Effects of electron coupling to intramolecular and intermolecular vibrational modes on the transport properties of single-crystal organic semiconductors

Electron coupling to intramolecular and intermolecular vibrational modes is investigated in models appropriate to single-crystal organic semiconductors, such as oligoacenes. The focus is on spectral and transport properties of these systems beyond perturbative approaches. The interplay between different couplings strongly affects the temperature-band renormalization that is the result of a subtle equilibrium between opposite tendencies: band narrowing due to interaction with local modes and band widening due to electron coupling to nonlocal modes. The model provides an accurate description of the mobility as a function of temperature: Indeed, it has the correct order of magnitude at low temperatures, it scales as a power law T(-delta) with the exponent delta larger than unity, and, at high temperatures, it shows a hopping behavior with a small activation energy.