Researchers at the Karlsruhe Institute of Technology (KIT) in Germany have designed sunglasses with colored, semitransparent organic solar cells fitted onto the lenses to power sensors, a microprocessor and two displays in the temples.
This emerging photovoltaic technology comprising organic semiconducting materials, such as polymers, offer unique properties like transparency, tunability in color and shape, and light weight, making them adaptable to solar designs previously not feasible. In this current design by KIT, the integrated organic solar cells particularly exploit the quality of transparency, which allows them to be integrated into the lenses, the largest available real estate on the glasses.
“The solar glasses demonstrate for the first time the integration of organic solar cells in smart devices,” says Dominik Landerer from the KIT Light Technology Institute. The yielded energy drives an electronic circuit that includes sensors, a microprocessor and two displays attached to the temples. The team reports that 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, such as a battery. Visually, the solar cells appear like toned lenses, so the user’s experience is no different from normal sunglasses.
Optimized colored, semi-transparent organic solar cells
Landerer says while the colored semi-transparent organic solar cells they used are not a completely new technology they have been optimized for the special use in their solar glasses. Each lens produced around 200 µW when used in 500-lux condition (typical indoor lighting) — enough to power an electronic circuit including sensors, a microprocessor and two displays.
The expert projects that, in addition to their electric power generation capability, the ability to customize this next generation of integrated PV devices for different applications will be essential for the acceptance of organic solar cells in consumer electronics. For implementation in the solar glasses, for instance, the transparency and the color perception are particularly important criteria. “The semi-transparent solar cells we used allow excellent color perception, which makes them perfectly suitable for sunglasses or windows,” Landerer says. “Hence, this case study provides an example for consumer-oriented mobile applications, self-powered by integrated solar cells that specifically exploit the unique properties of organic solar cells.”
Enabling new kinds of applications
The innovation emerging out of KIT could enable entirely new kinds of solar-powered applications that were not feasible before. “This study can be seen as a preliminary stage of an even smarter device with a more demanding functionality,” the researcher confirms, adding that applications such as hearing aids, Bluetooth interfaces or pedometers would be in the range of their new cell’s power output. “But the technology of organic solar cells itself could probably also address some other markets like Internet of Things, self-sustaining sensors, wearables or window-integration,” Landerer says. “Maybe they can also be incorporated into ‘smart glasses,’ such as the Google Glass headset, although these typically require several milliwatts of power. But the on-board solar energy could nevertheless reduce the size of the battery needed or limit the frequency of recharging.”
Exciting breakthrough technology
The new technology generates power under different lighting scenarios, allowing these solar cells to be used outdoors as well as indoors. “So we bring solar power to places where other solar technologies fail,” Landerer says. The breakthrough technology could enable self-sustaining devices for the Internet of Things or help to reduce the size of the battery in mobile devices. “Furthermore, their low weight, mechanical flexibility, semitransparency, aesthetic colorful appearance and excellent low-light behavior make them one of the most interesting photovoltaics technologies,” says Landerer.
Impact on future solar technologies
To Landerer’s min, this study could lead to an even smarter device with more demanding functionality. In the range of the power output are applications like hearing aids, Bluetooth interfaces, or pedometers. He adds that the technology of organic solar cells itself could probably also address some other markets like internet of thinks, self-sustaining sensors, wearables or window-integration.
In terms of next steps for his team, Landerer says he and his colleagues will focus on issues like advancing fabrication techniques and device architecture of the solar cells itself. “The solar glasses were made to demonstrate what is possible with organic photovoltaics and what future applications and markets are in range.”
The article “Solar Glasses: A Case Study on Semitransparent Organic Solar Cells for Self-Powered, Smart, Wearable Devices” is published in Energy Technology.
Written by Sandra Henderson, research editor Solar Novus Today