Nonfullerene Organic Solar Cells with 18.17% Efficiency Obtained Using a V2C/PEDOT:PSS Composite Hole-Transport Layer

More efficient promotion of charge collection and transport is an essential factor to achieve high efficiency of the devices; however, the matching of energy level between the PEDOT:PSS hole-transport layer (HTL) and indium tin oxide (ITO) is not perfect, which limits the efficiency of exciton utilization. Herein, the composite HTL of V2C/PEDOT:PSS is formed using two-dimensional (2D) conducting material V2C and PEDOT:PSS, which shows a lower work function (WF) and higher conductivity than the pure PEDOT:PSS films and shows advantages to improve the Ohmic contact between the active layer and electrode. The efficiency of the devices prepared with the V2C (0.075 mg/mL)/PEDOT:PSS composite HTL based on the nonfullerene PM6:BTP-eC9 system reaches 18.17%. The enhancement in performance can be ascribed to the interaction between the functional groups of V2C and PEDOT:PSS, as well as the increase in the overall hole-transport layer conductivity. The method proposed in this study to prepare this V2C/PEDOT:PSS composite HTL improves the efficiency of organic solar cells.