An organic carrier for the front silver paste of a crystalline silicon solar cell and a preparation method thereof

Abstract

The present invention discloses an organic carrier for the front silver paste of a crystalline silicon solar cell and a preparation method thereof, belonging to the technical field of solar cells. The organic carrier is composed of the following components in weight ratio: 6%-9% of resin, 87-92% of organic solvent, 1-3% of thixotropic agent, 0.1-1% of leveling agent, and 0.3%-1% of adhesion promoter; the resin is composed of resin A and resin B, and the resin A is at least one of melamine formaldehyde resin, nitrocellulose, urea formaldehyde resin, and nitrogen-containing phenolic resin, and the resin B is at least one of acrylic resin, ethyl cellulose, hydroxypropyl cellulose, butyl acetate cellulose, and PVB resin. The organic carrier of the present invention is used to prepare the front silver paste of a crystalline silicon solar cell, and the obtained front silver paste has excellent printing performance, the grid line is linear and full, and the aspect ratio is greater than 0.55.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and particularly relates to an organic carrier for front silver paste of crystalline silicon solar cells and a preparation method thereof. Background Art

[0002] Solar cells are a type of green energy that effectively utilizes the rich and pollution-free solar resources. In the existing commercial solar cell structures, the front electrode formed after sintering the front silver paste printed on the front of the cell plays the role of collecting current. The composition of the front silver paste mainly includes high-purity silver powder, inorganic glass powder, organic carrier and other additives. The shape of the front electrode is very important for solar cells. As the requirement for the photoelectric conversion efficiency of solar cells is increasing day by day, the market puts forward more and more stringent requirements for the printing performance of the front electrode paste. The printing performance of the front silver paste of solar cells is mainly determined by the organic carrier in the paste.

[0003] Currently, resin is used as a tackifier in the organic carrier components on the market. Common resin types include ethyl cellulose, epoxy resin, PVB resin, etc. During the drying and sintering processes after the cell is printed, the solvent components in the organic carrier can all volatilize, while the resin is difficult to remove completely. The residual carbon components will increase the bulk resistance of the fine grid lines and increase the series resistance, thus affecting the conversion efficiency of the cell. For example, Chinese Patent CN109897389A discloses an organic carrier for front silver paste of solar cells and a preparation method thereof. The organic carrier includes the following components in weight ratio: 10-16% resin, 55-70% solvent, 4-8% additives; the resin is one or a mixture of 2,6-di-tert-butyl-4-methylphenol, ethyl cellulose, polyvinyl butyral resin, ethylene-vinyl acetate resin, and rosin glyceride; the silver paste prepared with this carrier has a printing line width that can be lower than 40μm and an aspect ratio greater than 0.4; the resin used in the above formula is mainly the commonly used carrier resin at present, and the residual carbon components during the sintering process will have a certain impact on the grid line resistance.

[0004] Chinese Patent CN108586832A discloses a special carrier for front silver paste of solar cells containing a thermogel, which is composed of a thermogel and a conventional carrier; among them, the thermogel is composed of β-cyclodextrin, aromatic amine, chloride salt and dimethylformamide. It has a lower viscosity when stirred at room temperature and turns into a gel state when heated, and the viscosity increases, which is beneficial to alleviating the decrease in the aspect ratio of the grid line caused by the decrease in the viscosity of the silver paste during the sintering process; the aromatic amines, benzene and other organic solvents used in this patent have high toxicity and will cause certain pollution during the production process; the fine grid line type is not flat and there is still room for improvement in the aspect ratio. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies of the prior art and provide an organic carrier for the front silver paste of a crystalline silicon solar cell and a preparation method thereof. The organic carrier has good screen passing performance. When the organic carrier is used in the front silver paste of a crystalline silicon solar cell, the printing aspect ratio of the silver paste is greater than 0.55, which is more conducive to improving the photoelectric conversion efficiency of the crystalline silicon solar cell.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: In the first aspect, an organic carrier for the front silver paste of a crystalline silicon solar cell is provided, which is composed of the following components in weight ratio: 6%-9% of resin, 87-92% of organic solvent, 1-3% of thixotropic agent, 0.1-1% of leveling agent, and 0.3%-1% of adhesion promoter; the resin is composed of resin A and resin B, and the resin A is at least one of melamine formaldehyde resin, nitrocellulose, urea formaldehyde resin, and nitrogen-containing phenolic resin, and the resin B is at least one of acrylic resin, ethyl cellulose, hydroxypropyl cellulose, butyl acetate cellulose, and PVB resin.

[0007] In the present invention, by introducing resin A into the organic carrier, the nitrogen element in resin A is incorporated into the residual carbon component after sintering, providing more free electrons for the conduction band, thereby improving the conductivity of the residual carbon component and reducing the influence of the residual carbon component on the sheet resistance of the grid line. In the case of similar grid line shapes, the series resistance can be effectively reduced, and the photoelectric conversion efficiency of the crystalline silicon solar cell can be improved. By introducing resin B into the organic carrier, resin B can increase the viscosity of the front silver paste of the crystalline silicon solar cell and reduce the fluidity, thereby avoiding phase separation in the front silver paste. The two resins interact with each other to improve the overall performance of the crystalline silicon solar cell.

[0008] Preferably, the leveling agent is at least one of fluorine-modified acrylate leveling agent and phosphate-modified acrylate leveling agent.

[0009] In the present invention, by adding an acrylate leveling agent to the organic carrier, the surface tension of the front silver paste can be reduced, the wettability of the front silver paste to the substrate surface can be improved, and while maintaining a high viscosity, the front silver paste also has leveling properties, making the grid line shape straight and full.

[0010] *]]Preferably, the adhesion promoter is at least one of polyester-type adhesion promoter, epoxy phosphate-type adhesion promoter, and silane coupling agent.

[0011] In the present invention, by adding an adhesion promoter to the organic carrier, the adhesion promoter and the leveling agent interact with each other, which can further improve the wetting performance of the front silver paste to the substrate surface, form a strong interaction force between the substrate and the front silver paste, reduce the voids at the interface, and make the front silver paste completely adhere to the substrate, which is beneficial to the contact between the front silver paste and the substrate during the sintering process.

[0012] Preferably, the organic solvent is at least one of alcohol ester - 12, butyl carbitol, butyl carbitol acetate, terpineol, tributyl acetylcitrate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, methyl ester of nylon acid, diethylene glycol monomethyl ether, diethylene glycol dibutyl ether, tripropylene glycol butyl ether, dimethyl adipate, and diethyl adipate.

[0013] Preferably, the thixotropic agent is at least one of fumed silica, modified polyamide wax, or hydrogenated castor oil.

[0014] In a second aspect, a preparation method of an organic carrier for the front silver paste of a crystalline silicon solar cell is provided, including the following steps:

[0015] (1) Weigh the resin, organic solvent, thixotropic agent, dispersant, leveling agent, and adhesion promoter respectively according to the mass ratio.

[0016] (2) Add the solvent and resin to a dispersion stirrer in sequence and stir until the solution is clear and transparent to obtain a resin solution.

[0017] (3) Add the thixotropic agent, dispersant, leveling agent, and adhesion promoter to the resin solution obtained in step (2), and stir to obtain an organic carrier for the front silver paste of a crystalline silicon solar cell.

[0018] Preferably, the stirring temperature in step (2) is 70 - 100 °C.

[0019] Preferably, the stirring speed in step (3) is 1500 - 2500 r / min, the temperature is 50 - 70 °C, and the stirring time is 30 - 60 min.

[0020] Preferably, after the stirring in step (3) is completed, it is cooled to room temperature.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) By adding resin A to the organic carrier in the present invention, the influence of the residual carbon component in the electrode on the conductivity of the electrode after the front silver paste is sintered can be reduced, the grid line resistance of the electrode can be decreased, and the photoelectric conversion efficiency of the crystalline silicon solar cell can be improved.

[0023] (2) By adding a modified acrylic leveling agent to the organic carrier in the present invention, the grid line linearity of the front silver paste is improved, and the problem of increased resistance caused by insufficient leveling of the front silver paste is avoided.

[0024] (3) By adding an adhesion promoter to the organic carrier in the present invention, the wetting performance of the front silver paste on the substrate is improved, so that the front silver paste is completely adhered to the substrate before sintering, ensuring the corrosion effect of the front silver paste on the substrate surface during the sintering process and forming a good ohmic contact.

[0025] (4) The organic carrier of the present invention is used for preparing the front silver paste of crystalline silicon solar cells. The obtained front silver paste has excellent printing properties, with full and linear grid lines and an aspect ratio greater than 0.55. Detailed implementation manners

[0026] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0027] The materials, reagents, etc. used in the following examples and comparative examples can be purchased from commercial channels without special instructions.

[0028] The raw materials used in the following examples and comparative examples are described as follows, but are not limited to these materials:

[0029] Leveling agent 1: Fluorine-modified acrylate leveling agent, BASF EFKA3777;

[0030] Leveling agent 2: Phosphate-modified acrylate leveling agent, Xianchuang Modare X 043;

[0031] Leveling agent 3: Silicone leveling agent, Degussa 450;

[0032] Thixotropic agent: Modified polyamide wax, Disperbyk 6500;

[0033] Adhesion promoter 1: Polyester adhesion promoter, Degussa LTW;

[0034] Adhesion promoter 2: Phosphate adhesion promoter, Cytec ADDITOL-XL180.

[0035] Example 1

[0036] This example provides an organic carrier for the front silver paste of crystalline silicon solar cells, which is composed of the following components in weight ratio: 1% melamine formaldehyde resin, 7% ethyl cellulose, 30% butyl carbitol, 20% methyl esters of dimer acid, 30% ethylhexyl lactate, 10% dimethyl adipate, 1% thixotropic agent, 0.7% leveling agent 1, 0.3% adhesion promoter 1.

[0037] Example 2

[0038] This example provides an organic carrier for the front silver paste of crystalline silicon solar cells, which is composed of the following components in weight ratio: 1% melamine formaldehyde resin, 7% ethyl cellulose, 30% butyl carbitol, 20.5% methyl esters of dimer acid, 30% ethylhexyl lactate, 9.3% dimethyl adipate, 1% thixotropic agent, 0.5% leveling agent 1, 0.7% adhesion promoter 1.

[0039] Example 3

[0040] This embodiment provides an organic carrier for the front silver paste of a crystalline silicon solar cell, which is composed of components with the following weight ratios: 1% melamine formaldehyde resin, 5% ethyl cellulose, 25% butyl carbitol, 22% methyl ester of nylon acid, 35% alcohol ester-12, 10% dimethyl adipate, 1% thixotropic agent, 0.7% leveling agent 1, 0.3% adhesion promoter 1.

[0041] Example 4

[0042] This embodiment provides an organic carrier for the front silver paste of a crystalline silicon solar cell, which is composed of components with the following weight ratios: 1.5% melamine formaldehyde resin, 1.5% nitrocellulose, 3% ethyl cellulose, 3% acrylic resin, 34.9% diethylene glycol monoethyl ether acetate, 27% methyl ester of nylon acid, 10% tributyl acetyl citrate, 15% dimethyl adipate, 3% thixotropic agent, 0.1% leveling agent 2, 1% adhesion promoter 2.

[0043] Comparative Example 1

[0044] This comparative example provides an organic carrier for the front silver paste of a crystalline silicon solar cell. The only difference between the organic carrier of this comparative example and that of Example 4 is that the resin is 9% ethyl cellulose.

[0045] Comparative Example 2

[0046] This comparative example provides an organic carrier for the front silver paste of a crystalline silicon solar cell. The only difference between the organic carrier of this comparative example and that of Example 3 is that the leveling agent is leveling agent 3.

[0047] Comparative Example 3

[0048] This comparative example provides an organic carrier for the front silver paste of a crystalline silicon solar cell. The only difference between the organic carrier of this comparative example and that of Example 1 is that the resin A is polyamide.

[0049] The preparation methods of the organic carriers in Examples 1 to 4 and Comparative Examples 1 to 3 include the following steps:

[0050] (1) Weigh the resin, organic solvent, thixotropic agent, dispersant, leveling agent, and adhesion promoter respectively according to the mass ratio;

[0051] (2) Add the solvent and resin to the dispersion stirrer in sequence, and stir at a temperature of 70 - 100 °C until the solution is clear and transparent to obtain a resin solution;

[0052] (3) Add a thixotropic agent, a dispersant, a leveling agent, and an adhesion promoter to the resin solution obtained in step (2), stir at 60 °C, with a stirring speed of 2000 r / min and a stirring time of 45 min. After stirring, cool to room temperature to obtain an organic carrier for the front silver paste of crystalline silicon solar cells.

[0053] Effect Example 1

[0054] Use the organic carriers prepared in the above examples and comparative examples to prepare the front silver paste. The front silver paste is composed of the following components by mass ratio: silver powder 86.2%, aluminum powder 3%, glass powder 2%, organic carrier 8.5%, BYK110 0.3%.

[0055] Print the prepared front silver paste on the front surface of n-type TOPCon cell wafers for testing. Use a 3D microscope to measure the aspect ratio of the grid lines and observe the appearance of the grid lines. Use an IV tester to test the electrical properties. The test results are shown in Table 1.

[0056] Table 1

[0057]

[0058] It can be seen from the experimental data in Table 1 that the organic carrier of the present invention can reduce the grid line resistance of the front silver paste while ensuring a relatively high aspect ratio, and further improve the photoelectric conversion efficiency of the front silver paste.

[0059] Effect Example 2

[0060] This effect example studies the influence of the mass ratio between resin A and resin B on the performance of the front silver paste. Seven test groups are set up. The organic carriers of test groups 1-7 are the same as those of Example 1 except for the mass ratio between resin A and resin B. The mass ratio between resin A and resin B in the organic carriers of test groups 1-7 is shown in Table 2. Use the preparation methods of the organic carriers in Examples 1-4 and Comparative Examples 1-3 to prepare the organic carriers of test groups 1-7, and prepare and test the front silver paste containing the organic carriers of test groups 1-7 according to Effect Example 1. The test results are shown in Table 2.

[0061] Table 2

[0062]

[0063] It can be seen from the experimental data in Table 2 that the mass ratio between resin A and resin B affects the performance of the front silver paste. When the mass ratio between resin A and resin B is 1:5-7, the comprehensive performance of the front silver paste is better.

[0064] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An organic carrier for the front silver paste of a crystalline silicon solar cell, characterized in that, It is composed of components with the following weight ratios: 6%-9% of resin, 87-92% of organic solvent, 1-3% of thixotropic agent, 0.1-1% of leveling agent, and 0.3%-1% of adhesion promoter; the resin is composed of resin A and resin B, and the resin A is at least one of melamine formaldehyde resin, nitrocellulose, urea formaldehyde resin, and nitrogen-containing phenolic resin, and the resin B is at least one of acrylic resin, ethyl cellulose, hydroxypropyl cellulose, butyl acetate cellulose, and PVB resin; the mass ratio of resin A to resin B is 1:5-7; The leveling agent is at least one of fluorine-modified acrylate leveling agent and phosphate ester-modified acrylate leveling agent.

2. The organic carrier according to claim 1, wherein The adhesion promoter is at least one of polyester-type adhesion promoter, epoxy phosphate-type adhesion promoter, and silane coupling agent.

3. The organic carrier according to claim 1, wherein The organic solvent is at least one of alcohol ester-12, butyl carbitol, butyl carbitol acetate, terpineol, tributyl acetyl citrate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, methyl esters of nylon acid, diethylene glycol monomethyl ether, diethylene glycol dibutyl ether, tripropylene glycol butyl ether, dimethyl adipate, and diethyl adipate.

4. The organic carrier according to claim 1, wherein The thixotropic agent is at least one of fumed silica, modified polyamide wax, and hydrogenated castor oil.

5. A preparation method of an organic carrier for a front silver paste of a crystalline silicon solar cell according to any one of claims 1-4, characterized in that, It includes the following steps: (1) Weigh the resin, organic solvent, thixotropic agent, dispersant, leveling agent, and adhesion promoter respectively according to the mass ratio; (2) Add the solvent and resin to the dispersion stirrer in sequence and stir until the solution is clear and transparent to obtain a resin solution; (3) Add the thixotropic agent, dispersant, leveling agent, and adhesion promoter to the resin solution obtained in step (2) and stir to obtain an organic carrier for the front silver paste of crystalline silicon solar cells.

6. The preparation method according to claim 5, characterized in that, The stirring temperature in step (2) is 70-100°C.

7. The preparation method according to claim 5, wherein The stirring speed in step (3) is 1500-2500 r / min, the temperature is 50-70°C, and the stirring time is 30-60 min.

8. The preparation method according to claim 5, characterized in that, After the stirring in step (3) is completed, it is cooled to room temperature.

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