Fluorene Copolymer and Carbon Nanotube Interaction Modulates Network Transistor Performance

Conjugated polymer extraction (CPE)-enriched high-purity semiconducting (sc) single-walled carbon nanotubes (SWCNTs) have demonstrated significant application potential as emerging electronic materials. In this work, the interaction of three fluorene-based copolymers with sc-SWCNTs in a toluene solution was systematically compared, covering a wide range of concentrations while considering the phase behavior of the polymer itself. 2D photoluminescence excitation studies show that the polymer containing semiconjugated pyridine units had a higher binding affinity to the SWCNTs due to its twistable main chain conformation. The uniform and high-density SWCNT networks deposited on a silicon wafer have been characterized by SEM and spatial Raman spectroscopy, which reveals ultrahigh sc purity with a metallic tube content less than the parts per million level. The performance of thin-film transistors could be correlated with the structure of wrapping polymers. The threshold voltage shifted with the nitrogen content in their repeat units due to electron donation from the nitrogen atoms. The off-current was reduced with the flexible copolymer, which provided better wrapping and thus limited bundling during network formation.