Synthesis of Easily Transferred 2D Layered BiI₃ Nanoplates for Flexible Visible-Light Photodetectors

Bismuth triiodide, BiI₃, is one of the promising 2D layered materials from the family of metal halides. The unique electronic structure and properties make it an attractive material for the room-temperature gamma/X-ray detectors, high-efficiency photovoltaic absorbers, and Bi-based organic-inorganic hybrid perovskites. Other possibilities including optoelectronic devices and optical circuits are envisioned but rarely experimentally confirmed yet. Here, we report the synthesis of vertical 2D BiI₃ nanoplates using the physical vapor deposition mechanism. The obtained products were found easy to be separated and transferred to other substrates. Photodetectors employing such 2D nanoplates on polyethylene terephthalate substrate are demonstrated to be quite sensitive to red light (635 nm) with good responsivity (2.8 A W^-1), fast stable photoresponse (3/9 ms for raise/decay times), and remarkable specific detectivity (1.2 × 10¹² jones), which attest to high comparability of the assembled components with many latest 2D nanostructured light sensors. In addition, such photodetectors exhibit outstanding mechanical stability and durability under different bending strains within the theoretically affordable levels, suggesting a variety of potential applications of 2D BiI₃ for flexible devices.