HJT silver paste and preparation method therefor

Abstract

The present disclosure provides an HJT silver paste and a preparation method therefor. The HJT silver paste comprises the following components in percentages by mass: 85-92% of silver powder, 2-10% of a resin, 1-4% of a curing agent, 0-1% of silicone oil, 0-1% of an epoxy catalyst, 0-0.1% of a silicone oil catalyst, and 2-5% of an organic solvent, wherein the silver powder comprises spherical powder, quasi-spherical powder and flake powder. The silver powder at least comprises three types of powder having different particle sizes, wherein the first type is spherical and quasi-spherical powder having a D50 of 2-6 μm and a tap density of 5-6 g / mL and accounting for 30-50%; the second type is spherical and quasi-spherical powder having a D50 of 0.1-1 μm and a tap density of 3-5 g / mL and accounting for 20-40%, and the third type is flake powder having a D50 of 0.5-2 μm and a tap density of 3-5 g / mL and accounting for 5-10%.

Description

HJT Silver Paste and its Preparation Method Technical Field

[0001] This disclosure relates to the technical field of conductive silver paste and its preparation, and more particularly to an HJT silver paste and its preparation method. Background Technology

[0002] With the development of new energy vehicles, the demand for electricity is increasing year by year. Traditional thermal power generation has the disadvantage of high carbon emissions, while hydropower and nuclear power are environmentally friendly, but have high investment costs and slow development speed.

[0003] Solar photovoltaic (PV) technology, as a sustainable new energy source, is gaining increasing attention due to its ease of installation and low cost. Especially in recent years, solar cell technology has evolved rapidly, with TOPCON cells becoming the current mainstream in the market. HJT photovoltaic cells, also known as heterojunction cells, are a later entrant. They utilize passivation treatment on both the front and back surfaces of a crystalline silicon substrate to effectively prevent recombination of light-generated charge carriers and improve carrier lifetime, thereby increasing conversion efficiency. This type of cell combines the advantages of crystalline silicon cells and thin-film cells, improving conversion efficiency and is expected to replace TOPCON cells.

[0004] While HJT photovoltaic cells boast excellent conversion efficiency, their high cost has hindered their development. One significant factor influencing this cost is the multiple printing processes. As is well known, HJT silver paste printing involves both main grid printing and fine grid printing, making simultaneous printing of both impossible. This adds to the production process, impacts product yield, and ultimately increases cell costs.

[0005] Therefore, it is necessary to provide a new HJT silver paste and its preparation method to solve all or part of the above problems. Summary of the Invention

[0006] The purpose of this disclosure is to provide an HJT silver paste and its preparation method. This technical solution can achieve integrated main and fine grids, solve the problem of cumbersome paste printing, and reduce printing and production costs.

[0007] The technical solution is as follows:

[0008] An HJT silver paste, by weight percentage, comprises the following components: 85-92% silver powder, 2-10% resin, 1-4% curing agent, 0-1% silicone oil, 0-1% epoxy catalyst, 0-0.1% silicone oil catalyst, and 2-5% organic solvent;

[0009] Silver powder includes spherical powder, spherical powder, and flake powder;

[0010] The silver powder comprises at least three types of powder with different particle sizes: the first type consists of spherical powder and spheroidal powder with a D50 of 2-6 μm and a tap density of 5-6 g / mL, accounting for 30-50%; the second type consists of spherical powder and spheroidal powder with a D50 of 0.1-1 μm and a tap density of 3-5 g / mL, accounting for 20-40%; and the third type consists of flake powder with a D50 of 0.5-2 μm and a tap density of 3-5 g / mL, accounting for 5-10%.

[0011] Furthermore, the resin is composed of a main resin and auxiliary resins. The main resin is any two or any combination of the following: phenoxy resins JER1007, 1010, 1004, PKHB, PKHH; epoxy resins 4007P, 4010P, 7787, 3150, 2021P; polyester resins Vylon-GK888, BX-7000A, 270, ES410, ES420; and polyurethane resins TPU5778, TPU 5703, TPU58887.

[0012] The auxiliary resin is a modified resin, which is pre-synthesized from the first resin by a modifier. The modifier includes any two or any combination of silane coupling agents, titanate coupling agents, polyetheramines, silane coupling agents KH550, KH560, P-S496, SCA-A20F, titanate coupling agents TCA-KTTS, TCA-238J, TCA-K55, TCA-K44, TCA-KTTT, and polyetheramine phosphate Baxxodur EC301, EC302, D230, D400. The first resin used for modification includes any two or any combination of epoxy resins JER 827, 806, TT386, GE60, and polyester polyols Dynacoll 7110, 7111, 7360, 7380. The first resin is a low molecular weight liquid resin containing at least two functional groups.

[0013] Furthermore, in the synthesis of the auxiliary resin, the ratio of the modifier to the first resin used for modification is 1-5:100. The first resin to be modified is added to the reactor, the modifier is added gradually, the mixture is heated to 70-95℃, and stirred for 1-2 hours until the resin forms a homogeneous phase with no reaction. The mixture is then allowed to stand and cool to room temperature, and filtered through a 300-400 mesh screen to obtain the liquid modified resin.

[0014] The thixotropic agent may be any one or any combination of two of the following: hydrogen-containing silicone oil, dimethyl silicone oil, vinyl silicone oil, methoxy silicone oil, ethoxy silicone oil, polyether silicone oil, or hydroxyl silicone oil. The specific proportion of the thixotropic agent and / or the specific combination of silicone oils shall be matched and adjusted according to the type of silicone oil catalyst used.

[0015] The curing agents used are at least two types of blocked isocyanate curing agents, with an unblocking temperature of 80-150℃, and preferably a curing temperature of 90-130℃.

[0016] The epoxy catalyst used was an imidazole-diacid composite catalyst, with an imidazole to diacid molar ratio of 1:1. N-methylpyrrolidone was added to the reactor, and imidazole and diacid were added gradually and sequentially. The mixture was stirred at room temperature until homogeneous and no reaction was observed. The mixture was then allowed to stand and cool to room temperature to obtain the composite catalyst.

[0017] Furthermore, the imidazole is any one of benzimidazole, DBU, dimethyltetraethylimidazolium, PN23, PN23J, and PN40, and the diacid is any one of the organic diacids adipic acid, succinic acid, glutaric acid, and sebacic acid.

[0018] The silicone oil catalyst is any one of dibutyltin dilaurate, caster catalyst, stannous octoate, dibutyltin diacetate, DBPMH, BPO, platinum catalyst, and KAT670.

[0019] Furthermore, the organic solvent is any one or any combination thereof, propylene carbonate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate, dimethyl adipate, diethyl adipate, propylene glycol methyl ether acetate, terpineol.

[0020] The technical solution disclosed herein also includes a method for preparing HJT silver paste, which specifically includes the following steps:

[0021] 1) Add 2-5% organic solvent to the reaction vessel and mix, then add 2-10% resin, heat and stir, cool to room temperature, filter, and obtain resin solution; wherein the heating temperature is 70-95℃, the stirring speed is 200-300r / min, and the heating and stirring time is 1-2h.

[0022] 2) Add 0-1% epoxy catalyst, 0-1% silicone oil (thixotropic agent), 0-0.1% silicone oil catalyst, 1-4% curing agent and 1-2% diluent to the resin solution prepared in step 1) in sequence, and centrifuge to disperse to obtain organic carrier; wherein the centrifugation speed is 800-850 rpm and the centrifugation time is 2-4 min;

[0023] 3) Add 85-92% silver powder to the organic carrier prepared in step 2), centrifuge and disperse it, then shear and disperse it through a three-roll mill until the fineness of the slurry is less than 5μm, filter it, and obtain the finished silver paste; the specific process of centrifugation dispersion is as follows: disperse at 800rpm, 1000rpm, 1200rpm and 1600rpm for 1-3min each.

[0024] The HJT silver paste and its preparation method provided in the embodiments of this disclosure have at least one or a portion of the following advantages:

[0025] (1) It has good meshing properties of fine grid, low volume resistivity, excellent contact resistance, and high welding pull and adhesion of the main grid.

[0026] (2) Achieving multi-powder combination increases the effective contact points of silver powder, reduces the intrinsic resistance of HJT silver paste, and maintains high silver content to ensure that HJT silver paste has good conductivity.

[0027] (3) The use of low molecular weight resin in HJT silver paste introduces a curing agent with strong adhesion to react with the resin to generate a large number of hydroxyl groups, which can significantly improve the curing speed while taking into account the printability and adhesion of HJT silver paste.

[0028] (4) The curing of HJT silver paste adopts a combination of catalyst and curing agent. The catalyst is selected with imidazole diacid structure to obtain good latency of imidazole structure and thus extend the storage period. Imidazole and diacid participate in epoxy curing reaction at the same time (imidazole catalysis and diacid curing) to synergistically enhance the curing speed of resin and increase crosslinking density.

[0029] (5) The introduction of silicone oil catalyst can effectively suppress the side effects of silicone oil while improving the leveling properties of HJT silver paste printing and reducing the resistance value, thus ensuring the high welding pull of the main grid. Attached Figure Description

[0030] These and / or other aspects and advantages of this disclosure will become apparent and readily understood from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which:

[0031] Figure 1 is a rendering of an HJT silver paste integrating the main and fine grids according to an embodiment of the present disclosure applied to a solar cell;

[0032] Figure 2 is another effect diagram of HJT silver paste with integrated main and fine grids applied to a solar cell according to an embodiment of the present disclosure. Detailed Implementation

[0033] The features of this disclosure are further illustrated below through specific embodiments. The following description of embodiments of this disclosure with reference to the accompanying drawings is intended to explain the overall concept of this disclosure and should not be construed as a limitation thereof.

[0034] Example 1

[0035] An HJT silver paste, by mass percentage, comprises the following components: 85% silver powder, 10% resin, 3% curing agent, and 3% organic solvent.

[0036] The silver powder includes at least three types of powder with different particle sizes: the first type is spherical powder and spheroidal powder with a D50 of 4μm and a tap density of 5g / mL, accounting for 45%; the second type is spherical powder and spheroidal powder with a D50 of 0.5μm and a tap density of 4.5g / mL, accounting for 35%; and the third type is flake powder with a D50 of 1μm and a tap density of 3g / mL, accounting for 5%.

[0037] The resin is mainly epoxy resin: 6% phenyl oxy resin PKHH and 4% polyester resin 270.

[0038] Curing agent: Composed of isocyanate curing agent and auxiliary curing agent, specifically 1% XB-G282 isocyanate curing agent with a desealing temperature of 80℃, and 2% SBN-70D isocyanate curing agent with a desealing temperature of 120℃.

[0039] Organic solvent: 3% diethylene glycol butyl ether acetate.

[0040] The preparation method of this HJT silver paste includes the following steps:

[0041] (1) Mix 3% diethylene glycol butyl ether acetate organic solvent in a reaction vessel, gradually add 10% resin, heat to 85°C, stir at 260 r / min for 1 h until the resin is completely dissolved, let stand, cool to room temperature, filter with 300-400 mesh cloth to obtain resin solution.

[0042] (2) Take the prepared resin solution, and centrifuge and disperse 1% XB-G282 isocyanate curing agent and 2% SBN-70D isocyanate curing agent at 800 rpm for 2 min, and then mix thoroughly to obtain an organic carrier.

[0043] (3) Take the prepared organic carrier and add 35% D50 0.5μm ball powder and stir. Then centrifuge and stir at 800rpm, 1000rpm, 1200rpm and 1600rpm respectively for 1min.

[0044] (4) Slowly add the remaining silver powder while manually stirring. After all the silver powder is stirred evenly, centrifuge and stir at 800 rpm, 1000 rpm, 1200 rpm and 1600 rpm for 1 minute each. After centrifugation, use a three-roll mill to shear and disperse the slurry until the fineness of the slurry reaches below 2 μm, then stop the three-roll mill.

[0045] (5) Use a 500-mesh sieve to filter out impurities and large, uneven particles from the slurry to obtain HJT silver paste with integrated main and fine grids.

[0046] Example 2

[0047] An HJT silver paste, by mass percentage, comprises the following components: 92% silver powder, 3% resin, 1.5% curing agent, 0.1% silicone oil, and 3% organic solvent.

[0048] The silver powder includes at least three types of powder with different particle sizes: the first type is spherical powder and spheroidal powder with a D50 of 4μm and a tap density of 5g / mL, accounting for 42%; the second type is spherical powder and spheroidal powder with a D50 of 0.5μm and a tap density of 4.5g / mL, accounting for 40%; and the third type is flake powder with a D50 of 1μm and a tap density of 3g / mL, accounting for 10%.

[0049] The resin is mainly epoxy resin: 2% phenyl oxy resin PKHH and 1% polyester resin 270.

[0050] Curing agent: Composed of isocyanate curing agent and auxiliary curing agent, specifically 0.5% XB-G282 isocyanate curing agent with an unsealing temperature of 80℃ and 1% SBN-70D isocyanate curing agent with an unsealing temperature of 120℃.

[0051] Silicone oil: 0.1% hydroxyl silicone oil.

[0052] Organic solvent: 3% diethylene glycol butyl ether acetate.

[0053] The preparation method of this HJT silver paste includes the following steps:

[0054] (1) Mix 3% diethylene glycol butyl ether acetate organic solvent in a reaction vessel, gradually add 3% resin, heat to 85°C, stir at 260 r / min for 1 h until the resin is completely dissolved, let stand, cool to room temperature, filter with 300-400 mesh cloth to obtain resin solution;

[0055] (2) Take the prepared resin solution, and disperse 0.5% XB-G282 isocyanate curing agent, 0.1% hydroxy silicone oil and 1% SBN-70D isocyanate curing agent by centrifugation at 800 rpm for 2 min, and then mix thoroughly to obtain an organic carrier.

[0056] (3) Take the prepared organic carrier and add 40% D50 0.5μm ball powder and stir. Then centrifuge and stir at 800rpm, 1000rpm, 1200rpm and 1600rpm respectively for 1min.

[0057] (4) Slowly add the remaining silver powder while manually stirring. After all the silver powder is stirred evenly, centrifuge and stir at 800 rpm, 1000 rpm, 1200 rpm and 1600 rpm for 1 minute each. After centrifugation, use a three-roll mill to shear and disperse the slurry until the fineness of the slurry reaches below 2 μm, then stop the three-roll mill.

[0058] (5) Use a 500-mesh sieve to filter out impurities and large, uneven particles from the slurry to obtain HJT silver paste with integrated main and fine grids.

[0059] Comparative Example 1

[0060] An HJT silver paste, by mass percentage, comprises the following components: 92% silver powder, 3% resin (including 2% main resin and 1% auxiliary resin), 1.5% curing agent, 0.1% silicone oil, and 3% organic solvent.

[0061] The silver powder includes at least three types of powder with different particle sizes: the first type is spherical powder and spheroidal powder with a D50 of 4μm and a tap density of 5g / mL, accounting for 47%; the second type is spherical powder and spheroidal powder with a D50 of 0.5μm and a tap density of 4.5g / mL, accounting for 40%; and the third type is flake powder with a D50 of 1μm and a tap density of 3g / mL, accounting for 5%.

[0062] The main resin is epoxy resin: 1% phenyl oxy resin PKHH and 1% polyester resin 270.

[0063] Auxiliary resin: 1% added, synthesized from D400 (modifier) ​​and epoxy resin jER 827 (first resin) in a ratio of 1:50. Epoxy resin jER 827 is added to the reactor first, and D400 is slowly added dropwise to the reactor. The temperature is heated to 70℃ and the reaction is carried out for 2 hours. If no reaction occurs, the mixture is allowed to stand and cool to room temperature before use.

[0064] Curing agent: Composed of isocyanate curing agent and auxiliary curing agent, specifically 0.5% XB-G282 isocyanate curing agent with an unsealing temperature of 80℃ and 1% SBN-70D isocyanate curing agent with an unsealing temperature of 120℃.

[0065] Silicone oil: 0.1% hydroxyl silicone oil.

[0066] Organic solvent: 3% diethylene glycol butyl ether acetate.

[0067] The preparation method includes the following steps:

[0068] (1) Mix 3% diethylene glycol butyl ether acetate organic solvent in a reaction vessel, gradually add 3% resin, heat to 85°C, stir at 260 r / min for 1 h until the resin is completely dissolved, let stand, cool to room temperature, filter with 300-400 mesh cloth to obtain resin solution;

[0069] (2) Take the prepared resin solution, and disperse 0.5% XB-G282 isocyanate curing agent, 0.1% hydroxy silicone oil and 1% SBN-70D isocyanate curing agent by centrifugation at 800 rpm for 2 min, and then mix thoroughly to obtain an organic carrier.

[0070] (3) Take the prepared organic carrier and add 10% D50 0.5μm ball powder and stir. Then centrifuge and stir at 800rpm, 1000rpm, 1200rpm and 1600rpm for 1min respectively.

[0071] (4) Slowly add the remaining silver powder while manually stirring. After all the silver powder is stirred evenly, centrifuge and stir at 800 rpm, 1000 rpm, 1200 rpm and 1600 rpm for 1 minute each. After centrifugation, use a three-roll mill to shear and disperse the slurry until the fineness of the slurry reaches below 2 μm, then stop the three-roll mill.

[0072] (5) Use a 500-mesh sieve to filter out impurities and uneven large particles in the slurry to obtain HJT silver paste with integrated main and fine grid.

[0073] Comparative Example 2

[0074] An HJT silver paste, by mass percentage, comprises the following components: 92% silver powder, 3% resin (including 2% main resin and 1% auxiliary resin), 1.5% curing agent, 0.1% silicone oil, and 3% organic solvent.

[0075] The silver powder includes at least three types of powder with different particle sizes: the first type is spherical powder and spheroidal powder with a D50 of 4μm and a tap density of 5g / mL, accounting for 47%; the second type is spherical powder and spheroidal powder with a D50 of 0.5μm and a tap density of 4.5g / mL, accounting for 40%; and the third type is flake powder with a D50 of 1μm and a tap density of 3g / mL, accounting for 5%.

[0076] The main resin is epoxy resin: 1% phenyl oxy resin PKHH and 1% polyester resin 270.

[0077] Auxiliary resin: 1% added, synthesized from KH550 (modifier) ​​and epoxy resin jER 827 (first resin) in a ratio of 1:50. Epoxy resin jER 827 is added to the reactor first, and KH550 is slowly added dropwise to the reactor. The temperature is heated to 70℃ and the reaction is carried out for 2 hours. If no reaction occurs, the mixture is allowed to stand and cool to room temperature for later use.

[0078] Curing agent: Composed of isocyanate curing agent and auxiliary curing agent, specifically 0.5% XB-G282 isocyanate curing agent with an unsealing temperature of 80℃ and 1% SBN-70D isocyanate curing agent with an unsealing temperature of 120℃.

[0079] Silicone oil: 0.1% hydroxyl silicone oil.

[0080] Organic solvent: 3% diethylene glycol butyl ether acetate.

[0081] The preparation method of this HJT silver paste includes the following steps:

[0082] (1) Mix 3% diethylene glycol butyl ether acetate organic solvent in a reaction vessel, gradually add 3% resin, heat to 85°C, stir at 260 r / min for 1 h until the resin is completely dissolved, let stand, cool to room temperature, filter with 300-400 mesh cloth to obtain resin solution;

[0083] (2) Take the prepared resin solution, and disperse 0.5% XB-G282 isocyanate curing agent, 0.1% hydroxy silicone oil and 1% SBN-70D isocyanate curing agent by centrifugation at 800 rpm for 2 min, and then mix thoroughly to obtain an organic carrier.

[0084] (3) Take the prepared organic carrier and add 10% D50 0.5μm ball powder and stir. Then centrifuge and stir at 800rpm, 1000rpm, 1200rpm and 1600rpm for 1min respectively.

[0085] (4) Slowly add the remaining silver powder while manually stirring. After all the silver powder is stirred evenly, centrifuge and stir at 800 rpm, 1000 rpm, 1200 rpm and 1600 rpm for 1 minute each. After centrifugation, use a three-roll mill to shear and disperse the slurry until the fineness of the slurry reaches below 2 μm, then stop the three-roll mill.

[0086] (5) Use a 500-mesh sieve to filter out impurities and uneven large particles in the slurry to obtain HJT silver paste with integrated main and fine grid.

[0087] Comparative Example 3

[0088] An HJT silver paste, by mass percentage, comprises the following components: 92% silver powder, 3% resin (including 2% main resin and 1% auxiliary resin), 1.5% curing agent, 0.1% silicone oil, and 3% organic solvent.

[0089] The silver powder includes at least three types of powder with different particle sizes: the first type is spherical powder and spheroidal powder with a D50 of 4μm and a tap density of 5g / mL, accounting for 47%; the second type is spherical powder and spheroidal powder with a D50 of 0.5μm and a tap density of 4.5g / mL, accounting for 40%; and the third type is flake powder with a D50 of 1μm and a tap density of 3g / mL, accounting for 5%.

[0090] The main resin is epoxy resin: 1% phenyl oxy resin PKHH and 1% polyester resin 270.

[0091] Auxiliary resins: 1% addition, including two modified resins, each accounting for 0.5%. The first modified resin is synthesized from D400 (modifier) ​​and epoxy resin JER 827 (first resin) in a ratio of 1:50. Epoxy resin JER 827 is added to the reactor first, followed by D400 slowly added dropwise. The reactor is heated to 70℃ and reacted for 2 hours. No reaction was observed, and the mixture was allowed to cool to room temperature before use. The second modified resin is synthesized from KH550 (modifier) ​​and epoxy resin JER 827 (first resin) in a ratio of 1:50. Epoxy resin JER 827 is added to the reactor first, followed by KH550 slowly added dropwise. The reactor is heated to 70℃ and reacted for 2 hours. No reaction was observed, and the mixture was allowed to cool to room temperature before use.

[0092] Curing agent: Composed of isocyanate curing agent and auxiliary curing agent, specifically 0.5% XB-G282 isocyanate curing agent with an unsealing temperature of 80℃ and 1% SBN-70D isocyanate curing agent with an unsealing temperature of 120℃.

[0093] Silicone oil: 0.1% hydroxyl silicone oil.

[0094] Organic solvent: 3% diethylene glycol butyl ether acetate.

[0095] The preparation method of this HJT silver paste includes the following steps:

[0096] (1) Mix 3% diethylene glycol butyl ether acetate organic solvent in a reaction vessel, gradually add 3% resin, heat to 85°C, stir at 260 r / min for 1 h until the resin is completely dissolved, let stand, cool to room temperature, filter with 300-400 mesh cloth to obtain resin solution;

[0097] (2) Take the prepared resin solution, and disperse 0.5% XB-G282 isocyanate curing agent, 0.1% hydroxy silicone oil and 1% SBN-70D isocyanate curing agent by centrifugation at 800 rpm for 2 min, and then mix thoroughly to obtain an organic carrier.

[0098] (3) Take the prepared organic carrier and add 10% D50 0.5μm ball powder and stir. Then centrifuge and stir at 800rpm, 1000rpm, 1200rpm and 1600rpm for 1min respectively.

[0099] (4) Slowly add the remaining silver powder while manually stirring. After all the silver powder is stirred evenly, centrifuge and stir at 800 rpm, 1000 rpm, 1200 rpm and 1600 rpm for 1 minute each. After centrifugation, use a three-roll mill to shear and disperse the slurry until the fineness of the slurry reaches below 2 μm, then stop the three-roll mill.

[0100] (5) Use a 500-mesh sieve to filter out impurities and uneven large particles in the slurry to obtain HJT silver paste with integrated main and fine grid.

[0101] Comparative Example 4

[0102] An HJT silver paste, by mass percentage, comprises the following components: 92% silver powder, 3% resin (including 2% main resin and 1% auxiliary resin), 1.5% curing agent, 0.1% silicone oil, 0.1% synthesis catalyst, and 3% organic solvent.

[0103] The silver powder includes at least three types of powder with different particle sizes: the first type is spherical powder and spheroidal powder with a D50 of 4μm and a tap density of 5g / mL, accounting for 47%; the second type is spherical powder and spheroidal powder with a D50 of 0.5μm and a tap density of 4.5g / mL, accounting for 40%; and the third type is flake powder with a D50 of 1μm and a tap density of 3g / mL, accounting for 5%.

[0104] The main resin is epoxy resin: 1% phenyl oxy resin PKHH and 1% polyester resin 270.

[0105] Auxiliary resins: 1% addition, including two modified resins, each accounting for 0.5%. The first modified resin is synthesized from D400 (modifier) ​​and epoxy resin JER 827 (first resin) in a ratio of 1:50. Epoxy resin JER 827 is added to the reactor first, followed by D400 slowly added dropwise. The reactor is heated to 70℃ and reacted for 2 hours. No reaction was observed, and the mixture was allowed to cool to room temperature before use. The second modified resin is synthesized from KH550 and epoxy resin JER 827 (first resin) in a ratio of 1:50. Epoxy resin JER 827 is added to the reactor first, followed by KH550 slowly added dropwise. The reactor is heated to 70℃ and reacted for 2 hours. No reaction was observed, and the mixture was allowed to cool to room temperature before use.

[0106] Curing agent: Composed of isocyanate curing agent and auxiliary curing agent, specifically 0.5% XB-G282 isocyanate curing agent with an unsealing temperature of 80℃ and 1% SBN-70D isocyanate curing agent with an unsealing temperature of 120℃.

[0107] Silicone oil: 0.1% hydroxyl silicone oil.

[0108] The synthesis catalyst is an epoxy catalyst: a complex of 0.1% dimethyltetraethylimidazolium and succinic acid.

[0109] Organic solvent: 3% diethylene glycol butyl ether acetate.

[0110] The preparation method of this HJT silver paste includes the following steps:

[0111] (1) Mix 3% diethylene glycol butyl ether acetate organic solvent in a reaction vessel, gradually add 3% resin, heat to 85°C, stir at 260 r / min for 1 h until the resin is completely dissolved, let stand, cool to room temperature, filter with 300-400 mesh cloth to obtain resin solution;

[0112] (2) Take the prepared resin solution, and disperse 0.5% XB-G282 isocyanate curing agent, 0.1% hydroxy silicone oil and 1% SBN-70D isocyanate curing agent by centrifugation at 800 rpm for 2 min, and then mix thoroughly to obtain an organic carrier.

[0113] (3) Take the prepared organic carrier and add 10% D50 0.5μm ball powder and stir. Then centrifuge and stir at 800rpm, 1000rpm, 1200rpm and 1600rpm for 1min respectively.

[0114] (4) Slowly add the remaining silver powder while manually stirring. After all the silver powder is stirred evenly, centrifuge and stir at 800 rpm, 1000 rpm, 1200 rpm and 1600 rpm for 1 minute each. After centrifugation, use a three-roll mill to shear and disperse the slurry until the fineness of the slurry reaches below 2 μm, then stop the three-roll mill.

[0115] (5) Use a 500-mesh sieve to filter out impurities and uneven large particles in the slurry to obtain HJT silver paste with integrated main and fine grid.

[0116] Comparative Example 5

[0117] An HJT silver paste, by mass percentage, comprises the following components: 92% silver powder, 3% resin (including 2% main resin and 1% auxiliary resin), 1.5% curing agent, silicone oil (including 0.05% hydroxyl silicone oil and 0.05% methoxy silicone oil), 0.1% synthesis catalyst, 0.02% silicone oil catalyst, and 3% organic solvent.

[0118] The silver powder includes at least three types of powder with different particle sizes: the first type is spherical powder and spheroidal powder with a D50 of 4μm and a tap density of 5g / mL, accounting for 47%; the second type is spherical powder and spheroidal powder with a D50 of 0.5μm and a tap density of 4.5g / mL, accounting for 40%; and the third type is flake powder with a D50 of 1μm and a tap density of 3g / mL, accounting for 5%.

[0119] The main resin is epoxy resin: 1% phenyl oxy resin PKHH and 1% polyester resin 270.

[0120] Auxiliary resins: 1% addition, including two modified resins, each accounting for 0.5%. The first modified resin is synthesized from D400 (modifier) ​​and epoxy resin JER 827 (first resin) in a ratio of 1:50. Epoxy resin JER 827 is added to the reactor first, followed by D400 slowly added dropwise. The reactor is heated to 70℃ and reacted for 2 hours. No reaction was observed, and the mixture was allowed to cool to room temperature before use. The second modified resin, KH550, is synthesized from epoxy resin JER 827 (first resin) in a ratio of 1:50. Epoxy resin JER 827 is added to the reactor first, followed by KH550 slowly added dropwise. The reactor is heated to 70℃ and reacted for 2 hours. No reaction was observed, and the mixture was allowed to cool to room temperature before use.

[0121] Curing agent: Composed of isocyanate curing agent and auxiliary curing agent, specifically 0.5% XB-G282 isocyanate curing agent with an unsealing temperature of 80℃ and 1% SBN-70D isocyanate curing agent with an unsealing temperature of 120℃.

[0122] Silicone oil: 0.05% hydroxyl silicone oil and 0.05% methoxy silicone oil.

[0123] The synthesis catalyst is an epoxy catalyst: a complex of 0.1% dimethyltetraethylimidazolium and succinic acid.

[0124] Silicone oil catalyst: 0.02% KAT670.

[0125] Organic solvent: 3% diethylene glycol butyl ether acetate.

[0126] The preparation method of this HJT silver paste includes the following steps:

[0127] (1) Mix 3% diethylene glycol butyl ether acetate organic solvent in a reaction vessel, gradually add 3% resin, heat to 85°C, stir at 260 r / min for 1 h until the resin is completely dissolved, let stand, cool to room temperature, filter with 300-400 mesh cloth to obtain resin solution;

[0128] (2) Take the prepared resin solution, and centrifuge and disperse 0.02% KAT670, 0.05% methoxy silicone oil, 0.05% hydroxy silicone oil, 0.5% XB-G282 isocyanate curing agent and 1% SBN-70D isocyanate curing agent at 800 rpm for 2 min, and then mix thoroughly to obtain an organic carrier.

[0129] (3) Take the prepared organic carrier and add 10% D50 0.5μm ball powder and stir. Then centrifuge and stir at 800rpm, 1000rpm, 1200rpm and 1600rpm for 1min respectively.

[0130] (4) Slowly add the remaining silver powder while manually stirring. After all the silver powder is stirred evenly, centrifuge and stir at 800 rpm, 1000 rpm, 1200 rpm and 1600 rpm for 1 minute each. After centrifugation, use a three-roll mill to shear and disperse the slurry until the fineness of the slurry reaches below 2 μm, then stop the three-roll mill.

[0131] (5) Use a 500-mesh sieve to filter out impurities and uneven large particles in the slurry to obtain HJT silver paste with integrated main and fine grid.

[0132] Table 1. Composition of HJT silver paste raw materials in Examples 1-2 and Comparative Examples 1-5, and performance parameters of the prepared HJT silver paste.

[0133] Among them, Ag-1 is a spherical powder and a spherical-like powder with a D50 of 4μm and a tap density of 5g / mL; Ag-2 is a spherical powder and a spherical-like powder with a D50 of 0.5μm and a tap density of 4.5g / mL; Ag-3 is a flake powder with a D50 of 1μm and a tap density of 3g / mL; modified resin 1 is a modified resin synthesized from D400 and epoxy resin jER 827; modified resin 2 is a modified resin synthesized from KH550 and epoxy resin jER 827.

[0134] As shown in Table 1, compared with Example 1, Example 2 increased the proportion of flake powder and added silicone oil, which effectively reduced the volume resistivity of HJT silver paste, but had a negative impact on its ink application rate.

[0135] Compared to Example 2, Comparative Example 1 showed that by reducing the amount of flake powder added, the linear resistance of HJT silver paste decreased and the amount of ink applied increased, but the overall resistivity increased. At the same time, the strategy of increasing the preparation of auxiliary resin significantly improved the welding pull, which verifies that the auxiliary resin can effectively improve the adhesion of HJT silver paste and thus enhance the welding performance.

[0136] Compared to Comparative Example 1, Comparative Example 2 showed a slight increase in the volume resistivity of HJT silver paste, but a further improvement in weld pull strength, thus verifying that the type of auxiliary resin is one of the core variables determining weld pull performance. Further analysis revealed that while the D400 polyetheramine resin used in Comparative Example 1 imparted good flexibility to the HJT silver paste and helped reduce its volume resistivity, its heat resistance and adhesion were lower than those using KH550. KH550, as a commonly used silane coupling agent, works by effectively improving the adhesion of inorganic materials, thereby significantly optimizing weld pull performance by enhancing the interfacial bonding strength between the HJT silver paste and its substrate.

[0137] Comparative Example 3, based on Comparative Examples 1 and 2, achieved an improvement in volume resistivity and weld pull force comparable to Comparative Examples 1 or 2 by blending two auxiliary resins in a 1:1 ratio. This indicates that the synergistic effect of the two auxiliary resins can also effectively improve the conductivity and interfacial bonding strength of HJT silver paste.

[0138] Comparative Example 4, building upon the preparation strategy of using two auxiliary resins in Comparative Example 3, further introduced a composite catalyst containing imidazole / diacid. Through a dual mechanism of action—imidazole promoting deep curing of the HJT silver paste, and diacid simultaneously participating in and accelerating the epoxy resin curing reaction—the resin cross-linking network was significantly strengthened, resulting in a further improvement in weld tensile strength. This effect stems from the fact that the increased degree of resin curing directly enhances the adhesion between the resin and the substrate interface.

[0139] Comparative Example 5 further added a silicone oil catalyst matching the type of silicone oil to Comparative Example 4, achieving further optimization of welding pull while maintaining the aforementioned performance advantages. This silicone oil catalyst can specifically promote the curing of silicone oil components and effectively suppress the negative impact of free silicone oil on lap resistance.

[0140] While the addition of silicone oil helps HJT silver paste achieve better leveling and printing, reduces resistivity, and increases ink application, it also has negative effects such as weakening adhesion and increasing lap resistance. In this case, the introduction of a silicone oil catalyst can be controlled through curing regulation, significantly reducing its interfacial side effects while retaining the conductivity / printability advantages of silicone oil, ultimately achieving synergistic optimization of the solderability of HJT silver paste.

[0141] The effect diagram of this disclosure applied to solar cells can be seen in Figures 1 and 2. The HJT silver paste integrating the main and fine grids has good grid-forming properties, low volume resistivity, and excellent contact resistance for the fine grids, and high welding pull and adhesion for the main grids.

[0142] The HJT silver paste and its preparation method provided in the embodiments of this disclosure have at least one or a portion of the following advantages:

[0143] (1) It has good meshing properties of fine grid, low volume resistivity, excellent contact resistance, and high welding pull and adhesion of the main grid.

[0144] (2) Achieving multi-powder combination increases the effective contact points of silver powder, reduces the intrinsic resistance of the paste, and maintains a high silver content to ensure that HJT silver paste has good conductivity.

[0145] (3) The use of low molecular weight resin in HJT silver paste introduces a curing agent with strong adhesion to react with the resin to generate a large number of hydroxyl groups, which can significantly improve the curing speed while taking into account the printability and adhesion of HJT silver paste.

[0146] (4) The curing of HJT silver paste adopts a combination of catalyst and curing agent. The catalyst is selected with imidazole diacid structure to obtain good latency of imidazole structure and thus extend the storage period. Imidazole and diacid participate in epoxy curing reaction at the same time (imidazole catalysis and diacid curing) to synergistically enhance the curing speed of resin and increase crosslinking density.

[0147] (5) The introduction of silicone oil catalyst can effectively suppress the side effects of silicone oil while improving the leveling properties of HJT silver paste printing and reducing the resistance value, thus ensuring the high welding pull of the main grid.

[0148] The above descriptions are merely some embodiments of this disclosure. Those skilled in the art can make various modifications and improvements without departing from the technical concept of this disclosure, and all such modifications and improvements fall within the scope of protection of this disclosure.

Claims

1. An HJT silver paste, characterized in that, The HJT silver paste comprises, by weight percentage: Silver powder 85-92%, resin 2-10%, curing agent 1-4%, silicone oil 0-1%, epoxy catalyst 0-1%, silicone oil catalyst 0-0.1%, organic solvent 2-5%; The silver powder includes spherical powder, spherical powder, and flake powder; The silver powder comprises at least three types of powder with different particle sizes: the first type is spherical powder and spheroidal powder with a D50 of 2-6 μm and a tap density of 5-6 g / mL, accounting for 30-50%; the second type is spherical powder and spheroidal powder with a D50 of 0.1-1 μm and a tap density of 3-5 g / mL, accounting for 20-40%; and the third type is flake powder with a D50 of 0.5-2 μm and a tap density of 3-5 g / mL, accounting for 5-10%.

2. The HJT silver paste according to claim 1, characterized in that, The resin is composed of a main resin and an auxiliary resin, and the auxiliary resin is a modified resin.

3. The HJT silver paste according to claim 2, characterized in that, The main resin is any two or any combination thereof selected from phenoxy resins JER1007, 1010, 1004, PKHB, PKHH, epoxy resins 4007P, 4010P, 7787, 3150, 2021P, polyester resins Vylon-GK888, BX-7000A, 270, ES410, ES420, and polyurethane resins TPU5778, TPU 5703, and TPU58887.

4. The HJT silver paste according to claim 2, characterized in that, The modified resin is obtained by pre-synthesizing the first resin with a modifier, and the addition ratio of the modifier to the first resin is 1-5:

100.

5. The HJT silver paste according to claim 4, characterized in that, The modifier includes any two or any combination of silane coupling agents, titanate coupling agents, polyetheramines, silane coupling agents KH550, KH560, P-S496, SCA-A20F, titanate coupling agents TCA-KTTS, TCA-238J, TCA-K55, TCA-K44, TCA-KTTT, and polyetheramine phosphates Baxxodur EC301, EC302, D230, and D400. The first resin includes any two or any combination of epoxy resins JER 827, 806, TT386, GE60, polyester polyols Dynacoll 7110, 7111, 7360, and 7380, and the first resin is a low molecular weight liquid resin containing at least two functional groups.

6. The HJT silver paste according to any one of claims 1-5, characterized in that, The silicone oil is any one or any combination of two of the following: hydrogen-containing silicone oil, dimethyl silicone oil, hydroxyl silicone oil, methoxy silicone oil, ethoxy silicone oil, polyether silicone oil, and vinyl silicone oil, and the composition is adjusted accordingly based on the different silicone oil catalysts.

7. The HJT silver paste according to claim 6, characterized in that, The silicone oil catalyst is any one of dibutyltin dilaurate, caster catalyst, stannous octoate, dibutyltin diacetate, DBPMH, BPO, platinum catalyst, and KAT670.

8. The HJT silver paste according to claim 6, characterized in that, The curing agent is at least two types of blocked isocyanate curing agents, with an unblocking temperature of 80-150℃ and a curing temperature of 90-130℃.

9. The HJT silver paste according to claim 6, characterized in that, The epoxy catalyst is an imidazole diacid composite catalyst, wherein the molar ratio of imidazole to diacid is 1:

1.

10. The HJT silver paste according to claim 9, characterized in that, The imidazole is any one of benzimidazole, DBU, dimethyltetraethylimidazolium, PN23, PN23J, and PN40; The diacid is any one of the organic acids adipic acid, succinic acid, glutaric acid, and sebacic acid.

11. The HJT silver paste according to claim 6, characterized in that, The organic solvent is any one or any combination thereof, propylene carbonate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate, dimethyl adipate, diethyl adipate, propylene glycol methyl ether acetate, and terpineol.

12. A method for preparing HJT silver paste, said preparation method being used to prepare HJT silver paste according to any one of claims 1-11, characterized in that, The preparation method includes the following steps: 1) Add 2-5% organic solvent to the reaction vessel and mix, then add 2-10% resin, heat and stir, cool to room temperature, and filter to obtain resin solution; 2) Add 0-1% epoxy catalyst, 0-1% silicone oil, 0-0.1% silicone oil catalyst, 1-4% curing agent, and 1-2% diluent to the resin solution prepared in step 1) in sequence, and perform the first centrifugal dispersion process to obtain the organic carrier; 3) Add 85-92% silver powder to the organic carrier prepared in step 2), perform the second centrifugal dispersion process, and then shear and disperse it through a three-roll mill until the slurry fineness is less than 5μm. Filter to obtain the finished silver paste.

13. The preparation method according to claim 12, characterized in that, In step 1), the heating temperature is 70-95℃, the stirring speed is 200-300r / min, and the heating and stirring time is 1-2h.

14. The preparation method according to claim 12 or 13, characterized in that, In step 2), the first centrifugal dispersion speed is 800-850 rpm, and the centrifugal dispersion time is 2-4 min.

15. The preparation method according to any one of claims 12-14, characterized in that, In step 3), the specific process of the second centrifugal dispersion is as follows: disperse at 800 rpm, 1000 rpm, 1200 rpm and 1600 rpm for 1-3 minutes each.

16. The preparation method according to claim 15, characterized in that, When the resin includes an auxiliary resin, the first resin is pre-synthesized using a modifier to obtain the auxiliary resin. The pre-synthesis step specifically includes: The first resin is added to the reactor, and the modifier is gradually added. The mixture is heated to 70-95°C and stirred for 1-2 hours until the first resin forms a homogeneous phase with no reaction. The mixture is then allowed to stand and cool to room temperature and filtered through a 300-400 mesh screen to obtain the auxiliary resin.

17. The preparation method according to claim 16, characterized in that, The epoxy catalyst is a composite catalyst, and the preparation steps of the composite catalyst specifically include: N-methylpyrrolidone was added to a reaction vessel, and imidazole and diacid were added step by step and in sequence. The mixture was stirred at room temperature until homogeneous and no reaction was observed. The mixture was then allowed to stand and cool to room temperature to obtain the composite catalyst.

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