KR20140082369A - Organic Light Emitting Diode Display Device and Method for Manufacturing The Same - Google Patents

Abstract

According to an aspect of the present invention, an organic electroluminescent light emitting display device includes: an anode electrode provided on a substrate to supply a hole; a hole injection layer provided on the anode electrode to receive the hole from the anode electrode; a hole transport layer provided on the hole injection layer to move the hole; an electron blocking layer provided on the hole transport layer to prevent an electron from moving to the anode electrode; an organic light emitting layer provided on the electron blocking layer to emit light from the hole and the electron; an electron transport layer provided on the organic light emitting layer to transfer the electron to the organic light emitting layer; and a cathode electrode provided on the electron transport layer to supply the electron to the electron transport layer, wherein the electron blocking layer includes a p-dopant.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent display device,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting display and a method of manufacturing the same, and more particularly, to an active organic light emitting display and a method of manufacturing the same.

BACKGROUND ART Organic light emitting diodes (OLEDs), which have been actively under research in recent years, are self-luminous devices that emit themselves, and are flat display devices with high response speed and excellent characteristics such as luminous efficiency and brightness.

The organic light emitting display includes an anode and a cathode, and an organic light emitting layer is interposed between the anode and the cathode. The organic light emitting layer replaces the role of a backlight and a liquid crystal layer in a liquid crystal display device. That is, when an electric current flows through the anode electrode and the cathode electrode, light having a wavelength corresponding to the bandgap energy of the material is emitted according to the material of the organic light emitting layer.

The organic light emitting display device is divided into a WRGB type and an RGB type. The WRGB type includes an organic light emitting layer that emits white light, and emits red, green, and blue light for each pixel through a color filter or a color refiner. Further, it may further include a pixel that emits white light. In the RGB type, an organic light emitting layer emitting red, green, and blue light is independently formed for each pixel, and a color conversion member such as a color filter is not required.

The organic light emitting display may further include a functional layer between the anode and the cathode except for the organic emission layer to smooth the flow of holes and electrons. For example, a hole injection layer and a hole transportation layer may be provided between the anode electrode and the organic light emitting layer. In addition, for example, an electron injection layer and an electron transportation layer may be provided between the cathode electrode and the organic light emitting layer.

However, as the number of the functional layers formed to further facilitate the driving of the organic light emitting layer increases, a stress may be generated at the interface between the functional layers, and the driving voltage may increase. Further, since the materials for forming the functional layers are different, the energy difference of each material is another cause of the increase of the driving voltage. If the driving voltage is increased, the lifetime of the organic light emitting display device may be shortened in the long term.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic electroluminescent display device capable of improving the lifetime.

According to an aspect of the present invention, there is provided an organic light emitting display including: an anode electrode formed on a substrate and supplying holes; A hole injection layer formed on the anode electrode and supplied with the holes from the anode electrode; A hole transport layer formed on the hole injection layer, the hole transport layer moving the holes; An electron blocking layer formed on the hole transporting layer to prevent electrons from moving to the anode electrode; An organic emission layer formed on the electron blocking layer and emitting light by the holes and the electrons; An electron transport layer formed on the organic emission layer and transferring the electrons to the organic emission layer; And a cathode electrode formed on the transfer transport layer and supplying the electrons to the electron transport layer, wherein the electron blocking layer includes a p-dopant.

According to another aspect of the present invention, there is provided a method of manufacturing an organic light emitting display, including: forming an anode on a substrate; Forming a hole injecting layer and a hole transporting layer on the anode electrode; Depositing an electron blocking material and a p-dopant on the hole transport layer to form an electron blocking layer; And forming an organic light emitting layer, an electron transport layer, and a cathode electrode on the electron blocking layer.

According to the present invention, an electron blocking layer is introduced to prevent an excessive flow of electrons.

According to the present invention, there is an effect that light extraction efficiency can be improved by forming a micro cavity.

Further, according to the present invention, a p-dopant layer is formed in the electron blocking layer to reduce the interface stress, thereby preventing an increase in driving voltage.

In addition, according to the present invention, lifetime of the organic light emitting display device can be improved by preventing the driving voltage from rising.

1 is a cross-sectional view illustrating an organic light emitting display device according to an embodiment of the present invention;
2 is a cross-sectional view illustrating an organic light emitting display device according to another embodiment of the present invention;
3 is a cross-sectional view illustrating an organic light emitting display according to another embodiment of the present invention; And
4 is a cross-sectional view illustrating an organic light emitting display device according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

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

1, an organic light emitting display according to an exemplary embodiment of the present invention includes an anode electrode 101, a hole injection layer 110, a hole transport layer 120, an electron blocking layer 130, A second auxiliary hole transporting layer 150, an organic light emitting layer 160, an electron transporting layer 170, a cathode electrode 180, and an optical compensation layer 190. The first auxiliary hole transporting layer 140, the second auxiliary hole transporting layer 150,

First, the anode electrode 101 supplies holes. More specifically, an electric signal is supplied from a thin film transistor (not shown) connected to the anode electrode 101 to supply holes to the hole injection layer 110. In addition, the anode electrode 101 may include a reflective layer (not shown) for a micro cavity effect. The reflective layer may be formed under the anode electrode 101.

The anode electrode 211 is formed of a material having a large work function so as to supply holes. For example, it may be formed of a conductive oxide having a high work function and a conductive property. The conductive oxide is mostly transparent and includes, for example, indium tin oxide (ITO), indium zinc oxide (IZO), and indium tin zinc oxide (ITZO) .

Next, a hole injection layer 110 is formed on the anode electrode 101. [ The hole injection layer 110 receives the holes of the anode electrode 101 and transmits the holes to the hole transport layer 120. The hole injection layer 110 may be formed of a hole injection material.

Next, a hole transporting layer 120 is formed on the hole injecting layer 110. The hole transport layer 120 may be a kind of common layer formed in all the pixels. The hole transport layer 120 transfers the holes supplied from the hole injection layer 110 to the organic emission layer 160. Suitable hole transport materials are considered to be suitable materials for hole transport if the hole mobility is about several times greater than the electron mobility.

For example, the hole transport layer 120 includes any one of polyaniline, polypyrrole, polyphenylene vinylene, and other suitable semiconducting organic materials. In addition, the hole transport layer 120 may also be a mixture of the above materials and other suitable materials, and is not limited to the above description.

Next, an electron blocking layer 130 is formed on the hole transporting layer 120. The electron blocking layer 130 may be formed after the first auxiliary hole transport layer 140 and the second auxiliary hole transport layer 150 to be described later are formed.

The electron blocking layer 130 may block excessive electrons remaining after the electrons transferred from the cathode electrode 180 from bonding with the holes in the organic light emitting layer 160 to travel toward the anode electrode 101 through the organic light emitting layer 160 have. The electron blocking layer 130 may comprise a p-dopant. The addition of the p-dopant to the electron blocking layer 130 reduces the interfacial stress and improves the interfacial characteristics to prevent the electrons from migrating to the cathode electrode 180 while moving the holes to the organic light emitting layer 160 Can be improved. Thus, the driving voltage rise in the multilayer thin film structure can be mitigated to some extent to enable low voltage driving.

In addition, the concentration of the p-dopant increases toward the specific interface, thereby reducing the stress at the interface. For example, the concentration of the p-dopant may be increased toward the interface between the electron blocking layer 130 and the first auxiliary hole transporting layer 140. The p-dopant reduces the stress that may be caused by the increase of the driving voltage at the interface between the electron blocking layer 130 and the first auxiliary hole transporting layer 140, thereby reducing the damage that may occur at the interface, Can be improved.

In addition, the concentration of the p-dopant may be increased toward the interface between the electron blocking layer 130 and the second auxiliary hole transporting layer 150. The p-dopant reduces the stress that may be caused by the increase of the driving voltage at the interface between the electron blocking layer 130 and the second auxiliary hole transporting layer 150, thereby reducing the damage that may occur at the interface, Can be improved.

The electron blocking layer 130 may be formed by simultaneously depositing an electron blocking material and a p-dopant. When the electron blocking layer 130 starts to be formed, the concentration of the p-dopant is increased, and the concentration of the p-dopant is gradually decreased as the electron blocking material is evaporated, so that the electron blocking layer 130, which faces the hole transporting layer 120, Lt; RTI ID = 0.0 > p-dopant. ≪ / RTI >

Next, a first auxiliary hole transporting layer 140 is formed between the hole transporting layer 120 and the electron blocking layer 130. The first auxiliary hole transporting layer 140 may be formed on a pixel on the hole transporting layer 120 formed in common to all the pixels to form the optical distance of the microcavity. The first auxiliary hole transporting layer 140 may be formed, for example, in a red pixel.

The micro cavity forms a reflection space at a distance set to an integral multiple of a value corresponding to one-half of the peak wavelength of light emitted from each pixel, resonance occurs in which reflection is repeated in the reflection space, And the light amplified by the light source can be emitted to the outside. The optical distance means an integral multiple of a half wavelength of light emitted from each pixel. Therefore, the first auxiliary hole transporting layer 140 is formed in the red pixel and is formed between the hole transporting layer 120 and the electron blocking layer 130 to set an optical distance corresponding to an integral multiple of the half wavelength of red light .

The thickness of the first auxiliary hole transporting layer 140 may vary depending on the setting of the optical distance. In the case of the red visible light ray, since the wavelength range is approximately 610 to 700 nm, the resonance phenomenon may occur when the peak wavelength is about 655 nm, which is the intermediate value, and the optical distance is an integral multiple of approximately 327.5 nm which is half of 655 nm.

Next, the second auxiliary hole transporting layer 150 is formed between the hole transporting layer 120 and the electron blocking layer 130. The second auxiliary hole transporting layer 150 is also formed on a pixel on the hole transporting layer 120 formed in common to all the pixels to form an optical distance of a microcavity as in the case of the first auxiliary hole transporting layer 140 can do.

The thickness of the second auxiliary hole transporting layer 150 may also vary depending on the setting of the optical distance as in the case of the first auxiliary hole transporting layer 140. The second auxiliary hole transporting layer 150 may be formed, for example, in a green pixel. In the case of the green visible light ray, since the wavelength range is approximately 500 to 570 nm, if the peak wavelength is about 535 nm which is the intermediate value, the resonance phenomenon may occur if the optical distance is an integral multiple of about 267.5 nm which is half of 535 nm.

Next, an organic light emitting layer 160 is formed on the electron blocking layer 130. [ Although the RGB type organic light emitting display device is shown in the drawing, the present invention is not limited to this, and may be applied to a case of WRGB in which a light emitting layer emitting white light is formed as a common layer in all pixels.

The wavelength of the emitted light is changed according to the material to be formed, and the hole transported from the anode electrode 101 and the electron transported from the cathode electrode 180 meet to form an exciton , Emits light while falling to the ground state. The light is changed depending on the band gap of the material of the organic light emitting layer 160.

Next, an electron transporting layer 170 is formed on the organic light emitting layer 160. The electron transport layer 170 can adjust the electron transport speed so that electrons and holes meet in the organic emission layer 160 and emit light. Usually, the material of the electron transport layer 170 is formed of a material whose electron movement speed is several times larger than other materials. The electron transporting layer 170 may comprise, for example, tris (8-hydroxyquinolinate) aluminum (AlQ3). Alternatively, the electron transporting layer 170 may include bis (8-hydroxyquinolato) - (4-phenylphenolato) aluminum (BAlq).

Next, the cathode electrode 180 supplies electrons to the organic light emitting layer 160. The cathode electrode 180 may be a kind of common electrode because it applies the same voltage to all the pixels. Thus, it can be formed as a single layer that covers the entire surface of the substrate without being patterned. In order to prevent a driving problem due to an increase in resistance, an auxiliary electrode may be connected to an upper portion or a lower portion of the cathode electrode 180 to reduce the resistance.

The cathode electrode 180 is formed of an alloy of silver (Ag), aluminum (Al), molybdenum (Mo), or silver (Ag), which has high electric conductivity and low work function, And the like. In addition, the cathode electrode 180 may include a metal having a low work function such as lithium (Li), sodium (Na), calcium (Ca), or the like.

The cathode electrode 180 may be formed by vacuum deposition, electron beam deposition, or sputtering deposition. In the case of the top emission type, since the light emitted from the organic light emitting layer 160 must be transmitted through the cathode electrode 180, it can be formed thin to a thickness of several hundreds of ohms or less.

Next, an optical compensating layer 190 is formed on the cathode electrode 180. The optical distance of the optical compensation layer 190 refers to the distance between the reflective layer and the optical compensation layer 190 that may be included in the anode electrode 101 or below the anode electrode 101.

 The reflective layer may be formed of a material having a high reflectance of light, but the optical compensation layer 190 may be formed of a material having a large difference in refractive index from the cathode 180. The light emitted from the organic light emitting layer 160 is not emitted to the outside and is reflected toward the anode electrode 101 due to the total reflection phenomenon due to the refractive index difference. The reflected emission light is reflected again by the reflection layer and the amplified emission light is output to the outside while the reflection process is repeated as described above, so that the light extraction efficiency can be improved.

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

2, the organic light emitting display according to another embodiment of the present invention is characterized in that a first auxiliary hole transporting layer 140 is formed between the organic light emitting layer 160 and the electron blocking layer 130 to be.

1, the first auxiliary hole transport layer 140 and the second auxiliary hole transport layer 150 are formed between the hole transport layer 120 and the electron blocking layer 130. However, in the embodiment shown in FIG. 2, A transport layer 140 may be formed, for example, on red pixels. The first auxiliary hole transporting layer 140 is formed between the organic light emitting layer 160 of the red pixel and the electron blocking layer 130. The p-dopant in the electron blocking layer 130 may be increased toward the interface between the electron blocking layer 130 and the hole transporting layer 120.

The concentration of the p-dopant in the electron blocking layer 130 of the red pixel increases from the interface between the electron blocking layer 130 and the hole transporting layer 120 to the electron blocking layer 130 and the hole transporting layer 120, The interfacial stress due to the increase of the driving voltage at the interface of the gate electrode 120 can be reduced. Accordingly, the electron blocking layer 130 and the hole transport layer 120 are prevented from being damaged, and the lifetime of the organic light emitting display device can be improved.

The second auxiliary hole transporting layer 150 may be formed, for example, in a green pixel. Therefore, the p-dopant in the electron blocking layer 130 of the green pixel increases in concentration toward the interface between the electron blocking layer 130 and the second auxiliary hole transporting layer 150, .

In this embodiment, the hole transport layer 120 may be formed first, the second auxiliary hole transport layer 150 may be formed, and then the electron blocking layer 130 may be formed. Next, the first auxiliary hole transporting layer 140 may be formed and the organic light emitting layer 160 may be formed. That is, the first auxiliary hole transport layer 140 and the second auxiliary hole transport layer 150 are formed before and after the formation of the electron blocking layer 130 so that the first auxiliary hole transport layer 140 and the second auxiliary hole transport layer 150 are staggered Can be deployed.

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

3, in the organic light emitting display according to another embodiment of the present invention, a second auxiliary hole transporting layer 150 is formed between the organic light emitting layer 160 and the electron blocking layer 130 Feature.

Therefore, in the electron blocking layer 130 of the green pixel, the concentration of the p-dopant may increase toward the interface between the electron blocking layer 130 and the hole transporting layer 120. The electron blocking layer 130 includes a p-dopant at a higher concentration near the interface between the electron blocking layer 130 and the hole transporting layer 120 so that the electron blocking layer 130 is driven at the interface between the electron blocking layer 130 and the hole transporting layer 120 The interface stress due to the voltage rise can be reduced. Accordingly, the electron blocking layer 130 and the hole transport layer 120 are prevented from being damaged, and the lifetime of the organic light emitting display device can be improved.

The first auxiliary hole transporting layer may be formed, for example, in a red pixel. Therefore, the p-dopant in the electron blocking layer 130 of the red pixel increases in concentration toward the interface between the electron blocking layer 130 and the first auxiliary hole transporting layer 140, .

In this embodiment, the hole blocking layer 130 may be formed after the hole transport layer 120 is formed and the first auxiliary hole transport layer 140 is formed. Next, the second auxiliary hole transporting layer 150 may be formed to form the organic light emitting layer 160. That is, the first auxiliary hole transport layer 140 and the second auxiliary hole transport layer 150 are formed before and after the formation of the electron blocking layer 130 to form the first auxiliary hole transport layer 140 and the second auxiliary hole transport layer 150 in a direction opposite to that shown in FIG. The second auxiliary hole transporting layer 150 can be staggered.

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

4, an organic light emitting display according to another embodiment of the present invention includes an electron blocking layer 130 formed on a hole transport layer 120.

Since the electron blocking layer 130 is formed on the hole transporting layer 120 in all the pixels, the concentration of the p-dopant increases toward the interface between the electron blocking layer 130 and the hole transporting layer 120 The occurrence of stress at the interface can be prevented, and the lifetime of the organic light emitting display device can be improved.

In this embodiment, after the hole transport layer 120 is formed, the electron blocking layer 130 is formed, and the first auxiliary hole transport layer 140 and the second auxiliary hole transport layer 150 are formed of red pixels and green By forming them in pixels, a micro-cavity structure can be formed.

In the case of the blue pixel, since the length of the wavelength of the blue light emitted is the smallest, the optical distance may be the shortest, but the present invention is not limited to this, and an auxiliary hole transport layer (not shown) may be added for forming an appropriate optical distance. In addition, although the optical distance may be reduced in the order of red, green, and blue pixels as shown in the figure, the optical distance corresponds to an integral multiple of the half wavelength, so the optical distance of the green or blue pixel is not limited to the above description, Can be larger than the distance. This can vary depending on conditions such as process efficiency.

As described above, how the interface characteristics are changed by including a p-dopant in the electron blocking layer 130 can be confirmed through experimental data.

Condition Volt cd / A lm / W CIE_x CIE_v EQE (%) Remarks Red existing 5.1 38.0 28.9 0.665 0.333 24.7 -0.4V Invention 4.7 39.0 32.8 0.665 0.333 25.6 Green existing 4.6 48.0 32.7 0.297 0.684 24.1 -0.3V Invention 4.3 49.0 35.7 0.287 0.692 24.4 Blue existing 3.9 4.8 3.9 0.136 0.055 9.6 -0.1 V Invention 3.8 4.6 3.5 0.137 0.054 9.3

Table 1 shows experimental results showing the effect of reducing the driving voltage when the new structure proposed by the present invention is applied. That is, the p-dopant is added to the electron blocking layer 130 to improve the overall luminance and realize almost the same color coordinates, and the red, green, 0.3 V and 0.1 V are decreased.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

101: anode electrode 110: hole injection layer
120: hole transport layer 130: electron blocking layer
140: first auxiliary hole transporting layer 150: second auxiliary hole transporting layer
160: organic light emitting layer 170: electron transporting layer
180: cathode electrode 190: optical compensation layer

Claims (15)

An anode electrode formed on the substrate and supplying holes;
A hole injection layer formed on the anode electrode and supplied with the holes from the anode electrode;
A hole transport layer formed on the hole injection layer, the hole transport layer moving the holes;
An electron blocking layer formed on the hole transporting layer to prevent electrons from moving to the anode electrode;
An organic emission layer formed on the electron blocking layer and emitting light by the holes and the electrons;
An electron transport layer formed on the organic emission layer and transferring the electrons to the organic emission layer; And
And a cathode electrode formed on the transfer transport layer and supplying the electrons to the electron transport layer,
Wherein the electron blocking layer comprises a p-dopant.
The method according to claim 1,
Wherein the concentration of the p-dopant in the electron blocking layer increases as the electron blocking layer is closer to the interface of the electron blocking layer facing the hole transporting layer.
The method according to claim 1,
Wherein the substrate is defined as a first pixel, a second pixel, and a third pixel, and a first auxiliary hole transporting layer and a second auxiliary hole transporting layer are formed in the first pixel and the second pixel, respectively, Display device.
The method of claim 3,
Wherein a thickness of the first auxiliary hole transporting layer is different from a thickness of the second auxiliary hole transporting layer.
The method of claim 3,
Wherein the first auxiliary hole transporting layer and the second auxiliary hole transporting layer are formed between the hole transporting layer and the electron blocking layer.
The method of claim 3,
Wherein the first auxiliary hole transporting layer and the second auxiliary hole transporting layer are formed between the electron blocking layer and the organic light emitting layer.
The method of claim 3,
Wherein the first auxiliary hole transporting layer is formed between the hole transporting layer and the electron blocking layer and the second auxiliary hole transporting layer is formed between the electron blocking layer and the organic light emitting layer.
The method of claim 3,
Wherein the first auxiliary hole transporting layer is formed between the electron blocking layer and the organic light emitting layer and the second auxiliary hole transporting layer is formed between the hole transporting layer and the electron blocking layer.
Forming an anode electrode on the substrate;
Forming a hole injecting layer and a hole transporting layer on the anode electrode;
Depositing an electron blocking material and a p-dopant on the hole transport layer to form an electron blocking layer;
And forming an organic light emitting layer, an electron transporting layer, and a cathode electrode on the electron blocking layer.
10. The method of claim 9,
Wherein forming the electron blocking layer comprises:
And simultaneously depositing an electron blocking material and a p-dopant on the hole transport layer,
Wherein the deposition amount of the p-dopant is reduced as the deposition process proceeds.
10. The method of claim 9,
Wherein the substrate is defined as a first pixel, a second pixel, and a third pixel,
And forming a first auxiliary hole transport layer and a second auxiliary hole transport layer on the first pixel and the second pixel, respectively.
12. The method of claim 11,
Wherein the first auxiliary hole transporting layer and the second auxiliary hole transporting layer are formed on the hole transporting layer before forming the electron blocking layer.
12. The method of claim 11,
Wherein the first auxiliary hole transporting layer and the second auxiliary hole transporting layer are formed on the electron blocking layer before forming the organic light emitting layer.
12. The method of claim 11,
Wherein the first auxiliary hole transporting layer is formed on the hole transporting layer before the electron blocking layer is formed and the second auxiliary hole transporting layer is formed on the electron blocking layer before the organic light emitting layer is formed. A method of manufacturing an electroluminescent display device.
12. The method of claim 11,
Wherein the first auxiliary hole transporting layer is formed on the electron transporting layer before the organic light emitting layer is formed and the second auxiliary hole transporting layer is formed on the hole transporting layer before the electron transporting layer is formed. A method of manufacturing an electroluminescent display device.

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