Formamidinium lead triiodide (FAPbI3) perovskite solar cells (PSCs) are mainly fabricated by sequentially coating lead iodide and formamidinium iodide, or by coating a solution in which all components are dissolved in one solvent (one-pot process). The PSCs produced by both processes exhibited similar efficiencies; however, their long-term stabilities were notably different. We concluded that the major reason for this behaviour is the stabilization of the α-FAPbI3 phase by isopropylammonium cations produced by the chemical reaction between isopropyl alcohol, used as solvent, and methylammonium chloride, added during the process. On this basis, we fabricated PSCs by adding isopropylammonium chloride to the perovskite precursor solution for the one-pot process and achieved a certified power conversion efficiency of 23.9%. Long-term operational current density–voltage measurements (one sweep every 84 min under 1-Sun irradiation in nitrogen atmosphere) showed that the as-fabricated device with an initial efficiency of approximately 20% recorded an efficiency of about 23% after 1,000 h that gradually degraded to about 22% after an additional 1,000 h.
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This work was supported by the Basic Science Research Program (NRF-2018R1A3B1052820) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (MSIP). B.-w.P. acknowledges financial support from the Creative-Challenge Research Program (NRF-2020R1I1A1A01063868). T.J.S. acknowledges financial support under CAP-18-05-KAERI. This work was also supported by a brand project (1.210037.01) of UNIST. Experiments at the PLS-II 6D and 10A2 beamlines were supported in part by MSIT and POSTECH. We thank S. Y. Lee, J. H. Park, I. Choi, G. A. Lee, J. H. Lee, H. J. Mun, D. H. Lee and S.-P. Han of UCRF for their support in powder XRD, FIB sampling, HR-TEM, FESEM, GI-WAXD, ToF-SIMS and NMR analyses.
The authors declare no competing interests.
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Park, Bw., Kwon, H.W., Lee, Y. et al. Stabilization of formamidinium lead triiodide α-phase with isopropylammonium chloride for perovskite solar cells. Nat Energy 6, 419–428 (2021). https://doi.org/10.1038/s41560-021-00802-z