The addition of a few nanometers of a thin layer of aluminum oxide protects a perovskite solar cell against humidity – still a major stumbling block to the commercial application of this new type of solar cell. A surprising bonus is a yield boost of 3 percent. These are the findings of researchers at Eindhoven University of Technology (TU/e) and research institute ECN, part of the Solliance collective, published today in the journal Energy and Environmental Science.