Synthesis and light absorption properties of copper sulfide nanowire arrays on different substrates

A series of copper sulfide (Cu7S4) nanowire arrays were prepared via a solid-gas reaction on Si and indium tin oxide (ITO)-coated glass substrates. The characterization of the Cu7S4 nanowire arrays was performed using scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and diffuse reflectance spectroscopy. The nanowires on the Si wafer were orthorhombic and monoclinic Cu7S4, which were thin and straight, whereas the nanowires on ITO-coated glass were monoclinic Cu7S4, had a bigger diameter, and were bent. Although the average light absorption of Cu7S4 nanowire arrays on Si and ITO-coated glass substrates is lower than that of the Cu2S nanowire arrays grown directly on Cu foil, the light absorption of the nanowire arrays on the Si and ITO-coated glass substrates remains high (59% and 84%, respectively) across a wide range of wavelengths. The light absorption and composition of the nanowire arrays can be adjusted by changing the thickness of the precursor Cu film. Our results demonstrate that copper sulfide nanowire arrays could potentially be applied in photovoltaics.