14 DAY TRIAL // In a remarkable advancement, investigators in the United States were able to produce a new type of coating material based on semiconductor nanocrystals. According to the team, this innovation could be used to control heat coming from the Sun, while allowing surfaces to remain transparent.
What this implies is that scientists could soon develop energy-efficient windows that would control solar heat – potentially even for energy production – while letting light in the visible spectrum pass through. The nanocrystals are sensitive only to infrared radiation.
The coating is based heavily on existing electrochromic materials, which have the ability to change from transparent to tinted upon being subjected to a small jolt of electricity. This research takes that idea a step further, preparing the path for more advanced uses for this class of materials.
In addition, this breakthrough also sets a record for being the first technology that lets users control the amount of near infrared radiation that passes through a material in a selective manner. The amount of applications such a coating has is remarkable, even if fields other than energy efficiency research.
The material was developed by experts at the US Department of Energy's (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab), who were led by the director of the Inorganic Nanostructures Facility at the Lab’s Molecular Foundry, Delia Milliron.
She explains that energy wasted by buildings accounts for over 40 percent of the total amount of carbon dioxide that the United States emits yearly. Putting a dent in this number could contribute to reducing global warming, in addition to improving overall building efficiency.
The energy used by climate control and illumination systems could be reduced by 49 percent and 51 percent, respectively, simply by using window coatings. The data were collected by experts with the National Renewable Energy Laboratory (NREL).
“To have a transparent electrochromic material that can change its transmittance in the infrared portion of sunlight is completely unprecedented,” the team leader explains.
“What’s more, the coloration efficiency of our material – a figure of merit describing the amount of current needed to make this thing go – is substantially higher than standard electrochromic materials, which means it’s also very efficient,” she adds.
“Traditional electrochromic windows cannot selectively control the amount of visible and near infrared light that transmits through the film. When operated, these windows can either block both regions of light or let them in simultaneously,” adds graduate student Guillermo Garcia
“This work represents a stepping stone to the ideal smart window, which would be able to selectively choose which region of sunlight is needed to optimize the temperature inside a building,” the team member concludes.
Details of the new investigation appear in a paper entitled “Dynamically modulating the surface plasmon resonance of doped semiconductor nanocrystals,” which was published in the latest issue of the top scientific journal Nano Letters.
The DOE Office of Science provided the funds needed for this research through a grant awarded to the Berkeley Lab Molecular Foundry, one of the five DOE Nanoscale Science Research Centers (NSRC).