Significantly Enhanced Photoresponse of Self-Powered 2D MoS2/WS2 Heterojunction Photodiode via F4-TCNQ Doping

The formation of two-dimensional (2D) van der Waals heterojunctions offers opportunities to design micro- and nanoscale photodiodes. However, the strong carrier recombination induced by defect states in 2D materials leads to a low photoresponsivity of photodiodes. To achieve photodetectors with high responsivity and sensitivity, we designed a 2D semivertical MoS2/WS2 heterojunction photodiode with a single depletion region. A broadband response from 532 to 785 nm in self-powered mode was demonstrated for the photodiode. To further enhance the self-powered photodetection performance of the photodiode, we chose to dope the heterojunction with F4-TCNQ molecules and found that the device performance was significantly improved. The doping-induced depletion region facilitates the separation of photogenerated electron–hole pairs in the heterojunction. The sensitivity improvements at 532, 635, and 785 nm were more than 1110%, 278%, and 492%, respectively. The self-powered photodiode achieved high sensitivity, with a maximum responsivity of 0.288 A/W and a maximum detectivity of 1.04 × 1011 Jones after doping. The rise and fall times of the doped photodiode were extremely fast, with values of 11/19 μs. This research work provides a viable solution for achieving high-performance and broadband 2D photodetectors.