title: Observation and Mediation of the Presence of Metallic Lead in Organic-Inorganic Perovskite Films.
abstract: We have employed soft and hard X-ray photoelectron spectroscopies to study the depth-dependent chemical composition of mixed-halide perovskite thin films used in high-performance solar cells. We detect substantial amounts of metallic lead in the perovskite films, which correlate with significant density of states above the valence band maximum. The metallic lead content is higher in the bulk of the perovskite films than at the surface. Using an optimized postanneal process in air, we can reduce the metallic lead content in the perovskite film. This process reduces the amount of metallic lead and a corresponding increase in the photoluminescence quantum efficiency of the perovskite films can be observed. This correlation indicates that metallic lead impurities are likely a key defect whose concentration can be controlled by simple annealing procedures in order to increase the performance for perovskite solar cells.
authors.affiliation: †Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Golnaz
authors.initials: G
authors.lastname: Sadoughi
authors.affiliation: ‡Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: David E
authors.initials: DE
authors.lastname: Starr
authors.affiliation: ‡Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Handick
authors.affiliation: †Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Samuel D
authors.initials: SD
authors.lastname: Stranks
authors.affiliation: §Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Gorgoi
authors.affiliation: ‡Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.|∥Energy Materials In-Situ Laboratory (EMIL), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Regan G
authors.initials: RG
authors.lastname: Wilks
authors.affiliation: ‡Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.|∥Energy Materials In-Situ Laboratory (EMIL), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.|⊥Institut für Physik und Chemie, Brandenburgische Technische Universität Cottbus-Senftenberg, Platz der Deutschen Einheit 1, 03046 Cottbus, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Bär
authors.affiliation: †Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Snaith
keywords: PLQE; XPS; metallic lead; methylammonium lead iodide chloride; perovskite solar cell