Comparative study of hole transport in poly(p-phenylene vinylene) derivatives

The dc mobility of holes in four poly(p-phenylene vinylene) (PPV) derivatives (three fully conjugated polymers with different side chains and one partially conjugated PPV) is examined as a function of temperature T and applied electrical field E. In all cases the mobility $\mu$ follows the empirical $\mu \propto \exp \gamma \sqrt{E}$ law. The specific temperature and electrical field dependence of the mobility is fitted within a (correlated) Gaussian disorder model. From the fits the energetic disorder, localization length, and average transport-site separation are determined. In the case of the fully conjugated polymers the different T and E dependencies of $\mu$ are completely determined by the energetic disorder. The relation between the obtained microscopic transport parameters and the specific chemical composition of the polymer material is discussed.