The role of trap states in MoS₂-based photodetectors

Two-dimensional materials show great potential for future optoelectronic device applications, especially in the field of broadband optical detection, due to their high optical responsivity and tunable bandgap structure. In communication and sensing applications, the detection of weak light signals is crucial for improving the quality of signal transmission and the sensitivity of sensors. Although the photogating effect has been shown to provide high light sensitivity, the key features to achieve this dominant light response have not been fully discussed. In this study, we explain in detail the physical mechanism of the photoresponse of molybdenum disulphide-based photodetectors and propose a general basis of judgement for comparing the magnitude of the trap-state action. Through experimental and theoretical analyses, we reveal the physical mechanisms of photocurrents at various stages in the optical ON/OFF switching cycles and provide a theoretical basis for optimising the performance of two-dimensional material-based photodetectors. The results show that the trap states significantly affect the photoresponse characteristics of photodetectors, especially the photocurrent changes at different stages of the optical ON/OFF switching cycles. These findings not only deepen the understanding of the photoelectric properties of two-dimensional materials, but also provide important theoretical guidance for the design of high-performance photodetectors.