Figure 3. Effect of thickness and quality of graphene on the device performance.

(a–f), Transmittance spectra (under applied voltage ranging from 0 V to 5 V) of electrochromic devices using various thicknesses of MLG. Devices shown in (a–c) use MLG grown on copper foils while devices shown in (d–f) use MLG grown on nickel foils, respectively. The inset shows the estimated number of graphene layers. The color bar shows the applied voltage. (g,h) Variation of the transmittance (at 800 nm) of ECD using MLG grown on copper and nickel foils, respectively. (i), Maximum optical modulation plotted against the estimated number of graphene layers.