Supercritical ethanol (scEtOH), with its high solubility and reducibility, can be used as a medium to fabricate chalcogenide semiconductors from stable solid chalcogen sources. We fabricated Cu2ZnSn(S,Se)4 films via chalcogenization of Cu-Zn-Sn oxide precursor films using scEtOH to dissolve SeO2 and elemental sulfur (S8). The S/Se molar ratio and the bandgap of Cu2ZnSn(S,Se)4 films were controlled by changing the input ratio of selenium source (SeO2) to sulfur source (S8). Analysis indicated that high-density atomic chalcogens are the dominant reactive species. This process may contribute to the development of non-vacuum fabrication methods for chalcogenide-semiconductor solar cells.
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