Visible-Blind Self-Powered\nUltraviolet Photodetector\nBased on CuI/TiO₂ Nanostructured Heterojunctions

Abstract

An\nultraviolet (UV) photodetector (PD) is an indispensable element\nin the field of optoelectronics. However, the current PDs often need\nhigh driving voltages, which hinder the continued development of the\ndevices. P–n junctions have been used in the construction of\nself-powered UVPDs. In this work, we fabricated a self-powered UVPD\nbased on the CuI/TiO₂ nanostructured film. To investigate\nthe effects of the 80 nm thick CuI film on the device performance,\nwe 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\nan on–off ratio of 10³ and a peak responsivity of\n28 mA W^–1 at 330 nm. It is worth noting that the\nCuI/TiO₂ device demonstrated a fast photo-response time\nof 35 ms and a decay time of 40 ms. The uniform CuI-nanostructured\nfilm spin-coated on the TiO₂ film constructs a built-in\nfield with the TiO₂ film to separate the photogenerated\ncarriers and transport them to both sides of the CuI/TiO₂ nanostructured heterojunction, which is the main reason for the\nself-powered performance of the CuI/TiO₂ UVPD. These results\nprovide a feasible means for the development of heterojunction self-powered\nUVPDs.