Oxygen and carbon behaviors and minority-carrier lifetimes in multi-crystalline silicon （mc-Si） used for solar cells are investigated by FTIR and QSSPCD before and after annealing at 750～ 1150℃ in N2 and O2 ambient. For comparison, the annealing of CZ silicon with nearly the same oxygen and carbon concentrations is also carried out under the same conditions. The results reveal that the oxygen and carbon concentrations of mc-Si and CZ-Si have a lesser decrease,which means oxygen precipitates are not generated,and grain boundaries in mc-Si do not affect carbon behavior. Bulk lifetime of mc-Si increases in N2 and O2 ambient at 850,950,and 1150℃ ,and the lifetime of mc-Si wafers annealed in 02 are higher than those annealed in N2, which shows that a lot of impurities in mc-Si at high temperature annealing diffuse to grain boundaries,greatly reducing recombination centers. Interstitial Si atoms filling vacancies or recombination centers increases lifetime.
