Direct Observation of Perovskite Photodetector Performance Enhancement by Atomically Thin Interface Engineering

Lead trihalide perovskites have been integrated with atomically thin WS₂ and served as absorption layers to improve photoresponsivity in photodetectors. The combination of perovskites and two-dimensional (2D) transition-metal dichalcogenide (TMDC) materials provides the platform to study light–matter interactions and charge transfer mechanisms in optoelectronic devices. Herein, conductive and photoconductive atomic force microscopy were used to image the dark current and photocurrent generated in WS₂/CH₃NH₃PbI₃ (MAPbI₃) heterostructures. Dark current measurement in the applied voltage range displays characteristic diode behavior, which can be well described by thermionic emission theory. Under laser illumination at 532 nm, the spatially resolved photocurrent images exhibit location-dependent photoresponse, where the photocurrent increases remarkably for the WS₂/MAPbI₃ heterostructures compared with the bare MAPbI₃ regions. Furthermore, comparative surface roughness and 2D Fourier analysis of the topographic and current maps reveal that the interfacial conditions of the WS₂/MAPbI₃ heterojunctions play an important role in the charge separation process. In addition, WS₂/MAPbI₃-based photodetectors have been fabricated. Our study provides direct evidence that atomically thin TMDC monolayers can effectively assist the charge separation process and improve the light-to-electric energy conversion, which aids in the design principles and understanding of 2D heterostructured optoelectronic devices.