Electron transport in electrodes consisting of metal oxide nano-particles filled with electrolyte solution

Electron transport property of nano-porous TiO2 films filled with electrolyte solution is studied by pulsed-laser-induced photocurrent transient measurements. It is found that the diffusion coefficients of the films depend on the annealing temperature and crystallinity of TiO2 nano-particles, in addition to that on the diffusion coefficient and concentration of cation in the solution. The diffusion coefficient is interpreted with ambipolar diffusion and trapping models. In order to obtain the fast charge transfer in the films, high cation concentration in the electrolyte and high crystallinity of metal oxide particles are preferred. However, for the crystallinity, small portion of surface amorphous layer on the particles seems to form effective neck between particles by annealing.