Bifunctional MoO₃-WO₃/Ag/MoO₃-WO₃ Films for Efficient ITO-Free Electrochromic Devices

Dielectric-metal-dielectric (DMD) trilayer films, served as both electrochromic (EC) film and transparent conductor (TC), have exhibited great potential application in low-cost, ITO-free electrochromic devices (ECDs). However, recent reports on the DMD-based ECDs revealed that the response time and the optical modulation properties were not very satisfactory. Here, the mixed MoO₃-WO₃ materials were first introduced as the dielectric layer to construct an EC-TC bifunctional MoO₃-WO₃/Ag/MoO₃-WO₃ (MWAMW) film, which demonstrates strong and broad-band optical modulation in the visible light region, fast color-switching time (2.7 s for coloration and 4.1 s for bleaching), along with high coloration efficiency (70 cm² C^-1). The electrical structure and electrochemical reaction kinetics analysis revealed that the improved EC performances are associated with the increased electron intervalence transition together with the fast charge-transfer and ion-diffusion dynamics.