An ingot casting method for reducing the width of the red edge of a polycrystalline silicon ingot, a polycrystalline silicon ingot and a crucible for polycrystalline silicon ingot casting

Abstract

The invention provides an ingot casting method capable of reducing the red edge width of a polycrystalline silicon ingot. The method includes the following steps that a crucible is provided, wherein the crucible comprises a base and a side wall extending upwards from the base, the base and the side wall define a containing space together, a barrier layer is arranged on the surface, facing the containing space, of the side wall, a high-purity sheet with the melting point higher than that of silicon and the purity being 99.99% or above is selected as the barrier layer, and the material of the high-purity sheet is selected from at least one of a transition metal elementary substance, a transition metal compound, graphite, an aluminum compound and a boron compound; then, a silicon material in a molten state is placed in the crucible; the temperature in the crucible is controlled to rise gradually in the upward direction perpendicular to the bottom of the crucible to form a temperature gradient, and thus the silicon material in the molten state starts to crystallize; after the silicon material crystallizes completely, the polycrystalline silicon ingot is obtained through annealing cooling. By arranging the barrier layer on the side wall of the crucible, impurities in the crucible can be prevented from entering the silicon ingot / silicon melt, the red edge width of the silicon ingot is reduced, and the minority carrier lifetime of the polycrystalline silicon ingot is prolonged.

Description

technical field [0001] The invention relates to the field of polycrystalline silicon ingot casting, in particular to an ingot casting method for reducing the width of the red edge of a polycrystalline silicon ingot, a polycrystalline silicon ingot and a crucible for polycrystalline silicon ingot casting. Background technique [0002] In the existing polycrystalline ingot casting process, impurities in the crucible, especially metal impurities, will diffuse into the silicon ingot at high temperature, resulting in a low minority carrier lifetime of less than 2 μs in the silicon ingot near the side wall of the crucible, usually Call this region of low birthrates the red edge. Such as figure 1 The dotted frame area in is the red edge. After the red edge is made into a battery sheet, a black edge phenomenon will appear under the EL (electroluminescence) or PL (photoluminescence) test. Black edges will lead to low photoelectric conversion efficiency, which will affect the perfo...

AI Technical Summary

Problems solved by technology

The method of reducing the width of the side red edge by widening the crucible has the following disadvantages: 1. The width of the red edge is reduced by increasing the thickness of the cut side skin, which will affect the yield of silicon ingots and increase the cost of casting ingots; 2. The crucible The widened size is limited by the ingot furnace and other accessories, and the increased width is limited

The method of adopting a high-purity crucible has the following disadvantages: 1. The high-purity crucible is expensive, which increases the purchase cost of the crucible

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