Influence of the porosity on diffusion and lifetime in porous TiO2 layers

Photocurrent transients were investigated on pressed and sintered porous $\mathrm{Ti}{\mathrm{O}}_2$ layers which were immersed in electrolyte during the measurements. Unpressed porous $\mathrm{Ti}{\mathrm{O}}_2$ layers were prepared by electrophoretic deposition. The porosity of the layers was changed systematically by pressing. The surfaces of the $\mathrm{Ti}{\mathrm{O}}_2$ nanoparticles and the intimate contact between them were identically conditioned by sintering in air at $450°\mathrm{C}$ after pressing. With decreasing porosity, the diffusion coefficient increased while the electron lifetime decreased. The results are discussed on the base of the change of the mean coordination number between $\mathrm{Ti}{\mathrm{O}}_2$ nanoparticles.