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Nano Research

Article Title

Low-temperature solution process for preparing flexible transparent carbon nanotube film for use in flexible supercapacitors

Keywords

transparent electrode, manganese dioxide, carbon nanotube, Congo red, flexible electronics, supercapacitors

Abstract

Single-walled carbon nanotubes (SWNTs) possess high conductivity, mechanical strength, transparency, and flexibility, and are thus suitable for use in flexible electronics, transparent electrodes, and energy-storage and energy-harvesting applications. However, to exploit these properties, SWNTs must be de-bundled in a surfactant solution to permit processing and use. We report a new method to prepare a SWNT-based transparent conducting film (TCF) using the diazo dye 3,3'-([1,1'-biphenyl]-4,4'-diyl)bis(4-amino naphthalene-1-sulfonic acid), commonly known as Congo red (CR), as a dispersant. Uniform 20-nm-thick TCFs were prepared on rigid glass and flexible polyethylene terephthalate (PET) substrates. The CR-SWNT dispersion and the CR-SWNT TCFs were characterized via UV-Vis-NIR, Raman spectroscopy, FT-IR spectroscopy, transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM) and dynamic light scattering (DLS) measurements. The sheet resistivity of the CRSWNT TCF was ~34 ± 6.6 Ω/□ with a transmittance of 81% at 550 nm, comparable to that of indium tin oxide-based films. Unlike SWNT dispersions prepared in common surfactants, such as sodium dodecyl sulfate (SDS), sodium cholate (SC), and Triton X-100, the CR-SWNT dispersion was amenable to forming TCF by drop coating. The CR-SWNT TCF was also very stable, maintaining a very low sheet resistivity even after 1,000 consecutive bending cycles of 8 mm bending radius. Further, manganese dioxide (MnO2) was electrochemically deposited on the CR-SWNT-PET film (MnO2-CR-SWNT-PET). The as-prepared MnO2- CR-SWNT-PET electrode exhibited high specific capacitance and bendability, demonstrating promise as a candidate electrode material for flexible supercapacitors.

Graphical Abstract

Publisher

Tsinghua University Press

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