Dresden 2017 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 4: Focused Session: Inhomogeneous Materials for Solar Cells I

HL 4.1: Topical Talk

Montag, 20. März 2017, 09:30–10:00, CHE 89

Inhomogeneities in chalcopyrites and kesterites — •Claudia S. Schnohr — Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany

Thin film solar cells based on Cu(In,Ga)(Se,S)2 have reached a record efficiency of 22.6 %, thus closing the gap to silicon-based technology. Cu2ZnSn(Se,S)4 has also attracted great attention as non-toxic, earth-abundant alternative and a record efficiency of 12.6 % has already been demonstrated. Both material systems typically feature inhomogeneities such as grain boundaries, interfaces, and compositional variations, that may deteriorate or improve the device performance. We therefore applied high-resolution X-ray fluorescence analysis using a synchrotron nanobeam to study the elemental composition of chalcopyrite- and kesterite-type thin films on a micrometer and submicrometer scale. To that end, thin cross section lamellas were prepared with a focused ion beam system. For Cu(In,Ga)(Se,S)2, the depth-dependent Ga gradient shows a strong dependence on the growth conditions in a sequential two-stage process. Furthermore, we find subtle lateral variations in the material composition and a significant In enrichment for some of the grain boundaries. For highly non-stoichiometric Cu2ZnSn(Se,S)4, different binary secondary phases coexist within a distance of only a few micrometers and the local compositions of the kesterite-type domains differ tremendously from the integral layer composition. Detailed knowledge of these compositional variations, which directly affect the electronic properties of the material, will thus help to exploit the full potential of chalcopyrite- and kesterite-based thin film solar cells.

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