Zinc Oxide Brings Solar Cell Efficiency

Wednesday, April 23, 2014 @ 11:04 AM gHale


After coating cufflink-sized cells with a thin layer of zinc oxide, a solar cell reached a conversion efficiency of 14 percent, the highest efficiency ever in a 9 millimeter-squared cell made of gallium arsenide.

A small array of these cells – as few as nine to 12 – generate enough energy for small light-emitting diodes and other devices, said engineering researchers at the University of Arkansas. But surface modification can scale up, and the cells can package in large arrays of panels to power large devices such as homes, satellites, or even spacecraft.

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An alternative to silicon, gallium arsenide is a semiconductor used to manufacture integrated circuits, light-emitting diodes and solar cells.

The surface modification, achieved through a chemical synthesis of thin films, nanostructures and nanoparticles, suppressed the sun’s reflection so the cell could absorb more light. But even without the surface coating, the researchers were able to achieve 9 percent efficiency by manipulating the host material.

“We want to increase the efficiency of small cells,” said Yahia Makableh, doctoral student in electrical engineering. “With this specific material, the theoretical maximum is 33 percent efficiency, so we have some work to do. But we’re making progress. The beauty of zinc oxide is that it’s cheap, non-toxic and easy to synthesize.”

Makableh said the surface modification could also apply to other solar cells, including those made of indium-arsenide and gallium-arsenide quantum dots. Solar cells made of these materials may be able to achieve 63 percent conversion efficiency, which would make them ideal for future development of solar cells.

Makableh used equipment and instrumentation in the College of Engineering’s Optoelectronics Research Lab, directed by Omar Manasreh, professor of electrical engineering who led the research team. Researchers in the lab grow and functionalize semiconductors, nanostructured anti-reflection coatings, self-cleaning surfaces and metallic nanoparticles to see use in solar cells. Their ultimate goal is to fabricate and test photovoltaic devices with greater solar-energy conversion efficiency.



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