Interface polaron formation in organic field-effect transistors

A model describing the low-density carrier state in an organic single-crystal field-effect transistor (FET) with high-kappa gate dielectrics is studied. The interplay between charge-carrier coupling with intermolecular vibrations in the bulk of the organic material and the long-range interaction induced at the interface with a polar dielectric is investigated. This interplay is responsible for the stabilization of a polaronic state with an internal structure extending on few lattice sites, at much lower coupling strengths than expected from the polar interaction alone. This effect could drive the carriers close to self-trapping in high-kappa organic FETs without invoking unphysically large values of the carrier-interface interaction.