Gallium arsenide thin-film photovoltaic cells are expected to break energy efficiency records

According to the website of the American Physicists Organization on November 8 (Beijing time), American scientists have used gallium arsenide to create a thin-film solar cell with a maximum conversion efficiency of 28.4% through a new approach that is contrary to traditional scientific research. The key to improving the efficiency of this solar cell is not to allow it to absorb more photons but to allow it to release more photons. In the future, solar cells made of gallium arsenide are expected to break the limit of energy efficiency conversion records.

In the past, scientists have emphasized improving the efficiency of solar cells by increasing the number of photons absorbed by the sun. The electrons generated by solar cells after absorbing sunlight must be extracted as electricity, and those electrons that are not extracted quickly enough will decay and release their energy.

Research led by Eli Yabrunovich, a scientist at the U.S. Department of Energy's Lawrence Berkeley National Laboratory, shows that the output voltage of a solar cell can be increased if this released energy is emitted as external fluorescence. "Our research shows that the more efficiently a solar cell releases photons, the more efficient its energy conversion and the voltage it provides," Yabrunovich said. "External fluorescence is the key to solar cell conversion efficiency reaching the theoretical maximum value - the Shockley-Queisser efficiency limit. For a single pn junction solar cell, this maximum value is about 33.5%."

Owen Miller, a researcher involved in the study, explained that in the open circuit environment of a solar cell, electrons have nowhere to go, so they are crowded together. Ideally, they emit external fluorescence to precisely balance the incident sunlight.

Based on this, Alta Equipment, co-founded by Yabrunovich, used the single-crystal thin-film technology developed by Yabrunovich earlier - epitaxial layer peeling technology, to produce thin-film solar cells with a maximum conversion efficiency of 28.4% using gallium arsenide. This type of battery not only breaks the previous conversion efficiency, but also costs less than other solar cells. Currently, the most efficient commercial solar cells are made of single-crystal silicon rounds with a maximum conversion efficiency of 23%. Although gallium arsenide is more expensive than silicon, it is more efficient in collecting photons. In terms of cost-effectiveness, gallium arsenide is an ideal material for making solar cells.

"The high performance of solar cells is related to external fluorescence," Yabrunovich said. "Our theory will significantly change the face of future solar cells. We will live in a world where solar cells are very cheap and efficient."