Researchers at the University of Arkansas have succeeded in achieving the highest efficiency ever in a 9 millimetre-squared solar cell made of gallium arsenide. A conversion efficiency of 14 percent was achieved after coating the tiny cells with a thin layer of zinc oxide.
A small array of these cells can generate sufficient energy for small light-emitting diodes and other devices. The cells can also be easily be arranged in large arrays of panels in order to harness power for large scale applications such as a solar rooftop.
The research team was led by Omar Manasreh, professor of electrical engineering. The study has been published in Applied Physics Letters and the April 2014 issue of Solar Energy Materials and Solar Cells.
Gallium arsenide is not as popular as silicon in making solar cells but is widely used as a semiconductor for manufacturing 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 be applied 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.