KR101081075B1

KR101081075B1 - Solar cell and method of fabricating the same

Info

Publication number: KR101081075B1
Application number: KR1020090056759A
Authority: KR
Inventors: 최성범
Original assignee: 엘지이노텍 주식회사
Priority date: 2009-06-25
Filing date: 2009-06-25
Publication date: 2011-11-07
Also published as: KR20100138299A

Abstract

A solar cell according to an embodiment includes a solar cell formed in a cell region on a substrate including a cell region and a peripheral region; A first bus bar formed on the solar cell in a first direction on the cell region and a peripheral region; And a second bus bar formed in a second direction on the peripheral area, wherein the solar cell comprises: a plurality of back electrode patterns spaced apart from each other on the cell area on the substrate; A light absorbing layer disposed on the substrate on which the rear electrode pattern is disposed, and forming a contact pattern for connection between electrodes; A front electrode formed on the light absorption layer; And a separation pattern divided into unit cells through the front electrode and the light absorbing layer, wherein the front electrode is inserted into the contact pattern to be electrically connected to the back electrode pattern, and the first bus bar and the second bus bar. The parts are stacked and electrically connected.

Solar cell

Description

SOLAR CELL AND METHOD OF FABRICATING THE SAME

An embodiment relates to a solar cell and a manufacturing method thereof.

Recently, as the demand for energy increases, development of solar cells for converting solar energy into electrical energy is in progress.

In particular, CIGS-based solar cells, which are pn heterojunction devices having a substrate structure including a glass substrate, a metal back electrode layer, a p-type CIGS-based light absorbing layer, a high resistance buffer layer, an n-type window layer, and the like, are widely used.

After forming such a solar cell, a bus bar is formed between the upper electrode of the solar cell and the junction box in order to transmit a signal of the upper electrode to a junction box.

The embodiment provides a solar cell and a method for manufacturing the same, which may increase efficiency by improving electrical conductivity of a bus bar.

A method of manufacturing a solar cell according to an embodiment includes forming a plurality of back electrode patterns spaced apart from each other on a substrate; Forming a light absorbing layer formed on the substrate on which the rear electrode pattern is disposed and including a contact pattern for connection between electrodes; Forming a front electrode on the light absorbing layer including the contact pattern to form a solar cell including the back electrode pattern, the light absorbing layer, and the front electrode; And forming a bus bar on the solar cell, wherein the bus bar is formed by a deposition process.

In the solar cell and the manufacturing method thereof according to the embodiment, since the bus bar is formed in the vacuum chamber, the series resistance with the front electrode is reduced, and thus the electrical conductivity of the bus bar can be improved.

In addition, the front electrode may be doped with aluminum, and thus, the bus bar and the front electrode, which are metal materials, may have strong adhesion.

That is, by using the same metal material as the metal atoms doped in the front electrode, the bonding force between the front electrode and the bus bar is improved, it is possible to improve the efficiency of the solar cell.

In the description of the embodiments, where each substrate, layer, film, or electrode is described as being formed "on" or "under" of each substrate, layer, film, or electrode, etc. , "On" and "under" include both "directly" or "indirectly" formed through other components. In addition, the upper or lower reference of each component is described with reference to the drawings. The size of each component in the drawings may be exaggerated for the sake of explanation and does not mean the size actually applied.

1 to 12 are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment.

First, as shown in FIG. 1, the back electrode 201 is formed on the substrate 100.

The substrate 100 may be glass, and a ceramic substrate such as alumina, stainless steel, a titanium substrate, or a polymer substrate may also be used.

Soda lime glass may be used as the glass substrate, and polyimide may be used as the polymer substrate.

In addition, the substrate 100 may be rigid or flexible.

The back electrode 201 may be formed of a conductor such as metal.

For example, the back electrode 201 may be formed by a sputtering process using a molybdenum (Mo) target.

This is because of high electrical conductivity of molybdenum (Mo), ohmic bonding with the light absorbing layer, and high temperature stability under Se atmosphere.

In addition, although not shown in the drawing, the back electrode 201 may be formed of at least one layer.

When the back electrode 201 is formed of a plurality of layers, the layers constituting the back electrode 201 may be formed of different materials.

In this case, the back electrode 201 may have a sheet resistance of 0.1 to 10 mΩ and a thickness of 100 to 1000 nm.

As shown in FIG. 2, a patterning process is performed on the back electrode 201 to form a back electrode pattern 200.

In addition, the back electrode pattern 200 may be arranged in a stripe form or a matrix form and may correspond to each cell.

However, the back electrode pattern 200 is not limited to the above form and may be formed in various forms.

In this case, in order to pattern the back electrode 201, a laser may be irradiated onto the substrate 100 to form the back electrode pattern 200.

The gap P1 of the back electrode pattern 200 may be 50 to 70 μm.

3, the light absorbing layer 300, the first buffer layer 400, and the second buffer layer 500 are formed on the back electrode 201.

The light absorbing layer 300 may include a Ib-IIIb-VIb-based compound and may be formed to a thickness of 1000 to 3500 nm.

In more detail, the light absorbing layer 300 includes a copper-indium-gallium-selenide-based (Cu (In, Ga) Se ₂ , CIGS-based) compound.

Alternatively, the light absorbing layer 300 may include a copper-indium selenide-based (CuInSe ₂ , CIS-based) compound or a copper-gallium-selenide-based (CuGaSe ₂ , CIS-based) compound.

For example, in order to form the light absorbing layer 300, a CIG-based metal precursor film is formed on the back electrode 130 using a copper target, an indium target, and a gallium target.

Thereafter, the metal precursor film is reacted with selenium (Se) by a selenization process to form a CIGS-based light absorbing layer 300.

In addition, during the process of forming the metal precursor film and the selenization process, an alkali component included in the substrate 100 may pass through the back electrode pattern 200, and the metal precursor film and the light absorbing layer ( 300).

An alkali component may improve grain size and improve crystallinity of the light absorbing layer 300.

The light absorbing layer 300 receives external light and converts the light into electrical energy. The light absorbing layer 300 generates photo electromotive force by the photoelectric effect.

The first buffer layer 400 may be formed by stacking cadmium sulfide (CdS) on the light absorbing layer 300.

In this case, the first buffer layer 400 is an n-type semiconductor layer, and the light absorbing layer 300 is a p-type semiconductor layer. Thus, the light absorbing layer 300 and the first buffer layer 400 form a pn junction.

In addition, the second buffer layer 500 may be formed of a transparent electrode layer including any one of ITO, ZnO, and i-ZnO.

The first buffer layer 400 and the second buffer layer 500 are disposed between the light absorbing layer 300 and the front electrode to be formed later.

That is, since the difference between the lattice constant and the energy band gap between the light absorbing layer 300 and the front electrode is large, the first buffer layer 400 and the second buffer layer 500 having a band gap between the two materials are disposed. Can be inserted to form a good bond.

The first buffer layer 400 and the second buffer layer 500 may be formed to a thickness of 50 ~ 200 nm.

In the present embodiment, two buffer layers are formed on the light absorbing layer 300, but the present invention is not limited thereto, and the buffer layer may be formed of only one layer.

As shown in FIG. 4, a contact pattern 310 penetrating the light absorbing layer 300, the first buffer layer 400, and the second buffer layer 500 is formed.

The contact pattern 310 may be formed by a mechanical method or by irradiating a laser, and a portion of the back electrode pattern 200 is exposed.

In this case, the second buffer layer 500 may be processed by using a laser having a wavelength different from that of the light absorbing layer 300 and the first buffer layer 400, or the intensity according to the degree of concentration of the laser through the lens. It can also proceed by adjusting).

Since the second buffer layer 500 has a high energy band gap, a laser having a relatively high output power is used, and the first buffer layer 400 and the light absorbing layer 300 have a relatively low energy band gap. The contact pattern 310 may be formed using a laser of low power.

Width P2 of the contact pattern 310 may be formed to 70 ~ 90 μm, the distance (G1) from one end of the back electrode pattern 200 to the width (P2) of the contact pattern 310 is It can be formed from 60 to 100 μm.

Subsequently, as shown in FIG. 5, a transparent conductive material is stacked on the second buffer layer 500 to form the front electrode 600 and the connection wiring 700.

When the transparent conductive material is stacked on the second buffer layer 500, the transparent conductive material may also be inserted into the contact pattern 310 to form the connection wiring 700.

The back electrode pattern 200 and the front electrode 600 are electrically connected by the connection wiring 700.

The front electrode 600 is sputtered with zinc oxide doped with aluminum on the second buffer layer 500, and has a sheet resistance of 10 to 100 Ω, a transmittance of 90%, and a thickness of 500 nm. Can be formed.

The front electrode 600 is a window layer forming a pn junction with the light absorbing layer 300. Since the front electrode 600 functions as a transparent electrode on the front of the solar cell, zinc oxide (ZnO) having high light transmittance and good electrical conductivity is provided. Is formed.

In this case, an electrode having a low resistance value may be formed by doping aluminum to the zinc oxide.

The zinc oxide thin film as the front electrode 600 may be formed by a method of depositing using a ZnO target by RF sputtering, reactive sputtering using a Zn target, and an organometallic chemical vapor deposition method.

In addition, a double structure in which an indium tin oxide (ITO) thin film having excellent electro-optical properties is laminated on a zinc oxide thin film may be formed.

6, a bus bar 800 is formed on the front electrode 600.

The bus bar 800 is formed of any one of silver (Ag), copper (Cu), gold (Au), aluminum (Al), tin (Sn), nickel (Ni) by a sputtering method, or It may be formed of an alloy of.

In addition, the material forming the bus bar 800 is not limited thereto, and at least one of silver (Ag), copper (Cu), gold (Au), aluminum (Al), tin (Sn), and nickel (Ni). The materials may be formed by lamination, or may be formed by laminating materials made of alloys thereof.

In addition, when the bus bar 800 is formed by stacking at least one or more materials, the bus bar 800 may be formed of one to three layers.

The bus wave 800 may have a thickness T of 0.5 to 10 μm and a width W of 2 to 6 mm.

Both the front electrode 600 and the bus bar 800 are processed in a vacuum chamber, and may be performed in the same chamber.

In this case, since the bus bar 800 is formed in the vacuum chamber, the series resistance with the front electrode 600 is reduced, so that the electrical conductivity of the bus bar 800 may be improved.

In addition, the front electrode 600 may be doped with aluminum so that the bus bar 800 and the front electrode 600, which are metal materials, may have strong adhesion.

That is, by using the same metal material as aluminum doped to the front electrode 600, the bonding force between the front electrode 600 and the bus bar 800 can be improved.

Subsequently, as illustrated in FIG. 7, a separation pattern 320 penetrating the light absorbing layer 300, the first buffer layer 400, the second buffer layer 500, and the front electrode 600 is formed.

The separation pattern 320 may be formed by a mechanical method, or may be formed by irradiating a laser, and may be formed to expose the top surface of the back electrode pattern 200.

In this case, the width P3 of the separation pattern 320 may be 70 to 90 μm, and the gap G2 of the connection wiring 700 and the separation pattern 320 may be 60 to 100 μm. Can be.

The first buffer layer 400, the second buffer layer 500, and the front electrode 600 may be separated by the separation pattern 320, and each cell C1 and C2 may be separated by the separation pattern 320. May be separated from each other.

The first buffer layer 400, the second buffer layer 500, and the light absorbing layer 300 may be arranged in a stripe form or a matrix form by the separation pattern 320.

The separation pattern 300 is not limited to the above form and may be formed in various forms.

Cells C1 and C2 including the back electrode pattern 200, the light absorbing layer 300, the first buffer layer 400, the second buffer layer 500, and the front electrode 600 by the separation pattern 320. Is formed.

In this case, each of the cells C1 and C2 may be connected to each other by the connection wiring 700. That is, the connection wiring 700 electrically connects the back electrode pattern 200 of the second cell C2 and the front electrode 600 of the first cell C1 adjacent to the second cell C2. do.

By forming the separation pattern 320, an active area (AA) and a non-active area (NAA) of the solar cell may be defined.

Subsequently, although not shown, a process of removing a portion of an edge region of the substrate 100 may be further performed.

8 is a plan view schematically illustrating the substrate 100 in which an edge deletion process is performed.

As shown in FIG. 8, each cell is formed in a stripe form with a gap D in the substrate 100, and a bus bar 800 is formed on the front electrode 600 of the cell formed at the outermost part. do.

In this case, the bus bar 800 may be formed up to the hole 1 disposed in the substrate 100.

The hole 1 is disposed to connect a signal formed from the bus bar 800 to a junction box disposed on the rear surface of the substrate 100.

9 schematically illustrates a chamber 10 forming the busbar 800.

The chamber 10 may perform a process for forming the front electrode 600 and the bus bar 800.

That is, the front electrode 600 and the bus bar 800 may be formed in the same chamber. After the front electrode 600 is formed, the substrate 100 may be lowered to the second target 30. After moving, the process for forming the bus bar 800 is performed.

The chamber 10 includes a first target 20 and a second target 30, which may form the front electrode 600 and the bus bar 800, and is located outside the second target 30. A shield 40 may be disposed to block a portion of the second target 30.

The first target 20 for forming the front electrode 600 may be a zinc oxide target (ZnO target), the second target 30 for forming the bus bar 800 is silver (Ag), It may be a target made of any one of copper (Cu), gold (Au), aluminum (Al), tin (Sn), nickel (Ni) or an alloy thereof.

The shield 40 may serve as a mask for forming the bus bar 800, and the second target 30 may be exposed in the shape of the bus bar 800.

That is, since the plasma is generated only in the region exposed by the shield 40 during the process of sputtering, the bus bar 800 may be formed only in a part of the front electrode 600.

Each target is spaced apart from each other so as not to affect each process.

Although not shown in the drawing, a shutter may be disposed to block each target so that neighboring targets may selectively use each target without affecting the substrate 100.

The second target 30 may be partially blocked by using the shield 40, but the present invention is not limited thereto, and the shape of the target may be changed or the shape of the shield 40 to which the target is exposed may be changed. It may be formed by going through more than one process.

That is, as shown in FIG. 10 and FIG. 11, by placing the third target 50 and the fourth target 60 separately in the chamber 10, the bus bar 800 in two processes Can be formed.

First, the shape of the third target 50 is disposed in the first direction, which is the longitudinal direction of the cell, and the fourth target 60 is disposed in the second direction, which is the direction in which the hole 1 of the substrate 100 is formed. Place it.

The third target 50 and the fourth target 60 may be formed of the same material as the second target 40.

In addition, the first bus bar pattern 801 is formed in the outermost cell using the third target 50, and the first bus bar pattern 801 is formed using the fourth target 60. The bus bar 800 may be formed by forming a second bus bar pattern 802 in a second direction so that) may be connected to the hole 1.

That is, the bus bar 800 may be formed by performing at least one deposition process, such as a sputter process.

After the first bus bar pattern 801 is formed, the second bus bar pattern 802 is formed, and a part of the first bus bar pattern 801 is stacked on the second bus bar pattern 802. Can be formed.

In this case, the portions 5 formed in addition to the region where the bus bar 800 is to be formed may be removed after the edge deletion process.

When the portion removed by the edge removing process is called the peripheral region B and the portion of the cell remaining is called the cell region A, the first bus bar pattern 801 is formed on the cell region A. It may be formed to extend to the peripheral region (B).

In addition, the second bus bar pattern 802 is connected to the first bus bar pattern 801 on the peripheral area B to form the hole 1.

FIG. 12 is a side cross-sectional view of I-I 'which is a portion where the first bus bar pattern 801 and the second bus bar pattern 802 formed in the peripheral area B are connected.

As shown in FIG. 12, a portion of the first bus bar pattern 801 formed in the peripheral area B and a lower portion of the second bus bar pattern A may include a cell formed in the cell area A; A dummy cell 650 having the same structure is formed.

In addition, after the first bus bar pattern 801 is formed, the second bus bar pattern 802 is formed so that the first bus bar pattern 801 and the second bus bar pattern 802 overlap each other. do.

In the present exemplary embodiment, the first bus bar pattern 801 is disposed below the second bus bar pattern 802. However, the first bus bar pattern 801 is not limited thereto. The first bus bar pattern 801 may be formed, and the second bus bar pattern 802 may be formed under the first bus bar pattern 801.

In the solar cell and the manufacturing method thereof according to the embodiment described above, since the bus bar is formed in the vacuum chamber, the series resistance with the front electrode is reduced, and thus the electrical conductivity of the bus bar may be improved.

That is, by using the same metal material as aluminum doped to the front electrode, the bonding force between the front electrode and the bus bar is improved, it is possible to improve the efficiency of the solar cell.

Although described above with reference to the embodiment is only an example and is not intended to limit the invention, those of ordinary skill in the art to which the present invention does not exemplify the above within the scope not departing from the essential characteristics of this embodiment It will be appreciated that many variations and applications are possible. For example, each component specifically shown in the embodiment can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

Claims

A solar cell formed in a cell region on a substrate including a cell region and a peripheral region;

A first bus bar formed on the solar cell in a first direction on the cell region and a peripheral region; And

A second bus bar formed in a second direction on the peripheral area;

The solar cell,

A plurality of back electrode patterns spaced apart from each other on the cell area on the substrate;

A light absorbing layer disposed on the substrate on which the rear electrode pattern is disposed, and forming a contact pattern for connection between electrodes;

A front electrode formed on the light absorption layer; And

It includes a separation pattern divided into a unit cell through the front electrode and the light absorbing layer,

The front electrode is inserted into the contact pattern and electrically connected to the back electrode pattern,

The first bus bar is formed on the front electrode and the solar cell laminated with the second bus bar.

delete

The method of claim 1,

A solar cell having a dummy cell formed in the same structure as the solar cell in the lower portion of the second bus bar formed on the peripheral area.

The method of claim 1,

The first bus bar and the second bus bar may be formed by stacking at least one of silver (Ag), copper (Cu), gold (Au), aluminum (Al), tin (Sn), and nickel (Ni). Solar cells formed by laminating, or a material made of an alloy thereof.

The method of claim 1,

The first bus bar and the second bus bar is a solar cell formed to a thickness of 0.5 ~ 10 μm.

Forming a plurality of back electrode patterns spaced apart from each other on the substrate;

Forming a light absorbing layer formed on the substrate on which the rear electrode pattern is disposed and including a contact pattern for connection between electrodes;

Forming a front electrode on the light absorbing layer including the contact pattern to form a solar cell including the back electrode pattern, the light absorbing layer, and the front electrode; And

Forming a bus bar on the solar cell;

The busbar is a method of manufacturing a solar cell is formed by depositing in a vacuum chamber.

The method of claim 6,

Forming the bus bar,

Forming a first bus bar pattern in a first direction on a substrate on which the solar cell is formed; And

Forming a second busbar pattern on the substrate in a second direction to form a busbar formed of the first busbar pattern and the second busbar pattern;

The first bus bar pattern and the second bus bar pattern is a method of manufacturing a solar cell electrically connected.

The method of claim 6,

After forming the bus bar,

Patterning the front electrode and the light absorbing layer to form a separation pattern for dividing into unit cells;

The front electrode is inserted into the contact pattern is a manufacturing method of a solar cell electrically connected to the back electrode pattern.

The method of claim 6,

The front electrode and the bus bar is a solar cell manufacturing method formed in the same chamber.