Theory of the anomalous diffusion of carriers in disordered organic materials under conditions of the CELIV experiment

Abstract

Analytical solutions for the transient current in the СELIV (Charge Extraction by Linearly Increasing Voltage) experiment are found in both the quasi-equilibrium (taking into account field-enhanced diffusion) and dispersive transport modes. The ratio of the time of current passage through the maximum to the transit time significantly decreases with increasing disorder. Simple analytical expressions for this ratio, containing only one dimensionless parameter characterizing the given material in each case, are obtained. The conditions of applicability of the known CELIV theory (without diffusion) are determined. The result allows calculations of the transit time in the case where the transient-current signal is sharply asymmetric and slowly decreases over long times.