Front silver-aluminum paste for topcon solar cell, preparation method therefor, and use thereof

Abstract

The present invention relates to the field of solar cells. Specifically disclosed are a front silver-aluminum paste for a TOPCon solar cell, a preparation method therefor, and the use thereof. The conductive silver-aluminum paste contains 80-95 wt% of conductive powder, 0.1-7 wt% of glass powder and 1.5-15 wt% of an organic vehicle paste composition, the organic vehicle paste composition comprising a compound resin, a compound dispersant, an organic solvent and an additive. The compound resin and the compound dispersant can effectively solve the problems of low mass production yield and conversion efficiency of cells on narrow-linewidth screen printing plates due to the high solid content and viscosity and the poor ink permeability of conductive silver-aluminum paste.

Description

A front silver-aluminum paste for TOPCon solar cells, and its preparation method and application Technical Field

[0001] The present invention relates to the field of solar cells, and in particular to a thin-line silver-aluminum conductive paste, a front silver-aluminum paste for tunneling oxide passivated contact crystalline silicon solar cells (TOPCon), and a preparation method and application thereof. Background Art

[0002] The front light-receiving surface of the solar cell silicon wafer has a conductive sub-grid electrode formed on it, which reduces the light-receiving area of ​​the silicon wafer and affects its efficiency. Therefore, it is hoped that a finer electrode can be formed on the front light-receiving surface of the silicon wafer to increase the light-receiving area and thus improve the photovoltaic conversion efficiency of the cell. In existing mass production technology, a tendency is to use a screen printing technology with a narrower opening to produce electrodes in large quantities and quickly. The fine-line grid electrode obtained by this technology has a relatively small light-shielding area on the silicon wafer, which can obtain a higher photocurrent and further obtain better photovoltaic conversion efficiency. In addition, the design of the screen with a narrower opening is also in line with the trend of overcoming the demand for cost reduction, and can simultaneously meet the needs of reducing costs and improving efficiency within the industry, achieving an optimal price-performance ratio.

[0003] Compared to the currently mass-produced PERC cell structure, the new generation of TOPCon tunneling oxide passivated contact crystalline silicon solar cells utilizes an ultra-thin tunneling oxide layer and a doped polysilicon layer for backside passivation. The electrodes are in contact only with the polysilicon layer, and carriers conduct through the tunneling effect, avoiding severe metal-semiconductor recombination, effectively improving cell conversion efficiency. The TOPCon front-side conductive paste utilizes two conductive powders: silver and aluminum. By etching the SiNx / AlOx dielectric layer through glass, local channels are opened. Low-melting-point silver and aluminum liquid phases interdiffuse with silicon to form silver-aluminum spikes, which form direct contact with the p+ emitter and the metal grid line. This significantly improves contact resistance and is the most critical material for the overall TOPCon cell conversion efficiency. Compared to traditional PERC conductive pastes using pure silver, these pastes tend to have higher solids content and higher viscosity, which is detrimental to paste storage stability, mass production yield on narrow linewidth screens, and long-term printing performance.

[0004] Therefore, there is an urgent need to provide a silver-aluminum conductive paste that is evenly dispersed, has low viscosity, and is more suitable for printing screens with narrow line diameters and small openings, so as to improve the above-mentioned mass production issues and thereby improve battery conversion efficiency. Summary of the Invention

[0005] The main purpose of the present invention is to provide a silver-aluminum conductive paste for the front side of a crystalline silicon solar cell with a tunneling oxide passivation contact having fine lines and good ink permeability, so as to solve the mass production problem of the conductive paste in the prior art, which has low cell conversion efficiency due to poor mesh permeability.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A silver-aluminum paste for the front side of TOPCon solar cells comprises 80-95 wt% of conductive powder, 0.1-7 wt% of glass powder, and 1.5-15 wt% of an organic vehicle paste composition. The organic vehicle paste composition comprises a compounded resin, a compounded dispersant, an organic solvent, and additives. The compounded resin content in the conductive paste is 0.2-5 wt%, and the compounded dispersant content is 0.01-2 wt%.

[0008] The composite resin comprises at least two of cellulose acetate, cellulose acetate butyrate, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, polyisobutyl acrylate, styrene-acrylate copolymer, acrylonitrile-styrene-acrylate copolymer, hydrogenated styrene-isoprene copolymer, styrene-butadiene-styrene copolymer and styrene-[ethylene-(ethylene-propylene)]-styrene copolymer.

[0009] Preferably, the compounded resin is selected from at least two of cellulose acetate, cellulose acetate butyrate, ethyl cellulose, polybutyl acrylate, styrene-acrylate copolymer, hydrogenated styrene-isoprene copolymer or styrene-butadiene-styrene copolymer.

[0010] First, the compounded resin can more completely coat conductive powders such as silver powder and aluminum powder, which is beneficial to the grinding and dispersion effect in the subsequent slurry process, reduces the proportion of silver flakes, and helps the high-solid content conductive paste formed have good ink flow. The compounded resin has a cohesive effect on the silver-aluminum conductive paste, which can prevent the powder from collapsing or flowing significantly during high-temperature sintering, maintain the height morphology of the grid line, and thus effectively control the thinning ability of the secondary grid. The compounded resin also has an adhesive effect, which can adapt to the different degrees of suede polish on the silicon wafer, avoid the grid line from falling off due to the rapid shrinkage of the organic carrier and the volatilization of the solvent during high-temperature drying and sintering, and further improve the bonding strength between the slurry and the substrate.

[0011] The compound dispersant comprises at least two of TDO, oleic acid, ED120, ED350, ED420, isomeric decanol polyoxyethylene ether, isomeric undecanol polyoxyethylene ether and isomeric tridecanol polyoxyethylene ether.

[0012] Compound dispersants can improve the dispersion of inorganic powders in conductive pastes, balance the properties of the various components in the paste, prevent powder agglomeration, and ultimately achieve the lowest viscosity within the high-solids paste formulation to meet the mass production requirements of screen printing. This is especially true when compared to other resin and dispersant combinations.

[0013] The organic solvent accounts for 1 to 10 wt % of the conductive paste. Preferably, the organic solvent is selected from the group consisting of ethyl cellosolve, butyl cellosolve, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, monobutyl ether acetate, propylene glycol monomethyl ether, diethylene glycol butyl ether acetate, alcohol ester dodecahydrate, tripropylene glycol monomethyl ether, triacetin, triethylene glycol dibenzoate and terpineol.

[0014] The additives include thixotropic agents and plasticizers, accounting for 0.5 to 5 wt % of the conductive paste. Preferably, the additives are selected from one or more of the group consisting of polyvinyl butyral, polyurethane polyamide, polyamide, polydimethylsiloxane, polymethylphenylsiloxane, polyether polysiloxane copolymer, aminosiloxane and fumed silica.

[0015] Furthermore, the conductive powder comprises at least one conductive inorganic powder; preferably, the inorganic powder is silver powder and aluminum powder, the average particle size D50 of the silver powder is 0.1-5 μm, and the average particle size D50 of the aluminum powder is 0.3-8 μm.

[0016] Preferably, the glass powder is a glass powder based on lead oxide-tellurium oxide-bismuth oxide-zinc oxide; the glass powder further contains one or more selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, phosphorus oxide, zinc oxide, silicon dioxide, boron oxide, titanium oxide and nickel oxide; preferably, the particle size (D50) of the glass powder is 1.5 to 2.0 μm.

[0017] Furthermore, the silver-aluminum conductive paste comprises 83-93.5 wt% of conductive powder, 0.8-4.5 wt% of glass frit, 2-8.5 wt% of organic solvent, 1-4.5 wt% of additive, 0.4-3.5 wt% of resin, and 0.05-1.2 wt% of dispersant, wherein the resin is composed of cellulose acetate butyrate, ethyl cellulose, and styrene-acrylate copolymer; preferably, in the composition of the resin, the weight ratio of cellulose acetate butyrate, ethyl cellulose, and styrene-acrylate copolymer is (1-2):(1-2.5):(4-8); wherein the dispersant is TDO and oleic acid; preferably, the weight ratio of TDO and oleic acid is (1-1.5):(1-2);

[0018] Furthermore, the silver-aluminum conductive paste comprises 84.7-92.6 wt% of conductive powder, 1.3-4 wt% of glass powder, 2.7-9 wt% of organic solvent, 2-4 wt% of additives, 0.7-3 wt% of compound resin and 0.05-1.6 wt% of compound dispersant, wherein the resin is composed of cellulose acetate, polybutyl acrylate, and styrene-acrylate copolymer; preferably, in the composition of the resin, the weight ratio of cellulose acetate, polybutyl acrylate, and styrene-acrylate copolymer is (1-1.6):(1-2.3):(3-5.5); wherein the dispersant is ED350 and isomeric decanol polyoxyethylene ether; preferably, in the dispersant, the weight ratio of ED350 and isomeric decanol polyoxyethylene ether is (1-1.35):(1-1.6);

[0019] Furthermore, the silver-aluminum conductive paste comprises 87-94 wt% of conductive powder, 2.5-5 wt% of glass powder, 3.5-9.3 wt% of organic solvent, 2.5-4.2 wt% of additives, 0.45-2.8 wt% of compound resin, and 0.1-1.3 wt% of compound dispersant, wherein the resin is composed of polybutyl acrylate, styrene-acrylate copolymer, or styrene-butadiene-styrene copolymer; preferably, in the composition of the resin, the weight ratio of polybutyl acrylate, styrene-acrylate copolymer, or styrene-butadiene-styrene copolymer is (1-2):(1-3):(2-4); wherein the dispersant is oleic acid and isotridecyl alcohol polyoxyethylene ether; preferably, in the dispersant, the weight ratio of oleic acid and isotridecyl alcohol polyoxyethylene ether is (1-1.4):(1-2.5);

[0020] Furthermore, the silver-aluminum conductive paste contains 85-94.7 wt% of conductive powder, 3.5-6 wt% of glass powder, 2.5-8.6 wt% of organic solvent, 2-4.5 wt% of additives, 0.5-2.9 wt% of compound resin and 0.2-1 wt% of compound dispersant, wherein the resin is composed of polybutyl acrylate, styrene-acrylate copolymer and hydrogenated styrene-isoprene copolymer; preferably, in the composition of the resin, the weight ratio of polybutyl acrylate, styrene-acrylate copolymer and hydrogenated styrene-isoprene copolymer is (1-3.4):(1-2.2):(3-5.5); wherein the dispersant is TDO and isomeric undecyl alcohol polyoxyethylene ether; preferably, in the dispersant, the weight ratio of TDO and isomeric undecyl alcohol polyoxyethylene ether is (1-1.8):(1-2).

[0021] The silver-aluminum conductive paste of the present invention has a wide range of applicability when applied to screen printing. It is applicable to screen sizes of 480 / 500 / 520, wire diameters of 9-11 μm, yarn thicknesses of 12.5-15 μm, film thicknesses of 3.5-7 μm, and screen openings of 11-18 μm. Within this opening range, it can maintain the requirements for fine lines while also taking into account excellent ink flow. According to one aspect of the present invention, a solar cell electrode is provided, prepared from the silver-aluminum conductive paste described above. Preferably, the solar cell electrode has a width of 15-35 μm.

[0022] The beneficial effects achieved by the present invention are: the use of a specific type of resin carrier and dispersant combination in the present invention can form a better match with other components such as conductive powder, and the components as a whole have a better synergistic effect, and will not bring any negative impact on the subsequent electrode production or application under high temperature sintering in solar cells, such as electrode conductivity, electrode aspect ratio and battery conversion efficiency. Furthermore, such a combination of resin and dispersant can effectively reduce the viscosity of the slurry with a high solid content, thereby improving the processing performance of the slurry in the subsequent printing process, such as: improving the ink-passing performance of the slurry, having better ink permeability, thereby promoting lower electrode resistance, avoiding the phenomenon of grid line breakage during electrode production or uneven ink return caused by adhesion to processing devices such as printing scrapers, thereby improving battery conversion efficiency. Most importantly, the above-mentioned conductive paste has a relatively wide printing operation window, which is more suitable for advanced narrow line width opening printing screen operations, obtaining finer line electrodes, reducing the shading of the light-receiving area of ​​the silicon wafer, improving photocurrent generation, and thus obtaining higher battery conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0024] FIG1 is a schematic diagram of a preparation process of the present invention;

[0025] FIG2 is a schematic diagram of a preparation process of the present invention;

[0026] FIG3 is a schematic diagram of a preparation process of the present invention;

[0027] FIG4 is a schematic diagram of a preparation process of the present invention;

[0028] FIG5 is a schematic diagram of a preparation process of the present invention;

[0029] FIG6 is a schematic diagram of a preparation process of the present invention;

[0030] FIG7 is a schematic diagram of a preparation process of the present invention;

[0031] FIG8 is a schematic diagram of a preparation process of the present invention;

[0032] FIG9 is a schematic diagram of a preparation process of the present invention;

[0033] Among them, 10, N-type silicon substrate; 20, P layer; 30, front passivation layer; 40, back passivation layer; 50, back main grid silver electrode (after high-temperature sintering); 60, back auxiliary grid silver electrode (after high-temperature sintering); 70, front main grid silver electrode (after high-temperature sintering); 80, front auxiliary grid silver electrode (after high-temperature sintering). Implementation Method

[0034] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. Example

[0035] An embodiment of a method for manufacturing an N-type silicon-based solar cell is shown below. However, the present invention is not limited to the following embodiment.

[0036] FIG. 1 shows an N-type silicon substrate 10 .

[0037] 2 shows the formation of a reverse conductive P layer 20 through boron thermal diffusion (generally using boron tribromide BBr3 as the boron diffusion source). The crystalline silicon substrate is composed of an N-type silicon substrate 10 and a P layer 20, forming a PN junction.

[0038] An anti-corrosion agent is used to protect the surface of the P layer 20 , and the surrounding and bottom layers of the P layer 20 are removed by etching, leaving only the main surface. Then, an organic solvent is used to remove excess anti-corrosion agent, as shown in FIG3 .

[0039] As shown in FIG4 , a passivation layer 30 is formed on the P layer 20 using Al 2 O 3 and SiN x as passivation layer materials by plasma chemical vapor deposition (PECVD), and a passivation layer 40 is formed on the back side of the N layer 10 using SiN x as passivation layer material.

[0040] As shown in FIG. 5 , the back busbar silver paste 50 is printed onto the passivation layer 40 by screen printing and then dried.

[0041] As shown in FIG. 6 , the back side grid silver paste 60 is printed on the passivation layer 40 by screen printing and then dried.

[0042] As shown in FIG. 7 , a front busbar silver paste 70 is printed onto the passivation layer 30 by screen printing and then dried.

[0043] As shown in Figure 8 , a front-side sub-gate silver-aluminum paste 80 is screen-printed onto the passivation layer 30 and dried. The paste is then sintered in an infrared furnace at a peak temperature ranging from 400°C to 950°C. Depending on the belt speed of the sintering equipment, the total sintering time from entering the furnace to exiting the furnace ranges from 30 seconds to 5 minutes, ensuring that the N-type silicon substrate 10 does not suffer from overheating or warping defects.

[0044] As shown in Figure 9, after high-temperature sintering, the dried back-side silver paste forms a back-side silver main grid electrode 50 and a back-side silver sub-grid 60, while the front side forms a front-side silver main grid electrode 70 and a back-side silver sub-grid 80. High-temperature sintering forms a good ohmic contact between the front silver / aluminum / silicon interface and the back silver / silicon interface, achieving electrical connection.

[0045] The front silver-aluminum conductive silver paste in the present invention can achieve the expected narrow line width of the front silver-aluminum electrode through advanced screen printing screen design. With different screen opening designs, the electrode width after sintering in different embodiments is 17 to 30 μm.

[0046] The present invention takes N-type silicon-based solar cells as an example, but is not limited thereto and may also be applicable to P-type silicon-based solar cells, back-contact solar cells, or other solar cell technologies formed using conductive pastes.

[0047] The present invention also provides a solar cell, comprising an electrode, wherein the electrode is the solar cell electrode as described above.

[0048] Based on the above reasons, the battery of the present invention has a better battery conversion rate.

[0049] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0050] The conductive pastes in the examples and comparative examples were made of the following materials.

[0051] Conductive powder: Spherical silver powder with a particle size (D50) of 1.2-2.1 μm. Aluminum powder with a D50 of 0.3-8 μm. The silver powder is manufactured in Japan using the DOWA 4-8FD brand, while the aluminum powder is manufactured in Japan using the Toyal TFH-A02P brand.

[0052] Glass powder: Glass powder based on lead oxide-tellurium oxide-bismuth oxide-zinc oxide. Particle size (D50) is 1.5-2.0 μm. Brand: BASS T2.

[0053] Resins: including at least two of Eastman™ cellulose acetate butyrate, ethyl cellulose, and hydroxyethyl cellulose; Shanghai Macklin Biochemical Technology Co., Ltd.'s polyethyl acrylate and polybutyl acrylate; Andes' synthetic latex AT-928 styrene-acrylate copolymer; and Taiwan Rubber Corporation's styrene-butadiene-styrene copolymer.

[0054] Dispersants: including TDO from AkzoNobelDuomeen®; oleic acid from Shanghai Yuanji Chemical Co., Ltd. and two types of isomeric undecyl alcohol polyoxyethylene ether and isomeric tridecyl alcohol polyoxyethylene ether provided by BASF.

[0055] The brand of the thixotropic agent is Kusumoto DISPARLON® 6500. The brand of the plasticizer is Dow Corning 200 Fluid 50 cSt.

[0056] The amounts of the above ingredients added are shown in Table 1.

[0057] The conductive paste is prepared by mixing an organic solvent, resin, additives, and dispersant and stirring at 50-60°C with high shear for 1-2 hours. Glass powder, silver powder, and aluminum powder are added to the mixture and the paste composition is repeatedly rolled using a three-roll mill until the fineness of grain (FOG) is 15 / 10 μm or less.

[0058] Performance characterization:

[0059] (1) Viscosity testing

[0060] 13-5 g of slurry was sampled and the slurry viscosity value was measured using a Brookfield DV1 viscometer and a spindle SC-14 at 25°C / 50 rpm / 30 seconds.

[0061] (2) Electrode width and printability test

[0062] The conductive pastes used in the above examples and comparative examples were screen-printed onto the SiN layer of a silicon wafer substrate (182×182 mm). The electrical (electrode printing screen for testing cell conversion efficiency) and printing screen specifications used were: a 500-mesh, 9-μm wire diameter, 18-18.5-μm total thickness, and 13-μm openings (narrow side openings); and a 500-mesh, 9-μm wire diameter, 18-18.5-μm total thickness, and openings of 16, 14, 12, and 10 μm (narrow side openings), respectively. The cells were dried in an infrared drying oven and then sintered in a belt furnace at 920–930°C for 40 seconds. The sintered conductive paste was cooled to form electrodes. The electrode width was measured using an optical microscope and a micro-imaging instrument. The resistance values ​​at different screen openings (16μm, 14μm, 12, 10μm) were directly measured using a resistance tester.

[0063] The ink flow performance (printability test) of the slurry at different screen openings is expressed as resistance value. The higher the resistance, the worse the ink flow ability.

[0064] (3) Battery conversion efficiency test

[0065] The resulting solar cells were placed in a Berger solar cell tester under a single light source to measure efficiency. A xenon arc lamp in the tester simulates sunlight of known intensity and irradiates the cell's light-receiving front surface. The voltage (V) and current (I) were measured using a four-point contact method under a load resistance setting of approximately 400 Ω to determine the cell's voltage-current curve. The cell's conversion efficiency (EFF) was then calculated based on this curve.

[0066] Table 1

[0067]

[0068]

[0069] Table 1

[0070]

[0071]

[0072] Table 1

[0073]

[0074]

[0075] The differences between Examples 1 to 6 are that, while maintaining the same ratios of other raw materials, when comparing additive combinations at 0.55% addition, Examples 3, 4, and 5 all exhibit lower slurry viscosities at 50 rpm and lower resistance values ​​at different line widths. These combinations, using TDO / isotridecyl alcohol polyoxyethylene ether, oleic acid / isoundecanol polyoxyethylene ether, and oleic acid / isotridecyl alcohol polyoxyethylene ether, respectively, were used. These three dispersant combinations were subsequently used to further adjust the ratios of other raw materials.

[0076] The main difference between Examples 7 and 8 and Example 3 is the increase in the amount of silver powder. Accordingly, Example 7 increases the silver powder by 0.25wt%, reduces the additive by 0.15wt% and the solvent by 0.1%; Example 8 increases the silver powder by 0.5wt%, reduces the additive by 0.2wt% and the solvent by 0.3%.

[0077] The main difference between Examples 9 and 10 and Example 4 is the increase in the amount of silver powder. Accordingly, Example 9 increases the silver powder by 0.25wt%, reduces the additive by 0.15wt% and the solvent by 0.1%; Example 10 increases the silver powder by 0.5wt%, reduces the additive by 0.2wt% and the solvent by 0.3%.

[0078] The main difference between Examples 11 and 12 and Example 5 is the increase in the amount of silver powder. Accordingly, Example 11 increases the silver powder by 0.25wt%, reduces the additive by 0.15wt% and the solvent by 0.1%; Example 12 increases the silver powder by 0.5wt%, reduces the additive by 0.2wt% and the solvent by 0.3%.

[0079] The above adjustment of increasing the silver content by 0.25-0.5wt%, using Examples 7 and 8 of TDO / isomeric tridecanol polyoxyethylene ether, obtained higher viscosity and resistivity, but was not reflected in the improvement of efficiency. Using Examples 9 and 10 of oleic acid / isomeric undecanol polyoxyethylene ether, the increase in viscosity was also obtained, which was reflected in a reasonable increase in resistivity, and also an improvement of 0.08-0.09% in efficiency was obtained. Using Examples 11 and 12 of oleic acid / isomeric tridecanol polyoxyethylene ether, it was also reflected in the improvement of viscosity and resistivity, but the efficiency gain was not obvious. The above results can show that oleic acid / isomeric undecanol polyoxyethylene ether can provide the widest printing window, with less viscosity improvement, narrower electrode width and best printability resistance value performance, and can be further matched with the adjustment of organic carrier or inorganic powder to provide efficiency gain, and find the critical value of raw material addition.

[0080] The main difference between Examples 13 and 14 and Example 4 is that the amount of silver powder used is further increased. Accordingly, Example 13 increases silver powder by 0.75wt%, reduces additives by 0.25wt% and solvent by 0.5%; Example 14 increases silver powder by 1wt%, reduces additives by 0.3wt% and solvent by 0.7%. Example 13, which adds 0.75wt% silver powder, shows further efficiency gains compared to Examples 4, 9, and 10, while viscosity and line resistivity remain within controllable ranges. Compared to Example 14, which adds 1wt% silver powder, the overall viscosity and line resistivity exceed the theoretical standards, and there is no efficiency gain, falling within the adjustment range of outliers.

[0081] The main difference between Examples 15 and 16 and Example 10 is the adjustment of the ratio of the resin cellulose acetate butyrate and styrene-butadiene-styrene copolymer. Accordingly, Example 15 reduces 0.15wt% of cellulose acetate butyrate and increases 0.15wt% of styrene-butadiene-styrene copolymer; Example 16 increases 0.15wt% of cellulose acetate butyrate and reduces 0.15wt% of styrene-butadiene-styrene copolymer. Example 15, which reduces the high-polarity resin cellulose acetate butyrate and increases the low-polarity resin styrene-butadiene-styrene copolymer, can reduce the overall slurry viscosity, further improve the efficiency by 0.03% and have a lower line resistivity. On the contrary, Example 16, which increases the high-polarity resin cellulose acetate butyrate and reduces the low-polarity resin styrene-butadiene-styrene copolymer, has a slightly worse printability due to the increased viscosity, the line resistivity increases, and the overall grid line height decreases instead of increases, resulting in no efficiency advantage.

[0082] Examples 17 and 18 further adjust the proportion and ratio of the dispersant composition, taking into account the advantages of increasing the silver content in Example 13 and reducing the high-polarity resin cellulose acetate butyrate in Example 15, while increasing the low-polarity resin styrene-butadiene-styrene copolymer. Accordingly, Example 17 fixes the total amount of dispersant at 0.55wt%, increases the proportion of oleic acid to that of isomeric undecyl alcohol polyoxyethylene ether; Example 18 fixes the ratio of oleic acid to isomeric undecyl alcohol polyoxyethylene ether, and reduces the overall addition amount by 0.25wt%. Both Example 17, which increases the proportion of dispersant oleic acid, and Example 18, which fixes the proportion of dispersant and reduces the addition amount, can provide lower viscosity and lower line resistance than Example 13 at the same silver content. Better ink permeability also further contributes to a slight increase in efficiency, and has better adaptability for mass production.

[0083] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A front silver-aluminum paste for TOPCon solar cells, characterized in that: Containing 80-95wt% of conductive powder, 0.1-7wt% of glass powder and 1.5-15wt% of organic vehicle paste composition; The organic carrier paste composition comprises a compound resin, a compound dispersant, an organic solvent and an additive; the proportions of each component in the front silver-aluminum paste are: 0.2-5wt% of the compound resin, 0.01-2wt% of the compound dispersant, 1-10wt% of the organic solvent, and 0.5-5wt% of the additive; The composite resin comprises at least two of cellulose acetate, cellulose acetate butyrate, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, polyisobutyl acrylate, styrene-acrylate copolymer, acrylonitrile-styrene-acrylate copolymer, hydrogenated styrene-isoprene copolymer, styrene-butadiene-styrene copolymer and styrene-[ethylene-(ethylene-propylene)]-styrene copolymer; The compound dispersant comprises at least two of TDO, oleic acid, ED120, ED350, ED420, isomeric decanol polyoxyethylene ether, isomeric undecanol polyoxyethylene ether and isomeric tridecanol polyoxyethylene ether.

2. The front silver-aluminum paste for TOPCon solar cells according to claim 1, characterized in that: The compounded resin is selected from at least two of cellulose acetate, cellulose acetate butyrate, ethyl cellulose, polybutyl acrylate, styrene-acrylate copolymer, hydrogenated styrene-isoprene copolymer or styrene-butadiene-styrene copolymer.

3. The front silver-aluminum paste for TOPCon solar cells according to claim 1, characterized in that: The organic solvent is selected from one or more of the group consisting of ethyl cellosolve, butyl cellosolve, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, monobutyl ether acetate, propylene glycol monomethyl ether, diethylene glycol butyl ether acetate, alcohol ester dodecahydrate, tripropylene glycol monomethyl ether, triacetin, triethylene glycol dibenzoate and terpineol.

4. The front silver-aluminum paste for TOPCon solar cells according to claim 1, characterized in that: The additive is one or more selected from the group consisting of polyvinyl butyral, polyurethane polyamide, polyamide, polydimethylsiloxane, polymethylphenylsiloxane, polyether polysiloxane copolymer, aminosiloxane and fumed silica.

5. The front silver-aluminum paste for TOPCon solar cells according to claim 1, characterized in that: The conductive powder is composed of silver powder and aluminum powder. The average particle size D50 of the silver powder is 0.1-5 μm, and the average particle size D50 of the aluminum powder is 0.3-8 μm.

6. The front silver-aluminum paste for TOPCon solar cells according to claim 1, characterized in that: The glass powder is a glass powder based on lead oxide-tellurium oxide-bismuth oxide-zinc oxide, and also contains one or more selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, magnesium oxide, barium oxide, phosphorus oxide, silicon dioxide, boron oxide, titanium oxide and nickel oxide. The particle size D50 of the glass powder is 1.5 to 2.0 μm.

7. The front silver-aluminum paste for TOPCon solar cells according to claim 1, characterized in that: The invention comprises 83-93.5wt% of conductive powder, 0.8-4.5wt% of glass powder, 2-8.5wt% of organic solvent, 1-4.5wt% of additive, 0.4-3.5wt% of compound resin and 0.05-1.2wt% of compound dispersant; wherein the compound resin is composed of cellulose acetate butyrate, ethyl cellulose and styrene-acrylate copolymer; and the weight ratio of cellulose acetate butyrate, ethyl cellulose and styrene-acrylate copolymer is 1-2:1-2.5:4-8, and the compound dispersant is TDO and oleic acid; and the weight ratio of TDO and oleic acid is 1-1.5:1-2; Or the front silver aluminum paste for TOPCon solar cells comprises 84.7-92.6wt% of conductive powder, 1.3-4wt% of glass powder, 2.7-9wt% of organic solvent, 2-4wt% of additives, 0.7-3wt% of compound resin and 0.05-1.6wt% of compound dispersant; the compound resin is composed of cellulose acetate, polybutyl acrylate and styrene-acrylate copolymer; preferably, the weight ratio of cellulose acetate, polybutyl acrylate and styrene-acrylate copolymer is 1-1.6:1-2.3:3-5.5; the compound dispersant is ED350 and isomeric decanol polyoxyethylene ether, and the weight ratio of ED350 and isomeric decanol polyoxyethylene ether is 1-1.35:1-1.6; Or the front silver aluminum paste for TOPCon solar cells comprises 87-94wt% of conductive powder, 2.5-5wt% of glass powder, 3.5-9.3wt% of organic solvent, 2.5-4.2wt% of additives, 0.45-2.8wt% of compound resin and 0.1-1.3wt% of compound dispersant; the compound resin is composed of polybutyl acrylate, styrene-acrylate copolymer or styrene-butadiene-styrene copolymer; and the weight ratio of polybutyl acrylate, styrene-acrylate copolymer or styrene-butadiene-styrene copolymer is 1-2:1-3:2-4; the compound dispersant is oleic acid and isotridecyl alcohol polyoxyethylene ether; and the weight ratio of oleic acid to isotridecyl alcohol polyoxyethylene ether is 1-1.4:1-2.5; Or the front silver-aluminum paste for TOPCon solar cells comprises 85-94.7wt% of conductive powder, 3.5-6wt% of glass powder, 2.5-8.6wt% of organic solvent, 2-4.5wt% of additives, 0.5-2.9wt% of compound resin and 0.2-1wt% of compound dispersant; the composition of the compound resin is polybutyl acrylate, styrene-acrylate copolymer and hydrogenated styrene-isoprene copolymer; and the weight ratio of polybutyl acrylate, styrene-acrylate copolymer and hydrogenated styrene-isoprene copolymer is 1-3.4:1-2.2:3-5.5; the dispersant is TDO and isomeric undecyl alcohol polyoxyethylene ether; and the weight ratio of TDO and isomeric undecyl alcohol polyoxyethylene ether is 1-1.8:1-2.

8. The method for preparing the front silver-aluminum paste for TOPCon solar cells according to claim 1, characterized in that: The organic solvent, compound resin, additive and compound dispersant are mixed, and stirred at 50-60°C with high shear force for 1-2 hours; glass powder, silver powder and aluminum powder are added to the above mixture, and the paste composition is repeatedly rolled with a three-roll mill to grind to a fineness (FOG) of 15 / 10 μm or less.

9. Use of the front silver-aluminum paste for TOPCon solar cells according to any one of claims 1 to 7 in the preparation of solar cells.

10. A solar cell electrode, characterized in that: The solar cell electrode is prepared from the front silver-aluminum paste for TOPCon solar cells according to any one of claims 1 to 7, wherein the width of the solar cell electrode is 15 to 35 μm.

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