An Emerging Lead-Free Double-Perovskite Cs2AgFeCl6:In Single Crystal

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 Cs 2 AgFeCl 6 double perovskite is developed. Its crystallographic structure and band structure are demonstrated to be capable of tuning by means of In 3+ incorporation. The as-prepared Cs 2 AgIn x Fe 1− x Cl 6 (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.