Chemistry
The Chemistry of Smart Windows: Electrochromic Materials and Their Limitations
Quick fact
Tungsten trioxide (WO3) is the most common electrochromic material: when lithium ions and electrons are injected into its crystal lattice, it turns deep blue—a color change driven by the reduction of W6+ to W5+.
Why this is interesting
Imagine a window that dims at the flick of a switch, without curtains or blinds. How can a pane of glass change its color on command?