Toward High-Performance Self-Driven Photodetectors via Multistacking Van der Waals Heterostructures.

The unique optoelectronic properties of layered van der Waals (vdW) heterostructures open up exciting opportunities for high-performance photodetectors. Self-driven photodetectors are desirable for reducing power consumption and minimizing the device size. Here, a semiconductor-insulator-semiconductor-type multistacking WSe/graphene/-BN/MoS vdW heterostructure is demonstrated to realize an enhanced self-powered photodetector with a high on-off current ratio of about 1.2 × 10 and a high photoresponsivity of 3.6 A/W without applying bias, which is the highest photoresponsivity ever reported for self-powered photodetectors. Because of the difference in the Fermi level, a built-in electrical field is formed at the WSe/graphene junction, where the photoexcited electrons and holes can be efficiently separated and the carriers can easily tunnel through the MoS/-BN junction driven by the enhanced potential. Therefore, the enhanced self-powered photodetection is attributable to highly efficient carrier tunneling through large -BN electron barriers. By comparison, when the stacking sequence is changed to make WSe/MoS p-n heterojunctions lay on graphene/-BN, the self-powered photocurrent is still generated because of the type-II band alignment, which exhibits lower but still relevant values with a light on/off ratio of ∼8 × 10 and a photoresponsivity of ∼2.39 A/W. The efficient enhancement demonstrates that multistacking heterostructures significantly elevate the performance of self-powered photodetectors, providing a feasible route to develop high-performance self-powered optoelectronic devices and extend their applications in integrated optoelectronic systems.