Low temperature conductive paste and its use

Abstract

The application discloses a low-temperature conductive paste and application thereof. The low-temperature conductive paste comprises silver-coated copper powder 68-88%, spherical silver powder 2-20%, organic binder 2-5%, auxiliary agent 0.5-2.5% and solvent 2-6%, and the total silver content is 6-33%; the silver-coated copper powder comprises a copper core and a silver layer coated on the outer surface of the copper core, and the ratio of the grain size of the copper core to the average particle size D50 is 0.015-0.4. The copper core grain boundary of the silver-coated copper powder is moderate, the silver layer is continuous and dense, and the silver-coated copper powder has good sintering activity and conductivity during low-temperature solidification. The low-temperature conductive paste is printed on a heterojunction cell sheet, and conductive grid lines are formed through low-temperature solidification, so that the photoelectric conversion efficiency is 0.03-0.1% higher than that of traditional silver-coated copper paste, long-term reliability is excellent, and the low-temperature conductive paste is suitable for low-silver-content photovoltaic conductive paste.

Description

Technical Field

[0001] This invention belongs to the field of conductive paste technology for photovoltaic cells, specifically relating to a low-temperature conductive paste and its application. Background Technology

[0002] With the photovoltaic industry's increasing demand for cost reduction and efficiency improvement, low-temperature conductive pastes are evolving from pure silver paste to silver-coated copper paste. Silver-coated copper powder, by coating a silver layer on the surface of copper powder, aims to reduce material costs while maintaining good conductivity.

[0003] However, the copper powder substrate used in existing silver-coated copper powders has significant defects: physically atomized copper powder has a rough surface, oxide layer, and depressions, resulting in a loose silver coating and easy copper leakage; while conventional chemically reduced polycrystalline copper powder has a large number of large-angle grain boundaries and crystal defects. These defects lead to a common problem: when these silver-coated copper powders are applied to conductive pastes with low silver content (e.g., total silver content less than 30%), the conductivity of the paste drops sharply. Fundamentally, the grain structure of the copper powder is key—excessively fine grains and too many grain boundaries will exacerbate electron scattering and cause local galvanic cell corrosion during silver plating, while coarse grains and too few grain boundaries (high crystallinity) lack sufficient atomic diffusion paths during low-temperature curing (≤250℃), making it difficult to form an effective sintering neck.

[0004] Therefore, how to balance the bulk resistance and low-temperature sintering activity of copper powder by controlling the grain structure of copper powder under low silver content conditions, so as to ensure the conductivity and battery efficiency of silver-coated copper paste, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a silver-coated copper powder for photovoltaic conductive paste, a low-temperature conductive paste, and its application, so as to solve the problem of poor conductivity of existing silver-coated copper powder at low silver content.

[0006] In a first aspect, the present invention provides a low-temperature conductive paste, the specific technical solution of which is as follows: A low-temperature conductive paste, based on 100% of its total mass, comprises the following components: Silver-plated copper powder: 68%–88%; Spherical silver powder 2%–20%; Organic adhesives 2%–5%; Additives: 0.5%–2.5%; Solvent 2%–6%; The silver-coated copper powder includes a copper core and a silver layer covering the outer surface of the copper core. The ratio of the grain size of the copper core to the average grain size D50 is 0.015~0.4.

[0007] This invention, through extensive experimentation, reveals that the performance of silver-coated copper powder in low-temperature conductive pastes does not simply vary with silver content or copper powder particle size, but is strongly correlated with the grain boundary density within the copper core (characterized by the ratio of "grain size / average grain size"). This ratio reflects the number of grain boundaries per unit grain size. If the ratio is too small (<0.015), it means that the grains are too fine and there are too many grain boundaries. The enhanced electron scattering leads to an increase in the resistance of the copper core. Furthermore, during silver plating, silver ions are prone to rapid penetration along the grain boundaries, causing localized corrosion and making it impossible to form a continuous and dense silver layer.

[0008] If the ratio is too high (>0.4), it means that the grains are coarse and the grain boundaries are scarce, and the copper core is close to a single crystal state. Although the bulk resistivity is low, when solidifying at low temperature (≤250℃), the diffusion path of atoms along the grain boundaries is severely insufficient, and it is difficult for particles to form a strong conductive channel through sintering, resulting in increased contact resistance.

[0009] This invention creatively controls the ratio of the copper core's grain size to its average grain size D50 within a suitable range of 0.015 to 0.4. Within this range, the copper core possesses an appropriate number of grain boundaries, providing sufficient atomic diffusion channels to ensure good sintering activity during low-temperature curing; while avoiding the high bulk resistivity caused by excessive grain boundaries. Combined with the graded filling of spherical silver powder, a low-resistance, highly dense conductive network can be constructed after low-temperature curing.

[0010] Furthermore, the ratio of the grain size to the average grain size D50 of the copper core is <0.1, resulting in better sintering activity and lower contact resistance during low-temperature curing.

[0011] Furthermore, the average particle size D50 of the copper core is 2–6 μm. This particle size range matches the existing screen printing process window, which is beneficial for balancing printing resolution and paste rheological properties.

[0012] Furthermore, the silver layer comprises 3% to 15% of the total mass of the silver-coated copper powder. This range of silver content, combined with the appropriate grain size of the copper core, facilitates the formation of a continuous and dense silver shell, effectively preventing copper oxidation.

[0013] Furthermore, the specific surface area of ​​the silver-coated copper powder is 0.25–0.55 m². 2 / g.

[0014] Furthermore, the spherical silver powder has an average particle size D50 of 0.2–1 μm and a specific surface area of ​​1.5–2.9 m². 2 / g.

[0015] Furthermore, the total silver content of the low-temperature conductive paste is 6% to 33%.

[0016] Furthermore, the organic adhesive is selected from any one or a combination of at least two of the following: ethyl cellulose with an average molecular weight of 10,000 to 300,000; polyurethane prepolymer with an average molecular weight of 800 to 6,000; epoxy resin with an epoxy equivalent of 156 to 180; EVA resin with an average molecular weight of 50,000 to 300,000 and a vinyl acetate content of 30% to 46%; and polyester resin with an average molecular weight of 10,000 to 60,000.

[0017] Secondly, this invention provides an application of a low-temperature conductive paste in crystalline silicon solar cells. The low-temperature conductive paste is printed onto a crystalline silicon solar cell and cured by heating to form conductive grid lines. Crystalline silicon solar cells include heterojunction (HJT) cells and tunnel oxide passivated contact (TOPCon) cells, etc. Among them, the transparent conductive oxide (TCO) layer of HJT cells has stringent requirements for the low-temperature curing conditions (typically ≤250℃) and contact performance of the paste; although TOPCon cells can use high-temperature sintering processes, good low-temperature sintering activity is also required when using low-temperature overprinting processes. The silver-coated copper powder in the paste of this invention has a copper core grain size to average particle size D50 ratio controlled at 0.015–0.4, possessing a moderate grain boundary density. During low-temperature curing, it can form an effective sintering neck (avoiding poor sintering caused by high crystallinity) and maintain a low bulk resistivity (avoiding scattering caused by excessive grain boundaries). Meanwhile, the dense silver layer coating the copper core, combined with the synergistic effect of spherical silver powder filling, enables the construction of a continuous conductive network even with a total silver content as low as 6%–33%. Experiments show that this paste, when printed onto HJT solar cells or used as an overprinting paste for TOPCon cells, achieves excellent conductivity and photoelectric conversion efficiency.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) By controlling the ratio of the grain size of the copper core to the average grain size D50 to 0.015 to 0.4, the present invention avoids the problem of poor sintering when high crystallinity is solidified at low temperature, and at the same time reduces the resistance increase caused by excessive grain boundaries, so that good conductivity can still be maintained when the total silver content is as low as 6% to 33%. (2) In this invention, the copper core has few surface defects and moderate grain boundaries. During silver plating, silver atoms are uniformly nucleated and epitaxially grown to form a continuous and dense silver layer, which effectively prevents the copper core from oxidizing and improves the long-term reliability of the paste. (3) When the low-temperature conductive paste of the silver-coated copper powder of the present invention is used in heterojunction cells, the photoelectric conversion efficiency can be improved by 0.03% to 0.1% compared with the traditional silver-coated copper paste. Attached Figure Description

[0019] Figure 1A This is a transmission electron microscope (TEM) image of the copper core A of the present invention; Figure 1BThis is the electron diffraction pattern of copper core A in this invention; Figure 2A For comparison, a transmission electron microscope (TEM) image of copper core I used in Example 1; Figure 2B The electron diffraction pattern of copper core I used in Comparative Example 1; Figure 3 This is a scanning electron microscope (SEM) image of the grid line cross-section after the low-temperature conductive paste in Example 10 was printed onto a heterojunction solar cell and cured. Figure 4 The image shows a scanning electron microscope (SEM) image of the grid line cross-section after the low-temperature conductive paste described in Example 13 was printed onto a heterojunction solar cell and cured. Figure 5 This is a scanning electron microscope (SEM) image of the silver-coated copper powder used in the low-temperature conductive paste described in Example 14; Figure 6 This is a scanning electron microscope (SEM) image of the silver-coated copper powder used in the low-temperature conductive paste described in Example 14; Figure 7 This is a scanning electron microscope (SEM) image of the silver-coated copper powder (Ag@Cu-A) in Example 1 after heat treatment in air at 300°C for 30 minutes. Figure 8 The image is a scanning electron microscope (SEM) image of the silver-coated copper powder (Ag@Cu-I) in Comparative Example 5 after heat treatment in air at 300°C for 30 minutes. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] [Testing Method] 1. Determination of average particle size D50 The volume average particle size (D50) of silver-coated copper powder or copper powder was determined using a laser particle size analyzer (Malvern Mastersizer 3000). Simultaneously, the particle morphology was observed using a scanning electron microscope (SEM, JEOL JSM-7100F), and the particle size of more than 300 primary particles was statistically analyzed. The average value was taken as the mean particle size, which was basically consistent with the D50 results.

[0022] 2. Grain size determination Copper powder was tested using an X-ray diffractometer (PANalytical X'pert PRO), with Cu Kα rays and a scanning range of 30°~90°. Based on the (111) diffraction peak of copper, the grain size of the copper core was calculated using the Scherrer formula: D=Kλ / (βcosθ), where K=0.89, λ=0.15406nm, and β is the full width at half maximum (FWHM) in radians.

[0023] 3. Calculation of the grain size / average grain size ratio Divide the grain size (nm) calculated by XRD by the average grain size (μm) statistically obtained by SEM, and convert it to the same unit to obtain a dimensionless ratio.

[0024] 4. Determination of specific surface area The specific surface area of ​​the powder was determined using the nitrogen adsorption BET method (Micromeritics TriStar II 3020).

[0025] 5. Determination of silver content The mass percentage of silver in silver-coated copper powder was determined using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0026] 6. Powder resistivity test The powder was pressed into discs under a pressure of 10 MPa, and the room temperature resistivity was tested using the four-probe method. High temperature resistivity test: The discs were heated in air at 200℃, 250℃, and 300℃ for 30 minutes respectively, and the resistivity was measured after cooling.

[0027] 7. Slurry resistivity test The paste was screen-printed onto a glass substrate and cured at 200°C for 30 minutes to form lines 10cm long, 1mm wide, and approximately 10μm thick. The line resistance was tested using the four-probe method, and the resistivity was calculated based on the line width and thickness.

[0028] 8. Battery efficiency test The paste was printed onto the corresponding solar cells using MWHJT screen printing equipment or TOPCon printing equipment, and then cured at 200℃ for 30 minutes to form grid lines. The photoelectric conversion efficiency was tested using a solar simulator (Halm) under standard test conditions (AM1.5, 1000W / m², 25℃).

[0029] 9. Adhesion Test After the printed and cured battery cells are immersed in 85°C deionized water for 3 hours, they are removed, dried, and then 3M tape is used to stick to the surface of the grid lines. The tape is then quickly peeled off, and the grid lines are observed to see if they have fallen off.

[0030] [Obtaining Copper Cores] The present invention selects polycrystalline copper powder with few grain boundaries in the range of 0.015 to 0.4, which can be obtained through commercial channels or made by referring to the following methods.

[0031] The specifications of the copper core used in each embodiment / comparative example are shown in the table below.

[0032] Table 1 - Copper Core Specifications

[0033] in, Copper core A can be obtained by self-making, and the specific steps are as follows: (1) Preparation of copper salt solution: Weigh 160g of anhydrous copper sulfate, add 150mL of ammonia water, dissolve in 600mL of deionized water, stir in a 60℃ water bath for 1 hour to obtain a blue transparent solution.

[0034] (2) Preparation of reducing agent solution: Weigh 125g sodium hypophosphite (reducing agent), 150mL ammonia water, 300g cyclodextrin and 15g ammonium benzoate, dissolve in 2400mL deionized water, stir in a 60℃ water bath for 1 hour to obtain a colorless and transparent solution.

[0035] (3) Reduction reaction: The above copper salt solution and reducing agent solution were mixed in a reaction vessel, and the reaction temperature was controlled at 95℃. The mixture was stirred for 1.5 hours. During the reaction, the solution was observed to gradually turn brownish-red, and copper powder precipitate was formed.

[0036] (4) Post-processing: After the reaction is complete, allow the precipitate to stand and discard the supernatant. Add deionized water, stir and allow to stand, and repeat washing 6 times. Then add anhydrous ethanol, stir and allow to stand, and repeat washing 2 times. Place the obtained copper powder in a vacuum oven at 55℃ and dry for 12 hours. After slight crushing, grinding and sieving, pure polycrystalline copper powder with few grain boundaries is obtained, which is denoted as copper core A.

[0037] The specific specifications of copper core A, as tested, are shown in Table 1. TEM and electron diffraction patterns (e.g.) Figure 1A , Figure 1B The regular dot pattern shown indicates that it has few grain boundaries and good crystallinity.

[0038] All copper core BH were obtained through commercial channels. Tests showed that the ratio of their grain size to average grain size was in the range of 0.015 to 0.4.

[0039] Copper core I was prepared using a conventional chemical reduction method: 160 g of anhydrous copper sulfate was weighed and dissolved in 800 mL of deionized water. An appropriate amount of polyvinylpyrrolidone was added, and while stirring, 20% sodium hydroxide solution was added dropwise to adjust the pH to 11. Then, 10% glucose solution was added dropwise, and the reaction was carried out at 90°C for 2 hours. Post-treatment was the same as in Preparation Example 1, yielding conventional polycrystalline copper powder I. TEM showed that it contained a large number of grain boundaries and dislocations (such as…). Figure 2A , Figure 2B (As shown).

[0040] Copper core J is commercially available gas-atomized copper powder (purity ≥99.5%), which was sieved and classified. The fraction with D50 = 4.0 μm was selected and denoted as copper core J. Its surface is rough, with an oxide layer and depressions, and its specific surface area is 0.58 m². 2 / g. Because the copper powder produced by the aerosol method has very fine grains and many defects, the XRD peaks are severely broadened, making it impossible to accurately calculate the grain size. Therefore, the ratio of grain size to average particle size D50 is not listed in Table 1.

[0041] [Preparation of silver-coated copper powder] Examples 1-8 and Comparative Examples 1-4 all used the displacement silver plating method to coat the surface of copper powder with a silver layer. The specific steps are as follows: Add 500 mL of deionized water to the reaction vessel. Calculate the required silver salt (silver sulfate) based on the target silver content, and add an appropriate amount of ammonia (to make Ag...). + A silver ammonia solution was obtained by mixing 3.5 g of EDTA-2Na with NH3 in a molar ratio of 1:2 to 1:4 and stirring for 30 minutes. 100 g of copper powder was dispersed in 200 mL of deionized water, and the silver ammonia solution was added dropwise to the copper powder dispersion with stirring over approximately 1 hour. After the addition was complete, the reaction continued for another hour. The mixture was allowed to settle, the supernatant was discarded, and the precipitate was washed twice with deionized water and then twice with anhydrous ethanol. Finally, it was dried in a 50°C oven for 6 hours to obtain silver-coated copper powder.

[0042] The only differences between the various embodiments / comparative examples are the type of copper core used and the target silver content (amount of silver salt used); all other process parameters are exactly the same. By adjusting the amount of silver salt used, silver-coated copper powder with different silver contents can be prepared.

[0043] The specifications of the copper core used in each embodiment / comparative example are shown in Table 1 (Copper Core Specification Table), and the differences in raw materials and process parameters are summarized in Table 2.

[0044] Table 2 Raw material and process parameters for the examples and comparative examples

[0045] Note: The amount of silver salt used is calculated based on 100 g of copper powder, and the actual amount should be adjusted proportionally.

[0046] The specifications of the silver-coated copper powder prepared by the above method are summarized in Table 3 after testing.

[0047] Table 3 - Performance Parameters of Copper Powder in Examples / Comparative Examples

[0048] [Preparation of Low-Temperature Conductive Paste] According to the formula in Table 4, the organic binder, solvent and additives are premixed evenly, then spherical silver powder and silver-coated copper powder are added, dispersed evenly using a homogenizer, and then ground 3 to 5 times with a three-roll mill until the fineness is ≤10μm to obtain a low-temperature conductive paste.

[0049] The organic binder used in all embodiments and comparative examples was a mixture of polyurethane prepolymer (weight-average molecular weight approximately 2000), epoxy resin (epoxy equivalent 165), and polyester resin (weight-average molecular weight approximately 30000) in a mass ratio of 1:1:0.5. The solvent was diethylene glycol butyl ether acetate. Additives included boronamine curing agents and hydrogenated castor oil in a mass ratio of 1:1. The average particle size D50 of the spherical silver powder was 0.4 μm, and the specific surface area was 2.3 m² / g.

[0050] The types, amounts, and total silver content of the silver-coated copper powder used in each embodiment / comparative example are detailed in the table below.

[0051] Table 4 - Slurry formulations (mass percentage) for each example and control example

[0052] Note 1: In Example 14, Ag@Cu-E2 (10% silver) was used at 10%, and Ag@Cu-E1 (3% silver) was used at 76.5%, for a total of 86.5% silver-coated copper powder.

[0053] Note 2: The Ag@Cu-C used in Example 15 was silver-coated copper powder that had been stored for one year (from the same batch as in Example 12, stored at room temperature and sealed for 12 months); the Ag@Cu-J1 used in Comparative Example 8 was silver-coated copper powder that had been stored for one year using aerosol method (from the same batch as in Comparative Example 6, stored under the same conditions for 12 months).

[0054] [Performance Test Results] 1. Powder properties High-temperature resistivity tests were performed on Ag@Cu-A from Example 1 and Control Example 5 (i.e., Ag@Cu-I, conventional polycrystalline 8% silver), and the results are shown in Table 5.

[0055] Table 5 - Powder resistivity as a function of temperature (unit: μΩ·cm)

[0056] As shown in Table 5: The resistivity of Ag@Cu-A remained stable from room temperature to 250 °C (27.55→31.16 μΩ·cm), and although it increased at 300 °C, it was still much lower than that of the control example. In contrast, the resistivity of control example 5 increased sharply to 116.29 μΩ·cm at 250 °C and reached as high as 1230.65 μΩ·cm at 300 °C. SEM images after heat treatment at 300 °C for 30 minutes show that the Ag@Cu-A silver layer remained continuous and dense (see reference). Figure 7 Ag@Cu-I silver layer cracked, copper core severely oxidized (see reference) Figure 8 The values ​​are consistent with the resistivity data. This indicates that the silver layer of the silver-coated copper powder within the ratio range of this invention is dense and exhibits excellent high-temperature oxidation resistance.

[0057] 2. Slurry properties HJT cell printing and TOPCon cell overprinting tests were conducted on each slurry example (Examples 10-18) and control examples (Control Examples 5-8). The test results are shown in Table 6. In the HJT cell printing process, the slurry is printed onto the cell. In the TOPCon overprinting process, a silver seed layer (wet weight approximately 10 mg) is first formed on the cell substrate, and then the slurry is overprinted onto the seed layer.

[0058] Table 6 - Test Results of Slurry and Battery Performance

[0059] Note: In the TOPCon test, the wet weight of the seed layer was 10 mg. TOPCon was not measured in Example 14 and Control Examples 5 and 8.

[0060] Figure 3 The SEM image of the grid line cross-section in Example 10 shows that the silver-coated copper particles form a dense conductive network after curing, and the particles are well sintered. Figure 4 The cross-section of the gate line in Example 13 shows that a higher silver content results in a denser conductive network, corresponding to lower resistivity and higher efficiency. For example... Figure 5 , Figure 6 As shown, the silver-coated copper powder used in Example 14 has a regular morphology and a dense silver layer.

[0061] As shown in Table 6: HJT battery light conversion efficiency: Under similar wet weight, the example battery has better light conversion efficiency. Example 14 still achieves an efficiency of 25.22% with only 8.4% total silver, with an efficiency loss of only about 0.1%, achieving extreme cost reduction.

[0062] Resistivity: The resistivity of the slurries in the examples was significantly lower than that of the conventional polycrystalline copper-based and aerosol slurries in the control examples. The resistivity of Examples 12-13 was as low as 5.5 μΩ·cm and 5.2 μΩ·cm, respectively.

[0063] Long-term stability: The efficiency of Example 15 (Ag@Cu-C stored for one year) was almost the same as that of Example 12, and the resistivity was the same; the efficiency of Control Example 8 (aerosol method stored for one year) decreased from 25.32% to 25.24%, and the resistivity increased from 7.2 to 7.8 μΩ·cm, indicating that the silver-coated copper powder of the present invention has excellent oxidation resistance due to the dense silver layer, and its performance remains stable after long-term storage.

[0064] TOPCon overprinting: The TOPCon efficiency of Examples 10-14 and 16-18 is higher than that of Control Examples 6 and 7, and the resistivity is lower. Figure 3 , Figure 4 The dense grid structure shown is also applicable to the TOPCon overprinting process.

[0065] Adhesion: After boiling in water at 85°C for 3 hours, all samples showed no detachment when tested with 3M tape, indicating that the slurry of this invention has good adhesion to the battery cells and seed layer.

[0066] The above embodiments and comparative examples demonstrate that the silver-coated copper powder of the present invention, by controlling the ratio of the copper core grain size to the average particle size D50 to be 0.015~0.4, combined with a particle size of 2~6 μm, a silver layer content of 3%~15%, and a specific surface area of ​​0.25~0.55 m² / g, exhibits excellent conductivity, oxidation resistance, and printability in low-silver-content pastes (total silver 6%~33%). Low-temperature conductive pastes prepared using this silver-coated copper powder, when used in HJT battery printing or TOPCon battery overprinting processes, can achieve photoelectric conversion efficiency 0.03%~0.1% higher than that of traditional silver-coated copper pastes, and exhibit excellent long-term reliability.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-temperature conductive paste, characterized in that, Based on 100% of the total mass of the low-temperature conductive paste, it includes the following components: Silver-plated copper powder: 68%–88%; Spherical silver powder 2%–20%; Organic adhesives 2%–5%; Additives: 0.5%–2.5%; Solvent 2%–6%; The silver-coated copper powder includes a copper core and a silver layer covering the outer surface of the copper core. The ratio of the grain size of the copper core to the average grain size D50 is 0.015~0.

4.

2. The low-temperature conductive paste according to claim 1, characterized in that: The ratio of the grain size to the average grain size D50 of the copper core is <0.

1.

3. The low-temperature conductive paste according to claim 1, characterized in that: The average particle size D50 of the copper core is 2–6 μm.

4. The low-temperature conductive paste according to claim 1, characterized in that: The silver layer accounts for 3% to 15% of the total mass of the silver-coated copper powder.

5. The low-temperature conductive paste according to claim 1, characterized in that: The specific surface area of ​​the silver-coated copper powder is 0.25–0.55 m². 2 / g.

6. The low-temperature conductive paste according to any one of claims 1-5, characterized in that: The spherical silver powder has an average particle size D50 of 0.2–1 μm and a specific surface area of ​​1.5–2.9 m². 2 / g.

7. The low-temperature conductive paste according to claim 6, characterized in that: The total silver content of the low-temperature conductive paste is 6% to 33%.

8. The low-temperature conductive paste according to claim 6, characterized in that: The organic adhesive is selected from any one or a combination of at least two of the following: ethyl cellulose with an average molecular weight of 10,000 to 300,000; polyurethane prepolymer with an average molecular weight of 800 to 6,000; epoxy resin with an epoxy equivalent of 156 to 180; EVA resin with an average molecular weight of 50,000 to 300,000 and a vinyl acetate content of 30% to 46%; and polyester resin with an average molecular weight of 10,000 to 60,000.

9. The application of the low-temperature conductive paste according to any one of claims 1-8 in crystalline silicon solar cells, characterized in that: The low-temperature conductive paste is printed onto a crystalline silicon solar cell and then cured by heating to form conductive grid lines.

Images