CdS/Cu(In,Ga)Se2 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.