Solar cells with efficiencies above 20% and produced at low costs – perovskites make this possible. Now, researchers of Karlsruhe Institute of Technology (KIT) have gained fundamental insight into the function of perovskite solar cells. They found that bound states of electron-hole pairs can form during the absorption of light. Still, these pairs can be separated easily for current to flow. In addition, they enhance absorption. Work of the scientists is reported in the journal Applied Physics Letters.