Vapor-Deposited Cs₂AgBiCl₆ Double Perovskite Films toward Highly Selective and Stable Ultraviolet Photodetector

Double perovskites have shown great potentials in addressing the toxicity and instability issues of lead halide perovskites toward practical applications. However, fabrication of high-quality double perovskite thin films has remained challenging. Here, sequential vapor deposition is used to fabricate high-quality Cs₂AgBiCl₆ perovskite films with balanced stoichiometry, superior morphology, and highly oriented crystallinity, with an indirect bandgap of 2.41 eV. Using a diode structure, self-powered Cs₂AgBiCl₆ ultraviolet (UV) photodetectors are demonstrated with high selectivity centered at 370 nm, with low dark current density (≈10^-7 mA cm^-2), high photoresponsivity (≈10 mA W^-1), and detectivity (≈10¹² Jones). Its detectivity is among the highest in all double-perovskite-based photodetectors reported to date and surpassing the performance of other perovskite photodetectors as well as metal oxide in the UV range. The devices also show excellent environmental and irradiation stability comparable to state-of-the-art UV detectors. The findings help pave the way toward application of double perovskites in optoelectronic devices.