KR100622229B1 - Luminescence display devices using the fullerene based carbon compounds and method for preparing the same - Google Patents

Abstract

The present invention relates to a light emitting display device using a fullerene-based carbon compound and a manufacturing method thereof. A light emitting display device according to the present invention includes at least two organic material layers between a pair of electrodes, the one organic material layer is a light emitting layer, and the other organic material layer is a hole transport layer doped with a fullerene-based carbon compound in a hole transport material. . In the light emitting display device according to the present invention, the hole transport layer may be improved by doping the fullerene-based carbon compound to improve current injection characteristics, and the life of the light emitting display device may be extended by preventing the inflow of electrons into the hole transport layer.

Fullerene, hole transport layer, luminescence

Description

Luminescence display devices using the fullerene based carbon compounds and method for preparing the same}

1 illustrates a structure of a light emitting display device according to an exemplary embodiment of the present invention.

2 is a flowchart illustrating a method of manufacturing a light emitting display device according to an embodiment of the present invention.

3 is a view showing the structure of a fullerene (C60) according to the present invention.

<Description of the symbols for the main parts of the drawings>

10 .. substrate 20 .. anode electrode

30 .. hole injection layer 40 .. hole transport layer

50 .. Light emitting layer 60 .. Electron transport layer

70 .. electron injection layer 80 .. cathode electrode

The present invention relates to a light emitting display device and a manufacturing method thereof. More particularly, the present invention relates to a light emitting display device and a method of manufacturing the same, which improve current injection characteristics by using a hole transport layer doped with a fullerene-based carbon compound, and prevent the inflow of electrons into the hole transport layer, thereby minimizing the reduction in life.

Recently, an organic light emitting display device has attracted attention as a next generation display device due to advantages such as thin, wide viewing angle, light weight, small size, fast response speed, and power consumption, compared to a cathode ray tube (CRT) or a liquid crystal device (LCD). In particular, since the organic light emitting display device has a simple structure of an anode, an organic material layer, and a cathode, it can be easily manufactured through a simple manufacturing process. The organic material layer may be composed of several layers depending on its function, and generally includes a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer.

In the OLED, holes are injected from the anode, which is a transparent electrode, and holes are injected to the light emitting layer through the hole injection layer and the hole transport layer, and electrons are injected to the light emitting layer through the electron injection layer and the electron transport layer. Transmitted electrons and holes are combined to emit light in the light emitting layer

In general, an organic light emitting display device is manufactured by depositing or spin coating an organic material layer on an anode ITO in the order of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer, and depositing or sputtering a metal cathode thereon. Is done.

As the hole transport layer of the organic material layer, a polymer series and a low molecule series are generally used. As polymers, polyaniline, PEDOT using poly (3,4) -ethylenedioxythiophene and polystyrenesulfonate, polymers of aromatic amines, etc. are widely used. Is being used.

The characteristics required for the hole transport layer are excellent hole transport properties, and the anode and HOMO energy levels are similar to facilitate hole injection, to prevent electrons from moving, and to be stable to temperature changes. It is required to have

In particular, in order to improve the lifetime, which is the biggest disadvantage of the organic light emitting display, it is required to prevent the diffusion of oxygen, ionic materials or low molecular materials from or through the hole transport layer. For this purpose, a thin film having a high structure with a high glass transition temperature should be formed to minimize the lifespan degradation caused by the hole transport layer.

Various methods have been studied to improve the lifespan of the organic light emitting display device by improving the hole transport layer. For example, US Pat. No. 6,392,339 discloses a mixed region composed of a mixture of a hole transporting material and an electron transporting material between the hole transporting layer and the electron transporting layer, wherein any one of the hole transporting material and the electron transporting material becomes a light emitter. It is. Further, U. S. Patent No. 6,392, 339 also includes a mixed region composed of a mixture of a hole transporting material and an electron transporting material and a dopant material between the hole transporting layer and the electron transporting layer, wherein any one of the hole transporting material and the electron transporting material is a light emitter. It is disclosed that becomes. All of the above US patents extend the efficiency and lifespan of the light emitting display device by forming a mixed region composed of a mixture of a hole transporting material and an electron transporting material. U. S. Patent No. 5,773, 929 discloses a method of double doping a hole transport layer and an electron transport layer with fluorescent dye molecules, through which the luminous efficiency and luminance are improved.

However, there is still a continuous demand in this field to improve the efficiency and lifespan of the light emitting display device by improving each layer constituting the light emitting display device by optimizing the characteristics required for each layer. Is in progress.

Accordingly, the present inventors have studied the improvement method for minimizing the efficiency and lifespan of the light emitting display device, and in order to receive the electrons injected from the light emitting layer and prevent the hole transport layer from deteriorating its characteristics by electrons, the hole transport layer may act as an electron acceptor. In the case of forming together with a material capable of transporting a hole and a material for hole transport, the present invention has been found to prevent degradation of properties caused by electrons, and to minimize luminous efficiency and lifespan degradation.

Accordingly, an object of the present invention is to provide a light emitting display device which minimizes the lifetime degradation by using a hole transport layer containing a fullerene-based carbon compound.

Another object of the present invention is to provide a method of manufacturing a light emitting display device in which a hole transport layer is formed by doping with a fullerene-based carbon compound to minimize lifetime degradation.

In order to achieve the first technical problem, the present invention provides a light emitting display device including at least two organic material layers between a pair of electrodes, wherein one organic material layer is a light emitting layer, and another organic material layer is formed of a material for hole transport. Provided is a hole transport layer doped with a fullerene-based carbon compound, wherein the LUMO of the hole-transporting material is lower than that of the fullerene-based carbon compound.

In the light emitting display device according to the present invention, the doping concentration of the fullerene-based carbon compound is preferably in the range of 0.1 to 1% by weight.

In addition, the hole transport material is N, N'-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine (NPD), N, N, N ', N'-tetrabiphenylbenzidine , Bis (4-dimethylamino-2-methyl phenyl) phenylmethane, 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane, and 1,1, -bis (4-di-p-tolyl At least one selected from the group consisting of aminophenyl) -4-phenyl cyclohexane is preferable, and as the fullerene-based carbon compound, at least one selected from the group consisting of C60, C70, and C84 is preferable.

In the light emitting display device according to the present invention, the hole transport layer preferably has a thickness in a range of 5 to 100 nm.

In order to achieve the second technical problem, the present invention comprises the steps of forming a first electrode on the substrate; Forming a hole transport layer on the first electrode; Forming a light emitting layer on the hole transport layer; And forming a second electrode on the light emitting layer, wherein the hole transport layer is formed by doping a hole transport material with a fullerene-based carbon compound, and the LUMO of the hole transport material is a fullerene-based carbon compound. Provided is a method of manufacturing a light emitting display device that is lower than LUMO.

In the method of manufacturing a light emitting display device according to the present invention, the doping concentration of the fullerene-based carbon compound is preferably 0.1% by weight to 1% by weight.

In addition, the hole transport material is N, N'-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine (NPD), N, N, N ', N'-tetrabiphenylbenzidine , Bis (4-dimethylamino-2-methyl phenyl) phenyl methane, 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane, and 1,1, -bis (4-di-p-tolyl At least one selected from the group consisting of aminophenyl) -4-phenyl cyclohexane is preferable, and as the fullerene-based carbon compound, at least one selected from the group consisting of C60, C70, and C84 is preferable.

On the other hand, the hole transport layer is preferably formed to a thickness of 5 to 100nm.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

The light emitting display device according to the present invention is based on a stacked structure of a first electrode / organic layer / second electrode, and the organic layer includes a light emitting layer and a hole transport layer doped with a fullerene-based carbon compound in a hole transport material. It features.

In addition to the light emitting layer and the hole transport layer, a hole injection layer or an electron injection layer / electron transport layer may be appropriately employed as the organic material layer of the light emitting display device according to the present invention. For example, the first electrode (anode electrode) / hole It may consist of an injection layer / hole transport layer / light emitting layer / second electrode (cathode electrode) or an anode electrode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode electrode. Various structures are possible.

1 illustrates a structure of a light emitting display device according to an embodiment of the present invention.

Referring to FIG. 1, a light emitting display device according to the present invention has a structure including a light emitting layer 50 between an anode electrode 20 and a cathode electrode 80, and between the anode electrode 20 and the light emitting layer 50. The hole injection layer 30 and the hole transport layer 40 are included, and the electron transport layer 50 and the electron injection layer 70 are included between the light emitting layer 50 and the cathode electrode 80.

2 is a flowchart illustrating a method of manufacturing a light emitting display device according to an embodiment of the present invention.

Referring to FIG. 2, a light emitting display device according to the present invention is manufactured through the following process. First, the anode electrode 20 is formed by coating an anode electrode material on the substrate 10 (S11). Here, the substrate 10 may be a substrate generally used in this field, and a glass substrate or a transparent plastic substrate excellent in transparency, surface smoothness, ease of handling, and waterproofness is particularly preferable. In addition, as an anode electrode material formed on the substrate, indium tin oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), and the like, which are transparent and have excellent conductivity, may be used.

A hole injection layer 30 is formed on the anode electrode 20 (S12). The hole injection layer forming step S12 is an optional process that may be omitted as necessary. The hole injection layer may be formed through a conventional method such as vacuum deposition or spin coating, and is not particularly limited as a material for the hole injection layer, for example, CuPc (copper phthalocyanine) or IDE 406 (Idemitsu Kosan) Can be used.

Subsequently, the hole transport layer 40 is formed on the hole injection layer 30 (S13). In this case, the hole transport layer 40 may be formed on the hole injection layer 30, but may also be formed directly on the anode electrode. The hole transport layer 40 may be formed by a solution process such as vacuum deposition, spin coating, inkjet, or the like, and may also be formed through a laser transfer (LITI) process.

The hole transport layer 40 is formed by doping a fullerene-based carbon compound in the hole transport material. In this case, the LUMO of the hole transporting material must be lower than that of the fullerene-based carbon compound.

As the hole transporting material doped with a fullerene-based carbon compound to satisfy this, an aromatic tertiary amine derivative including benzene or naphthalene units may be used. Specifically, N, N'-di (naphthalen-1-yl)- N, N'-diphenyl-benzidine (NPD), N, N, N ', N'-tetrabiphenylbenzidine, bis (4-dimethylamino-2-methyl phenyl) phenylmethane, 1,1-bis ( 4-di-p-tolylaminophenyl) cyclohexane, 1,1, -bis (4-di-p-tolylaminophenyl) -4-phenyl cyclohexane, and the like can be used, but preferably N, N '-Di (naphthalen-1-yl) -N, N'-diphenyl-benzidine (NPD) or N, N, N', N'-tetrabiphenylbenzidine is used. The LUMO of the hole transporting material is lower than that of the fullerene-based carbon compound. In addition, when the LUMO of the hole transporting material is lower than that of the fullerene-based carbon compound, the electron inflow from the light emitting layer to the hole transporting layer is received by the fullerene-based carbon compound, which is the electron acceptor, and the hole transporting layer is deteriorated by electrons. The phenomenon can be suppressed.

The fullerene-based carbon compound may be selected, for example, from the group consisting of C60, C70, and C84.

The content of the doped fullerene-based carbon compound is preferably 0.1% by weight to 1% by weight based on the total weight of the hole transporting layer, so that the life increase effect is not observed when it is out of this range, that is, less than 0.1% by weight, and 1% by weight. When it exceeds%, efficiency falls and it is unpreferable.

In addition, the thickness of the hole transport layer 40 is preferably formed within the range of 5 to 100nm. Although the thickness of the hole transport layer 40 may vary depending on the type of each layer, the type and use of the hole transport material, etc. of the entire light emitting display device, 5 to 100 nm is preferable in consideration of the doping of the fullerene-based carbon compound. Do.

Subsequently, the light emitting layer 50 is formed on the hole transport layer 40 through a conventional method, for example, vacuum deposition, spin coating, or the like (S14). The light emitting layer material is not particularly limited and may be formed by depositing together using a conventional host and a dopant.

In addition, the electron transport layer 60 is formed on the light emitting layer 50 (S15). The electron transport layer shaping step S15 is also an optional process. A vacuum deposition method or a spin coating method may be used to form the electron transport layer, and the material for the electron transport layer is not particularly limited, but may be an aluminum complex (for example, Alq 3 (tris (8-quinolinolato) -aluminum)). Can be used.

The electron injection layer 70 may be selectively formed on the electron transport layer 60 using a method such as vacuum deposition or spin coating (S16). In this case, the material for the electron injection layer 70 is not particularly limited, but materials such as LiF, NaCl, and CsF may be used.

Subsequently, the cathode electrode 80 is formed on the electron injection layer 70 through vacuum deposition (S17) to complete the light emitting display device. The metal for the cathode is calcium (Ca), magnesium (Mg), lithium fluoride-aluminum (LiF / Al), barium (Ba), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag) Etc. are used. After the cathode electrode 80 is deposited, a light emitting display device is manufactured through an encapsulation process.

Accordingly, the light emitting display device according to the present invention has a stacked structure as shown in FIG. 1, and if necessary, one or two intermediate layers, for example, a hole suppression layer, may be further formed. The electron transport layer or the electron injection layer may be omitted. In addition, the thickness of each layer of the light emitting display device may be determined as needed within the range generally used in the art.

Hereinafter, a preferred embodiment of the present invention. However, the following examples are only presented to aid the understanding of the present invention, and the present invention is not limited to the following examples.

Example 1

4,4 ', 4 "-tris (3-methylphenylphenylamino) triphenylamine (MTDATA) was vacuum deposited on the surface of the substrate on which the ITO film was formed as an anode electrode to form a hole injection layer at 30 nm. Doping '-di (naphthalen-1-yl) -N, N'-diphenyl benzidine (NPD) with 0.1 wt% of bulkysterster fullerene (C60) to deposit a hole transport layer on the hole injection layer with a thickness of 15 nm After forming the hole transporting layer, 8-trishydroxyquinoline aluminum (Alq3) was vacuum deposited to form a light emitting layer and an electron transporting layer to a thickness of 25 nm, and LiF and Al were vacuum deposited to a thickness of 300 nm on the electron transporting layer. An LiF / Al electrode was formed and then encapsulated using a metal can and barium oxide to manufacture an organic light emitting display device.

Example 2

An organic light emitting display device was manufactured in the same manner as in Example 1, except that the doping concentration of the bulkimster fullerene (C60) was 0.5 wt% when forming the hole transport layer.

Example 3

An organic light emitting display device was manufactured in the same manner as in Example 1, except that the doping concentration of the bulkimster fullerene (C60) was 1 wt% when forming the hole transport layer.

Comparative Example 1

An organic light emitting display device was manufactured in the same manner as in Example 1, except that bulkimster fullerene (C60) was not used to form the hole transport layer.

Comparative Example 2

An organic light emitting display device was manufactured in the same manner as in Example 1, except that doping of bulkyster fullerene (C60) with 2 wt% was used to form the hole transport layer.

Test Example 1

In the organic light emitting display devices manufactured in Examples 1 to 4 and Comparative Example 1, luminance, efficiency, and lifetime were measured, and the results are shown in Table 1 below.

Luminance (8 V) Efficiency (cd / A) Life (hours) * Example 1 4400 2.3 120 Example 2 4300 2.4 250 Example 3 4500 2.2 600 Comparative Example 1 4300 2.3 100 Comparative Example 2 3800 1.5 500

Lifespan: When the display device is driven at 900 cd / m 2, it exhibits a half-life life of up to 50% of luminance.

As shown in Table 1 above, when the bulk transporter bulk doping (C60) in the hole transport layer between 0.1 to 1% by weight (Examples 1 to 3) compared with Comparative Example 1 without doping the fullerene (C60) Although the brightness and efficiency were similar, it can be seen that the addition of fullerene (C60) improves the lifetime by up to 6 times or more. On the other hand, in the case of Comparative Example 2, the excessive use of fullerene no longer increased the life time, but rather indicates that the efficiency is reduced. This indicates that the preferred amount of fullerene is in the range of 0.1 to 1% by weight.

The light emitting display device according to the present invention improves the current injection characteristics of the hole transport layer by improving the hole transport layer by using a fulleron-based carbon compound, and also prevents electron injection into the hole transport layer to reduce the brightness and efficiency of the light emitting display device. Lifespan can be significantly increased without

Claims (11)

A light emitting display device comprising at least two organic material layers between a pair of electrodes, Wherein the one organic layer is a light emitting layer, the other organic layer is a hole transport layer doped with a fullerene-based carbon compound in a hole transporting material, and the LUMO of the hole transporting material is lower than that of the fullerene-based carbon compound. The light emitting display device of claim 1, wherein a doping concentration of the fullerene-based carbon compound is in a range of about 0.1 wt% to about 1 wt%. The method of claim 1, wherein the hole transport material N, N'-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine (NPD), N, N, N ', N'-tetrabiphenylbenzidine, Bis (4-dimethylamino-2-methyl phenyl) phenylmethane, 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane, and A light emitting display device characterized in that at least one selected from the group consisting of 1,1, -bis (4-di-p-tolylaminophenyl) -4-phenyl cyclohexane. The method of claim 3, wherein the hole-transporting material is N, N'-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine (NPD) or N, N, N ', N'- A light emitting display device comprising tetrabiphenylbenzidine. The light emitting display device of claim 1, wherein the fullerene-based carbon compound is selected from at least one selected from the group consisting of C60, C70 and C84. The light emitting display device of claim 1, wherein the hole transport layer has a thickness of about 5 nm to about 100 nm. Forming a first electrode on the substrate; Forming a hole transport layer on the first electrode; Forming a light emitting layer on the hole transport layer; And Forming a second electrode on the light emitting layer; Wherein the hole transport layer is formed by doping a hole transport material with a fullerene-based carbon compound, wherein the LUMO of the hole transport material is lower than that of the fullerene-based carbon compound. The method of claim 7, wherein a doping concentration of the fullerene-based carbon compound is 0.1 wt% to 1 wt%. The method of claim 7, wherein the hole transport material N, N'-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine (NPD), N, N, N ', N'-tetrabiphenylbenzidine, Bis (4-dimethylamino-2-methyl phenyl) phenylmethane, 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane, and A method for manufacturing a light emitting display device, characterized in that at least one member is selected from the group consisting of 1,1, -bis (4-di-p-tolylaminophenyl) -4-phenyl cyclohexane. The method of claim 7, wherein the fullerene-based carbon compound is selected from the group consisting of C 60, C 70, and C 84. The method of claim 7, wherein the hole transport layer has a thickness of about 5 nm to about 100 nm.

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