Photo-Impedance of the AgCl Electrode System

Abstract

The observed frequency response of the AgCl-electrode system indicates an equivalent parallel combination of capacitance and conductance in series with the bulk photoconductance. The voltage dependence of the capacitance suggests an exhaustion layer, presumably at the sample-electrode interface, and the magnitude of the capacitance indicates that the layer is thick. Qualitatively, the dependence of the layer capacitance and current on the intensity and wavelength of the exciting illumination, on temperature, and on voltage can then be understood in terms of a potential barrier. Alternatively, the results can be described in terms of layers, presumably at the surface, of lower conductivity than the bulk. An increase of the capacitance with the bulk conductivity, and so with the density of mobile electrons, suggests that the positive charge in the exhaustion region is determined at least in part by holes generated by illumination. The dependence of the bulk photoconductivity on temperature, voltage, intensity, and wavelength are discussed.