We have developed oligothiophene-containing coumarin dyes fully functionalized for dye-sensitized nanocrystalline TiO(2) solar cells (DSSCs). DSSCs based on the dyes gave good performance in terms of incident photon-to-current conversion efficiency (IPCE) in the range of 400-800 nm. A solar energy-to-electricity conversion efficiency (eta) of 7.4% was obtained with a DSSC based on 2-cyano-3-[5'-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)-[2,2']bithiophenyl-5-yl]acrylic acid (NKX-2677) under simulated AM 1.5G irradiation (100 mW cm(-2)) with a mask: short-circuit current density (J(sc)) = 13.5 mA cm(-2); open-circuit voltage (V(oc)) = 0.71 V; fill factor (FF) = 0.77. Transient absorption spectroscopy measurements indicated that electron injection from NKX-2677 to the conduction band of TiO(2) is very rapid (<100 fs), which is much faster than the emission lifetime of the dye (1.0 ns), giving a highly efficient electron injection yield of near unity.

Four hemicyanine derivatives, (E)-N- (3-sulfopropyl-4-[2-(4-dimethylaminophenyl) ), have been synthesized and characterized with regard to their absorption and electrochemical properties. Photoelectrochemical experiments show that these hemicyanine dyes with D-π-A systems can yield efficient charge separation under illumination of simulated solar light. Alkyl chain has a remarkable effect on dye adsorbance, incident photon-to-electron conversion efficiency, and overall energy conversion yield. The overall yield is approximately doubled when the methyl group replaces the long alkyl chain. Action spectrum of QS displayed a broad feature with 33.8% of maximum monochromatic incident photon-to-electron conversion efficiency (IPCE), and a thin-layer sandwich-type solar cell based on nanocrystalline TiO 2 film modified with QS produced about 2% of overall yield. For the first time, a photovoltaic liquid-junction solar cell based on nanostructured TiO 2 electrode sensitized by hemicyanine dyes is reported.