KR101511549B1 - Organic Light Emitting Display Device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode (OLED) display, and more particularly, to a white organic light emitting diode (OLED) display capable of coping with a large substrate size and having high device efficiency.

The organic light emitting display according to the present invention includes a first light emitting group formed on a substrate, a second light emitting group formed on the first light emitting group, and a second light emitting group formed between the first light emitting group and the second light emitting group Generating group,

The charge generation group is characterized by comprising a charge generation layer formed of lithium oxide (Li ₂ O).

As described above, the organic light emitting diode display according to the present invention has a structure in which the first light emitting group and the second light emitting group are stacked, so that the light efficiency can be more easily increased compared with the conventional case where the light emitting layer is a single layer And by using lithium oxide as the charge generation layer, it is possible to increase the lifetime of the device and increase the efficiency.

An organic light emitting display, a charge generation layer, a light efficiency

Description

[0001] The present invention relates to an organic light emitting display device,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode (OLED) display, and more particularly, to a white organic light emitting diode (OLED) display capable of coping with a large substrate size and having high device efficiency.

With the development of the information society, there is a demand for the development of a new image display device which improves disadvantages such as a heavy weight and a large volume of a conventional CRT (Cathode Ray Tube)

Accordingly, a display device such as an LCD (Liquid Crystal Display Device), an OLED (Organic Light Emitting Diode Display Device), a PDP (Plasma Panel Display Device), a SED (Surface-conduction Electron- A variety of flat panel display devices have attracted attention.

Among them, an organic light emitting diode (OLED) device is a device that recombines electrons and holes to form an exciton, and emits light of a specific wavelength by energy from the excitons formed. Diode has excellent display characteristics such as a contrast ratio and a response time and is easily attracted attention as an ideal next generation display since it is easy to implement a flexible display.

Generally, an organic light emitting display device has a cathode electrode for injecting electrons and an anode electrode for injecting holes, and electrons and holes from the cathode electrode and the anode electrode, respectively, And is an element that emits light when an exciton formed by injecting electrons and holes is excited from an excited state to a ground state.

Unlike the conventional thin film liquid crystal display device, this principle does not require a separate light source, which is advantageous in that the volume and weight of the device can be reduced. Further, the organic electroluminescent device exhibits high-quality panel characteristics (low power, high brightness, high response speed, low weight).

Because of these characteristics, the organic light emitting display device has been used in portable digital applications such as mobile communication terminals, Car Navigation System (CNS), camcorders, digital cameras, and the like, It is considered to be a powerful next generation display.

In addition, since the manufacturing process is simple, the production cost can be reduced more than that of the conventional liquid crystal display device.

1 is a view illustrating a structure of a conventional organic light emitting display device. 1, a conventional OLED display includes a first electrode 10, a hole injection layer 20, a hole transport layer 30, an organic emission layer 40, an electron transport layer 50, A layer 60, and a second electrode 70 are stacked in this order.

The first electrode may be, for example, an anode electrode, and injects holes. The second electrode may be, for example, a cathode electrode and injects electrons.

However, in the case of an organic light emitting diode display having one organic light emitting layer, in order to realize high device efficiency, the injection density of holes and electrons to be injected must be high, and the holes and electrons are efficiently recombined It is important to use organic materials with a low difference in work function between the electrodes and to control the thickness of each organic layer.

However, in the structure having one organic light emitting layer, when the efficiency of the device is increased by depositing a thicker layer of a specific layer, there is a problem that the light emitting state is not uniformed without being uniformly deposited on the entire surface of the substrate there was.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a structure of an organic light emitting diode display capable of increasing the efficiency of a device in response to a large-sized substrate.

In order to achieve the above object, an OLED display according to an embodiment of the present invention includes:

A first light emitting group formed on the substrate, a second light emitting group formed on the first light emitting group, and a charge generation group interposed between the first light emitting group and the second light emitting group,

Wherein the charge generating group comprises a charge generating layer formed of lithium oxide (Li ₂ O).

According to an embodiment of the present invention, the thickness of the charge generation layer formed of lithium oxide is 20 to 40 ANGSTROM, preferably 30 ANGSTROM.

The organic light emitting display according to the embodiment of the present invention can efficiently improve the efficiency of the device even if the substrate is made larger than the method of controlling the thickness of the specific layer through the structure in which the first light emitting group and the second light emitting group are stacked It has an effect that can be increased.

The organic light emitting display according to an embodiment of the present invention may further include a charge generation layer interposed between the first light emitting group and the second light emitting group, the charge generation layer including a charge generation layer formed of lithium oxide, Thereby improving the efficiency of the device and extending the lifetime of the device.

Next, the organic light emitting display according to an embodiment of the present invention will be described in detail.

An organic light emitting display according to an embodiment of the present invention includes a first light emitting group formed on a substrate, a second light emitting group formed on the first light emitting group, and a second light emitting group formed between the first light emitting group and the second light emitting group. A charge generating group formed on the substrate,

Wherein the charge generating group comprises a charge generating layer formed of lithium oxide (Li ₂ O).

The organic light emitting display according to another embodiment of the present invention includes a first light emitting group formed on a substrate, a second light emitting group formed on the first light emitting group, And a charge generation group formed interposed therebetween,

The charge generation group may include at least one of an electron transport layer doped with lithium oxide or a hole injection layer doped with lithium oxide.

The first light emitting group includes a first electrode and a first organic light emitting layer formed on the first electrode. The organic light emitting display device may further include a first common layer formed between the first electrode and the first organic light emitting layer.

The first common layer includes a first hole injection layer formed on the first electrode and a first hole transport layer formed on the first hole injection layer.

The charge generation group includes, for example, a first electron transport layer formed on the first light emitting group, a charge generation layer formed of lithium oxide on the first electron transport layer, and a second hole And an injection layer. The charge generation group may include a first electron transport layer formed on the first light emitting group and a second hole injection layer formed on the first electron transport layer. The first electron transport layer and the second electron transport layer At least one of the hole injection layers may be formed to be doped with lithium oxide.

The second light emitting group includes a second organic light emitting layer formed on the charge generation group and a second electrode formed on the second organic light emitting layer. The organic EL device may further include a second common layer formed between the charge generation group and the second organic emission layer, and a third common layer formed between the second organic emission layer and the second electrode.

The second common layer is composed of a second hole transport layer formed on the charge generation group. The third common layer is composed of a second electron transporting layer formed on the second organic light emitting layer and an electron injection layer formed on the electron transporting layer.

When the charge generating layer is formed of lithium oxide (Li ₂ O), the thickness of the charge generating layer is 20 to 40 Å, preferably 30 Å.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

2 is a cross-sectional view illustrating an example of an organic light emitting display according to an exemplary embodiment of the present invention.

As shown in FIG. 2, the organic light emitting display according to the embodiment of the present invention includes:

A first light emitting group 200 formed on the substrate 100 and a second light emitting group 400 formed on the first light emitting group 200 and a second light emitting group 400 formed on the first light emitting group 200 and the second light emitting group 200. [ And a charge generation group 300 interposed between the charge generation groups 400,

The charge generating group 300 may include a charge generating layer 320 formed of lithium oxide (Li ₂ O).

The first light emitting group 200 includes a first electrode 210 and a first organic emission layer 230 formed on the first electrode 210. In addition, the organic light emitting display device may further include a first common layer 220 formed between the first electrode 210 and the first organic emission layer 230.

The first common layer 220 includes a first hole injection layer 222 formed on the first electrode and a first hole transport layer 224 formed on the first hole injection layer 222.

The charge generation group 300 includes a first electron transport layer 310 formed between the first light emitting group 200 and the charge generation layer 320 and a second electron transport layer 310 formed between the second light emitting group 400 and the charge generation layer 320 And a second hole injection layer 330 formed between the first hole injection layer 330 and the second hole injection layer 330.

The second light emitting group 400 includes a second organic light emitting layer 420 formed on the charge generation group 300 and a second electrode 440 formed on the second organic light emitting layer 420 do. A second common layer formed between the charge generation group 300 and the second organic emission layer 420 and a third common layer formed between the second organic emission layer 420 and the second electrode 440 430). ≪ / RTI >

The second common layer is composed of a second hole transport layer 412 formed on the charge generation group 300. The third common layer 430 includes a second electron transport layer 432 formed on the second organic emission layer 420 and an electron injection layer 434 formed on the second electron transport layer 432 .

In the organic light emitting diode display according to an embodiment of the present invention, the charge generation layer 320 is formed of lithium oxide (Li ₂ O) and has a thickness of 20 to 40 Å, preferably 30 Å. Thus, when the charge generation layer is formed of lithium oxide, the efficiency of the device can be increased and the lifetime of the device can be prolonged.

The first light emitting group 200 and the second light emitting group 400 may emit light of the same color or emit light of different colors. When the colors of light emitted from the first light emitting group and the second light emitting group are the same, each group preferably emits white light. When the colors of light emitted from the first light emitting group and the second light emitting group are different from each other, the light emitted from each group may be mixed with each other to form white light.

The first light emitting group and the second light emitting group emit light through a fluorescence or phosphorescence mechanism.

In addition, the first light emitting group 200 and the second light emitting group 400 are electrically connected in series.

As described above, the first light emitting group and the second light emitting group are connected to each other in series, and the charge generating layer is interposed between the first light emitting group and the second light emitting group. The organic light emitting display according to the present invention has an effect of increasing the efficiency of the device without controlling the thickness of a specific layer.

As the substrate 100, for example, a glass substrate made of glass can be used. In order to realize a flexible display, a plastic substrate or an ultra thin glass substrate substrate. < / RTI >

The first electrode 110 may be, for example, an anode electrode. When the first electrode is an anode electrode, the first electrode 200 may be formed of indium-tin oxide (ITO), indium-zinc oxide (IZO), indium- It may be preferable to use a transparent and electrically conductive metal such as indium tin zinc oxide (ITZO) or aluminum oxide doped zinc oxide (AZO).

It is preferable that the first common layer to the third common layer and the charge generation group have a good interface property with the other layer and use a material having little absorption in the visible light region in order to improve the luminous efficiency . Further, in order to secure thermal stability, it is preferable to have a high glass transition temperature (Tg).

The first hole injection layer is a material which functions to inject holes injected from the first electrode into the first light emitting layer smoothly. The work function of the first electrode and the HOMO (Highest Occupied Molecular Orbital) A material having an excellent interfacial characteristic with the first electrode is used.

The second hole injection layer plays a role to inject holes injected from the charge generation layer into the second light emitting layer smoothly, and also uses a material having excellent interface characteristics with the charge generation layer.

As the first hole injection layer and the second hole injection layer, for example, materials having an aromatic amine structure may be used, and DNTPD, spiro-TPD, or the like may be used.

The first hole transporting layer and the second hole transporting layer are preferably formed of a material having a high degree of hole mobility and thermal stability, for example, a compound having an aromatic amine structure having a rigid structure You can do it. When the light emitting layer is formed of a phosphorescent material, it is possible to use, for example, TCTA or CBP as the first hole transport layer and the second hole transport layer.

The first electron transporting layer and the second electron transporting layer function to smoothly transfer the electrons generated in the second electrode or the charge generating layer to the light emitting layer and have a large electron mobility and a LUMO Lowest Unoccupied Molecular Orbital).

For example, it is possible to use materials such as Alq3, oxidiazole, triazole, phenathroline, imidazole, silole, and MADN.

As the electron injection layer, for example, an insulating material such as LiF, CsF, NaF, or BaF ₂ may be used and aluminum (Al) may be used for the second electrode.

Next, an OLED display according to another embodiment of the present invention will be described in detail.

3 is a cross-sectional view illustrating a configuration of an OLED display according to another embodiment of the present invention.

3, the OLED display according to another embodiment of the present invention includes a first light emitting group 200 formed on a substrate 100, a second light emitting group 200 formed on the first light emitting group 200, Emitting group 400 and a charge generation group 300 interposed between the first light emitting group 200 and the second light emitting group 400,

The charge generation group 300 includes an electron transport layer and a hole injection layer, and at least one of the electron transport layer and the hole injection layer is doped with lithium oxide (Li ₂ O).

The first light emitting group 200 includes a first electrode 210 formed on the substrate 100, a first common layer 220 formed on the first substrate, And a first organic emission layer 230. The first common layer 220 includes a first hole injection layer 212 formed on the first electrode 210 and a first hole transport layer 214 formed on the first hole injection layer 212 do.

The charge generation group 300 may include a first electron transport layer 310 formed on the first organic emission layer 310 and a second hole injection layer 330 formed on the first electron transport layer 300, At least one of the first electron transport layer and the second hole injection layer is doped with lithium oxide.

The second light emitting group 400 includes a second common layer formed on the charge generation group, a second organic emission layer 420 formed on the second common layer, and a third organic emission layer 420 formed on the second organic emission layer. A common layer 430, and a second electrode 440 formed on the third common layer.

The second common layer may be formed of a second hole transport layer 412, for example. The third common layer 430 may include a second electron transport layer 432 formed on the second organic emission layer 420 and an electron injection layer 434 formed on the electron transport layer 432 It will be possible.

As described above, in the organic light emitting display according to another embodiment of the present invention, the charge generating group formed to include the electron transporting layer and the hole injecting layer does not include a separate charge generating layer, and the electron transporting layer and the hole injecting layer At least one of which is formed by doping lithium oxide, provides an effect of improving the efficiency of the device and extending the lifetime while simplifying the process.

Table 1 below shows the comparison of the driving voltage, the light efficiency and the color coordinates, and the external quantum efficiency (EQE) of the organic light emitting diode display according to the embodiment of the present invention and the OLED display of the conventional single structure. It is a table.

For reference, a reference sample includes a first electrode (ITO), a hole injecting layer (50 Å), a hole transporting layer (1000 Å), an organic light emitting layer (250 Å), an electron transporting layer (10 Å), and a second electrode (Al, 1000 Å) are stacked in this order. Sample 1 was prepared by forming on a glass substrate a first common layer formed of a first electrode (ITO), a first hole injection layer (50 Å) and a first hole transport layer (1000 Å), a first organic emission layer (250 Å) A charge generating group formed of a first electron transporting layer (200 Å), a charge generating layer (10 Å) and a second hole injecting layer (50 Å), a second hole transporting layer (1000 Å), a second organic light emitting layer 200 Å), an electron injection layer (10 Å), and a second electrode (Al, 1000 Å) are stacked in this order. Sample 2 had the same structure as Sample 1 and had a thickness of only 30 Å in the thickness of the charge generating layer. In both Sample 1 and Sample 2, the charge generating layer was formed of lithium oxide.

division
Driving voltage
Light efficiency
Color coordinates
External quantum efficiency
cd / A lm / W x y reference 5.5 6.2 3.5 0.138 0.205 4.4 Sample 1 11.4 5.7 1.6 0.137 0.217 4.1 Sample 2 6.4 13.9 6.8 0.132 0.253 9.2

As can be seen from the above Table 1, in the case of the sample 2, the light efficiency and the external quantum efficiency are significantly improved as compared with the reference sample. That is, when the charge generation layer is formed of lithium oxide, its thickness is also an important factor. The thickness of the charge generating layer is preferably 20 to 40 ANGSTROM, and preferably 30 ANGSTROM.

Outside of the above range, when the thickness of the charge generating layer is smaller than 20 ANGSTROM or larger than 40 ANGSTROM, the light efficiency may be reduced.

4 is a graph showing a reference curve and a life curve of the sample 2 together. The lifespan curve of Fig. 4 was measured under the conditions of 25 캜, 1 atmospheric pressure, and 5000 nits of brightness.

As can be seen from FIG. 4, in the case of the organic light emitting diode display (sample 2) according to the embodiment of the present invention, the lifetime of the device is improved compared to the conventional one.

 As described above, the organic light emitting display according to the embodiment of the present invention can improve the efficiency of a device without controlling the thickness of a specific layer through the structure in which the first light emitting group and the second light emitting group connected in series are stacked So that it is possible to easily cope with the large-sized substrate.

The present invention also provides an effect of improving the lifetime and efficiency of the device by including a charge generation layer formed of lithium oxide between the first light emitting group and the second light emitting group or by including an organic layer doped with lithium oxide.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. Will be clear to those who have knowledge of.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a configuration of a conventional organic light emitting display device. FIG.

2 is a cross-sectional view illustrating an example of an organic light emitting display according to an embodiment of the present invention.

3 is a cross-sectional view illustrating an example of an organic light emitting display according to another embodiment of the present invention.

4 is a graph comparing lifetime curves between an OLED display and a reference sample according to an embodiment of the present invention.

Claims (5)

A first electrode formed on a substrate; A first light emitting group formed on the first electrode and including a first organic light emitting layer; A charge generating group formed on the first light emitting group; A second light emitting group formed on the charge generating group and including a second organic light emitting layer; And And a second electrode formed on the second light emitting group, The first light emitting group may further include a first hole injection layer and a first hole transport layer formed between the first electrode and the first organic light emitting layer, The charge generation group includes a first electron transport layer formed on the first organic emission layer, a charge generation layer formed of lithium oxide (Li ₂ O) on the first electron transport layer, and a second electron transport layer formed on the first charge transport layer A hole injection layer, The second light emitting group may include a second hole transport layer formed between the second hole injection layer and the second organic emission layer, a second electron transport layer formed on the second organic emission layer, and a second electron transport layer formed on the second electron transport layer And an electron injection layer disposed between the first electrode and the second electrode. A first electrode formed on a substrate; A first light emitting group formed on the first electrode and including a first organic light emitting layer; A charge generating group formed on the first light emitting group; A second light emitting group formed on the charge generating group and including a second organic light emitting layer; And And a second electrode formed on the second light emitting group, The first light emitting group may further include a first hole injection layer and a first hole transport layer formed between the first electrode and the first organic light emitting layer, Wherein the charge generation group comprises a first electron transporting layer formed on the first organic light emitting layer and a second hole injection layer formed on the first electron transporting layer, The second light emitting group may include a second hole transport layer formed between the second hole injection layer and the second organic emission layer, a second electron transport layer formed on the second organic emission layer, and a second electron transport layer formed on the second electron transport layer Further comprising an electron injection layer, Wherein at least one of the first electron transport layer and the second hole injection layer is doped with lithium oxide (Li ₂ O). The method according to claim 1, Wherein the thickness of the charge generation layer is 20 ANGSTROM or more and 40 ANGSTROM or less. The method of claim 3, And the thickness of the charge generation layer is 30 ANGSTROM. delete

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