Research On Preparation,Characterization And Application Of P-Type Polysilicon Passivation Contact Structure With Different Silicon Oxide Interlayers

In order to further optimize the output parameters of single crystal silicon?c-Si?solar cells,a Tunnel Oxide Passivated Contact?TOPCon?solar cells were developed.TOPCon solar cells are new type of solar cells that use ultra-thin silicon oxide?Si O_x?and heavy doped polysilicon?poly-Si?to prepare carrier selective passivation contact structure.Because the high-quality boron-doped?B?p⁺-poly-Si/Si O_x structure?p-TOPCom?is more compatible with the existing PERC solar cell production line,it can also be used for the preparation of double-sided TOPCon solar cells based on n-c-Si or for the research of perovskite/crystalline silicon stacked battery.Therefore,p-TOPCon has the advantages of wide research scope,great potential,and further reduction of manufacturing costs for enterprises.But p-TOPCon structure has poor passivation contact level and battery performance and need to be further improved.This work mainly focuses on the properties of Si O_x prepared by different methods,the passivation level of Si O_x/c-Si interface,the crystalline quality of p⁺-poly-Si thin film,and the diffusion distribution of B atoms to single crystal silicon substrate during the crystallization annealing process.At the same time,the conductivity of silicon oxide and boron-doped polysilicon films to current was also studied,and the research results were initially applied to the preparation of double-sided TOPCon solar cells.The research contents and related conclusions are as follows:1.First,three different methods were used to prepare the silicon oxide:NAOS-Si O_x prepared by hot nitric acid oxidation,PANO-Si O_x prepared by plasma-assisted nitrous oxide?N₂O?gas oxidation,and Thermal-Si O_x prepared by thermal oxidation.With TEM measurements,it was found that the thicknesses of NAOS-Si O_x and Thermal-Si O_x were both 1.8±0.2nm,and the thickness of PANO-Si O_x was 1.5±0.2nm.Although the thicknesses of the three Si O_x layers are different,they allmeet the requirements for high efficiency TOPCon solar cells.The componsitional property of the three kinds of silicon oxide was analyzed by XPS.It is found that Thermal-Si O_x has the highest proportion of Si O₂(Si⁴⁺)in the total content of Si and Si O_x?22.57%?,followed by PANO-Si O_x?16.32%?,and NAOS-Si O_x?14.83%?,which means that from the componsitional quality point of view,Thermal-Si O_x is the best amoung the three kinds of silicon oxide.And the interface passivation quality of Thermal-Si O_x/c-Si is also the highest.2.Based on the property analysis,the three kinds of silicon oxide were applied to the preparation of p-TOPCon passivation structures on n-type silicon substrate.The study found that the optimal annealing temperatures of p-TOPCon passivation samples with different silicon oxides are different at 820?for NAOS-Si O_x samples,880?for PANO-Si O_x samples,and 930?for Thermal-Si O_x samples,which achieved the best passivation quality with i V_oc=722 m V,?_eff=1.56 ms at 1?10¹⁵ cm^-3,and J_0,S=5.95f A/cm² using the Thermal-Si O_x annealed at 930?C,the mediocre with i V_oc=718 m V,?_eff=1.85 ms at 1?10¹⁵ cm^-3,and J_0,S=7.9 f A/cm² using the NAOS-Si O_x,and the worst with i V_oc=703 m V,?_eff=1.65 ms at 1?10¹⁵ cm^-3,and J_0,S=18.5 f A/cm² using the PANO-Si O_x.3.In addition to obtain the optimal passivation quality of p-TOPCon with different silicon oxides,the effects of different silicon oxides and different crystallization temperatures on the crystalline structure of the samples were also analyzed by Raman spectroscopy.The B dopant distribution through different silicon oxides and anndealed at different temperatures was analyzed by ECV.The study found that the higher the crystallization temperature,the better the crystalline quality of the film,and the more serious the diffusion phenomenon of the B dopant,while Thermal-Si O_x has a stronger barrier to B atom diffusion than NAOS-Si O_x and PANO-Si O_x.Furthermore,the reasons of p-TOPCon passivation samples with different silicon oxides having different optimal crystallization temperatures and different levels of passivation at the optimal crystallization temperature were further analyzed.4.In order to measure the conductivity of each silicon oxide and the boron-doped polysilicon on each silicon oxide to current,the contact resistivity of p-TOPCon with different silicon oxides?NAOS-Si O_x,PANO-Si O_x,Thermal-Si O_x?annealed at the optimal crystallization temperature were measured.It was found that the conductivity of boron-doped polysilicon prepared on different silicon oxides was very good by TLM method,with 3.3m?·cm²?4.3m?·cm²?10.0m?·cm²for NAOS-Si O_x?PANO-Si O_x?Thermal-Si O_xsamples,respectively.It was found that the contact resistivity of the p-TOPCon with the three silicon oxides meets the requirements for high TOPCon solar cells by the CS method,with 15.6m?·cm²?16.9m?·cm²?50.3m?·cm²for NAOS-Si O_x?PANO-Si O_x?Thermal-Si O_xsamples,respectively.5.Combining the above p-TOPCon research with different silicon oxides,we fabicated double-sided TOPCon solar cells on n-type silicon substrate.At present,the best-double-side TOPCon solar cell is achieced using using aluminum-doped zinc oxide?Zn O:Al,AZO?as the transparent conductive oxide layer?TCO?,and PANO-Si O_x as tunneling oxide layer,with solar cells efficiency of 17.41%.