WO2010114278A2

WO2010114278A2 - Flexible substrate, and solar cell using same

Info

Publication number: WO2010114278A2
Application number: PCT/KR2010/001926
Authority: WO
Inventors: 이영호; 이병일; 이유진; 김동제
Original assignee: 주식회사 티지솔라
Priority date: 2009-03-31
Filing date: 2010-03-30
Publication date: 2010-10-07
Also published as: TW201041166A; KR20100108941A; WO2010114278A3; KR101011522B1

Abstract

Disclosed are a flexible substrate, and a solar cell using same. The flexible substrate and the solar cell using same according to the present invention comprise: a substrate (100) made of a conductive material; a buffer layer (110) formed on the substrate (100), and made of a material having a melting point lower than that of the substrate (100); and a barrier layer (120) formed on the buffer layer (110).

Description

Flexible substrate and solar cell using same

The present invention relates to a flexible substrate and a solar cell using the same. More specifically, the present invention relates to a flexible substrate and a solar cell using the same, which can prevent the substrate from being deformed in the heat treatment of the semiconductor layer formed on the substrate.

Flexible substrate technology includes display devices such as liquid crystal displays (LCDs), organic light emitting diodes (OLEDs), or photoelectric devices such as thin-film type solar cells. It is a core technology that improves the portability of the device and at the same time, various installation places thereof such as windows, automobiles, exterior walls of houses or buildings.

Such flexible substrates include plastic-based substrates and metal-based substrates, and a technique using a metal foil-type flexible substrate capable of simultaneously performing an electrode function with excellent heat resistance is generally used. have.

However, when such a flexible substrate is used in a polycrystalline silicon solar cell, there is a problem in that the flexible substrate is deformed. That is, it is generated by a heat treatment process cycle including a crystallization temperature of about 550 ° C. to 650 ° C., which is typically required in the process of crystallizing the amorphous silicon layer (a-si) to the polycrystalline silicon layer (p-si) on the flexible substrate. There was a problem in that the bending phenomenon of the flexible substrate appeared due to residual stress.

In addition, such a high temperature crystallization process may cause unnecessary chemical reaction between the flexible substrate and the semiconductor layer (silicon layer), thereby degrading the characteristics of the solar cell or peeling the semiconductor layer from the flexible substrate.

The present invention is to solve the above problems of the prior art, an object of the present invention is to provide a flexible substrate that can absorb the residual stress generated during the solar cell manufacturing process.

Another object of the present invention is to provide a flexible substrate capable of preventing chemical reactions at the interface between the substrate and the semiconductor layer.

Another object of the present invention is to provide a flexible substrate capable of preventing the thin film (for example, a semiconductor layer) formed on the flexible substrate from being peeled off.

In addition, another object of the present invention is to provide a solar cell having improved photoelectric conversion efficiency and increased reliability and lifetime.

According to the present invention, the flexible substrate includes a buffer layer to absorb stress to prevent the occurrence of warpage of the substrate.

In addition, according to the present invention, the flexible substrate includes a barrier layer to prevent diffusion between layers and to improve interface characteristics.

In addition, according to the present invention, it is possible to prevent the thin film on the flexible substrate from being peeled off and obtain good interfacial characteristics.

In addition, according to the present invention, by implementing the solar cell on the above-described flexible substrate, the photoelectric conversion efficiency of the solar cell can be improved and life and reliability can be increased.

1 and 2 are views showing a process for manufacturing a flexible substrate according to an embodiment of the present invention.

3 is a photograph of the state of the substrate according to the comparative example and the experimental example of the present invention.

4 and 5 are views illustrating a manufacturing process of a solar cell using a flexible substrate according to an embodiment of the present invention.

6 is a cross-sectional view of another type of solar cell using a flexible substrate according to an embodiment of the present invention.

100: substrate

110: buffer layer

120: barrier layer

200, 300: photoelectric device

400: upper electrode

The object of the present invention is a substrate of a conductive material; A buffer layer formed on the substrate but having a lower melting point than the substrate; And it is achieved by a flexible substrate comprising a barrier layer formed on the buffer layer.

In addition, the object of the present invention is a substrate of a conductive material; A buffer layer formed on the substrate but having a lower melting point than the substrate; A barrier layer formed on the buffer layer; A semiconductor layer formed on the barrier layer; And it is also achieved by a solar cell comprising an upper electrode formed on the semiconductor layer.

In this case, the buffer layer may be Al.

The barrier layer may be TiN.

The barrier layer may have a stacked structure of Ti / TiN / Ti.

The substrate may be a sus (SUS) or an invar.

The semiconductor layer comprises a first polycrystalline semiconductor layer; A second polycrystalline semiconductor layer formed on the first polycrystalline semiconductor layer; And a third polycrystalline semiconductor layer formed on the second polycrystalline semiconductor layer.

Details of the above object and technical configuration of the present invention and the effects thereof according to the present invention will be more clearly understood by the following detailed description with reference to the drawings showing preferred embodiments of the present invention.

Flexible board

In the present specification, a flexible substrate is to be understood as a generic term for a substrate capable of forming an electronic device that can be driven by an electrical stimulus using a metal foil as a substrate.

In the following detailed description, for convenience, a description will be given based on a technique of forming a thin film solar cell on a flexible substrate, but the present invention is not limited thereto.

First, referring to FIG. 1, a substrate 100 having a flexible property is provided, and the material of the substrate 100 may be stainless steel or invar manufactured in the form of a metal foil. .

Subsequently, a buffer layer 110 may be formed on the substrate 100 to absorb residual stresses generated during the subsequent high temperature heat treatment. The buffer layer 110 may be formed by electron beam evaporation or sputtering. It may be formed by using physical vapor deposition (PVD), such as (sputtering).

In this case, the buffer layer 110 preferably uses a metal such as aluminum (Al) having a lower melting point than that of the substrate 100, which is melted during high temperature heat treatment (for example, when the amorphous silicon layer is crystallized). This is because a function of absorbing residual stress generated in the thin film layer (for example, the semiconductor layer) formed on the substrate 100 and the substrate 100 can be performed.

Next, referring to FIG. 2, a barrier layer 120 may be further formed on the buffer layer 110. The barrier layer 120 may be a physical vapor deposition method such as electron beam deposition or sputtering, or a plasma chemical vapor deposition method (Plasma). Chemical Vapor Deposition (CVD) such as Enhanced Chemical Vapor Deposition (PECVD), Low Pressure Chemical Vapor Deposition (LPCVD) and Metal Organic Chemical Vapor Deposition (MOCVD) Can be formed.

In this case, the barrier layer 120 may be formed of titanium nitride (TiN) to effectively prevent diffusion between the substrate 100 and the semiconductor layer in a high temperature heat treatment process. In this case, it is preferable that the multilayer structure includes TiN to improve the interfacial properties to improve the adhesion between the barrier layer 120 and the semiconductor layer to be formed thereon. For example, the barrier layer 120 may use a titanium / titanium nitride / titanium (Ti / TiN / Ti) structure, but the present invention is not limited thereto.

In order to help more detailed understanding of the flexible substrate of the present invention, the following Comparative Examples and Experimental Examples are presented. However, the following experimental examples are only for helping the understanding of the present invention, and the present invention is not limited to the following experimental examples.

[Comparative Example]

In the following comparative example, a predetermined semiconductor layer was formed on a conventional flexible substrate, and the state of the substrate was photographed after performing a crystallization process.

First, an amorphous silicon layer was formed as a semiconductor layer on a stainless steel substrate 100 having a foil shape having a thickness of 200 μm. Subsequently, heat treatment was performed at a temperature of 650 ° C. to crystallize the amorphous silicon layer into a polycrystalline silicon layer, and then the state of the substrate 100 was observed.

Experimental Example

In the following experimental example, the buffer layer 110 and the barrier layer 120 are formed on the substrate 100, the predetermined semiconductor layer is formed thereon, and the crystallization process is performed, like the flexible substrate according to the exemplary embodiment of the present invention. After performing the state of the substrate 100 was taken. First, a 40 nm thick Al buffer layer 110 was formed by sputtering on a 200 μm-thick foil-shaped stainless steel substrate 100. Subsequently, a barrier layer 120 having a stacked structure of Ti (100 nm) / TiN (300 nm) / Ti (40 nm) was formed on the Al buffer layer 110 by sputtering. Subsequently, an amorphous silicon layer was formed on the barrier layer 120 as a semiconductor layer. Subsequently, heat treatment was performed at a temperature of 650 ° C. to crystallize the amorphous silicon layer into a polycrystalline silicon layer, and then the state of the substrate was observed.

The state of the substrate according to the above experimental example and comparative example will be apparent in the following description with reference to FIG. 3.

Referring to FIG. 3, in the substrate 100 according to the comparative example, the warpage phenomenon 10 and the reaction region 20 can be clearly identified with the naked eye (see FIG. 3A). On the other hand, in the substrate 100 according to the experimental example, it can be seen that neither the warpage phenomenon 10 nor the reaction region 20 exist (see FIG. 3B).

Therefore, as compared with the conventional flexible substrate, the flexible substrate 100 according to an embodiment of the present invention has a function of preventing the bending of the substrate 100 by suppressing the occurrence of residual stress during high temperature heat treatment by providing the buffer layer 110. In addition, since the barrier layer 120 is provided, a function of suppressing diffusion between the substrate 100 and the semiconductor layer during the high temperature heat treatment and improving the interface characteristics may be performed.

Solar Cell Using Flexible Substrate

4 and 5 are cross-sectional views of a solar cell using a flexible substrate according to an embodiment of the present invention.

First, referring to FIG. 4, on the buffer layer 110 and the barrier layer 120 of the flexible substrate 100 according to an embodiment of the present invention, three amorphous silicon layers 210, 220, and 230 are examples of semiconductor layers. ) May be stacked and formed. In more detail, the first amorphous silicon layer 210 is formed on the barrier layer 120, and then the second amorphous silicon layer 220 is formed on the first amorphous silicon layer 210, followed by the second amorphous silicon layer 210. The third amorphous silicon layer 230 may be formed on the silicon layer 220. In this case, the first to third amorphous silicon layers 210, 220, and 230 may be formed using chemical vapor deposition such as PECVD or LPCVD.

Next, referring to FIG. 5, a process of crystallizing the first, second, and third amorphous silicon layers 210, 220, and 230 may be performed. That is, the first amorphous silicon layer 210 is the first polycrystalline silicon layer 211, the second amorphous silicon layer 220 is the second polycrystalline silicon layer 221, and the third amorphous silicon layer 230 is formed of the first amorphous silicon layer 210. Each of the three polycrystalline silicon layers 231 is crystallized. As a result, the photoelectric device 200 including the first, second, and third polycrystalline silicon layers 211, 221, and 231 is formed on the barrier layer 120.

The photovoltaic device 200 is a structure in which a polycrystalline silicon layer is stacked and a pin diode in which p-type, i-type, and n-type polycrystalline silicon layers are stacked in order to generate power using photovoltaic power generated by receiving light. Can be.

Here, the i type means intrinsic without impurities. In addition, in the n-type or p-type doping, it is preferable to dope the impurities in situ when forming the amorphous silicon layer. It is common to use boron (B) as an impurity in P-type doping and phosphorus (P) or arsenic (As) as an impurity in n-type doping, but it is not limited to this, and well-known techniques can be used without limitation.

Crystallization methods of the first, second, and third amorphous silicon layers 210, 220, and 230 may include Solid Phase Crystallization (SPC), Excimer Laser Annealing (ELA), Sequential Lateral Solidification (SLS), Metal Induced Crystallization (MIC), And MILC (Metal Induced Lateral Crystallization). Since the crystallization method of the amorphous silicon is a known technique, a detailed description thereof will be omitted herein.

In the above description, the first, second, and third amorphous silicon layers 210, 220, and 230 are all formed, and the layers are simultaneously crystallized, but the present invention is not limited thereto. For example, the crystallization process may be performed separately for each amorphous silicon layer, and the two amorphous silicon layers may simultaneously undergo a crystallization process and the other amorphous silicon layer may be separately crystallized.

Although not shown, the first polycrystalline silicon layer 211, the second polycrystalline silicon layer 221, and the third polycrystalline silicon layer 231 may further perform a defect removal process to further improve the properties of the polycrystalline silicon. have. In the present invention, the polycrystalline silicon layer may be subjected to high temperature heat treatment or hydrogen plasma treatment to remove defects (eg, impurities and dangling bonds) present in the polycrystalline silicon layer.

Subsequently, an upper electrode 400 of a transparent conductive material is formed on the third polycrystalline silicon layer 231. The material of the upper electrode 400 may be any one of indium tin oxide (ITO), ZnO, BZO (ZnO: B), IZO (ZnO: In), AZO (ZnO: Al), and FTO (SnO ₂ : F). Preferred but not necessarily limited thereto. The method of forming the upper electrode 400 may include a physical vapor deposition method such as sputtering and a chemical vapor deposition method such as LPCVD, PECVD, and MOCVD.

On the other hand, in the solar cell according to the present embodiment, the lower electrode becomes the flexible substrate 100 itself. Therefore, when the solar cell module is manufactured using the solar cell of FIG. 5 as a unit cell as described above, the flexible substrate 100 of the solar cell and the upper electrode of the solar cell adjacent to the solar cell are not shown. Can be electrically connected.

When the optoelectronic device 200 is formed on the flexible substrate 100 on which the buffer layer 110 and the barrier layer 120 are formed as described above, the curvature of the substrate, the peeling of the semiconductor layer, and the chemical reaction between the substrate and the semiconductor layer may be suppressed. It can improve the photoelectric conversion efficiency of solar cells and can also expect the effect of increasing the reliability and lifespan.

Referring to FIG. 6, another optoelectronic device 300 may be further formed on the optoelectronic device 200 described above. The optoelectronic device 300 has a structure in which an amorphous semiconductor layer is stacked, for example, three layers. The amorphous silicon layers 310, 320, and 330 may be formed.

In more detail, the first amorphous silicon layer 310 is formed on the photoelectric device 200 positioned below, and the second amorphous silicon layer 320 is formed on the first amorphous silicon layer 310. Subsequently, a third amorphous silicon layer 330 is formed on the second amorphous silicon layer 320 to form a photoelectric device 300 having a pin diode structure such as the photoelectric device 300. In this case, the first, second, and third amorphous silicon layers 310, 320, and 330 may be formed using chemical vapor deposition such as PECVD or LPCVD.

Subsequently, an upper electrode 400 of a transparent conductive material is formed on the third amorphous semiconductor layer 330. The material and manufacturing method of the upper electrode 400 are the same as described with reference to FIG. 5.

Although not shown, a connection layer of a transparent conductive material may be further formed between the third polycrystalline silicon layer 231 and the first amorphous silicon layer 310. In this case, the connection layer may be any one of ITO, AZO (ZnO: Al), GZO (ZnO: Ga), BZO (ZnO: B), and FTO (SnO ₂ : F), which may transmit light. The formation method of the connection layer may include a physical vapor deposition method such as sputtering and a chemical vapor deposition method such as LPCVD, PECVD, and MOCVD.

Such a connection layer allows ohmic contact between the third polycrystalline silicon layer 231 and the first amorphous silicon layer 310, and as a result, better photoelectric conversion efficiency of the solar cell can be expected.

As a result, a tandem solar cell including the optoelectronic device 200 made of a polycrystalline silicon layer and the optoelectronic device 300 made of an amorphous silicon layer may be obtained. In this case, since the photoelectric device 200 is made of a polycrystalline silicon layer, the photoelectric conversion efficiency is good for the long wavelength light, and the photoelectric device 300 is made of the amorphous silicon layer, and thus the photoelectric conversion efficiency is good for the short wavelength light. Do. Therefore, the tandem structured solar cell according to the present invention can absorb light in various wavelength bands, thereby improving photoelectric conversion efficiency.

In the above detailed description, a tandem structure in which the

optoelectronic devices

200 and 300 are stacked has been described as an example. Alternatively, the optoelectronic devices may be stacked in double or more as necessary. In addition, the

optoelectronic devices

200 and 300 may use n-i-p type, p-n type, n-p type or the like instead of p-i-n type.

Although the present invention has been shown and described with reference to preferred embodiments as described above, it is not limited to the above embodiments and various modifications made by those skilled in the art without departing from the spirit of the present invention. Modifications and variations are possible. Such modifications and variations are intended to fall within the scope of the invention and the appended claims.

Claims

A substrate made of a conductive material;

A buffer layer formed on the substrate but having a lower melting point than the substrate; And

A barrier layer formed on the buffer layer

Flexible substrate comprising a.
The method of claim 1,

The buffer layer is Al, characterized in that the flexible substrate.
The method of claim 1,

The barrier layer is a flexible substrate, characterized in that the TiN.
The method of claim 3,

The barrier layer is a flexible substrate, characterized in that the laminated structure of Ti / TiN / Ti.
The method of claim 1,

The substrate is a flexible substrate, characterized in that the sus (SUS) or Invar (Invar).
A substrate made of a conductive material;

A buffer layer formed on the substrate but having a lower melting point than the substrate;

A barrier layer formed on the buffer layer;

A semiconductor layer formed on the barrier layer; And

An upper electrode formed on the semiconductor layer

Solar cell comprising a.
The method of claim 6,

The buffer layer is a solar cell, characterized in that Al.
The method of claim 6,

The barrier layer is a solar cell, characterized in that TiN.
The method of claim 8,

The barrier layer is a solar cell, characterized in that the laminated structure of Ti / TiN / Ti.
The method of claim 6,

The semiconductor layer comprises a first polycrystalline semiconductor layer;

A second polycrystalline semiconductor layer formed on the first polycrystalline semiconductor layer; And

And a third polycrystalline semiconductor layer formed on the second polycrystalline semiconductor layer.