KR101244787B1 - Process for Preparation of Solar Cell - Google Patents

Abstract

The present invention is to form a metal pattern or metal layer for electrode wiring on the front and / or rear of the pn junction substrate in the manufacturing process of the solar cell, the substrate film with a pressure roll in a state in which the metal pattern or metal layer on the base film facing the pn junction substrate By applying pressure to the metal pattern or the metal layer is coated on the pn junction substrate, there is provided a method for manufacturing a solar cell greatly shortened the overall manufacturing process, such as not going through a drying process.

Description

Process for Preparation of Solar Cell

1 is a schematic process diagram of a solar cell manufacturing method according to the prior art using a screen printing method;

FIG. 2 is a process schematic diagram of a process of coating an Al layer by roll pressing on the back side of a pn junction substrate in accordance with one embodiment of the present invention; FIG.

3 is a process schematic diagram of a process of simultaneously forming electrodes on the front and rear surfaces of a pn junction substrate according to another embodiment of the present invention;

4A and 4B are side cross-sectional views of a process of forming a back electrode on a pn junction substrate according to embodiments of the present invention;

5A and 5B are plan schematic views of a coating film including an Al layer and an Ag pad to be formed on the back side of a pn bonded substrate according to embodiments of the present invention;

6A and 6B are schematic top views of a coating film including an Al layer and Ag pad and adhesive to be formed on the back side of a pn bonded substrate according to further embodiments of the present invention;

7A and 7B are schematic top views of a coating film including Ag bus bars and Ag fingers to be formed on the front surface of a pn bonding substrate according to embodiments of the present invention.

The present invention relates to a method of manufacturing a solar cell, and more particularly, in forming a metal pattern or metal layer for electrode wiring on the front and / or rear of the pn junction substrate in the manufacturing process of the solar cell, The present invention relates to a manufacturing method for solving the problems of the conventional screen printing method by applying a pressure to the base film with a pressure roll in a state in which the metal layer faces the pn bonded substrate, thereby coating the metal pattern or the metal layer on the pn bonded substrate.

Recently, with increasing interest in environmental problems and energy depletion, there is a growing interest in solar cells as an alternative energy with abundant energy resources, no problems with environmental pollution, and high energy efficiency.

Solar cells can be divided into solar cells that generate steam required to rotate a turbine using solar heat, and solar cells that convert photons into electrical energy using properties of semiconductors. Among them, researches on solar cells that convert light energy into electrical energy by absorbing light to generate electrons and holes have been actively conducted.

Looking at the structure of the photovoltaic cell, a second conductive semiconductor layer of opposite conductivity type is formed on the first conductive semiconductor substrate and includes a pn junction at an interface thereof. And a back electrode in contact with at least a portion and a front electrode in contact with at least a portion of the second conductivity type semiconductor layer.

A p-type silicon substrate is mainly used as the first conductivity type semiconductor substrate, and an n-type emitter layer is used as the second conductivity type semiconductor layer. In addition, a front electrode is formed on the emitter layer with an Ag pattern, and a back electrode is formed on the back surface of the silicon substrate with an Al layer. The formation of the front electrode and the back electrode is performed by screen printing.

Figure 1 shows a schematic process diagram of a solar cell manufacturing method according to the prior art using a screen printing method.

Referring to FIG. 1, as a general manufacturing process, a pn junction is formed on a pn junction substrate, and then, an Ag pad is screen printed on the rear surface of the substrate for soldering to facilitate electrical connection with other cells or an external circuit. Again, the Al layer for electrodes is screen printed on the rear surface, and the Ag pattern for electrodes is screen printed on the front surface of the substrate.

The screen printing process is performed by applying a paste containing a metal powder, a binder, and a solvent to the front or rear surface of the substrate, and after the coating process, as shown in FIG. 1, the solvent must be removed through a drying process. . This drying process has to be repeated as many times as the screen printing process, and thus serves as one of the main factors to lengthen the overall manufacturing process of the solar cell.

Therefore, there is a high need for a technique capable of fundamentally solving such problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

That is, an object of the present invention is to provide a method for forming the electrode of the solar cell by a simple apparatus and method without using a conventional screen printing method.

Still another object of the present invention is to provide a solar cell including the electrode manufactured by the above method.

The method of manufacturing a solar cell according to the present invention for achieving the above object, in forming a metal pattern for electrode wiring or a metal layer on the front and / or rear of the pn junction substrate during the manufacturing of the solar cell, the metal pattern on the base film for coating Or applying a pressure to the base film with a pressure roll in a state in which the metal layer faces the pn bonded substrate, thereby coating the metal pattern or the metal layer on the pn bonded substrate.

Therefore, the manufacturing method of the present invention can greatly shorten the entire manufacturing process and seek the simplification of the apparatus by not undergoing the drying process required by the screen printing method, and also by using no paste for screen printing. The electrode in the form can be produced more precisely.

The pn junction substrate refers to a basic operating structure of a solar cell, in which a second conductive semiconductor layer of an opposite conductivity type is formed on a first conductive semiconductor substrate and includes a pn junction at an interface thereof. In one preferred example, the first conductivity type semiconductor substrate is a p-type silicon substrate, and the second conductivity type semiconductor layer may be an n-type emitter layer.

Preferably, the roll press forms a metal pattern on the front surface of the pn junction substrate to form an electrode (“front electrode”), and a metal layer is formed on the back surface of the pn junction substrate to form an electrode (“back electrode”). The manufacturing process of the front electrode and the rear electrode can be performed at the same time, further shortening the manufacturing process.

The front electrode may be formed of, for example, an Ag pattern. In order to form the Ag pattern, Ag bus bars and Ag fingers are added to the coating base film. In order to provide a high adhesion of the Ag pattern to the pn-bonded substrate in the coating process, preferably, an adhesive may be filled in at least a portion between the Ag bus bar and the Ag finger formed on the base film. The adhesive is decomposed and easily removed during the co-firing process, and only serves to help the Ag pattern adhere well to the pn bonding substrate during the roll pressing process. For example, an epoxy resin, an acrylate, a cyanoacrylate, a phenol resin, or the like may be used as the adhesive.

The back electrode can be added, for example, as an Al layer and, in some cases, such soldering when soldering for electrical connection with Ag of another solar cell or external circuit in the manufacture of a solar cell module. One or more Ag pads may be included for ease of ease. Such Ag pads are included in contact with or partially overlapped with the Al layer, and in some overlapping overlapping widths of, for example, 2 mm or less are preferred.

The following three methods can be considered as a preferred method of improving the adhesion when the Al layer is attached to the pn bonded substrate by coating by roll pressing.

First, a method of using a coating having a composition comprising a porous Al layer and an adhesive layer applied to the outer surface of the Al layer on the base film for coating. The adhesive layer improves the adhesion of the Al layer to the pn bonding substrate, and may be decomposed during the sintering process and removed via the porous Al layer.

Second, a method of using a coating having a composition including an Al layer having a plurality of through holes formed on the base film for coating and an adhesive filled in at least a portion of the through holes. The adhesive improves the adhesion of the Al layer to the pn bonding substrate and can be decomposed during the sintering process and removed through the through hole.

Third, a method of using a coating having a structure including an Al layer in which a plurality of grooves are formed in a lattice form on a coating base film and an adhesive filled in at least a portion of the grooves. The adhesive may be decomposed during the sintering process and discharged to the outside along the groove.

The present invention also relates to a solar cell comprising as an electrode a metal pattern and / or a metal layer produced by the above method.

In the solar cell of the present invention, the front electrode preferably includes an Ag pattern formed in a thickness of 1 to 30 μm on the silicon pn junction substrate, and the rear electrode is preferably 0.5 to 50 μm on the silicon pn junction substrate. It includes an Al layer formed to a thickness.

Since the structure of a solar cell including a metal pattern and a metal layer as electrodes on the front and rear surfaces of a pn junction substrate, and a method of manufacturing the same, are well known to those skilled in the art, the description thereof is omitted herein.

Hereinafter, the contents of the present invention will be described in detail with reference to the drawings, but since the contents of the drawings show only some embodiments of the present invention, the scope of the present invention is not limited thereto.

FIG. 2 is a process schematic diagram of a process of coating an Al layer by roll pressing on a rear surface of a pn bonded substrate according to one embodiment of the present invention.

Referring to FIG. 2, the pn bonded substrate 100 moves in the direction of the arrow between a pair of pressing rolls 200 with its rear surface 110 positioned upward. The back surface 110 of the pn bonding substrate 100 comes into contact with the coating film 300 supplied from a feeding roll 210 and provided through guide rolls 220 and 222.

The coating film 300 has an Al layer formed on the base film, the Al layer of which is attached to the rear surface of the pn bonded substrate 100 by the pressure roll 200, and only the base film 310 is a winding roll (winding) roll: 230). Accordingly, an Al layer is formed as a back electrode on the pn junction substrate 100 by a roll pressing method, and the electrode forming process by the roll pressing method is very simple compared to the screen printing method and requires a drying process for removing the solvent. Do not

3 is a process schematic diagram of a process of simultaneously forming electrodes on the front and back of the pn junction substrate according to another embodiment of the present invention.

Referring to FIG. 3, the pn-bonded substrate 100 is formed of Al as a rear electrode by the first coating film 300 from the first supply roll 210 in a state where the rear surface thereof is positioned upward as in FIG. 2. Coat the layer.

At the same time, in a substantially symmetrical structure, a second coating film 400 is provided from the second feed roll 211 to coat the Ag pattern as an electrode on the front surface 120 of the pn bonding substrate 100.

Therefore, the Al layer as the back electrode and the Ag pattern as the front electrode can be formed at the same time, and since the same pressure is applied to the front surface 120 and the rear surface 110, it does not cause deformation to the pn bonding substrate 100.

4A and 4B are schematic cross-sectional views of a process of forming a back electrode on a pn junction substrate according to embodiments of the present invention.

First, referring to FIG. 4A, the coating film 300 includes a porous Al layer 320 on the base film 310 and an adhesive layer 330 thereon. By pressing the film 300 with the adhesive layer 330 facing the rear surface of the pn bonded substrate 100 by the roll pressing coating as in FIG. 2, the pn bonded substrate 100 / adhesive layer 330 / Al layer In the order of 320, a laminated structure is obtained. The adhesive layer 330 between the pn junction substrate 100 and the Al layer 320 is decomposed during the sintering process and removed to the outside through the porous Al layer 320.

Referring to FIG. 4B, the coating film 301 is attached with an Al layer 322 having a plurality of through holes 340 formed on the base film 310, and an adhesive 332 attached to the through holes 340. Is filled. The adhesive 331 assists in attaching the Al layer 322 to the pn bonding substrate 100 during roll pressing coating, and serves as a passage through which the adhesive 332 decomposed during the sintering process is discharged.

5A and 5B schematically show plan views of a coating film including an Al layer and an Ag pad to be formed on the back side of a pn junction substrate in accordance with embodiments of the present invention.

Referring to these figures, the Al layer 324 serves as a back electrode and the Ag pad 335 is used to facilitate soldering in manufacturing the solar cell module. The Al layer 324 and the Ag pad 350 are simultaneously formed on a pn bonded substrate (not shown) by the same process as in FIG. 2 and are in close contact with each other without overlapping each other or have a width of up to 2 mm or less. Nested A plurality of Ag pads 350 may be formed, and may be formed across the entire Al layer 324 as shown in FIG. 5A, and may be discontinuously formed only on a portion of the Al layer 324 as shown in FIG. 5B. It may be.

6A and 6B schematically show plan views of a coating film including an Al layer, an Ag pad, and an adhesive to be formed on the rear surface of a pn bonding substrate according to still other embodiments of the present invention.

The coating structures in these figures differ from FIGS. 5A and 5B in that an adhesive 332 is added to increase the adhesion of the Al layers 326 and 328 to the pn junction substrate (not shown). The additional form of the adhesive 332 may vary, as shown in FIG. 6A, in which the through hole 340 is formed in the Al layer 326 and the adhesive 332 is filled therein, and FIG. As in 6b, the adhesive 332 may be added in a checkered shape over the entire surface or a partial surface of the Al layer 328. In the latter case, a continuous groove 342 is formed on the surface of the Al layer 328, and the structure in which the adhesive 332 is filled therein may be sufficient.

The structure of the Ag pad 350 is the same as in FIG. 5A.

7A and 7B schematically show plan views of a coating film including Ag bus bars and Ag fingers to be formed on the front surface of a pn bonding substrate according to embodiments of the present invention.

First, referring to FIG. 7A, the Ag bus bar 420 and the Ag finger 430 cross each other on the base film 410. Accordingly, the front electrode can be formed by roll pressing the Ag bus bar 420 and the Ag finger 430 to face the entire surface of the pn junction substrate (not shown). Furthermore, as shown in FIG. 7B, when the adhesive 332 is filled in the space between the Ag bus bar 420 and the Ag finger 430, their adhesion to the pn bonded substrate is increased, and this adhesive 332 ) Are decomposed and easily removed in the sintering process.

Although the present invention has been described in detail with reference to specific examples, it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention, and such modifications and modifications belong to the appended claims. .

As described above, according to the present invention, since the electrode of the solar cell can be formed by a very simple process and apparatus, such as eliminating the drying process in comparison with the conventional screen printing method, the entire manufacturing process of the solar cell is shortened The manufacturing cost of the product can be lowered.

Claims (12)

In manufacturing a solar cell, when forming a metal pattern or metal layer for electrode wiring on the front surface of the pn junction substrate or forming a metal pattern or metal layer for electrode wiring on the rear surface of the pn junction substrate, the metal pattern or metal layer on the coating substrate film is pn junction And applying the pressure to the base film with a pressure roll in a state facing the base material to coat the metal pattern or the metal layer on the pn bonded base material, Forming a metal pattern or metal layer for electrode wiring on the front surface of the pn junction substrate to form a front electrode, a method of manufacturing a solar cell, characterized in that the back electrode is formed by forming a metal pattern or metal layer for electrode wiring on the rear surface of the pn junction substrate. The solar cell of claim 1, wherein the pn junction substrate is a basic operating structure of a solar cell having a second conductivity type semiconductor layer opposite to that formed on the first conductivity type semiconductor substrate and including a pn junction at an interface thereof. Manufacturing method characterized in that. 3. The method of claim 2, wherein the first conductivity type semiconductor substrate is a p-type silicon substrate and the second conductivity type semiconductor layer is an n-type emitter layer. delete The method of claim 1, wherein the front electrode is formed as an Ag pattern, and an Ag bus bar and Ag fingers are added on the base film for coating to form the Ag pattern. The method according to claim 5, wherein an adhesive is filled in at least a part between the Ag bus bar and the Ag finger added on the base film. The method according to claim 1, wherein the back electrode is formed as an Al layer and includes one or more Ag pads to facilitate soldering. The method of claim 7, wherein a porous Al layer and an adhesive layer applied to an outer surface of the Al layer are added to the base film for coating to form the back electrode. The method of claim 7, wherein an Al layer in which a plurality of through holes are formed and an adhesive filled in at least a portion of the through holes are added on the coating base film to form the back electrode. According to claim 7, To form the back electrode, on the coating base film is characterized in that a plurality of grooves (grooves) is formed in a lattice form and an adhesive filled in at least a portion of the grooves are added. Manufacturing method. A solar cell comprising at least one of a metal pattern and a metal layer produced by the method according to any one of claims 1 to 3 and 5 to 10 as an electrode. The method of claim 11, wherein the front electrode includes an Ag pattern formed on the silicon pn junction substrate to a thickness of 1 to 30 ㎛, the rear electrode is formed of an Al layer formed of a thickness of 0.5 to 50 ㎛ on the silicon pn junction substrate A solar cell comprising the same.

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