Crystallization method for improving bottom crystal flowers of polycrystalline silicon ingot

Abstract

The invention relates to a crystallization method for improving bottom crystal flowers of a polycrystalline silicon ingot in the technical field of solar energy polycrystalline silicon ingots, whereinthe crystallization method includes the following steps: firstly, a raw material of the polycrystalline silicon ingot is placed in a crucible of a polycrystalline ingot furnace, a furnace body is closed, the polycrystalline ingot furnace is started up, and heating is performed to make the solid raw material completely melted into a liquid state; secondly, the opening degree of a heat insulating cage at the periphery of the crucible is gradually opened, the molten solution starts to gradually grow crystals from the bottom of the crucible, when the crystal growth height is 3-6 mm and the opening degree of the heat insulating cage is 10+ / -0.5 cm, the opening degree of the heat insulating cage is decreased to 4.5-5.5 cm, and the crystal growth rate is reduced to form a fine microcrystal layer, 0.5 h later, gradual rising goes on, the heat insulating cage is opened, the opening degree of the heat insulating cage is gradually increased, and the crystal growth height is gradually increased until the crystal growth is finished; and the opening degree of the heat insulating cage represents the opened distance between the heat insulating cage and the bottom plate when the heat insulating cage is lifted upward, and the opening degree of the heat insulating cage before the crystal growth starts is 0; and thirdly, after the crystal growth is finished, furnace internal annealing is performed and cooling is performed until the product is discharged out of the furnace.

Description

technical field [0001] The invention relates to the production technology of polycrystalline silicon ingots in the technical field of solar cell manufacturing, in particular to a crystallization method for improving crystal flowers at the bottom of polycrystalline silicon ingots. Background technique [0002] The nucleation of crystal flowers at the bottom of the ingot in the existing full-melting ingot casting process is mainly through the homogeneous nucleation of black silicon at the bottom of the crucible to produce small and uniform crystal flowers. When the process is stable, the uniformity and size of the crystal flowers are mainly It is determined by the particle size and density of black silicon at the bottom of the crucible, so it is difficult to ensure the size and uniformity of the crystal flowers at the bottom of the crystal ingot, resulting in high-density dislocations and affecting the conversion efficiency of the battery. Contents of the invention [0003] ...

AI Technical Summary

Problems solved by technology

[0002] The nucleation of crystal flowers at the bottom of the ingot in the existing full-melting ingot casting process is mainly through the homogeneous nucleation of black silicon at the bottom of the crucible to produce small and uniform crystal flowers. When the process is stable, the uniformity and size of the crystal flowers are mainly It is determined by the particle size and density of black silicon at the bottom of the crucible, so it is difficult to ensure the size and uniformity of crystal flowers at the bottom of the ingot, resulting in high-density dislocations and affecting the conversion efficiency of the battery

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