A small-bundle single-wall carbon nanotube electrothermal film for smart windows

The incorporation of electrothermal films into smart windows has been of intense research interest in developing highly conductive transparent films. However, achieving a high optical transparency and exceptional electrothermal performance simultaneously remains a great challenge. We report a transparent conductive single-wall carbon nanotube (SWCNT) film comprised of highly-crystalline, long SWCNTs in small bundles. The SWCNT film with an average bundle diameter of 7.1 nm had a low sheet resistance of 26 Ω/□ at a transmittance of 82 %, and had a constant temperature of 102°C at a low applied voltage of 20 V. Integrating this transparent heating film with thermochromic materials enabled the fabrication of a flexible smart window with thermally triggered dynamic transparency. The device has a broad reversible visible light transparency range (~78 %) and excellent cycling stability.