Effect of the composition and anion vacancies in the band gap and band levels of Cu–In–Se–Te thin films

Abstract

Cu–In–Se–Te thin films grown by ‘‘flash’’ evaporation present stoichiometric deviations with anion vacancies and Cu excess. These changes in composition produce a different band structure. The effect of composition variations and anion vacancies in the energy gap is analyzed and a schematic band level is drawn. Samples with lower numbers of anions present conduction band minima (CBM) and valence band maxima (VBM) lower than samples with higher numbers of anions. The variation in VBM is greater than in CBM.