Tuning electron-phonon and Coulomb interactions in organic field effect transistors

Abstract

Recent experiments have demonstrated that the performances of organic FETs strongly depend on the dielectric properties of the gate insulator. In particular, it has been shown that the temperature dependence of the mobility evolves from a metallic-like to an insulating behavior upon increasing the dielectric constant of the gate material. This phenomenon can be explained in terms of the formation of small polarons, due to the polar interaction of the charge carriers with the phonons at the organic/dielectric interface. Building on this model, it is shown that the Coulomb repulsion between the carriers can lead to a further reduction of the electron mobility at high concentrations, as can be reached in devices with highly polarizable gate dielectrics. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.