KR20130052475A - Solar cell and method of fabricating the same - Google Patents

Abstract

PURPOSE: A solar cell and a manufacturing method thereof are provided to improve a filling rate and an open voltage of a solar cell by increasing the quantity of metal ions doped in a light absorbing layer. CONSTITUTION: A rear electrode layer(200) is arranged on a support substrate. A light absorbing layer(300) is arranged on the rear electrode layer. A buffer layer(400) is arranged on the light absorbing layer. A front electrode layer(600) is arranged on the buffer layer. The light absorbing layer is arranged under the buffer layer and includes a doping region(310) in which metal included in the buffer layer is doped. The buffer layer includes CdS or ZnS.

Description

SOLAR CELL AND METHOD OF FABRICATING THE SAME

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

A manufacturing method of a solar cell for solar power generation is as follows. First, a substrate is provided, a back electrode layer is formed on the substrate, and patterned by a laser to form a plurality of back electrodes.

Thereafter, a light absorbing layer, a buffer layer, and a high resistance buffer layer are sequentially formed on the back electrodes. A method of forming a light absorbing layer of copper-indium-gallium-selenide (Cu (In, Ga) Se2; CIGS) while simultaneously evaporating copper, indium, gallium, and selenium to form the light absorbing layer; The method of forming a metal precursor film and forming it by a selenization process is widely used. The energy band gap of the light absorbing layer is about 1 to 1.8 eV.

Thereafter, a buffer layer containing cadmium sulfide (CdS) is formed on the light absorbing layer by a sputtering process. The energy bandgap of the buffer layer is about 2.2 to 2.4 eV. Thereafter, a high resistance buffer layer including zinc oxide (ZnO) is formed on the buffer layer by a sputtering process. The energy bandgap of the high resistance buffer layer is about 3.1 to 3.3 eV.

Thereafter, a groove pattern may be formed in the light absorbing layer, the buffer layer, and the high resistance buffer layer.

Thereafter, a transparent conductive material is stacked on the high resistance buffer layer, and the groove pattern is filled with the transparent conductive material. Accordingly, a transparent electrode layer is formed on the high resistance buffer layer, and connection wirings are formed inside the groove pattern, respectively. Examples of the material used for the transparent electrode layer and the connection wiring include aluminum doped zinc oxide and the like. The energy band gap of the transparent electrode layer is about 3.1 to 3.3 eV.

Thereafter, a groove pattern is formed in the transparent electrode layer, and a plurality of solar cells may be formed. The transparent electrodes and the high resistance buffers correspond to respective cells. The transparent electrodes and the high resistance buffers may be arranged in a stripe form or a matrix form.

The transparent electrodes and the back electrodes are misaligned with each other, and the transparent electrodes and the back electrodes are electrically connected to each other by the connection wirings. Accordingly, a plurality of solar cells can be electrically connected in series with each other.

As such, in order to convert sunlight into electrical energy, various types of photovoltaic devices may be manufactured and used. Such a photovoltaic device is disclosed in Patent Publication No. 10-2008-0088744 and the like.

Embodiments provide a solar cell having improved photoelectric conversion efficiency.

The solar cell according to the embodiment includes a support substrate; A rear electrode layer disposed on the support substrate; A light absorbing layer disposed on the back electrode layer; A buffer layer disposed on the light absorbing layer; And a front electrode layer disposed on the buffer layer, wherein the light absorbing layer includes a doped region disposed under the buffer layer and doped with a metal included in the buffer layer, and the buffer layer includes cadmium sulfide (CdS) or zinc sulfide ( ZnS).

A method of manufacturing a solar cell according to an embodiment includes forming a back electrode layer on a support substrate; Forming a light absorbing layer on the back electrode layer; Placing the support substrate on which the light absorption layer is formed in a reaction apparatus sealed from the outside; And forming a buffer layer in the reactor.

In the method of manufacturing a solar cell according to the embodiment, the buffer layer forming process may be performed in a reaction apparatus sealed from the outside. The buffer layer forming process may be performed at a high pressure through the sealed reactor. Therefore, process time can be shortened.

In addition, through the high pressure process, it is possible to induce the diffusion of metal ions to the defect site (defect site) included in the light absorbing layer. That is, the amount of metal ions doped in the light absorbing layer can be increased. Therefore, the open voltage and the filling rate of the solar cell manufactured through this can be improved.

1 is a cross-sectional view showing a cross section of a solar cell according to an embodiment.
2 to 4 are views for explaining a method of manufacturing a solar cell according to the embodiment.

In the description of embodiments, each layer, region, pattern, or structure may be “on” or “under” the substrate, each layer, region, pad, or pattern. Substrate formed in ”includes all formed directly or through another layer. Criteria for the top / bottom or bottom / bottom of each layer will be described with reference to the drawings.

The thickness or the size of each layer (film), region, pattern or structure in the drawings may be modified for clarity and convenience of explanation, and thus does not entirely reflect the actual size.

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

1, a solar cell according to an embodiment will be described in detail. 1 is a cross-sectional view showing a cross section of a solar cell according to an embodiment.

Referring to FIG. 1, the solar cell 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 front electrode layer 600.

The supporting substrate 100 has a plate shape and supports the rear electrode layer 200, the light absorbing layer 300, the buffer layer 400, the high resistance buffer layer 500, and the front electrode 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. The supporting substrate 100 may be transparent. The support substrate 100 may be rigid or flexible.

The back electrode layer 200 is disposed on an upper surface of the support substrate 100. The back electrode layer 200 is a conductive layer. Examples of the material used as the back electrode layer 200 may include a metal such as molybdenum (Mo).

In addition, 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.

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

The light absorbing layer 300 includes a doped region 310 and an undoped region 320.

The doped region 310 is disposed under the buffer layer 400 and doped with metal included in the buffer layer 400. In this case, the metal may include cadmium (Cd) or zinc (Zn). Specifically, when the buffer layer 400 is cadmium sulfide (CdS), the doped region 310 may include cadmium. In addition, when the buffer layer 400 is zinc sulfide (ZnS), the doped region 310 may include zinc.

The doped region 310 may have a thickness of about 70 nm to about 130 nm. Specifically, the thickness of the doped region 310 may be 100 nm. As the doped region 310 is formed thick, an open voltage and a filling rate may increase.

The undoped region 320 is positioned between the doped region 310 and the back electrode layer 200. That is, the undoped region 320 is located below the doped region 310.

The energy band gap of the light absorption layer 300 may be about 1 eV to 1.8 eV.

The buffer layer 400 is disposed on the light absorbing layer 300. The buffer layer 400 is in direct contact with the light absorbing layer 300.

The high resistance buffer layer 500 is disposed on the buffer layer 400. The high resistance buffer layer 500 includes zinc oxide (i-ZnO) that is not doped with impurities. The energy band gap of the high resistance buffer layer 500 may be about 3.1 eV to 3.3 eV.

The front electrode layer 600 is disposed on the light absorbing layer 300. In more detail, the front electrode layer 600 is disposed on the high resistance buffer layer 500.

The front electrode layer 600 is disposed on the high-resistance buffer layer 500. The front electrode layer 600 is transparent. Examples of the material used as the front electrode layer 600 include aluminum doped ZnO (AZO), indium zinc oxide (IZO), indium tin oxide (ITO), and the like. Can be.

The front electrode layer 600 may have a thickness of about 500 nm to about 1.5 μm. In addition, when the front electrode layer 600 is formed of zinc oxide doped with aluminum, aluminum may be doped at a ratio of about 2.5 wt% to about 3.5 wt%. The front electrode layer 600 is a conductive layer.

Hereinafter, a method of manufacturing a solar cell according to an embodiment will be described with reference to FIGS. 2 to 4. For the sake of clarity and simplicity, detailed description of parts identical or similar to those described above will be omitted. 2 to 4 are views for explaining a method of manufacturing a solar cell according to the embodiment.

First, a metal such as molybdenum is deposited on the support substrate 100 by a sputtering process, and the back electrode layer 200 is formed. The rear electrode layer 200 may be formed by two processes having different process conditions.

An additional layer such as a diffusion barrier may be interposed between the support substrate 100 and the back electrode layer 200.

Subsequently, the light absorbing layer 300 is formed on the back electrode layer 200. The light absorption layer 300 may be formed by a sputtering process or an evaporation process.

For example, a copper-indium-gallium-selenide-based (Cu (In, Ga) Se 2; CIGS-based) light-emitting layer is formed while simultaneously evaporating copper, indium, gallium, A method of forming the light absorbing layer 300 and a method of forming the metal precursor film 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.

Subsequently, the metal precursor film is formed of a copper-indium-gallium-selenide (Cu (In, Ga) Se 2; CIGS-based) light absorbing layer 300 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.

Subsequently, the support substrate 100 on which the light absorbing layer 300 is formed may be positioned in the reactor 10. Referring to FIG. 2, the reactor 10 may have a structure sealed from the outside.

Subsequently, in the reactor 10, a buffer layer 400 may be formed on the light absorbing layer 300. In detail, the forming of the buffer layer 400 may be performed by first disposing a reaction solution 30 including metal ions in the reaction apparatus 10. Referring to FIG. 3, a bath 20 containing the reaction solution 30 may be located in the reactor 10, and the reaction solution 30 may be disposed in the bath 20.

Subsequently, the supporting substrate 100 in which the light absorbing layer 300 is formed may be immersed in the reaction solution 30.

Subsequently, the reaction solution 30 may be heated in a sealed state of the reactor 10. In this case, the heating may be performed at a temperature of 100 ℃ to 200 ℃. In addition, the forming of the buffer layer 400 may be performed at a pressure higher than atmospheric pressure. That is, the forming of the buffer layer 400 may be performed at a pressure of 760 torr or more. Preferably, it may be at a pressure of at least 940 torr where the molecules will have energy above the boiling point.

The buffer layer 400 forming process may be performed at a high pressure through the sealed reactor 10. This can greatly increase the process temperature. This is because the boiling point of the reaction solution 30 increases as the pressure inside the reactor 10 increases. Therefore, process time can be shortened.

In addition, a high pressure process may induce diffusion of metal ions into a defect site included in the light absorbing layer 300. That is, the amount of metal ions doped in the light absorbing layer 300 can be increased. Therefore, the open voltage and the filling rate of the solar cell manufactured through this can be improved.

Through the series of processes, the buffer layer 400 may be formed by chemical bath deposition.

In addition, referring to FIG. 4, the metal included in the reaction solution 30 may be doped into the light absorbing layer 300. For example, when the reaction solution 30 includes cadmium, part of the light absorbing layer 300 may be doped with cadmium.

Subsequently, although not illustrated, zinc oxide may be deposited on the buffer layer 400 by a sputtering process, and the high resistance buffer layer 500 may be formed.

In addition, the front electrode layer 600 is formed on the high resistance buffer layer 500. In order to form the front electrode layer 600, a transparent conductive material is stacked on the high resistance buffer layer 500. Examples of the transparent conductive material include aluminum doped zinc oxide and the like.

The features, structures, effects and the like described in the foregoing embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. In addition, 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 clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiments may be modified. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

Claims (7)

Forming a back electrode layer on the support substrate;
Forming a light absorbing layer on the back electrode layer;
Placing the support substrate on which the light absorption layer is formed in a reaction apparatus sealed from the outside; And
Forming a buffer layer in the reaction apparatus manufacturing method of a solar cell. The method of claim 1,
The forming of the buffer layer may include disposing a reaction solution containing metal ions in the reactor;
Dipping the support substrate on which the light absorbing layer is formed in the reaction solution; And
A method of manufacturing a solar cell comprising heating the reaction solution in a sealed state of the reactor. The method of claim 2,
Forming the buffer layer is a method of manufacturing a solar cell is formed by chemical bath deposition (chemical bath deposition). The method of claim 2,
Forming the buffer layer is a method of manufacturing a solar cell made at 100 ℃ to 200 ℃. The method of claim 2,
Forming the buffer layer is a method of manufacturing a solar cell made at a pressure above atmospheric pressure. The method of claim 2,
Forming the buffer layer is a method of manufacturing a solar cell made at a pressure of 940 torr or more. Support substrate;
A rear electrode layer disposed on the support substrate;
A light absorbing layer disposed on the back electrode layer;
A buffer layer disposed on the light absorbing layer; And
A front electrode layer disposed on the buffer layer,
The light absorbing layer includes a doped region disposed under the buffer layer and doped with a metal included in the buffer layer.
The buffer layer is a solar cell including cadmium sulfide (CdS) or zinc sulfide (ZnS).

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