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

Polycrystalline CuInGaSe2 (CIGS) and CuInSe2 (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 300 K 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 78 K is discussed