Abstract: The effects of deposition parameters of tube plasma enhanced chemical vapor deposition （PECVD） on the heavily doped polysilicon passivated contact （SiO_x/Poly-Si（n⁺）） of silicon solar cells are reported.The doped polysilicon of TOPCon solar cells is achieved by high temperature crystallization of deposited amorphous silicon.a-Si （n⁺） films with different thickness,crystallinity and doping concentration can be obtained by changing the deposition temperature,the flow rate of Ar and PH₃,deposition RF power and other deposition parameters of PECVD.Then different Poly-Si（n⁺） films are obtained by annealing at high temperature,resulting in different characteristics of SiO_x/Poly-Si（n⁺） passivated contact in terms of passivating quality and carrier selectivity.Finally,under the deposition temperature of 480°C,Ar flow rate of 8 L/min,PH₃ flow rate of 0.8 L/min,deposition RF power of 12000 W,annealing temperature of 920℃，the optimal double-side SiO_x/Poly-Si（n⁺）/SiN_x passivated contact is obtained.The minority lifetime reaches to6445μs,the implied open circuit voltage (iV_oc) reaches to 742.7 mV,and the single-side saturation current density J₀ is as low as 4.2fA/cm~2.