@article{ZuSchultzWolffetal.2020,
  author    = {Zu, Fengshuo and Schultz, Thorsten and Wolff, Christian Michael and Shin, Dongguen and Frohloff, Lennart and Neher, Dieter and Amsalem, Patrick and Koch, Norbert},
  title     = {Position-locking of volatile reaction products by atmosphere and capping layers slows down photodecomposition of methylammonium lead triiodide perovskite},
  series = {RSC Advances},
  volume    = {10},
  journal   = {RSC Advances},
  number    = {30},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2046-2069},
  doi       = {10.1039/d0ra03572f},
  pages     = {17534 -- 17542},
  year      = {2020},
  abstract  = {The remarkable progress of metal halide perovskites in photovoltaics has led to the power conversion efficiency approaching 26\%. However, practical applications of perovskite-based solar cells are challenged by the stability issues, of which the most critical one is photo-induced degradation. Bare CH3NH3PbI3 perovskite films are known to decompose rapidly, with methylammonium and iodine as volatile species and residual solid PbI2 and metallic Pb, under vacuum under white light illumination, on the timescale of minutes. We find, in agreement with previous work, that the degradation is non-uniform and proceeds predominantly from the surface, and that illumination under N-2 and ambient air (relative humidity 20\%) does not induce substantial degradation even after several hours. Yet, in all cases the release of iodine from the perovskite surface is directly identified by X-ray photoelectron spectroscopy. This goes in hand with a loss of organic cations and the formation of metallic Pb. When CH3NH3PbI3 films are covered with a few nm thick organic capping layer, either charge selective or non-selective, the rapid photodecomposition process under ultrahigh vacuum is reduced by more than one order of magnitude, and becomes similar in timescale to that under N-2 or air. We conclude that the light-induced decomposition reaction of CH3NH3PbI3, leading to volatile methylammonium and iodine, is largely reversible as long as these products are restrained from leaving the surface. This is readily achieved by ambient atmospheric pressure, as well as a thin organic capping layer even under ultrahigh vacuum. In addition to explaining the impact of gas pressure on the stability of this perovskite, our results indicate that covalently "locking" the position of perovskite components at the surface or an interface should enhance the overall photostability.},
  language  = {en}
}
@article{PerdigonToroZhangMarkinaetal.2020,
  author    = {Perdig{\´o}n-Toro, Lorena and Zhang, Huotian and Markina, Anastaa si and Yuan, Jun and Hosseini, Seyed Mehrdad and Wolff, Christian Michael and Zuo, Guangzheng and Stolterfoht, Martin and Zou, Yingping and Gao, Feng and Andrienko, Denis and Shoaee, Safa and Neher, Dieter},
  title     = {Barrierless free charge generation in the high-performance PM6:Y6 bulk heterojunction non-fullerene solar cell},
  series = {Advanced materials},
  volume    = {32},
  journal   = {Advanced materials},
  number    = {9},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0935-9648},
  doi       = {10.1002/adma.201906763},
  pages     = {9},
  year      = {2020},
  abstract  = {Organic solar cells are currently experiencing a second golden age thanks to the development of novel non-fullerene acceptors (NFAs). Surprisingly, some of these blends exhibit high efficiencies despite a low energy offset at the heterojunction. Herein, free charge generation in the high-performance blend of the donor polymer PM6 with the NFA Y6 is thoroughly investigated as a function of internal field, temperature and excitation energy. Results show that photocurrent generation is essentially barrierless with near-unity efficiency, regardless of excitation energy. Efficient charge separation is maintained over a wide temperature range, down to 100 K, despite the small driving force for charge generation. Studies on a blend with a low concentration of the NFA, measurements of the energetic disorder, and theoretical modeling suggest that CT state dissociation is assisted by the electrostatic interfacial field which for Y6 is large enough to compensate the Coulomb dissociation barrier.},
  language  = {en}
}
@misc{WolffCanilRehermannetal.2020,
  author    = {Wolff, Christian Michael and Canil, Laura and Rehermann, Carolin and Nguyen, Ngoc Linh and Zu, Fengshuo and Ralaiarisoa, Maryline and Caprioglio, Pietro and Fiedler, Lukas and Stolterfoht, Martin and Kogikoski, Junior, Sergio and Bald, Ilko and Koch, Norbert and Unger, Eva L. and Dittrich, Thomas and Abate, Antonio and Neher, Dieter},
  title     = {Correction to 'Perfluorinated self-assembled monolayers enhance the stability and efficiency of inverted perovskite solar cells' (2020, 14 (2), 1445-1456)},
  series = {ACS nano},
  volume    = {14},
  journal   = {ACS nano},
  number    = {11},
  publisher = {American Chemical Society},
  address   = {Washington, DC},
  issn      = {1936-0851},
  doi       = {10.1021/acsnano.0c08081},
  pages     = {16156 -- 16156},
  year      = {2020},
  language  = {en}
}
@article{WangSmithSkroblinetal.2020,
  author    = {Wang, Qiong and Smith, Joel A. and Skroblin, Dieter and Steele, Julian A. and Wolff, Christian Michael and Caprioglio, Pietro and Stolterfoht, Martin and K{\"o}bler, Hans and Turren-Cruz, Silver-Hamill and Li, Meng and Gollwitzer, Christian and Neher, Dieter and Abate, Antonio},
  title     = {Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells},
  series = {Solar RRL},
  volume    = {4},
  journal   = {Solar RRL},
  number    = {9},
  publisher = {WILEY-VCH},
  address   = {Weinheim},
  pages     = {9},
  year      = {2020},
  abstract  = {Inorganic perovskites with cesium (Cs+) as the cation have great potential as photovoltaic materials if their phase purity and stability can be addressed. Herein, a series of inorganic perovskites is studied, and it is found that the power conversion efficiency of solar cells with compositions CsPbI1.8Br1.2, CsPbI2.0Br1.0, and CsPbI2.2Br0.8 exhibits a high dependence on the initial annealing step that is found to significantly affect the crystallization and texture behavior of the final perovskite film. At its optimized annealing temperature, CsPbI1.8Br1.2 exhibits a pure orthorhombic phase and only one crystal orientation of the (110) plane. Consequently, this allows for the best efficiency of up to 14.6\% and the longest operational lifetime, T-S80, of approximate to 300 h, averaged of over six solar cells, during the maximum power point tracking measurement under continuous light illumination and nitrogen atmosphere. This work provides essential progress on the enhancement of photovoltaic performance and stability of CsPbI3 - xBrx perovskite solar cells.},
  language  = {en}
}
@misc{StolterfohtGrischekCaprioglioetal.2020,
  author    = {Stolterfoht, Martin and Grischek, Max and Caprioglio, Pietro and Wolff, Christian Michael and Gutierrez-Partida, Emilio and Pe{\~n}a-Camargo, Francisco and Rothhardt, Daniel and Zhang, Shanshan and Raoufi, Meysam and Wolansky, Jakob and Abdi-Jalebi, Mojtaba and Stranks, Samuel D. and Albrecht, Steve and Kirchartz, Thomas and Neher, Dieter},
  title     = {How to quantify the efficiency potential of neat perovskite films},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {17},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51662},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-516622},
  pages     = {12},
  year      = {2020},
  abstract  = {Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28\%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit.},
  language  = {en}
}
@article{StolterfohtGrischekCaprioglioetal.2020,
  author    = {Stolterfoht, Martin and Grischek, Max and Caprioglio, Pietro and Wolff, Christian Michael and Gutierrez-Partida, Emilio and Pe{\~n}a-Camargo, Francisco and Rothhardt, Daniel and Zhang, Shanshan and Raoufi, Meysam and Wolansky, Jakob and Abdi-Jalebi, Mojtaba and Stranks, Samuel D. and Albrecht, Steve and Kirchartz, Thomas and Neher, Dieter},
  title     = {How to quantify the efficiency potential of neat perovskite films},
  series = {Advanced Materials},
  volume    = {32},
  journal   = {Advanced Materials},
  number    = {17},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0935-9648},
  doi       = {10.1002/adma.202000080},
  pages     = {1 -- 10},
  year      = {2020},
  abstract  = {Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28\%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit.},
  language  = {en}
}
@misc{WangSmithSkroblinetal.2020,
  author    = {Wang, Qiong and Smith, Joel A. and Skroblin, Dieter and Steele, Julian A. and Wolff, Christian Michael and Caprioglio, Pietro and Stolterfoht, Martin and K{\"o}bler, Hans and Turren-Cruz, Silver-Hamill and Li, Meng and Gollwitzer, Christian and Neher, Dieter and Abate, Antonio},
  title     = {Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {9},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-52537},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-525374},
  pages     = {11},
  year      = {2020},
  abstract  = {Inorganic perovskites with cesium (Cs+) as the cation have great potential as photovoltaic materials if their phase purity and stability can be addressed. Herein, a series of inorganic perovskites is studied, and it is found that the power conversion efficiency of solar cells with compositions CsPbI1.8Br1.2, CsPbI2.0Br1.0, and CsPbI2.2Br0.8 exhibits a high dependence on the initial annealing step that is found to significantly affect the crystallization and texture behavior of the final perovskite film. At its optimized annealing temperature, CsPbI1.8Br1.2 exhibits a pure orthorhombic phase and only one crystal orientation of the (110) plane. Consequently, this allows for the best efficiency of up to 14.6\% and the longest operational lifetime, T-S80, of approximate to 300 h, averaged of over six solar cells, during the maximum power point tracking measurement under continuous light illumination and nitrogen atmosphere. This work provides essential progress on the enhancement of photovoltaic performance and stability of CsPbI3 - xBrx perovskite solar cells.},
  language  = {en}
}