A Model for Electron-Beam-Induced Current Analysis of mc-Si Addressing Defect Contrast Behavior in Heavily Contaminated PV Material

Much work has been done to correlate electron-beam-induced current (EBIC) contrast behavior of extended defects with the character and degree of impurity decoration. However, existing models fail to account for recently observed contrast behavior of defects in heavily contaminated mc-Si PV cells. We have observed large increases in defect contrast with decreasing temperature for all electrically active defects, regardless of their initial contrast signatures at ambient temperature. This negates the usefulness of the existing models in identifying defect character and levels of impurity decoration based on the temperature dependence of the contrast behavior. By considering the interactions of transition metal impurities with the silicon lattice and extended defects, we attempt to provide an explanation for these observations. Our findings will enhance the ability of the PV community to understand and mitigate the effects of these types of defects as the adoption of increasingly lower purity feedstocks for mc-Si PV production continues.