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

Abstract

Nowadays, a stack of heavily doped polysilicon (poly‐Si) and tunnel oxide (SiOx) 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 SiOx. Herein, an in‐line ozone‐gas oxidation (OGO) process to prepare the tunnel SiOx 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 N2O oxidation (PANO) process. In order to explore the underlying mechanism, the electrical properties of the OGO and PANO tunnel SiOx are analyzed by deep‐level transient spectroscopy technology. Notably, continuous interface states in the band gap are detected for OGO tunnel SiOx, with the interface state densities (Dit) of 1.2 × 1012–3.6 × 1012 cm−2 eV−1 distributed in Ev + (0.15–0.40) eV, which is significantly lower than PANO tunnel SiOx. Furthermore, X‐ray photoelectron spectroscopy analysis indicate that the percentage of SiO2 (Si4+) in OGO tunnel SiOx is higher than which in PANO tunnel SiOx. Therefore, we ascribe the lower Dit to the good inhibitory effects on the formation of low‐valent silicon oxides during the OGO process. In a nutshell, OGO tunnel SiOx has a great potential to be applied in n‐type TOPCon silicon solar cell, which may be available for global photovoltaics industry.