Harmonic analysis of the electrical response of an n-TiO2/electrolyte circuit to periodic laser pulses

The photovoltage response of a semiconductor electrode to the periodic exci tation by short laser pulses has been described in a quasi-steady-state app roximation. Measurements with electrically-biased single- and polycrystalli ne n-TiO2 electrodes illuminated by a N-2 impulse laser (337 nm, 10 ns) wer e used to demonstrate the validity of the proposed model for harmonic compo nents in the frequency spectrum of the photovoltage and to illustrate its a pplication to highly doped semiconductors. It has been shown that the highe r harmonics of the ac photovoltage can be used to obtain information on the potential and frequency dependence of space-charge capacitance, which is n ot distorted by the influence of other elements of the equivalent circuit. The approach developed opens the possibility of determining the flatband po tential and doping density in the case of polycrystalline semiconductor ele ctrodes showing quite dispersive non-linear Mott-Schottky behaviour. (C) 20 00 Elsevier Science S.A. All rights reserved.