Photoresponse of Solution-Processed Molybdenum Disulfide Nanosheet-Based Photodetectors

Molybdenum disulfide (MoS2) is an emerging two-dimensional (2D) material for next-generation optoelectronic and energy storage devices. Although various efforts have been made to understand the photocurrent generation mechanisms and to improve the photoresponse behavior of 2D MoS2 nanosheets (NSs), little is understood about the mechanisms underlying the photocurrent response of few-layer MoS2 NSs, particularly the fast response of photocurrent followed by a slow rise under pulsed illumination. In this work, we have investigated the mechanisms behind the photoresponse of few-layer MoS2 NS-based two-terminal devices via time-resolved photocurrent measurements. The photoresponse of such devices under different bias voltages and light intensities is measured and the photocurrent initially shows a fast response in the time scale of ∼95 μs followed by a slow-rise current (SRC) with a rise-time constant of ∼50 s. The photocurrent increases sublinearly with intensity and exponentially with temperature, indicating the presence of traps. This work reports a systematic study of the photocurrent and SRC in few-layer MoS2 NSs and concludes that the SRC effects can be ascribed to the photobolometric and trap-assisted photogating processes. Besides, this study points out a correlation of the SRC in MoS2 with the temperature and vacuum level.