Effect of various parameters on sorting semiconducting carbon nanotubes using polyfluorene for high-performance field-effect transistors

Abstract

High-purity, large-diameter (>1.1 nm) semiconducting single-walled carbon nanotubes (s-SWNTs) are required to fabricate high-performance field-effect transistors (FETs). In this study, we optimized the key parameters for s-SWNT sorting, including polymer concentration, sonication time, and temperature, to selectively achieve high-purity (>99 %) and large-diameter s-SWNTs suitable for advanced FET applications. These parameters strongly influence the absorbance, yield, and purity of the large-diameter s-SWNTs. Increasing polymer concentration enhanced the yield of s-SWNTs but reduced their purity, likely due to excessive polymer interactions with metallic SWNTs. In contrast, both the yield and purity improved with longer sonication times, with 2.5 h identified as the optimal duration to maximize de-bundling and minimize residual bundles. Shorter sonication times (1–1.5 h) resulted in lower purity due to insufficient de-bundling. The optimal sonication temperature was found to be 35 °C, balancing the thermodynamic and kinetic conditions for effective SWNT dispersion and polymer dissolution. The FETs with the s-SWNTs prepared under the optimal condition showed an ON/OFF ratio of 10⁴ and an electron mobility of 43.6 cm² V⁻¹ s⁻¹, which are high values reported for random network FETs with SWNTs.