Fingerprints Indicating Superior Properties of Internal Interfaces in Cu(In,Ga)Se Thin-Film Solar Cells.

Growth of Cu(In,Ga)Se (CIGS) absorbers under Cu-poor conditions gives rise to incorporation of numerous defects into the bulk, whereas the same absorber grown under Cu-rich conditions leads to a stoichiometric bulk with minimum defects. This suggests that CIGS absorbers grown under Cu-rich conditions are more suitable for solar cell applications. However, the CIGS solar cell devices with record efficiencies have all been fabricated under Cu-poor conditions, despite the expectations.