Dresden 2003 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 30: Photovoltaik

HL 30.12: Vortrag

Mittwoch, 26. März 2003, 17:15–17:30, BEY/81

Investigation of the chemical and electronic properties of the deeply buried Cu(In,Ga)(S,Se)₂/Mo interface in thin film solar cells — •L. Weinhardt¹, O. Fuchs¹, C. Heske¹, E. Umbach¹, J. Reichardt², M. Bär², I. Lauermann², I.M. Kötschau², A. Grimm², A. Sokoll², Ch.H. Fischer², M.Ch. Lux-Steiner², T.P. Niesen³, F. Karg³, Ch. Jung⁴, and W. Gudat⁴ — ¹Exp. Physik II, Universität Würzburg — ²SE 2, Hahn-Meitner-Institut, Berlin — ³Shell Solar GmbH, Munich — ⁴BESSY GmbH, Berlin

For a further optimization of Cu(In,Ga)(S,Se)₂ thin film solar cells a detailed understanding of the chemical and electronic properties at the various interfaces is needed. In contrast to the interface between the absorber and the buffer layer, the understanding of its interface towards the Mo back contact is still poor because it is buried underneath the 2 µm-thick absorber. To get access to this interface we used suitable lift-off techniques to remove the absorber from its back contact. Then we investigated both the CIGSSe absorber back side as well as the Mo surface with X-ray emission spectroscopy and photoelectron spectroscopy. Both techniques give detailed information about electronic and chemical properties, albeit in a different way and with a different information depth (∼10-200 nm and ∼1 nm, respectively).
We find a formation of MoS₂, but no Mo on the absorber back side, and an increased Na content at the Mo surface. Furthermore, we observe pronounced differences between the external CIGSSe surface and the absorber back side. Based on these findings an electronic and compositional picture of the CIGSSe/Mo interface will be discussed.