WO2016085044A1 - Method for manufacturing multi-junction solar battery using compound thin film and multi-junction solar battery - Google Patents

Abstract

The present invention relates to a method for manufacturing a multi-junction solar battery having a plurality of compound thin film solar battery cells, the method comprising the steps of: forming transparent electrode layers on the upper side and the lower side of a substrate; simultaneously forming light absorption layers on the upper side and the lower side of the substrate having the transparent electrode layers formed thereon; forming buffer layers on the upper side and the lower side of the substrate having the light absorption layers formed thereon; and forming a front electrode on the upper side of the substrate having the buffer layers formed thereon, and forming a rear electrode on the lower side thereof. The present invention enables an upper cell and a lower cell to be respectively formed on the upper side and the lower side around a substrate without continuously stacking the upper cell and the lower cell in one direction, thereby having effects of avoiding, when a lower cell and an upper cell are sequentially manufactured in a conventional method: a problem in which a light absorption layer of a firstly manufactured cell deteriorates by the heat generated during a manufacturing step of a cell manufactured later; and damage occurring on an interface between the light absorption layer and a buffer layer of the firstly manufactured cell. In addition, compared with when the upper cell and the lower cell are respectively manufactured, the number of steps is reduced, and a problem occurring during the process of separately manufacturing and bonding the upper cell and the lower cell can be prevented.

Description

Manufacturing method and multijunction solar cell using compound thin film

The present invention relates to a multi-junction solar cell and a method for manufacturing the same, and more particularly, to a multi-junction solar cell having a plurality of compound thin film solar cell cells and a method of manufacturing the same.

Recently, the importance of developing the next generation of clean energy is increasing due to severe environmental pollution and depletion of fossil energy. Among them, the solar cell is a device that directly converts solar energy into electrical energy, and is expected to be an energy source capable of solving future energy problems due to its low pollution, infinite resources, and a semi-permanent lifetime.

Solar cells are classified into various types according to materials used as light absorption layers, and at present, the most commonly used are silicon solar cells using silicon. However, as prices have soared recently due to a shortage of silicon, interest in thin-film solar cells is increasing. Thin-film solar cells are manufactured with a thin thickness, so the materials are consumed less and the weight is lighter, so the application range is wide. As a material of such a thin-film solar cell, CIGS (Copper Indium Gallium Selenide) having a high light absorption coefficient has been in the spotlight. This is because high conversion efficiency can be obtained by using CIGS in the manufacture of thin film solar cells.

Meanwhile, interest in tandem solar cells having a multi-junction structure, which is proposed as a method for further increasing the efficiency of CIGS solar cells, is increasing. Tandem solar cell refers to a multi-layered solar cell in which two single-cell CIGS solar cells are stacked. However, in the case of such a tandem solar cell, the lower cell is manufactured and then the upper cell is formed thereon, so that the lower cell already formed is damaged in the process of forming the upper cell, thereby making it difficult to obtain the expected energy conversion efficiency. There is.

In order to solve this problem, a technique of manufacturing the upper cell and the lower cell and then combining them has been developed. However, the manufacturing process is complicated and a problem arises in the process of attaching a separately manufactured cell.

[Preceding technical literature]

[Patent Documents]

(Patent Document 1) Republic of Korea Patent Publication 10-2010-0028729

(Patent Document 2) United States Patent Publication 2012-0204939

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the prior art, and a purpose of the present invention is to provide a multi-junction solar cell and a method of manufacturing the same, in which the manufacturing process is simple and there is no problem of cell degradation.

Multi-junction solar cell manufacturing method using a compound thin film for achieving the above object comprises the steps of forming a transparent electrode layer on the upper and lower surfaces of the substrate; Forming a light absorption layer on upper and lower surfaces of the substrate on which the transparent electrode layer is formed; Forming a buffer layer on an upper surface and a lower surface of the substrate on which the light absorption layer is formed; And forming a front electrode on a top surface of the substrate on which the buffer layer is formed and a back electrode on a bottom surface of the substrate.

Multi-junction solar cell manufacturing method using a compound thin film of another form, forming a transparent electrode layer on the upper and lower surfaces of the substrate; Forming a buffer layer on an upper surface and a lower surface of the substrate on which the transparent electrode layer is formed; Forming a light absorption layer on upper and lower surfaces of the substrate on which the buffer layer is formed; And forming a front electrode on an upper surface of the substrate on which the light absorption layer is formed and a rear electrode on a lower surface of the substrate.

In the solar cell manufactured as described above, an upper upper cell and a lower lower cell are formed symmetrically with respect to the substrate, and an energy band gap of the light absorbing layer including the energy band gap of the light absorbing layer included in the lower cell is included in the upper cell. It is characterized by a narrower.

In this case, the method may further include electrically connecting the upper cell and the lower cell, wherein the transparent electrode layer of the upper cell and the rear electrode of the lower cell are electrically connected or the front electrode of the upper cell and the transparent electrode layer of the lower cell are electrically connected. The electrical current must be connected electrically.

The light absorbing layer is preferably one or more materials selected from CIGS, CdTe, CZTS, group III-V semiconductor and perovskite structure material, but is not limited thereto.

Furthermore, in the step of forming the light absorption layer, it is preferable to simultaneously form the light absorption layer in the upper cell and the lower cell. In addition, the buffer layer may be simultaneously formed in the upper cell and the lower cell in the step of forming the buffer layer, and the transparent electrode layer may be simultaneously formed on both sides of the substrate in the step of forming the transparent electrode layer, thereby reducing the process.

Another method of manufacturing a multi-junction solar cell using a compound thin film includes: forming a transparent electrode layer on an upper surface and a lower surface of a substrate; Forming a first buffer layer on only one of an upper surface and a lower surface of the substrate on which the transparent electrode layer is formed; Forming a light absorption layer on upper and lower surfaces of the substrate on which only the first buffer layer is formed; Forming a second buffer layer on an upper surface and a lower surface of the substrate on which the light absorption layer is formed, on which the first buffer layer is not formed; And forming a front electrode on an upper surface of the upper cell based on the substrate and forming a rear electrode on a lower surface of the lower cell, wherein the energy band gap of the light absorption layer included in the lower cell is included in the upper cell. It is characterized in that the narrower than the energy band gap of the light absorption layer.

Unlike the conventional multi-junction solar cell formed sequentially from the bottom to the top or from the top to the bottom, the present invention is characterized in that the upper side forms an upper cell and the lower side forms a lower cell centering on a substrate.

Multi-junction solar cell using a compound thin film for achieving the above object, the substrate; A first transparent electrode layer formed on an upper surface of the substrate and a second transparent electrode layer formed on a lower surface of the substrate; A first light absorbing layer formed on the first transparent electrode layer and a second light absorbing layer formed under the second transparent electrode layer; A first buffer layer formed over the first light absorbing layer and a second buffer layer formed under the second light absorbing layer; A front electrode formed on the first buffer layer; And a rear electrode formed under the second buffer layer, wherein the upper upper cell and the lower lower cell are symmetrically configured based on the substrate, and the energy band gap of the light absorption layer included in the lower cell is the upper cell. It is characterized in that the narrower than the energy bandgap of the light absorption layer included in.

Multi-junction solar cell using another type of compound thin film, substrate; A first transparent electrode layer formed on an upper surface of the substrate and a second transparent electrode layer formed on a lower surface of the substrate; A second buffer layer formed below the first transparent electrode layer and the first buffer layer formed on the first transparent electrode layer; A first light absorbing layer formed above the first buffer layer and a second light absorbing layer formed below the second buffer layer; A front electrode formed on the first light absorption layer; And a rear electrode formed below the second light absorbing layer, wherein the upper upper cell and the lower lower cell are symmetrically configured based on the substrate, and an energy band gap of the light absorbing layer included in the lower cell is upper than the upper electrode. It is characterized in that the narrower than the energy bandgap of the light absorption layer contained in the cell.

The solar cell is manufactured by the above method and has a symmetrical shape with respect to the substrate, and may have a structure in which the first transparent electrode layer and the rear electrode are electrically connected or the second transparent electrode layer and the front electrode are electrically connected.

Preferably, the light absorption layer is made of CIGS material, and the rear electrode is made of metal reflective electrode.

The present invention configured as described above, the upper cell and the lower cell are formed in the upper and lower centers around the substrate, respectively, without continuously stacking in one direction, so that in the case of manufacturing the lower cell and the upper cell sequentially in the past There is an effect of avoiding the problem that the light absorbing layer of the first cell is degraded by the heat generated in the manufacturing process of the cell to be manufactured and the damage occurring at the interface between the light absorbing layer and the buffer layer of the cell previously manufactured.

In addition, the number of processes is reduced as compared to the case of manufacturing the upper cell and the lower cell, respectively, there is an effect that can prevent the problem occurring in the process of separately manufacturing the upper cell and the lower cell.

1 to 5 are schematic diagrams showing a method of manufacturing a multi-junction solar cell according to the present embodiment.

6 is a view showing the electrical connection of the multi-junction solar cell according to the present embodiment.

7 is a schematic diagram showing the structure of a multi-junction solar cell according to a second embodiment of the present invention.

8 is a view showing the electrical connection relationship of a multi-junction solar cell according to a second embodiment of the present invention.

9 is a schematic diagram showing the structure of a multi-junction solar cell according to a third embodiment of the present invention.

10 is a schematic diagram showing the structure of a multi-junction solar cell according to a fourth embodiment of the present invention.

[Description of the code]

100: substrate 210: first transparent electrode layer

220: first light absorbing layer 230: first buffer layer

240: front electrode 310: second transparent electrode layer

320: second light absorbing layer 330: second buffer layer

340: rear electrode

With reference to the accompanying drawings will be described embodiments of the present invention;

1 to 5 are schematic diagrams showing a method of manufacturing a multi-junction solar cell according to the present embodiment.

As shown in FIG. 1, the first transparent electrode layer 210 and the second transparent electrode layer 310 are formed on the top and bottom surfaces of the substrate 100, respectively.

Since the substrate 100 is positioned in the center of the multi-junction solar cell of the present embodiment, the light is transmitted through the upper cell to the lower cell, and the insulating material is preferably an electrically insulating material, but is not limited thereto.

The first transparent electrode layer 210 and the second transparent electrode layer 310 is generally a TCO such as ITO, but is not limited thereto. The transparent electrode layer 210 and the second transparent electrode layer 310 may be made of a material through which electricity flows while transmitting light.

The first transparent electrode layer 210 and the second transparent electrode layer 310 are sequentially or simultaneously formed on both surfaces of the substrate 100. The number of processes is reduced when the first transparent electrode layer 210 and the second transparent electrode layer 310 are formed at the same time.

As shown in FIG. 2, the first light absorbing layer 220 and the second light absorbing layer 320 are formed on the upper and lower surfaces of the first transparent electrode layer 210 and the second transparent electrode layer 310. At this time, it is preferable to simultaneously form the first light absorbing layer 220 and the second light absorbing layer 320, but it is also not necessary, and the first light absorbing layer 220 and the second light absorbing layer 320 may be sequentially formed. Do.

In the present embodiment, the first light absorbing layer 220 and the second light absorbing layer 320 are light absorbing layers made of CIGS material, except that a light absorbing layer is formed on both sides of the substrate, thereby forming a conventional CIGS light absorbing layer. All methods can be applied. Specifically, both a non-vacuum method using a nanoparticle precursor or a solution precursor of a raw material and a vacuum method such as three-stage co-vacuum evaporation methods are possible. However, the energy band gaps of the first light absorbing layer 220 and the second light absorbing layer 320 are different from each other, and the energy band gap of the second light absorbing layer 320 constituting the lower cell constitutes the upper cell. It is configured to be narrower than the energy band gap of the one light absorption layer 220. Meanwhile, although CIGS is used as a material of the light absorption layer in the present embodiment, the present invention is not limited thereto.

As shown in FIG. 3, the first and second buffer layers 230 and 330 are formed on the upper and lower surfaces of the first and second light absorbing layers 220 and 320, respectively.

The method of forming the first buffer layer 230 and the second buffer layer 330 is not particularly limited. Specifically, a CdS film is generally formed by a chemical bath deposition (CBD) process, a ZnS film or a ZnSe film may be formed by a CBD process, or an In _x Se _y film or a ZnIn _x Se _y film may be formed by an evaporation method. An In _x Se _y film or a ZnSe film may be formed by the step. The first buffer layer 230 and the second buffer layer 330 may be formed at the same time, or may be formed sequentially. The number of processes is reduced when the first buffer layer 230 and the second buffer layer 330 are simultaneously formed.

As such, by simultaneously forming the first light absorbing layer 220 and the second light absorbing layer 320, when the lower cell and the upper cell are sequentially manufactured, the first light absorbing layer 220 and the second light absorbing layer 320 are first formed by the heat generated during the manufacturing process of the cell. The problem of deterioration of the light absorbing layer of the manufactured cell and damage occurring at the interface between the light absorbing layer and the buffer layer of the manufactured cell can be avoided. In addition, the number of processes is reduced compared to the case of manufacturing the upper and lower cells, respectively. Furthermore, there is an effect that can prevent a problem occurring in the process of separately manufacturing the upper cell and the lower cell bonding.

Next, as shown in FIG. 4, the front electrode 240 and the rear electrode 340 are formed.

At this time, the front electrode 240 is formed on the surface of the upper cell to the light incident to form a transparent electrode, the rear electrode 340 is an electrode located on the lower surface of the lower cell metal material that can reflect the light To form a reflective electrode.

In order to electrically connect the upper cell and the lower cell, the rear electrode 340 and the first transparent electrode layer 210 are electrically connected as shown in FIG. 5.

The solar cell manufactured according to the present embodiment has a structure in which the upper cell and the lower cell have a symmetrical shape with respect to the substrate, and when the circuit diagram for the solar cell configuration is shown, as shown in FIG. It is an arranged form. Therefore, when the lower electrode of the upper cell and the upper electrode of the lower cell are electrically connected as in the conventional tandem solar cell, electricity does not flow, and the rear electrode 340 and the first transparent electrode layer 210 are electrically connected to each other. The electrode 240 and the second transparent electrode layer 310 must be electrically connected. Meanwhile, even in the 4-terminal structure in which the upper cell and the lower cell are individually connected without being connected in series, the direction of the current according to the structure of the solar cell should be considered.

In addition, in the lower cell of the solar cell manufactured according to the present embodiment, since the junction surface of the second light absorbing layer and the second buffer layer 330 is disposed at a position relatively far from the second transparent electrode layer 310, the photocells are collected. In order to increase the efficiency, the second light absorption layer 320 is preferably thin. Specifically, the thickness of the second light absorption layer 320 is preferably 1 μm or less.

Furthermore, this embodiment has been described for manufacturing a tandem solar cell having a basic structure, and various structures or processes may be added to increase the efficiency of the solar cell in a range that does not impair the technical features of the present invention.

7 is a schematic diagram showing the structure of a multi-junction solar cell according to a second embodiment of the present invention.

The solar cell of FIG. 7 is the first solar cell of FIG. 5 in that the first buffer layer 230 and the second buffer layer 330 are first formed, and the first light absorption layer 220 and the second light absorption layer 320 are formed. There is a difference. Other parts except this are the same as the first solar cell, so a detailed description thereof will be omitted.

Meanwhile, since the pn junction is arranged in the opposite direction as shown in FIG. 8, the solar cell illustrated in FIG. 7 electrically connects the back electrode 340 and the first transparent electrode layer 210 or the front electrode 240. ) And the second transparent electrode layer 310 must be electrically connected.

However, in the upper cell of the solar cell manufactured according to the embodiment of FIG. 7, since the junction surface of the first light absorbing layer and the first buffer layer 230 is disposed at a position relatively far from the first transparent electrode layer 210, photoelectric In order to increase the collection efficiency, the first light absorbing layer 220 is preferably thin. Specifically, the thickness of the first light absorption layer 220 is preferably 1 μm or less.

9 and 10 are schematic diagrams showing the structure of a multi-junction solar cell manufactured according to the third and fourth embodiments.

The illustrated embodiments are characterized in that after forming the first transparent electrode layer 210 and the second transparent electrode layer 310 on both surfaces of the substrate 100, the buffer layer is first formed on only one surface thereof.

Specifically, in the solar cell of FIG. 9, only the first buffer layer 230 is first formed, the first light absorption layer 220 and the second light absorption layer 320 are formed, and the second buffer layer 330 is formed. It is done. In the solar cell of FIG. 10, only the second buffer layer 330 is first formed, and then, the first light absorption layer 220 and the second light absorption layer 320 are formed, and the first buffer layer 230 is formed. .

Since the solar cells manufactured in this order are arranged in the order of pn-pn or np-np, the first transparent electrode layer 210 and the second transparent electrode layer 310 are electrically connected to each other.

While the present invention has been described through the preferred embodiments, the above-described embodiments are merely illustrative of the technical idea of the present invention, and various changes may be made without departing from the technical idea of the present invention. Those of ordinary skill will understand. Therefore, the protection scope of the present invention should be interpreted not by the specific embodiments, but by the matters described in the claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

Claims (18)

Forming transparent electrode layers on upper and lower surfaces of the substrate; Forming a light absorption layer on upper and lower surfaces of the substrate on which the transparent electrode layer is formed; Forming a buffer layer on an upper surface and a lower surface of the substrate on which the light absorption layer is formed; And And forming a front electrode on an upper surface of the substrate on which the buffer layer is formed and forming a rear electrode on a lower surface thereof. The upper upper cell and the lower lower cell are formed symmetrically with respect to the substrate, and the energy band gap of the light absorbing layer included in the lower cell is narrower than the energy band gap of the light absorbing layer included in the upper cell. Junction solar cell manufacturing method. Forming transparent electrode layers on upper and lower surfaces of the substrate; Forming a buffer layer on an upper surface and a lower surface of the substrate on which the transparent electrode layer is formed; Forming a light absorption layer on upper and lower surfaces of the substrate on which the buffer layer is formed; And And forming a front electrode on a top surface of the substrate on which the light absorption layer is formed and a back electrode on a bottom surface thereof. The upper upper cell and the lower lower cell are formed symmetrically with respect to the substrate, and the energy band gap of the light absorbing layer included in the lower cell is narrower than the energy band gap of the light absorbing layer included in the upper cell. Junction solar cell manufacturing method. The method according to claim 1 or 2, The method of manufacturing a multi-junction solar cell further comprising the step of electrically connecting the upper cell and the lower cell. The method according to claim 3, Method of manufacturing a multi-junction solar cell, characterized in that for electrically connecting the transparent electrode layer of the upper cell and the rear electrode of the lower cell. The method according to claim 3, Method of manufacturing a multi-junction solar cell, characterized in that for electrically connecting the front electrode of the upper cell and the transparent electrode layer of the lower cell. The method according to claim 1 or 2, The light absorption layer is a multi-junction solar cell manufacturing method, characterized in that at least one material selected from CIGS, CdTe, CZTS, III-V group semiconductor and perovskite structure material. The method according to claim 1 or 2, In the step of forming the light absorption layer, a multi-junction solar cell manufacturing method, characterized in that to form two light absorption layer at the same time. The method according to claim 1 or 2, In the forming of the buffer layer, a multi-junction solar cell manufacturing method characterized in that to form two buffer layers at the same time. The method according to claim 1 or 2, In the forming of the transparent electrode layer, a multi-junction solar cell manufacturing method characterized in that to form two transparent electrode layers at the same time. Forming transparent electrode layers on upper and lower surfaces of the substrate; Forming a first buffer layer on only one of an upper surface and a lower surface of the substrate on which the transparent electrode layer is formed; Forming a light absorption layer on upper and lower surfaces of the substrate on which only the first buffer layer is formed; Forming a second buffer layer on an upper surface and a lower surface of the substrate on which the light absorption layer is formed, on which the first buffer layer is not formed; And Forming a front electrode on an upper surface of an upper cell based on the substrate and forming a rear electrode on a lower surface of a lower cell; The energy band gap of the light absorbing layer included in the lower cell is narrower than the energy band gap of the light absorbing layer included in the upper cell. Board; A first transparent electrode layer formed on an upper surface of the substrate and a second transparent electrode layer formed on a lower surface of the substrate; A first light absorbing layer formed on the first transparent electrode layer and a second light absorbing layer formed under the second transparent electrode layer; A first buffer layer formed over the first light absorbing layer and a second buffer layer formed under the second light absorbing layer; A front electrode formed on the first buffer layer; And Including; a rear electrode formed under the second buffer layer, The upper upper cell and the lower lower cell are symmetrically configured based on the substrate, and the energy band gap of the light absorbing layer included in the lower cell is narrower than the energy band gap of the light absorbing layer included in the upper cell. Junction solar cell. Board; A first transparent electrode layer formed on an upper surface of the substrate and a second transparent electrode layer formed on a lower surface of the substrate; A second buffer layer formed below the first transparent electrode layer and the first buffer layer formed on the first transparent electrode layer; A first light absorbing layer formed above the first buffer layer and a second light absorbing layer formed below the second buffer layer; A front electrode formed on the first light absorption layer; And Including; a rear electrode formed under the second light absorption layer; The upper upper cell and the lower lower cell are symmetrically configured based on the substrate, and the energy band gap of the light absorbing layer included in the lower cell is narrower than the energy band gap of the light absorbing layer included in the upper cell. Junction solar cell. The method according to claim 11 or 12, Multi-junction solar cell, characterized in that the first transparent electrode layer and the back electrode is electrically connected. The method according to claim 11 or 12, The multijunction solar cell of claim 2, wherein the second transparent electrode layer and the front electrode are electrically connected. The method according to claim 11 or 12, Multi-junction solar cell, characterized in that the light absorption layer is a CIGS material. The method according to claim 11 or 12, The back electrode is a multi-junction solar cell, characterized in that the metal reflective electrode. The method according to claim 11, Multi-junction solar cell, characterized in that the thickness of the second light absorption layer is 1 ㎛ or less. The method according to claim 12, Multi-junction solar cell, characterized in that the thickness of the first light absorption layer is 1 ㎛ or less.

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