The influence of reducing the chalcogen to metal ratio on phase transitions during the crystallisation of photovoltaic materials CuIn(S,Se)2

Time resolved monitoring of the crystallisation of the thin film absorber materials CuIn(S,Se)2 while annealing stacked elemental layers (SEL) yields phase transitions proceeding during the chalcopyrite synthesis. In-situ XRD and DSC measurements on similar processed precursors provide complementary information on intermediate phases and the reaction kinetics of the chalcopyrite formation can be obtained. Thin layers of metals and chalcogens are deposited onto Mo-coated substrates by DC-magnetron sputtering and thermal evaporation, respectively. The XRD powder diagrams recorded while annealing the SEL are quantitatively analysed by Rietveld refinements. Miscellaneous binary selenides and sulfides as well as ternary sulfoselenides are observed by the chalcogenisation of the intermetallic alloy yielding different educts for the chalcopyrite formation depending on the chalcogen content. The presented study is focused on the influence of reducing the chalcogen to metal ratio on the processing of photovoltaic materials CuIn(S,Se)2.