We have fabricated bulk heterojunction (BHJ) photovoltaic devices based on the as cast and thermally annealed P [6 6]-phenyl-C-61-butyric acid methyl ester (PCBM) blends and found that these devices gave power conversion efficiency (PCE) of about 1 15 and 1 60% respectively P is a novel alternating phenylenevinylene copolymer which contains 2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid units along the backbone and was synthesized by Heck coupling This copolymer was soluble in common organic solvents and showed long-wavelength absorption maximum at 390-420 nm with optical band gap of 1 94 eV The improvement of PCE after thermal annealing of the device based on the P PCBM blend was attributed to the increase in hole mobility due to the enhanced crystallinity of P Induced by thermal treatment In addition we have fabricated BHJ photovoltaic devices based on the as cast and thermally annealed PB P PCBM ternary blend PB is a low band gap alternating phenylenevinylene copolymer with BF2-azopyrrole complex units which has been previously synthesized in our laboratory We found that the device based on this ternary blend exhibited higher PCE (2 56%) as compared to either P PCBM (1 15%) or PB PCBM (1 57%) blend This feature was associated with the well energy level alignment of P PB and PCBM the higher donor-acceptor interfaces for the exciton dissociation and the improved light harvesting property of the ternary blend The further increase in the PCE with thermally annealed ternary blend (3 48%) has been correlated with the increase in the crystallinity of both P and PB Finally we used copolymer P as sensitizer for quasi solid state dye-sensitized solar cell and we achieved PCE of approximately 3 78% (C) 2010 Elsevier B V All rights reserved