Synthesis of a ZnS shell on the ZnO nanowire and its effect on the nanowire-based dye-sensitized solar cells

A thin ZnS shell was formed on ZnO nanowires using ZnSO₄ and thiourea in an NH₄OH (ZTA) precursor solution, and its effect on the performance of a dye-sensitized solar cell (DSSC) was investigated. As compared to hydrothermal and successive ionic layer adsorption and reaction methods, it was observed that the ZnS shell was effectively synthesized on the ZnO nanowires using the ZTA solution. ZnO nanowires with a ZnS shell had lower absorption intensities over the entire wavelength range compared with those of nanowires without the ZnS shell, which can cause dye to absorb more light in the DSSC operation. Because the intensity of visible emission decreased after the formation of a ZnS shell on the ZnO nanowires, it is proposed that surface defects that provide recombination sites will be reduced at the anode/electrolyte interface. The cell performance of the ZnO nanowire-based DSSC was greatly improved by the deposition of a thin ZnS shell onto the ZnO nanowires in the ZTA solution, which resulted from the reduced visible absorption of the semiconductor and defect sites on the semiconductor surface.