Environmentally Friendly Cs ₃ Cu ₂ I ₅ -Based Heterostructures for Highly Stable Self-Powered Ultraviolet Photodetectors with Imaging Capability

Self-powered ultraviolet photodetectors are of great interest for next-generation optoelectronic and nanoelectronic applications. In this work, all-inorganic lead-free Cs 3 Cu 2 I 5 perovskite films were successfully fabricated via vacuum evaporation. Further optimizing the interface state between GaN and Cs 3 Cu 2 I 5 by introducing a CuI layer. As a result, a Cs 3 Cu 2 I 5 /CuI/GaN heterojunction photodetector was constructed, exhibiting strong ultraviolet sensitivity and a distinct self-powered photoresponse. The device achieves a peak responsivity of 42.9 mA/W at 344 nm, and its performance is enhanced by several orders of magnitude compared with the device without the CuI modification layer. Moreover, the device shows excellent reproducibility and long-term stability, maintaining stable operation after two months without encapsulation. This study demonstrates the potential of Cs 3 Cu 2 I 5 for short-wavelength optoelectronic devices and provides an efficient and stable architecture for self-powered UV photodetectors. In terms of applications, the device was further applied to UV imaging and enabled clear pattern reconstruction under self-powered operation.