KR20130084119A - Thin film type solar cell and the fabrication method thereof - Google Patents

Abstract

PURPOSE: A thin film type solar cell and a manufacturing method thereof are provided to improve the energy conversion efficiency of the solar cell by preventing a shunt in a space without colloid. CONSTITUTION: A back electrode (120) is formed on a substrate. A light absorption layer (130) is formed on the back electrode. A buffer layer (140) is formed on the light absorption layer. A transparent electrode is formed on the buffer layer. The buffer layer is formed by multiple deposition processes and ultrasonic treatment processes interposed between the deposition processes.

Description

Thin film type solar cell, manufacturing method thereof {thin film type solar cell and the fabrication method

The present invention relates to a thin-film solar cell, and more particularly, to a thin-film solar cell formed with a uniform thickness of the buffer layer, and a manufacturing method thereof.

Typically, a solar cell, which is a photoelectric conversion element that converts light such as the sun into electrical energy, is infinite and environmentally friendly, unlike other energy sources, and therefore its importance is increasing over time. The most basic structure of a solar cell is in the form of a diode composed of a PN junction, which is classified according to the material of the light absorbing layer.

Solar cells using silicon as the light absorption layer can be classified into crystalline (monocrystalline) substrate (Wafer) solar cells and thin film (amorphous, polycrystalline) solar cells. In addition, compound thin-film solar cells, group III-V solar cells, dye-sensitized solar cells, and organic solar cells using copper-indium-gallium-selenide-based (Cu (In, Ga) Se ₂ ; CIGS-based) or CdTe Representative solar cells.

Hetero-Junction solar cells, which are crystalline solar cells, use a crystalline semiconductor substrate as a light absorbing layer, and are formed by forming a non-single crystal semiconductor layer different from the semiconductor substrate.

Conventional CIGS-based solar cells have a buffer layer that serves as an n-type, and it is necessary to form the buffer layer with a uniform thickness. If the buffer layer is not formed to have a uniform thickness, the colloid formed on the surface of the buffer layer may be separated from the buffer layer in a process such as cleaning, so that space may be generated at the separated portion, thereby forming a shunting path. Accordingly, the energy conversion efficiency is lowered due to the reduction of the fill factor (FF) of the solar cell.

The present invention provides a thin-film solar cell capable of producing a buffer layer having a uniform thickness by chemical solution deposition, and a method of manufacturing the same.

Method of manufacturing a thin film solar cell according to an embodiment of the present invention,

Forming a back electrode on the substrate; and

Forming a light absorbing layer on the back electrode; and

Forming a buffer layer on the light absorbing layer;

Forming a transparent electrode on the buffer layer;

The buffer layer is formed by a plurality of deposition processes and an ultrasonic treatment interposed therebetween.

In an embodiment, in the forming of the buffer layer,

Forming a first buffer layer on the surface of the light absorbing layer by dipping the substrate into a buffer layer solution;

An ultrasonic treatment step of removing the colloid attached to the surface of the first buffer layer by ultrasonic processing the substrate on which the first buffer layer is formed; And

And a second deposition process step of forming a second buffer layer on the surface of the first buffer layer by dipping the colloid-free substrate into a buffer layer solution.

In one embodiment, in the sonication process step,

The substrate on which the first buffer layer is formed is ultrasonically processed by dipping into a buffer layer solution, and deposition is performed to a space where colloid has been removed during the ultrasonic treatment.

In one embodiment, after the second buffer layer is formed,

The foreign material remaining on the surface of the second buffer layer is removed by a rinse process on the substrate on which the second buffer layer is formed.

In one embodiment, the buffer layer is formed using any one selected from cadmium sulfide, zinc sulfide, or indium sulfide.

In one embodiment, the back electrode is formed using molybdenum.

In one embodiment, the light absorption layer is copper-indium-gallium-selenide-based, copper-indium-selenide-based, copper-gallium-selenide-based, copper-indium-gallium-selenide-sulfur, copper-indium It is formed using any one selected from selenium-sulfur or copper-gallium-selenide-sulfur materials.

In one embodiment, the transparent electrode is formed using any one selected from zinc oxide or indium tin oxide.

Thin film solar cell according to another embodiment of the present invention,

A substrate;

A back electrode formed on the substrate;

A light absorbing layer formed on the back electrode;

A buffer layer formed on the light absorbing layer;

Including; a transparent electrode formed on the buffer layer;

At least a plurality of buffer layers are stacked in the buffer layer.

In one embodiment, the buffer layer includes a first buffer layer formed from the surface of the light absorbing layer, and a second buffer layer formed from the surface of the first buffer layer.

In one embodiment, the buffer layer is further formed in the space generated by the removal of the colloid from the surface of the first buffer layer.

In one embodiment, the buffer layer includes any one selected from cadmium sulfide, zinc sulfide, and indium sulfide.

In one embodiment, the buffer layer has a thickness of 50 nanometers or less.

In one embodiment, the back electrode comprises molybdenum.

In one embodiment, the light absorption layer is copper-indium-gallium-selenide-based, copper-indium-selenide-based, copper-gallium-selenide-based, copper-indium-gallium-selenide-sulfur, copper-indium -Selected from selenium-sulfur or copper-gallium-selenide-sulfur materials.

In one embodiment, the transparent electrode includes any one selected from zinc oxide or indium tin oxide.

As described above, the thin-film solar cell of the present invention and a method for manufacturing the same further include a buffer layer in a space where colloids are removed from the surface of the buffer layer by inserting a plurality of deposition processes at the time of forming the buffer layer and an ultrasonic treatment therebetween. As it can form, the thickness of a buffer layer can be made uniform.

Moreover, as the thickness of the buffer layer can be formed uniformly, shunt in the space where the colloid has escaped is prevented in advance, thereby increasing the fill factor. Thereby, the energy conversion efficiency of a solar cell can be improved.

1 is a cross-sectional view showing a thin film solar cell according to an embodiment of the present invention;
2A through 2D are cross-sectional views sequentially illustrating a process of forming the thin film solar cell of FIG. 1.
2A is a cross-sectional view illustrating a state after a back electrode, a light absorbing layer, and a first buffer layer are formed on the substrate of FIG. 1;
FIG. 2B is a cross-sectional view illustrating a state in which a colloid is removed on the substrate of FIG. 2A;
2C is a cross-sectional view illustrating a state in which a second buffer layer is formed on the substrate of FIG. 2B;
2D is a cross-sectional view illustrating a state after a transparent electrode is formed on the substrate of FIG. 2C;
3 is a flowchart sequentially illustrating a process of forming the thin film solar cell of FIG. 1.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and particular embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by terms. Terms are used only for the purpose of distinguishing one component from another.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, Should not be construed to preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 illustrates a thin film solar cell 100 according to an embodiment of the present invention.

Referring to the drawings, the thin film solar cell 100 includes a substrate 110. The substrate 110 may be an insulating substrate, for example, a glass substrate or a plastic substrate. Alternatively, the substrate 110 may use a metallic material such as aluminum foil. When using a metallic material, it is preferable to further form an insulating material on the upper surface of the substrate 110.

The back electrode 120 is formed on the substrate 110. The back electrode 120 includes a conductive material, for example, a metal such as molybdenum (Mo). The back electrode 120 should withstand the high temperature applied during the heat treatment of the light absorbing layer 130 to be formed later, for example, at a high temperature of about 500 to 600 ° C., and is preferably a material that does not leave the substrate 110 during the heat treatment. . The back electrode 120 has a thickness of about 0.5 to 1 micrometer. The back electrode 120 is formed of at least one layer.

The p-type light absorbing layer 130 is formed on the back electrode 120. The light absorbing layer 130 may be a copper indium gallium selenide thin film layer, a copper indium selenide thin film layer, a copper gallium selenide system, a copper indium gallium selenide sulfur system, or copper. Indium-selenium-sulfur or copper-gallium-selenium-sulfur thin film layer. The light absorbing layer 130 has a thickness of about 2 to 3 micrometers.

An n-type buffer layer 140 is formed on the light absorbing layer 130. The buffer layer 140 may use any one selected from cadmium sulfide (CdS), zinc sulfide (ZnS), and indium sulfide (In ₂ S ₃ ). The buffer layer is ultra thin, for example, 50 nm or less in thickness, and preferably has high resistance film characteristics.

The buffer layer 140 may be formed by chemical bath deposition, which is a dipping method. Alternatively, the buffer layer 140 may be formed by an atomic layer deposition (ALD) method.

The transparent electrode 150 is formed on the buffer layer 140. The transparent electrode 150 includes a transparent and conductive material such as zinc oxide (ZnO), indium tin oxide (ITO), or the like. The transparent electrode 150 has a thickness of about 1 to 2.5 micrometers.

Here, the buffer layer 140 may be formed to have a uniform thickness by inserting at least two deposition processes and an ultrasonic treatment therebetween.

Looking at the process of manufacturing the thin-film solar cell 100 having the structure as described above are as follows.

2A to 2D illustrate a process for manufacturing the solar cell 100 of FIG. 1 in each step, and FIG. 3 is a flowchart sequentially illustrating a process for manufacturing the solar cell 100 of FIG. 1. .

Referring to FIG. 2A, a back electrode 120 is formed on the substrate 110. The back electrode 120 is formed by depositing a metal such as molybdenum on the substrate 110 by a sputtering process or the like. In this case, the thickness of the back electrode 120 is formed to be about 0.5 to 1 micrometer (S 10).

Subsequently, the light absorbing layer 130 is formed on the back electrode 120. The light absorbing layer 130 is a step of selenization or selenization-sulfurization after sputtering an element material for a copper-indium-gallium thin film layer, an element material for a copper-indium thin film layer, or an element material for a copper-gallium thin film layer. It is formed on the light absorbing layer 130 by a method such as co-evaporation, high temperature heat treatment process. In this case, the light absorbing layer 130 is formed to have a thickness of about 2 to 3 micrometers.

Next, a buffer layer 140 is formed on the light absorbing layer 130. In this case, the buffer layer 140 is formed to have a two-layer structure through at least two deposition processes.

That is, the first buffer layer 141 is formed on the surface of the light absorbing layer 130. To this end, the substrate 110 on which the light absorbing layer 130 is formed is dipped in a solution containing sulfur ions and zinc ions, and a first buffer layer 141 is deposited on the light absorbing layer 130 (S30).

In this case, the colloid 142 may be deposited on the surface of the first buffer layer 141 during the first deposition process for forming the first buffer layer 141 on the light absorbing layer 130.

When the colloid 142 is deposited, the colloid 142 having a relatively weak adhesion by the rinse process is separated from the first buffer layer 141. Therefore, it is preferable to remove the colloid 142 from the surface of the first buffer layer 141. However, since the buffer layer 140 is a thin film-type high resistance film having a thickness of 50 nanometers or less, when the colloid 142 is removed through brush cleaning or the like, damage to the film may occur.

In addition, when the colloid 142 is separated from the first buffer layer 141, a space may be generated at the separated portion, thereby forming a shunt. When shunting occurs, the fill factor of the solar cell is reduced, so that the energy conversion efficiency may be lowered. In order to prevent this, ultrasonication is performed.

Referring to FIG. 2B, the substrate 110 on which the first buffer layer 141 is formed is colloid bonded to the surface of the first buffer layer 141 with a relatively weak adhesive force by ultrasonication in a bath in which an ultrasonic unit is installed. 142). Accordingly, the portion from which the colloid 142 is removed is present in the space 201.

In this case, the substrate 110 in which the first buffer layer 141 is formed is dipped in a solution containing sulfur ions and zinc ions even when the colloid 142 having relatively weak adhesion in the ultrasonic bath is removed. Deposition continues to occur on the surface of the first buffer layer 141 (S 30).

Next, referring to FIG. 2C, the substrate 141 from which the colloid has been removed with the weak adhesive force by ultrasonic treatment is again subjected to the second deposition process by dipping sulfur ions and zinc ions in a supersaturated solution. do. This is because filling the space (201 in FIG. 2B) that can act as the shunt in the portion where the colloid has been removed can suppress the shunt.

Accordingly, the second buffer layer 143 is redeposited on the surface of the first buffer layer 141. In this case, the space in which the colloid is removed is filled in the second deposition process in which the second buffer layer 143 is deposited.

Through the above process, the first buffer layer 141 and the second buffer layer 143 are continuously stacked on the surface of the light absorbing layer 130 while filling the space in which the colloid has been separated by ultrasonic treatment, A buffer layer 140 having a thickness may be formed (S 50).

Subsequently, after the buffer layer 140 is completed, the substrate 110 in which the buffer layer 140 is formed is dipped in a cleaning bath to rinse impurities such as ammonia, which may remain on the surface of the buffer layer 140. (S 60)

Subsequently, referring to FIG. 2D, the transparent electrode 150 is formed on the buffer layer 140. The transparent electrode 150 is formed by depositing a transparent conductive material such as zinc oxide or indium tin oxide on the buffer layer 140. At this time, the thickness of the transparent electrode 150 is formed to be about 1 to 2.5 micrometers (S 70).

As described above, the buffer layer 140 is formed through two deposition processes, an ultrasonic treatment process interposed therebetween, and a rinse process, thereby removing a portion that may act as a shunt. Therefore, the buffer layer 140 may be manufactured to have a uniform thickness.

100 ... Solar cell 110 ... substrate
120 ... backside electrode 130 ... light absorbing layer
140 ... Buffer layer 141 ... First buffer layer
142 ... colloid 143 ... second buffer layer
144 ... transparent electrode

Claims (16)

Forming a back electrode on the substrate; and
Forming a light absorbing layer on the back electrode; and
Forming a buffer layer on the light absorbing layer;
Forming a transparent electrode on the buffer layer;
The buffer layer is a method of manufacturing a thin-film solar cell formed by a plurality of deposition process and the ultrasonic treatment step interposed therebetween. The method of claim 1,
In the step of forming the buffer layer,
Forming a first buffer layer on the surface of the light absorbing layer by dipping the substrate into a buffer layer solution;
An ultrasonic treatment step of removing the colloid attached to the surface of the first buffer layer by ultrasonic processing the substrate on which the first buffer layer is formed; And
And a second deposition process step of forming a second buffer layer on the surface of the first buffer layer by dipping the colloid-removed substrate into a buffer layer solution. 3. The method of claim 2,
In the sonication process step,
Ultrasonic processing by dipping the substrate on which the first buffer layer is formed in a buffer layer solution, so that the deposition is performed in the colloid-free space during the ultrasonic treatment. 3. The method of claim 2,
After the second buffer layer is formed,
The manufacturing method of the thin film type solar cell which removes the foreign material which remains on the surface of the said 2nd buffer layer by the rinse process of the board | substrate with which the said 2nd buffer layer was formed. The method of claim 1,
The buffer layer is a method of manufacturing a thin film solar cell formed using any one selected from cadmium sulfide, zinc sulfide, and indium sulfide. The method of claim 1,
The back electrode is a method of manufacturing a thin film solar cell formed using molybdenum. The method of claim 1,
The light absorbing layer may be copper-indium-gallium-selenide-based, copper-indium-selenide-based, copper-gallium-selenide-based, copper-indium-gallium-selenide-sulfur, copper-indium-selenide-sulfur, A method of manufacturing a thin film solar cell formed by using any one selected from copper-gallium-selenium-sulfur-based materials. The method of claim 1,
The transparent electrode is formed using a thin film solar cell formed using any one selected from zinc oxide and indium tin oxide. A substrate;
A back electrode formed on the substrate;
A light absorbing layer formed on the back electrode;
A buffer layer formed on the light absorbing layer;
Including; a transparent electrode formed on the buffer layer;
The buffer layer is a thin film solar cell in which at least a plurality of buffer layers are stacked. The method of claim 9,
And the buffer layer comprises a first buffer layer formed from a surface of the light absorbing layer and a second buffer layer formed from a surface of the first buffer layer. 11. The method of claim 10,
The thin film solar cell of claim 1, wherein a buffer layer is further formed in a space generated by removing the colloid from the surface of the first buffer layer. The method of claim 9,
The buffer layer is a thin film solar cell including any one selected from cadmium sulfide, zinc sulfide, and indium sulfide. The method of claim 9,
The thickness of the buffer layer is a thin film solar cell of 10 to 50 nanometers. The method of claim 9,
The back electrode includes molybdenum thin film solar cell. The method of claim 9,
The light absorbing layer may be a copper indium gallium selenide system, a copper indium selenide system, a copper gallium selenide system, a copper indium gallium selenide sulfur system, a copper indium selenium sulfur system, Thin-film solar cell comprising any one selected from copper-gallium-selenium-sulfur-based materials. The method of claim 9,
The transparent electrode is a thin film solar cell including any one selected from zinc oxide or indium tin oxide.

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