Enhanced detectivity of PbS quantum dots infrared photodetector by introducing the tunneling effect of PMMA.

With extremely high optical absorption coefficient in infrared regime, lead sulfide (PbS) quantum dots (QDs)-based photodetectors are promising for diverse applications. In recent years, synthesis of materials has made great progress, but the problem of low sensitivity of quantum dots photodetector still unresolved. In this work, the introduction of a tunneling organic layer effectively address this problem. The dark current is decreased by the appropriate thickness of polymethyl methacrylate (PMMA) barrier layer by suppressing the spontaneous migration of ions, and the photogenerated carriers are little effected, thereby the responsivity of the device is improved. As a result, the device exhibits a high responsivity of 3.73*105 mA/W and a giant specific detectivity of 4.01*1013 Jones at a low voltage of -1 V under 1064 nm illumination. In the self-powered mode, the light/dark current ratio is about 107, the responsivity reaches a value of 157.6 mA/W, and the detectivity up to 5.9*1011 Jones. The performance of the photodetectors is obviously better than most of the reported QDs photodetectors. The design of this device structure provides a new solution to the problem of low sensitivity and high leakage current of quantum dots based infrared photodetectors.