Lattice and Bandgap Modulation in Metal Halide Perovskites by B‐Site Ions Substitution

Abstract Metal halide perovskites have attracted much attention due to their properties and wide applications in optoelectronic devices. B‐site ion substitution, especially heterovalency substitution, is proven to be one of the practical approaches to modulate lattice structure and improve physicochemical properties. Here, lattice and bandgap modulation in all‐inorganic perovskites CsPbX 3 are achieved by substituting Pb 2+ with Bi 3+ . A series of CsPb 1‐ x Bi x Br 3 (0 ≤ x ≤ 1) microplates with the x values precisely tuned are prepared by a chemical vapor deposition (CVD) method. The lattice structure varies from single crystal CsPbBr 3 with a cubic structure to the single crystal Cs 3 Bi 2 Br 9 with a hexagonal structure. Correspondingly, three photoluminescence (PL) bands gradually emerge during the substituting: green, blue, and broad red‐to‐near‐infrared emission. From micro‐area photoluminescence spectra as a function of excitation power and temperature, combined with time‐resolved PL characterization, the emission bands are confirmed from band‐edge and self‐trapped excitons (STEs) emission. From density functional theory (DFT) calculations, the STE emission in CsPb 0.9 Bi 0.1 Br 3 and CsPb 0.1 Bi 0.9 Br 3 is highly related to a combined defect contributed by bromide vacancy and the substitution of B‐site ions. This study paves a new way for expanding the spectral range of perovskite emitters and even preparing white light‐emitting devices.