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 prepare d 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 anchor ed to nanocrystalline TiO2, present good light harvesting properties a nd provide enhanced spectral response of the TiO2 electrodes to visibl e light in regenerative solar cells. The derivative with one coordinat ed ppy, cis-[(dcbH(2))(2)Ru(ppy)(H2O)](2+) resulted in considerably hi gher incident photon-to-current conversion efficiency values, as well as in a broader spectral response in longer wavelengths than the corre sponding derivative with two coordinated ppy, cis-[(dcbH(2))(2)Ru(ppy) (2)](2+). The results show that the number of azine ligands coordinate d to the non-attached side of the (dcbH(2))(2)RuLL' dye can be control led and plays an important role to extend spectral sensitivity to the visible light, as well as in tuning the overall properties of the syst em. (C) 1998 Elsevier Science S.A. All rights reserved.