Novel photosensitized dyes containing 4-trifluoromethylthiazole-5-carboxylic acid as an acceptor are synthesized. Stilbene-type dyes with this acceptor show high performance as dye-sensitized solar cells. The trifluoromethyl group is assumed to act as a suppressor of electron back-donation from the TiO2 conduction band to the electrolyte and as an accelerator of charge separation in the photoexcited state.