title: Stabilization of the Perovskite Phase of Formamidinium Lead Triiodide by Methylammonium, Cs, and/or Rb Doping.
abstract: In this work we perform a computational study comparing the influence of monovalent cation substitution by methylammonium (MA+), cesium (Cs+), and rubidium (Rb+) on the properties of formamidinium lead triiodide (FAPbI3)-based perovskites. The relative stability of the desired, photoactive perovskite α phase ("black phase") and the nonphotoactive, nonperovskite δ phase ("yellow phase") is studied as a function of dopant nature, concentration and temperature. Cs+and Rb+are shown to be more efficient in the stabilization of the perovskite α phase than MA+. Furthermore, varying the dopant concentration allows changing the relative stability at different temperatures, in particular stabilizing the α phase already at 200 K. Upon Cs+or Rb+doping, the corresponding onset of the optical spectrum is blue-shifted by 0.1-0.2 eV with respect to pure FAPbI3.
authors.affiliation: Laboratory of Computational Chemistry and Biochemistry and ‡Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Olga A
authors.identifier: http://orcid.org/0000-0002-0270-4621
authors.initials: OA
authors.lastname: Syzgantseva
authors.affiliation: Laboratory of Computational Chemistry and Biochemistry and ‡Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Saliba
authors.affiliation: Laboratory of Computational Chemistry and Biochemistry and ‡Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Michael
authors.identifier: http://orcid.org/0000-0002-0068-0195
authors.initials: M
authors.lastname: Grätzel
authors.affiliation: Laboratory of Computational Chemistry and Biochemistry and ‡Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Ursula
authors.initials: U
authors.lastname: Rothlisberger