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 c onducting polymer thin-film electrodes [poly(thiophene-3-acetic acid)] by m eans of electrochemical impedance measurements. This type of electrical beh avior yields conductance responses exhibiting frequency dispersion at frequ encies 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 mat rix is directly modulated by the insertion of anions via the applied potent ial, some relevant aspects of the doping process, such as the dimensionalit y of the ion insertion, can be properly investigated. (C) 2001 American Ins titute of Physics.