Antireflection (AR) coatings on plastics have a multitude of practical applications, including glare reduction on eyeglasses, computer monitors and the display on your smartphone when outdoors. Now, National Science Foundation-funded researchers have developed an AR coating that improves on existing coatings to the extent that it can make transparent plastics, such as Plexiglas, virtually invisible. They needed an antireflection coating that worked well over the entire solar spectrum and at multiple angles as the sun crossed the sky. They also needed a coating that could stand up to weather over long periods of time outdoors. That was a tall order. Although it is comparatively easy to make a coating that will eliminate reflection at a particular wavelength or in a particular direction, one that could fit all their criteria did not exist. For instance, eyeglass AR coatings are targeted to the narrow visible portion of the spectrum. But the solar spectrum is about five times as broad as the visible spectrum, so such a coating would not perform well for a concentrating solar cell system.
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