Surface Recombination at n-TiO2 Electrodes in Photoelectrolytic Solar Cells

Abstract

The photocurrent?potential behavior of photoelectrodes in liquid junction configuration is investigated. The Gartner model is modified to include the surface recombination. Impedance and photocurrent?potential measurements reveal the presence of a high density of surface states at the interface, covering more than half a monolayer. A total of four parameters are used to characterize the surface states. Two of these parameters appear in the expression for both the quantum efficiency?potential dependence and the expression for the capacitance due to these states. The other two parameters appear separately in conjunction with each experiment. The model is tested by perturbating the steady state of the system by strong background illumination which induces higher injection rate of carriers. The effect of the background illumination is interpreted as the change in the equilibrium distribution of the surface states which will result in the increase in surface recombination of photocarriers.