KR20200040626A - Method for forming solar cell electrode, solar cell electrode manufactured therefrom and solar cell - Google Patents

Abstract

Provided are a method for forming a solar cell electrode with excellent conversion efficiency, a solar cell electrode manufacture therefrom, and a solar cell including the solar cell electrode. The method for forming the solar cell electrode comprises the steps of: forming a first finger electrode pattern by applying a composition for electrode formation containing conductive powder, first glass frits, and organic vehicles; forming a second finger electrode pattern and a bus electrode pattern by applying a second composition for electrode formation containing conductive powder, second glass frits containing 1 to 20 mole percent of manganese (Mn) element, and organic vehicles; and sintering the compositions for electrode formation.

Description

A method for forming a solar cell electrode, a solar cell electrode and a solar cell manufactured therefrom. METHOD FOR FORMING SOLAR CELL ELECTRODE, SOLAR CELL ELECTRODE MANUFACTURED THEREFROM AND SOLAR CELL

A method for forming a solar cell electrode, and a solar cell electrode and solar cell prepared therefrom.

The silicon-based solar cell is composed 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 enters a solar cell having such a structure, electrons are generated as a plurality of carriers in an emitter layer made of an n-type silicon semiconductor by photovoltaic effect, and holes are generated as a plurality of carriers in a substrate made of a p-type silicon semiconductor. do. Electrons and electrons generated by the photovoltaic effect move to the front electrode and the rear electrode bonded to the top and bottom of the emitter layer, respectively, and current flows when these electrodes are connected by wires. The solar cell electrode may be formed on the substrate surface by application, patterning, and firing of the composition for forming a solar cell electrode.

As a composition for forming an electrode for a solar cell, a conductive paste containing a conductive powder, a glass frit, an organic vehicle, etc. is used. Among them, the glass frit dissolves an antireflection film formed on the semiconductor substrate so that the conductive powder is electrically connected to the semiconductor substrate. Make contact. In particular, the reactivity of the glass frit with the anti-reflection film affects the electrical characteristics of the solar cell such as the series resistance (Rs) and the open voltage (Voc) of the formed electrode, so the fill factor and conversion efficiency of the solar cell may vary accordingly. have.

On the other hand, the solar cell electrode includes a finger electrode and a bus electrode, and the bus electrode is attached to the ribbon during the process of soldering during the modularization process after manufacturing the solar cell. Therefore, the bus electrode must have high adhesion to the ribbon.

It is an object of the present invention to provide a method for forming a solar cell electrode having excellent adhesion to a ribbon and implementing an improved open voltage, which has excellent conversion efficiency, and a solar cell electrode and a solar cell manufactured therefrom.

According to one aspect, a first finger electrode pattern is formed by applying a composition for forming a first electrode including a conductive powder, a first glass frit, and an organic vehicle, and a conductive powder, 1 to 20 mol% of manganese (Mn) element A method of forming a solar cell electrode, comprising forming a second finger electrode pattern and a bus electrode pattern by applying a composition for forming a second electrode including a second glass frit and an organic vehicle, and firing.

The first glass frit may contain no manganese (Mn) element.

The second glass frit may further include lead (Pb), bismuth (Bi), and tellurium (Te) elements.

The second glass frit further includes lead (Pb), bismuth (Bi), and tellurium (Te) elements, and lead (Pb) and bismuth (Bi) elements are contained in the second glass frit by 20 to 50 mol%. It is included in a total amount, and may contain 30 to 60 mol% of the tellurium (Te) element in the second glass frit.

The composition for forming the first electrode may include 60 to 95% by weight of the conductive powder, 0.1 to 20% by weight of the first glass frit, and 1 to 30% by weight of the organic vehicle.

The composition for forming the second electrode may include 60 to 95% by weight of the conductive powder, 0.1 to 20% by weight of the second glass frit, and 1 to 30% by weight of the organic vehicle.

According to another aspect, a solar cell electrode manufactured according to the above-described method for forming a solar cell electrode is provided.

According to another aspect, a solar cell including a solar cell electrode manufactured according to the above-described method for forming a solar cell electrode is provided.

The electrode produced by the method for forming a solar cell electrode of the present invention has excellent adhesion to a ribbon, and the solar cell including the electrode has an effect of excellent conversion efficiency.

1 schematically shows a structure of a solar cell according to an embodiment of the present invention.

In the present specification, a singular expression includes a plural expression unless the context clearly indicates otherwise.

Terms such as include or have in the present specification mean that a feature or component described in the specification exists, and does not exclude the possibility of adding one or more other features or components in advance.

Terms such as first and second used in the present specification may be used to describe various components, but the components should not be limited by terms. The terms are used only to distinguish one component from other components.

Hereinafter, a method of forming a solar cell electrode will be described in more detail.

Preparation of compositions for forming first and second electrodes

The composition for forming a first electrode may be prepared by mixing a conductive powder, a first glass frit, and an organic vehicle, and the composition for forming a second electrode may be prepared by mixing a conductive powder, a second glass frit, and an organic vehicle.

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 various shapes of particles may be used, for example, spherical, plate-shaped, or amorphous-shaped particles.

The conductive powder may be a nano- or micro-sized particle 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, it is also possible to use a conductive powder by mixing two or more different conductive powders.

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, 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 ultrasonically dispersing the conductive powder in isopropyl alcohol (IPA) for 3 minutes at 25 ° C.

The amount of the conductive powder is not particularly limited, for example, the conductive powder is 60 to 95% by weight, for example 70 to 90% by weight, of the total composition of the first solar cell electrode forming composition or the second solar cell electrode forming composition. It can be included as In the above range, the conversion efficiency of the solar cell is excellent, and paste can be smoothly made.

First glass frit and second glass frit

The first glass frit and the second glass frit are 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 first glass frit and the second glass frit improve the adhesion between the conductive powder and the wafer and soften during sintering to induce an effect of lowering the firing temperature.

The composition for forming a first electrode includes a first glass frit.

The first glass frit may be the same as or different from the second glass frit included in the composition for forming the second electrode.

For example, the first glass frit may or may not contain a manganese (Mn) element.

According to one embodiment, the first glass frit may contain no manganese (Mn) element. In this case, the contact resistance may be lowered, so that the conversion efficiency of the solar cell may be excellent.

The first glass frit may be, for example, a lead-bismuth-tellurium-oxide (Pb-Bi-Te-O) -based glass frit containing elements of lead (Pb), bismuth (Bi), and tellurium (Te). have. By using a glass frit containing lead (Pb), bismuth (Bi) and tellurium (Te) elements, it may be effective to realize excellent conversion efficiency at a wider range of firing temperatures.

The total amount of lead (Pb) and bismuth (Bi) elements in the first glass frit may be 20 to 50 mol%, for example, 30 to 50 mol%. It may be effective to realize excellent series resistance at a firing temperature in a wider range in the above range.

The first glass frit may contain 30 to 60 mol% of the tellurium (Te) element, for example 30 to 50 mol% or 30 to 47 mol%. A more uniform glass frit can be produced in the above range.

The first glass frit may further include other metal elements in addition to lead (Pb), bismuth (Bi), and tellurium (Te). For example, the first glass frit is 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) and may further include one or more of manganese (Mn).

According to one embodiment, the first glass frit may include a lead-bismuth-tellurium-lithium-oxide (Pb-Bi-Te-Li-O) -based glass frit. According to another embodiment, the first glass frit may include, but is not limited to, a lead-bismuth-tellurium-lithium-silicon-oxide (Pb-Bi-Te-Li-Si-O) -based glass frit. .

The first glass frit may include 0.1 to 20% by weight, for example, 0.5 to 10% by weight of the total weight of the composition for forming the first solar cell electrode. It may be effective to improve the efficiency of the solar cell by implementing excellent open voltage and series resistance in the above range.

The composition for forming a second solar cell electrode includes a second glass frit containing 1 to 20 mol% of manganese (Mn) elements. When the second glass frit includes the manganese (Mn) element in the above range, the solar cell efficiency can be improved by minimizing the loss of the open voltage, and the adhesion to the ribbon may be excellent.

For example, the lower limit of the manganese (Mn) element content included in the second glass frit is selected from 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 mol%, and the second glass frit The upper limit of the manganese (Mn) element content to be included may be selected from 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 and 10 mol%. For another example, the second glass frit may contain more than 1, 2, 3, 4, 5, 6, 7, 8 or 9 mol% of manganese (Mn) elements to 20, 19, 18, 17, 16, 15, 14 , 13, 12 or 11 mol%.

The second glass frit is, for example, manganese-lead-bismuth-tellurium-oxide (Mn-Pb-Bi-) containing elements of manganese (Mn), lead (Pb), bismuth (Bi) and tellurium (Te). Te-O) may be a glass frit. By using a glass frit containing manganese (Mn), lead (Pb), bismuth (Bi), and tellurium (Te) elements, it improves solar cell efficiency by implementing excellent open voltage and series resistance at a wider range of firing temperatures. It may be effective.

The total amount of lead (Pb) and bismuth (Bi) elements in the second glass frit may be 20 to 50 mol%, for example, 30 to 50 mol%. It may be effective to realize excellent series resistance at a firing temperature in a wider range in the above range.

The second glass frit may contain 30 to 60 mol% of tellurium (Te) elements, for example, 30 to 50 mol% or 30 or 47 mol%. A more uniform glass frit can be produced in the above range.

The second glass frit may further include other metal elements in addition to manganese (Mn), lead (Pb), bismuth (Bi), and tellurium (Te). For example, the second glass frit is 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), and may further include one or more of zirconium (Zr).

According to one embodiment, the second glass frit may include a manganese-lead-bismuth-tellurium-lithium-oxide (Mn-Pb-Bi-Te-Li-O) -based glass frit. According to another embodiment, the second glass frit may include manganese-lead-bismuth-tellurium-lithium-silicon-oxide (Mn-Pb-Bi-Te-Li-Si-O) based glass frit, It is not limited.

The second glass frit may include 0.1 to 20% by weight, for example, 0.5 to 10% by weight of the total weight of the composition for forming the second solar cell electrode. It may be effective to improve the efficiency of the solar cell by implementing excellent open voltage and series resistance in the above range.

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

The first glass frit and the second glass frit can be made from the metals and / or metal oxides described above using conventional methods. For example, after mixing the aforementioned metal and / or metal oxide using a ball mill or a planetary mill, the mixed composition is melted at 800 to 1,300 ° C., and 25 ° C. After quenching in, the obtained product can be obtained by pulverizing with a disk mill, planetary mill, or the like.

Organic vehicle

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

As the organic vehicle, an organic vehicle 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 or cellulose-based resin may be used. According to one embodiment, ethyl cellulose may be used as the binder resin. According to another embodiment, ethyl hydroxyethyl cellulose, nitrocellulose, a mixture of ethyl cellulose and phenolic resin as a binder resin, alkyd resin, phenolic resin, acrylic ester-based resin, xylene-based resin, polybutene-based resin, polyester-based Resin, urea-based resin, melamine-based resin, vinyl acetate-based resin, wood rosin or alcohol polymethacrylate 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) or the like may be used alone or in combination.

The amount of the organic vehicle is not particularly limited, for example, the organic vehicle is 1 to 30% by weight, for example 3 to 25% by weight of the total composition of the composition for forming the first solar cell electrode or the composition for forming the second solar cell electrode It can be included as In the above range, sufficient adhesive strength and excellent printability can be secured.

additive

The composition for forming the first solar cell electrode or the composition for forming the second solar cell electrode is a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, an antifoaming agent, as necessary, in order to improve flow characteristics, process characteristics, and stability, in addition to the components described above, respectively. Pigments, ultraviolet stabilizers, antioxidants, coupling agents, etc. may be included alone or in combination of 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 the first solar cell electrode or the composition for forming the second solar cell electrode, but the content may be changed as necessary.

Preparation of solar cell electrodes

The composition for forming the first electrode is applied to a surface of the substrate in a predetermined pattern and then dried to form a first finger electrode pattern.

Thereafter, the composition for forming the second electrode is coated on a substrate on which the first finger electrode pattern is formed, followed by drying to form a pattern of the second finger electrode pattern and the bus electrode.

For the application of the composition for forming the first solar cell electrode and the composition for forming the second electrode, for example, a method such as a screen printing method, a gravure offset method, a rotary screen printing method, a lift-off method, etc. may be used. no.

The drying of the composition for forming the first solar cell electrode and the composition for forming the second electrode may be performed, for example, at about 200 to 400 ° C. for about 10 to 60 seconds, but is not limited thereto.

Thereafter, an electrode pattern formed from the composition for forming a first solar cell electrode and the composition for forming a second electrode is fired to form a solar cell electrode. The firing process may be performed, for example, at about 400 to 980 ° C (eg, about 600 to 900 ° C) for about 60 to 210 seconds, but is not limited thereto.

According to another aspect, a solar cell electrode manufactured by the solar cell electrode forming method, and a solar cell including the solar cell electrode are provided.

1 schematically shows a 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 back electrode 21 and the front electrode 23. For example, after printing the composition for forming the first solar cell electrode on the front surface of the wafer and drying it to form a first finger electrode pattern, after printing the composition for forming the second solar cell electrode and drying the second finger electrode The pattern and the bus electrode pattern may be formed to perform a preliminary preparation step for the front electrode. In addition, after printing the aluminum paste on the back side of the wafer, it can be dried at about 200 to 400 ° C. for about 10 to 60 seconds to perform a preliminary preparation step for the back electrode. Thereafter, a firing process is performed at about 400 to 950 ° C, for example, about 600 to 900 ° C for about 30 to 210 seconds to form a front electrode and a rear electrode.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, this is presented as a preferred example of the present invention, and in no sense can be interpreted as limiting the present invention.

Example

Preparation Example 1

After sufficiently dissolving 3% by weight of ethyl cellulose as a binder resin (Dow Chemical, STD4) and 6.5% by weight as a solvent, butyl carbitol (Samjeon Chemical Co., Ltd.) at 60 ° C, as a conductive powder, an average particle diameter of 2.0㎛ Silver powder (Dowa Hightech, AG-4-8) 86.9% by weight, glass frit A of Table 1 below 3.1% by weight, dispersant (BYK Chemie, BYK102) 0.2% by weight and thixotropic agent (Elementis, Thixatrol ST) The composition for forming a solar cell electrode was prepared by uniformly mixing 0.3% by weight and mixing and dispersing with a 3-roll kneader.

Preparation Examples 2 to 14

A composition for forming a solar cell electrode was prepared using the same method as in Production Example 1, except that instead of the glass frit A in Production Examples 2 to 14, glass frits B to N in Table 1 below were used.

When preparing the composition
Used glass frit MnO ₂ PbO Bi ₂ O ₃ TeO ₂ Li ₂ CO ₃ ZnO MgO Total Preparation Example 1 Glass frit A One 19 30 45 5 - - 100 Preparation Example 2 Glass frit B 5 15 30 45 5 - - 100 Preparation Example 3 Glass frit C 10 10 30 45 5 - - 100 Preparation Example 4 Glass frit D 20 10 25 40 5 - - 100 Preparation Example 5 Glass frit E 15 15 20 45 5 - - 100 Preparation Example 6 Glass frit F 7 18 25 45 5 - - 100 Preparation Example 7 Glass frit G 3 20 25 47 5 - - 100 Preparation Example 8 Glass frit H 17 13 25 40 5 - - 100 Preparation Example 9 Glass frit I - 15 30 45 5 - 5 100 Preparation Example 10 Glass frit J - 10 30 50 5 5 - 100 Preparation Example 11 Glass frit K - 15 30 50 5 - - 100 Preparation Example 12 Glass frit L - 10 30 45 5 5 5 100 Preparation Example 13 Glass frit M 25 10 20 40 5 - - 100 Preparation Example 14 Glass frit N 30 10 20 35 5 - - 100

(Unit: mol%)

Example 1

Wafer (textured on the front surface of a p-type wafer doped with boron, then formed an n ⁺ layer with POCl ₃ and a silicon nitride (SiNx: H) formed thereon as an anti-reflective film. The screen for printing the electrode forming composition according to Preparation Example 12 (using glass frit L) on the front side of) was dried at 250 ° C. for 45 seconds using an infrared drying furnace to form a first finger electrode pattern. After screen-printing the composition for electrode formation according to Preparation Example 1 (using glass frit A) on the dried first finger electrode pattern, dry it at 200 ° C. for 45 seconds using an infrared drying furnace to obtain a second finger electrode pattern and a bus electrode pattern. Formed. Thereafter, an aluminum paste was printed on the back side of the wafer and then dried at 300 ° C. for 45 seconds using an infrared drying furnace. The cells formed by the above process were baked at 600 to 900 ° C. for 60 to 210 seconds using a belt-type kiln to prepare solar cell cells.

Examples 2 to 8 and Comparative Examples 1 to 6

When forming the second finger electrode pattern and the bus electrode pattern, a solar cell was prepared using the same method as in Example 1, except that the electrode forming compositions according to Preparation Examples 2 to 14 were used, respectively.

Evaluation Example 1: Adhesion measurement

Flux (Flux, Kester Co., 952S) was applied on the bus electrode pattern of the solar cell prepared in Examples 1 to 8 and Comparative Examples 1 to 6, and ribbon (62Sn / 36Pb / 2Ag, thickness 0.18mm, width 1.5) mm) is adhered at a temperature of 360 ° C using an iron, and the end of the ribbon is fixed at an angle of 180 degrees using a tester (Tinius Olsen, Mocel H5K-T), and the value is measured by pulling at a speed of 50 mm / min. And the results are shown in Table 2 below.

Evaluation Example 2: Electrical properties

For the solar cell produced in Examples 1 to 8 and Comparative Examples 1 to 6, using an open cell efficiency measuring equipment (Fortix tech, Halm), open voltage (Voc, unit: mV) and conversion efficiency (Eff., Unit:%) was measured, and the results are shown in Table 2 below.

Composition used when forming the second finger electrode pattern and the bus electrode pattern Adhesion (N / mm) Voc (mV) Eff. (%) Example 1 Composition of Preparation Example 1 2.82 637.8 19.72 Example 2 Composition of Preparation Example 2 3.65 638.2 19.76 Example 3 Composition of Preparation Example 3 4.70 638.8 19.79 Example 4 Composition of Preparation Example 4 2.30 639.9 19.86 Example 5 Composition of Preparation Example 5 3.9 639.1 19.80 Example 6 Composition of Preparation Example 6 3.84 638.3 19.79 Example 7 Composition of Preparation Example 7 3.34 638.1 19.77 Example 8 Composition of Preparation Example 8 3.36 639.3 19.88 Comparative Example 1 Composition of Preparation Example 9 2.23 637.7 19.70 Comparative Example 2 Composition of Preparation Example 10 1.42 636.8 19.65 Comparative Example 3 Composition of Preparation Example 11 1.54 637.2 19.67 Comparative Example 4 Composition of Preparation Example 12 1.76 637.1 19.68 Comparative Example 5 Composition of Preparation Example 13 1.02 636.0 19.62 Comparative Example 6 Composition of Preparation Example 14 0.68 625.7 19.32

As can be seen through Table 2, the solar cells according to Examples 1 to 8 showed better values of electrical characteristics (open voltage, conversion efficiency) than the solar cells of Comparative Examples 1 to 6, and also showed adhesive strength. You can see that it is excellent.

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 (8)

A first finger electrode pattern is formed by applying a composition for forming a first electrode including a conductive powder, a first glass frit, and an organic vehicle,
A second finger electrode pattern and a bus electrode pattern are formed by applying a composition for forming a second electrode including a conductive powder, a second glass frit containing 1 to 20 mol% of manganese (Mn) elements, and an organic vehicle,
A method of forming a solar cell electrode comprising the step of firing.
According to claim 1,
The first glass frit is a method of forming a solar cell electrode containing no manganese (Mn) element.
According to claim 1,
The second glass frit further comprises a lead (Pb), bismuth (Bi), and tellurium (Te) element solar cell electrode forming method.
According to claim 3,
The second glass frit includes a lead (Pb) and bismuth (Bi) elements in a total amount of 20 to 50 mol%, and a method for forming a solar cell electrode comprising 30 to 60 mol% of tellurium (Te) elements.
According to claim 1,
The composition for forming the first electrode comprises 60 to 95% by weight of the conductive powder, 0.1 to 20% by weight of the first glass frit, and 1 to 30% by weight of the organic vehicle.
According to claim 1,
The composition for forming the second electrode comprises 60 to 95% by weight of the conductive powder, 0.1 to 20% by weight of the second glass frit, and 1 to 30% by weight of the organic vehicle.
A solar cell electrode manufactured according to the method for forming a solar cell electrode according to any one of claims 1 to 6.
A solar cell comprising the solar cell electrode of claim 7.

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