WO2011105660A1

WO2011105660A1 - Low-priced low-temperature transparent electrode

Info

Publication number: WO2011105660A1
Application number: PCT/KR2010/002824
Authority: WO
Inventors: 김대일; 최종인; 채주현
Original assignee: 울산대학교 산학협력단
Priority date: 2010-02-26
Filing date: 2010-05-04
Publication date: 2011-09-01

Abstract

The present invention relates to a low-priced low-temperature transparent electrode, and more particularly, to a low-priced low-temperature transparent electrode comprising: a metal layer; and a titanium oxynitride (TiON) layer deposited on one surface or both surfaces of the metal layer. The low-priced low-temperature transparent electrode according to the present invention uses a titanium oxynitride (TiON) thin film, which is a transition metal priced lower than ITO, and thus cuts down the prime cost, thereby reducing the production cost. In addition, the low-priced low-temperature transparent electrode according to the present invention can be implemented without heat treatment because an oxygen plasma pretreatment process which resulted from the usage of the conventional ITO can be omitted, and a superior work function, a higher electrical conductivity and a higher visible light transmittance than the conventional ITO can be implemented.

Description

Low Temperature Low Cost Transparent Electrode

The present invention relates to a low temperature low cost transparent electrode, and more particularly, to a low temperature low cost transparent electrode having improved materials for transparent electrodes used in displays and solar cells such as LCDs, PDPs, and OLEDs.

In general, OLEDs are used to arrange one or more organic layers 30 between the metal electrode 10 of the cathode and the transparent electrode 20 of the anode, as shown in FIG. 1, wherein the organic layer 30 is usually vacuum deposited ( It is formed through evaporation, spin-coating, chemical self-assembly, and consists of an electron injection layer 31, an organic light emitting layer 32, and an ion injection layer 33.

Until now, ITO (Sn-added In ₂ O ₃ ) is most commonly used as a material of the transparent electrode 20, but has a Fermi level of about 4.5 eV without any treatment, but a Fermi level (EF). Highest Occupied Molecular Orbital (HOMO) level of hole transfer layer (HTL) or emission material layer (EML) material is generally 5.0 eV or less This creates a larger energy barrier between the transparent electrode 20 of the anode and the organic layer 30, and furthermore, the ITO (In ₂ O ₃ ) has a hydrophilic surface with a contact angle of 0 to 30 °, while many HTL or EML The materials exhibit hydrophobicity near the contact angle of 90 °.

This massive surface energy mismatch at the ITO / HTL or ITO / EML interface creates intrinsic microstructual instability and degrades device stability, thus allowing holes to cross the energy barrier or tunnel in the ITO / HTL or ITO / EML interface. In order to improve the contact and improve the contact, the transparent electrode 20 of the anode needs to be improved.

Due to the problem of energy barrier and interfacial contact, oxygen plasma pretreatment is performed prior to depositing HTL or EML material on the ITO substrate, thereby increasing the work function of the ITO to 4.8 eV.

However, despite the efforts to improve the ITO anode as described above, ITO is economically expensive and has a disadvantage in that the electrical resistance is somewhat high to be applied as the transparent electrode material of the improved flexible display color filter. In the production process, there are many limitations to conducting oxygen plasma treatment of a certain strength on a wide electrode surface.

Accordingly, an object of the present invention is to provide a low-temperature low-cost transparent electrode that can implement a better work function, electrical conductivity and visible light transmittance than ITO by depositing a transition metal titanium nitrate thin film on both sides of the metal layer.

In order to achieve the object of the present invention as described above, the present invention is a metal layer; And it provides a low-temperature low-cost transparent electrode including a titanium nitride (TiON) layer deposited on both sides of the metal layer.

In one embodiment of the present invention, the metal layer and titanium nitride layer is any one selected from the group consisting of vacuum deposition, electron beam deposition, sputtering, reactive magnetron sputtering, ion plating, pulsed laser deposition and chemical vapor deposition method Can be deposited.

In one embodiment of the present invention, the metal layer may be any one selected from the group consisting of silver (Ag), gold (Au) and copper (Cu).

In one embodiment of the present invention, the thickness of the metal layer may be 40 ~ 60Å.

In one embodiment of the present invention, the thickness of the titanium nitride layer deposited on one surface of the metal layer is 400 ~ 500Å, the thickness of the titanium nitride layer deposited on the other surface may be 450 ~ 550Å.

In one embodiment of the present invention, the thickness of the titanium nitride layer deposited on one surface of the metal layer is 40 ~ 60Å, the thickness of the titanium nitride layer deposited on the other surface may be 850 ~ 950Å.

In one embodiment of the present invention, the visible light transmittance of the transparent electrode may be 70 ~ 80%.

In one embodiment of the present invention, the work function of the transparent electrode may be 4.5 ~ 5.0 eV.

In addition, the present invention comprises the steps of forming a first titanium nitride (TiON) thin film; Forming any one metal layer selected from the group consisting of silver (Ag), gold (Au), and copper (Cu) on the first titanium nitride film; And it provides a low-temperature low-cost transparent electrode comprising the step of depositing a second titanium nitride (TiON) thin film on the metal layer.

The low-temperature low-cost transparent electrode according to the present invention can reduce the manufacturing cost by using a transition metal titanium nitrate (TiON) thin film cheaper than ITO to reduce the manufacturing cost, it can omit the oxygen plasma pretreatment process using the conventional ITO It is possible to realize a low-temperature low-cost transparent electrode without heat treatment, it is possible to implement a work function, electrical conductivity and visible light transmittance superior to conventional ITO.

1 is a view showing a display structure used in a commonly used OLED.

2 is a view showing the structure of a low temperature low-cost transparent electrode according to the present invention.

3 is a reference diagram showing the structure of a deposition apparatus used in the present invention.

4 is a graph showing the transmittances of thin films on which TiON having a thickness of 450 kPa and 500 kPa, respectively, are deposited on both surfaces of the metal layer (gold, silver, copper) according to the present invention.

5 is a graph showing a change in transmittance of a thin film (total thickness 1000Å) deposited by changing a thickness of gold (Au) according to the present invention.

6 is a graph showing a work function of a thin film on which TiON having a thickness of 50 mW and 900 mW is deposited on both surfaces of gold (Au) having a thickness of 50 mV according to the present invention.

The present invention relates to a low temperature low-cost transparent electrode, a metal layer; And a low temperature low cost transparent electrode including a titanium nitride (TiON) layer deposited on one or both surfaces of the metal layer.

The inventors of the present invention developed a low-temperature low-cost transparent electrode to replace the expensive transparent electrode, which is similar to ITO widely used as a transparent electrode by depositing a titanium nitride (TiON) thin film on both sides of the metal. The present invention has been completed by identifying that the function and the visible light transmittance can be realized.

Hereinafter, a low temperature low cost transparent electrode according to the present invention will be described in detail with reference to the accompanying drawings.

1 illustrates a display structure of a commonly used OLED, wherein an electron injection layer 31, an organic light emitting layer 32, and an ion injection layer 33 are disposed between a metal electrode 10 of a cathode and a transparent electrode 20 of an anode. An organic material layer 30 composed of) is formed.

Figure 2 shows the structure of a low temperature low-cost transparent electrode according to an embodiment of the present invention. The transparent electrode 20 of the present invention includes a metal layer 22 and

titanium nitride layers

21 and 23, and has a structure in which a titanium nitride layer (TiON) layer is deposited on both surfaces of the metal layer 22.

In the present invention, the metal layer and the titanium nitrate layer are deposited using a general deposition method, specifically It can be deposited by any one method selected from the group consisting of vacuum deposition method, electron beam deposition method, sputtering method, reactive magnetron sputtering method, ion plating method, pulsed laser deposition method and chemical vapor deposition method.

The metal layer 22 is made of any one material selected from the group consisting of silver (Ag), gold (Au), and copper (Cu), and the metal layer has a thickness of 40 to 60 GPa, preferably 45 to 55 GPa. If the thickness of the metal layer is less than the above range, the electrical conductivity does not meet the expectations. If the thickness is above the above range, as the thickness increases, the absolute amount of free electrons increases, the electrical conductivity is improved, but the amount of light absorption increases, and thus the visible light transmittance is not good. This is not suitable as a transparent electrode.

In addition, the

titanium nitride layers

21 and 23 may be deposited on both sides of the metal layer, and are formed amorphous. In the present invention, the thickness of the titanium nitride layer deposited on both sides of the metal layer is deposited differently. If the thickness of the titanium nitride layer 21 deposited on one surface of the metal layer is 400 ~ 500Å, the thickness of the titanium nitride layer 23 deposited on the other side may be comprised of 450 ~ 550Å, and the titanium nitride deposited on one side of the metal layer When the thickness of the layer 21 is 40 to 60 mm 3, the thickness of the titanium nitride layer 23 deposited on the other surface may be configured to be 850 to 950 mm 3. In one embodiment of the present invention, the titanium nitride layer is 450 Å / metal layer (gold, silver or copper) 50 질 / titanium nitrate layer 500 Å, titanium nitrate layer 50 Å / metal layer (gold, silver or copper) 50 Å / titanium nitrate layer 900 Å. .

On the other hand, the present invention comprises the steps of forming a first titanium nitride (TiON) thin film; Forming any one metal layer selected from the group consisting of silver (Ag), gold (Au), and copper (Cu) on the first titanium nitride film; And it provides a low-temperature low-cost transparent electrode comprising the step of depositing a second titanium nitride (TiON) thin film on the metal layer.

Here, when the first titanium nitride thin film 23 is deposited to a thickness of 450 to 550 kPa, the metal layer may be deposited to a thickness of 40 to 60 kPa, and the second titanium nitride film 21 may be deposited to a thickness of 400 to 500 kPa. In addition, when the first titanium nitride thin film 23 is deposited to a thickness of 850 to 950 kPa, the metal layer may be deposited to a thickness of 40 to 60 kPa, and the second titanium nitride film 21 may be deposited to a thickness of 40 to 60 kPa.

In the present invention, the metal layer and the titanium nitride layer may be deposited using a general deposition method, and may be deposited by any one method selected from the group consisting of a vacuum deposition method, an electron beam deposition method, a sputtering method, a reactive magnetron sputtering method, and an ion plating method.

Looking at the deposition method of the titanium nitride layer / metal layer / titanium nitride layer thin film using the reactive magnetron sputtering method according to an embodiment of the present invention. First, the ultra-high vacuum state is formed by a pump, and then argon, oxygen, and nitrogen gas are injected. Next, after the plasma discharge of the TiN target surface is started, a substrate of TiN target particles is deposited by target collision of argon ions and continuous sputtering, and TiN thin films are deposited by mixing and growing nitrogen and oxygen gas and sputtered TiN thin films. .

Then, the interlayer metals such as gold (Au), silver (Ag), copper (Cu), and the like are deposited to a specific thickness by a target collision of argon ions, and a substrate of TiON target particles is deposited again on top of each other. The sputtered TiON thin film is mixed and grown to deposit a titanium nitride (TiON) thin film.

The above method is merely an embodiment of the present invention, and the method of depositing the metal layer and the titanium nitrate layer in the present invention is not limited thereto, and any vacuum deposition method may be used.

The transparent electrode according to the present invention can obtain a 70 to 80% visible light transmittance and a work function of 4.5 to 5.0 eV by depositing a titanium nitride thin film as a transition metal nitrate on both sides of the metal layer. These characteristics indicate that the electrical conductivity and visible light transmittance similar to the work function superior to the conventional ITO can be realized at a low price.

Therefore, the low-temperature low-cost transparent electrode according to the present invention can reduce the manufacturing cost by using a transition metal titanium nitrate (TION) thin film cheaper than ITO, and can implement a work function, electrical conductivity and visible light transmittance superior to conventional ITO.

Hereinafter, the present invention will be described in detail with reference to Examples and drawings. However, these examples are intended to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.

<실시예 1><Example 1>

The present inventors fabricated a transparent electrode by depositing a titanium nitride layer having a thickness of 500 ms on one side of the metal layer and a titanium nitride layer having a thickness of 450 ms on the other side using a metal layer having a thickness of 50 ms. The visible light transmittance, electrical conductivity, and work function of the thin film deposited with a thickness of 500 Å titanium nitride layer (TiON), 50 Å metal layer, and 450 Å titanium nitride layer (TiON) were measured.

<1-1> 질산화티타늄층/금속층/질산화티타늄층 박막의 증착<1-1> Deposition of Titanium Nitride Layer / Metal Layer / Titanium Nitride Layer Thin Film

The present inventors used a reactive magnetron sputtering method to deposit a titanium nitride layer (TiON) / metal layer / titanium nitride layer thin film. First, an ultrahigh vacuum state was formed by a pump, and then argon, oxygen, and nitrogen gas were injected. Next, after the plasma discharge of the TiN target surface is started, a substrate of TiN target particles is deposited by target collision of argon ions and continuous sputtering, and the TiON thin film is 500 Å thick by mixing and growing nitrogen and oxygen gas and the sputtered TiN thin film. Was deposited.

Next, gold (Au), silver (Ag), and copper (Cu) were used as interlayer metals, respectively, so as to have a thickness of 50 kPa by a target collision of argon ions. Next, a TiN target particle was deposited on the metal layer by the target impingement of argon ions and continuous sputtering, and the TiON thin film was deposited by mixing and growing nitrogen and oxygen gas and the sputtered TiN thin film by 450 Å thickness. The total thickness of the thin film composed of a titanium nitride layer (TiON) / metal layer / titanium oxide layer was 1000 kPa.

Figure 3 shows the structure of the reactive magnetron sputter deposition equipment used in one embodiment of the present invention. The deposition apparatus includes a vacuum system for forming and maintaining a vacuum, a plasma generator for generating nitrogen ions, and an RF magnetron sputter gun. The deposition system is made of stainless steel and has a cylindrical structure.

The vacuum system exhausts by using a rotary pump and a turbo-molecular pump in order to secure the initial vacuum conditions, the degree of vacuum measurement using a Pirani gauge and an ionization gauge, the mass flow is mass Mass flow controller is used to control the amount of gas.

<1-2> 가시광 투과율 및 전기전도도 측정<1-2> Visible Light Transmittance and Electrical Conductivity Measurement

First, a UV-Vis spectrophotometer was used to measure the visible light transmittance of the TiON / metal layer / TiON (hereinafter referred to as TMT) thin film deposited as described above, and the wavelength range of the UV-Vis spectrophotometer was 100 to At 1000 nm, the light absorption of molecules in this region is related to the electronic structure of the molecules, ie the absorption of ultraviolet and visible light molecules leads to the transition of electrons, especially valence electrons, in the molecule. In the present invention, the transmittance was measured only in the visible light region, and the resistance and electrical conductivity of the deposited thin film were measured using a Hall-Effect measuring apparatus.

TMT thin film was deposited by varying the type of inner metal layer to gold (Au), silver (Ag), and copper (Cu) under the deposition conditions of the bottom and upper electrode materials, and the transmittance and conductivity analysis results showed gain index. was quantified by _{(figure of Merit (φ TC)} ), wherein the gain factor is one of the key indicator for evaluating the performance of the transparent conductive oxide (TCO) film, it can be expressed as shown in equation 1 below.

Equation 1

In Equation 1, T represents visible light transmittance (550 nm in the present invention), and Rs represents sheet resistance.

The transmittance of the TMT thin film according to the present invention is shown in Table 1 and FIG. 4.

Table 1

Visible Light Transmission Characteristics of TiON / Metal Layers / TiON Thin Films

Sample (TMT, total thickness 1000Å)	Visible light transmittance (%)
TiON 500Å / Au 50Å / TiON 450Å	77%
TiON 500Å / Ag 50Å / TiON 450Å	77%
TiON 500Å / Cu 50Å / TiON 450Å	71%

As a result, as shown in Table 1 and FIG. 4, although the thin film using silver showed an even transmittance as a whole, the transmittance of gold and silver was the same when the wavelength was 550 nm, and gold was long in the long wavelength region of 550 nm or more. It was found that the transmittance of was better.

In addition, the electrical properties of the TMT thin film are shown in Table 2 below.

TABLE 2

Electrical Characteristics of TiON / Metal Layers / TiON Thin Films

Sample (TMT, total thickness 1000Å)	Resistance (R, × 10 ^-3 ㎝)
TiON 500Å / Au 50Å / TiON 450Å	30 to 36 Ω
TiON 500Å / Ag 50Å / TiON 450Å	80-100 yen
TiON 500Å / Cu 50Å / TiON 450Å	320 to 380 Ω

As a result, as shown in Table 2, the electrical resistance of titanium nitride (TiON) deposited on both surfaces of gold (Au) is 30 to 36 Ω, and the electrical resistance of titanium nitride deposited on both surfaces of silver (Ag) is 80 to 100 Ω. The electrical resistance of titanium nitride deposited on both sides of copper (Cu) was found to be 320 ~ 380Ω, and the highest electrical resistance when using copper as the metal layer was measured, and the highest when using gold. It was measured low.

<1-3> 일함수 측정<1-3> Work function measurement

The inventors measured the work function of the TMT thin film by using Ultraviolet Photoelectron Spectroscopy (UPS). UPS is a device that can detect the component of the sample non-destructively by detecting the photoelectron that protrudes by irradiating UV to the sample to be analyzed. In addition, there is a movement of the binding energy of electrons according to the surrounding environment when the photoelectron is emitted, through which information on the chemical bond form and valence band of the component can be obtained.

The UPS conditions used in this example were measured at an initial vacuum of 8.0 x 10 ^-8 Torr, a resolution of 5 eV, a scan step of 0.025 eV / step, and a sample bias of -20V.

As a result, the work function of titanium nitride deposited on both sides of the gold, titanium nitride deposited on both sides of the silver, and titanium nitride deposited on both sides of the copper was measured to be 4.6 eV to 4.8 eV.

<실시예 2><Example 2>

The present inventors select gold having the best electrical and optical properties among the three types of metal layers described in <Example 1> and use it as an internal metal layer to fabricate specimens having a thickness of 50, 100, 150, and 200 각각, respectively. After that, the transmittance and electrical properties were analyzed, and the results are shown in Tables 3 and 5, and the gain index (Figure of Merit) was calculated and shown in Table 4 below.

TABLE 3

Electrical Properties of TMT Thin Films with Inner Gold Layer Thickness

Sample (TMT, total thickness 1000Å)	Conductivity (σ, × 10 ^-3 )	Resistivity (ρ, × 10 ^-4 cm)	Concentration (N _b , × 10 ²¹ / cm 3)	Mobility (μ, × 10 ¹ / Vs)
Au 50Å	2.97	3.36	-1.20	2.73
Au 100Å	5.17	1.93	-1.03	3.13
Au 150Å	10.2	0.98	-1.71	3.72
Au 200Å	51.1	0.20	-12.1	2.63

Table 4

Figure of merit of TMT thin film (φ <sub> TC </ sub>)

Sample (TMT total thickness 1000Å, bottom TiON thickness 500Å)	율 Transmittance (total = 1, including substrate)	Figure of merit (φ _TC , 10 ^-4 Ω ^-1 )
Au 50Å	0.69	7.27
Au 100Å	0.65	6.96
Au 150Å	0.58	4.40
Au 200Å	0.49	4.07

As a result, as the thickness of Au increased, the absolute amount of free electrons increased and the amount of light absorbed increased, so that the overall transmittance steadily decreased, while the electrical conductivity steadily improved. From these results, it can be seen that when the thickness of Au is 50 μs, the TMT thin film exhibits the best permeable conductivity.

<실시예 3><Example 3>

The present inventors fabricated a transparent electrode by depositing titanium nitride having a thickness of 50 GPa on one surface of gold having a thickness of 50 GPa and titanium nitride having a thickness of 900 GPa on the other surface. In the present embodiment, the process of depositing the titanium nitride layer / metal layer / titanium nitride layer thin film was performed in the same manner as in <Production Example 1>, and only the thickness of each layer was different.

Meanwhile, a work function of a TMT thin film composed of titanium nitride 900 μs / gold 50 μs / titanium nitride 50 μs was measured using a UPS, and the results are shown in FIG. 6.

As a result, it was found that the surface work function improved from about 4.4 eV to about 4.8 eV (see FIG. 6).

In summary, the present invention used gold (Au), silver (Ag), and copper (Cu) thin films having a thickness of 50 μs as the internal metal layer in the TMT thin film, among which the gold 50 Au thin film was the most excellent. It can be seen that the characteristics of the transparent conductive thin film, the titanium nitride layer (TiON) is formed amorphous, regardless of the presence or absence of the metal layer.

In addition, as the thickness of the inner gold (Au) thin film was increased, the transmittance of the TiON / Au / TiON thin film was decreased and the electrical conductivity was increased. It was found that it was a thin film of Au.

The transparent conductive thin film according to the present invention can omit the oxygen plasma pretreatment process using the conventional ITO, so that low-temperature low-cost transparent electrodes can be realized without heat treatment, and exhibit excellent electrical conductivity and visible light transmittance, and at the same time, similar to ITO. It is excellent in that it can implement the function 4.8eV value.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

Claims

Metal layer; And

Titanium nitrate (TiON) layer deposited on both sides of the metal layer

Low temperature low cost transparent electrode comprising a.
The method of claim 1,

The metal layer and the titanium nitrate layer is a low temperature low-cost type, characterized in that the deposition by any one method selected from the group consisting of vacuum deposition, electron beam deposition, sputtering, reactive magnetron sputtering, ion plating, pulsed laser deposition and chemical vapor deposition method Transparent electrode.
The method of claim 1,

The metal layer is a low temperature low-cost transparent electrode, characterized in that any one selected from the group consisting of silver (Ag), gold (Au) and copper (Cu).
The method of claim 1,

The low-temperature low-cost transparent electrode, characterized in that the thickness of the metal layer is 40 ~ 60Å.
The method of claim 1,

Low-temperature low-temperature transparent electrode, characterized in that the thickness of the titanium nitride layer deposited on one surface of the metal layer is 400 ~ 500Å, the thickness of the titanium nitride layer deposited on the other surface is 450 ~ 550Å.
The method of claim 1,

Low-temperature low-temperature transparent electrode, characterized in that the thickness of the titanium nitride layer deposited on one surface of the metal layer is 40 ~ 60Å, the thickness of the titanium nitride layer deposited on the other surface is 850 ~ 950Å.
The method of claim 1,

Low-temperature low-cost transparent electrode, characterized in that the visible light transmittance of the transparent electrode is 70 ~ 80%.
The method of claim 1,

Low temperature low-cost transparent electrode, characterized in that the work function of the transparent electrode is 4.5 ~ 5.0 eV.
Forming a first titanium nitride (TiON) thin film;

Forming any one metal layer selected from the group consisting of silver (Ag), gold (Au), and copper (Cu) on the titanium nitride oxide thin film; And

Depositing a second titanium nitride (TiON) thin film on the metal layer

Method for producing a low temperature low-cost transparent electrode comprising a.
The method of claim 9,

The metal layer and the titanium nitrate layer is a low temperature low-cost type, characterized in that the deposition by any one method selected from the group consisting of vacuum deposition, electron beam deposition, sputtering, reactive magnetron sputtering, ion plating, pulsed laser deposition and chemical vapor deposition method Method of manufacturing a transparent electrode.