Different ligand exchange solvents effect on the densification of CuIn _0.7 Ga _0.3 Se ₂ prepared using the heating-up method

The effects of different ligand exchange solvents and heat treatment conditions on the densification and microstructure development of CuIn _0.7 Ga _0.3 Se ₂ (CIGS) crystallites synthesized using the heating-up method were studied in this work. The heat treatment effects on the organic molecules and crystalline structure were investigated using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was observed that oleylamine (OLA) adsorbed onto the CIGS surface was difficult to remove during sintering. Ligand-exchange with m-xylene or 1-hexanethiol can promote the removal of oleylamine adsorbed onto the CIGS surface and prevent the residual carbon from forming during sintering, which leads to grain growth and densification. A dense CuIn _0.7 Ga _0.3 Se ₂ can be obtained using the precursor powders after ligand-exchange with 1-hexanethiol and m-xylene to remove organic molecules and sintering at 600 °C for 2 h under Se atmosphere.