Low-T Anneal as Cure for LeTID in Mc-Si PERC Cells

Light and elevated temperature induced degradation (LeTID) is known to be affected by the last dark anneal that the silicon wafers or cells experience prior to illumination. Here we study how low-temperature dark anneal performed on fully processed multicrystalline silicon (mc-Si) passivated emitter and rear solar cells (PERC) influences LeTID characteristics, both the intensity of the degradation and the degradation kinetics. Our results show that a relatively long anneal at 300 degrees C provides an efficient means to minimize LeTID while too short dark anneal at the same temperature seems to have a negative impact on the subsequent degradation under light soaking. Finally, we compare the experimental results with the model originally developed for metal precipitation and discuss the possibility of metals being involved in LeTID mechanism.