Van der Waals Coupled Organic Molecules with Monolayer MoS₂ for Fast Response Photodetectors with Gate-Tunable Responsivity

Abstract

As a direct-band-gap transition metal dichalcogenide (TMD), atomic thin MoS₂ has attracted extensive attention in photodetection, whereas the hitherto unsolved persistent photoconductance (PPC) from the ungoverned charge trapping in devices has severely hindered their employment. Herein, we demonstrate the realization of ultrafast photoresponse dynamics in monolayer MoS₂ by exploiting a charge transfer interface based on surface-assembled zinc phthalocyanine (ZnPc) molecules. The formed MoS₂/ZnPc van der Waals interface is found to favorably suppress the PPC phenomenon in MoS₂ by instantly separating photogenerated holes toward the ZnPc molecules, away from the traps in MoS₂ and the dielectric interface. The derived MoS₂ detector then exhibits significantly improved photoresponse speed by more than 3 orders (from over 20 s to less than 8 ms for the decay) and a high responsivity of 430 A/W after Al₂O₃ passivation. It is also demonstrated that the device could be further tailored to be 2-10-fold more sensitive without severely sacrificing the ultrafast response dynamics using gate modulation. The strategy presented here based on surface-assembled organic molecules may thus pave the way for realizing high-performance TMD-based photodetection with ultrafast speed and high sensitivity.