Preparation method of sphere-like silver powder for photovoltaic positive silver electrode

Abstract

The invention relates to the technical field of preparation of silver powder for photovoltaic, in particular to a preparation method of spheroidic silver powder for a photovoltaic positive silver electrode, and aims to solve the problems that the overall series resistance of silver powder paste is high and the application quality of the silver powder paste is reduced due to the fact that the spheroidic silver powder for the photovoltaic positive silver electrode is large in particle gap and poor in mixing effect at present. According to the method, a wet reduction mode is adopted, dispersing agents of different doses are added, under the stirring condition, part of a reducing agent solution is taken and added into a silver-ammonia solution, then the reducing agent solution is poured into the silver-ammonia solution at a time to reduce Ag < + >, after an upper-layer mixed solution becomes clear, Ag < + > is thoroughly reduced, and therefore silver powder slurry is prepared; and washing the silver powder slurry for more than three times, and adding a dispersing agent for surface treatment and drying to finally obtain the spherical-like silver powder with high dispersity and uniform particle size, so that the purposes of high dispersity and uniform particle size distribution of the silver powder are achieved.

Description

Technical Field

[0001] This invention relates to the field of silver powder preparation technology for photovoltaic applications, and specifically to a method for preparing spherical silver powder for photovoltaic positive silver electrodes. Background Technology

[0002] Conductive silver paste for the positive electrode of solar cells is the main material used in solar cell fabrication. Its preparation technology is crucial for improving the photoelectric conversion efficiency of solar cells. Silver powder, as a filler in the conductive paste, has fundamental powder characteristics such as morphology, particle size, specific surface area, tap density, and loose packing density that significantly influence its performance. Among these, silver powder particle size is a key indicator affecting its application in electronic pastes. Currently, silver powder prepared by general processes often has a uniform particle size, resulting in larger gaps between particles and increasing the crosstalk resistance of the silver paste. To reduce the gaps between silver powder particles and increase the tap density, it is usually necessary to synthesize silver powders of different particle sizes separately and then mix them using physical mixing methods. This process is complex, results in poor mixing effects, and makes uniform mixing difficult. Summary of the Invention

[0003] This invention provides a method for preparing spherical silver powder for photovoltaic positive silver electrodes, in order to solve the problems mentioned above.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing near-spherical silver powder for photovoltaic positive silver electrodes, characterized by comprising the following steps: Step 1: Preparation of silver ammonia solution: Dissolve silver nitrate with a concentration of 140g / L-160g / L in deionized water, and mix it with ammonia water with a concentration of 220-240g / L to prepare silver ammonia solution, and then add deionized water to make up to 1.5 L-2.5L.

[0005] Step 2: Dissolve the reducing agent in deionized water to obtain a reducing agent solution with a concentration of 130 g / L-150 g / L.

[0006] Step 3: Add a pH adjuster with a concentration of 80g / L-100g / L to the silver ammonia solution from Step 1 to adjust the pH of the silver ammonia solution to 8.5-10.5.

[0007] Step 4, Reduction: Under the condition of stirring speed of 280rpm-300rpm, take 0-1ml of the reducing agent solution in step 2 and add it to the silver ammonia solution in step 3 to obtain silver powder slurry. Then add the remaining reducing agent solution in step 2 to the silver powder slurry.

[0008] Step 5: Wash the silver powder slurry obtained in Step 4 3-7 times, and add a surfactant at a ratio of 0.5%-1.8% of the mass of silver nitrate in Step 1 for surface treatment and drying to obtain a tap density > 2.83 g / cm³. 3 Spherical silver powder.

[0009] Furthermore, the reducing agent in step 2 is selected from at least one of triethanolamine, glyoxal, ascorbic acid, and hydrazine hydrate.

[0010] Furthermore, the pH adjuster in step 3 is selected from at least one of ammonia, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, sodium carbonate, and sodium hydroxide.

[0011] Furthermore, the surfactant in step 5 is selected from at least one of PVP, Tween-40, and Tween-80.

[0012] The present invention has the following beneficial effects: This invention provides a method for preparing near-spherical silver powder for photovoltaic positive silver electrodes. The method employs a wet reduction process, adding different dosages of dispersant. Under stirring conditions, a portion of the reducing agent solution is added to a silver ammonia solution, followed by the complete reduction of Ag+ ions by pouring the reducing agent solution into the silver ammonia solution. After the upper mixed solution becomes clear, the Ag+ ions are completely reduced, thus preparing a silver powder slurry. The silver powder slurry is then washed at least three times, and a dispersant is added for surface treatment and drying. Finally, near-spherical silver powder with high dispersibility and uniform particle size is obtained, effectively ensuring uniform particle size distribution and high dispersibility, with particle size controlled between 5.69-5.92 μm. This method solves the problem of large interparticle gaps and poor mixing effects in current near-spherical silver powder for photovoltaic positive silver electrodes, leading to high overall series resistance in the silver powder slurry and reduced application quality. The silver powder prepared using this method produces a high-performance silver paste with wide applications in fields such as conductive silver paste for solar cells. Attached Figure Description

[0013] Figure 1 This is a scanning electron microscope image of the spherical silver powder in Embodiment 1 of the present invention.

[0014] Figure 2 This is a scanning electron microscope image of the spherical silver powder in Embodiment 2 of the present invention. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0016] Example 1 Preparation of silver ammonia solution: Take 250g of silver nitrate, add deionized water and dissolve it completely. Mix the ammonia water with the silver nitrate solution to prepare silver ammonia solution, and add water to make up to 2.5L.

[0017] Weigh out 60g of the reducing agent ascorbic acid, add 375ml of deionized water and dissolve completely. Set aside for later use.

[0018] Weigh 2.5g of sodium hydroxide, add 25ml of deionized water, dissolve, and add to the silver ammonia solution to control the pH value of the silver ammonia solution to 8.5.

[0019] Reduction: Under stirring conditions, with the stirring speed controlled at 300 rpm, add 0.1 ml of reducing agent solution to the silver ammonia solution, and then pour the reducing agent solution into the silver ammonia solution all at once to reduce Ag. + Once the upper mixed solution becomes clear, Ag + The reduction was complete, and spherical silver powder was prepared.

[0020] The silver powder slurry obtained from the reduction was washed three times with deionized water, surface-treated with Tween-40, and dried to obtain spherical silver powder with high dispersibility and uniform particle size. The scanning electron microscope image of the obtained spherical silver powder is shown below. Figure 1 As shown.

[0021] Example 2 Preparation of silver ammonia solution: Take 250g of silver nitrate, add deionized water and dissolve it completely. Mix the ammonia water with the silver nitrate solution to prepare silver ammonia solution, and add water to make up to 2.5L.

[0022] Weigh out 60g of the reducing agent ascorbic acid, add 375ml of deionized water and dissolve completely, then set aside for later use.

[0023] Weigh 2.5g of sodium hydroxide, add 25ml of deionized water, dissolve, and add to the silver ammonia solution to control the pH value of the silver ammonia solution to 10.

[0024] Reduction: Under stirring conditions, with the stirring speed controlled at 280 rpm, take 1 ml of reducing agent solution and add it to a concentrated solution. Then, pour the reducing agent solution into the silver ammonia solution in one go to reduce Ag. + Once the upper mixed solution becomes clear, Ag + The reduction was complete, and spherical silver powder was prepared.

[0025] The silver powder slurry obtained from the reduction was washed four times with deionized water, surface-treated with Tween-40, and dried to obtain spherical silver powder with high dispersibility and uniform particle size. The scanning electron microscope image of the obtained spherical silver powder is shown below. Figure 2 As shown.

[0026] The physical properties of the near-spherical silver powder obtained in Examples 1 and 2 are shown in Table 1 after testing.

[0027] Table 1. Physical properties of near-spherical silver powder

Claims

1. A method for preparing near-spherical silver powder for photovoltaic positive silver electrodes, characterized in that, The process includes the following steps: Step 1: Preparation of silver ammonia solution: Dissolve silver nitrate with a concentration of 140g / L-160g / L in deionized water, and mix it with ammonia water with a concentration of 220-240g / L to prepare silver ammonia solution, and then add deionized water to make up to 1.5 L-2.5L. Step 2: Dissolve the reducing agent in deionized water to obtain a reducing agent solution with a concentration of 130 g / L-150 g / L; Step 3: Add a pH adjuster with a concentration of 80g / L-100g / L to the silver ammonia solution from Step 1 to adjust the pH of the silver ammonia solution to 8.5-10.

5. Step 4, Reduction: Under the condition of stirring speed of 280rpm-300rpm, take 0-1ml of the reducing agent solution in step 2 and add it to the silver ammonia solution in step 3 to obtain silver powder slurry. Then add the remaining reducing agent solution in step 2 to the silver powder slurry. Step 5: Wash the silver powder slurry obtained in Step 4 3-7 times, and add a surfactant at a ratio of 0.5%-1.8% of the mass of silver nitrate in Step 1 for surface treatment and drying to obtain a tap density > 2.83 g / cm³. 3 Spherical silver powder.

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