A protective layer of fluoride can increase the stability of perovskite solar cells significantly, writes an international research collaboration in the leading journal Nature Energy. The finding by scientists from DIFFER, Eindhoven University of Technology, Peking University and University of Twente holds much promise for the future of perovskite solar cells. Perovskite is cheap, easy to produce and almost as efficient as the traditional solar cell material silicon. However, perovskite degrades quickly, severely limiting its efficiency and stability over time. With an added fluoride layer, the researchers found that their cells retain 90 percent of their efficiency after 1000 hours operation at various extreme testing conditions.