Low-temperature electrolysis of sio using ionic liquids 2 Method for preparing high-purity silicon thin film

Abstract

The invention provides a method for preparing a high-purity silicon thin film by electrolyzing SiO2 at a low temperature through ionic liquid. The method includes the following steps that (1) the raw materials, namely, the fluorinated imidazole ionic liquid, cryolite, a hydrofluoric acid solution and silicon dioxide, of an electrolyte are prepared; (2) the electrolyte is prepared in an electrolytic cell, and silicon dioxide is electrolyzed under the inert gas circulation and stirring condition; (3) silicon dioxide is supplemented in the electrolysis process; (4) working electrodes are replaced every 1-2 h; and (5) a silicon film is peeled off, washed and dried. According to the method, silicon electro-deposition can be conducted at a low temperature, and obtained silicon is high in purity; the technical reserve is provided for environment-friendly preparation of low-cost and low-pollution solar-grade silicon thin films.

Description

technical field [0001] The invention belongs to the field of material technology, in particular to a low-temperature electrolysis of SiO using ionic liquid 2 A method for preparing high-purity silicon thin films. Background technique [0002] The rapid development of industry consumes a large amount of fossil fuels and emits a large amount of greenhouse gases. Under the dual pressure of energy and the environment, the development of renewable energy has become a current hot spot and focus; solar photovoltaic power generation is a renewable energy that countries around the world focus on. One of the technologies with the broadest development prospects. [0003] China is very rich in solar energy resources, with a theoretical reserve of 1.7 trillion tons of standard coal per year; according to my country's current plan, the cumulative installed capacity of photovoltaic power generation in China will reach 600GWp by 2050; The installed capacity of electricity will account for ...

AI Technical Summary

Problems solved by technology

[0006] In recent years, many studies have focused on the development of new technologies for the low-cost preparation of solar-grade high-purity silicon, which are divided into the following categories: (1) fluoride systems (such as LiF-KF, NaF-CaF 2 , LiF-KF-NaF, etc.) or chloride system (such as CaCl 2 , NaCl-CaCl 2 -CaO, etc.) as the supporting electrolyte, using silicate or silicon dioxide as the solute to electrodeposit silicon; this process has high energy consumption, discontinuous production, and the use of carbon anodes will bring a certain amount of impurities such as boron and phosphorus into the product silicon, which increases the difficulty for the subsequent physical or chemical purification of silicon; (2) with high-purity SiO 2 As cathode, in CaCl 2 Direct electrodeoxidation in molten salt, solid SiO 2 reduced to silicon; due to SiO 2 The electrical conductivity of the material is poor, resulting in a slow internal reduction rate and incomplete reduction that are not in contact with the cathode conductive filament, and the product Si and the raw material SiO 2 Coexistence, the efficiency is too low; (3) SiCl 4 As a solute, in an ionic liquid (such as 1-ethyl-3-methylimidazole, 1-butyl-2-methylpyrrolidine bisimide, 3-methyl-n-hexylammonium bisimide, etc.) Electrodeposition of Si in medium; due to the silicon source SiCl used 4 is chlorinated or SiO by direct heating of Si 2 Prepared by adding carbochlorination, the reactants of these two chlorination processes Cl 2 and product SiCl 4 Both are toxic substances, requiring additional treatment, long process flow, and high production costs; (4) in organic solvents (such as propylene carbonate, ethylene glycol, a mixture of acetonitrile and tetrahydrofuran, etc.), SiCl 4 / SiHCl 3 Electrodeposition of silicon for solutes

The silicon prepared by this method contains impurities such as C, O, N, and Cl, which cannot meet the purity requirements of solar-grade Si, and there are problems such as weak conductivity of organic solvents, low deposition rate, and volatile electrolytes.

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