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 p hotocurrent transients. The results are discussed using a diffusion model a nd compared with previous results on TiO2. The charge transport was highly dependent on the potential giving apparent diffusion coefficients for the e lectron ranging from 1 x 10(-4) to 1 x 10(-6) cm(2)/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 pronou nced for ZnO than for TiO2. The charge transport was also dependent on the electrolyte giving a linear dependence between the conductivity of the elec trolyte and the apparent electronic diffusion coefficient. The dependence o f the light intensity was also studied. Intensity-dependent tosses were obs erved. (C) 2000 Elsevier Science B.V. All rights reserved.