Researchers from EPFL, Universität Tübingen and University of Fribourg, led by Professor Michael Grätzel at EPFL’s School of Basic Sciences, used a novel method with multimodal host-guest complexation to significantly improve the stability of perovskite solar cells while also reducing the release of lead into the environment. The strategy involves using a member of the crown ethers, a family of cyclic compounds whose ring-like atomic structure resembles a crown.

The researchers used the dibenzo-21-crown-7 in the fabrication of formamidinium lead iodide perovskite solar cells. They demonstrated the efficiency of this synergistic approach with cesium metal ions, for which the crown ether shows a strong affinity. Acting as a vehicle, the crown ether assembles at the perovskite film’s interface and delivers the cesium ions into its interior.

“We use this multimodal host–guest-complexation to modulate the surface of the perovskite films as well as their bulk composition at the same time,” explains Dr. Jovana V. Milić, who was involved in the study.

“It is also very exciting to see that photoactive formamidinium lead iodide perovskite can be stabilized in humid environmental conditions for more than one year,” says EPFL scientist Dr. Hong Zhang, the first author of the study.



The overall effect is a greatly improved stability of the perovskite solar cells, showing power-conversion efficiency above 24% and an enhanced operational stability, maintaining more than 95% of their performance for 500 h under continuous operation. As an added bonus, the crown ether also helps bind lead ions, reducing their release into the environment.

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