The effect of spatial disorder on the mobility of charge carriers hopping through energetically disordered dipolar lattices

The mobilities of charge carriers hopping through cubic lattices occupied b y a site fraction, C, of randomly oriented dipoles have been evaluated usin g Monte Carlo simulations. Spatial disorder is introduced in the simulation s through random assignment of the occupied lattice sites. Computed mobilit ies (mu) are found to depend upon the applied electric field (F), where the type of held dependence determined by the magnitude of F relative to a cri tical field (F-c). When F > F-c mu proportional to F-1, due to saturation o f the carrier velocities, whereas for F < F-c, mu proportional to exp (root F), in agreement with reported dependence for doped organic materials. The magnitude of F, is affected by the amounts of energetic and spatial disord er employed in the simulations. As C is reduced, F, decreases and hopping i ncreasingly involves sites which are less correlated. (C) 2000 Elsevier Sci ence B.V. All rights resented.