Back polishing additive for reducing alkali consumption and preparation method and application thereof
By using back polishing additives containing a catalyst with a nitrobenzene structure in the alkali-polishing process, the problems of high alkali consumption and limited alkali reduction capacity in the prior art are solved, and more efficient silicon wafer back polishing treatment and cell efficiency improvement are achieved.
Patent Information
- Application Number
- CN202411682904.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-22
- Publication Date
- 2025-02-25
AI Technical Summary
The existing alkali-throwing process consumes a large amount of alkaline solution in the back polishing of silicon wafers, resulting in high environmental pollution and production costs, and the alkali-reducing ability of conventional additives is limited.
The corrosion effect of alkali on the silicon wafer is adjusted by using a catalyst, defoaming agent and preservative containing a nitrobenzene structure to reduce alkali consumption by the interaction force between the surfactant and the surface of the silicon wafer.
The polishing reaction is realized under conditions that are lower than the alkali concentration or consumption required for conventional additives, which significantly reduces alkali consumption and improves the polishing effect of the silicon wafer surface and the conversion efficiency of the cell.
Smart Images
Figure CN119505712A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of silicon wafer back polishing, and in particular relates to a back polishing additive for reducing alkali consumption, and a preparation method and application thereof. Background Art
[0002] The back polishing process is an important step in the production process of photovoltaic cells. The main purpose of this process is to polish the velvet surface on the back of the silicon wafer to change the pyramid structure into a tower base structure. The flat tower base structure can increase the internal reflection of the transmitted light on the back of the silicon wafer, so that the light returns to the inside of the silicon wafer again, thereby increasing the utilization rate of light and improving the photoelectric conversion efficiency. In addition, improving the flatness of the back of the silicon wafer is also conducive to increasing the density and uniformity of the back passivation film, thereby improving the passivation effect.
[0003] There are two main methods for back polishing of silicon wafers: acid polishing and alkaline polishing. Acid polishing uses nitric acid and hydrofluoric acid to etch the back of the silicon wafer, while alkaline polishing uses alkali for etching. At present, the mainstream process uses alkaline polishing for back polishing of silicon wafers. In the alkaline polishing production process, a large amount of alkaline solutions containing sodium hydroxide (NaOH) or potassium hydroxide (KOH) are usually used. The use of these chemicals will produce emissions and cause environmental pollution, and will also have a great negative impact on production costs. In response to these problems, the industry has currently adopted alkaline polishing additives to optimize the alkaline polishing production process. The main function of alkaline polishing additives is to improve the surface flatness of silicon wafers, reduce surface defects, and reduce the alkali consumption during the alkaline polishing process. Although the use of conventional alkaline polishing additives can reduce the amount of alkali to a certain extent, its consumption reduction ability is general. At present, there is no alkaline polishing additive with a significant alkali reduction ability on the market. Therefore, considering the industry competition and the urgent need to reduce costs, increase efficiency and reduce environmental pollution, the market is in urgent need of launching an alkaline polishing additive that can significantly reduce alkali consumption and improve the efficiency of battery cells. Summary of the invention
[0004] Purpose of the invention: In view of the above technical problems, the purpose of the present invention is to provide a back polishing additive for significantly reducing alkali consumption and improving conversion efficiency during alkali polishing production, as well as a preparation method and application thereof. The additive can cause low-concentration NaOH or KOH to fully etch the back of the silicon wafer, thereby improving the polishing effect of the silicon wafer surface. Therefore, compared with conventional alkali polishing additives, the additive of the present invention has a greater alkali reduction ability, and also has a significant gain effect on efficiency, thereby taking into account the dual purposes of environmental protection and cost reduction and efficiency improvement.
[0005] Technical solution: In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:
[0006] A back polishing additive for reducing alkali consumption, the back polishing additive comprising the following components in percentage by mass:
[0007] 0.01%-0.5% of a catalyst containing a nitrobenzene structure, 0.1%-1% of a degassing agent, 0.5%-1.5% of a preservative, and the rest is water.
[0008] Preferably, the back polishing additive comprises the following components in percentage by mass:
[0009] 0.02%-0.1% of a catalyst containing a nitrobenzene structure, 0.1%-0.2% of a degassing agent, 0.5%-0.6% of a preservative, and the rest being water.
[0010] As a specific implementation scheme, the catalyst containing nitrobenzene structure has a structural formula as shown below:
[0011]
[0012] Wherein, R1, R2, R3, R4, R5 are independently selected from H, halogen, alkyl, alkoxy, amine, amide, aldehyde, hydrazine, sulfonic acid / sulfonate, phenol / phenolate, carboxyl or ester.
[0013] As a further embodiment, R1, R2, R3, R4, and R5 are independently selected from H, halogen, C1-C10 alkyl, -NH2, -(CH2) m CONH2, -(CH2) p CHO, -NHNH2, -SO3R6, -OR7 or -COOR8, wherein m and p are natural numbers, and m=0-5, p=0-5, R6 is selected from H or a metal atom, and R7 and R8 are independently selected from H, a metal atom or a C1-C5 alkyl group.
[0014] As a preferred embodiment, R1, R2, R3, R4, and R5 are independently selected from H, halogen, C1-C3 alkyl, -NH2, -CONH2, -CHO, -NHNH2, -SO3R6, -OR7, and -COOR8; R6 is selected from H, Na or K, and R7 and R8 are independently selected from H, Na, K or C1-C2 alkyl; at least three of R1, R2, R3, R4, and R5 are selected from H.
[0015] As a specific embodiment, the defoaming agent is selected from the group consisting of 10 O5) n One or more of the polysaccharide compounds, wherein C6H 10 O5 represents the monosaccharide unit after removing one water molecule, and n represents the number of monosaccharide units in the polysaccharide.
[0016] As a specific embodiment, the defoaming agent is selected from one or a combination of maltose, starch, lactose, cellulose, chitin, inulin, polymannan, and polyxylose.
[0017] As a specific embodiment, the preservative is selected from organic acid compounds; preferably, the preservative is selected from one or a combination of succinic acid or its salts, citric acid or its salts, sorbic acid or its salts, benzoic acid or its salts, propionic acid or its salts, acetic acid or its salts, dehydroacetic acid or its salts, lactic acid or its salts, fumaric acid or its salts, phenylalanine, propyl benzoate, parahydroxybenzoates, and sulfites.
[0018] The present invention also provides a method for preparing the back polishing additive for reducing alkali consumption, comprising the following steps:
[0019] According to the mass percentage, a catalyst containing nitrobenzene structure, a defoaming agent and a preservative are added into water, and the mixture is stirred and mixed evenly to obtain the product.
[0020] The invention also provides application of the back-polishing additive in back-polishing of silicon wafers.
[0021] As a specific implementation, the back polishing additive is used in the alkali polishing reaction of silicon wafers to reduce the alkali consumption.
[0022] As a specific implementation scheme, the application includes:
[0023] (1) dissolving soda ash in water and mixing uniformly to obtain an alkaline solution, and then adding the back polishing additive to the prepared alkaline solution and mixing uniformly to prepare a mixed polishing agent;
[0024] (2) Immerse the silicon wafer in the above mixed polishing agent to perform alkaline polishing reaction.
[0025] As a further implementation:
[0026] In step (1), the alkali is selected from NaOH or KOH; the mass concentration of the alkali solution is 0.2%-0.7%; the mass ratio of the back-polishing additive to the alkali solution is 0.3-1:100;
[0027] In step (2), the temperature of the alkali-blending reaction is controlled between 60-75° C., and the reaction time is between 120 s and 240 s.
[0028] Beneficial effects: Compared with the prior art, the present invention has the following advantages:
[0029] (1) When the additive of the present invention is applied to the alkaline polishing reaction of silicon wafer production, the anisotropic corrosion effect of the alkali on the silicon wafer is adjusted through the interaction between the surfactant and the surface of the silicon wafer. Under the condition that the PN junction on the front side of the silicon wafer is not damaged, the corrosion rate of OH- on the back side of the silicon wafer is promoted. The additive of the present invention can carry out the polishing reaction under the condition of lower alkali concentration or consumption required by conventional additives, and has a greater alkali reduction ability than conventional additives, thereby achieving the purpose of reducing production costs and reducing environmental pollution.
[0030] (2) The silicon wafer surface tower base obtained after alkaline polishing reaction using the additive of the present invention has good flatness and high reflectivity, has a better polishing effect, and has a significant effect on improving battery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 A microscope image of the polished surface of the silicon wafer obtained after the alkaline polishing reaction in Example 2 is shown.
[0032] Figure 2 A microscope image of the polished surface of the silicon wafer obtained after the alkaline polishing reaction in Comparative Example 2 is shown. DETAILED DESCRIPTION
[0033] The present invention is further described by the following examples. These examples are purely illustrative and are only used to specifically describe the present invention and should not be construed as limiting the present invention. The invention is further described below in conjunction with the accompanying drawings and examples:
[0034] Example 1
[0035] Preparation of additives: The additives are composed of 0.1% by mass of sodium m-nitrobenzene sulfonate as a catalyst, 0.2% of maltose (n=2, C 12 H 22 O 11 ), 0.5% of preservative succinic acid and the rest of deionized water are mixed evenly to prepare the product.
[0036] Add 450L of deionized water to a 500L alkaline polishing reaction tank, heat the temperature to 70°C, add 2L of 45% NaOH solution, stir until dissolved to obtain a 0.296% alkaline solution, and then add 1.5L of the additive prepared in the above steps to the alkaline solution to make a mixed polishing agent. After the reaction liquid in the tank circulates evenly, immerse the silicon wafer in the tank for a 200s polishing reaction. After the alkaline polishing reaction is completed, the silicon wafer enters the subsequent battery process preparation process, and finally makes a battery cell, and the electrical performance indicators of the battery cell are tested.
[0037] Comparative Example 1
[0038] Add 450L of deionized water to a 500L alkaline polishing reaction tank, heat the temperature to 70°C, add 2L of 45% NaOH solution, stir until dissolved to obtain a 0.296% alkaline solution, and then add 1.5L of conventional alkaline polishing additives currently available on the market (alkaline polishing additives with perchlorate as the main catalytic component) to the alkaline solution. After the reaction liquid in the tank circulates evenly, immerse the silicon wafer in the tank for a 200s polishing reaction. After the alkaline polishing reaction is completed, the silicon wafer enters the subsequent battery process preparation process, and finally makes a battery cell, and the electrical performance indicators of the battery cell are tested.
[0039] Table 1 shows the average electrical performance data of 1000 cells obtained after alkaline blasting reaction in Example 1 and Comparative Example 1. According to the data in Table 1, under the condition of low alkali dosage, the average efficiency of the cells made using the additive of the present invention is 26.78%, while the average efficiency of the cells made using the conventional additive is 26.43%. The use of the additive of the present invention has an efficiency gain of 0.35% over the conventional additive. Therefore, the use of the additive of the present invention has a significant effect on improving the conversion efficiency of the cell.
[0040] Table 1
[0041] additive Efficiency Eta(%) Open circuit voltage Voc Short circuit current Isc Fill Factor FF Example 1 26.78 0.7373 14.149 85.47 Comparative Example 1 26.43 0.7361 14.152 85.36
[0042] Example 2
[0043] Preparation of additives: The additives are composed of 0.1% by mass of sodium m-nitrobenzene sulfonate as a catalyst, 0.2% of maltose (n=2, C 12 H 22 O 11 ), 0.5% of preservative succinic acid and the rest of deionized water are mixed evenly to prepare the product.
[0044] Add 30L of deionized water to a 40L alkaline polishing reaction tank, heat the temperature to 60°C, add 100g of NaOH, stir until dissolved to obtain a 0.333% alkaline solution, and then add 100g of the additive prepared in the above steps to the alkaline solution. After stirring evenly, a mixed polishing agent is prepared, and the silicon wafer is immersed in the tank for a polishing reaction of 180s. After the reaction is completed, the silicon wafer is dried and characterized and analyzed.
[0045] Example 3
[0046] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the additive was composed of 0.05% by mass of the catalyst sodium p-nitrobenzoate, 0.1% by mass of the defoaming agent lactose (n=2, C 12 H 22 O 11 ), 0.6% of preservative benzoic acid and the balance of deionized water.
[0047] Example 4
[0048] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.07% (mass percentage) of p-nitrobenzenesulfonic acid.
[0049] Example 5
[0050] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.05% (mass percentage) of sodium 2-methoxy-5-nitrophenolate.
[0051] Example 6
[0052] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.04% (mass percentage) of 2-methoxy-4-nitrophenol potassium.
[0053] Example 7
[0054] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.02% (mass percentage) of sodium 3-nitrobenzoate.
[0055] Example 8
[0056] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.08% (mass percentage) of p-nitrobenzoic acid.
[0057] Example 9
[0058] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.05% (mass percentage) of 2-nitroaniline.
[0059] Example 10
[0060] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.03% (mass percentage) of p-chloronitrobenzene.
[0061] Embodiment 11
[0062] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.09% (mass percentage) of sodium 2-nitroaniline-4-sulfonate.
[0063] Example 12
[0064] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.06% (mass percentage) of methyl p-nitrobenzoate.
[0065] Embodiment 13
[0066] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.03% (mass percentage) of 3-nitrobenzamide.
[0067] Embodiment 14
[0068] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.04% (mass percentage) of p-nitrophenyl ethyl ether.
[0069] Embodiment 15
[0070] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.07% (mass percentage) of p-nitrophenylhydrazine.
[0071] Example 16
[0072] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the catalyst in the additive was 0.02% (mass percentage) of 2-nitrobenzaldehyde.
[0073] Comparative Example 2
[0074] The additive and the mixed polishing agent were prepared according to the method of Example 2 for alkaline polishing reaction, except that the additive used was a conventional alkaline polishing additive currently available on the market (an alkaline polishing additive with perchlorate as the main catalytic component).
[0075] The micrograph of the polished surface of the silicon wafer obtained in Example 2 is as follows Figure 1 As shown, the micrograph of the polished surface of the silicon wafer obtained by Comparative Example 2 is as follows Figure 2 The characteristic data of the silicon wafer obtained after the reaction of Example 2-Example 16 and Comparative Example 2 are shown in Table 2. Combined with the data in Table 2, by comparing Figure 1 and Figure 2 It can be concluded that under the condition of low alkali dosage, compared with conventional alkali polishing additives on the market, the silicon wafer polishing surface tower base made using the alkali polishing additive of the present invention (containing nitrobenzene structure catalyst) has better flatness, larger tower base size and higher reflectivity.
[0076] Table 2
[0077] additive Weight loss (g) Reflectivity(%) Tower base size (um) Example 2 0.23 46.24 10-11 Example 3 0.2 45.97 9-10 Example 4 0.24 46.13 10-11 Example 5 0.25 46.09 10-11 Example 6 0.23 45.98 10-11 Example 7 0.19 45.93 10-11 Example 8 0.18 45.78 9-10 Example 9 0.2 45.85 9-10 Example 10 0.22 46.13 10-11 Embodiment 11 0.25 46.29 11-12 Example 12 0.23 46.17 10-11 Embodiment 13 0.21 46.05 10-11 Embodiment 14 0.26 46.31 11-12 Embodiment 15 0.19 45.83 10-11 Example 16 0.24 46.27 11-12 Comparative Example 2 0.15 43.67 8-9
[0078] The above content only describes representative embodiments of the present invention and does not limit the protection scope of the present invention. It should be emphasized that various modifications and optimizations made by technicians in this field without violating the technical principles of the present invention are within the protection scope of the present invention.
Claims
1. A back polishing additive for reducing alkali consumption, characterized in that: The back polishing additive includes the following components in percentage by mass: 0.01%-0.5% of a catalyst containing a nitrobenzene structure, 0.1%-1% of a degassing agent, 0.5%-1.5% of a preservative, and the rest is water.
2. The back polishing additive for reducing alkali consumption according to claim 1, characterized in that: The catalyst containing nitrobenzene structure has a structural formula as shown below: Wherein, R1, R2, R3, R4, and R5 are independently selected from H, halogen, alkyl, alkoxy, amine, amide, aldehyde, hydrazine, sulfonic acid / sulfonate, phenol / phenolate, carboxyl, or ester.
3. The back polishing additive for reducing alkali consumption according to claim 2, wherein R1, R2, R3, R4, and R5 are independently selected from H, halogen, C1-C10 alkyl, -NH2, -(CH2) m CONH2, -(CH2) p CHO, -NHNH2, -SO3R6, -OR7 or -COOR8, wherein m, p are both natural numbers, and m=0-5, p=0-5, R6 is selected from H or a metal atom, and R7 and R8 are independently selected from H, a metal atom or a C1-C5 alkyl group.
4. The back polishing additive for reducing alkali consumption according to claim 2, wherein R1, R2, R3, R4, and R5 are independently selected from H, halogen, C1-C3 alkyl, -NH2, -CONH2, -CHO, -NHNH2, -SO3R6, -OR7, and -COOR8; R6 is selected from H, Na or K, and R7 and R8 are independently selected from H, Na, K or C1-C2 alkyl; at least three of R1, R2, R3, R4, and R5 are selected from H.
5. The back polishing additive for reducing alkali consumption according to claim 1, characterized in that: The defoaming agent is selected from the group consisting of (C6H 10 O5) n One or more of the polysaccharide compounds, wherein C6H 10 O5 represents a monosaccharide unit after removing a water molecule, and n represents the number of monosaccharide units in the polysaccharide; the defoaming agent is selected from one or a combination of maltose, starch, lactose, cellulose, chitin, inulin, polymannan, and polyxylose; the preservative is selected from organic acid compounds; preferably, the preservative is selected from one or a combination of succinic acid or its salts, citric acid or its salts, sorbic acid or its salts, benzoic acid or its salts, propionic acid or its salts, acetic acid or its salts, dehydroacetic acid or its salts, lactic acid or its salts, fumaric acid or its salts, phenylalanine, propyl benzoate, parabens, and sulfites.
6. The method for preparing the back polishing additive for reducing alkali consumption according to any one of claims 1 to 5, characterized in that: The following steps are involved: According to the mass percentage, a catalyst containing nitrobenzene structure, a defoaming agent and a preservative are added into water, and the mixture is stirred and mixed evenly to obtain the product.
7. Use of the back polishing additive according to any one of claims 1 to 5 in back polishing of silicon wafers.
8. The use according to claim 7, characterized in that: The back polishing additive is used in the alkali polishing reaction of silicon wafers and can reduce the alkali consumption.
9. The use according to claim 7, characterized in that: The applications include: (1) dissolving soda ash in water and mixing uniformly to obtain an alkaline solution, and then adding the back polishing additive to the prepared alkaline solution and mixing uniformly to prepare a mixed polishing agent; (2) Immerse the silicon wafer in the above mixed polishing agent to perform alkaline polishing reaction.
10. The use according to claim 9, characterized in that: In step (1), the alkali is selected from NaOH or KOH; the mass concentration of the alkali solution is 0.2%-0.7%; the mass ratio of the back-polishing additive to the alkali solution is 0.3-1:100; In step (2), the temperature of the alkali-blending reaction is controlled between 60-75° C., and the reaction time is between 120 s and 240 s.