Stable and Self-Powered Solar-Blind Ultraviolet Photodetectors Based on a Cs₃Cu₂I₅/β-Ga₂O₃ Heterojunction Prepared by...

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 (∼1.2 pA), a high solar-blind/UVA rejection ratio (∼1.0 × 10³), a relatively fast photoresponse speed (37/45 ms), and a high photo-to-dark current ratio (∼5.1 × 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.