Low base crystalline silicon etching liquid additive, etching liquid and method

Abstract

The application provides a low-alkali crystalline silicon etching liquid additive, which comprises glucose, sodium lactate, sodium benzenesulfonate, hydrochloric acid, a sulfonic acid group-containing surfactant and water. The low-alkali crystalline silicon etching liquid additive is added into an etching reaction, so that the weight reduction of the back surface of a silicon wafer is effectively improved, the brightness of the back surface etching is effectively improved, the uniformity is obviously improved, the open circuit voltage of subsequent screen printing is improved, and the photoelectric conversion efficiency of the crystalline silicon cell is improved. In the low-alkali environment, the positive surface protective layer of the crystalline silicon wafer is little corroded, the short-circuit current of the cell is effectively improved, and the photoelectric conversion efficiency of the crystalline silicon cell is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic material preparation, and more particularly to a low-alkali crystalline silicon etching liquid additive, an etching liquid and a method. BACKGROUND

[0002] With the global energy constraints becoming more and more great, the energy problem has become an important factor restricting the global economic development, especially under the trend of global high attention to environmental protection, how to develop new energy markets has become a problem that each country highly values, especially strengthening the use of new energy has become the trend of the times.

[0003] Crystalline silicon solar cells are important new energy and have green environmental protection advantages, so the development of crystalline silicon solar cells must be highly valued. Although China's crystalline silicon solar cells have made important development in general, in the case of increasingly fierce global market, China must vigorously promote the development of high efficiency, low cost and large scale of crystalline silicon cells. For crystalline silicon cells, to reduce cost and improve cell conversion efficiency, the manufacturing process of crystalline silicon cells needs to be continuously improved, and the existing technology often uses high-alkali base liquid when etching crystalline silicon, and the etching rate is not high. SUMMARY

[0004] The present application provides a low-alkali crystalline silicon etching liquid additive, an etching liquid and a method, which can effectively improve the etching efficiency of the back surface of the crystalline silicon and effectively improve the protection of the front surface, reduce the amount of alkali used in production, improve the efficiency of the cell, etc.

[0005] The technical solution of the present application is as follows:

[0006] The present application provides a low-alkali crystalline silicon etching liquid additive, which comprises: glucose, sodium lactate, sodium benzenesulfonate, hydrochloric acid, a sulfonic acid group-containing surfactant and water.

[0007] Preferably, by mass percentage: glucose is 0.1-3.0%, sodium lactate is 2-5%, sodium benzenesulfonate is 8-15%, hydrochloric acid is 0.1-1%, the sulfonic acid group-containing surfactant is 5-8%, and the balance is water.

[0008] Preferably, the sulfonic acid group-containing surfactant is sodium perfluorooctyl sulfonate.

[0009] The present application provides a low-alkali crystalline silicon etching liquid, which comprises the above-mentioned low-alkali crystalline silicon etching liquid additive and a low-alkali base liquid.

[0010] Preferably, the low-alkali base liquid is a 0.2-1% sodium hydroxide aqueous solution or a 0.3-1.5% potassium hydroxide aqueous solution.

[0011] Preferably, the volume ratio of the low-alkali silicon etching solution additive to the low-alkali base liquid is 1:100-300.

[0012] Another aspect of the present invention provides a low-alkali silicon etching method, comprising the following steps:

[0013] By mass percentage, mix 0.1-3.0% glucose, 2-5% sodium lactate, 8-15% sodium benzenesulfonate, 0.1-1% hydrochloric acid, 5-8% sulfonate-containing surfactant and the balance water, control the temperature at 50℃, stir for 2 hours to obtain a low-alkali crystalline silicon alkaline etching additive.

[0014] Prepare a sodium hydroxide base solution at a mass ratio of 0.2-1%, or a potassium hydroxide base solution at a mass ratio of 0.3-1.5%.

[0015] Mix low-alkali silicon etching additive and base solution at a volume ratio of 1:100-300, and heat to a temperature of 60-78℃ to obtain etching solution.

[0016] The silicon wafer to be processed is placed in the etching solution prepared above and reacted for 150-350 seconds to obtain the etched silicon wafer.

[0017] The beneficial effects of this invention are as follows:

[0018] (1) The low-alkali crystalline silicon etching additive of the present invention is added to the etching reaction, which effectively improves the brightness of the back etching and significantly improves the uniformity, which is beneficial to the subsequent screen printing to improve the open circuit voltage and improve the photoelectric conversion efficiency of crystalline silicon cells.

[0019] (3) In a low-alkali environment, the corrosion of the protective layer on the front side of the crystalline silicon wafer is small, which can effectively increase the short-circuit current of the cell and improve the photoelectric conversion efficiency of the crystalline silicon cell.

[0020] (2) Alkali consumption is significantly reduced under low-alkali conditions, which greatly reduces production costs. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a low-alkali silicon etching method, comprising the following steps:

[0023] S1. By mass percentage, mix 0.1-3.0% glucose, 2-5% sodium lactate, 8-15% sodium benzenesulfonate, 0.1-1% hydrochloric acid, 5-8% sulfonate-containing surfactant and the balance deionized water, control the temperature at 50℃, stir for 2 hours to obtain a low-alkali crystalline silicon alkaline etching additive.

[0024] S2. Prepare a sodium hydroxide base solution at a mass ratio of 0.2-1%, or a potassium hydroxide base solution at a mass ratio of 0.3-1.5%.

[0025] S3. Mix low-alkali silicon etching additive and base solution at a volume ratio of 1:100-300, and heat to a temperature of 60-78℃ to obtain etching solution.

[0026] S4. Place the silicon wafer to be processed in the etching solution prepared above and react for 150-350 seconds to obtain the etched silicon wafer.

[0027] The components in this invention function as follows: glucose improves the wettability of the base solution, enabling good interfacial contact between the base solution and the silicon wafer during the reaction, ensuring a continuous and stable reaction; sodium lactate reduces the surface tension of the liquid, allowing bubbles generated during the reaction to quickly detach from the silicon wafer surface; sodium benzenesulfonate accelerates the reaction between the base solution and the silicon wafer; hydrochloric acid adjusts the pH value of the additive, maintaining its stability; and the sulfonate-containing surfactant further reduces the surface tension of the liquid, allowing bubbles generated during the reaction between the base solution and the silicon wafer to detach from the interface and be discharged more quickly. The additives of this invention can effectively reduce the amount of alkali used, thus reducing costs, and while used with a low-alkali base solution, they also improve the photoelectric conversion efficiency of silicon wafer solar cells. Example 1

[0028] Mix 0.1g glucose, 2g sodium lactate, 8g sodium benzenesulfonate, 0.1g hydrochloric acid, 8g sodium perfluorooctyl sulfonate and the balance water to prepare 100g, stir in a water bath at 50℃ for 2 hours to obtain a low-alkali silicon etching additive.

[0029] Prepare a 1% (w / w) sodium hydroxide base solution using electronic-grade sodium hydroxide;

[0030] Take 50 ml of the above-mentioned low-alkali silicon etching additive, mix it with 15000 ml of base solution, heat it to 60-78℃, then place the silicon wafer to be treated in it, react for 150 seconds, and obtain the silicon wafer with complete etching. Example 2

[0031] Mix 3g glucose, 5g sodium lactate, 15g sodium benzenesulfonate, 1g hydrochloric acid, 5g sodium perfluorooctyl sulfonate and the remaining water to prepare 100g, stir in a water bath at 50℃ for 2 hours to obtain a low-alkali silicon etching additive.

[0032] Electron-grade sodium hydroxide was used to prepare a 1.5% potassium hydroxide base solution.

[0033] Take 100ml of the above-mentioned low-alkali silicon etching additive, mix it with 10000ml of base solution, heat it to 60-78℃, then place the silicon wafer to be treated in it, react for 200s, and obtain the silicon wafer with complete etching. Example 3

[0034] Mix 2g glucose, 4g sodium lactate, 10g sodium benzenesulfonate, 0.8g hydrochloric acid, 6g sodium perfluorooctyl sulfonate and the remainder water to prepare 100g, stir in a water bath at 50℃ for 2 hours to obtain a low-alkali silicon etching additive.

[0035] Prepare a 0.2% (w / w) sodium hydroxide base solution using electron-free grade sodium hydroxide;

[0036] Take 50 ml of the above-mentioned low-alkali silicon etching additive, mix it with 10000 ml of base solution, heat it to 60-78℃, then place the silicon wafer to be treated in it, react for 300s, and obtain the silicon wafer with complete etching. Example 4

[0037] Mix 1g glucose, 3g sodium lactate, 15g sodium benzenesulfonate, 0.5g hydrochloric acid, 8g sodium perfluorooctyl sulfonate and the remainder water to prepare 100g, stir in a water bath at 50℃ for 2 hours to obtain a low-alkali silicon etching additive.

[0038] Electron-grade sodium hydroxide was used to prepare a 0.3% potassium hydroxide base solution.

[0039] Take 50 ml of the above-mentioned low-alkali silicon etching additive, mix it with 10000 ml of base solution, heat it to 60-78℃, then place the silicon wafer to be treated in it, react for 350 s, and obtain the silicon wafer with complete etching.

[0040] Comparative Example 1:

[0041] Mix 2g sodium persulfate, 1g citric acid, 0.2g tartaric acid and the remaining water to prepare 100g, stir in a water bath at room temperature (25℃) for 2 hours to obtain a silicon etching additive.

[0042] Prepare a 4% sodium hydroxide base solution using electronic-grade sodium hydroxide;

[0043] Take 50 ml of the above-mentioned silicon etching additive, mix it with 10000 ml of base solution, heat it to 60-78℃, then place the silicon wafer to be treated in it, react for 350 s, and obtain the silicon wafer with complete etching.

[0044] Comparative Example 2:

[0045] Based on Example 4, the difference is that the low-alkaline base solution is replaced with a 4% sodium hydroxide base solution.

[0046] Comparative Example 3

[0047] Based on Example 4, the difference is that sodium perfluorooctane sulfonate is not added.

[0048] When the above-mentioned low-alkali silicon etching additive was applied to the crystalline silicon solar cell manufacturing process, the parameters obtained from the test are shown in the table below:

[0049] Group Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Alkaliper 1% NaOH 1.5% K0H 0.2% NaOH 0.3% K0H 4% NaOH 4% NaOH 0.3% K0H Reaction Slow reaction, bubbles quickly detached, no corrosion on the front side Slow reaction, bubbles quickly detached, no corrosion on the front side Slow reaction, bubbles quickly detached, no corrosion on the front side Slow reaction, bubbles quickly detached, no corrosion on the front side Fast reaction, bubbles quickly detached, slight corrosion on the front side Fast reaction, bubbles quickly detached, corrosion on the front side Slow reaction, bubbles hanging phenomenon, no corrosion on the front side Ref 42.1% 43.3% 43.0% 44.1% 33.4% 34.3% 39.5% Uoc / V 0.7364 0.7367 0.7365 0.7362 0.6643 0 .6813 0.7266 Isc / A 14.135 14.141 14.143 14.145 12.13 12.45 14.119 Eta 26.621% 26.637% 26.662% 26.627% 20.334% 21.456% 24.852%

[0050] Analysis of the table shows that:

[0051] In Comparative Examples 1-2 and existing processes, high-alkali methods are often used to bypass the anisotropic region of the silicon-alkali reaction, achieving uniform silicon etching. However, the rapid reaction between alkali and silicon in a high-alkali environment can easily lead to excessive back-side etching, making the etching rate difficult to control. An excessively fast reaction weakens the protective layer on the front side, resulting in a decrease in short-circuit current. Furthermore, the large number of bubbles generated during the reaction affects the reaction in the upper part of the liquid, causing uneven reaction effects between the upper and lower parts and reducing the performance of various product parameters. Additionally, the high-alkali environment significantly corrodes the front side of the silicon, easily damaging the protective film.

[0052] Examples 1-4 and Comparative Example 3, using a low-alkali environment, effectively avoid the adverse effects of a high-alkali environment, significantly reducing the reaction rate and making it controllable, while simultaneously improving front-side protection. In a low-alkali environment, the reaction between alkali and silicon is slow, and anisotropic corrosion during the reaction easily forms tiny pyramidal structures as residues. Compared to the comparative example, the examples, by adding the surfactant of this invention, reduce or prevent the generation of anisotropy, while increasing wettability to effectively guide away the hydrogen gas generated in the reaction, making the liquid contact with the silicon wafer more efficient and the reaction more uniform. Therefore, this is reflected in improved performance parameters of the product; moreover, it relatively increases the reaction rate on the back side of the crystalline silicon without affecting the protection of the front side.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-alkali silicon etching solution, characterized in that, The material comprises a low-alkali silicon etching solution additive and a low-alkali base solution. The low-alkali silicon etching solution additive, by mass percentage, includes: 0.1-3.0% glucose, 2-5% sodium lactate, 8-15% sodium benzenesulfonate, 0.1-1% hydrochloric acid, 5-8% sulfonate-containing surfactant, and the balance being water; the sulfonate-containing surfactant is sodium perfluorooctyl sulfonate; the low-alkali base solution is an aqueous solution containing 0.2-1% sodium hydroxide or an aqueous solution containing 0.3-1.5% potassium hydroxide.

2. The low-alkali silicon etching solution as described in claim 1, characterized in that, The volume ratio of the low-alkali silicon etching solution additive to the low-alkali base solution is 1:100-300.

3. A low-alkali silicon etching method, characterized in that, Includes the following steps: By mass percentage, mix 0.1-3.0% glucose, 2-5% sodium lactate, 8-15% sodium benzenesulfonate, 0.1-1% hydrochloric acid, 5-8% sulfonate-containing surfactant and the balance water, control the temperature at 50℃, stir for 2 hours to obtain a low-alkali crystalline silicon alkaline etching additive. Prepare a sodium hydroxide base solution at a mass ratio of 0.2-1%, or a potassium hydroxide base solution at a mass ratio of 0.3-1.5%. Mix low-alkali silicon etching additive and base solution at a volume ratio of 1:100-300, and heat to a temperature of 60-78℃ to obtain etching solution. The silicon wafer to be processed is placed in the etching solution prepared above and reacted for 150-350 seconds to obtain the etched silicon wafer.