KR101231398B1 - Solar cell apparatus and method of fabricating the same - Google Patents

Solar cell apparatus and method of fabricating the same Download PDF

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Publication number
KR101231398B1
KR101231398B1 KR1020110030883A KR20110030883A KR101231398B1 KR 101231398 B1 KR101231398 B1 KR 101231398B1 KR 1020110030883 A KR1020110030883 A KR 1020110030883A KR 20110030883 A KR20110030883 A KR 20110030883A KR 101231398 B1 KR101231398 B1 KR 101231398B1
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South Korea
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layer
back electrode
contact
electrode layer
solar cell
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KR1020110030883A
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Korean (ko)
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KR20120113131A (en
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최철환
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엘지이노텍 주식회사
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Abstract

Solar cell according to the embodiment is a substrate; A back electrode layer on the substrate; A light absorbing layer on the back electrode layer; A buffer layer on the light absorbing layer; A window layer on the buffer layer; And a contact layer in contact with the top surface of the back electrode layer under the through grooves formed so that a portion of the top surface of the back electrode layer is exposed, and including at least one of In, Sn, and Sr.

Description

SOLAR CELL AND MANUFACTURING METHOD THEREOF {SOLAR CELL APPARATUS 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, a CIGS-based solar cell, which is a pn heterojunction device having a support substrate structure including a glass support substrate, a metal back electrode layer, a p-type CIGS-based light absorbing layer, a buffer layer, an n-type transparent electrode layer, and the like, is widely used.

In addition, various studies are underway to increase the efficiency of such solar cells.

The embodiment is to provide a solar cell and a method for manufacturing the photovoltaic conversion efficiency is improved by reducing the contact resistance.

Solar cell according to the embodiment is a substrate; A back electrode layer on the substrate; A light absorbing layer on the back electrode layer; A buffer layer on the light absorbing layer; A window layer on the buffer layer; And a contact layer in contact with the top surface of the back electrode layer under the through grooves formed so that a portion of the top surface of the back electrode layer is exposed, and including at least one of In, Sn, and Sr.

A method of manufacturing a solar cell according to an embodiment includes forming a back electrode layer on a substrate; Forming a light absorbing layer and a buffer layer on the back electrode layer; Removing a portion of the light absorbing layer and the buffer layer to form through grooves to expose a portion of the top surface of the back electrode layer; Forming a contact layer in contact with an upper surface of the back electrode layer in the through grooves and including at least one of In, Sn or Sr; And forming a window layer on the buffer layer and the contact layer.

In example embodiments, a contact layer may be formed on an upper surface of the back electrode layer to reduce contact resistance between the window layer and the back electrode layer.

Accordingly, the series resistance can be reduced and the efficiency of the solar cell can be increased.

1 is a plan view illustrating a solar cell apparatus according to an embodiment.
FIG. 2 is a cross-sectional view illustrating a cross section taken along AA ′ in FIG. 1.
3 to 6 are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment.

In the description of the embodiments, when each support substrate, layer, film, or electrode is described as being formed "on" or "under" of each support substrate, layer, film, or electrode, etc. As used herein, “on” and “under” include both “directly” or “indirectly” other components. In addition, the upper or lower reference of each component is described with reference to the drawings. In the drawings, the size of each component may be exaggerated for description, and does not mean the size to be actually applied.

FIG. 1 is a plan view illustrating a photovoltaic device according to an embodiment, and FIG. 2 is a cross-sectional view illustrating a cross section taken along a line A-A 'of FIG. 1.

2, a solar cell according to an embodiment includes a support substrate 100, a back electrode layer 200 on the support substrate 100, a light absorbing layer 300 on the back electrode layer 200, and the light absorbing layer. A buffer layer 400 and a high resistance buffer layer 500 on the 300, a contact layer 650 in contact with the back electrode layer 200, and a window layer 600 on the high resistance buffer layer 500.

The support substrate 100 has a plate shape and supports the back electrode layer 200, the light absorbing layer 300, the buffer layer 400, the high resistance buffer layer 500, the contact layer 650, and the window layer 600. do.

The support substrate 100 may be an insulator. The support substrate 100 may be a glass substrate, a plastic substrate, or a metal substrate. In more detail, the support substrate 100 may be a soda lime glass substrate.

When the support substrate 100 is soda lime glass, sodium (Na) contained in the soda lime glass may be diffused into the light absorbing layer 300 formed of CIGS during the manufacturing process of the solar cell, whereby the light absorbing layer 300 ), The charge concentration may increase. This may be a factor that can increase the photoelectric conversion efficiency of the solar cell.

In addition, a ceramic substrate such as alumina, stainless steel, a flexible polymer, or the like may be used as the material of the support substrate 100. The support substrate 100 may be transparent, rigid, or flexible.

The back electrode layer 200 is disposed on the support substrate 100. The back electrode layer 200 is a conductive layer. The back electrode layer 200 may allow electric current generated in the light absorbing layer 300 of the solar cell to move so that current flows to the outside of the solar cell. The back electrode layer 200 should have high electrical conductivity and low specific resistance in order to perform this function.

In addition, the back electrode layer 200 must maintain high temperature stability during heat treatment in a sulfur (S) or selenium (Se) atmosphere accompanying the formation of the CIGS compound. In addition, the back electrode layer 200 should be excellent in adhesion with the support substrate 100 so that the backing layer and the support substrate 100 are not peeled due to a difference in thermal expansion coefficient.

The back electrode layer 200 may be formed of any one of molybdenum (Mo), gold (Au), aluminum (Al), chromium (Cr), tungsten (W), and copper (Cu). Among them, in particular, molybdenum (Mo) has a small difference between the support substrate 100 and the coefficient of thermal expansion compared to other elements, and thus excellent adhesion can be prevented from occurring in the peeling phenomenon. Overall required properties can be met.

The back electrode layer 200 may include two or more layers. In this case, each of the layers may be formed of the same metal, or may be formed of different metals.

First through holes TH1 are formed in the back electrode layer 200. The first through holes TH1 are open regions exposing a portion of an upper surface of the support substrate 100. The first through holes TH1 may have a shape extending in one direction when viewed in a plan view.

The width of the support substrate 100 exposed by the first through holes TH1 may be about 40 μm to 150 μm.

The back electrode layer 200 is divided into a plurality of back electrodes by the first through holes TH1. That is, back electrodes are defined by the first through holes TH1.

The back electrodes are arranged in a stripe shape. Alternatively, the back electrodes may be arranged in a matrix form. At this time, the first through grooves TH1 may be formed in a lattice form when viewed from a plane.

The light absorbing layer 300 may be formed on the back electrode layer 200. The light absorbing layer 300 includes a p-type semiconductor compound. In more detail, the light absorbing layer 300 includes a group I-III-VI compound. For example, the light absorbing layer 300 is copper-indium-gallium-selenide-based (Cu (In, Ga) Se 2; CIGS-based) crystal structure, a copper-indium-selenide-based or copper-gallium-selenide Crystal structure.

The buffer layer 400 and the high resistance buffer layer 500 may be formed on the light absorbing layer 300. The solar cell having the CIGS compound as the light absorbing layer 300 forms a pn junction between the CIGS compound thin film as the p-type semiconductor and the window layer 600 thin film as the n-type semiconductor. However, since the two materials have a large difference in lattice constant and band gap energy, a buffer layer having a band gap in between the two materials is required to form a good junction.

Materials for forming the buffer layer 400 include CdS, ZnS and the like, and CdS is relatively excellent in terms of power generation efficiency of the solar cell.

The high resistance buffer layer 500 includes zinc oxide (i-ZnO) that is not doped with impurities. The energy bandgap of the high resistance buffer layer 500 is about 3.1 eV to 3.3 eV.

The window layer 600 is formed on the high resistance buffer layer 500. The window layer 600 is transparent and is a conductive layer. In addition, the resistance of the window layer 600 is higher than the resistance of the back electrode layer 200.

The window layer 600 includes an oxide. For example, the window layer 600 may include zinc oxide, indium tin oxide (ITO), or indium zinc oxide (IZO).

In addition, the oxide may include conductive impurities such as aluminum (Al), alumina (Al 2 O 3 ), magnesium (Mg), or gallium (Ga). More specifically, the window layer 600 may be formed of aluminum doped zinc oxide (AZO), boron doped zinc oxide (BZO), or gallium doped zinc oxide (GZO). ) May be included.

The contact layer 650 may be formed on the top surface of the back electrode layer 200 exposed by the second through holes TH2.

As shown, a portion of the upper surface of the back electrode layer 200 may be exposed by the second through holes TH2. In addition, a plurality of solar cells may be connected in series by the window layer 600 formed to fill the second through holes TH2.

The window layer 600 generally includes AZO, BZO, or GAZO. Since the window layer 600 has a large contact resistance with the back electrode layer 200, the series resistance Rs increases. The photoelectric conversion efficiency of the solar cell is reduced.

In order to reduce the above problems, the contact layer 650 is formed on the exposed upper surface of the back electrode layer 200. The contact layer 650 may be formed on an upper surface of the back electrode layer 200 exposed by the second through holes TH2, and the contact layer formed on the upper surface of the high resistance buffer layer 500 may be formed by etching. Can be removed.

A contact layer 650 including a material having a low resistance may be formed between the window layer 600 and the back electrode layer 200 to reduce contact resistance with the back electrode layer 200.

The thickness W1 of the contact layer 650 may be formed in a range of 5 nm to 100 nm.

The contact layer 650 may include at least one of strontium doped with Ba, Cd 2 InO 4, or Cd 2 SnO 4 .

As discussed above, the contact layer 650 may be formed on the upper surface of the back electrode layer 200 exposed by the second through holes TH2 to reduce contact resistance with the back electrode layer 200. have.

Accordingly, the series resistance can be reduced and the efficiency of the solar cell can be increased.

3 to 6 are cross-sectional views illustrating a method of manufacturing the solar cell apparatus according to the embodiment. The description of this manufacturing method refers to the description of the photovoltaic device described above.

Referring to FIG. 3, the back electrode layer 200 is formed on the support substrate 100, and the back electrode layer 200 is patterned to form first through holes TH1. Accordingly, a plurality of back electrodes are formed on the support substrate 100. The back electrode layer 200 may be patterned by a laser.

The first through holes TH1 may expose an upper surface of the support substrate 100 and have a width of about 40 μm to about 150 μm.

In addition, an additional layer, such as a diffusion barrier, may be interposed between the support substrate 100 and the back electrode layer 200, wherein the first through holes TH1 expose the top surface of the additional layer. .

Referring to FIG. 4, the light absorbing layer 300, the buffer layer 400, and the high resistance buffer layer 500 are formed on the back electrode layer 200.

The light absorption layer 300 may be formed by a sputtering process or an evaporation process.

In order to form the light absorbing layer 300, for example, copper, indium, gallium, selenium, or copper-indium-gallium-selenide-based (Cu (In, Ga) Se 2 ; CIGS-based) A method of forming the light absorbing layer 300 and a method of forming a metal precursor film and then forming it by a selenization process are widely used.

After the metal precursor film is formed and then subjected to selenization, a metal precursor film is formed on the back electrode 200 by a sputtering process using a copper target, an indium target, and a gallium target.

Thereafter, the metal precursor film is formed of a copper-indium-gallium-selenide-based (Cu (In, Ga) Se 2 ; CIGS-based) light absorbing layer by a selenization process.

Alternatively, the copper target, the indium target, the sputtering process using the gallium target, and the selenization process may be performed simultaneously.

Alternatively, the CIS-based or CIG-based optical absorption layer 300 can be formed by using only a copper target and an indium target, or by a sputtering process and a selenization process using a copper target and a gallium target.

Thereafter, cadmium sulfide is deposited by a sputtering process or a chemical bath depositon (CBD) or the like, and the buffer layer 400 is formed.

Then, zinc oxide is deposited on the buffer layer 400 by a sputtering process or the like, and the high-resistance buffer layer 500 is formed.

The buffer layer 400 and the high resistance buffer layer 500 are deposited to a low thickness. For example, the thickness of the buffer layer 400 and the high resistance buffer layer 500 is about 1 nm to about 100 nm.

Thereafter, a portion of the light absorbing layer 300, the buffer layer 400, and the high resistance buffer layer 500 is removed to form second through holes TH2.

The second through grooves TH2 may be formed by a mechanical device such as a tip or a laser device.

In this case, the width of the second through holes TH2 may be about 50 μm to about 200 μm.

In addition, the second through holes TH2 are formed to expose a portion of the top surface of the back electrode layer 200.

Referring to FIG. 5, a contact layer 650 is formed on an upper surface of the back electrode layer 200 exposed by the second through holes TH2. The contact layer 650 may be formed by a method of sputtering or metal organic chemical vapor deposition (MOCVD), but is not limited thereto.

The contact layer 650 may be formed on the top surface of the back electrode layer 200 inside the second through holes TH2. The contact layer formed outside the second through holes TH2 may be removed by etching.

Next, a window layer 600 is formed on the high resistance buffer layer 500 and on the contact layer 650. That is, the window layer 600 is formed by depositing a transparent conductive material on the high resistance buffer layer 500 and inside the second through holes TH2. The window layer 600 is connected to the top surface of the contact layer 650.

In this case, the transparent conductive material is filled in the second through holes TH2, and the window layer 600 is electrically connected to the back electrode layer 200 through the contact layer 650.

The window layer 600 may be formed by depositing a transparent conductive material. In more detail, the window layer 600 may be formed by depositing zinc oxide doped with aluminum in an inert gas atmosphere containing no oxygen, but is not limited thereto.

The contact layer 650 is formed on the upper surface of the high resistance buffer layer 500 and the second through holes TH2, and the contact layer formed on the upper surface of the high resistance buffer layer 500 is etched by a solution such as hydrochloric acid. Afterwards, the window layer 600 may be formed on an upper surface of the high resistance buffer layer 500 and an upper surface of the contact layer 650 exposed by the etching.

Referring to FIG. 6, portions of the buffer layer 400, the high resistance buffer layer 500, and the window layer 600 are removed to form third through holes TH3. Accordingly, the window layer 600 is patterned to define a plurality of windows and a plurality of cells C1, C2... The width of the third through holes TH3 may be about 80 μm to about 200 μm.

As shown, the contact layer 650 connects adjacent cells to each other. In more detail, the contact layer 650 connects the window layer 600 and the back electrode included in the cells C1, C2... Adjacent to each other.

As described above, according to the exemplary embodiment, since the contact layer 650 is formed on the upper surface of the second through holes TH2, the contact layer 650 contacts the back electrode layer 200, so that the series resistance may be reduced. Accordingly, it is possible to provide a solar cell having improved photoelectric conversion efficiency.

In addition, the features, structures, effects and the like described in the embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, and the like illustrated in each embodiment may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (9)

Board;
A back electrode layer on the substrate;
A light absorbing layer on the back electrode layer;
A buffer layer on the light absorbing layer;
A window layer on the buffer layer; And
And a contact layer in contact with the top surface of the back electrode layer under the through grooves formed so that a portion of the top surface of the back electrode layer is exposed, and including at least one of In, Sn or Sr.
The contact layer is a solar cell comprising Ba doped Sr. The method of claim 1,
The contact layer is a solar cell formed to a thickness of 5nm to 100nm. The method of claim 1,
The contact layer is a solar cell containing cadmium and oxygen. delete The method of claim 1,
The window layer fills the through grooves and in contact with the top surface of the contact layer. The method of claim 1,
The window layer includes at least one of AZO, BZO and GAZO. delete Forming a back electrode layer on the substrate;
Forming a light absorbing layer and a buffer layer on the back electrode layer;
Removing a portion of the light absorbing layer and the buffer layer to form through grooves to expose a portion of the top surface of the back electrode layer;
Forming a contact layer in contact with an upper surface of the back electrode layer in the through grooves and including at least one of In, Sn or Sr; And
Forming a window layer on the buffer layer and the contact layer,
The contact layer is a solar cell manufacturing method comprising Sr doped Ba. 9. The method of claim 8,
The contact layer is a solar cell manufacturing method formed by the method of sputtering or MOCVD.
KR1020110030883A 2011-04-04 2011-04-04 Solar cell apparatus and method of fabricating the same KR101231398B1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007123532A (en) * 2005-10-27 2007-05-17 Honda Motor Co Ltd Solar cell
JP2007317858A (en) * 2006-05-25 2007-12-06 Honda Motor Co Ltd Chalcopyrite solar cell, and manufacturing method thereof
KR20090025303A (en) * 2006-07-31 2009-03-10 산요덴키가부시키가이샤 Solar cell module
KR20110001813A (en) * 2009-06-30 2011-01-06 엘지이노텍 주식회사 Solar cell and method of fabircating the same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007123532A (en) * 2005-10-27 2007-05-17 Honda Motor Co Ltd Solar cell
JP2007317858A (en) * 2006-05-25 2007-12-06 Honda Motor Co Ltd Chalcopyrite solar cell, and manufacturing method thereof
KR20090025303A (en) * 2006-07-31 2009-03-10 산요덴키가부시키가이샤 Solar cell module
KR20110001813A (en) * 2009-06-30 2011-01-06 엘지이노텍 주식회사 Solar cell and method of fabircating the same

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