A novel, heteroleptic ruthenium dye comprising a vinyl group between the carboxylate and bipyridine segments as well as extended pi-conjugation of the ancillary ligand, employing alkyl-bithiophene, was synthesized. The dye displayed a remarkably high absorption coefficient of 2.51 x 10(4) M(-1) cm(-1) (at 562 nm) for its metal-to-ligand charge transfer band. The photo-to-current conversion efficiency of the corresponding dye-sensitized solar cell was 9.12% under AM 1.5 (100 mW/cm(2)) irradiation. Furthermore, owing to both the very strong metal-to-ligand charge transfer band and the large number of dye molecules adsorbed on the TiO(2) electrode, the conversion efficiency of the dye-sensitized cell was >7.5% at a light intensity <= 198 mW cm(-2). (C) 2009 Elsevier Ltd. All rights reserved.