Exact Zero-Field Hopping Rates in a Gaussian Energy Distribution

Abstract

Models of photoconductors used in xerography are based on donors with a Gaussian energy distribution whose width is inferred from the zero-field mobility, μ(T). Exact mean dwell times for Marcus, Miller-Abrahams and symmetric rates are obtained at zero field for lattices with energetic, positional and orientational disorder. Monte Carlo simulations of μ(T) and hopping rates bring out the role of disorder-induced steps. Evidence for such steps in molecularly doped polymer comes from the concentration dependence of μ(T). Transport involves fast, repetitive steps with small displacement and geometrical disorder increases the T dependence of μ(T). Present analyses of μ(T) overestimate energetic disorder.