High Mobility, Air-Stable Organic Transistors from Hexabenzocoronene/Carbon Nanotube Bilayers†

The pick-up-stick transistor concept is demonstrated using materials that are both air-stable and fully solution processable. In this paper, the thin film transistor (TFT) semiconductor is a bilayer structure with an array of carbon nanotubes (CNTs) as an underlayer and an alkyl-substituted hexabenzocoronene (HBC) overcoat. Electrical current flowing through the structure favors the low resistance CNTs, and therefore, the effective channel length, transconductance, and charge carrier mobility are modulated by the CNT density. With this structure, we measure a field effect mobility of 0.1 cm2/Vs which represents a factor of 6 improvement over that of HBC without a CNT underlayer. All fabrication is carried out in a bright, air-filled environment.