Air-Stable Self-Driven UV Photodetectors on Controllable Lead-Free CsCu₂I₃ Microwire Arrays

The rapid evolution of the Internet of Things has engendered increased requirements for low-cost, self-powered UV photodetectors. Herein, high-performance self-driven UV photodetectors are fabricated by designing asymmetric metal–semiconductor–metal structures on the high-quality large-area CsCu₂I₃ microwire arrays. The asymmetrical depletion region doubles the photocurrent and response speed compared to the symmetric structure device, leading to a high responsivity of 233 mA/W to 355 nm radiation. Notably, at 0 V bias, the asymmetric device produces an open-circuit voltage of 356 mV and drives to a short-circuit current of 372 pA; meanwhile, the switch ratio (I_ph/I_dark) reaches up to 10³, indicating its excellent potential for detecting weak light. Furthermore, the device maintains stable responses throughout 10000 UV-light switch cycles, with negligible degradation even after 90-day storage in air. Our work establishes that CsCu₂I₃ is a good candidate for self-powered UV detection and thoroughly demonstrates its potential as a passive device.