In this study, monodispersed colloidal titanium dioxide (TiO2) was synthesized and applied with poly(3-octylthiophene-2,5-diyl) (P3OT), phenyl-C61-butyric acid methyl ester (PCBM), poly(3,4-ethylene dioxythiophene) (PEDOT), and poly(styrenesulfonate (PSS) to fabricate an aluminum/calcium/P3OT:PCBM: TiO2/PEDOT:PSS/indium tin oxide hybrid solar cell using spin coating and evaporation deposition. The effects of the TiO2 content and annealing temperature on cell performances were investigated. The results showed that optimization of the TiO2 content (15 wt.%) and annealing temperature (150 degrees C) effectively enhanced the performance of the hybrid solar cells. The PCBM and TiO2 absorbed more light photons in the P3OT:PCBM: TiO2 active layer. The charge transfer in the P3OT:PCBM:TiO2 active layer was more efficient, increasing the amount of photoluminescence quenching. The increased active layer surface roughness reduced the charge-transport distance and enhanced the internal light scattering and light absorption. The best values for the open circuit voltage, short-circuit current density, fill factor, and efficiency for the prepared hybrid solar cell were 0.61 V, 9.50 mA/cm(2), 34.46%, and 2.09%, respectively. (C) 2013 Elsevier B. V. All rights reserved.