Assessing the role of transition metals in shunting mechanisms using synchrotron-based techniques

Shunts in RGS and BaySix materials have been analyzed using a powerful combination of techniques including lock-in thermography, x-ray beam induced current, and x-ray fluorescence microscopy. Transition metals have been identified at shunt locations in both materials. Titanium and silver were found at a shunt in BaySix material, suggesting a process-induced defect related to faulty metallization grid deposition. Iron and copper were found at inversion channels in RGS material, suggesting these extended defects are effective gettering sites for transition metals, which enhance the generation- recombination current in this extended space-charge region. The role of transition metals in certain shunting mechanisms in multicrystalline silicon (mc-Si) solar cells is assessed in light of these experimental data.