An organic vehicle for conductive silver paste, its preparation method and application

Abstract

The application relates to an organic carrier for conductive silver paste, a preparation method and application thereof, and belongs to the technical field of crystalline silicon solar energy. The organic carrier comprises the following components in percentage by weight: 0.1-6.0 wt% of an elastic resin, 0.5-20.0 wt% of a thickening agent, 70.0-95.0 wt% of an organic solvent and 0.05-5.0 wt% of a first additive; wherein the elastic resin is a polystyrene-polyolefin block copolymer. The polystyrene-polyolefin block copolymer is used in the organic carrier to replace a traditional polyamide wax thixotropic agent, effectively solves the printing durability problem of the paste, can maintain stable photoelectric conversion efficiency of a solar cell piece, and does not need to be cleaned and wiped due to screen blockage during the printing process, thereby avoiding the trouble of shutdown. Meanwhile, the grid line has a high aspect ratio, thereby improving the photoelectric conversion efficiency of the solar cell.

Description

Technical Field

[0001] This application relates to the field of crystalline silicon solar energy technology, and in particular to an organic carrier for conductive silver paste, its preparation method, and its application. Background Technology

[0002] Among numerous renewable energy technologies, photovoltaic (PV) power generation is undoubtedly one of the most promising. Crystalline silicon solar cells, in particular, have seen the fastest development in recent years, with significantly higher levels of research and development investment and industrialization compared to other types of PV cells. Clearly, crystalline silicon solar cells have become the mainstream technology in PV power generation.

[0003] A photovoltaic (PV) cell is a device that converts light energy into electrical energy. The structure of a PV cell uses silicon as a substrate, with one side being a P-type semiconductor and the other an N-type semiconductor. At the interface between these two semiconductors, a semiconductor PN junction is formed due to the diffusion of electrons and holes. When sunlight shines on the PV cell, electron-hole pairs are generated within the cell. Due to the effect of the semiconductor PN junction, these pairs separate; electrons flow to the N-type semiconductor region, while holes move in the opposite direction to the P-type semiconductor region. This results in the N-region becoming negatively charged and the P-region becoming positively charged, creating a potential difference between the two regions. When a circuit is connected, an electric current is generated.

[0004] Since semiconductors are based on silicon, current cannot be directly conducted through electrical wires. Therefore, a metallization process is required at both ends of the P-type and N-type semiconductors to reduce resistance and allow the current generated after illumination to flow through the metal wires into the electronic device. The metallization process involves coating or printing metal paste onto the corresponding locations as needed, and then sintering the silicon and metal together at high temperature.

[0005] In the manufacturing process of crystalline silicon solar cells, silver paste is typically chosen as the metallizing material for silicon. Currently, most manufacturers use screen printing to apply the silver paste onto the silicon. Compared to other methods of coating silver paste onto photovoltaic silicon wafers to form grid lines, screen printing offers advantages such as faster production speed and lower cost. Therefore, the screen printing characteristics of silver paste have always been a key focus for product improvement. In recent years, the market's requirements for the photoelectric conversion efficiency of solar cells have been increasing. As a key material for screen printing, the aspect ratio of the grid lines after printing directly affects the cell efficiency, and the requirements are becoming increasingly stringent. In addition to the requirements for the aspect ratio of the silver electrode cross-section, printing durability has also become a requirement in recent years. After prolonged and repeated printing on the screen, the grid lines must remain unbroken, and the line shape and cross-sectional aspect ratio must not change. Traditional thixotropic agents, especially polyamide wax thixotropic agents, are prone to screen clogging due to their inherent characteristics and complex dispersion processes, and the clogging becomes more severe with longer printing times. Silver paste clogging can affect the photoelectric conversion efficiency of solar cells and require shutdown for repairs, causing production disruptions. With advancements in technology, the printability of the paste has become increasingly important. In addition to continuous grid printing, factors such as grid line width, aspect ratio, and long-term printability must be considered. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this application provides a novel organic carrier for conductive silver paste. This organic carrier uses a polystyrene-polyolefin block copolymer to replace the traditional polyamide wax thixotropic agent, effectively solving printing problems such as ink permeability and durability of conductive silver paste containing this organic carrier. After long-term, large-volume, multi-sheet printing, there will be no screen clogging or grid breakage. Furthermore, the printed grid lines have a high aspect ratio, thereby improving the photoelectric conversion efficiency of solar cells.

[0007] To this end, the first aspect of this application provides an organic carrier for conductive silver paste, wherein the organic carrier comprises, by weight percentage: 0.1 to 6.0 wt% of an elastic resin, 0.5 to 20.0 wt% of a thickener, 70.0 to 95.0 wt% of an organic solvent and 0.05 to 5.0 wt% of a first additive; wherein the elastic resin is a polystyrene-polyolefin block copolymer.

[0008] Because polyamide wax thixotropic agents are insoluble in organic solvents at room temperature and have complex dispersion processes, the organic carrier is prone to containing fine, undispersed particles. This further leads to silver powder agglomeration during the subsequent conductive silver paste preparation process, resulting in problems such as plate clogging and printout interruptions during long-term printing. To address the poor long-term printability caused by polyamide wax thixotropic agents and the various inconveniences of complex preparation processes, this application uses a polystyrene-polyolefin block copolymer instead of the traditional polyamide wax thixotropic agent in the organic carrier. The polystyrene-polyolefin block copolymer is completely soluble in some organic solvents, and the dispersion process is simple. Therefore, it can produce fine silver paste that does not clog the plate or break the grid during long-term printing, effectively solving the problem of silver paste printing durability. Simultaneously, the polystyrene-polyolefin block copolymer has high elasticity, and the conductive silver paste prepared using this organic carrier has a high storage modulus. During the printing process, the paste avoids continuous line expansion due to excessively low viscosity during fine grid printing, thus resulting in grid lines with a high aspect ratio and improving the photoelectric conversion efficiency of solar cells.

[0009] In some specific embodiments, the content of elastic resin in the organic carrier can be 0.1 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, 3.0 wt%, 4.0 wt%, 5.0 wt%, or 6.0 wt%. In some preferred embodiments, the content of elastic resin in the organic carrier is 3-5 wt%. In some most preferred embodiments, the content of elastic resin in the organic carrier is 4 wt%.

[0010] This application helps to further improve the printing performance of silver paste formulated using the organic carrier by optimizing the content of elastic resin in the organic carrier.

[0011] In some embodiments, the monomer molar ratio of polystyrene to polyolefin in the polystyrene-polyolefin block copolymer is (10:90) to (90:10).

[0012] In some preferred embodiments, the monomer molar ratio of polystyrene to polyolefin in the polystyrene-polyolefin block copolymer is (35:65) to (65:35).

[0013] This application does not explicitly limit the molecular weight range of the polystyrene-polyolefin block copolymer. In some specific embodiments, the molecular weight of the polystyrene-polyolefin block copolymer may be, for example, 500 to 100,000.

[0014] In some embodiments, the polymerizing monomer of the polyolefin is selected from at least one of ethylene, propylene, 1-butene, 1,3-butadiene, 1-pentene, isoprene, 1-hexene, 1-octene, 4-methyl-1-pentene, and cycloolefins.

[0015] The polyolefins described in this application are homopolymerized or copolymerized from α-olefins (ethylene, propylene, 1-butene, 1,3-butadiene, 1-pentene, isoprene, 1-hexene, 1-octene, 4-methyl-1-pentene) and / or cycloolefins, etc., and the polyolefins can be saturated polyolefins or unsaturated polyolefins.

[0016] In some specific embodiments, the polystyrene-polyolefin block copolymer may be, for example, a polystyrene-poly(ethylene-butene)-polystyrene block copolymer (SEBS).

[0017] In some embodiments, the mass ratio of the elastic resin to the thickener is (1:4) to (4:1).

[0018] In some specific embodiments, the mass ratio of the elastic resin to the thickener can be 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, or 4:1, etc. In some preferred embodiments, the mass ratio of the elastic resin to the thickener is 1:1.

[0019] By controlling the mass ratio of elastic resin to thickener within the above-mentioned range, this application enables the silver paste formulated using this organic carrier to have a more suitable viscosity, thereby further improving the printing performance of the silver paste.

[0020] In some embodiments, the thickener is selected from at least one of ethyl cellulose (EC), cellulose acetate butyrate (CAB), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), and modified acrylic resin.

[0021] In this application, the thickener can work with the elastic resin to increase the viscosity of the organic carrier and the prepared silver paste, preventing it from flowing, thereby helping to improve the printing performance of the subsequently prepared paste and increase the aspect ratio of the printed lines.

[0022] In some embodiments, the thickener is a mixture of cellulose acetate butyrate and polyvinyl butyral, and the mass ratio of cellulose acetate butyrate to polyvinyl butyral in the mixture is 1:(1-5). In some preferred embodiments, the mass ratio of cellulose acetate butyrate to polyvinyl butyral in the mixture is 1:3.

[0023] By selecting the thickeners described above, this application helps to further improve the printing performance of silver paste formulated with this organic carrier.

[0024] In some embodiments, the organic solvent is selected from at least one of ethylene glycol butyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, tripropylene glycol methyl ether, ethylene glycol phenyl ether, propylene glycol phenyl ether, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate, ethylene glycol phenyl ether acetate, propylene glycol phenyl ether acetate, dodecyl alcohol ester, hexadecyl alcohol ester, terpineol, terpineol, dimethyl adipate, and divalent ester (DBE).

[0025] The organic solvent used in this application is an alcohol ether solvent, used to mix other components of the raw materials for preparing the organic carrier into a homogeneous fluid. In some preferred embodiments, the organic solvent is a mixed solvent of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, dodecyl alcohol ester, and dimethyl adipate. Using this mixed solvent can better dissolve the elastic resin, thickener, and additives in the organic carrier.

[0026] The first additive in this application includes, but is not limited to, commercially available surfactants, such as saturated and unsaturated fatty acids (e.g., oleic acid), saturated and unsaturated fatty acid amides, coupling agents, and polyoxyethylene surfactants (e.g., Triton X-100, Tween-20).

[0027] A second aspect of this application provides a method for preparing an organic support as described in the first aspect of this application, the method comprising the following steps:

[0028] S1, the organic solvent is heated to 50-90°C, and then the heated organic solvent is mixed with the elastic resin, thickener and first additive to form a mixture;

[0029] S2, after the mixture is kept at a constant temperature and stirred until all raw materials are dissolved, the organic carrier for the conductive silver paste is obtained.

[0030] The preparation method of the organic carrier described in this application differs from that of organic carriers containing polyamide wax thixotropic agents. Traditional polyamide wax thixotropic agents require a thermal activation process, but the temperature range and heating time must be precisely controlled to avoid deactivation of the polyamide wax thixotropic agent. Therefore, the preparation process of organic carriers containing polyamide wax thixotropic agents is relatively complex. In contrast, the preparation method of the organic carrier described in this application is simpler. The polystyrene-polyolefin block copolymer has good compatibility with other components, such as thickeners and additives, thus simplifying the preparation process and eliminating concerns about thixotropic agent deactivation during preparation.

[0031] The process of mixing various raw materials described in this application can be carried out by stirring, and there is no need to be restricted by stirring conditions, such as speed, method, rotor or blade type, etc.

[0032] In some preferred embodiments, the organic solvent is heated to 70–85°C to facilitate the dissolution and mixing of the raw materials.

[0033] A third aspect of this application provides a conductive silver paste, which, by weight percentage, comprises the following components:

[0034] The organic carrier as described in the first aspect of this application: 5.0–15.0 wt%;

[0035] Silver powder: 70.0–92.0 wt%;

[0036] Glass powder: 1.0–10.0 wt%;

[0037] Aluminum powder: 0-10.0 wt%;

[0038] Second auxiliary agent: 0.01–5.0 wt%.

[0039] In some preferred embodiments, the conductive silver paste comprises, by weight percentage, the following components:

[0040] The organic carrier as described in the first aspect of this application: 7.5–8.5 wt%;

[0041] Silver powder: 85.0–87.0 wt%;

[0042] Glass powder: 2.2–3.5 wt%;

[0043] Aluminum powder: 0-5 wt%;

[0044] Second auxiliary agent: 0.5-1.0 wt%.

[0045] The organic carrier in the conductive silver paste described in this application uses polystyrene-polyolefin block copolymer instead of polyamide wax thixotropic agent, which makes the conductive silver paste less prone to agglomeration and clumping. It does not cause screen clogging after long-term, large-volume, multi-sheet printing, effectively solving the problem of printing durability of conductive silver paste. At the same time, the viscosity of the conductive silver paste is moderate, and the prepared grid lines have a high aspect ratio.

[0046] In this application, the shape of the silver powder used can be, for example, spherical, flake, or irregular, and the particle size range of the silver powder is 0.1 to 10 μm; the shape of the aluminum powder used can be, for example, spherical, flake, or irregular, and the particle size range of the aluminum powder is 0.1 to 10 μm.

[0047] This application does not explicitly limit the composition of the glass powder used, and those skilled in the art can make conventional selections. In some specific embodiments, the glass powder used is a Pb-BMO based glass powder, wherein M represents one or more of MoO3, WO3, V2O5, Nb2O5, Ta2O5, TiO2, ZrO2, HfO2, SiO2, TeO2, Al2O3, In2O3, Tl2O3, ZnO, NiO, La2O3, CuO, alkali metal oxides, and alkaline earth metal oxides.

[0048] In this application, the second additive may be a mixture of one or more additives, including but not limited to silicone oil (PDMS), silicone oil derivatives, and surfactants.

[0049] In this application, the method for preparing the conductive silver paste may include the following steps:

[0050] (1) Silver powder, aluminum powder, glass powder, organic carrier and second additive are placed in a pre-dispersion container for pre-dispersion to obtain a pre-dispersion slurry;

[0051] (2) Grind and disperse the pre-dispersed slurry, and then stir to obtain the conductive silver paste.

[0052] The fourth aspect of this application provides a solar cell in which the electrodes or grid lines are made using conductive silver paste as described in the third aspect of this application.

[0053] The conductive silver paste described in this application has good stability and is not prone to agglomeration. During screen printing, the conductive silver paste passes through the screen more easily, reducing grid breakage. Therefore, during the production process, a stable photoelectric conversion efficiency of the solar cell can be maintained. At the same time, there is no need to clean and wipe the screen due to clogging during the printing process, which would cause downtime.

[0054] The beneficial technical effects of this application are as follows: The organic carrier provided in this application uses a polystyrene-polyolefin block copolymer instead of the traditional polyamide wax thixotropic agent. The polystyrene-polyolefin block copolymer is completely soluble in organic solvents, and the dispersion process is simple. Therefore, a fine conductive silver paste that can be prepared without clogging the printing plate or causing grid breakage during long-term printing can be obtained, effectively solving the problem of paste printing durability. This maintains a stable photoelectric conversion efficiency of the solar cell, and eliminates the need for cleaning and wiping the printing plate during the printing process, thus avoiding downtime. Simultaneously, the polystyrene-polyolefin block copolymer has high elasticity, and the conductive silver paste prepared using this organic carrier has a high storage modulus. During the printing process, the paste avoids continuous line expansion due to excessively low viscosity during fine grid printing, thereby resulting in a higher aspect ratio of the prepared grid lines and improving the photoelectric conversion efficiency of the solar cell. Attached Figure Description

[0055] Figure 1 The image shows an EL image of a battery cell printed with the conductive silver paste from Application Example 2, as shown in Test Example 2.

[0056] Figure 2 The image shows an EL image of a battery cell printed with conductive silver paste as used in Comparative Application Example 1, as shown in Test Example 2.

[0057] Figure 3 The image shows an EL image of a battery cell printed with the conductive silver paste used in Comparative Application Example 2, as shown in Test Example 2. Detailed Implementation

[0058] To make this application easier to understand, the following detailed description will be provided with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of this application. Unless otherwise specified, the raw materials or components used in this application can be obtained commercially or by conventional methods.

[0059] Cellulose acetate butyrate used in the following examples was purchased from Shanghai Chuangsai Technology Co., Ltd.; polyvinyl butyral was purchased from Shanghai Jizhi Biochemical Technology Co., Ltd.; and polyvinylpyrrolidone was purchased from Shanghai Mairui Biochemical Technology Co., Ltd.

[0060] Example 1: Preparation of organic carrier for conductive silver paste. Raw material composition: elastic resin: 2.0 wt%, thickener: 4.0 wt%, surfactant-oleic acid: 1.0 wt%, organic solvent: 93.0 wt%. The elastic resin is polystyrene-poly(ethylene-butene)-polystyrene block copolymer (SEBS), in which the molar ratio of polystyrene to polyolefin monomers in SEBS is 35:65, the molecular weight is 50,000, and the polymerizing monomers of polyolefin are ethylene and butene in a molar ratio of 1:1; the thickener is a mixture of cellulose acetate butyrate (1.0 wt%) and polyvinyl butyral (3.0 wt%), in which the mass ratio of cellulose acetate butyrate to polyvinyl butyral in the mixture is 1:3; the mass ratio of elastic resin SEBS to thickener is 1:2; the organic solvent is a mixed solvent of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, dodecyl alcohol ester and dimethyl adipate, in which the mass ratio of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, dodecyl alcohol ester and dimethyl adipate in the mixed solvent is 1:1:1:1.

[0061] Preparation: An organic solvent was added to a reaction vessel, stirred, and heated to 70°C. Under stirring conditions, elastic resin, thickener, and oleic acid were added to the heated organic solvent, and then kept at 70°C until all raw materials dissolved into a homogeneous phase, thus obtaining an organic carrier for conductive silver paste.

[0062] Example 2: Preparation of organic carrier for conductive silver paste. Raw material composition: basically the same as in Example 1, except that the content of elastic resin is 4.0 wt%, the content of organic solvent is 91.0 wt%, and the mass ratio of elastic resin to thickener is 1:1.

[0063] Preparation: Same as in Example 1.

[0064] Example 3: Preparation of organic carrier for conductive silver paste. Raw material composition: basically the same as in Example 2, except that the molar ratio of polystyrene to polyolefin monomers in the elastic resin is 10:90.

[0065] Preparation: Same as in Example 1.

[0066] Example 4: Preparation of Organic Carrier for Conductive Silver Paste. Raw material composition: basically the same as in Example 2, except that the molar ratio of polystyrene to polyolefin monomers in the elastic resin is 90:10. Preparation: same as in Example 1.

[0067] Example 5: Preparation of organic carrier for conductive silver paste. Raw material composition: basically the same as in Example 2, except that the thickener is a mixture of cellulose acetate butyrate (content 2.0 wt%) and polyvinyl butyral (content 2.0 wt%), and the mass ratio of cellulose acetate butyrate to polyvinyl butyral in the mixture is 1:1.

[0068] Preparation: Same as in Example 1.

[0069] Example 6: Preparation of organic carrier for conductive silver paste. Raw material composition: basically the same as in Example 2, except that the thickener is a mixture of cellulose acetate butyrate (content 0.8wt%) and polyvinyl butyral (content 3.2wt%), and the mass ratio of cellulose acetate butyrate to polyvinyl butyral in the mixture is 1:4.

[0070] Preparation: Same as in Example 1.

[0071] Example 7: Preparation of organic carrier for conductive silver paste. Raw material composition: basically the same as in Example 2, except that the thickener is cellulose acetate butyrate (content 4wt%).

[0072] Preparation: Same as in Example 1.

[0073] Example 8: Preparation of organic carrier for conductive silver paste. Raw material composition: basically the same as in Example 2, except that the thickener is polyvinyl butyral (content 4wt%).

[0074] Preparation: Same as in Example 1.

[0075] Example 9: Preparation of organic carrier for conductive silver paste. Raw material composition: basically the same as in Example 2, except that the thickener is polyvinylpyrrolidone (content 4wt%).

[0076] Preparation: Same as in Example 1.

[0077] Example 10: Preparation of organic carrier for conductive silver paste

[0078] Raw material composition: basically the same as in Example 2, except that the organic solvent is diethylene glycol butyl ether.

[0079] Preparation: Same as in Example 1.

[0080] Comparative Example 1: Preparation of Organic Carrier for Conductive Silver Paste. Raw material composition: basically the same as in Example 2, except that the elastic resin was replaced with polyamide wax. MAX.

[0081] Preparation: An organic solvent was added to a reaction vessel, stirred, and heated to 70°C. Under stirring, polyamide wax, thickener, and oleic acid were added to the heated organic solvent. The mixture was then kept at 70°C until all raw materials dissolved into a homogeneous phase, thus obtaining an organic carrier for conductive silver paste.

[0082] Comparative Example 2: Preparation of Organic Carrier for Conductive Silver Paste. Raw material composition: basically the same as in Example 2, except that the content of elastic resin is 8.0 wt%, the content of organic solvent is 87.0 wt%, and the mass ratio of elastic resin to thickener is 2:1.

[0083] Preparation: Same as in Example 1.

[0084] Application Example 1: Preparation of Conductive Silver Paste Raw Material Composition: Organic carrier prepared in Example 1: 7.5 wt%, silver powder: 86.5 wt%, aluminum powder: 2 wt%, glass powder: 3.5 wt%, additive (silicone oil): 0.5 wt%. The silver powder includes silver powder A (66.5 wt%) and silver powder B (20 wt%), both of which are spherical powders. The average particle size of silver powder A is 1.5 μm, and the average particle size of silver powder B is 3 μm. The aluminum powder is spherical powder with an average particle size of 3.0 μm. The glass powder is a Pb-BMO spherical glass powder with the following composition: 86 wt% PbO, 10 wt% B2O3, 2 wt% Al2O3, and 2 wt% Li2O. The glass powder includes glass powder A (2.1 wt%) with an average particle size of 1.0 μm and glass powder B (1.4 wt%) with an average particle size of 1.5 μm.

[0085] Preparation: Organic carrier, silver powder, aluminum powder, glass powder, and silicone oil are placed in a pre-dispersion container, which is then placed in a rotary dispersion device for pre-dispersion. The dispersed slurry is then placed in a three-roll mill and milled six times for further dispersion. The milled and dispersed slurry is then stirred once more using a mixer to obtain conductive silver paste.

[0086] Application Example 2-10: Preparation of Conductive Silver Paste

[0087] The preparation process is basically the same as in Application Example 1, except that the organic carrier prepared in Example 1 is replaced with the organic carrier prepared in Examples 2-10.

[0088] Application Example 11: Preparation of Conductive Silver Paste Raw material composition: Organic carrier prepared in Example 1: 8.5 wt%, silver powder: 87 wt%, aluminum powder: 0 wt%, glass powder: 4 wt%, additive (silicone oil): 0.5 wt%. The silver powder and glass powder are the same as in Example 1.

[0089] Comparative Application Example 1-2: Preparation of Conductive Silver Paste

[0090] The preparation process is basically the same as in Application Example 1, except that the organic carrier prepared in Example 1 is replaced with the organic carrier prepared in Comparative Examples 1-2.

[0091] Test Example 1

[0092] The conductive silver pastes prepared in Application Examples 1-11 and Comparative Application Examples 1-2 were used to screen print and sinter 10 N-type TOPCOn silicon wafers using a screen with an aperture of 14 μm and a film thickness of 2.5 μm to produce solar cells with printed grid lines. The line height and line width of the grid lines were measured using a 3D optical microscope, and the number of broken grids on each wafer was observed. The photoelectric conversion efficiency of the solar cells prepared with each conductive silver paste was tested under standard test conditions (STC) using a dedicated solar cell testing instrument. The test results are shown in Table 1.

[0093] Table 1

[0094]

[0095] As shown in Table 1, the performance of solar cells prepared using the conductive silver paste from Application Examples 1-11 of this application is significantly better than that of Comparative Application Example 1. This indicates that replacing the polyamide wax thixotropic agent in the organic carrier with elastic resin significantly improves the printing performance of the conductive silver paste, thereby increasing the photoelectric conversion efficiency of the solar cells. In Comparative Application Example 2, the conductive silver paste used had an excessively high content of elastic resin in the organic carrier, resulting in high viscosity. Although the printed linewidth was better, the conductive silver paste was prone to clogging during printing, leading to a large number of broken grids and consequently lower photoelectric conversion efficiency of the solar cells.

[0096] Test Example 2

[0097] To further highlight the excellent printability of the conductive silver paste prepared using the organic carrier of this application, a screen printing test was conducted using a screen that is more difficult to print on. The conductive silver pastes prepared in Application Examples 1-2 and Comparative Application Examples 1-2 were each used on 10 N-type TOPCOn silicon wafers, and screens with an aperture of 14 μm and a film thickness of 5.0 μm were used for screen printing and sintering to produce solar cells with printed grid lines. The line height, line width, and number of broken grid lines of the printed grid lines were observed. Simultaneously, the photoelectric conversion efficiency of the solar cells was measured using the same method as in Test Example 1. The test results are shown in Table 2, and the EL images of the solar cells printed using the conductive silver pastes in Application Example 2 and Comparative Application Examples 1-2 are shown in Figures 1-3, respectively.

[0098] Table 2

[0099]

[0100] As shown in Table 2, the conductive silver paste prepared in Application Example 1, due to the increased screen thickness, resulted in printing difficulties and a significant increase in EL grid breaks, leading to a decrease in the photoelectric conversion efficiency of the battery. Conversely, the conductive silver paste prepared in Application Example 2, due to its higher viscosity, also experienced a significant increase in EL grid breaks with increased screen thickness. The conductive silver pastes prepared in Application Examples 1 and 2, however, maintained printability, and the photoelectric conversion efficiency of the prepared batteries remained at the same level as in Application Example 1. Meanwhile, from... Figure 1-3 It can be seen that the number of broken grids in the solar cells prepared in Comparative Application Example 1 and Comparative Application Example 2 is much higher than that in Application Example 2.

[0101] It should be noted that the embodiments described above are only for explaining this application and do not constitute any limitation on this application. This application has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to this application within the scope of the claims, and revisions can be made to the invention without departing from the scope and spirit of this application. Although the application described herein relates to specific methods, materials, and embodiments, it does not mean that this application is limited to the specific examples disclosed herein; on the contrary, this application can be extended to all other methods and applications with the same function.

Claims

1. An organic carrier for conductive silver paste, characterized in that, The organic carrier comprises, by weight percentage, the following components: 0.1-6.0 wt% of elastic resin, 0.5-20.0 wt% of thickener, 70.0-95.0 wt% of organic solvent, and 0.05-5.0 wt% of first auxiliary agent; wherein the elastic resin is a polystyrene-polyolefin block copolymer, and the molar ratio of polystyrene to polyolefin monomers in the polystyrene-polyolefin block copolymer is (35:65) to (65:35). The thickener is a mixture of cellulose acetate butyrate and polyvinyl butyral, and the mass ratio of cellulose acetate butyrate to polyvinyl butyral in the mixture is 1:(3~4). The mass ratio of the elastic resin to the thickener is 1:1; the organic solvent is a mixture of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, dodecyl alcohol ester and dimethyl adipate.

2. The organic carrier according to claim 1, characterized in that, The polymer monomer of the polyolefin is selected from at least one of ethylene, propylene, 1-butene, 1,3-butadiene, 1-pentene, isoprene, 1-hexene, 1-octene, 4-methyl-1-pentene, and cycloolefins.

3. A method for preparing an organic carrier as described in claim 1 or 2, characterized in that, The method includes the following steps: S1, the organic solvent is heated to 50~90°C, and then the heated organic solvent is mixed with the elastic resin, thickener and first additive to form a mixture; S2, after the mixture is kept at a constant temperature and stirred until all raw materials are dissolved, the organic carrier for the conductive silver paste is obtained.

4. A conductive silver paste, comprising, by weight percentage, the following components: The organic carrier as described in claim 1 or 2: 5.0~15.0 wt% Silver powder: 70.0~92.0 wt%; Glass powder: 1.0~10.0 wt%; Aluminum powder: 0~10.0wt% Second auxiliary agent: 0.01~5.0wt%.

5. A solar cell, characterized in that, The electrodes or grid lines in the solar cell are made using the conductive silver paste as described in claim 4.

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