Cd and Impurity Redistribution at the CdS/CIGS Interface After Annealing of CIGS-Based Solar Cells Resolved by Atom Probe Tomography

Cd and impurity redistribution in the vicinity of the CdS/C(In,Ga)Se
₂
(CIGS) interface is studied by means of atom probe tomography. We find an increase of the Cd content in the CIGS layer and redistribution of O (in form of O
⁺
and OH
⁺
) at the CdS/CIGS interface after annealing the samples at 200, 250, and 300 °C. About 0.2 at% of Na impurity is observed at the interface, across the range of heat treatments performed here. Simultaneously, the J-V measurements of the treated samples show a drop in the open-circuit voltage and fill factor, and thus of the cell efficiency, compared with the untreated sample.