Intrinsic transport properties in polypyrrole

We have studied transport properties in polypyrrole (PPy) doped with CF3SO3− and ClO4−. We measured the dc resistivity rdc(T), the absolute thermoelectric power S(T), and the dc resistivity with the VSC (voltage-shorted-compaction) technique ϱvsc(T) as a function of temperature. We aim to abstract the intrinsic transport properties inherent in the crystallized regions in PPy. At high temperatures between 10 and 200K, ϱvsc(T) shows a metallic behavior following a temperature dependence approximately expressed by T1, which is weaker than in the ordinary metals. Below 4K, ϱvsc(T) in ClO4− doped PPy shows to be semiconducting. The result is interpreted in terms of a metal-insulator transition within the crystallized regions.