Scientists use light-bending of gemstones for better solar cells

Properties found in gemstones to reflect, diffract and bend incoming light could up solar cell efficiency and bring low-cost solar energy, U.S. scientists say. Researchers at Purdue University report using synthetic crystals with a structure called an "inverse opal" to make use of and enhance properties found in the gemstones. The 3-D "photonic crystals" can absorb more sunlight than conventional thin-film cells, they said. "Usually, in thin-film silicon solar cells much of the sunlight comes right back out, but using our approach the light comes in and it is diffracted, causing it to propagate in a parallel path within the film," electrical and computer engineering Professor Peter Bermel said. Thin film solar panels cost just one-hundredth of a panel made with silicon wafers, but up to now have been less efficient, he said. "The question is, can we make up that lower efficiency by introducing new approaches to light trapping for thin film solar cells?" Bermel said. "Can we combine low cost and high performance?" The 3-D photonic crystals yielded roughly a 10 percent increase in efficiency over conventional silicon thin films, with further potential for improvement, the researchers said.