American scientists have developed solar cells that can both emit light and absorb light

Scientists believe that the more light that a solar cell absorbs, the more electricity it will provide. However, a US research team does the opposite and proposes and demonstrates a new design concept. The solar cell is designed to glow. A diode (LED) can both absorb light and emit light. They said that the latest design is expected to allow solar cells to break through the limits of conversion efficiency.

The team's principal, Eli Yabrunnovic, a professor of electronic engineering at the University of California, Berkeley, said: "The results of the demonstration show that the more photons emitted by solar cells, the higher the voltage generated and the conversion efficiency achieved."

Scientists have known since 1961 that there is a theoretical maximum in the photoelectric conversion efficiency of solar cells: about 33.5%. But 50 years have passed and no one has ever exceeded this limit. In 2010, scientists achieved a conversion efficiency of 26% for flat-panel single-node solar cells that can absorb light waves of specific frequencies.

In order to achieve higher conversion efficiency, the Jablonovic team proposed the above design concept based on the mathematical correlation between light absorption and light emission. Owen Miller, a researcher, said that when photons in the sun “attack” a semiconductor in a solar cell, the battery generates electricity. Photons provide energy that loosens the electrons in the material and allows them to move freely, but this process (the process of luminescence) may also generate new photons. The idea behind new solar cells is that these new photons, which do not come directly from the sun, should easily escape from the battery. Miller said: "Although this is counter-intuitive, mathematically speaking, the new photon escape will make the battery generate more voltage."

Miller explained: “Basically, there is a thermodynamic relationship between the absorption and emission of solar cells. Let the solar cells emit light, then the photons will not be 'lost' in the solar cell, it will increase the production of solar cells. The better the glow, the higher the voltage generated by the solar cell and the higher the conversion efficiency.” Miller said that although the theory that the cold light emission process will increase the voltage is not new, no one ever thought of using it to design it. Solar battery.

Yabrunnovic said that the solar cell model made of gallium arsenide, which Alta Equipment Co., Ltd., which he founded and used a new concept last year, has achieved a record conversion efficiency of 28.3%. This progress should be attributed in part to the fact that when designing batteries, they also allow light to escape from the battery as easily as possible. The technologies they use include improving the backside of the battery and ensuring that the photons generated are reflected back into the material, generating more power.

Jablonovic hopes to use the latest technology to make solar cells convert more than 30%. The study applies to all types of solar cells and is expected to benefit the entire solar cell field. Scientists will read the latest results at the Laser and Electronic Equipment Conference held in San Francisco, California from May 6th to 11th.

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