Making Contacts to n-Type Organic Transistors Using Carbon Nanotube Arrays

We investigated the performance of carbon nanotube (CNT) array electrodes applied to n-type and ambipolar phenyl-C61-butyric acid methyl ester (PCBM) thin film transistors on a SiO2 dielectric substrate. Compared to conventional Au electrodes, CNT arrays provide better injection efficiency, improved switching behavior, higher electron mobility, and lower contact resistance. Experiments on ambipolar PCBM transistors indicate that the injection performance is enhanced by the electrostatics of the CNT contacts, which promotes electron and hole tunneling across Schottky barriers at the PCBM/nanotube interface. The use of CNT arrays is a valid replacement to low workfunction metals, which are often reactive in air and difficult to process. Our work paves the way for a widespread use of carbon nanotube array electrodes in high-performance n-type and p-type organic thin film transistors.