Al-enhanced PECVD SiNx induced hydrogen passivation in string ribbon silicon

The effectiveness of manufacturable gettering and passivation technologies is investigated for their ability to improve the quality of a promising Si photovoltaic. material. The results of this study indicate that a lifetime enhancement of 30 mus is attained when a backside screen-printed aluminum l ayer and a thin film of SiNx, applied by plasma-enhanced chemical vapor dep osition (PECVD), are simultaneously annealed at 850 degreesC in a lamp-heat ed belt furnace. Based on the results of this study, a model is proposed to describe the Al-enhanced SiNx induced hydrogen defect passivation in Strin g Ribbon silicon due to the simultaneous anneal. According to this model, t hree factors play an important role: i) the release of hydrogen from the Si Nx film into the substrate; ii) the retention of hydrogen at defect sites i n silicon; and iii) the generation of vacancies at the Al-Si interface due to the alloying process which increases the incorporation of hydrogen and c reates a chemical potential gradient which enhances the migration of hydrog en in the substrate. A PC1D device simulation indicates that: screen-printe d cell efficiencies approaching 16% can be achieved if the gettering and pa ssivation treatments examined in this study are employed, the substrate thi ckness is reduced, and a high-quality surface passivation scheme is applied .