In this paper, we have investigated the of the bulk heterojunction organic solar cells based on CuI- polyvinyl alcohol (CuI-PVA) nanocomposite as electron donor and [6,6] –phenyl C60 –butyric acid methyl ester (PCBM) or modified PCBM i.e. F. The power conversion efficiencies (PCEs) of the 0.46 and 0.68 % were achieved for the photovoltaic devices based on as cast CuI-PVA:PCBM and CuI-PVA:F blend films, respectively. The higher PCE for the organic solar cell based on F as electron acceptor accounts for the increase in both short circuit current (Jsc) and open circuit voltage (Voc), due to the increased absorption of F in visible region and its higher LUMO level. The PCE of the organic solar cells further increased to 0.54 % and 0.80 % for thermally annealed CuI-PVA:PCBM and CuI-PVA:F blends, respectively. The increase in PCE is mainly due to the increase in Jsc which has been attributed to the improvement in hole mobility and broadening of the absorption band in the longer wavelength region. The improved hole mobility results more balanced charge transport in the devices based on thermally annealed blends.