Enhanced Passivation Effect of Tunnel Oxide Prepared by Ozone‐Gas Oxidation (OGO) for n‐Type Polysilicon Passivated Contact (TOPCon) Solar Cells

Nowadays, a stack of heavily doped polysilicon ( poly ‐Si) and tunnel oxide (SiO x ) is widely employed to improve the passivation performance in n ‐type tunnel oxide passivated contact (TOPCon) silicon solar cells. In this case, it is critical to develop an in‐line advanced fabrication process capable of producing high‐quality tunnel SiO x . Herein, an in‐line ozone‐gas oxidation (OGO) process to prepare the tunnel SiO x is proposed to be applied in n ‐type TOPCon solar cell fabrication, which has obtained better performance compared with previously reported in‐line plasma‐assisted N 2 O oxidation (PANO) process. In order to explore the underlying mechanism, the electrical properties of the OGO and PANO tunnel SiO x are analyzed by deep‐level transient spectroscopy technology. Notably, continuous interface states in the band gap are detected for OGO tunnel SiO x , with the interface state densities ( D it ) of 1.2 × 10 12 –3.6 × 10 12 cm −2 eV −1 distributed in E v + (0.15–0.40) eV, which is significantly lower than PANO tunnel SiO x . Furthermore, X‐ray photoelectron spectroscopy analysis indicate that the percentage of SiO 2 (Si 4+ ) in OGO tunnel SiO x is higher than which in PANO tunnel SiO x . Therefore, we ascribe the lower D it to the good inhibitory effects on the formation of low‐valent silicon oxides during the OGO process. In a nutshell, OGO tunnel SiO x has a great potential to be applied in n ‐type TOPCon silicon solar cell, which may be available for global photovoltaics industry.