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.