Construction of Bi₂O₂Se/Bi₂Se₃ Van Der Waals Heterostructures for Self-Powered and Broadband Photodetectors

Due to its superior carrier mobility and high air stability, the emerging two-dimensional (2D) layered bismuth oxyselenide (Bi₂O₂Se) nanosheets have attracted extensive attention, showing great potential for applications in the electronic and optoelectronic fields. However, a high mobility easily leads to a high dark current, seriously restricting optoelectronic applications, especially in the field of photodetectors. In this paper, we report a high-quality Van der Waals (vdWs) Bi₂O₂Se/Bi₂Se₃ heterostructure on a fluorophlogopite substrate, exhibiting excellent photodiode characteristics. By means of the effective separation of photogenerated electrons and holes by a junction barrier at the interface, the current on/off ratio is up to about 3 × 10³ under 532 nm laser illumination with zero bias. In addition, the photodetector not only achieves a fast response speed of 41 ms but also has a broadband photoresponse from 532 to 1450 nm (visible–NIR). Additionally, the responsivity can reach 0.29 A/W, and the external quantum efficiency exceeds 69% when the device operates in the reverse bias condition. The results indicate that the Bi₂O₂Se/Bi₂Se₃ vdWs heterostructure has great potential for self-powered, broadband, and fast photodetection applications.