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How Solar-powered Sunglasses Work

Dye-sensitized Solar Cells
Two designers have come up with some conceptual shades that generate power.
Two designers have come up with some conceptual shades that generate power.

­Dye-sensitized solar cell (DSC) technology, also called Grätzel cells, were first introduced in 1991 by Michael Grätzel, a chemist at the Swiss Federal Institute of Technology, Lausanne, and his colleagues.

There have been a few iterations of DSC technology, and the latest type of solar cell belongs to a new age of thin-film photovoltaic devices. They are engineered in layers: a photosensitive layer made of ultrathin, nano-sized semiconductor crystals over a thin layer of titanium dioxide. When photons (from sunlight) hit the photosensitive layer, the freed electrons accumulate on the layer of titanium dioxide and create an electrical current. Previously, a liquid electrolyte was needed to carry the electrons from one layer to another but in the newest generation of Grätzel cells, a dye made of amorphous organic material is used to coat the titanium dioxide -- the dye absorbs light and attracts excited electrons, which generates a charge.

The results are cells that can be used to create low-cost, lightweight, transparent and flexible sheets or dye that could be used to coat glass, such as the windows of your house to supply energy to your home. Or it could be used to coat the lenses of sunglasses and provide power to small-device batteries.

­DSC technology is highly efficient compared to other forms of solar cells, producing efficiencies greater than 11 percent -- meaning that 11 percent of the captured solar energy is converted to electrical energy -- rather than 4 to 5 percent [source: ScienceDaily]. But in small applications, such as in sunglasses, there could be one potential problem: Solar cells need to be facing the sun to absorb rays. How often do you stare into the sun?