Beyond boron-oxygen-deactivation: industrial feasible LID-free p-type Czochralski silicon

Today’s industry standard B-doped monocrystalline silicon still suffers from light-induced degradation of the carrier lifetime. Illumination at elevated temperature leads to a so-called regeneration, i.e. a recovery of the carrier lifetime as well as the solar cell efficiency. However, even though the carrier lifetime on test wafers increases from about 1 ms after processing to 3 ms after regeneration, the corresponding PERC+ cell efficiencies in both states are identical. We discuss possible reasons for this discrepancy. Additionally, we evaluate B-doped Czochralski silicon wafers with an ultra-low oxygen content of 2.6 ppma as well as industrial Ga-doped wafers. Both wafer materials are completely LID-free in lifetime measurements and PERC+ cell efficiencies and enable up to 0.4%abs higher efficiencies than present industry-typical boron-doped wafers.