Conductive copper paste and preparation method and application thereof

Abstract

The invention discloses conductive copper paste and a preparation method thereof, and belongs to the technical field of photovoltaic materials. The conductive copper paste takes base metal copper instead of noble metal silver as a core conductive component, and solves the problem of high cost of the existing conductive silver paste. The copper paste comprises the following components in percentage by weight: 72-85% of copper powder, 2.5-8% of glass powder, 8-12% of an organic carrier and 1-9% of an additive, the copper powder is spherical powder with D50: 0.5-5 [mu] m, preferably 1-2 [mu] m; the glass powder is prepared from at least two components such as PbO and SiO2 through a specific process, and the additive comprises an organic antioxidant and an inorganic antioxidant, so that a dual antioxidant system is formed. The special low-temperature glass powder is used for reducing the sintering temperature and blocking diffusion of copper ions, the copper paste is sintered at the high temperature of 500-600 DEG C in the air without inert gas protection in cooperation with a dual-oxidation-resistant scheme, the photoelectric conversion efficiency of the prepared solar cell reaches 26.586% to the maximum and is equal to that of commercially available silver paste, the raw material cost is only 1 / 100 of that of the silver paste, and the application range is wide. And the method adapts to the existing silicon-based battery process, and can realize commercialized large-scale mass production.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic materials technology, specifically to a conductive copper paste, its preparation method, and its application. Background Technology

[0002] The core development goal of the photovoltaic industry is to continuously improve efficiency and reduce costs. Currently, in the metallization scheme of silicon-based solar cells, conductive silver paste, with silver powder as the main raw material, accounts for as much as 80-90%. Due to the monetary properties of metallic silver, its price is high and fluctuates frequently, resulting in high production costs for solar cells, which seriously restricts the large-scale development of the industry.

[0003] Copper, a base metal, has a conductivity similar to that of silver and is much cheaper, making it an ideal alternative to silver as a core component of conductive pastes. However, silicon-based solar cells typically employ a high-temperature, rapid-burning process, and the application of copper paste faces two major technical challenges: First, copper is highly susceptible to oxidation at high temperatures, and the resulting copper oxide can disrupt conductive pathways, leading to a sharp decline in conductivity or even complete failure. Second, copper ions are highly reactive and diffuse rapidly within silicon wafers, easily forming deep-level defects that become electron recombination centers, significantly reducing the photoelectric conversion efficiency of solar cells.

[0004] Existing technologies, such as the copper paste technology disclosed in patent CN115038673B, have many shortcomings: they do not mention the use of glass powder, but only use oxide combinations as a substitute, making it difficult to achieve multiple functions such as reducing sintering temperature, bonding metal grid lines to silicon wafers, and blocking copper ion diffusion; the surface of the copper powder used needs to be coated with metal nanoparticles, which increases production costs and process control difficulty; the addition of phosphorus-containing substances in the formula is corrosive to the screen printing plate in the screen printing process, shortening the screen's lifespan; the copper powder contains 7-8μm coarse powder, which cannot meet the fine-line printing requirements of existing battery processes, limiting the improvement of battery performance.

[0005] Therefore, developing a conductive copper paste that is compatible with existing silicon-based cell sintering processes, solves the problems of copper oxidation and ion diffusion, and is low in cost and stable in performance has become an urgent technical need for the photovoltaic industry. Summary of the Invention

[0006] The purpose of this invention is to provide a conductive copper paste, its preparation method, and its application, so as to solve the technical problems of easy oxidation of existing copper paste at high temperatures and diffusion of copper ions.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: Conductive copper paste composition design Based on the total weight of the conductive copper paste, the weight percentages of each component are as follows: copper powder 72%-85%, glass powder 2.5%-8%, organic carrier 8%-12%, and additives 1%-9%.

[0008] Copper powder: Select spherical powder with D50: 0.5-5μm[A1], preferably 1-2μm. No coating treatment is required. It is suitable for fine line printing process to ensure the continuity and density of conductive path.

[0009] Glass powder: composed of at least two of PbO, SiO2, ZnO, Al2O3, Bi2O3, B2O3, Li2CO3, and Na2CO3, is produced by melting at 1100℃, cooling, grinding and grading. The specific formula includes 8 types from G1 to G8. It can effectively reduce the sintering temperature of copper paste, avoid burning through the SiN passivation film on the battery surface, form an inorganic phase protective layer to block the diffusion of copper ions, and at the same time achieve a firm bond between the metal grid lines and the silicon wafer.

[0010] Organic carrier: The fixed components are 2.0wt% saturated polyester resin (molecular weight 10000-30000), 1.0wt% polyvinyl butyral, 4.8wt% diethylene glycol butyl ether acetate, 0.5wt% dodecayl alcohol ester, and 0.2wt% dimethyl silicone oil; The additive includes 1-5 wt% organic antioxidant and 1-10 wt% inorganic antioxidant. The organic antioxidant is selected from at least one of ammonium formate, ascorbic acid, formate, PVP, PVA, and PMMA, and the inorganic antioxidant is at least one of stannous oxide, antimony oxide, and graphene with a wavelength of 10-1000 nm, forming a dual antioxidant system.

[0011] Dual antioxidant mechanism Low temperature zone (200-300℃): Organic antioxidants (such as PVP, PVA, PMMA) in the organic carrier react to prevent copper powder oxidation, and at the same time react with reducing agent precursors to generate inorganic antioxidants; High-temperature zone (500-600℃): Inorganic antioxidants play a role in reducing copper oxide generated by oxidation back to copper; After sintering: The antioxidant and glass powder together form a dense nano-scale protective layer, which effectively prevents the copper grid lines from oxidizing.

[0012] Preparation method Glass powder preparation: Mix raw materials according to a preset ratio, melt at 1100℃ for 30 minutes, and rapidly cool to below 100℃ to obtain glass slag. After coarse grinding for 30 minutes and wet grinding and classification, the target glass powder is obtained. Preparation of conductive paste: Weigh each component according to the proportion, first mix glass powder, inorganic additives and organic carrier to prepare glass paste, then mix with copper powder, and grind evenly by three-roll mill. Solar cell fabrication: Copper paste is printed onto TOPCon monocrystalline silicon wafers using screen printing. Rapid sintering is performed at a peak sintering temperature of 500-600℃ and a heating time of 16 seconds. Cells with pure copper electrodes or Cu+Ag seed layer electrodes can be selected. The silver seed layer needs to be prepared by sintering at 720-760℃ first.

[0013] The present invention has the following beneficial effects: This invention significantly reduces the raw material cost of photovoltaic conductive paste by replacing the precious metal silver with copper, a base metal with a conductivity close to that of silver, as the core conductive component, thus fundamentally alleviating the industry's dependence on expensive silver paste. By leveraging the synergistic effect of an organic-inorganic dual antioxidant system and a specially formulated glass powder with an optimized formula, it effectively solves the key technical challenges of easy oxidation of copper paste during high-temperature sintering and rapid diffusion of copper ions within silicon wafers, ensuring the stability of the conductive path and the photoelectric performance of solar cells. Special glass powder simultaneously achieves multiple functions such as reducing sintering temperature, preventing passivation film burn-through, and firmly bonding metal grid lines to silicon wafers, enabling copper paste to be sintered at high temperatures in air without the need for inert gas protection. It is fully compatible with the existing high-temperature fast-burning process of silicon-based solar cells and requires no additional modification to production equipment. Furthermore, the copper powder used in this invention is a conventional spherical powder, which does not require complex coating treatment. The formula does not contain corrosive phosphorus-containing substances, and the particle size of the copper powder is suitable for fine-line printing processes. This reduces the difficulty and cost of paste preparation, extends the service life of screen printing stencils, and reduces maintenance costs during production, thus demonstrating good prospects for commercial application. Attached Figure Description

[0014] Figure 1 A diagram illustrating the specific steps involved in the preparation of the invention. Detailed Implementation

[0015] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0016] I. Raw Material Preparation Chemical reagents: ZnO, SiO2, B2O3, PbO, Al2O3, Na2CO3, Li2CO3, and Bi2O3 are all of the 4N grade; Copper powder: spherical powder with D50 of 0.5-5 μm [A2], preferably copper powder with D50 of 1-2 μm; Silicon wafer: 182*182mm TOPCon monocrystalline silicon wafer; Organic carrier: by weight percentage, it contains 2.0% saturated polyester resin (molecular weight 10,000-30,000), 1.0% polyvinyl butyral, 4.8% diethylene glycol butyl ether acetate, 0.5% dodecayl alcohol ester, and 0.2% dimethyl silicone oil; Organic antioxidants: ammonium formate, ascorbic acid, formate, PVP, PVA, PMMA; Inorganic antioxidants: stannous oxide, antimony oxide, and graphene in the 10-1000nm range.

[0017] II. Preparation of Glass Powder (Examples G1-G8) Weigh each raw material according to the formula shown in Table 1, mix them evenly, and put them into a platinum crucible. Place the crucible in a muffle furnace and melt it at 1100℃ for 30 minutes. Pour the glass molten block into a cold rolling mill or deionized water and cool it rapidly to below 100℃ to obtain glass slag. Place the glass slag in a ball mill and coarsely grind it for 30 minutes. Then, perform wet grinding and classification to obtain glass powders G1-G8 respectively.

[0018] Table 1. Composition of glass powder (by weight percentage) ; III. Preparation of Conductive Paste (Examples 1-8) Weigh out copper powder, glass powder, organic carrier and additives according to the proportions shown in Table 2. Use a planetary mixer to mix the glass powder, inorganic additives and organic carrier evenly to obtain glass paste. Then mix the glass paste with copper powder and grind it thoroughly with a three-roll mill to obtain the conductive copper paste of Examples 1-8.

[0019] Table 2 Composition of conductive paste (by weight percentage) ; IV. Solar Cell Fabrication and Performance Testing Test method: The photoelectric conversion efficiency (Eta), open circuit voltage (Voc), short circuit current (Isc), and fill factor (FF) of the solar cells were tested using the commercial IV tester "cetisPV-Celltest4-BF" from HalmElektronik GmbH.

[0020] Preparation of pure copper electrode solar cells (samples 1-8): The conductive copper paste of Examples 1-8 was screen printed onto 182*182mm TOPCon monocrystalline silicon wafers. The wafers were then rapidly sintered at a peak sintering temperature of 500-600℃ and a time of 16 seconds from room temperature to peak temperature to obtain solar cells with pure copper electrodes. The performance test results are shown in Table 3.

[0021] Table 3 Performance of Solar Cells Prepared with Pure Copper Paste

[0022] Preparation of Cu+Ag seed layer electrode solar cells (samples 3# and 4#): Step 1: Silver conductive paste is screen-printed onto TOPCon monocrystalline silicon wafers in a specific pattern. The wafers are then rapidly sintered at a peak sintering temperature of 720-760℃ and a time of 16 seconds from room temperature to peak temperature to obtain a semi-finished solar cell with a silver seed layer. Step 2: The conductive copper paste from Examples 3 and 4 is screen-printed onto the semi-finished product to ensure that the copper paste covers the silver seed layer. The product is then rapidly sintered at a peak sintering temperature of 500-600℃ and a heating time of 16 seconds to obtain the target battery cell.

[0023] Comparative sample preparation: Commercially available silver conductive paste was screen-printed onto TOPCon monocrystalline silicon wafers and rapidly sintered at a peak sintering temperature of 720-760℃ and a heating time of 16 seconds to obtain pure silver electrode solar cells.

[0024] The performance comparison results of copper paste + silver seed layer battery and pure silver paste battery are shown in Table 4.

[0025] Table 4 Performance comparison of batteries prepared with copper paste + seed layer and pure silver paste

[0026] As shown in Table 3, the photoelectric conversion efficiency of the pure copper paste solar cell prepared by this invention is between 24.933% and 25.646%, and the fill factor is above 85.03%, proving that copper paste can achieve good conductivity and electrode contact performance under high-temperature sintering conditions in air. As shown in Table 4, the photoelectric conversion efficiency of the solar cell with copper paste + silver seed layer scheme reaches 26.563%-26.586%, which is basically consistent with the efficiency of commercially available pure silver paste solar cells (26.566%), and fully meets the performance requirements for commercial mass production.

[0027] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the invention. For example, the glass powder formulation can be adjusted within the component range defined in the claims according to actual process requirements, the specific types of additives can be selected based on antioxidant effect and cost, and the sintering temperature of the copper paste can be finely adjusted within the range of 500-600℃ according to the type of battery cell. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A conductive copper paste, characterized in that, Based on the total weight of the conductive copper paste, it comprises the following components by weight percentage: 72%-85% copper powder, 2.5%-8% glass powder, 8%-12% organic carrier, and 1%-9% additives; the copper powder is spherical powder with D50: 0.5-5μm [Al]; the glass powder is composed of at least two of PbO, SiO2, ZnO, Al2O3, Bi2O3, B2O3, Li2CO3, and Na2CO3, and is prepared by melting at 1100℃, cooling, grinding, and grading; the organic carrier contains 2 The composition comprises 0.0 wt% saturated polyester resin, 1.0 wt% polyvinyl butyral, 4.8 wt% diethylene glycol butyl ether acetate, 0.5 wt% dodecyl alcohol ester, and 0.2 wt% dimethyl silicone oil; the additives include 1-5 wt% organic antioxidants and 1-10 wt% inorganic antioxidants, wherein the organic antioxidants are selected from at least one of ammonium formate, ascorbic acid, formate, PVP, PVA, and PMMA, and the inorganic antioxidants are at least one of stannous oxide, antimony oxide, and graphene with a wavelength of 10-1000 nm; The molecular weight of saturated polyester resin is 10,000-30,000.

2. The conductive copper paste according to claim 1, characterized in that, The copper powder has a D50 of 1-2 μm.

3. The conductive copper paste according to claim 1, characterized in that, The glass powder is selected from any one of the following formulations G by weight percentage: G1: PbO83%, SiO22.5%, ZnO2%, B2O310%, Na2CO32.5%; G2: PbO83%, SiO22%, ZnO1.5%, B2O311%, Na2CO32.5%; G3: PbO76%, SiO24%, ZnO4.5%, Bi2O32%, B2O310%, Na2CO33.5%; G4: PbO80%, SiO25%, ZnO5.5%, B2O36%, Na2CO33.5%; G5: PbO76%, ZnO7.5%, Bi2O33%, B2O310%, Li2CO31.5%, Na2CO32%; G6: PbO88%, SiO23%, Al2O31.0%, Bi2O32%, B2O34%, Li2CO32%; G7: PbO65%, SiO23.5%, ZnO3.5%, Al2O30.5%, Bi2O320%, B2O34.5%, Li2CO33%; G8: PbO76%, SiO22%, ZnO2%, Bi2O310%, B2O35%, Li2CO35%.

4. The conductive copper paste according to claim 1, characterized in that, The organic antioxidant is at least one of PVP, PVA, and PMMA, and the inorganic antioxidant is stannous oxide or graphene.

5. A method for preparing conductive copper paste, characterized in that, Includes the following steps: S1 Preparation of glass powder: At least two of PbO, SiO2, ZnO, Al2O3, Bi2O3, B2O3, Li2CO3, and Na2CO3 are mixed evenly in a predetermined ratio, placed in a platinum crucible, and melted in a muffle furnace at 1100℃ for 30 min. The glass molten block is poured into a cold rolling mill or deionized water and rapidly cooled to below 100℃ to obtain glass slag. The glass slag is placed in a ball mill for coarse grinding for 30 min, and then wet-ground and classified to obtain the target glass powder. S2 Preparation of conductive paste: Weigh copper powder, glass powder obtained in S1, organic carrier and additives according to weight percentage. Use a planetary mixer to first mix glass powder, inorganic additives and organic carrier to obtain glass paste. Then mix glass paste with copper powder and grind it evenly through a three-roll mill to obtain conductive copper paste. S3 Solar Cell Fabrication: Conductive copper paste is screen-printed onto a 182*182mm TOPCon monocrystalline silicon wafer, and rapidly sintered at a peak sintering temperature of 500-600℃ and a time of 16 seconds from room temperature to peak temperature to obtain a solar cell with pure copper electrodes.

6. The preparation method according to claim 5, characterized in that, The copper powder in step S2 has a D50 of 1-2 μm, the organic antioxidant is at least one of PVP, PVA, and PMMA, and the inorganic antioxidant is stannous oxide or graphene.

7. The preparation method according to claim 5, characterized in that, S3 also includes the preparation of a silver seed layer: First, silver conductive paste is screen-printed onto a 182*182mm TOPCon monocrystalline silicon wafer in a specific pattern, and then sintered at a peak sintering temperature of 720-760℃ and a time of 16 seconds from room temperature to peak temperature to obtain a solar cell semi-finished product; then, the conductive copper paste obtained in S2 is screen-printed onto the semi-finished product and covered with a silver seed layer, and sintered at a peak sintering temperature of 500-600℃ and a heating time of 16 seconds to obtain a solar cell with Cu+Ag seed layer electrodes.

8. The preparation method according to claim 5, characterized in that, The weight percentages of each component in S2 are as follows: copper powder 80%-85%, glass powder 3.5%-5%, organic carrier 8%-11%, and additives 2%-5.5%.

9. The preparation method according to claim 5, characterized in that, The raw material in S1 is a 4N grade chemical reagent, and the screen printing in step S3 is adapted to the fine line printing process.

10. The application of the conductive copper paste according to claims 1-4 in the preparation of silicon-based solar cells.

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