Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 61: Posters III (Organic-inorganic perovskite semiconductors; Organic photovoltaics and electronics; Photovoltaics; Energy science; New materials and concepts)

HL 61.30: Poster

Wednesday, March 18, 2015, 15:00–20:00, Poster F

Investigation of order–disorder related band gap changes in Cu₂ZnSn(S,Se)₄ solar cells using electroreflectance — Christoph Krämmer¹, Christian Huber¹, Christian Zimmermann¹, Mario Lang¹, •Alexander Opolka¹, Thomas Schnabel², Tobias Abzieher^1,2, Erik Ahlswede², Heinz Kalt¹, and Michael Hetterich¹ — ¹Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany — ²Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg, 70565 Stuttgart, Germany

Cu₂ZnSn(S,Se)₄ (CZTSSe) has attracted attention in thin-film photovoltaics due to its similarity to the well-established Cu(In,Ga)(S,Se)₂. However, the use of the low-cost and earth-abundant constituents Zn and Sn promise to overcome the weak point of the Cu(In,Ga)(S,Se)₂ system, although up to now the gap in efficiency between these two systems could not be closed. Among other things a high amount of point defects is made responsible for this deficit. In this contribution we demonstrate reversible band gap shifts which are induced by post-annealing of finished CZTSSe solar cells and are attributed to changes in the disorder within the Cu–Zn lattice planes. These changes follow the stochastic Vineyard model which further predicts a critical temperature above which the kesterite structure is entirely Cu–Zn disordered.