Non variable range hopping transport on doped polypyrrole films

The conductivity of electrochemically synthesized polypyrrole films doped by p-toluene sulphonic acid was investigated in the temperature range 50 – 300K. For the most doped sample the room temperature conductivity is of the order of 20S/cm and the conductivity vs. temperature curve has the usual convex shape. However, the analysis of the temperature dependence of these samples reveals an anomalous behavior: A variable range hopping model with fixed integer dimensionality does not describe the data throughout the entire temperature interval. A more detailed statistical analysis of the data suggests that for the present samples an extra term should be included in the functional form of the temperature dependence of the conductivity. The same statistical analysis is used for an extensive comparison of these results with previous experimental work on doped polypyrrole samples.