Charge transport properties in the nanostructured ZnO thin film electrode – electrolyte system studied with time resolved photocurrents

The charge transport in nanoporous ZnO was studied by laser flash induced photocurrent transients. The results are discussed using a diffusion model and compared with previous results on TiO2. The charge transport was highly dependent on the potential giving apparent diffusion coefficients for the electron ranging from 1×10−4 to 1×10−6 cm2/s with an applied bias of +100 and +300 mV vs. Ag/AgCl in ethanol, respectively. The electrolyte was 0.5 M LiClO4 in ethanol. The potential dependence was much more pronounced for ZnO than for TiO2. The charge transport was also dependent on the electrolyte giving a linear dependence between the conductivity of the electrolyte and the apparent electronic diffusion coefficient. The dependence of the light intensity was also studied. Intensity-dependent losses were observed.