Phosphoric diffusion technology for metallurgical-grade polysilicon solar cells

Abstract

The invention relates to diffusion technology for manufacturing solar cells, in particular to phosphoric diffusion technology for metallurgical-grade polysilicon solar cells. The technology comprises the following steps: firstly, performing high temperature grain boundary gettering, wherein high temperature is used to make impurity atoms released at the prior settling position and simultaneously diffused and move to the position of a grain boundary defect to settle to form a clean area near the grain boundary; secondly, performing medium-low temperature phosphoric deposition, wherein diffusion deposition of fresh phosphorus is performed for a short time at a medium low diffusion temperature to finish surface low concentration phosphorus deposition to prepare for long time high temperaturedrive-in in a next step; thirdly, performing diffusion passivation of high temperature deep grain boundary, wherein high temperature long time phosphoric source drive-in is performed to form deep PNjunction at the position of the grain boundary so as to make phosphor generate phosphoric gettering and passivation of phosphoric drift field at the position of the grain boundary; and finally, performing the diffusion again for adjusting to a needed sheet resistance value. The technology greatly reduces the composite of minority carrier originally happening in the position of the grain boundary by utilizing the properties of the diffusion of impurities in the polycrystalline silicon; and after the process is finished, the minority carrier lifetime of a silicon chip is improved compared with that of a silicon clip produced by a normal process, which has an active effect on the final performance of the cells.

Description

technical field [0001] The invention relates to a diffusion process for manufacturing solar cells, in particular to a phosphorus diffusion process for metallurgical grade polycrystalline silicon solar cells. Background technique [0002] The existing metallurgical-grade silicon diffusion process generally uses the diffusion process of normal solar cells, and on this basis, high-resistance heavy diffusion is performed. In this way, the short-circuit current of the battery is abandoned, but the open-circuit voltage and fill factor of the battery can be greatly improved, and the efficiency of metallurgical-grade silicon batteries can be improved to a certain extent. However, this process is not ideal for improving the recombination in the solar cell body. Contents of the invention [0003] The technical problem to be solved by the present invention is: the impurity content of metallurgical grade polysilicon is higher than that of normal polysilicon, which leads to the techni...

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Problems solved by technology

However, this process is not ideal for improving the recombination of solar cells.

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