Local versus global electronic properties of chalcopyrite alloys: X-ray absorption spectroscopy and ab initio calculations

摘要

Structural and electronic properties of Cu(In,Ga)S2 (CIGS) alloys as a function of the In/Ga ratio are studied by combining near edge X-ray absorption fine structure and extended X-ray absorption fine structure spectroscopy with density functional theory calculations. While the S absorption edge shifts with the change of the In/Ga ratio, consistently with the corresponding variation of the band gap, the edges of the other elements are largely independent of composition. Our calculations reproduce this behavior and identify its origin in the dependence of the electronic properties on the local atomic environment. These results point to the importance of an accurate atomic-scale description of the structure of this family of alloys for reliable calculations of their electronic properties.