Ultrahigh-Performance BiI₃/CdSe Heterojunction Photodetectors With Broadband Response

Bismuth triiodide (BiI₃) is a promising 2D metal halide for gamma/X-ray detection, photovoltaics, and hybrid devices. In this work, two-dimensional BiI₃ nanosheets grown on vertical substrates were successfully prepared by physical vapor deposition. After that, a BiI₃/CdSe heterojunction photodetector was constructed by a dry transfer process. It not only realized a broadband response in the visible range of 400-800 nm but also has excellent performance, including responsivity of up to 4.95 × 10³ A/W, a switching ratio of 0.97 × 10⁶, a response speed of 140/200 μs (rise/decay time), an external quantum efficiency of 1.45 × 10⁶%, and a specific detectivity of 1.25 × 10¹⁴ Jones. The photodetection mechanism was explored by photocurrent scanning imaging and energy band analysis. Imaging measurements confirmed its imaging capability with high resolution and high contrast. This study demonstrates the potential application of BiI₃ materials in optoelectronic devices and provides new ideas for the development of a new generation of high-performance photodetectors.