Study On TOPCon N-pert Double-sided Solar Cell Technology

Photovoltaic industry is one of the decisive forces to promote energy transformation and implement the revolution of energy production and consumption.Reducing cost and increasing efficiency of the products is the basis of realizing photovoltaic affordable access in China.Developing new structure and technology has always been an important link in the production and manufacture on photovoltaic cells.The TOPCon type N-PERT high efficiency cell has the advantages of high lifetime,no light induced degradation and lower temperature coefficient compared with the traditional P type crystal silicon cell.This paper aims at key technology research and process optimization of TOPCon N-PERT double-sided battery.The main contents are as follows:1.The basic parameters of the cell structure is preliminarily determined by simulation of the key parts affecting the battery performance.The result is that 70 nm SiNx:H is used on the front surface of the battery structure refl,ex film,and then is 2 nm Al2O3 layer,1?2 nm SiO2 layer.Back surface is included with 80 nm SiNxH antireflection film layer,and then is 120 nm phosphorus doped polysilicon layer and 1.2 nm tunneling oxide layer.2.Boron diffusion process was studied and optimized.The best diffusion process was obtained by reducing the emitter saturation current density and emitter-metal contact resistivity.The standard deviation of the optimized block resistance was reduced from the initial 5.12 ?/?to 2.56?/?.At the same time,through the systematic study of the passivation mechanism of the front surface,it is determined that the optimum combination of passivation layers is SiO2/Al2O3/SiNx:H.3.Intrinsic Poly-Si layer deposition,tunneling oxide layer growth,and Poly-Si doping processes have been investigated.The results show that the optimal thickness of the tunneling oxide layer is 1.2 nm,and the optimal ion implantation dose is 3.5e+15 cm-2 to obtain the optimal cell conversion efficiency.The doping concentration of Poly-Si layer is 2?3×1020 cm-3and when the phosphorus-doped source forms a certain diffusion "band tail" state in the back surface of n-Si.The back surface has the optimal passivation level,and the average conversion efficiency of the battery can reach 22.44%.4.The effect of BOE cleaning and back printing metallization on the electrical performance is studied,and the processes matching and optimization are realized.The datas show that TOPCon battery structure can achieve 1%conversion efficiency improvement compared with the conventional N-PERT battery structure.