Lead‐Free Halide CsAg2I3 with 1D Electronic Structure and High Stability for Ultraviolet Photodetector

Abstract Lead halide perovskites have gained extensive attention in the photodetectors (PDs) field, but the problems of intrinsic toxicity and poor stability still hamper their practical applications. Furthermore, ultraviolet (UV) PDs have rarely been explored due to challenges, including the lack of suitable materials and the costly and complicated fabrication processes. In order to solve the above problems, herein it is reported a novel all‐inorganic lead‐free halide CsAg 2 I 3 single crystal (SC) with pure phase and high quality. This CsAg 2 I 3 SC shows ultra‐stable crystal structure, steady chemical properties, and good optical properties, and it can be stable up to 893 K. Its 1D crystal structure and soft crystal lattice support the formation of self‐trapped excitons, leading to a broadband emission at 610 nm with a large Stokes shift of 315 nm (2.23 eV). The strong absorption for UV light combined with direct bandgap, large Stokes shift, and ultra‐high stability promises an environment‐friendly, low‐cost, and high‐performance UV PD based on the 1D all‐inorganic silver (I) halides.