KR20130074700A - Solar cell apparatus and method of fabricating the same - Google Patents

Abstract

PURPOSE: A solar cell and a method for manufacturing the same are provided to improve photoelectric conversion efficiency by increasing the grain size of a light absorption layer. CONSTITUTION: A light absorption layer (300) is formed on the upper surface of a first electrode (320). The light absorption layer includes copper and a group III element. The component ratio of the copper and the group III element is 0.8 to 1. A buffer layer (400) is formed on one surface of the light absorption layer. A window layer is formed on the upper surface of 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 energy resources such as petroleum and coal are expected to be depleted, interest in alternative energy to replace them is increasing, and solar cells that produce electric energy from solar energy are attracting attention.

Solar cells (Solar Cells or Photovoltaic Cells) are the key elements of photovoltaic power generation that convert sunlight directly into electricity.

For example, when solar light having energy greater than the band-gap energy (Eg) is incident on a solar cell made of a pn junction of a semiconductor, electron-hole pairs are generated, and these electron-holes are formed in an electric field formed at a pn junction. As a result, electrons are gathered into the n-layer and holes are gathered into the p-layer, whereby electromotive force (photovoltage) is generated between pn. At this time, when the load is connected to the electrodes at both ends, current flows.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrodeposition for depositing metal electrochemically, and to a technique for attaching a substance to an electrode surface by applying a direct current voltage by placing an electrode plate in a solution.

When CIGS is deposited by a conventional electrodeposition method, the closer the Cu / III ratio is to 0.9, the better the grain, but the peeling off between the CIGS film and the back electrode layer acting as a light absorbing layer. The phenomenon easily occurs.

In order to prevent this, CIGS may be deposited by reducing the ratio of Cu, but in this case, photo-electric conversion efficiency is reduced, and the size of grain is reduced, resulting in a problem of low fill factor.

According to an embodiment of the present invention, the ratio of Cu / III is electrodeposited to approach 0.9, thereby improving the size of grain, thereby improving photoelectric conversion efficiency.

A solar cell according to an embodiment of the present invention includes a light absorbing layer: and a buffer layer formed on one surface of the light absorbing layer, wherein the light absorbing layer includes copper and group 3 elements, and the component ratio of the copper and group 3 elements is It is formed to have a value of 0.8 to 1.

According to an embodiment of the present invention, the ratio of Cu / III is electrodeposited to approach 0.9, thereby improving the size of grain, thereby improving photoelectric conversion efficiency.

1 is a cross-sectional view illustrating a method of forming an electrodeposition film by electrodepositing an electrodeposition liquid on a first electrode layer according to an embodiment of the present invention.
2 to 4 are views illustrating a process of manufacturing a solar cell according to the embodiment.
5 is a diagram illustrating a solar cell according to another 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” 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 illustrating a method of forming an electrodeposition film by electrodepositing an electrodeposition liquid on a surface of a first electrode layer according to an embodiment of the present invention. 2 to 4 are views illustrating a process of manufacturing a solar cell according to the embodiment.

Referring to FIG. 1, an electrolyte solution 10, a first electrode layer 320, an electrodeposition film 300, and an electrodeposition electrode 340 are included in an electrolytic cell 310.

The electrolytic cell 310 contains an electrolyte solution 10. The electrolytic cell 310 of the present invention may be made of a transparent corrosion resistant material such as quartz, glass, transparent organic material, or the like.

The electrolyte solution 10 in the electrolyzer 310 may be composed of metal ions and acid radicals such as copper sulphate, nickel chloride, and the like. Depending on the different requirements required for the metal to be deposited, the electrolyte solution 10 may contain only one or more metal ions.

And, depending on the different requirements required for the metal to be deposited, the electrolyte solution 10 may contain only one or more acid radicals, such as sulfide radicals, nitride radicals. The electrolyte solution 10 may include a group I-III-VI compound. For example, the electrolyte solution 10 may include a compound of copper indium gallium selenide (Cu (In, Ga) Se ₂ ; CIGS), copper indium selenide, or copper gallium selenide. Can be.

Specifically, the electrolyte solution 10 may include a metal salt of CuCl ₂ , InCl ₃ , H ₂ SeO ₃ , GaCl ₃ . The metal salt is CuCl ₂ each is 1.5mM, InCl ₃ is 2.4mM, H ₂ SeO ₃ is 4.47mM, GaCl ₃ can be synthesized at a rate of 10mM.

Supporting electrolyte may include LiCl. The LiCl may be added 0.24M.

The buffer solution may include potassium biphthalic acid (POTASSIUM BIPHTHALATE). The acidity of the buffer solution may be 2.5pH to 3pH.

The electrodeposition layer may be formed by mixing the metal salt and the supporting electrolyte at the same time, and then adding a buffer solution into the electrolytic cell 310 after the supporting electrolyte is dissolved, and the voltage at this time may be -0.55V, but at a specific value. It will not be limited.

As described above, the electrolyte solution 10 includes copper and Cu / III, which is a ratio with the group 3 element, may have a value of 0.8 to 1.

Appropriate additives may be added to the electrolyte solution 10 to reduce the stress of the deposited metal and to improve the flatness of the deposited metal, depending on the process of electrochemically depositing different electrolyte solutions and metals. .

The cathode is connected to the first electrode layer 320 and the anode is connected to the electrode electrode 340 to apply DC power for a predetermined time. As the metal cations present on the surface of the semiconductor compound move under the direct electric field to the first electrode 320, which is the cathode, the semiconductor compound also moves, while the anion moves to the electrodeposition electrode 340, which is the anode.

By the above process, as shown in FIG. 2, the light absorbing layer 300 is formed on the upper surface of the first electrode 320. 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 energy band gap of the light absorbing layer 300 may be about 1.1 eV to 1.2 eV.

Next, a buffer layer 400 is formed on the upper surface of 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 500 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.

The energy bandgap of the buffer layer 400 may be 2.2 eV to 2.5 eV. 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 buffer layer 400 may be formed by PVD or plating.

The buffer layer 400 may be formed to a thickness of 10nm to 100nm, preferably 50nm to 80nm.

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

Since the Cu / III ratio of the light absorbing layer 300 and the first electrode layer 320 is close to 0.9, the grain size becomes large, and thus the adhesive force is reduced. Accordingly, the light absorbing layer 300 and the first electrode layer 320 may be separated by taping the upper surface of the buffer layer 400.

Next, as shown in FIG. 3, the window layer 500 is disposed on the buffer layer 400. The window layer 500 is transparent and a conductive layer. In addition, the resistance of the window layer 500 is higher than that of the back electrode layer 200.

The window layer 500 includes an oxide. For example, the window layer 500 may include zinc oxide, indium tin oxide (ITO), or indium zinc oxide (IZO).

In addition, the window layer 500 may include aluminum doped zinc oxide (AZO) or gallium doped zinc oxide (GZO).

Next, as shown in FIG. 4, a rear electrode layer 200 is disposed on a lower surface of the light absorbing layer 300 which is separated from the first electrode layer 320 and exposed. The back electrode layer 200 is a conductive layer. The back electrode layer 200 may allow electric charges generated in the light absorbing layer 300 of the solar cell to move to allow current to flow 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 should maintain high temperature stability during heat treatment under sulfur (S) or selenium (Se) atmosphere accompanying CIGS compound formation. In addition, the back electrode layer 200 should be excellent in adhesion with the support substrate 100 so that peeling does not occur with the support substrate (not shown) due to a difference in thermal expansion coefficient.

As the material for forming the back electrode layer 200, a material having a low difference between the support substrate and the coefficient of thermal expansion should be considered to have excellent adhesiveness and prevent peeling from occurring. Molybdenum (Mo) may be used as such a material.

5 is a diagram illustrating a solar cell according to another embodiment. 5 is different from the embodiment of FIG. 4, the back electrode layer 200 may be manufactured in a superstrate manner in which the uppermost layer is disposed.

As discussed above, the solar cell according to the embodiment of the present invention may improve the photo-electric conversion efficiency by improving the size of the grains of the light absorbing layer 300.

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 (13)

Light absorbing layer: and,
And a buffer layer formed on one surface of the light absorbing layer.
The light absorbing layer includes copper and a group 3 element, and the component ratio of the copper and group 3 elements is formed to have a value of 0.8 to 1. The method of claim 1,
The light absorbing layer is a solar cell including a copper-indium-gallium-selenide-based (Cu (In, Ga) Se ₂ ; CIGS-based). Forming a light absorbing layer on the upper surface of the first electrode layer by an electrodeposition method using an electrolyte solution;
Forming a buffer layer on an upper surface of the light absorbing layer;
Forming a tape on the buffer layer; And
Separating the light absorbing layer and the first electrode layer so that the bottom surface of the light absorbing layer is exposed while removing the tape. The method of claim 3,
The light absorbing layer includes a copper and a group 3 element, and the component ratio of the copper and group 3 element is formed to have a value of 0.8 to 1. The method of claim 3,
Forming a rear electrode layer on the lower surface of the light absorbing layer. The method of claim 3,
Forming a window layer on the upper surface of the buffer layer; manufacturing method of a solar cell comprising a. The method of claim 3,
The first electrode layer is a manufacturing method of a solar cell connected to the cathode. The method of claim 3,
The electrolyte solution is a method of manufacturing a solar cell containing a metal salt (CuCl ₂ , InCl ₃ , H ₂ SeO ₃ , GaCl ₃ ). 9. The method of claim 8,
The metal salt is a method of manufacturing a solar cell is synthesized in a ratio of CuCl ₂ 1.5mM, InCl ₃ 2.4mM, H ₂ SeO ₃ 4.47mM, GaCl ₃ 10mM. The method of claim 3,
The electrolyte solution includes a supporting electrolyte (Supporting Electrolyte), the supporting electrolyte manufacturing method of a solar cell containing LiCl. The method of claim 10,
LiCl is a manufacturing method of the solar cell is 0.24M is injected. The method of claim 3,
The electrolyte solution includes a buffer solution (Buffer Solution), the buffer solution manufacturing method of a solar cell containing potassium biphthalic acid (POTASSIUM BIPHTHALATE). The method of claim 12,
The acidity of the buffer solution is 2.5pH to 3pH method of manufacturing a solar cell.

Images