Roles of intramolecular and intermolecular electron-phonon coupling on the formation and transport of large polarons in organic semiconductors

Polaronic charge transport of organic semiconductors under thermal fluctuations is analyzed based on semiclassical Ehrenfest dynamics. We consider a coarse-grained model of rubrene crystal accounting for intra- and intermolecular electron-phonon couplings as well as anisotropy of transfer integrals. The charge carrier is distributed over hundreds of molecules under thermal fluctuations, forming a large polaron. The charge mobility is decreased, with increasing the temperature and decreasing the rigidity of lattice. The extent to which the large polaron is delocalized is determined by the transfer integral and the lattice disorder due to the intermolecular electron-phonon coupling. The intramolecular electron-phonon coupling plays a crucial role in facilitating the diffusion of a polaron from a low-energy region of the lattice.