Glass powder for front silver paste of N-type crystalline silicon solar cell and its preparation method

Abstract

The present invention discloses a glass powder for front silver paste of N-type crystalline silicon solar cells and a preparation method thereof. It comprises oxide powder and a leveling agent. The leveling agent comprises a modified silicone oil and a silane coupling agent; the oxide powder comprises PbO, SiO 2 , B 2 O 3 , Al 2 O 3 , Bi 2 O 3 , ZnO and MgO; the modified silicone oil is prepared by reacting a low hydrogen content silicone oil with an alkenyl quaternary ammonium salt and has a structure shown in formula A below, where m = 120 - 160 and n = 15 - 20. The glass powder for front silver paste of N-type crystalline silicon solar cells provided by the present invention has good dispersibility, strong fluidity and excellent compatibility in the silver paste, and can effectively improve the photoelectric conversion efficiency of the solar cell.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly relates to a glass powder for front silver paste of an N-type crystalline silicon solar cell and a preparation method thereof. Background Art

[0002] Since the birth of solar cells, crystalline silicon solar cells have been widely used, with their conversion efficiency continuously improving and production costs continuously decreasing. As a clean energy source, crystalline silicon solar cells are playing an increasingly important role in changing the energy structure and alleviating environmental pressure.

[0003] According to the doping type of the substrate, crystalline silicon solar cells are divided into P-type crystalline silicon solar cells and N-type crystalline silicon solar cells. Compared with P-type crystalline silicon solar cells, N-type crystalline silicon solar cells have higher conversion efficiency and impurity tolerance, and basically no light-induced degradation. Since N-type crystalline silicon has a longer minority carrier lifetime than P-type crystalline silicon, N-type crystalline silicon cells can usually be made into double-sided PERC cells to increase the output power of the cells, and the increase value is generally more than 20%.

[0004] Double-sided PERC solar cells are a special type of crystalline silicon solar cells, and their main feature is that an additional layer or multiple layers of passivation film structures are plated on both the front and back surfaces of the solar cells based on silver paste. 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 binder and other additives. The inorganic glass powder is mainly composed of oxide powders (such as BiO 3 、SiO 2 、B 2 O 3 etc.), accounting for 2%-5% of the slurry. Although the proportion of glass powder in the conductive silver paste is not much, it plays the role of corroding silicon nitride and silicon wafers and bonding the silver film and silicon wafers. After the organic carrier volatilizes completely, the glass powder softens into a glass liquid, infiltrates the silver particles and the surface of the silicon wafer, and can effectively reduce the surface tension of the metal melt and increase the surface contact between the silver particles and the silicon wafer.

[0005] With the development of solar cell technology, new high-efficiency cells and new battery process technologies are upgraded relatively fast, and the performance requirements for inorganic glass powder are also getting higher and higher. The compatibility of the glass powder in the prior art with other components in the silver paste is insufficient, and the dispersibility needs to be further improved. Moreover, its flowability is insufficient, which affects the printing performance when the slurry is applied to the electrode sheet with a narrow grid line width, thereby affecting the photoelectric conversion efficiency.

[0006] Therefore, there is currently a need for a glass powder for front silver paste of an N-type crystalline silicon solar cell with good dispersibility, strong flowability and excellent compatibility in silver paste. Summary of the Invention

[0007] Object of the Invention: Aiming at the defects of the prior art, the object of the present invention is to provide a glass powder for the front silver paste of an N-type crystalline silicon solar cell, which has good dispersibility, strong fluidity and excellent compatibility in the silver paste, and a preparation method thereof.

[0008] Technical Solution:

[0009] A glass powder for the front silver paste of an N-type crystalline silicon solar cell, comprising oxide powder and a leveling agent;

[0010] The leveling agent comprises a modified silicone oil and a silane coupling agent;

[0011] The modified silicone oil has a structure shown in the following formula A:

[0012]

[0013] Where m = 120 - 160 and n = 15 - 20.

[0014] By adding a leveling agent to the glass powder of the present invention, the dispersibility of the glass powder can be enhanced through the combined action of the modified silicone oil and the silane coupling agent, reducing the recombination in the metal-semiconductor contact region, and thus improving the conversion efficiency of the battery.

[0015] Further, the silane coupling agent is selected from one of KH-560, KH-570, KH-580 or KH-590; the mass ratio of the modified silicone oil to the silane coupling agent in the leveling agent is 2 - 4:1.

[0016] Further, the mass ratio of the oxide powder to the leveling agent is (90 - 100):(3 - 5).

[0017] Further, the oxide powder comprises PbO, SiO 2 , B 2 O 3 , Al 2 O 3 , Bi 2 O 3 , ZnO and MgO; the weight parts of each component in the oxide powder are: 30 - 60 parts of PbO, 5 - 15 parts of SiO 2 5 - 15 parts, 5 - 10 parts of B 2 O 3 , 3 - 5 parts of Al 2 O 3 , 15 - 25 parts of Bi 2 O 3 15 - 25 parts, 5 - 10 parts of ZnO, and 5 - 10 parts of MgO.

[0018] Further, the sintering temperature of the glass powder is 700 - 900 °C

[0019] Further, the preparation method of the modified silicone oil is as follows: in a reactor, add a solvent, a low hydrogen content silicone oil, and an alkenyl quaternary ammonium salt, heat to 90 - 110 °C, then add a catalyst, stir and react for 6 - 8 hours, and then remove the solvent to obtain the modified silicone oil.

[0020] Further, the hydrogen content of the low hydrogen content silicone oil is 0.15% - 0.2%; the catalyst is a platinum catalyst; the content of effective platinum in the catalyst is 1.0×10 -5 -5.0×10 -5 ; the mass ratio of the low hydrogen content silicone oil to the alkenyl quaternary ammonium salt is 5:1 - 2.

[0021] Further, the alkenyl quaternary ammonium salt has the structure shown in Formula B below:

[0022]

[0023] The leveling agent is added to the glass powder of the present invention. On the one hand, the modified silicone oil can make the glass powder cover the surface of the electrode sheet smoothly and evenly, reducing the generation of defects; on the other hand, grafted to the structure of the hydrogen-containing silicone oil through the alkenyl quaternary ammonium salt, the quaternary ammonium salt and the silicon methyl structure can greatly improve the dispersibility and fluidity of the hydrogen-containing silicone oil, making it applicable to printing with a narrower grid line width, thereby obtaining a higher aspect ratio, increasing the effective area for the solar cell to receive sunlight, and improving the photoelectric conversion efficiency of the solar cell.

[0024] Further, the preparation method of the alkenyl quaternary ammonium salt is as follows: in a reactor, add diisopropylamino trimethylsilane and an organic solvent, stir and mix evenly, under nitrogen protection, heat to 35 - 45 °C, then slowly dropwise add allyl bromide, the dropping time is 2 - 3 hours, after the dropping is completed, heat to 50 - 55 °C, keep warm and react for 18 - 24 hours, then remove the solvent, and obtain the alkenyl quaternary ammonium salt after recrystallization.

[0025] Further, the molar ratio of diisopropylamino trimethylsilane to allyl bromide is 1:1 - 1.2.

[0026] The preparation method of the glass powder for the front silver paste of an N-type crystalline silicon solar cell according to any one of the above, includes the following steps:

[0027] (1) Mix the modified silicone oil and the silane coupling agent, stir evenly to obtain a leveling agent for standby;

[0028] (2) Put the oxide powder into a mixer according to the weight parts, stir and rotate for 1 - 2 hours;

[0029] (3) Divide the mixed oxide powder into crucibles and place them in a forced-air drying oven. Dry at 120 - 140 °C for 2 - 4 hours;

[0030] (4) Place the dried mixture in a muffle furnace, heat it to 850 - 1100 °C and melt for 1 - 2 hours to form a homogeneous glass liquid. Pour the high-temperature molten glass liquid quickly into deionized water for water quenching to obtain blocky glass;

[0031] (5) Dry the water-quenched blocky glass at 120 - 140 °C for 16 - 24 hours, add a leveling agent and then crush it until the particle size is D50 = 0.8 - 1.5 μm to obtain the glass powder for the front silver paste used in N-type crystalline silicon solar cells.

[0032] The glass powder provided by the present invention has better compatibility with the organic binder and silver powder in the silver paste, can be evenly dispersed in the silver paste, and then evenly cover the surface of the electrode sheet, can form a good ohmic contact, and improve the photoelectric conversion efficiency.

[0033] Further, in the step (4), the particle size range of the crushed glass powder is D50 = 0.8 - 1.5 μm.

[0034] Beneficial effects:

[0035] 1. The leveling agent is added to the glass powder for the front silver paste used in N-type crystalline silicon solar cells provided by the present invention. Through the combined action of modified silicone oil and silane coupling agent, the dispersibility of the glass powder can be enhanced, the recombination in the metal-semiconductor contact region can be reduced, and thus the conversion efficiency of the battery can be improved.

[0036] 2. The leveling agent is added to the glass powder for the front silver paste used in N-type crystalline silicon solar cells provided by the present invention. On the one hand, the modified silicone oil can make the glass powder cover the surface of the electrode sheet flat and evenly, reducing the generation of defects; on the other hand, through the grafting of alkenyl quaternary ammonium salt into the structure of hydrogen-containing silicone oil, the quaternary ammonium salt and silicon methyl structure can greatly improve the dispersibility and fluidity of the hydrogen-containing silicone oil, making it applicable to printing with a narrower grid line width, and thus obtaining a higher aspect ratio, increasing the effective area for the solar cell to receive sunlight, and improving the photoelectric conversion efficiency of the solar cell.

[0037] 3. The glass powder for the front silver paste used in N-type crystalline silicon solar cells provided by the present invention has better compatibility with the organic binder and silver powder in the silver paste, can be evenly dispersed in the silver paste, and then evenly cover the surface of the electrode sheet, can form a good ohmic contact, and improve the photoelectric conversion efficiency. Specific embodiments

[0038] The present invention will be described below in conjunction with specific implementation embodiments. It should be noted that the following embodiments are examples of the present invention, which are only used to illustrate the present invention and not to limit the present invention. Without departing from the gist or scope of the present invention, other combinations and various improvements within the concept of the present invention can be made.

[0039] The platinum catalyst was diluted to a mass fraction of 4.0×10 -3 with 965005 purchased from J&K Scientific Ltd.; the low hydrogen content silicone oil was purchased from Huangshan Kobery New Materials Technology Co., Ltd.; the organic binder was the 305 conductive silver adhesive purchased from Changchun Aides New Materials Co., Ltd.; the commercially available glass powder was BYBP-1 purchased from Guizhou Baibo New Materials Technology Co., Ltd.; the commercially available leveling agent was Dow Corning DC51 purchased from Shanghai Kayin Chemical Co., Ltd. The remaining reagents and equipment are conventional reagents and equipment in the technical field.

[0040] Preparation of Modified Silicone Oil-1

[0041] (1) The alkenyl quaternary ammonium salt was prepared through the following steps:

[0042] In a reactor, 0.1 mol of diisopropylaminotrimethylsilane and 50 mL of absolute ethanol were added, stirred and mixed evenly. After heating to 40 °C under nitrogen protection, 0.1 mol of allyl bromide was slowly added dropwise over 3 hours. After the addition was completed, the temperature was raised to 55 °C and the reaction was kept warm for 24 hours. Then, the absolute ethanol was removed and the alkenyl quaternary ammonium salt was obtained after recrystallization.

[0043] Mass spectrometry data of the alkenyl quaternary ammonium salt: The product was analyzed by LC-MS. The m / z of the product was 214.20 (100.0%), 215.20 (18.7%), 216.20 (4.9%).

[0044] (2) The modified silicone oil-1 was prepared through the following steps:

[0045] In a three-necked flask equipped with a stirrer, a reflux condenser and a thermometer, 50 ml of ethylene glycol dimethyl ether, 10 g of low hydrogen content silicone oil and 3 g of alkenyl quaternary ammonium salt were added. The mixture was heated to 90 °C and 0.1 ml of platinum catalyst was added dropwise at a constant temperature. The reaction was stirred for 6 hours. The ethylene glycol dimethyl ether solvent was removed by vacuum distillation from the system to obtain the modified silicone oil-1.

[0046] Preparation of Modified Silicone Oil-2

[0047] Basically the same as the preparation of modified silicone oil-1, the difference is that the alkenyl quaternary ammonium salt was replaced with an equal amount of 1-octene.

[0048] Preparation of Modified Silicone Oil-3

[0049] Basically the same as the preparation of modified silicone oil-1, the difference is that the alkenyl quaternary ammonium salt was replaced with an equal amount of allyltrimethylsilane.

[0050] Example 1

[0051] The glass powder for the front silver paste used in N-type crystalline silicon solar cells was prepared through the following steps:

[0052] (1) Mix modified silicone oil-1 and KH-560, and stir evenly to obtain a leveling agent for standby;

[0053] (1) Put the oxide powder into a mixer according to the weight parts, and stir and rotate for mixing for 2 hours;

[0054] (2) Divide the mixed oxide powder into crucibles, place them in a blast drying oven, and dry at 130°C for 4 hours;

[0055] (3) Place the dried mixture in a muffle furnace, heat to 900°C and melt for 2 hours to form a uniform glass liquid. Pour the high-temperature molten glass liquid quickly into deionized water for water quenching to obtain blocky glass;

[0056] (4) Dry the water-quenched blocky glass at 120°C for 24 hours, add the leveling agent and then pulverize it until the particle size range is D50 = 1μm, to obtain the glass powder for the front silver paste used in N-type crystalline silicon solar cells.

[0057] Among them, the mass ratio of modified silicone oil-1 to KH-560 in the leveling agent is 3:1; the mass ratio of the oxide powder to the leveling agent is 95:5; the weight parts of each component in the oxide powder are: 60 parts of PbO, 10 parts of SiO 2 10 parts of B 2 O 3 10 parts of Al 2 O 3 5 parts of Bi 2 O 3 15 parts of ZnO, 5 parts of MgO.

[0058] Example 2

[0059] Basically the same as Example 1, the difference is that the mass ratio of the oxide powder to the leveling agent is 100:3.

[0060] Example 3

[0061] Basically the same as Example 1, the difference is that the mass ratio of the oxide powder to the leveling agent is 90:5.

[0062] Comparative Example 1

[0063] Commercially available glass powder.

[0064] Comparative Example 2

[0065] Basically the same as Example 1, except that the leveling agent is changed to an equal amount of commercially available leveling agent.

[0066] Comparative Example 3

[0067] Basically the same as Example 1, except that the modified silicone oil-1 is changed to an equal amount of low hydrogen-containing silicone oil.

[0068] Comparative Example 4

[0069] Basically the same as Example 1, except that the modified silicone oil-1 is changed to an equal amount of modified silicone oil-2.

[0070] Comparative Example 5

[0071] Basically the same as Example 1, except that the modified silicone oil-1 is changed to an equal amount of modified silicone oil-3.

[0072] Performance Test

[0073] The glass powders prepared in Examples 1-3 and Comparative Examples 1-5 above were used to prepare the front silver paste, and the front silver paste was composed of the following components by mass ratio: 85% silver powder, 3% aluminum powder, 3% glass powder, and 9% organic binder.

[0074] Photovoltaic conversion efficiency detection: The prepared front silver paste was printed on the front surface of the N-type PERC cell for testing, and the I-V curve was detected using a TMC-PV1A solar cell tester to detect the photovoltaic conversion efficiency of the cell.

[0075] Contact resistance detection: The commonly used TLM (transmission line model) was selected to detect the contact resistance.

[0076] Metal recombination detection: The prepared front silver paste was printed on the cell, and a Sinton tester was used to detect the grid line metal recombination. The detection results are shown in the following table.

[0077]

[0078]

[0079] According to the comparison of the detection results of Examples 1-3 and Comparative Example 1, it can be seen that the glass powder provided by the present invention has good dispersibility, can reduce the metal recombination of the cell, reduce the recombination between the metal and the semiconductor, and thus improve the photovoltaic conversion efficiency of the cell, and can also make the silver paste have a low contact resistance and a high photovoltaic conversion efficiency when printed on the surface of the electrode sheet.

[0080] From the comparison of the test results of Examples 1-3 and Comparative Examples 3-5, it can be seen that the addition of a leveling agent to the glass powder provided by the present invention can improve the flowability of the glass powder; the modified silicone oil is grafted with a quaternary ammonium salt and a silicon methyl structure, which can greatly improve the dispersibility and fluidity of the silicone oil, thereby improving the uniformity and printing performance of the glass powder in the silver paste and enhancing the photoelectric conversion efficiency.

[0081] Detection of the printing grid line width range: The prepared front silver paste was printed on a solar cell with a grid line width of 14-20 μm, and its wire breakage situation and photoelectric conversion efficiency were detected.

[0082]

[0083] From the comparison of the test results of Examples 1-3 and Comparative Example 1, it can be seen that the glass powder provided by the present invention has excellent printing performance and can be applied to a narrower grid line width without wire breakage, thereby increasing the effective area of the solar cell for receiving sunlight and improving the photoelectric conversion efficiency of the solar cell.

[0084] From the comparison of the test results of Examples 1-3 and Comparative Examples 3-5, it can be seen that the modified silicone oil added to the glass powder provided by the present invention can improve the dispersibility and fluidity of the glass powder, and thus the prepared silver paste can be applied to electrode sheets with a narrower grid line width.

[0085] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it. It should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A glass powder for front silver paste used in N-type crystalline silicon solar cells, characterized in that, it comprises oxide powder and a leveling agent; the leveling agent comprises a modified silicone oil and a silane coupling agent; the modified silicone oil has a structure shown in the following formula A: ， where m = 120 - 160 and n = 15 - 20.

2. The glass powder for front silver paste used in N-type crystalline silicon solar cells according to claim 1, characterized in that, the mass ratio of the oxide powder to the leveling agent is (90 - 100):(3 - 5).

3. The glass powder for front silver paste used in N-type crystalline silicon solar cells according to claim 1, characterized in that, the silane coupling agent is selected from one of KH-560, KH-570, KH-580 or KH-590; the mass ratio of the modified silicone oil to the silane coupling agent in the leveling agent is 2 - 4:

1.

4. The glass powder for front silver paste used in N-type crystalline silicon solar cells according to claim 1, characterized in that, The oxide powder contains PbO, SiO 2 , B 2 O 3 , Al 2 O 3 , Bi 2 O 3 , ZnO and MgO; the weight parts of each component in the oxide powder are: 30 - 60 parts of PbO, 5 - 15 parts of SiO 2 , 5 - 10 parts of B 2 O 3 , 3 - 5 parts of Al 2 O 3 , 15 - 25 parts of Bi 2 O 3 , 5 - 10 parts of ZnO, 5 - 10 parts of MgO.

5. The glass powder for front silver paste used in N-type crystalline silicon solar cells according to claim 1, characterized in that, the sintering temperature of the glass powder is 700 - 900 °C.

6. The glass powder for front silver paste used in N-type crystalline silicon solar cells according to claim 1, characterized in that, the preparation method of the modified silicone oil is: in a reactor, add a solvent, a low hydrogen content silicone oil and an alkenyl quaternary ammonium salt, heat to 90 - 110 °C and then add a catalyst, stir and react for 6 - 8 hours and then remove the solvent to obtain the modified silicone oil.

7. The glass powder for front silver paste used in N-type crystalline silicon solar cells according to claim 6, characterized in that, the alkenyl quaternary ammonium salt has a structure shown in the following formula B: 。 8. The glass powder for front silver paste used in N-type crystalline silicon solar cells according to claim 7, characterized in that, the preparation method of the alkenyl quaternary ammonium salt is: in a reactor, add diisopropylamino trimethylsilane and an organic solvent, stir and mix evenly, under nitrogen protection, heat to 35 - 45 °C and then slowly dropwise add allyl bromide, the dropping time is 2 - 3 hours, after the dropping is completed, heat to 50 - 55 °C, keep warm and react for 18 - 24 hours, then remove the solvent, and obtain the alkenyl quaternary ammonium salt after recrystallization.

9. The glass powder for front silver paste used in N-type crystalline silicon solar cells according to claim 8, characterized in that, the molar ratio of diisopropylamino trimethylsilane to allyl bromide is 1:1 - 1.

2.

10. The preparation method of the glass powder for front silver paste used in N-type crystalline silicon solar cells according to any one of claims 1 - 8, characterized in that, it comprises the following steps: (1) Mix the modified silicone oil and the silane coupling agent, stir evenly and prepare the leveling agent for standby; (2) Put the oxide powder into a mixer according to the weight parts, stir and rotate for 1 - 2 hours; (3) Divide the mixed oxide powder into crucibles, place them in a blast drying oven, and dry at 120 - 140 °C for 2 - 4 hours; (4) Place the dried mixture in a muffle furnace, heat it to 850 - 1100 °C and melt it for 1 - 2 hours to form a homogeneous glass liquid. Pour the rapidly heated molten glass liquid into deionized water for water quenching to obtain blocky glass. (5) Dry the water-quenched blocky glass at 120 - 140 °C for 16 - 24 hours, add a leveling agent and then crush it until the particle size reaches D50 = 0.8 - 1.5 μm to prepare the glass powder for the front silver paste used in N-type crystalline silicon solar cells.

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