Lead-Free Double Perovskite Cs SnX : 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 Cs SnX (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 SnX 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 , as well as the lower formation enthalpy for Cs SnX . Additionally, photodetectors based on Cs SnI 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.