Conductive silver paste for solar cells and solar cells

Abstract

The present application relates to the technical field of solar cells, and in particular to a conductive silver paste for solar cells and a solar cell. The conductive silver paste comprises silver powder, glass powder, a carrier, an additive, and a solvent; the silver powder comprises first silver powder particles and second silver powder particles; the first silver powder particles are flaky, and along the thickness direction, the first silver powder particles comprise a first plane and a second plane relative to each other, the average area of ​​the first plane being denoted as S1, and the average area of ​​the second plane being denoted as S2; the second silver powder particles are spherical, and the average equivalent particle size of the second silver powder particles is denoted as D; S1, S2, and D satisfy the following conditions: 0.8D≤S1≤2D, 0.8D≤S2≤2 D. Glass frit includes the following components in molar percentages: Na2CO3 3%-10%; Al2O3 0.2%-1%; SiO2 1%-5%; ZnO 1%-5%; TeO2 30%-50%; WO3 0.1%-2%; Pb3O4 20%-40%; Bi2O3 5%-10%; Li2CO3 10%-20%; B2O3 1%-5%; Fe2O3 0.05%-0.5%; and CuO 0.05%-1.5%. This combined conductive paste meets the printing requirements of fine-grid printing stencils, enabling the production of gate electrodes with high aspect ratios while maintaining excellent conductivity.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a conductive silver paste for solar cells and a solar cell. Background Art

[0002] Conductive silver paste includes high-temperature sintering silver paste and low-temperature curing silver paste. It is the key material for preparing solar cell electrodes. High-temperature sintering silver paste or low-temperature curing silver paste can be selected according to the needs of different types of solar cells. Taking high-temperature sintering silver paste as an example, it is usually composed of silver powder, glass powder, carrier and additives. Among them, the main function of the carrier is to improve the wetting, printability, appearance and aspect ratio of the powder; the main function of the glass powder is to corrode the insulating silicon nitride anti-reflective film, help form ohmic contact, and provide adhesion; the main function of silver powder is to serve as a conductive medium to form electrode grid lines and provide a good conductive network; the main function of the additive is to improve the filling, printing, tension and other properties of the paste.

[0003] With the development of technology, higher requirements are placed on the resistance and width of the gate electrode of solar cells. The gate electrode prepared by the current conductive silver paste has high resistance and large width, which cannot adapt to the development of new technologies. Summary of the Invention

[0004] Based on this, the first aspect of the present application provides a conductive silver paste for solar cells, and its technical solution is as follows:

[0005] A conductive silver paste comprising silver powder, glass powder, a carrier, an additive and a solvent;

[0006] The silver powder includes a first silver powder particle and a second silver powder particle; the first silver powder particle is in a flake shape, and along the thickness direction, the first silver powder particle includes a first plane and a second plane relative to each other, and the average area of ​​the first plane is recorded as S1, in μm 2 The average area of ​​the second plane is recorded as S2, and the unit is μm 2 The second silver powder particles are spherical, and the average equivalent particle size of the second silver powder particles is recorded as D, in μm; the S1, S2 and D satisfy: 0.8D≤S1≤2D, 0.8D≤S2≤2D;

[0007] The glass powder includes the following components in molar percentages:

[0008] Na2CO33%~10%;

[0009] Al2O30.2%~1%;

[0010] SiO21%~5%;

[0011] ZnO1%~5%;

[0012] TeO230%~50%;

[0013] WO30.1%~2%;

[0014] Pb3O420%~40%;

[0015] Bi2O35%~10%;

[0016] Li2CO310%~20%;

[0017] B2O31%~5%;

[0018] Fe2O30.05%~0.5%;

[0019] CuO0.05%~1.5%.

[0020] A second aspect of the present application provides a solar cell, comprising a gate electrode, wherein the gate electrode is made of the conductive silver paste for solar cells as described above.

[0021] Compared with traditional solutions, this application has the following beneficial effects:

[0022] Silver powder is the conductive functional phase in the conductive silver paste, which directly affects the conductive performance. The present application uses a first silver powder and a second silver powder with a specific morphology in combination, and uses a specific glass powder formula. Among them, the Pb, W, Zn, Te, and Li elements in the glass powder can reduce the softening temperature of the glass powder. The glass powder melts and releases heat, which can reduce the sintering temperature of the above-mentioned silver powder. When sintered at a lower temperature, there is a large amount of point-to-surface contact between the first silver powder and the second silver powder. After sintering, the contact resistance and grid line resistance can be effectively reduced. The above-mentioned conductive silver paste can be used as a front silver paste in crystalline silicon solar cells, which can form a good ohmic contact with the silicon substrate, form good conductivity, effectively reduce the contact resistance and grid line resistance, and increase the current. At the same time, the matched conductive paste can meet the printing requirements of fine grid printing screens, and can prepare grid electrodes with a high aspect ratio, which is suitable for the preparation of fine grids. At the same time, it can also save the use of silver and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more fully understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0024] Figure 1 This is an SEM image of a mixture of first silver powder particles and second silver powder particles according to one embodiment;

[0025] Figure 2 FIG. 1 is a SEM image of a mixture of the third silver powder particles and the second silver powder particles according to a comparative embodiment. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below with reference to specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the present application's disclosure.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0028] the term

[0029] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0030] In this application, "plurality", "multiple", "multiple times", "multiples", etc., unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0031] In this application, the terms "optionally," "optional," and "optional" refer to options that are optional and may or may not be present, i.e., to the selection of either option from the two parallel options of "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or constraints, each "option" is independent.

[0032] In this application, the terms "first," "second," "third," "fourth," etc., in the "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the indicated technical features. Furthermore, "first," "second," "third," "fourth," etc., are only used for non-exhaustive enumeration and description purposes, and should be understood not to constitute a closed-ended limitation on quantity.

[0033] In this application, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional values ​​within the numerical interval is considered continuous and includes the two numerical endpoints of the numerical range (i.e., the minimum and maximum values), as well as every numerical value between these two numerical endpoints. Unless otherwise specified, when a numerical interval refers only to integers within the numerical interval, it includes the two numerical endpoints of the numerical range, as well as every integer between the two numerical endpoints. In this document, this is equivalent to directly listing each integer. For example, "t is an integer selected from 1 to 10" means that t is any integer selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. In addition, when multiple ranges are provided to describe a feature or characteristic, these ranges may be combined. In other words, unless otherwise specified, ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0034] Unless otherwise specified, the temperature parameters in this application allow for both constant temperature treatment and temperature fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows for temperature fluctuations within the accuracy range of instrument control. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.

[0035] In this application, when referring to percentage content, unless otherwise specified, for solid-liquid mixing and solid-solid mixing, it refers to mass percentage, and for liquid-liquid mixing, it refers to volume percentage.

[0036] In this application, references to percentage concentrations, unless otherwise specified, refer to final concentrations, which are the percentage of an added component in the system after the addition of that component.

[0037] In this application, %(w / w) and wt% both refer to weight percentage, %(v / v) refers to volume percentage, and %(w / v) refers to mass volume percentage.

[0038] The average equivalent particle size of the present invention can be measured by a laser particle size analyzer.

[0039] In a first aspect, the present application provides a conductive silver paste for solar cells. In one embodiment, the conductive silver paste includes silver powder, glass powder, a carrier, an additive, and a solvent;

[0040] The silver powder includes a first silver powder particle and a second silver powder particle; the first silver powder particle is in a flake shape, and along the thickness direction, the first silver powder particle includes a first plane and a second plane relative to each other, and the average area of ​​the first plane is recorded as S1, in μm 2 The average area of ​​the second plane is recorded as S2, and the unit is μm 2The second silver powder particles are spherical, and the average equivalent particle size of the second silver powder particles is recorded as D, in μm; the S1, S2 and D satisfy: 0.8D≤S1≤2D, 0.8D≤S2≤2D;

[0041] The glass powder includes the following components in molar percentages:

[0042] Na2CO33%~10%;

[0043] Al2O30.2%~1%;

[0044] SiO21%~5%;

[0045] ZnO1%~5%;

[0046] TeO230%~50%;

[0047] WO30.1%~2%;

[0048] Pb3O420%~40%;

[0049] Bi2O35%~10%;

[0050] Li2CO310%~20%;

[0051] B2O31%~5%;

[0052] Fe2O30.05%~0.5%;

[0053] CuO0.05%~1.5%.

[0054] Silver powder is the conductive functional phase in the conductive silver paste, which directly affects the conductive performance. The present application uses a first silver powder and a second silver powder with a specific morphology in combination, and uses a specific glass powder formula. Among them, the Pb, W, Zn, Te, and Li elements in the glass powder can reduce the softening temperature of the glass powder. The glass powder melts and releases heat, which can reduce the sintering temperature of the above-mentioned silver powder. When sintered at a lower temperature, there is a large amount of point-to-surface contact between the first silver powder and the second silver powder. After sintering, the contact resistance and grid line resistance can be effectively reduced. The above-mentioned conductive silver paste can be used as a front silver paste in crystalline silicon solar cells, which can form a good ohmic contact with the silicon substrate, form good conductivity, effectively reduce the contact resistance and grid line resistance, and increase the current. At the same time, the matched conductive paste can meet the printing requirements of fine grid printing screens, and can prepare grid electrodes with a high aspect ratio, which is suitable for the preparation of fine grids. At the same time, it can also save the use of silver and reduce costs.

[0055] The first silver powder particles are in the form of flakes, and the contact between the particles is a mixed mode of surface contact, line contact, and point contact. The contact area in the conductive network is sufficient, and the contact resistance and grid line resistance can be very low, thus achieving excellent conductive performance. At the same time, the flake silver powder can reduce the amount of the second spherical silver powder particles used in combination. While ensuring conductivity, the amount of silver powder used in the production process can be effectively reduced, thereby reducing costs. However, a major problem faced by the use of flake silver powder is that it is difficult to adapt to the printing requirements of fine grid screens. The present application overcomes this problem by controlling S1, S2, and D to form a conductive silver paste that can be used to print and form fine grid lines.

[0056] Optionally, the S1 is at 0.8 μm 2 ~2μm 2 For example, the S1 is 0.8 μm 2 , 1μm 2 , 1.2μm 2 , 1.4μm 2 , 1.6μm 2 , 1.8μm 2 , 2μm 2 .

[0057] Optionally, the circularity of the first plane is in the range of 0.5 to 1. For example, the circularity of the first plane is 0.5, 0.6, 0.7, 0.8, 0.9, or 1. The circularity of the first plane refers to the degree of closeness between the orthographic projection of the first plane of the particle and a circle, and can be expressed as follows: e1 = (4π × orthographic projection area) / (perimeter × perimeter), where e1 is the circularity of the first plane. When e1 = 1, the first plane of the particle is a circle, and the smaller e, the greater the difference between the first plane and the circle.

[0058] Optionally, the first plane has a plurality of straight edges, and two adjacent straight edges are smoothly connected. The two adjacent straight edges are smoothly connected to form a chamfer.

[0059] Optionally, the first planes with three straight edges account for 5% to 10% of the total number of first planes of the first silver powder particles. For example, the first planes with three straight edges account for 5%, 6%, 7%, 8%, 9%, and 10% of the total number of first planes of the first silver powder particles. A higher number of particles with triangular chamfered corners contributes to lower resistance and better conductivity in the paste line.

[0060] Optionally, the S2 is at 0.8 μm 2 ~2μm 2 For example, the S2 is 0.8 μm 2 , 1μm 2 , 1.2μm 2 , 1.4μm 2 , 1.6μm2 , 1.8μm 2 , 2μm 2 .

[0061] Optionally, the circularity of the second plane is in the range of 0.5 to 1. For example, the circularity of the second plane is 0.5, 0.6, 0.7, 0.8, 0.9, or 1. The circularity of the second plane refers to how closely the orthographic projection of the second plane of the particle approaches a circle, and can be expressed as follows: e² = (4π × orthographic projection area) / (perimeter × perimeter), where e² is the circularity of the first plane. When e² = 1, the second plane of the particle is circular. The smaller e, the greater the difference between the first plane and the circle.

[0062] Optionally, the second plane has a plurality of straight edges, and two adjacent straight edges are smoothly connected. The two adjacent straight edges are smoothly connected to form a chamfer.

[0063] Optionally, the second planes with three straight edges account for 5% to 10% of the total number of second planes of the first silver powder particles. For example, the second planes with three straight edges account for 5%, 6%, 7%, 8%, 9%, and 10% of the total number of second planes of the first silver powder particles. A higher number of particles with triangular chamfered corners contributes to lower resistance and better conductivity in the paste line.

[0064] Optionally, the first silver powder particles have an average equivalent particle size of 0.5 μm to 1.6 μm. For example, the first silver powder particles have an average equivalent particle size of 0.5 μm, 0.7 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, or 1.6 μm. Compared to typical flaky particles with a particle size of 2 μm or more, the first silver powder has a smaller particle size.

[0065] Optionally, D is in the range of 0.4 μm to 1 μm, for example, D is 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm.

[0066] Optionally, the sphericity of the second silver powder particles is 60% to 80%, for example, the sphericity of the second silver powder particles is 60%, 70%, or 80%.

[0067] Optionally, the specific surface area of ​​the second silver powder is in the range of 0.6 g / mL to 0.9 g / mL. For example, the specific surface area of ​​the second silver powder is 0.6 g / mL, 0.7 g / mL, 0.8 g / mL, or 0.9 g / mL.

[0068] The first silver powder and the second silver powder can be commercially available.

[0069] Optionally, the mass ratio of the first silver powder particles to the second silver powder particles is 1:(1.5-5). For example, the mass ratio of the first silver powder particles to the second silver powder particles is 1:1.5, 1:2, 1:3, 1:4, or 1:5.

[0070] Optionally, the melting point of the first silver powder particles is higher than the melting point of the second silver powder particles.

[0071] Optionally, the silver powder accounts for 86% to 96% by weight of the conductive silver paste, for example, 86%, 90%, 91%, 93%, or 96% by weight of the conductive silver paste.

[0072] At the same time, when the above-mentioned silver powder is combined with specific glass powder, the conductive silver paste can effectively reduce the contact resistance and gate line resistance.

[0073] In the glass powder, the molar percentage of Na2CO3 includes but is not limited to 3%, 5%, 7%, 9%, and 10%; the molar percentage of Al2O3 includes but is not limited to 0.2%, 0.5%, and 1%; the molar percentage of SiO2 includes but is not limited to 1%, 3%, and 5%; the molar percentage of ZnO includes but is not limited to 1%, 3%, and 5%; the molar percentage of TeO2 includes but is not limited to 30%, 40%, and 50%; the molar percentage of WO3 includes but is not limited to 0.1%, 0.5%, 1%, and 2%; the molar percentage of Pb3O4 includes but is not limited to 20%, 30%, and 40%; the molar percentage of Bi2O3 includes but is not limited to 5%, 8%, and 10%; the molar percentage of Li2CO3 includes but is not limited to 10%, 15%, and 20%; the molar percentage of B2O3 includes but is not limited to 1%, 3%, and 5%; the molar percentage of Fe2O3 includes but is not limited to 0.05%, 0.1%, 0.3%, and 0.5%; and the molar percentage of CuO includes but is not limited to 0.05%, 1%, 0.5%, 1%, and 1.5%.

[0074] Optionally, the glass powder accounts for 1% to 3% by mass in the conductive silver paste. For example, the glass powder accounts for 1%, 2%, or 3% by mass in the conductive silver paste.

[0075] Optionally, the carrier is selected from one or more of dibutyl phthalate, dimethyl oxalate and hydrogenated rosin pentaerythritol ester.

[0076] Optionally, the carrier accounts for 1% to 5% by weight of the conductive silver paste. For example, the carrier accounts for 1%, 3%, or 5% by weight of the conductive silver paste.

[0077] Optionally, the additive is selected from one or more of ethyl cellulose, hydrogenated castor oil, polyamide wax, polyvinyl alcohol and metal soap.

[0078] Optionally, the additive accounts for 1.5% to 6% by weight of the conductive silver paste. For example, the additive accounts for 1.5%, 2%, 3%, 4%, or 6% by weight of the conductive silver paste.

[0079] Optionally, the solvent is selected from one or more of dodecyl alcohol ester, hexadecanol ester, diethylene glycol butyl ether acetate, tripropylene glycol butyl ether, diethylene glycol monobutyl ether and diethylene glycol dibutyl ether.

[0080] Optionally, the mass proportion of the solvent in the conductive silver paste is 0.5% to 1.5%, for example, the mass proportion of the solvent in the conductive silver paste is 0.5%, 1%, or 1.5%.

[0081] A second aspect of the present application provides a solar cell, comprising a gate electrode, wherein the gate electrode is prepared from the above-mentioned conductive silver paste.

[0082] The following is further described in conjunction with specific examples and comparative examples. Unless otherwise specified, the raw materials involved in the following specific examples and comparative examples can be sourced from commercial sources. The instruments used can be sourced from commercial sources unless otherwise specified. The processes involved can be selected conventionally by those skilled in the art unless otherwise specified.

[0083] The first silver powder is FD-3, purchased from Jiangxi Beiteli New Materials Co., Ltd., and the second silver powder is 814B, purchased from Shenzhen Ha Shen Zhi Cai Co., Ltd. The first silver powder and the second silver powder are mixed in a mass ratio of 1:5. The SEM image of the mixed powder is as follows: Figure 1 As shown. Figure 1 It can be seen that the first silver powder particles 11 are in the form of flakes. Along the thickness direction, each first silver powder particle includes a first plane and a second plane. The average area of ​​the first plane is recorded as S1, in μm. 2 The average area of ​​the second plane is recorded as S2, and the unit is μm 2 , S1 at 1.2μm 2 The circularity of the first plane is in the range of 0.5 to 1, and it has multiple straight edges, two adjacent straight edges are smoothly connected, and the number of straight edges of the first plane is 3, which accounts for 5% to 10% of the total number of first planes of the first silver powder particles. S2 is 1.2 μm. 2The second plane has a circularity of about 0.5 to 1, multiple straight edges, and two adjacent straight edges are smoothly connected. The second planes with three straight edges account for 5% to 10% of the total number of second planes of the first silver powder particles. The second silver powder particles are spherical, and the average equivalent particle size of the second silver powder particles is D, which is approximately 1.2 μm.

[0084] The third silver powder is 708B, purchased from Shenzhen Ha Shen Zhi Cai Co., Ltd. The third silver powder is mixed with the second silver powder at a mass ratio of 1:5. The SEM image of the mixed powder is as follows: Figure 2 As shown. Figure 2 It can be seen that the third silver powder 13 is in the form of flakes. Along the thickness direction, each third silver powder particle includes an average area relative to the first plane and the second plane, and the average area of ​​the first plane is recorded as S1, in μm. 2 The average area of ​​the second plane is recorded as S2, and the unit is μm 2 , S1 at 5μm 2 Around, S2 at 5μm 2 about.

[0085] Example 1

[0086] This embodiment provides a conductive silver paste, which is prepared by mixing a first silver powder, a second silver powder, a glass powder, dibutyl phthalate (carrier), dodecyl alcohol ester (solvent), and ethyl cellulose (additive) in the mass ratio shown in Table 1, and stirring the mixture to obtain a conductive silver paste. The glass powder is prepared by mixing the components in the amounts and molar percentages shown in Table 2.

[0087] Example 2

[0088] This embodiment provides a conductive silver paste, the preparation method of which is as follows: according to the mass ratio shown in Table 1, a first silver powder, a second silver powder, a glass powder, dimethyl oxalate (carrier), hexadecanol ester (solvent) and hydrogenated castor oil (additive) are mixed and stirred uniformly to obtain a conductive silver paste, wherein the preparation method of the glass powder is the same as that of Example 1.

[0089] Example 3

[0090] This embodiment provides a conductive silver paste, the preparation method of which is as follows: according to the mass ratio shown in Table 1, a first silver powder, a second silver powder, a glass powder, hydrogenated rosin pentaerythritol ester (carrier), diethylene glycol butyl ether acetate (solvent) and a polyamide wax (additive) are mixed and stirred uniformly to obtain a conductive silver paste, wherein the preparation method of the glass powder is the same as that of Example 1.

[0091] Example 4

[0092] This embodiment provides a conductive silver paste, the preparation method of which is as follows: according to the mass ratio shown in Table 1, a first silver powder, a second silver powder, a glass powder, dibutyl phthalate (carrier), tripropylene glycol butyl ether (solvent) and polyvinyl alcohol (additive) are mixed and stirred uniformly to obtain a conductive silver paste, wherein the preparation method of the glass powder is the same as that of Example 1.

[0093] Example 5

[0094] This embodiment provides a conductive silver paste, the preparation method of which is as follows: according to the mass ratio shown in Table 1, a first silver powder, a second silver powder, a glass powder, dibutyl phthalate (carrier), diethylene glycol monobutyl ether (solvent) and a metal soap (additive) are mixed and stirred uniformly to obtain a conductive silver paste, wherein the preparation method of the glass powder is the same as that of Example 1.

[0095] Example 6

[0096] This embodiment provides a conductive silver paste, which is prepared by mixing a first silver powder, a second silver powder, a glass powder, dibutyl phthalate (carrier), dodecyl alcohol ester (solvent), and ethyl cellulose (additive) in the mass ratio shown in Table 1, and stirring the mixture to obtain a conductive silver paste. The glass powder is prepared by mixing the components in the amounts and molar percentages shown in Table 2.

[0097] Example 7

[0098] This embodiment provides a conductive silver paste, which is prepared by mixing a first silver powder, a second silver powder, a glass powder, dibutyl phthalate (carrier), dodecyl alcohol ester (solvent), and ethyl cellulose (additive) in the mass ratio shown in Table 1, and stirring the mixture to obtain a conductive silver paste. The glass powder is prepared by mixing the components in the amounts and molar percentages shown in Table 2.

[0099] Example 8

[0100] This embodiment provides a conductive silver paste, which is prepared by mixing a first silver powder, a second silver powder, a glass powder, dibutyl phthalate (carrier), dodecyl alcohol ester (solvent), and ethyl cellulose (additive) in the mass ratio shown in Table 1, and stirring the mixture to obtain a conductive silver paste. The glass powder is prepared by mixing the components in the amounts and molar percentages shown in Table 2.

[0101] Example 9

[0102] This embodiment provides a conductive silver paste, which is prepared by mixing a first silver powder, a second silver powder, a glass powder, dibutyl phthalate (carrier), dodecyl alcohol ester (solvent), and ethyl cellulose (additive) in the mass ratio shown in Table 1, and stirring the mixture to obtain a conductive silver paste. The glass powder is prepared by mixing the components in the amounts and molar percentages shown in Table 2.

[0103] Comparative Example 1

[0104] This comparative example provides a conductive silver paste, the preparation method of which is as follows: according to the mass ratio shown in Table 1, the third silver powder, the second silver powder, the glass powder, dibutyl phthalate (carrier), dodecyl alcohol ester (solvent) and ethyl cellulose (additive) are mixed and stirred uniformly to obtain a conductive silver paste, wherein the preparation method of the glass powder is the same as that in Example 1.

[0105] Comparative Example 2

[0106] This comparative example provides a conductive silver paste, the preparation method of which is as follows: according to the mass ratio shown in Table 1, a first silver powder, a second silver powder, a glass powder, dibutyl phthalate (carrier), dodecyl alcohol ester (solvent) and ethyl cellulose (additive) are mixed and stirred uniformly to obtain a conductive silver paste, wherein the glass powder is prepared by mixing the components according to the components and their molar percentages shown in Table 2.

[0107] The formulas of the conductive silver pastes of the embodiments and comparative examples are summarized in Table 1.

[0108] Table 1

[0109]

[0110] Table 2

[0111]

[0112] test

[0113] The conductive silver paste of each embodiment and comparative example was printed onto the battery substrate and subjected to the same sintering conditions to form a gate electrode with the same circuit. The aspect ratio of the gate electrode is shown in Table 3. The conductivity of the gate electrode was tested by a TLM contact resistance tester, and the results are shown in Table 3.

[0114] Table 3

[0115]

[0116] It can be seen from the above table that in Examples 1 to 9, when the first silver powder, the second silver powder, the glass powder and other reagents are added to the conductive silver paste, the gate electrode prepared by printing can have a higher aspect ratio, can meet the printing requirements of fine grids, and at the same time has a low line resistance, providing good conductivity.

[0117] Comparison between Comparative Example 1 and Example 5 shows that the combination of the first silver powder and the second silver powder is more conducive to preparing a gate electrode with a high aspect ratio and a lower resistance of the gate electrode, indicating that the morphology of the silver powder affects the conductivity and processability of the conductive silver paste.

[0118] A comparison of Comparative Example 2 and Example 5 shows that the composition of the glass frit affects the conductivity and processability of the conductive silver paste. By combining glass frit with the first and second silver powders in a specific ratio and composition, the conductivity of the conductive silver paste is improved, and a gate electrode with a higher aspect ratio is obtained.

[0119] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0120] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A conductive silver paste for solar cells, characterized in that: Including silver powder, glass powder, carrier, additives and solvent; The silver powder includes a first silver powder particle and a second silver powder particle; the first silver powder particle is in a flake shape, and along the thickness direction, the first silver powder particle includes a first plane and a second plane relative to each other, and the average area of ​​the first plane is recorded as S1, and the unit is μm 2 The average area of ​​the second plane is recorded as S2, and the unit is μm 2 The second silver powder particles are spherical, and the average equivalent particle size of the second silver powder particles is recorded as D, in μm; the S1, S2 and D satisfy: 0.8D≤S1≤2D, 0.8D≤S2≤2D, the S1 is 0.8μm 2 ~2μm 2 range, the S2 is at 0.8μm 2 ~2μm 2 In the range, D is in the range of 0.4 μm to 1 μm; The mass ratio of the first silver powder particles to the second silver powder particles is 1:(1.5-5); The glass powder includes the following components in molar percentages: Na2CO3 3%~10%; Al2O3 0.2%~1%; SiO2 1%~5%; ZnO 1%~5%; TeO2 30%~50%; WO3 0.1%~2%; Pb3O4 20%~40%; Bi2O3 5%~10%; Li2CO3 10%~20%; B2O3 1%~5%; Fe2O3 0.05%~0.5%; CuO 0.05%~1.5%.

2. The conductive silver paste for solar cells according to claim 1, wherein: The circularity of the first plane is in the range of 0.5 to 1.

3. The conductive silver paste for solar cells according to claim 1, wherein: The circularity of the second plane is in the range of 0.5 to 1.

4. The conductive silver paste for solar cells according to claim 3, wherein: Include at least one of the following features: (1) The first plane has a plurality of straight edges, and two adjacent straight edges are smoothly connected; (2) The second plane has multiple straight edges, and two adjacent straight edges are smoothly connected.

5. The conductive silver paste for solar cells according to claim 4, characterized in that: Include at least one of the following features: (1) The first plane having three straight edges accounts for 5% to 10% of the total number of first planes of the first silver powder particles; (2) The second planes having three straight edges account for 5% to 10% of the total number of the second planes of the first silver powder particles.

6. The conductive silver paste for solar cells according to claim 1, wherein: The sphericity of the second silver powder particles is 60% to 80%.

7. The conductive silver paste for solar cells according to claim 1, wherein: The specific surface area of ​​the second silver powder is in the range of 0.6 g / mL to 0.9 g / mL.

8. The conductive silver paste for solar cells according to any one of claims 1 to 7, characterized in that The melting point of the first silver powder particles is higher than the melting point of the second silver powder particles.

9. The conductive silver paste for solar cells according to any one of claims 1 to 7, characterized in that: Include at least one of the following features: (1) The mass proportion of the silver powder in the conductive silver paste is 86% to 96%; (2) The mass proportion of the glass powder in the conductive silver paste is 1% to 3%; (3) The mass proportion of the carrier in the conductive silver paste is 1% to 5%; (4) The carrier is selected from one or more of dibutyl phthalate, dimethyl oxalate and hydrogenated rosin pentaerythritol ester; (5) The additive accounts for 1.5% to 6% by mass in the conductive silver paste; (6) The additive is selected from one or more of ethyl cellulose, hydrogenated castor oil, polyamide wax, polyvinyl alcohol and metal soap; (7) The mass proportion of the solvent in the conductive silver paste is 0.5% to 1.5%; (8) The solvent is selected from one or more of dodecyl alcohol ester, hexadecanol ester, diethylene glycol butyl ether acetate, tripropylene glycol butyl ether, diethylene glycol monobutyl ether and diethylene glycol dibutyl ether.

10. A solar cell, characterized in that: The invention comprises a gate electrode, wherein the gate electrode is prepared from the conductive silver paste for solar cells according to any one of claims 1 to 9.

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