XPS studies of Ru-polypyridine complexes for solar cell applications

A series of Ru-polypyridine dyes has been studied with electron spectroscop y using AlK alpha and synchrotron radiation. Both pure complexes and comple xes adsorbed on nanostructured TiO2 (anatase) surfaces have been examined a nd special emphasis was given to the dye complex cis-bis(4,4'-dicarboxy-2,2 '-bipyridine)-bis-(isothiocyanato)-ruthenium(II) [Ru(dcbpy)(2)(NCS)(2)]. Th e measurements provide information concerning the energy level matching bet ween the dyes and the TiO2, which is of importance in photoinduced charge t ransfer reactions and in applications such as dye-sensitized solar cells. T he measurements also support the general picture of bonding of carboxylated complexes to the surfaces via the carboxyl groups of a single bi-isonicoti nic acid ligand, and that, for Ru(dcbpy)(2)(NCS)(2), the NCS-ligand-TiO2 in teraction is small. Corroborative support is provided via quantum chemical calculations on the ligand (bi-isonicotinic acid) adsorbed on a TiO2 anatas e (101) surface. (C) 1999 American Institute of Physics. [S0021-9606(99)703 28-4].