Berlin 2018 – scientific programme
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DS: Fachverband Dünne Schichten
DS 6: Thin Film Applications
DS 6.1: Talk
Monday, March 12, 2018, 15:00–15:15, H 0111
Chalkopyrite thin film solar cells conditioned with RbF — •Tim Kodalle1, Marc Daniel Heinemann1, Hasan Arif Yetkin1,2, Iver Lauermann1, Rutger Schlatmann1,3, and Christian Alexander Kaufmann1 — 1PVcomB/Helmholtz-Zentrum Berlin, Germany — 2Technical University Berlin, Germany — 3Hochschule für Technik und Wirtschaft Berlin, Germany
We investigate the impact of an RbF post deposition treatment (PDT) on the material and device properties of Cu(In,Ga)Se2 thin-film solar cells in dependence of both the PDT’s parameters (e.g. the duration of the PDT) and the copper to group III elemental ratio ([Cu]/([Ga]+[In]) = CGI).
A clear trade-off between increasing open-circuit-voltage (VOC) and decreasing fill factor (FF) with longer RbF-deposition could be observed. We propose a model explaining the gain in VOC by an increased carrier concentration and the formation of an (Rb,Na)-InxSey surface layer during the PDT. Additionally we build a model to explain the decreasing FF based on the generation of additional acceptor-like defects at the buffer/window-interface by temperature-induced alkali-migration during sputtering of the window layer.
Furthermore we investigate the performance of the optimized PDT on absorbers with varied CGI. Here we find, that the PDT is most efficiently when being applied to thin films close to stoichiometry. Thereby we were able to overcome the FF-loss and increase the maximum efficiency up to 17.5%, which is about 1.1% (abs.) higher than the reference value.