Structural, Optical, and Thermal Properties of Cs2SnI6–xBrx Mixed Perovskite Solid Solutions

Abstract

Cs2SnI6‐xBrx (x = 0–6) solid solutions have been synthesized by chemical solid solution reaction in conjunction with sintering under vacuum. The Rietveld refinements of powder X‐ray diffraction (XRD) patterns indicate that all the samples are cubic, with a symmetry of Fm3m. The lattice parameter a decreases linearly as a function of the Br content in Cs2SnI6‐xBrx. Raman spectra suggest that the new Raman peaks might derive from the short‐range ordering of I/Br anions. The UV/Vis reflection spectra reveal a nonlinear trend of energy band gap (Eg) from 1.25 eV to 3.01 eV with increasing Br content. Hence the wide range of Eg of Cs2SnI6‐xBrx solid solutions are capable to overlay almost the entire visual spectrum. Thermogravimetric analysis (TGA) results suggest that the thermal stability of Cs2SnI6‐xBrx increases gradually with increasing Br content. Cs2SnI6‐xBrx with the fine thermal stability and tunable Eg indicate high potential in the applications of solar cell devices.