Selective Purity Modulation of Semiconducting Single-Walled\nCarbon Nanotube Networks for High-Performance Thin-Film Transistors

Abstract

Single-walled\ncarbon nanotube (SWCNT) random networks have become\nstrong candidates for next-generation electronics due to their exceptional\nmechanical, electrical, and optical properties. However, metallic\nnanotubes in networks generally incur a trade-off between the charge\ncarrier mobility and on/off ratio, limiting the performance of SWCNT-based\ndevices. Therefore, various methods to increase the purity of semiconducting\nnanotubes in entire random networks have been reported, but this direction\nhas faced other issues, such as nanotube shortening, higher cost,\nand higher energy. Here, we introduce SWCNT random network-based thin-film\ntransistors (SWCNT TFTs) with a varying purity profile of semiconducting\nSWCNTs across the channel, exploiting the superior mobility of metallic\nSWCNTs by partially tuning the semiconducting SWCNT purity and developing\na novel perspective on metallic nanotubes in semiconductor channels.\nBased on the high-precision drop-on-demand capability of inkjet printing\nand various concentrations of semiconducting SWCNT ink, we form selectively\npatterned channel regions with different semiconducting SWCNT purities.\nThe metallic nanotube-dominant region drastically increases the carrier\ndensity with a minimized Schottky barrier, while high-purity semiconducting\nregions at the channel boundaries effectively block off-state leakage\nthrough carrier depletion. As a result, the SWCNT TFTs with selectively\npatterned metallic nanotube regions show superior carrier mobility\n(75.50 cm² V^–1 s^–1)\nand channel width normalized on-current (34.33 nA μm^–1) without compromising the on/off ratio (1.62 × 10⁷). To show the feasibility of our device in high-performance electronics,\nwe demonstrate all-inkjet-printed flexible display driving circuits\nwith two transistors that enable low-power, high-performance operation\nin display applications.