title: Incorporation of rubidium cations into perovskite solar cells improves photovoltaic performance.
abstract: All 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°C for 500 hours under full illumination and maximum power point tracking.
authors.affiliation: Laboratory of Photonics and Interfaces, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland. michael.saliba@epfl.ch michael.graetzel@epfl.ch.
authors.forename: Michael
authors.initials: M
authors.lastname: Saliba
authors.affiliation: Laboratory of Photonics and Interfaces, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland. Advanced Research Division, Materials Research Laboratory, Panasonic Corporation, 1006 Kadoma, Kadoma City, Osaka 571-8501, Japan.
authors.forename: Taisuke
authors.initials: T
authors.lastname: Matsui
authors.affiliation: Laboratory of Photonics and Interfaces, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Konrad
authors.initials: K
authors.lastname: Domanski
authors.affiliation: Laboratory of Photonics and Interfaces, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Ji-Youn
authors.initials: JY
authors.lastname: Seo
authors.affiliation: Laboratory of Photonics and Interfaces, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Amita
authors.initials: A
authors.lastname: Ummadisingu
authors.affiliation: Laboratory of Photonics and Interfaces, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Shaik M
authors.initials: SM
authors.lastname: Zakeeruddin
authors.affiliation: Laboratory of Photomolecular Science, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Juan-Pablo
authors.initials: JP
authors.lastname: Correa-Baena
authors.affiliation: Laboratory of Photonics and Interfaces, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Tress
authors.affiliation: Laboratory of Photonics and Interfaces, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Antonio
authors.initials: A
authors.lastname: Abate
authors.affiliation: Laboratory of Photomolecular Science, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Anders
authors.initials: A
authors.lastname: Hagfeldt
authors.affiliation: Laboratory of Photonics and Interfaces, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland. michael.saliba@epfl.ch michael.graetzel@epfl.ch.
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel