Composite Semiconductor Material of Carbon Nanotubes and Poly[5,5′-bis(3-dodecyl-2-thienyl)-2,2′-bithiophene] for High-Performance Organic Thin-Film Transistors

A nonpercolating network of non-covalently functionalized single-walled carbon nanotubes was embedded within air-stable poly[5,5′-bis(3-dodecyl-2-thienyl)-2,2′-bithiophene] (PQT-12) thin films for the purpose of enhancing the field-effect mobility in thin-film transistors. The host polymer was used to stabilize the nanotubes in suspension through π-orbital overlap caused by simple application of ultrasonication. The stable nanotube suspension was cast into two different device architectures, both of which exhibited excellent on/off ratios ranging from 105 to 106 and dramatically improved mobilities compared with pristine PQT-12 semiconductor. A single-layer film with nanotubes embedded throughout was easy to fabricate and had mobility up to 0.34 cm2/Vs, an enhancement of over 3× compared with PQT-12. Placing the nanotubes closer to the dielectric surface in a dual-layer approach resulted in a mobility improvement of up to six times (0.58 cm2/Vs). The effects of the nanotube content on the polymer interaction within the suspension, film morphology, and electrical properties were investigated as well.