Investigation of spatially non-uniform defect passivation in EFG Si by scanning photoluminescence technique

This paper shows that both hydrogenation of defects from SiN_x coating and thermally-induced dehydrogenation of defects are rapid and occur simultaneously in EFG Si during cell processing. Room-temperature scanning photoluminescence mappings, before and after the SiNx-induced hydrogenation, revealed that hydrogenation of defective regions is effective and pronounced, with more than an order of magnitude increase in lifetime, compared to the rest of the bulk. In addition, FTIR measurements showed the concentration of bonded hydrogen in the SiN_x film decreases with the increase in annealing temperature and time. However, the rate of release of hydrogen from the SiN_x film decreases sharply after the first few seconds. Based on this understanding, a process was developed for a co-firing of SiN_x film and screen-printed Al and Ag in RTP unit, which produced 4 cm² EFG Si cell with highest efficiency of 16.1%.