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Research Paper

Applied Science and Convergence Technology 2024; 33(1): 23-26

Published online January 30, 2024


Copyright © The Korean Vacuum Society.

Effect of δ-CsPbI3 Phase Separation in CsxFA1−xPbI3 under Ambient Conditions

Muntae Hwang , Jaewon Oh , Hyunbok Lee , and Mee-Yi Ryu

kangwon national universityDepartment of Physics and Institute of Quantum Convergence Technology, Kangwon National University, Chuncheon 24341, Republic of Korea

Correspondence to:myryu@kangwon.ac.kr

These authors contributed equally to this work.

Received: December 13, 2023; Accepted: January 5, 2024

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc-nd/4.0/) which permits non-commercial use, distribution and reproduction in any medium without alteration, provided that the original work is properly cited.


Formamidinium-based metal halide perovskites (FAPbI3) have gained prominence as materials for high-efficiency solar cells owing to their superior optoelectronic properties compared to those of traditional methylammonium-based perovskites. However, it is difficult to maintain the photo-active α-phase of FAPbI3 owing to the structural instability at room temperature. Although this issue can be addressed by partially substituting cesium (Cs), most reported CsFAPbI3 perovskites are produced in inert environments because of their low stability under ambient conditions. In this study, ethyl acetate, which protects the perovskite wet film from moisture during synthesis, was used as an antisolvent to optimize the Cs concentration in CsxFA1−xPbI3 under ambient conditions. Despite the formation of δ-CsPbI3 with increasing Cs concentration, the carrier lifetime was enhanced, resulting in improved power conversion efficiency. Highest reproducibility of solar cell was observed at a Cs concentration of 22 %.

Keywords: Cesium, Formamidinium, Mixed-cation, Perovskite, Photovoltaic

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