@misc{SchulzeBettBivouretal.2020, author = {Schulze, Patricia S. C. and Bett, Alexander J. and Bivour, Martin and Caprioglio, Pietro and Gerspacher, Fabian M. and Kabakl{\i}, {\"O}zde Ş. and Richter, Armin and Stolterfoht, Martin and Zhang, Qinxin and Neher, Dieter and Hermle, Martin and Hillebrecht, Harald and Glunz, Stefan W. and Goldschmidt, Jan Christoph}, title = {25.1\% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {7}, issn = {1866-8372}, doi = {10.25932/publishup-52566}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-525668}, pages = {12}, year = {2020}, abstract = {Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10\% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80\% and up to 25.1\% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3\% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30\% tandem efficiency in the near future.}, language = {en} } @article{SchulzeBettBivouretal.2020, author = {Schulze, Patricia S. C. and Bett, Alexander J. and Bivour, Martin and Caprioglio, Pietro and Gerspacher, Fabian M. and Kabakl{\i}, {\"O}zde Ş. and Richter, Armin and Stolterfoht, Martin and Zhang, Qinxin and Neher, Dieter and Hermle, Martin and Hillebrecht, Harald and Glunz, Stefan W. and Goldschmidt, Jan Christoph}, title = {25.1\% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber}, series = {Solar RRL}, volume = {4}, journal = {Solar RRL}, number = {7}, publisher = {John Wiley \& Sons, Inc.}, address = {New Jersey}, pages = {10}, year = {2020}, abstract = {Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10\% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80\% and up to 25.1\% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3\% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30\% tandem efficiency in the near future.}, language = {en} } @article{StolterfohtLang2022, author = {Stolterfoht, Martin and Lang, Felix}, title = {All-perovskite tandems get flexible}, series = {Nature energy}, volume = {7}, journal = {Nature energy}, number = {8}, publisher = {Nature Publishing Group}, address = {London}, issn = {2058-7546}, doi = {10.1038/s41560-022-01087-6}, pages = {688 -- 689}, year = {2022}, abstract = {Flexible all-perovskite tandem photovoltaics open up new opportunities for application compared to rigid devices, yet their performance lags behind. Now, researchers show that molecule-bridged interfaces mitigate charge recombination and crack formation, improving the efficiency and mechanical reliability of flexible devices.}, language = {en} } @article{StolterfohtWolffAmiretal.2017, author = {Stolterfoht, Martin and Wolff, Christian Michael and Amir, Yohai and Paulke, Andreas and Perdigon-Toro, Lorena and Caprioglio, Pietro and Neher, Dieter}, title = {Approaching the fill factor Shockley-Queisser limit in stable, dopant-free triple cation perovskite solar cells}, series = {Energy \& Environmental Science}, volume = {10}, journal = {Energy \& Environmental Science}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1754-5692}, doi = {10.1039/c7ee00899f}, pages = {1530 -- 1539}, year = {2017}, abstract = {Perovskite solar cells now compete with their inorganic counterparts in terms of power conversion efficiency, not least because of their small open-circuit voltage (V-OC) losses. A key to surpass traditional thin-film solar cells is the fill factor (FF). Therefore, more insights into the physical mechanisms that define the bias dependence of the photocurrent are urgently required. In this work, we studied charge extraction and recombination in efficient triple cation perovskite solar cells with undoped organic electron/hole transport layers (ETL/HTL). Using integral time of flight we identify the transit time through the HTL as the key figure of merit for maximizing the fill factor (FF) and efficiency. Complementarily, intensity dependent photocurrent and V-OC measurements elucidate the role of the HTL on the bias dependence of non-radiative and transport-related loss channels. We show that charge transport losses can be completely avoided under certain conditions, yielding devices with FFs of up to 84\%. Optimized cells exhibit power conversion efficiencies of above 20\% for 6 mm(2) sized pixels and 18.9\% for a device area of 1 cm(2). These are record efficiencies for hybrid perovskite devices with dopant-free transport layers, highlighting the potential of this device technology to avoid charge-transport limitations and to approach the Shockley-Queisser limit.}, language = {en} } @article{PerdigonToroZhangMarkinaetal.2020, author = {Perdigon-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} } @article{LeCorreStolterfohtPerdigonToroetal.2019, author = {Le Corre, Vincent M. and Stolterfoht, Martin and Perdig{\´o}n-Toro, Lorena and Feuerstein, Markus and Wolff, Christian Michael and Gil-Escrig, Lidon and Bolink, Henk J. and Neher, Dieter and Koster, L. Jan Anton}, title = {Charge Transport Layers Limiting the Efficiency of Perovskite Solar Cells: How To Optimize Conductivity, Doping, and Thickness}, series = {ACS Applied Energy Materials}, volume = {2}, journal = {ACS Applied Energy Materials}, number = {9}, publisher = {American Chemical Society}, address = {Washington}, issn = {2574-0962}, doi = {10.1021/acsaem.9b00856}, pages = {6280 -- 6287}, year = {2019}, abstract = {Perovskite solar cells (PSCs) are one of the main research topics of the photovoltaic community; with efficiencies now reaching up to 24\%, PSCs are on the way to catching up with classical inorganic solar cells. However, PSCs have not yet reached their full potential. In fact, their efficiency is still limited by nonradiative recombination, mainly via trap-states and by losses due to the poor transport properties of the commonly used transport layers (TLs). Indeed, state-of-the-art TLs (especially if organic) suffer from rather low mobilities, typically within 10(-5) and 10(-2) cm(-2) V-1 s(-1), when compared to the high mobilities, 1-10 cm(-2) V-1 s(-1), measured for perovskites. This work presents a comprehensive analysis of the effect of the mobility, thickness, and doping density of the transport layers based on combined experimental and modeling results of two sets of devices made of a solution-processed high-performing triple-cation (PCE approximate to 20\%). The results are also cross-checked on vacuum-processed MAPbI(3) devices. From this analysis, general guidelines on how to optimize a TL are introduced and especially a new and simple formula to easily calculate the amount of doping necessary to counterbalance the low mobility of the TLs.}, 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{ShoaeeArminStolterfohtetal.2019, author = {Shoaee, Safa and Armin, Ardalan and Stolterfoht, Martin and Hosseini, Seyed Mehrdad and Kurpiers, Jona and Neher, Dieter}, title = {Decoding Charge Recombination through Charge Generation in Organic Solar Cells}, series = {Solar RRL}, volume = {3}, journal = {Solar RRL}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2367-198X}, doi = {10.1002/solr.201900184}, pages = {8}, year = {2019}, abstract = {The in-depth understanding of charge carrier photogeneration and recombination mechanisms in organic solar cells is still an ongoing effort. In donor:acceptor (bulk) heterojunction organic solar cells, charge photogeneration and recombination are inter-related via the kinetics of charge transfer states-being singlet or triplet states. Although high-charge-photogeneration quantum yields are achieved in many donor:acceptor systems, only very few systems show significantly reduced bimolecular recombination relative to the rate of free carrier encounters, in low-mobility systems. This is a serious limitation for the industrialization of organic solar cells, in particular when aiming at thick active layers. Herein, a meta-analysis of the device performance of numerous bulk heterojunction organic solar cells is presented for which field-dependent photogeneration, charge carrier mobility, and fill factor are determined. Herein, a "spin-related factor" that is dependent on the ratio of back electron transfer of the triplet charge transfer (CT) states to the decay rate of the singlet CT states is introduced. It is shown that this factor links the recombination reduction factor to charge-generation efficiency. As a consequence, it is only in the systems with very efficient charge generation and very fast CT dissociation that free carrier recombination is strongly suppressed, regardless of the spin-related factor.}, language = {en} } @misc{ShoaeeArminStolterfohtetal.2019, author = {Shoaee, Safa and Armin, Ardalan and Stolterfoht, Martin and Hosseini, Seyed Mehrdad and Kurpiers, Jona and Neher, Dieter}, title = {Decoding charge recombination through charge generation in organic solar cells}, series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {773}, issn = {1866-8372}, doi = {10.25932/publishup-43751}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-437512}, pages = {8}, year = {2019}, abstract = {The in-depth understanding of charge carrier photogeneration and recombination mechanisms in organic solar cells is still an ongoing effort. In donor:acceptor (bulk) heterojunction organic solar cells, charge photogeneration and recombination are inter-related via the kinetics of charge transfer states—being singlet or triplet states. Although high-charge-photogeneration quantum yields are achieved in many donor:acceptor systems, only very few systems show significantly reduced bimolecular recombination relative to the rate of free carrier encounters, in low-mobility systems. This is a serious limitation for the industrialization of organic solar cells, in particular when aiming at thick active layers. Herein, a meta-analysis of the device performance of numerous bulk heterojunction organic solar cells is presented for which field-dependent photogeneration, charge carrier mobility, and fill factor are determined. Herein, a "spin-related factor" that is dependent on the ratio of back electron transfer of the triplet charge transfer (CT) states to the decay rate of the singlet CT states is introduced. It is shown that this factor links the recombination reduction factor to charge-generation efficiency. As a consequence, it is only in the systems with very efficient charge generation and very fast CT dissociation that free carrier recombination is strongly suppressed, regardless of the spin-related factor.}, language = {en} } @article{GrischekCaprioglioZhangetal.2022, author = {Grischek, Max and Caprioglio, Pietro and Zhang, Jiahuan and Pena-Camargo, Francisco and Sveinbjornsson, Kari and Zu, Fengshuo and Menzel, Dorothee and Warby, Jonathan H. and Li, Jinzhao and Koch, Norbert and Unger, Eva and Korte, Lars and Neher, Dieter and Stolterfoht, Martin and Albrecht, Steve}, title = {Efficiency Potential and Voltage Loss of Inorganic CsPbI2Br Perovskite Solar Cells}, series = {Solar RRL}, volume = {6}, journal = {Solar RRL}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2367-198X}, doi = {10.1002/solr.202200690}, pages = {12}, year = {2022}, abstract = {Inorganic perovskite solar cells show excellent thermal stability, but the reported power conversion efficiencies are still lower than for organic-inorganic perovskites. This is mainly caused by lower open-circuit voltages (V(OC)s). Herein, the reasons for the low V-OC in inorganic CsPbI2Br perovskite solar cells are investigated. Intensity-dependent photoluminescence measurements for different layer stacks reveal that n-i-p and p-i-n CsPbI2Br solar cells exhibit a strong mismatch between quasi-Fermi level splitting (QFLS) and V-OC. Specifically, the CsPbI2Br p-i-n perovskite solar cell has a QFLS-e center dot V-OC mismatch of 179 meV, compared with 11 meV for a reference cell with an organic-inorganic perovskite of similar bandgap. On the other hand, this study shows that the CsPbI2Br films with a bandgap of 1.9 eV have a very low defect density, resulting in an efficiency potential of 20.3\% with a MeO-2PACz hole-transporting layer and 20.8\% on compact TiO2. Using ultraviolet photoelectron spectroscopy measurements, energy level misalignment is identified as a possible reason for the QFLS-e center dot V-OC mismatch and strategies for overcoming this V-OC limitation are discussed. This work highlights the need to control the interfacial energetics in inorganic perovskite solar cells, but also gives promise for high efficiencies once this issue is resolved.}, language = {en} }