Tunable optical properties in the (110)ₚ-oriented layered halide perovskite FA₄Pb₂I₇.₅(SCN)₀.₅ by Br substitution

Organic–inorganic hybrid halide perovskites have been explored extensively for optoelectronic functional materials. Here, we report (110)p-oriented layered halide perovskite thin films with nominal compositions of FA₄Pb₂(BrₓI₁₋ₓ)₇.₅(SCN)₀.₅ (x = 0, 0.25, 0.5, 0.75, and 1). X-ray diffraction measurements and UV-visible diffuse reflectance measurements demonstrate the successful formation of a solid solution between iodide and bromide. The band gap gradually changes from 2.18 eV to 2.81 eV with increasing Br content, and PL emission of 750 nm was observed for the x = 0 film. We also report a single crystal sample of x = 1.