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ShareOct. 9, 2008 — A few years ago, the U.S. Defense Advanced Research Projects Agency (DARPA) launched its Very High Efficiency Solar Cell (VHESC) program. DARPA challenged the industry and the research community to make solar cells more efficient -- as measured by how well a solar cell converts the light it absorbs into electrical energy.
The goal is to be able to provide soldiers in the field with inexpensive portable solar power generators -- the sort that would be no larger than a laptop and would be able to recharge that laptop in an hour or so.
The problem with making such small solar power generators is that even the most advanced solar cells available today are not efficient enough. The highest efficiencies demonstrated so far have been just more than 40 percent, but those demonstrations have taken place in carefully controlled laboratory settings and not with portable field units as the DARPA program calls for.
Besides that, the most efficient laboratory cells rely on expensive-to-manufacture materials that cost some $50,000 to $70,000 per square meter. The sort of commercial solar panels you might buy today to have installed on your rooftop are much cheaper, but they are even less efficient, topping out at 16 to 17 percent. The DARPA program calls for efficiencies of 50 percent.
University of Rochester Professor Duncan Moore is part of a team reaching for DARPA's goal under the VHESC program. Their approach to achieving the higher efficiency involves using special coatings on solar cells that split light into colors like blue and red, which scientists estimate will increase efficiency by 50 percent. They then use different types of solar cell materials that each optimally absorbs energy from a different color light.
Moore's research enhances this further by finding ways to intensify the light. In his Frontiers in Optics talk, Moore will describe how he is designing an optical cover for solar panels that concentrates sunlight -- much as a magnifying glass can concentrate sunlight enough that it can burn wood.
The scientists are presenting their research at the 92nd Annual Meeting of the Optical Society (OSA), being held from Oct. 19-23 in Rochester, N.Y.
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