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HL: Fachverband Halbleiterphysik

HL 48: Poster 2

HL 48.77: Poster

Donnerstag, 26. März 2009, 15:00–17:30, P2

New buffer layer materials for CIGS solar cells. — •Thomas Gruhn¹, David Kieven², and Claudia Felser¹ — ¹Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg University, 55099 Mainz — ²Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Glienicker Str. 100, 14109 Berlin

The compound semiconductor CuIn_xGa_(1−x)Se₂ (CIGSE) are used as absorber material in thin-film photovoltaic cells. In conventional CIGSE based solar cells a thin CdS layer (buffer) significantly improves the photovoltaic performance and efficiencies up to 19.9% have been realized. Since Cd is a toxic heavy metal there is a demand for suitable substitute materials. The first requirements for these materials are an adequate band gap, a crystal structure compatible to that of CIGSE, and an n-type conductivity. An interesting class of materials are half-Heuslers, which are ternary compounds with a C1_b MgAgAs structure. For many half-Heusler compounds the crystal structure matches well with the [100] layer of the tetragonal CIGS unit cell. Using ab initio calculations based on B3LYP hybrid functionals, we have studied electronic properties of the most promising half-Heusler materials. Our results affirm the band gap rule for 8-electron half-Heuslers presented in [1].
The authors gratefully acknowledge financial support by the DfG (Research Unit 559).
[1] H. C. Kandpal, C. Felser, and R. Seshadri, J. Phys. D: Appl. Phys. 39, 776 (2005).