KR20120090394A - Solar cell apparatus and method of fabricating the same - Google Patents

Abstract

PURPOSE: A solar battery and a manufacturing method thereof are provided to improve chemical resistance by doping one element either a 6-group element or a 9-group element on a window layer. CONSTITUTION: A back surface electrode layer(200) is formed on the top of a substrate. A light absorption layer(300) is formed on the back surface electrode layer. A buffer layer(400) is formed on the light absorption layer. A first window layer(600) comprises one or more impurities of a 6-group element or a 9-group element. The impurity comprises at least one among Cr2O3, CoO or CoCl2. Doping concentration of the impurity is 0.1wt% to 5wt% of the first window layer. A second window layer is formed between the buffer layer and the first window layer.

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.

Embodiments provide a solar cell and a method of manufacturing the same having improved reliability, including a window layer having improved chemical 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; And a first window layer including an impurity of at least one of a Group 6 element and a Group 9 element on the buffer layer.

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 on the back electrode layer; Forming a buffer layer on the light absorbing layer; And forming a first window layer on the buffer layer, wherein the first window layer comprises an impurity of at least one of a Group 6 element and a Group 9 element.

In general, the window layer of a CIS solar cell is vulnerable to acids and bases and thus has low chemical resistance. Accordingly, in the patterning process for separating the plurality of solar cells, over etching may occur in addition to the etching region, which may cause contact failure. In addition, when the window layer is exposed to the outdoors, there is a problem that the reliability is lowered depending on the surrounding environment.

Accordingly, in the present invention, by doping at least one of the Group 6 element or Group 9 element to the window layer to improve the chemical resistance, it is possible to provide a solar cell that prevents contact failure and improved reliability.

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 is a cross-sectional view showing a poor contact of the window layer according to the prior art.
4 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.

1 is a plan view illustrating a photovoltaic device according to an embodiment, FIG. 2 is a cross-sectional view illustrating a cross section taken along line AA ′ in FIG. 1, and FIG. 3 is a contact failure of a window layer according to the prior art. It is sectional drawing.

2, the solar cell according to the embodiment includes a support substrate 100, a back electrode layer 200, a light absorbing layer 300, a buffer layer 400, a high resistance buffer layer 500, and a window layer 600. do.

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, and the window layer 600.

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 (ZnO), indium tin oxide (ITO), indium zinc oxide (IZO), or the like.

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 window layer 600 is a layer located on the upper layer in the PV cell of the solar cell, and is easily exposed to the external environment. The window layer 600 is easily oxidized by an external environment such as water and oxygen due to its weak chemical resistance. This may lower the reliability of the device.

In addition, referring to FIG. 3, third through holes TH3 are formed in a patterning process for separating into a plurality of solar cells. In addition, overetching is performed in addition to the etching region TH3 in the forming process through etching. This can happen. Accordingly, the connection parts 650 and the window layer 600 may be electrically insulated as in the 'B' region, causing contact failure.

Therefore, in order to prevent this, chemical resistance must be secured in a range capable of maintaining electrical conductivity of the window layer 600. To do this, an impurity may be doped, and the impurity may include a Group 6 element or a Group 9 element. In detail, the impurities may include Cr ₂ O ₃ , CoO, or CoCl ₂ . The doping concentration of the impurity may be 0.1 wt% to 5 wt% of the window layer 600.

Since the impurities have excellent chemical resistance, it is possible to prevent a phenomenon in which the connection parts 650 and the window layer 600 are electrically insulated in an etching process for forming the third through holes TH3.

For example, CoCl ₂ (chromium oxide) is a corundum structure and is formed as a hexagonal close packed array of oxygen anions. CoCl ₂ is a brittle material having a strong Mohs hardness of 8 to 8.5 and exhibiting strong chemical properties against acids and bases.

At least one impurity of the Group 6 element or Group 9 element may be doped at the time of window layer deposition, and the Group 6 element or Group 9 element after deposition of the window layer in which at least one of the Group 6 element or Group 9 element is not doped At least one of the impurities may be formed a window layer.

In detail, when at least one of the Group 6 elements or the Group 9 elements is doped when the window layer 600 is deposited, the window layer 600 may include, for example, ZnO, and Al may contain 1 wt% to 3 wt%. Doped in a ratio, Cr ₂ O ₃ may be doped in a ratio of 0.1wt% to 5wt%.

When the window layer including at least one of the Group 6 element or the Group 9 element is deposited after the window layer is not doped with the impurity of the Group 6 element or the Group 9 element, the window layer 600 is an example. For example, Al may include ZnO: Al doped at a ratio of 1 wt% to 3 wt%, and ZnO: Al, ie, Al is doped at a ratio of 1 wt% to 3 wt%, and at least one of a Group 6 element or a Group 9 element. An impurity doping layer doped with an impurity of 0.1 wt% to 5 wt% may be formed.

A window layer doped with at least one impurity of the Group 6 element or Group 9 element may be deposited to a thickness of 10 nm to 80 nm.

Connection parts 650 are disposed inside the second through holes TH2. The connection parts 650 extend downward from the window layer 600 and are connected to the back electrode layer 200. For example, the connection parts 650 extend from the window of the first cell and are connected to the back electrode of the second cell.

Therefore, the connection parts 650 connect adjacent cells to each other. In more detail, the connection parts 650 connect the windows and the back electrodes included in the cells C1, C2 ... adjacent to each other.

The connection parts 650 are integrally formed with the window layer 600. That is, the material used as the connection parts 650 is the same as the material used as the window layer 600.

A plurality of solar cells may be connected in series by the connection parts 650.

As discussed above, since the chemical resistance is improved due to impurities included in the window layer 600, a contact failure that may occur in the process of forming the third through holes TH3 may be prevented, thereby improving reliability. A battery can be provided.

4 to 6 are cross-sectional views illustrating a method of manufacturing the solar cell apparatus according to the embodiment. For a description of the present manufacturing method, refer to the description of the photovoltaic device described above.

Referring to FIG. 4, 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. 5, 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 absorbing layer 300 may be formed by a sputtering process or an evaporation method.

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.

When the metal precursor film is formed and selenization is subdivided, 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.

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

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 holes 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. 6, a window layer 600 is formed on the high resistance buffer layer 500. 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.

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 connection parts 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.

Next, a portion of the buffer layer 400, the high resistance buffer layer 500, and the window layer 600 is 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.

The third through holes TH3 may be formed by a mechanical device such as a tip, a laser device, or the like, or may be formed by wet etching. As described above, the window layer 600 having improved chemical resistance may be etched by impurities. In the process of forming the third through holes TH3 through, the window layer 600 is prevented from being etched in a region other than the etching region, so that a poor bonding occurs, thereby causing the connection parts 650 and the window layer 600 to be etched. Insulation can be prevented.

The impurity may be formed by including a Group 6 element or a Group 9 element, and the Group 6 element has a high melting point and a boiling point, the highest valence of +6, and is low in chemical reactivity.

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

As such, according to the embodiment, the chemical resistance of the window layer 600 may be improved to provide a solar cell having improved reliability.

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 the embodiments 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 (7)

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; And
And a first window layer including an impurity of at least one of a Group 6 element and a Group 9 element on the buffer layer. The method of claim 1,
The impurities include at least one of Cr ₂ O ₃ , CoO or CoCl ₂ . The method of claim 1,
The doping concentration of the impurity is a solar cell of 0.1wt% to 5wt% of the first window layer. The method of claim 1,
And a second window layer comprising zinc oxide doped with aluminum between the buffer layer and the first window layer. The method of claim 4, wherein
The first window layer is a solar cell is deposited to a thickness of 10nm to 80nm. Forming a back electrode layer on the substrate;
Forming a light absorbing layer on the back electrode layer;
Forming a buffer layer on the light absorbing layer; And
Forming a first window layer on the buffer layer, the first window layer including at least one impurity of a Group 6 element or a Group 9 element. The method of claim 6,
Forming a second window layer comprising zinc oxide doped with aluminum between the first window layer and the buffer layer.

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