CN107858752A - A kind of crystal silicon Woolen-making liquid and preparation method thereof - Google Patents

Abstract

The invention discloses a crystalline silicon texturing liquid, which comprises, in terms of mass percentage: 30% to 50% of sodium hydroxide; 0.2% to 0.5% of isopropanol; and 0.4% to 0.8% of absolute ethanol %; the content of liquid carbon dioxide is 5% to 10%; the content of sodium hypochlorite is 5% to 10%; the content of alkali catalyst is 2% to 5%; the content of nonionic surfactant is 3% to 8%; the balance is deionized water The present invention also discloses a method for preparing crystalline silicon texturing liquid, comprising the following steps: 1) adding deionized water to the reaction kettle, dissolving sodium hydroxide in deionized water, adding isopropanol and water ethanol; 2) adding liquid carbon dioxide and an alkali catalyst; 3) adding sodium hypochlorite and a nonionic surfactant to obtain a product. The invention can effectively reduce the consumption of conventional organic solvents such as isopropanol and absolute ethanol, greatly reduce the working environment pollution and waste water treatment costs caused by solvent volatilization, and reduce COD and production costs.

Description

A kind of crystal silicon texturing liquid and preparation method thereof

technical field

The invention relates to the technical field of semiconductor texturing, in particular to a crystal silicon texturing liquid and a preparation method thereof.

Background technique

In the information age, with the continuous consumption of energy, the importance of renewable energy will become more and more prominent, such as solar energy, wind energy, tidal energy and other renewable energy. Energy, its rapid development is unprecedented, and my country, as the world's largest photovoltaic industry, is advancing towards a strong country, but its supporting electronic chemicals industry is relatively backward, which seriously restricts the advantageous development of the industrial chain.

Solar cells, also known as photovoltaic cells, are semiconductor devices that directly convert solar light energy into electrical energy. Because they are green and environmentally friendly products, they will not cause environmental pollution, and they are renewable resources. Therefore, in today's energy shortage situation Under the circumstances, solar cells are a new type of energy with broad development prospects.

At present, the preparation process of solar cells has been standardized, and the main steps are as follows:

1. Texturing: Through chemical reaction, the originally bright silicon wafer surface (including the front and back) forms an uneven structure to extend the propagation path on its surface, thereby improving the light absorption efficiency of solar cells.

2. Diffusion junction: After diffusion, the surface of the P-type silicon wafer becomes N-type, forming a PN junction, so that the silicon wafer has a photovoltaic effect. The concentration, depth, and uniformity of diffusion directly affect the electrical properties of solar cells. The total amount of diffused impurities is measured by sheet resistance. The smaller the total amount of impurities, the greater the sheet resistance.

3. Peripheral etching: the purpose of this step is to remove the conductive layer that short-circuits the two ends of the PN junction formed on the edge of the silicon wafer during etching.

4. Deposit anti-reflection film: At present, there are mainly two types of anti-reflection film, silicon nitride film and titanium oxide film, which mainly play the role of anti-reflection and passivation.

5. Printed electrodes.

6. Sintering: to form an alloy between the printed electrode and the silicon wafer.

In the main preparation process of solar cells, the texturing process is the first step process, its main function is to remove the damaged layer on the surface of the silicon wafer, and form a good textured surface on the surface to increase the absorption of light, while ensuring the subsequent Diffusion junction, deposition of anti-reflection film and other processes to ensure the efficiency of solar cells after screen sintering, so the size, shape, uniformity and brightness of the silicon wafer surface after the texturing process have a great impact on the entire solar energy The production of the cell and its final conversion efficiency have a crucial impact.

During the silicon wafer texturing production process, solution failure is the main reason for the fluctuation of the production process. The reason for the failure lies in the continuous consumption of NaOH and the continuous production of Na2SiO3 during the reaction process, which leads to a decrease in the concentration of the reactant -OH, and the surface of the silicon wafer cannot communicate with it. Obtain a sufficient contact rate; and because the reaction is carried out at a high temperature of about 80 to 90 degrees, a violent reaction often occurs to generate a large number of bubbles, and the resulting suede is not ideal.

But the existing traditional technology generally suppresses the progress of the reaction by adding sodium silicate and IPA (isopropanol), controls the reaction rate, thereby obtains a relatively good suede state, and the publication number is CN 104282796B "a kind of silicon crystal Texturing solution and its preparation method", which uses a large amount of isopropanol and absolute ethanol to inhibit the reaction, thereby making the texture better, but the use of a large amount of isopropanol and absolute ethanol will cause environmental pollution and high cost Wastewater treatment costs, unable to reduce production costs.

Contents of the invention

The object of the present invention is to provide a crystalline silicon texturing liquid and a preparation method thereof, so as to solve the problems raised in the above-mentioned background technology.

To achieve the above object, the present invention provides the following technical solutions:

A crystal silicon texturing liquid, by mass percentage, comprising:

Sodium hydroxide, the content is 30%～50%;

Isopropanol, the content is 0.2% to 0.5%;

Absolute ethanol, the content is 0.4% to 0.8%;

Liquid carbon dioxide, the content is 5% to 10%;

Sodium hypochlorite, the content is 5% to 10%;

Alkali catalyst, the content is 2% to 5%;

Non-ionic surfactant, the content is 3% to 8%;

The balance is deionized water.

Preferably, the nonionic surfactant is composed of sodium citrate, sodium fructose and lignosulfonate in a ratio of 1:1:3 by mass.

A preparation method of crystal silicon texturing liquid, comprising the following steps:

1), add deionized water into the reaction kettle, then dissolve sodium hydroxide in deionized water, then add isopropanol and absolute ethanol in turn;

2), pour the mixed solution obtained in step 1) into the storage tank, and add liquid carbon dioxide and alkali catalyst simultaneously;

3), pressurize and filter the storage tank in step 2), and then add sodium hypochlorite and nonionic surfactant to obtain the product.

Compared with prior art, the beneficial effect of the present invention is:

The present invention promotes the contact rate of Si and -OH by adding liquid carbon dioxide, sodium hypochlorite and an alkali catalyst in the solution, thereby stabilizing the solution system, prolonging the failure period of the solution, stabilizing the process, and widening the process tolerance range, thereby better aligning the crystal Silicon is used for texturing, and the amount of conventional organic solvents isopropanol and absolute ethanol is effectively reduced, greatly reducing the environmental pollution and waste water treatment costs caused by solvent volatilization, and reducing COD and production costs.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Embodiment one:

Add deionized water into the reaction kettle, according to the mass percentage, dissolve 30% sodium hydroxide in deionized water, then add 0.2% isopropanol and 0.4% absolute ethanol in turn, and then pour the mixed solution into the storage tank and add 5% liquid carbon dioxide and 2% alkali catalyst at the same time, then pressurize the storage tank, and finally add 5% sodium hypochlorite and 3% sodium citrate, fructose sodium and lignosulfonate to 1 : 1:3 non-ionic surfactant composed of 3 parts by mass to obtain the texturing liquid.

Use this texturing liquid to make texture on crystal silicon, keep the texture temperature at 80°C, and the texture time is 30 minutes. After the texture is completed, the thickness of crystal silicon is reduced by 6.3 microns, the corrosion effect is better, the reflectivity is reduced, and the corrosion The pits are more uniform.

Embodiment two:

Add deionized water into the reaction kettle, according to the mass percentage, dissolve 50% sodium hydroxide in deionized water, then add 0.5% isopropanol and 0.8% absolute ethanol in turn, then pour the mixed solution into the storage tank In, and add 10% liquid carbon dioxide and 5% alkali catalyst simultaneously, carry out pressurized filtration to storage tank then, finally add 10% sodium hypochlorite and 8% sodium citrate, fructose sodium and lignosulfonate to 1 : 1:3 non-ionic surfactant composed of 3 parts by mass to obtain the texturing liquid.

Use this texturing liquid to make texture on crystal silicon, keep the temperature of texture at 80°C, and the time for texture is 30 minutes. After the texture is completed, the thickness of crystal silicon is reduced by 6.7 microns, the corrosion effect is better, the reflectivity is reduced, and the corrosion The pits are more uniform.

Embodiment three:

Add deionized water into the reaction kettle, according to the mass percentage, dissolve 40% sodium hydroxide in deionized water, then add 0.3% isopropanol and 0.6% absolute ethanol in turn, then pour the mixed solution into the storage tank Inside, and add 8% liquid carbon dioxide and 3% alkali catalyst simultaneously, carry out pressurized filtration to storage tank then, finally add 7% sodium hypochlorite and 5% sodium citrate, fructose sodium and lignosulfonate with 1 : 1:3 non-ionic surfactant composed of 3 parts by mass to obtain the texturing liquid.

Use this texturing liquid to make texture on crystal silicon, keep the texture temperature at 80°C, and the texture time is 30 minutes. After the texture is completed, the thickness of crystal silicon is reduced by 6.5 microns, the corrosion effect is better, the reflectivity is reduced, and the corrosion The pits are more uniform.

The reaction principle of crystalline silicon texturing is shown in the equation: Si+2NaOH+H2O==Na2SiO3+2H2↑. In order to accelerate the contact rate between Si and -OH, sodium hypochlorite is added as an oxidant to oxidize Si to obtain SiO2. According to the equation: SiO2 +2NaOH====Na2SiO3+H2O, it can be obtained that after Si is oxidized, with the use of alkali catalyst, it can react with NaOH faster and further.

And the generation of Na2SiO3 can react with carbon dioxide liquid at the temperature of making texture, such as the equation: CO2+Na2SiO3+H2O==Na2CO3+H2SiO3, wherein Na2CO3 can improve the surface activity of crystal silicon, and the carbon dioxide solution will react Na2CO3 to promote this The equation is accelerated to the right, thereby accelerating the above-mentioned reaction between Si and NaOH, and further accelerating the contact rate between Si and -OH, so as to achieve the purpose of reducing the amount of isopropanol and absolute ethanol, and no longer need Inhibiting the reaction to a large extent can also make the texturing effect better and more uniform.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (3)

1. A crystalline silicon texturing liquid, characterized in that, by mass percentage, comprising: Sodium hydroxide, the content is 30%～50%; Isopropanol, the content is 0.2% to 0.5%; Absolute ethanol, the content is 0.4% to 0.8%; Liquid carbon dioxide, the content is 5% to 10%; Sodium hypochlorite, the content is 5% to 10%; Alkali catalyst, the content is 2% to 5%; Non-ionic surfactant, the content is 3% to 8%; The balance is deionized water. 2. a kind of crystal silicon texturing liquid according to claim 1, is characterized in that: The nonionic surfactant is composed of sodium citrate, sodium fructose and lignosulfonate in a ratio of 1:1:3 by mass. 3. a preparation method of crystal silicon texturing liquid as claimed in claim 1, is characterized in that, comprises the following steps: 1), add deionized water into the reaction kettle, then dissolve sodium hydroxide in deionized water, then add isopropanol and absolute ethanol in turn; 2), pour the mixed solution obtained in step 1) into the storage tank, and add liquid carbon dioxide and alkali catalyst simultaneously; 3), pressurize and filter the storage tank in step 2), and then add sodium hypochlorite and nonionic surfactant to obtain the product.