A glass powder for the front silver paste of a Topcon solar cell and a preparation method thereof

Abstract

The present invention discloses a glass powder for the front silver paste of a Topcon solar cell and a preparation method thereof. The glass powder of the present invention is a TeO2 surface-modified glass powder. The weight percentages of the components of the glass powder matrix before modification are as follows: 50% - 65% of Bi2O3, 15% - 20% of B2O3, 8% - 12% of SiO2, 3% - 5% of MgO, 3% - 5% of ZnO, 3% - 5% of Al2O3, 1% - 3% of Li2O, 1% - 3% of NaF; and then TeO2 surface modification is carried out on the surface of the glass powder matrix by a 0.1 - 0.3 mol / L TeCl4 solution. The glass powder of the present invention can effectively reduce the contact angle through TeO2 surface modification, enabling the glass phase to flow to the interface layer more easily, achieving the improvement of the adhesion of the silver paste, while reducing the residual glass phase in the silver layer and enhancing the compactness and tensile strength of the silver layer. And the present invention improves the silver dissolution and precipitation ability of the glass, reduces the resistance of the glass layer, and reduces the ohmic contact resistance between the silver electrode and the battery chip.

Description

Technical Field

[0001] The present invention relates to a glass powder for the front silver paste of a Topcon solar cell and a preparation method thereof, belonging to the technical field of solar cells. Background Art

[0002] Photovoltaic power generation has prominent advantages such as sustainability, cleanliness, and no geographical restrictions. China ranks first in the world in terms of photovoltaic production and installed capacity, and Topcon solar cells will occupy the main market in the future. In solar cells, the front electrode plays a role in leading out and collecting current. With the continuous development of solar cell technology, the thickness of Topcon solar cell wafers decreases, the thickness of the passivation layer decreases, the number of main grids on the front electrode increases while the width shrinks, which puts higher requirements on the conductivity and adhesion of the silver paste.

[0003] The main components of the existing front silver paste include: silver powder, glass powder, and organic carrier. Among them, the performance of the glass powder directly determines whether a good contact can be formed with the silicon substrate after the slurry is sintered. The glass powder for solar front silver paste requires a low melting temperature, and has good fluidity, wettability, and silver dissolution and precipitation ability after melting. Therefore, the glass powder is usually Bi-based glass powder and Te-based glass powder. The glass powder mainly composed of Bi2O3 has good silver dissolution and precipitation ability, and a large amount of nano-silver precipitates on the interface, resulting in a low interface resistance. However, the high-temperature fluidity and wettability of the glass are poor, resulting in that the glass powder cannot flow quickly to the silver-silicon interface during the low-temperature rapid sintering process, and part of it remains in the silver layer, increasing the silver film resistance, and resulting in insufficient glass phase at the interface, affecting the formation of a good contact between the silver layer and the silicon wafer, thereby reducing the adhesion of the sintered film layer of the slurry; The glass powder mainly composed of TeO2 has good high-temperature fluidity and wettability, and is easy to flow to the silver-silicon interface to form a uniform glass phase transition layer, but the silver dissolution and precipitation ability of the glass powder is poor, resulting in a small number of nano-silver particles precipitating on the silicon wafer and in the glass layer, and a good conductive path cannot be formed in the glass layer, resulting in a higher interface contact resistance.

[0004] The present invention combines the advantages of the two glass powders, uses the Bi glass powder as the matrix, and improves the high-temperature fluidity and wettability of the glass powder by attaching nano-TeO2 outside the glass powder, while meeting the requirements of Topcon solar cells for high adhesion and high conductivity of the silver paste. Summary of the Invention

[0005] The purpose of the present invention is to provide a glass powder for the front silver paste of a Topcon solar cell, which is used to solve the technical problems of relatively low adhesion per unit area and relatively high interface contact resistance existing in the prior art.

[0006] The glass powder in the present invention is TeO2 surface-modified glass powder. The composition of the glass powder matrix before modification is as follows by weight percentage: 50% - 65% of Bi2O3, 15% - 20% of B2O3, 8% - 12% of SiO2, 3% - 5% of MgO, 3% - 5% of ZnO, 3% - 5% of Al2O3, 1% - 3% of Li2O, and 1% - 3% of NaF.

[0007] Preferably, the average particle size of the glass powder in the present invention is less than 3 μm.

[0008] Another object of the present invention is to provide a preparation method of the glass powder for the front silver paste of Topcon solar cells, which specifically includes the following steps:

[0009] (1) Weigh the raw materials according to the ratio of each component, fully grind and stir to mix evenly to obtain a mixture, then place it in a muffle furnace for heating and insulation to obtain a glass melt, and then pour it into deionized water for water quenching to obtain glass fragment particles.

[0010] (2) Place the glass fragment particles obtained in step (1) in an agate ball milling tank and ball mill to obtain a glass powder matrix.

[0011] (3) Pour the glass powder matrix into a beaker, add deionized water, stir to obtain a glass mixed solution; add TeCl4 solution dropwise to the glass mixed solution, stir, and then perform ultrasonic dispersion to obtain a solution containing Te ions.

[0012] (4) Add a reducing agent to the solution containing Te ions obtained in step (3), stir and then perform ultrasonic dispersion to obtain a mixed solution.

[0013] (5) Add the mixed solution obtained in step (4) to a reaction kettle with a polytetrafluoroethylene liner, and then place it in a homogeneous reactor to react under the conditions of 130 - 150 °C and a rotation speed of 20 - 30 r / min, and naturally cool to room temperature to obtain a reaction product; wash the reaction product by centrifugation with deionized water and then dry it to obtain Te surface-modified glass powder.

[0014] Preferably, the heating conditions of the muffle furnace in step (1) of the present invention are: 1200 - 1300 °C, and keep warm for 0.5 - 1 h.

[0015] Preferably, the ball milling time in step (2) of the present invention is 20 - 24 h.

[0016] Preferably, the mass ratio of the glass powder matrix to deionized water in step (3) of the present invention is 1:9.

[0017] Preferably, in step (4) of the present invention, the concentration of the TeCl4 solution is 0.1 - 0.3 mol / L; the mass ratio of the TeCl4 solution to the glass mixed solution is 1:5; and ultrasonic dispersion is carried out for 10 - 15 min.

[0018] Preferably, in step (4) of the present invention, the reducing agent is one of a 1 - 3 mol / L KOH solution, a 1 - 3 mol / L H2O2 solution, and a 1 - 3 mol / L ammonia water. The mass ratio of the reducing agent solution to the Te ion-containing solution is 1:6; and ultrasonic dispersion is carried out for 10 - 15 min.

[0019] Preferably, in step (4) of the present invention, the reaction time is 6 - 8 h; the reaction product is centrifugally washed 4 - 6 times with deionized water and then dried at a temperature of 50°C - 70°C for 8 - 12 h to obtain the glass powder for the front silver paste of the Topcon solar cell.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) For the glass powder for the front silver paste of the Topcon solar cell of the present invention, the contact angle between its glass melt and the Topcon solar cell wafer is 20 - 24° after surface modification of TeO2. Effectively reducing the contact angle can make the glass phase easier to flow to the interface layer, achieving the improvement of the adhesion of the silver paste. At the same time, the residual of the glass phase in the silver layer is reduced, and the compactness and tensile strength of the silver layer are improved. Using this glass powder, the adhesion per unit area can exceed 4 N / mm 2 , and the volume resistivity of the silver layer can reach the lowest value.

[0022] (2) For the glass powder for the front silver paste of the Topcon solar cell of the present invention, since the main component of the glass powder matrix is Bi, its silver dissolution ability is good, and a large number of nano-silver particles will precipitate in the glass transition layer at the silver-silicon interface, reducing the resistance of the glass layer and the ohmic contact resistance between the silver electrode and the cell wafer. The minimum specific ohmic contact resistivity can reach 0.021 Ω·cm 2 .

[0023] (3) Before modification, the composition of the glass powder matrix is mainly Bi2O3, and the silver dissolution and precipitation ability of the glass melt is good. A large number of nano-silver particles will precipitate in the glass transition layer, reducing the resistance of the glass layer. However, the large amount of Bi2O3 present will cause the melting point of the glass to be relatively high, the contact angle between the glass melt and the Topcon solar cell wafer to be relatively large, and it is difficult for the glass phase to flow to the interface layer to form contact, resulting in poor adhesion of the silver paste and high ohmic contact resistance between the electrode and the cell wafer. Description of the Drawings

[0024] Figure 1 It is a diagram of the contact angle between the glass melt and the Topcon solar cell wafer in Example 1;

[0025] Figure 2 SEM image of precipitated nano - silver particles in the glass transition layer of the silver - silicon interface in Example 1. Specific implementation method

[0026] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the content described.

[0027] Example 1

[0028] A glass powder for the front silver paste of a Topcon solar cell and its preparation method, the composition of the glass powder matrix and its mass percentage are: Bi2O3 65%, B2O3 15%, SiO2 8%, MgO 3%, ZnO 4%, Al2O3 3%, Li2O 1%, NaF 1%.

[0029] The preparation method of the glass powder for the front silver paste of a Topcon solar cell includes the following steps:

[0030] (1) Weigh the raw materials according to the ratio of each component, fully grind, stir and mix them evenly to obtain a mixture, then place it in a muffle furnace, heat it up to 1200 °C, keep it warm for 0.5 h to obtain a glass melt, and then pour it into deionized water for water quenching to obtain glass fragment particles.

[0031] (2) Ball - mill the glass fragment particles for 22 h to obtain a glass powder matrix.

[0032] (3) Pour the glass powder matrix into a beaker, and add deionized water and stir to obtain a glass mixed solution, and the mass ratio of the glass powder matrix to deionized water is 1:9.

[0033] (4) Drop a TeCl4 solution with a concentration of 0.3 mol / L into the glass mixed solution, stir, and then perform ultrasonic dispersion to obtain a Te - ion - containing solution, and the mass ratio of the TeCl4 solution to the glass mixed solution is 1:5.

[0034] (5) Add a 1 mol / L KOH solution as a reducing agent to the Te - ion - containing solution, stir and then perform ultrasonic dispersion to obtain a mixed solution, and the mass ratio of the reducing agent solution to the Te - ion - containing solution is 1:6.

[0035] (6) Add the mixed solution to a reaction kettle with a polytetrafluoroethylene liner, and then place it in a homogeneous reactor to react at 130 °C and a rotation speed of 20 r / min, and naturally cool to room temperature to obtain a reaction product; wash the reaction product by centrifugation with deionized water and then dry it.

[0036] The prepared glass powder for the front silver paste of Topcon solar cells has an average particle size of 2.85 μm, the contact angle between its glass melt and the Topcon solar cell wafer is 20.5°, and the adhesion of the silver paste prepared therefrom is 4.13 N / mm 2 , and the specific contact resistivity is 0.021 Ω·cm 2 .

[0037] For the glass powder prepared in this example for the front silver paste of Topcon solar cells, the contact angle between its glass melt and the Topcon solar cell wafer is as Figure 1 shown; the scanning electron microscope image of the precipitation of nano-silver particles in the glass transition layer at the silver-silicon interface is as Figure 2 shown.

[0038] Example 2

[0039] A glass powder for the front silver paste of Topcon solar cells and its preparation method. The matrix composition of the glass powder and its mass percentage are: Bi2O3 55%, B2O3 18%, SiO2 10%, MgO 5%, ZnO 3%, Al2O3 5%, Li2O 2%, NaF 2%.

[0040] The preparation method of the glass powder for the front silver paste of Topcon solar cells includes the following steps:

[0041] (1) Weigh the raw materials according to the respective ratios, grind and stir them thoroughly to mix evenly to obtain a mixture, then place it in a muffle furnace, heat it up to 1300 °C, keep it warm for 1 h to obtain a glass melt, and then pour it into deionized water for water quenching to obtain glass fragment particles.

[0042] (2) Place the glass fragment particles in an agate ball milling tank and ball mill for 24 h to obtain a glass powder matrix.

[0043] (3) Pour the glass powder matrix into a beaker and add deionized water. The mass ratio of the glass powder matrix to deionized water is 1:9, and stir to obtain a glass mixed solution.

[0044] (4) Drop a TeCl4 solution with a concentration of 0.2 mol / L into the glass mixed solution, stir, and then ultrasonically disperse to obtain a Te ion-containing solution. The mass ratio of the TeCl4 solution to the glass mixed solution is 1:5.

[0045] (5) Add a 2 mol / L H2O2 solution as a reducing agent to the Te ion-containing solution, stir and then ultrasonically disperse to obtain a mixed solution. The mass ratio of the reducing agent solution to the Te ion-containing solution is 1:6.

[0046] (6) Add the mixed solution into a reactor with a polytetrafluoroethylene liner, and then place it in a homogeneous reactor to react at 150 °C with a rotation speed of 30 r / min. Naturally cool it to room temperature to obtain the reaction product; wash the reaction product by centrifugation with deionized water and then dry it.

[0047] The prepared glass powder for the front silver paste of Topcon solar cells has an average particle size of 2.73 μm, the contact angle between its glass melt and the Topcon solar cell wafer is 23.6°, and the adhesion of the silver paste prepared therefrom is 4.28 N / mm 2 , and the specific contact resistivity is 0.025 Ω·cm 2 .

[0048] Example 3

[0049] A glass powder for the front silver paste of Topcon solar cells and its preparation method, the matrix composition of the glass powder and its mass percentage are: Bi2O3 50%, B2O3 20%, SiO2 12%, MgO 4%, ZnO 5%, Al2O3 3%, Li2O 3%, NaF 3%.

[0050] The preparation method of the glass powder for the front silver paste of Topcon solar cells includes the following steps:

[0051] (1) Weigh the raw materials according to the ratio of each component, fully grind and stir to mix evenly to obtain a mixture, then place it in a muffle furnace, heat up to 1250 °C, keep it warm for 0.8 h to obtain a glass melt, and then pour it into deionized water for water quenching to obtain glass fragment particles.

[0052] (2) Place the glass fragment particles in an agate ball milling tank and ball mill for 20 h to obtain the glass powder matrix.

[0053] (3) Pour the glass powder matrix into a beaker and add deionized water. The mass ratio of the glass powder matrix to deionized water is 1:9; stir to obtain a glass mixed solution.

[0054] (4) Drop a TeCl4 solution with a concentration of 0.1 mol / L into the glass mixed solution. The mass ratio of the TeCl4 solution to the glass mixed solution is 1:5; stir and then ultrasonically disperse to obtain a Te ion-containing solution.

[0055] (5) Add 3 mol / L ammonia water as a reducing agent to the Te ion-containing solution. The mass ratio of the reducing agent solution to the Te ion-containing solution is 1:6; stir and then ultrasonically disperse to obtain a mixed solution.

[0056] (6) Add the mixed solution into a reaction kettle with a polytetrafluoroethylene inner liner, and then place it in a homogeneous reactor to react at 140 °C and a rotation speed of 25 r / min. Naturally cool it to room temperature to obtain a reaction product; wash the reaction product by centrifugation with deionized water and then dry it.

[0057] The prepared glass powder for the front silver paste of Topcon solar cells has an average particle size of 2.45 μm, the contact angle between its glass melt and the Topcon solar cell wafer is 22.4°, and the adhesion of the prepared silver paste is 4.46 N / mm 2 , and the specific contact resistivity is 0.028 Ω·cm 2 .

[0058] Comparative Example 1

[0059] This example is the same as Example 1, except that the glass powder is not surface-modified with TeO2. Specifically:

[0060] (1) Weigh the raw materials according to the ratio of each group, grind and stir them thoroughly to mix evenly to obtain a mixture, then place it in a muffle furnace, heat it up to 1200 °C, keep it warm for 0.5 h to obtain a glass melt, and then pour it into deionized water for water quenching to obtain glass fragment particles.

[0061] (2) Ball-mill the glass fragment particles for 22 h, wash them by centrifugation with deionized water, and then dry them to obtain glass powder.

[0062] The prepared glass powder for the front silver paste of Topcon solar cells has an average particle size of 2.53 μm, the contact angle between its glass melt and the Topcon solar cell wafer is 51.5°, and the adhesion of the prepared silver paste is 2.25 N / mm 2 , and the specific contact resistivity is 0.068 Ω·cm 2 .

[0063] It can be seen from the comparison that surface modification of Bi-based glass with TeO2 can reduce the contact angle between the glass melt and the Topcon solar cell wafer, improve the wettability of the glass melt to the Topcon solar cell wafer, thereby improving the adhesion of the silver paste and reducing the specific contact resistivity.

Claims

1. A glass powder for the front silver paste of a Topcon solar cell, characterized in that: The prepared glass powder is TeO2 surface-modified glass powder. The matrix composition of the glass powder before modification is as follows by weight percentage: 50% - 65% Bi2O3, 15% - 20% B2O3, 8% - 12% SiO2, 3% - 5% MgO, 3% - 5% ZnO, 3% - 5% Al2O3, 1% - 3% Li2O, 1% - 3% NaF; The preparation method of the glass powder for the front silver paste of Topcon solar cells specifically includes the following steps: (1) Weigh the raw materials according to the proportion of each group, fully grind, stir and mix them evenly to obtain a mixture. Then place it in a muffle furnace for heating and insulation to obtain a glass melt, and then pour it into deionized water for water quenching to obtain glass fragment particles; (2) Place the glass fragment particles obtained in step (1) into an agate ball milling jar and ball mill to obtain a glass powder matrix; (3) Pour the glass powder matrix into a beaker, add deionized water, stir to obtain a glass mixed solution; drop TeCl4 solution into the glass mixed solution, stir, and then ultrasonically disperse to obtain a solution containing Te ions; (4) Add a reducing agent to the solution containing Te ions obtained in step (3), stir and then ultrasonically disperse to obtain a mixed solution; (5) Add the mixed solution obtained in step (4) to a reaction kettle with a polytetrafluoroethylene inner lining, and then place it in a homogeneous reactor for reaction under the conditions of 130 - 150 °C and a rotation speed of 20 - 30 r / min. Naturally cool to room temperature to obtain a reaction product; use deionized water to centrifugally wash the reaction product and then dry it to obtain Te surface-modified glass powder.

2. The glass powder for the front silver paste of a Topcon solar cell according to claim 1, characterized in that: The average particle size of the glass powder is less than 3 μm.

3. The preparation method of the glass powder for the front silver paste of the Topcon solar cell according to claim 1, characterized in that, Specifically includes the following steps: (1) Weigh the raw materials according to the proportion of each group, fully grind, stir and mix them evenly to obtain a mixture. Then place it in a muffle furnace for heating and insulation to obtain a glass melt, and then pour it into deionized water for water quenching to obtain glass fragment particles; (2) Place the glass fragment particles obtained in step (1) into an agate ball milling jar and ball mill to obtain a glass powder matrix; (3) Pour the glass powder matrix into a beaker, add deionized water, stir to obtain a glass mixed solution; drop TeCl4 solution into the glass mixed solution, stir, and then ultrasonically disperse to obtain a solution containing Te ions; (4) Add a reducing agent to the solution containing Te ions obtained in step (3), stir and then ultrasonically disperse to obtain a mixed solution; (5) Add the mixed solution obtained in step (4) to a reaction kettle with a polytetrafluoroethylene inner lining, and then place it in a homogeneous reactor for reaction under the conditions of 130 - 150 °C and a rotation speed of 20 - 30 r / min. Naturally cool to room temperature to obtain a reaction product; use deionized water to centrifugally wash the reaction product and then dry it to obtain Te surface-modified glass powder.

4. The preparation method of the glass powder for the front silver paste of the Topcon solar cell according to claim 3, characterized in that: The heating condition of the muffle furnace in step (1) is: 1200 - 1300 °C, and the insulation time is 0.5 - 1 h.

5. The preparation method of the glass powder for the front silver paste of Topcon solar cells according to claim 3, characterized in that: The ball milling time in step (2) is 20 - 24 h.

6. The preparation method of the glass powder for the front silver paste of Topcon solar cells according to claim 3, characterized in that: The mass ratio of the glass powder matrix to deionized water in step (3) is 1:

9.

7. The preparation method of the glass powder for the front silver paste of the Topcon solar cell according to claim 3, characterized in that: In step (4), the concentration of the TeCl4 solution is 0.1 - 0.3 mol / L; the mass ratio of the TeCl4 solution to the glass mixed solution is 1:5; ultrasonic dispersion is carried out for 10 - 15 min.

8. The preparation method of the glass powder for the front silver paste of Topcon solar cells according to claim 3, characterized in that: In step (4), the reducing agent is one of a 1 - 3 mol / L KOH solution, a 1 - 3 mol / L H2O2 solution, and a 1 - 3 mol / L ammonia water. The mass ratio of the reducing agent solution to the Te ion-containing solution is 1:6; ultrasonic dispersion is carried out for 10 - 15 min.

9. The preparation method of the glass powder for the front silver paste of the Topcon solar cell according to claim 3, wherein: In step (5), the reaction time is 6 - 8 h; the reaction product is centrifugally washed 4 - 6 times with deionized water and then dried at a temperature of 50°C - 70°C for 8 - 12 h to obtain the glass powder for the front silver paste of the Topcon solar cell.

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