Extracting nondispersive charge carrier mobilities of organic semiconductors from simulations of small systems

Predictions of charge-carrier mobilities in amorphous semiconductors often rely on charge transport simulations in microscopically sized systems, where transport is dispersive and mobilities are system-size dependent. We propose a method for extrapolating a macroscopic nondispersive mobility from the temperature dependence of a microscopic one. The method is tested on an amorphous phase of tris(8-hydroxyquinoline) aluminum, for which the temperature dependence of a microscopic hole mobility is obtained by combining molecular-dynamics simulations for generating material morphologies, electronic-structure calculations for determining charge hopping rates, and kinetic Monte Carlo simulations for studying charge dynamics. The extracted value of the nondispersive mobility and its electric field dependence agree well with the results of time-of-flight experiments.