Rapid Evaluation of Dynamic Electronic Disorder in Molecular Semiconductors

One of the key factors limiting the charge mobility of molecular semiconductors is the fluctuation of transfer integrals, also known as dynamic disorder. This is a manifestation of the nonlocal electron-phonon coupling, a property that is computationally expensive to evaluate and, so far, prevented the study of this property on large datasets of molecules. In this article, we describe a methodology for the fast evaluation of the dynamic electronic disorder for molecular semiconductors from their crystalline structure. The computation is accelerated by (i) the evaluation of the Cartesian gradient of transfer integral and (ii) the use of approximate phonons evaluated within the rigid body approximation. The quality of the approximations is checked against less-approximated alternatives. This method is used to study a range of molecular crystals, and some general trends on the behavior of the nonlocal electron-phonon coupling are discussed. A strategy to find the optimal relative position between interacting molecules is proposed.