Effective passivation of p⁺ and n⁺ emitters using SiO₂/Al₂O₃/SiN_x stacks: Surface passivation mechanisms and application to industrial p-PERT bifacial Si solar cells

In this paper, we present an effective emitter passivation scheme using SiO₂/Al₂O₃/SiN_x stacks. Our study shows that SiO₂/Al₂O₃/SiN_x stacks can well passivate both p⁺ and n⁺ emitters due to an excellent chemical passivation combined with a weak field-effect passivation. Good quality boron and phosphorus emitters were achieved over a broad emitter-doping range, as demonstrated by post-fired emitter saturation current of 20 and 30 fA cm⁻², respectively. Based on the results obtained with SiO₂/Al₂O₃/SiN_x emitter passivation, we present an industrial roadmap for a p-PERT bifacial cell structure. Using this roadmap, we demonstrate industrial p-PERT bifacial cells with front side efficiency of 20.5%, rear side efficiency of 19.8% (bifaciality factor BF = 0.98) for rear textured cells and 17.5% (BF = 0.85) for rear planar cells. In particular, the cells with bifacial SiO₂/Al₂O₃/SiN_x passivation on both p⁺ and n⁺ emitters also demonstrate promising performance and a simplified cell process. The results show that SiO₂/Al₂O₃/SiN_x emitter passivation scheme is a promising candidate for photovoltaic industry.