Comparison of Band Alignments at Various CdS/Cu(In,Ga)(S,Se)2 Inter-Faces in Thin Film Solar Cells

The band alignment at the CdS/Cu(In,Ga)(S,Se)
₂
interface, as derived in our earlier publications, are compared for different absorber compositions. The discussed band alignments were directly determined using a combination of UV- and X-ray photoemission and inverse photoemission. While a flat conduction band alignment can be found for low-gap material, the cell structure with a high-gap absorber shows a cliff-like alignment. The different alignments can be correlated with the respective cell parameters, explaining why the expected linear gain in open circuit voltage for the high-gap absorbers has not yet been achieved