title: Investigation of the potassium fluoride post deposition treatment on the CIGSe/CdS interface using hard X-ray photoemission spectroscopy - a comparative study.
abstract: The impact of the potassium fluoride post deposition treatment on CIGSe chalcopyrite absorbers is investigated by means of depth resolved hard X-ray photoemission spectroscopy of the near surface region. Two similar, slightly Cu-poor CIGSe absorbers were used with one being treated by potassium fluoride prior to the chemical bath deposition of an ultrathin CdS layer. The thickness of the CdS layer was chosen to be in the range of about 10 nm in order to allow the investigation of the CIGSe/CdS interface by the application of hard X-rays, increasing the information depth up to 30 nm. Besides strong intermixing on both samples, an increased Cu depletion of the KF treated absorber was observed in combination with an increased accumulation of Cd and S. In addition, a general shift of about 0.15 eV to higher binding energies of the CIGSe valence band at the absorber surface as well as the CIGSe and CdS related core levels was measured on the KF treated sample. This phenomenon is attributed to the impact of additional cadmium which acts as donor and releases further electrons into the conduction band of the absorber. Finally, the electrons accumulate at the CdS surface after having passed the interface region. This additional surface charge leads to a pronounced shift in the photoemission spectra as observed on the KF treated CIGSe absorber compared to the non-treated absorber.
authors.affiliation: Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. buenyamin.uemsuer@helmholtz-berlin.de and Freie Universität Berlin, Department of Physics, Arnimallee 14, D-14195 Berlin, Germany.
authors.forename: Bünyamin
authors.initials: B
authors.lastname: Ümsür
authors.affiliation: Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. buenyamin.uemsuer@helmholtz-berlin.de.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Calvet
authors.affiliation: Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. buenyamin.uemsuer@helmholtz-berlin.de.
authors.forename: Alexander
authors.initials: A
authors.lastname: Steigert
authors.affiliation: Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. buenyamin.uemsuer@helmholtz-berlin.de.
authors.forename: Iver
authors.initials: I
authors.lastname: Lauermann
authors.affiliation: Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. buenyamin.uemsuer@helmholtz-berlin.de.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Gorgoi
authors.affiliation: Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. buenyamin.uemsuer@helmholtz-berlin.de.
authors.forename: Karsten
authors.initials: K
authors.lastname: Prietzel
authors.affiliation: Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. buenyamin.uemsuer@helmholtz-berlin.de.
authors.forename: Dieter
authors.initials: D
authors.lastname: Greiner
authors.affiliation: Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. buenyamin.uemsuer@helmholtz-berlin.de.
authors.forename: Christian A
authors.initials: CA
authors.lastname: Kaufmann
authors.affiliation: Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. buenyamin.uemsuer@helmholtz-berlin.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Unold
authors.affiliation: Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. buenyamin.uemsuer@helmholtz-berlin.de and Freie Universität Berlin, Department of Physics, Arnimallee 14, D-14195 Berlin, Germany.
authors.forename: Martha Ch
authors.initials: MCh
authors.lastname: Lux-Steiner