Abstract: By increasing the phosphorus doping concentration in the poly layer of TOPCon solar cells,the passivation effect between the poly layer and the silicon substrate can be enhanced,and the metalization contact ability between the poly layer and the metal electrode can be improved. However,excessive doping concentration can cause phosphorus atoms to diffuse to the silicon substrate,disrupting the interface passivation effect between the oxide layer and the silicon substrate. To address this issue,this paper proposes a scheme of adding a thin oxide layer as a barrier layer in the middle of the poly layer（i.e.,the stacked poly process,hereinafter referred to as the "stacked process"）. The originally one poly-Si phosphorus doping is distributed in a double-layer,with the bottom poly-Si lightly doped and the surface poly-Si heavily doped. After conducting comparative experiments on TOPCon solar cells prepared by conventional and stacked processes,the stacking process is further optimized,the thickness of the intermediate oxide layer is adjusted,and the influence of different stacking processes on electrical performance is studied. The experimental results show that:1) The stacking process can improve the electrical performance of TOPCon solar cells;2) When the thickness of the intermediate oxide layer is increased to 1.5 nm,the photoelectric conversion efficiency of TOPCon solar cells reaches its highest value（25.66%）. But the thickness of the intermediate oxide layer is a process parameter that requires precise control,and the optimal thickness balance point needs to be found to improve the performance of solar cells.