Influence of growth conditions on the structural quality of Cu(InGa)Se2 and CuInSe2 thin films

Polycrystalline CuInGaSe 2 (CIGS) and CuInSe 2 (CIS) thin films were synthesized on glass substrates by a two-stage selenization process. The surface morphology, phase structure and composition of the films were analyzed by scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray analysis, respectively. Photoluminescence, optical transmission and reflection spectra were measured at temperatures from 4.2 to 300K to characterize defects and the structural quality. The structural quality and evolution of defects in the CIS films grown at different temperatures and selenization time, and dependence of the band-gap energy on the content of Ga in CIGS films at 78K is discussed.