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Photosynthesis at work, inspiring the Graetzel cells

Lausanne, Switzerland (GenevaLunch) -  A dramatic improvement in the energy efficiency of solar cells by adding a dye that is sensitive to the blue and green wavelengths of the spectrum was announced by researchers at Lausanne’s EPFL and Stanford University in California, USA. Graetzel cells, invented by EPFL scientists Michael Graetzel and Brian O’Regan in the 1990s, generate an electric current when light stimulates a dye. In today’s cells the dye is sensitive only to the lower-energy red range of the spectrum. By adding a second dye, perylene, which is sensitive to blues and greens and transfers its energy to the red-sensitive phthalocyanines, the solar cell’s range sensitivity is broadened, allowing it to make better use of the light it absorbs. The research is published in the June 2009 issue of Nature Photonics.

The researchers claim a 26 percent efficiency increase and are certain that this can be improved. They say they were inspired by the action of chlorophyl molecules during photosynthesis in plants. Graetzel cells are of a variety of solar cells known as thin film solar cells, made of relatively inexpensive materials compared to the solid state silicon solar cells. They are also tougher and, being flexible, can be deployed more easily that the rigid silicon solar panels.