  Recent discoveries of the photoresponse of molybdenum disulfide (MoS2) have
shown the considerable potential of these two-dimensional transition metal
dichalcogenides for optoelectronic applications. Among the various types of
photoresponses of MoS2, persistent photoconductivity (PPC) at different levels
has been reported. However, a detailed study of the PPC effect and its
mechanism in MoS2 is still not available, despite the importance of this effect
on the photoresponse of the material. Here, we present a systematic study of
the PPC effect in monolayer MoS2 and conclude that the effect can be attributed
to random localized potential fluctuations in the devices. Notably, the
potential fluctuations originate from extrinsic sources based on the substrate
effect of the PPC. Moreover, we point out a correlation between the PPC effect
in MoS2 and the percolation transport behavior of MoS2. We demonstrate a unique
and efficient means of controlling the PPC effect in monolayer MoS2, which may
offer novel functionalities for MoS2-based optoelectronic applications in the
future.
