August 19, 2014 – A team of researchers at Michigan State University has developed a new type of solar concentrator that, when placed over a window, creates solar energy while allowing people to actually see through the window.

The ‘transparent luminescent solar concentrator’ can be used on buildings, cell phones and any other device that has a clear surface and, according to Richard Lunt of MSU’s College of Engineering, the key word here is “transparent”.

“No one wants to sit behind coloured glass,” said Lunt, an assistant professor of chemical engineering and materials science. “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.”

The solar harvesting system uses small organic molecules developed by Lunt and his team to absorb specific non-visible wavelengths of sunlight.

“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,” he said. The ‘glowing’ infrared light is guided to the edge of the plastic where it is converted to electricity by thin strips of photovoltaic solar cells.

“Because the materials do not absorb or emit light in the visible spectrum, they look exceptionally transparent to the human eye,” Lunt said.

One of the benefits of this new development is its flexibility. While the technology is at an early stage, it has the potential to be scaled to commercial or industrial applications at an affordable cost.

“It opens a lot of area to deploy solar energy in a non-intrusive way,” Lunt said. “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.”

Lunt said more work is needed to improve its energy-producing efficiency. Currently, the transparent luminescent solar concentrator is able to produce a solar conversion efficiency close to 1%; Lunt aims to reach efficiencies beyond 5% when fully optimized.

Other members of the research team include: Yimu Zhao, an MSU doctoral student in chemical engineering and materials science; Benjamin Levine, assistant professor of chemistry; and Garrett Meek, doctoral student in chemistry.

Photo 1: Yimu Zhao, a doctoral student in chemical engineering and materials science, and Richard Lunt, assistant professor of chemical engineering and materials science, run a test in Lunt’s lab. Lunt and his team have developed a new material that can be placed over windows and create solar energy. Photo by G.L. Kohuth.

Photo 2: Solar power with a view: MSU doctoral student Yimu Zhao holds up a transparent luminescent solar concentrator module. Photo by Yimu Zhao.

Photo 3: A transparent luminescent solar concentrator waveguide is shown with colourful traditional luminescent solar concentrators in the background. The new concentrator can create solar energy but is not visible on windows or other clear surfaces. Photo by G.L. Kohuth.