Here, we report the fabrication of high-efficiency poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C-61-butyric acid methyl ester (PCBM) blend photovoltaic device. Process parameters like solvent, solvent drying conditions, electron donor to acceptor ratio and cathodes structures are optimized in making the devices. For the first time, we used cosolvent systems to make active layer of P3HT:PCBM composite and G-PEDOT:PSS, made by mixing 6wt% glycerol to PEDOT:PSS, is used as a buffer layer. Highest efficiency of 4.64% was obtained for the device made with 1:0.7 ratio of P3HT to PCBM, o-dichlorobenzene:chloroform cosolvent, newly developed slow process and G-PEDOT:PSS. Film morphology is evaluated by atomic force microscopy (AFM). Time-of-flight (TOF) and incident photon-to-current conversion efficiency (IPCE) measurements are also performed for the best device. (C) 2007 Elsevier B.V. All rights reserved.