Carbon nanotube-grid infrared transparent electrodes for flexible electrochromic devices with visible to mid-infrared dual-band modulation

Flexible mid-infrared electrochromic devices (MIR-ECDs) have attracted wide attention due to the growing demands for thermal camouflage and body comfort. However, the normal conductive films (e.g., indium tin oxide/polyethylene terephthalate (ITO/PET) films) are unsuitable for MIR-ECDs due to low infrared transmittance. Herein, the infrared transparent carbon nanotube (CNT) grid films were prepared by designing the grid structure. The infrared transmittance of CNT grid film could reach 72 %; meanwhile, the visible transmittance could reach 75 %. The CNTs exhibited infrared modulation under different voltages due to the doping/de-doping of ions in electrolytes into the CNT network. The flexible electrochromic devices with visible to mid-infrared dual-band modulation were prepared by using CNT grid film as the electrode and poly (3,4 ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) as the electrochromic layer, which could realize the infrared synergistic modulation of PEDOT:PSS and CNT grid in the mid-infrared range and reversible color changes between light blue and dark blue in the visible range, showing promising applications in adaptive camouflage and thermal management.