Efficient charge carrier control on single walled carbon nanotube thin film transistors using water soluble polymer coatings

SWCNT-based thin-film transistors (TFTs) typically display unipolar p-type electrical characteristics in ambient condition due to the O 2 /H 2 O redox couple. However, complementary circuits that combine both p and n channels are preferred due to lower power requirements. Typical approaches with small molecule or polymeric dopants often yield ambipolar devices, or unstable n-type devices while concomitantly suppressing the on-current and mobility. Herein, we demonstrate a charge carrier control strategy using aqueous-based polymeric coatings that enable n-type devices with comparable performance to p-type devices. Specifically, we used a polyvinyl alcohol (PVA) coating layer containing a minority fraction of polyethyleneimine (PEI) (0.06–1.1 % w/w) to effectively switch the transfer characteristics from p-type to n-type, while maintaining decent electrical characteristics. Moreover, we demonstrate the ability to fine-tune the n branch threshold voltage via the annealing temperature. A similar strategy provides a balanced p branch on-current by incorporating PVA as a minor component (0.1-6 % w/w) into a polyacrylic acid (PAA) matrix. Through effective n-type conversion and p-type balancing, we demonstrate a simple SWCNT-based inverter. Considering the low-cost, environmentally friendly compositions and aqueous processability, this approach is attractive for large scale complementary printable circuits.