Effects of process parameters on the synthesis and characterization of CuIn1−xGaxSe2 nanopowders produced by new modified solvothermal method

In this research, CuIn1−xGaxSe2 (CIGS) nanopowders were synthesized by a new modified solvothermal process which utilized a controllable internal pressure and a stirring system during the process. The effects of process parameters on the synthesis and characterization of CIGS nanopowders were studied including reaction temperature, process time, applying internal imposed pressure, and Ga substitution with In. Chloride sources of copper, indium, and selenium powders along with gallium nitrate powder were used as precursor materials which were dissolved in triethylenetetramine as a solvent at various synthesis conditions to prepare final products in a specific autoclave. Crystal structure, morphology, and optical properties of prepared nanopowders were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), high-resolution transmission electron microscopy (HRTEM), and diffuse-reflectance UV/vis spectroscopy (DRS). The results indicate that using both a stirring system and internal imposed pressure of 400 kPa have significant effects on the synthesis of single phase CIGS nanopowders and their crystallinity in short process time. It is also showed that samples synthesized under conditions of internal imposed pressure and long process time could form the rosette-like particles. Furthermore, optical measurements revealed that the band gap energies for prepared particles (1.05-1.38 eV) are close to those of bulk materials.