Saliba, MichaelMatsui, TaisukeDomanski, KonradSeo, Ji-YounUmmadisingu, AmitaZakeeruddin, Shaik M.Correa-Baena, Juan-PabloTress, Wolfgang R.Abate, AntonioHagfeldt, AndersGratzel, Michael2017-01-242017-01-242017-01-24201610.1126/science.aah5557https://infoscience.epfl.ch/handle/20.500.14299/133747WOS:000387816500039All of the cations currently used in perovskite solar cells abide by the tolerance factor for incorporation into the lattice. We show that the small and oxidation-stable rubidium cation (Rb+) can be embedded into a "cation cascade" to create perovskite materials with excellent material properties. We achieved stabilized efficiencies of up to 21.6% (average value, 20.2%) on small areas (and a stabilized 19.0% on a cell 0.5 square centimeters in area) as well as an electroluminescence of 3.8%. The open-circuit voltage of 1.24 volts at a band gap of 1.63 electron volts leads to a loss in potential of 0.39 volts, versus 0.4 volts for commercial silicon cells. Polymer-coated cells maintained 95% of their initial performance at 85 degrees C for 500 hours under full illumination and maximum power point tracking.text::journal::journal article::research article