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Chemical Composition and Electronic Properties of CuInS2/Zn(S,O) Interfaces

Published online by Cambridge University Press:  31 January 2011

Rodrigo Sáez-Araoz ,
Iver Lauermann ,
Axel Neisser ,
Martha Ch Lux-Steiner  and
Ahmed Ennaoui
Rodrigo Sáez-Araoz
Affiliation:
[email protected], Helmholtz-Zentrum Berlin für materialien und Energie, Berlin, Germany
Iver Lauermann
Affiliation:
[email protected], Helmholtz-Zentrum-Berlin, Berlin, Germany
Axel Neisser
Affiliation:
[email protected], United States
Martha Ch Lux-Steiner
Affiliation:
[email protected], Helmholtz-Zentrum Berlin für materialien und Energie, Berlin, Germany
Ahmed Ennaoui
Affiliation:
[email protected], Helmholtz-Zentrum-Berlin, Heterogeneous Material Systems, Berlin, Germany
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Abstract

We report on the chemical deposition and electronic properties of CuInS2/Zn(S,O) interfaces. The Zn(S,O) buffer was grown by a new chemical bath deposition (CBD) process that allows the tailoring of the S/O ratio in the films. Resulting Zn(S,O) films exhibit transparencies above 80% (for λ>390 nm) and an optical energy band gap of 3.9 eV which decreases to 3.6 eV after annealing in air at 200°C. Production line CuInS2 (CIS) absorbers provided by Sulfurcell Solartechnik GmbH are used as substrates for the investigation of the CIS/Zn(S,O) interface and the chemical composition of Zn(S,O). A ZnS/(ZnS+ZnO) ratio of 0.5 is found by X-ray photoelectron spectroscopy and X-ray excited Auger electron spectroscopy (XPS and XAES). The valence band offset between the heterojunction partners (ΔEV = 1.8 ± 0.2 eV) has been determined by means of XPS and ultraviolet photoelectron spectroscopy (UPS). Considering the energy band gap of the CIS absorber and the measured band gap of Zn(S,O), the conduction band offset (ΔEC) is calculated as: resulting in a spike of 0.5±0.3 eV in the conduction band at the heterojunction before annealing. After the heat treatment, the valence band offset is reduced to 1.5±0.2 eV and the calculated conduction band offset remains at 0.5±0.3 eV.

Keywords

chemical compositionx-ray photoelectron spectroscopy (XPS)II-VI
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1165: Symposium M – Thin-Film Compound Semiconductor Photovoltaics–2009 , 2009 , 1165-M03-07
Copyright
Copyright © Materials Research Society 2009

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