Structural, compositional and photoluminescence characteristics of CuInSe2 thin films prepared by close-spaced vapor transport

Abstract The present work deals with the investigation of the growth temperature effects on the properties of polycrystalline Cu–In–Se thin films, prepared by the close-spaced vapor technique (CSVT) using iodine as a transport agent. The deposition was performed onto glass substrates heated at temperatures ranging from 300 to 550°C. Characterizations by means of compositional analysis, X-ray diffraction, scanning electron microscopy, spectrophotometry and photoluminescence (PL) measurements were carried out. Cu-rich, near stoichiometric and In-rich layers with varying morphology and thickness (up to 10 μm) were obtained. They were homogeneous and well-adherent to the substrate. Results also show that the physical properties are strongly dependent on the Cu/In ratio. Following vacuum annealing, the iodine generally present in the as-deposited Cu-rich samples disappeared while only the layers heat treated under a selenium atmosphere exhibit PL signals. These signals were used to locate, then to identify the energy levels associated with various intrinsic defects responsible for the electrical and optical properties.