HJT main gate conductive silver paste and preparation method thereof

Abstract

The invention provides HJT main gate conductive silver paste, and belongs to the technical field of HJT batteries. The total mass of the conductive silver paste is 100%, the conductive silver paste comprises the following components: 70-75% of micron-scale spherical silver powder, 3-5% of nano-scale spherical silver powder, 3-5% of silver nanowires, 6-8% of thermosetting resin, 0.2-0.5% of a curing agent, 1-3% of a flexible prepolymer, and the balance of an organic solvent, the length of the silver nanowires is micron-scale, and the length of the flexible prepolymer is 1-3%. And the diameter of the silver nanowire is nanoscale. The main grid prepared from the conductive silver paste has excellent welding tension and conductivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of HJT batteries, and in particular relates to a HJT main grid conductive silver paste and a preparation method thereof. Background Art

[0002] The PN junction of the HJT cell is composed of two semiconductor materials: an N-type silicon wafer substrate (c-Si) and a doped amorphous silicon film (a-Si), so it is called a heterojunction cell. From the perspective of the cell structure, the HJT cell uses an N-type silicon wafer as a substrate. First, an intrinsic hydrogenated amorphous silicon (a-Si:H) film is deposited on the front and back surfaces as a passivation structure; then a P-type doped hydrogenated amorphous silicon layer is deposited on the front surface to form a PN junction with the silicon wafer substrate, and an N-type doped hydrogenated amorphous silicon layer is deposited on the back to form a high-low junction (N+ / N) structure with the silicon wafer substrate; due to the large contact resistance of hydrogenated amorphous silicon, a metal oxide layer needs to be prepared as a transparent conductive film (TCO layer) to promote carrier penetration and reduce reflection (ARC); finally, silver paste is printed on the TCO layer on the front and back surfaces through screen printing to form a main grid.

[0003] The main grid of the HJT battery is printed in steps to meet the battery's requirements for conductivity and welding tension. Step-by-step printing includes main grid and sub-grid. The main grid is mainly used to provide welding tension and collect current, while the sub-grid is mainly used to form a low contact resistance with the TCO layer to collect current.

[0004] The high-tensile-force HJT main-grid conductive silver paste in the prior art generally increases the welding tensile force by increasing the resin content or increasing the proportion of large-particle silver powder, but this results in a relatively high volume resistivity and poor conductivity. Therefore, it is necessary to design a HJT main-grid conductive silver paste and a preparation method thereof, which can take into account both excellent welding tensile force and conductive performance. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, an embodiment of the present invention provides a HJT main grid conductive silver paste and a preparation method thereof.

[0006] In the first aspect, an embodiment of the present invention provides a HJT main grid conductive silver paste. Taking the total mass of the conductive silver paste as 100%, the conductive silver paste includes the following components: 70-75% of micron-sized spherical silver powder, 3-5% of nano-sized spherical silver powder, 3-5% of silver nanowires, 6-8% of thermosetting resin, 0.2-0.5% of curing agent, 1-3% of flexible prepolymer, and the balance is organic solvent. The length of the silver nanowire is in the micron level, and the diameter of the silver nanowire is in the nanometer level.

[0007] The advantages and technical effects brought by the conductive silver paste of the embodiment of the present invention are as follows:

[0008] (1) The conductive silver paste of the embodiment of the present invention contains a flexible prepolymer. When the main grid is subsequently printed and prepared, the flexible prepolymer reacts with a curing agent to generate a flexible polymer, which can effectively improve the welding tension of the main grid.

[0009] (2) The conductive silver paste of the embodiment of the present invention contains micron-sized spherical silver powder and nano-sized spherical silver powder. The pores between the spherical silver powder can be reduced by particle size grading, thereby improving the conductive performance of the main grid.

[0010] (3) The conductive silver paste of the embodiment of the present invention contains silver nanowires, the length of the silver nanowires is in the micrometer level, and the diameter of the silver nanowires is in the nanometer level. The silver nanowires can play a series role between the spherical silver powders, build more conductive channels for the conductive silver paste, and improve the conductive performance of the main grid.

[0011] In some embodiments, the flexible prepolymer is polydimethylsiloxane and / or polyurethane-based thermoplastic elastomer.

[0012] In some embodiments, the curing agent is at least one of methylvinyl cyclosiloxane, a cationic curing agent, and an imidazole curing agent.

[0013] In some embodiments, the Dv50 of the micron-sized spherical silver powder is 5-20 μm.

[0014] In some embodiments, the Dv50 of the nano-sized spherical silver powder is 2-6 nm.

[0015] In some embodiments, the silver nanowires have a length of 5-50 μm.

[0016] In some embodiments, the silver nanowires have a diameter of 2-6 nm.

[0017] In a second aspect, an embodiment of the present invention provides a method for preparing a HJT main grid conductive silver paste, comprising the following steps:

[0018] S1. mixing the micron-sized spherical silver powder, the nano-sized spherical silver powder, the silver nanowires and the organic solvent to obtain a silver powder dispersion;

[0019] S2. mixing the thermosetting resin, the flexible prepolymer and the silver powder dispersion to obtain a silver powder resin dispersion;

[0020] S3. The curing agent and the silver powder resin dispersion are mixed to obtain a semi-finished conductive silver paste;

[0021] S4. Grind the semi-finished conductive silver paste and sieve it to obtain the conductive silver paste.

[0022] The advantages and technical effects brought by the preparation method of the embodiment of the present invention are:

[0023] (1) The preparation method of the embodiment of the present invention is simple to operate and is convenient for industrial promotion.

[0024] (2) The conductive silver paste obtained by the preparation method of the embodiment of the present invention can enable the subsequently prepared main grid to have both excellent welding tensile strength and conductive properties.

[0025] In some embodiments, steps S1-S3 are all mixed under magnetic stirring.

[0026] In some embodiments, the fineness of the conductive silver paste is less than or equal to 20 μm. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0028] In the first aspect, an embodiment of the present invention provides a HJT main grid conductive silver paste. Taking the total mass of the conductive silver paste as 100%, the conductive silver paste includes the following components: 70-75% of micron-sized spherical silver powder, 3-5% of nano-sized spherical silver powder, 3-5% of silver nanowires, 6-8% of thermosetting resin, 0.2-0.5% of curing agent, 1-3% of flexible prepolymer, and the balance is organic solvent. The length of the silver nanowire is in the micron level, and the diameter of the silver nanowire is in the nanometer level.

[0029] The conductive silver paste of the embodiment of the present invention contains a flexible prepolymer. When the flexible prepolymer reacts with the curing agent during the subsequent printing to prepare the main grid, a flexible polymer will be generated, which can effectively improve the welding tension of the main grid. The conductive silver paste of the embodiment of the present invention contains micron-sized spherical silver powder and nano-sized spherical silver powder. The pores between the spherical silver powders can be reduced through particle size grading, thereby improving the conductivity of the main grid. The conductive silver paste of the embodiment of the present invention contains silver nanowires. The length of the silver nanowires is micron-sized and the diameter of the silver nanowires is nanometer-sized. The silver nanowires can play a series role between the spherical silver powders, build more conductive channels for the conductive silver paste, and improve the conductivity of the main grid. Therefore, the conductive silver paste of the embodiment of the present invention can enable the main grid prepared by subsequent printing to have both excellent welding tension and conductivity.

[0030] In some embodiments, the flexible prepolymer is polydimethylsiloxane and / or polyurethane thermoplastic elastomer. The flexible prepolymer is liquid before curing, and can generate a flexible polymer after curing, and the flexible polymer can increase the welding tension of the main grid. The flexible prepolymers listed above have the advantages of flexibility, low modulus, and easy processing, which are convenient for subsequent printing and preparation of the main grid.

[0031] In some embodiments, the Dv50 of the micron-sized spherical silver powder is 5-20 μm, such as 5 μm, 10 μm, 15 μm, 20 μm, etc.

[0032] In some embodiments, the Dv50 of the nano-sized spherical silver powder is 2-6 nm, such as 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, etc.

[0033] In some embodiments, the length of the silver nanowire is 5-50 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc. When the length of the silver nanowire is too small, it is not conducive to play a good role in the construction of a conductive channel in series. When the length of the silver nanowire is too long, the silver nanowire may agglomerate, which is not conducive to improving the dispersibility of the conductive material in the conductive silver paste, and thus is not conducive to improving the conductive uniformity of the main grid.

[0034] In some embodiments, the diameter of the silver nanowire is 2-6 nm, such as 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, etc. When the diameter of the silver nanowire is too small, the cost of the silver nanowire is high, which is not conducive to reducing the production cost of the conductive silver paste. When the diameter of the silver nanowire is too large, it is not conducive to playing a good role in the series connection and building a conductive channel.

[0035] The conductive silver paste of the embodiment of the present invention has no particular restrictions on the type of thermosetting resin, and can be any thermosetting resin used for HJT main grid conductive silver paste in the prior art. For example, the thermosetting resin can be bisphenol epoxy resin and / or alicyclic epoxy resin.

[0036] In some embodiments, the curing agent is at least one of methylvinylcyclosiloxane, a cationic curing agent and an imidazole curing agent. The curing agents listed above can achieve rapid curing.

[0037] The conductive silver paste of the embodiment of the present invention has no particular restrictions on the type of organic solvent, and can be any organic solvent used for HJT main grid conductive silver paste in the prior art. For example, the organic solvent can be at least one of diethylene glycol butyl ether, terpineol, ethylene glycol phenyl ether, diethylene glycol diethyl ether and dimethyl adipate.

[0038] In a second aspect, an embodiment of the present invention provides a method for preparing a HJT main grid conductive silver paste, comprising the following steps:

[0039] S1. mixing the micron-sized spherical silver powder, the nano-sized spherical silver powder, the silver nanowires and the organic solvent to obtain a silver powder dispersion;

[0040] S2. mixing the thermosetting resin, the flexible prepolymer and the silver powder dispersion to obtain a silver powder resin dispersion;

[0041] S3. The curing agent and the silver powder resin dispersion are mixed to obtain a semi-finished conductive silver paste;

[0042] S4. Grind the semi-finished conductive silver paste and sieve it to obtain the conductive silver paste.

[0043] The preparation method of the embodiment of the present invention is simple to operate and is convenient for industrial promotion. The conductive silver paste obtained by the preparation method of the embodiment of the present invention can enable the main grid prepared by subsequent printing to have both excellent welding tension and conductive properties.

[0044] In some embodiments, steps S1-S3 are all mixed under magnetic stirring, which helps to mix the materials evenly to form a uniformly dispersed conductive slurry.

[0045] In some embodiments, the fineness of the conductive silver paste is less than or equal to 20 μm, such as 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, etc. The fineness of the conductive silver paste is less than or equal to 20 μm, which is conducive to improving the uniformity of the main grid obtained by subsequent printing.

[0046] The present invention is described in detail below with reference to embodiments.

[0047] Example 1

[0048] The invention discloses a HJT main grid conductive silver paste. The conductive silver paste comprises the following components, based on the total mass of the conductive silver paste being 100%, 70% of spherical silver powder with a Dv50 of 5 μm, 3% of nano-scale spherical silver powder with a Dv50 of 2 nm, 3% of silver nanowires, the length of the silver nanowires being 5 μm, the diameter of the silver nanowires being 2 nm, 6% of a thermosetting resin bisphenol A type epoxy resin, 0.2% of a curing agent (including 0.1% of methylvinylcyclosiloxane and 0.1% of 2-methylimidazole), 1% of a flexible prepolymer polydimethylsiloxane, and the balance being an organic solvent dimethyl adipate.

[0049] The preparation method of the conductive silver paste is as follows:

[0050] (1) Micron-sized spherical silver powder, nano-sized spherical silver powder, silver nanowires and an organic solvent are stirred and mixed at 500 rpm to obtain a silver powder dispersion.

[0051] (2) The thermosetting resin, the flexible prepolymer and the silver powder dispersion are stirred and mixed at 500 rpm to obtain a silver powder resin dispersion.

[0052] (3) The curing agent and the silver powder resin dispersion are stirred and mixed at 500 rpm to obtain a semi-finished conductive silver paste.

[0053] (4) Grinding the semi-finished conductive silver paste for 6 times and then sieving to obtain a conductive silver paste, wherein the fineness of the conductive silver paste is less than or equal to 20 μm.

[0054] Example 2

[0055] The invention discloses a HJT main grid conductive silver paste. The conductive silver paste comprises the following components, based on the total mass of the conductive silver paste being 100%, 75% of spherical silver powder with a Dv50 of 20 μm, 3% of nano-scale spherical silver powder with a Dv50 of 6 nm, 5% of silver nanowires, the length of the silver nanowires being 5 μm, the diameter of the silver nanowires being 2 nm, 8% of a thermosetting resin bisphenol A type epoxy resin, 0.5% of a curing agent (including 0.2% of methylvinylcyclosiloxane and 0.3% of 2-methylimidazole), 3% of a flexible prepolymer polydimethylsiloxane, and the balance being an organic solvent dimethyl adipate.

[0056] The preparation method of the conductive silver paste of this embodiment is the same as that of embodiment 1.

[0057] Example 3

[0058] The invention discloses a HJT main grid conductive silver paste. The conductive silver paste comprises the following components, based on the total mass of the conductive silver paste being 100%, 72% of spherical silver powder with a Dv50 of 15 μm, 4% of nano-scale spherical silver powder with a Dv50 of 4 nm, 3% of silver nanowires, the length of the silver nanowires being 5 μm, the diameter of the silver nanowires being 2 nm, 8% of a thermosetting resin bisphenol A type epoxy resin, 0.5% of a curing agent (including 0.2% of methylvinylcyclosiloxane and 0.3% of 2-methylimidazole), 3% of a flexible prepolymer polydimethylsiloxane, and the balance being an organic solvent dimethyl adipate.

[0059] The preparation method of the conductive silver paste of this embodiment is the same as that of embodiment 1.

[0060] Example 4

[0061] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of embodiment 3, except that the conductive silver paste of this embodiment contains 4% silver nanowires.

[0062] Example 5

[0063] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of embodiment 3, except that the conductive silver paste of this embodiment contains 5% silver nanowires.

[0064] Example 6

[0065] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of Embodiment 3, except that in the conductive silver paste of this embodiment, the length of the silver nanowires is 10 μm.

[0066] Example 7

[0067] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of Embodiment 3, except that in the conductive silver paste of this embodiment, the length of the silver nanowires is 15 μm.

[0068] Example 8

[0069] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of Embodiment 3, except that in the conductive silver paste of this embodiment, the length of the silver nanowires is 20 μm.

[0070] Example 9

[0071] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of Embodiment 3, except that in the conductive silver paste of this embodiment, the length of the silver nanowires is 50 μm.

[0072] Example 10

[0073] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of Embodiment 3, except that in the conductive silver paste of this embodiment, the diameter of the silver nanowires is 4 μm.

[0074] Embodiment 11

[0075] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of Embodiment 3, except that in the conductive silver paste of this embodiment, the diameter of the silver nanowires is 6 μm.

[0076] Example 12

[0077] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of Embodiment 3, except that, in the conductive silver paste of this embodiment, the content of the flexible prepolymer polydimethylsiloxane is 1%.

[0078] Embodiment 13

[0079] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of Embodiment 3, except that, in the conductive silver paste of this embodiment, the content of the flexible prepolymer polydimethylsiloxane is 2%.

[0080] Embodiment 14

[0081] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of Embodiment 3, except that, in the conductive silver paste of this embodiment, the flexible prepolymer is a polyurethane thermoplastic elastomer.

[0082] Comparative Example 1

[0083] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of embodiment 3, except that the conductive silver paste of this embodiment does not contain silver nanowires, and the content of spherical silver powder with a Dv50 of 15 μm is 75%.

[0084] Comparative Example 2

[0085] The conductive silver paste and the preparation method thereof of this embodiment are the same as those of embodiment 3, except that the conductive silver paste of this embodiment does not contain the flexible prepolymer polydimethylsiloxane, and the content of the thermosetting resin bisphenol A epoxy resin is 11%.

[0086] The conductive silver paste prepared in each embodiment and comparative example was printed on the TCO layer of the semi-finished HJT battery, dried at 140°C, and then cured and sintered at 200°C for 30 minutes to obtain the HJT battery. The volume resistivity of the main grid was tested, and the sample to be tested was pulled off at a constant speed of 180° using a universal material testing machine to test the average tensile force. The results are shown in Table 1.

[0087] Table 1. Welding tension and volume resistivity of the main grid of each embodiment and comparative example

[0088]

[0089]

[0090] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0091] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A HJT main grid conductive silver paste, characterized in that: Taking the total mass of the conductive silver paste as 100%, the conductive silver paste comprises the following components: 70-75% of micron-sized spherical silver powder, 3-5% of nano-sized spherical silver powder, 3-5% of silver nanowires, 6-8% of thermosetting resin, 0.2-0.5% of curing agent, 1-3% of flexible prepolymer, and the balance being organic solvent. The length of the silver nanowires is in the micron level, and the diameter of the silver nanowires is in the nanometer level.

2. The HJT main grid conductive silver paste according to claim 1, characterized in that: The flexible prepolymer is polydimethylsiloxane and / or polyurethane thermoplastic elastomer.

3. The HJT main grid conductive silver paste according to claim 1 or 2, characterized in that: The curing agent is at least one of methylvinyl cyclosiloxane, a cationic curing agent and an imidazole curing agent.

4. The HJT main grid conductive silver paste according to claim 1 or 2, characterized in that: The Dv50 of the micron-sized spherical silver powder is 5-20 μm.

5. The HJT main grid conductive silver paste according to claim 1 or 2, characterized in that: The Dv50 of the nano-scale spherical silver powder is 2-6 nm.

6. The HJT main grid conductive silver paste according to claim 1 or 2, characterized in that: The length of the silver nanowire is 5-50 μm.

7. The HJT main grid conductive silver paste according to claim 1 or 2, characterized in that: The diameter of the silver nanowire is 2-6 nm.

8. The method for preparing HJT main grid conductive silver paste according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. mixing the micron-sized spherical silver powder, the nano-sized spherical silver powder, the silver nanowires and the organic solvent to obtain a silver powder dispersion; S2. mixing the thermosetting resin, the flexible prepolymer and the silver powder dispersion to obtain a silver powder resin dispersion; S3. The curing agent and the silver powder resin dispersion are mixed to obtain a semi-finished conductive silver paste; S4. Grind the semi-finished conductive silver paste and sieve it to obtain the conductive silver paste.

9. The preparation method according to claim 8, characterized in that: Steps S1-S3 are all mixed under magnetic stirring.

10. The preparation method according to claim 8, characterized in that: In step S4, the fineness of the conductive silver paste is less than or equal to 20 μm.

Images