Conductive copper paste, preparation method thereof and solar cell

Abstract

The embodiment of the invention relates to the photovoltaic field, and provides conductive copper paste, a preparation method thereof and a solar cell. The conductive copper paste comprises the following components in percentage by weight: 80%-90.0% of copper powder, 5%-15.0% of an organic solvent, 0.3%-2.0% of resin and 0.5%-5.0% of an additive, wherein the copper powder comprises first copper powder of which the D50 is 0.2 [mu] m-3. 0 [mu] m and second copper powder of which the D100 is 0.5 [mu] m-10 [mu] m. The technical scheme provided by the embodiment of the invention at least has the following advantages: 1, compared with conductive silver paste occupying a leading position, the conductive copper paste is lower in raw material cost, and about 70% of metallization cost can be reduced for a solar cell manufacturing link; 2, the conductor layer forms a good channel, and a compact layer is formed to prevent the second layer of conductive copper paste from diffusing to the base material; and 3, the conductive copper paste is used as a second conductive paste, forms good contact with the first layer of conductive silver paste through a low-temperature process, and does not directly contact with the substrate, so that the situation that copper damages a PN junction structure and reduces minority carrier lifetime to cause electric leakage is avoided.

Description

Technical Field

[0001] This application relates to the photovoltaic field, and in particular to a conductive copper paste, its preparation method, and a solar cell. Background Technology

[0002] In the increasingly competitive solar photovoltaic industry, the goal of major companies is to produce superior solar cells at a lower cost. Solar silver paste for photovoltaic applications is expensive, and replacing it with base metal pastes that offer good conductivity is a current area of ​​exploration in the industry. The application of conductive copper paste in solar cells can significantly reduce their cost per kilowatt-hour and also offers unique advantages in replacing traditional conductive silver paste.

[0003] However, copper easily forms a CuO / Cu2O insulating layer during high-temperature sintering, causing the resistivity to surge to 10. 4 High Ω·cm can cause battery failure. Simultaneously, copper atoms diffuse within the substrate at high temperatures, leading to PN junction leakage and impacting conversion efficiency. Furthermore, insufficient adhesion between copper and the substrate after introduction can easily reduce reliability. Summary of the Invention

[0004] This application provides a conductive copper paste, its preparation method, and a solar cell, which at least significantly reduces the metallization cost of solar cells.

[0005] According to some embodiments of this application, one aspect of this application provides a conductive copper paste, comprising the following components by weight percentage: Copper powder: 80%~90.0% Organic solvents: 5%~15.0%, Resin: 0.3%~2.0%, Additives: 0.5~5.0%, The copper powder includes a first copper powder with a D50 of 0.2μm to 3.0μm and a second copper powder with a D100 of 0.5μm to 10μm. The first copper powder includes at least one of spherical copper powder and near-spherical copper powder, and the second copper powder includes at least one of dendritic copper powder and flake copper powder.

[0006] In some embodiments, the mass ratio of the first copper powder to the second copper powder is 1:(0.05~1).

[0007] In some embodiments, the copper powder undergoes chemical modification, and the method of chemical modification is as follows: After removing the oxide layer from the surface of the copper powder, surface modification is performed using organic materials.

[0008] In some embodiments, the organic compound includes at least one of oleic acid, polyvinyl butyral, epoxy-modified acrylic resin, imidazole ionic liquid accelerator, graphene, and silane coupling agent.

[0009] In some embodiments, the resin includes at least one of ethyl cellulose, hydroxyethyl cellulose, acrylic resin, polyurethane, epoxy resin, cellulose acetate butyrate, terpene resin, and hydrogenated styrene-butadiene block copolymer.

[0010] In some embodiments, the organic solvent includes at least one of alcohols, ketones, lipids, aliphatic hydrocarbons, aromatic hydrocarbons, and naphtha.

[0011] In some embodiments, the alcohol compounds include at least one of n-propanol, n-pentanol, 2-methylbutanol, ethylene glycol butyl ether, diethylene glycol butyl ether, trimethylnonanol, and methyl isobutyl methanol; the ketone compounds include at least one of methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isoflurane diisobutyl ketone; and the aromatic hydrocarbon compounds include xylene.

[0012] In some embodiments, the additive includes at least one of a wetting and dispersing agent, a defoamer, and an antisettling agent.

[0013] According to some embodiments of this application, another aspect of this application provides a method for preparing conductive copper paste, comprising the following steps: After mixing organic solvent, resin and additives, copper powder is added, stirred and rolled to obtain conductive copper paste.

[0014] According to some embodiments of this application, another aspect of this application provides a method for manufacturing a solar cell, comprising: Provide battery body; A conductive silver paste and a conductive copper paste as described in any of the above embodiments are provided, and the conductive silver paste is printed onto the solar cell to form a first electrode pattern. The first electrode pattern is sintered to obtain a contact layer. The conductive copper paste is printed on the contact layer to form a second electrode pattern. The second electrode pattern is cured to obtain a conductive layer. The contact layer and the conductive layer constitute a grid line.

[0015] According to some embodiments of this application, another aspect of this application provides a solar cell, wherein the grid lines of the solar cell are formed using conductive copper paste as described in any of the above embodiments, or obtained by the manufacturing method of the solar cell described in the above embodiments.

[0016] The technical solution provided in this application has at least the following advantages: 1. Compared to the dominant conductive silver paste, copper paste has a lower raw material cost, which can reduce the metallization cost of solar cell manufacturing by about 70%. 2. The conductor layer forms good channels and a dense layer to prevent the diffusion of the second layer of conductive copper paste into the substrate; 3. The conductive copper paste, as the second type of conductive paste, forms good contact with the first layer of conductive silver paste through a low-temperature process, without directly contacting the substrate, thus preventing copper from entering the PN junction and causing minority carrier quenching.

[0017] 4. Through two precise overprinting processes, the copper paste linewidth can be controlled within 15μm, and the grid line aspect ratio is increased to over 0.6, effectively reducing shadow loss and improving carrier collection efficiency. Attached Figure Description

[0018] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the drawings in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 Box plots show the photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor of solar cells obtained by secondary printing using the conductive copper paste prepared in the embodiments of this application. Detailed Implementation

[0020] As is known from the background technology, in the fabrication of solar cell grid lines, copper paste is easily oxidized at high temperatures to form copper oxide, leading to increased resistivity and a sharp decrease in conductivity. Copper atoms diffuse within the substrate at high temperatures, causing leakage current in the PN junction and affecting conversion efficiency. Furthermore, the introduction of copper can result in insufficient adhesion between the copper and the substrate, potentially leading to reduced reliability.

[0021] According to some embodiments of this application, one aspect of this application provides a conductive copper paste, comprising the following components by weight percentage: Copper powder: 80%~90.0% Organic solvents: 5%~15.0%, Resin: 0.3%~2.0%, Additives: 0.5~5.0%, The copper powder includes a first copper powder with a D50 of 0.2μm to 3.0μm and a second copper powder with a D100 of 0.5μm to 10μm.

[0022] In some embodiments, the mass ratio of the first copper powder to the second copper powder is 1:(0.05~1).

[0023] In some embodiments, the copper powder undergoes chemical modification, and the method of chemical modification is as follows: After removing the oxide layer from the surface of the copper powder, surface modification is performed using organic materials.

[0024] In some embodiments, the organic compound includes at least one of oleic acid, polyvinyl butyral, epoxy-modified acrylic resin, imidazole ionic liquid accelerator, graphene, and silane coupling agent.

[0025] In some embodiments, the resin includes at least one of ethyl cellulose, hydroxyethyl cellulose, acrylic resin, polyurethane, epoxy resin, cellulose acetate butyrate, terpene resin, and hydrogenated styrene-butadiene block copolymer.

[0026] In some embodiments, the organic solvent includes at least one of alcohols, ketones, lipids, aliphatic hydrocarbons, aromatic hydrocarbons, and naphtha.

[0027] In some embodiments, the alcohol compounds include at least one of n-propanol, n-pentanol, 2-methylbutanol, ethylene glycol butyl ether, diethylene glycol butyl ether, trimethylnonanol, and methyl isobutyl methanol; the ketone compounds include at least one of methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isoflurane diisobutyl ketone; and the aromatic hydrocarbon compounds include xylene.

[0028] In some embodiments, the additive includes at least one of a wetting and dispersing agent, a defoamer, and an antisettling agent.

[0029] According to some embodiments of this application, another aspect of this application provides a method for preparing conductive copper paste, comprising the following steps: After mixing organic solvent, resin and additives, copper powder is added, stirred and rolled to obtain conductive copper paste.

[0030] According to some embodiments of this application, another aspect of this application provides a method for manufacturing a solar cell, comprising: Provide battery body; A conductive silver paste and a conductive copper paste as described in any of the above embodiments are provided, and the conductive silver paste is printed onto the solar cell to form a first electrode pattern. The first electrode pattern is sintered to obtain a contact layer. The conductive copper paste is printed on the contact layer to form a second electrode pattern. The second electrode pattern is cured to obtain a conductive layer. The contact layer and the conductive layer constitute a grid line.

[0031] According to some embodiments of this application, another aspect of this application provides a solar cell, wherein the grid lines of the solar cell are formed using conductive copper paste as described in any of the above embodiments, or obtained by the preparation method as described in any of the above embodiments.

[0032] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0033] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0034] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0035] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0036] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0037] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0038] In the accompanying drawings corresponding to the embodiments of this application, the thickness and area of ​​the layers are enlarged for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be a third component between the two components. Conversely, when describing a component on the surface of another component, or when another component is formed or disposed on the surface of a component, it indicates that there is no third component between the two components. Furthermore, when describing a component as being "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0039] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included. Furthermore, when a component such as a layer, film, region, or plate is referred to as being "on / located" on another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may be present therein. Moreover, when a component such as a layer, film, region, or plate is "directly located" on another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it indicates that no other components are located therein.

[0040] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "part" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0041] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0042] The manufacturers and models of copper powder used in the embodiments of this application are shown in Table 1.

[0043] Table 1

[0044] Example 1 This embodiment provides a method for preparing conductive copper paste, including the following steps: The ingredients are formulated according to the proportions shown in Table 2. The copper powder includes a first copper powder with a D50 of 1.8 μm (copper powder 1 in Table 1) and a second copper powder with a D100 of 6.0 μm (copper powder 5 in Table 1). The mass ratios of the first and second copper powders are shown in Table 3. The resin is ethyl cellulose. The organic solvent is n-propanol. The additive is ED-120.

[0045] After mixing organic solvent, resin and additives, copper powder is added and stirred. Then, the mixture is rolled 6 times on a three-roll mill to further disperse and homogenize it. When the scraper fineness is less than 5μm, it is filtered with a 400-mesh filter cloth to obtain conductive copper paste.

[0046] Example 2 This embodiment provides a method for preparing conductive copper paste, including the following steps: The ingredients are prepared according to the proportions shown in Table 2. The copper powder includes a first copper powder with a D50 of 0.5 μm (copper powder 2 in Table 1) and a second copper powder with a D100 of 3.8 μm (copper powder 6 in Table 1). The mass ratios of the first and second copper powders are shown in Table 3. The resin is acrylic resin. The organic solvent is diethylene glycol butyl ether. The additive is BYK141.

[0047] After mixing organic solvent, resin and additives, copper powder is added and stirred. Then, the mixture is rolled seven times on a three-roll mill to further disperse and homogenize it. When the scraper fineness is less than 4μm, it is filtered with a 500-mesh filter cloth to obtain conductive copper paste. Example 3 This embodiment provides a method for preparing conductive copper paste, including the following steps: The ingredients are prepared according to the proportions shown in Table 2. The copper powder includes a first copper powder with a D50 of 0.8 μm (copper powder 3 in Table 1) and a second copper powder with a D100 of 9.0 μm (copper powder 7 in Table 1). The mass ratios of the first and second copper powders are shown in Table 3. The resin is polyurethane. The organic solvent is methyl isobutyl methanol. The additive is BYK4510.

[0048] After mixing the organic solvent, resin and additives, copper powder is added and stirred. Then, the mixture is rolled eight times on a three-roll mill to further disperse and homogenize it. When the scraper fineness is less than 5μm, it is filtered with a 500-mesh filter cloth to obtain conductive copper paste.

[0049] Example 4 This embodiment provides a method for preparing conductive copper paste, including the following steps: The ingredients are prepared according to the proportions shown in Table 2. The copper powder includes a first copper powder with a D50 of 2.7 μm (copper powder 4 in Table 1) and a second copper powder with a D100 of 3.4 μm (copper powder 6 in Table 1). The mass ratios of the first and second copper powders are shown in Table 3. The resin is epoxy resin. The organic solvent is dimethyl succinate. The additive is polyoxyethylene lauryl ether.

[0050] After mixing organic solvent, resin and additives, copper powder is added and stirred. Then, the mixture is rolled six times on a three-roll mill to further disperse and homogenize it. When the scraper fineness is less than 5μm, it is filtered with a 600-mesh filter cloth to obtain conductive copper paste.

[0051] Example 5 This embodiment provides a method for preparing conductive copper paste, including the following steps: The ingredients are prepared according to the proportions shown in Table 2. The copper powder includes a first copper powder with a D50 of 0.5 μm (copper powder 2 in Table 1) and a second copper powder with a D100 of 9.0 μm (copper powder 7 in Table 1). The mass ratios of the first and second copper powders are shown in Table 3. The resin is cellulose acetate butyrate. The organic solvent is n-propanol. The additive is Span 85.

[0052] After mixing organic solvent, resin and additives, copper powder is added and stirred. Then, the mixture is rolled 6 times on a three-roll mill to further disperse and homogenize it. When the scraper fineness is less than 6μm, it is filtered with a 400-mesh filter cloth to obtain conductive copper paste.

[0053] Comparative Example 1 The only difference between this comparative example and Example 1 is that no second copper powder was added, and the missing weight was made up by the first copper powder.

[0054] Comparative Example 2 The only difference between this comparative example and Example 1 is that no first copper powder was added, and the missing weight was made up by the second copper powder.

[0055] Comparative Example 3 The only difference between this comparative example and Example 1 is that the mass ratio of the first copper powder to the second copper powder is 1:1.2.

[0056] Comparative Example 4 The only difference between this comparative example and Example 1 is that the mass ratio of the first copper powder to the second copper powder is 1:3.

[0057] This application also provides a method for manufacturing a solar cell, including: Provide battery body; A conductive silver paste and a conductive copper paste as described in any one of Examples 1-5 and Comparative Examples 1-4 are provided. The conductive silver paste is printed onto the solar cell to form a first electrode pattern. The first electrode pattern is sintered at a temperature below 950°C to obtain a contact layer. The conductive copper paste is printed on the contact layer to form a second electrode pattern. The second electrode pattern is cured at a temperature below 400°C to obtain a conductive layer. The contact layer and the conductive layer form a grid line.

[0058] Table 2

[0059] Table 3

[0060] Table 4

[0061] The performance of the solar cells obtained using the conductive copper alloy described in Examples 1-5 and Comparative Examples 1-4 was tested, and the results are shown in Table 4.

[0062] As can be seen from Examples 1 to 5 above, when the ratio of the first copper powder to the second copper powder is 1:(0.05~1), by adjusting the types and proportions of resin, organic solvent and additives, the fluctuation of the photoelectric conversion efficiency of the solar cell can be controlled within ±0.026%.

[0063] Comparing Comparative Example 1 with Example 1, the solar cell efficiency decreased by >0.2% when the second copper powder was missing; comparing Comparative Example 2 with Example 1, the solar cell efficiency decreased by >0.2% when the first copper powder was missing. The decreased solar cell efficiency in both Comparative Example 1 and Comparative Example 2 failed to meet the normal solar energy efficiency parameter requirements. This indicates that both the first and second copper powders must be added.

[0064] Comparing Comparative Example 3 with Example 1, the ratio of the first copper powder to the second copper powder was 1.2 (exceeding the 1:1 ratio range), resulting in a decrease in solar cell efficiency of >0.3%. Comparing Comparative Example 4 with Example 1, the ratio of the first copper powder to the second copper powder was 3.0 (exceeding the 1:1 ratio range), resulting in a decrease in solar cell efficiency of >0.5%. The decreased solar cell efficiency in both Comparative Examples 3 and 4 fails to meet normal solar cell efficiency parameter requirements. This indicates that a ratio of 1:(0.05~1) for the first copper powder to the second copper powder is the optimal ratio.

[0065] Using the copper paste prepared in Examples 2 and 5 of this application and the corresponding solar cell process, the short-circuit current of the solar cell can be increased, thereby improving the photoelectric conversion efficiency of the solar cell, based on a paste with 100% silver as the conductive phase. As shown in Examples 2 and 5, based on the application of the examples of this application, the fill factor (FF) of the solar cell is improved, thereby improving the efficiency of the solar cell; tests have shown that the improvement in fill factor comes from the reduction in contact resistance and release resistivity (e.g., ...). Figure 1 (As shown).

[0066] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A conductive copper paste, characterized in that, Includes the following components by weight percentage: Copper powder: 80%~90.0% Organic solvents: 5%~15.0%, Resin: 0.3%~2.0%, Additives: 0.5~5.0%, The copper powder includes a first copper powder with a D50 of 0.2μm to 3.0μm and a second copper powder with a D100 of 0.4μm to 10μm. The first copper powder includes at least one of spherical copper powder and near-spherical copper powder, and the second copper powder includes at least one of dendritic copper powder and flake copper powder.

2. The conductive copper paste according to claim 1, characterized in that, The mass ratio of the first copper powder to the second copper powder is 1:(0.05~1).

3. The conductive copper paste according to claim 1 or 2, characterized in that, The copper powder underwent chemical modification, and the method of chemical modification was as follows: After removing the oxide layer from the surface of the copper powder, surface modification is performed using organic materials.

4. The conductive copper paste according to claim 3, characterized in that, The organic compound includes at least one of oleic acid, polyvinyl butyral, epoxy-modified acrylic resin, imidazole ionic liquid accelerator, graphene, and silane coupling agent.

5. The conductive copper paste according to claim 1, characterized in that, The resin includes at least one of ethyl cellulose, hydroxyethyl cellulose, acrylic resin, polyurethane, epoxy resin, cellulose acetate butyrate, terpene resin, and hydrogenated styrene-butadiene block copolymer.

6. The conductive copper paste according to claim 1, characterized in that, The organic solvent includes at least one of alcohols, ketones, lipids, aliphatic hydrocarbons, aromatic hydrocarbons, and naphtha.

7. The conductive copper paste according to claim 6, characterized in that, The alcohols include at least one of n-propanol, n-pentanol, 2-methylbutanol, ethylene glycol butyl ether, diethylene glycol butyl ether, trimethylnonanol, and methyl isobutyl methanol; the ketones include at least one of methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isoflurane diisobutyl ketone; and the aromatic hydrocarbons include xylene.

8. The conductive copper paste according to claim 1, characterized in that, The additives include at least one of wetting and dispersing agents, defoamers, and antisettling agents.

9. A method for preparing conductive copper paste as described in any one of claims 1 to 8, characterized in that, Includes the following steps: After mixing organic solvent, resin and additives, copper powder is added, stirred and rolled to obtain conductive copper paste.

10. A method for manufacturing a solar cell, characterized in that, include: Provide battery body; A conductive silver paste and a conductive copper paste as described in any one of claims 1 to 9 are provided, and the conductive silver paste is printed onto the solar cell to form a first electrode pattern. The first electrode pattern is sintered to obtain a contact layer. The conductive copper paste is printed on the contact layer to form a second electrode pattern. The second electrode pattern is cured to obtain a conductive layer. The contact layer and the conductive layer constitute a grid line.

11. A solar cell, characterized in that, The grid lines of the solar cell are formed using the conductive copper paste described in any one of claims 1 to 9, or obtained by the method for manufacturing a solar cell as described in claim 10.

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