Ultrasensitive MoS ₂ /Cu@CuO Hybrid Heterojunction Photodetector

Ultrasensitive photodetectors with high responsivity, rapid response speed, and low dark current are in urgent demand for a wide range of applications. The coupling between plasmonic metals and heterojunctions can enhance light absorption capabilities and facilitate hot electrons injection. However, recent research on plasmonic heterojunction devices has primarily focused on enhancing the local electromagnetic field, while the practical use of hot electrons remains limited. This is due to the formation of defects when metal nanoparticles (NPs) are integrated onto the surface of heterojunctions. Energetic hot electrons and photogenerated carriers are trapped by defect states, resulting in prolonged carrier lifetimes. The excited-state carriers cannot be effectively utilized, which reduces the photoelectric conversion efficiency of the devices. In this study, we propose a Cu@CuO core–shell plasmonic structure designed for ultrasensitive photodetection. The presence of the CuO layer effectively reduces defects and establishes a Type-II band alignment for the device, thereby enhancing hot electrons injection efficiency and charge transfer. The MoS2/Cu@CuO photodetector exhibits a high responsivity (633 A/W) without sacrificing the response speed (28 ns). The core–shell architecture of metal NPs provides a viable strategy for further development of ultrasensitive photodetectors utilizing hot electrons injection.