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Mon12292014

Technology

Sulfur embedded black silicon absorbs infrared radiation, improves solar cells

Black silicon – which can absorb infrared radiation - could be the key to more efficient solar cells, found researchers at Germany’s Fraunhofer Institute.

Silicon solar cells can convert around three-quarters of the sun’s spectrum into energy – mostly through absorbing visible light – but about a quarter of the sun’s spectrum is infrared radiation. In standard solar cells this potential source of solar energy is lost.

In contrast, black silicon solar cells are specifically designed to absorb nearly all the sunlight that hits it, including infrared radiation.

“Black silicon is produced by irradiating standard silicon with femtosecond laser pulses under a sulfur containing atmosphere,” explains Dr. Stefan Kontermann, who heads the Research group “Nanomaterials for Energy Conversion“ within the Fraunhofer Project Group for Fiber Optical Sensor Systems at the Fraunhofer Institute for Telecommunications, Heinrich-Hertz-Institut, HHI.

This process integrates sulfur atoms into the silicon lattice, making the silicon appear black. This is also key to black silicon’s ability to absorb infrared light.

By modifying the laser pulse that drives the sulfur into the lattice, the researchers also found that they can change the energy level of the sulfur, altering the number of electrons that can be created by a photon of light.

The researchers have already successfully built prototypes of black silicon solar cells and their next step will be to try and merge these cells with commercial technology.

“We hope to be able to increase the efficiency of commercial solar cells – which currently stands at approximately 17 percent – by one percent by combining them with black silicon,” Dr. Kontermann says. – EcoSeed Staff



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