Effect of Sn doping on improvement of minority carrier lifetime of Fe contaminated p-type multi-crystalline Si ingot

The influence of Sn doping on improvement of minority carrier lifetime (MCL) of Fe contaminated directionally solidified p-type multi-crystalline Si ingots is studied. The macrostructure and resistivity distribution of the Si ingots indicate that no significant difference exists with and without Sn doping. The average MCL increase by 26.2%, 31.8%, 8.1% with 20ppmw, 40ppmw, 60ppmw Sn doping, respectively. The MCL was improved evidently due to the reduction of formation of interstitial Fe, FeB. The doping of Sn promotes formation of vacancies, which also contributes to passivation of interstitial Fe and FeB. A calculation of constitutional supercooling is carried out, which shows that Fe have great influence on the solidification interface stability, and Sn have little influence on the interface stability. •A positive effect of Sn doping on MCL in Fe contaminated Si ingot can be confirmed.•The strain field caused by Sn doping hinders the formation and diffusion of the Fei.•Fe atoms induce a great constitutional supercooling.•Sn atoms induce little constitutional supercooling comparing with that of Fe atoms.•Trace amount of Fe or Sn doping has no significant difference in macrostructures.