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B‑Site Metal Cation Exchange in Halide Perovskites

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journal contribution
posted on 02.05.2017, 14:48 by Giles E. Eperon, David S. Ginger
We demonstrate exchange of the B-site metal cation in hybrid organic–inorganic halide perovskite thin films. We exchange tin in formamidinium tin triiodide (CH­(NH2)2SnI3, or FASnI3) with lead at controllable levels, forming CH­(NH2)2SnxPb1–xI3 alloys with partial substitution and fully converting the film to CH­(NH2)2PbI3 with a large excess of Pb2+. We observe no evidence for phase segregation or bilayered films, indicating that conversion is uniform throughout the film. This facile technique provides a new way to control composition independently from the crystallization processes, allowing formation of the black phase of CH­(NH2)2PbI3 at much lower temperatures than those previously reported while also opening the door to new morphology–composition combinations. The surprising observation that the B-site metal cations are mobile may also provide insight into the nature of transient processes in these materials, suggesting that they may be involved in ionic conduction, and will be a critical consideration for long-term stability.