Low-alkali crystalline silicon etching liquid additive, etching liquid and method

Abstract

The invention provides a low-alkali crystalline silicon etching liquid additive which comprises glucose, sodium lactate, sodium benzenesulfonate, hydrochloric acid, a sulfonate-containing surfactant and water. When the low-alkali crystalline silicon etching additive is added into an etching reaction, the weight reduction of the back surface of a silicon wafer can be effectively improved, the brightness of back surface etching is effectively improved, the uniformity is obviously improved, the open-circuit voltage can be improved in subsequent silk-screen printing, and the photoelectric conversion efficiency of a crystalline silicon battery is improved. In a low-alkali environment, corrosion to a front protective layer of a crystal silicon wafer is small, short-circuit current of a battery piece can be effectively improved, and photoelectric conversion efficiency of a crystal silicon battery is improved.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic material preparation, and more specifically to a low-alkali crystalline silicon etching solution additive, etching solution and method. Background Art

[0002] As global energy constraints become increasingly severe, energy issues have become an important factor restricting global economic development. Especially as the world attaches great importance to environmental protection, how to open up new energy markets has become an issue that all countries attach great importance to. In particular, strengthening the use of new energy has become a general trend.

[0003] Crystalline silicon solar cells are an important new energy source and have the advantage of being green and environmentally friendly. Therefore, we must attach great importance to the development of crystalline silicon solar cells. Although overall, my country's crystalline silicon solar cells have made important progress, in the context of an increasingly fierce global market, my country must vigorously promote the high-efficiency, low-cost, and large-scale development of crystalline silicon cells. For crystalline silicon cells, in order to reduce costs and improve battery conversion efficiency, it is necessary to continuously improve the manufacturing process of crystalline silicon cells. The existing technology often uses a high-alkali base solution when etching crystalline silicon, and the etching rate is not high. Summary of the invention

[0004] The present invention provides a low-alkali crystalline silicon etching solution additive, etching solution and method, which can effectively improve the etching efficiency of the back side of crystalline silicon and effectively improve the protection of the front side, reduce the amount of alkali used in production, improve battery efficiency, etc.

[0005] The technical solution of the present invention is achieved in this way:

[0006] Another aspect of the present invention provides a low-alkali crystalline silicon etching solution additive, comprising: glucose, sodium lactate, sodium benzenesulfonate, hydrochloric acid, a sulfonate-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%, sulfate-containing surfactant is 5-8%, and the balance is water.

[0008] Preferably, the sulfate-containing surfactant is sodium perfluorooctane sulfonate.

[0009] Another aspect of the present invention provides a low-alkali crystalline silicon etching solution, comprising the above-mentioned low-alkali crystalline silicon etching solution additive and a low-alkali base solution.

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

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

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

[0013] Mixing 0.1-3.0% glucose, 2-5% sodium lactate, 8-15% sodium benzenesulfonate, 0.1-1% hydrochloric acid, 5-8% sulfate-containing surfactant and the balance water by mass percentage, controlling the temperature at 50° C., stirring for 2 hours, and obtaining a low-alkali crystalline silicon alkaline etching additive;

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

[0015] Add low-alkali crystalline silicon etching additive and base liquid in a volume ratio of 1:100-300, and heat to a temperature of 60-78° C. to obtain an etching solution;

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

[0017] The beneficial effects produced by the present invention are:

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

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

[0020] (2) Alkali consumption is significantly reduced in a low-alkali environment, which greatly reduces production costs. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

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

[0024] S2, prepare sodium hydroxide base liquid at a mass ratio of 0.2-1%, or prepare potassium hydroxide base liquid at a mass ratio of 0.3-1.5%;

[0025] S3, adding low-alkali crystalline silicon etching additive and base liquid in a volume ratio of 1:100-300, heating to a temperature of 60-78° C. to obtain an etching solution;

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

[0027] The functions of each component in the present invention are as follows: glucose improves the wettability of the base liquid, allows the base liquid to form a good interface contact with the silicon wafer during the reaction, and ensures that the reaction is carried out continuously and stably; sodium lactate reduces the surface tension of the liquid, allows the bubbles generated during the reaction to quickly detach from the silicon wafer surface; sodium benzenesulfonate accelerates the reaction between the base liquid and the silicon wafer; hydrochloric acid adjusts the pH value of the additive to keep the additive stable; and the sulfonate-containing surfactant further reduces the surface tension of the liquid, and allows the bubbles generated by the reaction of the base liquid and the silicon wafer to detach from the interface and be derived more quickly. The additive of the present invention can effectively reduce the amount of alkali used to reduce costs, and can also improve the photoelectric conversion efficiency of silicon wafer batteries when used with low-alkali base liquid.

[0028] Example 1

[0029] Mix 0.1 g of glucose, 2 g of sodium lactate, 8 g of sodium benzenesulfonate, 0.1 g of hydrochloric acid, 8 g of sodium perfluorooctane sulfonate and the remainder of water to make 100 g, and stir in a water bath at 50° C. for 2 hours to obtain a low-alkali crystalline silicon etching additive;

[0030] Use electronic grade sodium hydroxide to prepare a sodium hydroxide base solution with a mass fraction of 1%;

[0031] 50 ml of the above-mentioned low-alkali crystalline silicon etching additive is measured and mixed with 15000 ml of the base liquid, heated to 60-78° C., and then the crystalline silicon wafer to be treated is placed therein and reacted for 150 seconds to obtain an etched crystalline silicon wafer.

[0032] Example 2

[0033] Mix 3g of glucose, 5g of sodium lactate, 15g of sodium benzenesulfonate, 1g of hydrochloric acid, 5g of sodium perfluorooctane sulfonate and the remainder of water to make 100g, and stir in a water bath at 50°C for 2 hours to obtain a low-alkali crystalline silicon etching additive;

[0034] De-electronized sodium hydroxide is prepared into a 1.5% potassium hydroxide base solution;

[0035] 100 ml of the above-mentioned low-alkali crystalline silicon etching additive is measured and mixed with 10000 ml of the base liquid, heated to 60-78° C., and then the crystalline silicon wafer to be treated is placed therein, reacted for 200 seconds, and an etched crystalline silicon wafer is obtained.

[0036] Example 3

[0037] Mix 2 g of glucose, 4 g of sodium lactate, 10 g of sodium benzenesulfonate, 0.8 g of hydrochloric acid, 6 g of sodium perfluorooctane sulfonate and the remainder of water to make 100 g, and stir in a water bath at 50° C. for 2 hours to obtain a low-alkali crystalline silicon etching additive;

[0038] The de-electronized sodium hydroxide is prepared into a sodium hydroxide base solution with a mass fraction of 0.2%;

[0039] 50 ml of the above-mentioned low-alkali crystalline silicon etching additive is measured and mixed with 10000 ml of the base liquid, heated to 60-78° C., and then the crystalline silicon wafer to be treated is placed therein and reacted for 300 seconds to obtain an etched crystalline silicon wafer.

[0040] Example 4

[0041] Mix 1 g of glucose, 3 g of sodium lactate, 15 g of sodium benzenesulfonate, 0.5 g of hydrochloric acid, 8 g of sodium perfluorooctane sulfonate and the remainder of water to make 100 g, and stir in a water bath at 50° C. for 2 hours to obtain a low-alkali crystalline silicon etching additive;

[0042] De-electronized sodium hydroxide is prepared into a potassium hydroxide base solution with a mass fraction of 0.3%;

[0043] 50 ml of the above-mentioned low-alkali crystalline silicon etching additive is measured and mixed with 10000 ml of the base liquid, heated to 60-78° C., and then the crystalline silicon wafer to be treated is placed therein and reacted for 350 seconds to obtain an etched crystalline silicon wafer.

[0044] Comparative Example 1:

[0045] Mix 2g of sodium persulfate, 1g of citric acid, 0.2g of tartaric acid and the remainder of water to make 100g, and stir in a water bath at room temperature of 25°C for 2 hours to obtain a crystalline silicon etching additive;

[0046] Use electronic grade sodium hydroxide to prepare a 4% by mass sodium hydroxide base solution;

[0047] 50 ml of the above-mentioned crystalline silicon etching additive was measured and mixed with 10000 ml of the base liquid, heated to 60-78° C., and then the crystalline silicon wafer to be processed was placed therein and reacted for 350 seconds to obtain an etched crystalline silicon wafer.

[0048] Comparative Example 2:

[0049] Based on Example 4, the difference is that the low-alkali base solution is replaced with a 4% sodium hydroxide base solution.

[0050] Comparative Example 3

[0051] Based on Example 4, except that no sodium perfluorooctane sulfonate was added.

[0052] When the above-mentioned low-alkali crystalline silicon etching additive is applied to the crystalline silicon cell production process, the test parameters obtained are as follows:

[0053]

[0054] From the analysis table, we can see that:

[0055] In Comparative Examples 1-2 and the existing processes, high alkali is often used to bypass the anisotropic region of the reaction between crystalline silicon and alkali, so that the corrosion of silicon reaches uniformity. However, the reaction rate of alkali and silicon is fast in a high-alkali environment, which easily leads to too much etching on the back side, and the etching rate is fast, which is not easy to control. The reaction rate is too fast, which leads to the weakening of the front side to be protected, causing the short-circuit current to decrease. At the same time, a large number of bubbles will affect the reaction of the upper part of the liquid during the reaction, resulting in different reaction effects between the upper and lower parts, reducing the performance of various parameters of the product; at the same time, the corrosion of the front side of the crystalline silicon is obvious in a high-alkali environment, which easily causes the damage of the protective film on the front side.

[0056] The use of low alkali in Examples 1-4 and Comparative Example 3 can effectively avoid the disadvantages of a high alkali environment, significantly reduce the reaction speed, achieve controllability, and improve the front protection. In a low-alkali environment, the alkali reacts slowly with silicon, and it is easy to form a tiny pyramid structure residue due to anisotropic corrosion during the reaction. Compared with the comparative example, the embodiment reduces or prevents the generation of anisotropy by adding the surfactant of the present invention, and at the same time increases the wettability to effectively guide away the hydrogen generated by the reaction, so that the liquid and the silicon wafer are more effectively in contact, and the reaction is uniform, which is reflected in the improvement of the performance of various parameters of the product; and relatively increases the reaction speed of the back of the crystalline silicon without affecting the protection of the front.

[0057] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-alkali crystalline silicon etching solution additive, characterized in that: include: Glucose, sodium lactate, sodium benzenesulfonate, hydrochloric acid, sulfonate-containing surfactant and water.

2. The low-alkali crystalline silicon etching solution additive according to claim 1, characterized in that: Calculated 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%, sulfate-containing surfactant is 5-8%, and the balance is water.

3. The low-alkali crystalline silicon etching solution additive according to claim 1, characterized in that: The sulfate-containing surfactant is sodium perfluorooctane sulfonate.

4. A low-alkali crystalline silicon etching solution, characterized in that: The invention comprises the low-alkali crystalline silicon etching solution additive and the low-alkali base solution as described in any one of claims 1 to 3.

5. The low-alkali crystalline silicon etching solution according to claim 4, characterized in that: The low-alkali base liquid is an aqueous solution containing 0.2-1% sodium hydroxide, or an aqueous solution containing 0.3-1.5% potassium hydroxide.

6. The low-alkali crystalline silicon etching solution according to claim 4, characterized in that: The volume ratio of the low-alkali crystalline silicon etching solution additive to the low-alkali base solution is 1:100-300.

7. A low-alkali crystalline silicon etching method, characterized in that: The following steps are involved: Mixing 0.1-3.0% glucose, 2-5% sodium lactate, 8-15% sodium benzenesulfonate, 0.1-1% hydrochloric acid, 5-8% sulfate-containing surfactant and the balance water by mass percentage, controlling the temperature at 50° C., stirring for 2 hours, and obtaining a low-alkali crystalline silicon alkaline etching additive; Prepare sodium hydroxide base liquid at a mass ratio of 0.2-1%, or potassium hydroxide base liquid at a mass ratio of 0.3-1.5%; Add low-alkali crystalline silicon etching additive and base liquid in a volume ratio of 1:100-300, and heat to a temperature of 60-78° C. to obtain an etching solution; The crystalline silicon wafer to be processed is placed in the etching solution prepared above and reacted for 150-350 seconds to obtain an etched crystalline silicon wafer.

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