Effective passivation of p+ and n+ emitters using SiO2/Al2O3/SiNx 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/SiNx stacks. Our study shows that SiO2/Al2O3/SiNx 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/SiNx 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/SiNx passivation on both p+ and n+ emitters also demonstrate promising performance and a simplified cell process. The results show that SiO2/Al2O3/SiNx emitter passivation scheme is a promising candidate for photovoltaic industry.