Metallic alloy nanoparticle-based fabrication and optical properties of a Cu(In1−xGax)S2 absorber layer for solar cells

A highly-densified Cu(In1−xGax)S2 (CIGS2) absorber layer was fabricated using copper, indium and gallium (CIG) metallic alloy nanoparticles synthesized by salt-assisted ultrasonic spray pyrolysis (SAUSP) followed by direct thermal reduction. The reduction process in salt matrix minimized aggregation of CIG metallic alloy nanoparticles that have the potential to lead to higher film densification during sulfurization. To optimize the amount of salt, various NaCl/precursor ratios were used for SAUSP and Cu-In metallic alloy nanoparticles with average particle size of 79 nm were obtained. The CIGS2 obtained in the present study exhibited a variable band-gap ranging from 1.46 to 2.4 eV depending on the Ga/(In + Ga) ratio, which corresponded to the respective bulk materials.