Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 41: Topical Session Modern Atom Probe Tomography II - Functional Materials

MM 41.1: Talk

Wednesday, March 28, 2012, 16:45–17:00, H 0107

Impurity distributions in Cu(In,Ga)Se₂ thin-film solar cells studied by Atom Probe Tomography — •Ralf Schlesiger¹, Roland Würz², Jens Bastek¹, Katharina Hiepko¹, Nicolaas A. Stolwijk¹, and Guido Schmitz¹ — ¹Institute of Material Physics, Westf. Wilhelms-Universität Münster, Germany — ²Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg, Germany

To improve and understand the benchmarks of polycrystalline thin-film solar cells based on the compound semiconductor Cu(In,Ga)Se₂, detailed knowledge of the atomic-scale distribution of minority impurities is desirable and can only be obtained by atom probe tomography. During the growth process of the absorber at about 600^∘C, diffusion of impurity atoms from the substrate through the Mo back contact into the absorber layer is observed, affecting the efficiency of the absorber layer. In this work atom probe measurements were carried out to analyse the distribution of Na, Fe and Cd impurities within the Cu(In,Ga)Se₂ absorber layer. Na was exclusively introduced during crystal growth, whereas Cd and Fe were diffused at temperatures below 550^∘C from the front side of as-grown CIGS layers. It is clearly resolved that Na is mostly localized in the grain boundaries. While Fe is homogeneously distributed in the grain volume, with no enrichment at the grain boundaries, Cd shows a slight segregation to the grain boundaries. Concerning the Cu(In,Ga)Se₂ constituents at the grain boundaries, a depletion was found for Cu, with a simultaneous enrichment of In and Se.