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Defect compensation in formamidinium–caesium perovskites for highly efficient solar mini-modules with improved photostability

Nature Energy volume 6, pages 633–641 (2021)Cite this article

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Abstract

Formamidinium–caesium mixed-cation perovskites have shown better thermal stability than their methylammonium-containing counterparts but they suffer from photoinstability induced by iodide migration and phase segregation. Here we improve their photostability by adding slightly excessive AX (at a molar percentage of 0.25% to Pb2+ ions), where A is formamidinium or caesium and X is iodine. The excessive AX does not improve the initial solar cell efficiency. It compensates iodide vacancies and suppresses ion migration and defects generation during long-term illumination by around tenfold compared with AX-deficient devices. Consequently, generation of hole traps and phase segregation is impeded, with the former limiting solar cell efficiency after degradation. The perovskite mini-modules reached a certified stabilized efficiency of 18.6% with an aperture area of ~30 cm2, corresponding to an active area efficiency of 20.2%. The mini-module maintains 93.6% of the initial efficiency after continuous operation under 1 sun illumination for >1,000 h at 50 ± 5 °C in air.

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Fig. 1: Fabrication of FACs perovskites by blading.
Fig. 2: Excessive AX improves photostability of devices by maintaining fast photocarrier transport.
Fig. 3: FACs perovskite degradation mechanism and defect compensation by excessive AX.
Fig. 4: Excessive AX for high-performance FACs perovskite modules.

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All data generated or analysed during this study are included in the article and its Supplementary Information. Source data are provided with this paper.

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Acknowledgements

This work was supported by University of North Carolina at Chapel Hill. Part of the material is based on work supported by the Office of Naval Research under contract no. N68335-20-C-0390 through a subcontract from Perotech Inc. This work was performed, in part, at the Chapel Hill Analytical and Nanofabrication Laboratory (CHANL), a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), which is supported by the National Science Foundation (grant ECCS-1542015), as part of the National Nanotechnology Coordinated Infrastructure (NNCI).

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Authors and Affiliations

  1. Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

    Yehao Deng, Shuang Xu, Shangshang Chen, Xun Xiao, Jingjing Zhao & Jinsong Huang

  2. Perotech Inc, Chapel Hill, NC, USA

    Yehao Deng

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  1. Yehao Deng
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Contributions

J.H. and Y.D. conceived the idea. Y.D. designed the experiments, conducted most of the device fabrication and measurement, and prepared the modules for certification. Y.D. and S.X. conducted the photoluminescence studies. S.C. captured the SEM images. X.X. and J.Z. performed the XRD measurements. Y.D. and J.H. wrote the paper, and all authors reviewed the paper.

Corresponding author

Correspondence to Jinsong Huang.

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Competing interests

J.H. and Y.D. are inventors on a patent application related to this work filed by University of North Carolina Chapel Hill (US 63/060,451, filed 03 August 2020). J.H. has disclosed a significant financial interest in Perotech Inc. The other authors declare no competing interests.

Additional information

Peer review information Nature Energy thanks Jin-Wook Lee, Nam-Gyu Park and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–25.

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Supplementary Data 1

Source data for statistics in Supplementary Figs. 4, 6, 7, 8, 10, 16, 19.

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Source Data Fig. 2

Source data for statistics plot9.

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Source data for statistics plot9.

Source Data Fig. 4

Source data for statistics plot9.

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Deng, Y., Xu, S., Chen, S. et al. Defect compensation in formamidinium–caesium perovskites for highly efficient solar mini-modules with improved photostability. Nat Energy 6, 633–641 (2021). https://doi.org/10.1038/s41560-021-00831-8

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