Defects that reduce the minority-carrier lifetime in Si crystal were produced by minority-carrier injection (forward bias or light illumination) when the B-doped Czochralski-grown Si was used as a solar cell material. The number of induced defects was determined from changes in open-circuit voltage of the cells. It increases with the carrier injection time, and then became saturated. The saturated value increases as the ambient temperature increases, during the carrier injection. These defects were observed to be annihilated by thermal annealing (200C, 20min); thus indicating that they were in an unstable state and that some of them were annihilated even during carrier injection. Therefore, the total number of induced defects to be determined by the difference between the generation and the annihilation rates. The activation energies for the generation and annihilation processes were estimated to be 0.77 and 0.32eV, respectively.

Generation and Annihilation of Boron–Oxygen Related Defects in Boron-Doped Czochralski-Grown Si Solar Cells. T.K.Vu, Y.Ohshita, K.Araki, M.Yamaguchi: Journal of Applied Physics, 2002, 91[8], 4853-6