Dye sensitized cells are improved by passivation of the dyed titania electrode by silanizing the dyed surface with alkyl(trialkoxy)silanes. In cells utilizing the ruthenium dye bis(4.4'-dicarboxy-2,2'bipyridine)bis(thiocyanato)ruthenium (II) (N3) optimum performance is produced by treating the dyed electrode with octyl(trimethoxy)silane in dry toluene. Such treatment increases efficiency as Much as 66%, raising cells utilizing an ionic liquid electrolyte with high [I-3(-)] from 1.7% to 2.8% (1 sun AM 1.5). The effect on dark currents and on cell efficiencies of this silanization and of dyeing both the FTO and TiO2 surfaces is discussed for ionic liquid and acetonitrile based electrolytes. (c) 2005 Elsevier B.V. All rights reserved.