Bidirectionally Regulated Ultraviolet and Visible Dual-Band Photoresponse Characteristics of Self-Powered BiOI/WO3 Photodetectors

Images captured in inadequate illumination or uneven brightness conditions are prone to suffer from loss of detail and reduced contrast. Self-powered BiOI/WO₃ heterojunction PDs with bidirectionally regulated ultraviolet (UV) and visible dual-band photoresponse characteristics can help to solve the problems. By varying the growth time of BiOI nanoflakes (NFs) on WO₃ nanorod arrays (NRs), different stoichiometric ratios and crystal and band structures of BiOI are achieved. The I⁻ ions migration inside the BiOI controlled by applying a pre-bias voltage can induce the accumulation of polarized charges at the heterojunction interface, then alter the width of the depletion region as well as the height of the interface barrier, which in turn affects the dynamics of photo-generated carriers. Upon applying a positive (negative) pre-bias, the self-powered photocurrent decreases (increases) in the UV band, whereas increases (decreases) in the visible band. Based on BiOI/WO₃ heterojunction PDs, a machine vision imaging system is designed, which enhances image contrast and detail in strong and weak light conditions. This system facilitates rapid feature extraction and recognition, advancing the development of intelligent, real-time digital machine vision systems.