WO2017030352A1 - Flexible transparent electrode having azo/ag/azo multilayered thin film structure, and manufacturing method therefor - Google Patents

Abstract

The present invention relates to a flexible transparent electrode having an AZO/Ag/AZO multilayered thin film structure and, more specifically, to a flexible transparent electrode comprising: an Ag metal layer; and Al-doped ZnO layers which are respectively laminated on the upper surface and the lower surface of the Ag metal layer, wherein the thickness of the Ag metal layer is 15 nm to 23 nm, and the thickness of the Al-doped ZnO layers is 15 nm to 60 nm. The present invention is capable of providing a flexible transparent electrode having high transmittance comparable to conventional ITO electrodes and having a low surface resistance value. Further, the flexible transparent electrode is manufactured by a room temperature deposition process, and thus can be manufactured on a polymer substrate without the need of a high-temperature heat treatment.

Description

Flexible transparent electrode having AZO / AG / AZO multilayer thin film structure and manufacturing method thereof

The present invention relates to a flexible transparent electrode having an AZO / Ag / AZO multilayer thin film structure.

The flexible transparent electrode is an electrode in which a conductive pattern is formed on a flexible substrate, and is an electronic device usefully used in various fields such as a display, a transistor, a touch panel, and a solar cell.

Currently, the most widely used materials for flexible transparent electrodes are transparent conductive oxides, carbon nanotubes, graphene and polymer conductors. Among these materials, indium tin oxide (ITO), which is a kind of transparent conductive oxide, is known. Silver is widely used in most transparent electrodes because of its high light transmittance and conductivity.

However, the ITO electrode material is replaced by the high temperature heat treatment process in the manufacturing process, the limited supply of indium, a rare metal used for the production of ITO, and the difficulty in securing flexible properties. As various alternative materials for the purpose, research and development on conductive oxides, carbon nanotubes, graphene, silver nanowires, and conductive polymers are being actively conducted.

As an example, research has been conducted to replace ITO by doping other materials with ZnO and SnO ₂ , which are conductive oxides. In addition, carbon nanotubes, which have undergone considerable research and are highly commercially applicable in various fields, require various improvements with respect to doping, purification and synthesis. Furthermore, graphene can be produced using low-cost graphite, and has the advantage of superior surface roughness than carbon nanotubes, but it shows limitations in producing large crystalline large-area graphene films. In addition, the silver nanowire has a disadvantage that it is not easy to apply to a display because the surface roughness and haze is high compared to other materials. Lastly, although conductive polymers have been studied for a long time as a transparent electrode, the organic polymer has a unique color and lacks atmospheric stability.

On the other hand, as a material exhibiting properties closest to ITO, a transparent electrode of an oxide / metal / oxide multilayer structure has been proposed, which does not require a heat treatment process as compared to an ITO transparent electrode requiring high temperature heat treatment. It has the advantage of being applicable to manufacturing, the process is economical, and the large area is easy.

Relatedly, a multilayer transparent electrode having a multilayer structure of silicon oxynitride / silver / silicon oxynitride (Patent Document 1), a multilayer transparent electrode having a multilayer structure of a first transparent oxide layer / silver / second transparent oxide layer ( Various techniques such as patent document 2) have been known. In addition, as a layer forming material of multilayer transparent electrodes having a multilayer structure of such an oxide / metal / oxide, the applicability of various materials has been tested, and in particular, in the case of the AZO / Ag / AZO multilayer structure (AZO: Al doped ZnO), which has a high transmittance comparable to that of ITO, has a low sheet resistance value, and can be applied directly to a polymer substrate since it does not require a high temperature heat treatment process.

Therefore, a method of manufacturing a transparent conductive film coated with an AZO / Ag / AZO multilayer thin film and a technique related to a transparent conductive film formed by the method have been disclosed (Patent Document 3), and AZO / grown by a dual target DC sputtering method. The results of studies on the properties of the Ag / AZO multilayer structure have also been reported (Non Patent Literature 1), and the results of the research on the properties of the AZO / Ag / AZO multilayer structure deposited on the polyether sulfone substrate have also been reported.

However, in order to successfully apply this AZO / Ag / AZO multilayer structure to a flexible transparent electrode, various factors should be considered, and should have sufficient light transmittance, low sheet resistance and high flexibility, and bend several times. These characteristics must be maintained in the test.

(Patent literature)

Patent Document 1: Republic of Korea Patent Publication No. 10-2012-0028506

Patent Document 2: Republic of Korea Patent Publication No. 10-1996-0035092

Patent Document 3: Republic of Korea Patent Publication No. 10-2010-0089962

(Non-patent literature)

Non-Patent Document 1: Characteristics of indium-free GZO / Ag / GZO and AZO / Ag / AZO multilayer electrode grown by dual target DC sputtering at room temperature for low-cost organic photovoltaics, Solar Energy Materials & Solar Cells 93 (2009) 1994 -2002

[Non-Patent Document 2] Properties of AZO / Ag / AZO Multilayer Thin Film Deposited on Polyethersulfone Substrate, TRANSACTIONS ON ELECTRICAL AND ELECTRONIC MATERIALS, Vol. 14, No. 1, pp. 9-11, February 25, 2013

Accordingly, in the present invention, the AZO / Ag / AZO multilayer structure-based flexible structure that satisfies the characteristics such as light transmittance, sheet resistance, and flexibility, which are essential for applying the AZO / Ag / AZO multilayer structure to the flexible transparent electrode, is required. It is intended to provide a transparent electrode.

The present invention to solve the above problems,

Ag metal layer; And

A flexible transparent electrode comprising a ZnO layer doped with Al stacked on top and bottom surfaces of the Ag metal layer, respectively.

The Ag metal layer has a thickness of 15 nm to 23 nm,

The Al doped ZnO layer provides a flexible transparent electrode, characterized in that the thickness of 15 nm to 60 nm.

According to the exemplary embodiment of the present invention, the Ag metal layer may have a thickness of 19 nm, and the Al doped ZnO layers respectively stacked on the top and bottom surfaces of the Ag metal layer may each have a thickness of 36 nm.

According to another embodiment of the present invention, the ratio of the thickness of the Ag metal layer and the thickness of the Al-doped ZnO layer may be 1: 1 to 1: 4.

According to another embodiment of the present invention, the ratio of the thickness of the Ag metal layer and the thickness of the Al-doped ZnO layer may be 1: 2.

According to another embodiment of the present invention, the flexible transparent electrode has a light transmittance of 80% or more in the visible light wavelength band, 5 Ω / sq. It may have a sheet resistance value and a figure of merit of 10 or more.

According to another embodiment of the invention, the Ag metal layer and the Al-doped ZnO layer is on a flexible substrate selected from the group consisting of polyethersulfone, polyethylene terephthalate, polycarbonate, polyimide, polyethylene naphthalate and glass material Can be stacked on.

Moreover, in order to solve the said subject,

a) forming an Al doped ZnO layer on a substrate with a thickness of 15 nm to 60 nm;

b) forming an Ag metal layer having a thickness of 15 nm to 25 nm on the Al-doped ZnO layer; And

c) forming a ZnO layer Al-doped Al again on the Ag metal layer to a thickness of 15 nm to 60 nm.

According to the exemplary embodiment of the present invention, the Ag metal layer may have a thickness of 19 nm, and the Al doped ZnO layers respectively stacked on the top and bottom surfaces of the Ag metal layer may each have a thickness of 36 nm.

According to another embodiment of the present invention, the ratio of the thickness of the Ag metal layer and the thickness of the Al-doped ZnO layer may be 1: 1 to 1: 4.

According to another embodiment of the present invention, the ratio of the thickness of the Ag metal layer and the thickness of the Al-doped ZnO layer may be 1: 2.

According to another embodiment of the present invention, the steps a) to c) may be performed by any one process selected from the group consisting of sputtering, electron beam deposition, and continuous evaporation deposition.

According to another embodiment of the present invention, the steps a) to c) may be performed by a batch process.

In addition, the present invention provides a solar cell including the flexible transparent electrode.

In addition, the present invention provides a light emitting diode including the flexible transparent electrode.

According to the present invention, it is possible to provide a flexible transparent electrode having a high permeability comparable to that of a conventional ITO electrode, having a low sheet resistance value, and manufactured by a room temperature deposition process, which can be manufactured as it is on a polymer substrate without requiring a high temperature heat treatment. have.

1 is a transmission electron micrograph of a transparent electrode according to the invention prepared according to the method described in Example 1. FIG.

2A and 2B are graphs showing bending test photographs and test results for the transparent electrode 2a according to Example 1 and the conventional conventional ITO electrode 2b.

3A and 3B are graphs showing the results of measuring specific resistance and sheet resistance, respectively, for the five samples (3a) prepared in Example 1 and the five samples (3b) prepared in Example 2, respectively.

4A and 4B are graphs showing the results of measuring the transmittances of the five samples 4a prepared in Example 1 and the five samples 4b prepared in Example 2, respectively.

5A and 5B are graphs showing the results of measuring the performance indices of the five samples (5a) prepared in Example 1 and the five samples (5b) prepared in Example 2, respectively.

6 is a graph depicting the surface state RMS roughness of five samples prepared according to Example 1. FIG.

Hereinafter, the present invention will be described in more detail.

Much research has been done to date on transparent electrodes of an oxide / metal / oxide multilayer structure known to exhibit the closest properties to ITO. In particular, the transparent electrode of the AZO / Ag / AZO multilayer structure has various advantages such as excellent light transmittance, low sheet resistance, and no high temperature heat treatment during the manufacturing process.

The transparent electrode of the AZO / Ag / AZO multilayer structure is easy to large area, the surface resistance value is reduced to a minimum for the large area, and at the same time, the necessity of preventing the light transmittance is urgently needed. However, one of the well-known disadvantages of the AZO / Ag / AZO multilayer structure transparent electrode is that the sheet resistance value is lower than that of ITO, but the light transmittance is lowered due to the Ag layer interposed between the AZO layer and the AZO layer. Therefore, the thicker the Ag layer is, the lower the sheet resistance value is, but at the same time, the problem that the light transmittance is also one of the important problems to be overcome in the prior art.

Therefore, in the present invention, as a result of repeated studies to solve the above-described problems, when the thickness of the AZO layer and Ag layer is adjusted to within a predetermined range, and excellent when the thickness ratio of the AZO layer and Ag layer is adjusted to within a predetermined range The present invention has been accomplished by recognizing that sheet resistance and light transmitting properties can be achieved together.

Therefore, in the present invention,

Ag metal layer; And

A flexible transparent electrode comprising a ZnO layer doped with Al stacked on top and bottom surfaces of the Ag metal layer, respectively.

The Ag metal layer has a thickness of 15 nm to 23 nm,

The Al doped ZnO layer provides a flexible transparent electrode, characterized in that the thickness of 15 nm to 60 nm.

In the present invention, when the thickness of the Ag metal layer is 15 nm to 23 nm and the thickness of the AZO layer is 15 nm to 60 nm in the AZO / Ag / AZO multilayer structure, excellent sheet resistance characteristics and light transmission characteristics can be simultaneously achieved. In particular, as can be seen from the data of the following examples, it has been found that optimum characteristics can be achieved when the Ag metal layer is 19 nm thick and the AZO layer is 36 nm thick. That is, in order to simultaneously meet the physical flexibility, electrical characteristics, and optical characteristics required for the flexible transparent electrode, the thickness ratio of the Ag metal layer and the thickness of the AZO layer should also be present in a predetermined range, which is 1: 1 to 1: 4 ratio. It is preferably present in the range of, more preferably about 1: 2.

When satisfying the above-described thickness range and thickness ratio, the flexible transparent electrode according to the present invention has a light transmittance of 80% or more in the visible light wavelength band, and 5 Ω / sq. It has a sheet resistance value of less than 10 and a figure of merit of 10 or more.

The AZO / Ag / AZO multilayer structure according to the present invention can be fabricated as a flexible transparent electrode by laminating on a flexible substrate selected from the group consisting of polyethersulfone, polyethylene terephthalate, polycarbonate, polyimide, polyethylene naphthalate and glass materials. have.

On the other hand, the present invention,

a) forming an Al doped ZnO layer on a substrate with a thickness of 15 nm to 60 nm;

b) forming an Ag metal layer having a thickness of 15 nm to 23 nm on the Al-doped ZnO layer; And

c) forming a ZnO layer Al-doped Al again on the Ag metal layer to a thickness of 15 nm to 60 nm.

In the method according to the invention, the thickness of the Ag metal layer and the AZO layer and also the thickness ratio between the two layers are as described above.

In the method according to the present invention, the deposition of the Ag metal layer and the AZO layer may be performed using conventional flexible transparent electrode manufacturing methods such as, but not limited to, sputtering, electron beam deposition and continuous evaporation deposition. It is compatible with existing ITO processes, which is one of the most important advantages in practical industrial applications. In addition, the steps a) to c) may be performed by a batch type process.

The flexible transparent electrode manufactured according to the present invention can be usefully used for the production of solar cells, light emitting diodes, and the like which require excellent light transmittance, electrical conductivity and flexibility. In particular, the flexible transparent electrode according to the present invention can be manufactured as a flat and stable surface having a large area even without high temperature heat treatment, which has a great effect on the active layer of the organic material formed on the transparent electrode, thereby increasing the efficiency of a solar cell or a light emitting diode. It will be possible to improve.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are only intended to help the understanding of the present invention and do not limit the scope of the present invention.

Example 1 Preparation of Transparent Electrode with Different Ag Layer Thickness

The PET substrate was washed, and the AZO thin film was deposited to a thickness of 36 nm using the rf sputtering method at room temperature on the substrate. During deposition, the AZO target had a diameter of 2 inches and a sintered ZnO target doped with 2 wt% Al was used.

The rf power applied to the target was 90 W, the working vacuum was maintained at 10 mTorr, the distance between the target and the substrate was about 10 cm, and 30 sccm Ar gas was used as the sputtering gas.

Subsequently, using an Ag target on the AZO thin film, an Ag layer was deposited to a thickness of 19 nm under conditions of rf output 30 W, deposition pressure 10 mTorr, and Ar gas flow rate of 13 sccm. A 36 nm thick AZO thin film was deposited on the Ag layer.

1 shows a transmission electron micrograph of a transparent electrode prepared according to the above method.

Meanwhile, the transparent electrode was prepared by the same method as the above method, but four more samples having different thicknesses of Ag layers of 15, 17, 21, and 23 nm were prepared.

Example 2 Preparation of Transparent Electrode with Different AZO Layer Thickness

A transparent electrode was prepared in the same manner as in Example 1, but a transparent electrode in which the thicknesses of the AZO layers were laminated at 9, 18, 27, 36, and 45 nm, respectively.

Evaluation Example 1. Bend Test

The bending test was carried out for 1000 cycles on the transparent electrode manufactured according to Example 1 and the conventional conventional ITO electrode (thickness 100 nm), and the resistance change rate (ΔR / R ₀ : ΔR-resistance change value, R with increasing cycle) ₀ -initial resistance value) was measured. 2A (Example 1) and 2B (formerly conventional ITO electrodes) show graphically the bending test photographs and the results. The bending test was performed by fixing one side of the sample to the fixing device and narrowing the distance of the other side, and this process was performed by repeating 1000 times. 2A and 2B, the resistance change rate increased when 1000 cycles were performed in the conventional ITO electrode, but the resistance change rate remained almost constant even when the number of cycles was increased in the transparent electrode according to the first embodiment.

Evaluation Example 2. Sheet Resistance Measurement

For the five samples prepared in Example 1 and the five samples prepared in Example 2, specific resistance and sheet resistance were measured using a four-point sheet resistance measuring instrument, respectively, and the results are shown in FIGS. 3A (Example 1) and Shown in 3b (Example 2).

Referring to the drawings, the resistivity and sheet resistance of the samples decrease as the thickness of the Ag layer increases, and the resistivity increases as the thickness of the AZO layer increases, but in the case of sheet resistance, the AZO layer thickness tends to be almost constant. It can be seen that.

Evaluation Example 3 Measurement of Transmittance

For the five samples prepared in Example 1 and the five samples prepared in Example 2, the transmittance was measured at 200 to 100 nm, respectively, based on the polymer substrate, and the results are shown in FIGS. 4A (Example 1) and 4b (Example 2).

Referring to the drawings, it can be seen that the transmittance of the samples tends to increase as the thickness of the Ag and AZO layers decreases in the visible region.

Evaluation Example 4. Calculation of figure of merit

As can be seen from the evaluation examples 2 and 3, it can be seen that in the case of the transparent electrode, the electrical conductivity and the light transmittance are in a trade-off relationship with each other according to the thickness of the thin film. Therefore, in order to compare the characteristics of each transparent electrode, By introducing a performance index defined by (Journal of Applied Physics, Volume 47, Issue 9, pp. 4086-4089 (1976)), the corresponding performance index (Φ _TC ) is defined as:

<Equation 1>

Φ _TC = T ¹⁰ / R _sh

Where T is the transmittance of the sample and R _sh is the sheet resistance value.

Therefore, the performance index was calculated for each of the five samples prepared in Example 1 and the five samples prepared in Example 2, and the results are shown in FIGS. 5A (Example 1) and 5B (Example 2). .

Referring to the drawings, it can be seen that the samples according to Examples 1 and 2 have a significantly superior figure of merit compared to conventional ITO, in particular, the thickness of the Ag layer is 19 nm, It can be seen that the performance index of the sample having a thickness of 36 nm is the highest.

On the other hand, Figure 6 graphically shows the surface state RMS roughness of the five samples prepared according to Example 1. Referring to FIG. 6, when the thickness of the AZO layer is 36 nm, the AZO layer has the highest RMS roughness value, and thus, has the most even surface, and thus it can be seen that excellent characteristics can be exhibited even after various organic materials are stacked thereon. have.

Claims (14)

1. Ag metal layer; And

   A flexible transparent electrode comprising a ZnO layer doped with Al stacked on top and bottom surfaces of the Ag metal layer, respectively.

   The Ag metal layer has a thickness of 15 nm to 23 nm,

   The thickness of the Al-doped ZnO layer is a flexible transparent electrode, characterized in that 15 nm to 60 nm.
2. The method of claim 1,

   The Ag metal layer has a thickness of 19 nm, and the thickness of the Al-doped ZnO layer deposited on the top and bottom surfaces of the Ag metal layer, respectively, is 36 nm.
3. The method of claim 1,

   The ratio of the thickness of the Ag metal layer and the thickness of the Al-doped ZnO layer is 1: 1 to 1: 4, characterized in that the flexible transparent electrode.
4. The method of claim 3,

   The ratio of the thickness of the Ag metal layer and the thickness of the Al-doped ZnO layer is 1: 2, characterized in that the flexible transparent electrode.
5. The method of claim 1,

   The flexible transparent electrode has a light transmittance of 80% or more in the visible light wavelength band, 5 Ω / sq. A flexible transparent electrode having the following sheet resistance values and a performance index of 10 or more.
6. The method of claim 1,

   The Ag metal layer and the Al-doped ZnO layer are stacked on a flexible substrate selected from the group consisting of polyether sulfone, polyethylene terephthalate, polycarbonate, polyimide, polyethylene naphthalate and glass material .
7. a) forming an Al doped ZnO layer on a substrate with a thickness of 15 nm to 60 nm;

   b) forming an Ag metal layer having a thickness of 15 nm to 23 nm on the Al-doped ZnO layer; And

   c) forming an Al-doped ZnO layer on the Ag metal layer to a thickness of 15 nm to 60 nm.
8. The method of claim 7, wherein

   The thickness of the Ag metal layer is 19 nm, the thickness of the Al-doped ZnO layer laminated on the upper and lower surfaces of the Ag metal layer, respectively, 36 nm manufacturing method of a flexible transparent electrode.
9. The method of claim 7, wherein

   The ratio of the thickness of the Ag metal layer and the thickness of the Al-doped ZnO layer is 1: 1 to 1: 4 manufacturing method of a flexible transparent electrode.
10. 10. The method of claim 9, wherein the ratio of the thickness of the Ag metal layer and the thickness of the Al-doped ZnO layer is 1: 2.
11. The method of claim 7, wherein

    The steps a) to c) are performed by any one process selected from the group consisting of a sputtering method, an electron beam deposition method and a continuous evaporation deposition method.
12. The method of claim 7, wherein

    Step a) to c) is a method of manufacturing a flexible transparent electrode, characterized in that carried out by a batch process.
13. A solar cell comprising the flexible transparent electrode according to any one of claims 1 to 6.
14. A light emitting diode comprising the flexible transparent electrode according to any one of claims 1 to 6.

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