KR101380540B1

KR101380540B1 - Method for fabricating metal electrode of solar cell

Info

Publication number: KR101380540B1
Application number: KR1020090126239A
Authority: KR
Inventors: 이준성; 황명익; 조은철; 이원재
Original assignee: 현대중공업 주식회사
Priority date: 2009-12-17
Filing date: 2009-12-17
Publication date: 2014-04-03
Also published as: KR20110069487A

Abstract

The present invention relates to a method for forming a metal electrode of a solar cell that can improve the resistivity and contact resistance of the metal electrode and improve the solderability through the plating process, the method of forming a metal electrode of the solar cell according to the present invention is transparent Forming a plating pattern mask on the conductive oxide film, forming a first metal electrode on the transparent conductive oxide film exposed by the plating pattern mask through a plating process, and front and side surfaces of the first metal electrode. And forming a second metal electrode on the plating using a plating process.

Plating, Metal Electrode, Heterojunction

Description

Method for fabricating metal electrode of solar cell

The present invention relates to a method of forming a metal electrode of a solar cell, and more particularly, to a method of forming a metal electrode of a solar cell that can improve the specific resistance and contact resistance of the metal electrode through the plating process and improve the solderability (solderability). will be.

A solar cell is a core element of solar power generation that converts sunlight directly into electricity. Basically, it is a diode made of p-n junction. When the solar light is converted into electricity by the solar cell, when sunlight is incident on the pn junction of the solar cell, an electron-hole pair is generated, and the electric field moves the electrons to the n layer and the holes to the p layer Photovoltaic power is generated between the pn junctions, and when both ends of the solar cell are connected to each other, a current flows and the power can be produced.

On the other hand, one of the conditions for maximizing the photoelectric conversion efficiency of the solar cell is to minimize the recombination rate of electrons, holes. In general, a solar cell has a structure in which an n-type semiconductor layer is formed on a p-type silicon substrate, and the n-type semiconductor layer is formed by implanting n-type impurity ions into a substrate. It can be captured and recombined at interstitial sites or substitutional sites, which adversely affects photovoltaic conversion efficiency of solar cells.

In order to solve this problem, a so-called hetero-junction solar cell having an intrinsic layer between the p-type semiconductor layer and the n-type semiconductor layer has been proposed. The recombination rate can be lowered.

Meanwhile, in a heterojunction solar cell, an amorphous semiconductor layer (a-Si: H) is provided on an intrinsic layer, and a transparent conductive oxide film (TCO, transparent) is formed on an amorphous semiconductor layer to compensate for the low electrical conductivity of the amorphous semiconductor layer. conductive oxide) is provided as an auxiliary electrode. In addition, a metal electrode connected to an external circuit is provided on the transparent conductive oxide film, and the metal electrode is usually formed by screen printing a metal paste on a transparent conductive oxide film and then baking it.

At this time, in order to control the viscosity, plasticity, etc. of the metal paste, a conductive polymer is added to the metal paste. However, the conductive polymer has a problem that the specific resistance of the metal electrode is increased and the adhesive property between the metal electrode and the ribbon is reduced. .

The present invention has been made to solve the above problems, to provide a method for forming a metal electrode of the solar cell that can improve the specific resistance and contact resistance of the metal electrode through the plating process and improve the solderability (object) There is this.

Method of forming a metal electrode of a solar cell according to the present invention for achieving the above object is the step of forming a pattern mask for plating on the transparent conductive oxide film, a first on the transparent conductive oxide film exposed by the pattern mask for plating And forming a metal electrode through a plating process and forming a second metal electrode on the front and side surfaces of the first metal electrode by using a plating process.

The method of forming a metal electrode of a solar cell according to the present invention includes the steps of forming a seed layer on the transparent conductive oxide film, forming a pattern mask for plating on the seed layer, and a seed exposed by the pattern mask for plating. Forming a first metal electrode on the layer through a plating process, forming a second metal electrode on the front and side surfaces of the first metal electrode by using a plating process, and seeding the bottom of the second metal electrode. It is another feature that comprises a step of removing the seed layer on the transparent conductive oxide film except the layer.

Prior to forming the seed layer on the transparent conductive oxide film, the method may further include sequentially depositing an intrinsic layer, a second conductive amorphous silicon layer, and a transparent conductive oxide film on the first conductive crystalline silicon substrate. have. In addition, the plating process may use an electroless plating method or an electrolytic plating method, and may further include heat treatment after formation of the first metal electrode and the second metal electrode.

The metal electrode forming method of the solar cell according to the present invention has the following effects.

As the metal electrode is formed through the plating process, the specific resistance of the metal electrode itself can be reduced and the contact resistance of the metal electrode can be minimized. In addition, the weldability of the metal electrode can be improved to improve the adhesiveness with the ribbon.

Hereinafter, a method of forming a metal electrode of a solar cell according to an embodiment of the present invention will be described with reference to the drawings. 1 is a flowchart illustrating a metal electrode forming method of a solar cell according to a first embodiment of the present invention, Figures 2a to 2d is a method of forming a metal electrode of a solar cell according to a first embodiment of the present invention It is process cross section for doing this.

First, as shown in FIGS. 1 and 2A, a crystalline silicon substrate 201 of a first conductivity type is prepared (S101), and an intrinsic layer 202 and an amorphous semiconductor layer are formed on the substrate 201. (a-Si: H) 203 is laminated sequentially. Like the amorphous semiconductor layer 203, the intrinsic layer 202 is formed of an amorphous silicon layer, and the amorphous semiconductor layer 203 is doped with impurity ions of a second conductivity type. Here, the first conductivity type may be p type or n type, and the second conductivity type is opposite to the first conductivity type.

Subsequently, a transparent conductive oxide layer 204 is laminated on the amorphous semiconductor layer 203 (S102). The transparent conductive oxide film 204 may be formed of any one of ZnO, indium tin oxide (ITO), gallium zinc oxide (GZO), indium gallium zinc oxide (IGZO), indium gallium oxide (IGO), indium zinc oxide (IZO), and in2o3. Can be configured.

In the state where the transparent conductive oxide film 204 is stacked, a process of forming a metal electrode on the transparent conductive oxide film 204 is performed. Specifically, a plating pattern mask 205 for exposing the transparent conductive oxide film 204 corresponding to the portion where the metal electrode is to be formed is formed on the transparent conductive oxide film 204 (S103) (see FIG. 1A). The plating pattern mask 205 may be formed by screening or inkjet printing a plating resist or by applying a photoresist on the transparent conductive oxide film 204 and selectively patterning the same by using a photolithography process. It may be.

In the state where only the transparent conductive oxide film 204 of the portion where the metal electrode is formed by the plating pattern mask 205 is exposed, as shown in FIG. 2B, the exposed transparent conductive oxide film 204 is exposed through the plating process. The first metal electrode 206 is formed in step S104. The plating of the first metal electrode 206 may be performed using an electroless-plating method or an electro-plating method, and the first metal electrode 206 may be formed of copper (Cu) or nickel ( Ni) or the like.

In the state where the first metal electrode 206 is formed, as shown in FIG. 2C, a second metal electrode 207 is formed on the front and side surfaces of the first metal electrode 206 (S105). Like the first metal electrode 206, the second metal electrode 207 may use an electroless plating method or an electrolytic plating method, and may be formed of tin (Sn), silver (Ag), or the like. The second metal electrode 207 serves to prevent the first metal electrode 206 from being oxidized and to improve solderability in subsequent bonding with the ribbon. In addition, the second metal electrode 207 also serves as an etching mask when the pattern mask is subsequently etched and removed.

In the state where the first metal electrode 206 and the second metal electrode 207 are formed, the plating pattern mask 205 is removed as shown in FIG. 2D, and then a heat treatment process is performed (S106). By the heat treatment process, the adhesion and the compactness of the first metal electrode 206 and the second metal electrode 207 are improved.

Next, a method of forming a metal electrode of a solar cell according to a second embodiment of the present invention will be described. 3 is a flowchart illustrating a metal electrode forming method of the solar cell according to the first embodiment of the present invention, Figures 4a to 4f illustrate a metal electrode forming method of the solar cell according to the first embodiment of the present invention. It is process cross section for doing this.

First, as shown in FIGS. 3 and 4A, the intrinsic layer 402, the second conductive amorphous semiconductor layer 403, and the transparent conductive oxide film 404 are formed on the first conductive crystalline silicon substrate 401. Laminating sequentially (S301) (S302). Then, a seed layer 405 (seed layer) is stacked on the transparent conductive oxide film 404 (S303). The seed layer 405 is to reduce the contact resistance between the transparent conductive oxide film 404 and the first metal electrode 407 to be described later, and to reduce the specific resistance of the first metal electrode 407. (physical vapor deposition) For example, it may be formed through an evaporation or sputtering method. In addition, the seed layer 405 may be made of the same material as the material constituting the first metal electrode 407.

Subsequently, as shown in FIG. 4B, a plating mask 406 is formed on the seed layer 405 (S304). The plating pattern mask 406 exposes only the seed layer 405 of the portion where the first metal electrode 407 is formed, and the formation method is the same as in the first embodiment. That is, the plating resist may be formed by screen printing or inkjet printing, or may be formed by applying a photoresist on the transparent conductive oxide film 404 and selectively patterning the same by using a photolithography process.

Then, in the state where only the seed layer 405 of the portion where the first metal electrode 407 is formed by the plating pattern mask 406 is exposed, the exposed through the plating process as shown in Figure 4c A first metal electrode 407 is formed on the seed layer 405 (S305). The plating of the first metal electrode 407 may be performed using an electroless-plating method or an electro-plating method, and the first metal electrode 407 may be formed of copper (Cu) or nickel ( Ni) or the like.

In the state where the first metal electrode 407 is formed, as shown in FIG. 4D, the second metal electrode 408 is formed on the front and side surfaces of the first metal electrode 407 (S306). Like the first metal electrode 407, the second metal electrode 408 may use an electroless plating method or an electrolytic plating method, and may be formed of tin (Sn), silver (Ag), or the like. The second metal electrode 408 serves to prevent the first metal electrode 407 from being oxidized and to improve solderability during subsequent bonding to the ribbon. In addition, the second metal electrode 408 also serves as an etching mask when the pattern mask is subsequently etched and removed.

In the state where the first metal electrode 407 and the second metal electrode 408 are formed, the plating pattern mask 406 is removed as shown in FIGS. 4E and 4F, and then the second metal electrode ( The seed layer 405 other than the portion where the second metal electrode 408 is formed is removed using 408 as an etching mask (S307). Then, the heat treatment process (S308) to improve the adhesion and compactness of the first metal electrode 407 and the second metal electrode 408 to improve the metal electrode of the solar cell according to the second embodiment of the present invention The formation method is completed.

1 is a flowchart illustrating a metal electrode forming method of a solar cell according to a first embodiment of the present invention.

2A to 2D are cross-sectional views illustrating a method of forming a metal electrode of a solar cell according to a first embodiment of the present invention.

3 is a flowchart illustrating a metal electrode forming method of the solar cell according to the first embodiment of the present invention.

4A to 4F are cross-sectional views illustrating a method of forming a metal electrode of a solar cell according to a first embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

201: substrate 202: intrinsic layer

203: amorphous semiconductor layer 204: transparent conductive oxide film

205: pattern mask for plating 206: first metal electrode

207: second metal electrode

Claims

Forming a pattern mask for plating on the transparent conductive oxide film;

Forming a first metal electrode on the transparent conductive oxide film exposed by the plating pattern mask through a plating process; And

And forming a second metal electrode on the front and side surfaces of the first metal electrode by using a plating process.

Prior to forming the pattern mask for plating on the transparent conductive oxide film, further comprising the step of sequentially stacking an intrinsic layer, a second conductive amorphous silicon layer and a transparent conductive oxide film on the first conductivity type crystalline silicon substrate Forming a metal electrode of a solar cell, characterized in that.

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2. The method of claim 1, wherein the plating process uses an electroless plating method or an electrolytic plating method.

The method of claim 1, further comprising heat treatment after forming the second metal electrode.

Forming a seed layer on the transparent conductive oxide film;

Forming a plating mask on the seed layer;

Forming a first metal electrode on the seed layer exposed by the plating pattern mask through a plating process;

Forming a second metal electrode on a front surface and a side surface of the first metal electrode by using a plating process; And

And removing the seed layer on the transparent conductive oxide film except for the seed layer under the second metal electrode.

Prior to forming the seed layer on the transparent conductive oxide film, further comprising sequentially stacking an intrinsic layer, a second conductive amorphous silicon layer, and a transparent conductive oxide film on a crystalline silicon substrate of a first conductivity type. Method for forming a metal electrode of a solar cell.

The method of claim 5, wherein the seed layer is formed of the same material as the material constituting the first metal electrode.

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The method of claim 5, wherein the plating process uses an electroless plating method or an electrolytic plating method.