November 25, 2008

Fine-tuned reflector ups solar cell output

Come up with the right reflective backing for solar cells and you can make them 50 percent more efficient.

The reflector dramatically increases the amount of red and near-infrared light solar cells absorb. A 5-micron-thick silicon solar cell produced 10 percent more electricity with the reflector, and improvements should boost that to 28 percent. Simulations show that the reflector could boost the output of 2-micron-thick silicon solar cells by as much as 50 percent.

The textured photonic crystal reflector combines a one-dimensional photonic crystal with a reflection grating. A photonic crystal contains microscopic, regularly spaced air holes or semiconductor spheres or rods that tightly control lightwaves. A reflection grating is a mirror etched with fine, closely spaced parallel lines that reflect light at an angle. The combination keeps longer wavelength light from reflecting back out of the cells.

The reflector was developed two years ago (see further info below). This latest research optimizes the design and applied it to thin-film silicon solar cells.

Research paper:
Realization of Significant Efficiency Enhancement in Thin Film Silicon Solar Cells with Textured Photonic Crystal Backside Reflector (session P2.1)
Materials Research Society 2008 Fall Meeting; Boston, Massachusetts; December 2, 2008

Researchers' homepages:
Electronic Materials Research Group, Massachusetts Institute of Technology
Peter Bermel
Bernard Alamariu
Kurt Broderick
John Joannopoulos

Related stories and briefs:
Coating passes more light to solar cells -- related research

Further info:
New Solar Cells with Novel Light Trapping via Textured Photonic Crystal Back Reflector -- paper on precursor research
StarSolar -- startup company commercializing the technology

Back to ERN December 1/8, 2008



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