Dispersive and non-dispersive transport processes in polymers

Abstract

Based on Monte Carlo simulation techniques and analytic theory the influence of positional and energetic disorder as well as of multiple trapping on charge carrier motion in a random solid is discussed. While under realistic conditions positional disorder will not give rise to dispersive behavior on the time-scale of a carrier transit, both E-hopping and multiple trapping do so because of energetic relaxation of the carriers within the density of states (DOS). For a Gaussian DOS of width σ dynamic equilibrium can be attained under realistic experimental conditionsd resulting in a non-Arrhenius-type temperature dependence of the mobility. Representative recent literature results on dispersive and non-dispersive transport in polymeric systems are discussed in relation to the various disorder cases. Finally, the temperature dependence of the visocity of supercooled melts is shown to be tractable in terms of the concept developed for the diffusion and relaxation of excitations in a Gaussian DOS.