KR20130070461A - Solar cell and method of fabricating the same - Google Patents

Abstract

Solar cell according to the embodiment, the support substrate; A back electrode layer on the support substrate; A light absorption layer on the back electrode layer; A buffer layer on the light absorbing layer; And a front electrode layer positioned on the buffer layer, wherein the back electrode layer includes a wavelength conversion unit for changing a wavelength of light incident on the back electrode 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; And forming a front electrode layer on the light absorbing layer, and the forming of the back electrode layer further includes forming a wavelength converter on the back electrode layer.

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. In order to form the light absorbing layer, various methods such as a method of forming a light absorbing layer while simultaneously or separately evaporating copper, indium, gallium, and selenium have been used. Thereafter, a buffer layer containing cadmium sulfide (CdS) is formed on the light absorbing layer by a sputtering process. Thereafter, a high resistance buffer layer including zinc oxide (ZnO) is formed on the buffer layer by a sputtering process. 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. A groove pattern may be formed on the transparent electrode layer to form a plurality of solar cells. The transparent electrodes and the back electrodes are misaligned with each other, and the transparent electrodes and the back electrodes are connected to the connection wirings. Each of which is electrically connected. 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.

On the other hand, the light of the long wavelength transmitted without being absorbed by the light absorbing layer reaches the rear electrode layer, and the light of the long wavelength reflected from the rear electrode layer is not reflected and absorbed by the light absorbing layer as it is. Therefore, this causes a decrease in the efficiency of the solar cell.

The embodiment seeks to provide a high quality solar cell.

Solar cell according to the embodiment, the support substrate; A back electrode layer on the support substrate; A light absorption layer on the back electrode layer; A buffer layer on the light absorbing layer; And a front electrode layer positioned on the buffer layer, wherein the back electrode layer includes a wavelength conversion unit for changing a wavelength of light incident on the back electrode 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; And forming a front electrode layer on the light absorbing layer, and the forming of the back electrode layer further includes forming a wavelength converter on the back electrode layer.

The solar cell according to the embodiment may include a wavelength converter, and the wavelength converter may include a groove. Through the groove, the light having a long wavelength, which is not absorbed by the light absorbing layer and reaches the rear electrode layer, may be changed into light having a short wavelength by Bragg's law. Therefore, the short wavelength light reflected from the groove can be absorbed by the light absorbing layer again, and the efficiency of the solar cell can be improved. That is, the wavelength converter may change the wavelength of light incident on the back electrode layer.

In addition, the surface area of the rear electrode layer and the light absorbing layer may be widened through the groove to help improve adhesion.

The method of manufacturing a solar cell according to the embodiment may produce a solar cell having the above-described effect.

1 is a cross-sectional view showing a cross section of a solar cell according to an embodiment.
FIG. 2 is an enlarged view illustrating A of FIG. 1.
3 is a conceptual diagram illustrating a solar cell according to an 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. The criteria for top / bottom or bottom / bottom of each layer are 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.

Hereinafter, a solar cell according to an embodiment will be described in detail with reference to FIGS. 1 to 3. 1 is a cross-sectional view showing a cross section of a solar cell according to an embodiment. FIG. 2 is an enlarged view illustrating A of FIG. 1. 3 is a conceptual diagram illustrating a solar cell according to an embodiment.

1 to 3, a solar cell according to an embodiment includes a support substrate 100, a back electrode layer 200, a wavelength converter, a light absorbing layer 300, a buffer layer 400, and a front electrode layer 600. Include.

The support substrate 100 has a plate shape and supports the back electrode layer 200, the light absorbing layer 300, the buffer layer 400, 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 back electrode layer 200 includes a wavelength converter 250. The wavelength converter 250 is positioned on the top surface of the back electrode layer 200. That is, the wavelength converter 250 may be located at a portion where light is incident on the solar cell.

Referring to FIG. 2, the wavelength converter 250 may include a groove 210 formed inside the rear electrode layer 200. The groove 210 includes a first surface 211 and a second surface 212 facing the first surface 211 extending from the first surface 211. A first angle θ1 is included between the first surface 211 and the second surface 212.

The first angle θ1 may be 96 ° to 99 °. The first angle θ1 is an angle considering a wavelength band of light that can be absorbed by the light absorbing layer 300. That is, referring to FIG. 3, the light having a short wavelength λ 1, which is not absorbed by the light absorbing layer 300 and reaches the rear electrode layer 200 through the groove 210, has a short wavelength light (Bragg's law). λ2). Accordingly, the short wavelength light λ 2 reflected from the groove 210 may be absorbed by the light absorbing layer 300 again, and the efficiency of the solar cell may be improved. That is, the wavelength converter 250 may change the wavelength of light incident on the back electrode layer 200.

A plurality of grooves 210 may be provided. A plurality of grooves 210 may be arranged along a predetermined direction. Specifically, the number of the grooves 210 may be 1000 / mm to 1200 / mm per length of the back electrode layer 200.

The groove 210 may be a grating groove 210.

The surface area of the back electrode layer 200 and the light absorbing layer 300 is widened through the groove 210 to help improve adhesion.

The wavelength converter 250 may include an inclined surface 220 that is inclined from an imaginary reference line L that is parallel to a line extending from the upper surface of the support substrate 100. A second angle θ2 is included between the reference line L and the inclined surface 220. The second angle θ2 is 1 ° to 4 ° solar cell. The second angle θ2 is an angle considering a wavelength band of light that can be absorbed by the light absorbing layer 300.

Here, the inclined surface 220 may be provided in plurality. The inclined surface 220 may be arranged in a plurality in a predetermined direction.

Subsequently, 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 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 buffer layer 400 may include cadmium sulfide.

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 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 rate of about 1.5 wt% to about 3.5 wt%. The front electrode layer 600 is a conductive layer.

Hereinafter, a manufacturing method of a solar cell according to an embodiment will be described. The method of manufacturing a solar cell according to the embodiment may include forming a back electrode layer, forming a light absorbing layer, forming a buffer layer, and forming a front electrode layer.

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.

In general, the back electrode layer 200 may be formed by two processes having different process conditions.

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

The forming of the back electrode layer 200 may further include forming a wavelength converter 250 on the back electrode layer 200. In the forming of the wavelength converter 250, an upper surface of the back electrode layer 200 may be etched. However, the embodiment is not limited thereto, and in the forming of the wavelength converter 250, a top surface of the back electrode layer 200 may be formed by sandblasting.

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.

Then, the metal precursor film is formed with a light absorbing layer 300 of copper-indium-gallium-selenide (Cu (In, Ga) Se 2, CIGS system) 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 buffer layer 400 is formed on the light absorbing layer 300. Here, cadmium sulfide is deposited by a sputtering process or a chemical bath deposit (CBD) or the like, and the buffer layer 400 is formed.

Thereafter, zinc oxide may be deposited on the buffer layer 400 by a sputtering process, and the high resistance buffer layer 500 may be 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 80 nm.

Subsequently, the front electrode layer 600 is formed on the buffer layer 400. The front electrode layer 600 may be formed by depositing a transparent conductive material such as zinc oxide doped with aluminum on the buffer layer 400 by a sputtering process.

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. Further, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified in 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 (17)

Support substrate;
A back electrode layer on the support substrate;
A light absorption layer on the back electrode layer;
A buffer layer on the light absorbing layer; And
A front electrode layer on the buffer layer;
The back electrode layer comprises a wavelength conversion unit for changing the wavelength of the light incident on the back electrode layer. The method of claim 1,
The wavelength conversion unit is a solar cell located on the upper surface of the back electrode layer. The method of claim 2,
The wavelength converter includes a solar cell formed in the inner side of the back electrode layer. The method of claim 3,
The groove includes a first surface and a second surface facing the first surface extending from the first surface, the solar cell including a first angle between the first surface and the second surface. 5. The method of claim 4,
The first angle is a solar cell of 96 ° to 99 °. The method of claim 1,
Solar cell provided with a plurality of grooves. The method according to claim 6,
A solar cell provided with a plurality of the groove is arranged along a predetermined direction. The method according to claim 6,
The number of the grooves is a solar cell of 1000 / mm to 1200 / mm per length of the back electrode layer. The method of claim 3,
The wavelength conversion unit includes a grating groove. The method of claim 1,
The wavelength conversion unit includes a sloped surface inclined from an imaginary reference line parallel to the line extending from the upper surface of the support substrate. The method of claim 10,
A solar cell comprising a second angle between the reference line and the inclined surface. The method of claim 11,
The second angle is 1 ° to 4 ° solar cell. The method of claim 10,
Solar cell provided with a plurality of the inclined surface. The method of claim 13,
The solar cell is provided with a plurality of the inclined surface arranged in a predetermined direction. Forming a back electrode layer on the substrate;
Forming a light absorbing layer on the back electrode layer; And
Forming a front electrode layer on the light absorbing layer;
The forming of the back electrode layer, the method of manufacturing a solar cell further comprising the step of forming a wavelength conversion portion on the back electrode layer. 16. The method of claim 15,
The forming of the wavelength conversion unit is a method of manufacturing a solar cell to etch the top surface of the back electrode layer. 16. The method of claim 15,
In the step of forming the wavelength conversion portion of the solar cell manufacturing method of the sand blast (sand blast) process on the top surface of the back electrode layer.

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