Organic dyes incorporating the dithieno[3,2-b:2',3'-d]thiophene moiety for efficient dye-sensitized solar cells

New dipolar compounds incorporating a dithieno[3,2-b:2',3'-d]thiophene unit as the electron donor, an oligothiophene moiety as the conjugated spacer, and 2-cyanoacrylic acid as the electron acceptor have been synthesized. These nonarylamine type metal-free organic compounds have been successfully used as the sensitizers of dye-sensitized solar cells (DSSCs). The conversion efficiencies of the DSSCs range from 3.54 to 5.15% under AM 1.5 G irradiation. The best efficiency reached approximately 70% of the ruthenium dye N719-based standard cell fabricated and measured under similar conditions.