Charge-carrier mobilities in disordered semiconducting polymers: effects of carrier density and electric field

We model charge transport in disordered semiconducting polymers by hopping of charge carriers on a square lattice of sites with Gaussian on-site energy disorder, using Fermi-Dirac statistics. From numerically exact solns. of the Master equation, we study the dependence of the charge-carrier mobility on temp., carrier d., and elec. field. Our results are used in calcg. current-voltage characteristics of hole-only polymer diodes. It is found that very good fits to exptl. current-voltage characteristics can be obtained at different temps., with reasonable fitting parameters for the width of the Gaussian d. of states and the lattice const. In agreement with the expts. we find that the d. dependence is dominant over the field dependence. Only at high fields and low temps. the field dependence becomes noticeable. The potential and current distribution show strong inhomogeneities, which may have important consequences for the operation of polymer opto-electronic devices. [on SciFinder (R)