We present two sensitizers, Ru(4,4′-dicarboxyvinyl)-2,2′-bipyridine)(4,4′-dinonyl-2,2′-bipyridine)(NCS)2 (K9)
and Ru(4,4′-dicarboxy(phenylethenyl)-2,2′-bipyridine)(4,4′-dinonyl-2,2′-bipyridine)(NCS)2 (K23), which were
synthesized and characterized by analytical, spectroscopic, and electrochemical impedance measurements.
The two sensitizers that contain hydrophobic alkyl chains and an extended π-conjugation bridge between
carboxylic acid groups and the ruthenium chromophore center exhibit enhanced red response and higher
molar extinction coefficients when compared to the Ru(4,4′-dicarboxy-2,2′-bipyridine)(4,4′-dinonyl-2,2′-
bipyridine)(NCS)2 (Z907) sensitizer. The performances of the K9, K23, and Z907 sensitizers in nanocrystalline
TiO2-based thin film solar cells were studied using transparent 2.6-μm-thick mesoporous layers, which show
short-circuit photocurrent densities (Jsc) of 7.80, 8.31, and 7.16 mA/cm2, corresponding to overall conversion
efficiencies of 4.14, 4.41, and 4.06%, respectively. The increase in the Jsc of the cells with K9 and K23 with
respect to that with Z907 is due to the enhanced molar extinction coefficient of the new sensitizers. The
incident monochromatic photon-to-current conversion efficiency for the K23 is plotted as a function of excitation
wavelength show in the plateau region 79% and even at 700 nm 69%.