Transparent conductive thin films based on chemically assembled single-walled carbon nanotubes

Transparent conductive thin films were fabricated by the chemical assembly of carboxylated single-walled carbon nanotubes (ca-SWNTs) onto aminosilane-modified glass plates. The ca-SWNTs were deposited with multilayer structures by amidation reaction between the carboxylic acid groups of ca-SWNTs and amino groups of linker molecules with the aid of coupling agents. Unlike the chemically assembled SWNT layers reported thus far, these SWNT assemblies have high-density structures and excellent surface adhesion due to direct chemical bonding to their substrates, which results in high electrical conductivity. The covalent bonds of the SWNT thin film were characterized by X-ray photoelectron spectroscopy, and the structures of SWNTs in the conductive thin film were analyzed by Raman spectroscopy. Imaging by scanning electron microscopy shows that the SWNT thin film has a uniform morphology with high-density multilayer structure over large areas, and UV–vis spectroscopy analysis shows that the transmittance of SWNT thin film in visible light region is excellent and further improved to greater than 90% upon thermal treatment at 250 °C. The electrical resistivities of the ca-SWNT thin film were found to be 5–10 Ω cm, which was improved to 0.2–0.4 Ω cm by the thermal treatment. The work function measured by photoelectron spectroscopy in air was found to be 5.12 eV.