Last year, researchers at UCLA produced a solar cell with the ability to absorb energy from light while remaining visibly transparent. The panel, made using the two polymers PBDTT-DPP and PCBM for short, boasts a power conversion efficiency (PCE) of 4%, while remaining 66% visibly transparent .This is about half as efficient as current organic semiconductor solar panels today, but the ability to let most visible light pass through opens up many uses for the technology. Think of skyscrapers with office windows that can support (or at least supplement) the building energy demands during the day.
Figure 1: Visual Comparison of Normal Glass (left) to the Polymer Solar Cell (right) 
So how does this work? How does something absorb light energy without interfering with the light we see? Researchers tested many different polymers until coming across the right ones. They needed polymers that absorb light of relatively high and low wavelengths- light just outside of the visible spectrum. The first polymer they used absorbs energy from near-infrared light (NIR), and the second absorbs ultraviolet light (UV rays). Neither of the polymers absorb much light in our visible spectrum (400-650 nanometers), so the polymer blend allows light to pass through while absorbing the NIR and UV rays . The image below shows the relative absorption and transmission rates for different wavelengths of light:
Figure 2: Display of Absorption and Transmission at Different Wavelengths. 
The red line represents transmission, or how much light passes through the polymers. The green line represents absorption, or how much light energy is captured. The orange dotted lines show the range of visible light to humans, where transmittance is highest and absorption is the lowest.
Sounds like a done deal? Unfortunately, the introduction of these cells into the U.S. solar market seems bleak for now, as regular solar panel prices are dropping significantly (they have dropped 80% over the last five years) . The cost of see-through solar panels is likely to be very high, and with normal solar panels getting cheaper, with higher energy conversion, it seems improbable that there is enough current demand for this product for it to be commercialized. Solar energy is a relatively new field to begin with, and research has much progress to make before this product becomes economically sensible.
The drop in solar panel price is in part due to China’s dominance in the production field. China has reportedly given illegal subsidies to companies, allowing them to sell panels at lower prices . China has grown very aggressive in the solar energy field, as they are desperately trying to cut back on smog levels in their major cities . This has driven many U.S. solar production companies out of business, and it continues to hurt the production market. Of course, this is ultimately good for consumers, and the world will continue to increase solar energy capacity, which is good for the environment.
Only time will tell when and where these see-through energy windows will enter the market. I would guess that within the next decade, China will begin production, but that’s only assuming that current economic trends continue. Regardless, I can’t wait to work in a building that is self-powered by its very own windows.
Buckley, Sean. “UCLA Creates Transparent Solar Cell, Dreams of Current Generating Windows.” Engadget. N.p., 22 July 2012. Web. 19 Feb. 2013.
Chin, Chun-Chao et. al. “Visibly Transparent Polymer Solar Cells Produced by Solution Processing.” (n.d.): n. pag. Www.acsnano.org. ACSNano, June 2012. Web. 28 Feb. 2013.
”China to Boost Solar Power Goal 67% as Smog Envelops Beijing.” Bloomberg. N.p., n.d. Web. 24 Feb. 2013.
Shahan, Zachary. “Solar Power Graphs to Make You Smile.” CleanTechnica. N.p., 10 June 2011. Web. 19 Feb. 2013.
Wang, Ucilia. “180 Solar Panel Makers Will Disappear By 2015.” Forbes. Forbes Magazine, 16 Oct. 2012. Web. 19 Feb. 2013.