Polyol Mediated Solvothermal Synthesis and Characterization of CuIn(1−x)GaxS2 Nanocrystals

Gallium-substituted copper indium sulfide (CuIn(1−x)GaxS2) nanoparticles have been synthesized by a convenient solvothermal method without usage of surfactants or toxic reductants such as hydrazine. Thiourea, sodium hydroxide, CuCl2·2H2O, InCl3 and GaCl3 were used as starting materials and ethylene glycol as solvent and reducing agent. The reactions were performed at 200 °C for 16 h. Effect of sodium hydroxide on the reaction products is analyzed. The powders are mainly characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, BET surface area measurements and UV–Vis absorption spectroscopy. The results show that the gallium is successfully incorporated into the chalcopyrite crystal structure. The homogeneous powders obtained are constituted of nanoparticles with sizes in the range 20–30 nm and exhibit a specific surface area close to 65 m2/g. Further, the possible mechanism for the formation of CuIn(1−x)GaxS2 nanocrystals is explained. The optical band gap energies of the nanoparticles were in the range 1.48–1.75 eV.