Dresden 2011 – scientific programme
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DS: Fachverband Dünne Schichten
DS 43: Poster II: Thin Film Chalcogenide Photovoltaics; Thermoelectric Materials, Thin Films, and Nanostructures
DS 43.1: Poster
Wednesday, March 16, 2011, 15:00–17:30, P2
Aspects of designing an optimized molybdenum back contact in CIGS-technology — •Michael Oertel, Stefan Götz, Jakob Haarstrich, Heinrich Metzner, Udo Reislöhner, Carsten Ronning, and Werner Wesch — Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, 07743 Jena, Germany
In Cu(In,Ga)Se2(CIGS)-solar cell and module production, the sputtering of the molybdenum back contact is the first step in nearly all process lines. We present our results of experiments to elucidate the different aspects which have to be kept in mind when depositing the molybdenum back contact by dc-magnetron sputtering. These aspects include: I) The adhesion of the molybdenum to the glass substrate as well as the adhesion of the CIGS-layer to the molybdenum, II) electrical conductivity, III) sodium diffusion and IV) the specific contact resistance of the molybdenum to the aluminium doped zinc oxide (Al:ZnO) window layer. We present our three layer design of the back contact which combines an optimized adhesion to both the substrate and the absorber and also a high electrical conductivity. X-ray diffraction measurements (XRD) are employed to characterize each single layer. We also discuss I-U-measurements of CuInSe2-solar cells made in a sequential absorber layer process in order to study the sodium transport behaviour of molybdenum back contacts sputtered at different argon sputter pressures. The sodium content in the absorber and the different back contact layers is measured by secondary ion mass spectroscopy (SIMS). A lowest value of the specific contact resistance between the Mo and the Al:ZnO of (1.37±0.14)·105Ωcm2 was determined.