KR20210086186A - Paste For Solar Cell's Electrode And Solar Cell using the same - Google Patents

Abstract

The present invention relates to a conductive paste for a solar cell electrode, and specifically, to a conductive paste for a solar cell electrode comprising a metal powder, a glass frit, an organic vehicle and silicone oil, wherein the mass of the metal powder and the mass of the silicone oil are determined by MPP index defined by an equation 1, MPP index = (mass of metal powder) / (mass of silicone oil), and the MPP index is 20 to 500. It is possible to improve power generation efficiency of solar cells without major changes in conventional manufacturing conditions.

Description

Paste for a solar cell electrode and a solar cell manufactured using the same {Paste For Solar Cell's Electrode And Solar Cell using the same}

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

A solar cell is a semiconductor device that converts solar energy into electrical energy, and generally has a p-n junction type and has the same basic structure as a diode. A solar cell device is generally constructed using a p-type silicon semiconductor substrate having a thickness of 160 to 250 μm. On the light-receiving surface side of the silicon semiconductor substrate, an n-type impurity layer having a thickness of 0.3 to 0.6 mu m, an antireflection film and a front electrode are formed thereon. Further, a back electrode is formed on the back side of the p-type silicon semiconductor substrate.

The front electrode forms an electrode by applying a conductive paste mixed with silver powder, glass frit, organic binder, solvent, and additives on the anti-reflection film and then firing it. , the rear electrode is formed by applying an aluminum paste composition consisting of aluminum powder, glass frit, organic binder, solvent and additives by screen printing or the like, drying it, and then firing at a temperature of 660 ° C. (melting point of aluminum) or higher. During this firing, aluminum diffuses into the p-type silicon semiconductor substrate, thereby forming an Al-Si alloy layer between the back electrode and the p-type silicon semiconductor substrate, and at the same time forming a p+ layer as an impurity layer by diffusion of aluminum atoms. do. By the presence of such a p + layer, a BSF (Back Surface Field) effect of preventing recombination of electrons and improving the collection efficiency of generated carriers is obtained. A rear silver electrode may be further disposed under the rear aluminum electrode.

Meanwhile, the front electrode of the solar cell is mainly formed through a screen printing process. However, when the slip property of the paste is bad, the paste does not easily come out through the screen mesh during screen printing, so that the electrode pattern is not formed as designed, and there is a problem in that it is uneven or non-uniform. In particular, when a fine line width is implemented, disconnection occurs or resistance is greatly increased, so the slip property of the paste becomes a very important factor.

In the present invention, silicone oil is added to the paste in order to improve the slip property of the conductive paste for solar cell electrodes. However, if the silicone oil is not used in an appropriate amount, the resistance may increase to decrease the conversion efficiency, or a phase separation phenomenon may occur due to the silicone oil, thereby damaging the uniformity of the paste and lowering the storage stability.

Therefore, the present invention provides an electrode paste for a solar cell that can realize a stable fine line width while reducing resistance by adding silicone oil of an appropriate mass relative to the mass of silver powder when using silicone oil, and electrical characteristics of the electrode by increasing the short-circuit current accordingly. An object of the present invention is to provide an improved high-efficiency solar cell.

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

The present invention includes a paste composition for a solar cell electrode comprising a metal powder, a glass frit, an organic vehicle and a silicone oil, wherein the mass of the metal powder and the mass of the silicone oil are determined by the MPP index defined by Equation 1 below. It is determined, and the MPP index provides a paste for a solar cell electrode, characterized in that 20 to 500.

[Equation 1]

MPP index = (mass of metal powder) / (mass of silicone oil)

In addition, the MPP index is characterized in that 30 to 150.

In addition, the MPP index is characterized in that it can be substituted with the MPP conversion index by the following formula (2).

[Equation 2]

MPP conversion index = MPP index × (log(v)/3)

(Here, the MPP index is the MPP index of Equation 1, and v means the kinematic viscosity of the contained silicone oil.)

In addition, the molecular weight of the silicone oil is characterized in that 1-100,000cs.

In addition, the silicone oil is characterized in that it contains a linear molecule, a branched molecule, a cyclic molecule, or a mixture thereof.

In addition, the linear molecule is characterized in that it comprises at least one selected from decamethyltetrasiloxane, dodecamethylpentasiloxane, tetradecamethylhexasiloxane, and hexadecamethylheptasiloxane. do.

In addition, the cyclic molecule is characterized in that it comprises at least one selected from decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and tetradecamethylcycloheptasiloxane.

In addition, the present invention provides a solar cell including an electrode formed by using the solar cell electrode paste.

The present invention relates to an electrode paste for a solar cell that can realize a stable fine line width while reducing resistance by adding silicone oil of an appropriate mass relative to the mass of silver powder when silicone oil is used, and thus the short-circuit current rises to increase the electrical power of the solar cell electrode The property provides an effect that can be improved.

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

Throughout this specification and claims, unless stated otherwise, the term comprise, comprises, comprising is meant to include the stated object, step or group of objects, and steps, and any other object. It is not used in the sense of excluding steps or groups of objects or groups of steps.

On the other hand, various embodiments of the present invention may be combined with any other embodiments unless clearly indicated to the contrary. Any feature indicated as particularly preferred or advantageous may be combined with any other feature and features indicated as 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 use in forming a solar cell electrode, and may include a metal powder, a glass frit, an organic vehicle, and a silicone oil.

As the metal powder, silver, gold, palladium, platinum, copper, chromium, cobalt, aluminum, tin, lead, zinc, iron, iridium, osmium, rhodium, tungsten, molybdenum, nickel and indium tin oxide (ITO) may be used. However, for the front electrode, silver powder is mainly used. As the metal powder, one of the above-mentioned powders may be used alone, an alloy of the above-mentioned metal may be used, or at least two of the above-mentioned powders may be used as a mixed powder.

The content of the metal powder is preferably 40 to 95% by weight based on the total weight of the conductive paste composition in consideration of the thickness of the electrode formed during printing and the wire resistance of the electrode. If it is less than 40% by weight, the specific resistance of the formed electrode may be high, and if it is more than 95% by weight, there is a problem in that the content of other components is not sufficient, so that the metal powder is not uniformly dispersed. More preferably, it is included in an amount of 70 to 93% by weight.

When the conductive paste contains silver powder for forming the front electrode of a solar cell, the silver powder is preferably a pure silver powder. In addition, a silver-coated composite powder having at least a surface of a silver layer, or an alloy containing silver as a main component (alloy) and the like can be used. In addition, other metal powders may be mixed and used. For example, aluminum, gold, palladium, copper, nickel, etc. are mentioned.

The average particle diameter (D50) of the metal powder may be 0.1 to 10 μm, preferably 0.5 to 5 μm in consideration of ease of pasting and density during firing, and the shape is at least one of spherical, needle, plate, and amorphous. may be more than one species. The metal powder may be used by mixing two or more types of powders having different average particle diameters, particle size distributions, shapes, and the like.

The conductive metal powder may be coated using a coating agent. The coating agent is an alkylamine-based compound having an amine group in an alkyl chain having 8 to 20 carbon atoms or an alkylcarboxy compound having a carboxyl group in an alkyl chain having 8 to 20 carbon atoms. includes Preferably, it is good to include a compound having an amine group or a carboxyl group in an alkyl chain having 15 to 20 carbon atoms. If the carbon number of the alkyl chain is less than 8, there is a problem in that the desired effect is not expressed, if the carbon number exceeds 20, there is a problem in that it is difficult to dissolve in a solvent, and the surface treatment is not well. In addition, the coating agent can be used in both saturated or unsaturated alkyl chain.

The compound having an amine group in the alkyl chain is triethylamine, heptylamine, octadecylamine, hexadecylamine, decylamine, octylamine, didecyl It may include at least one selected from amine ( Didecylamine), and trioctylamine (Trioctylamine).

The compound having a carboxyl group in the alkyl chain is, as a saturated fatty acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid ), arachidic acid, the unsaturated fatty acid may include at least one selected from myristoleic acid, palmitoleic acid, oleic acid, and linoleic acid.

Most preferably, a silver powder coated with octadecylamine is used, and the coating agent is preferably coated on the surface of the metal powder to a thickness of 0.1 nm to 50 nm. The coating may be performed by adding a metal powder such as Ag powder to an organic solvent in which the coating agent is dissolved, stirring for a predetermined time, and then filtering.

As a specific coating method, an alcohol solution containing an alkylamine-based compound or an alkylcarboxyl-based compound is added to a solution in which the conductive metal powder is dispersed, and the surface is treated by stirring at 2000 to 5000 rpm for 10 to 30 minutes using a stirrer. An alcohol solution containing an alkylamine-based compound or an alkylcarboxyl compound may be an alcohol solution in which 5 to 20 wt% of the compound is dissolved based on the total weight of the solution, and the alcohol is methanol, ethanol, n-propanol, benzyl alcohol , terpineol, etc. may be used, preferably ethanol.

0.1 to 1.0 parts by weight of the coating agent may be used based on 100 parts by weight of the conductive metal powder. When mixed in less than 0.1 parts by weight, the amount of coating agent adsorbed to the surface of the conductive metal powder is small, so agglomeration occurs between the powders, the compatibility improvement effect of the silicone oil may be insignificant, and when mixed in more than 1.0 parts by weight, the conductive metal powder There is a problem in that an excessive amount of the surface treatment agent is adsorbed on the surface to lower the electrical conductivity of the manufactured electrode.

By using the conductive metal powder coated with the coating agent, the silicone oil included in the conductive paste can be positioned on the surface of the metal powder, so that phase separation in the vehicle can be completely prevented. That is, it is possible to control the degree of movement of the silicone oil to the surface of the conductive metal powder as it is coated by the coating agent. By preventing phase separation due to incompatibility of silicone oil with organic vehicles (organic solvents and organic binders, etc.), storage stability of the provided conductive paste can be secured, and excellent slip properties are ensured to provide the effect of realizing ultra-fine line width. .

Silicone oil may be included in the conductive paste to maximize slip properties. The type of the silicone oil is not limited, but it is preferable to use a linear molecule, a branched molecule, a cyclic molecule, or a mixture thereof.

Specifically, the silicone oil is a linear molecule and includes decamethyltetrasiloxane, dodecamethylpentasiloxane, tetradecamethylhexasiloxane, hexadecamethylheptasiloxane, and the like. , as a cyclic molecule, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, tetradecamethylcycloheptasiloxane, and the like can be exemplified. At least one of the silicone oils may be selected and used. In addition, the silicone oil is at least one selected from the group consisting of phenyl trimethione, dimethicone, cyclomethicone, polydimethylsiloxane, and silicone gum. may be included, and a modified silicone oil may also be used. Preferably, it may be polysiloxane such as polydimethylsiloxane, and it is preferable to use unmodified polysiloxane oil in consideration of slip properties.

In addition, it is preferable that the molecular weight of the silicone oil is 1-100,000cs. When the molecular weight of the silicone oil exceeds 100,000cs, the viscosity is too high, so that it is difficult to prepare a paste.

The silicone oil is included in an amount of 0.1 to 5% by weight based on the total weight of the conductive paste composition. When silicone oil is added in an amount of less than 0.1% by weight, there is a slight problem in improving the slip property, when it is added in excess of 5% by weight, there is a problem in phase separation and storage stability, and when the slip property is excessive, the coating state during printing is poor. There is a problem that can lead to disconnection. Preferably, it is included in an amount of 0.5 to 2% by weight.

The mass of the metal powder and the mass of the silicone oil included in the conductive paste according to an embodiment of the present invention may be determined by the MPP index defined by Equation 1 below.

[Equation 1]

MPP index = (mass of metal powder)/(mass of silicone oil)

According to Equation 1, the higher the MPP index, the smaller the mass of the silicone oil relative to the mass of the metal powder, and the lower the MPP index, the greater the mass of the silicone oil relative to the mass of the metal powder. The MPP index may be 20 to 500, preferably 30 to 150. When the MPP index is less than 20, when the solar cell is manufactured using the conductive paste, some silicone oil remains and acts as a resistance, and there is a problem in that the resistance of the manufactured solar cell increases and the conversion efficiency decreases, and the MPP index is 500 If it exceeds, the aspect ratio is lowered, so that a fine line width cannot be realized, which increases the resistance, and there is a problem in that the conversion efficiency of the manufactured solar cell is lowered due to a decrease in the short-circuit current.

The silicone oil may be substituted according to the kinematic viscosity (Centi Stokes, cs). Specifically, the silicone oil can be divided into kinematic viscosity units according to the molecular weight, and the MPP index can be expressed as the MPP conversion index, and the MPP conversion index can be calculated as in Equation 2 below.

[Equation 2]

MPP conversion index = MPP index × (log(v)/3)

(Here, the MPP index is the MPP index of Equation 1, and v means the kinematic viscosity of the contained silicone oil.)

For example, when silicone oil with a molecular weight of 10,000cs is used for manufacturing conductive paste, when the MPP index is 90, the MPP conversion index is 120 by multiplying the MPP index without considering the kinematic viscosity by log(10000)/3=4/3 can be expressed as In addition, when using a silicone oil having a molecular weight of 1,000cs, when the MPP index is 90, the MPP conversion index can be expressed as 90 by multiplying the MPP index by log(1000)/3=1.

If the MPP conversion index is used, the MPP index that does not consider the molecular weight can be supplemented, so even if a silicone oil with a different molecular weight is used when manufacturing a conductive paste, it can be manufactured at an optimized ratio according to the viscosity of the silicone oil, and a fine line width is realized. Thus, it is possible to manufacture a solar cell with high short-circuit current and high conversion efficiency.

The glass frit is not particularly limited in its composition, particle size, or shape. Lead-free glass frit as well as lead-free glass frit can be used. Preferably, as a component and content of the glass frit, PbO is 5 to 29 mol%, TeO ₂ is 20 to 34 mol%, Bi ₂ O ₃ is 3 to 20 mol%, SiO ₂ 20 mol% or less, B ₂ O ₃ 10 mol% or less, alkali metals (Li, Na, K, etc.) and alkaline earth metals (Ca, Mg, etc.) preferably contain 10 to 20 mol%. By combining the organic content of each component, it is possible to prevent an increase in electrode line width, to improve contact resistance in high sheet resistance, and to improve short-circuit current characteristics.

The average particle diameter of the glass frit is not limited, but may have a particle diameter within the range of 0.5 to 10 μm, and may be used by mixing various types of particles having different average particle diameters. Preferably, at least one glass frit having an average particle diameter (D50) of 2 μm or more and 10 μm or less is used.

The content of the glass frit is preferably 1 to 10% by weight based on the total weight of the conductive paste composition. If it is less than 1% by weight, there is a risk that incomplete firing is made to increase the electrical resistivity, and if it exceeds 10% by weight, the glass in the fired body of the metal powder is There is a possibility that the component is too large and the electrical resistivity is also increased.

When the surface of the glass frit is coated with fatty amines and fatty acids, dispersibility is improved, and uniform application of the glass frit may be possible during electrode formation. As a result, reactivity during firing is improved, damage to the n-layer can be minimized especially at high temperatures, adhesion is improved, and open-circuit voltage (Voc) can be excellent. In addition, it is possible to reduce the contact resistance between the electrode and the n-layer by making the penetration of the metal powder (eg, silver powder) uniform during firing. Providing such an effect may provide an additional effect of further facilitating control of the composition, particle size or shape of the glass frit.

The organic vehicle is not limited, but may include an organic binder and a solvent. Sometimes the solvent can be omitted. The organic vehicle is not limited, but preferably 1 to 30% by weight based on the total weight of the conductive paste composition.

The organic vehicle is required to maintain a uniformly mixed state of metal powder and glass frit. For example, when a conductive paste is applied to a substrate by screen printing, the conductive paste is homogenized, resulting in blurring of the printed pattern. and properties for suppressing the flow and improving the discharge property and the plate separation property of the conductive paste from the screen plate are required.

The organic binder included in the organic vehicle is not limited, but examples of the cellulose ester-based compound include cellulose acetate and cellulose acetate butyrate, and the cellulose ether compound includes ethyl cellulose, methyl cellulose, hydroxypropyl cellulose, and hydroxyethyl Examples include cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methyl cellulose, and examples of the acrylic compound include polyacrylamide, poly methacrylate, polymethyl methacrylate, polyethyl methacrylate, and the like. , polyvinyl butyral, polyvinyl acetate and polyvinyl alcohol may be exemplified as the vinyl type. At least one or more organic binders may be selected and used.

As a solvent used for dilution of the composition, alpha-terpineol, texanol, dioctyl phthalate, dibutyl phthalate, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol, ethylene glycol monobutyl ether, ethylene It is preferable to use at least one selected from the group consisting of 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 include, if necessary, commonly known additives, for example, a dispersant, a plasticizer, a viscosity modifier, a surfactant, an oxidizing agent, a metal oxide, a metal organic compound, and the like.

The above-described conductive paste composition for a solar cell electrode may be prepared by mixing and dispersing a metal powder, a coated glass frit, an organic vehicle, an additive, and the like, followed by filtration and defoaming.

The present invention also provides a method for forming an electrode of a solar cell, characterized in that the conductive paste is applied on a substrate, dried and fired, and a solar cell electrode manufactured by the method. In the method for forming a solar cell electrode of the present invention, except for using the conductive paste including the coated glass frit as described above, the substrate, printing, drying, and firing are methods commonly used for manufacturing solar cells. of course there is For example, the substrate may be a silicon wafer.

On the other hand, since the unit solar cell including the solar cell electrode formed as described above has a small electromotive force, a number of unit solar cells are connected to form a photovoltaic module having an appropriate electromotive force. When each unit solar cell cells are connected by lead-coated conductor ribbons of a certain length.

In addition, the conductive paste according to the present invention has 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), and a Passivated Emitter Real Locally Diffused (PERL). It can be applied to all modified printing processes such as double printing and dual printing.

Experimental example

(One) Experimental Example 1

After mixing 90 g of silver powder, 0.15 g of PDMS having a molecular weight of 1,000 cs, 3 g of glass frit, 7.85 g of an organic vehicle, and 1 g of an additive using a rotating vacuum stirring degassing device, a three-bone roll was used to obtain a conductive paste.

(2) Experimental Example 2

It was prepared in the same capacity and method as in Experimental Example 1, except that 0.2 g of PDMS and 7.8 g of organic vehicle were added.

(3) Experimental Example 3

It was prepared in the same capacity and method as in Experimental Example 1, except that 0.4 g of PDMS and 7.6 g of an organic vehicle were added.

(4) Experimental Example 4

It was prepared in the same capacity and method as in Experimental Example 1, except that 0.6 g of PDMS and 7.4 g of an organic vehicle were added.

(5) Experimental Example 5

It was prepared in the same capacity and method as in Experimental Example 1, except that 0.8 g of PDMS and 7.2 g of an organic vehicle were added.

(6) Experimental Example 6

It was prepared in the same capacity and method as in Experimental Example 1, except that 1.0 g of PDMS and 7.0 g of an organic vehicle were added.

(7) Experimental Example 7

It was prepared in the same capacity and method as in Experimental Example 1, except that 1.2 g of PDMS and 6.8 g of an organic vehicle were added.

(8) Experimental Example 8

It was prepared in the same capacity and method as in Experimental Example 1, except that 2.0 g of PDMS and 6.0 g of an organic vehicle were added.

(9) Experimental Example 9

It was prepared in the same capacity and method as in Experimental Example 1, except that 3.5 g of PDMS and 4.5 g of an organic vehicle were added.

(10) Experimental Example 10

It was prepared in the same capacity and method as in Experimental Example 1, except that 5.0 g of PDMS and 3.0 g of an organic vehicle were added.

(11) Experimental Example 11

It was prepared in the same capacity and method as in Experimental Example 1, except that PDMS having a molecular weight of 10cs was used.

(12) Experimental Example 12

It was prepared in the same capacity and method as in Experimental Example 3, except that PDMS having a molecular weight of 10cs was used.

(13) Experimental Example 13

It was prepared in the same capacity and method as in Experimental Example 8, except that PDMS having a molecular weight of 90,000cs was used.

The MPP index and MPP conversion index calculated according to the dose and physical properties of the compositions used in Experimental Examples 1 to 13, the dose of Ag powder, and the PDMS dose are shown in Tables 1 and 2.

Ag powder PDMS Glass
frit abandonment
vehicle additive PDMS molecular weight (cs) MPP Index Experimental Example 1 90g 0.15g 3g 7.85g 1 g 1,000 600 Experimental Example 2 90g 0.2g 3g 7.8g 1 g 1,000 440 Experimental Example 3 90g 0.4g 3g 7.6g 1 g 1,000 225 Experimental Example 4 90g 0.6g 3g 7.4g 1 g 1,000 150 Experimental Example 5 90g 0.8g 3g 7.2g 1 g 1,000 112.5 Experimental Example 6 90g 1.0g 3g 7.0g 1 g 1,000 90 Experimental Example 7 90g 1.2g 3g 6.8g 1 g 1,000 75 Experimental Example 8 90g 2.0g 3g 6.0g 1 g 1,000 45 Experimental Example 9 90g 3.5g 3g 4.5g 1 g 1,000 25.7 Experimental Example 10 90g 5.0g 3g 3.0g 1 g 1,000 18

Ag powder PDMS glass frit organic vehicle additive PDMS molecular weight (cs) MPP Index MPP
Conversion Index Experimental Example 1 90g 0.15g 3g 7.85g 1 g 1,000 600 600 Experimental Example 3 90g 0.4g 3g 7.6g 1 g 1,000 225 225 Experimental Example 8 90g 2.0g 3g 6.0g 1 g 1,000 45 45 Experimental Example 11 90g 0.15g 3g 7.85g 1 g 10 600 200 Experimental Example 12 90g 0.4g 3g 7.6g 1 g 10 225 75 Experimental Example 13 90g 2.0g 3g 6.0g 1 g 90,000 45 225

Experimental example - Evaluation of electrical characteristics of solar cells

The conductive paste prepared according to the above experimental example was pattern-printed on the entire surface of the wafer by a screen printing technique of 50 μm mesh, and dried at 200 to 350° C. for 20 to 30 seconds using a belt-type drying furnace. After that, Al paste was printed on the back side of the wafer and dried in the same way. The cell formed by the above process was fired using a belt-type firing furnace at 500 to 900° C. for 20 to 30 seconds to manufacture a solar cell.

The prepared cells were shown in Tables 3 and 4 by measuring the line width, aspect ratio, short-circuit current and conversion efficiency using a solar cell efficiency measuring device (Halm, cetisPV-Celltest 3).

Line width (um) Aspect Ratio (%) Short circuit current (A) Conversion Efficiency (%) monorail
(Count) Experimental Example 1 42.1 34.5 9.62 20.84 30 Experimental Example 2 40.2 38 9.662 20.88 30 Experimental Example 3 38.7 40 9.674 20.92 25 Experimental Example 4 38.2 41.6 9.684 21.18 3 Experimental Example 5 37.5 43 9.692 21.22 2 Experimental Example 6 35.1 46.7 9.7 21.35 2 Experimental Example 7 34.3 48 9.711 21.38 0 Experimental Example 8 33.2 50.2 9.726 21.42 One Experimental Example 9 38.9 40.2 9.676 21.09 One Experimental Example 10 36.5 44.8 9.698 20.88 30

Line width (um) Aspect Ratio (%) Short circuit current (A) Conversion Efficiency (%) monorail
(Count) Experimental Example 1 42.1 34.5 9.62 20.84 30 Experimental Example 3 38.7 40 9.674 20.92 25 Experimental Example 8 33.2 50.2 9.726 21.42 One Experimental Example 11 34.8 46.9 9.7 21.36 One Experimental Example 12 33.8 48.6 9.712 21.4 0 Experimental Example 13 36.38 45.8 9.698 21.34 6

As shown in Table 2, in Experimental Examples 1 and 10 having an MPP index of less than 20 or exceeding 500, it can be seen that the line width, aspect ratio, short-circuit current and conversion efficiency were significantly lower than those of Experimental Examples 2 to 9, and the number of disconnections You can also learn a lot.

More specifically, in the case of Experimental Examples 2 to 9, it can be seen that the short-circuit current value is increased compared to Experimental Examples 1 and 10 due to the decrease in line width, and thus the conversion efficiency is excellent. In particular, in the case of Experimental Examples 4 to 8, it was confirmed that the conversion efficiency was the most excellent.

As shown in Table 2, Experimental Examples 1 and 11, 3 and 12, 8 and 13 each use the same amount of composition, but have different molecular weights so that the MPP index is the same but silicone oil having a different MPP conversion index is used. Thus, a conductive paste was prepared.

As a result of the experiment, it can be seen that Experimental Examples 3, 8, and 11 showed excellent conversion efficiency, and Experimental Examples 1, 12, and 13 showed significantly lower conversion efficiency.

Specifically, when a conductive paste is prepared using the same composition and capacity as in Experimental Examples 1 and 11, the MPP conversion index is 600 when the molecular weight of PDMS is 1,000cs, and the conversion efficiency is low, but the molecular weight of PDMS is 90,000cs. When the MPP conversion index is 200, it can be seen that high conversion efficiency appears.

When a conductive paste was prepared using the same composition and capacity as in Experimental Examples 3 and 12, the MPP conversion index was 225 when the molecular weight of PDMS was 1,000cs, and the conversion efficiency was high, but when the molecular weight of PDMS was 10cs, the MPP conversion index was 75, it can be seen that the number of disconnections is relatively reduced and the conversion efficiency is higher.

When a conductive paste was prepared using the same composition and capacity as in Experimental Examples 8 and 13, the MPP conversion index was 45 when the molecular weight of PDMS was 1,000cs, and the conversion efficiency was high, but when the molecular weight of PDMS was 90,000cs, the MPP conversion index was It can be seen that the number of disconnections is relatively increased to 225 and lower conversion efficiency appears.

Features, structures, effects, etc. exemplified in each of the above-described embodiments may be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

Claims (8)

In the paste for a solar cell electrode comprising a metal powder, a glass frit, an organic vehicle and a silicone oil,
The mass of the metal powder and the mass of the silicone oil are determined by the MPP index defined by Equation 1 below,
The MPP index is a conductive paste for a solar cell electrode, characterized in that 20 to 500.
[Equation 1]
MPP index = (mass of metal powder) / (mass of silicone oil)

According to claim 1,
The MPP index is 30 to 150, the solar cell electrode paste.
According to claim 1,
The MPP index is a solar cell electrode paste that can be substituted with an MPP conversion index by the following Equation 2.
[Equation 2]
MPP conversion index = MPP index × (log(v)/3)
(Here, the MPP index is the MPP index of Equation 1, and v means the kinematic viscosity of the contained silicone oil.)
According to claim 1,
The molecular weight of the silicone oil is 1-100,000cs, a solar cell electrode paste.
According to claim 1,
The silicone oil contains a linear molecule, a branched molecule, a cyclic molecule, or a mixture thereof, a paste for a solar cell electrode.
6. The method of claim 5,
The linear molecule is characterized by comprising at least one selected from decamethyltetrasiloxane, dodecamethylpentasiloxane, tetradecamethylhexasiloxane, and hexadecamethylheptasiloxane Paste for solar cell electrodes.
6. The method of claim 5,
The cyclic molecule is a solar cell electrode paste comprising at least one selected from decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and tetradecamethylcycloheptasiloxane. .
A solar cell comprising an electrode formed using the paste for a solar cell electrode according to any one of claims 1 to 7.