Highly conducting, durable and large area carbon nanotube thick films for stretchable and flexible electrodes

We demonstrated a straightforward strategy to fabricate highly conductive carbon nanotube (CNT) films by introducing polyacrylic acid (PAA) as a dispersant and a dopant. A dispersion process was developed to fabricate highly concentrated and viscous aqueous suspensions, which enabled an easy deposition of uniform micrometer-thick CNT films on a large scale. The CNT-PAA hybrid film exhibited a ten fold increase in the conductivity as compared with the nondoped film. Furthermore, a mild acid-treatment was utilized to modify the CNTs before dispersion, resulting in a high density of small-bundle CNTs without clear structural damage and a further two fold increase in the conductivity. The CNT-PAA hybrid film with a thickness of around 5.1 μm exhibited a sheet resistance of 0.1 Ω/sq with a surprisingly high electrical conductivity of 19 600 ± 4000 S/cm. The conductivity of the hybrid film remained almost constant after aging tests under the conditions of 85 °C and 85% relative humidity for more than 1000 h, suggesting its outstanding long-term stability. Furthermore, HNO3 doping increased the conductivity to 35 000 ± 5000 S/cm.