Industrially applicable mitigation of BO-LID in Cz-Si PERC-type solar cells within a coupled fast firing and halogen lamp based belt-line regenerator – A parameter study

Abstract

The benefit of sophisticated rear surface passivation quality in highly efficient solar cell structures made of boron-doped oxygen-rich Cz-Si wafers (e.g. PERC) can be reduced if bulk lifetime becomes a limiting factor due to boron-oxygen related light-induced degradation (BO-LID). A permanent lifetime recovery can be achieved through a regeneration treatment under illumination at elevated temperature. To evaluate the applicability of BO mitigation by means of regeneration at industrial relevant conditions, industrially-made PERC solar cell precursors were processed in a coupled fast firing and regeneration tool where the latter comprises an illuminated zone through which the solar cells transit on a belt. The treatment was evaluated by a subsequent intentional degradation. The results show that untreated solar cells suffer from BO-LID while properly treated samples are almost free of BO-LID demonstrating the applicability of a fast (around 15–30 s) and coupled regeneration process in mass production. Furthermore, it is found that fluctuations in precursor quality and/or variations in firing conditions are of minor significance for the BO-LID mitigation process. The firing conditions process window (peak firing temperature and belt velocity) overlaps with the treatment conditions window having the benefit of independent optimization.