Intrinsic Charge Transport on the Surface of Organic Semiconductors

Abstract

The air-gap field-effect technique enabled realization of the intrinsic (not limited by static disorder) polaronic transport on the surface of rubrene (${\mathrm{C}}_{42}{\mathrm{H}}_{28}$) crystals over a wide temperature range. The signatures of this intrinsic transport are the anisotropy of the carrier mobility, $\mu$, and the growth of $\mu$ with cooling. Anisotropy of $\mu$ vanishes in the activation regime at low temperatures, where the transport is dominated by shallow traps. The deep traps, introduced by x-ray radiation, increase the field-effect threshold without affecting $\mu$, an indication that the filled traps do not scatter polarons.