Understanding of the RTP-assisted Reduction of Hydrogen Dissociation from Defects in EFG Si

Presented at the 14th International Photovoltaic Science and Engineering Conference; Chulalongkorn University, Bangkok, Thailand; January 26-30, 2004.This paper shows that very short, one second, firing of screen-printed Al on the back and SiN(x) anti-reflection coating on the front can significantly enhance the bulk lifetime in EFG Si through SiN(x)-induced hydrogenation of defects. This process improved average minority carrier lifetime from 3 μs to 93 μs, resulting in the open-circuit voltages as high as 613 mV. It is proposed that rapid firing at an appropriate temperature enhances the retention of hydrogen at defect sites by minimizing the hydrogen dissociation from defects. This is supported by a combination of simulations and experiments which reveal that the dissociation of hydrogen is extremely rapid at or below firing temperature of 700°C

Investigation of Spatially Non-Uniform Defect Passivation in EFG Si by Scanning Photoluminescence Technique

Presented at the 31st IEEE Photovoltaic Specialists Conference, Orlando, Florida; January 3-7, 2005. ©2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.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 SiN(x) 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 cm(2) EFG Si cell with highest efficiency of 16.1%