High-performance silver powder suitable for TOPCon battery fine grid silver paste, preparation method and silver paste

Abstract

The invention provides high-performance silver powder suitable for TOPCon battery fine grid silver paste, a preparation method of the high-performance silver powder and the silver paste, and belongs to the technical field of photovoltaic materials. The preparation method comprises the steps that a silver salt solution and a composite reducing agent are mixed, a first-stage hydrothermal reaction is carried out at the first temperature, a second-stage hydrothermal reaction is carried out at the second temperature, and silver powder is obtained after centrifugation, washing and drying; wherein the composite reducing agent is selected from a mixture of two of potassium tartrate, sodium sulfite and ferrous sulfate. According to the method, gradual growth and crystallinity improvement of silver crystal nucleuses are achieved through two-stage heating, particle aggregation or uneven morphology caused by rapid reduction is avoided, in addition, the adopted composite reducing agent combination is remarkably superior to a single reducing agent (such as ascorbic acid), and the morphology and particle size distribution of the silver powder can be more accurately regulated and controlled.

Description

Technical Field

[0001] This disclosure belongs to the field of photovoltaic materials technology, specifically relating to a high-performance silver powder and its preparation method suitable for fine grid silver paste in TOPCon cells, and the silver paste itself. Background Technology

[0002] Photovoltaic silver paste is a core material in the metallization process of solar cells, mainly used to prepare the conductive grid lines of the positive / negative electrodes. Silver powder, as the main functional phase of silver paste, directly affects the printability, conductivity, and cell conversion efficiency due to its morphology, particle size, dispersibility, and sintering properties.

[0003] Existing silver powders used in photovoltaic silver pastes still have the following problems: 1. Existing silver powders have insufficient dispersibility, leading to unstable rheological properties of the paste, resulting in problems such as printing grid breakage, high sintering shrinkage, and affecting adhesion during printing; 2. Commonly used reducing agents (such as ascorbic acid, hydrazine hydrate, and sodium borohydride) have a single reduction rate, which easily generates spherical or near-spherical silver powder, making it difficult to precisely control dendritic, lamellar, or porous structures, thus limiting the optimization of the paste sintering window and conductive network; 3. Competing silver powders generally have an FF ≤ 1 in TOPCon cells.

[0004] 82.5%, efficiency improvement has encountered a bottleneck. Summary of the Invention

[0005] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a high-performance silver powder and its preparation method, as well as the silver paste, suitable for TOPCon battery fine grid silver paste.

[0006] One aspect of this disclosure provides a method for preparing high-performance silver powder suitable for fine grid silver paste in TOPCon batteries, the method comprising:

[0007] A silver salt solution was mixed with a composite reducing agent, and a first-stage hydrothermal reaction was carried out at a first temperature, followed by a second-stage hydrothermal reaction at a second temperature. After centrifugation, washing, and drying, silver powder was obtained.

[0008] The composite reducing agent is selected from a mixture of two of potassium tartrate, sodium sulfite, and ferrous sulfate.

[0009] Optionally, the composite reducing agent includes potassium tartrate and sodium sulfite.

[0010] Optionally, the mass ratio of potassium tartrate to sodium sulfite is 1:(0.5-2).

[0011] Optionally, the mass ratio of the silver salt solution to the composite reducing agent is 1:(1.2-2).

[0012] Optionally, in the first stage of hydrothermal reaction, the first temperature is 80-90℃ and the reaction time is 1-2h.

[0013] Optionally, in the second stage of hydrothermal reaction, the second temperature is 100-180℃ and the reaction time is 3-6h.

[0014] Optionally, the silver powder has a D50 particle size of 0.8–1.5 μm and a tap density ≥5.8 g / cm³. 3 Its specific surface area is 0.6-0.9 m². 2 / g.

[0015] In another aspect of this disclosure, a high-performance silver powder suitable for TOPCon battery fine grid silver paste is proposed, wherein the high-performance silver powder is prepared by the preparation method described above.

[0016] In another aspect of this disclosure, a silver paste suitable for fine grids in TOPCon batteries is proposed, the silver paste comprising:

[0017] 85-90 parts by weight of silver powder, wherein the silver powder is the silver powder described above;

[0018] 1-5 parts by weight of glass powder;

[0019] 8-9 parts by weight of organic carrier.

[0020] Optionally, the silver paste has a sintering shrinkage rate ≤15%, a line resistance ≤1.5μΩ·cm, an FF value ≥83%, and a printing linewidth consistency of ±1μm.

[0021] This disclosure presents a high-performance silver powder and its preparation method for fine grid silver paste suitable for TOPCon batteries. The preparation method includes: mixing a silver salt solution with a composite reducing agent, carrying out a first-stage hydrothermal reaction at a first temperature, and a second-stage hydrothermal reaction at a second temperature, followed by centrifugation, washing, and drying to obtain silver powder; wherein the composite reducing agent is selected from a mixture of two of potassium tartrate, sodium sulfite, and ferrous sulfate. Through two-stage heating, the gradual growth of silver crystal nuclei and the improvement of crystallinity are achieved, avoiding particle agglomeration or uneven morphology caused by rapid reduction. The composite reducing agent combination is significantly superior to a single reducing agent (such as ascorbic acid), and can more precisely control the morphology and particle size distribution of the silver powder. Attached Figure Description

[0022] Figure 1 This is a SEM microstructure image of the high-performance silver powder suitable for TOPCon battery fine grid silver paste according to Embodiment 1 of this disclosure.

[0023] Figure 2 This is a SEM microstructure image of the high-performance silver powder suitable for TOPCon battery fine grid silver paste according to Embodiment 1 of this disclosure.

[0024] Figure 3 This is a cross-sectional electron microscope image of the silver paste after sintering according to Embodiment 1 of this disclosure. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0026] In one aspect of this disclosure, a method for preparing high-performance silver powder suitable for fine grid silver paste in TOPCon batteries is proposed. The preparation method includes: mixing a silver salt solution with a composite reducing agent, carrying out a first-stage hydrothermal reaction at a first temperature, carrying out a second-stage hydrothermal reaction at a second temperature, and obtaining silver powder after centrifugation, washing, and drying.

[0027] In the above preparation method, the composite reducing agent is selected from a mixture of two of potassium tartrate, sodium sulfite, and ferrous sulfate.

[0028] This embodiment achieves gradual growth of silver crystal nuclei and improved crystallinity through a two-stage heating process, avoiding particle agglomeration or uneven morphology caused by rapid reduction. The reducing agent is a mixture of two of potassium tartrate, sodium sulfite, and ferrous sulfate. Potassium tartrate provides slow-release reduction capability, controlling the growth rate of silver crystal nuclei, while sodium sulfite enhances dispersion stability and prevents particle agglomeration. This combination is significantly superior to a single reducing agent (such as ascorbic acid), enabling more precise control of the morphology and particle size distribution of the silver powder. Ferrous sulfate, as a morphology modifier, further promotes the formation of spherical particles, reduces irregular morphology, and improves the printing performance and sintering density of the silver powder.

[0029] In some preferred embodiments, the composite reducing agent is preferably potassium tartrate and sodium sulfite. Potassium tartrate, as a slow-release reducing agent, slowly releases silver ions through its complexation effect, controlling the growth rate of silver crystal nuclei and preventing rapid agglomeration, thereby forming spherical particles with uniform particle size. Sodium sulfite, as a dispersing stabilizer, prevents particle agglomeration through electrostatic repulsion and steric hindrance effects, significantly improving the dispersibility of silver powder and solving the problem of broken grid lines in printing.

[0030] As a further preferred option, the mass ratio of potassium tartrate to sodium sulfite is 1:(0.5-2).

[0031] In some other preferred embodiments, the mass ratio of silver salt solution to composite reducing agent is 1:(1.5-2.5).

[0032] In some other preferred embodiments, in the first stage of hydrothermal reaction, the first temperature is 80-90°C and the reaction time is 1-2 hours.

[0033] In some other preferred embodiments, in the second stage of hydrothermal reaction, the second temperature is 100-180°C and the reaction time is 3-6 hours.

[0034] In some other preferred embodiments, the D50 particle size of the silver powder is 0.8–1.5 μm, and the tap density is ≥5.8 g / cm³. 3 Its specific surface area is 0.6-0.9 m². 2 / g.

[0035] Another aspect of this disclosure is to propose a high-performance silver powder suitable for fine grid silver paste in TOPCon batteries. This silver powder is prepared using the preparation method described above. For details of the process, please refer to the above description, which will not be repeated here.

[0036] In another aspect of this disclosure, a silver paste suitable for the fine grid of TOPCon batteries is proposed, the silver paste comprising 85-90 parts by weight of silver powder, 1-5 parts by weight of glass powder and 8-9 parts by weight of organic carrier as described above.

[0037] The silver paste of this embodiment has a sintering shrinkage rate of ≤15% (800℃ / 2min), a line resistance of ≤1.5μΩ·cm, an FF value of ≥83%, a printing line width consistency of ±1μm, and a photoelectric conversion efficiency that is ≥0.3% higher than other conventional silver powders.

[0038] The preparation method of silver powder will be further explained below with reference to specific embodiments:

[0039] Comparative Example 1

[0040] The silver salt solution was mixed with a single reducing agent and subjected to a first-stage hydrothermal reaction at 140°C for 1 hour, followed by a second-stage hydrothermal reaction at 140°C for 4 hours. After rapid cooling, the silver powder was obtained by centrifugation, washing, and drying. The single reducing agent was potassium tartrate, and the molar ratio of Ag to potassium tartrate was 1:2.

[0041] The silver powder prepared in Comparative Example 1 had a relatively low tap density of 4.5 g / ml and a specific surface area of ​​0.63 m². 2 / g. Meanwhile, the preparation samples of Comparative Example 1 were repeated, and it was found that the D50 of the silver powder prepared under the above conditions fluctuated greatly, at 1.5±0.2, and the particle size distribution was wide.

[0042] Comparative Example 2

[0043] Prepare a silver ammonia solution containing 100 g / L silver nitrate and 100 g / L ammonia. Prepare a mixed reducing solution by mixing 71.5 g ascorbic acid and 7.8 g polyvinylpyrrolidone with deionized water. While stirring the mixed reducing solution at high speed, uniformly mix the silver ammonia solution and the mixed reducing solution to react, controlling the reaction temperature at 50℃ and the reaction time at 1 min. Post-treatment of the silver powder after reaction: After the reaction has settled for 45 min, discard the supernatant, then wash the precipitated silver powder with deionized water until the conductivity is less than 20 μS / cm, and then wash twice with anhydrous alcohol. Dry the washed silver powder in a forced-air drying oven at 60℃ for 3 hours. Finally, grind the dried silver powder and sieve it to obtain powder.

[0044] As shown in Table 1, the D50 particle size of the silver powder is 1.42 μm, and the tap density is ≥6.2 g / cm³. 3 The specific surface area is 0.61 m². 2 / g, ablation rate of 0.73% at 538℃.

[0045] As shown in Table 2, this example was made into a fine grid silver paste and printed on a TOPCon cell (M10 size). Its conversion efficiency was 26.01%, the fill factor was 81.7%, the line resistance was 1.85 μΩ·cm, the printing line width uniformity was 3 μm, and the sintering shrinkage rate was 18-22%.

[0046] Example 1

[0047] The silver salt solution was mixed with the composite reducing agent, and a first-stage hydrothermal reaction was carried out at 85°C for 1 hour, followed by a second-stage hydrothermal reaction at 140°C for 3 hours. After rapid cooling, the silver powder was obtained by centrifugation, washing, and drying. The molar ratio of Ag to composite reducing agent was 1:1.8, and the composite reducing agent consisted of potassium tartrate and sodium sulfite, with a mass ratio of potassium tartrate to sodium sulfite of 1:1.

[0048] As shown in Table 1, the D50 particle size of the silver powder is 1.53 μm, and the tap density is ≥5.9 g / cm³. 3 Its specific surface area is 0.45 m². 2 / g, ablation rate of 0.38% at 538℃.

[0049] As shown in Table 2, this example was made into a fine grid silver paste and printed on a TOPCon cell (M10 size). Its conversion efficiency was 26.35%, the fill factor was 83.2%, the line resistance was 1.28 μΩ·cm, the printing line width uniformity was 1 μm, and the sintering shrinkage rate was ≤15%.

[0050] like Figure 1 and Figure 2 As shown, the silver powder exhibits a highly uniform spherical morphology, with smooth particle surfaces and no obvious agglomeration.

[0051] like Figure 3 As shown, the cross-section of the sintered silver electrode reveals a continuous conductive network without pores.

[0052] In summary, the composite reducing agent used in this embodiment promotes the regular growth and dispersion of particles, reduces porosity and agglomeration, thereby increasing the packing density. The high tap density and regular morphology improve the density of the silver paste, reduce contact resistance, and the low specific surface area and low ablation rate reduce porosity after sintering, optimize the conductive network. The low shrinkage rate and high linewidth consistency ensure the accurate patterning of fine grid lines and low line resistance, thereby improving current collection efficiency.

[0053] Table 1. Silver powder parameters for Comparative Example 2 and Example 1

[0054]

[0055] Table 2. Silver paste test results for Comparative Example 2 and Example 1

[0056] batch Conversion efficiency Fill factor Line resistance Example 1 26.35％ 83.2％ 1.28 μΩ·cm Comparative Example 2 26.01％ 81.7％ 1.85 μΩ·cm

[0057] This disclosure proposes a silver powder and its preparation method, which is applicable to fine grid silver paste for TOPCon batteries. Compared with the prior art, it has the following advantages: The preparation process of this disclosure can control the micro-crystallization mode of silver powder and control the reaction rate and particle size, which can control the prepared silver powder crystal grains to be finer and have higher crystallinity, and the silver wire has better conductivity after high-temperature sintering.

[0058] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for preparing high-performance silver powder suitable for fine grid silver paste in TOPCon batteries, characterized in that, The preparation method includes: A silver salt solution was mixed with a composite reducing agent, and a first-stage hydrothermal reaction was carried out at a first temperature, followed by a second-stage hydrothermal reaction at a second temperature. After centrifugation, washing, and drying, silver powder was obtained. The composite reducing agent is selected from a mixture of two of potassium tartrate, sodium sulfite, and ferrous sulfate.

2. The preparation method according to claim 1, characterized in that, The composite reducing agent includes potassium tartrate and sodium sulfite.

3. The preparation method according to claim 2, characterized in that, The mass ratio of potassium tartrate to sodium sulfite is 1:(0.5-2).

4. The preparation method according to claim 1, characterized in that, The mass ratio of the silver salt solution to the composite reducing agent is 1:(1.2-2).

5. The preparation method according to claim 1, characterized in that, In the first stage of hydrothermal reaction, the initial temperature is 80-90℃ and the reaction time is 1-2 hours.

6. The preparation method according to claim 1, characterized in that, In the second stage of hydrothermal reaction, the second temperature is 100-180℃, and the reaction time is 3-6h.

7. The preparation method according to claim 1, characterized in that, The silver powder has a D50 particle size of 0.8–1.5 μm and a tap density ≥5.8 g / cm³. 3 Its specific surface area is 0.6-0.9 m². 2 / g.

8. A high-performance silver powder suitable for fine grid silver paste in TOPCon batteries, characterized in that, The high-performance silver powder is prepared by the preparation method described in any one of claims 1 to 7.

9. A silver paste suitable for fine grids in TOPCon batteries, characterized in that, The silver paste comprises: 85-90 parts by weight of silver powder, wherein the silver powder is the high-performance silver powder as described in claim 8; 1-5 parts by weight of glass powder; 8-9 parts by weight of organic carrier.

10. The silver paste according to claim 9, characterized in that, The silver paste has a sintering shrinkage rate of ≤15%, a line resistance of ≤1.5μΩ·cm, an FF value of ≥83%, and a printing linewidth consistency of ±1μm.

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