For photoelectric conversion, three of squarylium cyanine dyes were synthesized and their photoelectrochemical parameters were improved with increase in the adsorption ability of the dyes on nanocrystalline TiO2. A relatively high photoelectric conversion efficiency of 2.17% and the top incident photon-to-photocurrent conversion efficiency of 6.2% at 650 nm for the dye of highest adsorption ability among the three were obtained. Meanwhile, doping cis-Ru[4,4＇-(LL)](2) (NCS)(2) with 1% of the above-mentioned dye (molar ratio) as a photosensitizer, the photoelectrochemical solar cell made an efficient complement to light-harvesting capacity in almost the whole visible range with the photoelectric conversion efficiency increasing by 12% relative to that of pure cis-Ru[4,4＇-(LL)](2) (NCS)(2) (L = 2,2＇-bipyridyl-4,4＇-dicarboxylate).