Atomically Thin Oxyhalide Solar‐Blind Photodetectors

2D wide‐bandgap semiconductors demonstrate great potential in fabricating solar‐blind ultraviolet (SBUV) photodetectors. However, the low responsivity of 2D solar‐blind photodetectors still limits their practical applications. Here, high‐responsivity solar‐blind photodetectors are achieved based on 2D bismuth oxychloride (BiOCl) flakes. The 2D BiOCl photodetectors exhibit a responsivity up to 35.7 A W−1 and a specific detectivity of 2.2 × 1010 Jones under 250 nm illumination with 17.8 µW cm−2 power density. In particular, the enhanced photodetective performances are demonstrated in BiOCl photodetectors with increasing ambient temperature. Surprisingly, their responsivity can reach 2060 A W−1 at 450 K under solar‐blind light illumination, maybe owing to the formation of defective BiOCl grains evidenced by in situ transmission electron microscopy. The high responsivity throughout the solar‐blind range indicates that 2D BiOCl is a promising candidate for SBUV detection. This work demonstrates the synthesis of large‐size atomically thin BiOCl flakes via salt‐assisted chemical vapor deposition. The BiOCl flake based solar‐blind UV photodetectors exhibit a responsivity up to 35.7 A W−1 and detectivity of 2.2 × 1010 Jones at 250 nm, and also possess high responsivity across the solar‐blind range.