Cs2AgSbI6 Nanocrystals: a New Air-Stable Iodide Double-Perovskite (Elpasolite) Semiconductor

Three-dimensional (3D) iodide double perovskites (elpasolites) are extremely rare due to inherent instability issues. Here, we report the discovery of an air-stable iodide elpasolite semiconductor in the form of nanocrystals with the composition Cs2AgSbI6, synthesized via halide exchange from Cs2AgSbBr6 nanocrystals. This composition, previously considered thermodynamically unstable based on computational predictions, shows a ∼1.8 eV optical gap with near-infrared photoluminescence. The nanocrystals are stable in air up to at least 140 °C. As one of only a few known examples of intermediate-bandgap 3D iodide double perovskites, Cs2AgSbI6 represents a promising platform for further development of this family of materials as well as for fundamental and optoelectronic investigations.