Extracting energy from invisible light ...

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

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

We see the world through our eyes, a sense that is able to capture the photons reflected by the world around us. We can only capture, see, photons in very specific wavelengths (390 to 700nm). We can 't see ultraviolet nor infrared light (some animals can...). This out of visible spectrum light is as energetic as the one on the visible light.

Researchers at the Michigan State University have come up with a way to convert out of visible light photon energy into electrical power. They are using small organic molecules that can capture photons at ultraviolet and infrared wavelengths and convert them into sub-infrared wavelengths that can be converted into electrical power.

These small molecules, so small that they do not block photons in the visible spectrum (hence they are transparent to our eye), are embedded in a plastic like material to form a light concentrator, as they call it, that can be overlaid on a glass pane. The photons generated in the sub-infrared light are sent at the edges of the layer where they are converted into electrical power.

It is not the first time that researchers come up with a way to overlay a layer of special materials (or even to create special glasses) that can convert part of the incoming light energy into electricity, and I wrote a few posts on them. What is interesting here is that the energy converted is from photons that we don't "see", hence from our point of view there is no impact. All other solutions either resulted in a tinted light (white less the wavelengths converted into electricity) or in a "less" transparent glass (slightly greyish).

This layer could be overlaid on building windows or on a cell phone screen, an e-reader with no impact on the aesthetic or feeling perceived by us.

The problem today is the efficiency that is around 1% (only 1% of the incoming light energy is converted in electrical power). The best materials for capturing incoming light energy on a window are around 5-7% and that is the level the researchers at the University of Michigan are shooting to make their innovation appealing to the market. 

Author - Roberto Saracco

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