Harmonic analysis of pulsed photovoltaic response of titanium dioxide films under local illumination

A change in the photoelectrochemical behavior of a semiconductor-electrolyt e system after transition from overall to local illumination of the electro de surface is studied. The proposed model accounts for charge interactions between illuminated and dark electrode portions and describes the frequency spectrum of photopotential for an electrode locally illuminated by a perio dic sequence of light pulses a few nanoseconds in length. As shown with pol ycrystalline thin-film TiO2 electrodes, local values of concentrations of i onized donors and flat-band potentials of semiconductor electrodes may be d etermined with a harmonic analysis of frequency spectra of photovoltaic res ponses. The possibility of using the proposed approach in photoelectrochemi cal microscopy is discussed.