▎ 摘　　要

Self-powered photodetectors can convert light into electrical signals without external power input and are widely used in applications such as imaging, sensing, communication, and security. The most popular approach for constructing a self-powered photodetector is typically based on the fabrication of an asymmetric metal-semiconductor (MS) contact; however, this technique is seriously limited by the Fermi-level pinning effect. Here, we report a room-temperature photodetector based on multi-layer MoS2 sandwiched between two separated asymmetric graphene contacts. Our photodetector was driven by the built-in electric field generated by a van der Waals (vdW) contact instead of the traditional MS contact. Operating under zero-bias voltage, the highest photoresponsivity of 0.63 A W-1 and a specific detectivity of 7.71x10(12) Jones were achieved at a wavelength of 450 nm with 0.08 mu W cm(-2) incident power intensity. Compared with devices using symmetric contacts, a high ON/OFF current ratio of approximately 1520 and a fast response time on the order of microseconds were also observed in our asymmetric graphene contact device. Our experimental results may open a novel way toward the realization of vdW contacts for the fabrication of self-powered photodetectors.