Base doping and recombination activity of impurities in crystalline silicon solar cells

The optimisation of base doping for industrial crystalline silicon solar cells is examined with model calculations. Focus is on the relation between base doping and carrier recombination through the important impurities interstitial iron (Fe_i) and the metastable boron-oxygen (BO) complex. In p-type silicon, the optimum base resistivity is strongly dependent on defect concentration. In n-type silicon, recombination due to Fe_i is much lower and nearly independent of resistivity. Fe_i is likely representative for other transition metal impurities. In many real cells a balance between Fe_i or similar defects, and BO will occur.