Two-Dimensional Cs2AgBiBr6/WS2 Heterostructure-Based Photodetector with Boosted Detectivity via Interfacial Engineering

Two-dimensional (2D) transition metal dichalcogenide (TMDC) monolayers have been widely used for optoelectronic devices because of their ultrasensitivity to light detection acquired from their direct gap properties. However, the small cross-section of photon absorption in the atomically thin layer thickness significantly limits the generation of photocarriers, restricting their performance. Here, we integrate monolayer WS₂ with 2D perovskites Cs₂AgBiBr₆, which serve as the light absorption layer, to greatly enhance the photosensitivity of WS₂. The efficient charge transfer at the Cs₂AgBiBr₆/WS₂ heterojunction is evidenced by the shortened photoluminescence (PL) decay time of Cs₂AgBiBr₆. Scanning photocurrent microscopy of Cs₂AgBiBr₆/WS₂/graphene reveals that improved charge extraction from graphene leads to an enhanced photoresponse. The 2D Cs₂AgBiBr₆/WS₂/graphene vertical heterostructure photodetector exhibits a high detectivity (D*) of 1.5 × 10¹³ Jones with a fast response time of 52.3 μs/53.6 μs and an on/off ratio of 1.02 × 10⁴. It is worth noting that this 2D heterostructure photodetector can realize self-powered light detection behavior with an open-circuit voltage of ∼0.75 V. The results suggest that the 2D perovskites can effectively improve the TMDC layer-based photodetectors for low-power consumption photoelectrical applications.