Window coating that may save energy by cutting cooling cost

Researchers have designed a new material- a thin coating of nanocrystals embedded in glass- that can dynamically modify sunlight as it passes through a window.

A team of researchers as the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have designed the coating which provides selective control over visible light and heat-producing near-infrared (NIR) light, so windows can maximise both energy savings and occupant comfort in a wide range of climates.

Delia Milliron, a chemist at Berkeley Lab’s Molecular Foundry who led this research, and his team is already well known for their smart-window technology that blocks NIR without blocking visible light.

At the heart of the technology is a new “designer” electrochromic material, made from nanocrystals of indium tin oxide embedded in a glassy matrix of niobium oxide.

The resulting composite material combines two distinct functionalities—one providing control over visible light and the other, control over NIR—but it is more than the sum of its parts.

The researchers found a synergistic interaction in the tiny region where glassy matrix meets nanocrystal that increases the potency of the electrochromic effect, which means they can use thinner coatings without compromising performance. The key is that the way atoms connect across the nanocrystal-glass interface causes a structural rearrangement in the glass matrix.

The interaction opens up space inside the glass, allowing charge to move in and out more readily. Beyond electrochromic windows, this discovery suggests new opportunities for battery materials where transport of ions through electrodes can be a challenge.