Growth and properties of epitaxial Cu(In, Ga)Se2 thin films deposited by the three-stage process for solar cells

Epitaxial CIGS thin films were deposited by the modified three-stage process on epitaxially-grown Mo {110}/sapphire {0001} substrates. The crystallographic properties were investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The 2 μm-thick epitaxial CIGS thin films showed high flatness and a few grain boundaries with voids at the CIGS/MoSe₂ interface. The CIGS {112} plane grew parallel to hexagonal MoSe₂ {0001}/Mo {110}/sapphire {0001}. The misfit dislocations were not found in the CIGS or MoSe₂ films. Time resolved photo-luminescence (TR-PL) measurements revealed that the PL lifetime of the epitaxial CIGS thin films did not show a significant difference before or after the CBD-CdS process. This result contrasts clearly to polycrystalline CIGS thin films grown on soda-lime glass substrates.