Impedance spectroscopy characterisation of poly(dithienothiophene) films

Summary form only given. The process of electrochemical transition from reduced to oxidized state of poly[3,4:b,3´,4´:d-dithienothiorihene](PDTT)-covered electrode has been described by impedance spectra, registered at potentials from -0. I to 1. 25V in frequency range 100000-0.01 Hz. Values of equivalent electrical circuit elements were calculated numerically by means of NLLS-fit technique. Corresponding to the advance of anodic oxidation of PDTT, impedance spectra reveal growth of polymer conductivity, decrease of charge-transfer resistance of redox reaction and increased contribution of diffusion-related impedance in the overall frequency dispersion. The changes of values of constant phase element, which approximates the double-layer capacity corresponding to redox reaction, suggest that in reduced state of PDTT some residual reaction takes place on the outer surface of the polymer, whereas in the stage of oxidative doping the reaction transferres to the bulk of the film. In oxidated state the electrical elements characterizing the conductance of the layer disappear from the spectra. Numerical simulation of impedance spectra of a redox reaction within a conductive layer confirms overlapping of impedance responses from two sources: redox reaction and electrical features of the film.