Impedance Characteristics of Poly(4,4’- Bis(butylsulfanyl)-2,2’-bithiophene) Film Electrode as a Function of Different Oxidation Levels

The impedance characteristics of poly[4,4 ' -bis(butylsulfanyl)-2,2 ' -bithiophene] film electrode are studied at different p-doping levels. The impedance features can be coherently described modeling the polymer deposit by a 'generalized transmission line circuit', using different simplifications when dealing with different oxidation states. Through these simplifications, the parameters of the equivalent circuit can be calculated The deviation of the impedance plots of the oxidized state from the Warburg-impedance 45 degrees slope in the mid-frequency domain is attributed to a non-uniform ionic conductivity profile within the polymer film. The analysis of the plots suggests the high-frequency semicircle, detectable in the case of both the neutral and the p-doped polymer to be due to the ion transfer barrier at the polymer/solution interface.