By optimizing the P3OT/CISe ratio, TiO(2) content in the P3OT/CISe active layer, annealing temperature and time, this study investigated hybrid Al/Ca/P3OT:CISe:TiO(2)/PEDOT:PSS/ITO thin film solar cells with improved efficiency. Due to an increase in charge-carrier transport and a decrease of electron-hole recombination, it is possible to increase the efficiency of hybrid solar cells by adding TiO(2) nanoparticles to the P3OT:CISe active film. Also, performance enhancement of the solar cells can occur with an increase of CISe content in P3OT as well as the addition of a PEDOT:PSS layer to the cell structure. The optimum TiO(2) content in P3OT:CISe layer is 15 wt.%. The optimum annealing temperature and time are 125 degrees C and 30 min, respectively. The formation of large CISe and TiO(2) aggregates that reduce charge mobility may cause the decrease of efficiency. The rough surface may effectively reduce the charge-transport distance and provide nanoscale phase separation that further enhances internal light scattering and light absorption. The best results for the open circuit voltages (V(oc)), short-circuit current density (J(sc)), fill factor (FF), and efficiency (eta(e)) of Al/Ca/POCT15/PEDOT:PSS/ITO hybrid solar cells obtained at optimized conditions were V(oc) = 0.49, J(sc) = 3.20, FF=42.96, and eta(e) = 0.674, respectively. (C) 2011 Elsevier B.V. All rights reserved.