Differential scanning calorimetry experiments on mixed Cu 2-x S, ZnS, and SnS 2 precursors were conducted to better understand how Cu 2 ZnSnS 4 (CZTS) and Cu 2 SnS 3 form. The onset temperatures of Cu 2 SnS 3 reactions and CZTS suggest that the ZnS phase may mediate Cu 2 SnS 3 formation at lower temperatures before a final CZTS phase forms. We also found no evidence of a stable Cu 2 ZnSn 3 S 8 phase. The major diffraction peaks associated with Cu 2 ZnSnS 4 , and Cu 2 SnS 3 (overlaps with ZnS, as well) began to grow around 380 °C, although the final reaction to form Cu 2 ZnSnS 4 probably did not occur until higher temperatures were reached. An exothermic reaction was observed corresponding to formation of this phase. There was some variability in the onset temperature for reactions to form Cu 2 SnS 3 . At least 5 steps are involved in this reaction and several segments of the reaction had relatively reproducible energies.

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