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Direct Observation of Cation-Exchange in Liquid-to-Solid Phase Transformation in FA1−xMAxPbI3 Based Perovskite Solar Cells

Abstract

Mixed-organic-cation FA1-xMAxPbI3 perovskites are currently attracting intensive attention for their high photovoltaic performance. However, FA1-xMAxPbI3 usually has undesired non-perovskite phase leading to a compromised efficiency, and a facile strategy to achieve pure-phase FA1-xMAxPbI3 is rarely reported. Here, we demonstrate a facile approach to form δ-phase free FA1-xMAxPbI3 using non-stoichiometric precursor solution. It is found that a small amount of excessive methylammonium iodide (MAI) added in the precursor solution has a profound effect on perovskite crystallization during the liquid-to-solid phase transformation. Using an in-situ photoluminescence spectroscopy measurement, it is found that the excessive MAI can promote the formation of FA1-xMAxPbI3 and facilitate the cation-exchange between organic FA+ and MA+ during the film formation. Based on the optimized pure-phase FA1-xMAxPbI3, the perovskite solar cells exhibit an encouraging power conversion efficiency (PCE) of 17.40%. This study demonstrates a facile method to achieve high performance FA dominating mixed-organic-cation perovskite devices while providing insight into the ion-exchange process during perovskite crystallization.

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Publication details

The article was received on 17 Feb 2018, accepted on 10 Apr 2018 and first published on 11 Apr 2018


Article type: Paper
DOI: 10.1039/C8TA01642A
Citation: J. Mater. Chem. A, 2018, Accepted Manuscript
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    Direct Observation of Cation-Exchange in Liquid-to-Solid Phase Transformation in FA1−xMAxPbI3 Based Perovskite Solar Cells

    Y. Xie, B. Yu, C. Ma, X. Xu, Y. Cheng, S. Yuan, Z. Wang, H. T. Chandran, C. Lee, L. Liao and S. W. TSANG, J. Mater. Chem. A, 2018, Accepted Manuscript , DOI: 10.1039/C8TA01642A

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