Finite-displacement Boltzmann transport theory reveals the detrimental effects of high-frequency normal modes on mobility

Lattice vibrations can greatly reduce the charge-carrier mobilities of organic semiconductors by introducing dynamic structural disorder. The low-frequency regime is expected to contribute the most to this disorder since these vibrational modes result in the largest structural distortions and electronic coupling changes in time. In this work, a finite-displacement Boltzmann transport theory (A-BTE) method is developed to evaluate vibrationinduced mobility effects in periodic boundary conditions. A-BTE is tested on a model organic semiconductor crystal, i.e., tetracene, and it predicts that particular high-frequency ring-breathing modes significantly reduce its mobility through a transient carrier localization process, even when restricted to the zero-point vibrational energy level.