A General Equivalent Circuit Model for a Metal/Organic/Liquid/Metal System

A general equivalent circuit model for the metal/organic semiconductor (OSC)/liquid/metal system is presented. Each circuital element, representative of a physically observable phenomenon associated with the device working principle, is analyzed and discussed. Two case studies of electrochemical impedance spectroscopy of devices featuring NaCl (concentration of 0.1 M) and MilliQ water as liquid are reported, showing that both cases can be considered as a particular case of the general model presented in this paper. Experimental verification of the two practical cases is achieved by performing measurements onto electrodes coated by either an n-type or a p-type OSC deposited by sublimation or drop casting, respectively. The good agreement with the experimental data makes our model a useful tool for the characterization and failure analysis of electronic devices, such as water-gated transistors, electrophysiological interfaces, fuel cells, and others electrochemical systems.