Properties of Cu(In,Ga)Se2 Thin Film by Co-Evaporation

Cu(In,Ga)Se2 (CIGS) compound, which has high optical absorption coefficient as direct transition type semiconductor, is very suitable for thin film solar cell due to its high thermal stability and moisture tolerance as well as its low fabrication cost compared to the standard crystalline Si solar cell. In this research, it was tried to control the absorption capability of CIGS layer by changing Ga/(In + Ga) ratio. The composition of film was changed by controlling the effusion-cell temperature of Cu, In, Ga at a fixed Se flux. Each sample was analyzed by using SEM (scanning electron microscope), EDS (energy dispersive spectroscopy), XRD (X-ray diffractometer) to confirm the optimum composition ratio of Cu/(In + Ga) = 0.82∼0.95, Ga/(In + Ga) = 0.26∼0.31, Cu/Se = 0.5.