KR20100042766A - Conductive paste composition, preparation of electrode using same and solar cell comprising same - Google Patents

Abstract

PURPOSE: A conductive paste composition is provided to ensure high sintered density and low sintering shrinkage after plasticization and to secure low line resistance and contact resistance. CONSTITUTION: A conductive paste composition comprises 55-90 weight% compound powder consisting of micro conductive metal powder with average particle size of less than 0.5 micron and conductive metal powder with average particle size of 0.5-10 micron; 0.5-8 weight% inorganic binder resin; and 5-40 weight% organic vehicle. The mixing ratio of micro conductive metal powder to conductive metal powder is 10-70 weight% : 90-30 weight%.

Description

A conductive paste composition, a method of manufacturing an electrode using the same, and a solar cell including the same {CONDUCTIVE PASTE COMPOSITION, PREPARATION OF ELECTRODE USING SAME AND SOLAR CELL COMPRISING SAME}

The present invention relates to a conductive paste composition, a method for producing an electrode using the same, and a solar cell including the same.

A solar cell is a semiconductor device that converts solar energy into electrical energy, and its electrode material is coated with a conductive paste composition on a substrate by a general screen printing method to form an electrode circuit having a specific shape, drying and heat treatment. Electroconductivity is provided by this.

The commercially available printed electrode materials for solar cells have a microscopic point of view that defects inside the electrode due to burnout of organic matter during the heat treatment process or low sintering density due to a short time heat treatment process, resulting in increased line resistance. There is a problem that the contact resistance (contact resistance) with the silicon substrate is increased. In general, since defects inside the electrode combine with oxygen or sulfur in the air to form silver oxide or silver sulfide, the conductivity may be low, which may cause a problem that the efficiency of the silicon substrate solar cell gradually decreases over time.

As a method to solve this problem, for example, Korean Patent Publication No. 2006-0108545 uses a mixture of glass or oxide additives to fill the defects between the silver powder to provide sintered density and silicon substrate. A method of increasing the adhesion of However, the method can increase the contact resistance between the conductor and the silicon substrate when the glass and oxide additives are used excessively, in particular, the glass is used as an electrode material of the dopant doped in the N layer of the silicon substrate. It can cause diffusion and adversely affect the efficiency of solar cells.

In addition, in Korean Patent Laid-Open Publication No. 2005-0087249, the use of glass and oxide additives is limited by using a paste composed of silver powder of 100 nm or less, which may increase the line resistance due to sintering shrinkage of the electrode, and after firing Physical defects, such as cracks, can result in low sintered densities, which leads to problems that are vulnerable to long-term reliability.

Accordingly, an object of the present invention is to provide a conductive paste composition that can increase the efficiency of a solar cell by providing a high sintered density and low sintered shrinkage rate after firing to provide an electrode with low wire resistance and contact resistance.

Another object of the present invention is to provide a method for producing an electrode using the conductive paste composition according to the present invention.

Still another 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 mixed powder, an inorganic binder resin, and an organic vehicle of a fine conductive metal powder having an average particle size of less than 0.5 μm and a conductive metal powder of 0.5 to 10 μm.

The conductive paste composition according to the present invention exhibits high sintered density and low sintered shrinkage after sintering during electrode production, thereby providing low wire resistance and contact resistance of the electrode, thereby increasing efficiency of the solar cell.

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

The conductive paste composition according to the present invention is characterized by using a mixed powder of a fine conductive metal powder having an average particle size of less than 0.5 μm and a conductive metal powder of 0.5 to 10 μm as the conductive powder. According to a preferred embodiment of the present invention, the composition according to the present invention comprises 55 to 90% by weight of a mixed powder of conductive metal powder, 0.5 to 8% by weight of an inorganic binder resin and 5 to 40% by weight of an organic vehicle. It may include.

Hereinafter, each component is demonstrated.

(1) Mixed powder of conductive metal powder

The mixed powder of the conductive metal powder used in the conductive paste composition according to the present invention has a fine conductive metal powder having an average particle size of less than 0.5 µm, preferably 0.01 to 0.5 µm, and 0.5 to 10 µm, preferably 1 µm to 5 A mixed powder of conductive metal powder, which is 탆, is used. The mixing ratio of the fine conductive metal powder having an average particle size of less than 0.5 μm and the conductive metal powder of 0.5 to 10 μm is 10 wt% to 70 wt%: 90 wt% to 30 wt%, preferably 10 wt% to 50 wt% : 90 wt% to 50 wt%.

The conductive metal powder used in the paste composition according to the present invention is silver (Ag), gold (Au), platinum (Pt), rhodium (Rh), palladium (Pd), nickel (Ni), aluminum (Al) and copper ( One or more metal powders selected from the group consisting of Cu) may be used, among which silver powder is most preferred. For example, when silver powder is used, the shape may be mixed with one or two or more of amorphous, spherical, angular and flake types.

Fine conductive metal powder with an average particle size of less than 0.5 μm acts as a binder between particles, making it easy to metallize even at low temperatures and short heat treatment conditions, and the surface energy is large to increase the thixotrophic index of the paste. In this way, since the shape of the paste after printing is small, the ratio of the application area of the electrode material to the silicon substrate can be minimized, and the efficiency of the solar cell can be increased. In addition, the conductive metal powder having an average particle size of 0.5 to 10 μm can suppress shrinkage after firing, thereby making it possible to form a high density low shrink electrode.

The content of the mixed powder of the conductive metal powder may be used from 55 to 90% by weight based on the total weight of the composition, if less than 55% by weight of the electrode with a small conductive powder is thinner the thickness of the electrode can be increased sintering shrinkage can be increased to increase the wire resistance value There is a problem of resistance value variation due to lack of printability, and if it exceeds 90% by weight, it is difficult to paste.

(2) inorganic binder resin

The inorganic binder resin used in the present invention may be a glass frit that is commonly used, and has a softening temperature of 300 to 800 degrees, preferably 400 to 700 degrees, and an average particle diameter of 0.5 to 10 μm. Preference is given to using glass powders or bismuth-borosilicate glass powders.

The content of the inorganic binder resin may be 0.5 to 8% by weight based on the total weight of the composition, when less than 0.5% by weight may cause a problem of weak adhesion to the silicon substrate, if the content of the inorganic binder exceeds 8% by weight Resistance and contact resistance can be high.

(3) organic vehicle

The organic vehicle included in the paste composition of the present invention is not particularly limited, but at least one solvent selected from terpineol, butyl carbitol, butyl carbitol acetate, texanol, ethylene glycol, acetone, pine oil, isopropyl alcohol, and ethanol Or at least one resin selected from cellulose resins such as ethyl cellulose, methyl cellulose and nitrocellulose, acrylic resins such as acrylic esters and polyvinyl resins such as polyvinyl alcohol and polyvinyl butyral; Can be used. The content of the organic vehicle may be used in an amount of 5 to 40% by weight based on the total weight of the composition. When the content of the organic vehicle exceeds 40% by weight, the viscosity of the paste is increased, as well as the presence of excess organic vehicle causes the Problems may arise where xanthan remains in the electrode without being burned out completely.

(5) other additives

 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, thixotropic agents, defoamers, leveling agents and thixotropic agents. Among these, the thixotropic agent can improve the resolution of a fine printing pattern, and can increase the shape retention of a paste after printing. As an example of the thixotropic agent used in the present invention, an oxide-based or wax-based thixotropic agent having a specific surface area of 1.5 cm 2 / g or more, preferably 1.5 to 10 cm 2 / g may be used, and specific examples thereof include aerosil and amide. Amide wax.

The amount of the additive may vary depending on the content and type of the conductive metal mixed powder, but is not particularly limited, but is preferably used in an amount of 3 wt% or less.

The conductive paste composition according to the present invention has a viscosity of 50,000 to 500,000 cps (Brookfield DVII viscometer, spindle # 14), which can be used to prepare a surface electrode of a solar cell, using the conductive paste composition according to the present invention. The method of manufacturing an electrode includes applying a paste composition onto a substrate, drying the applied paste, and firing the dried paste to form an electrode.

The conductive paste composition according to the present invention may be applied to the substrate with a thickness of 5 to 50 µm using various coating methods such as screen printing or a spraying method using a nozzle having a specific diameter, for example, a nozzle having a diameter of 50 to 500 µm. have.

The electrode paste coated with the conductive paste composition according to the present invention may be dried at 60 to 300 ° C. for several minutes and calcined at a temperature of 600 to 850 ° C. for several seconds. The electrode manufactured by this method has a sintering shrinkage ratio of -6.5 to + 2%, which represents a plastic thickness to a dry thickness of the paste, a sintered density of 8 g / cm ³ or more after firing, and an area resistance of 7 mPa / sq. It is preferable that it is less than.

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

Example

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are intended to illustrate the present invention, but the scope of the present invention is not limited thereto.

<Production of Conductive Paste Composition>

Example 1

16% by weight spherical silver powder with an average particle size of 0.05 μm, 65% by weight plate silver with an average particle size of 3.5 μm, red-boro-silicate glass frit with a softening temperature of 500 ° C. and an average particle size of 1.5 μm 4 % By weight, 14% by weight of an organic vehicle prepared by dissolving an ethyl cellulose resin in a butylcarbitol acetate solvent, 1% by weight of an amide wax thixotropic agent and an organic acid leveling agent, and dispersed and triturated with a triaxial roll to obtain a viscosity of 150,000 to 250,000. A paste composition was prepared having a viscosity of cps (Brookfield DVII viscometer, spindle # 14).

Example 2

The same procedure as in Example 1 was carried out except that 20 wt% of the spherical silver powder having an average particle size of 0.05 μm and 61 wt% of the plate shaped silver powder having an average particle size of 3.5 μm had a viscosity of 150,000 to 250,000 cps. A paste composition was prepared.

Example 3

Example 1 and 5 except that 5% by weight of the spherical silver powder having an average particle size of 0.05 μm, 20% by weight of the spherical silver powder having an average particle size of 0.2 μm and 56% by weight of the plate-shaped silver powder having an average particle size of 3.5 μm were used. In the same manner, a paste composition having a viscosity of 150,000 to 250,000 cps was prepared.

Example 4

Example 1 and 5 except that 5% by weight of the spherical silver powder having an average particle size of 0.05 μm, 30% by weight of the spherical silver powder having an average particle size of 0.2 μm and 46% by weight of the plated silver powder having an average particle size of 3.5 μm were used. In the same manner, a paste composition having a viscosity of 150,000 to 250,000 cps was prepared.

Example 5

Example 1 and 10 except that 10% by weight of the spherical silver powder having an average particle size of 0.05 μm, 20% by weight of the spherical silver powder having an average particle size of 0.2 μm and 51% by weight of the plated silver powder having an average particle size of 3.5 μm were used. In the same manner, a paste composition having a viscosity of 150,000 to 250,000 cps was prepared.

Example 6

A paste having a viscosity of 150,000 to 250,000 cps was carried out in the same manner as in Example 1 except that 22 wt% of spherical silver powder having an average particle size of 0.2 μm and 59 wt% of plate-shaped silver powder having an average particle size of 3.5 μm were used. The composition was prepared.

Example 7

A paste having a viscosity of 150,000 to 250,000 cps by the same procedure as in Example 1 except that 28 wt% of spherical silver powder having an average particle size of 0.2 μm and 53 wt% of plate silver powder having an average particle size of 3.5 μm were used. The composition was prepared.

Example 8

A paste having a viscosity of 150,000 to 250,000 cps was carried out in the same manner as in Example 1 except that 34 wt% of the spherical silver powder having an average particle size of 0.2 μm and 47 wt% of the plate-shaped silver powder having an average particle size of 3.5 μm were used. The composition was prepared.

Example 9

Examples 1 and 13 were used except that 13 wt% of the spherical silver powder having an average particle size of 0.2 μm, 19 wt% of the spherical silver powder having an average particle size of 0.8 μm, and 49 wt% of the spherical silver powder having an average particle size of 1.5 μm were used. In the same manner, a paste composition having a viscosity of 150,000 to 250,000 cps was prepared.

Comparative Example 1

A paste composition having a viscosity of 150,000 to 250,000 cps was prepared in the same manner as in Example 1 except that 81 wt% of a spherical silver powder having an average particle size of 0.05 μm was used.

Comparative Example 2

A paste composition having a viscosity of 150,000 to 250,000 cps was prepared in the same manner as in Example 1 except that 81 wt% of spherical silver powder having an average particle size of 0.2 μm was used.

Comparative Example 3

A paste composition having a viscosity of 150,000 to 250,000 cps was prepared in the same manner as in Example 1 except that 81 wt% of a spherical silver powder having an average particle size of 0.8 μm was used.

Comparative Example 4

A paste composition having a viscosity of 150,000 to 250,000 cps was prepared in the same manner as in Example 1 except that 81 wt% of spherical silver powder having an average particle size of 1.5 μm was used.

Comparative Example 5

A paste composition having a viscosity of 150,000 to 250,000 cps was prepared in the same manner as in Example 1 except that 81 wt% of a plate-shaped silver powder having an average particle size of 3.5 μm was used.

Comparative Example 6

Ferro's CN 33-462 paste composition was purchased and evaluated for physical properties.

The absolute value of the paste properties may vary depending on the condition of the silicon substrate, printing conditions, drying conditions, and firing conditions.

Property evaluation

The paste compositions obtained in Examples 1-9 and Comparative Examples 1-6 were evaluated in the following manner, and the results are shown in Table 1 below:

1) Conversion efficiency

The paste composition was coated and dried on an n-type silicon semiconductor substrate having a thickness of 200 μm and a size of 127 mm × 127 mm by screen printing using a screen printing plate of 325 mesh so as to have a firing thickness of 10 to 20 μm.

The paste-coated n-type silicon semiconductor substrate was dried at 200 ° C., and then fired in a firing furnace having a maximum temperature of 740 to 790 ° C. for about 10 seconds to form an electrode, thereby manufacturing a solar cell.

The fabricated solar cell was measured for conversion efficiency using an efficiency meter (PASAN):

2) Sintering shrinkage was calculated as the increase and decrease ratio of the plastic thickness to the dry thickness.

3) The sintered density was calculated by forming a paste into a film, drying and sintering under the above conditions to form a paste sintered film, and then measuring the volume and mass using the Archimedes method .

4) The area resistance (Rs) is printed with a 325 mesh screen printing plate on an alumina substrate in a pattern having a width / length ratio of 1/500, dried and fired under the above conditions, and then measured with a resistance measuring instrument (Kisley 2470). Calculated by the formula below.

As can be seen from the results of Table 1, the paste composition of the present invention obtained in Examples 1 to 9 according to the present invention is a paste obtained in Comparative Examples 1 to 6 with a sintering shrinkage of +2 to -6% during electrode production Compared with the composition, the sintered density was 8 g / cm ³ or more, and the area resistance was low.

Claims (18)

A conductive paste composition comprising a mixed powder, an inorganic binder resin, and an organic vehicle of a fine conductive metal powder having an average particle size of less than 0.5 μm and a conductive metal powder of 0.5 to 10 μm. The method of claim 1, A conductive paste composition comprising from 55 to 90% by weight of a mixed powder of conductive metal powder, from 0.5 to 8% by weight of an inorganic binder resin and from 5 to 40% by weight of an organic vehicle, based on the total weight of the composition. The method according to claim 1 or 2, A conductive paste composition, characterized in that the mixing ratio of the fine conductive metal powder having an average particle size of less than 0.5 μm and the conductive metal powder of 0.5 to 10 μm is in the range of 10 wt% to 70 wt%: 90 wt% to 30 wt%. The method according to claim 1 or 2, The conductive metal powder is one selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), rhodium (Rh), palladium (Pd), nickel (Ni), aluminum (Al) and copper (Cu) It is an above metal powder, The electrically conductive paste composition characterized by the above-mentioned. The method according to claim 1 or 2, The conductive metal powder is silver (Ag) powder, characterized in that the conductive paste composition. The method of claim 5, The conductive paste composition, characterized in that the silver powder is mixed in one or more forms of amorphous, spherical, angular and flake type. The method according to claim 1 or 2, And the inorganic binder resin is glass frit. The method of claim 7, wherein The glass paste is a red-boro-silicate glass powder or bismuth-boro silicate-based glass powder having an average particle diameter of 0.5 to 10㎛ and a softening temperature of 300 to 800 degrees. The method according to claim 1 or 2, The organic vehicle is at least one solvent selected from terpineol, butyl carbitol, butyl carbitol acetate, texanol, ethylene glycol, acetone, pine oil, isopropyl alcohol and ethanol, or a cellulose-based resin or an acrylic resin in the solvent. And at least one resin selected from polyvinyl resins. The method according to claim 1 or 2, A conductive paste composition further comprising at least one additive selected from the group consisting of thixotropic agents, defoamers, leveling agents and thixotropic agents. The method of claim 10, The conductive paste composition, wherein the thixotropic agent is an oxide-based thixotropic agent or a wax-based thixotropic agent having a specific surface area of 1.5 cm 2 / g or more. The method according to claim 1 or 2, A conductive paste composition, having a viscosity (Brookfield DVII viscometer) of 50,000 to 500,000 cps. A method of manufacturing an electrode comprising applying the conductive paste composition according to claim 1 on a substrate, drying the applied paste, and baking the dried paste to form an electrode. The method of claim 13, And wherein the conductive paste composition is applied onto the substrate in a spraying manner using screen printing or a nozzle. The method of claim 13, The dried paste is characterized in that the firing at a temperature of 600 to 850 ℃. The method of claim 13, The electrode has a thickness of 5 to 50㎛ manufacturing method. The method of claim 13, The electrode is a manufacturing method, characterized in that the surface electrode of the solar cell. A solar cell comprising the electrode manufactured by the method of manufacturing an electrode according to claim 13 as a surface electrode.