ABSTRACTWe develop theoretical descriptions for charge transport in organic semiconductors and carbon nanomaterials. For the localized charges, we found the quantum nuclear tunneling effect is essential which could manifest isotope effect for mobility as well as exotic optical feature. Because the nuclear tunneling tends to favor electron transfer while heavier nuclei decrease the quantum effect, isotopic substitution should reduce carrier mobility. Moreover, the isotopic effect only occurs when the substituted nuclei contribute actively to vibrations with appreciable charge reorganization energy and coupling with carrier motion. For the band-like transport, we propose a Wannier extrapolation scheme for computing the electron-phonon interaction matrix for the Boltzmann equation. Our calculation indicates that the intrinsic electron-phonon scatterings in two-dimensional carbon materials are dominated by low-energy longitudinal-acoustic phonon scatterings over a wide range of temperatures, while by high-frequency optical phonons at high temperature. The electron mobilities of α- and γ-graphynes are predicted to be ca.104 cm2V-1s-1 at room temperature.
Coexistence of band-like and thermally activated charge transport through nuclear tunneling effect in organic semiconductors
