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Casting method for polycrystalline silicon ingot

A technology for polycrystalline silicon ingots and silicon materials, which is applied in the growth of polycrystalline materials, chemical instruments and methods, and crystal growth, and can solve problems such as easy generation of dislocations, low photoelectric conversion efficiency of solar cells, and excessive oxygen content

Active Publication Date: 2015-04-29
YANGZHOU RONGDE NEW ENERGY TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] The technical problem to be solved by the present invention is that the casting method of polycrystalline silicon ingots in the prior art tends to lead to uneven crystal grains, disordered crystal orientations, and dislocations, and the photoelectric conversion efficiency of solar cells made by using the polycrystalline silicon ingots is low. , and the cost of high-efficiency crucibles in the market is high, and it is easy to cause the problem of excessive oxygen content. A casting method for polycrystalline silicon ingots is provided

Method used

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  • Casting method for polycrystalline silicon ingot
  • Casting method for polycrystalline silicon ingot
  • Casting method for polycrystalline silicon ingot

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0078] Embodiment 1: the preparation of polycrystalline silicon ingot

[0079] Prepare silicon nitride slurry with silicon nitride powder, silica sol and water at a weight ratio of 1:1:7, spray on the inner surface of the side wall and the inner surface of the bottom of the crucible, and spray the above silicon nitride slurry again after drying At the bottom of the crucible; wherein, the thickness of the silicon nitride coating sprayed on the side wall of the crucible is 0.1mm, and the thickness of the silicon nitride coating sprayed on the bottom of the crucible is 0.2mm; the silicon nitride powder is β phase content accounting for 60wt%, D50 Silicon nitride powder with a particle size distribution of 2 μm and a bimodal distribution;

[0080] Soak the silicon powder in a mixed solution of concentrated nitric acid (69% by mass fraction) and water with a volume ratio of 1:1 for 60 minutes, then separate the silicon powder, rinse to neutral, dry the rinsed silicon powder, and th...

Embodiment 2

[0085] Embodiment 2: the preparation of polycrystalline silicon ingot

[0086] Prepare silicon nitride slurry with silicon nitride powder, silica sol and water in a weight ratio of 3:2:9, spray on the inner surface of the side wall and the inner surface of the bottom of the crucible, and spray the above silicon nitride slurry again after drying At the bottom of the crucible; wherein, the thickness of the silicon nitride coating sprayed on the side wall of the crucible is 0.2mm, and the thickness of the silicon nitride slurry coating sprayed on the bottom of the crucible is 0.3mm; the silicon nitride powder is β phase accounting for 80wt%, and the D50 value is Silicon nitride powder with a particle size distribution of 1 μm and a bimodal distribution;

[0087] Soak the silicon powder in a mixed solution of concentrated sulfuric acid (mass fraction: 98%) and water with a volume ratio of 1:1 for 30 minutes, then separate the silicon powder, rinse until neutral, dry the rinsed sil...

Embodiment 3

[0095] Embodiment 3: the preparation of polycrystalline silicon ingot

[0096] Prepare the silicon nitride slurry according to silicon nitride powder: silica sol: water = 1:1:9. When preparing, put in water first, then put in the silica sol and stir for five minutes, then put in the silicon nitride powder for preparation. The silicon nitride powder is a silicon nitride powder with a β phase accounting for 60 wt%, a D50 value of 2 μm, and a bimodal particle size distribution. Set the spraying temperature to 130°C and the pressure to 0.6Mpa, spray the prepared silicon nitride slurry on the inner surface of the side wall and the inner surface of the bottom of the crucible, and spray the above silicon nitride slurry on the bottom of the crucible again after drying. The thickness of the side wall coating is 2mm, and the thickness of the bottom coating is 3mm.

[0097] According to the ratio of silicon powder: concentrated nitric acid: water equal to 1:1:2, soak the silicon powder ...

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Abstract

The invention discloses a casting method for a polycrystalline silicon ingot. The casting method comprises a crucible pretreatment process and an ingot casting process, wherein the crucible pretreatment process comprises the steps of preparing silicon nitride slurry from silicon nitride powder, silica sol and water, spraying the silicon nitride slurry at the side wall and bottom of a crucible, and spraying other silicon nitride slurry at the bottom of the crucible; and soaking silicon powder in an acid solution with strong oxidizing property for 30-60 minutes, then, separating, washing to be neutral, drying the washed silicon powder, next, preparing slurry from the dried silicon powder, the silica sol and the water, spraying the slurry at the bottom of the obtained crucible, and sintering the treated crucible; and the melting stage of the ingot casting process comprises the step of immediately opening a cage to cool when a silicon material floats from the bottom of the crucible. The polycrystalline silicon ingot produced by using the casting method disclosed by the invention has the characteristics of short production period, low cost, long silicon ingot minority carrier lifetime, high primary silicon material utilization ratio and the like, and the obtained polycrystalline silicon wafer has the characteristics of uniform grain size, small defect density, high photoelectric conversion efficiency and the like.

Description

technical field [0001] The invention relates to the technical field of polycrystalline silicon solar cells, in particular to a method for casting polycrystalline silicon ingots. Background technique [0002] In recent years, with the depletion of non-renewable energy sources, solar cells have been developed rapidly. With the rapid development of the solar cell industry, polysilicon, which is low in cost and suitable for large-scale production, has gradually replaced Czochralski monocrystalline silicon in the solar cell material market and has become one of the most important photovoltaic materials in the industry. However, various defects in cast polysilicon, such as grain boundaries, dislocations, micro-defects, and impurity carbon and oxygen in the material, make the conversion efficiency of polysilicon cells lower than that of Czochralski monocrystalline silicon solar cells, thus becoming a limiting polysilicon solar cell development bottleneck. Therefore, improving the...

Claims

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Application Information

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IPC IPC(8): C30B28/06C30B29/06
Inventor 常传波杨振帮袁聪冯琰
Owner YANGZHOU RONGDE NEW ENERGY TECH
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