Bismuth Oxychalcogenide Nanosheet: Facile Synthesis, Characterization, and Photodetector Application

New 2D bismuth oxychalcogenide nanosheets have excellent theoretical properties such as high electronic mobility and excellent oxidation resistance, which have good application prospective for optoelectronic devices. In this paper, during the synthesis process via mild hydrothermal route, ammonium bismuth citrate (C₆H₁₃BiN₂O₇·H₂O) is selected as Bi source. Both Bi₂O₂S and Bi₂O₂Se nanosheets (lateral size: over 2.0 µm, thickness: ≈ 5.0 nm) are synthesized successfully using thiourea (CH₄N₂S) as S source, and sodium selenite (Na₂O₃Se) as Se source, respectively. The as-synthesized Bi₂O₂S and Bi₂O₂Se materials have desirable nanosheet-like morphologies. After adding C₆H₁₃BiN₂O₇·H₂O, [(NH₃)₂C₆H₇O₇]^3- can intercalate between the interlayers of Bi₂O₂S or Bi₂O₂Se, limiting the growth along c-axis direction, so that 2D sheets can be obtained. Finally, the photodetectors are fabricated based on Bi₂O₂S and Bi₂O₂Se films coated by thermal spraying. The experimental results show that the maximum responsivity and detectivity of Bi₂O₂S-based photodetector are 0.059 A W^-1 and 6.77 × 10⁹ Jones, respectively. As to Bi₂O₂Se-based photodetector, the maximum responsivity and detectivity can reach 75.14 A W^-1 and 3.95 × 10¹² Jones, respectively. The mild hydrothermal synthesis using ammonium bismuth citrate as Bi source is a universal and facile method to obtain Bi₂O₂S and Bi₂O₂Se nanosheets for optoelectronic applications.