A comprehensive study of spray coating technique parameters and chemical postdeposition treatments for transparent conducting SWCNT thin films

The demands for transparent conducting films (TCFs) are continuously increasing and the future of this industry is going toward large scale, cheap and mechanically stable electronics. This study shows a simple way to fabricate low-cost transparent conductive single-walled carbon nanotube (SWCNT) thin films by spray coating. The work employed here demonstrates that it is possible to fabricate highly efficient SWCNT TCFs without the use of expensive ultrasonic spray coating equipment. Highly conductive TCFs were prepared by dispersing SWCNTs in an N-Methyl-2-pyrrolidone (NMP) solution. The spray coated TCF properties were studied by the effect of spray gun carrier gas pressure, concentration, and volume sprayed onto the substrates. The prepared thin films were subjected to post treatments with nitric acid (HNO₃) using different treatment methods and times in order to improve the electrical conductivity. To further investigate the effect of p-doping in SWCNT thin films, HNO₃ treatments were combined with thionyl chloride (SOCl₂). The experimental results indicated that spray coating is an effective method to obtain highly conductive films without any chemical treatment, resulting in 273 Ω/sq sheet resistance, at 84% in the visible range. Additionally, the optimized films treated with both HNO₃ and HNO₃/SOCl₂ showed great improvements at 83%–85% in the visible range and in sheet resistances followed by 98 and 103 Ω/sq with very good FOM values (1.6 × 10⁻³ and 2 × 10⁻³, respectively).