DC-Conductivity and Magnetoresistance of Inherently Conducting Polymers.Polyacetylene and Poly(3-alkylthiophenes)

摘要

Inherently conducting polymers with optimal charge transport properties lie inthe vicinity of the M-I transition. The most powerful demonstration of this is potassium doped highly conducting polyacetylene (room temperature dc-conductivity 3000-4000 S/cm), the dc-conductivity of which shows a temperature dependence (power law) in perfect accordance with the theory for a material in the critical intermediate regime of the M-I transition. As suggested by earlier research, iodine doped polyacetylene (doped to the maximum of room temperature conductivity, 1 to 100,000 S/cm) is on the metallic side of the M-I transition. Based on dc-conductivity and magnetoresistance measurements, this work confirms the dominating role of weak localization effects on the charge transport in the temperature regime 2-60 K, and suggest that electron-electron interactions play an important role below 2 K. Ferric chloride doped poly(3-alkylthiophenes) (P3OT and P3HT, with room temperature conductivities 30-160 S/cm) show a temperature behavior of dc-conductivity due to localized charge carriers and are therefore on the insulating side of the M-I transition.