Charge-Dipole Model for the Universal Field Dependence of Mobilities in Molecularly Doped Polymers

Using the general result that the mobility $\mu$ of charge carriers driven in a spatially correlated random potential by an electric field $E$ can be expressed in terms of the Laplace transform of a particular correlation function related to the random potential, we demonstrate that the exponential dependence of $\mu$ on $\sqrt{E}$ universally observed in molecularly doped polymers arises naturally from the interaction of charge carriers with randomly distributed permanent dipoles.