Danish researchers have developed an inexpensive heat-resistant device made of tungsten and alumina layers that can absorb the sun’s broad-spectrum radiation and convert it to electricity.

Traditional solar panels convert sunlight efficiently within a narrow range of wavelengths determined by the material used in the photovoltaic cells. This limits their efficiency, as the energy of short-wavelength light is largely wasted and long wavelengths of sunlight are not converted at all.

Conventional solar panels convert sunlight efficiently within a relatively narrow range of wavelengths. Image credit: Pixabay.Conventional solar panels convert sunlight efficiently within a relatively narrow range of wavelengths. Image credit: Pixabay.

Broadband solar absorption previously has been achieved using metal-insulator-metal (MIM) resonators, which consist of an insulator sandwiched between a thick bottom and a thin top layer made of metals such as chromium and gold. However, the metals in standard MIM resonators melt at around 500 degrees Celsius, hindering their usefulness in solar cells.

Scientists led by Manohar Chirumamilla, postdoctoral researcher in Aalborg University's Department of Physics and Nanotechnology, have now devised an alternative method of broadband solar absorption from layered materials that can be fabricated using inexpensive and widely available film-deposition techniques. They are resistant to heat, including thermal shock, and exhibit stable physical and chemical properties at high temperatures.

In experiments, the tungsten and alumina absorbers were shown to operate at a temperature of 800 degrees Celsius and to absorb light of wavelengths ranging from 300 to 1750 nanometers, i.e., from ultraviolet to near-infrared wavelengths.

“This is the first step in utilizing the energy of the sun in a more efficient way than with current solar cells,” says Chirumamilla. “Using an emitter in contact with our absorber, the generated heat can then be used to illuminate a solar cell—which can then function more efficiently when it is placed directly in the sun.”

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