A conductive silver paste for photovoltaic cells based on active additives and its preparation method.

Abstract

This invention relates to the field of conductive silver paste technology, specifically to a conductive silver paste for photovoltaic cells based on active additives and its preparation method. It is made from the following raw materials in parts by weight: 2-5 parts functional additive A, 8-15 parts functional additive B, 70-80 parts ultrafine silver powder, 15-20 parts composite powder, 0.5-1 part antimony tin oxide, 1-2 parts bisphenol A type epoxy resin, and 0.3-0.5 parts nano-alumina. In this invention, functional additive A uses glass powder as the core, and further grafts silver-coated glass powder onto the surface using a titanate-modified coupling agent KH-560. One end of this coupling agent forms a coordination relationship with the silver layer, thereby constructing a chemical bridge between the filler and the organic carrier. This reduces the tendency of silver powder to agglomerate in the paste, keeps the filler dispersed in the coating, reduces the risk of interruption of local conductive pathways, and thus improves the interfacial adhesion of the conductive network and extends its service life.

Description

Technical Field

[0001] This invention relates to the field of conductive silver paste technology, specifically to a conductive silver paste for photovoltaic cells based on active additives and its preparation method. Background Technology

[0002] Conductive silver paste for photovoltaic cells is an electronic paste used in the manufacture of photovoltaic cells. It is applied to the surface of silicon wafers through screen printing and then sintered to form electrodes. Its core function is to collect and transport photogenerated charge carriers, which directly affects the photoelectric conversion efficiency of photovoltaic cells. This product is mainly used in the manufacture of crystalline silicon solar cells in the photovoltaic industry and is an indispensable material in the production process.

[0003] In existing technologies, the adhesion between the silver electrode layer formed after sintering of conductive silver paste and the silicon substrate is insufficient. This leads to electrode detachment or peeling during subsequent module encapsulation and long-term use, resulting in increased series resistance, decreased output power, and impacting the lifespan and power generation stability of the photovoltaic module. Therefore, this invention provides a conductive silver paste for photovoltaic cells based on active additives and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a conductive silver paste for photovoltaic cells based on active additives and its preparation method. The conductive silver paste prepared by this invention not only has good conductivity but also excellent tensile strength, effectively improving the performance of the conductive silver paste.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a conductive silver paste for photovoltaic cells based on active additives, made from the following raw materials in parts by weight: 2-5 parts of functional additive A, 8-15 parts of functional additive B, 70-80 parts of ultrafine silver powder, 15-20 parts of composite powder, 0.5-1 parts of antimony tin oxide, 1-2 parts of bisphenol A type epoxy resin and 0.3-0.5 parts of nano-alumina; The ultrafine silver powder has a particle size of 0.1-0.5 μm; The raw materials for the functional additive A include: anhydrous ethanol, deionized water, ammonia water with a mass fraction of 25%, glass powder, diammonium silver hydroxide, glucose solution, a treated coupling agent, and butyl acetate. The functional additive B raw materials include: ethyl cellulose, maleic anhydride, terpineol, propylene glycol methyl ether and diethylene glycol butyl ether, and silicon dioxide.

[0006] Preferably, the preparation method of the functional additive A includes the following steps: Step 1: Anhydrous ethanol, deionized water, and 25% ammonia solution are mixed at a volume ratio of (5-8):(2-4):1 and stirred for 1-2 minutes to obtain the first mixture. The first mixture is then mixed with glass powder at a mass ratio of (5-10):1 and stirred at 40-60℃ and 200-300 rpm for 30-60 minutes to obtain the first suspension. Step 2: Mix the first suspension, diamminesilver hydroxide and glucose solution at a mass ratio of (1-5):100:(8-10), stir for 30 min at 20-30℃ and 200-300 rpm, collect the solid after centrifugation, and dry to obtain the additive powder; Step 3: Mix the treated coupling agent KH-560 with butyl acetate at a mass ratio of 1:(20-30) to obtain a second mixture. Mix the additive powder with the second mixture at a mass ratio of 1:(3-5) and react at 130-140℃, 200-300rpm, and reflux for 4-6 hours. After the reaction is completed, filter and collect the filter residue. Vacuum dry at 50-70℃ to obtain the functional additive A.

[0007] Preferably, the preparation method of the treated coupling agent KH-560 includes the following steps: p-hydroxybenzoic acid, anhydrous ethanol, and dibutyltin dilaurate were mixed at a mass ratio of 1:(5-10):(0.1-0.3) and stirred at 60-80℃ and 200-300rpm for 10-20min to obtain a third mixture. Tetrabutyl titanate was added to the third mixture under nitrogen protection, and the mixture was stirred at 80-100℃ and 200-300rpm for 2-3h. The solvent was removed by vacuum distillation to obtain the first intermediate. The first intermediate, anhydrous toluene, and silane coupling agent KH-560 were then mixed according to a mass ratio of 1:(5-10):(0.1-0.3). Mix in a ratio of 1:(5-10):(0.3-0.5) and react at 90-110℃, 200-300rpm under reflux for 6-8h. After the reaction, remove the solvent by vacuum distillation to obtain the crude product. Separate the crude product by column chromatography using a treatment agent, collect the eluent of the target product, and concentrate it under vacuum to obtain the treated coupling agent KH-560. The treatment agent is prepared by mixing petroleum ether and ethyl acetate in a volume ratio of (3-5):1, and the mass ratio of the third mixture to tetrabutyl titanate is (10-15):1.

[0008] Preferably, the preparation method of the functional additive B includes the following steps: mixing ethyl cellulose, maleic anhydride and toluene, reacting at 70-80℃, 250-350rpm under nitrogen protection for 2-4h, removing the solvent by rotary evaporation to obtain treated ethyl cellulose for later use; mixing terpineol, propylene glycol methyl ether and diethylene glycol butyl ether at a mass ratio of (4-6):(2-4):(1-3), preheating at 45-55℃ to obtain a composite solvent; adding the treated ethyl cellulose to the composite solvent, stirring at 55-65℃ and 350-450rpm for 2 hours. After 5-35 minutes, a premix is ​​obtained. The premix is ​​then transferred to a high-shear emulsifier and emulsified at 4000-6000 rpm for 8-12 minutes. The mixture is then circulated 2-4 times using a microfluidic homogenizer at 1000-1400 bar pressure to obtain a fourth mixture. Finally, silica is added to the fourth mixture at an amount of 0.3-0.7% of the mass of the fourth mixture. The mixture is stirred at 150-250 rpm for 15-25 minutes, then degassed under vacuum and allowed to stand for 3-5 hours to obtain the functional additive B.

[0009] Preferably, the mass ratio of the treated ethyl cellulose to the composite solvent is 1:(7-9).

[0010] Preferably, the mass ratio of ethyl cellulose, maleic anhydride and toluene is 100:(3-7):(250-350).

[0011] Preferably, the method for preparing the composite powder includes: adding copper powder to dilute hydrochloric acid with a mass fraction of 5%, ultrasonically treating for 10-20 minutes, filtering and taking the filter residue, washing with deionized water until neutral to obtain treated copper powder, mixing the treated copper powder with ultrafine silver powder at a mass ratio of 1:(1-2), placing it in a ball mill jar, and ball milling at a speed of 300-400 rpm for 10-20 hours under an argon atmosphere, and after ball milling, passing it through a 100-200 mesh sieve to obtain the composite powder.

[0012] Preferably, the method for preparing the conductive silver paste for photovoltaic cells based on active additives includes the following steps: Step 1: Mix ultrafine silver powder, composite powder, functional additive A, antimony tin oxide and nano alumina to obtain a powder mixture; Step 2: Add bisphenol A epoxy resin and functional additive B to the powder mixture, and stir in a planetary mixer at a speed of 600-800 rpm for 30-60 minutes to obtain a coarse slurry. Step 3: Transfer the coarse slurry to a three-roll mill and grind it 3-5 times, with grinding gaps of 20μm, 10μm and 5μm respectively, to obtain the ground slurry; Step 4: Degas the ground slurry in a vacuum degassing machine for 20-30 minutes, and then filter it through a 200-mesh sieve to obtain conductive silver paste for photovoltaic cells based on active additives.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, functional additive A uses glass powder as the core and deposits a silver layer on the surface in situ under alkaline conditions using diammonium silver hydroxide to form a composite powder with a silver coating structure. The introduction of this silver layer enables the originally insulating glass powder to conduct electricity while retaining its softening fluidity at the sintering temperature. Furthermore, the silver-coated glass powder is grafted onto the surface using a titanate-modified coupling agent KH-560. One end of this coupling agent forms a coordination relationship with the silver layer, and the other end undergoes a cross-linking reaction with the resin matrix through epoxy groups, thereby constructing a chemical bridge between the filler and the organic carrier. This reduces the tendency of silver powder to agglomerate in the slurry, keeps the filler in a dispersed state in the coating, reduces the risk of interruption of local conductive pathways, and thus improves the interfacial adhesion of the conductive network and extends its service life.

[0014] 2. In this invention, functional additive B modifies ethyl cellulose by maleic anhydride esterification, introducing polar carboxyl active sites. This forms a stable hydrogen-bonded crosslinking network in a composite solvent system composed of terpineol, propylene glycol methyl ether, and diethylene glycol butyl ether. Simultaneously, nano-silica, with its abundant silanol groups on its surface, acts as multifunctional crosslinking points, forming multiple hydrogen bonds with the carboxyl groups of the modified ethyl cellulose. This significantly enhances the mechanical strength of the three-dimensional network skeleton within the slurry. During sintering, this network structure effectively anchors silver powder particles and forms a good fusion with the glass phase, improving the toughness and strength of the glass phase and making the connection between silver particles more robust. This results in excellent tensile properties, effectively ensuring the mechanical stability and long-term reliability of the electrode layer.

[0015] 3. In this invention, functional additive A and functional additive B achieve synergistic effects through a combination of chemical and physical processes. Functional additive A uses glass powder as a core, forms a silver coating layer through a silver mirror reaction, and then performs surface grafting with a titanate-modified coupling agent KH-560. The titanate groups form coordination bonds with the silver layer, and the epoxy groups undergo cross-linking reactions with the carboxyl groups of the modified ethyl cellulose and bisphenol A epoxy resin in functional additive B, constructing a chemical bridging network between the inorganic filler and the organic carrier. At the same time, the three-dimensional physical cross-linked skeleton formed by functional additive B spatially anchors the conductive filler. The synergistic effect of the two significantly reduces the agglomeration tendency of silver powder, ensuring that the conductive filler is uniformly dispersed in the coating, forming a continuous and stable conductive pathway, thereby improving the interfacial adhesion and conductivity of the conductive network. Attached Figure Description

[0016] Figure 1The present invention provides a flowchart of a conductive silver paste for photovoltaic cells based on active additives and its preparation method. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that the raw materials used in the following embodiments are all commercially available.

[0019] Example 1

[0020] 2 parts functional additive A, 8 parts functional additive B, 70 parts ultrafine silver powder, 15 parts composite powder, 0.5 parts tin antimony oxide, 1 part bisphenol A type epoxy resin and 0.3 parts nano alumina; The particle size of the ultrafine silver powder is 0.1 μm; The raw materials for functional additive A include: anhydrous ethanol, deionized water, ammonia water with a mass fraction of 25%, glass powder, diammonium silver hydroxide, glucose solution, post-treatment coupling agent and butyl acetate; The raw materials for functional additive B include: ethyl cellulose, maleic anhydride, terpineol, propylene glycol methyl ether and diethylene glycol butyl ether, and silicon dioxide.

[0021] The preparation method of functional additive A includes the following steps: Step 1: Anhydrous ethanol, deionized water and 25% ammonia water are mixed in a volume ratio of 5:2:1 and stirred for 1 min to obtain the first mixture. The first mixture is then mixed with glass powder in a mass ratio of 5:1 and stirred at 40℃ and 200 rpm for 30 min to obtain the first suspension. Step 2: Mix the first suspension, diamminesilver hydroxide and glucose solution at a mass ratio of 1:100:8, stir for 30 min at 20℃ and 200 rpm, collect the solid after centrifugation, and dry to obtain the additive powder; Step 3: Mix the treated coupling agent KH-560 with butyl acetate at a mass ratio of 1:20 to obtain a second mixture. Mix the additive powder with the second mixture at a mass ratio of 1:3 and react at 130℃, 200rpm and reflux for 4 hours. After the reaction is completed, filter and collect the residue. Dry it under vacuum at 50℃ to obtain the functional additive A.

[0022] The preparation method of the treated coupling agent KH-560 includes the following steps: p-hydroxybenzoic acid, anhydrous ethanol, and dibutyltin dilaurate were mixed at a mass ratio of 1:5:0.1 and stirred at 60°C and 200 rpm for 10 min to obtain a third mixture. Tetrabutyl titanate was added to the third mixture under nitrogen protection, and the mixture was stirred at 80°C and 200 rpm for 2 h. The solvent was removed by vacuum distillation to obtain a first intermediate. The first intermediate, anhydrous toluene, and silane coupling agent KH-560 were mixed at a mass ratio of 1:5:0.3 and reacted at 90°C and 200 rpm under reflux for 6 h. After the reaction was completed, the solvent was removed by vacuum distillation to obtain a crude product. The crude product was separated by column chromatography using a treatment agent, and the eluent of the target product was collected and concentrated under vacuum to obtain the treated coupling agent KH-560. The treatment agent was prepared by mixing petroleum ether and ethyl acetate at a volume ratio of 3:1, and the mass ratio of the third mixture to tetrabutyl titanate was 10:1.

[0023] The preparation method of functional additive B includes the following steps: Ethyl cellulose, maleic anhydride and toluene are mixed and reacted at 70℃, 250 rpm and nitrogen protection for 2 h. The solvent is removed by rotary evaporation to obtain treated ethyl cellulose for later use. Terpineol, propylene glycol methyl ether and diethylene glycol butyl ether are mixed at a mass ratio of 4:2:1 and preheated at 45℃ to obtain a composite solvent. The treated ethyl cellulose is added to the composite solvent and stirred at 55℃ and 350 rpm for 25 min to obtain a premix. The premix is ​​transferred to a high-shear emulsifier and emulsified at 4000 rpm for 8 min. Then it is circulated twice by a microfluidic homogenizer at 1000 bar pressure to obtain a fourth mixture. Finally, silica is added to the fourth mixture at an amount of 0.3% of the mass of the fourth mixture. The mixture is stirred at 150 rpm for 15 min, then vacuum degassed and allowed to stand for 3 h to obtain the functional additive B.

[0024] The mass ratio of ethyl cellulose to the composite solvent after treatment is 1:7.

[0025] The mass ratio of ethyl cellulose, maleic anhydride and toluene is 100:3:250.

[0026] The method for preparing the composite powder includes: adding copper powder to dilute hydrochloric acid with a mass fraction of 5%, ultrasonically treating for 10 minutes, filtering and taking the filter residue, washing with deionized water until neutral to obtain treated copper powder, mixing the treated copper powder with ultrafine silver powder at a mass ratio of 1:1, placing it in a ball mill jar, and ball milling at a speed of 300 rpm for 10 hours under an argon atmosphere, and after ball milling, passing it through a 100-mesh sieve to obtain the composite powder.

[0027] The preparation method of conductive silver paste for photovoltaic cells based on active additives includes the following steps: Step 1: Mix ultrafine silver powder, composite powder, functional additive A, antimony tin oxide and nano alumina to obtain a powder mixture; Step 2: Add bisphenol A epoxy resin and functional additive B to the powder mixture, and stir in a planetary mixer at 600 rpm for 30 minutes to obtain a coarse slurry; Step 3: Transfer the coarse slurry to a three-roll mill and grind it three times, with grinding gaps of 20μm, 10μm and 5μm respectively, to obtain the ground slurry; Step 4: Degas the ground slurry in a vacuum degassing machine for 20 minutes, and then filter it through a 200-mesh sieve to obtain conductive silver paste for photovoltaic cells based on active additives.

[0028] Example 2

[0029] 3 parts functional additive A, 11 parts functional additive B, 75 parts ultrafine silver powder, 18 parts composite powder, 0.5-1 part antimony tin oxide, 1-2 parts bisphenol A type epoxy resin and 0.3-0.5 parts nano alumina; The particle size of the ultrafine silver powder is 0.1-0.5μm; The raw materials for functional additive A include: anhydrous ethanol, deionized water, ammonia water with a mass fraction of 25%, glass powder, diammonium silver hydroxide, glucose solution, post-treatment coupling agent and butyl acetate; The raw materials for functional additive B include: ethyl cellulose, maleic anhydride, terpineol, propylene glycol methyl ether and diethylene glycol butyl ether, and silicon dioxide.

[0030] The preparation method of functional additive A includes the following steps: Step 1: Anhydrous ethanol, deionized water, and 25% ammonia solution are mixed at a volume ratio of (5-8):(2-4):1 and stirred for 1-2 minutes to obtain the first mixture. The first mixture is then mixed with glass powder at a mass ratio of (5-10):1 and stirred at 40-60℃ and 200-300 rpm for 30-60 minutes to obtain the first suspension. Step 2: Mix the first suspension, diamminesilver hydroxide and glucose solution at a mass ratio of (1-5):100:(8-10), stir for 30 min at 20-30℃ and 200-300 rpm, collect the solid after centrifugation, and dry to obtain the additive powder; Step 3: Mix the treated coupling agent KH-560 with butyl acetate at a mass ratio of 1:(20-30) to obtain a second mixture. Mix the additive powder with the second mixture at a mass ratio of 1:(3-5) and react at 130-140℃, 200-300rpm, and reflux for 4-6 hours. After the reaction is completed, filter and collect the filter residue. Vacuum dry at 50-70℃ to obtain the functional additive A.

[0031] The preparation method of the treated coupling agent KH-560 includes the following steps: p-hydroxybenzoic acid, anhydrous ethanol, and dibutyltin dilaurate were mixed at a mass ratio of 1:(5-10):(0.1-0.3) and stirred at 60-80℃ and 200-300rpm for 10-20min to obtain a third mixture. Tetrabutyl titanate was added to the third mixture under nitrogen protection, and the mixture was stirred at 80-100℃ and 200-300rpm for 2-3h. The solvent was removed by vacuum distillation to obtain the first intermediate. The first intermediate and anhydrous toluene were then... The mixture was prepared by mixing silane coupling agent KH-560 at a mass ratio of 1:8:0.4 and reacting at 100℃, 250rpm and reflux for 7h. After the reaction was completed, the solvent was removed by vacuum distillation to obtain the crude product. The crude product was separated by column chromatography using a treatment agent, and the eluent of the target product was collected and concentrated under reduced pressure to obtain the treated coupling agent KH-560. The treatment agent was prepared by mixing petroleum ether and ethyl acetate at a volume ratio of 4:1, and the mass ratio of the third mixture to tetrabutyl titanate was 12:1.

[0032] The preparation method of functional additive B includes the following steps: Ethyl cellulose, maleic anhydride and toluene are mixed and reacted at 75℃, 300 rpm and nitrogen protection for 3 h. The solvent is removed by rotary evaporation to obtain treated ethyl cellulose for later use. Terpineol, propylene glycol methyl ether and diethylene glycol butyl ether are mixed at a mass ratio of 5:3:2 and preheated at 50℃ to obtain a composite solvent. The treated ethyl cellulose is added to the composite solvent and stirred at 58℃ and 400 rpm for 30 min to obtain a premix. The premix is ​​transferred to a high-shear emulsifier and emulsified at 5000 rpm for 10 min. Then it is circulated three times by a microfluidic homogenizer at 1200 bar pressure to obtain a fourth mixture. Finally, silica is added to the fourth mixture at an amount of 0.5% of the mass of the fourth mixture. The mixture is stirred at 200 rpm for 20 min, then vacuum degassed and allowed to stand for 4 h to obtain the functional additive B.

[0033] The mass ratio of ethyl cellulose to composite solvent after treatment is 1:8.

[0034] The mass ratio of ethyl cellulose, maleic anhydride and toluene is 100:5:300.

[0035] The method for preparing the composite powder includes: adding copper powder to dilute hydrochloric acid with a mass fraction of 5%, ultrasonically treating for 15 minutes, filtering and taking the filter residue, washing with deionized water until neutral to obtain treated copper powder, mixing the treated copper powder with ultrafine silver powder at a mass ratio of 1:1.5, placing it in a ball mill jar, and ball milling at a speed of 350 rpm for 15 hours under an argon atmosphere, and after ball milling, passing it through a 150-mesh sieve to obtain the composite powder.

[0036] The preparation method of conductive silver paste for photovoltaic cells based on active additives includes the following steps: Step 1: Mix ultrafine silver powder, composite powder, functional additive A, antimony tin oxide and nano alumina to obtain a powder mixture; Step 2: Add bisphenol A epoxy resin and functional additive B to the powder mixture, and stir in a planetary mixer at 700 rpm for 45 minutes to obtain a coarse slurry; Step 3: Transfer the coarse slurry to a three-roll mill and grind it four times, with grinding gaps of 20μm, 10μm and 5μm respectively, to obtain the ground slurry; Step 4: Degas the ground slurry in a vacuum degassing machine for 25 minutes, and then filter it through a 200-mesh sieve to obtain conductive silver paste for photovoltaic cells based on active additives.

[0037] Example 3

[0038] 5 parts functional additive A, 15 parts functional additive B, 80 parts ultrafine silver powder, 20 parts composite powder, 1 part tin antimony oxide, 2 parts bisphenol A type epoxy resin and 0.5 parts nano alumina; The particle size of the ultrafine silver powder is 0.5 μm; The raw materials for functional additive A include: anhydrous ethanol, deionized water, ammonia water with a mass fraction of 25%, glass powder, diammonium silver hydroxide, glucose solution, post-treatment coupling agent and butyl acetate; The raw materials for functional additive B include: ethyl cellulose, maleic anhydride, terpineol, propylene glycol methyl ether and diethylene glycol butyl ether, and silicon dioxide.

[0039] The preparation method of functional additive A includes the following steps: Step 1: Anhydrous ethanol, deionized water and 25% ammonia water are mixed in a volume ratio of 8:4:1 and stirred for 2 minutes to obtain the first mixture. The first mixture is then mixed with glass powder in a mass ratio of 10:1 and stirred at 60°C and 300 rpm for 60 minutes to obtain the first suspension. Step 2: Mix the first suspension, diamminesilver hydroxide and glucose solution at a mass ratio of 5:100:10, stir for 30 min at 30℃ and 300 rpm, collect the solid after centrifugation, and dry to obtain the additive powder; Step 3: Mix the treated coupling agent KH-560 with butyl acetate at a mass ratio of 1:30 to obtain a second mixture. Mix the additive powder with the second mixture at a mass ratio of 1:5 and react at 140℃, 300rpm and reflux for 6 hours. After the reaction is completed, filter and collect the residue. Dry it under vacuum at 70℃ to obtain the functional additive A.

[0040] The preparation method of the treated coupling agent KH-560 includes the following steps: p-hydroxybenzoic acid, anhydrous ethanol, and dibutyltin dilaurate were mixed at a mass ratio of 1:10:0.3 and stirred at 80°C and 300 rpm for 20 min to obtain a third mixture. Tetrabutyl titanate was added to the third mixture under nitrogen protection, and the mixture was stirred at 100°C and 300 rpm for 3 h. The solvent was removed by vacuum distillation to obtain a first intermediate. The first intermediate, anhydrous toluene, and silane coupling agent KH-560 were mixed at a mass ratio of 1:10:0.5 and reacted at 110°C and 300 rpm under reflux for 8 h. After the reaction was completed, the solvent was removed by vacuum distillation to obtain a crude product. The crude product was separated by column chromatography using a treatment agent, and the eluent of the target product was collected and concentrated under vacuum to obtain the treated coupling agent KH-560. The treatment agent was prepared by mixing petroleum ether and ethyl acetate at a volume ratio of 5:1, and the mass ratio of the third mixture to tetrabutyl titanate was 15:1.

[0041] The preparation method of functional additive B includes the following steps: Ethyl cellulose, maleic anhydride and toluene are mixed and reacted at 80℃, 350rpm and nitrogen protection for 4h. The solvent is removed by rotary evaporation to obtain treated ethyl cellulose for later use. Terpineol, propylene glycol methyl ether and diethylene glycol butyl ether are mixed at a mass ratio of 6:4:3 and preheated at 55℃ to obtain a composite solvent. The treated ethyl cellulose is added to the composite solvent and stirred at 65℃ and 450rpm for 35min to obtain a premix. The premix is ​​transferred to a high-shear emulsifier and emulsified at 6000rpm for 12min. Then it is circulated 4 times by a microfluidic homogenizer at 1400bar pressure to obtain a fourth mixture. Finally, silica is added to the fourth mixture at an amount of 0.7% of the mass of the fourth mixture. The mixture is stirred at 250rpm for 25min, then vacuum degassed and allowed to stand for 5h to obtain the functional additive B.

[0042] The mass ratio of ethyl cellulose to the composite solvent after treatment is 1:9.

[0043] The mass ratio of ethyl cellulose, maleic anhydride and toluene is 100:7:350.

[0044] The method for preparing the composite powder includes: adding copper powder to dilute hydrochloric acid with a mass fraction of 5%, ultrasonically treating for 20 minutes, filtering and taking the filter residue, washing with deionized water until neutral to obtain treated copper powder, mixing the treated copper powder with ultrafine silver powder at a mass ratio of 1:2, placing it in a ball mill jar, and ball milling at a speed of 400 rpm for 20 hours under an argon atmosphere, and after ball milling, passing it through a 200-mesh sieve to obtain the composite powder.

[0045] The preparation method of conductive silver paste for photovoltaic cells based on active additives includes the following steps: Step 1: Mix ultrafine silver powder, composite powder, functional additive A, antimony tin oxide and nano alumina to obtain a powder mixture; Step 2: Add bisphenol A epoxy resin and functional additive B to the powder mixture, and stir in a planetary mixer at 800 rpm for 60 minutes to obtain a coarse slurry; Step 3: Transfer the coarse slurry to a three-roll mill and grind it 5 times, with grinding gaps of 20μm, 10μm and 5μm respectively, to obtain the ground slurry; Step 4: Degas the ground slurry in a vacuum degassing machine for 30 minutes, and then filter it through a 200-mesh sieve to obtain conductive silver paste for photovoltaic cells based on active additives.

[0046] Comparative Example 1: The difference between this comparative example and Example 1 is that this comparative example does not contain functional additive A.

[0047] Comparative Example 2 differs from Example 1 in that it does not contain functional additive B.

[0048] Comparative Example 3 differs from Example 1 in that the functional additive A was not coupled during its preparation.

[0049] Performance testing: The conductive silver pastes prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests. The following three performance tests were conducted according to GB / T17473-2025, and the test data are recorded in the table below: Table 1 Example 1 4.2 0 0.128 Example 2 4.0 0 0.135 Example 3 3.9 0 0.142 Comparative Example 1 9.8 3 0.065 Comparative Example 2 8.5 2 0.058 Comparative Example 3 8.1 2 0.093 In functional additive A, the silver-coated glass powder modified with a coupling agent softens and becomes fluid at the sintering temperature. Because organic functional groups are grafted onto the surface of the glass powder through the coupling agent, this softening and fluid behavior is confined to the interface region in close contact with the organic carrier. This allows the molten glass to uniformly wet the substrate surface and penetrate into the tiny unevenness of the substrate, forming a strong mechanical locking force and a cross-linked structure between the organic and inorganic interfaces. When functional additive A is missing in Comparative Example 1, the slurry lacks glass powder that can soften during sintering, making it impossible to form effective wetting and penetration of the molten glass onto the substrate surface. Consequently, it is impossible to establish a mechanical locking force to lock the electrode layer in the uneven structure of the substrate, and the chemical bonding ability brought by the coupling agent is lost, resulting in a decrease in adhesion.

[0050] In the preparation of functional additive B, functional additive B is the core component for constructing the three-dimensional network skeleton in this invention. The ethyl cellulose in its composition is esterified with maleic anhydride to introduce polar carboxyl groups. Under the synergistic effect of the composite solvents terpineol, propylene glycol methyl ether, and diethylene glycol butyl ether, a physical cross-linked network that runs through the slurry system is formed through hydrogen bonds. The abundant silanol groups on the surface of nano silica serve as multifunctional cross-linking points, forming multiple hydrogen bonds with the carboxyl groups of modified ethyl cellulose, which significantly enhances the mechanical strength of the network skeleton. During the sintering process, it is partially integrated into the glass phase, improving the toughness and strength of the glass phase and making the connection between silver particles more solid. When functional additive B is missing, there is no three-dimensional network anchoring in the slurry. The absence of nano silica increases the brittleness of the glass phase, making it prone to microcracks under bonding stress and significantly reducing the bonding tensile strength.

[0051] In performance testing, the superior conductivity of the conductive silver paste is mainly due to the precise control of the conductive filler interface by functional additive A. During the preparation of functional additive A, a silver layer is deposited on the surface of insulating glass powder through a silver mirror reaction, transforming it into conductive composite particles. This design increases the effective contact points of the conductive filler. The titanate-treated coupling agent KH-560 has titanate groups in its molecular structure that can form stable coordination bonds with the surface of the silver coating layer, while the terminal epoxy functional groups undergo cross-linking reactions with the bisphenol A type epoxy resin in the organic carrier and the active groups in functional additive B. This chemical bridging effect means that the conductive filler is no longer simply physically dispersed in the resin, but forms an integral whole with the organic system through chemical bonds. When functional additive A was prepared in Comparative Example 3 without coupling modification, the filler and resin lacked this strong interaction, which caused the silver powder to easily agglomerate in the paste. After sintering, the continuity of the conductive path deteriorated, and electrons encountered obstacles during conduction, thus increasing the sheet resistance. Although the adhesion and average bond pull were better than the other two comparative examples, they were still far lower than the example.

[0052] By comparing and analyzing the relevant data in the table, it can be seen that the conductive silver paste prepared by this invention not only has good conductivity but also excellent tensile strength. This indicates that the conductive silver paste for photovoltaic cells based on active additives provided by this invention has a broader market prospect and is more suitable for widespread application.

[0053] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0054] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A conductive silver paste for photovoltaic cells based on active additives, characterized in that, The product comprises the following components by weight: 2-5 parts functional additive A, 8-15 parts functional additive B, 70-80 parts ultrafine silver powder, 15-20 parts composite powder, 0.5-1 part antimony tin oxide, 1-2 parts bisphenol A type epoxy resin, and 0.3-0.5 parts nano alumina. The ultrafine silver powder has a particle size of 0.1-0.5 μm; The raw materials for the functional additive A include: anhydrous ethanol, deionized water, ammonia water with a mass fraction of 25%, glass powder, diammonium silver hydroxide, glucose solution, a treated coupling agent, and butyl acetate. The preparation method of the treated coupling agent KH-560 includes the following steps: p-hydroxybenzoic acid, anhydrous ethanol, and dibutyltin dilaurate were mixed at a mass ratio of 1:(5-10):(0.1-0.3) and stirred at 60-80℃ and 200-300rpm for 10-20min to obtain a third mixture. Tetrabutyl titanate was added to the third mixture under nitrogen protection, and the mixture was stirred at 80-100℃ and 200-300rpm for 2-3h. The solvent was removed by vacuum distillation to obtain the first intermediate. The first intermediate, anhydrous toluene, and silane coupling agent KH-560 were then mixed according to a mass ratio of 1:(5-10):(0.1-0.3). Mix in a ratio of 1:(5-10):(0.3-0.5) and react at 90-110℃, 200-300rpm under reflux for 6-8h. After the reaction, remove the solvent by vacuum distillation to obtain the crude product. Separate the crude product by column chromatography using a treatment agent, collect the target product eluent, concentrate it under vacuum to obtain the treatment coupling agent KH-560. The treatment agent is prepared by mixing petroleum ether and ethyl acetate in a volume ratio of (3-5):1, and the mass ratio of the third mixture to tetrabutyl titanate is (10-15):

1. The functional additive B raw materials include: ethyl cellulose, maleic anhydride, terpineol, propylene glycol methyl ether and diethylene glycol butyl ether, and silicon dioxide; The method for preparing the composite powder includes: adding copper powder to dilute hydrochloric acid with a mass fraction of 5%, ultrasonically treating for 10-20 minutes, filtering and taking the filter residue, washing with deionized water until neutral to obtain treated copper powder, mixing the treated copper powder with ultrafine silver powder at a mass ratio of 1:(1-2), placing it in a ball mill jar, and ball milling at a speed of 300-400 rpm for 10-20 hours under an argon atmosphere, and after ball milling, passing it through a 100-200 mesh sieve to obtain the composite powder.

2. The conductive silver paste for photovoltaic cells based on active additives according to claim 1, characterized in that, The preparation method of the functional additive A includes the following steps: Step 1: Mix anhydrous ethanol, deionized water and 25% ammonia water, stir for 1-2 minutes to obtain the first mixture, mix the first mixture with glass powder at a mass ratio of (5-10):1, stir at 40-60℃ and 200-300 rpm for 30-60 minutes to obtain the first suspension. Step 2: Mix the first suspension, diamminesilver hydroxide, and glucose solution, stir for 30 minutes at 20-30℃ and 200-300 rpm, collect the solid after centrifugation, and dry to obtain the additive powder; Step 3: Mix the treated coupling agent KH-560 with butyl acetate at a mass ratio of 1:(20-30) to obtain a second mixture. Mix the additive powder with the second mixture at a mass ratio of 1:(3-5) and react at 130-140℃, 200-300rpm, and reflux for 4-6 hours. After the reaction is completed, filter and collect the filter residue. Vacuum dry at 50-70℃ to obtain the functional additive A.

3. The conductive silver paste for photovoltaic cells based on active additives according to claim 2, characterized in that, The volume ratio of anhydrous ethanol, deionized water and ammonia is (5-8):(2-4):

1.

4. The conductive silver paste for photovoltaic cells based on active additives according to claim 2, characterized in that, The mass ratio of the first suspension, diamminesilver hydroxide and glucose solution is (1-5):100:(8-10).

5. The conductive silver paste for photovoltaic cells based on active additives according to claim 1, characterized in that, The preparation method of the functional additive B includes the following steps: Ethyl cellulose, maleic anhydride, and toluene are mixed and reacted at 70-80℃, 250-350rpm, and under nitrogen protection for 2-4 hours; the solvent is removed by rotary evaporation to obtain treated ethyl cellulose for later use; terpineol, propylene glycol methyl ether, and diethylene glycol butyl ether are mixed at a mass ratio of (4-6):(2-4):(1-3), and preheated at 45-55℃ to obtain a composite solvent; the treated ethyl cellulose is added to the composite solvent and stirred at 55-65℃ and 350-450rpm for 25-65 hours. After 35 minutes, a premixed liquid is obtained. The premixed liquid is transferred to a high-shear emulsifier and emulsified at 4000-6000 rpm for 8-12 minutes. Then, it is circulated 2-4 times by a microfluidic homogenizer at a pressure of 1000-1400 bar to obtain a fourth mixture. Finally, silica is added to the fourth mixture at an amount of 0.3-0.7% of the mass of the fourth mixture. The mixture is stirred at 150-250 rpm for 15-25 minutes, then degassed under vacuum and allowed to stand for 3-5 hours to obtain the functional additive B.

6. The conductive silver paste for photovoltaic cells based on active additives according to claim 5, characterized in that, The mass ratio of the treated ethyl cellulose to the composite solvent is 1:(7-9).

7. The conductive silver paste for photovoltaic cells based on active additives according to claim 5, characterized in that, The mass ratio of ethyl cellulose, maleic anhydride and toluene is 100:(3-7):(250-350).

8. A method for preparing conductive silver paste for photovoltaic cells based on active additives according to any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Mix ultrafine silver powder, composite powder, functional additive A, antimony tin oxide and nano alumina to obtain a powder mixture; Step 2: Add bisphenol A epoxy resin and functional additive B to the powder mixture, and stir in a planetary mixer at a speed of 600-800 rpm for 30-60 minutes to obtain a coarse slurry. Step 3: Transfer the coarse slurry to a three-roll mill and grind it 3-5 times, with grinding gaps of 20μm, 10μm and 5μm respectively, to obtain the ground slurry; Step 4: Degas the ground slurry in a vacuum degassing machine for 20-30 minutes, and then filter it through a 200-mesh sieve to obtain conductive silver paste for photovoltaic cells based on active additives.

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