Preparation method of small-size silver powder for solar cell back silver paste
By adding aluminum compounds to generate aluminum hydroxide precipitate during the silver powder preparation process, the particle size of the silver powder can be controlled, solving the problem of complex preparation processes and difficulty in refining the particle size of silver powder in the existing technology. This achieves the preparation of silver powder with regular and uniform particle size, which is suitable for silver paste on the back of solar cells.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JINCHUAN GROUP CO LTD
- Filing Date
- 2023-05-31
- Publication Date
- 2026-06-30
AI Technical Summary
Existing manufacturing processes are complex and make it difficult to effectively refine the particle size of silver powder used in silver paste on the back of solar cells, thus failing to meet the demand of downstream battery manufacturers for small-particle silver powder.
By employing steps such as preparing an oxidation solution, preparing a surface modifier solution, a reduction process, washing, dispersion, drying, and crushing, aluminum compounds are added to the reaction system to generate aluminum hydroxide precipitate, which inhibits the growth of silver powder grains, controls the particle size, and prepares silver powder with regular and uniform particle size.
The obtained silver powder has uniform particle size, good conductivity, and good compatibility with the paste, meeting the physicochemical performance requirements of the silver paste on the back of solar cells.
Smart Images
Figure CN116689777B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metal powder material preparation technology, specifically a method for preparing small-particle silver powder for silver paste on the back of solar cells. Background Technology
[0002] With the depletion of global petrochemical resources, solar cells have become a new research hotspot. Solar energy, due to its enormous energy output and harmless nature, is considered one of the most promising clean energy sources, and photovoltaic power generation will occupy an important strategic position in the future energy structure. Crystalline silicon solar cells are the most technologically mature among various photovoltaic cells and dominate solar cell applications. The global crystalline silicon solar cell market is growing rapidly, with 350GW of new photovoltaic installations expected globally in 2023, bringing a market worth tens of billions of dollars and ushering in a new development opportunity for the photovoltaic industry.
[0003] While the silver powder used in the back-side silver paste for solar cells has been domestically produced, the downstream paste market is highly competitive with numerous companies offering inconsistent formulations. This results in significant differences in the physicochemical properties of the silver powder required for back-side silver paste, and varying requirements for particle size. Furthermore, as downstream battery manufacturers demand increasingly narrower printing lines in their pastes, the demand for smaller-particle-size silver powder is growing. However, due to the high sintering activity of the silver powder used in the back-side silver paste for solar cells, existing preparation processes, such as chemical reduction and mechanical ball milling, are quite complex, making the development of small-particle-size silver powder challenging. Therefore, there is an urgent need to develop a method to refine the silver powder particle size without altering the surface microstructure, in order to meet the needs of downstream paste manufacturers. Summary of the Invention
[0004] The purpose of this invention is to address the aforementioned problems in the prior art by providing a simple, efficient, and particle size-controlled method for preparing small-particle silver powder for the back side silver paste of solar cells. The prepared silver powder can be used as a conductive filler in the preparation of back side silver paste for solar cells.
[0005] To achieve its purpose, the present invention adopts the following technical solution:
[0006] A method for preparing fine-particle silver powder for silver paste on the back of solar cells includes the following steps:
[0007] (1) Preparation of oxidation solution: Prepare silver nitrate solution by dissolving aluminum compound in silver nitrate solution, wherein the mass ratio of aluminum compound to silver nitrate solution is 1000:1 to 100:1, and stir thoroughly to obtain oxidation solution;
[0008] (2) Preparation of surface modifier solution: Dissolve the surface modifier in ethanol at 35~55℃ to obtain a surface modifier solution with a concentration of 5~10g / L;
[0009] (3) Reduction process: Add a reducing agent to the oxidation solution in step (1). The volume ratio of the reducing agent to the oxidation solution is 1:80~1:40. The reaction is carried out under stirring. When the temperature of the reaction solution reaches 20~35℃, adjust the pH of the reaction solution to 8~10 with hydroxide solution. Then start heating until the reaction solution is clear and the powder agglomerates and turns grayish-white. Stop the reaction and separate the silver powder.
[0010] (4) Washing treatment: Add 500~800L of pure water to the silver powder in step (3) each time and stir and wash until the conductivity of the washing solution is less than 20μs / cm;
[0011] (5) Dispersion, drying and crushing treatment: The washing liquid in step (4) is dried to obtain washed silver powder, and then the surface modifier solution in step (2) is added. The powder is dispersed by electric stirring, and finally dried in an oven and crushed by a mechanical crusher to obtain the finished product of small-particle silver powder for back silver paste.
[0012] As a further preferred embodiment of the technical solution of the present invention, in step (1), the concentration of silver nitrate solution is 0.1~0.5 kg / L.
[0013] Furthermore, in step (1), the aluminum compound is sodium aluminate or aluminum sulfate.
[0014] Furthermore, in step (2), the surface modifier is oleic acid or stearic acid.
[0015] Furthermore, in step (3), the reducing agent is added at a temperature of 20~25℃ for the oxidation solution.
[0016] Furthermore, in step (3), the reducing agent is any one of glycerol, hydrazine hydrate, or ascorbic acid.
[0017] Furthermore, in step (3), the hydroxide is sodium hydroxide or potassium hydroxide.
[0018] Furthermore, in step (5), the electric stirring frequency is 10~15HZ and the stirring time is 10~20min.
[0019] Furthermore, in step (5), the drying temperature is 80~100℃ and the drying time is 16~20h.
[0020] Furthermore, in step (5), the mechanical crushing frequency is 10~20HZ and the crushing time is 5~10min.
[0021] The beneficial effects of this invention are as follows:
[0022] In the synthesis process of silver powder for back-side silver paste in solar cells, this invention adds an aluminum compound. In the reaction system, the aluminum compound reacts with hydroxide to form aluminum hydroxide precipitate, which inhibits the growth of silver powder grains through a modification treatment, thereby refining the silver powder grains. The resulting silver powder does not change its surface microstructure, and the particle size can be controlled according to the amount of aluminum compound added. The product has a regular morphology, uniform particle size, good conductivity, and good compatibility with pastes. It can be used as a conductive filler in the preparation of silver paste for the back side of solar cells, meeting the physicochemical performance requirements of paste manufacturers for silver powder. Attached Figure Description
[0023] Figure 1 SEM image of silver powder prepared by adding 0.4g of aluminum sulfate in Example 1 of this invention;
[0024] Figure 2 SEM image of silver powder prepared by adding 0.8g of aluminum sulfate in Example 2 of this invention;
[0025] Figure 3 This is a SEM image of the silver powder prepared from the compound without aluminum in Comparative Example 1 of this invention. Detailed Implementation
[0026] The preparation method of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0027] The morphology of the crushed samples was detected using a SEM5000 field emission scanning electron microscope, the particle size was analyzed using a Mastersizer3000 laser particle size analyzer, and the specific surface area was analyzed using a JW-DX dynamic nitrogen adsorption surface area analyzer.
[0028] Example 1
[0029] Dissolve 35g of sodium hydroxide in 43.5ml of deionized water to obtain a sodium hydroxide solution, and cool it to 25℃ for later use.
[0030] Dissolve 0.57g of stearic acid in 100ml of ethanol and heat to 55℃ to dissolve, obtaining a surfactant solution for later use.
[0031] Dissolve 100g of silver nitrate in 1L of deionized water. Add 0.4g of aluminum sulfate to the silver nitrate solution. Add 15g of glycerol at 25℃ and stir thoroughly with an electric stirrer. Raise the temperature of the reaction system to 35℃ and add the aforementioned sodium hydroxide solution. At this point, the pH of the solution is 8. Continue heating until the system temperature reaches 70℃. When the solution becomes clear and the powder agglomerates and turns grayish-white, stop the reaction. Centrifuge to separate the silver powder. Add 800L of pure water to the silver powder each time and wash three times with stirring. Drain the washing liquid to obtain washed silver powder. Add a surface modifier solution to the washed silver powder and disperse it with an electric stirrer at a frequency of 15Hz for 10 minutes. Stop dispersing when it is fully dispersed and presents a continuously flowing slurry. Place it in an oven and dry at 90℃ for 18 hours to obtain dried silver powder. Finally, crush it in a mechanical crusher at a frequency of 10Hz for 5 minutes to obtain small-particle silver powder for the back silver paste of solar cells. The physical and chemical properties of silver powder are shown in Table 1.
[0032] Example 2
[0033] Dissolve 29g of potassium hydroxide in 43.5ml of deionized water to obtain a potassium hydroxide solution, and cool it to 25℃ for later use.
[0034] Dissolve 0.57g of oleic acid in 100ml of ethanol and heat to 35℃ to dissolve, obtaining a surfactant solution for later use.
[0035] Dissolve 100g of silver nitrate in 1L of deionized water. Add 0.8g of aluminum sulfate to the silver nitrate solution. Add 10g of hydrazine hydrate at 20℃ and stir thoroughly with an electric stirrer. Raise the temperature of the reaction system to 35℃ and add the aforementioned potassium hydroxide solution. At this point, the pH of the solution is 8. Continue heating until the system temperature reaches 70℃. When the solution becomes clear and the powder agglomerates and turns grayish-white, stop the reaction. Centrifuge to separate the silver powder. Add 500L of pure water to the silver powder each time and wash three times with stirring. Drain the washing liquid to obtain washed silver powder. Add a surface modifier solution to the washed silver powder and disperse it with an electric stirrer at a frequency of 10Hz for 20 minutes. Stop dispersing when it is fully dispersed and presents a continuously flowing slurry. Place it in an oven and dry at 100℃ for 16 hours to obtain dried silver powder. Finally, crush it in a mechanical crusher at a frequency of 20Hz for 10 minutes to obtain small-particle silver powder for the back silver paste of solar cells. The physical and chemical properties of silver powder are shown in Table 1.
[0036] Comparative Example 1: The compound without aluminum, under the same conditions as Example 2.
[0037] Dissolve 29g of potassium hydroxide in 43.5ml of deionized water to obtain a potassium hydroxide solution, and cool it to 25℃ for later use.
[0038] Dissolve 0.57g of oleic acid in 100ml of ethanol and heat to 35℃ to dissolve, obtaining a surfactant solution for later use.
[0039] Dissolve 100g of silver nitrate in 1L of deionized water. Add 10g of hydrazine hydrate to the system at 25℃ and stir thoroughly with an electric stirrer. Dissolve 29g of sodium hydroxide in 43.5ml of deionized water. After the sodium hydroxide solution cools to 25℃, raise the system temperature to 35℃ and pour the sodium hydroxide solution into the silver nitrate solution. At this point, the pH of the system solution is 8. Continue heating. When the system temperature reaches 70℃, the solution becomes clear, and the powder agglomerates and turns grayish-white; stop the reaction. Centrifuge to separate the silver powder. Add 500L of deionized water to the silver powder and wash three times with stirring. The washing solution was dried to obtain washed silver powder. A surface modifier solution was added to the washed silver powder, and it was dispersed for 20 minutes using an electric mixer at a frequency of 10 Hz until it was fully dispersed and formed a continuously flowing slurry. The dispersion was then stopped, and the powder was dried in an oven at 100°C for 16 hours to obtain dried silver powder. Finally, the powder was crushed in a mechanical crusher at a frequency of 20 Hz for 10 minutes to obtain silver powder for use as backing paste in solar cells. The physicochemical properties of the silver powder are shown in Table 1.
[0040] Table 1 Physicochemical Properties of Silver Powder
[0041]
[0042] As shown in Table 1 above, with the increase of aluminum compound content, the particle size of silver powder decreases significantly, while the specific surface area increases. The silver powder products in each embodiment have regular morphology and good dispersibility.
Claims
1. A method for preparing fine-particle silver powder for silver paste on the back of solar cells, characterized in that, An aluminum compound is added to a silver nitrate solution at a mass ratio of 1000:1 to 100:
1. The aluminum compound reacts with hydroxide to form aluminum hydroxide precipitate, which refines the silver powder particle size by inhibiting silver crystal growth. The specific steps include: (1) Preparation of oxidation solution: Prepare silver nitrate solution by dissolving aluminum compound in silver nitrate solution and stirring thoroughly to obtain oxidation solution; the concentration of silver nitrate solution is 0.1~0.5 kg / L; the aluminum compound is sodium aluminate or aluminum sulfate; (2) Preparation of surface modifier solution: Use ethanol as solvent to dissolve the surface modifier at 35~55℃ to obtain a surface modifier solution with a concentration of 5~10g / L; (3) Reduction process: Add a reducing agent to the oxidation solution in step (1), with a volume ratio of reducing agent to oxidation solution of 1:80~1:
40. The reaction is carried out under stirring. When the temperature of the reaction solution reaches 20~35℃, adjust the pH of the reaction solution to 8~10 with hydroxide solution, and then start heating until the reaction solution is clear and the powder agglomerates and turns grayish-white. Stop the reaction and separate the silver powder. The temperature of the oxidation solution is 20~25℃. The reducing agent is any one of glycerol, hydrazine hydrate or ascorbic acid. (4) Washing treatment: Add 500~800L of pure water to the silver powder in step (3) each time and stir and wash until the conductivity of the washing solution is less than 20μs / cm; (5) Dispersion, drying and crushing treatment: The washing liquid in step (4) is dried to obtain washed silver powder, and then the surface modifier solution in step (2) is added. The powder is dispersed by electric stirring, and finally dried in an oven and crushed by a mechanical crusher to obtain the finished product of small-particle silver powder for the back silver paste of solar cells.
2. The method for preparing fine-particle silver powder for back-side silver paste in solar cells as described in claim 1, characterized in that, In step (2), the surface modifier is oleic acid or stearic acid.
3. A method for preparing fine-particle silver powder for back-side silver paste in solar cells as described in claim 1 or 2, characterized in that, In step (3), the hydroxide is sodium hydroxide or potassium hydroxide.
4. A method for preparing fine-particle silver powder for back-side silver paste in solar cells as described in claim 1 or 2, characterized in that, In step (5), the electric stirring frequency is 10~15HZ and the stirring time is 10~20min.
5. A method for preparing fine-particle silver powder for back-side silver paste in solar cells as described in claim 1 or 2, characterized in that, In step (5), the drying temperature is 80~100℃ and the drying time is 16~20h.
6. A method for preparing fine-particle silver powder for back-side silver paste in solar cells as described in claim 1 or 2, characterized in that, In step (5), the mechanical crushing frequency is 10~20HZ and the crushing time is 5~10min.