Electrochemical Transfer via Surface States: A New Formulation for the Semiconductor/Electrolyte Interface

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Abstract
We present a simple model for the electrochemical transfer at the semiconductor/electrolyte interface, assuming the only pathway for electron transfer is via the intermediate of surface states. These are taken as a band extending through the semiconductor gap. Three parameters are involved: (i) an exchange current density between the surface states and the semiconductor bulk, (ii) an exchange current density between the surface states and the redox system, and (iii) the surface density of states, measured by a dimensionless quantity α. The predictions of the model are compared with experimental data on the n‐Si/acetonitrile system. For a given redox couple, the same set of three parameters is found to account quantitatively for the current‐voltage characteristics , the complex impedance , and the photocurrent as a function of electrode potential and light chopping frequency . Changing the redox couple results mainly in a change of . The approximations involved in the model and its applicability to other semiconductor/electrolyte systems are discussed.

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