Oxide nanoparticle-based fabrication and optical properties of Cu(In _{1 - x}Ga_x)S₂ absorber layer for solar cells

The compound Cu(In_{1 - x}Ga_x)S₂ (CIGS) was synthesized using copper oxide, indium oxide and gallium oxide mixture (CIGO) nanoparticles using salt-assisted ultrasonic spray pyrolysis (SAUSP). Under this method, CIGS can be produced without the complicated restrictions of a vacuum and an inert atmosphere. The band gap of CIGS can be controlled by introducing the desired stoichiometric quantities of starting materials. In order to synthesize CIGO nanoparticles, various NaCl/precursor ratios were used to accomplish the SAUSP process and ultimately monodisperse CIGO nanoparticles with average particle size of 9 nm without hard agglomeration were obtained. Subsequently, the CIGO nanoparticles were sulfurized to form the CIGS in H ₂S/Ar atmosphere at 500 °C. The CIGS obtained in the present study has the various band gap ranging from 1.67 to 2.34 eV depending on the Ga/(In + Ga) ratio, and those band gap correspond to the respective bulk materials.