Doping-level dependence of conductivity in polypyrroles and polythiophenes

In situ conductivity of some selected polypyrroles (polypyrrole and poly(N-methylpyrrole)) and polythiophenes (poly(4,4′-dipentoxydithiophene), poly(dithienylethylene) and two crown-5-substituted poly(cyclopentadithiophenes)) as a function of oxidative doping level is reported. The relationship is in general composed of three segments (threshold, linear increase and plateau). Doping-charge thresholds of conductivity are explained on the basis of charge pinning of polarons and bipolarons by anions and (in polythiophenes) by π-dimerization of polarons.