Effect of Au doping and defects on the conductivity of single-walled carbon nanotube transparent conducting network films

We examined the electrical conductivity and transmittance of six types of SWNT network films, developed for potential use in transparent conductive films, to investigate the effect of Au doping on single-walled carbon nanotube (SWNT) defects: (i) SWNT network films without Au doping (as-produced (AP-SWNTs), purified (P-SWNTs), and cut (C-SWNTs)) and (ii) Au-doped films of AP-SWNTs (Au/AP SWNTs), P-SWNTs (Au/P-SWNTs), and C-SWNTs (Au/C-SWNTs). The density of SWNT network films was varied systematically by controlling the SWNT concentration and mediating defect formation. The electrical conductivity of each SWNT film was found to be significantly enhanced upon Au doping, with a negligible loss of optical transmittance. The effects of Au doping differed depending on the type of nanotube network present: the electrical conductivity of Au/C-SWNTs was found to be similar to that of Au/AP-SWNTs for a given transmittance, whereas the conductivity of C-SWNTs is much lower than that of the AP-SWNTs prior to Au doping. Therefore, the electrical conductivity was enhanced by the hybridization of gold nanoparticles to a larger degree in the defect-containing SWNT networks than in the AP-SWNT networks. This unusual electrical behavior of SWNT network films may be attributed to an increased number of gold nanoparticles deposited onto C-SWNT surfaces, which are formed from C-SWNTs containing an abundance of carboxylic groups. These results highlight an important consideration in the fabrication of efficient transparent conducting SWNT films for applications in optoelectronic devices.