4-Phenylpyridine as ancillary ligand in ruthenium(II) polypyridyl complexes for sensitization of n-type TiO2 electrodes

In this work, the novel molecular sensitizers cis-[(dcbH(2))(2)Ru(ppy)(2)](2+) and cis-[(dcbH(2))(2)Ru(ppy) (H2O)](2+) where dcbH(2) = 4,4'-(CO2H)(2)-2,2'-bipyridine and ppy = 4-phenylpyridine, have been prepared and their effectiveness for sensitization of n-type TiO2 electrodes in thin-layer transparent solar cells has been investigated. Spectral and photoelectrochemical measurements show that both dyes, when anchored to nanocrystalline TiO2, present good light harvesting properties and provide enhanced spectral response of the TiO2 electrodes to visible light in regenerative solar cells. The derivative with one coordinated ppy, cis-[(dcbH(2))(2)Ru(ppy)(H2O)](2+) resulted in considerably higher incident photon-to-current conversion efficiency values, as well as in a broader spectral response in longer wavelengths than the corresponding derivative with two coordinated ppy, cis-[(dcbH(2))(2)Ru(ppy)(2)](2+). The results show that the number of azine ligands coordinated to the non-attached side of the (dcbH(2))(2)RuLL' dye can be controlled and plays an important role to extend spectral sensitivity to the visible light, as well as in tuning the overall properties of the system.