Study On The Properties Of N-Poly Si Layer Prepared By HWCVD Method For TOPcon Solar Cells

In high-efficiency solar cells,tunneling oxide passivation contact（TOPcon）solar cells have the advantages of extremely high theoretical limits,high conversion efficiency,and excellent interface passivation performance.The key technology lies in the preparation of doped polysilicon thin films.HWCVD has attracted widespread attention due to its fast deposition rate,no plasma damage,in situ or non in-situ doping,and compatibility with HIT battery production lines.In this paper,the preparation ofα-Si:H（n）thin films on ultra-thin Si O_xlayers using HWCVD deposition method was investigated.The effects of deposition process parameters on the passivation performance of the microstructure ofα-Si:H（n）and the（n）Poly-Si/Si O_xlaminated structure were systematically studied,as well as the effects of different annealing conditions on the passivation performance of the（n）Poly-Si/Si O_xlaminated structure.The main research conclusions are as follows:（1）The HWCVD deposition process has a significant impact on the microstructure ofα-Si:H（n）,but the passivation performance of（n）Poly-Si/Si O_xis not significantly affected within a certain"window period",because the high-temperature annealing process can partially repair the differences and defects in the microstructure ofα-Si:H（n）,in order to achieve the most stable bonding point and form a crystal structure,reflecting the wide process window for the preparation of（n）Poly-Si layers.After optimizing the process parameters,the passivation quality of（n）Poly-Si/Si O_xprepared is excellent(minority carrier lifetimeτ_teffexceeds 7ms,the implied open voltage i V_OCreaches 741m V,and the average saturation current density J₀is as low as4f A/cm².SEM image analysis shows that there is no blistering phenomenon.（2）Integrating the optimized process parameters onto a textured pyramid structure substrate,although the passivation quality is lower than that of a polished substrate,it also achieves good passivation results(τ_teffexceeds 1ms and the i V_OCreaches a maximum of 701m V,while the average value of J₀is as low as 60f A/cm².This verifies the feasibility and excellent performance of the HWCVD method applied to crystalline silicon substrates with different surface textures.（3）The passivation quality of（n）Poly-Si/Si O_xstructures increases first and then decreases as the annealing temperature increases.When the annealing temperature is850℃,the passivation quality is optimal(minority carrier lifetimeτ_teffexceeds 7ms,the implied open voltage i V_OCreaches 741m V,the average saturation current density J₀is as low as 4f A/cm²,and the crystallization rate of（n）Poly-Si reaches 84.76%,with a maximum grain size of 7nm.When the temperature is lower than 850℃,an effective field passivation effect cannot be formed,and the crystallization rate and carrier mobility of the thin film are low.When the temperature exceeds 850℃,although the degree of crystallization is higher,the passivation quality decreases,which may be due to the destruction of the ultra-thin oxide layer at high temperatures.At 850℃,the annealing time can reach 15minutes,and the passivation quality is almost the same as 30 minutes.The crystallization rate is 91.11%,and the grain size is 7nm.However,excessive annealing time does not affect the passivation quality.