Standard silicon solar cells on roofs convert the reddish tints of sunlight better into electricity than the blue ones. The companies are therefore launching into the race to the top of the silicon cells with another photovoltaic made from cheap crystalline materials called perovskites, which excel in blues capture. But making two superimposed solar cells entails additional costs, among other challenges. Researchers have announced that they have developed a simpler and potentially less expensive way to make a tandem solar cell. They enriched a classical lead perovskite with yttrium. The resulting film does not turn sunlight into electricity. On the contrary, it absorbs blue and violet photons and re-emits this energy in the form of near-infrared light, which the silicon cell then converts into electricity. According to the researchers, the new tandem could increase the production of silicon cells by nearly 20%, which is a major advantage.