[Image above] The solar glasses supply two sensors and electronics in the hanger with semi-transparent organic solar cells as spectacle lenses. Credit: Karlsruhe Institute of Technology 

After mankind discovered that the sun and a magnifying glass could start a fire back in 7th century B.C., scientists have been trying to harness the power of the sun ever since.

Solar research has come a long way, especially when it was propelled in the mid ‘50s by Daryl Chapin, Calvin Fuller, and Gerald Pearson, who developed the first silicon photovoltaic cell that could power a device for an extended period of time.

The primary semiconducting material used on most solar cells today is silicon. And although prices of silicon photovoltaics are declining, there are several factors—including the high energy costs associated with manufacturing, plus the additional materials required to make pure silicon perform its sun absorption job—that prohibit their use in applications beyond solar panels.

But researchers are now experimenting with alternative materials for photovoltaic cells, including that of organics. Organic solar cells use polymers, organic molecules, and other light-absorbing compounds to generate an electrical charge. Organics are less expensive and thinner than silicon, and are more suited to a wider variety of applications.

Alexander Colsmann, head of the Organic Photovoltaics Working Group at the Lichttechnisches Institut of Karlsruhe Institute of Technology (KIT), and his team have created a pair of self-powering sunglasses that can measure sun radiation as well as the ambient temperature, using organic solar cells and electronics.

The “smart glasses” are equipped with solar cells in the lenses, which fit into commercially available frames, according to the press release (German language) on KIT’s website. The frames contain microprocessors and two displays that depict information on the sun’s strength and temperature in a bar graph. The glasses also work indoors at normal lighting levels similar to office or home. In an indoor environment, the lenses produce “200 microwatts of electrical power which would be sufficient to allow applications such as a hearing aid or a step counter.”

Colsmann’s research team used a combination of a polymer and two fullerenes—called a ternary absorber blend—to build their organic solar cell. According to their paper, “ternary blends comprising two fullerenes are known to enhance the power conversion efficiency and thermal stability of organic solar cells.”

An additional benefit of using organic solar cells is the capability of modifying them to the application. “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 exciting material,” Dominik Landerer, PhD student and research team member adds in the release.

The solar glasses open the door for wider use of organic solar cells. Possible future applications include integration into buildings, such as windows and facades, as well as mobile electronics and smart wearables.

“The glasses are only one example for smart wearable devices, powered with organic solar cells,” Colsmann writes in an email. “The unique properties of organic solar cells will also enable their integration, e.g. into jackets where they may power electronics such as MP3 players or health monitors.”

Sounds like the future is indeed looking bright for organic solar cells.

The paper, published in Energy Technology is “Solar Glasses: A Case Study on Semitransparent Organic Solar Cells for Self-Powered, Smart, Wearable Devices” (DOI: 10.1002/ente.201700226).