Decoding High-performance | PV Cell Process—SE Laser Doping

As the core element of PV module, PV cell is not only the key part of a module to achieve the conversion of luminous?energy to electric energy, but also is a large proportion of module?cost (accounting for more than 60%). The working principle of PV?cells?is to create electron-hole pairs under the irradiation of sunlight, and then to generate a series of reactions through the P-N junction inside the cell, and finally an output current would be formed. A PV module is formed by packaging a plurality of cell stacks together in series.

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The TOPCon cell is a commonly used N-type PV crystalline silicon cell in the PV industry at present, for its theoretical limit efficiency reaches 28.7%, which is far higher than that of PERC cell（24.5%）. In other words, TOPCon cell is provided with great potential and it has been noticed by more and more enterprises owing. It is expected to replace PERC to be the PV cell with the highest market share in the near future.

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HY SOLAR obseves TOPCon’s technology advantages at an early stage and we have taken the lead in arranging TOPCon cell production.?On June 30 this year, the first batch of N-TOPCon cell successfully rolled off the production line of HY SOLAR Xuzhou Base, with the leading mass production efficiency of 25.6%. In addition,?HY SOLAR HT series modules, also adopt high-efficiency N-TOPCon cell. The technology advantages of HT series modules includes?higher efficiency, lower degradation and higher mass production cost.

The "secret" for breakthroughs in TOPCon performance is hidden in its manufacturing process. There are normally 12-13 steps for the N-TOPCon cell manufacturing, 2-3 more steps than that of PERC. In the following articles in this series, we will elaborate the essential manufacturing processes of TOPCon cell in three episodes to explore the “secret” of HY SOLAR cell’s high-efficiency together.

Let us start from the third process of TOPCon manufacturing——the SE laser doping process.

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High-efficiency Selective Emitter (SE) technology is adopted in the production process of HY SOLAR N-TOPCon cell.?After the process of cleaning and texturing, boron diffusion, the boron diffusion borosilicate glass is used as doping source by laser to form the selective heavily doped region, which is superimposed with TOPCon cell to effectively achieve 0.2%-0.4% improvement in efficiency under mass production. Besides, high-concentration doping is carried out on the contact part of wafer and metal grid line through laser so as to achieve the purpose of reducing the contact resistance of the part; while low-concentration doping is carried out on the position other than the electrode so as to achieve the purpose of reducing the recombination of the diffusion layer. By optimizing the emitter in the above manner, an increase in cell efficiency can be achieved.

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The selective emitter of N-TOPCon is different from that of PERC. Laser boron doping is required. Compared with PERC cell manufacturing process, this step requires higher laser energy. In this case, the wafer damage is more likely to be caused, which requires more precise process.?HY SOLAR TOPCon cell production line is imported into MES system for real-time monitoring in the whole process and SPC control for the key process is adopted, which helps to ensure the stable processing process, and the yield can reach 98%.