Organic solar cells (OSCs) made from PTB7:PC70BM, with different thicknesses of a conjugated electrolyte PFN (0, 5, 7, 10, and 15 nm) used as the cathode buffer layers, were fabricated partially in air. OSCs with 10 nm of PFN were the most efficient in experimental tests, at 7.41%. Numerical simulations of the cells were also performed using the physics-based Silvaco/ATLAS CAD simulator, which describe the OSCs using the metal-insulator-metal (MIM) model. Simulations were used to determine the optimum values of PFN thickness for achieving high overall performance, which lies in the region from 5 to 10 nm.