High-Efficiency TOPCon Solar Cells With Laser-Assisted Localized Boron Doping via Silicon Paste

In the present study, we establish a physical model for laser-assisted localized boron doping in N-type tunnel oxide passivated contact (TOPCon) solar cells by employing the fluid dynamics method. Our simulations reveal that a flat-top beam inflicts less thermal damage on silicon than a Gaussian beam at a constant laser energy density. Additionally, we observe an acceleration in the flow rate of molten silicon in the molten pool as the laser energy density increases. This acceleration facilitates efficient doping of boron atoms into the silicon substrate, albeit accompanied by an expansion of the local thermal damage range. In light of these findings, we utilized boron-doped silicon paste as a doping source in experiments conducted on a 15 MW TOPCon solar cells production line employing four distinct laser energy densities. The experiments yielded a reduction in the sheet resistance to 81.9 Ω/cm in the boron-doped regions, an increase in the peak boron doping concentration to 1.08 × 10 ¹⁹ atoms/cm ³ , and a doping depth of 2.38 μ m. Consequently, the highest efficiency enhancement recorded was 0.14%, culminating in an efficiency of 25.06%. This research outlines the mechanism of the laser-assisted localized boron doping process and provides insights for enhancing the efficiency of TOPCon solar cells.