Monocrystalline silicon solar cell alkaline polishing additive and application method thereof
By optimizing the combination of surfactants and defoamers, the problem of bubble adsorption during the alkaline polishing process of monocrystalline silicon solar cells was improved, the flatness of the back surface was increased, and the photoelectric conversion efficiency was enhanced.
Patent Information
- Application Number
- CN202311745705.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-19
- Publication Date
- 2026-02-06
AI Technical Summary
In the alkaline polishing process of monocrystalline silicon solar cells, the "raindrop marks" caused by the adsorption of air bubbles on the silicon wafer surface affect the flatness and thus reduce the photoelectric conversion efficiency.
By using a specific ratio of surfactants, defoamers, reaction promoters and inorganic salts, the types and proportions of defoamers are optimized to improve bubble adsorption. Through the effective combination of defoamers and surfactants, the defoaming effect is optimized and the smoothness of the back surface is improved.
The elimination of "raindrop marks" and the improvement of the flatness of the back surface enhance the photoelectric conversion efficiency of the solar cells.
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Figure CN121471820A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to an alkaline polishing additive for monocrystalline silicon solar cells and its application method, belonging to the field of solar cell technology. Background Technology
[0002] Monocrystalline silicon solar cells have the advantages of simple processing, low cost, and high compatibility with existing battery production lines, making them the mainstream direction for future high-efficiency solar cells.
[0003] Etching and polishing the back of solar cells is an important method to improve the photoelectric conversion efficiency of solar cells. Currently, the mainstream back polishing processes are acid polishing and alkaline polishing. Acid polishing uses a mixture of HF / HNO3 to etch the back of the silicon wafer, but its rapid etching can easily lead to a decrease in flatness, making it difficult to improve cell efficiency. At the same time, it places a heavy burden on wastewater treatment.
[0004] In contrast, alkaline polishing uses inorganic alkali to etch the back of the silicon wafer. The etching rate is controllable, making it easier to achieve better flatness, reducing back surface defects, and improving reflectivity.
[0005] To address the aforementioned issues, the inventors discovered that during the alkaline back polishing process, the bubbles formed by H2 generated from the silicon-alkali reaction adhere to the back surface of the silicon wafer due to the adsorption force on the wafer surface, resulting in "raindrop marks" after alkaline polishing. In severe cases, this can even affect the flatness after polishing, leading to "missed polishing" or "over-polishing," thereby affecting the photoelectric conversion efficiency of the solar cell. Summary of the Invention
[0006] In order to improve the defects in the existing alkaline back polishing process of monocrystalline silicon solar cells, where alkaline polishing affects the flatness, leading to "underpolishing" or "overpolishing", thus affecting the photoelectric conversion efficiency of solar cells, this application provides an alkaline polishing additive for monocrystalline silicon solar cells and its application method.
[0007] This application provides an alkaline polishing additive for monocrystalline silicon solar cells and its application method, employing the following technical solution:
[0008] An alkaline polishing additive for monocrystalline silicon solar cells, comprising the following percentages of substances:
[0009] 0.5-1% surfactant;
[0010] 1.5-2% defoamer;
[0011] 0.5-1% reaction accelerator;
[0012] 0.5-1% inorganic salts;
[0013] The remainder is deionized water.
[0014] Through the above technical solution, this application improves the traditional solution by effectively combining and optimizing the composition of defoamers and surfactants, thereby improving the phenomenon of bubbles adsorbing on the silicon wafer surface during alkaline polishing, thus eliminating "raindrop marks" and improving the flatness of the back surface, thereby further improving the photoelectric conversion efficiency of solar cells.
[0015] Based on this, this application further optimizes the addition ratio of defoamer. Since the defoamer has good compatibility with the system, the defoaming effect is not good, while the defoamer has poor compatibility with the system, the defoaming performance is stronger, but it will cause defects such as pinholes or fisheyes. Therefore, this application optimizes the content of defoamer, thereby balancing the relationship between defoaming effect and back surface flatness, thereby further improving the photoelectric conversion efficiency of solar cells.
[0016] Furthermore, the surfactant is one or more of sodium dodecylbenzenesulfonate, polyethylene glycol, polyoxyethylene ether, sodium lauryl sulfate, lauroyl glutamate, and phenoxylate O.
[0017] Furthermore, the defoamer is one or more of the following: tetramethylsiloxane, polyether-modified silicone oil, organic-modified polysiloxane, polyethylene glycol, polyacrylamide, polyacrylate, and emulsifier.
[0018] Through the above technical solutions, this application improves the defoaming effect by optimizing the types of defoamers and by combining defoamer materials.
[0019] Furthermore, the reaction promoter is one or more of the following: ethylenediaminetetraacetic acid, chloroplatinic acid, tartaric acid, benzoic acid, zinc dimethyl dithiocarbamate, zinc diethyl dithiophosphate, and polyhexamethylene diguanidine hydrochloride.
[0020] Furthermore, the inorganic salt is a combination of sodium chloride, sodium carbonate, sodium bicarbonate, sodium citrate, sodium silicate, and calcium bicarbonate.
[0021] Secondly, this application provides a method for applying alkaline polishing additives to monocrystalline silicon solar cells, including the following application steps:
[0022] After removing the PSG treatment, the silicon wafers are placed in an alkaline treatment solution for a first cleaning process.
[0023] The pre-cleaned silicon wafers are washed with water and then placed in an alkaline polishing tank containing alkaline polishing additives for monocrystalline silicon solar cells for alkaline polishing treatment.
[0024] After alkaline polishing is completed, the product undergoes a second water wash and is then placed in an alkaline treatment solution for a second cleaning process.
[0025] After cleaning, rinse three times with water and place in an acidic solution. After acid washing, rinse with water and dry.
[0026] Furthermore, the alkaline treatment solution is a mixed solution of KOH with a mass fraction of 0.2-0.5% and H2O2 with a mass fraction of 2-5%; the temperature of the primary cleaning treatment and the secondary cleaning treatment are both 45-50℃, and the treatment time is both 60-80s.
[0027] Furthermore, the alkaline polishing solution used in the alkaline polishing treatment includes 0.5-1% by mass of alkaline polishing additives for monocrystalline silicon solar cells and 1-1.5% by mass of NaOH; the alkaline polishing treatment temperature is 60-65℃, and the alkaline polishing treatment time is 200-240s.
[0028] Furthermore, the acidic solution is a 5% (w / w) aqueous HF solution.
[0029] In summary, this application has the following beneficial effects:
[0030] First, this application improves upon traditional methods by effectively combining and optimizing the composition of defoamers and surfactants, thereby reducing the phenomenon of bubbles adsorbing onto the silicon wafer surface during alkaline polishing. This eliminates "raindrop marks" and improves the flatness of the back surface, thus further enhancing the photoelectric conversion efficiency of solar cells.
[0031] Secondly, this application further optimizes the addition ratio of defoamer. Since the defoamer has good compatibility with the system, the defoaming effect is not good. On the other hand, the defoamer has poor compatibility with the system, so the defoaming performance is stronger, but it will cause defects such as pinholes or fisheyes. Therefore, this application optimizes the content of defoamer, thereby balancing the relationship between the defoaming effect and the flatness of the back surface, thereby further improving the photoelectric conversion efficiency of solar cells. Attached Figure Description
[0032] Figure 1 The surface of the silicon wafer after alkaline polishing with the alkaline polishing additive for monocrystalline silicon solar cells prepared in Example 1 of this application;
[0033] Figure 2 Scanning electron microscope image of silicon wafer surface after alkaline polishing with the alkaline polishing additive for monocrystalline silicon solar cells prepared in Example 1 of this application;
[0034] Figure 3 The surface of the silicon wafer after alkaline polishing with the alkaline polishing additive for monocrystalline silicon solar cells prepared in Example 2 of this application;
[0035] Figure 4 A scanning electron microscope was used to examine the surface of a silicon wafer after alkaline polishing with the alkaline polishing additive for monocrystalline silicon solar cells prepared in Example 2 of this application.
[0036] Figure 5The surface of the silicon wafer after alkaline polishing with the alkaline polishing additive for monocrystalline silicon solar cells prepared in Comparative Example 1 of this application;
[0037] Figure 6 Scanning electron microscope image of the silicon wafer surface after alkaline polishing with the alkaline polishing additive prepared in Comparative Example 1 of this application;
[0038] Figure 7 The surface of the silicon wafer after alkaline polishing with the alkaline polishing additive for monocrystalline silicon solar cells prepared in Comparative Example 2 of this application;
[0039] Figure 8 A scanning electron microscope was used to examine the surface of a silicon wafer after alkaline polishing with the alkaline polishing additive prepared in Comparative Example 2 of this application. Detailed Implementation
[0040] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.
[0041] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.
[0042] There are no particular restrictions on the purity of any of the raw materials used in this invention. However, this invention preferably adopts the purity requirements conventional in the field of analytical grade preparation.
[0043] All raw materials of this invention are conventional in the field, and each brand name and abbreviation is clear and distinct in its relevant application. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the brand name, abbreviation and corresponding application.
[0044] Example 1
[0045] This embodiment uses a small-batch testing method for alkaline polishing on the production line, with a total of 5 batches of 400 pieces per batch.
[0046] An alkaline polishing additive for monocrystalline silicon solar cells, comprising:
[0047] 15g sodium lauryl sulfate, 10g phenoxylate O, 30g polyether modified silicone oil, 20g emulsifier, 10g chloroplatinic acid, 15g benzoic acid, 20g sodium chloride, 5g sodium bicarbonate and 5L deionized water.
[0048] A method for applying an alkaline polishing additive to monocrystalline silicon solar cells includes the following steps:
[0049] After removing the PSG treatment, the silicon wafer is placed in a mixed solution of 0.2-0.5% KOH and 2-5% H2O2 by mass, and then cleaned again at 45-50℃ for 60-80 seconds.
[0050] The pre-cleaned silicon wafers are washed with water and then placed in an alkaline polishing tank containing an alkaline polishing additive for monocrystalline silicon solar cells for alkaline polishing treatment. The alkaline polishing solution includes 4.2L of 45% KOH, 1.7L of alkaline polishing additive for monocrystalline silicon solar cells, and 335L of deionized water. The treatment is carried out at a reaction temperature of 63℃ for 200s.
[0051] After the alkaline polishing is completed, after a second water wash, it is then cleaned again at 45-50℃ for 60-80 seconds.
[0052] After cleaning, rinse three times with water and place in a 5% (w / w) HF acidic solution. After acid washing, rinse with water and dry. This completes the alkaline polishing treatment for a single batch. At the same time, add 180ml KOH and 180ml alkaline polishing additive to each batch.
[0053] Example 2
[0054] This embodiment uses a large-scale testing method on the production line for alkaline polishing, with a total of 300 batches of 400 pieces per batch.
[0055] An alkaline polishing additive for monocrystalline silicon solar cells, comprising:
[0056] 600g sodium dodecylbenzenesulfonate, 400g polyoxyethylene ether, 800g polyether-modified silicone oil, 400g polyethylene glycol, 800g emulsifier, 400g polyhexamethylene biguanide hydrochloride, 1000g benzoic acid, 400g sodium chloride, 400g calcium bicarbonate, 200g sodium bicarbonate and 200L deionized water.
[0057] A method for applying an alkaline polishing additive to monocrystalline silicon solar cells includes the following steps:
[0058] After removing the PSG treatment, the silicon wafers were placed in a mixed solution of 0.5% KOH and 5% H2O2 by mass, and then cleaned for 80 seconds at 50°C.
[0059] The pre-cleaned silicon wafers are washed with water and then placed in an alkaline polishing tank containing an alkaline polishing additive for monocrystalline silicon solar cells for alkaline polishing treatment. The alkaline polishing solution includes 4.2L of 45% KOH, 1.7L of alkaline polishing additive for monocrystalline silicon solar cells, and 335L of deionized water. The treatment is carried out at a reaction temperature of 63℃ for 200s.
[0060] After alkaline polishing is completed, the product is washed twice with water, and then cleaned again at 50°C for 80 seconds.
[0061] After cleaning, rinse three times with water and place in a 5% (w / w) HF acidic solution. After acid washing, rinse with water and dry. This completes the alkaline polishing treatment for a single batch. At the same time, add 180ml KOH and 180ml alkaline polishing additive to each batch.
[0062] Comparative Example
[0063] Comparative Example 1
[0064] Compared with Example 1, Comparative Example 1 used 4.2L of 45% KOH, 1.7L of traditional alkaline polishing additive, and 335L of deionized water as the alkaline polishing solution in the alkaline polishing tank. The reaction temperature was set at 63°C, and 180ml of KOH and 180ml of alkaline polishing additive were added for each batch. Each batch was reacted for 200s, and after alkaline polishing, it was washed and dried. All other conditions and steps were the same as in Example 1.
[0065] Comparative Example 2
[0066] Compared with Example 2, Comparative Example 2 used 4.2L of 45% KOH, 1.7L of traditional alkaline polishing additive (JA10V10), and 335L of deionized water as the alkaline polishing solution in the alkaline polishing tank. The reaction temperature was set at 63°C, and 180ml of KOH and 180ml of alkaline polishing additive were added for each batch. Each batch was reacted for 200s. After alkaline polishing, the mixture was washed and dried. All other conditions and steps were the same as in Example 2.
[0067] Performance testing
[0068] The silicon wafers subjected to alkaline polishing in Examples 1-2 and Comparative Examples 1-2 were then used to fabricate crystalline silicon solar cells using the same process, and their performance was tested. The specific testing method was as follows:
[0069] The tests were conducted according to the national standards GB 6493-86 "Standard Solar Cells for Ground Use" and GB6495-86 "Test Methods for Electrical Performance of Ground-Based Solar Cells". The specific test results are shown in Table 1 below:
[0070] Table 1 Performance Test Table
[0071] Test volume Uoc Isc Rs Rsh FF Eta IRev2 Example 1 2000 0.6907 13.824 0.94215 875 82.69 23.707 0.061 Example 2 120000 0.6955 13.570 1.590 880.9 81.39 23.265 0.0396 Comparative Example 1 2000 0.6907 13.824 0.95005 884 82.65 23.694 0.058 Comparative Example 2 120000 0.6964 13.611 1.699 770.8 80.97 23.249 0.0613
[0072] According to Examples 1-2, Comparative Examples 1-2, Table 1 and Figure 1-8 The data will be analyzed and explained.
[0073] Compared with Example 1 and Comparative Example 1, the silicon wafers after alkaline polishing using the alkaline polishing additive for monocrystalline silicon solar cells prepared in the examples of this application showed no "raindrop marks" on their appearance, while the traditional alkaline polishing additive showed obvious "raindrop marks" after alkaline polishing. The base of the tower was indistinguishable, and the experimental group had higher flatness and improved efficiency by 0.013%.
[0074] Comparing Example 2 and Comparative Example 2, the silicon wafers after alkaline polishing with traditional additives in the middle and later stages showed very obvious "raindrop marks," while the silicon wafers after alkaline polishing in Example 2 had a smooth and uniform appearance without "raindrop marks," and the photoelectric conversion efficiency was also improved by 0.016%.
[0075] Therefore, through large-scale experiments, it is demonstrated that the alkaline polishing additive for monocrystalline silicon solar cells of the present invention can make the back of the silicon wafer free of "raindrop marks" after alkaline polishing, making it smoother and improving photoelectric conversion efficiency.
[0076] This demonstrates that by improving upon traditional methods and effectively combining and optimizing the composition of defoamers and surfactants, this application addresses the issue of air bubbles adsorbing onto the silicon wafer surface during alkaline polishing. This eliminates "raindrop marks" while simultaneously improving the flatness of the back surface, thereby further enhancing the photoelectric conversion efficiency of solar cells.
[0077] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.
Claims
1. An alkaline polishing additive for monocrystalline silicon solar cells, characterized in that, Composed of the following percentages of substances: 0.5-1% surfactant; 1.5-2% defoamer; 0.5-1% reaction accelerator; 0.5-1% inorganic salts; The remainder is deionized water.
2. The additive for alkali etching of a single crystal silicon solar cell according to claim 1, wherein The surfactant is one or more of sodium dodecylbenzenesulfonate, polyethylene glycol, polyoxyethylene ether, sodium lauryl sulfate, lauroyl glutamate, and phenoxylate O.
3. The additive for alkali etching of a single crystal silicon solar cell according to claim 1, wherein The defoamer is one or more of the following: tetramethylsiloxane, polyether-modified silicone oil, organic-modified polysiloxane, polyethylene glycol, polyacrylamide, polyacrylate, and emulsifier.
4. The alkaline polishing additive for monocrystalline silicon solar cells according to claim 1, characterized in that, The reaction promoter is one or more of the following: ethylenediaminetetraacetic acid, chloroplatinic acid, tartaric acid, benzoic acid, zinc dimethyl dithiocarbamate, zinc diethyl dithiophosphate, and polyhexamethylene diguanidine hydrochloride.
5. The alkaline polishing additive for monocrystalline silicon solar cells according to claim 1, characterized in that, The inorganic salt is a combination of sodium chloride, sodium carbonate, sodium bicarbonate, sodium citrate, sodium silicate, and calcium bicarbonate.
6. The method of applying the alkaline polishing additive for monocrystalline silicon solar cells according to any one of claims 1-5, characterized in that, The following application steps are included: After removing the PSG-treated silicon wafers, place them in an alkaline treatment solution for a first cleaning process. The pre-cleaned silicon wafers are washed with water and then placed in an alkaline polishing tank containing alkaline polishing additives for monocrystalline silicon solar cells for alkaline polishing treatment. After alkaline polishing is completed, the product undergoes a second water wash and is then placed in an alkaline treatment solution for a second cleaning process. After cleaning, rinse three times with water and place in an acidic solution. After acid washing, rinse with water and dry.
7. The application method of the alkaline polishing additive for monocrystalline silicon solar cells according to claim 6, characterized in that, The alkaline treatment solution is a mixed solution of 0.2-0.5% KOH and 2-5% H2O2 by mass; the temperature of the primary cleaning treatment and the secondary cleaning treatment are both 45-50℃, and the treatment time is 60-80s.
8. The application method of the alkaline polishing additive for monocrystalline silicon solar cells according to claim 6, characterized in that, The alkaline polishing solution used in the alkaline polishing treatment includes 0.5-1% by mass of alkaline polishing additives for monocrystalline silicon solar cells and 1-1.5% by mass of NaOH; the alkaline polishing treatment temperature is 60-65℃, and the alkaline polishing treatment time is 200-240s.
9. The application method of the alkaline polishing additive for monocrystalline silicon solar cells according to claim 6, characterized in that, The acidic solution is a 5% (w / w) aqueous HF solution.