Fabrication of SWCNT/AgNW/PEDOT: PSS nanocomposite transparent conductive films

Abstract

Transparent conductive films have become critical components in modern devices due to rapid developments in science and technology. These devices range from touch screens to solar cells that reach out to a large proportion of the industry and our daily lives. To date, progress in nanotechnology has led to the discovery of unique nanomaterials such as carbon nanotubes, metal nanowires, and conductive polymers. These nanomaterials have sparked many researchers' attention towards extensive research. However, it has been determined that each material has a number of drawbacks as well as benefits that restrict its use in large-scale production processes. Thus, researchers have focused their efforts on developing nanocomposites consisting of different materials in order to overcome the limitations imposed by these single components. The primary objective of this study is to develop nanocomposites that derive from SWCNTs, PEDOT:PSS and AgNWs to obtain highly conductive and transparent thin films. Highly conductive TCFs were prepared by dispersing SWCNTs in an NMP solution by spray coating method. Optoelectronic 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 Ω/sq and 103 Ω/sq with very good FOM values (1.6 x 10-3 and 2 x 10-3, respectively). The SWCNT films were introduced to different PEDOT: PSS dispersions (PH 1000, PH 500, Clevios FET) and thin films were fabricated with the spin coating method. Sheet resistance and optical transparency measurements of the films with different PEDOT: PSS solutions were evaluated, and the film quality of the films was also taken into consideration in determining the optimum concentration. The effect of DMSO on the overall conductivity of SWCNT/PEDOT: PSS thin films was also investigated in this thesis. As a result of these investigations, Clevios FET dispersions showed better film performance while the high acidity of PH 1000 and PH500 deteriorated the SWCNT film surface during spin coating fabrication. The sheet resistance of SWCNT/FET film was measured as 142 Ω/sq with a transmittace of 55%. Additionally, the DMSO post-treatments were found to be effective to decrease the sheet resistance of films fabricated using PH 500 dispersions, while the SWCNT/FET films were negatively impacted by the treatment. The inverse effects of the post-treatment method can be explained by the differences in PH 500 and Clevios FET's morphological structures and can be matched with other studies in the literature. The addition of AgNWs were incorporated into SWCNT and PEDOT:PSS inks using two different wet coating techniques. For the first strategy, the AgNWs were added to the PEDOT: PSS dispersion, and the SWCNT/PEDOT:PSS-AgNW nanocomposites were fabricated by the spin coating method. In the second approach, AgNWs were mixed into the SWCNT ink and films fabricated by the spray coating method. The PEDOT:PSS dispersion was spin coated in the final assembly of SWCNT-AgNW/PEDOT:PSS films. The addition of AgNWs did not result in a significant decrease in sheet resistance with either approach. The high surface resistance can be associated with the AgNWs' low electrical conductivity due to their low aspect ratio, bulk impurities, and/ or acid corrosion of AgNWs lead by PEDOT:PSS. SWCNT-AgNW/PEDOT:PSS nanocomposite made with the second method showed the best performance among these two methods, where the resistance of the film was measured as 220 W/sq with a 55% transmittance.