Rapid Stabilization of High-Performance Multicrystalline P-type Silicon PERC Cells

Light-induced or, more broadly, carrier-induced degradation (CID) in high-performance multicrystalline silicon (HP mc-Si) solar cells remains a serious issue for many manufacturers, and the root cause of the degradation is still unknown. In this paper, the impact of firing temperature on the stability of lifetime test structures is investigated, and it is found that substantial CID can be triggered if peak temperatures exceed approximately 700 degrees C. We then investigate two pathways to stabilize the performance of industrially produced HP mc-Si passivated emitter rear contact cells which have been fired at CID-activating temperatures (similar to 740 degrees C-800 degrees C) currently required for silver contact formation. The first is a fast-firing approach, whereby it is demonstrated that an additional firing step at a reduced temperature after cell metallization can suppress the extent of V-oc degradation by up to 80%. The second approach is the accelerated degradation and subsequent recovery of carrier lifetime through the use of high-intensity illumination during annealing at elevated temperatures. A 30 s process is found to suppress the maximum extent of degradation in Voc by up to 60% and up to 80% for longer processes. Ultimately, the results suggest that a combined approach of fast-firing and a high-intensity-illuminated anneal could achieve the best results in terms of V-oc stability.