Optimizing phosphorus-doped polysilicon in TOPCon structures using silicon oxide layers to improve silicon solar cell performance

Tunnel Oxide Passivated Contact (TOPCon) technology is one of the most influential and industrially viable solar cell technologies available today. Improving the quality of passivation contact has become a central focus of current research. Although the conventional monolayer polycrystalline silicon method is highly effective in TOPCon solar cells, it is limited by doping inhomogeneity, which impairs the passivation and electrical properties, and the cell's photovoltaic conversion efficiency remains suboptimal. To address this issue, this study investigates the deposition of two layers of silicon oxide and two layers of in-situ doped phosphorus amorphous silicon, termed double poly-Si/SiO_x structures, on n-type silicon wafers using plasma-enhanced chemical vapor deposition (PECVD). The effectiveness of the structure was confirmed through various characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Key findings indicate that the double-polysilicon structure significantly enhances the uniformity of phosphorus doping, improving the carrier lifetime of the cell and reducing the contact resistance. As a result, the average efficiency in the final production stage has a conversion efficiency gain of 0.23 % over the baseline group. This study underscores the potential of this PECVD methodology to advance the fabrication of high-efficiency solar cells by providing significant improvements in passivation, doping uniformity, and overall cell performance.