Solar modules need to be able to do two things well: they should convert sunlight into electricity in as efficient a manner as possible and be as inexpensive as possible to produce. At present, commercial solar cells comprise silicon crystals. Modules made from this material are now affordable and very stable: they reliably produce electricity over decades. However, silicon cells have a rather low efficiency rate. This value indicates what percentage of the solar energy is absorbed by the cells and converted into electricity. For silicon cells, the theoretically possible maximum efficiency level stands at just 29 % – a limit that stems from the material’s physical and chemical properties. Researchers are therefore seeking alternative materials that convert sunlight more efficiently. A few years ago, perovskite emerged as a very promising solution. Chemists from the EPFL have now further developed the production of cells made from this material.