Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 6: Photovoltaics I

HL 6.1: Talk

Monday, March 12, 2018, 09:30–09:45, EW 203

Formation process of the CIGSe absorber layers in a two stage sequential process — •Sven Schönherr, Philipp Schöppe, Michael Oertel, Udo Reislöhner, and Carsten Ronning — Institut für Festkörperphysik, Friedrich Schiller Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany

A sequential process is often used to produce Cu(In,Ga)Se₂ (CIGSe) solar cells, which show high efficiencies of light conversion. In our process, the metallic precursor on top of a molybdenum back contact was reactively annealed in a selenium vapour atmosphere where it is typically converted to an about 2 µm thick CIGSe absorber layer. The selenization was spilt in two stages to get a better control of the absorber formation process. Completing the solar cell, a CdS buffer layer was grown via chemical bath deposition and as front contact a ZnO layer was sputtered on top. For a more homogeneous CIGSe absorber layer we varied the substrate temperature and the selenization time in the second stage. Current-voltage and capacitance-voltage measurements were used for a first electrical characterization. X-ray diffraction were taken to investigate the phase formation in the final absorber and in the molybdenum diselenide layer at the back contact. Furthermore, thin cross section lamellas of the complete solar cell were prepared via a focused ion beam system to measure the gallium gradient via energy dispersive X-ray spectroscopy. Additionally, photoluminescence measurements at low temperatures were performed to characterize the defect structure and to get information about the ratio of group III elements.