KR20200091284A - Composition for forming solar cell electrode and electrode prepared using the same and solar cell - Google Patents

Abstract

Provided are a composition for forming a solar cell electrode, which contains a conductive powder; glass frits; cellulose polymer; silicone polymer; a thixotropic agent; and a solvent, and has, at 23°C and 0.1 rad/sec to 1,000 rad/sec, angular velocity at which a Tan δ maximum value is more than 80 rad/sec to 1,000 rad/sec, an electrode prepared using the same, and a solar cell including the electrode.

Description

A composition for forming a solar cell electrode, an electrode and a solar cell produced therefrom. {COMPOSITION FOR FORMING SOLAR CELL ELECTRODE AND ELECTRODE PREPARED USING THE SAME AND SOLAR CELL}

The present invention relates to a composition for forming a solar cell electrode, an electrode prepared therefrom, and a solar cell including the electrode.

As the fossil fuel energy resource is depleted, a solar cell that uses sunlight as a new alternative energy source has attracted attention. The solar cell is configured to generate electrical energy using a photoelectric effect of a p-n junction that converts photons of sunlight into electricity. The solar cell forms a front electrode and a rear electrode on a semiconductor wafer or a substrate on which a pn junction is formed, and a photon effect of the pn junction is induced by sunlight incident on the wafer, and electrons generated therefrom are formed. It is operated to provide a current flowing through the outside. The electrodes of these solar cells are formed on the wafer surface by application, patterning and firing of electrode paste.

In such solar cells, it is important to increase the conversion efficiency of converting solar energy into electric current. Conventional solar cell electrode paste compositions have mainly increased the conversion efficiency of solar cells by adjusting the size, surface treatment method or mixing ratio of 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 sizes also have limitations in printability and patternability. Therefore, by improving the efficiency of converting solar cells through improvement of organic matter, and improving the ejectability from the mesh during screen printing, the line width is narrow and the line height is increased to form a paste capable of forming a front electrode with a high aspect ratio. There has been a need to develop.

In order to improve the printability of the paste for solar cell electrodes, methods for increasing dispersibility or adjusting particle size or mixing ratio by using surface-treated conductive particles are proposed, while acrylate-based instead of the conventional cellulose-based binder resin. A method of using a binder has been proposed. However, methods of adjusting the surface treatment, particle size, or mixing ratio of conductive particles have limitations in terms of electrical properties, and in the case of acrylic binders, the synthesis process is simpler than that of cellulose-based binders, and desired properties are obtained by combining various monomers. While it has the advantage of being able to design, it has a small amount of residual carbon and a polar functional group is formed on the polymer side group, so it exhibits good dispersibility. However, it has less printing properties (thixotropy) than conventional cellulose-based binder resins. There is a problem. Existing methods are mostly material approaches and need to develop Rheology approach through analysis.

Background art of the present invention is disclosed in Japanese Patent Laid-Open No. 2015-144162 and the like.

One embodiment enables fine line width printing with a line width of 30 µm or less, improves ejectability from the mesh during screen printing, and at the same time, reduces the resistance by increasing the aspect ratio by increasing the aspect ratio by narrowing the line width and increasing the aspect ratio. It is to provide a composition for forming a solar cell electrode that can increase the.

Another embodiment is to provide an electrode formed of the composition for forming a solar cell electrode.

Another embodiment is to provide a solar cell including the electrode.

One embodiment is a conductive powder; Glass frit; Cellulose polymers; Silicone polymers; Thixotropic agents; And a solvent, and provides a composition for forming a solar cell electrode having an angular velocity of greater than 80 rad/sec to 1,000 rad/sec at 23° C. and 0.1 rad/sec to 1,000 rad/sec.

The composition for forming a solar cell electrode may have a maximum value of Tan δ of greater than 11 and less than or equal to 20 at 23° C. and 0.1 rad/sec to 1,000 rad/sec.

The composition for forming a solar cell electrode may have a storage modulus of 1,000 Pa to 10,000 Pa at 23°C and 1,000 rad/sec.

The cellulose polymer may have a weight average molecular weight of 50,000 g/mol to 200,000 g/mol.

The cellulose polymer may be an ethyl cellulose polymer.

The cellulose polymer may be included in an amount of 0.1% to 10% by weight based on the total amount of the composition for forming the solar cell electrode.

The silicone polymer may include linear siloxane, cyclic siloxane, or combinations thereof.

The linear siloxane may have a weight average molecular weight of 3,000 g/mol to 200,000 g/mol.

The silicone polymer may be included in an amount of 0.1 to 5% by weight based on the total amount of the composition for forming the solar cell electrode.

The thixotropic agent may include a bisamide-based thixotropic agent.

The composition for forming a solar cell electrode may include 60% to 95% by weight of the conductive powder; 0.5 to 20% by weight of the glass frit; 0.1% to 10% by weight of the cellulose polymer; 0.1% to 5% by weight of the silicone polymer; 0.1 to 5% by weight of the thixotropic agent; And the residual amount of the solvent.

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 It may include one or more metal elements selected from aluminum (Al).

The solvent is methyl cellosolve, methyl cellosolve, butyl cellosolve, aliphatic alcohol, α-terpineol, β-terpineol, Dihydro-terpineol, selected from ethylene glycol, ethylene glycol mono butyl ether, butyl cellosolve acetate and texanol It may include at least one.

The composition for forming a solar cell electrode may further include a dispersant, and the dispersant may be included in an amount of 0.1 to 5% by weight based on the total amount of the composition for forming the solar cell electrode.

The composition for forming a solar cell electrode may further include one or more additives selected from plasticizers, viscosity stabilizers, antifoaming agents, pigments, ultraviolet stabilizers, antioxidants, and coupling agents.

Another embodiment provides an electrode formed of the composition for forming a solar cell electrode.

Another embodiment provides a solar cell including the electrode.

The composition for forming a solar cell electrode according to one embodiment enables fine line width printing of line widths of 30 µm or less, improves ejection properties from a mesh during screen printing, and further increases line height by narrowing the line width By increasing the aspect ratio, resistance can be reduced and efficiency can be increased.

1 is a schematic diagram briefly showing the structure of a solar cell according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains may easily practice. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

In the drawings, thicknesses are enlarged to clearly represent various layers and regions. The same reference numerals are used for similar parts throughout the specification. When a portion of a layer, film, region, plate, etc. is said to be “above” another portion, this includes not only the case “directly above” the other portion but also another portion in the middle. Conversely, when one part is "just above" another part, it means that there is no other part in the middle.

Unless otherwise specified herein, "substitution" means at least one hydrogen atom is a halogen (F, Cl, Br or I), hydroxy group, C1 to C20 alkoxy group, nitro group, cyano group, amino group, imino group, azido group , Amidino group, hydrazino group, hydrazono group, carbonyl group, carbamyl group, thiol group, ester group, ether group, carboxyl group or salt thereof, sulfonic acid group or salt thereof, phosphoric acid group or salt thereof, C1 to C20 Alkyl group, C2 to C20 alkenyl group, C2 to C20 alkynyl group, C6 to C30 aryl group, C3 to C20 cycloalkyl group, C3 to C20 cycloalkenyl group, C3 to C20 cycloalkynyl group, C2 to C20 heterocycloalkyl group, C2 to C20 It means substituted with a substituent selected from a heterocycloalkenyl group, a C2 to C20 heterocycloalkynyl group, a C3 to C30 heteroaryl group, or a combination thereof.

In addition, unless otherwise specified herein, "hetero" means that at least one hetero atom of N, O, S, and P is contained in a ring group.

An electrode forming composition according to an embodiment includes a conductive powder; Glass frit; Organic binders; And solvents.

Hereinafter, the present invention will be described in detail.

The composition for forming a solar cell electrode according to an embodiment includes a conductive powder; Glass frit; Cellulose polymers; Silicone polymers; Thixotropic agents; And a solvent, wherein the composition for forming a solar cell electrode has an angular velocity (gelling point) in which a maximum value of Tan δ appears at 23° C. and 0.1 rad/sec to 1,000 rad/sec, more than 80 rad/sec to 1,000. rad/sec. In the above range, it is possible to print a fine line width of 30 µm or less in line width, and to improve the ejection property from the mesh during screen printing, and the line width is narrow during screen printing and the line height is increased to increase the aspect ratio to reduce resistance. And increase efficiency.

The composition for forming a solar cell electrode according to an embodiment may have a maximum value of Tan δ of 20 or less, such as 11 or more and 20 or less, at 23° C. and 0.1 rad/sec to 1,000 rad/sec. In the above range, it may be possible to effect fine line width printing and realize an electrode having a high aspect ratio.

The composition for forming a solar cell electrode according to an embodiment may have a storage modulus of 1,000 Pa to 10,000 Pa at 23° C. and 1,000 rad/sec. In the above range, it may be possible to effect fine line width printing and realize an electrode having a high aspect ratio.

The composition for forming a solar cell electrode according to an embodiment may have a viscosity of 40 KcPs to 100 KcPs, such as 40 KcPs to 55 KcPs, at 23° C. and 100 rpm. Must have the viscosity range can be used as a composition for forming a solar cell electrode.

Hereinafter, each component of the composition of the present invention will be described in detail.

Conductive powder

The composition for forming a solar cell electrode according to an embodiment may use a metal powder as a conductive powder.

The metal powder is silver (Ag), gold (Au), palladium (Pd), platinum (Pt), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir), rhenium (Re), titanium (Ti), Niobium (Nb), Tantalum (Ta), Aluminum (Al), Copper (Cu), Nickel (Ni), Molybdenum (Mo), Vanadium (V), Zinc (Zn), Magnesium (Mg), Yttrium (Y), cobalt (Co), zirconium (Zr), iron (Fe), tungsten (W), tin (Sn), may include one or more metals selected from chromium (Cr) and manganese (Mn), It is not limited to this.

The conductive powder may be a nano-sized or micro-sized particle size, for example, a conductive powder having a size of tens to hundreds of nanometers, a conductive powder having a size of several to several tens of micrometers, having two or more different sizes It is also possible to use by mixing the conductive powder.

The conductive powder may have a spherical shape, a plate shape, or an amorphous shape. The average particle diameter (D50) of the conductive powder is preferably 0.1 μm to 10 μm, and more preferably 0.5 μm to 5 μm. The average particle diameter is measured by using a 1064LD model manufactured by CILAS after dispersing the conductive powder in isopropyl alcohol (IPA) at room temperature (20°C to 25°C) for 3 minutes with ultrasonic waves. Within the above range, it is possible to have the effect of lowering the contact resistance and line resistance.

The conductive powder may be included in an amount of 60% to 95% by weight based on 100% by weight of the total composition for forming an electrode. In the above range, it is possible to prevent the conversion efficiency from being lowered due to an increase in resistance, and to prevent the pasting from being difficult due to a relative decrease in the amount of the organic vehicle. Preferably it may be included in 70% to 90% by weight.

Glass frit

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

In order to increase the efficiency of the solar cell, increasing the area of the solar cell may increase the contact resistance of the solar cell, so it is necessary to minimize the damage to the pn junction and at the same time minimize the series resistance. In addition, since the fluctuation range of the firing temperature increases as the substrate having various sheet resistance increases, it is preferable to use a glass frit capable of sufficiently securing thermal stability even at a wide firing temperature.

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

In one embodiment, two glass frits having different transition temperatures may be used. For example, a first glass frit having a transition temperature of 200°C or more and 350°C or less and a second glass frit having a transition temperature of 350°C or more and 550°C or less may be mixed and used in a weight ratio of 1:0.2 to 1:1.

As the glass frit, any one or more of a flexible glass frit and a lead-free glass frit used in a composition for forming an electrode may be used. For example, 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 one or more metal elements selected from aluminum (Al).

For example, the glass frit may be lead-free glass frit that does not contain lead. Specifically, the glass frit is bismuth (Bi, tellurium (Te), 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), manganese (Mn) Preferably, the glass frit may be a bismuth-tellurium-zinc-lithium-oxide (Bi-Te-Zn-Li-O)-based glass frit.

The glass frit is not particularly limited in shape and size. For example, a glass frit having an average particle diameter (D50) of 0.1 μm to 10 μm may be used. The shape of the glass frit can be spherical or irregular. The average particle diameter (D50) was measured using a 1064LD model manufactured by CILAS after dispersing glass frit in isopropyl alcohol (IPA) at 25°C for 3 minutes with ultrasonic waves.

The glass frit can be made from metal and/or metal oxide using conventional methods. For example, after mixing the tellurium oxide, bismuth oxide, and optionally the metal and/or metal oxide using a ball mill or a planetary mill, the mixed composition is 700 Melting under the conditions of ℃ to 1,300 ℃, quenching (quenching) at 20 ℃ to 25 ℃, the obtained result can be obtained by crushing by a disk mill (disk mill), planetary mill or the like.

The glass frit may be 0.1 wt% to 20 wt%, such as 0.5 wt% to 10 wt%, such as 1.5 wt% to 2 wt%, based on the total amount of the composition for forming a solar cell electrode. When included in the above range, it is possible to secure pn junction stability under various sheet resistances, minimize the series resistance value, and eventually improve the efficiency of the solar cell.

menstruum

The solvent has a boiling point of 100 °C or higher, methyl cellosolve, ethyl cellosolve, butylcellosolve, aliphatic alcohol, α-terpineol ), β-terpineol, dihydro-terpineol, ethylene glycol, ethylene glycol mono butyl ether, butyl cellosolve acetate, Texanol or the like may be used alone or in combination of two or more.

The solvent may be included in a residual amount with respect to the total amount of the composition for forming a solar cell electrode, for example, 1 to 30% by weight relative to the total amount of the composition for forming a solar cell electrode. In the above range, sufficient adhesive strength and excellent printability can be secured.

Cellulose polymer

The cellulose polymer may be an ethyl cellulose polymer.

For example, the cellulose polymer may have a weight average molecular weight of 50,000 g/mol to 200,000 g/mol, preferably 60,000 g/mol to 150,000 g/mol. The composition for forming a solar cell electrode according to one embodiment by using the cellulose polymer having the weight average molecular weight range together with a silicone polymer to be described later shows a maximum value of Tan δ at 23° C. and 0.1 rad/sec to 1,000 rad/sec. The angular velocity is greater than 80 rad/sec to 1,000 rad/sec, and at the same time, the maximum value of Tan δ may have a value of more than 11 and less than 20.

The cellulose polymer may be included in an amount of 0.1 wt% to 10 wt%, for example, 0.1 wt% to 5 wt%, based on the total amount of the composition for forming a solar cell electrode. The composition for forming a solar cell electrode according to one embodiment by using the cellulose polymer in the above range with a silicone polymer to be described later has an angular velocity of greater than 80 at 23° C. and 0.1 rad/sec to 1,000 rad/sec. rad/sec to 1,000 rad/sec.

Silicone polymer

In one embodiment, the silicone polymer can include linear siloxanes, cyclic siloxanes, or combinations thereof.

As the linear siloxane, for example, polymethylsiloxane, polyethylsiloxane, polydimethylsiloxane, polydiethylsiloxane, or a combination thereof may be used, but is not limited thereto.

The linear siloxane may have a weight average molecular weight of 3,000 g/mol to 200,000 g/mol. In the above range, each speed at which the maximum value of Tan δ appears at 23°C and 0.1 rad/sec to 1000 rad/sec is 0.1 rad/sec to 80 rad/sec, and at the same time, the maximum value of Tan δ is greater than 11 and less than or equal to 20. Can have

The cyclic siloxane is a cyclic siloxane compound having a ring of silicon-oxygen-silicon-oxygen, substituted or unsubstituted, cyclotrisiloxane, cyclotetrasiloxane, cyclopentasiloxane, cyclohexasiloxane, cycloheptasiloxane, cyclo Octasiloxane, cyclononanesiloxane, and cyclodecasiloxane. The "substituted or substituted" to "substituted" refers to an alkyl group having one or more hydrogen atoms having 1 to 5 carbon atoms (eg, methyl group, ethyl group, propyl group, butyl group, or pentyl group) bonded to silicon (Si) in siloxane, Means substituted with an alkenyl group having 2 to 5 carbon atoms (for example, vinyl group), an aryl group having 6 to 10 carbon atoms (for example, phenyl group), or a halogenated alkyl group having 1 to 5 carbon atoms (for example, trifluoropropyl group) do.

For example, the cyclic siloxane is hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, tetradecamethylcycloheptasiloxane, octadecamethylcyclononanesiloxane, tetramethylcyclotetra Tetramethyl-tetravinylcyclotetrasiloxane, 1,3,5, including siloxane, hexaphenylcyclotrisiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, and the like Tris(trifluoropropyl)-trimethylcyclotrisiloxane, hexadecamethylcyclooctasiloxane, penta, including tris(3,3,3-trifluoropropyl)-1,3,5-trimethylcyclotrisiloxane, etc. Methylcyclopentasiloxane, hexamethylcyclohexasiloxane, octaphenylcyclotetrasiloxane, triphenylcyclotrisiloxane, tetraphenylcyclotetrasiloxane, tetramethyl-tetraphenylcyclotetrasiloxane, tetravinyl-tetraphenylcyclotetrasiloxane, hexamethyl- Hexavinylcyclohexasiloxane, hexamethyl-hexaphenylcyclohexasiloxane, and hexavinyl-hexaphenylcyclohexasiloxane may include one or more, but are not limited thereto.

The silicone polymer may contain a linear siloxane alone or a mixture of the linear siloxane and a cyclic siloxane. When the mixture of the linear siloxane and the cyclic siloxane is used as a silicone polymer, the linear siloxane and the cyclic siloxane may be included in a weight ratio of 1:5 to 5:1, such as 1:2 to 2:1.

The silicone polymer may include 0.1 wt% to 5 wt% based on the total amount of the composition for forming a solar cell electrode. The composition for forming a solar cell electrode according to an embodiment by using the silicone polymer in the above range with the cellulose polymer has an angular rate of greater than 80 at 23° C. and 0.1 rad/sec to 1,000 rad/sec. It may be rad/sec to 1,000 rad/sec, and further, the area change rate of the composition for forming a solar cell electrode may be lowered, and an increase in resistance value may be prevented.

Thixotropic

In one embodiment, the thixotropic agent may include a bisamide-based thixotropic agent. The bisamide-based thixotropic agent may use a conventional type known to those skilled in the art, but for example, Thixatrol Max (Elementis) may be used.

The thixotropic agent may be included in an amount of 0.1 to 5% by weight based on the total amount of the composition for forming a solar cell electrode. In the range, the composition for forming a solar cell electrode according to one embodiment may have an angular velocity at which the maximum value of Tan δ is 23°C and 0.1rad/sec to 1000rad/sec, which may be 80 rad/sec to 1,000 rad/sec. .

The composition for forming a solar cell electrode according to an embodiment may not include a castor oil-based thixotropic agent. When the castor oil-based thixotropic agent is included, it may be difficult to achieve an angular velocity of greater than 80 rad/sec to 1,000 rad/sec in which the Tan δ maximum value of the present invention is exhibited.

Dispersant

The composition for forming a solar cell electrode according to an embodiment may further include a dispersant.

The dispersant may include an acid-based dispersant. The acid-based dispersant may be a conventional type known to those skilled in the art, but for example, as a saturated or unsaturated acid-based dispersant, a polycarboxylic acid-based dispersant such as a succinic acid-based dispersant or a tri- or more carboxylic acid-based dispersant may be used.

The dispersant may further include an amine salt-based dispersant. The amine salt-based dispersant can use any conventional kind known to those skilled in the art.

The dispersant may be 0.1 wt% to 5 wt% in the composition for forming a solar cell electrode. In the above range, the rate of change of the area of the composition can be lowered, and an increase in the resistance value can be prevented.

Other additives

The composition for forming a solar cell electrode according to the present invention may further include other conventional additives as necessary to improve flow characteristics, process characteristics, and stability in addition to the components described above. Specifically, a plasticizer, a viscosity stabilizer, an antifoaming agent, a pigment, an ultraviolet stabilizer, an antioxidant, and a coupling agent may be used alone or in combination of two or more. These may be included in 0.1% to 5% by weight of the composition for forming a solar cell electrode, but the content may be changed as necessary. The content of the additive may be selected in consideration of printing properties, dispersibility and storage stability of the composition for forming a solar cell electrode.

Solar cell electrode and solar cell including the same

Another embodiment provides an electrode formed from the composition for forming a solar cell electrode.

Another embodiment provides a solar cell including the electrode.

1 shows the structure of a solar cell according to one embodiment.

Referring to FIG. 1, the solar cell 100 forms an electrode 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. It is possible to form the back electrode 21 and the front electrode 23 by printing and firing the composition. For example, after printing and coating the composition for forming a solar cell electrode on the back surface of the wafer, drying may be performed at a temperature of about 200°C to 400°C for about 10 seconds to 60 seconds to perform a preliminary preparation step for the back electrode. In addition, the composition for forming a solar cell electrode may be printed on the front surface of the wafer and then dried to perform a preliminary preparation step for the front electrode. Subsequently, a front electrode and a rear electrode may be formed by performing a firing process of firing at 400°C to 980°C, preferably 700°C to 980°C for about 30 seconds to 210 seconds.

Hereinafter, the configuration and operation of the present invention through embodiments of the present invention will be described in more detail. However, the following examples are intended to help understanding of the present invention, and the scope of the present invention is not limited to the following examples.

Example 1

A mixture was prepared by mixing 90 parts by weight of silver powder and 2 parts by weight of glass frit. To the obtained mixture, 1 part by weight of ethyl cellulose polymer having a weight average molecular weight of 65,000 g/mol was added together with 5.6 parts by weight of texanol as a solvent. To the obtained mixture, at 60° C., 0.35 parts by weight of a polydimethylsiloxane polymer having a weight average molecular weight of 80,000 g/mol, 0.6 parts by weight of a bisamide-based thixotropic agent, and 0.45 parts by weight of a polycarboxylic acid-based dispersant were added, and after mixing, 3 The composition for forming a solar cell electrode was prepared by mixing and dispersing with a roll kneader.

Examples 2 to 7

In Example 1, a composition for forming a solar cell electrode was prepared in the same manner, except that the content and weight parts of each component were changed as shown in Table 1 below.

Comparative Examples 1 to 7

A composition for forming a solar cell electrode was prepared in the same manner as in Example 1, except that the content and weight part of each component were changed as shown in Table 2 below.

The following physical properties were evaluated for the composition for forming a solar cell electrode prepared in Examples and Comparative Examples, and the results are shown in Tables 1 and 2 below.

(1) Storage modulus (unit: KPa, @1,000 rad/sec): For the composition for forming a solar cell electrode, the storage modulus was evaluated using a frequency sweep method using ARES G2 of TA Instruments. The storage modulus was evaluated according to the angular velocity of 0.1 rad/sec to 1,000 rad/sec at 23°C. The storage modulus at each speed of 1,000 rad/sec was obtained.

(2) Tan δ maximum value (Tan delta max): The composition for forming a solar cell electrode was evaluated using a frequency sweep method using ARES G2 of TA Instruments. Tan δ was evaluated according to each frequency of 0.1 rad/sec to 1,000 rad/sec at an angular speed of 23°C, and the maximum tan δ value was obtained therefrom.

(3) The gelation point (angling rate, unit: rad/sec, @max Tan δ), which is the angular velocity at which the maximum Tan δ value appears: The maximum value of Tan δ is the frequency sweep method for the prepared composition for forming a solar cell electrode. The gelation point, which is the angular velocity, was evaluated.

(4) Whether the Tan δ minimum value exceeds 1: When the Tan δ minimum value is 1 or less, the printability characteristics deteriorate. That is, if the minimum value of Tan δ does not exceed 1, printing becomes poor.

(5) Viscosity (Unit: KcPs, @100rpm, @23°C): The prepared composition for solar cell electrode formation was evaluated for viscosity using a Brookfield viscometer at 100 rpm and 23°C.

For the composition for forming a solar cell electrode prepared in Examples and Comparative Examples, physical properties of Tables 1 and 2 below were evaluated when the electrode was formed. The results are shown in Table 1 and Table 2 below.

The composition for forming a solar cell electrode was printed by screen printing in a constant pattern using a 28 µm screen mask on the front surface of a wafer having a sheet resistance of 70 MPa/sq., and dried using an infrared drying furnace. Thereafter, the aluminum paste was completely printed on the back side of the wafer, and then dried in the same manner. Cells formed by the above process were fired for 30 to 50 seconds between 400°C and 900°C using a belt-type kiln. From this, printability, flooding, patternability and aspect ratio were evaluated according to the following criteria.

(6) Printability: The short circuit state of the pattern was confirmed, and the printability was evaluated according to the following criteria.

○: Less than 5 lines shorted

X: 5 or more line paragraphs

(7) Flooding: When the composition for forming a solar cell electrode was coated on a silicon wafer for a solar cell by a screen printing technique, it was evaluated whether flooding was uniform.

○: Uniformly made during 100 floodings

△: Made less than 20% uneven when flooding 100 times

X: When flooding 100 times, 50% or more is not uniform

(8) Patternability: The width of the obtained pattern was observed using a laser microscope.

○: Standard deviation of line width is less than 3 μm, and Rz value is less than 15 μm.

Δ: Standard deviation of line width is 3 µm or more and less than 5 µm, and Rz value is 15 µm or more and less than 20 µm.

×: Standard deviation of line width is 5 µm or more, and Rz value is 20 µm or more

(9) Aspect ratio: The height and width of the obtained pattern were observed using a laser microscope to calculate the aspect ratio (ratio of height to width).

○: Aspect ratio value of 25% or more

△: Aspect ratio value between 20% and 25%

×: aspect ratio value less than 20%

(Unit: parts by weight) Example One 2 3 4 5 6 7 (A) 90 90 90 90 90 90 90 (B) 2 2 2 2 2 2 2 (C) (C1) One - - - - - - (C2) - One - One One One One (C3) - - One - - - - (C4) - - - - - - - (C5) - - - - - - - (D) 5.6 5.6 5.6 5.35 5.35 5.6 5.6 (E) (E1) 0.35 0.35 0.35 0.4 0.4 0.35 0.35 (E2) - - - 0.2 0.2 - - (E3) - - - - - - - (E4) - - - - - - - (E5) - - - - - - - (F) (F1) 0.6 0.6 0.6 0.6 0.6 0.6 - (F2) - - - - - - 0.6 (G) 0.45 0.45 0.45 0.45 0.45 0.45 0.45 Storage modulus 4.1 4.6 4.9 4.6 4.6 4.6 4.3 Tan δ maximum 11.9 12.5 13.4 12.8 12.2 12.5 12.1 Gel point 125.4 125.4 125.4 88.5 88.5 99.6 99.6 Whether the Tan δ minimum value exceeds 1 ○ ○ ○ ○ ○ ○ ○ Viscosity 43 48 51 48 45 48 44 Printability ○ ○ ○ ○ ○ ○ ○ Flooding ○ ○ ○ ○ ○ ○ ○ Pattern ○ ○ ○ ○ ○ ○ ○ Aspect ratio ○ ○ ○ ○ ○ ○ ○

(Unit: parts by weight) Comparative example One 2 3 4 5 6 7 (A) 90 90 90 90 90 90 90 (B) 2 2 2 2 2 2 2 (C) (C1) - - - - - - - (C2) One One One - - One One (C3) - - - - - - - (C4) - - - One - - - (C5) - - - - One - - (D) 5.95 5.95 5.35 5.35 5.35 5.35 5.35 (E) (E1) - 0.5 - 0.5 0.5 - - (E2) - 0.1 - 0.1 0.1 0.1 0.1 (E3) - - 0.6 - - - - (E4) - - - - - 0.5 - (E5) - - - - - - 0.5 (F) (F1) 0.6 - 0.6 0.6 0.6 0.6 0.6 (F2) - - - - - - - (G) 0.45 0.45 0.45 0.45 0.45 0.45 0.45 Storage modulus 4.6 3.8 4.1 3.2 9.6 4.3 4.9 Tan δ maximum 9.5 4.5 7.9 8.4 10.8 8.3 12.4 Gel point 15.8 8.1 23.5 62.8 19.9 40 7.9 Whether the Tan δ minimum value exceeds 1 × ○ × ○ ○ ○ ○ Viscosity 60 44 56 36 80 58 63 Printability × × × × × ○ × Flooding × × △ ○ × ○ × Pattern × × △ △ × △ △ Aspect ratio △ × △ × △ △ △

(A) Silver powder: Average particle size 2.0㎛ (AG-5-11F, Dowa Hightech CO. LTD)

(B) Glass frit: Transition point 270℃, average particle diameter 2.0㎛ (ABT-1, Ashai Glass Co.)

(C) Cellulose polymer

(C1) Ethyl cellulose: weight average molecular weight 65,000 g/mol (Dow chemical)

(C2) Ethyl cellulose: Weight average molecular weight 115,000 g/mol (Dow chemical)

(C3) Ethyl cellulose: weight average molecular weight 130,000 g/mol (Dow chemical)

(C4) Ethyl cellulose: weight average molecular weight 40,000 g/mol (Dow chemical)

(C5) Ethyl cellulose: weight average molecular weight 300,000 g/mol (Dow chemical)

(D) Texanol (Eastman)

(E) silicone polymer

(E1) Polydimethylsiloxane: weight average molecular weight 80,000 g/mol (Shin-Etsu)

(E2) Cyclopentasiloxane (PMX-245, Dow Corning)

(E3) Carbon-based slip agent (120-CWP, Japan Wax)

(E4) Polydimethylsiloxane: weight average molecular weight 2,500 g/mol (Shin-Etsu)

(E5) Polydimethylsiloxane: weight average molecular weight 240,000 g/mol (Shin-Etsu)

(F) thixotropic agent

(F1) Bisamide-based thixotropic agent (BISAMIDE LA, NIPPON KASEI)

(F2) Bisamide-based thixotropic agent (SLIPACKS C, NIPPON KASEI)

(G) Dispersant: Amine salt system (TDO, Akzonovel)

As shown in Table 1 and Table 2, the composition for forming a solar cell electrode according to an embodiment has an angular velocity of greater than 80 rad/sec to a maximum value of Tan δ at 23° C. and 0.1 rad/sec to 1,000 rad/sec. It can be 1,000 rad/sec. Through this, the composition for forming a solar cell electrode according to one embodiment enables fine line width printing to improve printability, patternability, and make flooding uniform.

On the other hand, at 23°C and 0.1 rad/sec to 1000 rad/sec, the compositions according to Comparative Examples 1 to 7 in which the angular velocity at which the Tan δ maximum value appears exceeds 80 rad/sec to 1,000 rad/sec, and the fine line width is printed. It can be seen that printability and patternability are not good and flooding has occurred.

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

Claims (16)

Conductive powder; Glass frit; Cellulose polymers; Silicone polymers; Thixotropic agents; And a solvent, wherein the angular velocity at which the maximum value of Tan δ appears at 23° C. and 0.1 rad/sec to 1,000 rad/sec is greater than 80 rad/sec to 1,000 rad/sec.
According to claim 1,
The composition for forming a solar cell electrode is a composition for forming a solar cell electrode having a maximum value of Tan δ of 11 to 20 at 23° C. and 0.1 rad/sec to 1,000 rad/sec.
According to claim 1,
The composition for forming a solar cell electrode is a composition for forming a solar cell electrode having a storage modulus of 1,000 Pa to 10,000 Pa at 23°C and 1,000 rad/sec.
According to claim 1,
The cellulose polymer is a composition for forming a solar cell electrode having a weight average molecular weight of 50,000 g / mol to 200,000 g / mol.
According to claim 1,
The cellulosic polymer is a composition for forming a solar cell electrode contained in 0.1% to 10% by weight relative to the total amount of the composition for forming the solar cell electrode.
According to claim 1,
The silicone polymer is a composition for forming a solar cell electrode comprising a linear siloxane, a cyclic siloxane or a combination thereof.
The method of claim 6,
The linear siloxane is a composition for forming a solar cell electrode having a weight average molecular weight of 3,000 g/mol to 200,000 g/mol.
According to claim 1,
The silicone polymer is a composition for forming a solar cell electrode contained in an amount of 0.1 to 5% by weight relative to the total amount of the composition for forming the solar cell electrode.
According to claim 1,
The thixotropic agent composition for forming a solar cell electrode comprising a bisamide-based thixotropic agent.
According to claim 1,
The composition for forming a solar cell electrode
60 to 95% by weight of the conductive powder;
0.5 to 20% by weight of the glass frit;
0.1% to 10% by weight of the cellulose polymer;
0.1% to 5% by weight of the silicone polymer;
0.1 to 5% by weight of the thixotropic agent; And
Residual amount of the solvent
Composition for forming a solar cell electrode comprising a.
According to 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 one or more metal elements selected from aluminum (Al).
According to claim 1,
The solvent is methyl cellosolve, methyl cellosolve, butyl cellosolve, aliphatic alcohol, α-terpineol, β-terpineol, Dihydro-terpineol, selected from ethylene glycol, ethylene glycol mono butyl ether, butyl cellosolve acetate and texanol A composition for forming a solar cell electrode comprising at least one.
According to claim 1,
The composition for forming a solar cell electrode further comprises a dispersing agent, and the dispersing agent comprises 0.1 to 5% by weight based on the total amount of the composition for forming a solar cell electrode.
According to claim 1,
The composition for forming a solar cell electrode further comprises one or more additives selected from plasticizers, viscosity stabilizers, antifoaming agents, pigments, ultraviolet stabilizers, antioxidants, and coupling agents.
An electrode formed of the composition for forming a solar cell electrode according to any one of claims 1 to 14.
A solar cell comprising the electrode according to claim 15.

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