Organic carrier for conductive silver paste of photovoltaic module, preparation method of organic carrier and conductive silver paste

Abstract

The invention provides an organic carrier for conductive silver paste of a photovoltaic module, a preparation method of the organic carrier and the conductive silver paste, and the organic carrier for the conductive silver paste of the photovoltaic module comprises the following components in percentage by weight: 15%-25% of a high-boiling-point solvent, 50%-65% of a medium-boiling-point solvent, 10%-20% of a low-boiling-point solvent, 1%-2% of polymer resin, 3%-5% of thickening resin, 0.5%-1% of a dispersing agent and 0.3%-0.8% of a coupling agent, the boiling point of the high-boiling-point solvent is 230-260 DEG C, the boiling point of the medium-boiling-point solvent is 200-230 DEG C, and the boiling point of the low-boiling-point solvent is 180-200 DEG C.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic module manufacturing technology, and in particular to an organic carrier for conductive silver paste in photovoltaic modules, its preparation method, and the conductive silver paste. Background Technology

[0002] Traditional conductive silver paste organic carriers mainly consist of ethyl cellulose and terpineol. After printing on the TOPCon polycrystalline silicon layer, the solvent evaporates too quickly, resulting in poor paste leveling and the formation of micropores (porosity > 5%) after the grid lines solidify. Furthermore, incomplete decomposition of organic residues at high temperatures leads to loose grid lines after sintering (density < 90%), resulting in increased contact resistance (> 3.0 mΩ·cm²) and a battery efficiency loss of over 0.2%. While some processes use high-boiling-point solvents to improve leveling, this does not solve the problems of evaporation gradient and resin compatibility. Therefore, it is necessary to design an organic carrier for conductive silver paste in photovoltaic modules, its preparation method, and the conductive silver paste itself to solve the above problems. Summary of the Invention

[0003] The purpose of this invention is to provide an organic carrier for conductive silver paste in photovoltaic modules, its preparation method, and the conductive silver paste.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: an organic carrier for conductive silver paste in photovoltaic modules, comprising the following components in the following weight ratios: 15%-25% high-boiling-point solvent, 50%-65% medium-boiling-point solvent, 10%-20% low-boiling-point solvent, 1%-2% polymer resin, 3%-5% thickening resin, 0.5%-1% dispersant, and 0.3%-0.8% coupling agent, wherein the boiling point of the high-boiling-point solvent is 230-260℃, the boiling point of the medium-boiling-point solvent is 200-230℃, and the boiling point of the low-boiling-point solvent is 180-200℃.

[0005] As a further improvement of the present invention, the high-boiling-point solvent is selected from one or a mixture of two of ethylene glycol phenyl ether acetate and butyl carbitol acetate.

[0006] As a further improvement of the present invention, the medium-boiling solvent is selected from one or more of α-terpineol, β-terpineol, and γ-terpineol.

[0007] As a further improvement of the present invention, the low-boiling-point solvent is selected from one or more of diethylene glycol butyl ether, dipropylene glycol methyl ether, and diethylene glycol isopropyl ether.

[0008] As a further improved technical solution of the present invention, the polymer resin is selected from one of polyamide resin and modified polyamide resin, and the thickening resin is selected from one or more of ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methylcellulose, and methylcellulose.

[0009] As a further improvement of the present invention, the dispersant is a phosphate ester dispersant.

[0010] As a further improvement of the present invention, the coupling agent is a silane coupling agent.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: a conductive silver paste for photovoltaic modules, comprising the following components in the following weight ratios: 75%-85% silver powder, 2%-5% glass powder, and 10%-20% organic carrier for conductive silver paste for photovoltaic modules as described in any one of the above items, wherein the particle size of the silver powder is 0.5-1μm.

[0012] As a further improvement of the present invention, the glass powder is a PbO-B2O3-SiO2 system or a B2O3-SiO2 system.

[0013] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing an organic carrier for conductive silver paste for photovoltaic modules as described in any of the above claims, comprising the following steps: S1. Mix the high-boiling-point solvent, medium-boiling-point solvent and low-boiling-point solvent, heat and stir for 10 min to 1 h, with a stirring speed of 500-1000 rpm and a heating temperature of 40-60℃. S2. Then add the polymer resin and thickening resin in sequence, heat and stir for 1-2 hours, with a stirring speed of 100-300 rpm and a heating temperature of 60-80℃. S3. Cool to 40-60℃, add dispersant and coupling agent and disperse evenly; S4. Filter through a filter with a pore size ≤ 5μm.

[0014] As can be seen from the above technical solutions, the present invention achieves the following technical effects: 1. The organic carrier constructs a three-stage gradient evaporation system—"slow-medium-fast"—through a precise ratio of high-boiling-point, medium-boiling-point, and low-boiling-point solvents. The high-boiling-point solvent, acting as a slow-evaporating component, maintains the leveling properties of the surface paste after silver paste printing, delaying the surface curing rate and providing ample evaporation channels and time for the underlying medium- and low-boiling-point solvents. This design solves the problem of "surface drying first, underlying solvent retention" in traditional single-solvent systems, avoiding defects such as bubbles and pinholes formed when solvent escapes, resulting in a non-porous, continuous, and smooth conductive film layer after silver paste curing. Simultaneously, the gradient evaporation rate matches the drying curve of photovoltaic module printing processes (such as screen printing), ensuring the paste's shaping ability during printing while avoiding problems such as line deformation and edge burrs caused by excessively rapid drying, significantly improving the printability and yield of the silver paste. 2. The polymer resin and thickening resin in the organic carrier form a synergistic reinforcing system. Combined with the assistance of dispersants and coupling agents, this optimizes the film performance. During sintering, the polymer resin undergoes a cross-linking reaction, forming a three-dimensional network carbon skeleton structure. This structure precisely fills the tiny gaps between silver particles, significantly improving the density of the conductive film and enhancing the adhesion between the silver particles and the substrate, preventing film detachment and cracking. The thickening resin, by adjusting the viscosity and thixotropy of the slurry, along with the dispersing effect of the dispersant, ensures uniform dispersion of silver particles in the carrier, preventing agglomeration and further guaranteeing the uniformity and stability of conductivity. The addition of coupling agents optimizes the interfacial compatibility between the organic carrier and the inorganic silver powder and substrate, improving the adhesion and long-term reliability of the film, ensuring that the conductivity of the photovoltaic module does not degrade during long-term outdoor use. 3. The composition design of the organic carrier fully considers the large-scale production needs of the photovoltaic industry. All raw materials are common chemicals widely used in the industrial field, with no high-priced components such as precious metals or rare reagents added, thus reducing the production cost of conductive silver paste. While ensuring that the core performance of the film layer, such as density, conductivity, and stability, meets the standards, this low-cost formula not only enhances the competitiveness of the product but also conforms to the development trend of "low cost and high reliability" in the photovoltaic industry. Attached Figure Description

[0015] Figure 1 This is a SEM image of the cross-section of the gate line after the conductive silver paste was printed and sintered in Example 1.

[0016] Figure 2 This is a SEM image of the cross-section of the grid line after the conductive silver paste was printed and sintered in Comparative Example 1.

[0017] Figure 3 This is a 3D image of the gate lines after the conductive silver paste was printed and sintered in Example 1.

[0018] Figure 4This is a 3D image of the grid lines after the conductive silver paste was printed and sintered in Comparative Example 1. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Example 1

[0021] Step 1: Prepare the organic carrier according to the weight ratios of the components in Table 1: S1. Mix the high-boiling-point solvent, the medium-boiling-point solvent and the low-boiling-point solvent, heat and stir for 30 minutes at a stirring speed of 800 rpm and a heating temperature of 45°C. S2. Then add the polymer resin and thickening resin in sequence, heat and stir for 1 hour, stirring until completely dissolved. The stirring speed is 200 rpm and the heating temperature is 80℃. S3. Cool to 50℃, add dispersant and coupling agent and disperse evenly; S4. Filter through a filter with a pore size ≤ 5μm.

[0022] Step 2: Prepare conductive silver paste: Mix silver powder, glass powder and the above organic carrier according to the weight ratio in Table 2, and grind until the fineness is ≤10μm.

[0023] Example 2

[0024] Step 1: Prepare the organic carrier according to the weight ratios of the components in Table 1: S1. Mix the high-boiling-point solvent, the medium-boiling-point solvent and the low-boiling-point solvent, heat and stir for 30 minutes at a stirring speed of 700 rpm and a heating temperature of 50°C. S2. Then add the polymer resin and thickening resin in sequence, heat and stir for 1 hour, stirring until completely dissolved. The stirring speed is 200 rpm and the heating temperature is 70℃. S3. Cool to 50℃, add dispersant and coupling agent and disperse evenly; S4. Filter through a filter with a pore size ≤ 5μm.

[0025] Step 2: Prepare conductive silver paste: Mix silver powder, glass powder and the above organic carrier according to the weight ratio in Table 2, and grind until the fineness is ≤10μm.

[0026] Example 3

[0027] Step 1: Prepare the organic carrier according to the weight ratios of the components in Table 1: S1. Mix the high-boiling-point solvent, medium-boiling-point solvent and low-boiling-point solvent, heat and stir for 30 minutes at a stirring speed of 600 rpm and a heating temperature of 55°C. S2. Then add the polymer resin and thickening resin in sequence, heat and stir for 1 hour, stirring until completely dissolved. The stirring speed is 200 rpm and the heating temperature is 60℃. S3. Cool to 50℃, add dispersant and coupling agent and disperse evenly; S4. Filter through a filter with a pore size ≤ 5μm.

[0028] Step 2: Prepare conductive silver paste: Mix silver powder, glass powder and the above organic carrier according to the weight ratio in Table 2, and grind until the fineness is ≤10μm.

[0029] Comparative Example 1 Step 1: Prepare the organic carrier according to the weight ratios of the components in Table 1: S1. Add the thickening resin to α-terpineol, heat and stir for 1 hour until completely dissolved. The stirring speed is 200 rpm and the heating temperature is 80℃. S2. Cool down to 50℃, add dispersant castor oil polyoxyethylene ether and surfactant sodium dodecylbenzene sulfonate and disperse evenly. S3. Filter through a filter with a pore size ≤ 5μm.

[0030] Step 2: Prepare conductive silver paste: Mix silver powder, glass powder and the above organic carrier according to the weight ratio in Table 2, and grind until the fineness is ≤10μm.

[0031] Comparative Example 2 Step 1: Prepare the organic carrier according to the weight ratios of the components in Table 1: S1. Add the polymer resin and thickening resin to the high boiling point solvent in sequence, mix, heat and stir for 1 hour, stir until completely dissolved, the stirring speed is 200 rpm, and the heating temperature is 70℃. S2. Cool to 50℃, add dispersant and coupling agent and disperse evenly; S3. Filter through a filter with a pore size ≤ 5μm.

[0032] Step 2: Prepare conductive silver paste: Mix silver powder, glass powder and the above organic carrier according to the weight ratio in Table 2, and grind until the fineness is ≤10μm.

[0033] Comparative Example 3 Step 1: Prepare the organic carrier according to the weight ratios of the components in Table 1: S1. Add the polymer resin and thickening resin to the low boiling point solvent in sequence, heat and stir for 1 hour until completely dissolved. The stirring speed is 200 rpm and the heating temperature is 60℃. S2. Cool to 50℃, add dispersant and coupling agent and disperse evenly; S3. Filter through a filter with a pore size ≤ 5μm.

[0034] Step 2: Prepare conductive silver paste: Mix silver powder, glass powder and the above organic carrier according to the weight ratio in Table 2, and grind until the fineness is ≤10μm.

[0035] Table 1. Composition of the organic carriers in the examples and comparative examples.

[0036] Table 2. Composition of conductive silver paste in the examples and comparative examples.

[0037] The conductive silver paste prepared in the above examples and comparative examples was used to screen-print a fine grid (8 μm line width) on the front side of the TOPCon battery. Screen-printing parameters: squeegee pressure 55 N, speed 1500 mm / s. The samples were then subjected to the following tests (test conditions: temperature 25 ± 1℃, relative humidity 50 ± 5%): SEM images of the grid line cross-section were taken to observe and statistically analyze the porosity; 3D images of the grid line were taken to observe the surface undulation; the density of the sintered grid line was measured using an X-ray densitometer; the electrical performance parameters of the grid line and its application in the battery, as well as the battery efficiency, were determined. The results are shown in Tables 3-4 and 4. Figures 1-4 .

[0038] Table 3 Performance test table for examples and comparative examples

[0039] Table 4. Comparison of electrical performance between Example 1 and Comparative Example 1

[0040] The comparison reveals that, due to the use of a compound solvent of medium-boiling point, high-boiling point, and low-boiling point in the embodiment, the solvent evaporation rhythm is more reasonable, and the porosity of the grid lines in the embodiment is reduced to 1-2% (see reference). Figure 1 (SEM cross-sectional statistics) After sintering, the gate line density increased to over 95%, and the contact resistance decreased to 2.16 mΩ·cm. 2 Battery efficiency has been improved to 27.16%. See also... Figure 3 It can be seen that the flatness of the grid lines was also improved after sintering. In contrast, the comparative examples all used single-boiling-point solvent systems, resulting in an unbalanced evaporation rate and performance far inferior to the examples: Comparative Example 1 is a conductive silver paste prepared using a traditional process, employing α-terpineol as a boiling-point solvent. The solvent evaporation rate is relatively fast, easily leaving pores during sintering, leading to high porosity (please refer to...). Figure 2 The battery has low density, high contact resistance, and lower battery efficiency than the example. Figure 4It can be seen that the surface of the grid lines after sintering is uneven and has poor flatness. Comparative Example 2 uses only a high-boiling-point solvent, which evaporates too slowly, making it prone to bubble formation in the later stages of sintering. This results in higher porosity, lower density, and greater contact resistance, leading to a lower battery efficiency than Comparative Example 1. Comparative Example 3 uses only a low-boiling-point solvent, which evaporates too quickly, making it prone to "bursting" in the early stages of sintering. This results in the highest porosity, lowest density, and highest contact resistance, making it the worst battery among all groups.

[0041] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. The understanding of this specification should be based on those skilled in the art. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications or equivalent substitutions to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. An organic carrier for conductive silver paste in photovoltaic modules, characterized in that, The product comprises the following components in the indicated weight ratios: 15%-25% high-boiling-point solvent, 50%-65% medium-boiling-point solvent, 10%-20% low-boiling-point solvent, 1%-2% polymer resin, 3%-5% thickening resin, 0.5%-1% dispersant, and 0.3%-0.8% coupling agent. The high-boiling-point solvent has a boiling point of 230-260°C, the medium-boiling-point solvent has a boiling point of 200-230°C, and the low-boiling-point solvent has a boiling point of 180-200°C.

2. The organic carrier for conductive silver paste in photovoltaic modules as described in claim 1, characterized in that: The high-boiling-point solvent is selected from one or a mixture of two of ethylene glycol phenyl ether acetate and butyl carbitol acetate.

3. The organic carrier for conductive silver paste in photovoltaic modules as described in claim 1, characterized in that: The medium-boiling solvent is selected from one or more of α-terpineol, β-terpineol, and γ-terpineol.

4. The organic carrier for conductive silver paste in photovoltaic modules as described in claim 1, characterized in that: The low-boiling-point solvent is selected from one or more of diethylene glycol butyl ether, dipropylene glycol methyl ether, and diethylene glycol isopropyl ether.

5. The organic carrier for conductive silver paste in photovoltaic modules as described in claim 1, characterized in that: The polymer resin is selected from one of polyamide resin and modified polyamide resin, and the thickening resin is selected from one or more of ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methylcellulose, and methylcellulose.

6. The organic carrier for conductive silver paste in photovoltaic modules as described in claim 1, characterized in that: The dispersant is a phosphate ester dispersant.

7. The organic carrier for conductive silver paste in photovoltaic modules as described in claim 1, characterized in that: The coupling agent is a silane coupling agent.

8. A conductive silver paste for photovoltaic modules, characterized in that: The composition comprises the following components in the following weight ratios: 75%-85% silver powder, 2%-5% glass powder, and 10%-20% organic carrier for conductive silver paste for photovoltaic modules as described in any one of claims 1-7, wherein the silver powder has a particle size of 0.5-1 μm.

9. The organic carrier for conductive silver paste in photovoltaic modules as described in claim 8, characterized in that: The glass powder is a PbO-B2O3-SiO2 system or a B2O3-SiO2 system.

10. A method for preparing an organic carrier for conductive silver paste in photovoltaic modules as described in any one of claims 1-7, comprising the following steps: S1. Mix the high-boiling-point solvent, medium-boiling-point solvent and low-boiling-point solvent, heat and stir for 10 min to 1 h, with a stirring speed of 500-1000 rpm and a heating temperature of 40-60℃. S2. Then add the polymer resin and thickening resin in sequence, heat and stir for 1-2 hours, stirring speed is 100-300 rpm, heating temperature is 60-80℃. S3. Cool to 40-60℃, add dispersant and coupling agent and disperse evenly; S4. Filter through a filter with a pore size ≤ 5μm.

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