Impact of Se flux on the defect formation in polycrystalline Cu(In,Ga)Se2 thin films grown by three stage evaporation process

• Published in: Journal of applied physics Vol. 113; no. 6
• Main Authors: Islam, M. M., Uedono, A., Sakurai, T., Yamada, A., Ishizuka, S., Matsubara, K., Niki, S., Akimoto, K.
• Format: Journal Article
• Language: English
• Published: 14.02.2013
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4792049

Cu(InxGa1−x)Se2 (CIGS) films, grown under various Se fluxes, have been investigated by the positron annihilation spectroscopy. The line-shape parameter (S) of the positron annihilation spectra was used to characterize the defects in the CIGS films. When Se flux was decreased, the S parameter at the surface and subsurface region of the films increased. This phenomenon was attributed to the increased concentration of the defect complex formed between Se and Cu vacancies. S parameter at the surface region was significantly higher than that in the bulk region of each film. It was explained with the model of compositional inhomogeneities along the depth of the film. Solar cell performance strongly correlated to the S parameter at the surface region of the CIGS films. Sufficient Se flux was found to be effective to reduce the S parameter, thereby, to suppress the defects in the films.