CN116052923A

CN116052923A - Low-temperature slurry and heterojunction battery

Info

Publication number: CN116052923A
Application number: CN202211731942.8A
Authority: CN
Inventors: 洪玮; 汪山; 张林佳; 周欣山
Original assignee: Suzhou Jingyin New Material Technology Co ltd
Current assignee: Suzhou Jingyin New Material Technology Co ltd
Priority date: 2022-12-30
Filing date: 2022-12-30
Publication date: 2023-05-02

Abstract

The invention provides low-temperature slurry and a heterojunction battery. The conductive powder comprises a first metal powder and a second metal powder in a weight ratio of 20:80-70:30; the first metal powder is spherical powder, the average grain diameter is 1-3 mu m, and the tap density is more than 4.5 g/cc; the second metal powder is spherical powder with an average particle diameter of 0.1-1.5 μm and a tap density of more than 3.5 g/cc; the first metal powder and the second metal powder are subjected to surface treatment of an antioxidant. The low-temperature slurry comprises the conductive powder, thermosetting resin, a coupling agent, a curing agent, a solvent and an ion accelerator. The invention also provides a heterojunction battery with the raw material comprising the low-temperature slurry. The low-temperature slurry has low resistivity and good adhesion, is suitable for the production process of heterojunction batteries with fine-line printing and small-size texturing pyramids, and can effectively improve the electrical performance of the heterojunction batteries.

Description

Low-temperature slurry and heterojunction battery

Technical Field

The invention relates to the technical field of battery slurry manufacturing, in particular to a low-temperature slurry and a heterojunction battery.

Background

Under the current situation that the heterojunction battery has high metallization cost, the cost reduction requirement of the production end is increasingly strong. The thin-line printing is a necessary path for reducing the cost of the photovoltaic printing. The existing battery silver paste adopts flake silver powder in the paste, and the average granularity is controlled to be 3-5 mu m. At present, screen printing plates with openings of 28-35 microns and screen cloth with openings of 430 meshes are commonly adopted for low-temperature slurry printing, and screen printing plates with openings of 14-16 microns and screen cloth with openings of 520 meshes are used on PERC slurry in batches. However, the low-temperature slurry using the flake powder as a filler has poor matching property on fine line printing due to poor rolling property and screening property of the flake powder in the low-temperature slurry, and the probability of false printing and grid breakage is greatly increased.

Because of the need for heterojunction cell efficiency, the demand for light trapping is also increasing, so the size of the pyramid is reduced from 3-5 μm to 1-3 μm at present in the texturing. For the 1-3 mu m wool making pyramid, the 3-5 mu m flake silver powder is adopted to have a high probability of not filling the bottoms of the pyramids well, the flake silver powder is likely to be erected at the top ends of the two pyramids like a bridge, so that the bottom of the pyramid is not filled with the silver powder, the contact resistance is greatly increased, and finally the photoelectric conversion efficiency is reduced.

Disclosure of Invention

In order to solve the above problems, an object of the present invention is to provide a low temperature paste and a heterojunction battery. The low-temperature slurry provided by the invention has low resistivity and good adhesiveness after solidification, is suitable for the production process of heterojunction batteries with fine-line printing and small-size texturing pyramids, and can improve the electrical performance of the heterojunction batteries while reducing the cost.

In order to achieve the above object, the present invention provides a conductive powder comprising a first metal powder and a second metal powder in a weight ratio of 20:80 to 70:30; the first metal powder is spherical powder, the average particle size of the first metal powder is 1-3 mu m, and the tap density is more than 4.5 g/cc; the second metal powder is spherical powder, and the average particle size of the second metal powder is 0.1-1.5 mu m, and the tap density is more than 3.5 g/cc; the first metal powder is subjected to antioxidant surface treatment; the second metal powder is the second metal powder subjected to antioxidant surface treatment.

The conductive powder provided by the invention is global metal powder, has small particle size, can be matched with ultra-narrow opening screen printing plates with industrial openings below 20 mu m for batch screen printing, and solves the problems of large slurry consumption, high cost and filling and contact of the current texture-making small pyramid in the production process of heterojunction batteries.

In the above-mentioned conductive powder, if the spherical powder having a large particle diameter is too much, although the conductivity is improved, it causes a decrease in paste printability and also adversely affects the adhesiveness to the cured product; if the small particle size spherical powder is too much, although printability is improved, it may cause an increase in paste viscosity and resistivity, ultimately affecting the electrical properties of the battery. According to the invention, the slurry with higher conductivity and higher printability can be obtained by controlling the weight ratio of the first metal powder to the second metal powder subjected to the antioxidant surface treatment to be 20:80-70:30. Further, the weight ratio of the first metal powder to the second metal powder can be controlled to be 25:75-70:30, 30:70-60:40.

According to an embodiment of the present invention, the D10 particle size of the above-mentioned conductive powder is generally 0.3 to 0.9. Mu.m, further controllable to 0.5 to 0.8. Mu.m.

According to a specific embodiment of the present invention, the D50 particle size of the conductive powder of the above conductive powder is 1.2 to 3.0. Mu.m, further controllable to 1.3 to 2.0. Mu.m.

According to a specific embodiment of the present invention, the above-mentioned conductive powder has a D90 particle diameter of 2.5 to 6. Mu.m, further controllable to 3 to 4. Mu.m.

In the conductive powder, the antioxidant is used for carrying out surface treatment on the first metal powder and the second metal powder, so that not only can the oxidation of the metal powder be inhibited, but also the capability of passivating the valence-changing ions can be realized, thereby inhibiting the migration of the metal ions and prolonging the service life of the heterojunction battery assembly. The antioxidant comprises one or more of 2, 2-methylenebis (4-methyl-6-tert-butylphenol), 2, 6-di-tert-butyl-p-cresol, 1, 3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene, N '-hexamethylenebis-3 (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide, 2' -methylenebis (4-methyl-6-tert-butylphenol), 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxyphenyl) isocyanate, 4-hydroxydodecanoyl anilide, tris (nonylphenyl) phosphite, tris (2, 4-di-tert-butylphenyl) phosphite and dioctadecyl pentaerythritol diphosphite.

In a specific embodiment of the present invention, the surface treatment method may employ a chemical treatment method, specifically including: dispersing untreated first metal powder or second metal powder in a surface treatment liquid, and drying to obtain first metal powder with antioxidant coated on the surface or second metal powder with antioxidant coated on the surface; wherein the surface treatment liquid contains an antioxidant. The antioxidant is used for coating the surfaces of the first metal powder and the second metal powder, so that the surface modification of the first metal powder and the second metal powder can be realized.

In the above surface treatment method, the mass ratio of the above untreated first metal powder to the antioxidant is generally controlled to be (5-21): (14-83), the mass ratio of the untreated second metal powder to the antioxidant is generally (5-21): (14-83). In some embodiments, the dispersing mode may be ultrasonic, and the ultrasonic dispersing time may be controlled to be 20-60min. The drying conditions can be specifically as follows: vacuum drying for 1-2h at 60-90deg.C.

In the antioxidant solution, the mass ratio of the antioxidant to the surface treatment liquid can be controlled to be (14-83): 100. the solvent used for the surface treatment liquid may include one or a combination of two or more of acetone, ethyl acetate, butyl acetate, ethanol, isopropanol, and the like. Further, the surface treatment liquid may further include a coupling agent, which may include one or a combination of two or more of aminopropyl triethoxysilane, aminopropyl trimethoxysilane, glycidol-mazoxypropyl trimethoxysilane, n-octyl triethoxysilane, vinyl-tris (2-methoxyethoxy) silane, isopropyl trioleate acyloxy titanate, isopropyl tris (dodecylbenzenesulfonyloxy) titanate, isopropyl tris (dioctyl pyrophosphoyloxy) titanate, bis (dioctyl pyrophosphoyloxy) ethylene titanate, isopropyl tristearate titanate, isopropyl distearoyl oxyaluminate, and the like.

In the above conductive powder, the first metal powder and the second metal powder may each independently include one or a combination of two or more of silver powder, copper powder, silver-coated nickel powder, and silver-coated aluminum powder. Further, the first metal powder may be silver-coated copper powder, and the second metal powder may be one of copper powder, silver powder, or silver-coated copper powder.

The invention also provides low-temperature slurry, which comprises the following raw materials in parts by weight: 3-8 parts of thermosetting resin, 1-2 parts of coupling agent, 0.1-0.3 part of curing agent, 3-6 parts of solvent and 0.02-0.2 part of ion accelerator; wherein the conductive powder comprises 20-70 parts of the first metal powder (surface-treated) and 30-80 parts of the second metal powder (surface-treated).

In the above-described low-temperature paste, the use of the global-shaped metal powder as the conductive powder can reduce the size of the conductive powder, but also results in an increase in the resistivity of the low-temperature paste, compared to the use of the flake powder in the existing low-temperature paste. In contrast, the invention further adds a certain ion accelerator into the low-temperature slurry, and reduces the contact resistance of the slurry in cooperation with the conductive powder. After the resin in the low-temperature slurry is solidified, the ion accelerator can carry out electron transmission, and the resistivity of the resin is greatly reduced, so that the resistivity of the whole low-temperature slurry is reduced. Further, the reduction of the resin resistivity reduces the interfacial resistance of the cured paste in contact with the TCO of the heterojunction cell, thereby achieving higher cell light conversion efficiency.

According to a specific embodiment of the present invention, the weight ratio of the first metal powder, the second metal powder and the thermosetting resin may be controlled to be 25-70:30-75:3-8. That is, the raw materials of the low-temperature slurry include, in parts by weight: 3-8 parts of conductive powder, 1-2 parts of thermosetting resin, 0.1-0.3 part of coupling agent, 3-6 parts of solvent and 0.02-0.2 part of ion accelerator; wherein the conductive powder comprises 25-70 parts of first metal powder and 30-75 parts of second metal powder.

According to a specific embodiment of the present invention, the weight ratio of the first metal powder, the second metal powder and the thermosetting resin may be controlled to be 30-60:40-70:3-8. That is, the raw materials of the low-temperature slurry include, in parts by weight: 3-8 parts of conductive powder, 1-2 parts of thermosetting resin, 0.1-0.3 part of coupling agent, 3-6 parts of solvent and 0.02-0.2 part of ion accelerator; wherein the conductive powder comprises 30-60 parts of first metal powder and 40-70 parts of second metal powder.

According to a specific embodiment of the present invention, the weight ratio of the thermosetting resin to the ion accelerator may be further controlled to be 2-6:0.02-0.2, 3-6.5:0.02-0.2, 3-7:0.02-0.2, 3-7.5:0.02-0.2. That is, the raw materials of the low-temperature slurry may include, in parts by weight: 2-6 parts of conductive powder, 3-6.5 parts of 3-7 parts of 3-7.5 parts of thermosetting resin, 1-2 parts of coupling agent, 0.1-0.3 part of curing agent, 3-6 parts of solvent and 0.02-0.2 part of ion accelerator; the conductive powder includes 20-70 parts of a first metal powder and 30-80 parts of a second metal powder.

According to a specific embodiment of the present invention, the weight ratio of the solvent to the ion accelerator may be further controlled to be 3-5:0.02-0.2. That is, the raw materials of the low-temperature slurry may include, in parts by weight: 3-8 parts of conductive powder, 1-2 parts of thermosetting resin, 0.1-0.3 part of coupling agent, 3-5 parts of solvent and 0.02-0.2 part of ion accelerator; the conductive powder includes 20-70 parts of a first metal powder and 30-80 parts of a second metal powder.

In the above low-temperature slurry, the ion accelerator may be one or a combination of two or more of octadecyl hydroxyethyl dimethylamine nitrate, stearyl trimethyl ammonium chloride, lauramidopropyl trimethyl ammonium, alkyl sulfonate, alkyl sulfate, alkyl phosphate, alkylphenol polyoxyethylene sulfate, and the like. Wherein, the octadecyl hydroxyethyl dimethylamine nitrate can be octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate, the alkyl sulfate can comprise dodecyl triethanolamine sulfate, and the alkyl phosphate can comprise octadecyl phosphate.

In the above low temperature slurry, the thermosetting resin generally includes an epoxy resin and/or a polybutadiene resin, etc. The epoxy resin can specifically comprise one or a combination of more than two of bisphenol F epoxy resin, bisphenol A epoxy resin, resorcinol formaldehyde epoxy resin, polyglycerin triglycerol epoxy resin, amino-terminated liquid nitrile rubber and the like.

In the low-temperature slurry, the number average molecular weight of the epoxy resin is 1000-1500.

According to particular embodiments of the present invention, the weight ratio of the epoxy resin to the polybutadiene resin may be controlled to be 2-6:1-2, for example, 2-5:1-2, 2-6:1-1.5, 2-5:1-1.5, etc.

According to a specific embodiment of the present invention, the raw materials of the low-temperature slurry may specifically include, in parts by weight: 2-6 parts or 2-5 parts of epoxy resin, 1-2 parts or 1-1.5 parts of polybutadiene resin, 1-2 parts of coupling agent, 0.1-0.3 part of curing agent, 3-6 parts of solvent and 0.02-0.2 part of ion accelerator; wherein the conductive powder comprises 20-70 parts of the first metal powder (surface-treated) and 30-80 parts of the second metal powder (surface-treated).

In the low-temperature slurry, the coupling agent comprises a titanate coupling agent, an organosilicon coupling agent and the like. Specifically, the titanate coupling agent may include one or a combination of two or more of isopropyl tri-titanate, isopropyl dioleate acyloxy titanate, monoalkoxy unsaturated fatty acid titanate, isopropyl tri (dioctyl pyrophosphoryl oxy) titanate (FT 201), and the like; the organosilicon coupling agent may include one or a combination of two or more of 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane, 3- [ (2, 3) -glycidoxy ] propyl methyl dimethoxysilane, N- (beta-aminoethyl) -gamma-aminopropyl trimethoxysilane, N-aminoethyl-3-aminopropyl methyl dimethoxysilane, gamma-glycidoxypropyl trimethoxysilane (KH 560), and the like.

In the above low-temperature slurry, the curing agent includes one or a combination of two or more of boron trifluoride-monoethylamine complex, 2-methylimidazole, dicyandiamide, modified aliphatic amine, aromatic diamine, and the like.

In the above low temperature slurry, the solvent includes one or a combination of two or more of terpineol, butyl carbitol acetate, ethylene glycol butyl ether, ethylene glycol, propylene glycol, dibutyl diglycol, glycol ether, tributyl citrate, dibutyl phthalate, and the like. .

The invention also provides a heterojunction battery, and the conductive film and/or the conductive electrode of the heterojunction battery are formed by curing the low-temperature slurry.

The invention has the beneficial effects that:

1. the conductive powder and the low-temperature slurry provided by the invention can be suitable for batch screen printing of industrialized extremely-narrow opening screen plates and small-size texturing pyramids, and effectively solve the problems of large slurry consumption, high cost and filling and contact of the existing small-size texturing pyramids in the production process of heterojunction batteries.

2. The low-temperature slurry provided by the invention can be thermally cured in a low-temperature environment below 200 ℃, and the conductive film or the conductive electrode after the low-temperature slurry is completely cured has low resistivity and good adhesion, so that the photoelectric conversion efficiency of the heterojunction battery can be further improved.

Drawings

Fig. 1 is a laser particle size distribution diagram of the conductive powder of example 1, example 3, example 4.

Fig. 2 is a laser particle size distribution diagram of the conductive powder of example 2, example 5, example 8, example 9.

Fig. 3 is a laser particle size distribution diagram of the conductive powder of example 6.

Fig. 4 is a laser particle size distribution diagram of the conductive powder of example 7.

Fig. 5 is an SEM image of a 1-3 micron pyramid.

Fig. 6 is an SEM image of a 3-5 micron pyramid.

Detailed Description

The technical solution of the present invention will be described in detail below for a clearer understanding of technical features, objects and advantageous effects of the present invention, but should not be construed as limiting the scope of the present invention. A step of

In the following examples and comparative examples, the manufacturer of octadecyl hydroxyethyl dimethylamine nitrate used was Annean petrochemical in Jiangsu province and the model was antistatic agent SN (octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate). The titanate coupling agent is FT201, and the organosilicon coupling agent is KH560.

Example 1

The embodiment provides a low-temperature slurry, which comprises the following raw materials in parts by weight:

38 parts of first metal powder, 50 parts of second metal powder, 0.5 part of bisphenol F epoxy resin, 1.8 parts of resorcinol formaldehyde epoxy resin, 1.5 parts of polyglycerin triglycidyl epoxy resin, 1.5 parts of polybutadiene resin, 1 part of titanate coupling agent, 2 parts of terpineol, 2 parts of tributyl citrate, 1.45 parts of dibutyl phthalate, 0.2 part of boron trifluoride-monoethylamine complex and 0.05 part of octadecyl hydroxyethyl dimethylamine nitrate.

The first metal powder and the second metal powder form conductive powder. The first metal powder was spherical copper-clad silver powder having an average particle diameter of 2.8 μm and a tap density of 4.8g/cc. The second metal powder was spherical silver powder having an average particle diameter of 1.3 μm and tap density of 3.5g/cc.

The first metal powder is subjected to surface treatment, and the surface treatment method comprises the following steps of; mixing untreated first metal powder with surface treatment liquid according to the following ratio of 7: mixing the materials according to the mass ratio of 100, performing ultrasonic dispersion for 50min, and performing vacuum drying at 80 ℃ for 1.5h to obtain the first metal powder coated with the antioxidant.

Wherein the surface treatment liquid comprises the following components in percentage by mass: 5:83, 2-methylenebis (4-methyl-6-t-butylphenol), isopropyl tristearate titanate, and isopropanol.

The second metal powder is also a surface-treated second metal powder, and the surface treatment method (including steps and parameters) is the same as that of the first metal powder.

Bisphenol F epoxy resin, resorcinol formaldehyde epoxy resin and polyglycerin triglycidyl epoxy resin have a number average molecular weight of 1000-1500.

Example 2

38 parts of first metal powder, 50 parts of second metal powder, 1.5 parts of bisphenol F epoxy resin, 1.3 parts of resorcinol formaldehyde epoxy resin, 1.5 parts of polyglycerin triglycidyl epoxy resin, 1.0 part of polybutadiene resin, 1 part of titanate coupling agent, 2 parts of terpineol, 2 parts of tributyl citrate, 1.4 parts of dibutyl phthalate, 0.2 part of boron trifluoride-monoethylamine complex and 0.1 part of octadecyl hydroxyethyl dimethylamine nitrate.

Wherein the first metal powder and the second metal powder form conductive powder. The first metal powder is spherical copper-clad silver powder, the average particle diameter is 2.5 mu m, and the tap density is more than 4.9 g/cc. The second metal powder was spherical silver powder having an average particle diameter of 1.1 μm and a tap density of 3.7g/cc.

The first metal powder and the second metal powder are respectively subjected to surface treatment, and the surfaces of the first metal powder and the second metal powder are coated with an antioxidant 2, 2-methylenebis (4-methyl-6-tertiary butyl phenol). The specific surface treatment method was the same as in example 1.

Example 3

38 parts of first metal powder, 50 parts of second metal powder, 1.5 parts of bisphenol A epoxy resin, 1.3 parts of resorcinol formaldehyde epoxy resin, 1.5 parts of polyglycerin triglycidyl epoxy resin, 1.0 part of polybutadiene resin, 1 part of titanate coupling agent, 2 parts of terpineol, 1.8 parts of tributyl citrate, 1.4 parts of dibutyl phthalate, 0.2 part of boron trifluoride-monoethylamine complex and 0.2 part of octadecyl hydroxyethyl dimethylamine nitrate.

Wherein the first metal powder and the second metal powder form conductive powder. The first metal powder was spherical copper-clad silver powder having an average particle diameter of 2.8 μm and a tap density of 4.8g/cc. The second metal powder was spherical silver powder having an average particle diameter of 1.3 μm and tap density of 3.5g/cc.

Bisphenol A epoxy resin, resorcinol formaldehyde epoxy resin and polyglycerin triglycidyl epoxy resin have a number average molecular weight of 1000-1500.

Example 4

38 parts of first metal powder, 50 parts of second metal powder, 0.5 part of bisphenol F epoxy resin, 1.8 parts of resorcinol formaldehyde epoxy resin, 1.5 parts of polyglycerin triglycidyl epoxy resin, 1.5 parts of amino-terminated liquid nitrile rubber, 1 part of titanate coupling agent, 2 parts of terpineol, 1.9 parts of tributyl citrate, 1.5 parts of dibutyl phthalate, 0.2 part of boron trifluoride-monoethylamine complex and 0.1 part of triethanolamine lauryl sulfate.

Bisphenol F epoxy resin, resorcinol formaldehyde epoxy resin, polyglycerin triglycidyl epoxy resin and amino-terminated liquid nitrile rubber have a number average molecular weight of 1000-1500.

Example 5

38 parts of first metal powder, 50 parts of second metal powder, 0.5 part of bisphenol F epoxy resin, 1.8 parts of resorcinol formaldehyde epoxy resin, 1.5 parts of polyglycerin triglycidyl epoxy resin, 1.5 parts of polybutadiene resin, 0.5 part of titanate coupling agent, 1 part of organosilicon coupling agent, 1.5 parts of terpineol, 1.8 parts of tributyl citrate, 1.5 parts of dibutyl phthalate, 0.2 part of boron trifluoride-monoethylamine complex and 0.2 part of lauryl sulfuric acid triethanolamine.

Example 6

20 parts of first metal powder, 68 parts of second metal powder, 0.5 part of bisphenol F epoxy resin, 1.8 parts of resorcinol formaldehyde epoxy resin, 1.5 parts of polyglycerin triglycidyl epoxy resin, 1.5 parts of amino-terminated liquid nitrile rubber, 1 part of titanate coupling agent, 2 parts of terpineol, 1.9 parts of tributyl citrate, 1.5 parts of dibutyl phthalate, 0.2 part of boron trifluoride-monoethylamine complex and 0.1 part of lauryl sulfate triethanolamine.

Example 7

20 parts of first metal powder, 68 parts of second metal powder, 0.5 part of bisphenol F epoxy resin, 1.8 parts of resorcinol formaldehyde epoxy resin, 1.5 parts of polyglycerin triglycidyl epoxy resin, 1.5 parts of polybutadiene resin, 0.5 part of titanate coupling agent, 1 part of organosilicon coupling agent, 1.5 parts of terpineol, 1.8 parts of tributyl citrate, 1.5 parts of dibutyl phthalate, 0.2 part of boron trifluoride-monoethylamine complex and 0.2 part of lauryl sulfuric acid triethanolamine.

Example 8

38 parts of first metal powder, 50 parts of second metal powder, 0.5 part of bisphenol F epoxy resin, 1.8 parts of resorcinol formaldehyde epoxy resin, 1.5 parts of polyglycerin triglycidyl epoxy resin, 1.5 parts of polybutadiene resin, 0.5 part of titanate coupling agent, 1 part of organosilicon coupling agent, 1.5 parts of terpineol, 1.8 parts of tributyl citrate, 1.5 parts of dibutyl phthalate, 0.2 part of boron trifluoride-monoethylamine complex and 0.2 part of lauramidopropyl trimethyl ammonium.

Example 9

38 parts of first metal powder, 50 parts of second metal powder, 0.5 part of bisphenol F epoxy resin, 1.8 parts of resorcinol formaldehyde epoxy resin, 1.5 parts of polyglycerin triglycidyl epoxy resin, 1.5 parts of polybutadiene resin, 0.5 part of titanate coupling agent, 1 part of organosilicon coupling agent, 1.5 parts of terpineol, 1.8 parts of tributyl citrate, 1.5 parts of dibutyl phthalate, 0.2 part of boron trifluoride-monoethylamine complex and 0.2 part of octadecyl phosphate.

Comparative example 1

The comparative example provides a low-temperature slurry comprising, in parts by weight:

38 parts of first spherical silver powder, 50 parts of second spherical silver powder, 0.5 part of bisphenol F epoxy resin, 1.8 parts of resorcinol formaldehyde epoxy resin, 1.5 parts of polyglycerin triglycidyl epoxy resin, 1.5 parts of polybutadiene resin, 1 part of titanate coupling agent, 2 parts of terpineol, 2 parts of tributyl citrate, 1.5 parts of dibutyl phthalate and 0.2 part of boron trifluoride-monoethylamine complex.

Wherein the first spherical silver powder and the second spherical silver powder form conductive powder. The first spherical silver powder has an average particle diameter of 2.9 μm and a tap density of 4.2g/cc or more. The second spherical silver powder has an average particle diameter of 1.5 μm and a tap density of 3.6g/cc or more. Neither silver powder was surface treated.

Bisphenol F epoxy resin, resorcinol formaldehyde epoxy resin and polyglycerin triglycerol epoxy resin have an average molecular weight of 1000-1500.

The particle size distribution of the conductive powder used in the low-temperature slurries of examples 1 to 9 was characterized, and the results are shown in fig. 1 to 4.

The conductive powders used in examples 1,3 and 4 were identical, and fig. 1 shows the laser particle size distribution patterns of the conductive powders in examples 1,3 and 4. As can be seen from FIG. 1, the conductive powder had a D10 particle size of 0.861. Mu.m, a D50 particle size of 2.078. Mu.m, and a D90 particle size of 4.331. Mu.m.

The conductive powders used in examples 2, 5, 8 and 9 were identical, and fig. 2 shows the laser particle size distribution diagrams of the conductive powders in examples 2, 5, 8 and 9. As can be seen from FIG. 2, the conductive powder had a D10 particle size of 0.618 μm, a D50 particle size of 1.522 μm and a D90 particle size of 3.501. Mu.m.

Fig. 3 is a laser particle size distribution diagram of the conductive powder of example 6. As can be seen from FIG. 3, the conductive powder had a D10 particle size of 0.605. Mu.m, a D50 particle size of 1.366. Mu.m, and a D90 particle size of 3.251. Mu.m.

Fig. 4 is a laser particle size distribution diagram of the conductive powder of example 7. As can be seen from FIG. 4, the conductive powder had a D10 particle size of 0.605 μm, a D50 particle size of 1.375 μm and a D90 particle size of 2.860. Mu.m.

Test example 1

The low temperature slurries of examples 1 to 9 and comparative example 1 were tested for performance. And testing the low-temperature slurry to be tested on a battery with TCO substrates of ITO (97:3), ITO (90:10), IWO and ICO respectively, printing the slurry on the substrate through a screen, drying and curing at 200 ℃ to obtain a testable silver electrode grid line, and measuring the viscosity, the resistivity, the contact resistance and the like of the slurry. The performance test methods are as follows:

1. the viscosity test method comprises the following steps:

taking the conductive paste as a sample, and performing viscosity test by using a Bowler-femtocells viscometer, wherein 1) when the rotating speed is 1r/min, the reading time is 60s; 2) When the rotating speed is 10r/min, the reading time is 4min; 3) When the rotating speed is 100r/min, the reading time is 60s, and the viscosity of the conductive paste at different rotating speeds is measured.

2. Resistivity test: the resistance at both ends of the electrode was tested using a four-probe ohmmeter. The electrode is a heterojunction battery formed by TCO base material printed with conductive paste, and the specific measurement process is as follows: the resistance between the two points is tested by a resistance meter, the width and the height of the main grid are tested by a 3D microscope, and the resistivity result is calculated according to the following formula:

resistivity = resistance/main gate width x main gate height.

3. Contact resistance: (1) Printing a specific pattern on the heterojunction battery piece, and then drying and curing; (2) Cutting out the battery piece with the appointed size of the printing pattern area by using a laser slicer; (3) measuring contact resistance using a contact resistance device.

4. Texturing pyramid: the morphology of the texture-making pyramid is characterized by a Scanning Electron Microscope (SEM), and the size of the texture-making pyramid is measured to be 1-3 mu m and 3-5 mu m respectively, and the results are shown in fig. 5 and 6.

The test data for the low temperature slurries in the above examples are summarized in tables 1, 2. The contact resistance in Table 1 was tested with a texture pyramid of 3-5 μm; the contact resistance in Table 2 was tested at a texture pyramid of 1-3 μm.

TABLE 1

TABLE 2

As can be seen from table 1, the low temperature slurry of comparative example 1, to which no ion accelerator was added, had higher resistivity and contact resistance; whereas the low temperature slurries of examples 1 and 2, to which the ion accelerator was added, had a significant decrease in both resistivity and contact resistance. Example 3 the addition amount of the ion accelerator was increased based on examples 1 and 2, and the resistivity and contact resistance of the obtained low-temperature slurry were increased; examples 5, 8 and 9 demonstrate that by adjusting the type of ionic promoter, the properties of the slurry can be tailored.

The resistivity and contact resistance of the low-temperature slurry further decreased with the increase in the addition amount, compared to comparative example 1, in which the ion accelerator was added in examples 4 to 5.

As can be seen from Table 2, after the size of the texturing pyramid is changed from 3-5 μm to 1-3 μm, the contact resistance of comparative example 1 is greatly increased, and the photoelectric conversion efficiency is greatly affected; the contact resistance of each embodiment is reduced, which shows that the low-temperature slurry provided by the invention is suitable for heterojunction batteries with small-size texturing pyramids, can reduce the contact resistance of the batteries, and effectively improves the photoelectric conversion efficiency.

Claims

1. A conductive powder comprising a first metal powder and a second metal powder in a weight ratio of 20:80 to 70:30;

the first metal powder is spherical powder, the average particle size of the first metal powder is 1-3 mu m, and the tap density is more than 4.5 g/cc;

the second metal powder is spherical powder, the average grain diameter of the second metal powder is 0.1-1.5 mu m, and the tap density is more than 3.5 g/cc;

the first metal powder is subjected to antioxidant surface treatment; the second metal powder is the second metal powder subjected to antioxidant surface treatment.

2. The conductive powder according to claim 1, wherein the weight ratio of the first metal powder to the second metal powder is 25:75-70:30, preferably 30:70-60:40.

3. The conductive powder according to claim 1 or 2, wherein the conductive powder has a D10 particle size of 0.3-0.9 μm, a D50 particle size of 1.2-3.0 μm, and a D90 particle size of 2.5-6 μm;

preferably, the D10 particle size of the conductive powder is 0.5-0.8 μm;

preferably, the D50 particle size of the conductive powder is 1.3-2.0 μm;

preferably, the D10 particle size of the conductive powder is 3-4 μm.

4. The conductive powder of any of claims 1-3, wherein the antioxidant comprises one or more of 2, 2-methylenebis (4-methyl-6-t-butylphenol), 2, 6-di-t-butyl-p-cresol, 1,3 tris (2-methyl-4 hydroxy-5-t-butylphenyl) butane, 1,3, 5-trimethyl 2,4,6 tris (3, 5-di-t-butyl-4-hydroxybenzyl) benzene, N '-hexamethylenebis-3 (3, 5-di-t-butyl-4-hydroxyphenyl) propionamide, 2' -methylenebis (4-methyl-6-t-butylphenol), 1,3, 5-tris (3, 5-di-t-butyl-4-hydroxyphenyl) isocyanate, 4-hydroxydodecanoyl anilide, tris (nonylphenyl) phosphite, tris (2, 4-di-t-butylphenyl) phosphite, dioctadecyl diphosphite pentaerythritol.

5. The conductive powder according to any one of claims 1 to 3, wherein the first metal powder and the second metal powder each independently include one or a combination of two or more of silver powder, copper powder, silver-coated nickel powder, and silver-coated aluminum powder;

preferably, the first metal powder is silver-coated copper powder, and the second metal powder is one of copper powder, silver powder or silver-coated copper powder.

6. The low-temperature slurry comprises the following raw materials in parts by weight: 3-8 parts of a thermosetting resin, 1-2 parts of a coupling agent, 0.1-0.3 part of a curing agent, 3-6 parts of a solvent, 0.02-0.2 part of an ion accelerator, the conductive powder of any one of claims 1-5;

wherein the conductive powder comprises 20-70 parts of first metal powder and 30-80 parts of second metal powder.

7. The cryogenic slurry of claim 6, wherein the weight ratio of the first metal powder, the second metal powder and the thermosetting resin is 25-70:30-75:3-8, preferably 30-60:40-70:3-8.

8. The low temperature slurry of claim 6 or 7, wherein the ion accelerator comprises one or a combination of two or more of octadecyl hydroxyethyl dimethylamine nitrate, stearyl trimethyl ammonium chloride, lauramidopropyl trimethyl ammonium, alkyl sulfonate, alkyl sulfate, alkyl phosphate, alkylphenol ethoxylate sulfate;

preferably, the alkyl sulfate comprises triethanolamine lauryl sulfate;

preferably, the alkyl phosphate comprises octadecyl phosphate.

9. The low temperature slurry of claim 6 or 7, wherein the thermosetting resin comprises an epoxy resin and/or a polybutadiene resin;

preferably, the weight ratio of the epoxy resin to the polybutadiene resin is 2-6:1-2;

preferably, the epoxy resin comprises one or a combination of more than two of bisphenol F epoxy resin, bisphenol A epoxy resin, resorcinol formaldehyde epoxy resin, polyglycerin triglyceride epoxy resin and amino-terminated liquid nitrile rubber;

preferably, the epoxy resin has a number average molecular weight of 1000 to 1500.

10. The low temperature slurry of claim 6 or 7, wherein the coupling agent is a titanate coupling agent and/or a silicone coupling agent;

preferably, the titanate coupling agent comprises one or more than two of isopropyl tri-titanate, isopropyl dioleate acyloxy titanate, monoalkoxy unsaturated fatty acid titanate and isopropyl tri (dioctyl pyrophosphoryl oxy) titanate;

preferably, the organosilicon coupling agent comprises one or a combination of more than two of 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane, 3- [ (2, 3) -glycidoxy ] propyl methyl dimethoxy silane, N- (beta-aminoethyl) -gamma-aminopropyl trimethoxysilane, N-aminoethyl-3-aminopropyl methyl dimethoxy silane and gamma-glycidoxy propyl trimethoxysilane.

11. The low temperature slurry of claim 6 or 7, wherein the curing agent comprises one or a combination of two or more of boron trifluoride-monoethylamine complex, 2-methylimidazole, dicyandiamide, modified aliphatic amine, aromatic diamine.

12. The low temperature slurry of claim 6 or 7, wherein the solvent comprises one or a combination of two or more of terpineol, butyl carbitol acetate, ethylene glycol butyl ether, ethylene glycol, propylene glycol, dibutyl diglycol, glycol ether, tributyl citrate, dibutyl phthalate.

13. A heterojunction cell having a conductive film and/or electrode formed by curing the low-temperature slurry of any one of claims 6 to 12.