Perovskite-based solar cells are inching closer to market viability with the help of researchers at The University of Toledo.
As this promising thin-film photovoltaic technology now bests the silicon-based cells that are the industry standard in some categories, physicists are chipping away at the categories where it still lags. Three such researchers at UToledo’s Wright Center for Photovoltaics Innovation and Commercialization recently lent expert insights to research published in the peer-reviewed journal Nature Materials, part of the prestigious Nature Portfolio, which breaks ground in improving the ability of these solar cells to withstand rain and other real-world environmental conditions.
From left, the Wright Center for Photovoltaics Innovation and Commercialization’s Dr. Yanfa Yan, Dr. Jiahao Xie and Dr. Xiaoming Wang lent expert insights to research published in the journal Nature Materials.
“The best perovskite solar cells contain lead, which is highly toxic and can harm health and the environment,” said UToledo’s Dr. Jiahao Xie, a postdoctoral researcher who shares first-author credit with collaborators at the University of Wisconsin–Madison and the U.S. Department of Energy’s National Laboratory of the Rockies. “Tin perovskites are the leading lead-free alternative, but their drawback is that tin oxidizes easily in the presence of oxygen and moisture. Our research is significant because it supports a solution to this central challenge for tin-perovskite photovoltaics.”
UToledo is a leader in the research and development of thin-film photovoltaic technology, including cells that rely on the category of compound materials known as perovskites. Perovskite photovoltaics have long attracted researchers for their powerful potential to be a lower-cost, higher-efficiency alternative to solar cells that rely on silicon.
Campus research tackling the lingering challenges related to perovskite photovoltaics — chief among them durability and stability — contributes to a broader distinction in materials science that positions UToledo among U.S. News & World Report‘s Best Global Universities.
With two physicists credited among the most highly cited researchers in the world working out of the Wright Center for Photovoltaics Innovation and Commercialization, UToledo is further ranked No. 1 among all global universities for the percentage of total research publications that are among the top 1% most highly cited papers in the materials science category.
UToledo’s Dr. Xiaoming Wang, a research assistant professor, and Dr. Yanfa Yan, a Distinguished Professor of physics and Ohio Research Scholar Endowed Chair, join Xie as well as colleagues across the country as co-authors on the latest research in Nature Materials. Their research focuses on a type of photovoltaic technology that pairs perovskites with tin, which has lagged behind lead-perovskite technology as a result of stability challenges despite its powerful potential as a safer alternative to lead-perovskites.
To tackle stability challenges specifically related to oxidation, the research team advanced a previously established approach to protecting tin-perovskites by incorporating “spacer” molecules into the tin-iodide frameworks, creating thin layers that slow the entry of oxygen and water.
This advancement came by attaching chlorine to the standard spacer molecule. UToledo’s Xie, assisted by Wang and Yan, took the lead on the density functional theory calculations that explained the theory behind the approach.
“By mapping the pathways by which oxygen and water molecules move through the organic layer, we showed that the chlorinated spacer uniquely blocks the major pathways, suppressing oxygen and water diffusion by roughly seven to 11 orders of magnitude compared with the standard spacer,” he said.
The result?
The most air-stable tin-perovskite of its kind to date, which maintained its integrity for several months in air. The solar cells created with this material combined state-of-the-art efficiency with exceptional long-term stability, signifying a significant milestone on the path to market viability.
“It’s just as important as the results that we are able to explain why it works to use a chlorinated molecule as the spacer,” Xie said. “This gives us a clear design principle for future lead-free perovskites.”
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