阅读说明：本技术 Hjt导电银胶组成物及其制备方法和hjt太阳能电池 (HJT conductive silver colloid composition, preparation method thereof and HJT solar cell ) 是由 沈远征 赵科良 苏亚军 张嘉宁 饶龙来 姚威龙 赵云龙 于 2021-09-26 设计创作，主要内容包括：本发明公开了HJT导电银胶组成物及其制备方法和HJT太阳能电池,组成物包括：银粉、环氧树脂、柔性化合物、固化剂、稀释剂及助剂；所述柔性化合物包括柔性嵌段共聚物、柔性接枝共聚物和柔性共混聚合物中的一种或多种。按重量百分数计,包括：80～95wt%的银粉,1～10wt%的环氧树脂,1～10wt%的柔性化合物,1～5wt%的固化剂,1～5wt%的稀释剂,及0.01～0.5wt%助剂；本发明的导电银胶具有良好的焊锡浸润性、抗焊料侵蚀性,并且固化后树脂部分有对称的硬段结构可以提供更强的内聚力以分散消耗外部应力,在保证电性能的同时实现导电银胶高焊接拉力的性能。(The invention discloses a HJT conductive silver colloid composition, a preparation method thereof and a HJT solar cell, wherein the composition comprises the following components: silver powder, epoxy resin, a flexible compound, a curing agent, a diluent and an auxiliary agent; the flexible compound includes one or more of a flexible block copolymer, a flexible graft copolymer, and a flexible polymer blend. Comprises the following components in percentage by weight: 80-95 wt% of silver powder, 1-10 wt% of epoxy resin, 1-10 wt% of flexible compound, 1-5 wt% of curing agent, 1-5 wt% of diluent and 0.01-0.5 wt% of auxiliary agent; the conductive silver adhesive has good soldering tin wettability and solder erosion resistance, and the cured resin part has a symmetrical hard segment structure, so that stronger cohesive force can be provided to disperse and consume external stress, and the high welding tension performance of the conductive silver adhesive is realized while the electrical performance is ensured.)

1. An HJT conductive silver paste composition, comprising: silver powder, epoxy resin, a flexible compound, a curing agent, a diluent and an auxiliary agent;

the flexible compound includes one or more of a flexible block copolymer, a flexible graft copolymer, and a flexible polymer blend.

2. The HJT conductive silver paste composition as claimed in claim 1, wherein the flexible compound has an average functionality of 2 to 7 and a relative molecular weight Mr of 500 to 10000.

3. The HJT conductive silver paste composition of claim 1, wherein the flexible block copolymer is selected from a rubber toughened epoxy resin, a polyurethane modified epoxy resin, or a silicone modified epoxy resin; or the like, or, alternatively,

the flexible block copolymer is selected from a prepolymer of an isocyanate group-containing compound and polyester polyol, a prepolymer of an isocyanate group-containing compound and polyether polyol or a prepolymer of an isocyanate group-containing compound and polycarbonate polyol; or the like, or, alternatively,

the flexible block copolymer is selected from a prepolymer of an alcoholic hydroxyl hyperbranched compound and an isocyanate group, and a prepolymer of an alcoholic hydroxyl hyperbranched compound and an epoxy group; or the like, or, alternatively,

the flexible block copolymer is a prepolymer prepared from two or more of saturated polyester resin, unsaturated polyester resin, epoxy resin and isocyanate compounds.

4. The HJT conductive silver paste composition as set forth in claim 1,

the flexible polymer blend is selected from a mixture of an isocyanate group-containing compound and a polyester polyol, a mixture of an isocyanate group-containing compound and a polyether polyol, or a mixture of an isocyanate group-containing compound and a polycarbonate polyol; or the like, or, alternatively,

the flexible blend polymer is selected from a mixture of an alcoholic hydroxyl hyperbranched compound and an isocyanate group compound, and a mixture of an alcoholic hydroxyl hyperbranched compound and an epoxy group compound; or the like, or, alternatively,

the flexible blend polymer is a mixture of two or more of saturated polyester resin, unsaturated polyester resin, epoxy resin and isocyanate compounds.

5. The HJT conductive silver paste composition as set forth in any one of claims 1 to 4, comprising, in weight percent:

80-95 wt% of silver powder, 1-10 wt% of epoxy resin, 1-10 wt% of flexible compound, 1-5 wt% of curing agent, 1-5 wt% of diluent and 0.01-0.5 wt% of auxiliary agent;

the silver powder comprises flake silver powder and spherical silver powder; the mixing ratio of the spherical silver powder to the plate-like silver powder is (99: 1) to (1: 99).

6. The HJT conductive silver paste composition as claimed in claim 5, comprising, in weight percent:

the silver paste comprises 15-80 wt% of spherical silver powder, 15-80 wt% of flake silver powder, 1-10 wt% of epoxy resin, 1-10 wt% of flexible compound, 1-5 wt% of curing agent, 1-5 wt% of diluent and 0.01-0.5 wt% of auxiliary agent.

7. The HJT conductive silver paste composition as claimed in claim 5, comprising, in weight percent:

the silver paste comprises 30-60 wt% of spherical silver powder, 30-60 wt% of flake silver powder, 3-6 wt% of epoxy resin, 2-4 wt% of flexible compound, 0.5-1.0 wt% of curing agent, 1.5-2.5 wt% of diluent and 0.1-0.5 wt% of auxiliary agent.

8. The HJT conductive silver paste composition as set forth in claim 5,

the particle size of the spherical silver powder is 0.2-2.0 mu m, and the particle size distribution is that D100 is less than or equal to 2000nm and D50 is less than or equal to 800 nm; tap density of 3-8 g/ml, specific surfaceArea of 0.8-2.0 m²/g；

The flake diameter of the flake silver powder is 5-15 mu m, the particle size distribution is that D100 is less than or equal to 20 mu m, D50 is less than or equal to 8 mu m, the tap density is 3-6 g/ml, and the specific surface area is 0.5-1.3 m²/g。

9. The HJT conductive silver paste composition as set forth in claim 1,

the epoxy resin has an average functionality of 2-7 and an epoxy equivalent weight of 100-500; the epoxy resin is selected from: one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, alicyclic epoxy resin and novolac epoxy resin.

10. The HJT conductive silver paste composition as set forth in claim 1,

the curing agent is one or more of a closed isocyanate curing agent, a compound containing a closed isocyanate group, an organic anhydride curing agent, an imidazole curing agent, a microcapsule curing agent, dicyandiamide and a derivative curing agent thereof, an amine complex curing agent, a molecular sieve closed curing agent, a polyamine salt, an aromatic amine and inorganic salt complex curing agent, and a bisethylenediamine and derivative curing agent thereof.

11. The HJT conductive silver paste composition as set forth in claim 1,

the diluent is an active diluent or an inactive diluent, the solubility parameter of the diluent is 6-12, the boiling point is 150-250 ℃, and the volatilization rate is less than 2.5;

the reactive diluent is selected from one or more of allyl glycidyl ether, n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, ethylene glycol diglycidyl ether and hexanediol diglycidyl ether;

the non-reactive diluent is selected from one or more of ethylene glycol butyl ether, propylene glycol methyl ether acetate, solvent naphtha, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, isophorone, N-methyl pyrrolidone and terpineol.

12. The HJT conductive silver paste composition as set forth in claim 1,

the auxiliary agent comprises one or more of a dispersing agent, a flatting agent and an adhesion promoter;

the dispersant is a compound with terminal carboxyl;

the leveling agent is an organic silicon leveling agent or an acrylic acid leveling agent;

the adhesion promotion is a hydroxyl functional copolymer solution containing acidic groups.

13. The method for preparing HJT conductive silver paste composition according to any of claims 1 to 12, comprising the steps of:

mixing epoxy resin, a flexible compound, a curing agent, a diluent and an auxiliary agent according to a ratio, stirring to uniformly mix the epoxy resin, the flexible compound, the curing agent, the diluent and the auxiliary agent, and adding silver powder;

stirring uniformly and standing to fully infiltrate the silver powder to obtain a premixed mixture;

further dispersing and mixing the mixture by using a three-high mill to uniformly disperse all the components;

filtering with a filter screen to remove large-size agglomerates and silver flakes to obtain the HJT conductive silver colloid composition.

14. An HJT solar cell, characterized in that the main gate electrode of the HJT solar cell is prepared by screen printing the HJT conductive silver paste composition according to any of claims 1 to 12.

Technical Field

The invention belongs to the field of electronic paste, and particularly relates to an HJT conductive silver colloid composition, a preparation method thereof and an HJT solar cell.

Background

The HJT (heterojunction) solar cell is a next-generation solar cell technology based on an N-type silicon substrate, the mass production photoelectric conversion efficiency of the current production line of the HJT solar cell reaches more than 24.7%, compared with the traditional crystalline silicon and thin film cell, the HJT solar cell has the advantages of high photoelectric conversion efficiency, low process temperature, few production process steps and the like, and similar to the traditional crystalline silicon solar cell, the surface metallization of the HJT solar cell also adopts a screen printing process in industrial production, so that the conductive silver adhesive is one of the key materials of the HJT solar cell. The traditional crystalline silicon battery conductive silver paste is sintered at high temperature, the process temperature is above 730 ℃, the silver powders are mutually connected by surface melting, the glass phase melts silver to a certain extent and corrodes a SiNx passivation layer to form a relatively compact ohmic contact between a silver layer and a silicon substrate, the process temperature of the HJT solar battery is below 250 ℃, the sintering process of the silver powders and the glass phase is omitted, and the silver powders and the silver and an ITO film layer are bonded by organic resin phases to form good adhesive force and conductive performance.

The electrode preparation of the HJT solar cell adopts step-by-step printing to meet the requirements of the cell on electrical property and welding tension, the step-by-step printing is divided into a main grid and an auxiliary grid, the main grid is mainly used for providing the welding tension and collecting current, and the auxiliary grid is mainly used for collecting the current with low contact resistance formed by an ITO layer.

Currently, the HJT solar cell manufacturers mainly use imported HJT conductive silver paste, and have the problems of high production cost, long delivery period, low tensile force, poor weldability and the like.

The welding tension is improved by only increasing the resin content or the proportion of the large-particle-size silver powder in part of the high-tension HJT main grid conductive silver adhesive, the volume resistivity is relatively high, the tension value is generally marked as the peak value maximum tension, the average tension value is small, the process window is narrow, the process parameters of different HJT battery manufacturers cannot be well matched, and the long-term reliability risk exists for the surface pull-off of the substrate in the pull-off mode of the silver layer after welding.

Disclosure of Invention

The invention provides an HJT conductive silver adhesive composition, a preparation method thereof and an HJT solar cell, aiming at solving the problems in the prior art.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

an HJT conductive silver paste composition comprising: silver powder, epoxy resin, a flexible compound, a curing agent, a diluent and an auxiliary agent;

the flexible compound includes one or more of a flexible block copolymer, a flexible graft copolymer, and a flexible polymer blend.

As a further improvement of the invention, the flexible compound has an average functionality of 2-7 and a relative molecular weight Mr of 500-10000.

As a further improvement of the present invention, the flexible block copolymer is selected from rubber toughened epoxy, polyurethane modified epoxy or silicone modified epoxy; or the like, or, alternatively,

the flexible block copolymer is selected from a prepolymer of an isocyanate group-containing compound and polyester polyol, a prepolymer of an isocyanate group-containing compound and polyether polyol or a prepolymer of an isocyanate group-containing compound and polycarbonate polyol; or the like, or, alternatively,

the flexible block copolymer is selected from a prepolymer of an alcoholic hydroxyl hyperbranched compound and an isocyanate group, and a prepolymer of an alcoholic hydroxyl hyperbranched compound and an epoxy group; or the like, or, alternatively,

the flexible block copolymer is a prepolymer prepared from two or more of saturated polyester resin, unsaturated polyester resin, epoxy resin and isocyanate compounds.

As a further development of the invention, the flexible polymer blend is selected from the group consisting of a mixture of an isocyanate group-containing compound and a polyester polyol, a mixture of an isocyanate group-containing compound and a polyether polyol or a mixture of an isocyanate group-containing compound and a polycarbonate polyol; or the like, or, alternatively,

the flexible blend polymer is selected from a mixture of an alcoholic hydroxyl hyperbranched compound and an isocyanate group compound, and a mixture of an alcoholic hydroxyl hyperbranched compound and an epoxy group compound; or the like, or, alternatively,

the flexible blend polymer is a mixture of two or more of saturated polyester resin, unsaturated polyester resin, epoxy resin and isocyanate compounds.

As a further improvement of the invention, the paint comprises the following components in percentage by weight:

80-95 wt% of silver powder, 1-10 wt% of epoxy resin, 1-10 wt% of flexible compound, 1-5 wt% of curing agent, 1-5 wt% of diluent and 0.01-0.5 wt% of auxiliary agent;

the silver powder comprises flake silver powder and spherical silver powder; the mixing ratio of the spherical silver powder to the plate-like silver powder is (99: 1) to (1: 99).

As a further improvement of the invention, the paint comprises the following components in percentage by weight:

the silver paste comprises 15-80 wt% of spherical silver powder, 15-80 wt% of flake silver powder, 1-10 wt% of epoxy resin, 1-10 wt% of flexible compound, 1-5 wt% of curing agent, 1-5 wt% of diluent and 0.01-0.5 wt% of auxiliary agent.

As a further improvement of the invention, the paint comprises the following components in percentage by weight:

the silver paste comprises 30-60 wt% of spherical silver powder, 30-60 wt% of flake silver powder, 3-6 wt% of epoxy resin, 2-4 wt% of flexible compound, 0.5-1.0 wt% of curing agent, 1.5-2.5 wt% of diluent and 0.1-0.5 wt% of auxiliary agent.

As a further improvement of the invention, the particle size of the spherical silver powder is 0.2-2.0 μm, the particle size distribution is that D100 is less than or equal to 2000nm, and D50 is less than or equal to 800 nm; the tap density is 3-8 g/ml, and the specific surface area is 0.8-2.0 m²/g；

The flake diameter of the flake silver powder is 5-15 mu m, the particle size distribution is that D100 is less than or equal to 20 mu m, D50 is less than or equal to 8 mu m, the tap density is 3-6 g/ml, and the specific surface area is 0.5-1.3 m²/g。

As a further improvement of the invention, the average functionality of the epoxy resin is 2-7, and the epoxy equivalent weight is 100-500; the epoxy resin is selected from: one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, alicyclic epoxy resin and novolac epoxy resin.

As a further improvement of the invention, the curing agent is one or more of blocked isocyanate curing agents, compounds containing blocked isocyanate groups, organic acid anhydride curing agents, imidazole curing agents, microcapsule curing agents, dicyandiamide and derivatives thereof, amine complex curing agents, molecular sieve blocked curing agents, polyamine salts, complex curing agents of aromatic amine and inorganic salt, and diethylene glycol diamine and derivatives thereof.

As a further improvement of the invention, the diluent is an active diluent or an inactive diluent, the solubility parameter of the diluent is 6-12, the boiling point is 150-250 ℃, and the volatilization rate is less than 2.5;

the reactive diluent is selected from one or more of allyl glycidyl ether, n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, ethylene glycol diglycidyl ether and hexanediol diglycidyl ether;

the non-reactive diluent is selected from one or more of ethylene glycol butyl ether, propylene glycol methyl ether acetate, solvent naphtha, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, isophorone, N-methyl pyrrolidone and terpineol.

As a further improvement of the invention, the auxiliary agent comprises one or more of a dispersing agent, a leveling agent and an adhesion promoter;

the dispersant is a compound with terminal carboxyl;

the leveling agent is an organic silicon leveling agent or an acrylic acid leveling agent;

the adhesion promotion is a hydroxyl functional copolymer solution containing acidic groups.

A preparation method of an HJT conductive silver colloid composition comprises the following steps:

mixing epoxy resin, a flexible compound, a curing agent, a diluent and an auxiliary agent according to a ratio, stirring to uniformly mix the epoxy resin, the flexible compound, the curing agent, the diluent and the auxiliary agent, and adding silver powder;

stirring uniformly and standing to fully infiltrate the silver powder to obtain a premixed mixture;

further dispersing and mixing the mixture by using a three-high mill to uniformly disperse all the components;

filtering with a filter screen to remove large-size agglomerates and silver flakes to obtain the HJT conductive silver colloid composition.

The HJT solar cell is characterized in that a main gate electrode of the HJT solar cell is prepared by adopting the HJT conductive silver colloid composition through screen printing.

Compared with the prior art, the invention has the following advantages:

the HJT conductive silver colloid composition is applied to the manufacturing of the HJT photovoltaic cell, and due to the existence of the flexible compound, the flexible compound has a hard section structure and a soft section structure, so that stronger cohesive force can be provided to disperse and consume external stress and influence welding tension. Can provide a reliable conductive silver paste composition with excellent weldability, high welding tension, low volume resistivity, wide curing process window and excellent stripping mode. The invention starts from the special process and the use requirement of the HJT solar cell, fully considers the factors of low-temperature curing, conductivity, printability, storability, adhesion, weldability, reliability and the like, overcomes the defects of the prior art, and is used as the high-welding-tension conductive silver adhesive for the main grid of the HJT solar cell.

Drawings

FIG. 1 is a schematic diagram of a printed pattern for making a HJT photovoltaic cell test piece in an embodiment.

Detailed Description

To make the features and effects of the present invention comprehensible to those skilled in the art, general description and definitions are made below with reference to terms and expressions mentioned in the specification and claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

The theory or mechanism described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.

All features defined herein as numerical ranges or percentage ranges, such as values, amounts, levels and concentrations, are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to cover and specifically disclose all possible subranges and individual numerical values (including integers and fractions) within the range.

Unless otherwise specified herein, "comprising," including, "" containing, "" having, "or the like, means" consisting of … … "and" consisting essentially of … …, "e.g.," a comprises a "means" a comprises a and the other, "and" a comprises a only.

In this context, for the sake of brevity, not all possible combinations of features in the various embodiments or examples are described. Therefore, the respective features in the respective embodiments or examples may be arbitrarily combined as long as there is no contradiction between the combinations of the features, and all the possible combinations should be considered as the scope of the present specification.

The invention relates to a conductive silver colloid composition, in particular to: the main grid silver electrode pattern formed by printing on the HJT solar cell is heated and cured, so that a thermosetting conductive silver paste composition with strong conductivity, strong adhesive force and weldable convergence welding strip can be formed, and the preparation method belongs to the technical field of solar cells.

The invention provides a high-welding-tension conductive silver adhesive composition for a main grid of an HJT solar cell, which comprises the following components: silver powder, epoxy resin, a flexible compound, a curing agent, a diluent and an auxiliary agent.

The flexible compound comprises one or more of a flexible block copolymer, a flexible graft copolymer, and a flexible polymer blend.

Preferably, the flexible compound has an average functionality of 2-7 and a relative molecular weight Mr of 500-10000.

The flexible block prepolymer adopts (A-B)_nThe structure, n is 1, 1.5, 2, 2.5.. the A is a hard segment and the B is a soft segment, and the flexible block copolymer is selected from rubber toughened epoxy resin, polyurethane modified epoxy resin or organic silicon modified epoxy resin; or the like, or, alternatively,

the flexible block copolymer is selected from a prepolymer of an isocyanate group-containing compound and polyester polyol, a prepolymer of an isocyanate group-containing compound and polyether polyol or a prepolymer of an isocyanate group-containing compound and polycarbonate polyol; or the like, or, alternatively,

the flexible block copolymer is selected from a prepolymer of an alcoholic hydroxyl hyperbranched compound and an isocyanate group, and a prepolymer of an alcoholic hydroxyl hyperbranched compound and an epoxy group; or the like, or, alternatively,

the flexible block copolymer is a prepolymer prepared from two or more of saturated polyester resin, unsaturated polyester resin, epoxy resin and isocyanate compounds.

The flexible graft copolymer is a copolymer in which some atoms of a polymer main chain are connected with side chains of a flexible polymer chain segment with a chemical structure different from that of the main chain, and the flexible graft copolymer can be used for polymer chain segments grafted by rigid chains such as benzene rings.

The flexible polymer blend is selected from a mixture of an isocyanate group-containing compound and a polyester polyol, a mixture of an isocyanate group-containing compound and a polyether polyol, or a mixture of an isocyanate group-containing compound and a polycarbonate polyol; or the like, or, alternatively,

the flexible blend polymer is selected from a mixture of an alcoholic hydroxyl hyperbranched compound and an isocyanate group compound, and a mixture of an alcoholic hydroxyl hyperbranched compound and an epoxy group compound; or the like, or, alternatively,

the flexible blend polymer is a mixture of two or more of saturated polyester resin, unsaturated polyester resin, epoxy resin and isocyanate compounds.

The conductive silver adhesive provided by the invention has the advantages that the flexible compound is selected as a core component, the flexible compound forms a symmetrical hard segment structure due to the block-containing prepolymer, stronger cohesion can be provided to disperse and consume external stress, the solidified main grid electrode has high welding tension and strong bonding force with a substrate, and the conductive silver adhesive can be used as a high-welding-tension conductive silver adhesive for the main grid of the HJT solar cell.

One or more of the flexible compounds are selected, wherein the flexible compounds have an average functionality of 2-7 and a relative molecular weight Mr of 500-10000, and the reason is that: if the resin with the functionality of less than 2 is cured, the crosslinking density is small, the adhesion is influenced, and the reaction with the functionality of more than 7 is difficult to control; if the resin part does not form a symmetrical hard segment structure after the relative molecular weight Mr is less than 500 and is cured, stronger cohesive force can not be provided to disperse and consume external stress, and the welding tension is influenced; if the relative molecular weight Mr is more than 10000, the screen printing performance of the conductive silver paste is affected, the welding performance is deteriorated, and the volume resistivity of the conductive silver paste is increased.

In a preferred embodiment, the conductive silver paste comprises, by weight, 80-95 wt% of silver powder, 1-10 wt% of epoxy resin, 1-10 wt% of flexible compound, 1-5 wt% of curing agent, 1-5 wt% of diluent, and 0.01-0.5 wt% of auxiliary agent. The surface drying condition is 150-160 ℃ and 3-6 min, and the curing condition is 180-210 ℃ and 3.5-20 min. In the present invention, the sum of the percentages of all the components of the formulation is equal to 100%.

The silver powder comprises one or more of flake silver powder and spherical silver powder materials, the flexible compound comprises one or more of rubber toughened epoxy resin, polyurethane modified epoxy resin, organic silicon modified epoxy resin, block copolymer, graft copolymer and polymer blend materials, and the diluent comprises one or more of a reactive diluent and a non-reactive diluent material.

The silver powder comprises spherical silver powder and flake silver powder, the particle diameter of the spherical silver powder is 0.2-2.0 mu m, the flake diameter of the flake silver powder is 5-15 mu m, and specifically, the spherical silver powder: the mixing ratio of the flake silver powder is in the range of 99: 1-1: 99.

In one or more embodiments, the conductive silver paste comprises: the silver paste comprises 15-80 wt% of spherical silver powder, 15-80 wt% of flake silver powder, 1-10 wt% of epoxy resin, 1-10 wt% of flexible compound, 1-5 wt% of curing agent, 1-5 wt% of diluent and 0.01-0.5 wt% of auxiliary agent.

As a preferred embodiment, the conductive silver adhesive comprises the following components: the silver paste comprises 30-60 wt% of spherical silver powder, 30-60 wt% of flake silver powder, 3-6 wt% of epoxy resin, 2-4 wt% of flexible compound, 0.5-1.0 wt% of curing agent, 1.5-2.5 wt% of diluent and 0.1-0.5 wt% of auxiliary agent.

Preferably, the particle size distribution of the spherical silver powder is that D100 is less than or equal to 2000nm, D50 is less than or equal to 800nm, the tap density is 3-8 g/ml, and the specific surface area is 0.8-2.0 m²/g。

Preferably, the particle size distribution of the flake silver powder is D100 less than or equal to 20 microns, D50 less than or equal to 8 microns, the tap density is 3-6 g/ml, and the specific surface area is 0.5-1.3 m²/g。

The epoxy resin has an average functionality of 2-7 and an epoxy equivalent weight of 100-500; the epoxy resin is selected from: one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, alicyclic epoxy resin and novolac epoxy resin.

Glycidyl ether type epoxy resins such as bisphenol a type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol a type epoxy resin, aliphatic glycidyl ether resin epoxy resin; glycidyl ester type epoxy resins such as diglycidyl phthalate epoxy resin; glycidyl amine epoxy resins, such as tetraglycidyl diaminodiphenylmethane epoxy resin.

The main reasons for selecting an epoxy equivalent (g/eq.) of 100-500 are: if the epoxy equivalent of the epoxy resin is less than 100, the shrinkage rate is increased after the resin is cured, so that the adhesive force is influenced; if the epoxy equivalent of the epoxy resin is more than 500, the viscosity of the conductive silver adhesive is increased, the network property is deteriorated and the quality of a printed pattern is deteriorated in the screen printing process.

In one or more embodiments, the curing agent is one or more of blocked isocyanate-based curing agents, compounds containing blocked isocyanate groups, organic anhydride curing agents, imidazole-based curing agents, microcapsule-based curing agents, dicyandiamide and derivatives thereof, organic acid hydrazide curing agents, amine complex curing agents, molecular sieve blocked curing agents, polyamine salts and complex curing agents of aromatic amines and inorganic salts, and diethylene glycol diamine and derivatives thereof.

Blocked isocyanate curing agents, e.g. TDI in aromatic isocyanates, MDI, e.g. XDI, HDI, IPDI, H in aliphatic isocyanates₁₂MDI; compounds containing blocked isocyanate groups, such as adducts, biurets, dimers, trimers of polyisocyanates; organic acid anhydride curing agents, such as phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, succinic anhydride; imidazole-based curing agents such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1-benzyl-2-methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-aminoethyl-2-methylimidazole, 1-methylimidazole, 2-ethylimidazole; microencapsulated curing agents such as imidazoles, amines; selecting dicyandiamide and a derivative curing agent thereof, such as organic acid hydrazide; amine complex curing agents, e.g. boron trifluoride diethyl etherate, boron trifluoride phenol, piperidine boron trifluoride, boron trifluoride acetic acid, boron trifluoride monoethyl amine, boron trifluoride triethanolamine, boron trifluorideBoron monoethanolamine.

One or more of the above curing agents can be selected as the curing agent, and a curing agent which is easily dispersible, has small steric hindrance, high reactivity and long pot life is preferred in specific selection.

In one or more embodiments, the diluent comprises a reactive diluent and a non-reactive diluent, wherein the diluent is required to be mutually soluble and phase-separation-free with the epoxy resin, the curing agent and the flexible compound, the solubility parameter (delta) is 6-12, the boiling point (DEG C) is 150-250, and the volatilization rate (acetobutyl) is less than 2.5.

Reactive diluents, such as allyl glycidyl ether, n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, ethylene glycol diglycidyl ether or hexanediol diglycidyl ether;

non-reactive diluents such as ethylene glycol butyl ether, propylene glycol methyl ether acetate, solvent naphtha, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, isophorone, N-methylpyrrolidone, or terpineol;

one or more of the above diluents may be used in the selection.

In one or more embodiments, the auxiliary agent is one or more of a dispersant, a leveling agent, an adhesion promoter; one or more of the dispersing agent, the leveling agent and the adhesion promoter can be selected according to actual needs.

Preferred dispersants are compounds with terminal carboxyl groups. The preferred leveling agent is an organosilicon leveling agent or an acrylic leveling agent. Preferred adhesion promoters are hydroxyl functional copolymer solutions containing acidic groups.

The invention also provides a method for preparing the conductive silver colloid, which comprises the steps of mixing and uniformly stirring all the components of the conductive silver colloid, and then rolling by using a three-high mill to obtain the conductive silver colloid.

The invention also provides a screen printing plate pattern for evaluating the tension and resistivity of the conductive silver paste for the HJT photovoltaic cell, and a test sample wafer of the HJT photovoltaic cell is prepared by printing the conductive silver paste through the screen printing plate pattern.

The conductive silver paste is used for preparing the main grid electrode of the HJT solar cell. When the conductive silver adhesive is used for a main grid electrode of an HJT solar cell, the conductive silver adhesive has good soldering tin wettability and solder corrosion resistance to a Pb, Bi and Sn component low-temperature circular soldering strip with the diameter of phi 0.18 mm-0.4 mm, and a cured resin part has a symmetrical hard segment structure, so that stronger cohesive force can be provided to disperse and consume external stress, and the high soldering tension performance of the conductive silver adhesive is realized while the electrical performance is ensured.

The conductive silver adhesive can be obtained by mixing and uniformly stirring the components of the conductive silver adhesive and then rolling the mixture by a three-roll mill; the rolled conductive silver paste can be filtered to remove large-size agglomerate and flaky silver particles, and for example, a filter screen with the mesh number of 400-600 meshes can be used for filtering.

In an embodiment, the conductive silver paste is prepared by a method comprising the steps of:

the method comprises the following steps of: firstly, weighing epoxy resin, a flexible compound, a curing agent, a diluent and an auxiliary agent according to the amount designed by a formula and placing the epoxy resin, the flexible compound, the curing agent, the diluent and the auxiliary agent in a container; stirring the organic materials in the container by using a dispersion stirrer to uniformly mix the organic materials, weighing silver powder according to the amount designed by the formula, and adding the silver powder into the uniformly mixed organic material container;

the method comprises the following steps: stirring all the materials in the container by using a dispersion stirrer to uniformly mix the materials, and standing for several hours after stirring to fully infiltrate the silver powder into the organic materials;

rolling: further dispersing and mixing the stirred mixture of two or more kinds by a three-roll mill to ensure that the components are uniformly dispersed and ground to a certain fineness;

fourth, filtering: filtering the rolled conductive silver adhesive through a filter screen with 400-600 meshes to remove large-size agglomerates and flaky silver particles;

the environmental temperature in the step of the process is controlled to be 20-25 ℃, and the environmental humidity is controlled to be less than 65 RH%.

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

The following examples use instrumentation conventional in the art. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers. The various starting materials used in the examples which follow, unless otherwise indicated, are conventional commercial products having specifications which are conventional in the art. In the description of the present invention and the following examples, "%" represents weight percent, "parts" represents parts by weight, and proportions represent weight ratios, unless otherwise specified.

In an embodiment, the test method employed is as follows:

and (3) testing welding tension:

printing the prepared conductive silver adhesive on an HJT silicon substrate by using a screen printing plate pattern of FIG. 1, and welding Pad points with the size of 0.8 x 1 mm;

secondly, put the sample with good printing into the oven, cure according to following 3 kinds of solidification technological parameters:

a. surface drying at 160 deg.C for 6min, and curing at 180 deg.C for 20 min;

b. surface drying at 160 deg.C for 3min, and curing at 195 deg.C for 6.5 min;

c. surface drying at 160 deg.C for 3min, and curing at 210 deg.C for 3.5 min;

thirdly, welding the low-temperature circular welding strip with the components of Pb14, Bi43 and Sn43 with the diameter of 0.35mm on the Pad point in the figure 1 at the temperature of 315 ℃;

fourthly, the tensile machine reverses 180 degrees, the adhesion tension between the solder strip and the solidified conductive silver adhesive is tested, the test value of each Pad point is recorded, the average value is calculated, and the appearance of the pull-off surface is visually checked and recorded;

and (3) volume resistivity test:

1) printing the prepared conductive silver adhesive on an HJT silicon substrate by using a screen printing plate pattern of FIG. 1, wherein the size of a line resistance test pattern is 0.6x60 mm;

2) placing the printed sample into an oven, and curing according to the following 3 curing process parameters:

a, curing process parameters: surface drying at 160 deg.C for 6min, and curing at 180 deg.C for 20 min;

b, curing process parameters: surface drying at 160 deg.C for 3min, and curing at 195 deg.C for 6.5 min;

c, curing process parameters: surface drying at 160 deg.C for 3min, and curing at 210 deg.C for 3.5 min;

3) the resistance value of a pattern of the cured sample of 0.6x60mm is tested by using a precision resistance meter, the thickness of a film layer of the pattern is tested by using a film thickness meter, and the volume resistivity value of the conductive silver adhesive can be calculated.

The conductive silver paste of the present invention will be described in detail with reference to specific examples.

Example 1

A high-welding-tension conductive silver adhesive for main grids of HJT photovoltaic cells comprises the following components: the content of spherical silver powder was 45.0wt%, the content of plate-like silver powder was 44.8wt%, the content of glycidyl ether epoxy resin (epoxy equivalent (g/eq.) was 200) was 3.0wt%, the content of flexible block copolymer was rubber-toughened epoxy resin, the content of relative molecular weight Mr 1000 was 4.0wt%, the content of curing agent was amine complex was 0.5wt%, the content of reactive diluent was 2-ethylhexyl glycidyl ether was 1.0wt%, the content of non-reactive diluent was 1.5wt%, the content of auxiliary agent was 0.1wt%, and the content of adhesion promoter was 0.1 wt%.

The particle size distribution of the spherical silver powder is that D100 is less than or equal to 2000nm, D50 is less than or equal to 800nm, the tap density is 3-8 g/ml, and the specific surface area is 0.8-2.0 m²/g。

The particle size distribution of the flake silver powder is that D100 is less than or equal to 20 mu m, D50 is less than or equal to 8 mu m, the tap density is 3 to 6g/ml, and the specific surface area is 0.5 to 1.3m²/g。

The preparation method and the test method of the example 1 are carried out according to the requirements of the specific implementation mode.

Example 2

A high-welding-tension conductive silver adhesive for main grids of HJT photovoltaic cells comprises the following components: the content of spherical silver powder was 45.0wt%, the content of plate-like silver powder was 44.8wt%, the content of glycidyl ether epoxy resin (epoxy equivalent (g/eq.) 300) was 3.0wt%, the content of flexible blend polymer was 4wt% of a mixture of a compound containing isocyanate groups and polyester polyol, the relative molecular weight Mr 2000, the content of curing agent was 0.5wt% of amine complex, the content of reactive diluent was 1.0wt% of 2-ethylhexyl glycidyl ether, the content of non-reactive diluent was 1.5wt% of butyl carbitol acetate, the content of auxiliary agent was 0.1wt% of dispersant, and the content of acrylic leveling agent was 0.1 wt%.

The particle size distribution of the spherical silver powder is that D100 is less than or equal to 2000nm, D50 is less than or equal to 800nm, the tap density is 3-8 g/ml, and the specific surface area is 0.8-2.0 m²/g。

The particle size distribution of the flake silver powder is that D100 is less than or equal to 20 mu m, D50 is less than or equal to 8 mu m, the tap density is 3 to 6g/ml, and the specific surface area is 0.5 to 1.3m²/g。

The preparation method and the test method of the example 2 are carried out according to the requirements of the specific implementation mode.

Comparative example 1

A high-welding-tension conductive silver adhesive for main grids of HJT photovoltaic cells comprises the following components: 45 wt% of flake silver powder, 45 wt% of spherical silver powder, 2.7 wt% of hydrogenated bisphenol A epoxy resin, 2.7 wt% of phenolic epoxy resin, 1.35wt% of a compound containing a blocked isocyanate group as a curing agent, 0.25wt% of an amine complex, 2.5wt% of butyl carbitol acetate as a diluent, and 0.5wt% of palmitic acid as an auxiliary agent.

The particle size distribution of the spherical silver powder is that D100 is less than or equal to 2000nm, D50 is less than or equal to 800nm, the tap density is 3-8 g/ml, and the specific surface area is 0.8-2.0 m²/g。

The particle size distribution of the flake silver powder is that D100 is less than or equal to 20 mu m, D50 is less than or equal to 8 mu m, the tap density is 3 to 6g/ml, and the specific surface area is 0.5 to 1.3m²/g。

The preparation and testing methods of comparative example 1 were carried out in accordance with the specific embodiments.

The test results are shown in table 1:

TABLE 1 results of various property tests of conductive silver paste prepared in examples 1-2 and comparative example 1

As can be seen from table 1, the conductive silver paste prepared in embodiments 1-2 by the present invention has excellent solderability after curing, high soldering tension, low volume resistivity, wide curing process window, and excellent and reliable pull-off mode, and is particularly suitable for preparing the main gate electrode of the HJT photovoltaic cell. The conductive silver paste of comparative example 1, which does not contain a block prepolymer and does not form a symmetrical hard segment structure, cannot provide stronger cohesive force to disperse and consume external stress, the welding tension of the cured main gate electrode is low, the bonding force with the substrate is also poor, the pull-off mode is bottom pull-off, and the surface of the substrate is exposed.

The invention also provides other embodiments, and the original proportion in the specific embodiment is shown in table 2. The specific procedure was the same as in example 1.

TABLE 2

The specific raw material selections in each example in table 2 are as follows:

example 3

The flexible compound is polyurethane modified epoxy resin, the average functionality is 4, and the relative molecular weight Mr is 8000. The epoxy resin has an average functionality of 5 and an epoxy equivalent weight of 500; the epoxy resin is selected from glycidyl ether epoxy resin. The curing agent is a closed isocyanate curing agent TDI. The diluent is allyl glycidyl ether, the solubility parameter is 12, the boiling point is 200 ℃, and the volatilization rate is less than 2.5; the auxiliary agent is a dispersing agent and a flatting agent.

Example 4

The flexible compound is a prepolymer of a compound containing isocyanate groups and polyether polyol, the average functionality is 2, and the relative molecular weight Mr is 8000. The epoxy resin has an average functionality of 3 and an epoxy equivalent weight of 300; the epoxy resin is selected from glycidyl amine epoxy resin and alicyclic epoxy resin. The curing agent is an organic acid hydrazide curing agent. The diluent is diethylene glycol ethyl ether acetate, the solubility parameter is 8, the boiling point is 230 ℃, and the volatilization rate is less than 2.5; the auxiliary agent is a dispersing agent and an adhesion promoter.

Example 5

The flexible compound is a prepolymer of an alcoholic hydroxyl hyperbranched compound and an isocyanate group, the average functionality is 7, and the relative molecular weight Mr is 10000. The epoxy resin has an average functionality of 6 and an epoxy equivalent weight of 200; the epoxy resin is selected from novolac epoxy resins. The curing agent is imidazole curing agent 2-methylimidazole. The diluent is ethylene glycol diglycidyl ether, the solubility parameter is 11, the boiling point is 160 ℃, and the volatilization rate is less than 2.5; the auxiliary agent is a dispersant.

Example 6

The flexible compound is a mixture of a compound containing isocyanate groups and polyester polyol, has an average functionality of 6 and a relative molecular weight Mr of 5000. The epoxy resin has an average functionality of 2 and an epoxy equivalent weight of 300; the epoxy resin is selected from cycloaliphatic epoxy resins. The curing agent is bisethylenediamine. The diluent is hexanediol diglycidyl ether, the solubility parameter is 6, the boiling point is 250 ℃, and the volatilization rate is less than 2.5; the auxiliary agent is a leveling agent.

Example 7

The flexible compound is a mixture of saturated polyester resin, epoxy resin and isocyanate compound, the average functionality is 4, and the relative molecular weight Mr is 3000. The epoxy resin has an average functionality of 2 and an epoxy equivalent weight of 100; the epoxy resin is selected from glycidyl amine epoxy resin. The curing agent is an organic acid hydrazide curing agent. The diluent is n-butyl glycidyl ether, the solubility parameter is 10, the boiling point is 150 ℃, and the volatilization rate is less than 2.5; the auxiliary agent is a dispersing agent, a flatting agent and an adhesion promoter.

The conductive silver paste prepared by the embodiments 3-7 in table 2 has excellent solderability after curing, high welding tension, low volume resistivity, wide curing process window, excellent and reliable pull-off mode, and is particularly suitable for preparing the main gate electrode of the HJT photovoltaic cell. The conductive silver adhesive can provide stronger cohesion to disperse and consume external stress due to the containing of the flexible compound, the welding tension of the main grid electrode after curing is high, and the adhesion force with the substrate is also strong.

Other examples are given below to illustrate the formulation of the HJT conductive silver paste composition of the present invention.

Example 8

30 wt% of flake silver powder and 50 wt% of spherical silver powder, wherein the flexible compound is a prepolymer of epoxy resin and isocyanate compound, and the content of the flexible compound is 6 wt%; average functionality 4, relative molecular weight Mr 8000. The epoxy resin has an average functionality of 5 and an epoxy equivalent weight of 500; the epoxy resin is selected from bisphenol A type epoxy resin, and the content is 10 wt%. The curing agent is H₁₂MDI in an amount of 2.5 wt.%. The diluent is terpineol, the content is 2.5wt%, the solubility parameter is 12, the boiling point is 200 ℃, and the volatilization rate is less than 2.5; the auxiliary agent is a dispersant and a flatting agent, and the content of the auxiliary agent is 0.5 wt%.

Example 9

40 wt% of flake silver powder and 41 wt% of spherical silver powder, wherein the flexible compound is a prepolymer of a compound containing isocyanate groups and polyether polyol, and the content is 10 wt%; average functionality 2, relative molecular weight Mr 8000. The epoxy resin has an average functionality of 3 and an epoxy equivalent weight of 300; the epoxy resin is selected from hydrogenated bisphenol A type epoxy resin, and the content is 2 wt%. The curing agent is 1-cyanoethyl-2-methylimidazole with the content of 5 wt%. The diluent is diethylene glycol butyl ether, the content is 1.9 wt%, the solubility parameter is 8, the boiling point is 230 ℃, and the volatilization rate is less than 2.5; the auxiliary agent is a dispersing agent and an adhesion promoter, and the content of the auxiliary agent is 0.1 wt%.

Example 10

44.99 wt% of flake silver powder and 50 wt% of spherical silver powder, wherein the flexible compound is a prepolymer of an alcoholic hydroxyl hyperbranched compound and an epoxy group, the content is 2 wt%, the average functionality is 7, and the relative molecular weight Mr is 10000. The epoxy resin has an average functionality of 6 and an epoxy equivalent weight of 200; the epoxy resin is selected from diglycidyl phthalate epoxy resin, and the content is 1 wt%. The curing agent is imidazole curing agent 2-methylimidazole with the content of 1 wt%. The diluent is solvent naphtha, the solubility parameter is 11, the boiling point is 160 ℃, and the volatilization rate is less than 2.5; the auxiliary agent is a dispersant, and the content of the auxiliary agent is 0.01 wt%.

Example 11

15 wt% of flake silver powder and 70 wt% of spherical silver powder, wherein the flexible compound is a prepolymer of saturated polyester resin and unsaturated polyester resin, the content is 3 wt%, the average functionality is 6, and the relative molecular weight Mr is 5000. The epoxy resin has an average functionality of 2 and an epoxy equivalent weight of 300; the epoxy resin is selected from aliphatic glycidyl ether resin, the content of the epoxy resin is 5wt%, the curing agent is imidazole type microcapsule type curing agent, the content of the curing agent is 2 wt%, the diluent is ethylene glycol diglycidyl ether, the content of the diluent is 4.7 wt%, the solubility parameter is 6, the boiling point is 250 ℃, and the volatilization rate is less than 2.5; the auxiliary agent is a leveling agent, and the content of the auxiliary agent is 0.3 percent.

Example 12

75 wt% of flake silver powder and 15 wt% of spherical silver powder, wherein the flexible compound is a mixture of epoxy resin and isocyanate compound, and the content is 2 wt%; average functionality 4, relative molecular weight Mr 3000. The epoxy resin has an average functionality of 2 and an epoxy equivalent weight of 100; the epoxy resin is selected from bisphenol A type epoxy resin, and the content is 3 wt%. The curing agent is boron trifluoride phenol with the content of 1 wt%. The diluent is allyl glycidyl ether with the content of 3.8 wt%. The solubility parameter is 10, the boiling point is 150 ℃, and the volatilization rate is less than 2.5; the auxiliary agent comprises a dispersing agent, a flatting agent and an adhesion promoter, and the content of the auxiliary agent is 0.2 wt%.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.