http://www.sciencemag.org/news/2019/04/marrying-two-types-solar-cells-draws-more-power-sun

Silicon solar cells could get a boost in electrical output with a coating of perovskite materials.

ORLANDO, FLORIDA—The promising solar cell materials called perovskites need a partner. Researchers marry a layer of perovskite, which absorbs high-energy blue photons in sunlight, with standard silicon, which gobbles up lower-energy light. In theory, such tandem cells should deliver a double dose of power, with electricity coming from both layers. But building two complete solar cells, one atop the other, adds cost and other challenges. Last week, a team reported advancing a potentially simpler, cheaper way to make a tandem.