High quantum yield sensitization of nanocrystalline titanium dioxide photoelectrodes with cis-dicyanobis(4,4′-dicarboxy-2,2′-bipyridine)osmium(II) ortris(4,4′-dicarboxy-2,2′-bipyridine)osmium(II) complexes

Osmium polypyridyl complexes were used as sensitizers in solar cells that utilize nanocrystalline titanium dioxide photoelectrodes. Exposure of TiO2 electrodes to sources of Os-II(H2L')(2)(CN)(2) (where L' is 4,4'-dicarboxylato-2,2'-bipyridine) or Os-II(H2L')(3)(2+) extended the light absorption and spectral response of the cell to longer wavelengths than did exposure of TiO2 to Ru(H2L')(2)(NCS)(2). The Os complexes also provided very high external quantum yields for photocurrent flow and produced open-circuit voltages similar to those of the Ru complex. The Os-based systems therefore offer promise in developing efficient dye-sensitized nanocrystalline TiO2-based photoelectrochemical cells.