Impact of iron, nickel and chromium in feedstock on multicrystalline silicon solar cell properties

The effect of metal contamination in multicrystalline silicon ingots on solar cell performance is investigated. Metal impurities have been added to the silicon feedstock and the solar cell performance has been compared to a reference uncontaminated ingot. A larger crystal defect density is observed in the top and in the bottom of the contaminated ingots with respect to the reference. Adding 50 ppmw of iron or 40 ppmw of nickel or chromium to the silicon feedstock in p-type ingots, the solar cell performances are comparable to the reference in the range of 40 to 70% ingot height. Addition of Fe, Ni or Cr does not only have a direct impact on the diffusion length, but also on the crystal growth and shunting behaviour.