Lead‐Free Double Perovskite Cs2SnX6: Facile Solution Synthesis and Excellent Stability

Abstract Long‐term instability and possible lead contamination are the two main issues limiting the widespread application of organic–inorganic lead halide perovskites. Here a facile and efficient solution‐phase method is demonstrated to synthesize lead‐free Cs 2 SnX 6 (X = Br, I) with a well‐defined crystal structure, long‐term stability, and high yield. Based on the systematic experimental data and first‐principle simulation results, Cs 2 SnX 6 displays excellent stability against moisture, light, and high temperature, which can be ascribed to the unique vacancy‐ordered defect‐variant structure, stable chemical compositions with Sn 4+ , as well as the lower formation enthalpy for Cs 2 SnX 6 . Additionally, photodetectors based on Cs 2 SnI 6 are also fabricated, which show excellent performance and stability. This study provides very useful insights into the development of lead‐free double perovskites with high stability.