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purify drinking water effectively. The cooker uses a system of mirrored strips tilted at different angles to concentrate sunlight onto an "absorber," which converts the sun's energy into useable heat. The process is known as "concentrating solar power" (CSP) and is an area in which Cranfield is regarded as the number one research team in the UK. Cranfield's, Dr. Chris Sansom, the UK's leading expert on concentrating solar power, said, "This is a very exciting project as there are many areas of the world where solar cookers and water purifiers could impact significantly on people's quality of life." As well as heating food, the cookers store heat and generate electrical power for essential mobile communications or air conditioning. The solar cooker project was funded by the Government of Pakistan, which recognized the need to improve the lives of those living in remote regions. and mechanical flexibility. But they are inefficient; nearly 50% of their absorbed light energy never transmits as electrical power, mainly because their polymer networks are not sufficiently lined up at the nanoscale to enable energy to exit the cell. By introducing a squaraine dye into polymer solar cells that are based on a well-established biochemical mechanism, Förster resonance energy transfer (FRET) researchers achieved a 38% increase in power conversion efficiency, they said. In this type of solar cell-FRET-based heterojunction (the interface occurring between two layers or regions of dissimilar crystalline semiconductors) the polymer solar cell's extra energy migrates from one molecule to another over long distances. The dye, which is highly absorbent in the near-infrared region, broadens the spectral absorption of solar cells and enhances electricity transmission. The approach allows different light-absorbing materials to work synergistically and leads to well-ordered polymer networks without any need of post-processing, compared to traditional polymer solar cells. "Our strategy solves a number of issues at the same time," said lead author, JingShun Huang, a postdoctoral associate in Taylor's lab. "By strategically combining different materials that have been successfully used to absorb solar energy to take advantage of FRET, we demonstrate higherperforming solar cells." The National Science Foundation, Yale Climate and Energy Institute, NASA, and USDOE provided support for the research. n SOLAR CELLS ABSORB LIGHT AND CONVERT IT INTO ELECTRICAL POWER Scientists at Yale University in New Haven Connecticut have improved the ability of a promising type of solar cell to absorb light and convert it into electrical power by adding a fluorescent organic dye to the cell layer. This squaraine dye boosts light absorption and recycles electrons, improving the conversion of light into energy. The results suggest a new route for the development of lower-cost, higher-efficiency photovoltaics, the scientists said. "People can apply our approach in designing advanced solar cells with higher efficiencies," said Andre D. Taylor, the assistant professor of chemical and environmental engineering at Yale, who led the research published May 5, 2013. Solar cells are a renewable energy technology for directly converting light into electricity. Polymer solar cells, the type involved in the research, are appealing for their low cost, low weight, large area, JULY 2013 www.resourceworld.com 43

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