KR101160113B1

KR101160113B1 - Edge isolation method and solar cell thereof

Info

Publication number: KR101160113B1
Application number: KR1020090038325A
Authority: KR
Inventors: 김은지; 양정엽
Original assignee: 주식회사 효성
Priority date: 2009-04-30
Filing date: 2009-04-30
Publication date: 2012-06-26
Also published as: KR20100119291A

Abstract

The present invention relates to an edge separation method and a solar cell thereof. In the edge separation process of the present invention, first, the semiconductor layer having the opposite conductivity type is doped on the surface of the p-type semiconductor substrate to form the emitter layer 112 and the anti-reflection film 114, and the lower portion of the semiconductor substrate 110 The front electrode 116 is formed on the rear electrode 118 and the anti-reflective film 114. In such a state, an edge separation process is performed on the edge portion 120 of the semiconductor substrate 110 to separate the front electrode 116 and the back electrode 118. The edge separation process is performed by a laser chemical process (LCP). That is, LCP irradiates a p-type dopant to the edge portion 120 at the same time as a laser so that the edge portion 120 is selectively doped so that the np junction and the semiconductor substrate in the emitter layer 112 region are formed. High concentration doped regions 122 and p + are generated at 110. According to the present invention, it is possible to reduce the physical defects in the edge separation portion than using only the laser, and to increase the collection probability of the carrier due to the doped barrier, the efficiency of the solar cell is improved There is this.

Solar cells, edge separation, laser chemical process,

Description

EDGE ISOLATION METHOD AND SOLAR CELL THEREOF

The present invention relates to a solar cell, and more particularly, to an edge separation method for separating a front electrode and a rear electrode of a solar cell from each other using a laser chemical process (LCP), and a solar cell manufactured thereby.

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. The solar cell is an energy conversion device that converts light energy of the sun into electrical energy using a photovoltaic phenomenon.

In order to manufacture the solar cell, a p-n junction must be formed by doping n-type (or p-type) impurities to a p-type (or n-type) substrate. When light is emitted in the p-n junction state, electrons and holes are generated inside, and electrodes are formed on surfaces of the p-type semiconductor and the n-type semiconductor to flow electrons to an external circuit to generate current.

In this case, the edge portion of the semiconductor substrate is doped in the process for forming the p-n junction. However, when the back electrode of the solar cell is formed entirely, the result is that the front electrode and the rear electrode of the solar cell are electrically connected, thereby reducing the efficiency of the solar cell.

Therefore, an edge isolation process of electrically separating the front electrode and the back electrode from each other by removing the doped portion of the semiconductor substrate from the p-n junction of the solar cell is necessarily performed.

FIG. 1 is a flowchart illustrating a method of manufacturing a solar cell including the edge separation process.

Referring to FIG. 1, in order to manufacture a solar cell, a cutting and etching process (S10) of cutting a wafer for a solar cell into a required size and then removing surface marks generated during cutting is performed.

A texturing process (s12), which is a scratching operation, is performed on the wafer after the etching process.

Then, a doping process s14 is performed to diffuse the wafer and other types of impurities to form an emitter in order to make the wafer conductive.

After the doping process is completed, performing an etching process (s16) to remove the phosphorus silicate glass (PSG) generated when the emitter is formed, and forming an anti-reflection film to prevent the reflection of sunlight to increase the efficiency (s18) This is done.

Next, an electrode forming process for forming the back electrode and the front electrode is performed.

Finally, an edge isolation process s22 is performed.

In the edge separation process, since the doping material is also doped to the edge portion of the semiconductor substrate as described above, the front electrode and the rear electrode of the semiconductor substrate are electrically connected, which causes a decrease in efficiency. It is a process to separate the front electrode and the back electrode. The edge separation process may be performed after the doping process.

The edge separation process is performed using a dry laser after forming the front electrode and the back electrode.

2 is a cross-sectional view of a solar cell in which an edge separation process is completed in a semiconductor substrate. 2 shows the emitter layer 32, the antireflection film 34, the back electrode 36, the front electrode 38, and the back electric field layers (BSF, P +) 39 formed on the semiconductor substrate 30. The edge portion 40 of the emitter layer 32 and the antireflection film 34 is removed. By doing so, the back electrode 36 and the front electrode 38 are prevented from being shunted.

However, the solar cell manufacturing method according to the conventional method has the following problems.

That is, since the edge separation process according to the prior art is performed using a dry laser, the machining surface inside the groove from which the edge portion 40 is removed by thermal damage is incompletely processed. That is, residues remain on the processed surface or cracks occur on the inner surface of the grooves.

In addition, when a dry laser is used, a burr having a shape in which the emitter layer 32 adjacent to the groove is roughened is formed, thereby causing a problem that the emitter layer 32 formed on the semiconductor substrate is damaged.

In addition, the surface recombination of electrons occurs in the edge separation portion, there is a problem that the output of the solar cell is lowered.

As a result, when edge separation is performed using a dry laser, the efficiency of the solar cell is lowered. If a separate process is required to solve this problem, there is a problem in that the cumbersome and manufacturing costs of the process are increased.

Accordingly, an object of the present invention is to solve the above problems, and to reduce the various defects by smoothly and cleanly processing the processing surface inside the groove to be separated by the edge.

Another object of the present invention is to reduce the surface recombination of electrons in the portions which are edge separated.

According to a feature of the present invention for achieving the above object, a step of forming an emitter layer by doping a semiconductor layer having an opposite conductivity type on the surface of the semiconductor substrate; Forming an anti-reflection film on the emitter layer to prevent sunlight reflection; Forming a back electrode under the semiconductor substrate and forming a front electrode on the anti-reflection film when the anti-reflection film is formed; And performing edge separation on an edge of the semiconductor substrate to separate the front electrode and the back electrode, wherein the edge separation includes the edge portion using a laser and a dopant having the same conductivity type as that of the semiconductor substrate. And forming a dopant region in the emitter layer region and a heavily doped region in the semiconductor substrate by performing groove formation and doping in the semiconductor substrate.

During the doping, when the semiconductor substrate is a p-type semiconductor, a barrier caused by pn junction is generated according to p − type doping to prevent recombination, and when the semiconductor substrate is an n type semiconductor, np junction according to n − type doping This creates a barrier to prevent recombination of holes, thereby increasing the carrier collection probability.

In addition, when a high concentration doped region is formed in the semiconductor substrate due to the doping, the surface recombination rate of electrons and holes in the edge portion is reduced.

According to another feature of the invention, a semiconductor substrate having a first conductivity type; A second conductive semiconductor layer having a conductivity type opposite to that of the first conductive type doped on a surface of the semiconductor substrate; An anti-reflection film formed on the second conductive semiconductor layer; A back electrode formed under the first conductive semiconductor substrate; At least one front electrode in contact with a portion of the second conductive semiconductor layer; And an edge separation groove in which a laser and a chemical are simultaneously supplied to a laser chemiacal process (LCP) device at an edge portion of the semiconductor substrate, thereby forming a pn junction in the emitter layer region and a highly doped region in the semiconductor substrate. It provides a solar cell comprising a.

The chemical supplies a p-type dopant of a trivalent element such that the semiconductor substrate is p-type doped when the semiconductor substrate is a p-type semiconductor, wherein the p-type dopant is boron (B), aluminum (Al), or gallium (Ga). In the case where the semiconductor substrate is an n-type semiconductor, n-type dopants of pentavalent elements are supplied to be n-type doped, and the n-type dopants are phosphorus (P) and arsenic (As).

In the present invention, an edge separation process of irradiating a dopant along a semiconductor substrate to an edge portion at the same time as a laser and selectively doping the edge portion is performed. Physical defects can be reduced, and the collection probability of the carrier can be increased due to the doped barrier, thereby improving the efficiency of the manufactured solar cell.

Hereinafter, an edge separation method using an LCP and a preferred embodiment of a solar cell thereof according to the present invention will be described in detail with reference to the accompanying drawings.

First, the laser chemical process (LCP) is used for the edge separation process of the present invention. The LCP is a device for doping by simultaneously supplying the laser and the chemicals of the p-type or n-type dopant to the grooves that are edge-separated, this device is a publicly known device, the detailed description thereof is omitted in this embodiment Let's do it.

3 is a flowchart of an overall process of performing edge separation using LCP in a solar cell according to a preferred embodiment of the present invention.

First, referring to FIG. 3, a semiconductor layer of a second conductive type having a conductivity type opposite to that of the first conductive type is formed on a semiconductor substrate having a first conductive type (S100). That is, a p-n junction is formed by doping n-type (or p-type) impurities to a p-type (or n-type) substrate. Here, since the semiconductor layer functions as an emitter, the following description will be referred to as an emitter layer.

A process of forming an anti-reflection film to prevent sunlight reflection on the emitter layer is performed (S102).

When the anti-reflection film is formed, an electrode forming process of forming a back electrode under the first conductive semiconductor substrate and a front electrode on the anti-reflection film is performed (S104).

Then, an edge separation process is performed to prevent the front electrode and the back electrode from being electrically shunted (s106). The edge separation uses an LCP device. In other words, when the laser and chemical particles are irradiated from the LCP device to the groove where the edges are separated from each other, the surface of the semiconductor substrate to which the laser is irradiated is melted, and the dopant diffuses into the molten portion to be doped. The doping may improve the efficiency of the solar cell, in particular by reducing the surface recombination of the solar cell, since the groove portion which is edge-separated is heavily doped. In addition, the edge-separated grooves may be cleanly processed by the cooling effect of the chemical particles provided with the laser as the LCP device.

Hereinafter, an edge separation process will be described in detail using, for example, a p-type semiconductor and an n-type semiconductor.

4 illustrates a schematic configuration diagram of a solar cell in which an emitter layer is formed by doping an n-type impurity onto a textured p-type semiconductor substrate.

Referring to FIG. 4, an emitter layer 112 is formed on a textured p-type semiconductor substrate 110, and an anti-reflection film 114 is formed on the emitter layer 112. In addition, the front electrode 116 is formed on the front surface and the rear electrode 118 is formed on the front surface.

In this state, a process of forming grooves 120 (hereinafter referred to as 'edge separation grooves') for edge separation is performed on a portion of the front surface of the p-type semiconductor substrate 110. Once the edge separation groove 120 is formed, an air barrier is formed between the groove 120 and the emitter layer 112.

P-type doping is performed on the edge separation groove 120 using the LCP. In the p-type doping, boron (B), aluminum (Al), gallium (Ga), or the like is used as a dopant supplied from the LCP. According to the edge separation process, a p-type doped region is formed in the portion instead of the air barrier.

An example of the p-type doped state is shown in FIG. 5. Referring to FIG. 5, first, the peripheral region 122 of the edge separation groove 120 is doped with p-type, and the junction portion of the p-type semiconductor substrate 110 and the edge separation groove 120 is doped at a high concentration (P +). The junction between the emitter layer 112 and the edge separation groove 120 is a portion doped at a relatively low concentration (P). It can also be seen that the emitter layer 112 is composed of n-p junctions.

That is, when p-type doping is performed around the edge separation groove 120 as shown in FIG. 5, the emitter layer 112 is np bonded to generate an electric field effect at the edge separation groove 120. Recombination of electrons on the surface of the semiconductor substrate 110 is reduced.

In addition, the p-type doped barrier can cause electrons to retreat from the barrier, increasing the collection probability of the carrier. This is shown in FIG. Referring to FIG. 6, it can be seen that a barrier is formed according to an n-p junction due to p-type doping, whereby electrons do not continue and are blocked by the barrier and are returned.

In the edge separation process of the textured p-type semiconductor substrate 110, using an LCP device that irradiates the p-type semiconductor substrate 110 with impurities for laser and p-type doping, the edge separation groove ( 120) may be doped to reduce surface recombination. In addition, since the laser and the dopant are irradiated together, physical damage in the edge separation groove 120 may be prevented due to the cooling effect of the dopant than when using only the conventional laser.

Next is the edge separation process in the n-type semiconductor.

FIG. 7 is a schematic diagram illustrating a solar cell in which an emitter layer is formed by doping a p-type impurity onto a textured n-type semiconductor substrate.

Referring to FIG. 7, an emitter layer 132 is formed on a textured n-type semiconductor substrate 130, and an anti-reflection film 134 is formed on the emitter layer 132. In addition, the front electrode 136 is formed on the front surface and the rear electrode 138 is formed on the front surface.

In this state, an edge separation groove 140 is formed in a portion of the front surface of the n-type semiconductor substrate 130. The edge separation groove 140 forms an air barrier between the emitter layer 132.

N-type doping is performed on the edge separation groove 140 using the LCP. In the n-type doping, phosphorus (P), arsenic (As), or the like is used as the dopant supplied from the LCP as a pentavalent element. According to the edge separation process, an n-type doped region is formed in the portion instead of the air barrier.

An example of the n-type doped state is shown in FIG. 8. Referring to FIG. 8, first, the peripheral region 142 of the edge separation groove 140 is doped with n-type, and the junction portion of the n-type semiconductor substrate 130 and the edge separation groove 140 is doped at a high concentration (n +). The junction between the emitter layer 112 and the edge separation groove 120 is a portion doped at a relatively low concentration (n). In addition, it can be seen that the emitter layer 132 is composed of a p-n junction.

That is, when n-type doping is performed around the edge separation groove 140 as shown in FIG. 8, the emitter layer 132 is pn-bonded to generate an electric field effect at the edge separation groove 140. Recombination of holes in the surface of the semiconductor substrate 130 is reduced.

In addition, the n-type doped barrier can cause holes to exit from the barrier, increasing the collection probability of the carrier. This is shown in FIG. Referring to FIG. 9, it can be seen that a barrier is formed by p-n junction due to n-type doping, so that holes cannot be continued and are blocked by the barrier and returned.

In the edge separation process of the textured n-type semiconductor substrate 130, using an LCP device that irradiates the n-type semiconductor substrate 130 with impurities for laser and n-type doping, the edge separation groove ( 140 may be doped with n-type to reduce surface recombination. In addition, since the laser and the dopant are irradiated together, physical damage in the edge separation groove 140 may be prevented due to the cooling effect of the dopant than when using only the conventional laser.

As described above, the present embodiment performs the edge separation process in the semiconductor substrate using the LCP, it can be seen that the efficiency of the solar cell is improved than when using only a conventional dry laser device.

The scope of the present invention is not limited to the embodiments described above, but is defined by the claims, and various changes and modifications can be made within the scope of the claims by those skilled in the art. It is self evident.

1 is a flowchart showing a method of manufacturing a solar cell including an edge separation process according to the prior art.

2 is a cross-sectional view of a solar cell in which an edge separation process is completed in a semiconductor substrate according to the related art.

FIG. 4 is a schematic configuration diagram of a solar cell in which an emitter layer is formed by doping n-type impurities into a p-type semiconductor substrate textured according to the method of FIG. 3.

5 is an enlarged view of the edge separation groove of FIG. 4.

6 is an exemplary state diagram showing a path of movement of electrons in the edge separation groove of FIG. 5;

FIG. 7 is a schematic configuration diagram of a solar cell in which an emitter layer is formed by doping p-type impurities into a n-type semiconductor substrate textured according to the method of FIG. 3.

8 is an enlarged view of the edge separation groove of FIG. 7;

FIG. 9 is an exemplary state diagram illustrating a movement path of holes in an edge separation groove of FIG. 8; FIG.

* Description of the symbols for the main parts of the drawings *

110 p-type semiconductor substrate 112 emitter layer

114: antireflection film 116: front electrode

118: rear electrode 120: edge separation groove

122: doped region

Claims

Doping a semiconductor layer having an opposite conductivity type on a surface of the semiconductor substrate to form an emitter layer;

Forming an anti-reflection film on the emitter layer to prevent sunlight reflection;

Forming a back electrode under the semiconductor substrate and forming a front electrode on the anti-reflection film when the anti-reflection film is formed; And,

And performing edge separation on the edge of the semiconductor substrate to separate the front electrode and the back electrode.

The edge separation may be performed by forming a groove and doping the edge portion with a laser and a dopant of the same conductivity type as the semiconductor substrate to generate a pn junction in the emitter layer region and a highly doped region in the semiconductor substrate. Edge separation method.

2. The edge of claim 1, wherein when the doping is performed, the semiconductor substrate is a p-type semiconductor to prevent recombination due to barrier formation due to a pn junction according to p − type doping, thereby increasing a collection probability of a carrier. Separation Method.

The method of claim 1, wherein when the doping is performed, when the semiconductor substrate is an n-type semiconductor, holes are prevented from being recombined by barrier formation due to np junction according to n − type doping, thereby increasing a carrier collection probability. Edge separation method.

4. The method according to any one of claims 1 to 3,

If the doping region is a high concentration dopant in the semiconductor substrate due to the doping, the surface recombination rate of electrons and holes in the edge portion is reduced.

A semiconductor substrate having a first conductivity type;

A second conductive semiconductor layer having a conductivity type opposite to that of the first conductive type doped on a surface of the semiconductor substrate;

An anti-reflection film formed on the second conductive semiconductor layer;

A back electrode formed under the first conductive semiconductor substrate;

At least one front electrode in contact with a portion of the second conductive semiconductor layer; And,

Simultaneously supplying laser and chemicals to the edge portion of the semiconductor substrate with a laser chemiacal process (LCP) device to separate the pn junction in the semiconductor layer region of the second conductivity type and the edge separation in which the highly doped region is formed in the semiconductor substrate. Solar cell, characterized in that configured to include a groove.

The method of claim 5,

The chemical supplies a p-type dopant of a trivalent element such that the semiconductor substrate is p-type doped when the semiconductor substrate is a p-type semiconductor, wherein the p-type dopant is boron (B), aluminum (Al), or gallium (Ga). ) A solar cell.

The method of claim 5,

Wherein the chemical material, when the semiconductor substrate is an n-type semiconductor to supply n- type dopant of the pentavalent element so that n- type doping, wherein the n- type dopant is phosphorus (P), arsenic (As), characterized in that Solar cell.