Analysis on impedance characteristics of a photo‐conductive film using distributed parameter circuit model

Abstract

AbstractIn the measurement of AC impedance of a photo‐conductive layer, the sample is sandwiched between a metal substrate and a transparent conductive surface film. A conductive ring is contacted at the outer edge of this transparent film, forming one electrode. Equivalent parallel resistance and equivalent parallel capacitance representing the bulk properties are calculated from the measured impedance assuming a lumped constant circuit.However, in this method, an error due to the surface impedance of the transparent conductive layer increases with frequency and reaches nonnegligible value at high frequencies.In this work, the impedance is theoretically calculated using a distributed constant circuit model and the error contained in the equivalent parallel resistance and parallel capacitance from assuming a lumped constant circuit is clarified.On the other hand, this theory can also be used for the output calculation of photovoltaic device. The design of short output current, open output voltage, and optimized load is also discussed.