A stable, self-regulating, flexible, ITO-free electrochromic smart window for energy-efficient buildings

Electrochromic devices (ECDs) as smart windows can modulate transmittance of sunlight under an electric potential. There is significant research interest in applying the design principles of ECDs to flexible systems. Herein, we report a smart, self-powered, flexible electrochromic system with self-regulating features and state-of-the-art stability and flexibility. The flexible ECD (FECD) system is composed of Ag@Au core-shell nanowires as flexible transparent electrodes, ethyl viologen as chromophore, and commercial solar cells. The FECDs exhibit high optical contrast (40.3% at 605 nm), cyclic stability, flexibility, and energy-storage performance (6.02 mF/ cm2), which are superior to those of the FECD using indium tin oxide (ITO) as electrodes. Furthermore, when connected with a commercial solar cell, the obtained electrochromic system can adjust the transmittance with the sunlight intensity in real time, demonstrating potential as a smart curtain for saving energy and improving living experience.