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

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 Cs2SnX6 (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, Cs2SnX6 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 Sn4+, as well as the lower formation enthalpy for Cs2SnX6. Additionally, photodetectors based on Cs2SnI6 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. The lead‐free perovskite Cs2SnX6 (X = Br, I) with a well‐defined vacancy‐ordered defect‐variant crystal structure is synthesized via a facile and efficient solution route. Ascribed to the stable chemical composition and the lower formation enthalpy, Cs2SnX6 displays excellent stability against moisture, light, and high temperature. Photodetectors based on Cs2SnX6 exhibit remarkable performance and excellent stability.