Nanoscale Engineering for High Performance Solar Cells
published: Sept. 16, 2013, recorded: May 2009, views: 2660
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How much energy does it take to turn on a lightbulb? Way too much in the U.S., where 22% of all electricity gets channeled into illuminating homes, businesses and thoroughfares. Vladimir Bulovic wants to end the exorbitant use of power for lighting, and simultaneously brighten our lives more pleasantly, with the application of nanostructure materials called quantum dots.
Incandescent bulbs, he tells the MIT Museum audience, are hugely wasteful, with just 5% efficiency converting electricity to light. Fluorescents do the job somewhat better, and light emitting diodes better still, but these more efficient bulbs often emit colors that feel harsh to the eye. Bulovic and other researchers have been designing a fix for both the color and power conversion problems, a new kind of photo cell based on special inorganic crystals called quantum dots. The size of a human hair sliced lengthwise 5,000 times (10 nanometers), these crystals fluoresce in precise, predictable colors at different sizes: bigger chunks look red, smaller ones look blue.
Bulovic has been experimenting with nanocrystal suspensions -- applying a thin film of quantum dot solution onto a surface that can be excited by shining light or by electricity. “By tuning mixtures of quantum dots, we can make…any color of the rainbow.” New sorts of lights, and displays with “fantastic responsiveness” and true blacks are emerging from this research, along with power consumption half that of today’s LCDs and plasma screens, and the potential of reducing energy use 20 fold down the road. Some versions of photo cells could be used in laptops, and the technology has the capacity to scale up fairly quickly.
The world, well on its way to 9 billion people (many of whom still clamor for electric power), and a climate crisis, desperately needs this kind of new technology, believes Bulovic. He wonders if nanostructure materials might help with some of the hurdles engineers have encountered in scaling up solar energy solutions. For instance, the silicon used in most photovoltaics could be made more efficient by using films consisting of nanostructures that capture spectra of light that silicon can’t. While solar won’t solve the world’s energy problems alone, it figures to be one very prominent solution, and Bulovic hopes nanotechnology will help generate energy independence, “in a controlled, clean way,” helping to “uplift the world.”
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