A window can admit welcome daylight but also let in unwanted heat, taxing air conditioning systems. Darkening the glass helps control glare, but the absorption of sunlight warms it. An ideal window would block more incoming heat while also letting trapped heat escape.

To address this challenge, researchers at the Chinese Academy of Sciences, Northeast Forestry University and collaborating institutions have developed a colorful smart window with a reflective silver layer that activates when a voltage is applied. The layer turns a tinted, see-through pane opaque, providing shade and privacy. A separate outer coating helps the window release heat to the outside of the building.

In outdoor tests, small structures covered by the prototype window stayed cooler than those covered by quartz glass or other commercial smart windows. The study, published in Nano Letters reveals a technology that manages daylight, privacy and heat at the same time.