'Smart Windows' Offer Control Over Amount of Heat and Light Allowed Through

A new material consisting of a thin coating of nanocrystals embedded in glass could revolutionize the world of windows and energy efficiency, according to those behind it.

"In the US, we spend about a quarter of our total energy on lighting, heating and cooling our buildings," Delia Milliron, a chemist at Berkeley Lab's Molecular Foundry who led this research, said in a press release. "When used as a window coating, our new material can have a major impact on building energy efficiency."

The value of the material lies in its selective control over visible light as well as heat-producing near-infrared (NIR) light -- a feat made possible through an electrochromic effect in which a jolt of electricity switches the material's NIR-blocking abilities on and off. Thus, by allowing users to enjoy natural lighting without letting unwanted heat in through their windows, the new technology has the potential to cut back on both the need for air-conditioning and artificial lighting. Other options include a dark mode in which both heat and light are blocked, or a bright, fully transparent mode.

Key to the new material's capabilities is the structural rearrangement in the glass matrix that results as atoms connect across the nanocrystal-glass interface, opening up space inside the glass and allowing charge to move in and out more easily.

"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," Milliron explained.

However, the researcher explained that for her, "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."