Mechanical integrity and environmental reliability of a single wall carbon nanotube as a flexible transparent conducting electrode

We investigated a single wall carbon nanotube (SWCNT) electrode as a potential flexible transparent conducting electrode. The mechanical integrity of an SWCNT electrode spray-coated onto a polyethylene terephthalate substrate was investigated via outer/inner bending, twisting, stretching, and adhesion tests. In particular, its environmental reliability under high-temperature and high-humidity conditions was characterized. The spray-coated SWCNT electrode showed a sheet resistance of 200 Ω/square and a transparency of 83%. The SWCNT electrode showed a constant resistance change (ΔR/R₀) within an outer and inner bending radius of 2.5 mm. The bending fatigue test showed that the SWCNT electrode can withstand 10,000 bending cycles at a bending radius of 5mm. Furthermore, the resistance change of the stretched SWCNT electrode was fairly constant up to a strain of 5%, which is quite stable compared with the resistance change of conventional amorphous indium tin oxide electrodes. The SWCNT electrode also showed good adhesion strength. The environmental storage test at a high temperature (85 °C) indicated that change in the electrical resistance of the SWCNT electrode is less than 9% after 100h test. In the environmental reliability tests at 85% relative humidity (RH) and 60°C/90% RH, the ΔR/R₀ of the SWCNT electrode was very small. These results indicate that the SWCNT electrode has good environmental stability.