Investigation on the frequency‐dependence of the impedance of the nearly ideally polarizable semiconductor electrodes CdSe, CdS and TiO₂

Abstract The impedance of several nearly ideally polarizable semiconductor electrodes (CdSe, CdS, TiO 2 ) has been studied as a function of applied voltage and of frequency. The differential capacitance and resistance appear to obey to simple frequency laws. A mathematical model accounting for these laws is presented, in which a distribution of time constants is assumed, associated with dielectric relaxation phenomena in the double layer at the semiconductor/electrolyte interface. The experimental results indicate, that the source of the frequency‐dependence has to be sought in structural irregularities of the surface region of the electrode. The proposed model appears to be also applicable to results, mentioned in the literature, concerning other semiconductor/electrolyte systems. The possibility of determining the flat‐band potential from frequency‐dependent capacitance data is discussed.