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NATURE
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woah! This transparent solar cell
could make every window a power source!
Back in August 2014, researchers at Michigan
State University have created a fully transparent solar concentrator, which could turn any
window or sheet of glass (like your smartphone’s screen) into a photovoltaic solar cell.
Unlike other “transparent” solar cells that we’ve
reported on in the past, this one really is transparent, as you can see in the photos throughout this story. According to Richard Lunt, who
led the research at the time, the team is confident the transparent solar panels can be efficiently deployed in a wide range of settings,
from “tall buildings with lots of windows or any
kind of mobile device that demands high aesthetic quality like a phone or e-reader.”
Today, Ubiquitous Energy, an MIT startup we
first reported on in 2013, is now getting closer
to bringing its transparent solar panels to market. Lunt cofounded the company and remains
assistant professor of chemical engineering
and materials science at Michigan State University. Essentially, what they’re doing is instead of
shrinking the components, they’re changing the
way the cell absorbs light. The cell selectively
harvests the part of the solar spectrum we can’t
see with our eye, while letting regular visible
light pass through.
Scientifically, a transparent solar panel is something of an oxymoron. Solar cells, specifically
the photovoltaic kind, make energy by absorbing photons (sunlight) and converting them
into electrons (electricity). If a material is transparent, however, by definition it means that
all of the light passes through the medium to
strike the back of your eye. This is why previous
transparent solar cells have actually only been
partially transparent — and, to add insult to injury, they usually they cast a colorful shadow
too.
To get around this limitation, the Michigan
State researchers use a slightly different technique for gathering sunlight. Instead of trying
to create a transparent photovoltaic cell (which
is nigh impossible), they use a transparent luminescent solar concentrator (TLSC). The TLSC
consists of organic salts that absorb specific
non-visible wavelengths of ultraviolet and infrared light, which they then luminesce (glow)
as another wavelength of infrared light (also
non-visible). This emitted infrared light is guided to the edge of plastic, where thin strips of
conventional photovoltaic solar cell convert it
into electricity. [Research paper: DOI: 10.1002/
adom.201400103 – “Near-Infrared Harvesting
Transparent Luminescent Solar Concentrators”]