Preparation method of high-dispersed spherical silver powder for solar cell front silver paste

Abstract

The application discloses a preparation method of high-dispersible spherical silver powder for solar cell front silver paste, and specifically comprises the following steps: (1) preparing a silver-containing solution, with a silver ion concentration of 100-500 g / L; (2) preparing a reducing liquid containing a reducing agent; (3) preparing a pH adjusting solution and adding the pH adjusting solution into the silver-containing solution; (4) preparing a dispersant solution, adding the dispersant solution into the reducing liquid, and then rapidly mixing the silver-containing solution and the reducing liquid to generate silver powder through a reduction reaction, and then performing solid-liquid separation, cleaning, drying at 60-100 DEG C, and crushing and screening to obtain superfine silver powder. The superfine silver powder obtained by the application has good dispersibility, uniform particle size distribution, good sintering activity, and the like, and has the advantages of improving the printing performance of the paste, improving the contact performance between a screen printing electrode and a silicon substrate, reducing the contact resistance, and improving the short-circuit current density (J sc ) and open-circuit voltage (V OC ) of a photovoltaic device, and the like.

Description

Technical Field

[0001] This invention relates to the field of silver powder preparation technology, and specifically to a method for preparing highly dispersed spherical silver powder for use in front-side silver paste of solar cells. Background Technology

[0002] Crystalline silicon solar cells, as highly efficient devices that directly convert solar energy into electrical energy, have been widely used. In recent years, their photoelectric conversion efficiency has been continuously improved through structural adjustments and interface passivation technology optimization. In crystalline silicon solar cells, photogenerated electrons and holes are separated through the pn junction and then collected by the front and back electrodes before being led to the external circuit. The front electrode is formed by screen printing and sintering front silver paste. Therefore, the viscosity, rheology, thixotropy, printability, and sintering activity of the front silver paste are crucial to the conversion efficiency of photovoltaic devices. The front silver paste mainly consists of three parts: silver powder (conductive phase), glass powder (binder phase), and organic dielectric (dispersed phase). The silver powder content exceeds 80%, so the properties of the silver powder are key factors affecting the conductivity and density of the front grid electrode of the device.

[0003] With the continuous iteration of solar cell technology and the development of technologies such as zero-busbar, higher requirements have been placed on the particle size distribution, dispersibility, surface morphology, and sintering activity of silver powder used in photovoltaic front-side silver paste. Therefore, preparing ultrafine silver powder with high dispersion, narrow particle size distribution, and high sintering activity is crucial for reducing the contact resistance of solar cells and improving their photoelectric conversion efficiency. Summary of the Invention

[0004] To address the problems existing in the background technology, the present invention provides a method for preparing highly dispersed spherical silver powder for front-side silver paste of solar cells. The silver powder prepared by this method has good sphericity, narrow particle size distribution, uniform particle size, monodispersity, high tap density, and good sintering activity. It is suitable for conductive paste on the front side of solar cells and is compatible with both PERC and TOP-Con crystalline silicon photovoltaic devices, both of which exhibit high photoelectric conversion efficiency.

[0005] The present invention adopts the following technical solution:

[0006] A method for preparing highly dispersed spherical silver powder for front-side silver paste in solar cells, characterized by comprising the following steps:

[0007] 1) Prepare a silver-containing solution, ensuring that the concentration of silver ions in the solution is 100~500g / L. To control the reaction rate, keep the solution temperature at 30~80℃. The silver-containing solution is a silver nitrate solution or a silver ammonia solution.

[0008] 2) Prepare a reducing agent solution, ensuring that the concentration of the reducing agent in the solution is 50~150g / L, and keep it at 20~80℃ to control the generation and growth of crystal nuclei during the reaction process; the reducing agent is one or a combination of tannic acid and nicotinamide.

[0009] 3) Prepare a pH adjustment solution and add it to the silver-containing solution to adjust the pH of the silver-containing solution to 8-10; the pH adjustment solution is a sodium hydroxide solution or a potassium hydroxide solution.

[0010] 4) Prepare a dispersant solution, ensuring the concentration of the dispersant solution is 2~10g / L. Then add the dispersant solution to the reducing agent solution, stir thoroughly, and keep warm at 20~80℃. The dispersant is one or more combinations of gelatin, gum arabic, PVP, Tween, PEG, oleic acid, and linoleic acid.

[0011] 5) Quickly stir and mix the silver-containing solution and reducing agent solution treated in steps 3) and 4), and check the mixture for the presence of Ag. + Once the reaction is complete, stop stirring. Then, after solid-liquid separation and washing, dry at 60~100℃ for 10~16h, and then pulverize and sieve to obtain ultrafine spherical silver powder.

[0012] The solar cell front-side silver paste prepared by the above method uses highly dispersed spherical silver powder with a silver powder particle size D. 50 The micrometer diameter is 1.3~1.8μm, and the tap density is not less than 5.5g / cm³. 3 Specific surface area not less than 0.45m² 2 / g.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The prepared silver powder has a small particle size (D 90 It has good monodispersity, narrow particle size distribution, high tap density, and micro-wrinkles on the surface, as well as high sintering activity. It overcomes the problems of poor monodispersity, wide particle size distribution, and high crystallinity of silver powder used in current mainstream photovoltaic front-side silver paste, which leads to poor thixotropy, high viscosity, and high sintering temperature of silver paste. Attached Figure Description

[0015] Figure 1 This is a scanning electron microscope image of the spherical silver powder prepared in Example 1 of the present invention at a magnification of 10 μm;

[0016] Figure 2 This is a scanning electron microscope image of the spherical silver powder prepared in Example 1 of the present invention at a magnification of 1 μm;

[0017] Figure 3 This is a scanning electron microscope image of the spherical silver powder prepared in Example 2 of the present invention at a magnification of 10 μm;

[0018] Figure 4 This is a scanning electron microscope image of the spherical silver powder prepared in Example 2 of the present invention at a magnification of 1 μm;

[0019] Figure 5 This is a scanning electron microscope image of the spherical silver powder prepared in Example 3 of the present invention at a magnification of 10 μm;

[0020] Figure 6 This is a scanning electron microscope image of the spherical silver powder prepared in Example 3 of the present invention at a magnification of 1 μm;

[0021] Figure 7 This is a scanning electron microscope image of the spherical silver powder prepared in the comparative example of this invention at a magnification of 10 μm;

[0022] Figure 8 This is a scanning electron microscope image of the spherical silver powder prepared in the comparative example of this invention at a magnification of 1 μm. Detailed Implementation

[0023] The present invention will be further explained and described below with reference to the embodiments.

[0024] Example 1

[0025] Preparation of silver-containing solution: Dissolve 200g of silver nitrate in 2000mL of deionized water in a 5000mL beaker, add 25% ammonia solution with a mass ratio of ammonia solution to silver nitrate of 2:1, stir thoroughly, and keep the temperature at 40±1℃.

[0026] Preparation of reducing agent solution: Dissolve 30 g of nicotinamide in 300 mL of deionized water in a 1000 mL beaker, and keep the temperature at 40±1℃.

[0027] Prepare pH adjuster: Dissolve 2g sodium hydroxide in 20mL deionized water in a 50mL beaker, add to the silver-containing solution, stir thoroughly, and adjust the pH to 8-10;

[0028] Preparation of dispersant solution: Dissolve 0.5g PEG in 20mL deionized water in a 50mL beaker, then add the dispersant solution to the reducing solution, stir thoroughly, and control the temperature at 40±1℃;

[0029] The reducing solution containing the dispersant was quickly poured into the silver-containing solution, stirred thoroughly, and the presence of Ag in the reaction solution was checked. + The reaction was determined to be complete at a certain time, stirring was stopped, and after solid-liquid separation and washing, the mixture was dried at 60℃ for 14 hours, then pulverized and sieved to obtain ultrafine silver powder.

[0030] Example 2

[0031] Preparation of silver-containing solution: Dissolve 200g of silver nitrate in 2000mL of deionized water in a 5000mL beaker, add 25% ammonia water with a mass ratio of ammonia water to silver nitrate of 2:1, stir thoroughly, and keep the temperature at 40±1℃.

[0032] Preparation of reducing agent solution: Dissolve 30g of tannic acid in 300ml of deionized water in a 1000mL beaker, and keep the temperature at 40±1℃.

[0033] Prepare pH adjuster: Dissolve 2g sodium hydroxide in 20mL deionized water in a 50mL beaker, add to the silver-containing solution, stir thoroughly, and adjust the pH to 8-10;

[0034] Preparation of dispersant solution: Dissolve 0.5g PEG in 20mL deionized water in a 50mL beaker, then add the dispersant solution to the reducing solution, stir thoroughly, and control the temperature at 40±1℃;

[0035] The reducing solution containing the dispersant was quickly poured into the silver-containing solution, stirred thoroughly, and the presence of Ag in the reaction solution was checked. + The reaction was determined to be complete at a certain time, stirring was stopped, and after solid-liquid separation and washing, the mixture was dried at 60℃ for 14 hours, then pulverized and sieved to obtain ultrafine silver powder.

[0036] Example 3

[0037] Preparation of silver-containing solution: Dissolve 200g of silver nitrate in 2000mL of deionized water in a 5000mL beaker, add 25% ammonia water with a mass ratio of ammonia water to silver nitrate of 2:1, stir thoroughly, and keep the temperature at 40±1℃.

[0038] Preparation of reducing agent solution: Dissolve 15g nicotinamide and 15g tannic acid in 300mL deionized water in a 1000mL beaker, and keep the temperature at 40±1℃.

[0039] Prepare pH adjuster: Dissolve 2 g sodium hydroxide in 20 mL deionized water in a 50 mL beaker, add to the silver-containing solution, stir thoroughly, and adjust the pH to 8-10;

[0040] Preparation of dispersant solution: Dissolve 0.5g PEG in 20mL deionized water in a 50mL beaker, then add the dispersant solution to the reducing solution, stir thoroughly, and control the temperature at 40±1℃;

[0041] The reducing solution containing the dispersant was quickly poured into the silver-containing solution, stirred thoroughly, and the presence of Ag in the reaction solution was checked. +The reaction was determined to be complete at a certain time, stirring was stopped, and after solid-liquid separation and washing, the mixture was dried at 60 ℃ for 14 hours, then pulverized and sieved to obtain ultrafine silver powder.

[0042] Comparative Example 1

[0043] Preparation of silver-containing solution: Dissolve 200g of silver nitrate in 2000mL of deionized water in a 5000mL beaker, add 25% ammonia water with a mass ratio of ammonia water to silver nitrate of 2:1, stir thoroughly, and keep the temperature at 40±1℃.

[0044] Preparation of reducing agent solution: Dissolve 30g of tannic acid in 300mL of deionized water in a 1000mL beaker, and keep the temperature at 40±1℃.

[0045] Prepare the pH adjuster: Dissolve 2 g of sodium hydroxide in 20 mL of deionized water in a 50 mL beaker, add to the silver-containing solution, and stir thoroughly;

[0046] The reducing solution was quickly poured into the silver-containing solution, stirred thoroughly, and the reaction solution was tested to detect the absence of Ag. + The reaction was determined to be complete at a certain time, stirring was stopped, and after solid-liquid separation and washing, the mixture was dried at 60 ℃ for 14 hours, then pulverized and sieved to obtain ultrafine silver powder.

[0047] The performance comparison of Examples 1-3 and the comparative examples is shown in Table 1 below:

[0048] Table 1 Performance test data of Examples 1-3 and comparative examples

[0049]

[0050] As can be seen from Table 1, the D of silver powder prepared in Examples 1-3 90 All are less than 3μm, and all have a tap density greater than 5.5g / cm³. 3 The comparative silver powder prepared had a wide particle size distribution, D 90 Greater than 3μm, tap density less than 5.5g / cm³ 3 ; and in conjunction with the accompanying drawings, compared to Figure 1-6 , Figure 7 , 8 The silver powder has poor monodispersity and a wide particle size distribution, with very obvious large and small particles. This will result in a high viscosity and poor thixotropy after the silver powder is slurried, which will affect the printing performance after slurry preparation.

Claims

1. A method for preparing highly dispersed spherical silver powder for front-side silver paste in solar cells, characterized in that, Includes the following steps: 1) Prepare a silver-containing solution, wherein the silver-containing solution is a silver ammonia solution, ensuring that the concentration of silver ions in the solution is 100~500g / L, and to control the reaction rate, keep the solution temperature at 30~80℃; 2) Prepare a reducing agent solution, wherein the reducing agent is one or a combination of two of tannic acid and nicotinamide, ensuring that the concentration of the reducing agent in the solution is 50~150g / L, and keep the temperature at 20~80℃ to control the generation and growth of crystal nuclei during the reaction process; 3) Prepare a pH adjustment solution, which is a sodium hydroxide solution or a potassium hydroxide solution, and add it to the silver-containing solution to adjust the pH of the silver-containing solution to 8-10; 4) Prepare a dispersant solution, wherein the dispersant is one or more of gelatin, gum arabic, PVP, Tween, PEG, oleic acid, and linoleic acid, ensuring that the concentration of the dispersant solution is 2~10g / L. Then add the dispersant solution to the reducing agent solution, stir thoroughly, and keep warm at 20~80℃. 5) Quickly stir and mix the silver-containing solution and reducing agent solution treated in steps 3) and 4), and check the mixture for the presence of Ag. + Once the reaction is complete, stop stirring. Then, after solid-liquid separation and washing, dry at 60~100℃ for 10~16h, and then pulverize and sieve to obtain ultrafine spherical silver powder.

2. A highly dispersed spherical silver powder for use in solar cell front-side silver paste prepared by the method described in claim 1, characterized in that, The silver powder particle size D 50 The micrometer diameter is 1.3~1.8μm, and the tap density is not less than 5.5g / cm³. 3 Specific surface area not less than 0.45m² 2 / g.

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