Morphology study of CZTS formed at diverse annealing conditions using different precursor routes
Verena Harum(a), Christine Buchmaier(a), Thomas Rath(a), Stefan Müller(b), Ferdinand Hofer(c), Roland Resel(d), Gregor Trimmel(a)
15:00 - 17:00 Thursday 23 October 2014 Rechbauerstrasse 12, HSII Kesterite-type Cu2ZnSnS4 (CZTS) is a very promising absorber material for low cost and high efficiency thin film photovoltaic modules due to its direct band gap of 1.5 eV and due to its high absorption coefficient. Especially direct solution coating approaches for depositing kesterite absorbers are very interesting since they offer all the requirements essential for a low-cost roll-to-roll PV technology.
In this contribution we investigated different annealing conditions of the precursor layers in order to obtain high purity CZTS with large crystallite size. Therefore, different precursor routes, such as metal salts with thiourea or thioacetamide as sulfur source and DMSO as solvent were applied. In another approach, metal xanthates were used as precursors. This route offers the advantages that no chlorides are present in the precursor layer, no additional sulfur source is necessary and the precursor compounds decompose at temperatures below 200 °C.
We compared different heating rates, annealing times, temperatures and atmospheres. The main focus was set on differences in roughness, crystallinity, chemical composition, purity and morphology of the prepared CZTS thin films. Moreover, based on these results, first solar cells were fabricated. We used surface profilometry, X-ray diffraction, Raman spectroscopy and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDX) for the characterization of the thin films.
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