Conductive slurry, and preparation method therefor and use thereof

Abstract

A conductive slurry, and a preparation method therefor and use thereof. The conductive slurry comprises a conductive filler and a non-resin binder, wherein the non-resin binder comprises epoxy-terminated siloxane, an active diluent and a curing agent, the epoxy-terminated siloxane comprising a first repeating unit. The non-resin binder can improve the curing efficiency, binding capacity and storage stability of the conductive slurry, reduce preparation costs, and facilitate wide application of the conductive slurry.

Description

Conductive paste and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 29, 2023, with application number 202311871362.3 and invention name “Conductive Paste, Preparation Method and Application Thereof”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of batteries, and in particular to a conductive paste and a preparation method and application thereof. Background Art

[0003] The electrodes in solar cells are usually prepared by low-temperature curing of conductive paste. In order to improve the photoelectric conversion efficiency of solar cells, the curing time of the conductive paste needs to be more than 30 minutes, but too long a curing time will lead to low production efficiency of solar cells and cannot meet industrial production needs. In order to improve the curing efficiency of the conductive paste, the amount of curing agent in the conductive paste can be increased. However, adding too much curing agent will lead to an increase in the viscosity of the conductive paste, which is not conducive to screen printing, and too much curing agent is easy to react with other components, reducing the storage stability of the conductive paste, increasing the storage cost of the conductive paste, and is not conducive to the widespread application of solar cells. Therefore, it is necessary to develop a conductive paste with low cost, good storage stability, and high curing efficiency.

[0004] Summary of the Invention

[0005] In view of this, the present application provides a conductive paste and its preparation method and application. The conductive paste includes a conductive filler and a non-resin binder. The non-resin binder can improve the curing efficiency, bonding ability and storage stability of the conductive paste, reduce the preparation cost, and is conducive to the wide application of the conductive paste.

[0006] In a first aspect, the present application provides a conductive paste, comprising a conductive filler and a non-resin binder, wherein the non-resin binder comprises an end-epoxysiloxane, a reactive diluent, and a curing agent, wherein the end-epoxysiloxane comprises a first repeating unit, wherein the first repeating unit is as shown in formula (I),

[0007] The R 1 and the R 2 Independently selected from substituted or unsubstituted alkyl or The R 3 Including substituted or unsubstituted alkyleneoxy, the R 4 The terminal epoxysiloxane comprises a substituted or unsubstituted alkylene group or a single bond, and the relative molecular mass of the terminal epoxysiloxane is less than or equal to 3000.

[0008] In one embodiment, the terminal epoxy group has a structural formula as shown in formula (II-1),

[0009] Wherein, the R1, the R2, the R5, the R6, the R 5 、The R 6 、The R 7 、The R 8 , and said R7 is independently selected from substituted or unsubstituted alkyl or The R 3 and said R3 includes a substituted or unsubstituted alkyleneoxy group, said R 4 , the R4 includes a substituted or unsubstituted alkylene group or a single bond, the sum of n and m is less than or equal to 5, and the values ​​of n and m are not both 0.

[0010] In one embodiment, the mass percentage of the terminal epoxy siloxane in the conductive paste is 1%-5%.

[0011] In one embodiment, the mass percentage of the conductive filler in the conductive paste is 85%-94%.

[0012] In one embodiment, the conductive filler includes at least one of silver powder, copper powder, and silver-coated copper powder.

[0013] In one embodiment, the silver powder includes at least one of flaky silver powder and spherical silver powder, the particle size D50 of the flaky silver powder is 2 μm-5 μm, and the tap density of the flaky silver powder is 4 g / cm 3 -4.5g / cm 3 The particle size D50 of the spherical silver powder is 0.2 μm-1.5 μm, and the tap density of the spherical silver powder is 5.5 g / cm 3 -6.5g / cm 3 .

[0014] In one embodiment, the mass percentage of the active diluent in the conductive paste is 0.2%-1.5%, and the active diluent includes at least one of cyclohexane-1,2-dicarboxylic acid diglycidyl ester, 1,4-butanediol diglycidyl ether, phenyl glycidyl ether, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, and 1,2-epoxy-4-vinylcyclohexane.

[0015] In one embodiment, the mass percentage of the curing agent in the conductive paste is 0.2%-0.6%, and the curing agent includes at least one of an imidazole curing agent, an acid anhydride curing agent, and a Lewis acid amine complex curing agent.

[0016] In one embodiment, the non-resin binder further includes at least one of a thixotropic agent, a dispersant, a curing accelerator, a silane coupling agent, and an organic solvent.

[0017] In one embodiment, the mass percentage of the thixotropic agent in the conductive paste is 0.1%-1%, and the thixotropic agent includes at least one of an unsaturated polycarboxylic acid polymer thixotropic agent, a polycarboxylic acid alkyl ammonium salt thixotropic agent, a modified urea thixotropic agent, and a urea-modified non-polar polyamide thixotropic agent.

[0018] In one embodiment, the mass percentage of the dispersant in the conductive paste is 0.1%-1%, and the dispersant includes at least one of polyphosphate, polyethylene glycol, and carboxylic acid.

[0019] In one embodiment, the mass percentage of the curing accelerator in the conductive paste is less than or equal to 0.6%, and the curing accelerator includes at least one of benzoyl peroxide, diethylaminopropylamine, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, and 3-(p-chlorophenyl)-1,1-dimethylurea.

[0020] In one embodiment, the mass percentage of the silane coupling agent in the conductive paste is less than or equal to 2%, and the silane coupling agent includes at least one of 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 3-(2,3-epoxypropyloxy)propylmethyldimethoxysilane.

[0021] In one embodiment, the mass percentage of the organic solvent in the conductive paste is 1.6%-5%, and the organic solvent includes at least one of butyl acetate, diethylene glycol butyl ether acetate, butyl carbitol acetate, propylene glycol methyl ether acetate, diethyl carbonate, diethylene glycol butyl ether, diethylene glycol diethyl ether, propylene glycol ethyl ether, and dipropylene glycol butyl ether.

[0022] In one embodiment, the volume resistivity of the conductive paste is less than or equal to 10×10 -6 Ω·cm, and the fineness of the conductive paste is less than or equal to 7 μm.

[0023] The non-resin binder in the conductive paste provided in the present application does not contain a resin component, which can avoid the reaction between the resin component and the curing agent during the storage of the conductive paste, thereby improving the storage stability of the conductive paste. At the same time, the terminal epoxysiloxane can improve the curing efficiency of the conductive paste and enhance the bonding ability of the conductive paste, which is conducive to obtaining a conductive paste with high curing efficiency, suitable resistivity and excellent bonding ability, and is conducive to the use of the conductive paste.

[0024] In a second aspect, the present application provides a method for preparing a conductive paste, comprising:

[0025] The terminal epoxy siloxane, the reactive diluent and the curing agent are first mixed to obtain a non-resin binder; and the conductive filler and the non-resin binder are second mixed to obtain a conductive paste.

[0026] In one embodiment, the first mixing time is 30 min-60 min, and the first mixing temperature is 20°C-30°C; the second mixing time is 3 h-5 h, and the second mixing temperature is 0°C-10°C.

[0027] The preparation method of the conductive paste provided in the present application is novel and has a simple preparation process, and can produce a conductive paste with high curing efficiency, suitable resistivity, excellent bonding ability and good storage stability.

[0028] In a third aspect, the present application provides a solar cell comprising a silicon substrate and a first film layer arranged on the surface of the silicon substrate and a second film layer arranged on the surface of the silicon substrate facing away from the first film layer; a first electrode and a second electrode are respectively provided on the surfaces of the first film layer and the second film layer, and at least one of the first electrode and the second electrode is obtained by curing the conductive paste according to the first aspect or the conductive paste prepared by the preparation method according to the second aspect.

[0029] The solar cell provided in this application has high photoelectric conversion efficiency and strong product competitiveness.

[0030] In a fourth aspect, the present application provides a method for preparing a solar cell, comprising: forming a first electrode on the surface of a silicon substrate, and forming a second electrode on the surface of the silicon substrate in a direction away from the first electrode to obtain a solar cell; at least one of the first electrode and the second electrode is obtained by curing the conductive paste according to the first aspect or the conductive paste prepared by the preparation method according to the second aspect.

[0031] The solar cell preparation method provided in the present application is simple, easy to operate, and has high production efficiency, and can realize large-scale production of solar cells, which is conducive to the widespread use of solar cells.

[0032] In a fifth aspect, the present application provides an electrical device, which includes the solar cell according to the third aspect or the solar cell manufactured according to the preparation method according to the fourth aspect.

[0033] The electrical equipment provided in this application has excellent comprehensive performance, which is conducive to the wide application of electrical equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] FIG1 is a flow chart of a method for preparing a conductive paste provided in one embodiment of the present application.

[0036] FIG2 is a schematic cross-sectional view of a solar cell provided in accordance with an embodiment of the present application.

[0037] FIG3 shows the bonding performance test results of the conductive paste prepared in Example 1.

[0038] FIG4 is a test result of the bonding performance of the conductive paste prepared in Comparative Example 1.

[0039] FIG5 is a test result of the bonding performance of the conductive paste prepared in Comparative Example 3.

[0040] Description of reference numerals: 100 - solar cell, 10 - first film layer, 20 - silicon substrate, 30 - second film layer. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0042] The present application provides a conductive paste, comprising a conductive filler and a non-resin binder, wherein the non-resin binder comprises a terminal epoxy siloxane, a reactive diluent, and a curing agent, wherein the terminal epoxy siloxane comprises a first repeating unit, and the first repeating unit is as shown in formula (I):

[0043] R 1 and R 2 Independently selected from substituted or unsubstituted alkyl or R 3 Including substituted or unsubstituted alkyleneoxy, R 4Including substituted or unsubstituted alkylene groups or single bonds, the relative molecular mass of the terminal epoxysiloxane is less than or equal to 3000. In the conductive paste provided by the present application, the conductive filler mainly plays a conductive role in the conductive paste, which can directly affect the key factors such as the conductivity of the conductive paste; the non-resin binder plays a bonding and curing role, improving the bonding ability and curing efficiency of the conductive paste, and the terminal epoxysiloxane in the non-resin binder replaces the resin component in the binder of the prior art, avoiding the problems caused by the reaction between the resin component and the curing agent during the storage of the conductive paste, and improving the storage stability of the conductive paste. The siloxane bond in the terminal epoxysiloxane has excellent hydrophobicity and adhesion, which can further improve the bonding ability of the conductive paste; the curing agent enables the conductive paste to undergo a curing and cross-linking reaction, promoting the curing and molding of the conductive paste; the active diluent can participate in the curing reaction, constitute a part of the curing cross-linking network, and improve the curing efficiency of the conductive paste. The reaction activity of the terminal epoxysiloxane with the reactive diluent and curing agent at room temperature in the conductive paste is low. When the three exist alone in the conductive paste, no cross-linking and curing occurs, and no polymer is formed, which can improve the storage stability of the conductive paste; during curing, the low molecular weight terminal epoxysiloxane has high activity when forming a cured cross-linked network, which is beneficial to the continuous migration of the curing agent and the reactive diluent in the terminal epoxysiloxane, thereby improving the curing reaction efficiency; the terminal epoxysiloxane has good curing ability, which can avoid the use of conductive fillers with smaller particle size to improve the curing efficiency and reduce the preparation cost of the conductive paste. The conductive paste provided in this application uses terminal epoxysiloxane instead of the resin component, which can improve the curing efficiency, storage stability and bonding ability of the conductive paste, reduce the preparation cost of the conductive paste, and thus improve the comprehensive performance of the conductive paste.

[0044] In the present application, the conductive filler is the main component of the conductive paste. The conductive filler plays a conductive role in the conductive paste and affects the conductivity of the conductive paste. In one embodiment of the present application, the mass percentage of the conductive filler in the conductive paste is 85%-94%. Specifically, the mass percentage of the conductive filler in the conductive paste can be, but is not limited to, 85%, 88%, 89%, 90%, 92% or 94%. In one embodiment of the present application, the mass percentage of the conductive filler in the conductive paste is 88%-93%, which can further improve the conductivity and fluidity of the conductive paste. In another embodiment of the present application, the mass percentage of the conductive filler in the conductive paste is 85%-92%, which can further improve the conductivity and bonding ability of the conductive paste.

[0045] In one embodiment of the present application, the conductive filler includes at least one of silver powder, copper powder and silver-coated copper powder. Silver powder, copper powder and silver-coated copper powder all have good electrical conductivity, which is conducive to obtaining a conductive paste with low resistivity. In one embodiment of the present application, the conductive filler can be silver-coated copper powder, which can obtain a conductive paste with good conductivity and low preparation cost. In another embodiment of the present application, the conductive filler can be silver powder, which has excellent electrical conductivity and is conducive to improving the conductive properties of the conductive paste. In one embodiment, the silver powder includes flake silver powder and spherical silver powder, wherein the flake silver powder has a large contact area, which can expand the coverage area, improve the density of the conductive paste after curing, reduce the resistance of the conductive paste, and improve the conductive properties; the spherical silver powder has a high sphericity and a small contact area with other components, which is conducive to improving the fluidity of the conductive paste; when the two are used at the same time, the conductive paste can take into account both excellent fluidity and conductivity. Specifically, the mass ratio of the flaky silver powder to the spherical silver powder is 1:(0.25-4). For example, the mass ratio of the flaky silver powder to the spherical silver powder can be, but is not limited to, 1:0.25, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, or 1:4. In one embodiment of the present application, the mass ratio of the flaky silver powder to the spherical silver powder is 1:(0.25-3). In another embodiment of the present application, the mass ratio of the flaky silver powder to the spherical silver powder is 1:(2-4).

[0046] In one embodiment of the present application, the particle size D50 of the flaky silver powder is 2 μm-5 μm, and the tap density of the flaky silver powder is 4 g / cm 3 -4.5g / cm 3 , which can improve the compaction density and energy density of the electrode sheet. Specifically, the particle size D50 of the flaky silver powder can be, but is not limited to, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm; the tap density of the flaky silver powder can be, but is not limited to, 4 g / cm 3 , 4.1g / cm 3 , 4.2g / cm 3 , 4.3g / cm 3 , 4.4g / cm 3 or 4.5g / cm 3 In one embodiment of the present application, the particle size D50 of the flaky silver powder is 2 μm-3.5 μm, and the tap density of the flaky silver powder is 4 g / cm 3 -4.2g / cm 3 In another embodiment of the present application, the particle size D50 of the flaky silver powder is 3 μm-5 μm, and the tap density of the flaky silver powder is 4.1 g / cm 3 -4.5g / cm 3 .

[0047] In one embodiment of the present application, the particle size D50 of the spherical silver powder is 0.2 μm-1.5 μm, and the tap density of the spherical silver powder is 5.5 g / cm 3 -6.5g / cm 3 , which can improve the fluidity and coating ability of the conductive paste. Specifically, the particle size D50 of the spherical silver powder can be, but is not limited to, 0.2 μm, 0.5 μm, 0.7 μm, 0.8 μm, 1 μm, 1.3 μm or 1.5 μm; the tap density of the spherical silver powder can be, but is not limited to, 5.5 g / cm 3 , 5.6g / cm 3 , 5.8g / cm 3 , 6g / cm 3 、6.3g / cm 3 or 6.5g / cm 3 In one embodiment of the present application, the particle size D50 of the spherical silver powder is 0.2 μm-0.9 μm, and the tap density of the spherical silver powder is 5.5 g / cm 3 -6g / cm 3 In another embodiment of the present application, the particle size D50 of the spherical silver powder is 0.8 μm-1.5 μm, and the tap density of the spherical silver powder is 5.8 g / cm 3 -6.5g / cm 3 .

[0048] In one embodiment of the present application, the conductive filler includes silver powder and glass powder, wherein the glass powder can promote the bonding of the silver powder, thereby improving the conductivity of the conductive paste. In one embodiment of the present application, the mass ratio of the glass powder to the silver powder is 1: (19-99), which can promote the curing efficiency of the conductive paste. Specifically, the mass ratio of the glass powder to the silver powder can be, but is not limited to, 1:19, 1:25, 1:40, 1:50, 1:60, 1:75, 1:85 or 1:99. In one embodiment of the present application, the mass ratio of the glass powder to the silver powder can be 1: (19-65). In another embodiment of the present application, the mass ratio of the glass powder to the silver powder can be 1: (55-99).

[0049] In one embodiment of the present application, the conductive filler may include at least one of copper powder and silver-coated copper powder, as well as silver powder. This helps maintain a high conductivity of the conductive paste while reducing the preparation cost of the conductive paste, facilitating the industrial application of the conductive paste. The conductive filler may also include glass powder. In one embodiment of the present application, the conductive filler is silver powder and copper powder. Copper powder has excellent electrical and thermal conductivity and is inexpensive. Using copper powder to replace part of the silver powder can reduce the preparation cost of the conductive paste. In one embodiment of the present application, the mass ratio of copper powder to silver powder is 1:(0.67-2.34), which can reduce the preparation cost of the conductive paste and improve the conductivity of the conductive paste. Specifically, the mass ratio of copper powder to silver powder can be, but is not limited to, 1:0.67, 1:1, 1:1.2, 1:1.6, 1:1.8, 1:2, or 1:2.34. In one embodiment of the present application, the mass ratio of copper powder to silver powder can be 1:(0.67-1.8). In another embodiment of the present application, the mass ratio of copper powder to silver powder can be 1:(1-2.34). In one embodiment of the present application, the conductive filler is silver powder and silver-coated copper powder; wherein the silver-coated copper powder has the advantages of high conductivity of silver powder and low cost of copper powder, and also has the advantages of stability and not easy to oxidize. In one embodiment of the present application, the mass ratio of silver-coated copper powder to silver powder is 1:(0-1), which can improve the storage stability of the conductive paste. Specifically, the mass ratio of silver-coated copper powder to silver powder can be, but is not limited to, 1:0, 1:0.2, 1:0.5, 1:0.6, 1:0.8, 1:0.9 or 1:1, etc. In one embodiment of the present application, the mass ratio of silver-coated copper powder to silver powder can be 1:(0-0.7). In another embodiment of the present application, the mass ratio of silver-coated copper powder to silver powder can be 1:(0.3-1).

[0050] In the related art, the binder in the conductive paste includes a resin component (such as epoxy resin, etc.), the curing agent reacts with the resin component, the molecular chain continues to grow to form a cross-linked network, and solidifies into shape, but as the reaction continues, the cross-linked network becomes tighter, resulting in a decrease in the reaction rate of the curing agent and the resin component, and a decrease in the curing reaction rate, which affects the curing rate of the conductive paste; in order to increase the curing rate of the conductive paste, the content of the curing agent in the conductive paste can be increased, however, the increase in the curing agent causes the resin component to react with the curing agent during the storage of the conductive paste, thereby increasing the viscosity of the conductive paste and affecting the use of the conductive paste. The non-resin binder in the present application uses terminal epoxy siloxane instead of the macromolecular resin component. The epoxy group at the terminal position of the terminal epoxy siloxane can undergo ring-opening polymerization with the curing agent to form a cross-linked network, thereby improving the curing ability of the conductive paste; the siloxane group of the terminal epoxy siloxane is a chain structure and does not have a benzene ring or cycloalkane group, which can increase the activity of the curing agent and the reactive diluent in the cross-linked network, accelerate the migration speed of the curing agent and the reactive diluent, and improve the efficiency of the curing reaction; the siloxane group has excellent hydrophobicity and adhesion, reduces the adverse effects of water on the conductive paste, and improves the bonding ability and coating ability of the conductive paste; the terminal epoxy siloxane has low reaction activity with the reactive diluent and curing agent during the storage of the conductive paste, and is difficult to undergo cross-linking reaction, which is beneficial to improving the storage stability of the conductive paste.

[0051] In the present application, the terminal epoxysiloxane includes a first repeating unit, and the first repeating unit is as shown in formula (I),

[0052] R 1 and R 2 Independently selected from substituted or unsubstituted alkyl or R 3 Including substituted or unsubstituted alkyleneoxy, R 4 In some embodiments, the terminal epoxysiloxane has an epoxy group at one end, even if R 1 and R 2 When the alkyl group is a substituted or unsubstituted alkyl group, the terminal epoxysiloxane still has an epoxy group at one end.

[0053] In one embodiment of the present application, the structural formula of the terminal epoxysiloxane is as shown in Formula (II-1),

[0054] Among them, R1, R2, R5, R6, R 5 、R 6 、R 7 、R 8 , and R7 are independently selected from substituted or unsubstituted alkyl or R3 and R3 includes substituted or unsubstituted alkyleneoxy, R 4 , R4 includes substituted or unsubstituted alkylene or a single bond, the sum of n and m is less than or equal to 5, and the values ​​of n and m are not both 0. The sum of n and m is less than or equal to 5, which limits the number of siloxanes in the main chain, and avoids excessively long siloxane chains that increase the viscosity of the conductive paste and reduce the curing rate. Specifically, the sum of n and m can be, but is not limited to, 1, 2, 3, 4 or 5. In one embodiment of the present application, the sum of n and m can be 2 or 3, which can further improve the curing rate, bonding properties, and coating and screen printing capabilities of the conductive paste. When one of m and n is 0, the structural formula of the terminal epoxysiloxane is as shown in Formula (II-2),

[0055] Among them, R 1 and R 2 Independently selected from substituted or unsubstituted alkyl or Specifically, a can be, but is not limited to, 1, 2, 3, 4 or 5.

[0056] In one embodiment of the present application, R 5 、R 8 and R 6 、R 7 When the selection is the same, in formula (II-1) The structure of The structures of the two are the same; further, when the sum of m and n is the same as the value of a, the structural formulas of the two are exactly the same.

[0057] In one embodiment of the present application, the terminal epoxy siloxane may be composed of The compound is obtained by hydrosilylation of a compound containing an epoxy group and a double bond. Exemplarily, the preparation process of the terminal epoxy siloxane is shown in formula (III),

[0058] In one embodiment of the present application, the compound containing epoxy groups and double bonds does not have a polyether group, which can reduce the generation of bubbles during the curing process of the conductive paste, improve the density of the conductive network, reduce the hydrophilicity of the conductive paste, improve the moisture resistance of the conductive paste, and improve the storage stability and storage period of the conductive paste.

[0059] In this application, multiple groups can be selected from When the structural formula of the terminal epoxysiloxane contains two or more groups selected from When R3 and R4 in different groups can be the same or different.

[0060] In one embodiment of the present application, an alkyl group is an alkane molecule with one hydrogen atom removed, including straight-chain alkyl groups and branched-chain alkyl groups. The number of carbon atoms in the alkyl group is 1-10. Specifically, the number of carbon atoms in the alkyl group may be, but is not limited to, 1, 2, 3, 4, 5, 7, 8, 9, or 10. For example, the alkyl group may include, but is not limited to, at least one of a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an isobutyl group, an n-pentyl group, a 2-methylbutyl group, a 2,2-dimethylpropyl group, an n-hexyl group, a heptyl group, a 2-methylhexyl group, a 5-methylpentyl group, a 2-ethylbutyl group, a 3-ethylbutyl group, a nonyl group, and a decyl group. In one embodiment of the present application, the alkyl group may be a methyl group. In another embodiment of the present application, the alkyl group may be an ethyl group.

[0061] In one embodiment of the present application, an alkylene group is an alkane molecule with two hydrogen atoms removed, including a straight-chain alkylene group and a branched-chain alkylene group. The number of carbon atoms of the alkylene group is 1-8. Specifically, the number of carbon atoms of the alkylene group may be, but is not limited to, 1, 2, 3, 4, 5, 6, 7, or 8. Exemplary, the alkylene group may include, but is not limited to, methylene, ethylene, propylene, butylene, heptylene, nonylene, and decylene. In one embodiment of the present application, the alkylene group may be ethylene.

[0062] In one embodiment of the present application, an alkyleneoxy group is a composite group formed by linking an alkylene group and an oxygen group, including a straight-chain alkyleneoxy group and a branched alkyleneoxy group. The number of carbon atoms of the alkyleneoxy group is 3-8. Specifically, the number of carbon atoms of the alkyleneoxy group may be, but is not limited to, 3, 4, 5, 6, 7 or 8. Exemplary, the alkyleneoxy group may include, but is not limited to, at least one of -CH2CH2CH2O-, -CH2CH2CH2CH2O-, -CH2CH2CH2CH2CH2O-, -CH2C(CH3)2CH2CH2O- and -CH2CH2CH2CH2CH2CH2O-. In one embodiment of the present application, the alkyleneoxy group may be -CH2CH2CH2O-. In the present application, a substituted group (such as an alkyl group, an alkylene group and an alkyleneoxy group) refers to a group substituted by a substituent. In one embodiment of the present application, the substituent includes at least one of a halogen, a nitrogen atom, an oxygen atom, a sulfur atom, a hydroxyl group, a nitro group, an amino group, a thiol group, a methoxy group and a cyano group.

[0063] In one embodiment of the present application, the number of epoxy groups in the terminal epoxysiloxane is greater than or equal to 1. The terminal epoxy groups can undergo a rapid curing reaction with the curing agent. The number of terminal epoxy groups affects the curing efficiency of the conductive paste. Bi-terminal epoxysiloxanes or even multi-terminal epoxysiloxanes can further improve the curing efficiency of the conductive paste. Specifically, the number of epoxy groups in the terminal epoxysiloxane is 2 or more, 3 or more, 4 or more, 5 or more, etc.

[0064] In one embodiment of the present application, the terminal alkoxysiloxane may include at least one of the compounds represented by formula (IV-1) to formula (IV-8).

[0065] In the present application, the relative molecular mass of the terminal epoxysiloxane is less than or equal to 3000. The terminal epoxysiloxane is a low molecular weight compound, which is different from the high molecular weight resin component in the prior art. It can increase the storage period of the conductive paste, reduce storage costs, increase the curing reaction rate, and accelerate the rapid curing of the conductive paste. Specifically, the relative molecular mass of the terminal epoxysiloxane can be, but is not limited to, less than or equal to 3000, less than or equal to 2800, less than or equal to 2500, less than or equal to 2000, less than or equal to 1700, less than or equal to 1500, less than or equal to 1000, or less than or equal to 800. In one embodiment of the present application, the relative molecular mass of the terminal epoxysiloxane can be less than or equal to 1800. In another embodiment of the present application, the relative molecular mass of the terminal epoxysiloxane can be less than or equal to 1000.

[0066] In one embodiment of the present application, the mass percentage of the terminal epoxy siloxane in the conductive paste is 1%-5%. Specifically, the mass percentage of the terminal epoxy siloxane can be, but is not limited to, 1%, 1.5%, 2%, 3%, 4%, or 5%. In one embodiment of the present application, the mass percentage of the terminal epoxy siloxane can be 2.7%-5%, which can further improve the curing efficiency, adhesion, and stability of the conductive paste. In another embodiment of the present application, the mass percentage of the terminal epoxy siloxane can be 3%-5%.

[0067] In this application, the reactive diluent is a low-molecular-weight epoxy compound containing an epoxy group. It can participate in the curing reaction, forming part of the cured cross-linked network, and improving the curing efficiency of the conductive paste. In one embodiment of the present application, the reactive diluent may include, but is not limited to, at least one of cyclohexane-1,2-dicarboxylic acid diglycidyl ester, 1,4-butanediol diglycidyl ether, phenyl glycidyl ether, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, and 1,2-epoxy-4-vinylcyclohexane. In one embodiment of the present application, the reactive diluent may be 1,4-butanediol diglycidyl ether.

[0068] In one embodiment of the present application, the mass percentage of the active diluent in the conductive paste is 0.2%-1.5%. Suitable active diluents can improve the curing efficiency of the conductive paste. Specifically, the active diluent can be, but is not limited to, 0.2%, 0.5%, 0.7%, 0.9%, 1.2%, 1.4%, or 1.5%. In one embodiment of the present application, the mass percentage of the active diluent can be 0.5%-1.5%, which is beneficial for improving the curing ability and bonding ability of the conductive paste. In another embodiment of the present application, the mass percentage of the active diluent can be 0.5%-1%, which can further improve the curing efficiency of the conductive paste.

[0069] In the present application, the curing agent enables the conductive paste to undergo a curing and crosslinking reaction, promotes the curing and forming of the conductive paste, and improves the curing efficiency of the conductive paste. In one embodiment of the present application, the curing agent includes at least one of an imidazole curing agent, an acid anhydride curing agent, and a Lewis acid amine complex curing agent. For example, the imidazole curing agent may include, but is not limited to, at least one of 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenyl-4-methylimidazole; the acid anhydride curing agent may include, but is not limited to, at least one of tetrahydrophthalic anhydride, pyromellitic anhydride, and maleic anhydride; and the Lewis acid amine complex curing agent may include, but is not limited to, at least one of boron trifluoride monomethylamine, boron trifluoride monoethylamine, and boron trifluoride triethanolamine. In one embodiment of the present application, when the curing agent is an imidazole curing agent, the imidazole curing agent may be 2-ethyl-4-methylimidazole. In another embodiment of the present application, when the curing agent is a Lewis acid amine complex curing agent, the Lewis acid amine complex curing agent may be boron trifluoride monoethylamine.

[0070] In one embodiment of the present application, the mass percentage of the curing agent in the conductive paste is 0.2%-0.6%. An appropriate curing agent can enhance the bonding ability of the conductive paste. Specifically, the mass percentage of the curing agent can be, but is not limited to, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.5%, or 0.6%. In one embodiment of the present application, the mass percentage of the curing agent can be 0.3%-0.5%, which can further improve the curing ability and curing efficiency of the conductive paste. In another embodiment of the present application, the mass percentage of the curing agent can be 0.25%-0.6%.

[0071] In one embodiment of the present application, the non-resin binder further includes at least one of a thixotropic agent, a dispersant, a curing accelerator, a silane coupling agent, and an organic solvent, which can further improve the curing efficiency and bonding ability of the conductive paste.

[0072] In the present application, a thixotropic agent can improve the thixotropic properties of the conductive paste. In one embodiment of the present application, the thixotropic agent includes at least one of an unsaturated polycarboxylic acid polymer thixotropic agent, a polycarboxylic acid alkylammonium salt thixotropic agent, a modified urea thixotropic agent, and a urea-modified non-polar polyamide thixotropic agent. In one embodiment of the present application, the thixotropic agent can be a modified urea thixotropic agent. In another embodiment of the present application, the thixotropic agent can be a high molecular weight urea-modified non-polar polyamide thixotropic agent.

[0073] In one embodiment of the present application, the mass percentage of the thixotropic agent in the conductive paste is 0.1%-1%. An appropriate thixotropic agent can enhance the thixotropic properties of the conductive paste and improve the overall performance of the conductive paste. Specifically, the mass percentage of the thixotropic agent can be, but is not limited to, 0.1%, 0.2%, 0.3%, 0.4%, 0.6%, 0.8%, or 1%. In one embodiment of the present application, the mass percentage of the thixotropic agent can be 0.2%-0.8%, which can further enhance the thixotropic properties of the conductive paste. In another embodiment of the present application, the mass percentage of the thixotropic agent can be 0.6%-1%.

[0074] In this application, the dispersant wets and disperses the conductive filler, preventing agglomeration of the conductive paste and reducing its viscosity. In one embodiment of this application, the dispersant may include, but is not limited to, at least one of polyphosphate, polyethylene glycol, and carboxylic acid. In one embodiment of this application, the dispersant may be a polyphosphate. In another embodiment of this application, the dispersant may be a low molecular weight carboxylic acid.

[0075] In one embodiment of the present application, the mass percentage of the dispersant in the conductive paste is 0.1%-1%. The dispersant can improve the dispersion ability of the conductive filler and enhance the coating ability of the conductive paste. Specifically, the mass percentage of the dispersant can be, but is not limited to, 0.1%, 0.2%, 0.3%, 0.4%, 0.6%, 0.8%, or 1%. In one embodiment of the present application, the mass percentage of the dispersant can be 0.1%-0.9%. In another embodiment of the present application, the mass percentage of the dispersant can be 0.2%-0.6%, which can improve the dispersion of the conductive filler in the conductive paste and reduce the viscosity of the conductive paste.

[0076] In the present application, a curing accelerator can enhance the curing effect of the curing agent and improve the curing efficiency of the conductive paste. In one embodiment of the present application, the curing accelerator may include, but is not limited to, at least one of benzoyl peroxide, diethylaminopropylamine, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, and 3-(p-chlorophenyl)-1,1-dimethylurea. In one embodiment of the present application, the curing accelerator may be benzoyl peroxide. In another embodiment of the present application, the curing accelerator may be 3-(p-chlorophenyl)-1,1-dimethylurea.

[0077] In one embodiment of the present application, the mass percentage of the curing accelerator in the conductive paste is less than or equal to 0.6%. Specifically, the mass percentage of the curing accelerator may be, but is not limited to, less than or equal to 0.1%, less than or equal to 0.2%, less than or equal to 0.3%, less than or equal to 0.4%, less than or equal to 0.5%, or less than or equal to 0.6%. In one embodiment of the present application, the mass percentage of the curing accelerator may be less than or equal to 0.3%, that is, the non-resin binder may not contain a curing accelerator, and an appropriate curing accelerator may enhance the curing effect of the curing agent. In another embodiment of the present application, the mass percentage of the curing accelerator may be 0.2%-0.5%, which is beneficial to improving the curing rate and bonding ability of the conductive paste.

[0078] In the present application, a silane coupling agent can improve the bonding ability of the conductive paste. In one embodiment of the present application, the silane coupling agent may include, but is not limited to, at least one of 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 3-(2,3-epoxypropyloxy)propylmethyldimethoxysilane. In one embodiment of the present application, the silane coupling agent may be 3-glycidyloxypropyltriethoxysilane. In another embodiment of the present application, the silane coupling agent may be 3-glycidyloxypropyltrimethoxysilane.

[0079] In one embodiment of the present application, the weight percentage of the silane coupling agent in the conductive paste is less than or equal to 2%. Specifically, the weight percentage of the silane coupling agent may be, but is not limited to, less than or equal to 0.5%, less than or equal to 0.8%, less than or equal to 1%, less than or equal to 1.2%, less than or equal to 1.5%, less than or equal to 1.8%, or less than or equal to 2%. In one embodiment of the present application, the weight percentage of the silane coupling agent may be less than or equal to 1%, and the non-resin binder may not contain a silane coupling agent. An appropriate silane coupling agent can improve the bonding ability of the conductive paste. In another embodiment of the present application, the weight percentage of the silane coupling agent may be 0.7%-1.3%, which is beneficial for improving the bonding ability of the conductive paste.

[0080] In the present application, the organic solvent can adjust the viscosity of the conductive paste and improve the curing reaction rate and coating ability of the conductive paste. In one embodiment of the present application, the boiling point of the organic solvent is 120°C-300°C, so that a conductive paste that is easy to store, has good conductivity and high curing efficiency can be obtained. Specifically, the boiling point of the organic solvent can be, but is not limited to, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 260°C, 280°C or 300°C, etc. In one embodiment of the present application, the boiling point of the organic solvent can be 180°C-250°C, which can further improve the curing efficiency, conductivity and storage period of the conductive paste. In another embodiment of the present application, the boiling point of the organic solvent can be 150°C-230°C.

[0081] In one embodiment of the present application, the organic solvent may include, but is not limited to, at least one of butyl acetate, diethylene glycol butyl ether acetate, butyl carbitol acetate, propylene glycol methyl ether acetate, diethyl carbonate, diethylene glycol butyl ether, diethylene glycol diethyl ether, propylene glycol ethyl ether, and dipropylene glycol butyl ether. In some embodiments, the organic solvent is formed by mixing and compounding two or more organic solvents, and the volatility characteristics of the organic solvent can be adjusted so that the organic solvent forms a hierarchical volatilization, avoiding the adverse effects caused by the volatilization of a single organic solvent too fast or too slow. In one embodiment of the present application, the organic solvent may include diethylene glycol butyl ether acetate and diethylene glycol butyl ether, and the mass ratio of diethylene glycol butyl ether acetate and diethylene glycol butyl ether may be 1: 1, which can improve the curing efficiency of the conductive paste. In another embodiment of the present application, the organic solvent may be butyl acetate.

[0082] In one embodiment of the present application, the non-resin organic binder comprises, by mass percentage, 1%-5% of an end-group epoxy siloxane, 0.2%-1.5% of a reactive diluent, 0.2%-0.6% of a curing agent, and the balance being an organic solvent. In another embodiment of the present application, the non-resin organic binder comprises, by mass percentage, 1%-5% of an end-group epoxy siloxane, 0.2%-1.5% of a reactive diluent, 0.2%-0.6% of a curing agent, 0.1%-1% of a thixotropic agent, 0.1%-1% of a dispersant, 0.6% or less of a curing accelerator, and 2% or less of a silane coupling agent, and the balance being an organic solvent.

[0083] In one embodiment of the present application, the weight percentage of the organic solvent in the conductive paste is 1.6%-5%. The appropriate organic solvent can adjust the viscosity of the conductive paste. Specifically, the weight percentage of the organic solvent can be, but is not limited to, 1.6%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. In one embodiment of the present application, the weight percentage of the organic solvent can be 3.6%-5%, which can improve the coating ability and curing efficiency of the conductive paste. In another embodiment of the present application, the weight percentage of the organic solvent can be 2%-4%, which can further improve the coating ability of the conductive paste.

[0084] In one embodiment of the present application, the volume resistivity of the conductive paste is less than or equal to 10×10 -6 Ω·cm, which can improve the conductivity of the conductive paste and improve the photoelectric conversion efficiency of solar cells. Specifically, the volume resistivity of the conductive paste can be but is not limited to less than or equal to 10×10 -6 Ω·cm, less than or equal to 9×10 -6 Ω·cm, less than or equal to 8×10 -6 Ω·cm, less than or equal to 7×10 -6 Ω·cm, less than or equal to 6×10 -6 Ω·cm or less than or equal to 5.2×10 -6 Ω·cm, etc. In one embodiment of the present application, the volume resistivity of the conductive paste may be less than or equal to 5.2×10 -6 Ω·cm.

[0085] In one embodiment of the present application, the fineness of the conductive paste is less than or equal to 7 μm. The fineness represents the degree of dispersion of the conductive filler in the conductive paste. The greater the fineness, the lower the degree of dispersion of the conductive filler in the conductive paste, which is detrimental to the conductivity, coating ability, and adhesion of the conductive paste. The smaller the fineness, the higher the degree of dispersion of the conductive filler in the conductive paste, which can improve the overall performance of the conductive paste. Specifically, the fineness of the conductive paste can be, but is not limited to, less than or equal to 7 μm, less than or equal to 6.5 μm, less than or equal to 6 μm, less than or equal to 5.5 μm, less than or equal to 5 μm, or less than or equal to 4 μm. In one embodiment of the present application, the fineness of the conductive paste can be less than or equal to 6 μm.

[0086] In one embodiment of the present application, the rate of change in viscosity of the conductive paste at 25°C between the 0th and 15th days of storage is less than or equal to 0.6 Pa·s / d (Pascal·second / day), and the rate of change in viscosity between the 15th and 30th days of storage is less than or equal to 1 Pa·s / d. The small change in viscosity of the conductive paste over time indicates that the conductive paste has better storage stability, a longer storage period, and lower storage costs, which is conducive to the widespread application of the conductive paste. Specifically, the viscosity change rate of the conductive paste at 25°C between the 0th day and the 15th day may be, but is not limited to, less than or equal to 0.6 Pa·s / d, less than or equal to 0.5 Pa·s / d, less than or equal to 0.4 Pa·s / d, less than or equal to 0.3 Pa·s / d, less than or equal to 0.2 Pa·s / d, or less than or equal to 0.1 Pa·s / d; the viscosity change rate of the conductive paste between the 15th day and the 30th day may be, but is not limited to, less than or equal to 1 Pa·s / d, less than or equal to 0.8 Pa·s / d, less than or equal to 0.7 Pa·s / d, less than or equal to 0.6 Pa·s / d, or less than or equal to 0.5 Pa·s / d. In one embodiment of the present application, the viscosity change rate of the conductive paste at 25°C between the 0th day and the 15th day is less than or equal to 0.2 Pa·s / d, and the viscosity change rate of the conductive paste between the 15th day and the 30th day is less than or equal to 0.7 Pa·s / d.

[0087] In one embodiment of the present application, the viscosity of the conductive paste is 200 Pa·s-270 Pa·s. The viscosity used can improve the coating performance of the conductive paste. Specifically, the viscosity of the conductive paste can be, but is not limited to, 200 Pa·s, 210 Pa·s, 220 Pa·s, 250 Pa·s, 260 Pa·s, or 270 Pa·s. In one embodiment of the present application, the viscosity of the conductive paste can be 200 Pa·s-250 Pa·s, which can further improve the coating and bonding ability of the conductive paste. In another embodiment of the present application, the viscosity of the conductive paste can be 230 Pa·s-270 Pa·s.

[0088] Please refer to FIG1 , which is a flow chart of a method for preparing a conductive paste according to one embodiment of the present application, including:

[0089] S101: performing a first mixing of terminal epoxy siloxane, a reactive diluent, and a curing agent to obtain a non-resin binder;

[0090] S102: performing a second mixing of the conductive filler and the non-resin binder to obtain a conductive paste.

[0091] The conductive paste preparation method provided in this application is novel, simple in process, and low in preparation cost. It can produce a conductive paste with high curing efficiency, suitable resistivity, excellent bonding ability, and good storage stability. In one embodiment of the present application, the first mixing time is 30 minutes to 60 minutes. Specifically, the first mixing time can be, but is not limited to, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, or 60 minutes. In one embodiment of the present application, the first mixing time can be 30 minutes to 50 minutes. In another embodiment of the present application, the first mixing time can be 45 minutes to 60 minutes.

[0092] In one embodiment of the present application, the temperature of the first mixing is 20°C-30°C, at which point the components have not yet reacted. Specifically, the temperature of the first mixing can be, but is not limited to, 20°C, 21°C, 23°C, 25°C, 26°C, 27°C, or 30°C. In one embodiment of the present application, the temperature of the first mixing can be 20°C-27°C. In another embodiment of the present application, the temperature of the first mixing can be 26°C-30°C.

[0093] In one embodiment of the present application, the first mixing speed is 100 rpm-150 rpm. Specifically, the first mixing speed can be, but is not limited to, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, or 150 rpm. In one embodiment of the present application, the first mixing speed can be 100 rpm-130 rpm. In another embodiment of the present application, the first mixing speed can be 120 rpm-150 rpm.

[0094] In one embodiment of the present application, the second mixing time is 3 hours to 5 hours. Specifically, the second mixing time can be, but is not limited to, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours. In one embodiment of the present application, the second mixing time can be 3 hours to 4.5 hours. In another embodiment of the present application, the second mixing time can be 4 hours to 5 hours.

[0095] In one embodiment of the present application, the temperature of the second mixing is 0°C-10°C. In the initial stage of the second mixing, the conductive filler has not been completely dispersed, and a large amount of heat will be generated during mixing, which will adversely affect the stability of the non-resin binder. Therefore, mixing at a lower temperature can improve the stability of the non-resin binder. Specifically, the temperature of the second mixing can be, but is not limited to, 0°C, 3°C, 5°C, 6°C, 7°C, 8°C, 9°C or 10°C. In one embodiment of the present application, the temperature of the second mixing can be 0°C-7°C. In another embodiment of the present application, the temperature of the second mixing can be 6°C-10°C.

[0096] In one embodiment of the present application, the second mixing speed is 100 rpm-150 rpm. Specifically, the second mixing speed can be, but is not limited to, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, or 150 rpm. In one embodiment of the present application, the second mixing speed can be 100 rpm-130 rpm. In another embodiment of the present application, the second mixing speed can be 120 rpm-150 rpm.

[0097] In one embodiment of the present application, the non-resin binder further comprises at least one of a thixotropic agent, a dispersant, an organic solvent, a curing accelerator, and a silane coupling agent. In other words, the method for preparing the conductive paste further comprises: first mixing an epoxy-terminated siloxane, a reactive diluent, a curing agent, a thixotropic agent, a dispersant, an organic solvent, a curing accelerator, and a silane coupling agent to obtain a non-resin binder; and second mixing a conductive filler and the non-resin binder to obtain a conductive paste. The resulting conductive paste has advantages such as good bonding ability, high curing efficiency, good storage stability, a long shelf life, and low preparation cost.

[0098] In one embodiment of the present application, after the second mixing, three-roller grinding and dispersion is also included to reduce the fineness of the conductive paste and improve the dispersion of the conductive filler in the conductive paste. The three-roller grinding and dispersion achieves the grinding effect by squeezing the surfaces of three horizontal rollers against each other and rubbing at different speeds. In one embodiment of the present application, the three-roller grinding and dispersion includes the following steps: Step 1: Setting the initial roller gap to 80 μm and the final roller gap to 40 μm, mixing 3 times; Step 2: Setting the initial roller gap to 40 μm and the final roller gap to 20 μm, mixing 3 times; Step 3: Setting the initial roller gap to 20 μm and the final roller gap to 10 μm, mixing 3 times; Step 4: Setting the initial roller gap to 10 μm and the final roller gap to 7 μm, mixing 3 times to obtain the conductive paste.

[0099] In one embodiment of the present application, the rolling temperature of the three-roll milling dispersion is 20°C-25°C, and the speed of the three-roll milling dispersion is 100rpm-150rpm. Specifically, the rolling temperature of the three-roll milling dispersion can be, but is not limited to, 20°C, 21°C, 22°C, 23°C, 24°C, or 25°C; the speed of the three-roll milling dispersion can be, but is not limited to, 100rpm, 110rpm, 120rpm, 130rpm, 140rpm, or 150rpm. In one embodiment of the present application, the speed of the three-roll milling dispersion can be 100rpm-130rpm. In another embodiment of the present application, the speed of the three-roll milling dispersion can be 120rpm-150rpm.

[0100] The present application provides an electrode, wherein the raw material of the electrode includes the conductive paste in any one of the above embodiments. The electrode provided by the present application has low resistivity, good conductivity, and strong bonding ability.

[0101] Please refer to Figure 2, which is a schematic cross-sectional view of a solar cell provided in one embodiment of the present application. Solar cell 100 includes a silicon substrate 20, a first film layer 10 disposed on a surface of the silicon substrate, and a second film layer 30 disposed on a surface of the silicon substrate facing away from first film layer 10. First and second electrodes are disposed on the surfaces of first film layer 10 and second film layer 30, respectively. At least one of the first and second electrodes is obtained by curing a conductive paste according to any of the aforementioned embodiments or a conductive paste prepared by any of the aforementioned preparation methods. The solar cell provided in this application has high photoelectric conversion efficiency and excellent electrochemical performance.

[0102] This application also provides a method for preparing a solar cell, comprising: forming a first electrode on the surface of a silicon substrate, and forming a second electrode on the surface of the silicon substrate in a direction away from the first electrode, to obtain a solar cell; at least one of the first electrode and the second electrode is obtained by curing the conductive paste according to any one of claims 1 to 15 or the conductive paste prepared by the preparation method according to claim 16 or 17. The solar cell preparation method provided in this application is simple, easy to operate, and has high production efficiency, enabling large-scale production of solar cells. The resulting solar cells have high photoelectric conversion efficiency and excellent electrochemical performance.

[0103] In one embodiment of the present application, a conductive paste can be applied to the surface of a silicon substrate by screen printing, coating, or other methods, and then cured to form a first electrode and / or a second electrode. In some embodiments, the silicon substrate may include, but is not limited to, at least one of single-crystal silicon, polycrystalline silicon, and amorphous silicon. In some embodiments, at least one of the first and second film layers includes a transparent conductive layer and an electrode disposed on the transparent conductive layer. The electrode may be in the form of an electrode layer or a gate line, etc. In one embodiment of the present application, the solar cell is an N-type heterojunction cell, comprising a single-crystal silicon substrate, a first film layer disposed on the surface of the single-crystal silicon substrate, and a second film layer disposed on the surface of the single-crystal silicon substrate facing away from the first film layer. Along the direction from the single-crystal silicon substrate to the first film layer, the first film layer includes a first amorphous silicon layer, a first amorphous silicon doped layer, a first transparent conductive layer, and a first electrode stacked in sequence. Along the direction from the single-crystal silicon substrate to the second film layer, the second film layer includes a second amorphous silicon layer, a second amorphous silicon doped layer, a second transparent conductive layer, and a second electrode stacked in sequence. In one embodiment of the present application, a conductive paste is applied to the silicon substrate.

[0104] In one embodiment of the present application, the curing temperature is 180°C-200°C. Specifically, the curing temperature may be, but is not limited to, 180°C, 185°C, 190°C, 192°C, 198°C or 200°C. In one embodiment of the present application, the curing temperature may be 180°C-190°C. In another embodiment of the present application, the curing temperature may be 185°C-200°C. In one embodiment of the present application, the curing time is 5 min-10 min. Specifically, the curing time may be, but is not limited to, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min. In one embodiment of the present application, the curing time may be 5 min-8 min.

[0105] In one embodiment of the present application, a drying treatment is also included before curing, and the temperature of the drying treatment is 120°C-160°C. The drying treatment can preheat the conductive paste, so that the organic solvent begins to volatilize, accelerate the diffusion in the conductive paste, and improve the volatilization efficiency of other components; it can promote the slow curing reaction of other components, reduce the gaps between particles in the conductive paste, and help improve the curing efficiency of the conductive paste. Specifically, the temperature of the drying treatment can be, but is not limited to, 120°C, 125°C, 130°C, 140°C, 150°C or 160°C, etc. In one embodiment of the present application, the temperature of the drying treatment can be 120°C-140°C. In another embodiment of the present application, the temperature of the drying treatment can be 135°C-160°C.

[0106] The present application provides an electrical device, which includes the solar cell described in any of the above embodiments. The electrical device provided by the present application has excellent comprehensive performance and strong market competitiveness. The electrical devices include mobile phones, tablets, watches, VR glasses, vehicles, photovoltaic modules, etc. In one embodiment of the present application, the solar cell can be used in a vehicle to improve the photoelectric utilization efficiency of the vehicle. In another embodiment of the present application, the solar cell can be applied to a photovoltaic module, which can reduce the use of traditional energy and is conducive to the construction of a green and friendly environment.

[0107] The effects of the technical solution of this application are further illustrated below through specific examples.

[0108] Example 1

[0109] The non-resin-containing composite was prepared by mixing terminal epoxysiloxane (bis(3-glycidyloxypropyl)polydimethylsiloxane, n=2), a reactive diluent (cyclohexane-1,2-dicarboxylic acid diglycidyl ester), a curing agent (boron trifluoride monoethylamine), a curing accelerator (2,4,6-tris(dimethylaminomethyl)phenol), an organic solvent (the mass ratio of diethylene glycol butyl ether acetate and diethylene glycol butyl ether was 1:1), a thixotropic agent (modified urea thixotropic agent), a dispersant (low molecular weight carboxylic acid mixed solution) and a silane coupling agent. Binder; a conductive filler (the mass ratio of spherical silver powder and flake silver powder is 6:4) and a non-resin binder are mixed, and after dispersion by three-roll grinding, a conductive paste is obtained with a fineness of less than 7 μm; wherein, the conductive paste includes, by mass percentage, 92% of a conductive filler, 2.7% of an end-group epoxy siloxane, 0.7% of a reactive diluent, 0.3% of a curing agent, 0.2% of a curing accelerator, 2.8% of an organic solvent, 0.3% of a thixotropic agent, 0.3% of a dispersant and 0.7% of a silane coupling agent.

[0110] Example 2

[0111] The difference from Example 1 is that the terminal epoxysiloxane is bis(3-glycidyloxypropyl)polydimethylsiloxane with n=1.

[0112] Example 3

[0113] The difference from Example 1 is that the terminal epoxysiloxane is bis(3-glycidyloxypropyl)polydimethylsiloxane with n=4.

[0114] Example 4

[0115] The difference from Example 1 is that no curing accelerator is included. The conductive paste includes, by mass percentage, 92% of conductive filler, 2.8% of terminal epoxy siloxane, 0.8% of reactive diluent, 0.3% of curing agent, 2.8% of organic solvent, 0.3% of thixotropic agent, 0.3% of dispersant and 0.7% of silane coupling agent.

[0116] Example 5

[0117] The difference from Example 1 is that no silane coupling agent is included, and the conductive paste includes, by mass percentage, 92% of conductive filler, 3.2% of terminal epoxy siloxane, 0.9% of active diluent, 0.3% of curing agent, 0.2% of curing accelerator, 2.8% of organic solvent, 0.3% of thixotropic agent and 0.3% of dispersant.

[0118] Example 6

[0119] The difference from Example 1 is that, by mass percentage, the conductive paste includes 85% of conductive filler, 5.0% of terminal epoxy siloxane, 1.5% of reactive diluent, 0.5% of curing agent, 0.5% of curing accelerator, 5% of organic solvent, 0.6% of thixotropic agent, 0.6% of dispersant and 1.3% of silane coupling agent.

[0120] Example 7

[0121] The difference from Example 1 is that, by mass percentage, the conductive paste includes 94% conductive filler, 2.0% terminal epoxy siloxane, 0.5% reactive diluent, 0.3% curing agent, 0.2% curing accelerator, 2.2% organic solvent, 0.2% thixotropic agent, 0.2% dispersant and 0.4% silane coupling agent.

[0122] Example 8

[0123] The difference from Example 1 is that, by mass percentage, the conductive paste includes 92% of conductive filler, 5.0% of terminal epoxy siloxane, 0.5% of reactive diluent, 0.3% of curing agent, 0.1% of curing accelerator, 1.6% of organic solvent, 0.2% of thixotropic agent, 0.2% of dispersant and 0.1% of silane coupling agent.

[0124] Example 9

[0125] The difference from Example 1 is that, by mass percentage, the conductive paste includes 92% conductive filler, 1.0% terminal epoxy siloxane, 1.0% reactive diluent, 0.3% curing agent, 0.2% curing accelerator, 3.6% organic solvent, 0.6% thixotropic agent, 0.3% dispersant and 1.0% silane coupling agent.

[0126] Example 10

[0127] The difference from Example 1 is that, by mass percentage, the conductive paste includes 85% conductive filler, 10% terminal epoxy siloxane, 0.7% reactive diluent, 0.3% curing agent, 0.2% curing accelerator, 3.2% organic solvent, 0.3% thixotropic agent and 0.3% dispersant.

[0128] Comparative Example 1

[0129] The difference from Example 1 is that the terminal epoxy siloxane is replaced by bisphenol F epoxy resin.

[0130] Comparative Example 2

[0131] The difference from Example 1 is that the terminal epoxysiloxane is replaced by bisphenol F epoxy resin, the mass percentage of bisphenol F epoxy resin is 2.6%, and the mass percentage of curing accelerator is 0.3%.

[0132] Comparative Example 3

[0133] The difference from Example 1 is that terminal epoxy siloxane is not included, and the mass percentage of the active diluent is 3.4%.

[0134] Performance testing

[0135] The conductive pastes prepared in Examples 1-10 and Comparative Examples 1-3 were tested for volume resistivity according to GB / T 17473.3-2008. A fixed pattern (20 mm × 20 mm, average thickness 20 μm) was printed using the conductive paste on a substrate (alumina ceramic sheet). After drying at 150°C for 3 minutes and curing at 200°C for 5 minutes, electrodes were obtained. The volume resistivity of the electrodes was measured using a four-probe ohmmeter. The results are shown in Table 1.

[0136] The conductive pastes prepared in Examples 1-10 and Comparative Examples 1-3 were tested for viscosity according to GB / T 17473.5-2008. The rheological curve of the conductive pastes after three-roll milling and dispersion was measured using a rheometer set at 25°C and a shear rate of 5s. -1 The data at that time was used as the viscosity value. The viscosity test time points were: when the preparation was completed (day 0), and on the 15th and 30th days of storage after preparation. The results are shown in Table 1. The viscosity of the conductive paste at different time points was tested and the rate of change of viscosity over time was calculated as shown in formula (V):

[0137] Wherein, x is the viscosity test value on the (x)th day, y is the viscosity test value on the (y)th day, and z is the difference between the xth day and the yth day. The calculation results are shown in Table 2.

[0138] The conductive pastes prepared in Examples 1-10 and Comparative Examples 1-3 were tested for their bonding ability according to ASTM D3359-09. A fixed pattern (size 20 mm × 20 mm, average thickness 20 μm) was printed on a substrate (alumina ceramic sheet) using the conductive paste. After drying at 150°C for 3 minutes and curing at 200°C for 5 minutes, a cured pattern was obtained. The bonding ability was tested using a tape test. The tape was pasted on the cured pattern, and after ensuring that it was flat and fitted, it was quickly torn off. The peeling of the pattern was observed, and the bonding ability of the conductive paste after curing was evaluated based on the remaining area after pasting. Figure 3 shows the bonding performance test results of the conductive paste prepared in Example 1, Figure 4 shows the bonding performance test results of the conductive paste prepared in Comparative Example 1, and Figure 5 shows the bonding performance test results of the conductive paste prepared in Comparative Example 3. Among them, Figure 3 shows that the remaining area after the conductive paste adhesion test is 100%, and there is no peeling phenomenon; Figure 4 shows that the remaining area after the conductive paste adhesion test is greater than 50% and less than 100%, and partial peeling occurs; Figure 5 shows that the remaining area after the conductive paste adhesion test is less than 50%, and most of it is peeling.

[0139] Table 1 Performance test results

[0140] Table 2 Viscosity change rate

[0141] As can be seen from Examples 1-10 and Comparative Example 3, terminal epoxysiloxanes can increase the curing rate and bonding ability, reduce resistivity, facilitate the application of conductive pastes, and further improve the structural stability and photoelectric conversion efficiency of electrodes. As can be seen from Examples 1-3, when the value of n of the terminal epoxysiloxane is 2-3, the conductive paste prepared has strong bonding ability and suitable viscosity, which is conducive to screen printing of the conductive paste. As can be seen from Example 10, when the terminal epoxy group content increases, the conductive paste still maintains high conductivity, storage stability, and bonding ability without adding a curing accelerator and / or a silane coupling agent. Compared to Examples 7, 9, and 10, the conductive pastes prepared in Examples 1, 6, and 8, when the mass percentage of conductive filler was 85%-92%, the mass percentage of terminal epoxysiloxane was 2.7%-5%, the mass percentage of reactive diluent was 0.5%-1.5%, and the mass percentage of curing agent was 0.3%-0.5%, exhibited excellent conductivity, bonding ability, and curing efficiency, a low viscosity change rate, and excellent storage stability. Compared to Example 7, Example 1 had an appropriate solid content, strong contact between the components, was less susceptible to volatilization and diffusion, had a reduced viscosity change rate, and enhanced bonding ability. The use of resin components in Comparative Examples 1 and 2 reduced the curing reaction rate and bonding ability. The use of a curing accelerator in Comparative Example 2 increased the curing speed of the conductive paste, resulting in a high viscosity change rate during storage, which was not conducive to long-term storage. Therefore, the conductive paste provided in this application has high bonding ability and good storage stability.

[0142] The above is a preferred embodiment of the present application, but it should not be construed as limiting the scope of the present application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present application, and such improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A conductive paste, characterized in that, The conductive paste includes a conductive filler and a non-resin binder. The non-resin binder includes an end-group epoxy-functional siloxane, an active diluent, and a curing agent. The end-group epoxy-functional siloxane includes a first repeating unit, and the first repeating unit is shown in Formula (I). Said R 1 and said R 2 are independently selected from substituted or unsubstituted alkyl or The R 3 includes a substituted or unsubstituted alkyleneoxy, and the R 4 includes a substituted or unsubstituted alkylene group or a single bond, and the relative molecular mass of the terminal epoxy group-containing siloxane is less than or equal to 3000.

2. The conductive paste according to claim 1, wherein The structural formula of the terminal epoxy group is shown in Formula (II-1), Among them, the R1, the R2, the R5, the R6, the R 5 , the R 6 , the R 7 , the R 8 , and the R7 are independently selected from substituted or unsubstituted alkyl or The R 3 and the R3 include a substituted or unsubstituted alkyleneoxy, the R 4 , the R4 includes a substituted or unsubstituted alkylene group or a single bond, the sum of n and m is less than or equal to 5, and n and m are not both 0 at the same time.

3. The conductive paste according to claim 1 or 2, characterized in that, The mass percentage of the terminal epoxy group siloxane in the conductive paste is 1%-5%.

4. The conductive paste according to any one of claims 1 to 3, characterized in that, The mass percentage of the conductive filler in the conductive paste is 85%-94%.

5. The conductive paste according to any one of claims 1-4, characterized in that, The conductive filler includes at least one of silver powder, copper powder, and silver-coated copper powder.

6. The conductive paste according to claim 5, wherein The silver powder includes at least one of flaky silver powder and spherical silver powder. The D50 of the flaky silver powder is 2 μm - 5 μm, and the tapped density of the flaky silver powder is 4 g / cm 3 - 4.5 g / cm 3 , the D50 of the spherical silver powder is 0.2 μm - 1.5 μm, and the tapped density of the spherical silver powder is 5.5 g / cm 3 - 6.5 g / cm 3 .

7. The conductive paste according to any one of claims 1-6, characterized in that, The mass percentage of the reactive diluent in the conductive paste is 0.2%-1.5%, and the reactive diluent includes at least one of cyclohexane-1,2-dicarboxylic acid diglycidyl ester, 1,4-butanediol diglycidyl ether, phenyl glycidyl ether, hexahydrophthalic acid bisglycidyl ester, tetrahydrophthalic acid bisglycidyl ester, 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, and 1,2-epoxy-4-vinylcyclohexane.

8. The conductive paste according to any one of claims 1-7, characterized in that, The mass percentage of the curing agent in the conductive paste is 0.2%-0.6%, and the curing agent includes at least one of imidazole curing agents, anhydride curing agents, and Lewis acid amine complex curing agents.

9. The conductive paste according to any one of claims 1-8, characterized in that, The non-resin binder further includes at least one of a thixotropic agent, a dispersant, a curing accelerator, a silane coupling agent, and an organic solvent.

10. The conductive paste according to claim 9, characterized in that, The mass percentage of the thixotropic agent in the conductive paste is 0.1%-1%, and the thixotropic agent includes at least one of unsaturated polycarboxylic acid polymer thixotropic agents, polycarboxylic acid alkyl ammonium salt thixotropic agents, modified urea thixotropic agents, and urea-modified non-polar polyamide thixotropic agents.

11. The conductive paste according to claim 9, wherein, The mass percentage of the dispersant in the conductive paste is 0.1%-1%, and the dispersant includes at least one of polyphosphate esters, polyethylene glycols, and carboxylic acids.

12. The conductive paste according to claim 9, wherein, The mass percentage of the curing accelerator in the conductive paste is less than or equal to 0.6%, and the curing accelerator includes at least one of benzoyl peroxide, diethylaminopropylamine, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, and 3-(p-chlorophenyl)-1,1-dimethylurea.

13. The conductive paste according to claim 9, wherein, The mass percentage of the silane coupling agent in the conductive paste is less than or equal to 2%, and the silane coupling agent includes at least one of 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane.

14. The conductive paste according to claim 9, characterized in that, The mass percentage of the organic solvent in the conductive paste is 1.6%-5%, and the organic solvent includes at least one of butyl acetate, diethylene glycol butyl ether acetate, butyl carbitol acetate, propylene glycol methyl ether acetate, diethyl carbonate, diethylene glycol butyl ether, diethylene glycol diethyl ether, propylene glycol ethyl ether, and dipropylene glycol butyl ether.

15. The conductive paste according to any one of claims 1-14, characterized in that, The volume resistivity of the conductive paste is less than or equal to 10×10 -6 Ω·cm, and the fineness of the conductive paste is less than or equal to 7μm.

16. A preparation method of a conductive paste, characterized in that, Including: Performing a first mixing (S101) on the terminal epoxy group siloxane, the reactive diluent, and the curing agent to obtain a non-resin binder; And Performing a second mixing (S102) on the conductive filler and the non-resin binder to obtain a conductive paste.

17. The preparation method according to claim 16, characterized in that, The time of the first mixing is 30 min - 60 min, and the temperature of the first mixing is 20°C - 30°C; The time of the second mixing is 3 h - 5 h, and the temperature of the second mixing is 0°C - 10°C.

18. A solar cell (100), characterized in that, The solar cell (100) includes a silicon substrate (20), a first film layer (10) disposed on the surface of the silicon substrate (20), and a second film layer (30) disposed on the surface of the silicon substrate (20) on the side facing away from the first film layer (10); a first electrode and a second electrode are respectively disposed on the surfaces of the first film layer (10) and the second film layer (30), and at least one of the first electrode and the second electrode is obtained by curing a conductive paste according to any one of claims 1-15 or a conductive paste prepared by the preparation method according to claim 16 or 17.

19. A method for preparing a solar cell (100), characterized in that, Comprising: Forming a first electrode on the surface of the silicon substrate (20), and forming a second electrode on the surface of the silicon substrate (20) in a direction away from the first electrode, to obtain a solar cell (100); at least one of the first electrode and the second electrode is obtained by curing a conductive paste according to any one of claims 1-15 or a conductive paste prepared by the preparation method according to claim 16 or 17.

20. An electrical device, characterized in that, The electrical equipment includes the solar cell (100) according to claim 18 or the solar cell (100) prepared by the preparation method according to claim 19.

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