Influence of the active layer nanomorphology on device performance for ternary PbS_xSe_1-x quantum dots based solution-processed infrared photodetector

In this paper, the influence of the active layer nanomorphology on device performance for ternary PbS_xSe_1-x quantum dot-based solution-processed infrared photodetector is presented. Firstly, ternary PbS_xSe_1-x quantum dots (QDs) in various chemical composition were synthesized and the bandgap of the ternary PbS_xSe_1-x QDs can be controlled by the component ratio of S/(S + Se), and then field-effect transistor (FET) based photodetectors Au/PbS_0.4Se_0.6:P3HT/PMMA/Al, in which ternary PbS_0.4Se_0.6 QDs doped with poly(3-hexylthiophene) (P3HT) act as the active layer and poly(methyl methacrylate) (PMMA) as the dielectric layer, were presented. By changing the weight ratio of P3HT to PbS_0.4Se_0.6 QDs (K = M_P3HT:M_QDs) in dichlorobenzene solution, we found that the device with K = 2:1 shows optimal electrical property in dark; however, the device with K = 1:2 demonstrated optimal performance under illumination, showing a maximum responsivity and specific detectivity of 55.98 mA W^-1 and 1.02 ×10¹⁰ Jones, respectively, at low V _DS = -10 V and V _G = 3 V under 980 nm laser with an illumination intensity of 0.1 mW cm^-2. By measuring the atomic force microscopy phase images of PbS_0.4Se_0.6:P3HT films in different weight ratio K, our experimental data show that the active layer nanomorphology has a great influence on the device performance. Also, it provides an easy way to fabricate high performance solution-processed infrared photodetector.