Cu2ZnSnS4 ("CZTS") is a promising photovoltaic material due to its direct band gap of ~1.5 eV, large absorption coefficient, abundance of component materials, and relative biocompatibility. CZTS heterostructures have also been shown to be photocatalytically active in the presence of a sacrificial electron donor using methylene blue reduction as a model system. While the conduction band of CZTS is high enough in energy to photoreduce hydronium ions to hydrogen, its valence band does not have enough energy to photooxidize water. In order to make CZTS truly photocatalytic and be able to use it as a standalone, sacrificial agent-free photocatalytic semiconductor, we have attempted to lower the energy of its valence band by substituting a more electronegative oxygen- or nitrogen-based anion in lieu of sulfur. Specific experiments conducted to date include roasting the CZTS nanocrystals in air or with urea. The nanocrystalline products are characterized by powder X-ray diffraction, solution phase optical absorption spectroscopy, and transmission electron microscopy.

Lowering the valence band of Cu2ZnSnS4 through anion substitution: Can it be done?

251st National Meeting (2016)

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