KR20190050877A - Electrode Paste For Solar Cell's Electrode And Solar Cell using the same - Google Patents

Abstract

The present invention relates to a conductive paste for an electrode of a photovoltaic cell. The conductive paste for an electrode of a photovoltaic cell comprises metal powder, glass frit, an organic binder, and a solvent. A surface of the metal powder is coated with an alkylamine-based material having 6 to 24 carbon atoms. By coating the surface of the metal powder with a low solvability coating agent, the generating efficiency of the photovoltaic cell may be increased by stably implementing a fine line width of a front electrode of the photovoltaic cell formed by using the metal powder and improving the electrical characteristics of the electrode.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste for a solar cell electrode,

The present invention relates to a conductive paste used for forming an electrode of a solar cell and a solar cell manufactured using the conductive paste.

A solar cell is a semiconductor device that converts solar energy into electrical energy. It has a p-n junction type and its basic structure is the same as a diode. FIG. 1 shows a structure of a general solar cell element. The solar cell element is generally constituted by using a p-type silicon semiconductor substrate 10 having a thickness of 180 to 250 .mu.m. On the light receiving surface side of the silicon semiconductor substrate, an n-type impurity layer 20 having a thickness of 0.3 to 0.6 占 퐉, an anti-reflection film 30 and a front electrode 100 are formed thereon. A back electrode 50 is formed on the back side of the p-type silicon semiconductor substrate.

The front electrode 100 is formed by applying a conductive paste, which is a mixture of silver powder, glass frit, organic binder, solvent, and additives, which are mainly composed of silver, on the antireflection coating 30, And the back electrode 50 is formed by applying an aluminum paste composition composed of aluminum powder, glass frit, organic binder, solvent and additives by screen printing or the like, drying the paste, drying the paste at a temperature of 660 캜 (melting point of aluminum) Followed by firing. Aluminum is diffused into the p-type silicon semiconductor substrate at the time of firing, so that an Al-Si alloy layer is formed between the back electrode and the p-type silicon semiconductor substrate, and the p + layer 40 Is formed. The existence of such a p + layer prevents the recombination of electrons and improves the collection efficiency of the generated carriers, thereby obtaining a BSF (Back Surface Field) effect. A rear silver electrode 60 may be further disposed under the rear aluminum electrode 50.

On the other hand, the front electrode of the solar cell is mainly formed through a screen printing process. Therefore, although the front and rear electrode paste compositions are manufactured in consideration of printability of the screen printing process, it is difficult to realize a good resolution by reproducing the desired line width of the front electrode.

In particular, the silver powder used in the conventional crystalline solar cell generally uses a powder coated with a fatty acid such as stearic acid or oleic acid. In the case of the coating agent, the compatibility with the solvent is excellent, so that the window for selecting the solvent is wide, but the content of the solvent in the paste must be large due to the effect of the solubility too high. there is a problem.

In the present invention, by coating the surface of a metal powder in a composition of a conductive paste for a solar cell electrode with a low-solubility coating agent, the fine line width of the front electrode of the solar cell formed using the coating is stably realized, And to improve the power generation efficiency of the battery.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

The present invention provides a conductive paste for a solar cell electrode, comprising a metal powder, a glass frit, an organic binder and a solvent, wherein the surface of the metal powder is coated with an alkylamine-based material having 6 to 24 carbon atoms.

The alkylamine-based material may be at least one selected from the group consisting of triethylamine, heptylamine, octadecylamine, hexadecylamine, decylamine, octylamine, Isopropylamine, diethylamine, diethylamine, diisopropylamine, diisopropylamine, diisopropylamine, diisopropylamine, diisopropylamine,

The solvent may also be selected from the group consisting of alpha-terpineol, texanol, dioctyl phthalate, dibutyl phthalate, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate , Diethylene glycol monobutyl ether, and diethylene glycol monobutyl ether acetate, wherein the solubility of the alkylamine-based material in the solvent is lower than the solubility of the fatty acid in the solvent .

The fatty acid may be at least one selected from the group consisting of lauric acid, oleic acid, stearic acid, palmitic acid and acetic acid.

Further, the metal powder may be a first metal powder, and the conductive paste may further include a second metal powder, wherein the surface of the second metal powder is not coated or is coated with a fatty acid.

The conductive paste has a viscosity of 40 to 60 Pa · s at 25 ° C.

The present invention also provides a solar cell having a front electrode on a substrate and a back electrode on the bottom of the substrate, wherein the front electrode is formed by applying the conductive paste for a solar cell electrode, followed by drying and firing And the like.

The conductive paste according to the present invention includes a metal powder coated with an alkylamine-based material having low solubility characteristics with respect to a solvent, and can realize a fine line width of a front electrode of a solar cell formed using the metal powder, It is possible to improve the electric power generation efficiency of the solar cell by improving the electrical characteristics of the electrode by reducing the line resistance and increasing the short circuit current according to the fine line width.

1 is a schematic cross-sectional view of a general solar cell element.
FIGS. 2A to 2D are images taken after adding coating agents to representative solvents, and show the result of the transparency evaluation of a solution to which a coating agent is added.

Before describing the present invention in detail, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is defined solely by the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise stated.

Throughout this specification and claims, the word "comprise", "comprises", "comprising" means including a stated article, step or group of articles, and steps, , Step, or group of objects, or a group of steps.

On the contrary, the various embodiments of the present invention can be combined with any other embodiments as long as there is no clear counterpoint. Any feature that is specifically or advantageously indicated as being advantageous may be combined with any other feature or feature that is indicated as being preferred or advantageous. Hereinafter, embodiments of the present invention and effects thereof will be described with reference to the accompanying drawings.

The paste according to an embodiment of the present invention is a paste suitable for forming a solar cell electrode, and provides a conductive paste containing a metal powder coated with an alkylamine-based material having 6 to 24 carbon atoms. More specifically, the conductive paste according to the present invention comprises a metal powder, a glass frit, an organic binder, a solvent, and other additives.

The metal powder may be a silver (Ag) powder, a copper (Cu) powder, a nickel (Ni) powder, or an aluminum (Al) powder and the surface thereof may be coated with an alkylamine- have. Preferably, the surface of the metal powder may be coated with an alkylamine-based material having 10 to 20 carbon atoms. As the alkylamine-based substance, a substance having solubility in the solvent lower than that of the fatty acid in the solvent may be used. For example, the alkylamine-based material may be selected from the group consisting of triethylamine, heptylamine, octadecylamine, hexadecylamine, decylamine, octylamine, At least one selected from the group consisting of lauric acid, oleic acid, stearic acid, palmitic acid, and acetic acid. .

Preferably, silver powder coated with octadecylamine is mainly used for the front electrode, and aluminum powder coated with octadecylamine is mainly used for the back electrode. The octadecylamine is preferably coated on the surface of the metal powder to a thickness of 0.1 nm to 50 nm. The coating of the octadecylamine may be carried out by adding a metal powder such as Ag powder to an organic solvent in which octadecylamine is dissolved, stirring the mixture for a predetermined period of time, and then filtering.

As the surface of the metal powder is coated with an alkylamine-based material having low solubility characteristics with respect to the solvent, the content of the solvent in the conductive paste composition can be effectively reduced while satisfying the required characteristics (for example, viscosity) of the paste. This is attributable to the oil-absorbing property of the coating agent to the solvent. As the solubility of the coating agent is lower, the amount of the solvent absorbed by the coating agent becomes smaller, and it is possible to prepare a conductive paste composition satisfying the properties required even with a small amount of solvent .

In another embodiment of the present invention, the metal powder may include a first metal powder coated with an alkylamine-based material having 6 to 24 carbon atoms, and a second metal powder coated with a fatty acid. Each of the first and second metal powders may include a silver (Ag) powder, a copper (Cu) powder, a nickel (Ni) powder, or an aluminum (Al) powder. The alkylamine-based material may be at least one selected from the group consisting of triethylamine, heptylamine, octadecylamine, hexadecylamine, decylamine, octylamine, Wherein the fatty acid comprises at least one selected from the group consisting of lauric acid, oleic acid, stearic acid, palmitic acid and acetic acid. The first metal powder and the second metal powder coated with the materials having different solubility characteristics as the metal powder are mixed and used so that the content of the solvent in the conductive paste can be easily controlled.

As another embodiment of the present invention, the first metal powder may be a metal powder coated with the alkylamine-based material, and the second metal powder may be a metal powder not coated with the alkylamine-based material.

The content of the metal powder is in the range of 40 to 95% by weight based on the total weight of the conductive paste composition, taking into consideration the electrode thickness formed at the time of printing and the line resistance of the electrode. More preferably 60 to 90% by weight.

In the case where the conductive paste contains silver powder for forming the front electrode of the solar cell, the silver powder is preferably a pure silver powder, and in addition, a silver-coated composite powder having at least a silver layer on its surface, An alloy or the like can be used. At this time, the outer surface of the silver powder may be coated with the alkylamine-based material. Further, other metal powders may be mixed and used. For example, other metal powders include aluminum, gold, palladium, copper, and nickel.

The average particle diameter of the metal powder may be in the range of 0.1 to 10 占 퐉. The average particle diameter of the metal powder is preferably 0.5 to 5 占 퐉 in consideration of ease of paste formation and compactness at the time of firing, and may be at least one of spherical, acicular, have. The metal powder may be a mixture of powders of two or more kinds having different average particle diameter, particle size distribution and shape.

The composition, particle diameter and shape of the glass frit are not particularly limited. It is possible to use not only flexible glass frit but also lead-free glass frit. Preferably, the content and content of the glass frit are 5 to 29 mol% of PbO, 20 to 34 mol% of TeO ₂ , 3 to 20 mol% of Bi ₂ O ₃ , 20 mol% or less of SiO ₂ , 10 mol% or less of B ₂ O ₃ , 10 to 20 mol% of an alkali metal (Li, Na, K, etc.) and an alkaline earth metal (Ca, Mg, etc.) By combining the organic components of the above components, it is possible to prevent an increase in the line width of the electrode, to improve the contact resistance in the high-surface resistance, and to improve the short-circuit current characteristic.

The average particle diameter of the glass frit is not limited, but it may have a particle diameter in the range of 0.5 to 10 mu m, and a mixture of various particles having different average particle diameters may be used. Preferably, at least one kind of glass frit has an average particle diameter (D50) of not less than 2 mu m and not more than 10 mu m. As a result, the reactivity at the time of firing can be improved, the damage of the n-layer at the high temperature can be minimized, the adhesion can be improved, and the open-circuit voltage (Voc) can be improved. Also, the increase in the line width of the electrode during firing can be reduced.

The content of the glass frit is preferably 1 to 10% by weight based on the total weight of the conductive paste composition. If the content is less than 1% by weight, incomplete firing may occur to increase the electrical resistivity. If more than 10% by weight, There is a possibility that the electrical resistivity becomes too high due to too much component.

The organic vehicle including the organic binder and the solvent is required to maintain uniform mixing of the metal powder and the glass frit. For example, when the conductive paste is applied to the substrate by screen printing , It is required to make the conductive paste uniform, to suppress the blur and flow of the printed pattern, and to improve the dischargeability and the plate separability of the conductive paste from the screen plate.

Examples of the organic binder include cellulose ester compounds such as cellulose acetate and cellulose acetate butyrate. Examples of the cellulose ether compound include ethylcellulose, methylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, Examples of the acrylic compound include polyacrylamide, polymethacrylate, polymethylmethacrylate, and polyethylmethacrylate. Examples of the vinyl compound include polyvinyl butyral , Polyvinyl acetate, polyvinyl alcohol, and the like. At least one or more organic binders may be selected and used.

The organic binder is not limited, but is preferably 1 to 15% by weight based on the total weight of the conductive paste composition. If the content of the organic binder is less than 1% by weight, the viscosity of the composition and the adhesion of the formed electrode pattern may be deteriorated. If the content of the organic binder is more than 15% by weight, the amount of metal powder, solvent,

The solvent may be selected from the group consisting of alpha-terpineol, texanol, dioctyl phthalate, dibutyl phthalate, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol, ethylene glycol monobutyl ether, ethylene Glycol monobutyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, and the like.

The conductive paste composition according to the present invention may further contain additives commonly known in the art, for example, dispersants, plasticizers, viscosity regulators, surfactants, oxidizing agents, metal oxides, metal organic compounds and the like.

The conductive paste composition for a solar cell electrode may be prepared by mixing and dispersing a metal powder, a glass frit, an organic binder, a solvent, an additive, etc., followed by filtration and defoaming.

The viscosity of the conductive paste composition according to the present invention has a low viscosity of 40 to 60 Pa · s at 25 ° C in spite of a small amount of solvent, so that the content of the composition can be easily controlled and the stability is excellent.

The present invention also provides a method of forming an electrode of a solar cell and a solar cell electrode produced by the method, wherein the conductive paste is applied on a substrate, followed by drying and firing. Printing, drying, and firing methods commonly used in the manufacture of solar cells can be used, except that the conductive paste containing the metal powder coated as described above is used in the method of forming a solar cell electrode of the present invention Of course it is. For example, the substrate may be a silicon wafer.

When the electrode is formed using the conductive paste according to the present invention, the content of the solvent in the conductive paste can be effectively reduced, and the line width spreading phenomenon can be improved at the time of electrode formation. As a result, it is possible to stably realize the electrode having the fine line width, and to reduce the line resistance according to the excellent tap density characteristic and to increase the short circuit current (Isc) according to the fine line width The electrical characteristics of the electrode can be improved and the power generation efficiency of the solar cell can be improved.

In addition, the conductive paste according to the present invention may be applied to a structure such as a crystalline solar cell (P-type, N-type), a passivated emitter solar cell (PESC), a passivated emitter and rear cell (PERC), a passivated emitter real locally diffused It can be applied to all printing processes such as double printing and dual printing.

Examples 1 to 5 and Comparative Examples 1 to 4

The glass frit, the organic binder, the solvent and the dispersant were put in a composition (for example,% by weight) as shown in the following Table 1 and dispersed using a triple mill, and then the coated silver powder (spherical, And dispersed using a triple mill. Thereafter, vacuum degassing was conducted to prepare a conductive paste. Table 2 shows the types of coating materials and the tap density of the silver powder used in Examples 1 to 5 and Comparative Examples 1 to 4.

division Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Coated
Silver Powder 88 88 88 88 88 88 88 88 88 bookbinder 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 menstruum
(texanol) 7 7 7 7 7 7 7 7 7 Dispersant 3 3 3 3 3 3 3 3 3 Glass frit 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Viscosity (Pa · s) 20 40 25 30 40 50 70 80 70

division Coating agent Tap density (g / cm ³ ) Comparative Example 1 Silver Powder-1 Lauric Acid 5.4 Comparative Example 2 Silver powder-4 Oleic Acid 5.1 Comparative Example 3 Silver Powder -5 Iso-Palmitic Acid 5.3 Comparative Example 4 Silver powder-6 Iso-Stearic Acid 4.9 Example 1 Silver Powder-8 Octadecyl Amine 5.8 Example 2 Silver Powder-9 Triethyl Amine 5.5 Example 3 Silver Powder-10 Decyl Amine 5.6 Example 4 Silver Powder-11 Didecyl Amine 5.7 Example 5 Silver Powder-12 Trioctyl Amine 5.5

Examples 6 to 10 and Comparative Examples 5 to 8

The glass frit, the organic binder, the solvent and the dispersing agent were put in a composition (for example,% by weight) as shown in Table 3 below, dispersed using a triple mill, and then the coated silver powder (spherical, And dispersed using a triple mill. Thereafter, vacuum degassing was conducted to prepare a conductive paste. The coating type and the measured tap density of the silver powder used in Examples 6 to 10 and Comparative Examples 5 to 8 are shown in Table 4 below.

division Example 6 Example 7 Example 8 Example 9 Example 10 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Coated
Silver Powder 88 88 88 88 88 88 88 88 88 bookbinder 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 menstruum
(texanol) 5 6 5.5 5.5 6 7 8 9 8 Dispersant 5 4 4.5 4.5 4 3 2 One 2 Glass frit 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Viscosity (Pa · s) 50 50 50 50 50 50 50 50 50

division Coating agent Tap density (g / cm ³ ) Comparative Example 5 Silver Powder-1 Lauric Acid 5.4 Comparative Example 6 Silver powder-4 Oleic Acid 5.1 Comparative Example 7 Silver Powder -5 Iso-Palmitic Acid 5.3 Comparative Example 8 Silver powder-6 Iso-Stearic Acid 4.9 Example 6 Silver Powder-8 Octadecyl Amine 5.8 Example 7 Silver Powder-9 Triethyl Amine 5.5 Example 8 Silver Powder-10 Decyl Amine 5.6 Example 9 Silver Powder-11 Didecyl Amine 5.7 Example 10 Silver Powder-12 Trioctyl Amine 5.5

Experimental Example

(1) Evaluation of solubility of coating agent on solvent

The solubility of each representative solvent was evaluated by adding the coating agent to each type. The comparative evaluation of the solubility was carried out by visually observing the transparency of the solution to which the coating agent was added. FIGS. 2A to 2D are images taken after adding coating agents to representative solvents, and show the result of the transparency evaluation of a solution to which a coating agent is added. The results are shown in Table 5.

Representative solvent Coating agent 1 Coating agent 4 Coating agent 5 Coating agent 6 Coating agent 8 Lauric Acid Oleic Acid Iso-Palmitic
Acid Iso-Stearic
Acid Octadecyl Amine A DB Soluble Soluble Soluble Soluble Insoluble B DBA Soluble Soluble Soluble Soluble Insoluble C Texanol Soluble Soluble Soluble Soluble Insoluble F DBE Insoluble Soluble Soluble Soluble Insoluble

Referring to FIGS. 2A to 2D and Table 5, it can be seen that the solution to which the coating agent 8 is added is opaque than the other solutions to which the coating agents 1, 4, 5, and 6 are added. That is, the solubility of octadecylamine in each representative solvent is lower than the solubility of fatty acid in each representative solvent. From this, it can be deduced that for the representative solvents, the solubility of the alkylamine-based material is lower than the solubility of the fatty acid.

(2) Viscosity measurement

The results of measuring the viscosity of the conductive paste prepared according to Examples 1 to 5 and Comparative Examples 1 to 4 under the conditions of P35 Ti L spindle, 30 RPM and 25 DEG C using RV1 rheometer (HAAKE) are shown in Table 1 . As shown in Table 1, the same composition (for example, the same amount of solvent) shows that the viscosity varies depending on the coating agent in the production of the paste. For example, the viscosity of the conductive paste according to Example 1 is about 20 Pa · s, which is lower than that of Comparative Example 1 in Comparative Example 1.

(3) Measurement of the amount of solvent to obtain the same viscosity

According to Examples 6 to 10 and Comparative Examples 5 to 8, when the conductive paste was prepared, the respective pastes were adjusted to have a certain viscosity (about 50 Pa · s at 25 ° C) by varying the solvent content. The composition of the solvent (for example,% by weight) for obtaining the same viscosity is as shown in Table 3. As shown in Table 3, in order to obtain the same viscosity as in the case of using an alkylamine-based material having 6 to 24 carbon atoms as a coating agent (Examples 6 to 10) and using a fatty acid as a coating agent (Comparative Examples 5 to 8) It can be confirmed that the amount of the solvent is small. As a result, it can be seen that the lower the solubility of the coating agent on the solvent, the smaller the amount of the solvent required for producing the paste having a constant viscosity level.

(4) Conversion efficiency and resistance measurement

The conductive paste prepared according to Examples 6 to 10 and Comparative Examples 5 to 8 was pattern-printed on the entire surface of the wafer by opening screen of 32 to 16 mils with a 16 to 16 mesh screen printing method and dried at 200 to 350 ° C For 20 seconds to 30 seconds. Then, Al paste was printed on the back side of the wafer and dried by the same method. The cells thus formed were fired at 500 to 900 ° C for 20 seconds to 30 seconds using a belt-type firing furnace to produce a solar cell.

The prepared cell was measured for short circuit current (Isc), open circuit voltage (Voc), conversion efficiency (Eff), curve factor (FF), serial resistance (CtisVV) using a solar cell efficiency measuring device Rs, line resistance and linewidth were measured and are shown in Table 6 below.

division Isc
(A) Voc
(V) Eff
(%) FF
(%) Rs
(mΩ) Rline-1
(Ω) Rline-2
(Ω) Line width
(μm) Example 6 9.172 0.6326 18.97 79.20 0.00121 22.1 22.7 28.2 Example 7 9.168 0.6322 18.94 79.28 0.00122 22.8 23.8 28.8 Example 8 9.170 0.6325 18.95 79.24 0.00121 22.4 23.0 28.5 Example 9 9.169 0.6324 18.96 79.25 0.00122 22.6 23.1 28.6 Example 10 9.167 0.6322 18.93 79.28 0.00123 23.0 23.9 29.0 Comparative Example 5 9.122 0.6318 18.89 79.38 0.00121 25.2 25.3 32.0 Comparative Example 6 9.165 0.6316 18.92 79.16 0.00134 25.5 26.5 30.2 Comparative Example 7 9.133 0.6316 18.84 79.10 0.00135 25.8 25.2 31.5 Comparative Example 8 9.119 0.6324 18.81 78.99 0.00136 26.1 26.4 32.1

As shown in Table 6, in the case of the electrodes formed with the conductive pastes (Examples 6 to 10) according to the embodiments of the present invention, the electrodes had a narrower line width than that of Comparative Examples 5 to 8, , And it can be understood that the electric conduction characteristic of the solar cell thus manufactured is excellent.

In addition, in the case of Examples 6 to 10, the short circuit current and conversion efficiency are higher than those of Comparative Examples 5 to 8, indicating that the power generation efficiency of the solar cell is excellent.

The features, structures, effects, and the like illustrated in the above-described embodiments can be combined and modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

10: P-type silicon semiconductor substrate
20: N-type impurity layer
30: antireflection film
40: P + layer (BSF: back surface field)
50: rear aluminum electrode
60: rear silver electrode
100: front electrode

Claims (7)

Metal powder, glass frit, organic binder and solvent,
Wherein the surface of the metal powder is coated with an alkylamine-based material having 6 to 24 carbon atoms.
The method according to claim 1,
The alkylamine-based material may be selected from the group consisting of triethylamine, heptylamine, octadecylamine, hexadecylamine, decylamine, octylamine, didecylamine ), Or trioctylamine. ≪ Desc / Clms Page number 13 >
The method according to claim 1,
Wherein the solvent is selected from the group consisting of alpha-terpineol, texanol, dioctyl phthalate, dibutyl phthalate, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, Diethylene glycol monobutyl ether, and diethylene glycol monobutyl ether acetate,
Wherein the solubility of the alkylamine-based material in the solvent is lower than the solubility of the fatty acid in the solvent.
The method of claim 3,
Wherein the fatty acid comprises at least one selected from the group consisting of lauric acid, oleic acid, stearic acid, palmitic acid and acetic acid.
The method according to claim 1,
Wherein the metal powder is a first metal powder,
Wherein the conductive paste further comprises a second metal powder,
Wherein the surface of the second metal powder is not coated or is coated with a fatty acid.
The method according to claim 1,
Wherein the conductive paste has a viscosity of 40 to 60 Pa · s at 25 ° C.
1. A solar cell having a front electrode on a substrate and a back electrode on a bottom of the substrate,
Wherein the front electrode is manufactured by applying the conductive paste for a solar cell electrode of any one of claims 1 to 6, followed by drying and firing.

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