KR101293207B1 - Sheet for adhering paste and Solar cell using the same - Google Patents

Abstract

The present invention relates to a paste adhesive sheet and a solar cell using the same. More specifically, the present invention, two release film facing each other; And an aluminum paste adhesive sheet interposed between the two release films, the aluminum paste adhesive composition layer including an aluminum powder, glass frit powder, an organic binder, and an adhesive. The aluminum paste adhesive sheet of the present invention is useful for making the solar cell rear electrode more easily and uniformly formed.

Description

Paste adhesive sheet and solar cell using same {Sheet for adhering paste and Solar cell using the same}

The present invention relates to a paste adhesive sheet and a solar cell using the same, and more particularly, to an aluminum paste adhesive sheet used to form a back electrode of a solar cell and a solar cell using the same.

Recently, as energy resources such as oil and coal are expected to be depleted, interest in alternative energy to replace them is increasing. Among them, solar cells are attracting particular attention because of their abundant energy resources and environmental pollution problems.

Solar cells are classified into solar cells that generate steam required to rotate turbines using solar heat, and solar cells that convert photons into electrical energy using the properties of semiconductors. It refers to a solar cell (hereinafter referred to as a solar cell).

Solar cells are divided into silicon solar cell, compound semiconductor solar cell and tandem solar cell according to raw materials. Of these three types of solar cells, silicon solar cells are the mainstream in the solar cell market.

1 is a cross-sectional view showing a basic structure of a silicon solar cell. Referring to the drawings, a silicon solar cell includes a substrate 101 made of a p-type silicon semiconductor and an emitter layer 102 made of an n-type silicon semiconductor, and a diode 101 is formed at the interface between the substrate 101 and the emitter layer 102. [ A pn junction is formed.

When sunlight is incident on a solar cell having the above structure, electrons and holes are generated in a silicon semiconductor doped with impurities by a photovoltaic effect. For reference, electrons are generated in a majority carrier in the emitter layer 102 made of an n-type silicon semiconductor, and holes are generated in a majority carrier in the substrate 101 made of a p-type silicon semiconductor. Electrons and electrons generated by the photovoltaic effect are attracted toward the n-type silicon semiconductor and the p-type silicon semiconductor, respectively, and are electrically connected to the front and back electrodes 103 and 104 bonded to the bottom of the substrate 101 and the top of the emitter layer 102, When the electrodes 103 and 104 are connected by a wire, a current flows.

Typically, an aluminum paste composition is used to form the back electrode 104. The back electrode 104 forms an aluminum layer so that aluminum is diffused onto the wafer to form a p + layer from the aluminum-silicon alloy layer. This is called a back surface field (BSF) layer, which plays an important role in improving the efficiency of solar cells.

As a method of applying the aluminum paste composition used for forming the back electrode 104 on the wafer substrate, a screen printing method is usually used. In the screen printing method, a screen mask on which discharge holes are formed is placed on a wafer substrate, a paste is coated on the screen mask, and then a paste is printed on the substrate by pushing the paste into the discharge holes of the screen mask with a squeegee.

However, the pressure applied by the squeegee to discharge the paste causes a difference between the center portion and the outer portion of the mask. This pressure difference causes a problem that the amount of the aluminum paste composition printed on the wafer is different from each other at the center and the outer portion of the substrate.

In order to solve this problem, a more sophisticated screen printer operation is required in the screen printing method, but there is a problem that productivity is lowered and the limitation of the screen printing method still exists.

Accordingly, an object of the present invention is to provide an aluminum paste adhesive sheet capable of applying the aluminum paste composition to a wafer substrate more easily and uniformly.

In addition, the problem to be solved by the present invention is to provide a method for forming a back electrode of a solar cell having excellent productivity using the aluminum paste adhesive sheet and a solar cell manufactured therefrom.

In order to solve the above problems, the present invention, two release film facing each other; And an aluminum paste adhesive sheet interposed between the two release films, the aluminum paste adhesive composition layer including an aluminum powder, glass frit powder, an organic binder, and an adhesive.

In the present invention, the pressure-sensitive adhesive may include, for example, acrylic resins, silicone resins, rubber resins, urethane resins, polyester resins, epoxy resins, or the like, alone or in combination of two or more thereof.

In the present invention, the pressure-sensitive adhesive may be added in various amounts as necessary, for example, may have a content of 100 to 900 parts by weight relative to 100 parts by weight of aluminum powder, but is not limited thereto.

In order to solve the above problems, the present invention also comprises the steps of preparing a pressure-sensitive adhesive solution containing (S1) pressure-sensitive adhesive; (S2) adding and mixing aluminum powder, glass frit powder, and an organic binder to the adhesive solution; And (S3) applying the mixture to the first release film and then laminating a second release film thereon, to provide a method of manufacturing an aluminum paste adhesive sheet.

In order to solve the above problems, the present invention also, (S1) removing the first release film of the aluminum paste adhesive sheet of claim 1; (S2) attaching the aluminum paste adhesive sheet from which the first release film is removed to the back surface of the silicon substrate such that the exposed aluminum paste adhesive composition layer contacts the back surface of the silicon semiconductor substrate; And (S3) removing the second release film of the aluminum paste adhesive sheet attached to the back surface of the silicon substrate, and then performing heat treatment.

Through the aluminum paste adhesive sheet of the present invention, the aluminum paste can be easily and uniformly applied to the wafer substrate.

In addition, the aluminum paste adhesive sheet of the present invention, because the aluminum paste is present in the form of a sheet, it is very easy to store, transport and management.

In addition, the back electrode forming method of the solar cell using the aluminum paste adhesive sheet of the present invention does not require a cleaning operation performed in the screen printing process.

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

2 schematically shows an embodiment of an aluminum paste adhesive sheet 10 according to the present invention. It should be noted, however, that the embodiments shown in the following description and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It should be understood that various equivalents and modifications may be present.

The aluminum paste adhesive sheet 10 of the present invention includes an aluminum paste adhesive composition 12 interposed between two release films 11 facing each other and the two release films 11.

As described above, the aluminum paste composition printed on the wafer substrate by the conventional screen printing method was a very difficult task to apply a uniform amount on the wafer substrate, which becomes more serious when applied in large areas.

However, since the aluminum paste adhesive sheet 10 of the present invention includes an aluminum paste composition layer uniformly formed in advance, the aluminum paste composition may be uniformly applied to the wafer substrate by attaching it on the wafer substrate. Let's do it. Further, since the application of the aluminum paste composition to the substrate is simply performed by the attachment of the sheet, even if the area of the wafer is large, only the size of the sheet can be adjusted to easily and uniformly apply. In addition, since the aluminum paste composition used to form the back electrode can be stored in the form of a sheet, it is easy to manage and transport.

The aluminum paste adhesive composition layer 12 according to the present invention further includes an adhesive in order to secure adhesiveness with the wafer substrate in addition to the aluminum powder, glass frit powder, and the organic binder, which are conventionally included in the aluminum paste composition.

In the present invention, a pressure-sensitive adhesive may be used alone or a mixture of the above-mentioned resin and a suitable solvent as the pressure-sensitive adhesive. Examples of the adhesive resin include acrylic resins, silicone resins, rubber resins, urethane resins, polyester resins, epoxy resins, and the like, but are not limited thereto.

In the present invention, when the acrylic resin is used, the acrylic resin may be, for example, an acrylic copolymer made of a (meth) acrylic acid ester monomer and a crosslinkable functional group-containing monomer.

The kind of the (meth) acrylic acid ester monomer is not particularly limited, and for example, alkyl (meth) acrylate can be used. At this time, when the alkyl group contained in the monomer is too long, the cohesive force of the pressure-sensitive adhesive may be lowered, and the glass transition temperature and the adhesiveness may become difficult to control. Therefore, the alkyl group having 1 to 14, preferably 2 to 8 carbon atoms It is preferable to use the (meth) acrylic acid ester system monomer which has. Examples of such monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, t-butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl ( Meta) acrylate, 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, etc. Can be used individually or in mixture of 2 or more types, respectively.

The (meth) acrylic acid ester monomer as described above is preferably included in an amount of 90 parts by weight to 99.9 parts by weight based on 100 parts by weight of the total copolymer. If the content is less than 90 parts by weight, there is a risk that the initial adhesive strength of the pressure-sensitive adhesive may be lowered, and if it exceeds 99.9 parts by weight, there is a fear that a problem of cohesion decreases.

The crosslinkable functional group-containing monomer is provided with a crosslinkable functional group in the acrylic copolymer to provide a crosslinking point for the reaction with the multifunctional crosslinking agent described later. As an example of the crosslinkable functional group containing monomer which can be used by this invention, a hydroxyl group containing monomer, a carboxyl group containing monomer, a nitrogen containing monomer, etc. can be used individually or in mixture of 2 or more types, respectively. Examples of the hydroxy group-containing monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acryl Latex, 8-hydroxyoctyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, 2-hydroxypropylene glycol (meth) acrylate, and the like; Examples of the carboxyl group-containing monomers include acrylic acid, methacrylic acid, 2- (meth) acryloyloxy acetic acid, 3- (meth) acryloyloxy propyl acid, 4- (meth) acryloyloxy butyl acid and acrylic acid Dimers, itaconic acid, maleic acid, maleic anhydride and the like; Examples of nitrogen-containing monomers include 2-isocyanatoethyl (meth) acrylate, 3-isocyanatopropyl (meth) acrylate, 4-isocyanatobutyl (meth) acrylate, and (meth) acrylic Amides, N-vinyl pyrrolidone, N-vinyl caprolactam, and the like, but are not limited thereto.

In the present invention, the crosslinkable functional group-containing monomer as described above is preferably included in an amount of 0.1 parts by weight to 10 parts by weight based on 100 parts by weight of the total acrylic copolymer. If the content is less than 0.1 parts by weight may cause a problem that the cohesive force is lowered, if more than 10 parts by weight there is a possibility that the compatibility is lowered, the surface migration occurs or the problem that the adhesive properties are lowered due to the reduction of flow characteristics.

Optionally, the acrylic copolymer according to the present invention may further comprise any comonomer in view of the control of the glass transition temperature and the provision of other functionalities. The type of comonomer which can be used is a monomer containing a copolymerizable vinyl group, and is not particularly limited as long as the glass transition temperature is -130 ° C to 50 ° C in the non-crosslinked state. Examples of such comonomers include monomers represented by the following formula (1).

In Formula 1,

R ₁ to R ₃ each independently represent hydrogen or alkyl;

R ₄ represents cyano, alkyl substituted or unsubstituted phenyl, acetyloxy, or COR ₅ , wherein R ₅ represents amino or glycidyloxy unsubstituted or substituted with alkyl or alkoxyalkyl.

Alkyl or alkoxy in the definition of R ₁ to R ₅ of Formula 1 means alkyl or alkoxy having 1 to 8 carbon atoms, preferably methyl, ethyl, methoxy, ethoxy, propoxy or butoxy.

Specific examples of the monomer that can be represented by Formula 1 include nitrogen-containing monomers such as (meth) acrylonitrile, (meth) acrylamide, N-methyl (meth) acrylamide or N-butoxymethyl (meth) acrylamide. ; Styrene-based monomers such as styrene or methylstyrene; Glycidyl (meth) acrylate; Or carboxylic acid vinyl esters such as vinyl acetate, but are not limited thereto. When the functional monomer as described above is included in the acrylic copolymer of the present invention, the content is preferably 20 parts by weight or less based on 100 parts by weight of the total copolymer. When the content exceeds 20 parts by weight, there is a fear that the flexibility and / or peeling force of the pressure-sensitive adhesive composition is lowered.

The method for producing the acrylic copolymer containing each of the above components is not particularly limited, and for example, it can be prepared through a general polymerization method such as solution polymerization, photopolymerization, bulk polymerization, suspension polymerization, emulsion polymerization. In the present invention, it is particularly preferable to use a solution polymerization method, and solution polymerization is preferably performed at a polymerization temperature of 50 ° C to 140 ° C by mixing an initiator in a state where each monomer is uniformly mixed. Initiators which can be used at this time include azo polymerization initiators such as azobis isobutyronitrile or azobiscyclohexane carbonitrile; And / or conventional initiators such as peroxides such as benzoyl peroxide or acetyl peroxide.

The type of crosslinking agent that can be used in the present invention is not particularly limited, and for example, a general crosslinking agent such as an isocyanate compound, an epoxy compound, an aziridine compound, or a metal chelate compound may be used.

In the crosslinking agent, examples of the isocyanate compound include tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoform diisocyanate, tetramethylxylene diisocyanate, naphthalene diisocyanate and double At least one selected from the group consisting of reactants with any one polyol (eg, trimethylol propane); Examples of epoxy compounds include ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N, N, N ', N'-tetraglycidyl ethylenediamine and glycerin diglycidyl ether. At least one selected from the group consisting of, Examples of the aziridine-based compound is N, N'-toluene-2,4-bis (1-aziridinecarboxamide), N, N'-dimethylmethane-4, At least one selected from the group consisting of 4'-bis (1-aziridinecarboxamide), triethylene melamine, bisisoprotaloyl-1- (2-methylaziridine) and tri-1-aziridinylphosphineoxide One may be mentioned. In addition, examples of the metal chelate-based compound may be a compound in which a polyvalent metal such as aluminum, iron, zinc, tin, titanium, antimony, magnesium, and / or vanadium is coordinated with acetyl acetone, ethyl acetoacetate, or the like. It is not limited.

The multifunctional crosslinking agent is preferably included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the adhesive resin. If the content is less than 0.01 parts by weight, the crosslinking reaction may not proceed well, and the cohesive force of the pressure-sensitive adhesive may be reduced. If the content is more than 10 parts by weight, the crosslinking reaction may proceed excessively and the adhesive properties may be lowered.

Optionally, the pressure-sensitive adhesive of the present invention, at least one selected from the group consisting of silane coupling agent, ultraviolet stabilizer, antioxidant, colorant, reinforcing agent, filler, antifoaming agent, surfactant and plasticizer in the range that does not affect the effect of the present invention It may further comprise an additive of.

The pressure-sensitive adhesive may be added in various amounts as needed, for example, may have a content of 100 to 900 parts by weight relative to 100 parts by weight of aluminum powder, but is not limited thereto. If the content is less than 100 parts by weight, it is difficult to adhere to the wafer substrate due to the poor adhesion, and if it is more than 900 parts by weight, the content of aluminum powder is relatively reduced, so that an excessive amount of paste composition should be used to form an aluminum layer having an appropriate thickness.

The aluminum powder included in the aluminum paste adhesive composition 12 of the present invention may be adopted without limitation, which is commonly used in the aluminum paste composition. For example, the particles of the aluminum powder may have an average particle diameter of 2 to 7 ㎛. In addition, the content of the aluminum powder is preferably 60 to 80 parts by weight based on 100 parts by weight of the total composition.

Glass frit powder that can be used in the present invention may be used without limitation the glass frit used in the art. Examples of such glass frit powders may include lead oxides and / or bismuth oxides. Specifically, SiO ₂ -PbO system, SiO ₂ -PbO-B ₂ O ₃ system, Bi ₂ O ₃ -B ₂ O ₃ -SiO ₂ system, or PbO-Bi ₂ O ₃ -B ₂ O ₃ -SiO ₂ system Powders and the like may be used alone or in combination of two or more, but is not limited thereto. The content of the glass frit powder is preferably 1 to 5 parts by weight based on 100 parts by weight of the total composition.

The aluminum powder, glass frit powder and silicon nitride are prepared in paste form, and an organic binder is added to maintain dispersibility and have a viscosity suitable for printing. The organic binder used in the present invention may be used without limitation as long as it is an organic binder used in the art for producing an aluminum paste composition. For example, cellulose (celluose), preferably ethyl cellulose may be used as the binder resin, but butyl carbitol acetate, terpineol, toluene, etc. may be used as the solvent. It is not limited to this. The content of the organic binder is preferably 20 to 30 parts by weight based on 100 parts by weight of the total composition.

Optionally, the aluminum paste composition of the present invention may further include additional additives without departing from the scope of the present invention. For example, stearic acid, p-toluenesulfonic acid monohydrate, or the like may be added, and the content may be 0.1 to 5 parts by weight based on 100 parts by weight of the composition.

Hereinafter, the manufacturing method of the aluminum paste adhesive sheet of this invention is demonstrated.

One embodiment of the manufacturing method of the aluminum paste adhesive sheet according to the present invention, preparing a pressure-sensitive adhesive (S1); (S2) mixing the pressure-sensitive adhesive with aluminum powder, glass frit powder and an organic binder; And (S3) applying the mixture to the first release film and then laminating a second release film thereon.

The adhesive is preferably in solution phase in order to be easily mixed with the other components. As a suitable solvent, the same thing as the organic binder and solvent which concern on this invention, or a different solvent can be easily selected by a person skilled in the art according to the kind of adhesive.

In the method of manufacturing an aluminum paste adhesive sheet of the present invention, after applying a mixed solution of aluminum powder, glass frit powder, an organic binder, and an adhesive to the first release film, a drying process may be further performed to increase the adhesiveness. have. If the pressure sensitive adhesive of the present invention contains a crosslinking agent, the crosslinking reaction by the crosslinking agent is preferably controlled for uniform application after the mixed solution is applied to the release film. As the crosslinking reaction proceeds in the pressure-sensitive adhesive, cohesive force may be improved, thereby improving adhesiveness and cuttability of the pressure-sensitive adhesive. In addition, after applying the mixed solution, it is preferable to sufficiently remove bubble-inducing components such as volatile components or reaction residues in the mixed solution.

Release film used in the present invention may be used a release film used in a conventional pressure-sensitive adhesive. For example, a PET film subjected to silicone release treatment is used, but is not limited thereto.

Hereinafter, an embodiment of a method of forming a back electrode of a silicon solar cell using the aluminum paste adhesive sheet 10 manufactured according to the present invention will be described with reference to FIG. 3. 3 schematically shows an embodiment of a method of forming a back electrode of a silicon solar cell according to the present invention.

First, the first release film 11 of the aluminum paste adhesive sheet of claim 1 is removed (S1). Next, the aluminum paste adhesive sheet from which the first release film is removed is attached to the back surface of the silicon substrate 20 so that the exposed aluminum paste adhesive composition layer 12 contacts the back surface of the silicon semiconductor substrate 20 ( S2). Subsequently, the second release film 11 of the aluminum paste adhesive sheet attached to the back surface of the silicon substrate 20 is removed and then heat treated (not shown) (S3).

Through the heat treatment process, the organic component included in the aluminum paste adhesive composition layer 12 is removed, and aluminum is diffused through the rear surface of the substrate 20 so that a back surface field is not shown on the interface between the rear electrode and the substrate. A layer can be formed. The heat treatment may be performed at a conventional temperature applied when forming the back electrode, and may be, for example, 700 to 950 ° C.

Hereinafter, a silicon solar cell manufactured using the aluminum paste adhesive sheet of the present invention will be described with reference to FIG. 4 as an example.

4 is a cross-sectional view schematically showing the structure of a silicon solar cell according to an embodiment of the present invention.

Referring to FIG. 4, the silicon solar cell according to the present invention includes a silicon semiconductor substrate 201, an emitter layer 202 formed on the substrate 201, and an anti-reflection film formed on the emitter layer 202. 203, a front electrode 204 penetrating the antireflection film 203 and connected to the upper surface of the emitter layer 202, and a rear electrode 205 connected to the rear surface of the substrate 201.

The substrate 201 may be doped with group III elements B, Ga, In, etc. as p-type impurities, and the emitter layer 202 may have group 5 elements P, As, Sb, etc. with n-type impurities as impurities. Can be doped. When the substrate 201 and the emitter layer 202 are doped with an impurity of the opposite conductivity type, a p-n junction is formed at the interface between the substrate 201 and the emitter layer 202. On the other hand, the p-n junction may be formed by doping the substrate 201 with an n-type impurity and doping the emitter layer 202 with a p-type impurity.

The antireflection film 203 immobilizes defects (e.g., dangling bonds) existing in the surface or bulk of the emitter layer 202 and reduces the reflectance of sunlight incident on the front surface of the substrate 201. When defects existing in the emitter layer 202 are passivated, the recombination sites of the minority carriers are removed and the open circuit voltage of the solar cell is increased. When the reflectance of the solar light is reduced, the amount of light reaching the p-n junction is increased to increase the short circuit current of the solar cell. When the open-circuit voltage and the short-circuit current of the solar cell are increased by the antireflection film 203, the conversion efficiency of the solar cell is improved accordingly.

The antireflection film 203 may be a single film selected from the group consisting of a silicon nitride film, a silicon nitride film containing hydrogen, a silicon oxide film, a silicon oxynitride film, MgF ₂ , ZnS, MgF ₂ , TiO ₂ and CeO ₂ , But not limited to, a multi-film structure in which two or more material films are combined. The anti-reflection film 203 may be formed by vacuum deposition, chemical vapor deposition, spin coating, screen printing, or spray coating. However, the method of forming the anti-reflection film 203 according to the present invention is not limited thereto.

The front electrode 204 and the rear electrode 205 are metal electrodes made of silver and aluminum, respectively. The front electrode 204 is made of the aluminum paste composition of the present invention. The silver electrode is excellent in electrical conductivity, the aluminum electrode is excellent in electrical conductivity, and has good affinity with the substrate 201 made of a silicon semiconductor and has good merit.

The front electrode 204 and the rear electrode 205 can be manufactured by various known techniques, but are preferably formed by a screen printing method. That is, the front electrode 204 is formed by screen printing the silver paste composition on the front electrode formation point and then performing heat treatment. When the heat treatment is performed, the front electrode penetrates the antireflection film 203 and is connected to the emitter layer 202 by a punch through phenomenon.

The back electrode 205 may be formed according to the method for forming a back electrode of the present invention described above. As described above, when the rear field layer is formed through heat treatment, the carrier may be prevented from recombining by moving to the rear surface of the substrate 201. When the recombination of the carriers is prevented, the open voltage and the fidelity are increased and the conversion efficiency of the solar cell is improved.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

<Production of Adhesives-Acrylic Copolymer>

In a 1 L reactor equipped with a refrigeration apparatus for reflux of nitrogen gas and easy temperature control, a monomer mixture comprising 98.3 parts by weight of n-butyl acrylate (BA) and 1.7 parts by weight of hydroxyethyl methacrylate (2-HEMA) Then, 100 parts by weight of ethyl acetate (EAc) was added as a solvent. Subsequently, the nitrogen gas was purged for about 1 hour for oxygen removal, maintained at 62 ° C., the mixture was homogenized, and then azobisisobutyronitrile diluted to 50% in ethyl acetate with a reaction initiator ( AIBN) 0.03 parts by weight was added. Subsequently, the mixture was reacted for about 8 hours to prepare an acrylic copolymer.

<Adhesive sheet manufacture>

To 100 parts by weight of the acrylic copolymer prepared above, 0.5 parts by weight of tolylene diisocyanate adduct (TDI-1) of trimethylol propane was mixed as a crosslinking agent. An aluminum powder adhesive composition was prepared by mixing the pressure-sensitive adhesive with an aluminum powder so as to have a weight ratio of aluminum powder: adhesive = 10: 90, and adding glass frit powder and ethyl acetate to 0.14 parts by weight and 30 parts by weight, respectively, based on 100 parts by weight of aluminum powder. It was.

The prepared aluminum paste adhesive composition was bar-coated on the first silicone treated PET release film, and dried at 110 ° C. for 3 minutes. When the drying is completed, the aluminum paste adhesive sheet was prepared by covering the second silicone-treated PET release film on the aluminum paste adhesive composition layer.

<Back electrode formation>

After removing one release film of the prepared aluminum paste adhesive sheet and attaching the aluminum paste adhesive composition layer to one surface of the wafer, the other release film was also removed and heat treated in a belt firing furnace to form a rear electrode. It was.

The SEM image of the surface state of the heat treated aluminum back electrode is shown in FIG. 5, and the SEM picture of the cross section is shown in FIG. 5, and it can be seen that the aluminum back electrode layer 2 is effectively formed on the wafer 1. .

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.

1 is a cross-sectional view showing a schematic structure of a silicon solar cell according to the prior art.

Figure 2 is a schematic cross-sectional view of the aluminum paste adhesive sheet prepared according to an embodiment of the present invention.

3 is a view schematically illustrating a method of forming a back electrode of a silicon solar cell according to an embodiment of the present invention in order.

4 is a schematic cross-sectional view of a solar cell manufactured according to an embodiment of the present invention.

5 is a SEM photograph of a cross section of a back electrode formed on a silicon substrate manufactured according to an embodiment of the present invention.

<Main reference number in drawing>

201: substrate 202: emitter layer

203: antireflection film

204: front electrode 205: rear electrode

Claims (12)

Two release films facing each other; And It is interposed between the two release film, and provided with an aluminum paste adhesive composition layer comprising an aluminum powder, glass frit powder, an organic binder, an adhesive, and a multifunctional crosslinking agent, The pressure-sensitive adhesive is a pressure-sensitive resin alone or a mixture of the pressure-sensitive resin and a solvent, the pressure-sensitive resin is an acrylic copolymer made of a (meth) acrylic acid ester monomer and a crosslinkable functional group-containing monomer, The pressure-sensitive adhesive is 100 to 900 parts by weight based on 100 parts by weight of aluminum powder, In addition, the polyfunctional crosslinking agent is an aluminum paste adhesive sheet is 0.01 to 10 parts by weight relative to 100 parts by weight of the adhesive resin. delete delete delete The method of claim 1, The glass frit powder is SiO ₂ -PbO-based, SiO ₂ -PbO-B ₂ O ₃ -based, Bi ₂ O ₃ -B ₂ O ₃ -SiO ₂ -based, and PbO-Bi ₂ O ₃ -B ₂ O ₃ -SiO An aluminum paste adhesive sheet comprising any one selected from the group consisting of _two- based powders or a mixture of two or more thereof. The method of claim 1, The organic binder is an aluminum paste adhesive sheet comprising cellulose as a binder resin and butyl carbitol acetate, terpineol, toluene, or a mixture thereof as a solvent. (S1) preparing a pressure-sensitive adhesive solution containing a pressure-sensitive adhesive; (S2) adding and mixing a multifunctional crosslinking agent, aluminum powder, glass frit powder, and an organic binder to the adhesive solution; And (S3) after applying the resultant of the step (S2) to the first release film, and laminating a second release film thereon, The pressure-sensitive adhesive is a pressure-sensitive resin alone or a mixture of the pressure-sensitive resin and a solvent, the pressure-sensitive resin is an acrylic copolymer made of a (meth) acrylic acid ester monomer and a crosslinkable functional group-containing monomer, The pressure-sensitive adhesive is 100 to 900 parts by weight based on 100 parts by weight of aluminum powder, In addition, the polyfunctional crosslinking agent is 0.01 to 10 parts by weight relative to 100 parts by weight of the adhesive resin manufacturing method of the aluminum paste adhesive sheet. delete delete delete (S1) removing the first release film of the aluminum paste adhesive sheet of claim 1; (S2) attaching the aluminum paste adhesive sheet from which the first release film is removed to the back surface of the silicon substrate such that the exposed aluminum paste adhesive composition layer contacts the back surface of the silicon semiconductor substrate; And (S3) removing the second release film of the aluminum paste adhesive sheet attached to the back surface of the silicon substrate and heat-treating Method of forming a back electrode of a silicon solar cell comprising a. A silicon semiconductor substrate; An emitter layer formed on the substrate; An antireflection film formed on the emitter layer; A front electrode penetrating the antireflection film and connected to the emitter layer; And a back electrode connected to a rear surface of the substrate, The back electrode is a silicon solar cell, characterized in that formed according to the method of claim 11.

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