Evaluating Intrinsic Defects Across CIGS Absorber via X-ray Absorption Near Edge Structures

X-ray Absorption Near Edge Structures (XANES) is a powerful tool to unravel chemical environment as it is sensitive to oxidation state and small structural variations. In this work, we measured XANES spectra and simulated structures to fit the Se local structures, including intrinsic defects around Se atoms, inside the absorber layer of Cu(In,Ga)Se2 (CIGS) solar cells. This work reveals for the first time the distributions of point defects in the absorber, across the Mo and CdS interfaces, validating the presence of selenium vacancies (VSe) and copper vacancies (VCu) proposed by multiple authors but also suggesting that there are more clusters of VSe and VCu on the CdS side and more VCu clusters on the Mo side.