Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 32: Photovoltaic
HL 32.15: Vortrag
Mittwoch, 29. März 2006, 18:15–18:30, BEY 118
Interface properties of Cu(In,Ga)(S,Se)2 absorbers with various bufferlayers in thin film solar cells — •F. Erfurth1, L. Weinhardt1, T.P. Niesen2, S. Visbeck2, C. Heske3, and E. Umbach1 — 1Experimentelle Physik II, Universität Würzburg — 2Shell Solar GmbH, München — 3Department of Chemistry, University of Nevada, Las Vegas
To better meet the environmental requirements of thin film solar cells based on Cu(In,Ga)(S,Se)2 (CIGSSe),
the substitution of the CdS buffer layer is of great interest. By depositing alternative layer
compositions like (Zn,Mg)O or Zn(S,OH), using conventional sputter and chemical bath deposition techniques, efficiencies close to or comparable
to those of CdS containing solar cells are obtained. To understand the chemical and electrical characteristics
of the buffer layer and its influence on the absorber, we investigated the absorber-buffer interface using
photoelectron spectroscopy and inverse photoemission. The combination of both techniques provides the
determination of the chemical and stoichiometric properties as well as the alignment of the conduction and valence band at the heterojunction.
We analyze the pure and Cd-treated absorber surface and the
interface to alternative buffer layers. Measurements are presented
observing diffusion and accummulation processes of certain absorber
elements at the interface, which depend on temperature
treatments. Furthermore the alignment of both, the valence and
conduction band at the interface is deduced. In conclusion, we attempt to
explain differences in cell efficiencies arising from different
buffer layers.