Charge recombination between dye-sensitized nanocrystalline TiO2 electrodes and the I3-/I- couple in nonaqueous solution is described. The sensitizer was [RuL2(NCS)2] (L = 2,2‘-bipyridyl-4,4‘-dicarboxylic acid). An apparent inequality between the dark current and the recombination current is ascribed to a voltage shift caused by a potential drop at the SnO2/TiO2 interface, ohmic losses in the SnO2 and TiO2, and an overpotential for the redox reaction at the Pt counter electrode. Treating the dye-coated TiO2 electrodes with pyridine derivatives (4-tert-butylpyridine, 2-vinylpyridine, or poly(2-vinylpyridine)) improves significantly both the open-circuit photovoltage Voc (from 0.57 to 0.73 V) and the cell conversion efficiency (from 5.8 to 7.5%) at a radiant power of 100 mW/cm2 (AM 1.5) with respect to the untreated electrode. An analytical expression relating Voc to the interfacial recombination kinetics is derived, and its limitations are discussed. Analysis of Voc vs radiant power data with this expressi...