Stable and Self-Powered Solar-Blind Ultraviolet Photodetectors Based on a Cs₃Cu₂I₅/β-Ga₂O₃Heterojunction Prepared by Dual-Source Vapor Codeposition

Self-powered solar-blind ultraviolet (UV) photodetectors have drawn worldwide attention in recent years because of their important applications in military and civilian areas. In this study, a dual-source vapor codeposition technique was employed, for the first time, to prepare a nontoxic copper halide Cs3Cu2I5, which was integrated with the β-Ga2O3 wafer to construct a type-II heterojunction for photodetection applications. By optimizing the annealing conditions, high-quality Cs3Cu2I5 films with dense morphology, high crystallinity, and a long carrier lifetime of 1.02 μs were acquired. Because of the high material integrity of Cs3Cu2I5 films and effective interfacial carrier transfer from Cs3Cu2I5 to β-Ga2O3, a heterojunction device demonstrates a good solar-blind UV response property and operates at zero bias. Typically, the photodetector presents a low dark current (μ1.2 pA), a high solar-blind/UVA rejection ratio (μ1.0 × 103), a relatively fast photoresponse speed (37/45 ms), and a high photo-to-dark current ratio (μ5.1 × 104) at zero bias. Moreover, even after 12-h continuous working and 2-month storage without encapsulation in ambient air, the photodetection ability of the device can almost be maintained, demonstrating outstanding air stability. Our results suggest that nontoxic Cs3Cu2I5 is able to serve as a prospective candidate for stable solar-blind UV photodetection.