Windows Get ‘Smarter’ with Coatings


A new window coating that allows users to control both visible and near-infrared light has emerged from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory.

The windows can maximize both energy savings and occupant comfort in a wide range of climates, according to a recent announcement on the project.

The thin coating of nanocrystals embedded in glass can “dynamically modify sunlight as it passes through a window,” Berkeley Lab says.

Major Impact

“In the U.S., we spend about a quarter of our total energy on lighting, heating and cooling our buildings,” says Delia Milliron, a chemist at Berkeley Lab’s Molecular Foundry, who led the research.

“When used as a window coating, our new material can have a major impact on building energy efficiency.”

Milliron and her team are said to be in the early stages of commercializing the technology.

The team recently published its work in an article, “Tunable near-infrared and visible light transmittance in nanocrystal-in-glass composites,” in the journal Nature.

In April, the scientists received a $3 million grant from the DOE’s Advanced Research Projects Agency-Energy for the project.

All about Control

In announcing the discovery Aug. 14, Berkeley Lab said the technology centered on an electrochromic effect, in which a small jolt of electricity switches the material between NIR-transmitting and NIR-blocking states.

The new advance takes that technology to the “next level” by providing independent control over both visible and NIR light, the team said.

Berkeley Lab

(From left) Guillermo Garcia, Delia Milliron and Anna Llordés say their development, now in the early stages of commercialization, could have a major impact on building energy efficiency.

Independent control over NIR light means that occupants can have natural lighting indoors without unwanted thermal gain, reducing the need for both air-conditioning and artificial lighting, the scientists report.

The same window can also be switched to a dark mode, blocking both light and heat, or to a bright, fully transparent mode.

‘Designer’ Material

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 research institute reports.

“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 team says.

Thinner and Performing

The researchers found what they call 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 team says.

The way the 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.

Nanocrystals of indium tin oxide
Berkeley Lab

Nanocrystals of indium tin oxide (shown in blue) embedded in a glassy matrix of niobium oxide (green) form a composite material that can switch between NIR-transmitting and NIR-blocking states with a small jolt of electricity. A synergistic interaction in the region where glassy matrix meets nanocrystal increases the potency of the electrochromic effect, according to the team.

Beyond windows, this discovery suggests new opportunities for battery materials where transport of ions through electrodes can be a challenge, the team reports.

“From a materials-design perspective, we’ve shown that you can combine very dissimilar 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,” says Milliron.

Exciting Journey

Milliron says the best part of the project has been the journey.

“The most exciting part has been taking this project all the way from synthesizing a new material, to understanding it in great detail, and finally to realizing a completely new functionality that can have a big impact on technology,” she said.

“Taking a materials development project all the way through that process is really quite remarkable. It really speaks to what we can do at Berkeley Lab, where you have access to not just the scientific facilities but also to people who can inform your perspective.”

The work at the Molecular Foundry was supported by the Department of Energy’s Office of Science.


Tagged categories: Coatings Technology; Coatings technology; Glass; Glass coatings; Lawrence Berkeley National Laboratory; Nanotechnology; Research; Windows

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