B-Site Metal Cation Exchange in Halide Perovskites

High Resolution Image Download MS PowerPoint Slide 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(NH 2 ) 2 SnI 3, or FASnI 3 ) with lead at controllable levels, forming CH(NH 2 ) 2 Sn x Pb 1– x I 3 alloys with partial substitution and fully converting the film to CH(NH 2 ) 2 PbI 3 with a large excess of Pb 2+ . 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(NH 2 ) 2 PbI 3 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.