Smart Windows Block Heat and Provide Light with New Nanocrystals

You wouldn't necessarily think that windows are "smart." But they certainly can be, especially with the new material that scientists have developed. The newly created windows have the ability to provide selective control over visible light and heat-producing near-infrared (NIR) light. That way, windows can maximize both energy savings and occupant comfort in climates that range from the icy to the heated.

The new material is made out of a thin coating of nanocrystals embedded in glass. These crystals can dynamically modify sunlight as it passes through a window. Researchers had already developed another technology for blocking NIR without blocking visible light. This previous technology hinged on an electrochromic effect, where a small jolt of electricity switched the material between NIR-transmitting and NIR-blocking states. This new work, though, takes things a step further.

The new windows provide independent control over both visible and NIR light. This means that the occupants of a building can have natural lighting indoors without the heat associated with it. This reduces the need for both air-conditioning and artificial lighting, which can mean huge energy savings. In addition, it'd be the perfect way to help reduce greenhouse gas emissions.

"We're very excited about the combination of unique optical function with the low-cost and environmentally friendly processing technique," said Anna Llordes, co-author of the new paper describing the windows, in a news release. "That's what turns this 'universal smart window' concept into a promising competitive technology."

The real trick of the new material lies in its combination of two distinct functionalities. One provides control over visible light while the other provides control over NIR. Within the tiny region where glassy matrix meets nanocrystal is a synergistic interaction. This interaction increases the potency of the electrochromic effect, which means that the researchers can use thinner coatings without compromising performance.

"From a materials-design perspective, we've shown that you can combine very similar materials to create new properties that are not accessible in a homogeneous single phase material, either amorphous or crystalline, by taking nanocrystals and putting them in glass," said Delia Milliron, one of the researchers, in a news release.

The details of the new material are published in the journal Nature.