Temperature dependence of mobility of conducting polymer polyaniline with secondary dopant

The conductivity σ and carrier density n of the conducting polymer polyaniline were investigated by changing the concentration x of a secondary dopant, meta-cresol. We found that σ changes by four orders of magnitude within the x-range of 1-10%, while n, as estimated from the Hall measurements, shows a weak dependence on x in the region of 2 % < x < 50 %. These results suggest that σ can be enhanced by the change in the mobility µ. We analyzed the temperature dependence of µ by not only the combination of two different types of scattering mechanism, but also by the polaron hopping model. The experimental data of µ(T) can be explained well by the latter model with reasonable fitting parameter values of a small-polaron binding energy and a longitudinal optical phonon frequency.