An international team of researchers has developed a new technology to improve the durability of flip-perovskite solar cells, an important step in bringing a new photovoltaic technology to market that can significantly reduce solar energy costs.
Unlike traditional solar cells, perovskite solar cells are made from nanosized crystals made from ultra-high purity silicon wafers. These perovskite crystals can be dispersed in liquids and cut using inexpensive and well-established methods.
In addition, by adjusting the thickness and chemical composition of the crystalline films, one can control the wavelength of light absorbed by the perovskite. Layers of perovskite tuned to different wavelengths can be stacked on top of each other or on top of traditional silicon cells, resulting in "tandem" cells that absorb more solar spectrum than current devices.
The latest work, published in the journal Science , involved researchers from the University of Toronto, Northwestern University, the University of Toledo and the University of Washington.
"Perovskite-based solar cells could exceed the efficiency limits of silicon solar cells," said study author Ted Sargent, who recently joined Northwestern University's Department of Chemistry, Electrical and Computer Engineering. T. Engineering U has a laboratory.
“They also lend themselves to manufacturing methods that are much more expensive than those used for silicon. However, one area where perovskites lag behind silicon is durability. In this study, we used a rational design approach to solve this problem in a new and unique way.”
In recent years, Sargent and colleagues have made several advances that have improved the performance of perovskite solar cells. But while much of their previous work has focused on improving efficiency, their latest work has been in reliability testing.
"The key to the vulnerability of solar cells is the contact between the perovskite layer and neighboring layers," said researcher Chongwen Li. He is from Toledo and one of the lead authors of the article.
“These layers repel electrons or holes passing through the circuit. If the chemical bond between these layers and the perovskite layer is damaged by light or heat, electrons or holes cannot enter the circuit, reducing the cell's overall efficiency." Lee said.
To solve this problem, an international research team went back to the original principles. They used density functional theory (DFT) computer simulations to predict which molecules are best suited to form bridges between the perovskite layer and the charge transport layer.
"Previous studies have shown that molecules known as Lewis bases are able to form strong bonds between these layers," said Bing Chen, a Sargent lab researcher who is now a research fellow at Northwestern University and a co-author. paper
“This is because one side of the molecule binds to the lead atoms in the perovskite layer and the other side to the nickel in the transport layer. Our modeling predicts that Lewis acids containing elements of phosphorus will have the best effect.”
In the lab, the team tested various formulations of the phosphorus-containing molecule. Their tests showed the best performance with a material called 1,3-bis(diphenylphosphino)propane or DPPP.
The team fabricated flipped perovskite solar cells with and without DPPP. They tested both solar cells by shining sunlight on them, simulating the conditions they would encounter in the field. They experienced intense heat in both light and darkness.
“With DPPP under ambient conditions, that is, without overheating, the overall energy conversion efficiency of the cell was high for about 3,500 hours,” Li said.
“In the previously published literature, perovskite solar cells lost significant efficiency after 1500 to 2000 hours, so this is a big improvement.”
Li said the group has applied for a patent on the DPPP method and is interested in commercial solar cell manufacturers.
“I think we have shown a new path: DFT modeling and rational design can point the way to promising solutions,” he says.
“But there may be better molecules. Ultimately, we want to get to the point where perovskite solar cells can compete commercially with silicon, today's photovoltaic technology. This is an important step in this direction, but here it is. There is still a long way to go.”
Further information : Chongwen Li et al., Rational Design of Lewis Base Molecules for Stable and Efficient Inverted Perovskite Solar Cells, Science (2023). DOI: 10.1126/science.ade3970
Citation: Researchers increase the durability of low-cost solar cells made from nanoscale crystals (2023, February 23) https://phys.org/news/2023-02-durability-low-cost-solar. - cells-nano-size.html
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