title: Intrinsic Halide Segregation at Nanometer Scale Determines the High Efficiency of Mixed Cation/Mixed Halide Perovskite Solar Cells.
abstract: Compositional engineering of a mixed cation/mixed halide perovskite in the form of (FAPbI3)0.85(MAPbBr3)0.15is one of the most effective strategies to obtain record-efficiency perovskite solar cells. However, the perovskite self-organization upon crystallization and the final elemental distribution, which are paramount for device optimization, are still poorly understood. Here we map the nanoscale charge carrier and elemental distribution of mixed perovskite films yielding 20% efficient devices. Combining a novel in-house-developed high-resolution helium ion microscope coupled with a secondary ion mass spectrometer (HIM-SIMS) with Kelvin probe force microscopy (KPFM), we demonstrate that part of the mixed perovskite film intrinsically segregates into iodide-rich perovskite nanodomains on a length scale of up to a few hundred nanometers. Thus, the homogeneity of the film is disrupted, leading to a variation in the optical properties at the micrometer scale. Our results provide unprecedented understanding of the nanoscale perovskite composition.
authors.affiliation: Group for Molecular Engineering of Functional Materials (GMF), Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology , CH-1951 Sion, Switzerland.
authors.forename: Paul
authors.initials: P
authors.lastname: Gratia
authors.affiliation: Group for Molecular Engineering of Functional Materials (GMF), Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology , CH-1951 Sion, Switzerland.
authors.forename: Giulia
authors.initials: G
authors.lastname: Grancini
authors.affiliation: Advanced Instrumentation for Ion Nano-Analytics (AINA), Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST) , L-4422 Belvaux, Luxembourg.
authors.forename: Jean-Nicolas
authors.initials: JN
authors.lastname: Audinot
authors.affiliation: Molecular Engineering of Optoelectronic Nanomaterials Lab (LIMNO), Swiss Federal Institute of Technology , CH 1015 Lausanne, Switzerland.
authors.forename: Xavier
authors.initials: X
authors.lastname: Jeanbourquin
authors.affiliation: Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM , Via Elce di Sotto 8, I-06123 Perugia, Italy.
authors.forename: Edoardo
authors.initials: E
authors.lastname: Mosconi
authors.affiliation: Group for Molecular Engineering of Functional Materials (GMF), Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology , CH-1951 Sion, Switzerland.
authors.forename: Iwan
authors.initials: I
authors.lastname: Zimmermann
authors.affiliation: Advanced Instrumentation for Ion Nano-Analytics (AINA), Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST) , L-4422 Belvaux, Luxembourg.
authors.forename: David
authors.initials: D
authors.lastname: Dowsett
authors.affiliation: Group for Molecular Engineering of Functional Materials (GMF), Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology , CH-1951 Sion, Switzerland.
authors.forename: Yonghui
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Laboratory for Photonics and Interfaces (LPI), Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology , CH-1015 Lausanne, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
authors.affiliation: Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM , Via Elce di Sotto 8, I-06123 Perugia, Italy.|Computet, Istituto Italiano di Tecnologia , Via Morego 30, I-16163 Genova, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: De Angelis
authors.affiliation: Molecular Engineering of Optoelectronic Nanomaterials Lab (LIMNO), Swiss Federal Institute of Technology , CH 1015 Lausanne, Switzerland.
authors.forename: Kevin
authors.initials: K
authors.lastname: Sivula
authors.affiliation: Advanced Instrumentation for Ion Nano-Analytics (AINA), Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST) , L-4422 Belvaux, Luxembourg.
authors.forename: Tom
authors.initials: T
authors.lastname: Wirtz
authors.affiliation: Group for Molecular Engineering of Functional Materials (GMF), Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology , CH-1951 Sion, Switzerland.
authors.forename: Mohammad Khaja
authors.initials: MK
authors.lastname: Nazeeruddin