Effect of tin (II and IV) iodide doping on organic–inorganic bismuth (III) iodide perovskite

Herein, effects of doping methylamine bismuth iodide (MBI, (CH₃NH₃)₃Bi₂I₉), a lead-free perovskite halide material, with bismuth (III) iodide with the molar equivalent of tin (II or IV) iodides are investigated. The doping changes optical properties, surface chemical states, and energy band structure of MBI. SnI₄ doping shifts the Fermi level toward the valence band, while SnI₂ doping shifts it toward the conduction band. Our result demonstrates that Fermi level of a halide perovskite can be modified by doping.