Charge carrier mobilities of organic semiconductors:ab initio simulations with mode-specific treatment of molecular vibrations

The modeling of charge transport in organic semiconductors usually relies on the treatment of molecular vibrations by assuming a certain limiting case for all vibration modes,such as the dynamic limit in polaron theory or the quasi-static limit in transient localization theory.These opposite limits are each suitable for only a subset of modes.Here,we present a model that combines these different approaches.It is based on a separation of the vibrational spectrum and a quantum-mechanical treatment in which the slow modes generate a disorder landscape,while the fast modes generate polaron band narrowing.We apply the combined method to 20 organic crystals,including prototypical acenes,thiophenes,benzothiophenes,and their derivatives.Their mobilities span several orders of magnitude and we find a close agreement to the experimental mobilities.Further analysis reveals clear correlations to simple mobility predictors and a combination of them can be used to identify high-mobility materials.