KR20100000685A - Conductive paste composition and preparation of electrode using same - Google Patents

Abstract

PURPOSE: A conductive paste composition is provided to prevent the collapse of a film when drying and firing after printing an electrode paste and to increase photo-detecting regions and photo conversion efficiency. CONSTITUTION: A conductive paste composition comprises a binder resin 1-10 weight%, diluent 5-25 weight%, conductive metal material 60-90 weight%, glass frit 1-10 weight% and inorganic thicksotropic agent 0.1-5 weight%. The conductive paste composition further comprises a dispersing agent 0.1-5 parts by weight based on the total weight of the composition.

Description

Conductive Paste Composition and Electrode Manufacturing Method Using the Same {CONDUCTIVE PASTE COMPOSITION AND PREPARATION OF ELECTRODE USING SAME}

The present invention relates to conductive paste compositions, in particular conductive paste compositions useful for the production of electrodes in photovoltaic cells.

A solar cell is a semiconductor device that converts solar energy into electrical energy. In general, a solar cell has a junction type of a p-type semiconductor and an n-type semiconductor, and its basic structure is the same as that of a diode.

When light enters a photovoltaic cell, it is absorbed and interacts with the materials that make up the semiconductor of the photovoltaic cell. In addition, electrons with negative and negative charges and holes that escape electrons are generated and current flows or electricity itself is generated. This is called the photoelectric effect of semiconductors.

There are two types of semiconductors: n-type semiconductors that attract positively-charged electrons and p-type semiconductors that attract positively-charged holes. When the electric charges are pulled toward the p-type semiconductor and collected at both electrode portions, the electric current flows when both electrodes are connected by wires, thereby obtaining power.

Crystalline silicon solar cells are largely divided into single crystalline and polycrystalline materials and are basically used in photovoltaic cells as p-n homojunctions. Single crystal is a high quality material with high purity and low crystal defect density, which can naturally achieve high efficiency, but it is expensive, whereas polycrystalline material is a low cost process that can be commercialized by processing a relatively low quality material in a low cost process. Used to produce It is known that a battery using single crystal silicon has an efficiency of about 24% when a light concentrator is not used, and a battery using a light concentrator has an efficiency of 28% or more. It is known that a polycrystalline silicon battery has an efficiency of about 18%, but practically, the limit of efficiency reaches 35% for single crystal and 19% for polycrystal.

However, the electrode paste composition used in the conventional photovoltaic cell manufacturing is subjected to heat drying for 1 to 2 minutes within a temperature range of 150 to 250 ° C. after printing the electrode paste, and then undergoing a baking process at 750 ° C. for several tens of seconds. There is a problem in that the aspect ratio is collapsed and the light receiving area is reduced, resulting in poor efficiency.

Accordingly, an object of the present invention is to provide a conductive paste composition that can improve film collapse during drying and firing after electrode paste printing.

It is a second object of the present invention to provide an electrode manufacturing method using the conductive paste composition according to the present invention.

A third object of the present invention is to provide a solar cell including an electrode manufactured by the electrode manufacturing method according to the present invention.

In accordance with the above object, the present invention provides a conductive paste composition comprising a binder resin, a diluent, a conductive metal material, a glass frit, and an inorganic thixotropic agent.

Specifically, the conductive paste composition includes 1 to 10 wt% of binder resin, 5 to 25 wt% of diluent, 60 to 90 wt% of conductive metal material, 1 to 10 wt% of glass frit and 0.1 to 5 wt% of inorganic thixotropic agent. do.

The composition of the present invention may further comprise 0.1 to 5 parts by weight of the dispersant based on the total weight.

Among the components of the composition of the present invention, the binder resin is a cellulose compound having a viscosity of 5 to 500 cps when dissolved in a diluent (toluene: ethanol = 8: 2) at 5%, or an acrylic having a molecular weight of 5,000 to 50,000 It is preferable that it is a resin compound.

The diluent is alpha-terpineol, texanol, dioctyl phthalate, dibutyl phthalate, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether It is preferably selected from the group consisting of acetate, diethylene glycol monobutyl ether and diethylene glycol monobutyl ether acetate.

In addition, the inorganic thixotropic agent is preferably bentonite or silica.

And it is preferable that the said electroconductive metal material is silver powder whose average particle diameter is 0.5-5 micrometers.

The composition of the present invention may further comprise at least one additive selected from the group consisting of photosensitizers, polymerization inhibitors, defoamers, leveling agents and thixotropic agents.

According to a second object of the present invention, the present invention provides a method for producing an electrode using the conductive paste composition.

Specifically, the method includes printing the conductive paste composition of the present invention on a substrate, drying the printed electrode paste, and baking the dried electrode paste to form an electrode.

Here, the electrode preferably has a thickness of 10 to 40㎛.

And, the printed electrode paste is preferably baked at a temperature of 700 to 900 ℃.

In addition, the conductive paste composition may be printed on the substrate by screen printing, gravure offset method, rotary screen printing method or lift off method.

In the production method according to the invention, the electrode is preferably a surface electrode of the solar cell.

According to a third object of the present invention, the present invention provides a photovoltaic cell comprising the electrode produced by the electrode manufacturing method as a surface electrode.

The electrode paste composition according to the present invention is subjected to a heat drying process after printing to improve the film collapse during firing. Therefore, if the surface electrode formed by the electrically conductive paste of this invention is applied to a photovoltaic cell, the photovoltaic cell with a large light receiving area and high photoelectric conversion rate can be obtained.

Hereinafter, the present invention will be described in more detail.

The conductive paste composition according to the present invention is characterized by comprising a binder resin, a diluent, a conductive metal material, a glass frit, and an inorganic thixotropic agent. According to a preferred embodiment of the invention, the composition according to the invention comprises 1 to 10% by weight binder resin, 5 to 25% by weight diluent, 60 to 90% by weight conductive metal material, 1 to 10% by weight glass frit, and inorganic components It may include 0.1 to 5% by weight of the agent. In addition, the composition of the present invention may further comprise 0.1 to 5 parts by weight of the dispersant based on the total weight.

In the conductive paste composition according to the present invention, the binder resin component is a cellulose-based compound having a viscosity of 5 to 500 cps when dissolved in a diluent (toluene: ethanol = 8: 2) by 5% by weight, or a molecular weight of 5,000 to 50,000 It is preferable that it is an acrylic resin type phosphorus.

Specifically, the binder resin is a cellulose compound such as cellulose acetate, cellulose acetate butyrate, ethyl cellulose, methyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, or polyacryl It may be an acryl-based compound such as amide, polymethacrylate, polymethylmethacrylate, polyethylmethacrylate, or a vinyl compound such as polyvinyl butyral, polyvinylacetate, polyvinyl alcohol, or a mixture thereof. .

Diluents used in the compositions according to the invention are alpha-terpineol, texanol, dioctylphthalate, dibutylphthalate, 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 mixtures thereof.

In addition, the inorganic thixotropic agent used in the composition according to the present invention is preferably bentonite or silica, and more specifically, it is more preferable that it is Aerosil of Degussa (Germany). The composition according to the present invention contains 0.1 to 5% by weight of the inorganic thixotropic agent, so that the change in the aspect ratio before and after the predetermined firing is small, thereby preventing the film from collapsing during preparation of the electrode.

As the conductive metal material used in the conductive paste according to the present invention, silver powder, copper powder, nickel powder, aluminum powder, and the like may be used, among which silver powder is most preferred. For convenience, the conductive metal material will be described using silver powder as an example.

The silver powder may be at least one or more of spherical, acicular, acicular, and amorphous. The average particle diameter of the silver powder is preferably 0.5 μm to 5 μm in consideration of the ease of pasting and the density during firing. In addition, the content of the silver powder is preferably contained in the conductive paste composition 60 to 90% by weight in consideration of the electrode thickness and the wire resistance of the electrode formed during printing.

In addition, the glass frit used in the composition of the present invention preferably has an average particle diameter of 0.5 to 5 μm, and the components thereof are 43 to 91 wt% of PbO, 21 wt% or less of SiO ₂ , and 25 wt% of B ₂ O ₃ + Bi ₂ O _3. At least 1 in glass powders of less than or equal to 7% by weight of Al ₂ O ₃ , up to 20% by weight of ZnO, up to 15% by weight of Na ₂ O + K ₂ O + Li ₂ O, and up to 15% by weight of BaO + CaO + MgO + SrO. One or more kinds can be used. And it is preferable that glass softening temperature is 320 degreeC-520 degreeC, and a thermal expansion coefficient is 62-110x10 <^-7> / ^degreeC . 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. There are too many components, and there exists a possibility that an electrical resistivity may also become high.

The composition according to the invention may further comprise one or more additives selected from the group consisting of additives commonly known as necessary, for example, photosensitizers, polymerization inhibitors, defoamers, leveling agents and thixotropic agents.

The conductive paste composition according to the present invention can be used for the production of surface electrodes of photovoltaic cells. In order to manufacture the electrode using the conductive paste composition according to the present invention, first, the conductive paste composition according to the present invention is directly printed on a substrate. And drying the printed electrode paste and baking the dried electrode paste to form an electrode.

The electrode according to the invention preferably has a thickness of 10 to 40 μm.

The electrode paste printed (or also referred to as patterning) with the conductive paste composition according to the present invention may be dried at 150 to 250 ° C. for several minutes and calcined at a temperature of 700 to 900 ° C. for several seconds.

The conductive paste composition according to the present invention may be printed on a substrate using various printing methods such as screen printing, gravure offset method, rotary screen printing method or lift off method.

As described above, the electrode manufactured using the conductive paste composition according to the present invention may be usefully used as a surface electrode of a solar cell.

1 is a schematic view illustrating the structure of a solar cell. The silicon substrate may be polycrystalline silicon or single crystal silicon. A p-n junction is formed near the light-receiving surface to generate an electromotive force upon receiving light. To form the p-n junction, the substrate may be p-type, the light receiving surface side may be n-type by diffusion, or conversely, the substrate may be n-type and the light receiving surface side may be p-type.

On the light receiving surface of the photovoltaic cell, an antireflection layer is provided by a method such as chemical vapor deposition (CVD) to prevent reflection on the light receiving surface and increase the light receiving efficiency. The antireflection layer can be formed of titanium oxide, silicon dioxide, silicon nitride, or the like, and among them, silicon nitride is preferable because of its excellent stability as a device. The antireflection layer can also be used as a passivation layer. The thickness of an antireflection layer is about 50-100 nm normally. The back electrode formed on the back surface of the silicon substrate is manufactured by coating and drying a conductive metal material such as aluminum. The conductive paste according to the present invention can be used for surface electrodes formed on the surface of the antireflection layer. After forming the surface electrode pattern and drying, the surface electrode and the back electrode are simultaneously fired. Examples of the shape of the pattern of the surface electrode include parallel lines and a lattice.

Photovoltaic cells produced using the compositions of the present invention may have additional elements to enhance their function. For example, a welding layer may be provided on the surface of the surface electrode to improve the reliability of battery performance.

Since the surface electrode formed of the conductive paste according to the present invention can realize an aspect ratio (height / width) of 0.3 or more, if the surface electrode is applied to a solar cell, the light receiving area of the solar cell can be increased to 93% or more. . In addition, the conductive paste according to the present invention can effectively use the electromotive force generated by light reception as a current because the line resistance is lowered when firing.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Preparation Example 1 Preparation of Binder Resin Mixture 1

10 g of ethyl cellulose (EC, trade name Ethocel Std 100, Dow Chemical, USA) was added to a 1 L flask, and 85 g of Texanol (5) and dioctylphthalate (DOP) were added as a mixed solvent. It was dissolved for 1 hour to prepare a mixed composition of a binder resin and a diluent.

Preparation Example 2 Preparation of Binder Resin Mixture 2

20 g of ethyl cellulose (EC, trade name Ethocel Std 45, Dow Chemical, USA) was added to a 1 L flask, and 75 g of Texanol (5%) and dioctylphthalate (DOP) were added as a mixed solvent. It was dissolved for 1 hour to prepare a mixed composition of a binder resin and a diluent.

Preparation of Conductive Paste Composition

<Example 1>

15 g of the binder resin mixture 1 prepared in Preparation Example 1 (1.5 g of binder resin and 13.5 g of diluent), 1 g of dispersant (BYK 110, BYK Chemi), 5 g of glass frit (average particle diameter: 1 micron) After dispersing using, 78.5 g of silver powder (spherical, average particle diameter: 1 micron) and 0.5 g of inorganic thixotropic agent (airzyl-200, Degussa) were added and mixed, and dispersed using a sambon mill. Thereafter, vacuum degassing was carried out to prepare a conductive paste. The conductive paste was filtered using a 325 sus mesh filter to evaluate physical properties.

<Example 2>

15 g of the binder resin mixture 1 prepared in Preparation Example 1 (1.5 g of binder resin and 13.5 g of diluent), 1 g of dispersant (BYK 110, BYK Chemis), and 5 g of glass frit (average particle diameter of 1 micron) were added and dispersed using a three-bone mill. After that, 78 g of silver powder (spherical, average particle diameter: 1 micron) and 1 g of inorganic thixotropic agent (Aerosil-200, Degussa) were added and mixed, and dispersed using a sambon mill. Thereafter, vacuum degassing was carried out to prepare a conductive paste. The conductive paste was filtered using a 325 sus mesh filter to evaluate physical properties.

<Example 3>

15 g of the binder resin mixture 2 prepared in Preparation Example 2 (3 g of binder resin and 12 g of diluent), 1 g of dispersant (BYK 110, BYK Chemisa), 5 g of glass frit (average particle diameter of 1 micron) were added and dispersed using a three-bone mill. After that, 78 g of silver powder (spherical, 1 micron in average particle diameter) and 1 g of inorganic thixotropic agent (Aerosil-200, Degussa Co.) were added and mixed, and dispersed using a sambon mill. Thereafter, vacuum degassing was carried out to prepare a conductive paste. The conductive paste was filtered using a 325 sus mesh filter to evaluate physical properties.

<Example 4>

13 g of the binder resin mixture 1 prepared in Preparation Example 1 (1.3 g of binder resin and 11.7 g of diluent), 1 g of dispersant (BYK 110, BYK Chemisa), 5 g of glass frit (average particle size of 1 micron) were added, and dispersed using a sambon mill. Then, 80 g of silver powder (spherical, 1 micron in average particle diameter) and 1 g of inorganic thixotropic agent (airzyl-200, Degussa Co., Ltd.) were mixed and dispersed using a sambon mill. Thereafter, vacuum degassing was carried out to prepare a conductive paste. The conductive paste was filtered using a 325 sus mesh filter to evaluate physical properties.

Example 5

11 g of the binder resin mixture 1 prepared in Preparation Example 1 (1.1 g of binder resin and 9.9 g of diluent), 1 g of dispersant (BYK 110, BYK Chemisa), 5 g of glass frit (average particle diameter of 1 micron) were added and dispersed using a three-bone mill. After that, 82 g of silver powder (spherical, 1 micron in average particle diameter) and 1 g of inorganic thixotropic agent (Aerosil-200, Degussa Co., Ltd.) were added and mixed, and dispersed using a sambon mill. Thereafter, vacuum degassing was carried out to prepare a conductive paste. The conductive paste was filtered using a 325 sus mesh filter to evaluate physical properties.

<Example 6>

15 g of the binder resin mixture 1 prepared in Preparation Example 1 (1.5 g of binder resin and 13.5 g of diluent), 1 g of dispersant (BYK 110, BYK Chemis), and 5 g of glass frit (average particle diameter of 1 micron) were added and dispersed using a three-bone mill. 38 g of silver powder (sphere, average particle diameter: 1 micron), 40 g of silver powder (flake shape, average particle diameter of 3 microns) and 1 g of inorganic thixotropic agent (aerosol-200, Degussa) were added and mixed. It was dispersed using. Thereafter, vacuum degassing was carried out to prepare a conductive paste. The conductive paste was filtered using a 325 sus mesh filter to evaluate physical properties.

<Example 7>

15 g of the binder resin mixture 1 prepared in Preparation Example 1 (1.5 g of binder resin and 13.5 g of diluent), 1 g of dispersant (BYK 110, BYK Chemis), and 5 g of glass frit (average particle diameter of 1 micron) were added and dispersed using a three-bone mill. After that, 78 g of silver powder (spherical, 2 microns in average particle diameter) and 1 g of inorganic thixotropic agent (airzyl-200, Degussa Co., Ltd.) were added and mixed, and dispersed using a sambon mill. Thereafter, vacuum degassing was carried out to prepare a conductive paste. The conductive paste was filtered using a 325 sus mesh filter to evaluate physical properties.

Comparative Example 1

15 g of the binder resin mixture 1 prepared in Preparation Example 1 (1.5 g of binder resin and 13.5 g of diluent), 1 g of dispersant (BYK 110, BYK Chemis), and 5 g of glass frit (average particle diameter of 1 micron) were added and dispersed using a three-bone mill. After that, 79 g of silver powder (spherical, 1 micron in average particle diameter) was added and mixed, and dispersed using a three-bone mill. Thereafter, vacuum degassing was carried out to prepare a conductive paste. The conductive paste was filtered using a 325 sus mesh filter to evaluate physical properties.

Comparative Example 2

15 g of the binder resin mixture 1 prepared in Preparation Example 1 (1.5 g of binder resin and 13.5 g of diluent), 1 g of dispersant (BYK 110, BYK Chemis), and 5 g of glass frit (average particle diameter of 1 micron) were added and dispersed using a three-bone mill. Then, 39 g of silver powder (spherical, 1 micron in average particle diameter) and 40 g of silver powder (flakes, 3 micron in average particle diameter) were added and mixed, and dispersed using a sambon mill. Thereafter, vacuum degassing was carried out to prepare a conductive paste. The conductive paste was filtered using a 325 sus mesh filter to evaluate physical properties.

Comparative Example 3

15 g of the binder resin mixture 1 prepared in Preparation Example 1 (1.5 g of binder resin and 13.5 g of diluent), 1 g of dispersant (BYK 110, BYK Chemis), and 5 g of glass frit (average particle diameter of 1 micron) were added and dispersed using a three-bone mill. After that, 78 g of silver powder (spherical, 1 micron in average particle diameter) and 1 g of organic thixotropic agent (BYK 410, BYK Chemisa) were added and mixed, and dispersed using a sambon mill. Thereafter, vacuum degassing was carried out to prepare a conductive paste. The conductive paste was filtered using a 325 sus mesh filter to evaluate physical properties.

Property evaluation

The physical property evaluation of the electrically conductive paste obtained in Examples 1-7 and Comparative Examples 1-3 was performed by the following method, and the result is shown in Table 1 below.

(1) viscosity and thixo index (T.I., thixo index)

The viscosity was measured at a shear rate of 10 s ⁻¹ using a bismeter (Hakke, RV1) and a Ti 35 spindle. The thixotropic index was similarly measured at the shear rates 1s ^-1 and 10s ^-1 , respectively, and the viscosity ratio was expressed as (viscosity measured at 1s ^-1 / 10s ^-1 ).

(2) aspect ratio

Printability of 100 micrometers in width was confirmed using the 325 mesh plate making. A screen printer was used to print at a squeeze speed of 40 cm / min. It dried at 150 degreeC after printing. Then, it baked at the maximum arrival point of 750 degreeC in the kiln (Sierra Sum Company), observed the printing shape, and calculated | required aspect ratio (A / R). The degree of film collapse during firing can be determined by comparing the change in aspect ratio before and after firing.

(3) resistance measurement

The line width and thickness of 100 micrometers in width were measured, and resistance was measured using the multimeter (Fluke), and specific resistance (= resistance x line width x thickness / length) was calculated.

In the results of Table 1, the conductive pastes of Examples 1 to 7 according to the present invention had a small change when comparing the aspect ratio before and after firing, but the film collapse was reduced, but the composition of the comparative example had a large change. It can be seen that the collapse is severe

In addition, comparing Examples 1 to 7, it can be seen that the aspect ratio increases as the amount of inorganic thixotropic agent increases, which means that the effect of preventing film collapse during firing is excellent. It can also be seen that the higher the silver powder content, the better the resistance and the higher the aspect ratio.

In particular, the conductive compound of Example 5 succeeded in improving not only the aspect ratio before baking (0.313) but also the aspect ratio after baking (0.284). By improving the aspect ratio, the light receiving area can be increased and the line resistance can be reduced.

1 is a schematic view illustrating the structure of a general photovoltaic cell.

Claims (14)

A conductive paste composition comprising a binder resin, a diluent, a conductive metal material, a glass frit, and an inorganic thixotropic agent. The method of claim 1, A conductive paste composition comprising 1 to 10% by weight of binder resin, 5 to 25% by weight of diluent, 60 to 90% by weight of conductive metal material, 1 to 10% by weight of glass frit, and 0.1 to 5% by weight of inorganic thixotropic agent. . The method of claim 1, Conductive paste composition, characterized in that it further comprises 0.1 to 5 parts by weight based on the total weight of the composition. The method of claim 1, The binder resin is a cellulose-based compound having a viscosity of 5 to 500 cps when dissolved in 5% by weight in a diluent solvent (toluene: ethanol = 8: 2), or an electrically conductive acrylic resin compound having a molecular weight of 5,000 to 50,000. Paste composition. The method of claim 1, The diluent is alpha-terpineol, texanol, dioctylphthalate, dibutyl phthalate, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, A conductive paste composition selected from the group consisting of diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, and mixtures thereof. The method of claim 1, The inorganic thixotropic agent is bentonite or silica, characterized in that the conductive paste composition. The method of claim 1, The conductive metal material is a conductive powder, characterized in that the silver powder having an average particle diameter of 0.5 to 5㎛. The method of claim 1, A conductive paste composition further comprising at least one additive selected from the group consisting of photosensitizers, polymerization inhibitors, defoamers, leveling agents and thixotropic agents. A method of printing a conductive paste composition according to any one of claims 1 to 8 on a substrate, drying the printed electrode paste, and baking the dried electrode paste to form an electrode. Electrode manufacturing method characterized in that. The method of claim 9, The electrode has a thickness of 10 to 40㎛ electrode manufacturing method, characterized in that. The method of claim 9, The printed electrode paste is fired at a temperature of 700 to 900 ℃ electrode manufacturing method. The method of claim 9, The conductive paste composition is an electrode manufacturing method characterized in that printed on the substrate by screen printing, gravure offset method, rotary screen printing method or lift off method. The method of claim 9, The electrode is a manufacturing method of the electrode, characterized in that the surface electrode of the solar cell. A photovoltaic cell comprising an electrode produced by the electrode manufacturing method according to claim 9 as a surface electrode.

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