Electronic Properties of the Boron-oxygen Defect Precursor in Silicon

Light-induced degradation (LID) occurring on mainstream boron-doped silicon solar cells has been investigated for decades. Its relationship with boron and oxygen concentrations in crystalline silicon has made it widely accepted to be the cause of such degradation. Post-fabrication methods have been developed to decrease the impact of its effects on solar cells. However, little is known about the responsible complex composition and its detailed electronic properties, due to the previous lack of a direct spectroscopic method to study its characteristics. In this work, we have applied a combination of lifetime spectroscopy and Deep Level Transient Spectroscopy (DLTS) following the observations of [1], [2] to further our understanding of its formation and dissociation. Our studies have revealed the presence of a newly found energy level on the pre-degraded state of the studied samples, in addition to the level reported in literature. These deep levels have been observed to inversely correlate with the formation and dissociation kinetics of the recombination active BO-LID defect. The results in this work presented therefore suggest that the defect(s) causing LID introduce multiple levels to the silicon band-gap.