Transparent “solar windows”

New material from Lunt’s lab, which can absorb sunlight without losing its transparency Researchers at Michigan State University (MSU) have…

New material from Lunt’s lab, which can absorb sunlight without losing its transparency

Researchers at Michigan State University (MSU) have developed a technology which uses transparent, uncoloured plastic, which can be placed over windows to produce electricity from sunlight. The new technology is called a transparent luminescent solar contractor and absorbs specific non-visible wavelengths.

Until now, technologies that tried to produce solar power using windows or other transparent surfaces had several disadvantages. They mainly used solar cells placed around luminescent materials and production of electricity was low with a maximum efficiency of about 7 %. Additionally the absorption leads to the “transparent” materials being coloured.

Richard Lunt of MSU’s College of Engineering illustrates how the new approach is different: “No one wants to sit behind coloured glass. It makes for a very colourful environment, like working in a disco. We take an approach where we actually make the luminescent active layer itself transparent.”

For the new solar harvesting system Lunt and his colleagues developed organic molecules that absorb specific wavelengths, which are not visible to the human eye. “We can tune these materials to pick up just the ultraviolet and the near infrared wavelengths that then ‘glow’ at another wavelength in the infrared”, the assistant professor of chemical engineering and materials science explains. Afterwards those are transported to thin strips of photovoltaic cells at the side of the plastic, which then convert the light into electricity. Since the absorbed wavelengths are not visible for us, the material looks transparent.

This means, if the technology can be scaled up, a whole new spectrum of photovoltaic applications will open up. “It can be used on tall buildings with lots of windows or any kind of mobile device that demands high aesthetic quality like a phone or e-reader. Ultimately we want to make solar harvesting surfaces that you do not even know are there”, says Lunt.

With energy efficiency around 1 %, there is still much room for improvement. As Lunt says, the group wants to reach efficiencies of 5 % as soon as their invention is fully optimized.