Achieving Excellent Surface Passivation with J0,s Less Than 0.5 fA cm-2 Utilizing a Carbon-Incorporated Intrinsic Polysilicon-Based Tunnel Oxide Passivating Contact Structure.

Abstract

Crystalline silicon solar cells are among the most efficient technologies in the photovoltaic industry, with their conversion efficiency being highly dependent on surface passivation. In this study, A carbon-incorporated intrinsic polysilicon layer is developed using plasma-enhanced chemical vapor deposition to form a tunnel oxide passivating contact (TOPCon)-like structure combined with silicon oxide. As a result, an implied open-circuit voltage (iV_oc) as high as 754 mV is achieved and a recombination current density as low as ≈0.3 fA cm^-2 for n-type lifetime wafers with a flat surface. Furthermore, the mechanism of the carbon atoms is elucidated, which indicates that the carbon atoms capture more H and increase the interfacial SiO_x integrity, thereby reducing defect state density to achieve excellent surface passivation. Additionally, carbon atoms effectively reduce the bulk Shockley-Read-Hall recombination to improve the film passivation. Consequently, this passivation technology is applied to back-junction TOPCon cells to reduce the coverage of the rear p-type TOPCon, achieving an improvement in iV_oc of 10 mV, with a 0.2% absolute increase in efficiency predicted by numerical simulations. Moreover, this passivation technology can also be applied to back-contact TOPCon cells, along with various scenarios requiring high passivation, presenting significant potential for application and widespread popularization.