Dye structure–charge transfer process relationship in efficient ruthenium-dye based dye sensitized solar cells

The characterization of the interfacial charge transfer processes taking place in dye solar cells made using the most efficient ruthenium complexes, namely cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)-ruthenium(II)bis-tetrabutylammonium (N719), tris(isothiocyanato)-ruthenium(II)-2,2′:6′,2′′-terpyridine-4,4′,4′′- tricarboxylic acid, tris-tertrabutylammonium salt (Black Dye) and cis-bis(isothiocanate)(4,4′-bis(5-hexylthiophene-2-yl)-2,2′-bipyridine)(4-carboxylic acid-4′-carboxylate-2,2′-bipyridine)ruthenium(II) sodium (C101), has been carried out. The comparison between these devices shows that devices made using N719 have the slowest recombination dynamics between the photo-injected electrons and the oxidized electrolyte. Moreover, for devices made using Black Dye, the dye ground state regeneration dynamics are faster than for C101 and N719. The implications for future ruthenium dyes are discussed.