Intrinsic charge transport on the surface of organic semiconductors

TL;DR

This study demonstrates intrinsic charge transport on organic semiconductor surfaces using a novel air-gap transistor technique, revealing anisotropic mobility and the effects of traps over a wide temperature range.

Contribution

It introduces a new method to observe intrinsic charge transport in organic semiconductors, highlighting the role of anisotropy and traps in mobility behavior.

Findings

Intrinsic transport observed over a wide temperature range

Mobility anisotropy decreases at lower temperatures

Deep traps increase threshold without affecting mobility

Abstract

The novel technique based on air-gap transistor stamps enabled realization of the intrinsic (not dominated by static disorder) transport of the electric-field-induced charge carriers on the surface of rubrene crystals over a wide temperature range. The signatures of the intrinsic transport are the anisotropy of the carrier mobility, mu, and the growth of mu with cooling. The anisotropy of mu vanishes in the activation regime at lower temperatures, where the charge transport becomes dominated by shallow traps. The deep traps, deliberately introduced into the crystal by X-ray radiation, increase the field-effect threshold without affecting the mobility. These traps filled above the field-effect threshold do not scatter the mobile polaronic carriers.