Cd And Impurity Redistribution At The P-N Junction Of Cigs Based Solar Cells Resolved By Atom-Probe Tomography

Cd and impurity redistribution in the vicinity of CdS/CIGS interface is studied by means of atom probe tomography (APT). We find an increase of the Cd content in the CIGS layer and redistribution of O at the CdS/CIGS interface after annealing the samples at 200 degrees C, 250 degrees C, or 300 degrees C. Very small amounts (similar to 0.1 at. %) of Na impurity where observed at the p-n junction independent on the heat treatment. Simultaneously, the I-V measurements of the treated samples show a drop in the open circuit voltage and thus of the efficiency compared to the untreated sample. The effect of Cd diffusion in CIGS and of O and Na segregation at the CdS/CIGS interface on the cell performance is discussed.