Transparent Solar Panels Otherwise Seen As Windows At UCLA

transparent-solar-panelsTransparent solar panels made possible by researchers at UCLA and MIT.

In 2012, a UCLA team of researchers from the California NanoSystems Instutue, the UCLA Henry Samueli School of Engineering and Applied Science and UCLA’s Department of Chemistry and Biochemistry, lead by study leader Professor Yang Yang of materials science and engineering, demonstrated a high-performance, solution-processed, visibly transparent polymer solar cell through the incorporation of near-infrared light-sensitive polymer using silver nano-wire composite films as the top transparent electrodes… In short, smart people at UCLA collaborated to devise a see through solar film that only harnesses the energy of invisible light!

The UCLA team described their new kind of polymer solar cell (PSC) that produces energy by absorbing mainly infrared light, not visible light, making the cells nearly 70% transparent to the human eye. Fortunately, this technology can be produced at high volume at low cost.

“These results open the potential for visibly transparent polymer solar cells as add-on components of portable electronics, smart windows and building-integrated photovoltaics and in other applications,” said study leader Yang Yang. “Our new PSCs (polymer solar cell) are made from plastic-like materials and are lightweight and flexible.”

Essentially, imagine, a downtown building that towers over the city has windows doubled as the power source for all of the lights shining inside throughout the night.

This schematic diagram shows the key components in the MIT transparent photovoltaic (PV) device, which transmits visible light clearly while capturing ultraviolet (UV) and near-infrared (NIR) light. The PV coating—the series of thin layers at the right—is deposited on the piece of glass, plastic, or other transparent whatever. At the core of the coating are the active layers which absorb the UV and NIR light and cause current to flow via two transparent electrodes through an external circuit. A reflector sends UV and NIR light back into the active layers, while the anti-reflective (AR) coatings on the outside reduce reflections of incoming light to the max.

This schematic diagram shows the key components in the MIT transparent photovoltaic (PV) device, which transmits visible light clearly while capturing ultraviolet (UV) and near-infrared (NIR) light. The PV coating—the series of thin layers at the right—is deposited on the piece of glass, plastic, or other transparent whatever. At the core of the coating are the active layers which absorb the UV and NIR light and cause current to flow via two transparent electrodes through an external circuit. A reflector sends UV and NIR light back into the active layers, while the anti-reflective (AR) coatings on the outside reduce reflections of incoming light to the max.

This new idea for “see-through” solar power generation has been the goal of research groups around the world. However, the results have teeter-tottered between efficiency and visibility. A solar powered window had not been as easily accomplished by striping windows with thick layers of photovoltaic panels or thinning the PV so much that they’d be inefficient. If there is a will there is a way.

Three years ago postdoc researcher at MIT, now assistant professor at the Department of Chemical Engineering and Materials Science at Michigan State University, Richard Lunt, thought to absorb all the of the energy in sunlight except the spectrum that allows us to see. That with the right materials and design, the light that we can detect would pass through a solar cell to our eyes, and the rest would be absorbed by the solar cell.

Inspired by Lunt’s notion, a team in MIT’s Organic and Nanostructured Electronics Laboratory began to develop a transparent PV. What they came up with is a PV with multiple layers that reflect the light contacting it internally absorbing only the infrared and ultraviolet particles-the wavelengths we can see pass right through to illuminate space. To be fair, transparency is achieved, but through the process 70% of the photons we can see pass through the transparent solar panels.

“We do let the visible photons [light particles] pass through, allowing them to efficiently light the room. But we try to catch all of the photons in the infrared and ultraviolet,” says Vladimir Bulović of MIT Electrical Engineering and Computer Science. “We try not to let any of those photons get through. So a honey bee—which sees in the ultraviolet—wouldn’t think it’s transparent, but we humans do.”

 

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