Printing of WO3/ITO nanocomposite electrochromic smart windows

Electrochromic smart devices with controllable optical property are the most promising alternative to traditional windows and curtains. State of the art preparation and commercialization of large-scale electrochromic films are mainly based on vapor phase deposition, but massive application is limited by high price (due to complex preparation process). Here, an all-solution technology is developed for large-area low-cost preparation of electrochromic films. A WO3/ITO dispersion was successfully developed; high electrical conductivity ITO nanoparticle networks along with ITO coating on glass can serve as extended 3-dimensional electrode, which can form microelectrical field and act as the pathways for electron diffusion to WO3 nanorods. In fact, experiment results show that the surface resistance of WO3/ITO nanocomposite film decreased to 32% of the pure WO3. In other words, the optimum WO3/ITO nanocomposite films in this study with "distributed conductive structure" and submicrometer-sized voids morphology have improved the electrochromic properties remarkably. Our optimized WO3/ITO films exhibit higher optical modulation than pristine WO3 (Delta T = 81.7% vs 62.5% at 630 nm) and a faster switching speed (t(b) = 6 s vs 22 s).