Influence of ordering in porous TiO2 layers on electron diffusion.

Layers of porous TiO(2) 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 x 10(-5) and 1.4 x 10(-4) cm(2)/s depending strongly on the solution temperature during the TiO(2) 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 TiO(2) layer.