Realizing Enhanced Self-Powered Broadband Photodetection via Type III Band-Aligned WSe₂/SnSe₂ van der Waals Heterostructure with Asymmetric Contacts

In recent years, two-dimensional (2D) materials, owing to their exceptional optical and electrical properties, unique structural characteristics, and superior photoelectric performance, have been extensively utilized in the development of self-powered photodetectors. Bandgap engineering in graphene-based photodetectors, coupled with atomically thin charge extraction channels in vertical architectures, boosts carrier transport and lowers potential barriers, while type III heterojunctions further enhance performance via band tunneling, interlayer transitions, and efficient photocarrier separation. Here, we investigate the performance of a Gr/WSe2/SnSe2-based type III heterojunction self-powered photodetector. A device exhibiting both photodetector and Zener diode properties is fabricated. Through structural morphology characterization and electrical testing, the device demonstrates a responsivity of 258.5 mA/W and an optical switching ratio of 4.6 × 104, enabling effective broadband spectral detection. The asymmetric contact design achieved by graphene integration enhances the photodetection performance by approximately 1 order of magnitude. These findings offer a straightforward and promising approach for fabricating high-performance WSe2/SnSe2 self-powered broadband photodetectors.