Nonlocal Electron–Phonon Coupling in Prototypical Molecular Semiconductors from First Principles

A substantial amount of evidence indicates a relevant role played by the nonlocal electron–phonon couplings in the mechanism of charge transport in organic semiconductors. In this work, we compute the nonlocal electron–phonon coupling for the prototypical molecular semiconductors rubrene and tetracene using the phonon modes obtained from ab initio methods. We do not make the rigid molecular approximation allowing a mixing of intra- and intermolecular modes, and we use a supercell approach to sample the momentum space. Indeed, we find that some low-frequency intramolecular modes are mixed with the rigid-molecule translations and rotations in the modes with the strongest electron–phonon coupling. To rationalize the results we propose a convenient decomposition of the delocalized lattice modes into molecular-based modes.