Studying of photo-excitation dynamics and photodetector based on MoSe2 nanosheet

Abstract The photo-excitation dynamics occurring in the nanosheet of MoSe2 have been studied by employing the transient absorption. We find that four types of dynamic behaviors participate in the relaxation of excited MoSe2 nanosheet by global fitting, which corresponds to the exciton-exciton interaction, exciton capture by trapping state, exciton dissociation and free charge movement. Since many free charge has generated after photo-excitation, the photo-detector based on MoSe2 nanosheet is fabricated and the period- and voltage-dependent photocurrent is further clarified. In addition, nanosecond transient photocurrent test probes the dynamics of carrier and confirms that illumination intensity would accelerate the lifetime of carrier recombination to 1 μs at high intensity and enhance the corresponding loss of carrier. Moreover, it is also found that the bias voltage would linearly facilitate the yield of free carriers in photo-detector and the lifetime of carrier recombination would decrease to 4 μs at 60 V. The final results could help people to further understand the photo-physical property of MoSe2 nanosheet and facilitate its application in the opto-electronic devices.