Transparent Solar Panels For Windows Hit Record 8% Efficiency

Bodhammer shares a report from the University of Michigan: In a step closer to skyscrapers that serve as power sources, a team led by University of Michigan researchers has set a new efficiency record for color-neutral, transparent solar cells. The team achieved 8.1% efficiency and 43.3% transparency with an organic, or carbon-based, design rather than conventional silicon. While the cells have a slight green tint, they are much more like the gray of sunglasses and automobile windows. The new material is a combination of organic molecules engineered to be transparent in the visible and absorbing in the near infrared, an invisible part of the spectrum that accounts for much of the energy in sunlight. In addition, the researchers developed optical coatings to boost both power generated from infrared light and transparency in the visible range — two qualities that are usually in competition with one another. The color-neutral version of the device was made with an indium tin oxide electrode. A silver electrode improved the efficiency to 10.8%, with 45.8% transparency. However, that version’s slightly greenish tint may not be acceptable in some window applications. Both versions can be manufactured at large scale, using materials that are less toxic than other transparent solar cells. The transparent organic solar cells can also be customized for local latitudes, taking advantage of the fact that they are most efficient when the sun’s rays are hitting them at a perpendicular angle. They can be placed in between the panes of double-glazed windows. [The team is] working on several improvements to the technology, with the next goal being to reach a light utilization efficiency of 7% and extending the cell lifetime to about 10 years. They are also investigating the economics of installing transparent solar cell windows into new and existing buildings. The research has been published in the journal Proceedings of the National Academy of Sciences.