KR20120085104A - Solar cell apparatus and method of fabricating the same - Google Patents

Abstract

Solar cell according to one embodiment includes a substrate; A barrier layer disposed on the substrate and comprising a Group 6 element; A back electrode layer disposed on the barrier layer; A light absorbing layer disposed on the back electrode layer; A buffer layer disposed on the light absorbing layer; And a window layer disposed on the buffer 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 solar cell which is a pn heterojunction device having a substrate structure including a glass substrate, a metal back electrode layer, a p-type CIGS-based light absorbing layer, a high resistance buffer layer, an n-type window layer, and the like is widely used.

In such a solar cell, research is being conducted to improve electrical characteristics such as low resistance and high transmittance.

The embodiment provides a solar cell and a method of manufacturing the same having improved reliability.

Solar cell according to one embodiment includes a substrate; A barrier layer disposed on the substrate and comprising a Group 6 element; A back electrode layer disposed on the barrier layer; A light absorbing layer disposed on the back electrode layer; A buffer layer disposed on the light absorbing layer; And a window layer disposed on the buffer layer.

A solar cell manufacturing method according to an embodiment includes forming a barrier layer including a group 6 element on a substrate; Forming a back electrode layer on the barrier layer; Forming a light absorbing layer on the back electrode layer; Forming a buffer layer on the light absorbing layer; And forming a window layer on the buffer layer.

According to the embodiment, it is possible to provide a solar cell capable of preventing impurities from diffusing the barrier layer from the substrate to the light absorbing layer and simultaneously implementing sodium doping effect by diffusing sodium contained in the barrier layer into the light absorbing layer.

1 is a cross-sectional view showing a solar cell according to an embodiment.
2 to 5 are views illustrating a process of manufacturing the solar cell panel according to the embodiment.

In the description of the embodiments, where each substrate, layer, film, or electrode is described as being formed "on" or "under" of each substrate, layer, film, or electrode, etc. , "On" and "under" include both "directly" or "indirectly" formed through other components. In addition, the upper or lower reference of each component is described with reference to the drawings. The size of each component in the drawings may be exaggerated for the sake of explanation and does not mean the size actually applied.

1 is a cross-sectional view showing a solar cell according to an embodiment. Referring to FIG. 1, the solar cell panel includes a support substrate 100, a barrier layer 200, a back electrode layer 300, a light absorbing layer 400, a buffer layer 500, a high resistance buffer layer 600, and a window layer ( 700).

The support substrate 100 has a plate shape and supports the barrier layer 200, the back electrode layer 300, the light absorbing layer 400, the buffer layer 500, the high resistance buffer layer 600, and the window layer 700. do.

The support substrate 100 may be an insulator. The support substrate 100 may be a glass substrate, a plastic substrate such as a polymer, or a metal substrate. 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 barrier layer 200 may be formed on the support substrate 100. The barrier layer 200 may include Na and SeO ₃ , and may be formed to a thickness of 100 nm to 1000 nm.

When the support substrate 100 is flexible, impurities included in the support substrate 100 may diffuse into the light absorbing layer 400 in the solar cell manufacturing process, thereby reducing reliability. In addition to the function of preventing the phenomenon, the barrier layer 200 according to the embodiment of the present invention may include sodium (Na) to diffuse sodium into the light absorbing layer 400 formed of CIGS during the manufacturing process of the solar cell. In this case, the charge concentration of the light absorbing layer 400 may be increased. This may be a factor for improving the photoelectric conversion efficiency of the solar cell.

That is, the barrier layer 200 may simultaneously implement a sodium doping effect on the barrier layer and the light absorbing layer.

The back electrode layer 300 is disposed on the barrier layer 200. The back electrode layer 300 is a conductive layer. The back electrode layer 300 may allow electric current generated in the light absorbing layer 400 of the solar cell to move so that current flows to the outside of the solar cell. In order to perform this function, the back electrode layer 300 should have high electrical conductivity and low specific resistance.

In addition, the back electrode layer 300 must maintain high temperature stability during heat treatment under sulfur (S) or selenium (Se) atmosphere accompanying CIGS compound formation. In addition, the back electrode layer 300 should be excellent in adhesion with the support substrate 100 so that peeling does not occur with the support substrate 100 due to a difference in thermal expansion coefficient.

The back electrode layer 300 may be formed of any one of molybdenum (Mo), gold (Au), aluminum (Al), chromium (Cr), tungsten (W), and copper (Cu). In particular, since molybdenum (Mo) has a smaller difference between the support substrate 100 and the coefficient of thermal expansion than other elements, it is excellent in adhesiveness and can prevent peeling from occurring. Overall required properties can be met.

The back electrode layer 300 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 400 may be formed on the back electrode layer 300. The light absorbing layer 400 includes a p-type semiconductor compound. In more detail, the light absorbing layer 400 includes a group I-III-VI compound. For example, the light absorbing layer 400 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 It may have a system crystal structure. The energy band gap of the light absorbing layer 400 may be about 1.1 eV to 1.2 eV.

The buffer layer 500 is disposed on the light absorbing layer 400. The solar cell having the CIGS compound as the light absorbing layer 400 forms a pn junction between the CIGS compound thin film as the p-type semiconductor and the transparent electrode layer 500 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 500 include CdS, ZnS and the like, and CdS is relatively excellent in terms of power generation efficiency of the solar cell. The energy band gap of the buffer layer 500 may be 2.2 eV to 2.5 eV.

The high resistance buffer layer 600 is disposed on the buffer layer 500. The high resistance buffer layer 600 includes zinc oxide (i-ZnO) that is not doped with impurities. The energy band gap of the high resistance buffer layer 600 is about 3.1 eV to 3.3 eV.

The window layer 700 is disposed on the high resistance buffer layer 600. The window layer 700 is transparent and is a conductive layer. In addition, the resistance of the window layer 700 is higher than the resistance of the back electrode layer 300.

The window layer 700 includes an oxide. For example, the window layer 700 may include zinc oxide, indium tin oxide (ITO), or indium zinc oxide (IZO).

In addition, the window layer 700 may include aluminum doped zinc oxide (AZO) or gallium doped zinc oxide (GZO).

According to the solar cell according to the embodiment of the present invention, the barrier layer 200 prevents impurities from being diffused from the support substrate 100 to the light absorbing layer 400, and sodium contained in the barrier layer 200 is lighted. Diffusion into the absorbing layer 400 may provide a solar cell that can simultaneously implement the sodium doping effect.

2 to 5 are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment. For a description of the present manufacturing method, refer to the description of the solar cell described above. The description of the solar cell described above may be essentially combined with the description of the present manufacturing method.

Referring to FIG. 2, a barrier layer 200 may be formed on the support substrate 100. The support substrate 100 may be flexible. The barrier layer 200 may include Na ₂ SeO ₃ . The barrier layer 200 may be formed by spray coating in a solution state or physical vapor deposition (PVD).

Referring to FIG. 3, a back electrode layer 300 may be formed on the barrier layer 200. The back electrode layer 300 may be deposited using molybdenum. The back electrode layer 300 may be formed by physical vapor deposition (PVD) or plating.

In addition, an additional layer such as a diffusion barrier may be interposed between the support substrate 100 and the back electrode layer 300.

Next, the light absorbing layer 400 is formed on the back electrode layer 300. The light absorbing layer 400 may be, for example, copper, indium, gallium, or selenium while simultaneously or separately evaporating a light absorbing layer (Cu (In, Ga) Se 2; CIGS). The method of forming 400 and the method of forming a metal precursor film and forming it by the 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.

Subsequently, the metal precursor film is formed of a copper-indium-gallium-selenide-based (Cu (In, Ga) Se 2; CIGS-based) light absorbing layer 400 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 absorbing layer 400 may be formed by a sputtering process and a selenization process using only a copper target and an indium target, or using a copper target and a gallium target.

In the process of forming the light absorbing layer 400, Na included in the barrier layer 200 may be separated and diffused into the light absorbing layer 400. As a result, the charge concentration of the light absorbing layer 400 increases to improve the photoelectric conversion efficiency of the solar cell.

Referring to FIG. 4, cadmium sulfide is deposited on the light absorbing layer 400 by a sputtering process, 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.

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.

Referring to FIG. 5, a window layer 700 is formed on the high resistance buffer layer 600. The window layer 700 is formed by depositing a transparent conductive material on the high resistance buffer layer 600.

Features, structures, effects, and the like described in the above 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 (9)

Board;
A barrier layer disposed on the substrate and comprising a Group 6 element;
A back electrode layer disposed on the barrier layer;
A light absorbing layer disposed on the back electrode layer;
A buffer layer disposed on the light absorbing layer; And
And a window layer disposed on the buffer layer. The method of claim 1,
The barrier layer comprises a selenium (Se). The method of claim 1,
The barrier layer is a solar cell comprising SeO ₃ . The method of claim 1,
The barrier layer is a solar cell containing Na. The method of claim 1,
The barrier layer is formed of a solar cell having a thickness of 100nm to 1000nm . The method of claim 1,
The substrate is a solar cell comprising a polymer. Forming a barrier layer comprising a Group 6 element on the substrate;
Forming a back electrode layer on the barrier layer;
Forming a light absorbing layer on the back electrode layer;
Forming a buffer layer on the light absorbing layer; And
Forming a window layer on the buffer layer; The method of claim 7, wherein
The barrier layer is a solar cell manufacturing method formed by the method of spray coating in a solution state. The method of claim 7, wherein
The barrier layer is formed using sodium (Na), selenium (Se) and oxygen (O) solar cell manufacturing method.

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