How a Transparent Window Coating can Harvest Solar Energy

MICHIGAN STATE UNIVERSITY, MICHIGAN, USA. The sunlight coming through your window as you read this article could one day be the source of the electricity your computer needs to run. In an article recently published in Advanced Optical Materials, researchers from Michigan State University presented a perfectly transparent luminescent solar concentrator that could be used on windows or smartphone screens to harvest solar energy.

The device works thanks to tiny organic molecules, synthesized by a group led by Professor Lunt, that are able to collect radiation in the near infrared (NIR) and ultraviolet (UV) spectral regions. The absorbed light is then re-emitted on another infrared wavelength and channeled toward the edge of the plastic, where it is collected by thin strips of photo-voltaic cells that convert it into electricity. Both NIR and UV radiation are outside the visible range, thus a surface absorbing light of these wavelengths looks perfectly transparent to the human eye. The idea of luminescent solar concentrators is not new, but up to now they existed only in heavily colored versions. This characteristic made them unsuitable to cover home or car windows.

The technology is not yet mature, since the conversion efficiency is now around 1%, while the goal is to reach 5%. The best non-trasparent solar concentrator available today scores 7%. A conventional solar cell of this kind already installed on private houses has an efficiency of around 15%.

However, this technology has a clear potential for scaling at commercial and industrial applications with reasonable costs. Future models of the device could offer a non intrusive way to gain clean energy from the sun, and take advantage of every surface light can shine on.