Novel UV–Visible Photodetector in Photovoltaic Mode with Fast Response and Ultrahigh Photosensitivity Employing Se/TiO₂ Nanotubes Heterojunction

Abstract

A feasible strategy for hybrid photodetector by integrating an array of self‐ordered TiO 2 nanotubes (NTs) and selenium is demonstrated to break the compromise between the responsivity and response speed. Novel heterojunction between the TiO 2 NTs and Se in combination with the surface trap states at TiO 2 help regulate the electron transport and facilitate the separation of photogenerated electron–hole pairs under photovoltaic mode (at zero bias), leading to a high responsivity of ≈100 mA W −1 at 620 nm light illumination and the ultrashort rise/decay time (1.4/7.8 ms). The implanting of intrinsic p‐type Se into TiO 2 NTs broadens the detection range to UV–visible (280–700 nm) with a large detectivity of over 10 12 Jones and a high linear dynamic range of over 80 dB. In addition, a maximum photocurrent of ≈10 7 A is achieved at 450 nm light illumination and an ultrahigh photosensitivity (on/off ratio up to 10 4 ) under zero bias upon UV and visible light illumination is readily achieved. The concept of employing novel heterojunction geometry holds great potential to pave a new way to realize high performance and energy‐efficient optoelectronic devices for practical applications.