High-performance type-II BiOI/CdS heterojunction photodetector for ultraviolet imaging and optical communication

Bismuth oxyiodide (BiOI), a ternary halide oxide with a tunable bandgap and strong UV-visible light absorption, has attracted significant attention for applications in photocatalysis, solar cells, and photodetection. However, its relatively low photocurrent and sluggish photoresponse limit its practical use in high-performance photodetectors. To overcome these challenges, a BiOI/CdS heterojunction photodetector was designed and fabricated, featuring a type-II band alignment to enhance charge separation efficiency. Under ultraviolet illumination (300 nm), the device exhibited an exceptionally high on/off current ratio of 1.82×107, rapid response and recovery times of 72 μs and 244 μs, respectively, a responsivity of 1.54 × 104 A/W, an external quantum efficiency (EQE) of 6.37 × 106 %, and a specific detectivity of 4.08 × 1014 Jones. These outstanding optoelectronic characteristics highlight the great potential of the BiOI/CdS heterostructure for advanced ultraviolet (UV) imaging and optical communication systems, offering a promising route for the design of next-generation BiOI-based optoelectronic devices.