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 MoO 3 –WO 3 materials were first introduced as the dielectric layer to construct an EC–TC bifunctional MoO 3 –WO 3 /Ag/MoO 3 –WO 3 (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 cm 2 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.