KR101551475B1 - Paste for preparing mask patterns and Back contact solar cell using the same - Google Patents

Abstract

The present invention relates to an etching mask paste and a rear electrode type solar cell using the same. More specifically, the etch mask paste of the present invention is applied onto a metal layer for electrodes to form an electrode pattern of a back electrode type solar cell, and includes a metal oxide powder containing SiO ₂ , a binder, and an organic solvent do. The etching mask paste of the present invention can be easily patterned by screen printing, and the formed mask pattern can be cleaned with water, thereby being economical and environmentally friendly.

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to an etching mask paste and a back electrode type solar cell using the same,

The present invention relates to an etching mask paste and a rear electrode type solar cell using the same. And more particularly, to an etch mask paste used for forming an electrode of a back electrode type solar cell and a back electrode type solar cell using the same.

With the recent depletion of existing energy resources such as oil and coal, interest in alternative energy to replace them is increasing. In particular, solar cells are attracting particular attention because they are rich in energy resources and have no problems with environmental pollution.

Solar cells include solar cells that generate the steam needed to rotate the turbine using solar heat, and solar cells that convert sunlight (photons) into electrical energy using the properties of semiconductors. (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 enters the solar cell having the above structure, electrons and holes are generated in a silicon semiconductor doped with impurities due to the photovoltaic effect (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 holes generated by the photovoltaic effect are attracted toward the n-type silicon semiconductor and the p-type silicon semiconductor, respectively, and move to the electrodes 103 and 104 bonded to the lower portion of the substrate 101 and the upper portion of the emitter layer 102, When the electrodes 103 and 104 are connected by a wire, current flows.

Various studies have been conducted to improve the efficiency of such a silicon solar cell. One of them is a back contact solar cell having a structure in which all the electrodes are located on the rear side.

2 is a cross-sectional view schematically showing a basic structure of a rear electrode type solar cell. Referring to the drawing, an n-type emitter 203 and a p-type emitter 204 are alternately formed on the rear surface of a silicon substrate 201. Each of the emitters has a passivation layer 205 interposed therebetween, (208, 209).

The rear electrode type solar cell has all the electrodes on the backside, eliminating the shading loss of the front surface, and eliminating the shunt due to the separation of the rear junction and the electrode. .

Such a back electrode type solar cell uses a photolithography method using a photoresist to form n-type and p-type emitters and each electrode pattern. In this case, various steps such as printing, drying, exposure, development, So that the process is complicated and not economical.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an etching mask paste for forming an electrode pattern of a rear electrode type solar cell which can be easily formed by a screen printing method.

Another object of the present invention is to provide an etch mask paste for forming an electrode pattern of a back electrode type solar cell which is economical and environmentally friendly because the formed mask pattern can be cleaned with water.

In order to solve the above problems, an etch mask paste for forming an electrode pattern of a back electrode type solar cell of the present invention comprises a metal oxide powder containing SiO ₂ , a binder, and an organic solvent.

In the present invention, the electrode may be formed of aluminum.

In the paste of the present invention, the metal oxide may further include TiO ₂ , P ₂ O ₅ , BaO, ZnO, ITO, Al ₂ O ₃ , and the like, either singly or in combination.

In the paste of the present invention, the binder may be used alone or as a mixture of two or more thereof, such as a cellulose-based resin, an epoxy-based resin, a polyurethane-based resin, a polystyrene-based resin, a polyacrylic resin and a polypropylene-

In the paste of the present invention, the organic solvent may be selected from the group consisting of butyl carbitol acetate, butyl carbitol, terpineol, and texanol. These organic solvents may be used alone or in combination.

The paste of the present invention may further include a plasticizer as required.

In order to solve the above problems, a method of forming an electrode pattern of a back electrode type solar cell according to the present invention comprises the steps of: (S1) forming a passivation layer on a rear surface of a rear electrode type solar cell, Forming a layer; (S2) etching the passivation layer according to an electrode pattern to be connected to the n-type emitter and the p-type emitter; (S3) depositing a metal layer for electrodes on the etched passivation layer; (S4) forming an etching mask pattern with an etching mask paste containing a metal oxide powder, a binder and an organic solvent at a position where the electrode pattern on the metal layer is to be formed; (S5) etching the electrode metal layer using the etching mask pattern as a mask; And (S6) removing the etch mask pattern with a cleaning solution comprising water.

The etching mask paste for forming an electrode pattern of the rear electrode type solar cell of the present invention is easy to apply by a screen printing method, has excellent adhesion to a metal layer for electrodes, and has excellent durability against an etchant.

In addition, the etch mask paste for forming an electrode pattern of the rear electrode type solar cell of the present invention is economical and environmentally friendly since it can be cleaned with water after the mask pattern is formed and can be easily removed.

Therefore, the manufacturing process of the rear electrode type solar cell using the etching mask paste for forming the electrode pattern of the rear electrode type solar cell of the present invention is economical and high in productivity.

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 conventional silicon solar cell.
2 is a cross-sectional view showing a schematic structure of a rear electrode type solar cell.
3 is a schematic view illustrating one embodiment of a method of forming an emitter of a back electrode type solar cell according to the present invention.
4 is a view schematically showing an embodiment of a method of forming an electrode pattern of a back electrode type solar cell according to the present invention.
FIG. 5 is an optical microscope photograph showing a state after a mask pattern formed of an etch mask paste manufactured according to an embodiment of the present invention is exposed to an etchant. FIG.

Hereinafter, the present invention will be described in detail. 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.

The term " parts by weight " as used in this specification and claims means the ratio of the weight among the plurality of constituents. The total weight of the total constituents is 100, and the weight Quot; is not meant to denote percent by weight.

The etching mask paste for forming an electrode pattern of the rear electrode type solar cell of the present invention is characterized by including a metal oxide powder containing SiO ₂ , a binder, and an organic solvent.

The inventors of the present invention have found that a metal oxide powder containing SiO ₂ , a binder, and an etch mask paste made of an organic solvent can be screen printed and have excellent adhesion to metal used as an electrode in the production of a rear electrode type solar cell, The inventors of the present invention have found out that the durability of the etchant for etching the metal is excellent, It has further been found that the mask pattern formed by the etching mask paste of the present invention can be cleaned with water after the etching process.

The etch mask paste of the present invention is applied on the metal electrode layer of the back electrode type solar cell so as to correspond to the electrode pattern in order to form the electrode pattern of the back electrode type solar cell. The metal layer for the electrode of the rear electrode type solar cell according to the present invention is a metal layer commonly used for the electrode of the back electrode type solar cell and is a metal layer formed of, for example, aluminum (Al) or silver (Ag) . After the etching mask paste of the present invention is coated on the metal layer as an electrode pattern and dried to form a mask pattern, an etching process is performed to etch portions of the metal layer where no mask pattern is formed, So that an electrode pattern is formed.

In the etching mask paste of the present invention, the metal oxide powder containing SiO ₂ is an inorganic component and plays a main role in maintaining the mask pattern in the etching process. The metal oxide powder according to the present invention is preferably included in an amount of 10 to 90 parts by weight based on 100 parts by weight of the entire etching mask paste. If the amount is less than 10 parts by weight, the printed pattern may not be maintained and may spread. When the amount is more than 90 parts by weight, printing defects may occur and desorption of the metal oxide from the substrate may occur during drying.

Alternatively, the metal oxide powder comprising SiO ₂ according to the present invention may be selected from the group consisting of TiO ₂ , P ₂ O ₅ , BaO, ZnO, ITO and Al ₂ O ₃ , Or a mixture of two or more thereof.

In the etching mask paste of the present invention, the binder may be any one selected from the group consisting of a cellulose-based resin, an epoxy-based resin, a polyurethane-based resin, a polystyrene-based resin, a polyacrylic resin, and a polypropylene- And may preferably include a polyacrylic resin.

In the etching mask paste of the present invention, the organic solvent may include any one selected from the group consisting of butyl carbitol acetate, butyl carbitol, terpineol, and Texanol, or a mixture of two or more thereof.

Since the binder according to the present invention is dissolved in the organic solvent and then added to the composition of the present invention, since solubility of the binder may vary according to specific types of the binder and the organic solvent, the binder and the organic solvent Is not particularly limited. However, the total content of the binder and the organic solvent is preferably 10 parts by weight to 90 parts by weight based on 100 parts by weight of the entire etching mask paste. If the amount is less than 10 parts by weight, the metal oxide may not be completely mixed with the binder. If the amount is more than 90 parts by weight, the printed pattern may not be maintained due to excessive binder, and the accuracy of the pattern may be deteriorated.

Alternatively, the etch mask paste of the present invention may further comprise a plasticizer. As the plasticizer usable in the present invention, a phthalate type, a benzoate type, an ester type, an epoxy type, an anti-chlorine type, a polyester type and the like can be used each alone or as a mixture of two or more kinds thereof. When the plasticizer is added, the amount of the plasticizer is preferably 0.1 to 30 parts by weight based on 100 parts by weight of the total of the etching mask paste.

Hereinafter, an embodiment of the present invention for forming an electrode pattern of a rear electrode type solar cell using the etching mask paste of the present invention will be described with reference to the drawings.

In order to form an electrode pattern on the rear electrode type solar cell, n-type and p-type emitters are alternately formed on the back surface of the substrate. The method for forming the n-type and p-type emitters can be used without limitation in a method commonly used in the art. An embodiment of this is shown schematically in Fig. Referring to FIG. 3, a method of forming n-type and p-type emitters will be described below.

First, an oxide layer 202 is deposited on a substrate 201 made of a silicon semiconductor doped with an impurity (Al). Here, the substrate 201 is a single crystal, polycrystalline or amorphous silicon semiconductor, and is doped with an n-type impurity such as P, As, or Sb, which is a Group 5 element. If the etching mask paste is directly applied to the semiconductor substrate 201 and the etching process is performed, it is difficult to grasp the degree of etching and the portion where the emitter is formed may be etched by the etchant. Therefore, ). As the material of the oxide layer, SiO ₂ is preferable.

After the oxide layer 202 is formed, the portion where the n-type emitter is to be formed is etched (A2). As a method of etching, photolithography or the like is usually used, but the present invention is not limited thereto, and any method used in the art can be used without limitation.

The oxide layer 202 is etched to expose a portion of the wafer where the n-type emitter is to be formed, to the diffusion furnace. Here, an n-type impurity source such as P, As, Sb or the like as a Group 5 element is implanted together with oxygen gas in the diffusion furnace to cause a thermal oxidation reaction to form an oxide film containing n-type impurities in a predetermined thickness . Then, the temperature of the diffusion furnace is raised to 800 to 900 DEG C, and the n-type impurity contained in the oxide film is driven-in to the portion where the n-type emitter on the back surface of the substrate 201 is to be formed. At this time, the diffusion time is sufficiently maintained so that a sufficient amount of the n-type impurity can be diffused into the substrate 201. Then, the n-type impurity contained in the oxide film is diffused through the surface of the wafer to etch the oxide layer 202 on the back surface of the substrate 201, thereby forming an n-type silicon semiconductor layer Type emitter 203 is formed (A3).

Thereafter, the oxide layer 202 is removed and the steps (A1) to (A3) are performed in the same manner as described above, except that the p-type impurity such as B, Ga, The p-type emitter 204 is formed in an area where the emitter 203 is not formed (A4).

After the n-type emitter 203 and the p-type emitter 204 are formed on the back surface of the silicon substrate 201 as described above, an electrode pattern can be formed. FIG. 4 schematically shows an embodiment of a method of forming an electrode pattern of a rear electrode type solar cell according to the present invention. Referring to FIG. 4, a method of forming an electrode pattern of a rear electrode type solar cell according to the present invention will now be described.

First, a passivation layer 205 is formed on the rear surface of a rear electrode type solar cell in which an n-type emitter 203 and a p-type emitter 204 are alternately formed (S1).

The passivation layer 205 can reduce the recombination loss and improve the efficiency of the solar cell. The passivation layer 205 is preferably a SiO ₂ layer.

Next, the passivation layer 205 is etched according to an electrode pattern to be connected to the n-type emitter 203 and the p-type emitter 204 (S2).

A method of etching is generally a photolithography method, but the present invention is not limited thereto, and any method that can be used in the art can be used.

When the etching is completed, a metal layer 206 for electrode is deposited on the passivation layer 205 (S3).

As the electrode metal, aluminum (Al) or silver (Ag) is generally used. The emitter and the metal electrode are connected through the deposition of the electrode metal layer. Hereinafter, a case where aluminum is deposited will be described as an embodiment.

In the case of depositing aluminum, a back surface field (not shown) layer may be formed at the interface with the p-type emitter 204 by diffusing aluminum through the lower portion of the substrate 201. When the rear-front layer is formed, the carrier can be prevented from moving to the lower portion of the substrate 201 and recombining. 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.

After the deposition of the metal layer is completed, an etching mask pattern 207 is formed on the metal layer at a position where the electrode pattern is to be formed, using an etching mask paste containing a metal oxide powder including SiO ₂ , a binder, and an organic solvent (S4).

As described above, the p-type emitter 204 connects aluminum (Al) and the n-type emitter 203 connects silver (Ag) as an electrode. However, as shown in (S3) of FIG. 4, the metal (aluminum) deposition as described above connects one kind of metal to both the n-type emitter 203 and the p-type emitter 204. Therefore, in the case of depositing aluminum, it is necessary to remove only the portion (second electrode pattern) connected to the p-type emitter 204 by etching and removing the portion (first electrode pattern) connected to the n-type emitter 203 have. Therefore, the etching mask pattern of the present invention is applied to the position where the second electrode pattern is to be formed, thereby forming the etching mask pattern 207. [ At this time, as described above, the etching mask paste of the present invention can be easily applied by a screen printing method.

Next, the electrode metal layer is etched using the etching mask pattern 207 as a mask (S5).

As the etchant for etching, both wet etchant and dry etchant can be used. In order to ensure the stability and reproducibility of the etching process, it is preferable to use wet etchant. As the wet etchant, aqueous solutions such as HNO ₃ , HF and CH ₃ COOH may be used alone or in admixture of two or more. Preferably, an etchant containing phosphoric acid is used to etch aluminum, and an etchant containing nitric acid may be used to etch silver.

When the etching is completed, only the portion masked by the etching mask pattern 207 forms the remaining electrode pattern 208. [ In the embodiment of the present invention, when aluminum is first deposited, only the portion connected to the p-type emitter 204 forms the south electrode pattern 208. [

Next, the etching mask pattern is removed with a cleaning solution containing water (S6).

Since the etching mask pattern 207 according to the present invention is well swelled by water, it can be easily cleaned with water. When the etching mask pattern 207 is removed, only the electrode pattern 208 is left.

One electrode pattern (the second electrode pattern when aluminum is deposited in one embodiment of the present invention) can be formed by the above-described method.

Thereafter, another electrode pattern (the first electrode pattern in one embodiment of the present invention) may be formed by a conventional method, for example, screen printing or the like (S7).

3 and 4 are merely the most preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention. Thus, various equivalents and variations Examples should be understood.

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  1-2

An etching mask paste was prepared with the composition (unit: parts by weight) shown in Table 1 below. A polyacrylic resin was used as a binder, a mixed solvent of butyl carbitol and terpineol was used as an organic solvent, and dipropylene glycol dibenzoate was used as a plasticizer.

SiO ₂ Binder + organic solvent Plasticizer Example 1 30 65 5 Example 2 20 75 5

The prepared etch mask face was coated on the aluminum thin film deposited on the wafer in a predetermined pattern and dried at 100 to 200 ° C to form a mask pattern. The wafer on which the mask pattern was formed was immersed in an etchant mixed with phosphoric acid and acetic acid for 5 minutes, and the temperature was maintained at 40 占 폚. When the etching was completed, the wafer was taken out and the etching mask pattern was removed with water.

The etched patterns were observed with an optical microscope, and the results are shown in Fig. 5 (a: Example 1, b: Example 2).

As can be seen from FIG. 5, it can be seen that the etching pattern formed using the etching mask pattern of the present invention is clearly formed, and that the etching mask pattern is completely removed by water.

For reference, in the case of printing a pattern with a paste prepared in the same manner as in Example 1 and Example 2 except that SiO ₂ was not added, the printed pattern was swelled during etching and completely removed from the substrate And thus it was confirmed that the etching pattern itself was not formed.

Claims (12)

As an etch mask paste for forming an electrode pattern of a back electrode type solar cell,
A metal oxide powder containing SiO ₂ , a binder, an organic solvent, and a plasticizer,
Wherein the content of the metal oxide powder is 10 parts by weight to 90 parts by weight, the content of the binder and the organic solvent is 10 parts by weight to 90 parts by weight, the content of the plasticizer is 0.1 weight part To 30 parts by weight,
Wherein the etch mask formed of the etch mask paste is washed with water. The method according to claim 1,
Wherein the electrode is formed of aluminum. The etching mask paste for forming an electrode pattern of a back electrode type solar cell according to claim 1, wherein the electrode is formed of aluminum. The method according to claim 1,
The metal oxide may be selected from the group consisting of TiO ₂ , P ₂ O ₅ , BaO, ZnO, ITO, and Al ₂ O ₃ And a mixture of two or more thereof. The etching mask paste for forming an electrode pattern of a rear electrode type solar cell according to claim 1, The method according to claim 1,
Wherein the binder comprises any one selected from the group consisting of a cellulose-based resin, an epoxy-based resin, a polyurethane-based resin, a polystyrene-based resin, a polyacrylic resin, and a polypropylene-based resin or a mixture of two or more thereof Etch mask paste for electrode pattern formation of solar cells. The method according to claim 1,
Wherein the organic solvent comprises any one selected from the group consisting of butyl carbitol acetate, butyl carbitol, terpineol, and texanol, or a mixture of two or more thereof, for forming an electrode pattern of a rear electrode type solar cell Etch mask paste. (S1) forming a passivation layer on a rear surface of a rear electrode type solar cell in which an n-type emitter and a p-type emitter are alternately formed;
(S2) etching the passivation layer according to an electrode pattern to be connected to the n-type emitter and the p-type emitter;
(S3) depositing a metal layer for electrodes on the etched passivation layer;
(S4) the etching mask pattern by applying an etch mask paste in position to the electrode pattern on the metal layer comprises a metal oxide powder, binder, organic solvent, and a plasticizer containing SiO _2, and dried at 100 to 200 ℃ Forming,
Wherein the content of the metal oxide powder is 10 parts by weight to 90 parts by weight, the content of the binder and the organic solvent is 10 parts by weight to 90 parts by weight, the content of the plasticizer is 0.1 weight part To 30 parts by weight;
(S5) etching the electrode metal layer using the etching mask pattern as a mask; And
(S6) removing the etching mask pattern with a cleaning solution containing water
Wherein the electrode pattern is formed on the surface of the back electrode type solar cell. The method according to claim 6,
Wherein the passivation layer is formed of SiO ₂ . The method according to claim 6,
Wherein the electrode metal layer in step (S3) is an aluminum layer. The method according to claim 6,
In the etching mask paste of the step (S4), the oxide of the metal oxide may be TiO ₂ , P ₂ O ₅ , BaO, ZnO, ITO, and Al ₂ O ₃ And a mixture of two or more thereof. The method for forming an electrode pattern of a back electrode type solar cell according to claim 1, The method according to claim 6,
In the etching mask paste of the step (S4), the binder may be any one selected from the group consisting of cellulose, epoxy resin, polyurethane resin, polystyrene resin, polyacrylic resin and polypropylene resin, Wherein the first electrode layer and the second electrode layer are formed on the substrate. The method according to claim 6,
In the etching mask paste of the step (S4), the organic solvent includes any one selected from the group consisting of butyl carbitol acetate, butyl carbitol, terpineol, and Texanol, or a mixture of two or more thereof A method of forming an electrode pattern of a rear electrode type solar cell. type emitter and a p-type emitter are alternately formed on the rear surface of the rear electrode type solar cell, the rear electrode type having a first electrode pattern and a second electrode pattern connected to the n-type emitter and the p- In solar cells,
Wherein at least one of the first electrode pattern and the second electrode pattern is formed by the forming method of claim 6.

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