We have synthesized a highly efficient organic dye for a dye-sensitized solar cell; the overall solar-to-energy conversion efficiency was 9.1% at AM 1.5 illumination (100 mW cm(-2)): short-circuit current density (J(sc)) = 18.1 mA cm(-2), open circuit photovoltage (V(oc)) = 743 mV and fill factor (ff) = 0.675.

We report here a dye-sensitized solar cell structure having two different dyes with complementary absorption properties, which is different from the dye-cocktail method. The developed method allows two different dyes to be adsorbed on the sintered TiO 2 layers without thermal decomposition, which the conventional procedure of dye-sensitized solar cell has been unable to do. The contribution of different dyes to photocurrent generation has been confirmed by incident-photon-to-current conversion efficiency ͑IPCE͒ and photocurrent transient spectroscopy. The heterosensitizer-junction type demonstrates higher IPCE than the single-sensitizer structure, thanks to complementary absorption characteristics.