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Ammonium cations with high pKa in perovskite solar cells for improved high-temperature photostability

Nature Energy volume 8, pages 1229–1239 (2023)Cite this article

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Abstract

Phenethylammonium (PEA+) and butylammonium (BA+) are widely used in three-dimensional (3D) perovskites to form two-dimensional perovskites at film surfaces and grain boundaries (GBs) for defect passivation and performance enhancement. Here we show that these cations are unstable with 3D formamidinium (FA+)-containing perovskites under high-temperature light soaking. PEA+ and BA+ are found to deprotonate to amines, which then react with FA+ to produce (phenethylamino)methaniminium (PEAMA+) and (butylamino)methaniminium (BAMA+), respectively, severely limiting device high-temperature photostability. Removing these cations greatly improves the photostability but compromises device efficiency by leaving non-fully passivated surfaces and GBs. Ammonium cations with a high acid dissociation constant (pKa), including PEAMA+ (pKa = 12.0) and BAMA+ (pKa = 12.0), can replace PEA+ or BA+ for passivation and are stable with FA-based perovskites due to their resistance to further deprotonation. P–i–n structure solar cells with PEAMA+ additive maintained over 90% of their initial efficiency after light soaking at open circuit and 90 °C for 1,500 hours.

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Fig. 1: Temperature-dependent photostability of FA0.9Cs0.1PbI3-perovskites with PEA+ additives.
Fig. 2: Phase changes in FACs-perovskite films with and without PEA+ under high-temperature light soaking.
Fig. 3: Chemical reactions in PEA+/FACsPbI3 films.
Fig. 4: Passivation of PEAMA+ cations.
Fig. 5: Device performance.

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The main data supporting the findings of this study are available within the published article and its Supplementary Information. Source data are provided with this paper.

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Acknowledgements

This work was mainly supported by the Solar Energy Technologies office within the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, under award number DE-EE0009520. The chemical synthesis and related charaterization were supported as part of the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center funded by the Office of Basic Energy Sciences, Office of Science within the US DOE. The University of California San Diego (UCSD) portion of the work was supported mainly by the Solar Energy Technologies office within the US DOE, Office of Energy Efficiency and Renewable Energy, under award number DE-EE0009527. The EBIC work was performed at the San Diego Nanotechnology Infrastructure of UCSD, an National Science Foundation-supported National Nanotechnology Coordinated Infrastructure site (ECCS-1542148). The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

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Author notes

  1. These authors contributed equally: Mengru Wang, Zhifang Shi.

Authors and Affiliations

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

    Mengru Wang, Zhifang Shi, Chengbin Fei, Guang Yang & Jinsong Huang

  2. Chemical Engineering Program, Department of NanoEngineering, University of California San Diego, La Jolla, CA, USA

    Zhewen J. D. Deng & David P. Fenning

  3. Department of NanoEngineering, University of California San Diego, La Jolla, CA, USA

    Sean P. Dunfield & David P. Fenning

  4. Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA, USA

    David P. Fenning

  5. Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

    Jinsong Huang

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Contributions

M.W. fabricated perovskite films and perovskite solar cells and conducted SEM, powder XRD, tDOS, mobile ion concentration and device stability measurements. Z.S. developed the empirical criterion and carried out organic systhesis, NMR, MS and SC-XRD measurements. Z.J.D.D. conducted the EBIC measurement and Monte Carlo simulation under the supervision of S.P.D. and D.P.F. C.F. conducted the PL and TRPL measurements. G.Y. performed TPV measurements. M.W, Z.S. and J.H. analysed data and wrote the paper, and all authors reviewed the paper.

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Correspondence to Jinsong Huang.

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Nature Energy thanks Shuping Pang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–15, Tables 1–3 and crystallographic information file (CIF).

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Supplementary Data 1

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Wang, M., Shi, Z., Fei, C. et al. Ammonium cations with high pKa in perovskite solar cells for improved high-temperature photostability. Nat Energy 8, 1229–1239 (2023). https://doi.org/10.1038/s41560-023-01362-0

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