Ultraviolet light-cured conductive paste, preparation method and application thereof

Abstract

This invention discloses a UV-curable conductive slurry, its preparation method, and its application. The raw materials, by weight, include 40-92 parts of conductive filler, 0.5-20 parts of UV-curable resin prepolymer, 1-10 parts of reactive diluent, 0.5-5 parts of initiator, and 0-1.5 parts of organic additives. The conductive filler includes silver-coated copper powder, and the initiator is a pyrolysis-type photoinitiator. This invention constructs a ternary composite conductive system of "micron-scale silver-coated copper framework + nano-silver filler + micron-scale silver reinforcement," and, in conjunction with the pyrolysis-type photoinitiator, can simultaneously and in-situ reduce copper oxide impurities present in the slurry into conductive elemental copper within the slurry system. This essentially eliminates ohmic losses caused by copper oxidation, ensuring low initial resistance and long-term stability of the electrode.

Description

Technical Field

[0001] This invention relates to the field of coating compositions, specifically to a UV-curable conductive paste, its preparation method, and its application. Background Technology

[0002] Heterojunction (HJT) solar cells possess high conversion efficiency, low temperature coefficient, and excellent bifacial power generation performance, making them an important research direction in the photovoltaic field. However, the mainstream paste for preparing HJT solar cells is silver paste, and the high cost of silver powder limits the development of HJT solar cells. Currently, silver-coated copper powder is used to replace silver powder to reduce costs. However, during paste preparation, storage, and curing, the copper nuclei in the silver-coated copper powder are easily oxidized through silver layer defects or diffusion, generating high-resistivity copper oxide, leading to increased electrode resistivity and performance degradation. Although copper oxidation can be suppressed by introducing reducing agents, these processes are complex, have limited effectiveness, and introduce new impurities. Therefore, developing a low-cost paste system that can achieve high conductive phase content and low organic solvent residue is crucial.

[0003] Chinese invention patent application CN114864178A discloses a UV-curable conductive silver paste and its preparation method. By introducing a specially structured titanate coupling agent as a conductive additive, the amount of silver powder used can be effectively reduced and the conductivity of the silver paste can be improved, but the conductivity is somewhat reduced. Chinese invention patent application CN109810576A discloses a UV-curable conductive ink and its preparation method. Using ultrafine silver powder as a conductive filler, it can significantly improve conductivity, but the production cost is high. Summary of the Invention

[0004] In order to develop a low-cost slurry system that can achieve a high content of conductive phase and low organic solvent residue, the first aspect of the present invention provides a UV-curable conductive slurry, the raw materials for which are prepared by weight include 40-92 parts of conductive filler, 0.5-20 parts of UV-curable resin prepolymer, 1-10 parts of reactive diluent, 0.5-5 parts of initiator, and 0-1.5 parts of organic additive; the conductive filler includes silver-coated copper powder, and the initiator is a pyrolysis photoinitiator.

[0005] This application introduces silver-coated copper powder to replace most of the silver powder, and synergizes it with a pyrolysis-type photoinitiator. After absorbing ultraviolet light, the pyrolysis-type photoinitiator can efficiently pyrolyze to generate benzoyl and phosphonyl free radicals with strong redox potentials. These free radicals not only rapidly initiate the polymerization reaction of acrylate double bonds to solidify the slurry, but their strong reducing properties also simultaneously and in-situ reduce copper oxide impurities (CuO / Cu2O) present in the slurry into conductive elemental copper within the slurry system. This achieves simultaneous solidification and reduction, fundamentally eliminating ohmic losses caused by copper oxidation and ensuring low initial resistance and long-term stability of the electrode.

[0006] Furthermore, the use of a pyrolysis-type photoinitiator enables rapid curing in seconds at temperatures below 200°C, significantly improving the conductivity, adhesion, and weather resistance of HJT battery electrodes, while greatly reducing dependence on the precious metal silver and overall production costs.

[0007] In one embodiment, the silver-coated copper powder is micron-sized silver-coated copper powder with a D50 particle size of 1-10 μm; the silver content of the silver-coated copper powder is 5-60 wt%, and the silver coating rate is ≥98%.

[0008] In one embodiment, the D50 particle size of the silver-coated copper powder is 2.5-3 μm; the silver content of the silver-coated copper powder is 10-20 wt%.

[0009] In one embodiment, the D50 particle size of the silver-coated copper powder is 2.0-2.5 μm; the silver content of the silver-coated copper powder is 20-30 wt%.

[0010] In one embodiment, the D50 particle size of the silver-coated copper powder is 2.0-2.2 μm; the silver content of the silver-coated copper powder is 5-10 wt%.

[0011] In one embodiment, the conductive filler further includes nano-silver powder and / or micro-silver powder, wherein the average particle size of the nano-silver powder is 10-100 nm; and the D50 particle size of the micro-silver powder is 0.5-3 μm.

[0012] In one embodiment, the average particle size of the nano-silver powder is 30-50 nm.

[0013] In one embodiment, the average particle size of the nano silver powder is 80-100 nm; the D50 particle size of the micron silver powder is 1.5-2.0 μm.

[0014] In one embodiment, the average particle size of the nano silver powder is 80-100 nm; the D50 particle size of the micron silver powder is 1.4-1.6 μm.

[0015] In one embodiment, the shapes of the silver-coated copper powder, nano silver powder, and micron silver powder include, but are not limited to, spherical, near-spherical, and flake-like.

[0016] In one embodiment, the silver-coated copper powder is in flake form.

[0017] This application constructs a ternary composite conductive system consisting of a "micron-sized silver-coated copper framework + nano-silver filler + micron-sized silver reinforcement". The sheet-like micron-sized silver-coated copper helps to form an effective two-dimensional contact surface in the printed film to provide an initial conductive barrier. The nano-silver powder fills the gaps between the micron-sized particles. Through the high surface activity and sintering activity of the nanoparticles, additional conductive bridges are formed after curing, significantly reducing the contact resistance. In formulations requiring extreme conductivity, the micron-sized silver powder works synergistically with the silver-coated copper powder to construct richer conductive pathways and further improve conductivity.

[0018] In one embodiment, the pyrolytic photoinitiator includes at least one of benzoin ether initiators, α-hydroxy ketone initiators, α-amino ketone initiators, or acylphosphine oxide initiators.

[0019] In one embodiment, the pyrolysis photoinitiator includes at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, 1-hydroxycyclohexylphenyl ketone, or 2-hydroxy-2-methyl-1-phenylpropanone.

[0020] In one embodiment, the photocurable resin prepolymer includes at least one of polyurethane acrylate, epoxy acrylate, or polyester acrylate.

[0021] In one embodiment, the reactive diluent includes at least one of ethoxytrimethylolpropane triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, or isoborneol acrylate.

[0022] By selecting low-viscosity, highly reactive resins and multifunctional acrylate diluent monomers, the total organic phase content can be controlled at a low level while ensuring the rheological properties of the slurry. This significantly increases the volume fraction of the conductive phase in the cured electrode, directly improving the conductivity.

[0023] As one embodiment, the UV-curable conductive paste has a photocuring energy of 300-2500 mJ / cm². 2 The curing temperature is <200℃.

[0024] As one embodiment, the UV-curable conductive paste has a photocuring wavelength of 160-420nm.

[0025] In one embodiment, the organic additives include, but are not limited to, at least one of dispersants, coupling agents, leveling agents, and defoamers.

[0026] A second aspect of the present invention provides a method for preparing a UV-curable conductive paste, comprising the following steps: Under light-proof and inert atmosphere protection, the photocurable resin prepolymer, reactive diluent, and organic additives are vacuum stirred and mixed evenly to obtain an organic carrier; Add the silver-coated copper powder to the organic carrier, stir at a low speed of 100-300 r / min first, then stir at a high speed of 1300-1800 r / min until uniformly mixed, then add nano silver powder and / or micron silver powder and continue stirring until uniformly mixed, perform primary vacuum degassing to obtain a premixed slurry; Grind the premixed slurry to a fineness of ≤10μm, add the photoinitiator under light-protected conditions, and stir at a low speed of 300-500r / min until uniform; After filtration and vacuum degassing again, a UV-curable conductive slurry is obtained.

[0027] A third aspect of the present invention provides an application of a UV-curable conductive paste for the fabrication of grid electrodes in heterojunction solar cells.

[0028] Compared with the prior art, the present invention has the following beneficial effects: (1) The UV-curable conductive paste of the present invention constructs a ternary composite conductive system of "micron-scale silver-coated copper skeleton + nano-silver filler + micron-scale silver reinforcement". The extremely low organic phase content brings high conductive filler load, so that the cured electrode film has extremely high metal volume density and rich conductive pathways, so that the bulk resistivity of the electrode can be as low as 3.0-4.5×10 -6 Ω·cm, close to the level of pure silver paste.

[0029] (2) The UV-curable conductive paste of the present invention introduces silver-coated copper powder to replace most of the silver powder, and works in conjunction with a pyrolysis-type photoinitiator to synchronously and in situ reduce the copper oxide impurities in the paste into conductive copper in the paste system, thereby eliminating the ohmic loss caused by copper oxidation and ensuring the initial low resistance and long-term stability of the electrode.

[0030] (3) The UV-curable conductive paste of the present invention uses high-quality silver-coated copper powder as the core. While ensuring performance, it minimizes the amount of precious metal silver used. The overall raw material cost is reduced by 40%-60% compared with traditional low-temperature silver paste, and the economic benefits are significantly improved.

[0031] (4) The UV-curable conductive paste of the present invention uses a synergistic pyrolysis photoinitiator, which can achieve a second-level curing speed, low energy consumption, and minimal heat input to the substrate during the curing process (temperature <200℃), perfectly meeting the low-temperature process requirements of HJT batteries and easy to integrate into existing production lines.

[0032] (5) The UV-curable conductive paste of the present invention has a dense polymer cross-linked network structure formed by photocuring, no solvent evaporation during the curing process, low porosity of the electrode film layer, strong resistance to damp heat and aging, and excellent reliability and stable performance under the aging conditions of double 85. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the electrode microstructure after the UV-curable conductive paste prepared in this invention has been cured. In the figure: 1. Silver-coated copper powder; 2. Nano silver powder; 3. Micron silver powder; 4. Resin film. Detailed Implementation

[0034] Example 1 A UV-curable conductive paste is prepared by means of 90 parts conductive filler, 4.5 parts UV-curable resin prepolymer, 4 parts reactive diluent, 0.5 parts initiator, and 1 part organic additive by weight.

[0035] The conductive filler comprises silver-coated copper powder and nano silver powder in a weight ratio of 88.5:1.5.

[0036] The D50 particle size of the silver-coated copper powder is 2.5-3.0 μm; the silver content of the silver-coated copper powder is 10 wt%, the silver coating rate is ≥99%, and it is purchased from Guangdong Nanhai Qiming Guangda, with the grade AC080.

[0037] The average particle size of the nano-silver powder is 30-50 nm, and it was purchased from Qiming Guangda in Nanhai, Guangdong, with the grade name B30.

[0038] The photocurable resin prepolymer is a polyurethane acrylate prepolymer, purchased from Zhanxin Resin, brand name EBECRYL8415.

[0039] The reactive diluent is dipentaerythritol hexaacrylate.

[0040] The initiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0041] The organic additives include dispersants, silane coupling agents, and leveling agents in a weight ratio of 0.3:0.5:0.2.

[0042] The dispersant is AkzoNobel TDO; the silane coupling agent is KH-560; and the leveling agent is purchased from BYK Chemical, brand name BYK-333.

[0043] A method for preparing a UV-curable conductive paste includes the following steps: Under light-proof and nitrogen atmosphere protection, the photocurable resin prepolymer, reactive diluent, and organic additives were mixed evenly by vacuum stirring at 500 r / min for 15 minutes to obtain the organic carrier. Add silver-coated copper powder to the organic carrier, stir at a low speed of 200 r / min for 20 min, then stir at a high speed of 1500 r / min for 30 min to mix evenly, then add nano silver powder and disperse at a speed of 1200 r / min for 20 min to mix evenly, and then perform primary vacuum degassing at -0.098 MPa to obtain premixed slurry; Grind the premixed slurry to a fineness of ≤8μm, add the photoinitiator under light-protected conditions, and stir at a low speed of 400r / min for 20min until uniform; The mixture is filtered through a 400-mesh nylon mesh and then degassed under vacuum to obtain a UV-curable conductive paste.

[0044] The prepared UV-curable conductive paste was screen-printed onto the TCO layer of the HJT battery using a 500-mesh screen, and a UV-LED light source with a wavelength of 170 nm and a wavelength of 1200 mJ / cm² was used. 2 Cured under energy irradiation and at 150℃ for 8 minutes. The volume resistivity of the cured grid lines was measured to be 3.8 × 10⁻⁶. -6 The adhesion strength to the TCO layer was 5B (ASTM D3359), measured in Ω·cm. The resulting solar cell exhibited a photoelectric conversion efficiency comparable to that of a cell using a reference pure silver paste. Specific performance test results are shown in Table 1-2.

[0045] Example 2 A UV-curable conductive paste is prepared by means of 90 parts conductive filler, 3 parts UV-curable resin prepolymer, 4.8 parts reactive diluent, 1.2 parts initiator, and 1 part organic additive by weight.

[0046] The conductive filler comprises silver-coated copper powder, nano silver powder, and micron silver powder in a weight ratio of 88:0.1:1.9.

[0047] The D50 particle size of the silver-coated copper powder is 2.0-2.5μm; the silver content of the silver-coated copper powder is 20.0wt%, the silver coating rate is ≥99%, and it is purchased from Guangdong Nanhai Qiming Guangda, with the grade AC060.

[0048] The average particle size of the nano-silver powder is 80-100nm, and it was purchased from Qiming Guangda in Nanhai, Guangdong, with the grade name B80.

[0049] The micron-sized silver powder has a D50 particle size of 1.5-2.0 μm and was purchased from China Banknote Printing and Minting Corporation, with the grade SF-III-140A.

[0050] The photocurable resin prepolymer is an epoxy acrylate prepolymer, purchased from Zhanxin Resin, brand name EBECRYL®600.

[0051] The active diluent is trimethylolpropane triacrylate ethoxylate.

[0052] The initiator is 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone.

[0053] The organic additives include dispersants, silane coupling agents, and leveling agents in a weight ratio of 0.3:0.5:0.2.

[0054] The dispersant is AkzoNobel TDO; the silane coupling agent is KH-560; and the leveling agent is purchased from BYK Chemical, brand name BYK-333.

[0055] A method for preparing a UV-curable conductive paste includes the following steps: Under light-proof and nitrogen atmosphere protection, the photocurable resin prepolymer, reactive diluent, and organic additives were mixed evenly by vacuum stirring at 500 r / min for 15 minutes to obtain the organic carrier. Silver-coated copper powder was added to the organic carrier, and the mixture was stirred at a low speed of 200 r / min for 20 min, followed by a high speed of 1500 r / min for 30 min to mix evenly. Then, nano silver powder and micron silver powder were added and dispersed at a speed of 1200 r / min for 20 min and stirred evenly. The mixture was then degassed under a primary vacuum of -0.098 MPa to obtain a premixed slurry. Grind the premixed slurry to a fineness of ≤8μm, add the photoinitiator under light-protected conditions, and stir at a low speed of 400r / min for 20min until uniform; The mixture is filtered through a 400-mesh nylon mesh and then degassed under vacuum to obtain a UV-curable conductive paste.

[0056] The prepared UV-curable conductive paste was screen-printed onto the TCO layer of the HJT battery using a 500-mesh screen, and a UV-LED light source with a wavelength of 365nm was used, with a wavelength of 800 mJ / cm². 2 Cured at 190℃ for 5 minutes under energy irradiation. The volume resistivity of the cured grid lines was measured to be 4.5 × 10⁻⁶. -6 The adhesion strength to the TCO layer was 4B (ASTM D3359), measured in Ω·cm. The resulting solar cell exhibited a photoelectric conversion efficiency comparable to that of a cell using a reference pure silver paste. Specific performance test results are shown in Table 1-2.

[0057] A schematic diagram of the electrode microstructure after curing of the UV-curable conductive paste is shown below. Figure 1 In the figure, micron-sized silver-coated copper powder 1 overlaps to form the main conductive network, nano-silver particles 2 fill the gaps between the micron particles and form sintering necks, and micron-sized silver powder 3 intersperses to jointly construct a three-dimensional highly conductive path. All conductive phases are coated and bonded by a dense resin film 4 formed by photocuring.

[0058] Example 3 A UV-curable conductive paste is prepared by means of 86 parts conductive filler, 6 parts UV-curable resin prepolymer, 4 parts reactive diluent, 2.5 parts initiator, and 1.5 parts organic additives.

[0059] The conductive filler comprises silver-coated copper powder, nano silver powder, and micron silver powder in a weight ratio of 50:2:34.

[0060] The D50 particle size of the silver-coated copper powder is 2.0-2.2 μm; the silver content of the silver-coated copper powder is 8.0 wt%, the silver coating rate is ≥98.5%, and it was purchased from Guangdong Nanhai Qiming Guangda, with the grade AC082.

[0061] The average particle size of the nano-silver powder is 80-100nm, and it was purchased from Qiming Guangda in Nanhai, Guangdong, with the grade name B80.

[0062] The micron-sized silver powder has a D50 particle size of 1.4-1.6 μm and was purchased from Shandong Jianbang 152-16N.

[0063] The photocurable resin prepolymer is a polyester acrylate prepolymer, purchased from Zhanxin Resin, brand name EBECRYL®1885.

[0064] The active diluent is isobornyl acrylate.

[0065] The initiator is 1-hydroxycyclohexylphenyl ketone.

[0066] The organic additives include dispersants, thixotropic agents, and coupling agents in a weight ratio of 0.5:0.2:0.8.

[0067] The dispersant is oleic acid; the silane coupling agent is KH-560; and the thixotropic agent is purchased from Kusunoki Chemical Co., Ltd., with the brand name 6500.

[0068] The preparation method of a UV-curable conductive paste is the same as in Example 2.

[0069] The prepared UV-curable conductive paste was screen-printed onto the TCO layer of the HJT battery using a 500-mesh screen, and a UV-LED light source with a wavelength of 395 nm and a wavelength of 1500 mJ / cm² was used. 2 Curing was performed under energy irradiation and a temperature of 200℃ for 3 minutes. The volume resistivity of the cured grid lines was measured to be 3.2 × 10⁻⁶. -6 The adhesion strength to the TCO layer was 5B (ASTM D3359), measured in Ω·cm. The prepared solar cell exhibited optimal conductivity. Specific performance test results are shown in Table 1-2.

[0070] Comparative Example 1 A low-temperature thermosetting conductive paste is prepared by means of 90 parts conductive filler, 6.5 parts resin prepolymer, 0.5 parts curing agent, 2 parts reactive diluent, and 1.5 parts organic additives by weight.

[0071] The conductive filler comprises silver-coated copper powder and nano silver powder in a weight ratio of 88.5:1.5.

[0072] The D50 particle size of the silver-coated copper powder is 2.5-3.0 μm; the silver content of the silver-coated copper powder is 10 wt%, the silver coating rate is ≥99%, and it is purchased from Guangdong Nanhai Qiming Guangda, with the grade AC080.

[0073] The average particle size of the nano-silver powder is 30-50 nm, and it was purchased from Qiming Guangda in Nanhai, Guangdong, with the grade name B30.

[0074] The resin prepolymer comprises aliphatic epoxy resin and bisphenol A epoxy resin in a weight ratio of 4.5:2.

[0075] The aliphatic epoxy resin was purchased from Daicel, and its brand name is EHPE3150.

[0076] The bisphenol A epoxy resin was purchased from Shuangmu, and its brand name is SM828.

[0077] The curing agent is a boron trifluoride-monoethylamine complex.

[0078] The active diluent is diethylene glycol butyl ether.

[0079] The organic additives include dispersants, silane coupling agents, and leveling agents in a weight ratio of 0.3:0.5:0.2.

[0080] The dispersant is AkzoNobel TDO; the silane coupling agent is KH-560; and the leveling agent is purchased from BYK Chemical, brand name BYK-333.

[0081] A method for preparing a low-temperature thermosetting conductive paste includes the following steps: The resin prepolymer, reactive diluent, curing agent, and organic additives were stirred at 500 r / min for 15 minutes to mix evenly, thus obtaining the organic carrier. Add silver-coated copper powder to the organic carrier, stir at a low speed of 200 r / min for 20 min, then stir at a high speed of 1500 r / min for 30 min to mix evenly, then add nano silver powder and disperse at a speed of 1200 r / min for 20 min to mix evenly, and then perform primary vacuum degassing at -0.098 MPa to obtain premixed slurry; Grind the premixed slurry to a fineness of ≤8μm; The material was filtered through a 400-mesh nylon mesh and then degassed under vacuum to obtain a low-temperature thermosetting conductive slurry.

[0082] The prepared low-temperature thermosetting conductive paste was screen-printed onto the TCO layer of the HJT battery using a 500-mesh screen and cured at 200℃ for 30 min. The bulk resistivity of the grid lines after curing was measured to be 3.8 × 10⁻⁶. -6 The adhesion strength to the TCO layer is 5B (ASTM D3359), measured in Ω·cm. Specific performance test results are shown in Table 1-2.

[0083] Comparative Example 2 A low-temperature thermosetting conductive paste, the specific implementation of which is the same as Comparative Example 1, except that the conductive filler includes silver-coated copper powder, nano silver powder and micron silver powder, in a weight ratio of 88:0.1:1.9.

[0084] The D50 particle size of the silver-coated copper powder is 2.0-2.5μm; the silver content of the silver-coated copper powder is 20.0wt%, the silver coating rate is ≥99%, and it is purchased from Guangdong Nanhai Qiming Guangda, with the grade AC060.

[0085] The average particle size of the nano-silver powder is 80-100nm, and it was purchased from Qiming Guangda in Nanhai, Guangdong, with the grade name B80.

[0086] The micron-sized silver powder has a D50 particle size of 1.5-2.0 μm and was purchased from China Banknote Printing and Minting Corporation, with the grade SF-III-140A.

[0087] Comparative Example 3 A low-temperature thermosetting conductive paste, the specific embodiment of which is the same as Comparative Example 1, except that the conductive filler is 86 parts by weight, and the conductive filler includes silver-coated copper powder, nano silver powder and micron silver powder, with a weight ratio of 50:2:34.

[0088] The D50 particle size of the silver-coated copper powder is 2.0-2.2 μm; the silver content of the silver-coated copper powder is 8.0 wt%, the silver coating rate is ≥98.5%, and it was purchased from Guangdong Nanhai Qiming Guangda, with the grade AC082.

[0089] The average particle size of the nano-silver powder is 80-100 nm, and it was purchased from Guangdong Nanhai Qiming Guangda, with the grade name B80.

[0090] The micron-sized silver powder has a D50 particle size of 1.4-1.6 μm and was purchased from Shandong Jianbang, with the grade 152-16N.

[0091] Performance testing 1. The IV characteristics of the solar cells before and after aging at 85℃ / 85%RH for 48 hours were tested using a solar cell IV tester, and the efficiency degradation rate was compared; the specific test results are shown in Table 1.

[0092] 2. The line resistivity of the solar cells was tested using the four-probe method after aging at 85℃ / 85%RH for 48 hours. The specific test results are shown in Table 2.

[0093] Table 1

[0094] Table 2

[0095] Table 1 shows that Example 1 has a 0.06% higher efficiency than Comparative Example 1, and a 6.1% lower decay rate after aging at 85℃ / 85%RH for 48 hours; Example 2 has a 0.049% higher efficiency than Comparative Example 2, and a 6.0% lower decay rate after aging at 85℃ / 85%RH for 48 hours; Example 3 has a 0.059% higher efficiency than Comparative Example 3, and a 7.9% lower decay rate after aging at 85℃ / 85%RH for 48 hours. This demonstrates that the UV-curable conductive paste of this invention has high conversion efficiency and strong resistance to high temperature and humidity.

[0096] As shown in Table 2, with the extension of high temperature and high humidity, the initial resistivity of the UV-curable conductive paste of this invention is relatively low. At the same time, the increase in resistivity after aging at 85℃ / 85%RH for 48 hours is smaller than that of conventional low temperature thermosetting conductive paste, which means it has a strong resistance to water vapor erosion.

Claims

1. A UV-curable conductive paste, characterized in that, The raw materials prepared by weight include 40-92 parts of conductive filler, 0.5-20 parts of photocurable resin prepolymer, 1-10 parts of reactive diluent, 0.5-5 parts of initiator, and 0-1.5 parts of organic additives; the conductive filler includes silver-coated copper powder, and the initiator is a pyrolysis-type photoinitiator.

2. The UV-curable conductive paste according to claim 1, characterized in that, The silver-coated copper powder is micron-sized, with a D50 particle size of 1-10 μm; the silver content of the silver-coated copper powder is 5-60 wt%, and the silver coating rate is ≥98%.

3. The UV-curable conductive paste according to claim 1, characterized in that, The conductive filler further includes nano-silver powder and / or micro-silver powder, wherein the average particle size of the nano-silver powder is 10-100 nm; and the D50 particle size of the micro-silver powder is 0.5-3 μm.

4. The UV-curable conductive paste according to claim 1, characterized in that, The pyrolytic photoinitiator includes at least one of benzoin ether initiators, α-hydroxy ketone initiators, α-amino ketone initiators, or acylphosphine oxide initiators.

5. The UV-curable conductive paste according to claim 4, characterized in that, The cleavage-type photoinitiator includes at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, 1-hydroxycyclohexylphenyl ketone, or 2-hydroxy-2-methyl-1-phenylpropanone.

6. The UV-curable conductive paste according to claim 1, characterized in that, The photocurable resin prepolymer includes at least one of polyurethane acrylate, epoxy acrylate, or polyester acrylate.

7. The UV-curable conductive paste according to claim 1, characterized in that, The active diluent includes at least one of ethoxytrimethylolpropane triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, or isobornyl acrylate.

8. The UV-curable conductive paste according to claim 1, characterized in that, The photocuring energy of the ultraviolet-curable conductive paste is 300-2500 mJ / cm. 2 The curing temperature is <200℃.

9. A method for preparing a UV-curable conductive paste according to any one of claims 3-8, characterized in that, Includes the following steps: Under light-proof and inert atmosphere protection, the photocurable resin prepolymer, reactive diluent, and organic additives are vacuum stirred and mixed evenly to obtain an organic carrier; Add the silver-coated copper powder to the organic carrier, stir at a low speed of 100-300 r / min first, then stir at a high speed of 1300-1800 r / min until uniformly mixed, then add nano silver powder and / or micron silver powder and continue stirring until uniformly mixed, perform primary vacuum degassing to obtain a premixed slurry; Grind the premixed slurry to a fineness of ≤10μm, add the photoinitiator under light-protected conditions, and stir at a low speed of 300-500r / min until uniform; After filtration and vacuum degassing again, a UV-curable conductive slurry is obtained.

10. An application of the UV-curable conductive paste according to any one of claims 3-8, characterized in that, It is used in the fabrication of grid electrodes for heterojunction solar cells.

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