New eyeglasses from Germany’s Karlsruhe Institute of Technology generate solar power. Featuring semitransparent organic solar cells, the eyewear powers a microprocessor and two small displays integrated into the solar glasses’ temples. In a Tech Briefs Q&A, one KIT researcher explains why the proof-of-concept is the first step to even smarter devices.

The self-powered Smart Solar Glasses, designed as a case study, measure and display the solar illumination intensity and ambient temperature. The 6-gram lenses, fitted to commercial frames, have a thickness of approximately 1.6 millimeters — comparable to the dimensions of traditional sunglasses.

Each of the “smart” lenses generates 200 microwatts of electric power — enough to operate devices such as a hearing aid or a step counter.

Is that kind of power significant? Tech Briefs spoke with Karlsruhe scientist Daniel Bahro.

Tech Briefs: What are the solar glasses equipped with? What do they look like?

Daniel Bahro: The solar glasses demonstrate, for the first time, the integration of organic solar cells into smart devices. This emerging photovoltaic technology, featuring organic semiconducting materials and polymers, offers some unique properties, like transparency, tunability in color, and shape. Here, the transparency allows the cells to be introduced into the lenses, the largest available area of the glasses.

Solar Glasses with lens-fitted semitransparent organic solar cells supply two sensors and electronics in the temples with electric power. (Photo: KIT)

The technology of organic photovoltaics has been under investigation now for about a decade in many universities and companies around the world. Since glasses offer nearly no space for batteries or other power supplies, we thought this to be the ideal demonstrator application.

Tech Briefs: What are the glasses designed to do?

Daniel Bahro: The energy yield is used to drive an electronic circuit including sensors, a microprocessor, and two displays attached to the temples. This very basic configuration of a smart device, even under indoor lighting conditions, continuously records the ambient temperature and the current output of the solar cells, without any additional power source like a battery. The user doesn’t feel any different to normal sunglasses since the solar cells appear the same as toned lenses.

Tech Briefs: What can be done with the power generated from the smart glasses? What other possibilities exist with this kind of integration of organic solar cells?

Daniel Bahro: This study can be seen as a preliminary stage of an even smarter device with a more demanding functionality. In the range of the power output are applications like hearing aids, Bluetooth interfaces, or pedometers. But the technology of organic solar cells itself could probably also address other markets, like Internet of Things, self-sustaining sensors, wearables, or window-integration.

Tech Briefs: Even if the technology powers a hearing aid, a hearing-aid battery is relatively inexpensive. What would you say in response about the value of the power that the glasses generate?

Daniel Bahro: The advantage of a solar-powered device is that battery changes can be avoided. This not only reduces harmful waste, but also simplifies the handling of the device. Even if, in future applications, a battery is needed to sustain the system in the dark, it can be designed much smaller than it has to be without additional solar power.

As organic solar cells are integrated into smart devices, what kinds of possibilities do you envision? Share your thoughts and comments below.

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