On the theory of hopping transport in organic solids with superimposed disorder and polaron effects

The theory of non-dispersive charge carrier hopping transport was developed for disordered organic solids for the weak-electric-field limit. In the framework of the effective-medium approach we obtained the equation for the effective hopping rate for charge transport taking into consideration an asymmetrical type of jump rate between two neighbouring charge transport sites. Energy disorder with a Gaussian type of density of states was considered. Using this equation we have calculated the temperature dependence of the effective hopping rate in disordered organic solids, for the cases of both the Miller-Abrahams jump rate and the small-polaron jump rate. The contributions from both the energy disorder and the polaron formation to the total activation energy of the effective hopping rate were found.