Nitrous Oxide-Plasma Silicon Oxide Coupled with Carbon-Incorporated Polycrystalline Silicon Enables Highly Passivated...

Tunnel oxide passivated contact (TOPCon) solar cells have become the industrial mainstream for high-efficiency crystalline silicon photovoltaics. Further efficiency gains critically depend on achieving ultrahigh passivation performance while maintaining full industrial compatibility. However, achieving highly passivated TOPCon through the synergy of chemical and electric field-effect passivation remains challenging, because simultaneously obtaining high-quality interfacial SiO_x and poly-Si films along with a suitable phosphorus-diffusion profile in the silicon substrate is difficult. In this study, we develop a highly passivated TOPCon structure featuring an ultrathin silicon oxide (SiO_x) layer prepared via N₂O plasma oxidation combined with a carbon-incorporated polycrystalline silicon (poly-Si) layer, resulting in a synergistic improvement in both chemical and field-effect passivation. Notably, a uniform, continuous, and amorphous ultrathin SiO_x film provides high chemical passivation, whereas the introduction of carbon into poly-Si suppresses poly-Si crystallization, increases hydrogen accumulation at the SiO_x/silicon interface, reduces the poly-Si work function, and forms favorable energy band bending, collectively contributing to superior passivation performance. As a result, the optimized TOPCon structure not only exhibits high tolerance to annealing temperature and carbon content but also achieves excellent passivation, with an implied open-circuit voltage (iV_oc) of 760 mV, an ultralow recombination current density (J_0,s) of 0.5 fA/cm², and a minority carrier lifetime (τ_eff) of 27.9 ms. Industrial validation shows an absolute efficiency gain of 0.05% in mass-produced large-area TOPCon cells, confirming the scalability and effectiveness of this TOPCon structure.