Highly stable phosphotungstic acid/Au dual doped carbon nanotube transparent conductive films for transparent flexible heaters

Abstract

Phosphotungstic acid (PTA) is a highly stable dopant. In this research, transparent conductive films (TCFs) with polyethylene terephthalate as a substrate and PTA/Au secondary p-type doped single-walled carbon nanotubes (SWCNTs) as a conductive layer were prepared by spraying and employed as heating devices. The films had excellent optoelectronic properties (sheet resistance of 46.7 Ω/sq with 87.1% transmittance), mechanical properties (only 0.03 change in sheet resistance after 5000 bending cycles), stability (29.4% change in sheet resistance after one week of exposure to 95% humidity) and electrical heating properties. Transparent flexible heaters (TFHs) made of PTA/Au dual p-type doped SWCNT TCFs have a quick response to temperature changes and outstanding cycling stability. At an operating voltage of 20 V, the temperature of the TFH rapidly reached its maximum steady-state temperature (Tmax) of ∼120 °C within less than 90 s. After 50 cycles at 15 V in the voltage-on-off cycle test, the Tmax achieved by the TFH did not change appreciably. The results of the performance evaluation indicate that the film has a bright future in flexible wearable devices for warmth, physiotherapy, or deicing/defrosting applications.