Conductive paste composition

Abstract

The present invention relates to a conductive paste composition. Particularly, the present invention relates to a conductive paste composition for a low-temperature curable solar cell, and more particularly, to a conductive paste composition for a low-temperature curable heterojunction (HJT) solar cell. The conductive paste composition according to the present invention enables screen printing and provides excellent adhesion to a substrate.

Description

conductive paste composition

[0001] The present invention relates to a conductive paste composition. Specifically, the present invention relates to a conductive paste composition for a low-temperature curing solar cell, and more specifically, to a conductive paste composition for a low-temperature curing heterojunction (HJT) solar cell.

[0002] A solar cell is a device that converts light energy into electrical energy using the photovoltaic effect. Depending on the material it is made of, it is classified into silicon solar cells, thin-film solar cells, dye-sensitized solar cells, and organic polymer solar cells.

[0003] In these solar cells, increasing conversion efficiency, which is the rate at which incident sunlight is converted into electrical energy, is crucial. Various research efforts are underway to improve conversion efficiency, and active development is underway to improve conversion efficiency by incorporating thin films with high absorption coefficients into solar cells.

[0004] Meanwhile, solar cells using sunlight can be divided into homojunction solar cells and heterojunction solar cells depending on the properties of the p region and n region used in the pn junction. Among them, heterojunction solar cells have a structure in which different crystal structures or different materials are combined. As one aspect of the heterojunction solar cell, amorphous / crystalline silicon heterojunction solar cells can be manufactured at a lower temperature than conventional diffused crystalline silicon solar cells and have a high open circuit voltage, so they are attracting much attention.

[0005] Conventionally, conductive pastes for electrodes used in the above heterojunctions have been used, which include conductive powder, binder resin, and a curing agent. Epoxy resin is mainly used as the binder resin. However, electrodes produced by heat-curing the electrode pastes developed in the past have the disadvantage of poor adhesion to ceramic and silicon substrates, and have limitations in forming fine line widths. Recently, with the demand for higher efficiency in heterojunction solar cells, there is a demand for electrode pastes that enable thinning through screen printing, and there is a demand for electrode pastes with excellent adhesion and printability.

[0006] Republic of Korea Patent No. 10-2263618 (June 4, 2021)

[0007] The present inventors have conducted extensive research to solve problems that arise when applying the conventional electrode conductive paste to screen printing, and as a result, have discovered that by using a specific combination of compositions, it is possible to apply the paste to screen printing, implement a fine line width, apply it to various types of screens, provide excellent printability, and form an electrode having excellent adhesion to a substrate and excellent film strength, thereby completing the present invention.

[0008] One object of the present invention is to provide a conductive paste composition that can reduce the production cost by reducing the content of silver powder, can be cured within 10 minutes at a temperature of 250°C or lower and 200°C or lower, can form an electrode with low resistivity under the low-temperature conditions, and can implement a fine line width of 50 μm or lower, 40 μm or lower, 35 μm or lower, and 30 μm or lower through screen printing, and has excellent printability.

[0009] In addition, the present invention aims to provide a conductive paste composition that can be used for purposes such as front electrodes of hetero-junction solar cells, and to provide a conductive paste composition that can form a coating film with low resistivity even when cured at a low temperature of 250°C or lower, more specifically, at 200°C or lower.

[0010] In addition, it is intended to provide a conductive paste composition that can be applied to screens manufactured with various slit angles and line widths and has excellent adhesion to a substrate and film strength.

[0011] In addition, the present invention aims to provide a conductive paste composition that can maintain low resistivity characteristics for a long period of time even when mixed with AgCu powder to reduce the content of silver powder. Specifically, the present invention aims to provide a conductive paste composition that exhibits little change in resistivity characteristics after being maintained for 10 days under conditions of 85°C and 85 RH% relative humidity. More specifically, the present invention aims to provide a conductive paste composition having a volume resistivity change rate of 15% or less.

[0012] Another object of the present invention is to provide a solar cell with excellent conversion efficiency by forming an electrode using a conductive paste according to one embodiment of the present invention. By using the conductive paste according to one embodiment of the present invention, a solar cell having a fill factor (FF) of 75% or more or 80% or more is provided.

[0013] The inventors of the present invention have discovered that by using a conductive powder mixed with AgCu powder and silver (Ag) powder and mixing a specific combination of components as a binder component that binds the conductive powder, it is possible to process at a low temperature, specifically, 250°C or lower, 200°C or lower, 180°C or lower, or 150°C or lower, and to form a coating film, specifically an electrode layer, with excellent adhesiveness and low resistivity. In addition, it is possible to form a fine line width through screen printing, has a low defect rate, and has excellent coating film strength, so that the cell efficiency can be greatly improved when forming the electrode layer. In addition, the inventors have discovered the effect of having little change in resistance even after maintaining it for 10 days under conditions of 85°C and a relative humidity of 85 RH%, thereby completing the present invention.

[0014] More specifically, the present invention has been completed by finding that the desired properties can be provided by providing a conductive paste composition comprising: a conductive powder mixed with AgCu powder and silver (Ag) powder; a liquid multifunctional epoxy compound; an alkoxysilane coupling agent having a reactive group; two or more binder resins selected from phenoxy resin, polysiloxane resin, and cellulose resin; an antioxidant that inhibits oxidation of copper; and a solvent.

[0015] One aspect of the present invention is a conductive powder comprising a mixture of AgCu powder and silver (Ag) powder;

[0016] Liquid multifunctional epoxy compound;

[0017] Alkoxysilane coupling agent having a reactive group;

[0018] Two or more binder resins selected from phenoxy resin, polysiloxane resin, and cellulose resin;

[0019] Antioxidants; and

[0020] A conductive paste composition including a solvent is provided.

[0021] In one aspect, the conductive powder may have a weight ratio of AgCu powder: silver (Ag) powder of 30 to 50:50 to 70.

[0022] In one aspect, the AgCu powder may be a core-shell powder in which the surface of the Cu powder is coated with Ag.

[0023] In one embodiment, the AgCu powder may be one selected from the group consisting of spherical and flake forms, or a mixture thereof.

[0024] In one embodiment, the AgCu powder may have an Ag content of 10 to 30 wt%.

[0025] In one aspect, the AgCu powder may have an average particle diameter (D50) of 2 to 7 μm and a maximum particle diameter (Dmax) of 5 to 8 μm.

[0026] In one aspect, the silver (Ag) powder may have an average particle diameter (D50) of 0.1 to 1 ㎛ and a maximum particle diameter (Dmax) of 1 to 2 ㎛.

[0027] In one aspect, the binder resin may include all of a phenoxy resin, a polysiloxane resin, and a cellulose resin.

[0028] In one embodiment, the antioxidant is malonic acid, glutaric acid, dimethyl malonate, methanesulfonic acid, abietic acid, p-toluene sulfonic acid, oxalic acid, 4-hydroxybenzoic acid, salicylic acid, 2-furoic acid, benzoic acid, lauric acid, palmitic acid, stearic acid, oleic acid, succinic acid, adipic acid, suberic acid, 1,3-diphenylguanidine, Cyclohexylamine, Diethylamine, Triethanolamine, Monoethanolamine, 2-Bromo propionic acid, 2-Bromobutyric acid, 2,3-Dibromopropionic acid, 2,3-Dibromosucinic acid, Hydroquinone, Benzimidazole, 2-Phenylimidazole, 2-Ethylimidazole, Triethanolamine, Dicyanodiamide, Ethylenediamine, Dimethylbenzylamine, Ethylenediamine tetraacetic acid,It may be one or a mixture of two or more selected from the group consisting of butylated hydroxy anisole (BHA), dibutyl hydroxyl toluene (BHT), t-butyl hydroquinone (TBHQ), 4-aminophenyl alcohol, 2-aminophenyl alcohol, 4-aminobenzyl alcohol, 3-aminobenzyl alcohol, and 2-(2-aminophenyl)ethanol.

[0029] In one embodiment, the conductive paste composition may have a viscosity of 400,000 cps or less when measured with a Brookfield viscometer (Brookfield DV2 @25 ℃, Spindle 14, 10 rpm).

[0030] In one embodiment, the conductive paste composition may include 85 to 96 wt% of a conductive powder; 0.2 to 5 wt% of a liquid multifunctional epoxy compound; 0.05 to 2 wt% of an alkoxysilane coupling agent having a reactive group; two or more binder resins selected from 0.01 to 5 wt% of a phenoxy resin, 0.1 to 2 wt% of a polysiloxane resin, and 0.01 to 2 wt% of a cellulose resin; 0.1 to 1 wt% of an antioxidant, and the remainder of a solvent.

[0031] In one embodiment, the volume resistance of the coating film applied with the conductive paste composition and heat-treated is 9 μΩ·cm or less and the contact resistance is 5 mΩ·cm. 2 Below, the film strength according to KS M ISO 15184 may be 3H or higher.

[0032] In one aspect, the conductive paste composition may have a finger line width of 40 ㎛ or less, a finger line thickness of 10 ㎛ or more, and a number of broken finger lines of 20 or less during screen printing.

[0033] In one embodiment, the liquid multifunctional epoxy compound is an alicyclic multifunctional epoxy compound having a molecular weight of 2000 or less, and the alkoxysilane coupling agent having the reactive group may be represented by the following chemical formula 1.

[0034] [Chemical Formula 1]

[0035] AnSi(OR)m

[0036] In the above chemical formula 1, A is a C2 to C6 alkyl group substituted with a glycidyl group, an epoxy group, a glycidyloxy group, an amine group, or a thiol group, R is a C1 to C4 alkyl group, n is an integer selected from 1 to 3, m is an integer selected from 1 to 3, and n+m is 4.

[0037] In one embodiment, the phenoxy resin may have a viscosity (Brookfield @25°C, 20% in cyclohexanone) of 700 cP or less, a weight average molecular weight of 3,000 to 60,000 g / mol, and a glass transition temperature of 100°C or less.

[0038] In one aspect, the conductive paste composition may further include one or more selected from a bisphenol-based epoxy resin, an imidazole-based compound, and a titanate-based coupling agent.

[0039] Another aspect of the present invention is a conductive film formed from the conductive paste composition according to the above aspect, selected from a finger electrode or a busbar electrode, having a volume resistance of 9 μΩ·cm or less and a contact resistance of 5 mΩ·cm. 2Below, a conductive film for a solar cell is provided, having a film strength of 3H or more according to KS M ISO 15184, a finger line width of 40 ㎛ or less, a finger line thickness of 10 ㎛ or more, and a number of broken finger lines of 20 or less.

[0040] In addition, another aspect of the present invention provides a solar cell including the conductive film.

[0041] In one aspect, the solar cell may be a heterojunction solar cell and have a fill factor (FF) of 75% or more.

[0042] The conductive paste composition according to the present invention has the effect of reducing production costs by reducing the content of silver powder.

[0043] In addition, the conductive paste composition according to the present invention can be used to form busbar electrodes, finger electrodes, etc., and in particular, when applied to finger electrodes, it can form microelectrodes having a fine line width, i.e., a finger line width of 50 ㎛ or less, 40 ㎛ or less, 35 ㎛ or less, or 30 ㎛ or less, through screen printing, thereby having the effect of achieving high efficiency of heterojunction solar cells.

[0044] In addition, the conductive paste composition according to the present invention can be applied to various screens for screen printing, and has excellent adhesion to the substrate, thereby providing an effect of even better printability.

[0045] In addition, the coating film formed through screen printing has a low defect rate and an excellent coating strength of 3H or higher. Preferably, the coating strength according to KS M ISO 15184 may be 3H or higher, more preferably 3H to 9H, and even more preferably 5H to 9H. In addition, after maintaining for 10 days under conditions of 85 ℃ and 85 RH% relative humidity, it can provide an effect of little change in the resistance characteristics of the electrode, more specifically, a volume resistance change rate of 15% or less.

[0046] A heterojunction solar cell formed with an electrode using the conductive paste composition of the present invention can achieve a significantly improved effect compared to conventional ones, with a curve factor (FF) of 75% or more, or 80% or more.

[0047] As an example of implementation, the conductive paste composition may provide a viscosity of 400,000 cps or less, and more preferably 350,000 cps or less, as measured by a Brookfield viscometer (Brookfield DV2 @25 ℃, Spindle 14, 10 rpm).

[0048] As an example, an electrode manufactured using the conductive paste composition may have a volume resistance of 9 μΩ·cm or less, 8 μΩ·cm or less, 7 μΩ·cm or less, or 6 μΩ·cm or less when measured using a measuring method according to an embodiment.

[0049] In one embodiment, the electrode manufactured with the conductive paste composition has a contact resistance of 8 mΩ.cm according to the method measured in the examples. 2 Below 5 mΩ.cm 2 Below, 3 mΩ.cm 2 Below, 2 mΩ.cm 2 or less, or 1 mΩ.cm 2 The following characteristics can be given:

[0050] In addition, the conductive paste composition according to one embodiment may have a finger line width of 45 ㎛ or less or 40 ㎛ or less, a finger line thickness of 9 ㎛ or more or 10 ㎛ or more, and a number of broken finger lines of 20 or less during screen printing. More preferably, the finger line width may be 45 ㎛ or less, 40 ㎛ or less, 35 ㎛ or less, 30 ㎛ or less, or 25 ㎛ or less, and may impart screen printing characteristics in which the finger line thickness is 9 ㎛ or more, 10 ㎛ or more, 11 ㎛ or more, 12 ㎛ or more, 13 ㎛ or more, or 14 ㎛ or more. In addition, the number of broken finger lines may be 20 or less.

[0051] The conductive paste composition according to one embodiment can provide an effect of imparting a characteristic of forming an electrode by curing at a low temperature of 250°C or lower, preferably 200°C or lower, for example, 150 to 250°C, or more preferably 150 to 200°C, when forming an electrode.

[0052] In one embodiment, the conductive paste composition can provide a property in which the electrode film is uniformly formed to have a thickness of 5 to 25 μm, or 10 to 20 μm.

[0053] In one embodiment, a conductive film selected from a finger electrode or a busbar electrode, wherein the volume resistance of the electrode is 9 μΩ·cm or less and the contact resistance is 5 mΩ·cm 2 Below, a conductive film for solar cells having a film strength of 3H or higher according to KS M ISO 15184 can be provided.

[0054] In one embodiment, the conductive film has a volume resistance of 7 μΩ·cm or less and a contact resistance of 3 mΩ·cm. 2The following may provide a conductive film for a solar cell having a film strength of 5H or higher according to KS M ISO 15184.

[0055] In one embodiment, the conductive film may provide a conductive film for a solar cell having a finger line width of 35 μm or less, a finger line thickness of 12 μm or more, and a number of broken finger lines of 20 or less.

[0056] One embodiment may be to provide a solar cell comprising a conductive film of the above aspect.

[0057] In one embodiment, the solar cell may be a heterojunction solar cell.

[0058] In one embodiment, the solar cell may be provided with a solar cell having a fill factor (FF) of 75% or greater, or 80% or greater.

[0059] The present invention will be described in more detail below. However, the following specific examples or examples are merely references for explaining the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

[0060] Additionally, unless otherwise defined, 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 pertains. The terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting.

[0061] Additionally, the singular forms used in the specification and the appended claims are intended to include the plural forms as well, unless the context clearly dictates otherwise.

[0062] Additionally, when a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0063] Additionally, “conductive paste” refers to a liquid composition containing conductive powder, and the resulting coating that is applied to a substrate and dried is called a “film.” When the coating is used as an electrode for a solar cell, it can be understood as an “electrode layer” that includes a busbar electrode or a finger electrode.

[0064] In addition, the average particle diameter (D50) refers to the particle diameter when the cumulative weight of particles is 50% of the total weight, and the maximum particle diameter (Dmax) refers to the maximum particle diameter (㎛) of the particles. The above average particle diameter (D50) and maximum particle diameter (Dmax) can be derived from the particle size distribution results analyzed using a particle size analyzer, Microtrac's S3500, by collecting a sample according to the ISO 13320-1 standard.

[0065] Below, each component of the present invention is described in more detail.

[0066] One aspect of the present invention is a conductive powder comprising a mixture of AgCu powder and silver (Ag) powder;

[0067] Liquid multifunctional epoxy compound;

[0068] Alkoxysilane coupling agent having a reactive group;

[0069] Two or more binder resins selected from phenoxy resin, polysiloxane resin, and cellulose resin;

[0070] Antioxidants; and

[0071] A conductive paste composition including a solvent is provided.

[0072] In one aspect, the conductive paste composition may be used for a heterojunction solar cell.

[0073] In one aspect, the conductive powder may be used in an amount equal to or less than the content of the AgCu powder compared to the content of the silver (Ag) powder.

[0074] In one embodiment, the content of the AgCu powder may be 30 to 50 wt%, and the content of the silver (Ag) powder may be 50 to 70 wt%. Although not limited thereto, within the above range, the effect of lowering the volume resistance and contact resistance may be provided, and a fine line having a finger line width of 45 ㎛ or less, 40 ㎛ or less, 35 ㎛ or less, or 30 ㎛ or less may be formed.

[0075] In one embodiment, the AgCu powder may be a core-shell powder in which the surface of the Cu powder is coated with Ag, and the AgCu powder may be one selected from spherical and flake forms or a mixture thereof.

[0076] In one embodiment, the AgCu powder may have an Ag content of 10 to 30 wt%, and is not limited thereto, and may prevent interfacial separation between Ag and Cu within the above range, form an Ag shell of uniform thickness, provide an effect of lowering volume resistance and contact resistance, and form a fine line having a finger line width of 45 µm or less, 40 µm or less, 35 µm or less, or 30 µm or less.

[0077] In one embodiment, the AgCu powder may have an average particle diameter (D50) of 2 to 7 ㎛, 3 to 6 ㎛, or 4 to 5 ㎛, and a maximum particle diameter (Dmax) of 5 to 8 ㎛ or 6 to 7 ㎛. Although not limited thereto, within the above range, the AgCu powder may provide an effect of lowering volume resistance and contact resistance, and may form fine lines having a finger line width of 40 ㎛ or less, 35 ㎛ or less, or 30 ㎛ or less.

[0078] In one embodiment, the silver (Ag) powder is not limited in its shape, and may have an average particle diameter (D50) of 0.1 to 1 ㎛ and a maximum particle diameter (Dmax) of 1 to 2 ㎛, but is not limited thereto.

[0079] In one aspect, the silver powder is D 50 It may be 0.1 to 1 ㎛, have a tap density of 3 to 6 g / cc, and have a specific surface area of ​​0.1 to 2 m2 / g.

[0080] The above tap density refers to the packing density, and refers to the mass per volume after placing a certain amount of powder in a certain container while moving it up and down, and is measured according to the JIS Z 2512:2006 method. Specifically, conductive silver powder (powder weight 100 g) was collected in a graduated glass container (capacity 100 ml) and tapped using a specified tapping device under the conditions of a tap stroke of 3 mm and a tap count of 100 times / minute.

[0081] One aspect of the present invention can further improve printability during screen printing by including the liquid multifunctional epoxy compound.

[0082] In one embodiment, the liquid multifunctional epoxy compound is not particularly limited, but for example, an alicyclic multifunctional epoxy compound having a molecular weight of 2000 or less is more preferred because it can achieve the purpose of the present invention, but is not limited thereto.

[0083] The above multifunctional epoxy compound is not particularly limited as long as it can achieve the above-described effect of the present invention, but for example, an alicyclic multifunctional epoxy compound having a glycidyl group and a molecular weight of 2000 or less is more preferred, but is not limited thereto.

[0084] Non-limiting examples of the above multifunctional epoxy compounds include diglycidyl 1,2-cyclohexanedicarboxylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-1-methylcyclohexyl-methyl-3,4-epoxy-1-methylcyclohexane carboxylate, 6-methyl-3,4-epoxycyclohexylmethylmethyl-6-methyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexane carboxylate, 3,4-epoxy-3-methylcyclohexyl-methyl-3,4-epoxy-3-methylcyclohexane carboxylate, Examples of suitable compounds include, but are not limited to, 3,4-epoxy-5-methylcyclohexyl-methyl-3,4-epoxy-5-methylcyclohexane carboxylate, 2,2-bis(4-hydroxycyclohexyl)propane, etc.

[0085] More preferably, one or more selected from diglycidyl 1,2-cyclohexanedicarboxylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, etc. may be used.

[0086] The above multifunctional epoxy compound may be used in an amount of 0.2 to 5 wt%, 0.2 to 4 wt%, 0.2 to 3 wt%, or 0.2 to 2 wt% in the conductive paste composition. Although it is preferred because it can exhibit excellent printability within the above range, it is not limited thereto.

[0087] One aspect of the present invention provides a composition having excellent printability, excellent film strength, and low defect rate during screen printing by mixing and using the multifunctional epoxy compound with two or more binder resins selected from phenoxy resin, polysiloxane resin, and cellulose resin. More preferably, by mixing and using the multifunctional epoxy compound with the phenoxy resin, polysiloxane resin, and cellulose resin, excellent printability, film strength, and cell efficiency can be achieved.

[0088] First, the phenoxy resin can be used to further improve the coating film properties, and in one embodiment, the phenoxy resin has a viscosity (Brookfield @25 ℃, 20% in cyclohexanone) of 700 cP or less, a weight average molecular weight of 3,000 to 60,000 g / mol, and a glass transition temperature of 100 ℃ or less, but is not limited thereto. Specifically, commercialized examples include PKHH, PKHB, PKHC from INCHEM, but are not limited thereto.

[0089] The phenoxy resin may be used in the composition in an amount of, for example, 0.01 to 5 wt%, more preferably 0.01 to 4 wt%, but is not limited thereto. In addition, the phenoxy resin may be mixed in a state of being dissolved in advance in a glycol ether solvent when mixed into the composition.

[0090] In one embodiment, the cellulose resin may be a variety of resins such as alkyl cellulose and hydroxyalkyl cellulose, and is not particularly limited in the present invention. However, it is more preferred to use an alkyl cellulose such as methyl cellulose or ethyl cellulose because it is easier to achieve the effects of the present invention.

[0091] In one embodiment, the cellulose resin may be an alkyl cellulose resin such as methyl cellulose or ethyl cellulose. The content thereof may be 0.01 to 2 wt%, more preferably 0.01 to 1.5 wt%, in the composition, but is not limited thereto.

[0092] In one embodiment, the polysiloxane resin is not particularly limited in the present invention, but when it is one or two or more selected from polydimethylsiloxane, polydiethylsiloxane, polymethylethylsiloxane, polymethylphenylsiloxane, and polyethylphenylsiloxane, the effects of the present invention can be more easily achieved, and thus this is preferred, and in particular, when it has a liquid form at room temperature, the effects of the present invention described above can be very easily achieved, and thus this is even more preferred.

[0093] In one embodiment, the polysiloxane resin may be used in an amount of 0.1 to 2 wt%, more preferably 0.1 to 1.5 wt%, and even more preferably 0.1 to 1 wt% in the total composition, but is not limited thereto.

[0094] In one aspect of the present invention, the alkoxysilane coupling agent having a reactive group as the coupling agent may be used alone, or the alkoxysilane coupling agent having the reactive group may be used in combination with a titanate coupling agent.

[0095] In one embodiment, the alkoxysilane coupling agent having the above reactive group may be represented by the following chemical formula 1.

[0096] AnSi(OR)m [chemical formula 1]

[0097] In the above chemical formula 1, A is a C2 to C6 alkyl group substituted with a glycidyl group, an epoxy group, a glycidyloxy group, an amine group, or a thiol group, R is a C1 to C4 alkyl group, n is an integer selected from 1 to 3, m is an integer selected from 1 to 3, and n+m is 4.

[0098] More specifically, in the above chemical formula 1, n may be 1 or 2, m may be 3 or 2, and n+m is 4.

[0099] Specifically, examples of the alkoxysilane coupling agent represented by the above chemical formula 1 include 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl tripropoxysilane, 3-aminopropyltrimethoxysilane, etc., and these may be used alone or in combination of two or more. More preferably, 3-glycidoxypropyl trimethoxysilane may be used.

[0100] The content of the coupling agent may be 0.05 to 2 wt%, more preferably 0.05 to 1.5 wt%, and even more preferably 0.05 to 1 wt%, based on the entire conductive paste composition, but is not limited thereto.

[0101] Additionally, a titanate coupling agent may be mixed and used together with the above alkoxysilane coupling agent.

[0102] An example of the above titanate-based coupling agent may be diisopropyl dioleyl titanate. The content may be 0.05 to 2 wt%, more preferably 0.05 to 1.5 wt%, and even more preferably 0.05 to 1 wt%.

[0103] In one aspect, the antioxidant is used to prevent oxidation of the conductive powder, and can be used without limitation as long as it is used to prevent oxidation of copper. For example, malonic acid, glutaric acid, dimethyl malonate, methanesulfonic acid, abietic acid, p-toluene sulfonic acid, oxalic acid, 4-hydroxybenzoic acid, salicylic acid, 2-furoic acid, benzoic acid, lauric acid, palmitic acid, stearic acid, oleic acid, succinic acid, adipic acid, suberic acid, 1,3-diphenylguanidine, Cyclohexylamine, Diethylamine, Triethanolamine, Monoethanolamine, 2-Bromo propionic acid, 2-Bromobutyric acid, 2,3-Dibromopropionic acid, 2,3-Dibromosucinic acid, Hydroquinone, Benzimidazole, 2-Phenylimidazole, 2-Ethylimidazole, Triethanolamine, Dicyanodiamide, Ethylenediamine,It may be any one selected from the group consisting of dimethylbenzylamine, ethylenediamine tetraacetic acid, butylated hydroxy anisole (BHA), dibutyl hydroxyl toluene (BHT), t-butyl hydroquinone (TBHQ), 4-aminophenyl alcohol, 2-aminophenyl alcohol, 4-aminobenzyl alcohol, 3-aminobenzyl alcohol, and 2-(2-aminophenyl)ethanol, or a mixture of two or more thereof, but is not limited thereto.

[0104] The content of the above antioxidant may be used as 0.1 to 1 wt%, 0.1 to 0.9 wt%, 0.2 to 0.8 wt%, or 0.2 to 0.5 wt% relative to the entire conductive paste composition, and may be preferred because it can provide an effect of lowering the volume resistivity change rate within the above range, but is not limited thereto.

[0105] The conductive paste composition of the present invention includes a solvent, which facilitates dispersion of conductive powder and facilitates adjustment to a viscosity suitable for printing.

[0106] The above solvent can be selected depending on the type of resin used, the solubility of the resin, the printing method, etc. The solvent that can be used is an ester solvent, a ketone solvent, a glycol ether solvent, an aliphatic solvent, an alicyclic solvent, an aromatic solvent, an alcohol solvent, and water. Examples of the ester solvent include, but are not limited to, ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and dimethyl carbonate.

[0107] Cyclic ester solvents include, but are not limited to, ε-caprolactone and γ-butyrolactone, for example. Ketone solvents include, but are not limited to, acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, diacetone alcohol, isophorone, and cyclohexanone, for example. Glycol ether solvents include, but are not limited to, monoethers such as ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, and ethylene glycol monobutyl ether, and their acetic acid esters, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether, and their acetic acid esters, for example.

[0108] Aliphatic solvents include, but are not limited to, n-heptane, n-hexane, cyclohexane, methylcyclohexane, and ethylcyclohexane. Aromatic solvents include, but are not limited to, toluene, xylene, and tetralin. The solvents may be used singly or in combination of two or more. More preferably, diethylene glycol dibutyl ether may be used as the solvent.

[0109] The content of the above solvent is not limited as long as it is a content that can be adjusted to a screen-printable viscosity, and more preferably, it is used so that the viscosity of the composition is 500,000 cps or less, 400,000 cps or less, or 350,000 cps or less when measured with a Brookfield viscometer (Brookfield DV2 @25 ℃, Spindle 14, 10 rpm).

[0110] In one aspect of the present invention, the conductive paste composition may include an imidazole compound as a curing agent. For example, imidazole, isoimidazole, 2-methyl imidazole, 2-ethyl-4-methylimidazole, 2,4-dimethylimidazole, butylimidazole, 2-heptadecenyl-4-methylimidazole, 2-methylimidazole, 2-undecenylimidazole, 1-vinyl-2-methylimidazole, 2-n-heptadecylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-propyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-Guanaminoethyl-2-methylimidazole, adduct of imidazole and methylimidazole, adduct of imidazole and trimellitic acid, 2-n-heptadecyl-4-methylimidazole, phenylimidazole, benzylimidazole, 2-methyl-4,5-diphenylimidazole, 2,3,5-triphenylimidazole, 2-styrylimidazole, 1-(dodecylbenzyl)-2-methylimidazole, 2-(2-hydroxyl-4-t-butylphenyl)-4,5-diphenylimidazole, 2-(2-methoxyphenyl)-4,5-diphenylimidazole, 2-(3-hydroxyphenyl)-4,5-diphenylimidazole, 2-(p-dimethyl-aminophenyl)-4,5-diphenylimidazole, 2-(2-hydroxyphenyl)-4,5-diphenylimidazole, di(4,5-diphenyl-2-imidazole)-benzene-1,4,2-naphthyl-4,5-diphenylimidazole, 1-benzyl-2-methylimidazole, and 2-p-methoxystyrylimidazole can be used. More preferably, it can be 1-cyanoethyl-2-ethyl-4-methylimidazole.

[0111] In addition to the above imidazole compounds, any curing agent and curing accelerator commonly used in the relevant field may be additionally used without limitation.

[0112] One embodiment of the present invention may use an additional bisphenol-based epoxy resin as needed. The additional epoxy resin component may be, specifically, one or more selected from the group consisting of a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a hydrogenated bisphenol type epoxy resin. More preferably, a bisphenol A type epoxy resin and a bisphenol F type epoxy resin may be mixed and used, or a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a hydrogenated bisphenol type epoxy resin may be mixed and used.

[0113] The content of the above bisphenol-based epoxy resin may be used in an amount of 0.01 to 2 wt%, more preferably 0.1 to 2 wt%, based on the entire conductive paste composition, but is not limited thereto.

[0114] The conductive paste composition according to one aspect of the present invention may further include additives used in the relevant field as needed. Specifically, the composition may include at least one selected from, but is not limited to, a friction-improving agent, an infrared absorber, an ultraviolet absorber, an aromatic, an antioxidant, a plasticizer, a flame retardant, an inorganic pigment, an organic pigment, a leveling agent, a viscoelasticity modifier, and an anti-foaming agent.

[0115] In one embodiment, the conductive paste composition may include 85 to 96 wt% of a conductive powder; 0.2 to 5 wt% of a liquid multifunctional epoxy compound; 0.05 to 2 wt% of an alkoxysilane coupling agent having a reactive group; two or more binder resins selected from 0.01 to 5 wt% of a phenoxy resin, 0.1 to 2 wt% of a polysiloxane resin, and 0.01 to 2 wt% of a cellulose resin; 0.1 to 1 wt% of an antioxidant; and a balance of a solvent.

[0116] In another embodiment, the composition may include: 85 to 96 wt% of a conductive powder; 0.2 to 5 wt% of a liquid multifunctional epoxy compound; 0.05 to 2 wt% of an alkoxysilane coupling agent having a reactive group; two or more binder resins selected from 0.01 to 5 wt% of a phenoxy resin, 0.1 to 2 wt% of a polysiloxane resin, and 0.01 to 2 wt% of a cellulose resin; 0.01 to 2 wt% of a bisphenol-based epoxy resin; 0.1 to 1 wt% of an antioxidant; and a balance of a solvent.

[0117] In another embodiment, the composition may include: 85 to 96 wt% of a conductive powder; 0.2 to 5 wt% of a liquid multifunctional epoxy compound; 0.05 to 2 wt% of an alkoxysilane coupling agent having a reactive group; two or more binder resins selected from 0.01 to 5 wt% of a phenoxy resin, 0.1 to 2 wt% of a polysiloxane resin, and 0.01 to 2 wt% of a cellulose resin; 0.01 to 0.3 wt% of an imidazole compound; 0.1 to 1 wt% of an antioxidant; and a balance of a solvent.

[0118] In another embodiment, the composition may include: 85 to 96 wt% of a conductive powder; 0.2 to 5 wt% of a liquid multifunctional epoxy compound; 0.05 to 2 wt% of an alkoxysilane coupling agent having a reactive group; two or more binder resins selected from 0.01 to 5 wt% of a phenoxy resin, 0.1 to 2 wt% of a polysiloxane resin, and 0.01 to 2 wt% of a cellulose resin; 0.01 to 0.3 wt% of an imidazole compound; 0.01 to 2 wt% of a bisphenol-based epoxy resin; 0.1 to 1 wt% of an antioxidant; and a balance of a solvent.

[0119] In another embodiment, the composition may include: 85 to 96 wt% of a conductive powder; 0.2 to 5 wt% of a liquid multifunctional epoxy compound; 0.05 to 2 wt% of an alkoxysilane coupling agent having a reactive group; 0.05 to 2 wt% of a titanate coupling agent; two or more binder resins selected from 0.01 to 5 wt% of a phenoxy resin, 0.1 to 2 wt% of a polysiloxane resin, and 0.01 to 2 wt% of a cellulose resin; 0.1 to 1 wt% of an antioxidant; and a balance of a solvent.

[0120] In another embodiment, the composition may include: 85 to 96 wt% of a conductive powder; 0.2 to 5 wt% of a liquid multifunctional epoxy compound; 0.05 to 2 wt% of an alkoxysilane coupling agent having a reactive group; 0.05 to 2 wt% of a titanate coupling agent; two or more binder resins selected from 0.01 to 5 wt% of a phenoxy resin, 0.1 to 2 wt% of a polysiloxane resin, and 0.01 to 2 wt% of a cellulose resin; 0.01 to 0.3 wt% of an imidazole compound; 0.01 to 2 wt% of a bisphenol epoxy resin; 0.1 to 1 wt% of an antioxidant; and a balance of a solvent.

[0121] In another embodiment, the composition may include: 85 to 96 wt% of a conductive powder; 0.2 to 5 wt% of a liquid multifunctional epoxy compound; 0.05 to 2 wt% of an alkoxysilane coupling agent having a reactive group; 0.05 to 2 wt% of a titanate coupling agent; two or more binder resins selected from 0.01 to 5 wt% of a phenoxy resin, 0.1 to 2 wt% of a polysiloxane resin, and 0.01 to 2 wt% of a cellulose resin; 0.01 to 0.3 wt% of an imidazole compound; 0.1 to 1 wt% of an antioxidant; and a balance of a solvent.

[0122] In another embodiment, the composition may include: 85 to 96 wt% of a conductive powder; 0.2 to 5 wt% of a liquid multifunctional epoxy compound; 0.05 to 2 wt% of an alkoxysilane coupling agent having a reactive group; 0.05 to 2 wt% of a titanate coupling agent; two or more binder resins selected from 0.01 to 5 wt% of a phenoxy resin, 0.1 to 2 wt% of a polysiloxane resin, and 0.01 to 2 wt% of a cellulose resin; 0.01 to 0.3 wt% of an imidazole compound; 0.01 to 2 wt% of a bisphenol epoxy resin; 0.1 to 1 wt% of an antioxidant; and a balance of a solvent.

[0123] In one embodiment, the conductive paste composition is not particularly limited as long as it achieves the purpose and effect according to the present invention, but for example, when measured using a Brookfield viscometer (Brookfield DV2) at 25°C and Spindle 14, 10 rpm, it is more preferable that the viscosity be 400,000 cps or less, and more preferably 350,000 cps or less.

[0124] In one embodiment, the coating film coated with the conductive paste composition and heat-treated may have a volume resistance of 9 μΩ·cm or less, more preferably 7 μΩ·cm or less, and even more preferably 6 μΩ·cm or less, as measured by the method measured in the embodiment of the present invention, and a contact resistance of 8 mΩ·cm or less. 2 Below 5 mΩ.cm 2 Below, preferably 4.5 mΩ.cm 2 Below, 4 mΩ.cm 2 Below, for example, 2 to 4 mΩ.cm 2 It could be.

[0125] In one aspect, the present invention is not particularly limited to this insofar as it achieves its purpose, but considering the applicability, surface smoothness, and prevention of occurrence of short-circuiting during application, etc., the viscosity is 350,000 cps or less, the volume resistance is 7 μΩ·cm or less, and the contact resistance is 3 mΩ·cm or less when measured with a Brookfield viscometer (Brookfield DV2 @25 ℃, Spindle 14, 10 rpm). 2 You may prefer something less than this.

[0126] In one embodiment, the conductive paste composition may have a finger line width of 40 ㎛ or less, 35 ㎛ or less, or 30 ㎛ or less during screen printing, for example, 25 to 40 ㎛, 25 to 35 ㎛, or 25 to 30 ㎛. In addition, the finger line thickness may be 10 ㎛ or more, 12 ㎛ or more, or 13 ㎛ or more, and the number of broken finger lines may be 20 or less, 10 or less, or preferably 5 or less. In addition, a conductive paste composition without spreading may be provided.

[0127] In one aspect, the conductive paste composition may have a finger line width of 30 ㎛ or less, a finger line thickness of 13 ㎛ or more, and a number of broken finger lines of 5 or less during screen printing.

[0128] In one aspect, the coating film formed using the above-described conductive paste composition may have a coating strength of 3H or higher according to KS M ISO 15184.

[0129] Another aspect of the present invention is a conductive film selected from a finger electrode or a busbar electrode using the conductive paste composition, wherein the volume resistance of the electrode is 9 μΩ·cm or less and the contact resistance is 5 mΩ·cm. 2 Below, a conductive film for a solar cell having a surface hardness of 3H or higher is provided.

[0130] In one embodiment, the conductive film may be formed from a conductive paste composition according to the above embodiment.

[0131] In one aspect, the conductive film has a volume resistance of 9 μΩ·cm or less and a contact resistance of 5 mΩ·cm. 2 Below, the film strength according to KS M ISO 15184 may be 3H or more, or better, 3 to 9 H.

[0132] In one aspect, the conductive film may have a finger line width of 40 ㎛ or less, a finger line thickness of 10 ㎛ or more, and a number of broken finger lines of 20 or less.

[0133] Another aspect of the present invention provides a solar cell including the conductive film.

[0134] In one aspect, the solar cell may be a heterojunction solar cell.

[0135] In one aspect, the film strength of the above-mentioned conductive film according to KS M ISO 15184 may be 3H or more, and more preferably 3 to 9 H.

[0136] In one aspect, the solar cell may have a fill factor (FF) of 75% or more or 80% or more.

[0137] The method for producing the conductive paste composition of the present invention is not particularly limited. In one embodiment, the conductive paste composition of the present invention can be produced by adding each component in a predetermined proportion to a mixer such as a Leica mixer, a propeller mixer, a kneader, a three-roll mill, or a pot mill, and mixing them.

[0138] The conductive paste composition of the present invention can be applied using a known coating method, and thus is not particularly limited thereto. An example of the application method is screen printing. When applied to the surface of a transparent electrode such as ITO using screen printing, the application can be carried out through a simple process, and thus can be drawn.

[0139] In addition, by applying a conductive paste composition to the surface of a transparent electrode or the like using the above method, and then heating the conductive paste composition at a predetermined temperature to harden it, a conductive film for a busbar electrode or a finger electrode can be formed. At this time, the heating temperature is preferably 250°C or lower, and more preferably 200°C or lower, which is the processing temperature during electrode formation. Specifically, the heating temperature for thermal hardening of the conductive paste composition is preferably 150 to 250°C, more preferably 150 to 200°C, or 150 to 180°C.

[0140] As an example of implementation, the thickness of the coating film formed from the conductive paste composition by applying it to the surface of a transparent electrode such as ITO is preferably 5 to 25 μm, more preferably 5 to 20 μm, or 10 to 20 μm.

[0141] The conductive film obtained by heating the conductive paste composition of the present invention has the characteristics of high adhesive strength to a solar cell substrate such as an ITO surface and low contact resistance.

[0142] The conductive paste composition of the present invention can be preferably used as a conductive paste for forming solar cell electrodes, such as bus bar electrodes or finger bar electrodes. More preferably, it can be suitably used for electrodes of heterojunction solar cells, and can also be used for forming electrodes and circuit patterns of semiconductor devices and electronic components.

[0143] The conductive paste composition for forming a solar cell electrode of the present invention preferably has a processing temperature of 250°C or lower, more preferably 200°C or lower, during electrode formation. The time for applying the processing temperature is not particularly limited, but is preferably within 10 minutes, for example. By forming the electrode at such a temperature, adverse effects on thin film materials that are vulnerable to high temperatures can be suppressed.

[0144] The film strength according to KS M ISO 15184 of the film formed using the conductive paste composition according to the present invention may be 3H or more, and more preferably 3 to 9 H.

[0145] A heterojunction solar cell including an electrode layer using a conductive paste composition according to one aspect of the present invention may have a curve factor (FF) of 75% or more, for example, 70 to 85%.

[0146] The present invention will be described in more detail based on the following examples and comparative examples. However, the following examples and comparative examples are merely illustrative examples for further explaining the present invention, and the present invention is not limited by the following examples and comparative examples.

[0147] The following physical properties were measured as follows.

[0148] 1) Viscosity

[0149] Brookfield viscometer (Brookfield DV2 @25 ℃, Spindle 14)

[0150] A single-cylinder rotational Brookfield viscometer (Brookfield DV2) with spindle 14 was used. The adapter and thermostat were connected and maintained at 25°C. The temperature of the instrument was controlled within ±0.1°C. Calibration was performed using a standard solution to complete the viscometer setup. The cylindrical container was filled with the sample, ensuring that the contents were neither too low nor too high, taking into account the spindle volume. The cylindrical container was attached to the adapter, and the spindle was fixed to a rotating ring beneath the viscometer, ensuring that the torque value was 0% (i.e., horizontal). The sample in the container was left to stand for approximately 10 minutes until it reached the specified temperature. The viscometer was switched to viscosity mode, the desired rpm was set, and the instrument was operated for 1 minute. The measured value was read once the display value stabilized. The measurement ranges were 1 rpm, 10 rpm, and 100 rpm, in that order. Tables 1 and 2 show the value at 10 rpm. Here, rpm is an abbreviation for (rotations per minute) and refers to the rotations per minute of the viscometer spindle 14, and the value of 10 rpm is the standard rotation speed for Brookfield DV2.

[0151] 2) Volume resistance

[0152] The resistance was measured using an ohmmeter at a point 30 mm from the test piece (20-30㎛ thick), and then calculated according to the following formula.

[0153] Volume resistivity (μΩ·cm) = (measured resistance × film width × film thickness) / measured film length

[0154] A transparent glass substrate measuring 200×200 mm, 1.0 mm thick, and with a TCO resistance of 10 to 13 Ω is used. An electrode measuring 5×60 mm and 30 um thick is formed on the TCO-coated surface through screen printing, and then cured using an infrared heat treatment drying furnace at 200°C for 10 minutes. The electrode resistance is measured using the 2-probe pin of the HIOKI RM 3545 resistance meter, and the electrode width and electrode thickness of the cured electrode are measured to obtain the volume resistivity according to the above calculation formula.

[0155] Additionally, the volume resistance change rate was calculated using the following equation.

[0156] Volume resistance change rate (%) = Volume resistance after maintenance under high temperature and high humidity conditions / Initial volume resistance × 100

[0157] The above high temperature and high humidity conditions are the volume resistance measured after maintaining the condition at 85 ℃ and relative humidity 85 RH% for 10 days, and the above initial volume resistance refers to the volume resistance before high temperature and high humidity treatment.

[0158] 3) Contact resistance

[0159] Contact resistance is measured using the TLM (Transfer Length Method) pattern. It is the simplest and most commonly used method of measuring unit contact resistance. Five electrode patterns with a width of 100 mm are formed at intervals of 200 ㎛, 400 ㎛, 600 ㎛, 800 ㎛, and 1000 ㎛. The electrodes are formed using a screen printing process on the surface of the TCO-treated wafer. A screen pattern with a wire diameter of 325 mesh, a wire diameter of 23 ㎛, and an emulsion of 10 ㎛ is used, and the screen printing equipment is the MT-650TV model from MICRO-TEC. After curing using an infrared heat treatment drying furnace at 200℃ for 10 minutes, the resistance according to the electrode distance is measured using a HIOKI RM 3545 resistance meter. The slope is obtained using the electrode distance and the measured resistance value, and the sheet resistance and contact resistivity (mΩ.cm) are calculated. 2 ) can be obtained.

[0160] 4) Finger line width, finger line thickness, and number of broken finger lines during screen printing

[0161] MICRO-TEC screen equipment was used, and the screen was manufactured by Brave. The screen specifications are S / T 430 Mesh, knotless, emulsion thickness 13 μm, and shoulder angle 5 degrees. The printing pattern is 9 bus bars, 100 finger lines, and width less than 22 μm. The printing pressure is 0.25 MPa for the squeegee and 0.1 MPa for the flood blade, and the printing conditions are fixed at 230 mm / s for the squeegee and 300 mm / s for the flood blade. For uniform printing application, a sample of 500 g or more was applied, and printing was discharged about 10 times in the beginning, and then printing was performed on a silicon wafer.

[0162] 5) Film strength

[0163] The electrode film strength was measured using the domestic standard method of KS M ISO 15184, 'Paints and varnishes - Determination of film strength by a pencil tester'. The measurement specimen was prepared by curing a film of 50㎛ or less on a slide glass. A Mitsubishi pencil was used, and the pencil was placed perpendicular to sandpaper and then abraded to make it flat. The measurement specimen was fixed to the stage, and the pencil and the specimen were placed at a 45-degree angle. A force of 7.5 N was applied by adjusting the weight of the weight and pushed at a constant speed. The test was performed by sequentially replacing the pencils from 8B to 8H, and the maximum hardness without damaging the film was read.

[0164] 6) Cell efficiency

[0165] Cell efficiency was measured using a solar simulator. The measurement conditions were Air Mass 1.5, 1 Sun (100 mW / cm) according to STC (Standard Test Conditions). 2 ), was performed at 25 ℃. When a certain amount of light energy is supplied, a current (I) is generated from the solar cell, and the amount of current is measured by varying the voltage (V). The efficiency (EFF) is the value obtained by finding the maximum point through the IV curve graph data obtained from the relationship between the current and voltage and dividing that value by the amount of sunlight. In addition, the efficiency can be measured by the correlation formula of short-circuit current (ISC), open circuit voltage (VOC), fill factor (FF), and area (A).

[0166]

[0167] 7) Curve factor

[0168] The fill factor (FF (Fill factor)) is expressed as the fill factor or charge factor, and can be obtained by drawing an IV curve (current, potential curve). I represents the short-circuit current Isc, and V represents the open circuit voltage Voc. The IV curve can represent the maximum current (Imp), maximum voltage (Vmp), and maximum power that a solar cell can generate, and using this, the FF can be obtained with the following equation.

[0169] FF = (Imp×Vmp) / (Isc×Voc)

[0170] [Examples 1 to 10]

[0171] A conductive paste composition was prepared with the composition and contents shown in Table 1 below. The content unit of each component is weight%.

[0172] In addition, the manufactured conductive paste composition was screen-printed under the following conditions to measure the volume resistance, contact resistance, finger line width, finger line thickness, number of broken finger lines, and film strength of the film, which are shown in Table 1 below.

[0173] Screen printing conditions: 430MESH / wire diameter 13 ㎛ / Emulsion over mesh height (EOM) 10 ㎛ / wire width 30 (top of screen) ~ 35 (bottom of screen) ㎛ / Finger 100ea, 9BB Half Cut pattern, M6 / Screen frame size: 450×450mm

[0174] In addition, heterojunction solar cells were manufactured and the curve factor among cell characteristics was measured, which is shown in Table 1 below.

[0175] [Comparative Examples 1 to 3]

[0176] A conductive paste composition was prepared with the composition and contents shown in Table 2 below. The unit of content of each component is weight%.

[0177] In addition, in Comparative Examples 1 to 3, the volume resistance, contact resistance, finger line width, finger line thickness, number of broken finger lines, and film strength of the film were measured by screen printing under the same printing conditions as in the examples, and the results are shown in Table 2 below. In addition, heterojunction solar cells were manufactured and the cells were measured, and the curve factor values ​​among the cell characteristics are shown in Table 2 below.

[0178] Ingredients Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 (A) Conductive powder AgCu powder 4 2 4 2 4 2 4 2 4 2 4 2 4 2 4 2 6 0 4 2 Ag powder 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 3 2 5 0 (B) Liquid multifunctional epoxy compound 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 (C) Coupling agent 0.5 ... 111111111-(G) Antioxidant 0.10.10.10.20.30.50.50.50.50.5(H) Solvent 1.11.11.11.00.90.70.70.70.71.7(I) Imidazole compound 0.30.30.30.30.30.30.30.30.30.30.3 Total components 100100100100100100100100100100100100Ag content of AgCu powder (wt%) 102030202020202020AgCu powder average particle size (㎛) 4.54.54.54.54.54.5344.54.5Maximum of AgCu powder Particle size (㎛) 6666666866 Viscosity (cps) 342,000 350,000 348,000 328,000 345,000 350,000 385,000 360,000 250,000 150,000 Volume resistivity (μΩ cm) 8.9 7.5 8.2 7.6 7.37.6 11.5 9.9 12.8 7.3 8 5℃ / 85RH% Volume resistivity change rate (%) 14.5 9 89.8 3.2 0.5 0.5 0.5 0.5 0.5 Contact resistance (mΩ cm) 2)3.23.53.43.53.23.34.23.983.5Finger line width (㎛)35.134.233.534.233.53237353245Finger line thickness (㎛)14.515.515.514.515.51611.513.215.59Number of broken lines (pieces)20 or less20 or less20 or less20 or less20 or less20 or less20 or less20 or less20 or less20 or less20 or less20 or less20 or less20 or less20 or lessFilm strength4H8H4H4H4H4H4H4H4H2BCurve factorFF(%)75~8075~8075~8075~8080~8575~8075~8070% or less70% or less

[0179] The ingredients shown in Table 1 above are as follows.

[0180] (A) conductive powder

[0181] AgCu powder: Core-shell powder with the surface of Cu powder coated with Ag. The Ag coating amount, average particle size (D50), and maximum particle size (Dmax) are as shown in Table 1.

[0182] Silver (Ag) powder: The average particle size (D50) is 0.5 ㎛, the maximum particle size (Dmax) is 2 ㎛, the tap density is 5.0 g / cc, and the specific surface area is 1.0 ㎡ / g.

[0183] (B) Liquid multifunctional epoxy compound: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate

[0184] (C) Coupling agent

[0185] 3-Glycidoxypropyl triethoxysilane, an alkoxysilane coupling agent, and diisopropyl dioleyl titanate, a titanate coupling agent, were mixed and used in a 1:1 weight ratio.

[0186] (D) Phenoxy resin: Use by mixing 30.0 wt% of phenoxy resin A (INCHEM, PKHC) and 70.0 wt% of ethylene glycol dibutyl ether acetate.

[0187] (E) Polysiloxane resin: polydimethyl siloxane (SHINETSU, KF-96)

[0188] (F) Cellulose resin: Ethyl cellulose (DOW, STD-100, solid content 15 wt%)

[0189] (G) Antioxidant: Dibutyl hydroxyl toluene (BHT) and 2-(2-aminophenyl)ethanol were mixed in a weight ratio of 1:1 and used.

[0190] (H) Solvent: Ethylene glycol dibutyl ether acetate

[0191] (I) Imidazole compound: 2-ethylimidazole

[0192] Ingredient Comparison Example 1 Comparison Example 2 Comparison Example 3 (A) Conductive powder AgCu powder 924242 Ag powder -5050 (B) Liquid multifunctional epoxy compound 1.51.51.5 (C) Coupling agent 0.50.51 (D) Phenoxy resin 333 (E) Polysiloxane resin 0.50.5- (F) Cellulose resin 11- (G) Antioxidant 0.5-0.5 (H) Solvent 0.71.21.6 (I) Imidazole compound 0.30.30.3 Total components 100100100 Ag content of AgCu powder (wt%) 202020 Average particle size of AgCu powder (㎛) 4.54.54.5 Maximum of AgCu powder Particle size (㎛) 666 Viscosity (cps) 97,000 280,000 150,000 Volume resistivity (μΩ cm) 247.5 8.3 85 ℃ / 85 RH% Volume resistivity change rate (%) 0.5 20 0.5 Contact resistance (mΩ cm) 2 )123.27.5 Finger line width (㎛)523447 Finger line thickness (㎛)614.57 Number of broken lines (pieces)20 or less20 or less20 or less Film strength3~5H3~5H3~5H Curve factor FF(%)70% or less75~80%70% or less

[0193] Each component of Table 2 above is the same as that described in Table 1.

[0194] As shown in Tables 1 and 2 above, the conductive paste compositions of Examples 1 to 10 according to the present invention were applicable to screen printing with a viscosity of 350,000 cps or less, and it was confirmed that they could be used as conductive films for solar cells. In addition, as shown in Examples 1 to 6, it was confirmed that even better properties could be provided under the conditions that the Ag content of the AgCu powder was 10 to 30 wt%, the average particle diameter was 4 to 5 ㎛, and the maximum particle diameter was 7 ㎛ or less, specifically 6 to 7 ㎛. Specifically, the volume resistance was 9 μΩ·cm or less, and the contact resistance was 5 mΩ·cm. 2 Below, it was confirmed that the finger line width was 40 ㎛ or less, the finger line thickness was 10 ㎛ or more, the number of broken finger lines was 20 or less, and the cell efficiency was confirmed to be 80% or more. In addition, it was confirmed that the volume resistance change rate was maintained at 15% or less under the conditions of 85℃ and 85RH%.

[0195] In addition, it was confirmed that when the average particle size of the AgCu powder was small and the maximum particle size was large, as in Examples 7 and 8, the volume resistivity increased somewhat compared to other examples.

[0196] In addition, it was confirmed that the volume resistance increased when the content of AgCu powder was used in large amounts compared to the content of Ag powder, as in Example 9. Therefore, it was confirmed that it is preferable to use a high content of Ag powder compared to the content of AgCu powder.

[0197] In addition, Example 10, which did not include ethyl cellulose in comparison to Examples 1 to 9, was confirmed to have lower film strength than the other examples. Therefore, it was confirmed that the simultaneous use of phenoxy resin, polydimethylsiloxane, and ethyl cellulose can satisfy the property of a film strength of 3H or higher.

[0198] As in Comparative Example 1, when AgCu powder was used alone, it was confirmed that the viscosity was very low, the volume resistance and contact resistance were high, and the finger line width and thickness were unsatisfactory.

[0199] Additionally, it was confirmed that the volume resistance change rate increased significantly in cases where no antioxidant was included, as in Comparative Example 2.

[0200] In addition, when phenoxy resin was used alone as a binder resin, as in Comparative Example 3, it was confirmed that the finger line width was thick at 47 ㎛ and the thickness was thin at 7 ㎛.

[0201] As described above, the present invention has been described through specific matters and limited examples, but these are provided only to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations based on this description.

[0202] Therefore, the idea of ​​the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the claims described below as well as the claims are considered to fall within the scope of the idea of ​​the present invention.

Claims

1. Conductive powder mixed with AgCu powder and silver (Ag) powder; Liquid multifunctional epoxy compound; Alkoxysilane coupling agent having a reactive group; Two or more binder resins selected from phenoxy resin, polysiloxane resin and cellulose resin; Antioxidants; and A challenging paste composition comprising a solvent.

2. In paragraph 1, The conductive powder is a conductive paste composition having a content of AgCu powder: silver (Ag) powder in a weight ratio of 30 to 50:50 to 70.

3. In paragraph 1, The above AgCu powder is a conductive paste composition in which the surface of the Cu powder is a core-shell powder coated with Ag.

4. In paragraph 1, A conductive paste composition wherein the AgCu powder is one selected from spherical and flake forms or a mixture thereof.

5. In paragraph 1, The above AgCu powder is a conductive paste composition having an Ag content of 10 to 30 wt%.

6. In paragraph 1, A conductive paste composition wherein the AgCu powder has an average particle diameter (D50) of 2 to 7 ㎛ and a maximum particle diameter (Dmax) of 5 to 8 ㎛.

7. In paragraph 1, A conductive paste composition wherein the silver (Ag) powder has an average particle diameter (D50) of 0.1 to 1 ㎛ and a maximum particle diameter (Dmax) of 1 to 2 ㎛.

8. In paragraph 1, A conductive paste composition wherein the binder resin includes all of phenoxy resin, polysiloxane resin, and cellulose resin.

9. In paragraph 1, The above antioxidants are malonic acid, glutaric acid, dimethyl malonate, methanesulfonic acid, abietic acid, p-toluene sulfonic acid, oxalic acid, 4-hydroxybenzoic acid, salicylic acid, 2-furic acid, benzoic acid, lauric acid, palmitic acid, stearic acid, oleic acid, succinic acid, adipic acid, suberic acid, 1,3-diphenylguanidine, Cyclohexylamine, Diethylamine, Triethanolamine, Monoethanolamine, 2-Bromo propionic acid, 2-Bromobutyric acid, 2,3-Dibromopropionic acid, 2,3-Dibromosucinic acid, Hydroquinone, Benzimidazole, 2-Phenylimidazole, 2-Ethylimidazole, Triethanolamine, Dicyanodiamide, Ethylenediamine, Dimethylbenzylamine, Ethylenediamine tetraacetic acid, butylated hydroxy anisole,A conductive paste composition, wherein the conductive paste composition is one or a mixture of two or more selected from the group consisting of BHA, dibutyl hydroxyl toluene (BHT), t-butyl hydroquinone (TBHQ), 4-aminophenyl alcohol, 2-aminophenyl alcohol, 4-aminobenzyl alcohol, 3-aminobenzyl alcohol, and 2-(2-aminophenyl)ethanol.

10. In paragraph 1, The above-mentioned conductive paste composition is a conductive paste composition having a viscosity of 400,000 cps or less when measured using a Brookfield viscometer (Brookfield DV2 @25 ℃, Spindle 14, 10 rpm).

11. In paragraph 1, The conductive paste composition comprises: 85 to 96 wt% of a conductive powder; 0.2 to 5 wt% of a liquid multifunctional epoxy compound; 0.05 to 2 wt% of an alkoxysilane coupling agent having a reactive group; two or more binder resins selected from 0.01 to 5 wt% of a phenoxy resin, 0.1 to 2 wt% of a polysiloxane resin, and 0.01 to 2 wt% of a cellulose resin; 0.1 to 1 wt% of an antioxidant, and the remainder of a solvent.

12. In paragraph 1, The volume resistance of the coating film coated with the above-mentioned challenging paste composition and heat-treated is 9 μΩ·cm or less and the contact resistance is 5 mΩ·cm or less. 2 A conductive paste composition having a film strength of 3H or higher according to KS M ISO 15184.

13. In paragraph 1, The above conductive paste composition is a conductive paste composition having a finger line width of 40 ㎛ or less, a finger line thickness of 10 ㎛ or more, and a number of broken finger lines of 20 or less during screen printing.

14. In paragraph 1, The above liquid multifunctional epoxy compound is an alicyclic multifunctional epoxy compound having a molecular weight of 2000 or less, A conductive paste composition wherein the alkoxysilane coupling agent having the above reactive group is represented by the following chemical formula 1. [Chemical Formula 1] AnSi(OR)m In the chemical formula 1, A is a C2 to C6 alkyl group substituted with a glycidyl group, an epoxy group, a glycidyloxy group, an amine group or a thiol group, R is a C1 to C4 alkyl group, n is an integer selected from 1 to 3, m is an integer selected from 1 to 3, and n+m is 4.

15. In paragraph 1, The above phenoxy resin is a conductive paste composition having a viscosity (Brookfield @25 ℃, 20% in cyclohexanone) of 700 cP or less, a weight average molecular weight of 3,000 to 60,000 g / mol, and a glass transition temperature of 100 ℃ or less.

16. In paragraph 1, The conductive paste composition further comprises one or more selected from a bisphenol-based epoxy resin, an imidazole-based compound, and a titanate-based coupling agent.

17. A conductive film formed from any one of the conductive paste compositions selected from items 1 to 16, selected from a finger electrode or a busbar electrode, having a volume resistance of 9 μΩ·cm or less and a contact resistance of 5 mΩ·cm. 2 A conductive film for solar cells having a film strength of 3H or higher according to KS M ISO 15184, a finger line width of 40 ㎛ or lower, a finger line thickness of 10 ㎛ or higher, and a number of broken finger lines of 20 or lower.

18. A solar cell comprising the challenge film of clause 17.

19. In paragraph 18, The above solar cell is a heterojunction solar cell and has a curvature factor (FF) of 75% or more.

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