AN ANALYSIS OF TRANSIENT PHOTOCURRENTS MEASURED ON PASSIVATED IRON ELECTRODES

The electronic properties of the passive film formed on iron in pH 6.5 borate solution were investigated by measuring the transient photocurrent. The charge and the time constant of decay of the spike-like photocurrent and the steady state photocurrent were measured as a function of potential. A simulation was made to explain the transient behavior of the photocurrent by assuming an equivalent circuit with generation of a photo-induced free carrier pair in the n-type passive film. From the simulation the transient photocurrent behavior can be explained from the relationship between thickness of the passive film, the recombination rate of photo-induced free carrier in the film, the density of surface states, and the charge transfer from or to the redox system in the solution. © 1990.