Influence of ordering in porous TiO₂ layers on electron diffusion

Layers of porous TiO₂ fabricated by electrophoretic deposition at different temperatures with subsequent sintering in air were investigated by transient photocurrent measurements in aqueous electrolyte. The effective diffusion coefficient of excess electrons changed between 1.6 × 10 ^-5 and 1.4 × 10^-4 cm²/s depending strongly on the solution temperature during the TiO₂ layer deposition. Characterization, in terms of average degree of preferred orientation, shows that low deposition temperature results in orientation of the nanocrystals forming the porous film. Consequently, the increase of effective diffusion coefficient is attributed to a higher degree of ordering in the nanoporous TiO₂ layer.