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Published on July 22nd, 2012 | by Zachary Shahan


Solar Cells for Windows Take Another Step Forward

July 22nd, 2012 by  

We’ve been covering research on windows that create solar power for years. We’re still not quite there, but advances seem to be speeding up. The latest step forward comes from UCLA. The day when we have windows producing solar power may soon be approaching. Here’s the full news below, posted first on sister site Planetsave:

Researchers from UCLA have developed a new transparent solar cell that is a significant step towards giving the windows in homes and other buildings the ability to generate electricity while still being transparent.

The research team “describes a 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.” They created the device from a photoactive plastic that generates an electrical current from infrared light.

“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, a UCLA professor of materials science and engineering, who also is director of the Nano Renewable Energy Center at California NanoSystems Institute (CNSI).



Yang also said that there has been a definite world-wide interest in polymer solar cells. “Our new PSCs are made from plastic-like materials and are lightweight and flexible,” he said.

“More importantly, they can be produced in high volume at low cost.”

“Polymer solar cells have attracted great attention due to their advantages over competing solar cell technologies. Scientists have also been intensely investigating PSCs for their potential in making unique advances for broader applications. Several such applications would be enabled by high-performance visibly transparent photovoltaic (PV) devices, including building-integrated photovoltaics and integrated PV chargers for portable electronics.”

“Previously, many attempts have been made toward demonstrating visibly transparent or semitransparent PSCs. However, these demonstrations often result in low visible light transparency and/or low device efficiency because suitable polymeric PV materials and efficient transparent conductors were not well deployed in device design and fabrication.”

“A team of UCLA researchers from the California NanoSystems Institute, the UCLA Henry Samueli School of Engineering and Applied Science and UCLA’s Department of Chemistry and Biochemistry have demonstrated high-performance, solution-processed, visibly transparent polymer solar cells through the incorporation of near-infrared light-sensitive polymer and using silver nanowire composite films as the top transparent electrode. The near-infrared photoactive polymer absorbs more near-infrared light but is less sensitive to visible light, balancing solar cell performance and transparency in the visible wavelength region.”

“Another breakthrough is the transparent conductor made of a mixture of silver nanowire and titanium dioxide nanoparticles, which was able to replace the opaque metal electrode used in the past. This composite electrode also allows the solar cells to be fabricated economically by solution processing. With this combination, 4% power-conversion efficiency for solution-processed and visibly transparent polymer solar cells has been achieved.”

“We are excited by this new invention on transparent solar cells, which applied our recent advances in transparent conducting windows (also published in ACS Nano) to fabricate these devices,” said Paul S.Weiss, CNSI director and Fred Kavli Chair in NanoSystems Sciences.

The new study appears in the journal ACS Nano.

A number of researchers and companies have been working on solar windows over the years. It will be interesting to see who comes out with the first commercial product.

Source: University Of California – Los Angeles
Image Credits: University of California – Los Angeles

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About the Author

is tryin' to help society help itself (and other species) with the power of the word. He spends most of his time here on CleanTechnica as its director and chief editor, but he's also the president of Important Media and the director/founder of EV Obsession and Solar Love. Zach is recognized globally as a solar energy, electric car, and energy storage expert. He has presented about cleantech at conferences in India, the UAE, Ukraine, Poland, Germany, the Netherlands, the USA, and Canada. Zach has long-term investments in TSLA, FSLR, SPWR, SEDG, & ABB — after years of covering solar and EVs, he simply has a lot of faith in these particular companies and feels like they are good cleantech companies to invest in. But he offers no professional investment advice and would rather not be responsible for you losing money, so don't jump to conclusions.

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  • Rahul

    Wow this is indeed a big stepping stone. BIPV systems may not be the same again if it clicks. But BOS sytems guys will have a tough time. No racking and mounting systems are rrequired.

    But overall gud for us consumers!!

  • rkt9

    This technology could replace the glass or plastic of greenhouses, or the screens of screened in pools, it doesn’t need to be used just in windows. 

  • Charlie Curcija

    There are two benefits of this invention, one is that there is less energy coming into the conditioned space in near infra-red portion of solar spectrum, which means less cooling energy required in the summer, while leaving visible transmittance (VT) nearly intact.  The second benefit is generation of power.  Article is not clear on what is the meaning of 4% efficiency, is it 4% of total available solar irradiation over the average of all incidence angles of Sun on the window, or is it 4% at normal incidence, in which case real efficiency could be really small.  Solar radiation intensity on a clear day is close to 1,000 W/m2, so 4% would be 40 W/m2.  In any case, the real significance of this technology is that it can lead to products with higher efficiency.  Most of solar conversion occurs in visible part of solar spectrum, so the very fact that this technology converts primarily in near infra-red (NIR) is very significant.  This can also lead to products that can convert in visible part of spectrum, possibly in switching mode (dynamic), where user can “dial” conversion (and corresponding solar transmittance reduction), this accomplishing what electrochromic windows do, while generating electricity instead of unwanted heat  Glazing that would convert in both visible and NIR would have efficiencies in 10-20% range.  

    All in all, excellent technology and promising new directions in smart glazings.

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  • Jerrza

    Buildings, Jimmy. Buildings.

  • Wouldn’t you want the solar cell on the TOP of the house, not the sides (where windows are)? How often does the sun shine horizontally? Last time I checked, it’s only there a short time at sunrise and sunset. The rest of the day it’s up in the sky. Seems a dubious invention. 

    • Tweedle2

       Oh Jimmy…Jimmy…Jimmy.  You have missed the point all together.  The windows just mean more surface at different times of the day.  Most homes have windows all around the house and passive lighting on the roof as well.  Make them collectors and waaa-laaa more surface to provide power DUH!!!!!

      • Fubar

        You most likely would consume more energy isnstalling these things not including the energy spent producing these things than the pitiful four percent they deliver.

        • MitchF

          So 4% of what?  How big of a window would it take to keep the lights on in a room for 1 hr, 2 hrs, the whole day?  Sure there is interest, but if you can’t power anything of significance for any length of time, then it is just a novelty

          • Bob_Wallace

            A specific solar window would not be hooked to a specific desk lamp.  Power produced will be used throughout the building/grid.

            Solar earlier and later than the normal “solar day” has value.  Look at how “south facing” solar in Germany is bringing down midday prices but leaving morning and afternoon prices as they were. 

            There’s a role for solar installations that lengthen the solar day.

            Cost – remember that we’re talking only the cost of the solar film/coating itself and some minor wiring needed to connect the window to the grid.

            The vast majority (frame, glass, labor) would be spent anyway for the window itself.

          • Ss

            Efficiency is one problem. The other problem is life time. Silicon is known to stay for decades, polymers have a much shorter lifetime. Polymers are cheap, but … the installation cost, the cost of invertor is now higher than the cost of material. With all this said, Si on your roof is the way to go. We are istalling 10kW for less than $1/W (with all the credits, of course). Some time ago someone said that $1/w is the goal. Well, we reached it already, now it is time to act. Our roof will pay off in 6 years (Texas! Lots of sun), even better deals are in California; however, I am surprised that people are slow to react.

          • Bob_Wallace

            Hard to say what material cost will be for window solar. Sprayed onto the inside of one of the panes of glass in a dual-pane window would be pretty cheap. Installation labor costs next to nothing. (Run wire, hook up.)
            Life, another unknown. First Solar is giving a 25 year warranty for their thin film panels.

            Inverter cost would be shared by east/south/west and rooftop panels. And I’m expecting inverter costs to start coming down rapidly as economies of scale are reached and multiple companies start competing for larger market share.

            If your company has broken the $1/watt threshold, including federal/state/local subsidies that’s great news!

            Perhaps you don’t wish to share your trade secrets with other companies, but if you’re willing to provide information about how you’re pulling that off you might email Zach and see if the two of you can put together a “Here’s How” piece.

          • This is science. It starts with nothing, moves on to novelty, and can eventually bring about a product that transforms the world.

          • Altair IV

            Think about how much surface area your average skyscraper has.  Even at only 4%, that can add up to significant wattage.

            The important factor for commercial viability, however, is whether the benefit received matches or exceeds the cost of installing it.  The actual numerical efficiency of it is not really that important.

          • Yes, the ‘efficiency card’ seems like it’s always just used as a distraction. Efficiency means almost nothing when it comes to the market — what matters is cost vs benefit. Of course, efficiency is an input into that, but focusing on efficiency without cost is nonsensical.

          • Jeffhre

            Energy efficiency has a similar issue. One window with air infiltration issues is just a whistling novelty. But billions of windows collecting small amounts of energy daily, over our entire lifetimes, is profound.

        • solar technology has advanced a ton in recent years. this is not a commercial product. but with more scientific advancements, i definitely think it will become one.

          there are top-notch teams working on this in various places.

    • Jsmichels

      hardly. think of all the afternoon and morning sun on sky scrapers, or even houses for that matter. and this could be added on top of existing windows, much cheaper.

    • Bob_Wallace

      It takes the Sun several hours to rise from the horizon to directly overhead.  During those hours east-facing solar panels/windows would be pumping power into the grid.  And west-facing collectors would take over in the afternoon.

      Altogether the ‘solar day’ gets longer by many hours.

      It all comes down to price.  If the cost of adding solar collecting to windows is low then it’s worthwhile.  All the “racking” and labor costs would be born by the cost of putting in windows.  Solar would get (almost) a free ride.  (A bit of additional wiring.)

      BTW, apparently solar panels installed on an east-facing or west-facing roof slope produce about 80% as much power as south-facing slope panels.  Having solar input earlier and later in the day has real value that likely offsets the 20% loss.  Especially as panels get cheaper.

    • As well.

      Not instead.

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