KR20050020281A - Organic electroluminescent display device - Google Patents

Abstract

PURPOSE: An organic electroluminescence display device is provided to lower a driving voltage and improve efficiency by enhancing a hole injection layer or a hole transport layer. CONSTITUTION: An organic electroluminescence display device comprises at least one or more organic light emitting layers(20) and at least one or more charge transfer layers arranged between the first electrode(50) and the second electrode(10) formed on a substrate. At least one of the charge transfer layers contains an organic compound having p-type semiconductor characteristics and a charge transfer material different from the material constituting the charge transfer layer. The charge transfer layer is a hole injection layer(40) and/or a hole transfer layer(30).

Description

Organic electroluminescent display device {ORGANIC ELECTROLUMINESCENT DISPLAY DEVICE}

[Industrial use]

The present invention relates to a high efficiency long life organic electroluminescent display device, and more particularly, to an organic electroluminescent display device having a low driving voltage, excellent efficiency and excellent life characteristics by improving an existing charge transport layer.

[Prior art]

Recently, an organic electroluminescent 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 small power consumption, compared to a cathode ray tube (CRT) or a liquid crystal device (LCD).

In particular, since the organic electroluminescent display device has a simple structure of an anode, an organic layer, and a cathode, there is an advantage that it can be easily manufactured through a simple manufacturing process. The organic layer may be composed of several layers depending on the function, and generally consists of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer.

1 is a view schematically showing a structure of a conventional organic electroluminescent display device.

Holes are injected from the anode, which is the transparent electrode 7, and the injected holes are transferred to the light emitting layer 4 through the hole injection layer 6 and the hole transport layer 5, and electrons are injected from the cathode 1 to form electrons. The light emitting layer 4 is transferred to the light emitting layer 4 through the injection layer 2 and the electron transport layer 3. The transferred electrons and holes combine to emit light in the light emitting layer.

The light emitting layer 4 has a structure in which a dopant is doped in a host, and electrons and holes are transferred to the dopant through the host to emit light.

The hole injection layer of the organic layer is a layer for facilitating hole injection from the anode to the hole transport layer or the light emitting layer, and the work function should be similar to that of the anode. As a result, the driving voltage, efficiency, and lifespan of the organic light emitting display device can be improved.

In order to improve the hole injection layer to improve driving voltage, efficiency, and life, much research has been made on the hole injection layer. US 20020158242 A1 reports an organic compound of formula 1 having p-type semiconductor properties in order to facilitate hole injection and transfer from the electrode to the light emitting layer.

R in Formula 1 is each or independently a hydrogen atom, a hydrocarbon having 1 to 12 carbon atoms, a halogen group, an alkoxy group, an arylamine group, an ester group, an amide, an aromatic hydrocarbon, a heterocyclic compound, a nitro group, or nitrile. Since the compound has a p-type semiconductor property, it has excellent hole mobility, and therefore, a device including the material has a low driving voltage. In addition, the life characteristics are superior to other hole injection layer materials.

 However, the organic compound having the p-type semiconductor characteristics has a disadvantage in that a lot of defects due to poor interface characteristics with the electrode, and there is a problem of leakage of current when applying reverse voltage, so that the application of the passive matrix device The current leakage problem must be solved.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems described above, and an object of the present invention is to improve a hole injection layer or a hole transport layer when forming an organic electroluminescent display device to provide a device structure with low driving voltage and high efficiency. To develop.

Another object of the present invention is to improve the hole injection layer or the hole transport layer to improve the stability of the organic electroluminescent display device to improve the lifetime and to reduce the current leakage of the organic electroluminescent display device.

The present invention to achieve the above object,

The present invention

At least one organic light emitting layer and at least one charge transport layer between the first electrode and the second electrode formed on the substrate, wherein at least one of the charge transport layers forms an organic compound having a p-type semiconductor characteristic and the charge transport layer Provided is an organic electroluminescent display device comprising a charge transport material different from the material described above.

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

2 is a view schematically illustrating a structure of an organic electroluminescent display device manufactured according to an embodiment of the present invention.

Referring to FIG. 2, the present invention provides a first electrode 50 and a second electrode 10 which are sequentially formed on a substrate 60, and the first electrode 50 and the second electrode 10. At least one organic light emitting layer 20 and at least one charge transport layer 70 between the ().

At least one charge transport layer of the charge transport layer 70 includes an organic compound having the characteristics of at least one p-type semiconductor to improve charge transport capacity.

However, organic compounds having p-type semiconductor properties doped or included in order to improve charge transport capability have poor interface characteristics, thereby solving these disadvantages, improving efficiency and life characteristics, and suppressing current leakage at reverse voltage. An organic compound layer having a p-type semiconductor characteristic is improved for application to a passive organic electroluminescent display device, and a charge transport material different from a material constituting the charge transport layer in the organic compound layer is a p-type semiconductor in the charge transport layer. Doping with organic compounds having properties.

The charge transport material is preferably a hole mobility greater than the electron mobility, to improve the interfacial characteristics and current characteristics of the organic compound having a p-type semiconductor characteristics, an aromatic amine-based compound which is an organic material or an organic-metal complex, Alternatively, a material having excellent interfacial properties with the electrode and having charge transporting properties, such as a metal-phthalocyanine compound, may be used.

When the charge transport material is doped into the organic compound layer having the p-type semiconductor properties, the crystalline p-type semiconductor material serves to fill the defects generated as the crystal grows, thus providing a gap between the electrode and the p-type semiconductor material. The defect is eliminated and the interface property is improved.

Improving the interfacial properties facilitates the injection of charges, particularly holes, from the electrode, and increases the efficiency of the device by eliminating defects. Therefore, the lifetime characteristics of the device are also improved, and the current leakage at the reverse voltage is remarkably reduced by doping a material that impedes the movement of electrons.

The efficiency, lifespan, and current characteristics are dependent on the type and concentration of the charge transport material, and the charge transport material having excellent interface properties and a large barrier to electron injection has properties of excellent efficiency, life, and current properties.

The content of the charge transport material is appropriately between 0.1% and 50% of the charge transport layer, the current injection characteristics are improved within the above concentration range, and the efficiency and lifetime characteristics are also improved. Above the above concentration, the current injection characteristic is lowered, the driving voltage is increased, and the concentration of the charge transport material is preferably 50% or less.

On the other hand, the organic compound having the p-type semiconductor characteristics may be used a compound represented by the following formula (1), the present invention is not limited to the above materials.

R in Formula 1 is each or independently a hydrogen atom, a hydrocarbon having 1 to 12 carbon atoms, a halogen group, an alkoxy group, an arylamine group, an ester group, an amide, an aromatic hydrocarbon, a heterocyclic compound, a nitro group, or nitrile.

On the other hand, in the present invention, it is preferable that the charges such as the charge transport layer and the charge transport material are holes.

In the present invention, the charge transport layer is preferably a hole injection layer 40 and / or a hole transport layer 30, the charge transport layer is organic and the first electrode 50 when the first electrode 50 is an anode electrode It is preferable to be formed between the light emitting layer 20, and when the first electrode 50 is a cathode electrode, it is preferably formed between the organic light emitting layer 20 and the second electrode 10.

By using the structure of the present invention, a device having excellent efficiency and lifespan characteristics can be manufactured while lowering a driving voltage as compared with a structure using a conventional hole injection layer or a hole transport layer.

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

Example 1

An organic compound having a p-type semiconductor property of Chemical Formula 1 having a nitrile substituent at the R position as a hole injection layer of an organic electroluminescent display device on an ITO transparent electrode was subjected to N, N'-di (1-naph) under a vacuum of 10 ^-6 Torr. Co-deposited to 20 nm thick at a concentration of 10% NPD with Tyl) -N, N'-diphenylbenzidine (NPD). After deposition, N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine (NPD) was deposited to a thickness of 50 nm under a vacuum of 10 ^-6 Torr as the hole transport layer.

After NPD deposition, iridium tris (phenylpyridine); Irppy ₃ was deposited on carbazole biphenyl (CBP) as a light emitting layer at a concentration of 5% to form a light emitting layer having a thickness of 30 nm. After deposition of a light emitting layer, a biphenoxy-bi (8-quinolinolato) aluminum (BAlq) was deposited to a thickness of 5 nm as a hole blocking layer and then tris (8-) as an electron transport layer. Tris (8-quinolinolato) aluminum (Alq) was deposited to a thickness of 20 nm under a vacuum of 10 ⁻⁶ Torr. After depositing the electron transport layer, LiF was deposited to a thickness of 1 nm as an electron injection layer. Finally, Al was deposited to a thickness of 300 nm on the LiF electron injection layer using a metal electrode, and then encapsulated using a metal can and barium oxide (BaO).

The organic electroluminescent display device manufactured using the above process showed a lifespan of 2,000 hours at 6V, brightness 3800 cd / m 2, efficiency 29.7 cd / A, and 4300 cd / m 2. In addition, the rectification ratio at -6V and 6V was 100,000, and defects between the electrode and the organic matter were eliminated and defects were suppressed.

Comparative Example 1

As the hole injection layer of the organic electroluminescent display device on the ITO transparent electrode, an organic compound having a p-type semiconductor property of Formula 1 having a nitrile substituent at the R position was deposited to a thickness of 20 nm under a vacuum of 10 ^-6 Torr and then to the hole transport layer. N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine (NPD) was deposited to a thickness of 50 nm under a vacuum of 10 ^-6 Torr. After NPD deposition, the first phosphorescent dopant including iridium (Ir) in carbazole biphenyl (CBP) as a light emitting layer and having a maximum emission wavelength of 608 nm was deposited at a concentration of 12% to form a light emitting layer having a thickness of 30 nm. 5 nm of biphenoxy-bi (8-quinolinolato) aluminum (BAlq) was deposited as a hole blocking layer after the emission layer was deposited, and then tris (8-quinolinola) was used as an electron transporting layer. Tris (8-quinolinolato) aluminum (Alq) was deposited to a thickness of 20 nm under vacuum of 10 ⁻⁶ Torr. After depositing the electron transport layer, LiF was deposited to a thickness of 1 nm into the electron injection layer. Finally, Al was deposited to a thickness of 300 nm on the LiF electron injection layer using a metal electrode, and then sealed using a metal can and barium oxide.

The organic light emitting display device manufactured using the above process showed a lifespan of 1,000 hours at 6 V at 3200 cd / m 2, efficiency of 27.0 cd / A, and 4300 cd / m 2. In addition, the rectification ratio at -6V and 6V was 1000, a defect occurred between the electrode and the organic material interface, and defects were observed during driving.

As described above, when an organic compound having a charge transfer characteristic or a metal-organic compound is doped with an organic compound having a p-type semiconductor characteristic in the present invention and used as a hole injection layer or a hole transport layer, Compared to using an organic compound as a single film, a device having improved luminance, efficiency, and lifetime characteristics can be fabricated, and current leakage at reverse voltage can be significantly reduced. In addition, defects and defects at the interface were suppressed.

1 is a view schematically showing a structure of a conventional organic electroluminescent display device.

2 is a diagram schematically illustrating a structure of an organic electroluminescent display device according to an embodiment of the present invention.

Claims (10)

At least one organic light emitting layer and at least one charge transport layer between the first electrode and the second electrode formed on the substrate, wherein at least one of the charge transport layers forms an organic compound having a p-type semiconductor characteristic and the charge transport layer An organic electroluminescent display device comprising a charge transport material different from a material to be described. The method of claim 1, And the charge transport material has a hole mobility greater than an electron mobility. The method of claim 1, And the charge transport material is an organic material or an organic-metal composite. The method of claim 3, wherein The organic material or the organic metal-composite is an aromatic amine-based compound or a metal-phthalocyanine-based compound. The method of claim 1, Wherein the content of the charge transport material is 0.1% to 50% of the total charge transport layer. The method of claim 1, An organic electroluminescent display device wherein the organic compound having a p-type semiconductor characteristic is a compound represented by Chemical Formula 1. In Formula 1, each R is independently or independently a hydrogen atom, a hydrocarbon having 1 to 12 carbon atoms, a halogen group, an alkoxy group, an arylamine group, an ester group, an amide, an aromatic hydrocarbon, a heterocyclic compound, a nitro group, or nitrile. The method of claim 1, And the charge transport material is co-deposited with each other. The method of claim 1, The first electrode is an anode electrode, and the second electrode is a cathode electrode. The method of claim 1, The first electrode is a cathode electrode, and the second electrode is an anode electrode. The method according to any one of claims 1, 8 and 9, And the charge transport layer is a hole injection layer and / or a hole transport layer.