The result of an extensive research on this material is the achievement of approaching 20% efficiency by the co-evaporation of copper, indium, gallium and selenium elements. Recently, photoluminescence (PL) spectra have been studied on Cu (In,Ga) Se2 (CIGS) thin films and CIGS solar cells, to clarify the carrier recombination process. The CIGS layers were grown on the Mo-coated soda-lime glass substrate by the three stage process and four sources co-evaporation of constituent elements onto a heated substrate. It has found that the structural and optical properties of the CIGS thin film was influenced by the Cu/Ga ratio (RCu/Ga) of the CIGS thin film compositional variation. The X-ray diffraction and PL spectra were used to characterize the structure property and carrier recombination mechanism of CIGS thin film.