Composite Film of Cellulose and PEDOT:PSS for Sustainable and Stable Electrochromic Materials

Flexible and environmentally friendly electrochromic devices (ECDs) show great application potential for active light management, such as smart color-changing windows and color-changing sunglasses. Natural cellulose, as an environmentally friendly, low-cost, and renewable material, has advanced the development of sustainable ECDs, while its hydrophilic nature leads to unstable performance, especially in humid and rainy conditions. Therefore, we presented the sandwich-structured cellulose acetate-cellulose (CA-C)/PEDOT:PSS by layer-by-layer assembly, which displays high water resistance and mechanical stability as well as a fast transmittance response to the external voltage. By applying a forward voltage of 3 V, the transmittance of the prepared electrochromic composite film quickly changes from 83% to 40%; under a backward voltage, it recovers to its initial state within 2 s. Additionally, the cellulose-based composite film also demonstrates stable electrochromic capability after 500 bending cycles or 24 h of working in an outside environment, even under high humidity. The developed CA-C/PEDOT:PSS electrochromic composite film paves the way toward advancing electrochromic materials to be more sustainable and stable in a low-carbon society.