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/TiO 2 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/TiO 2 film and TiO 2 film. Compared with the TiO 2 PD, the CuI/TiO 2 PD showed self-powered performance with an on–off ratio of 10 3 and a peak responsivity of 28 mA W –1 at 330 nm. It is worth noting that the CuI/TiO 2 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 TiO 2 film constructs a built-in field with the TiO 2 film to separate the photogenerated carriers and transport them to both sides of the CuI/TiO 2 nanostructured heterojunction, which is the main reason for the self-powered performance of the CuI/TiO 2 UVPD. These results provide a feasible means for the development of heterojunction self-powered UVPDs.