‘Metallic’ polymers: Interpretation of the electronic transport properties

Abstract

We summarize experimental data on the conductivity and thermoelectric power of highly-conducting polymers. The necessary requirements for models to give a quantitative account of the temperature dependence of these transport properties are then deduced. It appears that there are thin ‘barrier’ regions in which temperature-assisted conduction (e.g. by hopping or tunnelling) occurs in parallel with ‘metallic’ conduction. We point out that the observation of a linear thermopower in many of the highly-conducting polymers is a striking departure from usual metallic behaviour, which shows a change in slope due to electron-phonon enhancement. We suggest that this absence of a detectable electron-phonon interaction for thermopower in these polymers is another indicator of a huge intrinsic conductivity.