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Photo Credit: ICL

Solar cells are slowly becoming more efficient. But the newest, most promising light-absorbing material used in solar cells, organic lead halide perovskites, doesn't last very long. After just a few days, it can lose its efficiency advantages.

Researchers at Imperial College London have identified the mechanism that causes perovskite cells to degrade so quickly. Their findings could pave the way for a more efficient, longer-lasting solar cell.

Previous research by ICL chemists showed "superoxides" work to break down the perovskite material. Now, ICL researchers have discovered how superoxides form and do damage.

When light hits perovskite, electrons are released and react with oxygen to form superoxides. The formation of superoxides is aided by gaps in the perovskite nanostructure, gaps normally occupied by iodide. Superoxides take advantage of these iodide-less defects.

Researchers were able to prolong the lifespan of perovskite cells by applying an extra coat of iodide, but a better solution may require scientists to rethink the perovskite manufacturing process and prevent defects from forming.

"After identifying the role of iodide defects in generating superoxide, we could successfully improve the material stability by filling the vacancies with additional iodide ions," lead researcher Nicholas Aristidou, a chemist at ICL, said in a news release. "This opens up a new way of optimizing the material for enhanced stability by controlling the type and density of defects present."

Currently, engineers use glass to protect perovskite cells from oxidation, but the strategy limits the versatility offered by the flexible perovskite material.

"Glass encasement restricts movement and adds weight and cost to the cells. Improving the perovskite cell material itself is the best solution," ICL chemist Saif Haque said.

Thanks to the latest research -- published in the journal Nature Communications -- improved perovskite cell materials may not be far off.

"We have now provided a pathway to understand this process at the atomic scale and allow the design of devices with improved stability," Haque said.

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