Perovskites, manufactured crystals used in solar cells, have long promised to boost solar power, but internal defects have blunted their potential. Now, researchers at Princeton Engineering have corrected the defects by adding a novel combination of chemicals during fabrication.
The technique could translate to a 1% improvement in the power generation of even the most cutting-edge perovskite solar cells, said Dane deQuilettes, a senior author on the paper and assistant professor at Princeton. The advance is due to the defect-free perovskites’ ability to retain energy from sunlight 10 times longer than untreated perovskites.
The paper was published Oct. 8 in the journal Science.
Perovskites are semiconductors with a complex crystalline structure that makes them well suited to capturing solar energy and converting it to electricity. While perovskites can be found in nature, the ones used to create solar cells are engineered in labs. The ingredients that scientists use to make perovskites can be prepared in liquid form, so perovskite solar cells can be fabricated by printing the material in sheets, like ink on newsprint.
Most solar cells are made of silicon, which is highly durable, but perovskite solar cells may be cheaper and more sustainable to produce. Increasingly, silicon and perovskites are paired together, a thin coat of perovskite layered over a silicon solar cell. These tandem solar cells generate about 40% more power than a solar cell made from only one material.
One major hurdle in manufacturing perovskites for everyday use is that the printing and layering process often creates atomic-level defects in the material. These defects dampen the ability of electrons to retain their excess energy after they absorb sunlight. The longer electrons can retain excess energy, the more power can be generated from a solar cell, deQuilettes said.
Led by faculty at Princeton, the University of California-San Diego and Sungkyunkwan University in Korea, the research team found a way to mitigate these microscopic defects by adding a mixture of zinc bromide and methyl ammonium chloride early in the fabrication process. Adding these chemicals produces perovskites with fewer defects in the crystal structure, which allows electrons to retain energy from sunlight longer.
“We opened up this new class of chemical mixtures that improve the performance of perovskites,” deQuilettes said. The key is that the two chemicals need to have a lower melting point when combined, like adding salt to ice.
While researchers have been working to correct perovskite defects for years, this discovery was a surprise, deQuilettes said. A few years ago, Jason Yoo, a first author on the paper and then a researcher at the Korea Research Institute of Chemical Technology, contacted deQuilettes with questions about some unusual lab results.
“He told me the samples were behaving like nothing he had seen before,” deQuilettes said. “He asked if I could help study them.”
DeQuilettes’ lab develops tools to understand how electrons behave and interact inside perovskites. He was amazed by Yoo’s samples — deQuilettes showed that the electrons retained excess energy for up to 300 microseconds, about a hundred thousand times longer than many other semiconductors.
This decrease in the number of defects enables a more efficient perovskite layer that can be used to augment standard silicon solar cells. This boost in solar power generation could provide a new source of energy in a time when demand is rising, deQuilettes said, especially for AI and datacenter infrastructure. “The whole solar industry has been asking, what are the next set of technologies that are going to contribute to energy production?” he said.
The possible applications of these low defect perovskites go beyond solar cells, deQuilettes noted. Because electrons in the perovskite can retain energy for so long, it opens new possibilities for how the crystals can be used.
“Energy is living in the material for so long, it broadens what’s actually possible with a semiconductor,” DeQuilettes said. The research has raised more questions than it’s answered, he added. “It’s been really eye-opening.”
The paper, Volatile eutectics to tailor crystallization for perovskite optoelectronics, was published in Science on October 8. In addition to deQuilettes, authors include Jason Yoo and Bong Joo Kang at the Korea Research Institute of Chemical Technology; Connor J. Dolan, Zhewen J.D. Deng, Jack R. Palmer, Kelly X. Vences and David P. Fenning at the University of California-San Diego; Seongsik Nam, Jinho Lee, Kyu Min Kang, Daesoo Kim, Jang Hee Cho, Donghyuk Chung and Seong Sik Shin at Sungkyunkwan University in Korea; Rushik Desai and Arun Mannodi- Kanakkithodi at Purdue University; Niranjana Mohan Kumar, Mariana I. Bertoni and Arkita Chakrabarti at Arizona State University; Yanqi Luo, Barry Lai, Zhonghou Cai, Martin V. Holt and Tao Zhou at the Argonne National Laboratory; Andrew M. Kiss at Brookhaven National Laboratory; In Sun Cho at Ajou University in Korea; Dong Hyun Kim and Jun Hong Noh at Korea University in Korea.
