@misc{KirchartzMarquezStolterfohtetal.2020, author = {Kirchartz, Thomas and M{\´a}rquez, Jos{\´e} A. and Stolterfoht, Martin and Unold, Thomas}, title = {Photoluminescence-based characterization of halide perovskites for photovoltaics}, 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 = {26}, issn = {1866-8372}, doi = {10.25932/publishup-51970}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-519702}, pages = {23}, year = {2020}, abstract = {Photoluminescence spectroscopy is a widely applied characterization technique for semiconductor materials in general and halide perovskite solar cell materials in particular. It can give direct information on the recombination kinetics and processes as well as the internal electrochemical potential of free charge carriers in single semiconductor layers, layer stacks with transport layers, and complete solar cells. The correct evaluation and interpretation of photoluminescence requires the consideration of proper excitation conditions, calibration and application of the appropriate approximations to the rather complex theory, which includes radiative recombination, non-radiative recombination, interface recombination, charge transfer, and photon recycling. In this article, an overview is given of the theory and application to specific halide perovskite compositions, illustrating the variables that should be considered when applying photoluminescence analysis in these materials.}, language = {en} } @misc{KrueckemeierRauStolterfohtetal.2019, author = {Kr{\"u}ckemeier, Lisa and Rau, Uwe and Stolterfoht, Martin and Kirchartz, Thomas}, title = {How to report record open-circuit voltages in 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 = {1}, issn = {1866-8372}, doi = {10.25932/publishup-52528}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-525289}, pages = {13}, year = {2019}, abstract = {Open-circuit voltages of lead-halide perovskite solar cells are improving rapidly and are approaching the thermodynamic limit. Since many different perovskite compositions with different bandgap energies are actively being investigated, it is not straightforward to compare the open-circuit voltages between these devices as long as a consistent method of referencing is missing. For the purpose of comparing open-circuit voltages and identifying outstanding values, it is imperative to use a unique, generally accepted way of calculating the thermodynamic limit, which is currently not the case. Here a meta-analysis of methods to determine the bandgap and a radiative limit for open-circuit voltage is presented. The differences between the methods are analyzed and an easily applicable approach based on the solar cell quantum efficiency as a general reference is proposed.}, language = {en} } @misc{PisoniStolterfohtLockingeretal.2019, author = {Pisoni, Stefano and Stolterfoht, Martin and Lockinger, Johannes and Moser, Thierry and Jiang, Yan and Caprioglio, Pietro and Neher, Dieter and Buecheler, Stephan and Tiwari, Ayodhya N.}, title = {On the origin of open-circuit voltage losses in flexible n-i-p perovskite solar cells}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1110}, issn = {1866-8372}, doi = {10.25932/publishup-45961}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-459617}, pages = {12}, year = {2019}, abstract = {The possibility to manufacture perovskite solar cells (PSCs) at low temperatures paves the way to flexible and lightweight photovoltaic (PV) devices manufactured via high-throughput roll-to-roll processes. In order to achieve higher power conversion efficiencies, it is necessary to approach the radiative limit via suppression of non-radiative recombination losses. Herein, we performed a systematic voltage loss analysis for a typical low-temperature processed, flexible PSC in n-i-p configuration using vacuum deposited C-60 as electron transport layer (ETL) and two-step hybrid vacuum-solution deposition for CH3NH3PbI3 perovskite absorber. We identified the ETL/absorber interface as a bottleneck in relation to non-radiative recombination losses, the quasi-Fermi level splitting (QFLS) decreases from similar to 1.23 eV for the bare absorber, just similar to 90 meV below the radiative limit, to similar to 1.10 eV when C-60 is used as ETL. To effectively mitigate these voltage losses, we investigated different interfacial modifications via vacuum deposited interlayers (BCP, B4PyMPM, 3TPYMB, and LiF). An improvement in QFLS of similar to 30-40 meV is observed after interlayer deposition and confirmed by comparable improvements in the open-circuit voltage after implementation of these interfacial modifications in flexible PSCs. Further investigations on absorber/hole transport layer (HTL) interface point out the detrimental role of dopants in Spiro-OMeTAD film (widely employed HTL in the community) as recombination centers upon oxidation and light exposure. [GRAPHICS] .}, language = {en} } @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} } @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} } @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} } @misc{YeZhangWarbyetal.2022, author = {Ye, Fangyuan and Zhang, Shuo and Warby, Jonathan and Wu, Jiawei and Gutierrez-Partida, Emilio and Lang, Felix and Shah, Sahil and Saglamkaya, Elifnaz and Sun, Bowen and Zu, Fengshuo and Shoaee, Safa and Wang, Haifeng and Stiller, Burkhard and Neher, Dieter and Zhu, Wei-Hong and Stolterfoht, Martin and Wu, Yongzhen}, title = {Overcoming C₆₀-induced interfacial recombination in inverted perovskite solar cells by electron-transporting carborane}, 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 = {1317}, issn = {1866-8372}, doi = {10.25932/publishup-58770}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-587705}, pages = {12}, year = {2022}, abstract = {Inverted perovskite solar cells still suffer from significant non-radiative recombination losses at the perovskite surface and across the perovskite/C₆₀ interface, limiting the future development of perovskite-based single- and multi-junction photovoltaics. Therefore, more effective inter- or transport layers are urgently required. To tackle these recombination losses, we introduce ortho-carborane as an interlayer material that has a spherical molecular structure and a three-dimensional aromaticity. Based on a variety of experimental techniques, we show that ortho-carborane decorated with phenylamino groups effectively passivates the perovskite surface and essentially eliminates the non-radiative recombination loss across the perovskite/C₆₀ interface with high thermal stability. We further demonstrate the potential of carborane as an electron transport material, facilitating electron extraction while blocking holes from the interface. The resulting inverted perovskite solar cells deliver a power conversion efficiency of over 23\% with a low non-radiative voltage loss of 110 mV, and retain >97\% of the initial efficiency after 400 h of maximum power point tracking. Overall, the designed carborane based interlayer simultaneously enables passivation, electron-transport and hole-blocking and paves the way toward more efficient and stable perovskite solar cells.}, language = {en} }