LAUSR

The recently emerged hybrid lead halide perovskites demonstrate low‐cost fabrication and noteworthy performance, but they have intrinsically unstable properties and contain toxic Pb in a soluble form. Herein, a thus far unreported highly stable lead‐free Cs2AgFeCl6 double perovskite is developed. Its crystallographic structure and band structure are demonstrated to be capable of tuning by means of In3+ incorporation. The as‐prepared Cs2AgInxFe1−xCl6 (0 ≤ x ≤ 1) perovskite single crystals display a broadband absorbance in the range of 450–800 nm, which further enables a remarkable enhancement of photoluminescence quantum yields by a factor of ≈167. Equally important, the incorporation of In atoms is experimentally and theoretically shown to improve the carriers transport ability, which is associated with the substitution of Fe‐3d state by In‐5s state in the energy range between 1.5 and 2.5 eV that dominates the conductive process, and thereafter may benefit the potential applications in photoelectronic and photovoltaic devices.