Efficiency Potential and Loss Analysis of Inorganic CsPbI2Br Perovskite Solar Cells

Max Grischek^a^,^b, Pietro Caprioglio^c, Francisco Peña-Camargo^b, Jiahuan Zhang^a, Kari Sveinbjörnsson^a, Fenghuo Zu^d, Jarla Thiesbrummel^c, Jinzhao Li^e, Hampus Näsström^e, Hannes Hempel^f, José Antonio Márquez Prieto^f, Henry Snaith^c, Norbert Koch^d, Eva Unger^e, Thomas Unold^f, Dieter Neher^b, Martin Stolterfoht^b, Steve Albrecht^a

^aYoung Investigator Group Perovskite Tandem Solar Cells, Helmholtz-Zentrum Berlin, 12489 Berlin, Germany

^bInstitute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany

^cClarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK

^dInstitut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany

^eYoung Investigator Group Hybrid Materials Formation and Scaling, Helmholtz-Zentrum Berlin, 12489 Berlin, Germany

^fDept. Structure and Dynamics of Energy Materials, Helmholtz-Zentrum Berlin, 12489 Berlin, Germany

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Spring Meeting 2022 (NSM22)

#PeroSolarFab22. Perovskite solar cells: on the way from the lab to fab

Online, Spain, 2022 March 7th - 11th

Organizers: Yulia Galagan, Eugene Katz and Pavel Troshin

Contributed talk, Max Grischek, presentation 325
DOI: https://doi.org/10.29363/nanoge.nsm.2022.325
Publication date: 7th February 2022

Long-term operational stability is a prerequisite for the commercialization of perovskite solar cells. Inorganic perovskite solar cells exhibit a high thermal stability and efficiencies of 20.8 %, which corresponds to 72 % of the Shockley-Queisser limit for the band gap of 1.72 eV [1]. However, the reported PCE is still lower than for organic-inorganic perovskite solar cells, mainly due to lower open-circuit voltages (V_OC). The V_OC of the record inorganic perovskite solar cell with CsPbI_3-xBr_x composition and 1.72 eV band gap is 1.23 V, while organic-inorganic cells of the same band gap reach a V_OC of 1.31 V [2].

This study investigates state-of-the-art inorganic CsPbI₂Br perovskite solar cells to reveal the efficiency potential and the losses induced by each layer. This is achieved by measuring intensity-dependent photoluminescence (PL) of each layer stack. This technique enables us to construct potential JV curves, revealing not only the potential V_OC, but also the potential fill factor [3]. Based on realistic assumptions of the photocurrent, we can therefore calculate the efficiency potential of the solar cell or stack which could be reached by avoiding any transport losses.

For the present study, CsPbI₂Br solar cells in n-i-p and p-i-n configuration are fabricated using an air-annealing procedure specifically developed for this composition. The CsPbI₂Br films have an efficiency potential of 21.6 % when deposited on glass, 20.7 % on MeO-2PACz and 19.9 % on mesoporous TiO₂, suggesting a very low defect density in the CsPbI₂Br perovskite.

In the n-i-p CsPbI₂Br solar cells, losses in QFLS are caused in almost equal parts by the electron transport layer (ETL) and hole transport layer (HTL). In the p-i-n solar cells, the main part of the losses is caused by the ETL. Importantly, both configurations show a strong mismatch between the quasi Fermi level splitting (QFLS) in the perovskite layer and the measured V_OC at the contacts. The inorganic p-i-n solar cell has a QFLS-e∙V_OC mismatch of 170 meV. The organic-inorganic reference solar cell with the same band gap shows a QFLS- e∙V_OC mismatch of only 10 meV. Using ultraviolet photoelectron spectroscopy (UPS) measurements, we examine possible reasons for this striking difference and discuss potential solutions.

Overall, this study helps to identify the most promising layer stacks for inorganic n-i-p and p-i-n perovskite solar cells and reveals the contribution of each interface to the voltage and fill factor losses.

References:

[1] Gu, X.; Xiang, W.; Tian, Q.; Liu, S. Rational Surface-Defect Control via Designed Passivation for High-Efficiency Inorganic Perovskite Solar Cells. Angew. Chemie - Int. Ed. 2021, 60 (43), 23164–23170.

[2] Gharibzadeh, S.; Abdollahi Nejand, B.; Jakoby, M.; Abzieher, T.; Hauschild, D.; Moghadamzadeh, S.; Schwenzer, J. A.; Brenner, P.; Schmager, R.; Haghighirad, A. A.; Weinhardt, L.; Lemmer, U.; Richards, B. S.; Howard, I. A.; Paetzold, U. W. Record Open-Circuit Voltage Wide-Bandgap Perovskite Solar Cells Utilizing 2D/3D Perovskite Heterostructure. Adv. Energy Mater. 2019, 9 (21).

[3] Stolterfoht, M.; Grischek, M.; Caprioglio, P.; Wolff, C. M.; Gutierrez‐Partida, E.; Peña‐Camargo, F.; Rothhardt, D.; Zhang, S.; Raoufi, M.; Wolansky, J.; Abdi‐Jalebi, M.; Stranks, S. D.; Albrecht, S.; Kirchartz, T.; Neher, D. How To Quantify the Efficiency Potential of Neat Perovskite Films: Perovskite Semiconductors with an Implied Efficiency Exceeding 28%.

Acknowledgements:

M.G., S.A., and D.N. acknowledge funding from the Helmholtz Association via HI-SCORE (Helmholtz International Research School). M.G., J.Z., K.S. and S.A. acknowledge the Federal Ministry of Education and Research (BMBF) for funding of the Young Investigator Group Perovskite Tandem Solar Cells within the program “Materialforschung fuer die Energiewende” (grant no. 03SF0540).

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