Preparation method of spheroid-like polycrystal silver powder for solar cell electrode slurry

Abstract

This invention discloses a method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste, comprising the following steps: S1, preparing solution A: dissolving silver nitrate in deionized water and adding ammonia water with a mass concentration of 25%; S2, preparing solution B: dissolving a reducing agent in water, stirring continuously, and then adding a surfactant and NaOH solution; S3, preparing solution C: dissolving 200-300g of dispersant in water to obtain a base solution; S4, starting stirring, adding solution A and solution B concurrently to solution C at a rate of 0.2-1.2 L / min; S5, separating the silver powder into solid and liquid phases and washing it until the conductivity is <20 μs / cm to obtain a silver powder filter cake; S6, adding a surface treatment agent solution to the silver powder filter cake, stirring evenly, then drying, mechanically dispersing, and sieving to obtain near-spherical silver powder with a particle size of 1.3-2.5 μm.

Description

Technical Field

[0001] This invention relates to the technical field of precious metal material preparation methods, and in particular to a method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste. Background Technology

[0002] Silver powder is a functional powder with excellent electrical conductivity, thermal conductivity, and reflectivity. Due to its unique physical and chemical properties, it has been widely used in various fields, such as electronics, new energy, healthcare, and petrochemicals. Conductive silver powder paste is a key material for the metal electrodes of solar photovoltaic cells, mainly used in the metallization process of the cells. Through precise printing, the silver paste can form a conductive grid on the silicon wafer surface, effectively collecting the current generated by photoelectric conversion. As a conductive phase, silver powder accounts for 80-92% of the mass of the silver paste, and its performance directly affects the photoelectric conversion efficiency of the photovoltaic cell. The particle size distribution, dispersibility, and tap density of silver powder have a significant impact on the photoelectric performance of photovoltaic cells. Silver powder used in photovoltaic cells requires high purity, narrow particle size distribution, high tap density, and good dispersibility.

[0003] Liquid-phase reduction is one of the main methods for preparing silver powder, with advantages such as simple equipment, low cost, high efficiency, high powder purity, and controllable indicators, making it suitable for industrial production. However, silver powder prepared by liquid-phase reduction has disadvantages such as wide particle size distribution, difficulty in sedimentation during washing, and poor dispersibility. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste includes the following steps: S1. Prepare solution A: Dissolve silver nitrate in deionized water and add 25% ammonia solution to bring the volume to 2-3L. Keep the temperature constant at 25-60℃. The amount of silver nitrate used in the silver nitrate solution is 120-180g / L. S2. Prepare solution B: Dissolve the reducing agent in water and stir continuously. Then add the surfactant and NaOH solution and bring the volume to 2-3L. Keep the temperature constant at 25-60℃. The amount of reducing agent is 80-160g / L and the amount of surfactant is 0.1-1g / L. S3. Prepare solution C: Dissolve 200-300g of dispersant in water, bring the volume to 2-3L, and keep the temperature constant at 25-60℃ to obtain the base solution; S4. Turn on the stirrer and add liquids A and B to liquid C in parallel streams at a rate of 0.2-1.2 L / min. After the addition is complete, stir for another 2 minutes to end the reaction. S5. The silver powder is separated into solid and liquid and washed until the conductivity is <20μs / cm to obtain a silver powder filter cake. S6. Add a surface treatment agent solution to the silver powder filter cake, stir evenly, then dry, mechanically disperse, and sieve to obtain spherical silver powder with a particle size of 1.3-2.5μm. The amount of surface treatment agent added is 0.1%-0.6% of the weight of the silver powder.

[0006] In step S2, the reducing agent is any one of ascorbic acid, formaldehyde, glucose, hydrazine hydrate, and hydroquinone.

[0007] In step S2, the surfactant is any one of polyethylene glycol, Tween, erucic acid, and sodium citrate.

[0008] In step S3, the dispersant is any one of polyvinylpyrrolidone, Tween, gelatin, sodium alginate, and gum arabic.

[0009] In step S4, the liquid addition time is 2-10 minutes.

[0010] In step S6, the surface treatment agent is any one of oleic acid, erucic acid, dodecanoic acid, and stearic acid.

[0011] The temperatures of liquids A, B, and C must be kept constant.

[0012] In step S6, mechanical dispersion is performed by ball milling, balling, or mechanical crushing.

[0013] In step S6, the drying temperature is 60-85℃ and the drying time is 8-16h.

[0014] The beneficial effects of this invention are as follows: This invention prepares silver powder for solar cells by preparing a silver ammonia solution, a reducing agent solution, and a dispersant solution, and then adding the silver ammonia solution and the reducing agent solution in parallel flow to the dispersant solution. By controlling parameters such as the temperature of the reaction process, the amount of each reactant involved in the reaction, and the addition rate, silver powder is prepared. The addition of a surfactant improves the dispersibility of the silver powder, and by controlling the reaction rate, silver powder with a narrow particle size distribution, good sphericity, and good dispersibility is obtained. This invention is simple to operate, requires minimal equipment, uses abundant raw materials, and is easy to industrialize. Attached Figure Description

[0015] Figure 1 The image shown is a scanning electron microscope image of the product prepared in Example 1 of this invention. Figure 2The image shown is a scanning electron microscope image of the product prepared in Example 3 of this invention. Figure 3 This is a scanning electron microscope image of the product prepared in Example 4 of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.

[0017] Example 1 A method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste, the preparation process includes the following steps: a. Prepare solution A: Dissolve 250g of silver nitrate in 1.5L of water, add 220g of 25% ammonia solution, bring the volume to 2L, and keep the temperature constant at 30℃. b. Prepare solution B: Dissolve 200g of ascorbic acid in water, stirring continuously. Then add 1.6g of polyethylene glycol and 50g of NaOH solution, and bring the volume to 2L. Maintain the temperature at 30℃. c. Prepare solution C: Dissolve 200g of polyvinylpyrrolidone in water, bring the volume to 2L, and obtain the base solution. Keep the temperature constant at 30℃. d. Turn on the stirrer and add liquids A and B to liquid C in parallel streams at a rate of 0.5 L / min. After the addition is complete, stir for another 2 minutes to end the reaction.

[0018] e. The silver powder is subjected to solid-liquid separation and washed until the conductivity is <20μs / cm to obtain a silver powder filter cake.

[0019] f. A surface treatment agent solution with a mass concentration of 1 g / L was added to the silver powder filter cake. Specifically, 0.5 g of oleic acid was dissolved in 0.5 L of ethylene glycol, stirred evenly, and then dried, mechanically dispersed, and sieved to obtain spherical silver powder with a particle size of 1.3 μm. Its scanning electron microscope image is shown below. Figure 1 As shown.

[0020] Example 2 A method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste includes the following steps: a. Prepare solution A: Dissolve 250g of silver nitrate in 1.5L of water, add 240g of ammonia solution with a mass concentration of 25%, and bring the volume up to 2L. Keep the temperature constant at 40℃. b. Prepare solution B: Dissolve 220g of formaldehyde in water, stirring continuously. Then add 2g of Tween and 50g of NaOH solution, and bring the volume to 2L. Maintain the temperature at 40℃. c. Prepare solution C: Dissolve 200g of gum arabic in water, bring the volume up to 2L to obtain the base solution, and keep the temperature constant at 40℃. d. Turn on the stirrer and add liquids A and B to liquid C in parallel streams at a rate of 0.4 L / min. After the addition is complete, stir for another 2 minutes to end the reaction.

[0021] e. The silver powder is subjected to solid-liquid separation and washed until the conductivity is <20μs / cm to obtain a silver powder filter cake.

[0022] f. Add a surface treatment agent solution with a mass concentration of 0.5 g / L to the silver powder filter cake. Specifically, dissolve 0.8 g of erucic acid in 0.5 L of ethanol and stir until homogeneous. Then dry, mechanically disperse, and sieve to obtain spherical silver powder with a particle size of 1.5 μm.

[0023] Example 3 A method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste includes the following steps: a. Prepare solution A: Dissolve 250g of silver nitrate in 1.5L of water, add 250g of 25% ammonia solution, bring the volume to 2.5L, and keep the temperature constant at 45℃. b. Prepare solution B: Dissolve 230g of glucose in water while stirring continuously. Then add 2.2g of sodium citrate and 50g of NaOH solution, and bring the volume to 2.5L. Maintain the temperature at 45℃. c. Prepare solution C: Dissolve 250g of Tween in water, bring the volume to 2.5L, and keep the temperature at 45℃ to obtain the base solution; d. Turn on the stirrer and add liquids A and B to liquid C in parallel streams at a rate of 0.25 L / min. After the addition is complete, stir for another 2 minutes to end the reaction.

[0024] e. The silver powder is subjected to solid-liquid separation and washed until the conductivity is <20μs / cm to obtain a silver powder filter cake.

[0025] f. A surface treatment agent solution with a mass concentration of 0.5 g / L, wherein the surface treatment agent is dodecanoic acid and the solvent is ethanol, is added to the silver powder filter cake. Then, the mixture is dried, mechanically dispersed, and sieved to obtain spherical silver powder with a particle size of 2.0 μm. Its scanning electron microscope image is shown below. Figure 2 As shown.

[0026] Example 4 A method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste includes the following steps: a. Prepare solution A: Dissolve 400g of silver nitrate in 1.5L of water, add 280g of ammonia solution with a mass concentration of 25%, and bring the volume up to 3L. Keep the temperature constant at 25℃. b. Prepare solution B: Dissolve 240g of hydrazine hydrate in water, stirring continuously. Then add 3g of polyethylene glycol and 65g of NaOH solution, and bring the volume to 3L. Maintain the temperature at 25℃. c. Prepare solution C: Dissolve 300g of gelatin in water and bring the volume up to 3L to obtain the base solution at 25℃. d. Turn on the stirrer and add liquids A and B to liquid C in parallel streams at a rate of 1.2 L / min. After the addition is complete, stir for another 2 minutes to end the reaction.

[0027] e. The silver powder is subjected to solid-liquid separation and washed until the conductivity is <20μs / cm to obtain a silver powder filter cake.

[0028] f. A surface treatment agent solution with a mass concentration of 0.5 g / L, wherein the surface treatment agent is oleic acid and the solvent is ethanol, is added to the silver powder filter cake. Then, the mixture is dried, mechanically dispersed, and sieved to obtain spherical silver powder with a particle size of 2.2 μm. Its scanning electron microscope image is shown below. Figure 3 As shown.

[0029] Example 5 A method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste, the preparation process includes the following steps: a. Prepare solution A: Dissolve 250g of silver nitrate in 1.5L of water, add 220g of 25% ammonia solution, bring the volume to 2L, and keep the temperature constant at 30℃. b. Prepare solution B: Dissolve 200g of ascorbic acid in water, stirring continuously. Then add 1.6g of polyethylene glycol and 50g of NaOH solution, and bring the volume to 2L. Maintain the temperature at 30℃. c. Prepare solution C: Dissolve 200g of polyvinylpyrrolidone in water, bring the volume to 2L, and obtain the base solution. Keep the temperature constant at 30℃. d. Turn on the stirrer and add liquids A and B to liquid C in parallel streams at a rate of 0.5 L / min. After the addition is complete, stir for another 2 minutes to end the reaction.

[0030] e. The silver powder is subjected to solid-liquid separation and washed until the conductivity is <20μs / cm to obtain a silver powder filter cake.

[0031] f. Add a surface treatment agent solution with a mass concentration of 1 g / L to the silver powder filter cake. Specifically, dissolve 0.5 g of oleic acid in 0.5 L of ethylene glycol, stir evenly, then dry, mechanically disperse, and sieve to obtain spherical silver powder with a particle size of 2.5 μm.

[0032] Example 6 A method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste includes the following steps: a. Prepare solution A: Dissolve 250g of silver nitrate in 1.5L of water, add 240g of ammonia solution with a mass concentration of 25%, and bring the volume up to 2L. Keep the temperature constant at 40℃. b. Prepare solution B: Dissolve 220g of formaldehyde in water, stirring continuously. Then add 2g of Tween and 50g of NaOH solution, and bring the volume to 2L. Maintain the temperature at 40℃. c. Prepare solution C: Dissolve 200g of polyvinylpyrrolidone in water, bring the volume to 2L, and obtain the base solution. Keep the temperature constant at 40℃. d. Turn on the stirrer and add liquids A and B to liquid C in parallel streams at a rate of 0.4 L / min. After the addition is complete, stir for another 2 minutes to end the reaction.

[0033] e. The silver powder is subjected to solid-liquid separation and washed until the conductivity is <20μs / cm to obtain a silver powder filter cake.

[0034] f. Add a surface treatment agent solution with a mass concentration of 0.5 g / L to the silver powder filter cake. Specifically, dissolve 0.8 g of erucic acid in 0.5 L of ethanol and stir until homogeneous. Then dry, mechanically disperse, and sieve to obtain spherical silver powder with a particle size of 2.3 μm.

[0035] Example 7 A method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste includes the following steps: a. Prepare solution A: Dissolve 250g of silver nitrate in 1.5L of water, add 250g of 25% ammonia solution, bring the volume to 2.5L, and keep the temperature constant at 45℃. b. Prepare solution B: Dissolve 230g of glucose in water while stirring continuously. Then add 2.2g of sodium citrate and 50g of NaOH solution, and bring the volume to 2.5L. Maintain the temperature at 45℃. c. Prepare solution C: Dissolve 250g of Tween in water, bring the volume to 2.5L, and keep the temperature at 45℃ to obtain the base solution; d. Turn on the stirrer and add liquids A and B to liquid C in parallel streams at a rate of 0.25 L / min. After the addition is complete, stir for another 2 minutes to end the reaction.

[0036] e. The silver powder is subjected to solid-liquid separation and washed until the conductivity is <20μs / cm to obtain a silver powder filter cake.

[0037] f. A surface treatment agent solution with a mass concentration of 0.5 g / L, wherein the surface treatment agent is dodecanoic acid and the solvent is ethanol, is added to the silver powder filter cake. Then, the mixture is dried, mechanically dispersed, and sieved to obtain spherical silver powder with a particle size of 1.5 μm.

[0038] Example 8 A method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste includes the following steps: a. Prepare solution A: Dissolve 400g of silver nitrate in 1.5L of water, add 280g of ammonia solution with a mass concentration of 25%, and bring the volume up to 3L. Keep the temperature constant at 25℃. b. Prepare solution B: Dissolve 240g of hydrazine hydrate in water, stirring continuously. Then add 3g of polyethylene glycol and 65g of NaOH solution, and bring the volume to 3L. Maintain the temperature at 25℃. c. Prepare solution C: Dissolve 300g of gelatin in water and bring the volume up to 3L to obtain the base solution at 25℃. d. Turn on the stirrer and add liquids A and B to liquid C in parallel streams at a rate of 1.2 L / min. After the addition is complete, stir for another 2 minutes to end the reaction.

[0039] e. The silver powder is subjected to solid-liquid separation and washed until the conductivity is <20μs / cm to obtain a silver powder filter cake.

[0040] f. A surface treatment agent solution with a mass concentration of 0.5 g / L, wherein the surface treatment agent is oleic acid and the solvent is ethanol, is added to the silver powder filter cake. Then, the mixture is dried, mechanically dispersed, and sieved to obtain spherical silver powder with a particle size of 2 μm.

[0041] The preparation process of this invention is simple, low-cost, requires minimal equipment, and is easy to industrialize.

[0042] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste, characterized in that, Includes the following steps: S1. Prepare solution A: Dissolve silver nitrate in deionized water and add 25% ammonia solution to bring the volume to 2-3L. Keep the temperature constant at 25-60℃. The amount of silver nitrate used in the silver nitrate solution is 120-180g / L. S2. Prepare solution B: Dissolve the reducing agent in water and stir continuously. Then add the surfactant and NaOH solution and bring the volume to 2-3L. Keep the temperature constant at 25-60℃. The amount of reducing agent is 80-160g / L and the amount of surfactant is 0.1-1g / L. S3. Prepare solution C: Dissolve 200-300g of dispersant in water, bring the volume to 2-3L, and keep the temperature constant at 25-60℃ to obtain the base solution; S4. Turn on the stirrer and add liquids A and B to liquid C in parallel streams at a rate of 0.2-1.2 L / min. After the addition is complete, stir for another 2 minutes to end the reaction. S5. The silver powder is separated into solid and liquid and washed until the conductivity is <20μs / cm to obtain a silver powder filter cake. S6. Add a surface treatment agent solution to the silver powder filter cake, stir evenly, then dry, mechanically disperse, and sieve to obtain spherical silver powder with a particle size of 1.3-2.5μm. The amount of surface treatment agent added is 0.1%-0.6% of the weight of the silver powder.

2. The method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste according to claim 1, characterized in that, In step S2, the reducing agent is any one of ascorbic acid, formaldehyde, glucose, hydrazine hydrate, and hydroquinone.

3. The method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste according to claim 1, characterized in that, In step S2, the surfactant is any one of polyethylene glycol, Tween, erucic acid, and sodium citrate.

4. The method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste according to claim 1, characterized in that, In step S3, the dispersant is any one of polyvinylpyrrolidone, Tween, gelatin, sodium alginate, and gum arabic.

5. The method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste according to claim 1, characterized in that, In step S4, the liquid addition time is 2-10 minutes.

6. The method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste according to claim 1, characterized in that, In step S6, the surface treatment agent is any one of oleic acid, erucic acid, dodecanoic acid, and stearic acid.

7. The method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste according to claim 1, characterized in that, The temperatures of liquids A, B, and C must be kept consistent.

8. The method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste according to claim 1, characterized in that, In step S6, mechanical dispersion is performed by ball milling, balling, or mechanical crushing.

9. The method for preparing near-spherical polycrystalline silver powder for solar cell electrode paste according to claim 1, characterized in that, In step S6, the drying temperature is 60-85℃ and the drying time is 8-16h.

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