Impact of metal contamination in multicrystalline silicon solar cells: Case study for iron

The impact on solar cell performance of iron has been investigated. Iron has been intentionally added to silicon feedstock used to grow p-type directionally solidified multicrystalline silicon ingots. A state of the art screen print solar cell process has been applied to wafers from the bottom to top of the ingot. Adding 50 ppmwt of iron to silicon feedstock, results in comparable solar cell performances to reference uncontaminated material, in the range 40 to 70% of the ingot height. Iron causes a reduction in the diffusion length, which decreases with the ingot height.