Smart windows are aimed at saving on cooling and heating bills for homes and businesses.
Researchers in the Cockrell School of Engineering at The University of Texas at Austin in the US used a new low-temperature process for coating the new smart material on plastic, which makes it easier and cheaper to apply than conventional coatings made directly on the glass itself.
The team, led by Delia Milliron, an associate professor at University of Texas, demonstrated a flexible electrochromic device, which means a small electric charge (about four volts) can lighten or darken the material and control the transmission of heat-producing, near-infrared radiation.
Such smart windows are aimed at saving on cooling and heating bills for homes and businesses.
The team's low-temperature process generates a material with a unique nanostructure, which doubles the efficiency of the colouration process compared with a coating produced by a conventional high-temperature process.
It can switch between clear and tinted more quickly, using less power.
The new electrochromic material, like its high temperature processed counterpart, has an amorphous structure, meaning the atoms lack any long-range organisation as would be found in a crystal.
However, the new process yields a unique local arrangement of the atoms in a linear, chain-like structure.
While conventional amorphous materials produced at high temperature have a denser 3D bonded structure, the new linearly structured material, made of chemically condensed niobium oxide, allows ions to flow in and out more freely.
As a result, it is twice as energy efficient as the conventionally processed smart window material.
At the heart of the team's study is their rare insight into the atomic-scale structure of the amorphous materials, whose disordered structures are difficult to characterise.
Since there are few techniques for characterising the atomic-scale structure sufficiently enough to understand properties, it has been difficult to engineer amorphous materials to enhance their performance.
"There's relatively little insight into amorphous materials and how their properties are impacted by local structure," Milliron said.
"But, we were able to characterise with enough specificity what the local arrangement of the atoms is, so that it sheds light on the differences in properties in a rational way," she said.
The research appears in the journal Nature Materials.
Photograph: Reuters