Effects of reagent gas composition on the morphology and optical properties of Cu2S nanowire arrays

• The morphology of nanowire changes from “columnar” to “nail” as the change of reagent gas.
• Light absorption abilities of Cu2S nanowire arrays can be adjusted by changing the reagent gas.
• The amount and forming speed of Cu2O caused the different morphologies of Cu2S nanowire.
• The optical properties of Cu2S nanowire arrays show potential for the use in photovoltaic area.

Arrays of copper(I) sulfide (Cu2S) nanowires, with different morphologies, are prepared by the solid–gas reaction between Cu foil and a mixture of H2S and O2. Characterization of the Cu2S nanowires is performed by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and diffuse reflectance spectroscopy. Results show that Cu2S nanowires exhibit a Cu2S/CuxO (x = 1, 2) core/shell structure. The morphology and light absorption properties of the nanowires are shown to be dependent on the composition of the reagent gases, H2S and O2. When the H2S:O2 ratio is decreased from 1:0.5 to 1:0.8, the average diameter and length of the nanowires change from 270 nm to 3.1 μm to 114 nm and 8 um, respectively. A morphological change from columnar-like to wire-like structures is observed. When the H2S:O2 ratio is further decreased from 1:0.8 to 1:1, nanowires exhibit an average diameter and length of 670 nm and 3.7 um, respectively. A morphological change from wire-like to nail-like structures is also observed. Cu2S nanowire arrays presented strong enhanced light absorption properties, with a lowest recorded average light absorption value of 79%. Light absorption properties of Cu2S nanowire arrays are also determined by controlling the H2S:O2 reagent gas composition ratio. Results demonstrate good potential for the use of Cu2S nanowire arrays in solar energy applications.