Characterization of chalcopyrite Cu(In,Al)Se2 thin films grown by selenization of evaporated precursors.

Chalcopyrite Cu(In,Al)Se2 (CIAS) thin films were prepared by a two-stage process onto soda-lime glass substrates. Different Cu/(Al+In) atomic ratios have been evaporated in a vacuum chamber to be subsequently heated with elemental selenium in a quasi closed graphite box at 530 °C. The results on the dependence of the crystallite size, preferential orientation, roughness, optical transmittance and aluminium incorporation as a function of the stoichiometry have been studied, concluding that a Cu/(Al+In) atomic proportion near the 1.07 value seems to be the best choice to favour crystalline CIAS formation without substantial CuSe secondary phases segregation.