Combined impurity gettering and defect passivation in polycrystalline silicon solar cells

Polycrystalline silicon wafers have been subjected to annealing (700 °C, 1 h) and to a hydrogen plasma (350 °C, 30 min) during the processing of solar cells. The annealing treatment enhances the bulk minority-carrier recombination lifetime by 19%, presumably by impurity gettering. The plasma treatment improves the lifetime by 26%; hydrogen passivation accounts for at least 2/3 of this improvement. Gettering and passivation are found to be complementary: application of both treatments results in a 43% increase in lifetime compared to standard.