Theoretical study of charge transportation in dye-sensitized nanocrystalline TiO2 electrodes

The recombination process at the semiconductor–electrolyte interface in dye-sensitized nanocrystalline photoelectrochemical cells is examined theoretically. The diffusion length in the dye-sensitized porous TiO2 films under the short-circuit condition, estimated from the action spectra, is smaller than the film thickness even in the highest efficiency cells. When the recombination is independent of the applied potential, a high open-circuit voltage can be attained even if the recombination current under illumination is much larger than the reverse saturation current in darkness.