Fabrication of Cu(In,Al)(S,Se)2 films by sulfurization and selenization of co-sputtered Cu-In-Al precursors

Cu(In,Al)(S,Se)(2) (CIASSe) films were prepared on soda lime glass substrates by sulfuring and selenizing co-sputtered Cu-In-Al metal precursors. CIASSe film preparation was optimized and the film properties were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and ultraviolet-visible spectroscopy. Films that were annealed for 20 min formed a single-phase chalcopyrite structure, and those films annealed at 500 degrees C and 540 degrees C exhibited a smooth and dense surface topography. After being annealed at 450-540 degrees C, films contained reduced amounts of copper and close to ideal stoichiometric compositions. Their absorption coefficients were over 104 cm(-1), and the obtained optical band gap values were 1.37 eV, 1.42 eV, and 1.44 eV, respectively, which were close to the ideal optical band gaps for photovoltaic applications. (C) 2014 Elsevier B.V. All rights reserved.