CdS / Cu ( In , Ga ) Se 2 interface formation in high-efficiency thin film solar cells

The evolution of the CdS/Cu(In,Ga)Se2 interface in high-efficiency thin film solar cells was monitored by chemically sensitive x-ray emission spectroscopy as a function of CdS chemical bath deposition time. We find direct experimental evidence that, in the initial deposition steps, the sulfur atoms on the Cu(In,Ga)Se2 surface exist in at least two distinct chemical environments, namely CdS and a compound involving Ga and In. The findings indicate the complexity of the CdS/Cu(In,Ga)Se2 interface structure at the atomic scale.