A 2D/0D Heterostructure of Monolayer MoS2/CdS QDs for a UV/Blue-Sensitive Broadband Photodetector

Abstract A lithography-free 2D/0D heterostructure broadband photodetector has been fabricated that integrates solvothermally generated CdS quantum dots (QDs) with single flake monolayer (ML) 2D-MoS2 developed by chemical vapor deposition (CVD). This photodetector has been utilized for the broadband spectrum responsiveness of virgin MoS2 extended from the ultraviolet to the visible region, whereas wide-band-gap CdS QDs improve light absorption and subsequent charge carrier production and separation. Effective interfacial charge transfers from CdS QDs to the MoS2 monolayer are confirmed by photoluminescence quenching and red shift. The photodetector shows a broadband photoresponse covering 300−800 nm with a high photoresponsivity of ∼60 mA/W (under a 5 V bias) with an external quantum efficiency of ∼25% and a detectivity of ∼1011 Jones. Favorable Type-I band alignment of ML MoS2/CdS QDs, integrated electric fields at the 2D/0D interface, and effective carrier transport across the MoS2 monolayer are all responsible for the improved performance. Besides, the high in-plane mobility of 2D-MoS2 enables it to be a fast photoresponse device with a response time of 0.43 s (under UV irradiation) with a highly reversible photocurrent generation.