High-performance self-driven ultraviolet-visible photodetector based on type-II WS2/ReSe2 van der Waals heterostructure

Van der Waals (vdWs) heterojunctions constructed by varied two-dimensional materials provide a broader platform over traditional semiconductors to fabricate high-performance optoelectronic devices due to their superior optoelectronic properties. This paper demonstrates a photodetector based on WS2/ReSe2 vdWs heterostructure with photovoltaic effect. The ultraviolet photoelectron spectroscopy (UPS) confirms a type-II band alignment of the p-n junction with a conduction band offset of approximately 0.1 eV and a valence band offset of 0.78 eV. The photoresponse characteristics indicate that the device operates in photovoltaic mode under 350 nm illumination and photoconductive mode at 638 nm, respectively. Under 350 nm illumination, this photovoltaic device exhibits the extraordinary photoresponsivity of 2.78 mA/W and the specific detectivity of 1.05 × 1010 Jones in self-powered mode, and the corresponding values are 1.35 A/W and 5.88 × 1011 Jones under external bias, indicating synergistic development of the photoresponsivity and detection. In contrast, the photodetector shows ultrafast rise/decay times of 4/5 µs at 350 nm and a fast response speed of 50/55 µs at 638 nm, which is significantly rapider than most self-driven photodetectors currently published. Therefore, this work provides an ideal platform for the formation of high-performance photovoltaic device based on WS2/ReSe2 vdWs heterojunctions.