Numerical modeling of CdTe cell degradation

Time-dependent numerical modeling is employed in conjunction with experimental data to investigate degradation mechanisms in cadmium telluride (CdTe) solar cells. Two mechanisms are tested against the data: defect generation in the junction region caused by excess charge carriers, and back barrier increase due to ion migration. Junction effects result in stable J_sc with significant losses in V_oc and FF, in accordance with typical data for the type of stress conditions considered here. The back barrier increase causes additional FF loss. The results suggest that neutral defect centers dissociate into positive/negative pairs near the main junction as degradation proceeds.