‘Self-Healing’ Coating Minimizes Lead Leakage from Perovskite Cells

Adding a protective layer of epoxy resin to the top of a perovskite solar cell (PSC) can significantly reduce the amount of lead that the cell discharges into the environment, researchers at Okinawa Institute of Science and Technology (OIST) discovered. They further found that after a PSC was damaged, its epoxy resin coating could partially return to its original shape when heated by sunlight, and that this “self-healing” property contributed to its effectiveness as a solar cell coating. The researchers’ findings could help PSC technology overcome a key challenge to commercialization.

Researchers exposed the solar cells to brutal conditions to simulate worst-case weather scenarios. Adding a self-healing epoxy resin polymer to the cell minimized the leakage of lead from the cell. Courtesy of OIST.

“Although PSCs are efficient at converting sunlight into electricity at an affordable cost, the fact that they contain lead raises considerable environmental concern,” said professor Yabing Qi, who led the study.

The researchers explored different encapsulation methods for adding protective layers to PSCs by simulating realistic scenarios, such as hailstorms, in which various encapsulation techniques were used. Then they doused the cells with acidic water to simulate the rainwater that could transport leaked lead into the environment.

(l) to (r): Researchers Luis Ono, Longbin Qiu, and professor Yabing Qi, from the Energy Materials and Surface Sciences Unit. Courtesy of OIST.

They quantitatively measured the lead leakage rates under a variety of weather conditions and demonstrated that an encapsulation method based on an epoxy resin reduced the lead leakage rate by a factor of 375, compared with an encapsulation method based on a glass cover with a UV-cured resin.

The researchers believe that the superior protection provided by the epoxy resin is associated with its self-healing characteristics and its increased mechanical strength. Qi said that other self-healing polymers could potentially work even better, and that the team would build on the data it has collected to explore the best polymer choice.

These findings suggest that with appropriate encapsulation, perovskite photovoltaic products could be deployed with minimal lead leakage. A further challenge to PSC commercialization will be to scale up perovskite solar cells into perovskite solar panels. The team will also direct its attention to the long-standing challenge of renewable energy storage.

The research was published in Nature Energy (https://doi.org/10.1038/s41560-019-0406-2).

This perovskite solar module is better able to contain the lead within its structure when a layer of epoxy resin is added to its surface. This approach to tackling a long-standing environmental concern could help bring the technology closer to commercialization. Courtesy of OIST.