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

Abstract

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.