High-Performance Broadband Photoelectrochemical Photodetectors Based on Ultrathin Bi₂O₂S Nanosheets

Two-dimensional (2D) bismuth oxychalcogenide (Bi₂O₂X, X refers to S, Se, and Te) is one type of rising semiconductor with excellent electrical transport properties, high photoresponse, and good air stability. However, the research on 2D Bi₂O₂S is limited. In this work, ultrathin Bi₂O₂S nanosheets are synthesized by a facile and eco-friendly chemical synthesis method at room temperature. The thickness and lateral sizes are 2-4 nm and 20-40 nm, respectively. The 2D ultrathin Bi₂O₂S nanosheets have a broad absorption spectrum from ultraviolet (UV) to near-infrared (NIR). Photoelectrochemical (PEC) photodetectors based on 2D Bi₂O₂S nanosheets are fabricated by a simple drop-casting method. The 2D Bi₂O₂S-based PEC photodetectors show excellent photodetection performance with a broad photoresponse spectrum from 365 to 850 nm, a high responsivity of 13.0 mA/W, ultrafast response times of 10/45 ms, and good long-term stability at a bias voltage of 0.6 V, which are superior to most 2D material-based PEC photodetectors. Further, the 2D Bi₂O₂S PEC photodetector can function as a high-performance self-powered broadband photodetector. Moreover, the photoresponse performance can be effectively tuned by the concentration and the kind of electrolyte. Our results demonstrate that 2D Bi₂O₂S nanosheets hold great promise for application in high-performance optoelectronic devices.