Light Induced Degradation in Manufacturable Multi-crystalline Silicon Solar Cells

Traditional Czochralski grown Si solar cells are known to suffer from light induced degradation (LID) which adversely affects the minority carrier lifetime. Multi-crystalline Si has also been shown to show a similar degradation/recovery cycle after a phosphorus gettering step. In this paper, promising ribbon and cast multi-crystalline Si are examined for light induced degradation. High oxygen materials (≥10cm) like dendritic web, Baysix Cz, and conventional Cz show similar degradation/recovery, HEM cast multicrystalline with modest oxygen content (2.5x10cm) shows small LID, and EFG and string ribbon silicon with low oxygen content (< 2.5x10cm) show no LID. In addition light induced degradation is investigated at elevated temperatures. It is shown that bulk lifetime is degraded at 400C under tungsten halogen lamp illumination in a belt furnace suggesting that at 400C LID is greater than any annealing. At higher temperature belt processing under lamp (>400C) the net LID is partially reduced. On the other hand bulk lifetime is annealed in a conventional furnace at 400C with no lamp illumination.