Influence of carrier density spatial heterogeneities on the electrical breakdown of crystalline silicon solar cells: Experiment and simulation

In this work we investigate how spatial heterogeneities of the substrate hole density influence the reverse characteristics of UMG solar cells. Electroluminescence and current-voltage data on highly heterogeneous cells are compared with the predictions of TCAD simulations. Reverse-bias electroluminescence images reveal that the distribution of breakdown sites follows the general pattern of the carrier density distribution, but are highly localized at some specific defects. Measurements show that the overall breakdown voltage is governed by the highest carrier density across the wafer, suggesting that this maximum density should be controlled with care. These results are in good agreement with simulation showing that TCAD tools can successfully include the effect of spatial heterogeneities.