Heterovalent B-Site Co-Alloying Approach for Halide Perovskite Bandgap Engineering

Compositional engineering, which can enrich the database of prospective materials and offer new or enhanced properties, represents one of the key focal points within halide perovskite research. Compositional engineering studies often focus on A + and X – site substitutions, within the ABX 3 perovskite structure, due to the relative ease of varying these sites. However, alloying on the B site can play a more important role in generating novel properties and decreasing Pb toxicity for Pb-based systems. To date, B site substitution has primarily been confined to single-element alloying. Herein, a heterovalent co-alloying strategy for the B site of halide perovskites is proposed. Ag I Bi III and Ag I Sb III are co-alloyed into a host crystal of APbBr 3 (A = Cs and methylammonium), leading to a larger range of prospective alloying elements on the perovskite B site. Density functional theory-based first-principles calculations provide a possible rational for the red shift of the bandgap and blue shift of the photoluminescence (PL) in the alloying experiments.