High-field hopping mobility in molecular systems with spatially correlated energetic disorder

Abstract

Prior Monte Carlo simulations of hopping mobility μ versus electric field E using the Gaussian disorder model have shown, in disagreement with experiment, only a short range of fields where log μ α E12 (Poole-Frenkel type behavior). We demonstrate that the introduction of correlation of the energies of sites close together can lead to field dependences similar to the Poole-Frenkel one over the wide range of fields where it is usually seen experimentally. Such correlation is physically reasonable, for example, for systems in which the fluctuations of site energy are due to the interaction of charge carriers with permanent dipoles or to molecular density fluctuations.