Preparation method of high-efficiency polycrystalline silicon ingots

Abstract

The invention discloses a preparation method of high-efficiency polycrystalline silicon ingots. The method comprises the following steps: uniformly mixing a silicon sol with a highly pure quartz sand slurry to obtain a mixed slurry, and brushing the internal bottom of the crucible in a polycrystalline silicon ingot furnace with the mixed slurry to form an adhesive layer; brushing the adhesive layer with a nucleation source to form a nucleation source layer, and brushing the upper layer of the nucleation source layer and the inner sidewall of the crucible with a silicon nitride coating; adding a solid silicon material to the crucible, and melting to form a silicon fluid; and controlling the gradient of the temperature of the inside of the crucible to make a bottom-up vertical temperature gradient in the crucible, and opening a heat insulation cover to reduce the temperature of the bottom of the crucible. Polycrystalline silicon ingots prepared through the method have the advantages of high conversion efficiency, fine grains and uniform distribution, and corresponding minority carriers have the advantages of long life, few impurity points, regular crystal boundary distribution and no obvious dendrite and twin crystals.

Description

technical field [0001] The invention relates to a method for preparing high-efficiency polycrystalline silicon ingots, belonging to the technical field of polycrystalline silicon ingot casting. Background technique [0002] At present, polycrystalline silicon ingots in the prior art are mainly prepared by using a directional solidification system provided by GT Solar in the United States. This method usually includes steps such as heating, melting, crystal growth, annealing and cooling. During the solidification and growth process, the molten silicon liquid obtains sufficient supercooling degree at the bottom of the crucible to solidify and crystallize by controlling the temperature at the upper end and the opening of the side insulation cover. However, in the initial stage of crystal growth, since the bottom of the crucible has an isotropic structure, the initial nucleation cannot be effectively controlled during the crystallization of silicon liquid, and dislocations are e...

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Problems solved by technology

Although semi-melt seed growth technology can be used to obtain high-efficiency polysilicon ingots with low dislocation density, regular grain boundary structure and uniform grain distribution, there are the following defects: (1) The semi-melt seed growth process needs to pass Inserting high-purity quartz rods to control the melting height of the silicon material is difficult to operate; (2) Due to the semi-melt seeding growth process, there is part of the unmelted silicon material in the melting stage, resulting in uneven silicon material at the bottom of the silicon ingot. There are air holes on the side, which makes it difficult to grind and recycle the silicon material, resulting in a large loss of silicon material; (3) due to the unmelted silicon material at the bottom of the semi-melt seeding growth process, the effective utilization of silicon material in a single ingot is relatively small. The traditional silicon ingot production process has been significantly reduced, and the processing cost is relatively high, which is not conducive to the realization of the goal of grid parity for photovoltaics

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