KR20100090045A - Organic electro-luminescent diode - Google Patents

Abstract

PURPOSE: An organic electro-luminescent diode is provided to improve a color reproduction ratio by selectively controlling the concentration of a light-emitting dopant. CONSTITUTION: A hole implant layer is formed on a first electrode. A hole transport layer is formed on the hole implant layer. The hole transport layer includes a light emitting layer having a first layer(183a), a second layer(183b), and a third layer(183c). An electron-transport layer is formed on the light emitting layer. The electron implant layer is formed on the electron-transport layer. The second electrode layer is formed on the electron implant layer.

Description

Organic Electroluminescent Diode

The present invention relates to an organic light emitting diode, and more particularly to an organic light emitting diode that can improve the luminous efficiency and color reproducibility by applying a selective doping process.

In general, organic light emitting diodes, which are one of flat panel displays, have high luminance and low operating voltage characteristics. In addition, the self-luminous self-illuminating type provides high contrast ratio, enables ultra-thin display, easy response time with several microsecond response time, no restriction on viewing angle, and stable at low temperatures. Since it is driven at a low voltage of 5V to 15V of DC, it is easy to manufacture and design a driving circuit.

The organic light emitting diode having such characteristics is classified into a passive matrix type and an active matrix type. In the passive matrix method, since a scan line and a signal line cross each other to form a device in a matrix form, the scan lines are sequentially driven over time in order to drive each pixel. In order to bet, the instantaneous luminance is equal to the average luminance multiplied by the number of lines.

However, in the active matrix method, a thin film transistor, which is a switching element for turning on / off pixels, is positioned for each pixel, and the first electrode connected to the thin film transistor is turned on and off in units of pixels. The second electrode facing the first electrode is formed on the entire surface to become a common electrode.

In the active matrix method, a voltage applied to a pixel is charged in a storage capacitor (Cst), and the power is applied until the next frame signal is applied, thereby irrespective of the number of scan lines. Run continuously for one screen. Therefore, even when a low current is applied, the same luminance is achieved, and thus, low power consumption, high definition, and large size can be obtained. Recently, an active matrix type organic light emitting diode is mainly used.

Basic structure and operation characteristics of the organic light emitting diode of the active matrix method will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram illustrating a unit pixel of a conventional active matrix type organic light emitting diode.

As illustrated, the unit pixel of the active matrix organic light emitting diode according to the related art includes a switching transistor Ts, a driving transistor Td, a storage capacitor Cst, and an organic light emitting diode E.

That is, the gate line GL formed in one direction, the data line DL defining the pixel region P by crossing the gate line GL perpendicularly, and the power line voltage are spaced apart from the data line DL. Power wirings PL for application are respectively formed.

In addition, a switching transistor Ts is formed at an intersection point of the gate line GL and the data line DL, and a driving transistor Td electrically connected thereto is formed at one side spaced apart from the switching transistor Ts. do.

The driving transistor Td is electrically connected to the organic light emitting diode E. That is, the first electrode, which is one terminal of the organic light emitting diode E, is connected to the drain electrode of the driving transistor Td, and the second electrode, which is the other terminal, is connected to the power wiring PL. The power wiring PL serves to transfer the power voltage to the organic light emitting diode E. In addition, a storage capacitor Cst is formed between the gate electrode and the source electrode of the driving transistor Td.

Therefore, when a signal is applied through the gate line GL, the switching transistor Ts is turned on, and the signal of the data line DL is transferred to the gate electrode of the driving transistor Td and driven. The turn-on of the transistor Td enables light to be output by the electric field-pole pair of the organic light emitting diode E connected thereto. At this time, when the driving transistor Td is turned on, the level of the current flowing from the power supply line PL to the organic light emitting diode E is determined, which causes the organic light emitting diode E to have a gray scale. ) Can be implemented.

In addition, the storage capacitor Cst functions to keep the gate voltage of the driving transistor Td constant when the switching transistor Ts is turned off, so that the switching transistor Ts is turned off. Even if it is possible to maintain a constant level of the current flowing through the organic light emitting diode (E) until the next frame (frame).

2 is a cross-sectional view schematically showing an organic light emitting diode according to the related art, which will be described in more detail with reference to this.

As shown, the organic light emitting diode E according to the related art has a hole injecting layer 81 formed on the first electrode 70 on the substrate 10 and sequentially stacked on the first electrode 70. HIL), hole transporting layer (HTL), light emitting layer (83, emitting later (EL), electron transporting layer (ETL) and electron injecting layer (EIL) (85, 85) The second electrode 90 on the electron injection layer 85 is included.

The hole injection layer 81, the hole transport layer 82, the light emitting layer 83, the electron transport layer 84, and the electron injection layer 85 may be referred to as an organic light emitting layer 80. The first electrode 70, the organic emission layer 80, and the second electrode 90 form an organic light emitting diode (E).

The first electrode 70 may be an anode electrode made of a transparent conductive material, and the second electrode 90 may be used as a cathode electrode made of an opaque conductive material. At this time, the light emitting layer 83 may be a bottom emission type that emits light in a direction toward the first electrode 70 by recombination of the electron / electron pair. In addition, a top emission type that emits light in a direction toward the second electrode 90 may be applied by changing a stacking structure of the material forming the first electrode 70 and the second electrode 90 and the organic light emitting layer 80. It may be.

When holes and electrons are injected into the first electrode 70 and the second electrode 90 of the organic light emitting diode E, the holes are the hole injection layer 81 and the hole transport layer 82, and the electrons are the electrons. As it moves to the injection layer 85 and the electron transport layer 84, holes and electrons generate excitons through recombination of electron-electron pairs in the emission layer 83, and the excitons fall to the ground state. Will emit light.

The organic light emitting diode (E) has a great difference in lifespan and luminous efficiency of the organic light emitting diode (E) depending on the material used, the stacked structure, and the processing conditions such as the surface treatment of the first electrode 70. In particular, the organic light emitting diode (E) is in a situation in which deterioration or thermal stress is severe during driving, thereby failing to obtain satisfactory results in terms of lifespan and luminous efficiency.

Recently, as a part of improving the luminous efficiency of an organic light emitting diode, a host material and a dopant material are mixed by co-deposition.

3A is a cross-sectional view schematically illustrating an organic light emitting diode including an emission layer formed of a host material and a dopant material, and FIG. 3B is a graph illustrating a change in luminance according to a position where excitons are formed. .

First, as shown in FIG. 3A, the light emitting layer 83 is formed of a mixture of the host material M1 and the dopant material M2. In this case, the light emitting layer 83 made of a mixture of the host material M1 and the dopant material M2 has an advantage of increasing the luminous efficiency compared to the light emitting layer 83 made of only the host material M1. The dopant material M2 may be classified into a phosphorescent dopant and a fluorescent dopant.

In particular, in the above-described light emitting layer 83, the concentration of the dopant material M2 acts as an important factor affecting the driving voltage, color and life. In this case, in the case of fluorescent dopants, it is known that the doping treatment is about 1 to 2% to prevent concentration quenching and perfect energy transfer. However, the life characteristics are higher at 4 to 5% than 1 to 2%. This is proven by experiment.

This will be described with reference to FIG. 3B. 3B illustrates a change in luminance depending on the position of formation of the exciton when the doping concentration of the emission layer is set to 4 to 5%. At this time, the horizontal axis represents the position where the exciton is formed, 0 corresponds to the interface between the electron injection layer 84 and the light emitting layer 83, and 1 corresponds to the interface between the hole injection layer 82 and the light emitting layer 83, respectively.

As shown in the figure, it can be seen that the luminance increases proportionally according to the position where the exciton is formed. In particular, it can be seen that the luminance is increased as the exciton formation position in the light emitting layer 83 is closer to the hole injection layer 82.

However, in the related art, the dopant material M2 injected into the host material M1 is doped at an arbitrary position instead of setting a specific position when the light emitting layer 83 is formed. As such, the light emitting layer 83 designed to have a high doping concentration of 4 to 5% does not cause a big problem at the interface with the hole transport layer 82, but in the light emitting layer 83 corresponding to the position adjacent to the electron transport layer 84. It may act as a factor that interferes with the carrier transport ability of electrons or electrons, and furthermore, it causes a problem of deterioration of efficiency due to aggregation effect and concentration quenching between the dopant materials (M2).

In particular, in the conventional case, the thickness of the hole transport layer 82 is formed to about 50 to 150 nm, and the thickness of the electron transport layer 84 is formed to a thickness of 10 to 30 nm. In this structure, it is proved through experiments and simulations that the position where electrons and holes are actually recombined in the light emitting layer 83 to form excitons occurs in the light emitting layer 83 adjacent to the interface between the light emitting layer 83 and the hole transport layer 82. have.

In this case, in the light emitting layer 83 corresponding to a position far from the interface between the light emitting layer 83 and the hole transport layer 82, that is, the position adjacent to the electron transport layer 84, the light emitting plate that is not used when the electrons and the holes are recombined remains. The trap acts as a trap to hinder the movement of electrons, thereby acting as a factor to hinder the mobility of the carrier, and furthermore, a problem of lowering the luminous efficiency due to aggregation and concentration quenching between the light emitting dopants has emerged.

In addition, in the prior art, studies are being actively conducted on the structure of increasing the light emission efficiency by using the phosphorescent dopant instead of the fluorescent dopant. However, this does not set the position of the phosphorescent dopant doped in the light emitting layer 83. It uses the properties of phosphorescent dopants that have superior diffusion characteristics compared to the light source, and thus, there is a limit in maximizing luminous efficiency.

The present invention has been made to solve the above-described problem, and an object of the present invention is to provide an organic light emitting diode having excellent color sense characteristics and luminous efficiency and an improved lifetime through selectively adjusting the doping concentration of the light emitting layer.

The organic light emitting diode according to the present invention for achieving the above object is a first electrode; A hole injection layer on the first electrode; A hole transport layer on the hole injection layer; A first layer comprising a host material and a light emitting dopant over the hole transport layer, and a host material and a light emitting dopant over the first layer, wherein the light emitting dopant is doped to a lower concentration than the first layer A light emitting layer in which a second layer and a third layer made of only a host material are stacked on top of the second layer; An electron transport layer on the light emitting layer; An electron injection layer on the electron transport layer; It characterized in that it comprises a second electrode on the electron injection layer.

In this case, the host material is selected from the group consisting of anthracene, BeBq2, cyclopentadiene, poly (p-phenylenevinylene), aluminy quinolium complexes and derivatives thereof. The light emitting dopant is selected from rubrene, perylene, pyrene, anthracene-based DSA, derivatives thereof, and DCM derivatives.

The light emitting dopant in the first layer is 4 to 8%, the deposition thickness is 30 to 70 GPa, the light emitting dopant in the second layer is 1 to 2%, and the deposition thickness is 80 to 150 GPa. It is characterized by that.

In particular, the light emitting dopant is characterized in that the fluorescent dopant is less diffusion of exciton than the phosphorescent dopant. The deposition thickness of the entire light emitting layer is 250 ~ 400Å, the deposition thickness of the electron transport layer is characterized in that 100 ~ 350Å. The second layer of the light emitting layer may be made of only a host material. The host material and the light emitting dopant are formed by co-deposition.

The present invention has an effect of providing an organic light emitting diode having excellent color sense characteristics and luminous efficiency, and improved lifespan by selectively adjusting the doping concentration of the light emitting layer.

--- Example ---

The present invention is characterized in that the light emitting layer is doped at a high concentration in the region having excellent luminous efficiency, and the light emitting layer is formed by applying a selective doping process so as to dope the light emitting dopant at a low concentration or to be made of only a host material. do.

Hereinafter, an organic light emitting diode according to the present invention will be described with reference to the accompanying drawings.

4A is a schematic cross-sectional view of an organic light emitting diode according to the present invention, and FIG. 4B is an enlarged cross-sectional view of the light emitting layer of FIG. 4A.

As shown in FIGS. 4A and 4B, the organic light emitting diode E according to the present invention includes a first electrode 170 formed on the substrate 110 and a hole injection sequentially formed on the first electrode 170. The first layer 183a and the first layer 183a formed of a layer 181 and a hole transport layer 182 and a host material M1 and a light emitting dopant M2 on the hole transport layer 182. The second layer 183b and the second layer 183b formed of a host material M1 and a light emitting dopant M2 and doped with a light emitting dopant at a lower concentration than the first layer 183a. A light emitting layer 183 having a triple layer structure in which a third layer 183c consisting of only a host material M1 is stacked on top of the light emitting layer 183, and an electron transporting layer 184 and an electron injection layer sequentially formed on the light emitting layer 183. 185 and a second electrode 190 on the electron injection layer 185.

The hole injection layer 181, the hole transport layer 182, the emission layer 183, the electron transport layer 184, and the electron injection layer 185 may be referred to as an organic emission layer 180. In addition, the first electrode 170, the organic emission layer 180, and the second electrode 190 form an organic light emitting diode (E).

The first electrode 170 is an anode electrode made of a transparent conductive material including indium tin oxide (ITO) and indium zinc oxide (IZO), and the second electrode 190 is calcium (Ca) or magnesium ( Mg) and aluminum (Al) can be used as the cathode electrode made of an opaque conductive material selected from the group of relatively low work function metal materials.

The host material (M1) is anthracene (Anthracene), BeBq ₂ , cyclopentadiene (Cyclopentadiene), poly (p-phenylenevinylene) (PPV; poly (p-phenylenevinylene)), aluminy chinolium complex (Alq ₃ ) And derivatives thereof.

The light emitting dopant M2 is preferably selected from materials having high emission quantum efficiency, poor aggregation, and uniformly distributed in the host material M1 when mixed with the host material M1. Do. Such substances include rubrene, perylene, pyrene, anthracene-based DSA and derivatives thereof, and DCM (4 -dicyanomethylene-2metal-6-(p -dimethylaminostyryl)-4H-pyran) derivatives.

Formulas 1 to 6 list the molecular binding structure for the light emitting dopant, Formula 1 is antracene derivative, Formula 2 is styryl derivative, Formula 3 is pyryne derivative, Formula 4 is DCM derivative, Formula 5 is DCJTB derivative, Formula 6 is The perylene derivatives are shown respectively.

As shown in FIGS. 4A and 4B, a bottom emission type that emits light in a direction toward the first electrode 170 may be applied to the light emitting layer 183 by recombination of electron / electron pairs. In addition, a top emission type that emits light toward the second electrode 190 may be applied by changing the stacking structure of the material forming the first electrode 170 and the second electrode 190 and the organic light emitting layer 180. .

The reason for using the second electrode 190 as a metal having a low work function is to secure a high current density in electron injection by lowering a barrier formed between the second electrode 190 and the organic light emitting layer 180. .

When holes and electrons are injected into the first electrode 170 and the second electrode 190 of the organic light emitting diode (E), the holes are the hole injection layer 181 and the hole transport layer 182, and the electrons are the electrons. The injection layer 185 and the electron transport layer 184 respectively move, and holes and electrons generate excitons by recombination of electron-electron pairs in the light emitting layer 183, and the excitons fall to the ground state and light Will be emitted.

In this case, the first layer 183a and the second layer 183b of the light emitting layer 183 may each include a host material M1 and a light emitting dopant M2 inside the thermal evaporation deposition chamber (not shown). Co-deposition is performed by simultaneously operating the first and second evaporation sources (not shown) and simultaneously depositing the host material (M1) and the light emitting dopant (M2) at a constant ratio in the evaporation process. Can be.

In particular, when it is assumed that the light emitting layer 183 according to the present invention is designed to have a total thickness of 300 GPa, the first layer 183a of the light emitting layer 183 has a thickness of 30 to 70 GPa and the light emitting plate is formed on the host material M1. Doping so that 4 to 8% of Mt is contained. In addition, the second layer 183b of the light emitting layer 183 has a thickness of 80 to 150 GPa and is doped so that the light emitting dopant M2 is contained in the host material M1 in a range of 1 to 2%, and the third layer 183c is The light emitting layer 183 has a thickness except for the first layer 183a and the second layer 183b and is formed of only the host material M1.

In this case, the second layer 183b of the light emitting layer 183 may not be formed as necessary, and the portion corresponding to the second layer 183b when the second layer 183 is omitted is the third layer 183c. Is preferably designed to occupy.

That is, the first layer 183a of the light emitting layer 183a having excellent light emission efficiency in which excitons are actually formed by recombination of electrons and holes is doped with a light emitting dopant M2 of 4 to 8%, and the first layer of the light emitting layer The second layer 182b and the third layer 183c of the light emitting layer 183 except for the layer 183a have a structural advantage of maximizing the luminous efficiency by not doping.

In general, in the case of the fluorescent dopant, the diffusion phenomenon of the exciton is smaller than that of the phosphorescent dopant, so that the fluorescent dopant does not deviate much from the region of high luminous efficiency. Accordingly, the light emitting dopant M2 may be transferred to a fluorescent dopant having a better diffusion efficiency of excitons than a phosphorescent dopant, so that energy can be transferred to a region having excellent light emission efficiency, that is, the first layer 183a of the light emitting layer 183. When doping at a high concentration, a perfect energy transfer is possible to express a vivid color, and further improve the color reproduction of the organic light emitting diode (E).

In addition, the second layer 183b of the light emitting layer 183 may be doped at a lower concentration than the first layer 183a, and the third layer 183c may be formed of only the host material M1 or the second layer. An abbreviation 183b may be omitted and the region except for the first layer 183a may be formed of only the host material M1, thereby improving life expectancy according to maintaining the thickness of the light emitting layer 183. In this case, since only the host material M1 exists in the third layer 183c having low luminous efficiency, there is no fear of remaining light emitting dopants without contributing to light emission, thereby improving the efficiency deterioration problem due to the decrease in concentration quenching. It works.

Light emitting layer
Luminance
CIE x y (One) 1.9 0.146 0.098 (2) 2.26 0.146 0.108 (3) 2.22 0.146 0.105

Table 1 shows a comparison of the luminance and color reproducibility according to the prior art and the present invention, which will be described in more detail with reference to this.

In particular, Table 1 compares the luminance and the color reproducibility according to the structure of the light emitting layer. At this time, (1) relates to a structure in which a light emitting dopant is injected 4% into the host material and has a thickness of 300 μs without discriminating the stacking position in the light emitting layer.

(2) and (3) omit the 2nd layer from the structure of FIG. 4A, and are related with the double layer structure which consists of a 1st layer and a 3rd layer. At this time, (2) relates to a structure in which a first layer having a thickness of 10 μs and a 4% light emitting dopant is injected into the host material, and a third layer having a thickness of 290 μs and composed only of the host material are laminated.

(3) relates to a structure in which a first layer having a thickness of 50 μs and a 4% light emitting dopant injected into the host material and a third layer having a thickness of 250 μs and composed only of the host material are laminated.

As shown in Table 1, when (1) and (2) and (3) are compared, it can be seen that the luminance values in (2) and (3) are further improved compared to (1). When (2) and (3) were formed in the double layer structure which consists only of a 1st layer and a 3rd layer, it was confirmed that there was no big difference in color reproducibility.

That is, in (2) and (3), it was confirmed that the light emission efficiency was better in the case of (2) than in (3). Therefore, in forming the light emitting layer, the light emitting region for doping the light emitting dopant to the host material from the interface with the hole transport layer is set in the range of 10 to 50 kPa, and the region made of only the host material is the remaining thickness except the thickness of the light emitting region at 300 kPa. Formation of the resin has an effect that can prevent problems such as concentration quenching caused by a trap in a region made up of only a host material that emits less light.

HTL EL ETL Voltage (V) cd / A Im / W CIE_x CIE_y EQE (%) 1000Å (One) 200Å 3.5 3.4 3.1 0.144 0.103 4.1 1000Å (2) 200Å 3.5 4.4 3.8 0.145 0.097 5.4

Table 2 compares the luminance and color reproducibility according to the present invention, and more specifically, shows the experimental results for the structure in which the light emitting layer according to the present invention is formed of a triple layer. At this time, (1) corresponds to the conventional light emitting layer, and (2) corresponds to the light emitting layer according to the present invention. In (1) and (2), the hole transport layer was formed to be 1000 mW and the electron transport layer was 200 mW, respectively. In particular, the deposition thickness of the electron transport layer was formed to be thinner than about 350 kW to obtain an excellent effect on the luminous efficiency near the interface of the hole transport layer. Therefore, the deposition thickness of the electron transport layer is preferably formed to 100 ~ 350Å.

Particularly, the light emitting layer according to the present invention has a thickness of 50 μs and a first layer in which 4% of a light emitting dopant is injected into the host material, a second layer having a thickness of 100 μs and injecting a light emitting dopant into the host material of 1%, An example is a structure in which a third layer composed of only a host material and having a thickness of 150 μs is laminated.

As shown in Table 2, comparing (1) and (2), (2) compared with (1), the luminance was 3.4 cd / A to 4.4 cd / A, and the current density was 3.1 Im / W to 3.8 Im You can see that each improved with / W. In addition, CIE_x slightly increased from 0.144 to 0.145, and CIE_y decreased slightly from 0.103 to 0.097. Accordingly, it can be seen that the present invention is improved also in color reproducibility compared with the prior art.

In this case, in order to improve the efficiency of the organic light emitting diode, it is also important to improve the efficiency of exiting the light generated from the inside of the device to the outside of the device. Determined by the ratio of external quantum efficiency (EQE).

Also in the external quantum efficiency (EQE), (1) was 4.1% and (2) was 5.4%. Therefore, it can be seen that the luminous efficiency is greatly improved when applying the structure of the organic light emitting diode according to the present invention.

Figure 5a is a graph showing the voltage / current density relationship according to the prior art and the present invention, Figure 5b is a graph showing the voltage / luminance relationship according to the prior art and the present invention. At this time, (1) is conventionally, (2) is to apply the organic light emitting diode according to the present invention.

As shown in FIGS. 5A and 5B, it can be seen that as the voltage increases, the current density and luminance of (2) increase in proportion to (1), respectively.

Based on the above experimental data, rather than randomly doping the entire area of the light emitting layer, selectively doping at a high concentration in a region of high luminous efficiency, that is, the first layer of the light emitting layer adjacent to the interface between the light emitting layer and the hole transport layer, except for the second It can be seen that it is preferable to dope the light emitting dopant at a low concentration or not to perform the doping treatment on the layer and the third layer to maximize the luminous efficiency of the organic light emitting diode.

In other words, the use of a fluorescent dopant causes a large number of electron-electron pair recombination in the region of high luminous efficiency, and the excitons generated by the recombination are concentrated in the first layer of the light emitting layer, so that the luminous efficiency is approximately higher than that of the related art. It was confirmed that more than 30% improved.

Therefore, as in the present invention, the light emission efficiency and color reproducibility may be improved by selectively adjusting the doping concentration of the light emitting dopant at a specific position of the light emitting layer.

However, the present invention is not limited to the above embodiments, and it will be apparent that various modifications and changes can be made without departing from the spirit and the spirit of the present invention.

1 is a circuit diagram of a unit pixel of a conventional active matrix type organic light emitting display device.

Figure 2 is a schematic cross-sectional view of an organic light emitting diode according to the prior art.

3A is a schematic cross-sectional view of an organic light emitting diode including a light emitting layer made of a host material and a dopant material.

3B is a graph showing a change in luminance depending on the position of formation of excitons;

Figure 4a is a schematic cross-sectional view of an organic light emitting diode according to the present invention.

4B is an enlarged cross-sectional view of the light emitting layer of FIG. 4A.

Figure 5a is a graph showing the voltage / current density relationship according to the prior art and the present invention.

5b is a graph showing a voltage / luminance relationship according to the prior art and the present invention;

* Explanation of symbols for the main parts of the drawings *

183a: First layer of light emitting layer 183b: Second layer of light emitting layer

183c: Third layer of light emitting layer 183: Light emitting layer

Claims (10)

A first electrode; A hole injection layer on the first electrode; A hole transport layer on the hole injection layer; A first layer comprising a host material and a light emitting dopant over the hole transport layer, and a host material and a light emitting dopant over the first layer, wherein the light emitting dopant is doped to a lower concentration than the first layer A light emitting layer in which a second layer and a third layer made of only a host material are stacked on top of the second layer; An electron transport layer on the light emitting layer; An electron injection layer on the electron transport layer; A second electrode on the electron injection layer An organic light emitting diode comprising a. The method of claim 1, The host material is an organic light emitting diode, characterized in that selected from the group consisting of anthracene, BeBq2, cyclopentadiene, poly (p-phenylenevinylene), aluminy chironium complex and derivatives thereof. The method of claim 1, The light emitting dopant is an organic light emitting diode, characterized in that selected from rubrene, perylene, pyrene, anthracene-based DSA and derivatives thereof, and DCM derivatives. The method of claim 1, The organic light emitting diode of claim 1, wherein the ratio of the light emitting dopant to the first layer is 4 to 8%, and the deposition thickness is 30 to 70 Hz. The method of claim 1, The organic light emitting diode of claim 2, wherein the light emitting dopant occupies 1 to 2% and the deposition thickness thereof is 80 to 150 Hz. The method of claim 1, The light emitting dopant is an organic light emitting diode, characterized in that the fluorescent dopant is less diffusion of exciton than the phosphorescent dopant. The method of claim 1, The organic light emitting diode, characterized in that the deposition thickness of the entire light emitting layer is 250 ~ 400Å. The method of claim 1, The organic light emitting diode, characterized in that the deposition thickness of the electron transport layer is 100 ~ 350Å. The method of claim 1, And the second layer of the light emitting layer is made of a host material only. The method of claim 1, And the host material and the light emitting dopant are formed by co-deposition.

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