Hopping Mobility for Charge Carriers in Disordered Media with Permanent and Induced Charge-Dipole Interactions

Recent attempts to explain the observed field dependence of photoexcited carrier mobilities in molecularly-doped polymers have focused on the role played by local correlations in the energetic landscape characterizing the transport site manifold. Site energy correlations that fall off algebraically with distance have been shown to arise when the primary source of energetic disorder in the material is the interaction of carriers with random electric dipoles of the dopant and host molecules of the medium. In one dimension, such correlations lead to a Poole-Frenkel field dependence that is in qualitative agreement with experiment. We have recently investigated the stability of this one dimensional Poole-Frenkel prediction in the presence of other sources of disorder (e.g., charge-induced dipole interactions) that might lead to strong local energy fluctuations that fall off rapidly with distance. Our analysis suggests that local fluctuations of this type need not change the predicted field-dependence provided that they are themselves uncorrelated with the permanent dipole component of disorder