Visible-Blind Self-Powered Ultraviolet Photodetector Based on CuI/TiO₂ Nanostructured Heterojunctions

An ultraviolet (UV) photodetector (PD) is an indispensable element in the field of optoelectronics. However, the current PDs often need high driving voltages, which hinder the continued development of the devices. P–n junctions have been used in the construction of self-powered UVPDs. In this work, we fabricated a self-powered UVPD based on the CuI/TiO2 nanostructured film. To investigate the effects of the 80 nm thick CuI film on the device performance, we compared the performance of UVPDs based on the CuI/TiO2 film and TiO2 film. Compared with the TiO2 PD, the CuI/TiO2 PD showed self-powered performance with an on–off ratio of 103 and a peak responsivity of 28 mA W–1 at 330 nm. It is worth noting that the CuI/TiO2 device demonstrated a fast photo-response time of 35 ms and a decay time of 40 ms. The uniform CuI-nanostructured film spin-coated on the TiO2 film constructs a built-in field with the TiO2 film to separate the photogenerated carriers and transport them to both sides of the CuI/TiO2 nanostructured heterojunction, which is the main reason for the self-powered performance of the CuI/TiO2 UVPD. These results provide a feasible means for the development of heterojunction self-powered UVPDs.