2000086, 2020. Abstract | Links | BibTeX | Tags: GISAXS, in situ printing, low bandgap polymers, nonfullerene acceptors, slot-die coating @article{Wienhold2020b, title = {In Situ Printing: Insights into the Morphology Formation and Optical Property Evolution of Slot-Die-Coated Active Layers Containing Low Bandgap Polymer Donor and Nonfullerene Small Molecule Acceptor}, author = {Kerstin S Wienhold and Volker Körstgens and Sebastian Grott and Xinyu Jiang and Matthias Schwartzkopf and Stephan V Roth and Peter Müller-Buschbaum}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/solr.202000086}, doi = {https://doi.org/10.1002/solr.202000086}, year = {2020}, date = {2020-01-01}, journal = {Solar RRL}, volume = {4}, number = {7}, pages = {2000086}, abstract = {Printing of active layers for high-efficiency organic solar cells with the slot-die coating technique can overcome the challenge of upscaling, which will be needed for organic photovoltaics on its way to marketability. The morphology of a bulk-heterojunction organic solar cell has a very high impact on its power conversion efficiency. Therefore, it is of particular importance to understand the mechanisms of structure formation during printing of active layers to enable further optimization of the solar cell performance and upscaling of the production process. Meniscus-guided slot-die coating of the blend of a low bandgap conjugated polymer donor with benzodithiophene units PBDB-T-SF and the nonfullerene small molecule acceptor IT-4F is studied in situ with optical microscopy, Ultraviolet–visible spectroscopy, and grazing incidence small angle X-ray scattering. The structure formation is followed from the liquid to the final dry film state. Thereby, five regimes of morphology formation are determined. The morphological evolution in the printed active layer is correlated to changing optical properties of the thin film. In the final dry film, polymer domains of several tens of nanometers are observed, which will be favorable for application in high-efficiency organic solar cells.}, keywords = {GISAXS, in situ printing, low bandgap polymers, nonfullerene acceptors, slot-die coating}, pubstate = {published}, tppubtype = {article} } Printing of active layers for high-efficiency organic solar cells with the slot-die coating technique can overcome the challenge of upscaling, which will be needed for organic photovoltaics on its way to marketability. The morphology of a bulk-heterojunction organic solar cell has a very high impact on its power conversion efficiency. Therefore, it is of particular importance to understand the mechanisms of structure formation during printing of active layers to enable further optimization of the solar cell performance and upscaling of the production process. Meniscus-guided slot-die coating of the blend of a low bandgap conjugated polymer donor with benzodithiophene units PBDB-T-SF and the nonfullerene small molecule acceptor IT-4F is studied in situ with optical microscopy, Ultraviolet–visible spectroscopy, and grazing incidence small angle X-ray scattering. The structure formation is followed from the liquid to the final dry film state. Thereby, five regimes of morphology formation are determined. The morphological evolution in the printed active layer is correlated to changing optical properties of the thin film. In the final dry film, polymer domains of several tens of nanometers are observed, which will be favorable for application in high-efficiency organic solar cells. |
Chen, Wei; Tang, Haodong; Li, Nian; Scheel, Manuel A; Xie, Yue; Li, Depeng; Körstgens, Volker; Schwartzkopf, Matthias; Roth, Stephan V; Wang, Kai; Sun, Xiao Wei; Müller-Buschbaum, Peter Colloidal PbS quantum dot stacking kinetics during deposition via printing Journal Article Nanoscale Horiz., 5 , pp. 880-885, 2020. Abstract | Links | BibTeX | Tags: @article{Chen2020b, title = {Colloidal PbS quantum dot stacking kinetics during deposition via printing}, author = {Wei Chen and Haodong Tang and Nian Li and Manuel A Scheel and Yue Xie and Depeng Li and Volker Körstgens and Matthias Schwartzkopf and Stephan V Roth and Kai Wang and Xiao Wei Sun and Peter Müller-Buschbaum}, url = {http://dx.doi.org/10.1039/D0NH00008F}, doi = {10.1039/D0NH00008F}, year = {2020}, date = {2020-01-01}, journal = {Nanoscale Horiz.}, volume = {5}, pages = {880-885}, publisher = {The Royal Society of Chemistry}, abstract = {Colloidal PbS quantum dots (QDs) are attractive for solution-processed thin-film optoelectronic applications. In particular, directly achieving QD thin-films by printing is a very promising method for low-cost and large-scale fabrication. The kinetics of QD particles during the deposition process play an important role in the QD film quality and their respective optoelectronic performance. In this work, the particle self-organization behavior of small-sized QDs with an average diameter of 2.88 ± 0.36 nm is investigated for the first time in situ during printing by grazing-incidence small-angle X-ray scattering (GISAXS). The time-dependent changes in peak intensities suggest that the structure formation and phase transition of QD films happen within 30 seconds. The stacking of QDs is initialized by a templating effect, and a face-centered cubic (FCC) film forms in which a superlattice distortion is also found. A body-centered cubic nested FCC stacking is the final QD assembly layout. The small size of the inorganic QDs and the ligand collapse during the solvent evaporation can well explain this stacking behavior. These results provide important fundamental understanding of structure formation of small-sized QD based films prepared via large-scale deposition with printing with a slot die coater.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Colloidal PbS quantum dots (QDs) are attractive for solution-processed thin-film optoelectronic applications. In particular, directly achieving QD thin-films by printing is a very promising method for low-cost and large-scale fabrication. The kinetics of QD particles during the deposition process play an important role in the QD film quality and their respective optoelectronic performance. In this work, the particle self-organization behavior of small-sized QDs with an average diameter of 2.88 ± 0.36 nm is investigated for the first time in situ during printing by grazing-incidence small-angle X-ray scattering (GISAXS). The time-dependent changes in peak intensities suggest that the structure formation and phase transition of QD films happen within 30 seconds. The stacking of QDs is initialized by a templating effect, and a face-centered cubic (FCC) film forms in which a superlattice distortion is also found. A body-centered cubic nested FCC stacking is the final QD assembly layout. The small size of the inorganic QDs and the ligand collapse during the solvent evaporation can well explain this stacking behavior. These results provide important fundamental understanding of structure formation of small-sized QD based films prepared via large-scale deposition with printing with a slot die coater. |
Yin, Shanshan; Song, Lin; Xia, Senlin; Cheng, Yajun; Hohn, Nuri; Chen, Wei; Wang, Kun; Cao, Wei; Hou, Shujin; Müller-Buschbaum, Peter Key Factors for Template-Oriented Porous Titania Synthesis: Solvents and Catalysts Journal Article Small Methods, 4 (3), pp. 1900689, 2020. Abstract | Links | BibTeX | Tags: GISAXS, morphology, nanostructures, sol–gel synthesis, titania @article{Yin2020a, title = {Key Factors for Template-Oriented Porous Titania Synthesis: Solvents and Catalysts}, author = {Shanshan Yin and Lin Song and Senlin Xia and Yajun Cheng and Nuri Hohn and Wei Chen and Kun Wang and Wei Cao and Shujin Hou and Peter Müller-Buschbaum}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/smtd.201900689}, doi = {https://doi.org/10.1002/smtd.201900689}, year = {2020}, date = {2020-01-01}, journal = {Small Methods}, volume = {4}, number = {3}, pages = {1900689}, abstract = {Abstract Various types of titania nanostructures are synthesized with a polymer-templated sol–gel method based on the amphiphilic diblock copolymer polystyrene-b-polyethylene oxide (PS-b-PEO) in combination with selective incorporation of the titania precursor titanium tetraisopropoxide. Custom tailoring of different types of titania morphologies is realized by changing the phase separation behavior of the PS-b-PEO template. Particularly, application of solvents from different categories is found to have a major impact upon the phase separation behavior of PS-b-PEO and the final titania film morphology. The amount of available hydrochloric acid catalyst during the gelation process is seen as an additional key factor to induce controllable morphological changes. Scanning electron microscopy and grazing incidence small angle X-ray scattering measurements are carried out to study the surface and inner structure of porous titania films. Systematic analysis and comparison of different characterization results allow attributing the following three factors to the respectively formed titania nanostructure: the surface energy between PS blocks and surrounding solvent, the aggregation behavior of the titania nanoparticles, and the block-specific selectivity of the used solvent. For all synthesized titania thin films, an anatase-type crystallization is confirmed through X-ray powder diffraction.}, keywords = {GISAXS, morphology, nanostructures, sol–gel synthesis, titania}, pubstate = {published}, tppubtype = {article} } Abstract Various types of titania nanostructures are synthesized with a polymer-templated sol–gel method based on the amphiphilic diblock copolymer polystyrene-b-polyethylene oxide (PS-b-PEO) in combination with selective incorporation of the titania precursor titanium tetraisopropoxide. Custom tailoring of different types of titania morphologies is realized by changing the phase separation behavior of the PS-b-PEO template. Particularly, application of solvents from different categories is found to have a major impact upon the phase separation behavior of PS-b-PEO and the final titania film morphology. The amount of available hydrochloric acid catalyst during the gelation process is seen as an additional key factor to induce controllable morphological changes. Scanning electron microscopy and grazing incidence small angle X-ray scattering measurements are carried out to study the surface and inner structure of porous titania films. Systematic analysis and comparison of different characterization results allow attributing the following three factors to the respectively formed titania nanostructure: the surface energy between PS blocks and surrounding solvent, the aggregation behavior of the titania nanoparticles, and the block-specific selectivity of the used solvent. For all synthesized titania thin films, an anatase-type crystallization is confirmed through X-ray powder diffraction. |
Li, Nian; Song, Lin; Hohn, Nuri; Saxena, Nitin; Cao, Wei; Jiang, Xinyu; Müller-Buschbaum, Peter Nanoscale crystallization of a low band gap polymer in printed titania mesopores Journal Article Nanoscale, 12 , pp. 4085-4093, 2020. Abstract | Links | BibTeX | Tags: @article{Li2020, title = {Nanoscale crystallization of a low band gap polymer in printed titania mesopores}, author = {Nian Li and Lin Song and Nuri Hohn and Nitin Saxena and Wei Cao and Xinyu Jiang and Peter Müller-Buschbaum}, url = {http://dx.doi.org/10.1039/C9NR08055D}, doi = {10.1039/C9NR08055D}, year = {2020}, date = {2020-01-01}, journal = {Nanoscale}, volume = {12}, pages = {4085-4093}, publisher = {The Royal Society of Chemistry}, abstract = {The crystallization behavior of the low band gap polymer poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3′′′-di(2-octyldodecyl)2,2′;5′,2′′;5′′,2′′′-quaterthiophen-5,5′′′-diyl)] (PffBT4T-2OD) induced in printed mesoporous titania films with different pore sizes is studied to optimize the crystal orientation for an application in hybrid solar cells. The correlation between the crystal structure of PffBT4T-2OD and the titania pore size is investigated with a combination of grazing incidence wide-angle X-ray scattering (GIWAXS) and grazing incidence small-angle X-ray scattering (GISAXS). For comparison, poly(3-hexylthiophene) (P3HT) is also backfilled into the same four types of printed titania mesoporous scaffolds. Both, lattice constants and crystal sizes of edge-on oriented P3HT crystals decrease with increasing the titania pore size. Similarly and irrespective of the crystal orientation, a denser stacking of PffBT4T-2OD chains is found for larger pore sizes of the titania matrix. For an edge-on orientation, also bigger PffBT4T-2OD crystals are favorably formed in smaller pores, whereas for a face-on orientation, PffBT4T-2OD crystals increase with increasing size of the titania pores. Thus, the best ratio of face-on to edge-on crystals for PffBT4T-2OD is obtained through infiltration into large titania pores.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The crystallization behavior of the low band gap polymer poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3′′′-di(2-octyldodecyl)2,2′;5′,2′′;5′′,2′′′-quaterthiophen-5,5′′′-diyl)] (PffBT4T-2OD) induced in printed mesoporous titania films with different pore sizes is studied to optimize the crystal orientation for an application in hybrid solar cells. The correlation between the crystal structure of PffBT4T-2OD and the titania pore size is investigated with a combination of grazing incidence wide-angle X-ray scattering (GIWAXS) and grazing incidence small-angle X-ray scattering (GISAXS). For comparison, poly(3-hexylthiophene) (P3HT) is also backfilled into the same four types of printed titania mesoporous scaffolds. Both, lattice constants and crystal sizes of edge-on oriented P3HT crystals decrease with increasing the titania pore size. Similarly and irrespective of the crystal orientation, a denser stacking of PffBT4T-2OD chains is found for larger pore sizes of the titania matrix. For an edge-on orientation, also bigger PffBT4T-2OD crystals are favorably formed in smaller pores, whereas for a face-on orientation, PffBT4T-2OD crystals increase with increasing size of the titania pores. Thus, the best ratio of face-on to edge-on crystals for PffBT4T-2OD is obtained through infiltration into large titania pores. |
Stuke, Annika; Kunkel, Christian; Golze, Dorothea; Todorović, Milica; Margraf, Johannes T; Reuter, Karsten; Rinke, Patrick; Oberhofer, Harald Atomic structures and orbital energies of 61,489 crystal-forming organic molecules Journal Article Scientific Data, 7 (1), pp. 58, 2020, ISSN: 2052-4463. Abstract | Links | BibTeX | Tags: @article{Stuke2020, title = {Atomic structures and orbital energies of 61,489 crystal-forming organic molecules}, author = {Annika Stuke and Christian Kunkel and Dorothea Golze and Milica Todorović and Johannes T Margraf and Karsten Reuter and Patrick Rinke and Harald Oberhofer}, url = {https://doi.org/10.1038/s41597-020-0385-y}, doi = {10.1038/s41597-020-0385-y}, issn = {2052-4463}, year = {2020}, date = {2020-01-01}, journal = {Scientific Data}, volume = {7}, number = {1}, pages = {58}, abstract = {Data science and machine learning in materials science require large datasets of technologically relevant molecules or materials. Currently, publicly available molecular datasets with realistic molecular geometries and spectral properties are rare. We here supply a diverse benchmark spectroscopy dataset of 61,489 molecules extracted from organic crystals in the Cambridge Structural Database (CSD), denoted OE62. Molecular equilibrium geometries are reported at the Perdew-Burke-Ernzerhof (PBE) level of density functional theory (DFT) including van der Waals corrections for all 62 k molecules. For these geometries, OE62 supplies total energies and orbital eigenvalues at the PBE and the PBE hybrid (PBE0) functional level of DFT for all 62 k molecules in vacuum as well as at the PBE0 level for a subset of 30,876 molecules in (implicit) water. For 5,239 molecules in vacuum, the dataset provides quasiparticle energies computed with many-body perturbation theory in the G0W0 approximation with a PBE0 starting point (denoted GW5000 in analogy to the GW100 benchmark set (M. van Setten et al. J. Chem. Theory Comput. 12, 5076 (2016))).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Data science and machine learning in materials science require large datasets of technologically relevant molecules or materials. Currently, publicly available molecular datasets with realistic molecular geometries and spectral properties are rare. We here supply a diverse benchmark spectroscopy dataset of 61,489 molecules extracted from organic crystals in the Cambridge Structural Database (CSD), denoted OE62. Molecular equilibrium geometries are reported at the Perdew-Burke-Ernzerhof (PBE) level of density functional theory (DFT) including van der Waals corrections for all 62 k molecules. For these geometries, OE62 supplies total energies and orbital eigenvalues at the PBE and the PBE hybrid (PBE0) functional level of DFT for all 62 k molecules in vacuum as well as at the PBE0 level for a subset of 30,876 molecules in (implicit) water. For 5,239 molecules in vacuum, the dataset provides quasiparticle energies computed with many-body perturbation theory in the G0W0 approximation with a PBE0 starting point (denoted GW5000 in analogy to the GW100 benchmark set (M. van Setten et al. J. Chem. Theory Comput. 12, 5076 (2016))). |
Maeda, Takeshi; Liess, Andreas; Kudzus, Astrid; Krause, Ana-Maria; Stolte, Matthias; Amitani, Hitoshi; Yagi, Shigeyuki; Fujiwara, Hideki; Würthner, Frank Hydrogen bond-rigidified planar squaraine dye and its electronic and organic semiconductor properties Journal Article Chem. Commun., 56 , pp. 9890-9893, 2020. Abstract | Links | BibTeX | Tags: @article{Maeda2020, title = {Hydrogen bond-rigidified planar squaraine dye and its electronic and organic semiconductor properties}, author = {Takeshi Maeda and Andreas Liess and Astrid Kudzus and Ana-Maria Krause and Matthias Stolte and Hitoshi Amitani and Shigeyuki Yagi and Hideki Fujiwara and Frank Würthner}, url = {http://dx.doi.org/10.1039/D0CC04306K}, doi = {10.1039/D0CC04306K}, year = {2020}, date = {2020-01-01}, journal = {Chem. Commun.}, volume = {56}, pages = {9890-9893}, publisher = {The Royal Society of Chemistry}, abstract = {The one-step reaction of a dicyanovinyl-functionalized squaric acid with Fischer bases afforded C2v symmetric squaraine dyes with rigid planar structures due to intramolecular N–H⋯O hydrogen bonds. Dense molecular packing, decrease of HOMO level, and sufficient thermal stability for sublimation enabled vacuum-processed OTFTs with hole mobility up to 0.32 cm2 V−1 s−1 and current on/off ratio of 106.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The one-step reaction of a dicyanovinyl-functionalized squaric acid with Fischer bases afforded C2v symmetric squaraine dyes with rigid planar structures due to intramolecular N–H⋯O hydrogen bonds. Dense molecular packing, decrease of HOMO level, and sufficient thermal stability for sublimation enabled vacuum-processed OTFTs with hole mobility up to 0.32 cm2 V−1 s−1 and current on/off ratio of 106. |
Föller, Jelena; Friese, Daniel H; Riese, Stefan; Kaminski, Jeremy M; Metz, Simon; Schmidt, David; Würthner, Frank; Lambert, Christoph; Marian, Christel M On the photophysical properties of IrIII, PtII, and PdII (phenylpyrazole) (phenyldipyrrin) complexes Journal Article Phys. Chem. Chem. Phys., 22 , pp. 3217-3233, 2020. Abstract | Links | BibTeX | Tags: @article{Foeller2020, title = {On the photophysical properties of IrIII, PtII, and PdII (phenylpyrazole) (phenyldipyrrin) complexes}, author = {Jelena Föller and Daniel H Friese and Stefan Riese and Jeremy M Kaminski and Simon Metz and David Schmidt and Frank Würthner and Christoph Lambert and Christel M Marian}, url = {http://dx.doi.org/10.1039/C9CP05603C}, doi = {10.1039/C9CP05603C}, year = {2020}, date = {2020-01-01}, journal = {Phys. Chem. Chem. Phys.}, volume = {22}, pages = {3217-3233}, publisher = {The Royal Society of Chemistry}, abstract = {The absorption and emission characteristics of (ppz)2(dipy)IrIII, (ppz)(dipy)PtII and (ppz)(dipy)PdII, where ppz stands for phenylpyrazole and dipy for a phenyl meso-substituted dipyrrin ligand, have been investigated by means of combined density functional theory and multireference configuration interaction including scalar relativistic and spin–orbit coupling effects. These results were compared with experimental spectra. The complexes exhibit a high density of low-lying electronically excited states originating from ligand-centered (LC) and metal-to-ligand charge transfer (MLCT) states involving the dipyrrin ligand. In addition, metal-centered (MC) states are found to be low-lying in the Pd complex. In all three cases, the first strong absorption band and the phosphorescence emission band stem from LC excitations on the dipyrrin ligand with small MLCT contributions. The MLCT states show more pronounced relaxation effects than the LC states, with the consequence that the first excited state with predominant singlet multiplicity is of SMLCT/LC type in the heavier Ir and Pt complexes. Substantial spin–orbit coupling between SMLCT/LC and TLC enables fast and efficient intersystem crossing (ISC) and a high triplet quantum yield. Phosphorescence rate constants are rather small in accord with the dominant LC character of the transitions. Out-of-plane distortion promotes nonradiative decay of the excited state population via the MC states thus explaining the lower phosphorescence quantum yield of the Pt complex. The spectral properties of the Pd complex are different in many aspects. Optimization of the S1 state yields a dipyrrin intraligand charge transfer (ILCT) state with highly distorted nuclear arrangement in the butterfly conformers leading to nonradiative deactivation. In contrast, the primarily excited SLC state and the SMLCT/LC state of the twist conformer have nearly equal adiabatic excitation energies. The lack of a driving force toward the SMLCT/LC minimum, the high fluorescence rate constant of the bright SLC state and its moderately efficient ISC to the triplet manifold explain the experimentally observed dual emission of the Pd complex at room temperature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The absorption and emission characteristics of (ppz)2(dipy)IrIII, (ppz)(dipy)PtII and (ppz)(dipy)PdII, where ppz stands for phenylpyrazole and dipy for a phenyl meso-substituted dipyrrin ligand, have been investigated by means of combined density functional theory and multireference configuration interaction including scalar relativistic and spin–orbit coupling effects. These results were compared with experimental spectra. The complexes exhibit a high density of low-lying electronically excited states originating from ligand-centered (LC) and metal-to-ligand charge transfer (MLCT) states involving the dipyrrin ligand. In addition, metal-centered (MC) states are found to be low-lying in the Pd complex. In all three cases, the first strong absorption band and the phosphorescence emission band stem from LC excitations on the dipyrrin ligand with small MLCT contributions. The MLCT states show more pronounced relaxation effects than the LC states, with the consequence that the first excited state with predominant singlet multiplicity is of SMLCT/LC type in the heavier Ir and Pt complexes. Substantial spin–orbit coupling between SMLCT/LC and TLC enables fast and efficient intersystem crossing (ISC) and a high triplet quantum yield. Phosphorescence rate constants are rather small in accord with the dominant LC character of the transitions. Out-of-plane distortion promotes nonradiative decay of the excited state population via the MC states thus explaining the lower phosphorescence quantum yield of the Pt complex. The spectral properties of the Pd complex are different in many aspects. Optimization of the S1 state yields a dipyrrin intraligand charge transfer (ILCT) state with highly distorted nuclear arrangement in the butterfly conformers leading to nonradiative deactivation. In contrast, the primarily excited SLC state and the SMLCT/LC state of the twist conformer have nearly equal adiabatic excitation energies. The lack of a driving force toward the SMLCT/LC minimum, the high fluorescence rate constant of the bright SLC state and its moderately efficient ISC to the triplet manifold explain the experimentally observed dual emission of the Pd complex at room temperature. |
Menekse, Kaan; Renner, Rebecca; Mahlmeister, Bernhard; Stolte, Matthias; Würthner, Frank Bowl-Shaped Naphthalimide-Annulated Corannulene as Nonfullerene Acceptor in Organic Solar Cells Journal Article Organic Materials, 02 (03), pp. 229-234, 2020. @article{Menekse2020, title = {Bowl-Shaped Naphthalimide-Annulated Corannulene as Nonfullerene Acceptor in Organic Solar Cells}, author = {Kaan Menekse and Rebecca Renner and Bernhard Mahlmeister and Matthias Stolte and Frank Würthner}, doi = {10.1055/s-0040-1714283}, year = {2020}, date = {2020-01-01}, journal = {Organic Materials}, volume = {02}, number = {03}, pages = {229-234}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Pinterić, Marko; Roh, Seulki; Uykur, Ece; Hansen, Nis Hauke; Pflaum, Jens; Stolte, Matthias; Würthner, Frank; Dressel, Martin Trapped Exciton and Large Birefringence in Cl2–NDI Revealed by Optical Spectroscopy Journal Article The Journal of Physical Chemistry C, 124 (32), pp. 17829-17835, 2020. Abstract | Links | BibTeX | Tags: @article{Pinteric2020, title = {Trapped Exciton and Large Birefringence in Cl2–NDI Revealed by Optical Spectroscopy}, author = {Marko Pinterić and Seulki Roh and Ece Uykur and Nis Hauke Hansen and Jens Pflaum and Matthias Stolte and Frank Würthner and Martin Dressel}, url = {https://doi.org/10.1021/acs.jpcc.0c05165}, doi = {10.1021/acs.jpcc.0c05165}, year = {2020}, date = {2020-01-01}, journal = {The Journal of Physical Chemistry C}, volume = {124}, number = {32}, pages = {17829-17835}, abstract = {The n-type organic semiconductor, β-phase single crystalline dichloro naphthalene diimide, Cl2–NDI, is investigated in a broad frequency range via optical spectroscopy. The temperature-dependent absorbance spectra reveal the appearance of new molecular vibration modes; several of them exhibit a pronounced splitting and abnormal red shift. In the visible spectral range, we observe a splitting of the J-band upon cooling, which we attributed to self-trapped excitons via coupling between free excitons and molecular vibrations or trapping by disorder induced Lévy states. Additionally, we discover a strong birefringence of these crystals by pronounced polarization beat over a wide frequency range.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The n-type organic semiconductor, β-phase single crystalline dichloro naphthalene diimide, Cl2–NDI, is investigated in a broad frequency range via optical spectroscopy. The temperature-dependent absorbance spectra reveal the appearance of new molecular vibration modes; several of them exhibit a pronounced splitting and abnormal red shift. In the visible spectral range, we observe a splitting of the J-band upon cooling, which we attributed to self-trapped excitons via coupling between free excitons and molecular vibrations or trapping by disorder induced Lévy states. Additionally, we discover a strong birefringence of these crystals by pronounced polarization beat over a wide frequency range. |
Luo, Yinqi; Fang, Shaomao; Zheng, Nan; Liu, Linlin; Würthner, Frank; Xie, Zengqi ACS Applied Energy Materials, 3 (2), pp. 1694-1701, 2020. Abstract | Links | BibTeX | Tags: @article{Luo2020, title = {Increased Electron Transport and Hole Blocking in an Aqueous Solution Processed Dye-Doped ZnO Cathode Interlayer for High Performance Organic Solar Cells}, author = {Yinqi Luo and Shaomao Fang and Nan Zheng and Linlin Liu and Frank Würthner and Zengqi Xie}, url = {https://doi.org/10.1021/acsaem.9b02176}, doi = {10.1021/acsaem.9b02176}, year = {2020}, date = {2020-01-01}, journal = {ACS Applied Energy Materials}, volume = {3}, number = {2}, pages = {1694-1701}, abstract = {In this work, we report high electron transport and hole blocking capability of hybrid photoconductive interlayer materials manufactured from an aqueous solution, which are achieved by doping perylene bisimide dyes into zinc oxide (ZnO) through the formation of ionic bonding between the organic dopants and the inorganic matrix. Benzenesulfonic acid functional groups are introduced to perylene bisimide dye molecules, which enhance the solubility of the dye molecules in water and form ionic bonds with zinc atoms during the fabrication of the hybrid thin films. The ionic bonding assisted molecular dispersion endows the hybrid thin film with full photoconductive properties, which improves electron transport by photoinduced electron transfer from organic dye molecules to the conduction band of ZnO. Especially, the hole blocking ability is also highly increased. Both increased electron transport and hole blocking are benefits to the charge selectivity of the cathode interlayer, which results in a high fill factor in organic solar cells. A power conversion efficiency of up to 15.4% is achieved on the basis of such an aqueous solution processed hybrid interlayer when using PM6:Y6 as the active layer. In addition, the optimized thermal annealing temperature for the fabrication of the hybrid thin film is as low as 150 °C, which is a benefit for the application of such photoconductive materials in flexible devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, we report high electron transport and hole blocking capability of hybrid photoconductive interlayer materials manufactured from an aqueous solution, which are achieved by doping perylene bisimide dyes into zinc oxide (ZnO) through the formation of ionic bonding between the organic dopants and the inorganic matrix. Benzenesulfonic acid functional groups are introduced to perylene bisimide dye molecules, which enhance the solubility of the dye molecules in water and form ionic bonds with zinc atoms during the fabrication of the hybrid thin films. The ionic bonding assisted molecular dispersion endows the hybrid thin film with full photoconductive properties, which improves electron transport by photoinduced electron transfer from organic dye molecules to the conduction band of ZnO. Especially, the hole blocking ability is also highly increased. Both increased electron transport and hole blocking are benefits to the charge selectivity of the cathode interlayer, which results in a high fill factor in organic solar cells. A power conversion efficiency of up to 15.4% is achieved on the basis of such an aqueous solution processed hybrid interlayer when using PM6:Y6 as the active layer. In addition, the optimized thermal annealing temperature for the fabrication of the hybrid thin film is as low as 150 °C, which is a benefit for the application of such photoconductive materials in flexible devices. |
Malý, Pavel; Lüttig, Julian; Turkin, Arthur; Dostál, Jakub; Lambert, Christoph; Brixner, Tobias From wavelike to sub-diffusive motion: exciton dynamics and interaction in squaraine copolymers of varying length Journal Article Chem. Sci., 11 , pp. 456-466, 2020. Abstract | Links | BibTeX | Tags: @article{Maly2020, title = {From wavelike to sub-diffusive motion: exciton dynamics and interaction in squaraine copolymers of varying length}, author = {Pavel Malý and Julian Lüttig and Arthur Turkin and Jakub Dostál and Christoph Lambert and Tobias Brixner}, url = {http://dx.doi.org/10.1039/C9SC04367E}, doi = {10.1039/C9SC04367E}, year = {2020}, date = {2020-01-01}, journal = {Chem. Sci.}, volume = {11}, pages = {456-466}, publisher = {The Royal Society of Chemistry}, abstract = {Exciton transport and exciton–exciton interactions in molecular aggregates and polymers are of great importance in natural photosynthesis, organic electronics, and related areas of research. Both the experimental observation and theoretical description of these processes across time and length scales, including the transition from the initial wavelike motion to the following long-range exciton transport, are highly challenging. Therefore, while exciton dynamics at small scales are often treated explicitly, long-range exciton transport is typically described phenomenologically by normal diffusion. In this work, we study the transition from wavelike to diffusive motion of interacting exciton pairs in squaraine copolymers of varying length. To this end we use a combination of the recently introduced exciton–exciton-interaction two-dimensional (EEI2D) electronic spectroscopy and microscopic theoretical modelling. As we show by comparison with the model, the experimentally observed kinetics include three phases, wavelike motion dominated by immediate exciton–exciton annihilation (10–100 fs), sub-diffusive behavior (0.1–10 ps), and excitation relaxation (0.01–1 ns). We demonstrate that the key quantity for the transition from wavelike to diffusive dynamics is the exciton delocalization length relative to the length of the polymer: while in short polymers wavelike motion of rapidly annihilating excitons dominates, in long polymers the excitons become locally trapped and exhibit sub-diffusive behavior. Our findings indicate that exciton transport through conjugated systems emerging from the excitonic structure is generally not governed by normal diffusion. Instead, to characterize the material transport properties, the diffusion presence and character should be determined.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Exciton transport and exciton–exciton interactions in molecular aggregates and polymers are of great importance in natural photosynthesis, organic electronics, and related areas of research. Both the experimental observation and theoretical description of these processes across time and length scales, including the transition from the initial wavelike motion to the following long-range exciton transport, are highly challenging. Therefore, while exciton dynamics at small scales are often treated explicitly, long-range exciton transport is typically described phenomenologically by normal diffusion. In this work, we study the transition from wavelike to diffusive motion of interacting exciton pairs in squaraine copolymers of varying length. To this end we use a combination of the recently introduced exciton–exciton-interaction two-dimensional (EEI2D) electronic spectroscopy and microscopic theoretical modelling. As we show by comparison with the model, the experimentally observed kinetics include three phases, wavelike motion dominated by immediate exciton–exciton annihilation (10–100 fs), sub-diffusive behavior (0.1–10 ps), and excitation relaxation (0.01–1 ns). We demonstrate that the key quantity for the transition from wavelike to diffusive dynamics is the exciton delocalization length relative to the length of the polymer: while in short polymers wavelike motion of rapidly annihilating excitons dominates, in long polymers the excitons become locally trapped and exhibit sub-diffusive behavior. Our findings indicate that exciton transport through conjugated systems emerging from the excitonic structure is generally not governed by normal diffusion. Instead, to characterize the material transport properties, the diffusion presence and character should be determined. |
Schmode, Philip; Savva, Achilleas; Kahl, Robert; Ohayon, David; Meichsner, Florian; Dolynchuk, Oleksandr; Thurn-Albrecht, Thomas; Inal, Sahika; Thelakkat, Mukundan The Key Role of Side Chain Linkage in Structure Formation and Mixed Conduction of Ethylene Glycol Substituted Polythiophenes Journal Article ACS Applied Materials & Interfaces, 12 (11), pp. 13029-13039, 2020, (PMID: 32066232). Abstract | Links | BibTeX | Tags: @article{Schmode2020, title = {The Key Role of Side Chain Linkage in Structure Formation and Mixed Conduction of Ethylene Glycol Substituted Polythiophenes}, author = {Philip Schmode and Achilleas Savva and Robert Kahl and David Ohayon and Florian Meichsner and Oleksandr Dolynchuk and Thomas Thurn-Albrecht and Sahika Inal and Mukundan Thelakkat}, url = {https://doi.org/10.1021/acsami.9b21604}, doi = {10.1021/acsami.9b21604}, year = {2020}, date = {2020-01-01}, journal = {ACS Applied Materials & Interfaces}, volume = {12}, number = {11}, pages = {13029-13039}, abstract = {Functionalizing conjugated polymers with polar ethylene glycol side chains enables enhanced swelling and facilitates ion transport in addition to electronic transport in such systems. Here, we investigate three polythiophene homopolymers (P3MEET, P3MEEMT, and P3MEEET) having differently linked (without spacer and with methyl and ethyl spacer, respectively) diethylene glycol side chains. All the polymers were tested in organic electrochemical transistors (OECTs). They show drastic differences in the device performance. The highest μOECT C* product of 11.5 F/cm·V·s was obtained for ethyl-spaced P3MEEET. How the injection and transport of ions is influenced by the side-chain linkage was studied with electrochemical impedance spectroscopy, which shows a dramatic increase in volumetric capacitance from 80 ± 9 up to 242 ± 17 F/cm3 on going from P3MEET to P3MEEET. Thus, ethyl-spaced P3MEEET exhibits one of the highest reported volumetric capacitance values among p-type polymers. Moreover, P3MEEET exhibits in dry thin films an organic field-effect transistor (OFET) hole mobility of 0.005 cm2/V·s, highest among the three, which is one order of magnitude higher than that for P3MEEMT. The extracted hole mobility from OECT (oxidized swollen state) and the hole mobility in solid-state thin films (OFET) show contradictory trends for P3MEEMT and P3MEEET. In order to understand exactly the properties in the hydrated and dry states, the crystal structure of the polymers was investigated with wide-angle X-ray scattering (WAXS) and grazing incidence WAXS, and the water uptake under applied potential was monitored using electrochemical quartz crystal microbalance with dissipation monitoring (E-QCMD). These measurements reveal an amorphous state for P3MEET and a semicrystalline state for P3MEEMT and P3MEEEET. On the other hand, E-QCMD confirms that P3MEEET swells 10 times more than P3MEEMT in the oxidized state. Thus, the importance of the ethyl spacer toward crystallinity and mixed-conduction properties was clearly demonstrated, emphasizing the impact of side chain linkage of diethylene glycol. This detailed study offers a better understanding of how to design high-performance organic mixed conductors.}, note = {PMID: 32066232}, keywords = {}, pubstate = {published}, tppubtype = {article} } Functionalizing conjugated polymers with polar ethylene glycol side chains enables enhanced swelling and facilitates ion transport in addition to electronic transport in such systems. Here, we investigate three polythiophene homopolymers (P3MEET, P3MEEMT, and P3MEEET) having differently linked (without spacer and with methyl and ethyl spacer, respectively) diethylene glycol side chains. All the polymers were tested in organic electrochemical transistors (OECTs). They show drastic differences in the device performance. The highest μOECT C* product of 11.5 F/cm·V·s was obtained for ethyl-spaced P3MEEET. How the injection and transport of ions is influenced by the side-chain linkage was studied with electrochemical impedance spectroscopy, which shows a dramatic increase in volumetric capacitance from 80 ± 9 up to 242 ± 17 F/cm3 on going from P3MEET to P3MEEET. Thus, ethyl-spaced P3MEEET exhibits one of the highest reported volumetric capacitance values among p-type polymers. Moreover, P3MEEET exhibits in dry thin films an organic field-effect transistor (OFET) hole mobility of 0.005 cm2/V·s, highest among the three, which is one order of magnitude higher than that for P3MEEMT. The extracted hole mobility from OECT (oxidized swollen state) and the hole mobility in solid-state thin films (OFET) show contradictory trends for P3MEEMT and P3MEEET. In order to understand exactly the properties in the hydrated and dry states, the crystal structure of the polymers was investigated with wide-angle X-ray scattering (WAXS) and grazing incidence WAXS, and the water uptake under applied potential was monitored using electrochemical quartz crystal microbalance with dissipation monitoring (E-QCMD). These measurements reveal an amorphous state for P3MEET and a semicrystalline state for P3MEEMT and P3MEEEET. On the other hand, E-QCMD confirms that P3MEEET swells 10 times more than P3MEEMT in the oxidized state. Thus, the importance of the ethyl spacer toward crystallinity and mixed-conduction properties was clearly demonstrated, emphasizing the impact of side chain linkage of diethylene glycol. This detailed study offers a better understanding of how to design high-performance organic mixed conductors. |
Schmode, Philip; Schötz, Konstantin; Dolynchuk, Oleksandr; Panzer, Fabian; Köhler, Anna; Thurn-Albrecht, Thomas; Thelakkat, Mukundan Influence of ω-Bromo Substitution on Structure and Optoelectronic Properties of Homopolymers and Gradient Copolymers of 3-Hexylthiophene Journal Article Macromolecules, 53 (7), pp. 2474-2484, 2020. Abstract | Links | BibTeX | Tags: @article{Schmode2020a, title = {Influence of ω-Bromo Substitution on Structure and Optoelectronic Properties of Homopolymers and Gradient Copolymers of 3-Hexylthiophene}, author = {Philip Schmode and Konstantin Schötz and Oleksandr Dolynchuk and Fabian Panzer and Anna Köhler and Thomas Thurn-Albrecht and Mukundan Thelakkat}, url = {https://doi.org/10.1021/acs.macromol.0c00352}, doi = {10.1021/acs.macromol.0c00352}, year = {2020}, date = {2020-01-01}, journal = {Macromolecules}, volume = {53}, number = {7}, pages = {2474-2484}, abstract = {The nature of side chains and substituents influence the resulting electronic and structural properties of conjugated polymers. Here, we report fundamental studies on the influence of a ω-bromohexyl side chain in polythiophene (resulting in P3BrHT) as well as in a series of gradient copolymers using 3-hexylthiophene (3HT) comonomer. The rate of polymerization of 3BrHT is slower compared to that for 3HT. Temperature dependent absorption and emission show that, with increasing content of 3BrHT, aggregation, critical transition temperature, and the fraction of aggregates decrease. Wide angle X-ray scattering shows that P3BrHT has a triclinic crystal lattice; the crystallinity is almost half of that of P3HT and an increase in the crystallinity and a gradual monotonic decrease of the a and b crystal lattice parameters with decreasing 3BrHT content in copolymers is observed. Finally, the consequences of change in aggregation and crystallinity on charge transport are elucidated using OFET, giving a general explanation for the influence of a ω-bromo substituent in polythiophene copolymers.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The nature of side chains and substituents influence the resulting electronic and structural properties of conjugated polymers. Here, we report fundamental studies on the influence of a ω-bromohexyl side chain in polythiophene (resulting in P3BrHT) as well as in a series of gradient copolymers using 3-hexylthiophene (3HT) comonomer. The rate of polymerization of 3BrHT is slower compared to that for 3HT. Temperature dependent absorption and emission show that, with increasing content of 3BrHT, aggregation, critical transition temperature, and the fraction of aggregates decrease. Wide angle X-ray scattering shows that P3BrHT has a triclinic crystal lattice; the crystallinity is almost half of that of P3HT and an increase in the crystallinity and a gradual monotonic decrease of the a and b crystal lattice parameters with decreasing 3BrHT content in copolymers is observed. Finally, the consequences of change in aggregation and crystallinity on charge transport are elucidated using OFET, giving a general explanation for the influence of a ω-bromo substituent in polythiophene copolymers. |
Schötz, Konstantin; Askar, Abdelrahman M; Peng, Wei; Seeberger, Dominik; Gujar, Tanaji P; Thelakkat, Mukundan; Köhler, Anna; Huettner, Sven; Bakr, Osman M; Shankar, Karthik; Panzer, Fabian Double peak emission in lead halide perovskites by self-absorption Journal Article J. Mater. Chem. C, 8 , pp. 2289-2300, 2020. Abstract | Links | BibTeX | Tags: @article{Schoetz2020, title = {Double peak emission in lead halide perovskites by self-absorption}, author = {Konstantin Schötz and Abdelrahman M Askar and Wei Peng and Dominik Seeberger and Tanaji P Gujar and Mukundan Thelakkat and Anna Köhler and Sven Huettner and Osman M Bakr and Karthik Shankar and Fabian Panzer}, url = {http://dx.doi.org/10.1039/C9TC06251C}, doi = {10.1039/C9TC06251C}, year = {2020}, date = {2020-01-01}, journal = {J. Mater. Chem. C}, volume = {8}, pages = {2289-2300}, publisher = {The Royal Society of Chemistry}, abstract = {Despite the rapidly increasing efficiencies of perovskite solar cells, the optoelectronic properties of this material class are not completely understood. Especially when measured photoluminescence (PL) spectra consist of multiple peaks, their origin is still debated. In this work, we investigate in detail double peak PL spectra of halide perovskite thin films and single crystals with different material compositions. By different optical spectroscopic approaches and quantitative models, we demonstrate that the additional PL peak results from an extensive self-absorption effect, whose impact is intensified by strong internal reflections. This self-absorption accounts for the unusual temperature dependence of the additional PL peak and it implies that absorption until far into the perovskite's Urbach tail is important. The internal reflections entail that even for thin films self-absorption can have a significant contribution to the PL spectrum. Our results allow for a clear assignment of the PL peaks by differentiating between optical effects and electronic transitions, which is a necessary requirement for understanding the optoelectronic properties of halide perovskites.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Despite the rapidly increasing efficiencies of perovskite solar cells, the optoelectronic properties of this material class are not completely understood. Especially when measured photoluminescence (PL) spectra consist of multiple peaks, their origin is still debated. In this work, we investigate in detail double peak PL spectra of halide perovskite thin films and single crystals with different material compositions. By different optical spectroscopic approaches and quantitative models, we demonstrate that the additional PL peak results from an extensive self-absorption effect, whose impact is intensified by strong internal reflections. This self-absorption accounts for the unusual temperature dependence of the additional PL peak and it implies that absorption until far into the perovskite's Urbach tail is important. The internal reflections entail that even for thin films self-absorption can have a significant contribution to the PL spectrum. Our results allow for a clear assignment of the PL peaks by differentiating between optical effects and electronic transitions, which is a necessary requirement for understanding the optoelectronic properties of halide perovskites. |
Ehrmaier, Johannes; Huang, Xiang; Rabe, Emily J; Corp, Kathryn L; Schlenker, Cody W; Sobolewski, Andrzej L; Domcke, Wolfgang Molecular Design of Heptazine-Based Photocatalysts: Effect of Substituents on Photocatalytic Efficiency and Photostability Journal Article J. Phys. Chem. A, 124 (19), pp. 3698–3710, 2020, ISSN: 1089-5639. Abstract | Links | BibTeX | Tags: @article{Ehrmaier2020, title = {Molecular Design of Heptazine-Based Photocatalysts: Effect of Substituents on Photocatalytic Efficiency and Photostability}, author = {Johannes Ehrmaier and Xiang Huang and Emily J Rabe and Kathryn L Corp and Cody W Schlenker and Andrzej L Sobolewski and Wolfgang Domcke}, url = {https://doi.org/10.1021/acs.jpca.0c00488}, doi = {10.1021/acs.jpca.0c00488}, issn = {1089-5639}, year = {2020}, date = {2020-01-01}, journal = {J. Phys. Chem. A}, volume = {124}, number = {19}, pages = {3698--3710}, publisher = {American Chemical Society}, abstract = {Recently, a derivative of the heptazine (tris-triazine) molecule, trianisole-heptazine (TAHz), was synthesized and was shown to catalyze the oxidation of water to hydroxyl radicals under 365 nm LED light in a homogeneous reaction (E. J. Rabe et al., J. Phys. Chem. Lett. 2018, 9, 6257-6261). The possibility of water photo-oxidation with a precisely defined molecular catalyst in neat solvents opens new perspectives for clarifying the fundamental reaction mechanisms involved in water oxidation photocatalysis. In the present work, the effects of chemical substituents on the three CH positions of Hz on the photocatalytic reactivity were explored with wave function-based ab initio electronic-structure calculations for hydrogen-bonded complexes of Hz and three selected Hz derivatives (TAHz, trichloro-Hz, and tricyano-Hz) with a water molecule. While anisole is an electron-donating substituent, Cl is a weakly electron-withdrawing substituent and CN is a strongly electron-withdrawing substituent. It is shown that the barrier for the photoinduced abstraction of an H atom from the water molecule is raised (lowered) by electron-donating (electron-withdrawing) substituents. The highly mobile and reactive hydroxyl radicals generated by water oxidation can recombine with the reduced chromophore radicals to yield photohydrates. The effect of substituents on the thermodynamics of the photohydration reaction was computed. Among the four chromophores studied, TAHz stands out on account of the metastability of its photohydrate, which suggests self-healing of the photocatalyst after oxidation of TAHzH radicals by OH radicals. In addition, the effect of substituents on the H atom photodetachment reaction from the reduced chromophores, which closes the catalytic cycle, has been investigated. The energy of the repulsive 2πσ* state, which drives the photodetachment reaction is lowered (raised) by electron-donating (electron withdrawing) substituents. All four chromophores exhibit inverted S1/T1 gaps. This feature eliminates long-lived triplet states and thus avoids the activation of molecular oxygen to highly reactive singlet oxygen.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recently, a derivative of the heptazine (tris-triazine) molecule, trianisole-heptazine (TAHz), was synthesized and was shown to catalyze the oxidation of water to hydroxyl radicals under 365 nm LED light in a homogeneous reaction (E. J. Rabe et al., J. Phys. Chem. Lett. 2018, 9, 6257-6261). The possibility of water photo-oxidation with a precisely defined molecular catalyst in neat solvents opens new perspectives for clarifying the fundamental reaction mechanisms involved in water oxidation photocatalysis. In the present work, the effects of chemical substituents on the three CH positions of Hz on the photocatalytic reactivity were explored with wave function-based ab initio electronic-structure calculations for hydrogen-bonded complexes of Hz and three selected Hz derivatives (TAHz, trichloro-Hz, and tricyano-Hz) with a water molecule. While anisole is an electron-donating substituent, Cl is a weakly electron-withdrawing substituent and CN is a strongly electron-withdrawing substituent. It is shown that the barrier for the photoinduced abstraction of an H atom from the water molecule is raised (lowered) by electron-donating (electron-withdrawing) substituents. The highly mobile and reactive hydroxyl radicals generated by water oxidation can recombine with the reduced chromophore radicals to yield photohydrates. The effect of substituents on the thermodynamics of the photohydration reaction was computed. Among the four chromophores studied, TAHz stands out on account of the metastability of its photohydrate, which suggests self-healing of the photocatalyst after oxidation of TAHzH radicals by OH radicals. In addition, the effect of substituents on the H atom photodetachment reaction from the reduced chromophores, which closes the catalytic cycle, has been investigated. The energy of the repulsive 2πσ* state, which drives the photodetachment reaction is lowered (raised) by electron-donating (electron withdrawing) substituents. All four chromophores exhibit inverted S1/T1 gaps. This feature eliminates long-lived triplet states and thus avoids the activation of molecular oxygen to highly reactive singlet oxygen. |
Kraut, Max; Sirotti, Elise; Pantle, Florian; Jiang, Chang-Ming; Grötzner, Gabriel; Koch, Marvin; Wagner, Laura I; Sharp, Ian D; Stutzmann, Martin Control of Band Gap and Band Edge Positions in Gallium-Zinc Oxynitride Grown by Molecular Beam Epitaxy Journal Article J. Phys. Chem. C, 124 (14), pp. 7668–7676, 2020, ISSN: 1932-7447. Abstract | Links | BibTeX | Tags: @article{Kraut2020, title = {Control of Band Gap and Band Edge Positions in Gallium-Zinc Oxynitride Grown by Molecular Beam Epitaxy}, author = {Max Kraut and Elise Sirotti and Florian Pantle and Chang-Ming Jiang and Gabriel Grötzner and Marvin Koch and Laura I Wagner and Ian D Sharp and Martin Stutzmann}, url = {https://doi.org/10.1021/acs.jpcc.0c00254}, doi = {10.1021/acs.jpcc.0c00254}, issn = {1932-7447}, year = {2020}, date = {2020-01-01}, journal = {J. Phys. Chem. C}, volume = {124}, number = {14}, pages = {7668--7676}, publisher = {American Chemical Society}, abstract = {Gallium-zinc oxynitride (GZNO) is a promising material system for solar-driven overall water splitting, as it exhibits a tunable band gap in the visible range, beneficial positions of valence and conduction band edges, and promising long-term stability. Fabrication of GZNO is traditionally accomplished via a solid state reaction pathway. This limits the growth of thin films or large single crystals and the precise control of the composition, which complicates investigations about fundamental properties of the material, including, for example, the influence of the single constituent ratios on the band gap. In this work, we present the growth of GZNO thin films on sapphire by plasma-assisted molecular beam epitaxy (MBE). The thin films exhibit a crystallite size of up to 50 nm and a wurtzite crystal structure with distinct short-range disorder. Variations of Ga/Zn and N/O flux ratios are found to influence the optical absorption edge of the alloy without major impact on the Urbach energy. Controlled change of the composition of the alloy reveals that the band gap reduction is caused by both an increased valence band energy, which is correlated with the N content, and a decrease of the conduction band energy which is induced by increasing Zn content. Based on these findings, GZNO thin films with band gaps of down to 2.0 eV were fabricated and their photoelectrical properties assessed. Using MBE, we overcome compositional restrictions typically associated with stoichiometric GaN:ZnO solid solutions and provide unprecedented access to new compounds within this materials class. In doing so, we elucidate the specific role of individual elements on band edge energetics and demonstrate new routes to band gap engineering for future photocatalytic and photoelectrochemical applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Gallium-zinc oxynitride (GZNO) is a promising material system for solar-driven overall water splitting, as it exhibits a tunable band gap in the visible range, beneficial positions of valence and conduction band edges, and promising long-term stability. Fabrication of GZNO is traditionally accomplished via a solid state reaction pathway. This limits the growth of thin films or large single crystals and the precise control of the composition, which complicates investigations about fundamental properties of the material, including, for example, the influence of the single constituent ratios on the band gap. In this work, we present the growth of GZNO thin films on sapphire by plasma-assisted molecular beam epitaxy (MBE). The thin films exhibit a crystallite size of up to 50 nm and a wurtzite crystal structure with distinct short-range disorder. Variations of Ga/Zn and N/O flux ratios are found to influence the optical absorption edge of the alloy without major impact on the Urbach energy. Controlled change of the composition of the alloy reveals that the band gap reduction is caused by both an increased valence band energy, which is correlated with the N content, and a decrease of the conduction band energy which is induced by increasing Zn content. Based on these findings, GZNO thin films with band gaps of down to 2.0 eV were fabricated and their photoelectrical properties assessed. Using MBE, we overcome compositional restrictions typically associated with stoichiometric GaN:ZnO solid solutions and provide unprecedented access to new compounds within this materials class. In doing so, we elucidate the specific role of individual elements on band edge energetics and demonstrate new routes to band gap engineering for future photocatalytic and photoelectrochemical applications. |
Sirtl, Maximilian T; Armer, Melina; Reb, Lennart K; Hooijer, Rik; Dörflinger, Patrick; Scheel, Manuel A; Tvingstedt, Kristofer; Rieder, Philipp; Glück, Nadja; Pandit, Pallavi; Roth, Stephan V; Müller-Buschbaum, Peter; Dyakonov, Vladimir; Bein, Thomas Optoelectronic Properties of Cs2AgBiBr6 Thin Films: The Influence of Precursor Stoichiometry Journal Article ACS Appl. Energy Mater., 3 (12), pp. 11597–11609, 2020. Abstract | Links | BibTeX | Tags: @article{Sirtl2020, title = {Optoelectronic Properties of Cs2AgBiBr6 Thin Films: The Influence of Precursor Stoichiometry}, author = {Maximilian T Sirtl and Melina Armer and Lennart K Reb and Rik Hooijer and Patrick Dörflinger and Manuel A Scheel and Kristofer Tvingstedt and Philipp Rieder and Nadja Glück and Pallavi Pandit and Stephan V Roth and Peter Müller-Buschbaum and Vladimir Dyakonov and Thomas Bein}, url = {https://doi.org/10.1021/acsaem.0c01308}, doi = {10.1021/acsaem.0c01308}, year = {2020}, date = {2020-01-01}, journal = {ACS Appl. Energy Mater.}, volume = {3}, number = {12}, pages = {11597--11609}, publisher = {American Chemical Society}, abstract = {Lead-free double perovskites have recently attracted growing attention as possible alternatives to lead-based halide perovskites in photovoltaics and other optoelectronic applications. The most prominent compound Cs2AgBiBr6, however, presents issues such as a rather large and indirect band gap, high exciton binding energies, and poor charge carrier transport, especially in thin films. In order to address some of these challenges, we systematically modified the stoichiometry of the precursors used for the synthesis of thin films toward a BiBr3-deficient system. In combination with a stoichiometric excess of AgBr, we obtained highly oriented double perovskite thin films. These modifications directly boost the lifetime of the charge carriers up to 500 ns as observed by time-resolved photoluminescence spectroscopy. Moreover, time-resolved microwave conductivity studies revealed an increase of the charge carrier mobility from 3.5 to around ∼5 cm2/(V s). Solar cells comprising the modified films as planar active layers reached power conversion efficiency (PCE) values up to 1.11%, exceeding the stoichiometric reference film (∼0.97%), both on average and with champion cells. The results in this work underline the importance of controlling the nanomorphology of the bulk film. We anticipate that control of precursor stoichiometry will also offer a promising approach for enhancing the efficiency of other perovskite photovoltaic absorber materials and thin films.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Lead-free double perovskites have recently attracted growing attention as possible alternatives to lead-based halide perovskites in photovoltaics and other optoelectronic applications. The most prominent compound Cs2AgBiBr6, however, presents issues such as a rather large and indirect band gap, high exciton binding energies, and poor charge carrier transport, especially in thin films. In order to address some of these challenges, we systematically modified the stoichiometry of the precursors used for the synthesis of thin films toward a BiBr3-deficient system. In combination with a stoichiometric excess of AgBr, we obtained highly oriented double perovskite thin films. These modifications directly boost the lifetime of the charge carriers up to 500 ns as observed by time-resolved photoluminescence spectroscopy. Moreover, time-resolved microwave conductivity studies revealed an increase of the charge carrier mobility from 3.5 to around ∼5 cm2/(V s). Solar cells comprising the modified films as planar active layers reached power conversion efficiency (PCE) values up to 1.11%, exceeding the stoichiometric reference film (∼0.97%), both on average and with champion cells. The results in this work underline the importance of controlling the nanomorphology of the bulk film. We anticipate that control of precursor stoichiometry will also offer a promising approach for enhancing the efficiency of other perovskite photovoltaic absorber materials and thin films. |