TY - GEN A1 - Stolterfoht, Martin A1 - Grischek, Max A1 - Caprioglio, Pietro A1 - Wolff, Christian Michael A1 - Gutierrez-Partida, Emilio A1 - Peña-Camargo, Francisco A1 - Rothhardt, Daniel A1 - Zhang, Shanshan A1 - Raoufi, Meysam A1 - Wolansky, Jakob A1 - Abdi-Jalebi, Mojtaba A1 - Stranks, Samuel D. A1 - Albrecht, Steve A1 - Kirchartz, Thomas A1 - Neher, Dieter T1 - How to quantify the efficiency potential of neat perovskite films BT - Perovskite semiconductors with an implied efficiency exceeding 28% T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1434 KW - non-radiative interface recombination KW - perovskite solar cells KW - photoluminescence Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516622 SN - 1866-8372 IS - 17 ER - TY - JOUR A1 - Stolterfoht, Martin A1 - Grischek, Max A1 - Caprioglio, Pietro A1 - Wolff, Christian Michael A1 - Gutierrez-Partida, Emilio A1 - Peña-Camargo, Francisco A1 - Rothhardt, Daniel A1 - Zhang, Shanshan A1 - Raoufi, Meysam A1 - Wolansky, Jakob A1 - Abdi-Jalebi, Mojtaba A1 - Stranks, Samuel D. A1 - Albrecht, Steve A1 - Kirchartz, Thomas A1 - Neher, Dieter T1 - How to quantify the efficiency potential of neat perovskite films BT - Perovskite semiconductors with an implied efficiency exceeding 28% JF - Advanced Materials N2 - 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. KW - non-radiative interface recombination KW - perovskite solar cells KW - photoluminescence Y1 - 2020 U6 - https://doi.org/10.1002/adma.202000080 SN - 0935-9648 SN - 1521-4095 VL - 32 IS - 17 SP - 1 EP - 10 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Wolff, Christian Michael A1 - Canil, Laura A1 - Rehermann, Carolin A1 - Nguyen, Ngoc Linh A1 - Zu, Fengshuo A1 - Ralaiarisoa, Maryline A1 - Caprioglio, Pietro A1 - Fiedler, Lukas A1 - Stolterfoht, Martin A1 - Kogikoski, Junior, Sergio A1 - Bald, Ilko A1 - Koch, Norbert A1 - Unger, Eva L. A1 - Dittrich, Thomas A1 - Abate, Antonio A1 - Neher, Dieter T1 - Correction to 'Perfluorinated self-assembled monolayers enhance the stability and efficiency of inverted perovskite solar cells' (2020, 14 (2), 1445−1456) T2 - ACS nano Y1 - 2020 U6 - https://doi.org/10.1021/acsnano.0c08081 SN - 1936-0851 SN - 1936-086X VL - 14 IS - 11 SP - 16156 EP - 16156 PB - American Chemical Society CY - Washington, DC ER - TY - GEN A1 - Wang, Qiong A1 - Smith, Joel A. A1 - Skroblin, Dieter A1 - Steele, Julian A. A1 - Wolff, Christian Michael A1 - Caprioglio, Pietro A1 - Stolterfoht, Martin A1 - Köbler, Hans A1 - Turren-Cruz, Silver-Hamill A1 - Li, Meng A1 - Gollwitzer, Christian A1 - Neher, Dieter A1 - Abate, Antonio T1 - Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1210 KW - cesium lead halides KW - crystal orientation KW - inorganic perovskites KW - ISOS-L-1I protocol KW - phase purity KW - photostability Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-525374 SN - 1866-8372 IS - 9 ER - TY - JOUR A1 - Le Corre, Vincent M. A1 - Diekmann, Jonas A1 - Peña-Camargo, Francisco A1 - Thiesbrummel, Jarla A1 - Tokmoldin, Nurlan A1 - Gutierrez-Partida, Emilio A1 - Peters, Karol Pawel A1 - Perdigón-Toro, Lorena A1 - Futscher, Moritz H. A1 - Lang, Felix A1 - Warby, Jonathan A1 - Snaith, Henry J. A1 - Neher, Dieter A1 - Stolterfoht, Martin T1 - Quantification of efficiency losses due to mobile ions in Perovskite solar cells via fast hysteresis measurements JF - Solar RRL N2 - Perovskite semiconductors differ from most inorganic and organic semiconductors due to the presence of mobile ions in the material. Although the phenomenon is intensively investigated, important questions such as the exact impact of the mobile ions on the steady-state power conversion efficiency (PCE) and stability remain. Herein, a simple method is proposed to estimate the efficiency loss due to mobile ions via "fast-hysteresis" measurements by preventing the perturbation of mobile ions out of their equilibrium position at fast scan speeds (approximate to 1000 V s(-1)). The "ion-free" PCE is between 1% and 3% higher than the steady-state PCE, demonstrating the importance of ion-induced losses, even in cells with low levels of hysteresis at typical scan speeds (approximate to 100mv s(-1)). The hysteresis over many orders of magnitude in scan speed provides important information on the effective ion diffusion constant from the peak hysteresis position. The fast-hysteresis measurements are corroborated by transient charge extraction and capacitance measurements and numerical simulations, which confirm the experimental findings and provide important insights into the charge carrier dynamics. The proposed method to quantify PCE losses due to field screening induced by mobile ions clarifies several important experimental observations and opens up a large range of future experiments. KW - hysteresis KW - mobile ions KW - perovskite solar cells Y1 - 2021 U6 - https://doi.org/10.1002/solr.202100772 SN - 2367-198X VL - 6 IS - 4 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Saliba, Michael A1 - Stolterfoht, Martin A1 - Wolff, Christian Michael A1 - Neher, Dieter A1 - Abate, Antonio T1 - Measuring aging stability of perovskite solar cells T2 - Joule Y1 - 2018 U6 - https://doi.org/10.1016/j.joule.2018.05.005 SN - 2542-4351 VL - 2 IS - 6 SP - 1019 EP - 1024 PB - Cell Press CY - Cambridge ER - TY - JOUR A1 - Wang, Qiong A1 - Smith, Joel A. A1 - Skroblin, Dieter A1 - Steele, Julian A. A1 - Wolff, Christian Michael A1 - Caprioglio, Pietro A1 - Stolterfoht, Martin A1 - Köbler, Hans A1 - Turren-Cruz, Silver-Hamill A1 - Li, Meng A1 - Gollwitzer, Christian A1 - Neher, Dieter A1 - Abate, Antonio T1 - Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells JF - Solar RRL N2 - 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. KW - cesium lead halides KW - crystal orientation KW - inorganic perovskites KW - ISOS-L-1I protocol KW - phase purity KW - photostability Y1 - 2020 VL - 4 IS - 9 PB - WILEY-VCH CY - Weinheim ER - TY - JOUR A1 - Lang, Felix A1 - Köhnen, Eike A1 - Warby, Jonathan A1 - Xu, Ke A1 - Grischek, Max A1 - Wagner, Philipp A1 - Neher, Dieter A1 - Korte, Lars A1 - Albrecht, Steve A1 - Stolterfoht, Martin T1 - Revealing fundamental efficiency limits of monolithic perovskite/silicon tandem photovoltaics through subcell characterization JF - ACS Energy Letters N2 - Perovskite/silicon tandem photovoltaics (PVs) promise to accelerate the decarbonization of our energy systems. Here, we present a thorough subcell diagnosis methodology to reveal deep insights into the practical efficiency limitations of state-of-the-art perovskite/silicon tandem PVs. Our subcell selective intensity-dependent photoluminescence (PL) and injection-dependent electroluminescence (EL) measurements allow independent assessment of pseudo-V-OC and power conversion efficiencies (PCEs) for both subcells. We reveal identical metrics from PL and EL, which implies well-aligned energy levels throughout the entire cell. Relatively large ideality factors and insufficient charge extraction, however, cause each a fill factor penalty of about 6% (absolute). Using partial device stacks, we then identify significant losses in standard perovskite subcells due to bulk and interfacial recombination. Lastly, we present strategies to minimize these losses using triple halide (CsFAPb(IBrCI)(3)) based perovskites. Our results give helpful feedback for device development and lay the foundation toward advanced perovskite/silicon tandem PVs capable of exceeding 33% PCE. Y1 - 2021 U6 - https://doi.org/10.1021/acsenergylett.1c01783 SN - 2380-8195 VL - 6 IS - 11 SP - 3982 EP - 3991 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Stolterfoht, Martin A1 - Le Corre, Vincent M. A1 - Feuerstein, Markus A1 - Caprioglio, Pietro A1 - Koster, Lambert Jan Anton A1 - Neher, Dieter T1 - Voltage-Dependent Photoluminescence and How It Correlates with the Fill Factor and Open-Circuit Voltage in Perovskite Solar Cells JF - Acs energy letters N2 - Optimizing the photoluminescence (PL) yield of a solar cell has long been recognized as a key principle to maximize the power conversion efficiency. While PL measurements are routinely applied to perovskite films and solar cells under open circuit conditions (V-OC), it remains unclear how the emission depends on the applied voltage. Here, we performed PL(V) measurements on perovskite cells with different hole transport layer thicknesses and doping concentrations, resulting in remarkably different fill factors (FFs). The results reveal that PL(V) mirrors the current-voltage (JV) characteristics in the power-generating regime, which highlights an interesting correlation between radiative and nonradiative recombination losses. In particular, high FF devices show a rapid quenching of PL(V) from open-circuit to the maximum power point. We conclude that, while the PL has to be maximized at V-OC at lower biases < V-OC the PL must be rapidly quenched as charges need to be extracted prior to recombination. Y1 - 2019 U6 - https://doi.org/10.1021/acsenergylett.9b02262 SN - 2380-8195 VL - 4 IS - 12 SP - 2887 EP - 2892 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Stolterfoht, Martin A1 - Caprioglio, Pietro A1 - Wolff, Christian Michael A1 - Marquez, Jose A. A1 - Nordmann, Joleik A1 - Zhang, Shanshan A1 - Rothhardt, Daniel A1 - Hörmann, Ulrich A1 - Amir, Yohai A1 - Redinger, Alex A1 - Kegelmann, Lukas A1 - Zu, Fengshuo A1 - Albrecht, Steve A1 - Koch, Norbert A1 - Kirchartz, Thomas A1 - Saliba, Michael A1 - Unold, Thomas A1 - Neher, Dieter T1 - The impact of energy alignment and interfacial recombination on the internal and external open-circuit voltage of perovskite solar cells JF - Energy & environmental science N2 - Charge transport layers (CTLs) are key components of diffusion controlled perovskite solar cells, however, they can induce additional non-radiative recombination pathways which limit the open circuit voltage (V-OC) of the cell. In order to realize the full thermodynamic potential of the perovskite absorber, both the electron and hole transport layer (ETL/HTL) need to be as selective as possible. By measuring the photoluminescence yield of perovskite/CTL heterojunctions, we quantify the non-radiative interfacial recombination currents in pin- and nip-type cells including high efficiency devices (21.4%). Our study comprises a wide range of commonly used CTLs, including various hole-transporting polymers, spiro-OMeTAD, metal oxides and fullerenes. We find that all studied CTLs limit the V-OC by inducing an additional non-radiative recombination current that is in most cases substantially larger than the loss in the neat perovskite and that the least-selective interface sets the upper limit for the V-OC of the device. Importantly, the V-OC equals the internal quasi-Fermi level splitting (QFLS) in the absorber layer only in high efficiency cells, while in poor performing devices, the V-OC is substantially lower than the QFLS. Using ultraviolet photoelectron spectroscopy and differential charging capacitance experiments we show that this is due to an energy level mis-alignment at the p-interface. The findings are corroborated by rigorous device simulations which outline important considerations to maximize the V-OC. This work highlights that the challenge to suppress non-radiative recombination losses in perovskite cells on their way to the radiative limit lies in proper energy level alignment and in suppression of defect recombination at the interfaces. Y1 - 2019 U6 - https://doi.org/10.1039/c9ee02020a SN - 1754-5692 SN - 1754-5706 VL - 12 IS - 9 SP - 2778 EP - 2788 PB - Royal Society of Chemistry CY - Cambridge ER -