title: Characterization of Sulfur Bonding in CdS:O Buffer Layers for CdTe-based Thin-Film Solar Cells.
abstract: On the basis of a combination of X-ray photoelectron spectroscopy and synchrotron-based X-ray emission spectroscopy, we present a detailed characterization of the chemical structure of CdS:O thin films that can be employed as a substitute for CdS layers in thin-film solar cells. It is possible to analyze the local chemical environment of the probed elements, in particular sulfur, hence allowing insights into the species-specific composition of the films and their surfaces. A detailed quantification of the observed sulfur environments (i.e., sulfide, sulfate, and an intermediate oxide) as a function of oxygen content is presented, allowing a deliberate optimization of CdS:O thin films for their use as alternative buffer layers in thin-film photovoltaic devices.
authors.affiliation: †Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154-4003, United States.|‡Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 14109 Berlin, Germany.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Duncan
authors.affiliation: §Department of Mechanical Engineering, Colorado State University, Fort Collins, Colorado 80523, United States.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Kephart
authors.affiliation: †Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154-4003, United States.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Horsley
authors.affiliation: †Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154-4003, United States.|∥Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Monika
authors.initials: M
authors.lastname: Blum
authors.affiliation: †Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154-4003, United States.
authors.forename: Michelle
authors.initials: M
authors.lastname: Mezher
authors.affiliation: †Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154-4003, United States.|⊥ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany.|#Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany.|∇Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe, Germany.
authors.forename: Lothar
authors.initials: L
authors.lastname: Weinhardt
authors.affiliation: †Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154-4003, United States.|#Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Häming
authors.affiliation: ‡Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 14109 Berlin, Germany.
authors.forename: Regan G
authors.initials: RG
authors.lastname: Wilks
authors.affiliation: †Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154-4003, United States.
authors.forename: Timo
authors.initials: T
authors.lastname: Hofmann
authors.affiliation: ∥Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Wanli
authors.initials: W
authors.lastname: Yang
authors.affiliation: †Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154-4003, United States.|‡Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 14109 Berlin, Germany.|⊗Institut für Physik und Chemie, Brandenburgische Technische Universität Cottbus-Senftenberg, 03046 Cottbus, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Bär
authors.affiliation: §Department of Mechanical Engineering, Colorado State University, Fort Collins, Colorado 80523, United States.
authors.forename: Walajabad S
authors.initials: WS
authors.lastname: Sampath
authors.affiliation: †Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154-4003, United States.|⊥ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany.|#Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany.|∇Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: Heske
keywords: CdS; CdTe; XPS; alternative buffer layers; solar cells