Na+-doped lead-free double perovskite Cs2AgInCl6 for broadband solar-blind UV detection

As a new generation of photonic materials, lead-free halide double perovskite materials demonstrate strong UV-light excited broadband emission that are promising for solar-blind ultraviolet (UV) light detectors. However, their practical applications are strongly limited by the low photoluminescence quantum efficiency because of the parity-forbidden nature of electronic transitions. Herein, the idea of cation alloying into lead-free halide double perovskite is proposed to mitigate the weak electronic transition and to improve the luminescence yield. By using the hydrothermal method, a series of Cs2NaxAg1-xInCl6 microcrystals were fabricated and the influences of Na-doping on the structural evolution and optical properties are investigated. Notably, the luminescence properties can be greatly improved by introducing an alloying element. By leveraging the UV-to-visible spectral conversion capability of the developed halide crystals, we fabricated a luminescent composite film by incorporating Cs2NaxAg1-xInCl6 perovskite nanocrystals into a polymethyl methacrylate matrix. Using this composite film as a spectral converter, we successfully demonstrated a solar-blind ultraviolet light detector with broadband and efficient response. Our work provides a novel solution for broadband solar-blind UV detection that could have practical implications for commercialization of metal halide based luminescent materials.