Influence of the local electric field on ionic transport during redox switching of conducting polymers

This work aims to demonstrate the predominant role played by migration in ionic transport during redox switching of conducting polymers. For this purpose, we apply the "moving front" model in addition to a field driven motion of dopant ions, The local electric field inside the film is calculated by numerically solving the Poisson equation. Simulation of linear sweep voltammograms is performed using a Monte-Carlo procedure, and the shapes of the resulting curves are analysed, in relation with the dielectric constant of the film and the potential scan rate. The evolutions observed for the simulated voltammograms are correlated to the local electric field profiles. So, it has been demonstrated that the space charges created at the beginning of the oxidation process act as a barrier for the incorporation of dopants, This behaviour is observed as long as the electrode potential is not too high above the standard potential. These results differ notably from those established in the case of pure diffusional ionic motion. (C) 2000 Elsevier Science B.V. All rights reserved.