title: Impact of Film Stoichiometry on the Ionization Energy and Electronic Structure of CH3 NH3 PbI3 Perovskites.
abstract: The electronic structure of a large sample set of CH3 NH3 PbI3 -based perovskites is studied. Combined investigations by UV/X-ray photoelectron spectroscopy and X-ray diffraction reveal that interstitials present in the film lead to changes in the occupied density of states close to the valence band, which in turn influences the performance of solar cells. Changes in elemental composition tune the ionization energy of the perovskite film by almost 1 eV without introducing significant amounts of gap states.
authors.affiliation: Department of Chemistry, University of Cologne, Luxemburger Straße 116, 50939, Cologne, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Emara
authors.affiliation: Department of Chemistry, University of Cologne, Luxemburger Straße 116, 50939, Cologne, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Schnier
authors.affiliation: Institute of Electronic Devices, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119, Wuppertal, Germany.
authors.forename: Neda
authors.initials: N
authors.lastname: Pourdavoud
authors.affiliation: Institute of Electronic Devices, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119, Wuppertal, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Riedl
authors.affiliation: Department of Chemistry, University of Cologne, Luxemburger Straße 116, 50939, Cologne, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Meerholz
authors.affiliation: Department of Chemistry, University of Cologne, Luxemburger Straße 116, 50939, Cologne, Germany.
authors.forename: Selina
authors.initials: S
authors.lastname: Olthof
keywords: X-ray diffraction; perovskites; photoelectron spectroscopy; solar cells; stoichiometry