Anomalous transport on polymeric porous film electrodes in the dopant-induced insulator-to-conductor transition analyzed by electrochemical impedance

In the present letter, we have identified anomalous transport patterns on conducting polymer thin-film electrodes [poly(thiophene-3-acetic acid)] by means of electrochemical impedance measurements. This type of electrical behavior yields conductance responses exhibiting frequency dispersion at frequencies in excess of the ac onset omega (c). The study of impedance spectra under variation of the applied potential allows to determine the threshold potential at which a dopant-induced insulator-to-conductor transition takes place. Moreover, since the charge carrier concentration in the polymer matrix is directly modulated by the insertion of anions via the applied potential, some relevant aspects of the doping process, such as the dimensionality of the ion insertion, can be properly investigated. (C) 2001 American Institute of Physics.