KR102326611B1 - Composition for forming solar cell electrode and electrode prepared using the same - Google Patents

Abstract

It contains a conductive powder, a glass frit, and an organic vehicle, wherein Tan δ of the following formula 1 is more than 3 and less than 10 at an angular velocity of 1 rad/s, 4 or more and less than 12 at an angular velocity of 10 rad/s, and 2 at an angular velocity of 100 rad/s More than 10, a composition for forming a solar cell electrode is provided:
[Equation 1]
Tan δ = A / B
(In Equation 1, A and B are loss modulus and storage modulus, respectively, and A and B are log sweep mode ( It is measured by increasing the frequency from 0.1Hz to 100Hz in logarithmic sweep mode).

Description

A composition for forming a solar cell electrode and an electrode prepared therefrom

It relates to a composition for forming a solar cell electrode and an electrode prepared therefrom.

A silicon-based solar cell consists of a substrate made of a p-type silicon semiconductor and an emitter layer made of an n-type silicon semiconductor. A p-n junction is formed between the p-type substrate and the n-type emitter layer. When sunlight is incident on a solar cell having such a structure, electrons are generated as majority carriers in the emitter layer made of the n-type silicon semiconductor due to the photovoltaic effect, and holes are generated as majority carriers in the substrate made of the p-type silicon semiconductor do. Electrons and holes generated by the photovoltaic effect move to the front and rear electrodes bonded to the upper and lower portions of the emitter layer, respectively, and when these electrodes are connected with wires, a current flows. Typically, Ag paste is used to form the front electrode. The electrode paste should be able to realize an electrode shape that can maximize short-circuit current while minimizing line resistance, and at the same time ensure an increase in solar cell efficiency. In order to implement this, it is required to control the rheological properties and thixotrophy of the electrode paste.

Since not all of the sunlight incident on the solar cell is converted into electrical energy, it is necessary to reduce the loss factor for a high-efficiency solar cell. A loss factor in a solar cell can be largely divided into an optical loss and an electrical loss. Optical loss includes reflection from the surface that occurs when sunlight is incident, shadow loss by electrodes, and loss according to the wavelength of sunlight. A typical solar cell that is currently commercialized has an electrode formed on the front surface of which light is incident. Therefore, when the shadow formed on the electrode blocks sunlight, a dead area is created, which interferes with the absorption of sunlight. In order to eliminate such a hindrance factor, the shadowing phenomenon can be reduced by reducing the electrode line width, but simply reducing the electrode line width reduces the cross-sectional area of the electrode and increases the series resistance, so it is necessary to improve this.

The problem to be solved by the present invention is to provide a composition for forming a solar cell electrode that is excellent in fairness and reliability when forming an electrode by shortening the shrinkage distance of the electrode before and after firing.

Another object to be solved by the present invention is to provide a composition for forming a solar cell electrode having excellent electrical properties such as short-circuit current and series resistance after firing and high efficiency.

According to one aspect, it includes a conductive powder, a glass frit, and an organic vehicle, wherein Tan δ of the following formula 1 is greater than 3 and less than 10 at an angular velocity of 1 rad/s, and is greater than or equal to 4 and less than 12 at an angular velocity of 10 rad/s, and 100 rad/s There is provided a composition for forming a solar cell electrode, which is 2 or more and less than 10 at an angular velocity of s:

[Equation 1]

Tan δ = A / B

(In Equation 1, A and B are loss modulus and storage modulus, respectively, and A and B are logarithmic sweep mode by applying a strain of 1% at a temperature of 23° C. using a rheometer. mode) by increasing the frequency from 0.1 Hz to 100 Hz).

The composition may have a shrinkage distance of 300 μm or less in Formula 2:

[Equation 2]

Shrink distance = │L ₀ - L ₁ │

(In Formula 2, L ₀ is the length (unit: μm) of the bus electrode before drying and firing after printing the composition for forming a solar cell electrode,

L ₁ is the _{length of the bus electrode obtained by printing the composition for forming a solar cell electrode in the same manner as in L 0} , drying at 375° C. for 30 to 40 seconds, and then calcining at 600 to 900° C. for 60 to 90 seconds. (unit: μm)).

The organic vehicle may include a binder resin and a solvent, and a weight ratio of the conductive powder to the binder resin may be 70:5 to 90:0.5.

The organic vehicle may include a binder resin and a solvent, the conductive powder may be included in an amount of 70 to 90% by weight in the composition, and the binder resin may be included in an amount of 0.5 to 5% by weight in the composition.

The composition may include 70 to 90% by weight of the conductive powder, 0.1 to 20% by weight of the glass frit, and 3 to 25% by weight of the organic vehicle.

The composition may further include a dispersing agent.

The dispersant may include a compound in which amine-based and carboxylic acid-based functional groups are present simultaneously.

The dispersant may be included in an amount of 0.1 to 5% by weight in the composition.

The composition may further include one or more of a thixotropic agent, a plasticizer, a viscosity stabilizer, an antifoaming agent, a pigment, an ultraviolet stabilizer, an antioxidant, and a coupling agent in addition to the dispersing agent.

According to another aspect, an electrode formed of the above-described composition for forming an electrode for a solar cell is provided.

The composition for forming an electrode for a solar cell of the present invention provides an electrode with excellent processability and reliability when forming the electrode because the shrinkage distance of the electrode before and after firing is shortened.

The electrode prepared from the composition for forming a solar cell electrode of the present invention has excellent electrical properties such as short-circuit current and series resistance after firing and high efficiency.

1 schematically shows the structure of a solar cell according to an embodiment of the present invention.
Figure 2 shows a Tan δ plot (plot) graph according to the angular velocity of the composition for forming a solar cell electrode of Example 1 and Comparative Example 1.
3 shows optical micrographs for measuring the shrinkage distance after firing of the composition for forming a solar cell electrode of Example 1 (a), Example 2 (b) and Comparative Example 1 (c).

In this specification, the singular expression includes the plural expression unless the context clearly dictates otherwise.

In this specification, terms such as include or have means that the features or components described in the specification exist, and the possibility that one or more other features or components may be added is not excluded in advance.

Composition for forming a solar cell electrode

According to one aspect, the composition for forming a solar cell electrode includes a conductive powder, a glass frit, and an organic vehicle, and Tan δ of Equation 1 is greater than 3 and less than 10 at an angular velocity of 1 rad/s, and at an angular velocity of 10 rad/s 4 or more and less than 12, and 2 or more and less than 10 at an angular velocity of 100 rad/s. In the above range, there is an effect of reducing the shrinkage distance after firing when forming the electrode of the composition, and it can have excellent processability and reliability.

[Equation 1]

Tan δ = A / B

(In Equation 1, A and B are loss modulus and storage modulus, respectively, and A and B are applied with a strain of 1% at a temperature of 23°C using a rheometer to increase the frequency from 0.1Hz to 100Hz in a log-sweep mode. is measured).

More specifically, when measuring Tan δ of Equation 1, a solar cell electrode is formed between two parallel plates having a diameter of 25 mm disposed on a rheometer (Ares-G2) of TA-instrument set at 23° C. After positioning the composition, the distance of the parallel plate is gradually narrowed to 1.5 mm, a strain of 1% is applied, and A and B in Equation 1 are measured while increasing the frequency from 0.1 Hz to 100 Hz in a log-sweep mode. can do.

The method for making the composition for forming a solar cell electrode satisfy Tan δ at the specific angular frequency described above is not particularly limited, but for example, the content ratio of the conductive powder and the organic vehicle (eg, the binder resin in the organic vehicle) is control, the content of the conductive powder and the organic vehicle (eg, a binder resin in the organic vehicle) in the composition, or a specific additive is added, and the like can be used.

According to one embodiment, when the weight ratio of the conductive powder to the binder resin is 70:5 to 90:0.5 (eg, 75:4 to 85:1.5), the composition for forming a solar cell electrode at the specific angular frequency described above of Tan δ can be satisfied. Therefore, in the above range, there is an effect of reducing the shrinkage distance after firing when forming the electrode of the composition, and it can have excellent processability and reliability.

According to another embodiment, when 70 to 90% by weight of the conductive powder is included in the composition for forming a solar cell electrode, and 0.5 to 5% by weight of the binder resin, the composition for forming a solar cell electrode contains Tan at the specific angular frequency described above. δ can be satisfied. Therefore, in the above range, there is an effect of reducing the shrinkage distance after firing when forming the electrode of the composition, and it can have excellent processability and reliability.

According to another embodiment, when the composition for forming a solar cell electrode contains 0.1 to 5% by weight of a dispersant as an additive in the composition for forming a solar cell electrode, the composition for forming a solar cell electrode may satisfy Tan δ at the specific angular frequency described above, but this It is not limited.

The composition for forming a solar cell electrode may have a shrinkage distance of 300 µm or less (eg, 290 µm or less, or 280 µm or less) of Equation 2 below. In the above range, there is an effect of reducing the shrinkage distance after firing when forming the electrode of the composition, and it can have excellent processability and reliability.

[Equation 2]

Shrink distance = │L ₀ - L ₁ │

(In Formula 2, L ₀ is the length (unit: μm) of the bus electrode before drying and firing after printing the composition for forming a solar cell electrode,

L ₁ is the _{length of the bus electrode obtained by printing the composition for forming a solar cell electrode in the same manner as in L 0} , drying at 375° C. for 30 to 40 seconds, and then calcining at 600 to 900° C. for 60 to 90 seconds. (unit: μm)).

More specifically, when measuring the shrinkage distance of Equation 2, the composition for forming a solar cell electrode is printed with a maximum line width of 30 to 70 μm and a maximum height of 10 to 20 μm with an aspect ratio of 0.10 to 0.30, _{and L 0} and L in Equation 2 ₁ can be measured. More specifically, when measuring the shrinkage distance of Equation 2, the shrinkage distance may be measured by screen-printing the composition for forming a solar cell electrode on a crystalline silicon mono wafer.

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 of silver (Ag), gold (Au), platinum (Pt), palladium (Pd), aluminum (Al), and nickel (Ni), but is not 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 having a spherical, plate-like or amorphous shape may be used.

The conductive powder may be a powder having a particle size of a nano size or a micro size, for example, a conductive powder having a size of several tens to hundreds of nanometers, or a conductive powder having a size of several to several tens of micrometers. In addition, as the 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 the above range, the contact resistance and the series resistance may be lowered. The average particle diameter (D ₅₀ ) may be measured using a 1064LD model manufactured by CILAS, after ultrasonically dispersing 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 70 to 90% by weight based on 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 pasting can be performed smoothly.

glass frit

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

The glass frit may be a low melting point glass frit having a transition point of 200 to 300°C. In the above range, excellent contact resistance may be exhibited.

The glass frit may be a lead-free glass frit that does not contain lead. For example, the glass frit may be a bismuth-tellurium-oxide (Bi-Te-O)-based glass frit containing elements of bismuth and tellurium. By using a glass frit containing bismuth and tellurium elements, there may be an excellent effect of increasing contact resistance and open circuit voltage. The glass frit may further include other metal elements in addition to bismuth and tellurium. For example, glass frits are made of lithium (Li), zinc (Zn), phosphorus (P), germanium (Ge), gallium (Ga), cerium (Ce), iron (Fe), silicon (Si), 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), may further include one or more of manganese (Mn). According to one embodiment, the glass frit may include, but is not limited to, a bismuth-tellurium-zinc-lithium-oxide (Bi-Te-Zn-Li-O)-based glass frit.

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 ) may be measured using a 1064LD model manufactured by CILAS after ultrasonically dispersing the glass frit in isopropyl alcohol (IPA) at 25° C. for 3 minutes.

Glass frits can be made from tellurium oxide, bismuth oxide and optionally the metals and/or metal oxides described above using conventional methods. For example, after mixing tellurium oxide, bismuth oxide and optionally the above-mentioned metal and/or metal oxide using a ball mill or a planetary mill, etc., the mixed composition is mixed with 800 Melting at 1,300° C., quenching at 25° C., and then pulverizing the resulting product by a disk mill, a planetary mill, or the like.

The glass frit may be included in an amount of 0.1 to 20% by weight, for example, 0.5 to 10% by weight of the total weight of the composition for forming a solar cell electrode. In the above range, p-n junction stability can be secured under various sheet resistances, the series resistance value can be minimized, and ultimately, the efficiency of the solar cell can be improved.

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.

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

As the binder resin, an acrylate-based resin or a cellulose-based resin may be used. According to one embodiment, ethyl cellulose may be used as the binder resin. According to another embodiment, as the binder resin, ethyl hydroxyethyl cellulose, nitro cellulose, a mixture of ethyl cellulose and a phenol resin, an alkyd resin, a phenol-based resin, an acrylic acid ester-based resin, a xylene-based resin, a polybutene-based resin, a polyester-based resin Resin, urea-based resin, melamine-based resin, vinyl acetate-based resin, wood rosin or polymethacrylate of alcohol may be used.

Examples of the solvent include 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) and 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 3 to 25% by weight based on 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.

dispersant

The composition for forming a solar cell electrode may further include a dispersant as an additive for controlling rheological properties and thixotropic properties in addition to the above-described components. The dispersant may be one generally used for preparing a composition for forming a solar cell electrode. For example, as a dispersing agent, a compound in which an amine-based and a carboxylic acid-based functional group exists at the same time, specifically, a compound including a carboxyl group (or carboxylate group) and an amine group (or an amine salt) can be used at the same time. Examples of the compound in which the amine-based and carboxylic acid-based functional groups are present at the same time include, for example, a reaction product of a linear polycarboxylic acid and an amine compound or polyamine, a polyester having a free carboxylic acid and an amine compound or a polyamine reaction product, free ( free) a reaction product of a polyether having a carboxylic acid with an amine compound or polyamine. Commercially available dispersants include ED series (eg, ED-120) manufactured by Kusumoto chemical.

The amount of the dispersant used is not particularly limited, but, for example, the dispersant may be included in an amount of 0.1 to 5% by weight based on the total weight of the composition for forming a solar cell electrode. In the above range, there is an effect of reducing the shrinkage distance after firing when forming the electrode of the composition, and it can have excellent processability and reliability.

other additives

In addition to the above-mentioned components, the composition for forming a solar cell electrode may contain, as necessary, a thixotropic agent, a plasticizer, a viscosity stabilizer, an antifoaming agent, a pigment, a UV stabilizer, an antioxidant, a coupling agent, etc. alone or in order to improve flow characteristics, process characteristics and stability. Two or more types may be further included. These may be included in 0.1 wt% to 5 wt% of the total weight of the composition for forming a solar cell electrode, but the content may be changed as needed.

Solar cell electrode and solar cell including same

According to another aspect, an electrode formed from the composition for forming an electrode for a solar cell and a solar cell including the same are provided. 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 the composition for forming a solar cell electrode is printed and applied to the rear surface of the wafer, it is dried at about 200 to 400° C. for about 10 to 60 seconds to perform a pre-preparation step for the rear electrode. In addition, a pre-preparation step for the front electrode may be performed by printing the composition for forming a solar cell electrode on the front surface of the wafer and drying it. Thereafter, a firing process of firing at about 400 to 950° C., for example, about 700 to 950° C. for about 30 to 210 seconds, may be performed to form the front electrode and the rear electrode.

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

Example

Example 1

0.5 wt% of ethyl cellulose (Dow chemical, STD4) as a binder resin and 2.9 wt% of texanol (Eastman, texanol) as a binder resin were sufficiently dissolved at 60° C. (Dowa Hightech, AG-5-11F) Average of 90% by weight, bismuth oxide (15.8% by weight)-tellurium oxide (53.8% by weight)-zinc oxide (13.2% by weight)-lithium oxide (17.2% by weight) Bi-Te-Zn-Li-O glass frit with a particle size of 1.0 μm and a transition point of 273°C 5% by weight, dispersant (Kusumoto chemical, ED-120) 0.8% by weight, viscosity stabilizer (TEGO, Glide 410) 0.4 Weight% and 0.4% by weight of a thixotropic agent (Elementis, Thixatrol ST) were added, mixed evenly, and then mixed and dispersed in a 3-roll kneader to prepare a composition for forming a solar cell electrode.

Examples 2 to 6 and Comparative Examples 1 to 6

A composition for forming a solar cell electrode was prepared in the same manner as in Example 1, except that the content (unit: wt%) of each component was changed as described in Tables 1 and 2 below.

(Unit: % by weight) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 abandonment
vehicle binder resin 0.5 0.5 1.6 3.8 5 0.5 menstruum 2.9 3.3 7.2 15 18.8 23.3 conductive powder 90 90 85 75 70 70 glass frit 5 5 5 5 5 5 dispersant 0.8 0.4 0.4 0.4 0.4 0.4 Viscosity Stabilizer 0.4 0.4 0.4 0.4 0.4 0.4 thixotropic agent 0.4 0.4 0.4 0.4 0.4 0.4

(Unit: % by weight) Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 abandonment
vehicle binder resin 6 0.1 0.1 0.1 6 0.5 menstruum 27.8 0.7 3.7 13.8 17.8 3.7 conductive powder 60 93 90 70 70 90 glass frit 5 5 5 5 5 5 dispersant 0.4 0.4 0.4 0.4 0.4 0 Viscosity stabilizer 0.4 0.4 0.4 0.4 0.4 0.4 thixotropic agent 0.4 0.4 0.4 0.4 0.4 0.4

Evaluation Example 1: Measurement of Tan δ

The composition for forming a solar cell electrode prepared in Examples and Comparative Examples was placed between two parallel plates with a diameter of 25 mm disposed on a rheometer (Ares-G2) of TA-instrument set at 23°C. After compressing the composition by narrowing the distance of the parallel plate to 1.6 mm, the composition protruding outside the parallel plate was trimmed, and the distance of the parallel plate was again narrowed to 1.5 mm. The loss modulus (A) and storage modulus (B) were measured while increasing the frequency from 0.1 Hz to 100 Hz in a log sweep mode while applying a strain of 1%. By substituting A and B measured in Equation 1 above, Tan δ according to angular velocity (ω) was calculated, and the results are shown in Tables 3, 4 and FIG. 2 .

Evaluation Example 2: Measurement of shrinkage distance and aspect ratio

The compositions for forming solar cell electrodes prepared in Examples and Comparative Examples were screen-printed (screen mask: 360 mesh, emulsion 15, width 35 μm) in a uniform pattern on the entire surface of a crystalline silicon mono wafer. The shape of the electrode was trapezoidal, and the maximum width was 75 µm and the maximum height was 17 µm. Using a belt-type firing furnace, the electrode obtained by drying at 375° C. for 30 to 60 seconds and firing at 600 to 900° C. for 60 to 210 seconds was observed with a 3D laser microscope (KEYENCE, VK-9700), After measuring the shrinkage distance (unit: μm), measuring the thickness (unit: μm) and line width (unit: μm) of the electrode, the aspect ratio of the electrode was calculated, and the results are shown in Tables 3 and 4.

Evaluation Example 3: Electrical Characteristics

After texturing the entire surface of a p-type wafer doped with boron (Bron), an n ⁺ _{layer is formed with POCl 3} , and silicon nitride (SiN _x :H) is formed on it as an anti-reflection film The entire surface of the crystalline wafer) was screen-printed in a uniform pattern, and dried at 300 to 400° C. using an infrared drying furnace. After that, aluminum 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 at 400 to 900° C. for 60 seconds using a belt-type firing furnace to prepare a solar cell. The short-circuit current (unit: A), series resistance (unit: mΩ) and conversion efficiency (unit: %) of the solar cell manufactured as described above were measured using a solar cell efficiency measuring device (Passan, CT-801). and the results are shown in Tables 3 and 4 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Tan δ
(at ω=1 rad/s) 6.50 9.14 7.65 7.03 3.38 9.63 Tan δ
(at ω=10rad/s) 11.51 8.40 5.50 4.69 4.32 4.56 Tan δ
(at ω=100rad/s) 9.57 9.62 6.88 3.67 2.07 2.89 Shrinkage distance (㎛) 245 72 104 181 220 287 Short circuit current (A) 8.928 8.945 8.939 8.935 8.931 8.926 Series resistance (mΩ) 2.59 2.56 2.57 2.58 2.58 2.60 Conversion efficiency (%) 20.79 20.87 20.85 20.82 20.80 20.77 Thickness after firing (㎛) 14.8 15.4 15.3 15.4 15.1 14.5 Line width after firing (㎛) 56.9 57.0 58.8 59.2 55.9 58.0 Aspect ratio (thickness/line width) 0.26 0.27 0.26 0.26 0.27 0.25

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Tan δ
(at ω=1 rad/s) 2.27 0.71 1.18 6.35 4.54 2.54 Tan δ
(at ω=10rad/s) 3.57 6.25 5.14 8.14 4.60 5.98 Tan δ
(at ω=100rad/s) 1.44 9.30 7.51 1.26 1.85 1.21 Shrinkage distance (㎛) 423 354 310 328 317 379 Short circuit current (A) 8.873 8.881 8.904 8.890 8.899 8.879 Series resistance (mΩ) 2.91 2.85 2.81 2.83 2.82 2.87 Conversion efficiency (%) 20.55 20.61 20.68 20.65 20.66 20.59 Thickness after firing (㎛) 11.4 12.9 13.1 12.8 12.8 11.6 Line width after firing (㎛) 71.3 64.5 68.9 64 71.1 72.5 Aspect ratio (thickness/line width) 0.16 0.20 0.19 0.20 0.18 0.16

As can be seen from FIGS. 2 and 3, and Tables 3 and 4, Tan δ is greater than 3 and less than 10 at an angular velocity of 1 rad/s, 4 and less than 12 at an angular velocity of 10 rad/s, and at an angular velocity of 100 rad/s The composition for forming a solar cell electrode of Examples 1 to 6, which satisfies all of 2 or more and less than 10, had a short shrinkage distance and a high aspect ratio when forming an electrode compared to the composition for forming a solar cell electrode of Comparative Examples 1 to 6, which is not.

In addition, the solar cells of Examples 1 to 6 in which Tan δ satisfies all of more than 3 and less than 10 at an angular velocity of 1 rad/s, 4 or more and less than 12 at an angular velocity of 10 rad/s, and 2 or more and less than 10 at an angular velocity of 100 rad/s. The composition for forming an electrode showed a high short-circuit current, a low series resistance, and a high conversion efficiency when forming an electrode compared to the composition for forming an electrode for a solar cell of Comparative Examples 1 to 6, which is not.

Simple modifications or changes of the present invention can be easily carried out 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 (8)

a conductive powder, a glass frit and an organic vehicle;
Tan δ of the following formula 1 is greater than 3 and less than 10 at an angular velocity of 1 rad/s, 4 or more and less than 12 at an angular velocity of 10 rad/s, and 2 or more and less than 10 at an angular velocity of 100 rad/s, a composition for forming a solar cell electrode:
[Equation 1]
Tan δ = A / B
(In Equation 1, A and B are loss modulus and storage modulus, respectively, and A and B are logarithmic sweep mode by applying a strain of 1% at a temperature of 23° C. using a rheometer. mode) by increasing the frequency from 0.1 Hz to 100 Hz).
According to claim 1,
A composition for forming a solar cell electrode having a shrinkage distance of 300 μm or less of Formula 2:
[Equation 2]
Shrink distance = │L ₀ - L ₁ │
(In Formula 2, L ₀ is the length (unit: μm) of the bus electrode before drying and firing after printing the composition for forming a solar cell electrode,
L ₁ is the _{length of the bus electrode obtained by printing the composition for forming a solar cell electrode in the same manner as in L 0} , drying at 375° C. for 30 to 40 seconds, and then calcining at 600 to 900° C. for 60 to 90 seconds. (unit: μm)).
According to claim 1,
The organic vehicle includes a binder resin and a solvent,
A composition for forming a solar cell electrode having a weight ratio of the conductive powder to the binder resin of 70:5 to 90:0.5.
According to claim 1,
The organic vehicle includes a binder resin and a solvent,
The conductive powder is included in 70 to 90% by weight in the composition,
The binder resin is included in 0.5 to 5% by weight of the composition for forming a solar cell electrode.
According to claim 1,
70 to 90% by weight of the conductive powder,
0.1 to 20% by weight of the glass frit, and
A composition for forming a solar cell electrode comprising 3 to 25% by weight of the organic vehicle.
According to claim 1,
The composition is a composition for forming a solar cell electrode further comprising 0.1 to 5% by weight of a dispersant.
According to claim 1,
The composition is a composition for forming a solar cell electrode further comprising at least one of a thixotropic agent, a plasticizer, a viscosity stabilizer, an antifoaming agent, a pigment, an ultraviolet stabilizer, an antioxidant, and a coupling agent.
An electrode formed of the composition for forming a solar cell electrode according to any one of claims 1 to 7.

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