Ultrahigh Photoresponsivity Enabled by Carrier Multiplication in a Self-Powered Solar-Blind Photodetector Based on the WS2/Graphene Heterostructure

The development of high-performance, low-power solar-blind photodetectors (SBPDs) holds significant promise for both military and civilian applications. Compared with wide-bandgap semiconductors, two-dimensional (2D) materials exhibit advantageous characteristics in the threshold and efficiency of carrier multiplication (CM) due to enhanced Coulomb interaction and relaxed momentum conservation. This allows one incident high-energy photon to generate two or more electron-hole pairs effectively, positioning them as viable alternatives for the fabrication of high-performance self-powered SBPDs. Here, we have designed a vertically aligned 2D WS2/graphene photodetector with Au as the contact electrodes, forming a unilateral Schottky junction to facilitate the efficient transfer of high-energy electrons generated in the WS2 to the graphene without thermal relaxation. This enables efficient CM within graphene, resulting in an ultrahigh responsivity of 77 mA/W and an external quantum efficiency of 36% at 265 nm light with zero bias. This work offers invaluable insights into the development of next-generation SBPDs with high performance and low power consumption.