Author: Alexandra Taylor / Source: Science News for Students
Solar cells are devices that turn sunlight into electricity. This technology offers a more Earth-friendly way to produce power than burning coal and other fossil fuels.
But panels of solar cells need a lot of open, sunny space to harvest that sunlight. Where space is limited, people might have to choose between solar panels and fields to grow food. But what if you could produce crops and electricity at the same time? For Yang Yang, the solution is clear. Clear solar cells, that is.Yang is a physicist at the University of California, Los Angeles. He studies solar cells, also known as photovoltaic (Foh-toh-vol-TAY-ik) cells. Many are made using the element silicon. Yang instead works with carbon-based versions. These solar cells are known as OPVs, short for organic photovoltaics. OPVs are flexible and simple to make. Recently, several groups of scientists made OPVs that are transparent, or clear.
Because they let light pass through, one of Yang’s students suggested that they use OPVs on a greenhouse roof. This inspired Yang’s team to create and test a solar cell that could both make electricity and let enough light pass through to grow plants.
Sunlight is made up of many colors, or wavelengths, of light. The colors we see — from violet through red — are called visible light. Their wavelengths range from 400 to 700 nanometers. (A nanometer is a billionth of a meter.) Yang’s solar cells let visible light pass through, which makes them look clear. But solar cells must also absorb some light to generate electricity. Yang’s absorb infrared light, which has wavelengths between 700 nanometers and 1 millimeter. About half of the light that comes from the sun is infrared. People can’t see it, but some animals — such as snakes and bats — can sense infrared.
Plants don’t need infrared light. In fact, they need only a very small range…
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