Kempa, H.; Rissom, T.; Hlawatsch, U.; Gaudig, M.; Obereigner, F.; Kaufmann, C.A.; Scheer, R.: Metastability of solar cells based on evaporated chalcopyrite absorber layers prepared with varying selenium flux. Thin Solid Films 535 (2013), p. 340-342
10.1016/j.tsf.2012.10.036

Abstract:
Solar cells with Cu(In,Ga)Se2 absorber layers prepared by three-stage co-evaporation with varying seleniumto-metal flux ratio were studied in terms of their metastable properties. In particular, transient behaviour of the open-circuit voltage Voc after relaxation to the stable state was investigated. A linear dependence of Voc on a logarithmic time scale was observed, the slope of which is taken as ameasure for the degree ofmetastability. Surprisingly, upon variation of selenium flux, the slope parameter systematically varies between negative and positive values, and there are process parameters, for which the Voc transient disappears. We discuss these findings within the framework of the well-known Lany–Zunger model.