New Aspects of Variable-range-hopping Conductivity in Doped Polyaniline

Abstract

Temperature, T, dependence of the electrical conductivity, σ, of own-made polyaniline pellets, highly doped either by HCl or by dodecylbenzenesulphonic acid, is discussed. For the both dopants, a variable-range-hopping exponent 2/5 is found below T* ≈ 200 − 250 K. This result can be understood on the basis of a recent theory of Fogler, Teber and Shklovskii which takes into account Coulomb correlations in a three-dimensional system of chain-like conductors, predicting a power-law density of states for charge excitations around the Fermi energy. At T > T *, the σ(T) curves are steeper, implying a tendency towards nearest-neighbour hopping by a reduction of the average hopping length.</p