Interlayer of PMMA doped with Au nanoparticles for high-performance tandem photodetectors: a solution to suppress dark current and maintain high photocurrent.

Currently, colloidal quantum dots (CQDs) based photodetectors are widely investigated due to their low cost and easy integration with optoelectronic devices. The requirements for a high-performance photodetector are the low dark current and the high photocurrent. Normally, photodetectors with low dark-current also possess low photocurrent, or photodetectors with reduced dark-current and possess reduced photocurrent, resulting to low detectivity. In this paper, a solution to suppress dark current and maintain high photocurrent, i.e. by using polymethyl methacrylate doped with Au nanoparticles (NPs) (i.e. PMMA:Au) as the interlayer for enhanced-performance tandem photodetectors, is presented. Our experimental data showed that the dark current through the tandem photodetector ITO/PEDOT:PSS/PbS:CsSnBr3/ ZnO/PMMA:Au/CuSeN/PbS:CsSnBr3/ZnO/Ag is suppressed significantly, meanwhile the photocurrent is maintained high, after inserting the PMMA:Au interlayer between the two sub-detectors. The inserted PMMA:Au interlayer acts as the storage nodes for electrons, reducing the dark current through the device meanwhile the photocurrent can be enhanced under illumination. As a result, the specific detectivity of the tandem photodetector with 35 nm PMMA:Au interlayer was enhanced significantly from 5.01×1012 to 2.7×1015 Jones under 300 μW/cm2 532 nm illumination at low voltage of -1 V as compared to the control device without the PMMA:Au interlayer. Further, the physical mechanism for the enhanced performance is discussed in details.