Negative photoconductivity observed in polycrystalline monolayer molybdenum disulfide prepared by chemical vapor deposition

In this paper, the negative photoconductivity (NPC) was observed in molybdenum disulfide (MoS 2 ) prepared by chemical vapor deposition. The conductivity drops by 15% in stable light excitation. We speculate that the generation of NPC is due to the electronic transition to the defect state level, which reduces the rate of movement of non-equilibrium carrier. In the low-defect system, free excitons predominate, and the material exhibits positive photoconductivity. It is beneficial to the research on a new single-wavelength photodetector based on NPC.