Preparation method of silicon ingot and silicon ingot

Abstract

The invention provides a preparation method of a silicon ingot and a silicon ingot. The preparation method comprises the following steps: placing a crucible with a silicon raw material into an ingot furnace, heating the crucible, and enabling the silicon raw material to be primarily molten to form primary molten silicon; reducing the temperature on the bottom of the crucible, so that partial first molten silicon is primarily crystallized to form primary crystal silicon; heating the crucible, so that partial primary crystal silicon is secondarily molten, and forming secondary molten silicon in the crucible; reducing the temperature on the bottom of the crucible, so that the secondary molten silicon is secondarily crystallized to form secondary crystal silicon; and annealing and cooling the secondary crystal silicon to obtain silicon ingot. By adopting the preparation method, foreign matters can be further fractionally condensed, so that the content of foreign matters in the silicon ingot and the defect density can be reduced, and the quality of the silicon ingot formed in the growing manner can be improved.

Description

technical field [0001] The invention relates to the field of photovoltaic technology, in particular to a method for preparing a silicon ingot and the silicon ingot. Background technique [0002] At present, in the production of silicon ingots, semi-melting technology or high-efficiency polycrystalline technology with seed crystals (small crystal grains) are generally used. The main process of the so-called full-melting technology is to directly load the ingot material into the crucible without laying broken seed crystals at the bottom of the crucible, and then grow polycrystalline silicon ingots by melting and growing crystals. Since the bottom of the crucible is not covered with crushed seeds, the nucleation rate at the bottom of the crucible is small at the initial stage of crystal growth, resulting in a larger size of the grown crystal grains, which ultimately leads to a lower efficiency of the formed battery. The so-called semi-melting technology is to lay broken seed c...

AI Technical Summary

Problems solved by technology

Therefore, the red area at the bottom of high-efficiency polycrystalline silicon ingots with seed crystals is relatively high, which will affect the cell efficiency of silicon wafers at the bottom of the silicon ingot, and thus affect the yield of silicon ingots

[0004] There are two reasons for the rise of the red area at the bottom. The first is that the bottom of the silicon ingot contains more impurities (mostly carbon and metal elements). These impurities will cause distortion of the silicon crystal structure, thereby causing defects in the silicon ingot. Moreover, these elements will become stronger recombination centers, which will reduce the minority carrier lifetime, that is, increase the proportion of the red zone; the second aspect is that due to stress, seed crystal voids and other reasons in the early stage of crystal growth, there will be a larger Dislocation density, and dislocations are derivatized, which will extend and grow along the crystal growth direction, causing dislocations to increase in value, resulting in an increase in the dislocation density of the silicon ingot, which in turn increases the red area at the bottom

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