Effect of Radical Polymer Doping on the Carbon Nanotube Transistors

Single-walled carbon nanotubes (SWCNTs) have shown exceptional promise for electronic applications due to a complementary set of desirable properties. Due to adventitious atmospheric p-type doping of SWCNT thin film transistors (TFTs) under ambient conditions, p-type unipolar devices are easily attained and have been the focus of extensive optimization and integration. However, n-type doping of SWCNTs for ambipolar transistor operation has proven to be considerably more challenging. Here, we introduce here the use of an aliphatic polymer as an n-type dopant for producing ambipolar SWCNT TFTs. We have systematically studied the effect of doping with the use of aliphatic polymers bearing robust organic radicals as pendant groups on the macromolecular backbone. The large population of the radical redox sites allows for a significant amount of doping to occur between the radical polymers and the SWCNTs, and this affords the ability to tune the TFT performance. Thus, this combination of physical chemistry and device physics allows for never-before-seen behavior in SWCNT-radical polymer composite materials.