Morphology evolution and enhanced broadband photoresponse behavior of two-dimensional Bi₂Te₃nanosheets

Bismuth telluride (Bi₂Te₃), as an emerging two-dimensional (2D) material, has attracted extensive attention from scientific researchers due to its excellent optoelectronic, thermoelectric properties and topological structure. However, the application research of Bi₂Te₃mainly focuses on thermoelectric devices, while the research on optoelectronic devices is scarce. In this work, the morphology evolution and growth mechanism of 2D Bi₂Te₃nanosheets with a thickness of 12 ± 3 nm were systematically studied by solvothermal method. Then, the Bi₂Te₃nanosheets were annealed at 350 °C for 1 h and applied to self-powered photoelectrochemical-type broadband photodetectors. Compared with the as-synthesized Bi₂Te₃photodetector, the photocurrent of the photodetector based on the annealed Bi₂Te₃is significantly enhanced, especially enhanced by 18.3 times under near-infrared light illumination. Furthermore, the performance of annealed Bi₂Te₃photodetector was systematically studied. The research results show that the photodetector not only has a broadband response from ultraviolet to near-infrared (365-850 nm) under zero bias voltage, but also obtains the highest responsivity of 6.6 mA W^-1under green light with an incident power of 10 mW cm^-2. The corresponding rise time and decay time are 17 ms and 20 ms, respectively. These findings indicate that annealed Bi₂Te₃nanosheets have great potential to be used as self-powered high-speed broadband photodetectors with high responsivity.