Processing of Transparent Conducting Films from Colloidal Suspensions of Carbon Nanotubes

CNT-films are thought as possible replacement to Indium Tin Oxide for a variety of uses, including flat-panel displays, lasers, and solar cells. We report the fabrication of optically transparent and electrically conducting thin films of single-walled carbon nanotubes (SWNT) from surfactant stabilized CNT suspensions using two different processes: Spray-Coating and Roll-Coating - two scalable coating techniques used industrially.

Focus of this talk will be on the spray-coating method. The advantage of the spray-coating process is its applicability to irregular surfaces. In this method, an ultra-sonic droplet generator was utilized to form uniform droplets of the SWNT suspensions, which was deposited on a glass-substrate kept at a temperature of 150-200 ºC. Optimization of several processing parameters such as choice of surfactant and solvent, sonication time for dispersion synthesis, drying conditions, surfactant washing are critical for the fabrication of these films. The films were also treated with vapors of strong acids which lead to significant improvement in properties. Films with sheet resistance of 150 Ohm/sq at a transparency of 50% were obtained. Processing-property correlation of spray-coated CNT films will be discussed.