High-performance photodetector based on ReS₂/WSe₂/Te dual van der Waals heterojunctions

Self-powered photodiodes based on the photovoltaic effect have garnered substantial attention, addressing the pressing need for a new generation of optoelectronic nanodevices. However, conventional junction-type self-powered photodetectors exhibit performance limitations. In this paper, we propose a high-speed phototransistor incorporating a dual van der Waals heterostructure (vdWH) of ReS₂/WSe₂/Te. The device demonstrates a low dark current level (10⁻¹⁴ A). In self-powered mode, the device exhibits exceptional optical response at 785 nm laser (10 µW), achieving a responsivity of 13.98 mA·W⁻¹, a detectivity of 1.65 × 10¹¹ Jones, and an on/off ratio of up to 10⁶. Additionally, the device displays a fast rise/fall time of 7.2/7.14 µs at 532 nm laser (10 µW). Energy band analysis and carrier transfer studies reveal that the floating heterojunction at the bottom of the dual vdWH effectively increases the photogenerated carriers in the top vdWH layer as well as reduces their recombination. This photodetector design provides a practical pathway toward the development of high-performance phototransistors.