Transparent solar cells power smart sunglasses

July 06, 2017 // By Christoph Hammerschmidt
Researchers in Germany have developed sunglasses with coloured semi-transparent solar cells in the glass surfaces that supply a microprocessor and two displays with electric power.

"We bring the energy where there is no other solar technology," says Dr. Alexander Colsmann, Head of the Organic Photovoltaics Working Group at the Lichttechnisches Institut (LTI) of KIT. The "smart" sunglasses produced by the scientist and his team at the Karlsruhe Institute of Technology (KIT) as a product study supply themselves with electricity for integrated electronic devices – in this case, a circuit that measures and displays sun radiation intensity and ambient temperature. The solar cell coated lenses, which are fitted into a commercially available plastic frame, are each 1.6 millimeters thick and weigh about six grams - similar to the glasses of conventional sunglasses. The microprocessors and the two displays are integrated in the brackets, on which the information on the sun's strength and ambient temperature can be read in a bar graph. The solar glasses also function in the interior with a minimum lighting intensity of 500 lux, which corresponds to the usual office or living room lighting. Each of the two "smart" spectacle lenses under ambient lighting produces 200 microwatts of electrical power which would be sufficient to allow applications such as a hearing aid or a step counter.

"This is an example of the many conceivable mobile applications of organic solar cells, which classical photovoltaics do not allow," emphasizes PhD student Dominik Landerer, who has contributed significantly to the development of solar glasses at the KIT's Material Science Center for Energy Systems. Their mechanical flexibility and the possibility to adapt them in color, transparency, shape and size to the respective application, make the solar cells based on hydrocarbon compounds from the engineer's point of view an interesting material.