The performance of tunnel oxide passivated contact (TOPCon) solar cells is evaluated numerically by changing the tunnel dielectric materials. The conventional SiO2, Si3N4, and Al2O3 and the prospective TiO2 and HfO2 have unique tunnel parameters and fixed charge polarities, both of which affect cell performance. The critical tunnel dielectric thickness is determined by the majority-carrier effective mass, with a lighter majority-carrier effective mass capable of easing the tunnel dielectric thickness control at the wider thickness region. The fixed charge should be considered for the higher bulk lifetime condition, with a maximum cell efficiency impact of approximately 0.5%. By adopting p-type bulk with BO-cluster deactivation and higher resistivity as well as an Al2O3 tunnel dielectric thin film of 1 nm, a cell efficiency of 24.77% is achieved, approximately 0.2% higher than the record efficiency of a large-scale TOPCon that adopts FZ-Si bulk.
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