Polycrystalline silicon ingot and preparation method thereof

Abstract

The invention provides a preparation method of a polycrystalline silicon ingot. The preparation method is characterized by comprising the following steps: a) laying seed crystals at the bottom of a crucible, and covering a polycrystalline silicon material to obtain a filled silicon material, wherein the seed crystal is monocrystalline silicon with a single crystal orientation; and b) sequentiallycarrying out directional solidification growth, annealing and cooling on the filled silicon material obtained in the step a) to obtain the polycrystalline silicon ingot. Compared with the prior art, monocrystalline silicon with a single crystal orientation is adopted as the seed crystal, a specific preparation process is adopted, good interaction is achieved, the prepared polycrystalline silicon ingot has the consistent crystal orientation, the dislocation density, especially the dislocation density of the upper middle portion of the silicon ingot, can be reduced, and therefore the crystal quality and the photoelectric conversion efficiency are improved. Experimental results show that the polycrystalline silicon ingot prepared by the preparation method has a single crystal orientation consistent with that of the seed crystal; the crystal quality is good, and a polycrystalline silicon block and a polycrystalline silicon wafer can be further obtained; and the photoelectric conversion efficiency can reach 19.8% or above.

Description

technical field [0001] The invention relates to the technical field of polysilicon, and more specifically, relates to a polysilicon ingot and a preparation method thereof. Background technique [0002] In the solar photovoltaic industry, crystalline silicon is the most widely used solar cell material. There are two main types of substrates used in crystalline silicon cells: monocrystalline silicon wafers and polycrystalline silicon wafers. Among them, there is only one crystal grain on the surface of a monocrystalline silicon wafer, and the crystal orientation of the grain is fixed. The single wafer rod is mainly prepared by the pulling method, and then obtained through truncation, squaring, multi-wire cutting and other processes; the surface distribution of polycrystalline silicon wafers has There are multiple crystal grains, and the grains have different sizes, irregular shapes, and inconsistent crystal orientations. They are mainly obtained by preparing polycrystalline s...

AI Technical Summary

Problems solved by technology

However, this kind of crystalline silicon cannot solve dislocation problems such as dislocations and subgrain boundaries, especially in the upper and middle parts of the silicon ingot. The rapid proliferation of dislocation defects leads to low and scattered photoelectric conversion efficiency of the battery, many battery stalls, and difficulty in industrialization.

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