In this study, polymer:fullerene bulk-heterojunction hybrid solar cells with the structure, fluorine-doped tin oxide (FTO)/Cu2O/poly (3-hexylthiophene): 6,6-phenyl-C-61-butyric acid methyl ester (P3HT:PCBM):TiO2/Ca/ Al, were fabricated. The effect of a p-type Cu2O thin layer deposited between the active layer (P3HT:PCBM) and the FTO layer on cell performance was investigated; the p-type Cu2O thin layer was deposited through thermal evaporation. The results showed that the Cu2O interfacial layer increased the efficiency and stability of the hybrid solar cells. The optimal performance was obtained for the solar cell structure FTO/Cu2O (10 nm)/ P3HT:PCBM:TiO2 (15 wt.%)/Ca/Al (best cell structure), which had the following specifications: open-circuit voltage = 0.58 V, short circuit current density = 12.14 mA/cm(2), fill factor = 58.63%, and eta = 4.13%. The Cu2O layer prevented the rapid degradation of the interface, thereby increasing the lifetime of the hybrid solar cells. (C) 2016 Elsevier B.V. All rights reserved.