Charge-carrier transport in disordered polymers

The general properties of charge-carrier transport in disordered organic materials are discussed. The spatial correlation between energies of transport sites determined the form of drift-mobility field dependence. The type of spatial correlation in a disordered material depends on its nature. Mobility field dependences must be different in polar and nonpolar materials. Different methods of mobility calculation from the shape of photocurrent transient were analyzed. A widely used method is very sensitive to the variation of the shape of the transient and sometimes produces results that effectively masquerade the true dependence of the mobility on the electric field or trap concentration. Arguments in favor of the better, more reliable method are suggested. Charge transport in materials containing charged traps was considered without using the isolated trap approximation, and this led to qualitatively different results. The results indicated that the effect of charged traps can hardly be responsible for the experimentally observed transport properties of disordered organic materials. (C) 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2584-2594, 2003