Polyfluorene-Sorted Semiconducting Single-Walled Carbon Nanotubes for Applications in Thin-Film Transistors

Due to their superlative electrical and mechanical properties, single-walled carbon nanotubes (SWNTs) are capable of expanding the current scope of electronic device applications. Advancements in the selective isolation and purification of semiconducting SWNTs through the use of conjugated polymers has allowed for incorporation of high-quality SWNTs into solution-processed thin-film transistors (TFTs). In this study, we report an alternating copolymer based on fluorene and 2,5-dimethoxybenzene that is capable of selectively dispersing semiconducting SWNTs. The exceptional semiconductingSWNT purity (>99%) of the dispersion was confirmed by UV–vis and Raman spectroscopy, which exhibit negligible metallic SWNT features. TFTs fabricated with this polymer–SWNT complex exhibited maximum hole and electron mobilities of 19 and 7 cm2/V·s, respectively, with on/off ratios as high as 107. Device fabrication parameters including silane surface treatment, removal of excess polymer, and SWNT dispersion concentration were investigated. Evaluation of hole and electron mobilities indicates that the presence of excess polymer in the polymer–SWNT dispersion did not adversely affect device performance. Atomic force microscopy measurements showed that our polymer–SWNT dispersions were capable of forming a complete percolation pathway between electrodes, with individual SWNTs exfoliated by the polymer.