Breakthrough metamaterial could capture more sunlight than existing solar cells

Breakthrough metamaterial could capture more sunlight than existing solar cells
Researchers at MIT have found a way to use metamaterials to absorb a wide range of light with extremely high efficiency – a breakthrough they believe could lead to a new generation of solar cells or optical sensors.

While most thin materials used to fully capture light are limited to a very narrow range of wavelengths and angles of incidence, the new design uses a pattern of wedge-shaped ridges whose widths are precisely tuned to slow and capture light of a wide range of wavelengths and angles of incidence.

According to the researchers, these metamaterials can be extremely thin, saving weight and cost. The actual structure of the material is etched from alternating layers of metal and an insulating material called a dielectric, whose response to polarised light can be varied by changing an electric field applied to the material.

Postdoctoral researcher Kin Hung Fung explained: "What we have done is design a multilayer sawtooth structure that can absorb a wide range of frequencies with an efficiency of more than 95%. Previously, such efficiency could only be achieved with materials tuned to a very narrow band of wavelengths. High efficiency absorption has been achieved before, but this design has an extremely wide window for colours of light."

By using the tuned metamaterial, Hung and his team were able to slow light to less than one hundredth of its normal speed in a vacuum, making it much easier to trap inside the material.
In addition to potential uses in new kinds of solar cells or infrared detectors, he believes the principle could be used for infrared light emitting applications, such as devices for generating electricity from heat.

"The technology can also be scaled so it could be used to capture or emit electromagnetic radiation at other wavelengths, such as microwave and terahertz frequencies," Hung concluded. "It could even be used to produce visible light with extremely low energy loss, creating a new kind of high efficiency light bulb."

Author
Laura Hopperton

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