Solar cell with back local area doped heavily, and preparation method thereof

Abstract

The invention discloses a solar cell with a back local area doped heavily. The solar cell comprises a silicon base layer; a metallization area is arranged on the back surface of the silicon base layer; and a local heavily doped area is arranged in the metallization area. The invention provides the solar cell with the back local area doped heavily and a preparation method thereof. The invention discloses a technical method adopting two-time laser treatment. The first-time laser treatment aims to ablate a back passivation dielectric film of the metallization area to expose the silicon surface ofa bottom layer, and then the second-time laser treatment is carried out after doped slurry is printed in open film areas; the second-time laser treatment aims to push doping elements in the doped slurry into a silicon wafer, and then local area heavy doping is formed in the metallization area on the back surface of the solar cell; and then, a metallization process is carried out to complete the preparation of the solar cell with the back local area doped heavily. Therefore, the composite current of the metallization area on the back surface of the solar cell is reduced, and the contact resistance is reduced.

Description

technical field [0001] The invention relates to the technical field of solar cells, in particular to a back local heavily doped solar cell and a preparation method thereof. Background technique [0002] Conventional PERC cells (rear passivated solar cells) have silicon oxide / aluminum oxide / silicon nitride laminated passivation dielectric layer on the back, which has an excellent passivation effect on the surface of the cell and can reduce the surface recombination current to 15fA / cm 2 Below, the conversion efficiency of the battery is greatly improved. However, the recombination current in the metallized area on the back is as high as 600-1000fA / cm 2 , is the performance short board of PERC battery and the bottleneck of PERC battery efficiency improvement. At present, when the mass production efficiency of 5BB-SE-PERC cells in the industry reaches 22.2-22.5%, the improvement of the efficiency of the back metallization area at this time is largely determined by the recombin...

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Problems solved by technology

[0004] If you want to reduce the recombination current in the metallization area on the back, you need to increase the doping concentration in the metallization area. In the existing solutions, it cannot be properly solved in mass production.

The University of New South Wales adopts the mask thermal diffusion method, and can only use silicon oxide as the back passivation film, but now the aluminum oxide dielectric passivation film is widely used in mass production, and this layer of film can only withstand the temperature of about 600 ° C. For Boron diffusion at 900°C will cause alumina crystallization and lose its passivation effect; the industry proposes a scheme similar to CN103996746A to print boron paste first to achieve doping in the laser ablation process. Due to the heterogeneous effect, sufficient doping concentration and depth cannot be achieved, which is much higher than the sheet resistance of the 10Ω doped sheet obtained by the University of New South Wales

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