Conductive silver paste for HJT and preparation method, use method and application thereof

Abstract

The present application relates to a kind of HJT with conductive silver paste and its preparation method and use method and application.Conductive silver paste includes silver powder, first organic component, second organic component and organic solvent, wherein, the first organic component includes phenolic type epoxy resin, bisphenol A type epoxy resin, polyvinylidene fluoride and antioxidant, the second organic component includes curing agent and end-capped polyurethane resin.The conductive silver paste of the present application has the advantages of low resistivity, high welding tension, small influence of cold and hot environment change, etc.

Description

Technical Field

[0001] This invention relates to the photovoltaic field, specifically to a conductive silver paste for HJT, a method for preparing the conductive silver paste and its usage, and the application of the conductive silver paste in the photovoltaic field. Background Technology

[0002] HJT cells, short for Heterojunction with Intrinsic Thin-layer Technology, are a next-generation solar cell technology based on n-type silicon substrates. HJT cells combine the advantages of crystalline silicon cells and thin-film cells by depositing amorphous silicon thin films on crystalline silicon to form a heterojunction structure. HJT cells offer advantages such as high photoelectric conversion efficiency, low processing temperature, high stability, low degradation rate, and bifacial power generation, making them an important direction for current solar cell technology development.

[0003] Conductive silver paste is a key material in the production of high-temperature rotary electrode (HJT) batteries, especially in the preparation of the front electrode. Conductive silver paste for HJT front-side applications typically requires low-temperature curing properties, high conductivity, and good printability. This is because the processing temperature of HJT batteries is usually below 250°C, thus the conductive silver paste needs low-temperature curing properties to ensure good adhesion and conductivity at low temperatures. Simultaneously, HJT battery electrode preparation usually employs screen printing, requiring the conductive silver paste to have good printability to ensure the clarity and uniformity of the electrode pattern. Furthermore, since the conductivity of the conductive silver paste directly affects the photoelectric conversion efficiency of the battery, high conductivity is required. However, existing conductive silver pastes for HJT batteries suffer from problems such as high resistivity, low tensile strength and aging tensile strength, significant influence from thermal environmental changes, and poor corrosion resistance.

[0004] With the continuous development of HJT battery technology and the acceleration of industrialization, the performance of conductive silver paste for HJT batteries needs to be optimized and improved. Summary of the Invention

[0005] In view of the deficiencies in the existing technology, the purpose of this invention is to provide a conductive silver paste for HJT, its preparation method, usage method and application, and to solve the problems of high resistivity, low tensile strength and aging tensile strength, and large influence of changes in cold and hot environment in the existing conductive silver paste for HJT.

[0006] To achieve the above objectives, the first aspect of the present invention provides a conductive silver paste for HJT, which includes silver powder, a first organic component, a second organic component, and an organic solvent, wherein the first organic component includes phenolic epoxy resin, bisphenol A epoxy resin, polyvinylidene fluoride, and an antioxidant, and the second organic component includes a curing agent and an end-capped polyurethane resin.

[0007] Based on the above technical solution, preferably, the HJT uses conductive silver paste, which, by weight percentage, contains 80-90% silver powder, 2-5% first organic component, 2-5% second organic component, and 6-15% organic solvent.

[0008] Based on the above technical solution, preferably, the first organic component, by weight percentage, contains 50-70% phenolic epoxy resin, 20-25% bisphenol A epoxy resin, 4-8% polyvinylidene fluoride, and 6-20% antioxidant.

[0009] Based on the above technical solution, preferably, the weight ratio of phenolic epoxy resin to bisphenol A epoxy resin is 1:0.3-0.45.

[0010] Based on the above technical solution, preferably, the weight ratio of phenolic epoxy resin to polyvinylidene fluoride is 1:0.06-0.15.

[0011] Based on the above technical solution, preferably, the second organic component, by weight percentage, contains 80-90% curing agent and 10-20% end-capped polyurethane resin.

[0012] Based on the above technical solution, preferably, the weight ratio of the first organic component to the second organic component is 1:0.5-1.5.

[0013] Based on the above technical solution, preferably, the conductive silver paste for HJT further includes additives. More preferably, the additives are selected from one or more of dispersants, leveling agents, thixotropic agents, coupling agents, and defoamers. In this invention, the dispersant, leveling agent, thixotropic agent, coupling agent, and defoamer can be conventional options in the art. For example, the dispersant can be BYK-W980, etc.; the coupling agent can be a silane coupling agent, etc.; the leveling agent can be castor oil, etc.; and the defoamer can be dimethyl silicone oil, etc. In this invention, the amount of additive added, based on the total weight of the conductive silver paste for HJT, can be 0.1-0.5 parts by weight. For example, 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, etc.

[0014] Based on the above technical solution, preferably, the phenolic epoxy resin is F51 phenolic epoxy resin and / or F44 phenolic epoxy resin.

[0015] Based on the above technical solution, preferably, the bisphenol A type epoxy resin is one or more of bisphenol A type epoxy resin E03, bisphenol A type epoxy resin E44, and bisphenol A type epoxy resin E51.

[0016] Based on the above technical solution, preferably, the antioxidant is selected from antioxidant 168 and / or antioxidant 1010.

[0017] Based on the above technical solution, preferably, the curing agent is selected from one or more of phthalic anhydride, hexahydrophthalic anhydride, glutaric anhydride and dodecyl succinic anhydride.

[0018] Based on the above technical solution, preferably, the organic solvent is selected from one or more of diethylene glycol butyl ether acetate, dimethyl glutarate, dimethyl succinate, and dimethyl adipate.

[0019] A second aspect of the present invention provides a method for preparing the above-mentioned conductive silver paste for HJT, comprising:

[0020] Step 1. Mix phenolic epoxy resin, bisphenol A epoxy resin, polyvinylidene fluoride and antioxidant to obtain the first organic component;

[0021] Step 2. Mix the silver powder, the first organic component, and the organic solvent to obtain the first raw material;

[0022] Step 3. Mix the curing agent and the end-capped polyurethane resin to obtain the second raw material.

[0023] In this invention, steps 1 and 2 are sequential, while step 3 is not sequential with steps 1 and 2.

[0024] The third aspect of the present invention provides a method for using the above-mentioned conductive silver paste for HJT, comprising: mixing the first raw material and the second raw material and screen printing and curing them;

[0025] Based on the above technical solution, preferably, the curing conditions include: a temperature of 200-300℃ and a time of 1-8 hours.

[0026] The fourth aspect of this invention provides the application of the above-mentioned conductive silver paste for HJT in photovoltaics.

[0027] Based on the above technical solution, it is preferably applied to N-type HJT batteries.

[0028] The beneficial effects of this invention are:

[0029] (1) This invention utilizes both phenolic epoxy resin and bisphenol A epoxy resin to improve the aging performance and reduce brittleness of the slurry. The epoxy group functionality of phenolic epoxy resin is greater than 2, meaning that it can form a higher crosslinking density after curing, thereby improving the heat resistance and photolysis resistance of the conductive silver paste. Simultaneously, phenolic epoxy resin has good mechanical properties, exhibiting long lifespan and good stability in photovoltaic applications, reducing aging phenomena. Bisphenol A epoxy resin has good processing performance and is easily mixed with other materials for molding. Cured bisphenol A epoxy resin possesses excellent mechanical strength and good thermal stability. In a preferred embodiment, by using a suitable ratio of phenolic epoxy resin and bisphenol A epoxy resin, the advantages of both can be fully utilized, compensating for their respective shortcomings. The high crosslinking density and stable chemical structure of phenolic epoxy resin help improve the overall aging performance of the material, reducing performance degradation under harsh environments such as high temperature, humidity, and ultraviolet radiation. However, phenolic epoxy resins have a certain degree of brittleness, while the addition of bisphenol A epoxy resins can balance the brittleness of phenolic epoxy resins through their good processing and flexibility. When the two are mixed in a specific ratio and combined with other substances in the conductive paste, the photolysis resistance, aging resistance, brittleness, and adhesion of the conductive paste can be further increased.

[0030] (2) The crosslinking density of epoxy resin directly affects its physical and chemical properties, including hardness, strength, heat resistance, and solvent resistance. High crosslinking density usually means better mechanical properties and thermal stability, but it can also lead to brittleness, which is particularly evident under extreme conditions such as thermal shock. This invention, by introducing multifunctional polyurethane segments, can balance the brittleness of epoxy resin by maintaining sufficient crosslinking network density and utilizing the flexibility of the polyurethane segments. The polyurethane segments themselves have good flexibility and elasticity, which can absorb and disperse energy when epoxy resin is subjected to external impact, thereby effectively preventing the material from cracking or breaking. This toughening effect enables the modified epoxy resin to exhibit better durability and stability under harsh environments such as hot and cold, thereby improving the overall performance of the material. Detailed Implementation

[0031] In the following technical description, for ease of explanation, numerous details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be practiced without these details.

[0032] The terms "first," "second," etc., used in the specification and claims of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0033] The following are examples; in the following examples and comparative examples,

[0034] Hexamethylene diisocyanate-based polyisocyanate, purchased from Wanhua Chemical;

[0035] Polytetrahydrofuran diol (number average Mn approximately 2000) was purchased externally, CAS number 25190-06-1;

[0036] Phenolic epoxy resin F51 was purchased externally; CAS number is 24969-06-0.

[0037] Bisphenol A type epoxy resin E44 was purchased externally, CAS number 25085-99-8;

[0038] Polyvinylidene fluoride was purchased externally; CAS number 24937-79-9.

[0039] Hexahydrophthalic acid was purchased externally; CAS number is 85-42-7.

[0040] Antioxidant 168 was purchased externally; CAS number is 31570-04-4.

[0041] Diethylene glycol butyl ether acetate was purchased externally, with CAS number 124-17-4.

[0042] Preparation Example 1

[0043] Preparation of hydroxyl-terminated polyurethane resins:

[0044] 1000 parts by weight of dehydrated polytetrahydrofuran diol and 1 part by weight of dibutyltin dilaurate catalyst were added to a reactor and stirred until homogeneous. Nitrogen gas was then introduced into the reactor for protection. The temperature was raised to 65°C, and 100 parts by weight of hexamethylene diisocyanate-based polyisocyanate were added, controlled to be completed within 2 hours, with the temperature not exceeding 90°C. After the addition was complete, the internal temperature was maintained at 80-90°C for 3 hours. Finally, a sample was taken, and the -NCO content was determined using the di-n-butylamine method. When the test result was 0, hydroxyl-terminated polyurethane resin was obtained.

[0045] Example 1

[0046] Preparation of conductive silver paste for HJT:

[0047] Step 1: Mix 60 parts by weight of phenolic epoxy resin F51, 25 parts by weight of bisphenol A epoxy resin E44, 8 parts by weight of polyvinylidene fluoride and 7 parts by weight of antioxidant 168 to obtain the first organic component.

[0048] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0049] Step 3: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin. Take 2 parts by weight as the second raw material.

[0050] Example 2

[0051] Preparation of conductive silver paste for HJT:

[0052] Step 1: Mix 60 parts by weight of phenolic epoxy resin F51, 25 parts by weight of bisphenol A epoxy resin E44, 8 parts by weight of polyvinylidene fluoride and 7 parts by weight of antioxidant 168 to obtain the first organic component.

[0053] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 8.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0054] Step 3: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin. Take 3 parts by weight as the second raw material.

[0055] Example 3

[0056] Preparation of conductive silver paste for HJT:

[0057] Step 1: Mix 60 parts by weight of phenolic epoxy resin F51, 20 parts by weight of bisphenol A epoxy resin E44, 5 parts by weight of polyvinylidene fluoride and 15 parts by weight of antioxidant 168 to obtain the first organic component.

[0058] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0059] Step 3: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin. Take 2 parts by weight as the second raw material.

[0060] Example 4

[0061] Preparation of conductive silver paste for HJT:

[0062] Step 1: Mix 55 parts by weight of phenolic epoxy resin F51, 25 parts by weight of bisphenol A epoxy resin E44, 4 parts by weight of polyvinylidene fluoride and 16 parts by weight of antioxidant 168 to obtain the first organic component.

[0063] Step 2: Mix 80 parts by weight of silver powder, 5 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0064] Step 3: Mix 80 parts by weight of hexahydrophthalic anhydride curing agent and 20 parts by weight of end-capped polyurethane resin. Take 5 parts by weight as the second raw material.

[0065] Example 5

[0066] Preparation of conductive silver paste for HJT:

[0067] Step 1: Mix 69 parts by weight of phenolic epoxy resin F51, 21 parts by weight of bisphenol A epoxy resin E44, 4 parts by weight of polyvinylidene fluoride and 6 parts by weight of antioxidant 168 to obtain the first organic component.

[0068] Step 2: Mix 80 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0069] Step 3: Mix 90 parts by weight of hexahydrophthalic anhydride curing agent and 10 parts by weight of end-capped polyurethane resin. Take 2 parts by weight as the second raw material.

[0070] Example 6

[0071] Preparation of conductive silver paste for HJT:

[0072] Step 1: Mix 45 parts by weight of phenolic epoxy resin F51, 40 parts by weight of bisphenol A epoxy resin E44, 8 parts by weight of polyvinylidene fluoride and 7 parts by weight of antioxidant 168 to obtain the first organic component.

[0073] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0074] Step 3: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin. Take 2 parts by weight as the second raw material.

[0075] Example 7

[0076] Preparation of conductive silver paste for HJT:

[0077] Step 1: Mix 60 parts by weight of phenolic epoxy resin F51, 25 parts by weight of bisphenol A epoxy resin E44, 2 parts by weight of polyvinylidene fluoride and 13 parts by weight of antioxidant 168 to obtain the first organic component.

[0078] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0079] Step 3: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin. Take 2 parts by weight as the second raw material.

[0080] Example 8

[0081] Preparation of conductive silver paste for HJT:

[0082] Step 1: Mix 60 parts by weight of phenolic epoxy resin F51, 25 parts by weight of bisphenol A epoxy resin E44, 8 parts by weight of polyvinylidene fluoride and 7 parts by weight of antioxidant 168 to obtain the first organic component.

[0083] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 10.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0084] Step 3: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin. Take 1 part by weight as the second raw material.

[0085] Example 9

[0086] Preparation of conductive silver paste for HJT:

[0087] Step 1: Mix 60 parts by weight of phenolic epoxy resin F51, 25 parts by weight of bisphenol A epoxy resin E44, 8 parts by weight of polyvinylidene fluoride and 7 parts by weight of antioxidant 168 to obtain the first organic component.

[0088] Step 2: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin.

[0089] Step 3: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 2 parts by weight of the second organic component obtained in Step 2, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent, and 0.2 parts by weight of dispersant BYK-W980, and roll and disperse evenly in a three-roll mill to obtain conductive silver paste for HJT.

[0090] Comparative Example 1

[0091] Preparation of conductive silver paste for HJT:

[0092] The method is the same as in Example 1, except that the bisphenol A type epoxy resin E44 is replaced with phenolic type epoxy resin F51, that is:

[0093] Step 1: Mix 85 parts by weight of phenolic epoxy resin F51, 8 parts by weight of polyvinylidene fluoride and 7 parts by weight of antioxidant 168 to obtain the first organic component.

[0094] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0095] Step 3: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin. Take 2 parts by weight as the second raw material.

[0096] Comparative Example 2

[0097] Preparation of conductive silver paste for HJT:

[0098] The method is the same as in Example 1, except that the phenolic epoxy resin F51 is replaced with the bisphenol A epoxy resin E44, that is:

[0099] Step 1: Mix 85 parts by weight of bisphenol A type epoxy resin E44, 8 parts by weight of polyvinylidene fluoride and 7 parts by weight of antioxidant 168 to obtain the first organic component.

[0100] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0101] Step 3: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin. Take 2 parts by weight as the second raw material.

[0102] Comparative Example 3

[0103] Preparation of conductive silver paste for HJT:

[0104] The method is the same as in Example 1, except that polyvinylidene fluoride is replaced with phenolic epoxy resin F51, that is:

[0105] Step 1: Mix 68 parts by weight of phenolic epoxy resin F51, 25 parts by weight of bisphenol A epoxy resin E44 and 7 parts by weight of antioxidant 168 to obtain the first organic component.

[0106] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0107] Step 3: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin. Take 2 parts by weight as the second raw material.

[0108] Comparative Example 4

[0109] Preparation of conductive silver paste for HJT:

[0110] The method is the same as in Example 1, except that the end-capped polyurethane resin is replaced with hexahydrophthalic anhydride curing agent, i.e.:

[0111] Step 1: Mix 60 parts by weight of phenolic epoxy resin F51, 25 parts by weight of bisphenol A epoxy resin E44, 8 parts by weight of polyvinylidene fluoride and 7 parts by weight of antioxidant 168 to obtain the first organic component.

[0112] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0113] Step 3: Take 2 parts by weight of hexahydrophthalic anhydride curing agent as the second raw material.

[0114] Comparative Example 5

[0115] Preparation of conductive silver paste for HJT:

[0116] The method is the same as in Example 1, except that both phenolic epoxy resin F51 and bisphenol A epoxy resin E44 are replaced with 2,3-epoxypropyl acrylate, i.e.:

[0117] Step 1: Mix 85 parts by weight of 2,3-epoxypropylene acrylate, 8 parts by weight of polyvinylidene fluoride and 7 parts by weight of antioxidant 168 to obtain the first organic component.

[0118] Step 2: Mix 85 parts by weight of silver powder, 3 parts by weight of the first organic component obtained in Step 1, 9.6 parts by weight of diethylene glycol butyl ether acetate, 0.2 parts by weight of castor oil leveling agent and 0.2 parts by weight of dispersant BYK-W980 to obtain the first raw material;

[0119] Step 3: Mix 85 parts by weight of hexahydrophthalic anhydride curing agent and 15 parts by weight of end-capped polyurethane resin. Take 2 parts by weight as the second raw material.

[0120] Test case

[0121] Performance testing:

[0122] Test Examples 1-8 and Test Comparison Examples 1-5

[0123] The first and second raw materials of Examples 1-8 and Comparative Examples 1-5 were mixed and uniformly dispersed by rolling in a three-roll mill to obtain conductive silver paste for HJT. Alternatively, the conductive silver paste for HJT of Example 9 was directly tested. The resistivity, contact resistivity, peel strength, and aging performance of the electrodes prepared with the conductive silver paste were tested, and the results are shown in Table 1.

[0124] Test method:

[0125] (1) Resistivity Testing Method: The conductive pastes of the examples and comparative examples were screen-printed and coated onto crystalline silicon HJT solar blue films, and vacuum dried at room temperature for 3 hours. They were then cured at 150°C using circulating hot air for 30 minutes to obtain fine-wire electrodes. The resistance of the fine-wire electrodes was measured using an AEMC6240 micro-resistivity meter, and the width and length of the filaments were measured using a WI-5000 interferometric coaxial three-dimensional stereomicroscope. The pattern specifications of the formed fine-wire electrodes were as follows: the width of the middle line segment was 40 μm, the length was 9 cm, and the contact pads at the head and tail were 2 mm × 2 mm. The line resistance was measured by four-terminal sensing between the contact pads. The measured resistance was normalized by the grid line length and multiplied by the cross-sectional area (measured using an α-step profiler) to obtain the resistivity (ρ) of the grid line. Each resistivity dataset was obtained by averaging the values ​​measured for four different grid lines.

[0126] (2) Contact resistivity test method: The conductive pastes of the examples and comparative examples were screen-printed and coated onto crystalline silicon HJT solar blue films, and vacuum dried at room temperature for 3 hours. Then, they were cured at 150°C using circulating hot air for 30 minutes to obtain fine-line electrodes. The electrode pattern consisted of five linear electrodes with a line width of 0.5 mm and a length of 50 mm, with a line spacing of 3 mm. The resistance between the line electrodes with different spacings was then measured using an AEMC 6240 microresistivity meter, and the contact resistivity (Rt) with the substrate was calculated using the transmission line model (TLM) method. c ).

[0127] (3) Peel strength test method: The conductive pastes of the examples and comparative examples were screen-printed and coated onto crystalline silicon HJT solar blue films, and vacuum dried at room temperature for 3 hours. Then, they were cured at 150°C using circulating hot air for 30 minutes to obtain fine-wire electrodes. Electrode patterns were obtained. The test electrode pattern was 5cm long and 2mm wide, and then a 1mm wide tin-plated copper strip was soldered onto the test electrode. The substrate was fixed on a tension gauge platform to test the peel strength. The tension gauge type was an NLB-100 electronic push-pull pressure gauge. The test conditions were to peel the solder strip at a speed of 60mm / min at a 180° angle and obtain the tensile force value, recorded once per second. The obtained tension is the average value of a 5cm long electrode.

[0128] (4) Test method for aging resistance: 200 cycles of hot and cold cycling to test the decay of photoelectric conversion efficiency. Aging resistance (decay%) = (initial photoelectric conversion efficiency - photoelectric conversion efficiency after 200 cycles of hot and cold cycling) ÷ initial photoelectric conversion efficiency × 100%.

[0129] Table 1

[0130]

[0131]

[0132] As can be seen from the table above, the HJT conductive silver paste prepared using the formulation of this invention can reduce resistivity and contact resistance, and improve welding tensile strength and aging resistance. In particular, Examples 1-5 exhibit even better performance within the specific weight ratio ranges of phenolic epoxy resin to bisphenol A epoxy resin and the weight ratio range of phenolic epoxy resin to polyvinylidene fluoride of this invention.

[0133] As can be seen from the embodiments of the present invention, the formulation of the present invention can be rapidly cured at 150°C for 30 minutes and has a low resistivity after curing. Compared with most existing high-temperature curing conditions of 200°C-250°C, the formulation of the present invention represents a significant improvement and is more suitable for N-type HJT batteries.

[0134] Moreover, as can be seen from the embodiments of the present invention, compared with the pre-mixed embodiment 9, the formulation of the present invention is more suitable for mixing the first raw material component and the second raw material component before use, and the effect is better.

[0135] This application is not limited to the embodiments described above, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

[0136] In this application, each embodiment may focus on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other.

Claims

1. A conductive silver paste for HJT, comprising silver powder, a first organic component, a second organic component, and an organic solvent, wherein, The first organic component includes phenolic epoxy resin, bisphenol A epoxy resin, polyvinylidene fluoride and antioxidant; the second organic component includes curing agent and end-capped polyurethane resin. The HJT uses conductive silver paste, which, by weight percentage, contains 80-90% silver powder, 2-5% first organic component, 2-5% second organic component, and 6-15% organic solvent. The first organic component, by weight percentage, comprises 50-70% phenolic epoxy resin, 20-25% bisphenol A epoxy resin, 4-8% polyvinylidene fluoride, and 6-20% antioxidant. The weight ratio of phenolic epoxy resin to bisphenol A epoxy resin is 1:0.3-0.45; the weight ratio of phenolic epoxy resin to polyvinylidene fluoride is 1:0.06-0.

15. The second organic component, by weight percentage, comprises 80-90% curing agent and 10-20% end-capped polyurethane resin. The weight ratio of the first organic component to the second organic component is 1:0.5-1.

5.

2. The conductive silver paste for HJT according to claim 1, characterized in that, The conductive silver paste for HJT also includes additives.

3. The conductive silver paste for HJT according to claim 2, characterized in that, The additive is selected from one or more of dispersants, leveling agents, thixotropic agents, coupling agents, and defoamers.

4. The conductive silver paste for HJT according to claim 1, characterized in that, The phenolic epoxy resin is F51 phenolic epoxy resin and / or F44 phenolic epoxy resin.

5. The conductive silver paste for HJT according to claim 1, characterized in that, The bisphenol A type epoxy resin is one or more of bisphenol A type epoxy resin E03, bisphenol A type epoxy resin E44, and bisphenol A type epoxy resin E51.

6. The conductive silver paste for HJT according to claim 1, characterized in that, The antioxidant is selected from antioxidant 168 and / or antioxidant 1010.

7. The conductive silver paste for HJT according to claim 1, characterized in that, The curing agent is selected from one or more of phthalic anhydride, hexahydrophthalic anhydride, glutaric anhydride, and dodecyl succinic anhydride.

8. The conductive silver paste for HJT according to claim 1, characterized in that, The organic solvent is selected from one or more of diethylene glycol butyl ether acetate, dimethyl glutarate, dimethyl succinate, and dimethyl adipate.

9. A method for preparing conductive silver paste for HJT according to any one of claims 1-8, comprising: Step 1. Mix phenolic epoxy resin, bisphenol A epoxy resin, polyvinylidene fluoride and antioxidant to obtain the first organic component; Step 2. Mix the silver powder, the first organic component, and the organic solvent to obtain the first raw material; Step 3. Mix the curing agent and the end-capped polyurethane resin to obtain the second raw material.

10. The method of using the HJT conductive silver paste according to any one of claims 1-8, comprising: The first and second raw materials are mixed, screen printed, and cured.

11. The method of use according to claim 10, characterized in that, The curing conditions include a temperature of 200-300℃ and a time of 1-8 hours.

12. The application of HJT conductive silver paste according to any one of claims 1-8 in photovoltaics.

13. The application according to claim 12, characterized in that, Conductive silver paste is used in HJT batteries for N-type HJT cells.

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