KR20200106708A - Composition for forming solar cell electrode and solar cell electrode prepared using the same - Google Patents

Abstract

Disclosed are a composition for forming a solar cell electrode including conductive powder, organic frits, organic vehicles, and petrolatum and a solar cell electrode manufactured therefrom. Therefore, the solar cell electrode has the excellent conversion efficiency.

Description

Composition for solar cell electrode formation and solar cell electrode manufactured therefrom TECHNICAL FIELD {COMPOSITION FOR FORMING SOLAR CELL ELECTRODE AND SOLAR CELL ELECTRODE PREPARED USING THE SAME}

It relates to a composition for forming a solar cell electrode and a solar cell electrode prepared therefrom, and more specifically, a composition for forming a solar cell electrode having a high aspect ratio and excellent conversion efficiency while improving printability and dryness during screen printing, and from It relates to the manufactured solar cell electrode.

With the depletion of fossil fuel energy resources, solar cells using sunlight as a new alternative energy source are attracting attention. Solar cells are configured to generate electrical energy using the photoelectric effect of a p-n junction that converts photons of sunlight into electricity. In a solar cell, a front electrode and a rear electrode are formed on the upper and lower surfaces of the semiconductor wafer or substrate where the pn junction is formed, and the photoelectric effect of the pn junction is induced by sunlight incident on the wafer, and the electrons generated therefrom are electrode It is operated to provide an external current flowing through it. The electrodes of such solar cells are formed on the wafer surface by applying, patterning, and firing an electrode paste.

It is important to increase the conversion efficiency of converting solar energy into current in such solar cells. Existing compositions for solar cell electrode formation have mainly improved solar cell conversion efficiency by controlling the size, surface treatment method, or mixing ratio of the conductive powder. However, this method alone has limitations in increasing the conversion efficiency of solar cells, and attempts to improve sintering density or electrode resistance by mixing conductive powders having different particle diameters also have limitations in printability and patternability. Therefore, it is possible to develop a paste that can increase the conversion efficiency of solar cells through improvement of organic matter and at the same time improve the discharge from the mesh during screen printing to form a front electrode with a narrow line width and an increased line height, and a high aspect ratio. There is a need.

An object of the present invention is to provide a composition for forming a solar cell electrode with improved printability and dryness during screen printing, and a solar cell electrode prepared therefrom.

Another object of the present invention is to provide a composition for forming a solar cell electrode having a narrow line width and an increased line height and a high aspect ratio, and a solar cell electrode prepared therefrom.

Another object of the present invention is to provide a composition for forming a solar cell electrode having excellent conversion efficiency by increasing a short-circuit current (Isc), and a solar cell electrode manufactured therefrom.

1. According to one aspect, there is provided a composition for forming a solar cell electrode comprising a conductive powder, a glass frit, an organic vehicle, and petrolatum.

2. In 1 above, the petrolatum may be included in an amount of 0.01 to 5% by weight of the total weight of the composition for forming the solar cell electrode.

3. In 1 above, the composition for forming the solar cell electrode is

60 to 95% by weight of the conductive powder;

0.1 to 20% by weight of the glass frit;

1 to 30% by weight of the organic vehicle; And

It may contain 0.01 to 5% by weight of the petrolatum.

4. In any one of 1 to 3 above, the glass frit is lead (Pb), tellurium (Te), bismuth (Bi), lithium (Li), phosphorus (P), germanium (Ge), gallium (Ga) , Cerium (Ce), iron (Fe), silicon (Si), zinc (Zn), tungsten (W), magnesium (Mg), cesium (Cs), strontium (Sr), molybdenum (Mo), titanium (Ti) , Tin (Sn), indium (In), vanadium (V), barium (Ba), nickel (Ni), copper (Cu), sodium (Na), potassium (K), arsenic (As), cobalt (Co) , Zirconium (Zr), manganese (Mn) and aluminum (Al) may include one or more metal elements selected from.

5. In any one of the above 1 to 4, the composition for forming the solar cell electrode further comprises at least one of a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, an antifoaming agent, a pigment, an ultraviolet stabilizer, an antioxidant and a coupling agent. I can.

6. According to another aspect, a solar cell electrode prepared from the composition for forming a solar cell electrode of any one of the above 1 to 5 is provided.

The present invention provides a composition for forming a solar cell electrode having excellent conversion efficiency due to improved printability and dryness during screen printing, a narrow line width and an increased line height, and an increased short-circuit current, and a solar cell electrode manufactured therefrom. Has the effect of

1 schematically shows the structure of a solar cell according to an embodiment of the present invention.
FIG. 2 is an optical microscope image showing the results of evaluating dry atmosphere of solar cells of Example 2 and Comparative Example 1. FIG.

In describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

When'include','have','consists of' and the like mentioned in the present specification are used, other parts may be added unless'only' is used. In the case of expressing the constituent elements in the singular, it includes the case of including the plural unless specifically stated otherwise.

In addition, in the interpretation of the constituent elements, it is interpreted as including an error range even if there is no explicit description.

In addition, in the present specification, "to" in "a to b" indicating a numerical range is defined as ≥ a and ≤ b.

According to one aspect, the composition for forming a solar cell electrode may include a conductive powder, a glass frit, an organic vehicle, and petrolatum.

Hereinafter, each component of the composition for forming a solar cell electrode will be described in more detail.

Conductive powder

The conductive powder may include, for example, one or more metal powders selected from silver (Ag), gold (Au), platinum (Pt), palladium (Pd), aluminum (Al), and nickel (Ni), but is limited thereto. It is not. According to one embodiment, the conductive powder may include silver powder.

The particle shape of the conductive powder is not particularly limited, and particles of various shapes, for example, particles of a spherical shape, a plate shape, or an amorphous shape may be used.

The conductive powder may be a powder having a nano-sized or micro-sized particle diameter, for example, a conductive powder having a size of tens to hundreds of nanometers, or a conductive powder having a size of several to tens of micrometers. In addition, as a conductive powder, two or more conductive powders having different sizes may be mixed and used.

The average particle diameter (D ₅₀ ) of the conductive powder may be 0.1 to 10 μm, for example, 0.5 to 5 μm. In this range, contact resistance and series resistance may be lowered. The average particle diameter (D ₅₀ ) may be measured using a 1064LD model manufactured by CILAS after ultrasonic dispersion of the conductive powder in isopropyl alcohol (IPA) at 25° C. for 3 minutes.

The amount of the conductive powder used is not particularly limited, but, for example, the conductive powder may be included in an amount of 60 to 95% by weight of the total weight of the composition for forming a solar cell electrode. In the above range, the conversion efficiency of the solar cell is excellent, and the paste can be smoothly performed. According to one embodiment, the conductive powder may be included in 70 to 90% by weight of the total weight of the composition for forming a solar cell electrode, and according to another embodiment, 80 to 95% by weight.

Glass frit

The glass frit is for generating crystal particles of the conductive powder in the emitter region by etching the antireflection film during the firing process of the composition for forming a solar cell electrode and melting the conductive powder. In addition, the glass frit improves the adhesion between the conductive powder and the wafer and softens during sintering to induce an effect of lowering the firing temperature.

Glass frit is lead (Pb), tellurium (Te), bismuth (Bi), lithium (Li), phosphorus (P), germanium (Ge), gallium (Ga), cerium (Ce), iron (Fe), silicon (Si), zinc (Zn), tungsten (W), magnesium (Mg), cesium (Cs), strontium (Sr), molybdenum (Mo), titanium (Ti), tin (Sn), indium (In), vanadium (V), barium (Ba), nickel (Ni), copper (Cu), sodium (Na), potassium (K), arsenic (As), cobalt (Co), zirconium (Zr), manganese (Mn) and aluminum It may contain at least one metal element selected from (Al).

For example, glass frit is Bi-Te-O-based glass frit, Pb-Bi-O-based glass frit, Pb-Te-O-based glass frit, Pb-Te-Bi-O-based glass frit, Te-BO-based glass Frit, Te-Ag-O glass frit, Pb-Si-O glass frit, Bi-Si-O glass frit, Te-Zn-O glass frit, Bi-Te-Li-Zn-O glass frit , Bi-BO-based glass frit, Pb-BO-based glass frit, Bi-Mo-O-based glass frit, Mo-BO-based glass frit, and Te-Si-O-based glass frit. In this case, there may be an advantage of excellent balance of electrical properties of the solar cell electrode.

The shape and size of the glass frit are not particularly limited. For example, the shape of the glass frit may be spherical or irregular, and the average particle diameter (D ₅₀ ) of the glass frit may be 0.1 to 10 μm. The average particle diameter (D ₅₀ ) can be measured using a 1064LD model manufactured by CILAS after ultrasonically dispersing the glass frit in isopropyl alcohol at 25° C. for 3 minutes.

The glass frit can be prepared from the metals and/or metal oxides described above using conventional methods. For example, after mixing the above-described metal and/or metal oxide using a ball mill or planetary mill, etc., the mixed composition is melted at 800 to 1,300°C, and 25°C After quenching in, the resulting product can be pulverized by a disk mill or a planetary mill.

The amount of the glass frit used is not particularly limited, but, for example, the glass frit may be included in an amount of 0.1 to 20% by weight of the total weight of the composition for forming a solar cell electrode. Within the above range, the series resistance, open-circuit voltage, and short-circuit current are excellent, and the solar cell efficiency can be increased, so that the electrical characteristics are excellent and the adhesion improvement effect can be obtained. According to one embodiment, the glass frit may be included in 0.5 to 10% by weight of the total weight of the composition for forming a solar cell electrode, and according to another embodiment, 0.1 to 5% by weight.

Organic vehicle

The organic vehicle imparts viscosity and rheological properties suitable for printing to the composition through mechanical mixing with the inorganic component of the composition for forming a solar cell electrode.

The organic vehicle may be an organic vehicle typically used in a composition for forming a solar cell electrode, and may include a binder resin and a solvent.

As the binder resin, an acrylate-based or cellulose-based resin may be used. For example, ethyl cellulose may be used as the binder resin. Other examples include ethyl hydroxyethyl cellulose, nitro cellulose, a mixture of ethyl cellulose and phenol resin as a binder resin, alkyd resin, phenol resin, acrylic acid ester resin, xylene resin, polybutene resin, polyester resin , Urea resin, melamine resin, vinyl acetate resin, wood rosin or polymethacrylate of alcohol may be used.

As a solvent, for example, hexane, toluene, ethyl cellosolve, cyclohexanone, butyl cellosolve, butyl carbitol (diethylene glycol monobutyl ether), dibutyl carbitol (diethylene glycol dibutyl ether), Butyl carbitol acetate (diethylene glycol monobutyl ether acetate), propylene glycol monomethyl ether, hexylene glycol, terpineol, methyl ethyl ketone, benzyl alcohol, gamma butyrolactone, ethyl lactate or 2,2, 4-trimethyl-1,3-pentanediol monoisobutyrate (eg, texanol) or the like may be used alone or in combination.

The amount of the organic vehicle used is not particularly limited, but, for example, the organic vehicle may be included in an amount of 1 to 30% by weight of the total weight of the composition for forming a solar cell electrode. In the above range, sufficient adhesive strength and excellent printability can be ensured. According to one embodiment, the organic vehicle may be included in 3 to 20% by weight of the total weight of the composition for forming a solar cell electrode, and according to another embodiment, 1 to 15% by weight.

Petrolatum

Petrolatum is also referred to as petroleum jelly, and is a material having a semi-solid state at room temperature (20 to 25°C).

Since the composition for forming a solar cell electrode of the present invention includes petrolatum, it is possible to improve printability and dryness during screen printing. As a result, it is possible to form a solar cell electrode having a high aspect ratio and excellent conversion efficiency.

The amount of petrolatum used is not particularly limited, but, for example, petrolatum may be included in an amount of 0.01 to 5% by weight of the total weight of the composition for forming a solar cell electrode. In the above range, it is possible to improve printability and dryness to increase aspect ratio and improve conversion efficiency. According to one embodiment, petrolatum is 0.01 to 1% by weight of the total weight of the composition for forming a solar cell electrode, according to another embodiment 0.05 to 0.5% by weight, according to another embodiment more than 0.05 to less than 0.04% by weight, and According to another embodiment, it may be contained in an amount of 0.1 to 0.3% by weight.

additive

In addition to the above-described components, the composition for forming a solar cell electrode may contain a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, an antifoaming agent, a pigment, an ultraviolet stabilizer, an antioxidant, a coupling agent, etc. as needed to improve flow characteristics, process characteristics and stability. It may further include alone or two or more. These may be included in an amount of 0.1 to 5% by weight of the total weight of the composition for forming a solar cell electrode, but the content may be changed as necessary.

Solar cell electrode and solar cell including the same

According to another aspect, there is provided an electrode formed from the composition for forming a solar cell electrode and a solar cell including the same. 1 schematically shows the structure of a solar cell 100 according to an embodiment of the present invention.

Referring to FIG. 1, a composition for forming a solar cell electrode is printed on a wafer 10 or a substrate including a p-layer (or n-layer) 11 and an n-layer (or p-layer) 12 as an emitter. And firing to form the rear electrode 21 and the front electrode 23. For example, after printing the composition for forming a solar cell electrode on the rear surface of the wafer, it is dried at 200 to 400° C. for 10 to 60 seconds to perform a preliminary preparation step for the rear electrode. In addition, the composition for forming a solar cell electrode may be printed on the entire surface of the wafer and then dried to perform a preliminary preparation step for the front electrode. Thereafter, a firing process of firing at 400 to 950°C, for example 700 to 950°C for 30 to 210 seconds may be performed to form the front electrode and the rear electrode.

Hereinafter, a composition for forming a solar cell electrode according to an embodiment of the present invention will be described in more detail by way of examples. However, this has been presented as a preferred example of the present invention, and it cannot be construed as limiting the present invention in any sense.

Example

Specific specifications of the components used in the following Examples and Comparative Examples are as follows.

(A) Conductive powder: spherical silver powder with an average particle diameter (D ₅₀ ) of 2.8 μm (AG-5-11F, Dowa Hightech)

(B) Glass frit: Bi-Te-Li-Zn-O-based glass frit with a transition point of 270°C and an average particle diameter (D ₅₀ ) of 1.0 μm (Ashai Glass)

(C) Binder resin: ethyl cellulose (STD4, Dow chemical company)

(D) Solvent: texanol (Eastman)

(E) Petrolatum (vaseline, Daejeonghwa Geum)

(F) Paraffin wax, Sigma-Aldrich

(G) Mineral oil, SAMCHUN

(H) Dispersant: TEGO® Dispers 656, Evonik

(I) Thixotropic agent: Thixatrol ST, Elementis

Examples 1 to 6 and Comparative Examples 1 to 3

Each of the components was weighed according to the composition of Table 1 below, mixed evenly, and then mixed and dispersed with a 3-roll kneader to prepare a composition for forming a solar cell electrode. In Table 1 below, the usage unit of each composition is% by weight.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 (A) 88.55 88.55 88.55 88.55 88.55 88.55 88.55 88.55 88.55 (B) 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 (C) One One One One One One One One One (D) 7.10 7.05 6.95 6.85 6.75 6.65 7.15 6.95 6.75 (E) 0.05 0.1 0.2 0.3 0.4 0.5 - - - (F) - - - - - - - 0.2 - (G) - - - - - - - - 0.4 (H) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 (I) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4

The physical properties of the composition for forming a solar cell electrode of Examples and Comparative Examples prepared as described above were measured according to the following physical property evaluation method. The measurement results are shown in Table 2 below.

Property evaluation method

The composition for forming a solar cell electrode prepared in Examples and Comparative Examples was screen-printed on the entire surface of a silicon wafer having a sheet resistance of 70Ω/sq. in a constant pattern using a 28 μm screen mask, and dried using an infrared drying furnace. Thereafter, the aluminum paste was printed on the back side of the wafer and dried in the same manner. The solar cell formed by the above process is calcined at 400 to 900°C for 30 to 50 seconds using a belt-type kiln, and the printability, drying atmosphere, flooding, patterning, aspect ratio, and electrical characteristics of the manufactured solar cell are as follows. It was measured together.

(1) Printability: The short circuit state of the line pattern obtained by applying the composition for forming a solar cell electrode on a silicon wafer by a screen printing technique was checked, and printability was evaluated. A case in which there are 5 or less short circuits in a line pattern was evaluated as ⊚, and a case in which more than 5 paragraphs were evaluated as x.

(2) Waiting to dry: Apply the composition for solar cell electrode formation on a silicon wafer after waiting for 0 minutes, 5 minutes, and 10 minutes by printing using a screen mask having different sections with line widths of 25, 30 and 35㎛. The short-circuit state of the line pattern at each obtained line width was confirmed, and drying atmosphere characteristics were evaluated. ◎ if there are 5 or less paragraphs of the line pattern in each section after 10 minutes, ○ if there are 5 or less paragraphs in the line pattern in each section after 5 minutes ○, more than 5 paragraphs in the line pattern in each section after 5 minutes The case was evaluated as x.

(3) Flooding: When the composition for forming a solar cell electrode was applied on a silicon wafer by a screen printing technique, the case where flooding was uniformly performed was evaluated as ◎, and the case where it was not uniform or partially re-applied was evaluated as ×.

(4) Patterning: After applying the composition for forming a solar cell electrode on a silicon wafer by a screen printing technique and firing, the width of the obtained pattern was observed using a laser microscope. ◎ if the standard deviation of the line width is less than 3㎛ and the Rz value is less than 15 ◎, if the standard deviation of the line width is less than 5㎛ and the Rz value is less than 20 ○, the standard deviation of the line width is 5㎛ or more and the Rz value The case of 20 or more was evaluated as x.

(5) Aspect ratio: The aspect ratio was calculated by observing the height and width of the pattern obtained after applying and firing the composition for solar cell electrode formation on a silicon wafer by a screen printing technique using a laser microscope. A case in which the aspect ratio value was 25% or more was evaluated as ◎, a case in which the aspect ratio value was less than 20 to 25% was evaluated as ○, and a case where the aspect ratio value was less than 20% was evaluated as x.

(6) Short-circuit current (Isc, unit: mA) and conversion efficiency (Eff., unit: %): About the solar cell obtained after applying the composition for forming a solar cell electrode on a silicon wafer by screen printing and firing Short-circuit current and conversion efficiency were measured using a solar cell efficiency measurement equipment (Halm, Fortix tech, Inc.), and the increase or decrease value was displayed as a reference value for Comparative Example 1.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Printability ◎ ◎ ◎ ◎ ◎ ◎ × × ◎ Waiting to dry ○ ◎ ◎ ◎ ◎ ◎ × × ○ flooding ○ ○ ○ ○ ○ ○ ○ × ○ Pattern ◎ ◎ ◎ ◎ ○ ○ × × × Aspect ratio ◎ ◎ ◎ ◎ ○ ○ ○ × × Isc (mA) +8 +8 +13 +13 +8 +5 0 -3 -14 Eff. (%) +0.03 +0.05 +0.05 +0.04 +0.04 +0.04 0 -0.05 -0.04

From Table 2 above, the composition for forming a solar cell electrode of the Example including petrolatum improved printability and dryness during screen printing compared to the composition for forming a solar cell electrode of a comparative example that did not contain petrolatum, and the solar cell manufactured therefrom has an aspect ratio It can be seen that the conversion efficiency is excellent due to the high and short-circuit current.

Simple modifications or changes of the present invention can be easily implemented by those of ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (6)

A composition for forming a solar cell electrode comprising a conductive powder, a glass frit, an organic vehicle, and petrolatum.
The method of claim 1,
The petrolatum is a composition for forming a solar cell electrode comprising 0.01 to 5% by weight of the total weight of the composition for forming the solar cell electrode.
The method of claim 1,
60 to 95% by weight of the conductive powder;
0.1 to 20% by weight of the glass frit;
1 to 30% by weight of the organic vehicle; And
A composition for forming a solar cell electrode comprising 0.01 to 5% by weight of the petrolatum.
The method of claim 1,
The glass frit is lead (Pb), tellurium (Te), bismuth (Bi), lithium (Li), phosphorus (P), germanium (Ge), gallium (Ga), cerium (Ce), iron (Fe), Silicon (Si), zinc (Zn), tungsten (W), magnesium (Mg), cesium (Cs), strontium (Sr), molybdenum (Mo), titanium (Ti), tin (Sn), indium (In), Vanadium (V), barium (Ba), nickel (Ni), copper (Cu), sodium (Na), potassium (K), arsenic (As), cobalt (Co), zirconium (Zr), manganese (Mn) and A composition for forming a solar cell electrode comprising at least one metal element selected from aluminum (Al).
The method of claim 1,
The composition for forming a solar cell electrode further comprises at least one of a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, a defoaming agent, a pigment, an ultraviolet stabilizer, an antioxidant and a coupling agent.
A solar cell electrode prepared from the composition for forming a solar cell electrode according to any one of claims 1 to 5.

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