Annealing effects on the physical and optical properties of Cu 2 S/CIGS core/shell nanowire arrays

The effects of annealing on the physical and optical properties of Cu 2 S/CuIn 0.7 Ga 0.3 Se 2 (Cu 2 S/CIGS) core/shell nanowire arrays were studied. Cu 2 S nanowire arrays and CIGS shell layers were prepared by a solid–gas reaction and electrodeposition, respectively. The structure and light absorption properties of Cu 2 S/CIGS core/shell nanowire arrays were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and diffuse reflectance spectroscopy. The melting point of Cu 2 S nanowire arrays increased after the electrodeposition of CIGS. The crystallinity of the CIGS shell layer increased with increasing annealing temperature from 350 to 650 °C, and most of the amorphous area of the CIGS shell layer becomes twin crystals after thermal annealing. The Cu 2 S/CIGS core/shell structure collapsed when the annealing temperature increased to 800 °C. The light absorption properties of the Cu 2 S/CIGS core/shell structure were enhanced after thermal annealing, and the band gap corresponding to CIGS was also obtained. This study indicates that the annealing temperature should be controlled between 350 and 800 °C to convert this Cu 2 S/CIGS core/shell structure to a CuIn 0.7 Ga 0.3 (Se, S) 2 (CIGSS) one-dimensional nanostructure. This research demonstrates the potential for preparing CIGSS one-dimensional nanostructures by thermal annealing.