A Processing Route to Chalcogenide Perovskites Alloys with Tunable Band Gap via Anion Exchange

Abstract The synthesis of BaZr(S,Se)₃ chalcogenide perovskite alloys is demonstrated by selenization of BaZrS₃ thin films. The anion‐exchange process produces films with tunable composition and band gap without changing the orthorhombic perovskite crystal structure or the film microstructure. The direct band gap is tunable between 1.5 and 1.9 eV. The alloy films made in this way feature one‐hundred‐times stronger photoconductive response and a lower density of extended defects, compared to alloy films made by direct growth. The perovskite structure is stable in high‐selenium‐content thin films with and without epitaxy. The manufacturing‐compatible process of selenization in H₂Se gas may spur the development of chalcogenide perovskite solar cell technology.