A type of nanocrystal could be used to double the efficiency of solar cells, according to new research published in the journal Science.
Current solar cells have a maximum efficiency of about 31 percent because most of the excess energy from the sun is absorbed by electrons in traditional silicon semiconductors, and is quickly lost as heat before it can be converted into electricity.
Scientists from the University of Texas at Austin and the University of Minnesota have discovered that semiconductors made out of nanocrystals—or quantum dots—could be used to capture the “hot electrons,” theoretically increasing the efficiency of solar cells to as much as 66 percent.
“There are a few steps needed to create what I call this ‘ultimate solar cell,’” said researcher Dr. Xiaoyang Zhu, professor of the University of Texas at Austin, in a press release. “First, the cooling rate of hot electrons needs to be slowed down. Second, we need to be able to grab those hot electrons and use them quickly before they lose all of their energy.”
Previous research groups have shown that quantum dots can solve the first problem. Now Zhu’s team has found a way to transfer the hot electrons so that they can be used to produce electricity.
The researchers demonstrated that hot electrons captured by quantum dots made from lead selenide could be drawn out before they cooled by another semiconductor, titanium dioxide. Quantum dots made out of other materials could work just as well, said Zhu.
Current solar cells have a maximum efficiency of about 31 percent because most of the excess energy from the sun is absorbed by electrons in traditional silicon semiconductors, and is quickly lost as heat before it can be converted into electricity.
Scientists from the University of Texas at Austin and the University of Minnesota have discovered that semiconductors made out of nanocrystals—or quantum dots—could be used to capture the “hot electrons,” theoretically increasing the efficiency of solar cells to as much as 66 percent.
“There are a few steps needed to create what I call this ‘ultimate solar cell,’” said researcher Dr. Xiaoyang Zhu, professor of the University of Texas at Austin, in a press release. “First, the cooling rate of hot electrons needs to be slowed down. Second, we need to be able to grab those hot electrons and use them quickly before they lose all of their energy.”
Previous research groups have shown that quantum dots can solve the first problem. Now Zhu’s team has found a way to transfer the hot electrons so that they can be used to produce electricity.
The researchers demonstrated that hot electrons captured by quantum dots made from lead selenide could be drawn out before they cooled by another semiconductor, titanium dioxide. Quantum dots made out of other materials could work just as well, said Zhu.
“If we take the hot electrons out, we can do work with them,” said Zhu. “The demonstration of this hot electron transfer establishes that a highly efficient hot carrier solar cell is not just a theoretical concept, but an experimental possibility.”
But there is a lot more work to do before more efficient solar cells appear on the market, said the researchers, including building and studying an actual solar cell made with the quantum dots. One major problem—minimizing the loss of energy as the electrons are transferred through the titanium dioxide—still needs to be overcome.
The scientists, however, are optimistic about the future. “There is no reason that we cannot be using solar energy 100 percent within 50 years,” Zhu said.
Solar cells built based on this research would also be cheaper, said the researchers, as the manufacturing costs would be less.
The scientists, however, are optimistic about the future. “There is no reason that we cannot be using solar energy 100 percent within 50 years,” Zhu said.
Solar cells built based on this research would also be cheaper, said the researchers, as the manufacturing costs would be less.
