Generation and annihilation of boron-oxygen related defects in boron-doped Czochralski-grown Si solar cells

Defects that reduce the minority-carrier lifetime in silicon crystal are produced by minority-carrier injection (forward bias or light illumination) when the boron-doped Czochralski-grown silicon (Cz-Si) is used as a solar cell material. The number of induced defects is determined from changes in open-circuit voltage (V-OC) of the cells. It increases with the carrier injection time, and then becomes saturated. The saturated value increases as the ambient temperature increases, during the carrier injection. These defects are observed to be vanished by thermal annealing at 200 degreesC for 20 min, indicating that they are in an unstable state and that some of them are annihilated even during the 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 process and annihilation process are evaluated to be 0.77 eV and 0.32 eV, respectively. (C) 2002 American Institute of Physics.