KR100730132B1 - Organic luminescence display device - Google Patents

Abstract

The present invention provides an organic light emitting display device having a light emitting layer including a dopant between a first electrode and a second electrode, wherein the light emitting layer includes two or more phosphorescent host materials and one phosphorescent dopant material. Provided is an organic light emitting display device in which a host material and a phosphorescent dopant material exist to have a concentration gradient along the thickness of a light emitting layer. The organic light emitting diode display of the present invention can improve the efficiency and life characteristics of the device by using the concentration gradient of the host material and the dopant material.

Description

Organic luminescence display device

1A-1C are cross-sectional views of an organic light emitting diode display according to an exemplary embodiment of the present invention.

2 is a graph of concentration gradients of a plurality of light emitting layer host materials according to an exemplary embodiment of the present invention.

Figure 3 is a graph showing the life characteristics according to one embodiment and a comparative example of the present invention.

Figure 4 is a graph showing the efficiency characteristics according to one embodiment and a comparative example of the present invention.

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device in which efficiency and lifespan characteristics are improved by employing a light emitting layer having a concentration gradient of a host material.

Luminescent devices are self-luminous display devices that have a wide viewing angle, excellent contrast, and fast response time. EL elements are classified into inorganic EL elements and organic EL elements according to materials for forming an emitting layer. Herein, the organic EL device has an advantage of excellent luminance, driving voltage, and response speed, and multicoloring, compared to the inorganic EL device.

A typical organic light emitting display device has an anode formed on the substrate, and a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and a cathode are sequentially formed on the anode. Have Here, the hole transport layer, the light emitting layer and the electron transport layer are organic thin films made of an organic compound.

The driving principle of the organic EL element is that when a voltage is applied between the anode and the cathode, holes injected from the anode are moved to the light emitting layer via the hole transport layer. On the other hand, electrons are injected into the light emitting layer from the cathode via the electron transport layer, and carriers are recombined in the light emitting layer to generate excitons. The exciton is changed from the excited state to the ground state, whereby the fluorescent molecules in the light emitting layer emit light to form an image. At this time, the excited state falls to the ground state through the singlet excited state and emits light is called 'fluorescence', and the triplet excited state falls to the ground state through the excited state is called 'phosphorescence'. In the case of fluorescence, the probability of singlet excited state is 25% (triple state 75%) and there is a limit of luminous efficiency, whereas phosphorescence can be used to triplet 75% and singlet excited state 25%. Can be up to 100% internal quantum efficiency.

Phosphorescent materials generally have a structure of organometallic compounds containing heavy atoms, and the use of such phosphorescent materials causes excitons in the triplet state, which were originally forbidden transitions, to emit light through an allowable transition. The phosphorescent material can use triplet excitons with a 75% generation probability and can have a much higher luminous efficiency than fluorescent materials using singlet excitons with a 25% generation probability.

The light emitting layer using the phosphorescent material is composed of a host material and a dopant material that emits light by transferring energy therefrom. As the dopant material, various materials using iridium metal compounds have been reported at Princeton University and the University of Southern California. In particular, as the light emitting material, Ir compounds based on (4,6-F ₂ ppy) ₂ Irpic or fluorinated ppy ligand structures have been developed, and CBP (4,4 ') is a host material for these light emitting materials. -N, N'-dicarbazole-biphenyl) is widely used.

Recently, a method of using a carbazole compound having a triplet energy band gap larger than CBP as a host when forming a light emitting layer using a phosphorescent material has been known. However, even when a carbazole compound known to date is used, the efficiency and lifespan characteristics of the phosphorescent device have been improved. There was a lot of room for improvement because it did not reach a satisfactory level.

Accordingly, an aspect of the present invention is to provide an organic light emitting display device having improved efficiency and lifetime characteristics by solving the above problems.

In order to achieve the above technical problem, the present invention

In an organic light emitting display device having a light emitting layer between a first electrode and a second electrode,

The light emitting layer includes two or more phosphorescent host materials and one phosphorescent dopant material, and the two or more phosphorescent host materials and phosphorescent dopant materials are present to have a concentration gradient along the thickness of the light emitting layer. Provided is an element.

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

In the present invention, an organic light emitting display device in which two or more materials are used as a phosphorescent host when forming an emission layer including a phosphorescent host and a phosphorescent dopant, and the phosphorescent host material and the phosphorescent dopant material have a concentration gradient along the thickness of the emission layer. To provide.

According to one embodiment of the present invention, as the two or more phosphorescent host materials, a hole transporting material having a hole transporting property and an electron transporting material having an electron transporting property are used together, and the mixed phosphorescent host material and the phosphorescent dopant material have a concentration gradient. The luminous efficiency and lifespan characteristics of the organic light emitting display device are improved to have a.

According to one embodiment of the present invention, a hole transporting layer is formed between the first electrode and the light emitting layer, an electron transporting layer is formed between the light emitting layer and the second electrode, and the concentration of the hole transporting material is the hole transporting layer and the light emitting layer. It is preferable to gradually decrease along the film thickness of the light emitting layer from the contact portion to the portion where the electron transporting layer and the light emitting layer are in contact with each other.

According to another embodiment of the present invention, a hole transporting layer is formed between the first electrode and the light emitting layer, an electron transporting layer is formed between the light emitting layer and the second electrode, and the concentration of the electron transporting material is the hole transporting layer. It is preferable that the light emitting layer gradually increases along the film thickness of the light emitting layer toward the contacting area between the electron transporting layer and the light emitting layer.

The concentration of the phosphorescent dopant material may be gradually increased or decreased depending on the thickness of the light emitting layer from a portion where the hole transporting layer and the light emitting layer are in contact with each other.

According to another embodiment of the present invention, a hole transporting layer is formed between the first electrode and the light emitting layer, an electron transporting layer is formed between the light emitting layer and the second electrode, and the concentration of the hole transporting material is determined by the light emitting layer and the electron transporting layer. It is preferable to increase / decrease in the form of a quadratic function having a maximum value at the contact portion and a portion where the light emitting layer and the hole transport layer are in contact, having a minimum value at the center of the light emitting layer, and having a positive slope along the film thickness of the light emitting layer.

In addition, the concentration of the electron transporting material has a minimum value at a portion where the light emitting layer and the electron transporting layer are in contact with each other and a portion where the light emitting layer and the hole transporting layer are in contact with each other. It is preferable to increase or decrease in the form of a quadratic function.

The term " second order function " as used herein refers to a function represented by the equation y = ax ² + bx + c, and the graph refers to a parabola with an axis parallel to the y axis on the xy plane. If the slope is positive, i.e., a> 0, it is convex downward. If the slope is negative, i.e., a <0, it is convex upward.

Accordingly, the concentration of the hole transporting material has a maximum value in the quadratic function of the positive and negative coefficients a in a portion where the electron transporting layer and the light emitting layer are in contact with each other, and a hole transporting layer and the light emitting layer are in contact with each other. Has

In addition, the concentration of the electron transporting material has a minimum value in the quadratic increase / decrease form having a negative coefficient a and a portion where the electron transporting layer and the light emitting layer are in contact with each other, and the hole transporting layer and the light emitting layer are in contact with each other. Has

The light emitting layer may be formed of a carbazole-based host material, a fluorene-based host material, and a phosphorescent dopant material, and the concentration of the carbazole-based host material may be in the form of a quadratic function having a positive coefficient a along the thickness of the light emitting layer. The concentration of the oren-based host material may be in the form of a quadratic function with a negative coefficient a, and the concentration of the phosphorescent dopant material may be in the form of a quadratic function with a negative coefficient a.

On the other hand, the weight ratio of the hole transporting material to the electron transporting material is maintained between 9: 1 and 1: 9. If the weight ratio is greater than 9: 1 or less than 1: 9, it is not preferable because the properties are not improved compared to a single host, and the effect of the concentration gradient is not shown.

The hole transporting material having the hole transporting property uses a carbazole compound, and examples of the carbazole compound include, but are not limited to, 1,3,5-tricarbazolylbenzene, 4,4 ′. Biscarbazolylbiphenyl (CBP), polyvinylcarbazole, m-bis carbazolylphenyl, 4,4'-biscarbazolyl-2,2'-dimethylbiphenyl (dmCBP), 4,4 ', 4 " -Tri (N-carbazolyl) triphenylamine, 1,3,5-tri (2-carbazolylphenyl) benzene, 1,3,5-tris (2-carbazolyl-5-methoxyphenyl) benzene and bis It is preferably at least one selected from the group consisting of (4-carbazolylphenyl) silane.

The material having an electron transporting property may be at least one compound selected from an organometallic complex including a metal and an organic ligand, a spirofluorene compound, an oxadiazole compound, a phenanthroline compound, a triazine compound, and a triazole compound. Can be.

Examples of the organometallic complex include bis (8-hydroxyquinolato) biphenoxy metal and bis (8-hydroxyquinolato) phenoxy metal. hydroxyquinolato) phenoxy metal}, bis (2-methyl-8-hydroxyquinolato) biphenoxy metal {bis (2-methyl-8-hydroxyquinolato) biphenoxy metal}, bis (2-methyl-8-hydroxyqui Norlato) phenoxy metal) {bis (2-methyl-8-hydroxyquinolato) phenoxy metal} and bis (2- (2-hydroxyphenyl) quinolato) metal {bis (2- (2-hydroxyphenyl) quinolato) Metal} and at least one selected from the group consisting of: the metal is aluminum (Al), zinc (Zn), beryllium (Be), or gallium (Ga). The electron transporting materials are particularly preferably bis (8-hydroxyquinolato) biphenoxy aluminum, bis (8-hydroxyquinolato) phenoxy aluminum, bis (2-methyl-8-hydroxyquinolato) Phenoxy aluminum, bis (2-methyl-8-hydroxyquinolato) phenoxy aluminum or bis (2- (2-hydroxyphenyl) quinolato) zinc is preferred.

The spirofluorene-based compound is a structure having a linking ring between two spirofluorenes, the linkage is triazole, oxadiazole, naphthalene, anthracene Or phenyl, or the like, and the position 9 of each fluorene is substituted with O, S, Se, NR, PR, or the like, or NR or PR is substituted between two spirofluorenes. It can be a structure that directly connects. Each R is H, or a C 6 to C 20 alkyl group, a C 5 to 20 aryl group having 1 to 20 carbon atoms, a C 2 to 20 heteroaryl group, and a C 1 to 20 alkoxy group having 6 carbon atoms It is a substituent selected from the group which consists of an aryl group of 20. Preferably, the spirofluorene-based compound is 2,5-disspirobifluorene-1,3,4-oxadiazole (2,5-Dispirobifluorene-1,3,4-oxadiazole).

Examples of the oxadiazole-based compound include (4-biphenylyl) -5- (4-tertbutylphenyl) -1,3,4-oxadiazole and the like, and examples of the phenanthroline-based compound include 2,9-dimethyl-4,7-diphenyl-9,10-phenanthroline (BCP), and the like. Examples of the triazine-based compound include 2,4,6-tris (diphenylamino) -1. , 3,5-triazine, 2,4,6-tricarbazolo-1,3,5-triazine, 2,4,6-tris (N-phenyl-2-naphthylamino) -1,3, 5-triazine or 2,4,6-tris (N-phenyl-1-naphthylamino) -1,3,5-triazine, etc. are mentioned. Examples of the triazole-based compound include 3-phenyl-4- (1'-naphthyl) -5-phenyl-1,2,4-triazole.

In another embodiment of the present invention, the concentration of the dopant is a second function of increasing and decreasing the negative slope along the film thickness of the light emitting layer, the portion in contact with the electron transport layer and the light emitting layer, and the portion in contact with the hole transport layer and the light emitting layer It has a minimum value and has a maximum value at the center of the light emitting layer.

The content of the phosphorescent dopant is preferably 5 to 15 parts by weight based on 100 parts by weight of the total weight of the host contained in the light emitting layer, and the content of the phosphorescent dopant is secondarily functionally changed according to the film thickness of the light emitting layer.

As the phosphorescent dopant used in forming the light emitting layer of the present invention, an organic metal complex may be used as the light emitting material. For example, a platinum complex (PtOEP), a zinc complex (ZnTPP), Eu (TTFA) ₃ Phen, an iridium complex, or the like may be used. Non-limiting examples of the iridium complex, bisthienylpyridine acetylacetonate Iridium, bis (benzothienylpyridine) acetylacetonate iridium {bis (benzothienylpyridine) acetylacetonate Iridium}, bis (2 -Phenylbenzothiazole) acetylacetonate iridium {bis (2-phenylbenzothiazole) acetylacetonate Iridium}, bis (1-phenylisoquinoline) iridium acetylacetonate {bis (1-phenylisoquinoline) Iridium acetylacetonate}, tris (1-phenyliso Tris (1-phenylisoquinoline) Iridium}, tris (phenylpyridine) Iridium}, tris (2-phenylpyridine) Iridium}, tris Tris (3-biphenylpyridine) iridium, tris (4-biphenylpyridine) iridium, and the like.

According to another embodiment of the present invention, at least one selected from a hole injection layer and a hole transport layer between the first electrode and the light emitting layer may be further provided, a hole blocking layer, an electron transport layer and between the light emitting layer and the second electrode One or more selected from the electron injection layer may be further provided.

Hereinafter, a method of manufacturing an organic light emitting display device according to the present invention will be described.

Referring to FIGS. 1A-1C, a method of manufacturing an organic light emitting diode according to an exemplary embodiment of the present invention is as follows.

First, an anode is formed on a substrate by coating an anode material, which is a first electrode. Herein, a substrate used in a conventional organic light emitting display device is used, and a glass or organic substrate or a transparent plastic substrate having excellent transparency, surface smoothness, ease of handling, and waterproofness is preferable. The anode material may be a high work function metal (≥4.5 eV), or a transparent and highly conductive indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO ₂ ), and zinc oxide. (ZnO) or the like is used.

On the anode, the hole injection layer material is subjected to thermal evaporation in a high vacuum, or, depending on the type of material used, spin-coating or dip-coating after melting in a solution. , Doctor-blading, inkjet printing, or thermal transfer, organic vapor deposition (OVPD), or the like.

The hole injection layer HIL is selectively formed using a method such as the above-described vacuum thermal deposition or spin coating. It is preferable that the thickness of a hole injection layer is 50-1500 kPa here. If the thickness of the hole injection layer is less than 50 kV, the hole injection characteristic is lowered, and if the thickness of the hole injection layer is more than 1500 kV, it is not preferable because of the increase of the driving voltage.

The hole injection layer material is not particularly limited, and copper phthalocyanine (CuPc) or Starburst type amines such as TCTA, m-MTDATA, IDE406 (Idemitsu Corp. material), and the like may be used as the hole injection layer.

A hole transport layer (HTL) is selectively formed on the hole injection layer formed according to the above process by various methods such as vacuum thermal deposition or spin coating, as illustrated above. The hole transport material is not particularly limited, and N, N'-bis (3-methylphenyl) -N, N'-diphenyl- [1,1-biphenyl] -4,4'-diamine (TPD), N, N'-di (naphthalen-1-yl) -N, N'-diphenyl benzidine, N, N'-di (naphthalen-1-yl) -N, N'-diphenyl-benxidine: α-NPD) , IDE320 (Idemitsu Co., Ltd.), etc. are used. It is preferable that the thickness of a positive hole transport layer is 50-1500 kPa here. If the thickness of the hole transport layer is less than 50 kV, the hole transport property is deteriorated.

Subsequently, the light emitting layer EML is formed on the hole transport layer by using a mixture of the above-described electron transport material and hole transport material as a host and a phosphorescent dopant together. The light emitting layer forming method is not particularly limited, but various methods such as the above-described vacuum deposition, inkjet printing, laser transfer, photolithography, organic vapor deposition (OVPD), etc. may be used. .

It is preferable that the thickness of the said light emitting layer is 100-800 GPa. If the thickness of the light emitting layer is less than 100 kW, the efficiency and lifetime are lowered. If the thickness of the light emitting layer is more than 800 kW, the driving voltage increases, which is not preferable. The light emitting layer is formed to include two or more phosphorescent host materials and one phosphorescent dopant material, and the two or more phosphorescent host materials and phosphorescent dopant materials are formed to have a concentration gradient along the thickness of the light emitting layer. In order to form the light emitting layer having the concentration gradient of the present invention, organic vapor phrase deposition technique is preferably used. Source temperature, carrier gas flow rate, and chamber pressure are adjusted to precisely control the concentration of organic matter in the carrier gas to accurately reproduce the light emitting layer at various deposition rates. In the manufacturing method, it is possible to directly control the deposition rate of the organic material doped by the flow rate of the carrier gas. Since the flow rate of the gas can be controlled even in a very short time, a desired doping rate can be obtained, and a light emitting layer having a concentration gradient can be produced when the doping rate is continuously changed.

A hole blocking layer HBL is selectively formed on the light emitting layer by using a method such as vacuum deposition or spin coating described above. The material for the hole blocking layer used at this time is not particularly limited, but should have ionization potential higher than the light emitting compound while having electron transport ability, and typically Balq, BCP, TPBI and the like are used. If the thickness of the hole blocking layer is preferably 30 to 500 kPa. If the thickness of the hole blocking layer is less than 30 kW, the hole blocking property is not good and the efficiency is lowered. If the hole blocking layer is more than 500 kW, it is not preferable to increase the driving voltage.

An electron transport layer forms an electron transport layer (ETL) on the hole blocking layer as a vacuum deposition method or a spin coating method. It does not restrict | limit especially as an electron carrying layer material, Alq3 can be used. It is preferable that the thickness of the said electron carrying layer is 50-600 GPa. If the thickness of the electron transport layer is less than 50 kW, the lifespan characteristics are lowered. If the electron transport layer is more than 600 kW, it is not preferable to increase the driving voltage.

In addition, an electron injection layer EIL may be selectively stacked on the electron transport layer. As the electron injection layer forming material, materials such as LiF, NaCl, CsF, Li ₂ O, BaO, and Liq can be used. It is preferable that the thickness of the said electron injection layer is 1-100 kPa. If the thickness of the electron injection layer is less than 1 kW, the driving voltage is not high because it does not serve as an effective electron injection layer, and if it exceeds 100 kW, the driving voltage acts as an insulating layer.

Subsequently, a cathode, the second electrode, is formed on the electron injection layer by vacuum deposition, sputtering, and metal-organic chemical vapor deposition. Thus, the organic light emitting display element is completed.

The cathode metal is lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag ) And the like are used.

As described above, the organic light emitting display device of the present invention may further form an intermediate layer of one or two layers according to the needs of the anode, the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer, the electron injection layer, and the cathode. . In addition to the above-mentioned layers, a hole blocking layer and an electron blocking layer may also be included.

Hereinafter, the present invention will be described with reference to the following examples, but the present invention is not limited only to the following examples.

Example 1

The anode cuts a corning 15Ω / cm ² (1200Å) ITO glass substrate to 50mm x 50mm x 0.7mm and ultrasonically cleans for 5 minutes in isopropyl alcohol and pure water, followed by UV and ozone cleaning for 30 minutes. Was used.

N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine (NPD) was vacuum deposited on the substrate to form a hole transport layer having a thickness of 600 kPa.

4,4'-biscarbazolylbiphenyl (CBP), a hole transporting material, and 2,5-disspirobifluorene-1,3,4-oxadiazole (2), an electron transporting material, as a host on the hole transporting layer , 5-Dispirobifluorene-1,3,4-oxadiazole) formed a light emitting layer having a concentration gradient.

In this case, when the weight part y% of CBP is expressed as a quadratic function of the thickness x 의 of the light emitting layer, a function of y = 0.00356x ² -1.06667x + 90 follows. In addition, 2,5-disspirofluorene-1,3,4-oxadiazole having an opposite tendency to the opposite CBP follows the formula of y = -0.00356x ² + 1.06667x + 10.

In the portion having 0Å and 300Å, the CBP is 90 parts by weight based on 100 parts by weight of the host material, and the 2,5-disspirobifluorene-1,3,4-oxadiazole is 10 parts by weight. Is 150 의, CBP is 10 parts by weight based on 100 parts by weight of the host material, and 2,5-disspirofluorene-1,3,4-oxadiazole is 90 parts by weight. A structure having was formed. In addition, the phosphorescent dopant Ir (pq) ₂ (acac) is 5 parts by weight based on 100 parts by weight of the total content of the host and dopant material in the portion having a thickness of 0Å and 300Å, and 9 parts by weight at the portion having a thickness of 150Å. In order to maintain the concentration gradient of the difference function, vacuum deposition was performed by organic vapor deposition (OVPD) to form a light emitting layer having a thickness of about 300 Pa.

Again, when the weight part y% is expressed as a quadratic function of the thickness xÅ of the light emitting layer, a function of y = -0.00178x ² + 0.5333x + 50 is followed.

Alq3, an electron transporting material, was deposited on the emission layer to form an electron transporting layer having a thickness of about 300 kHz.

An LiF / Al electrode was formed by sequentially vacuum depositing LiF 10kV (electron injection layer) and Al 1000kV (cathode) on the electron transport layer to manufacture an organic light emitting display device.

Comparative Example 1

The anode cuts a corning 15Ω / cm ² (1200Å) ITO glass substrate to 50mm x 50mm x 0.7mm and ultrasonically cleans for 5 minutes in isopropyl alcohol and pure water, followed by UV and ozone cleaning for 30 minutes. Was used.

NPD was vacuum deposited on the substrate to form a hole transport layer having a thickness of 600 kHz. A light emitting layer was formed on the hole transport layer by vacuum depositing 5 wt% of a phosphorescent dopant Ir (pq) 2 (acac) on a host 4,4'-biscarbazolylbiphenyl (CBP).

Alq3, an electron transporting material, was deposited on the emission layer to form an electron transporting layer having a thickness of about 300 kHz.

LiF 10 Å (electron injection layer) and Al 1000 Å (cathode) were sequentially vacuum deposited on the electron transport layer to form a LiF / Al electrode to manufacture an organic light emitting display device as illustrated in FIG. 1A.

In the organic light emitting diode display device manufactured according to Example 1 and Comparative Example 1, the driving voltage, efficiency, and lifespan characteristics were investigated, and the results are shown in Table 1 below.

Luminance (cd / m2) Driving voltage (V) Efficiency (cd / V) Life time (hours) Comparative Example 1 1000 6.1988 31.8114 450 Example 1 1000 5.1165 40.1336 1100

In the case of Comparative Example 1 The driving voltage was 5.1165V, and in Example 1, the driving voltage was 6.1988V.

In the case of Comparative Example 1 For the embodiment was shown in the intensity 1000cd / m ² to the Efficiency 31.8114cd / A, Example 1, the luminance was at 1000cd / m ² to 40.1336cd / A.

In addition, the lifespan characteristics are represented by the time when the initial emission luminance decreases by 50%. The organic light emitting diode display of Example 1 is about 5,000 hours at 5,000 cd / m ² , and the organic light emitting diode display of Comparative Example 1 is 5,000 cd / m. It was about 500 hours at m ² , Example 1 was confirmed that the life characteristics are improved by about 2 times or more compared to Comparative Example 1.

The organic light emitting diode display of the present invention uses two or more host materials when forming a light emitting layer including a phosphorescent dopant, and manufactures a phosphorescent device by appropriately adjusting the concentration of the host material and the dopant according to the thickness of the light emitting layer, thereby improving efficiency and life characteristics. Can be improved.

Claims (21)

In an organic light emitting display device having a light emitting layer between a first electrode and a second electrode, The light emitting layer includes a phosphorescent host material of a hole transporting material and an electron transporting material having a weight ratio of 9: 1 to 1: 9, and one phosphorescent dopant material. The hole transport material has a maximum value at a portion where the light emitting layer, the electron transport layer and the hole transport layer contact each other, has a minimum value at the center of the light emitting layer, and has a positive slope along the film thickness of the light emitting layer. Increase and decrease, The concentration of the electron transporting material has a minimum value at a portion where the light emitting layer, the electron transporting layer, and the hole transporting layer are in contact with each other, has a maximum value at the center of the light emitting layer, and has a negative slope along the film thickness of the light emitting layer. An organic light emitting display device characterized by increasing and decreasing. delete delete delete The organic light emitting diode display as claimed in claim 1, wherein the concentration of the phosphorescent dopant material is gradually increased along the film thickness of the light emitting layer from a portion where the hole transporting layer and the light emitting layer are in contact with each other. . The organic light emitting diode display as claimed in claim 1, wherein the concentration of the phosphorescent dopant material gradually decreases along the film thickness of the light emitting layer from a portion where the hole transporting layer and the light emitting layer are in contact with each other. . delete delete 2. The secondary of claim 1, wherein the concentration of the dopant has a minimum at a portion where the light emitting layer is in contact with the electron transporting layer and the hole transporting layer, has a maximum value at the center of the light emitting layer, and has a negative slope along the film thickness of the light emitting layer. An organic light emitting display device, characterized in that the increase and decrease in the form of a function. delete The organic light emitting diode display of claim 1, wherein the light emitting layer comprises a carbazole-based host material, a fluorene-based host material, and a phosphorescent dopant material.  The method of claim 11, wherein the concentration of the carbazole-based host material in the light emitting layer is in the form of a quadratic function having a positive slope along the film thickness of the light emitting layer, the concentration of the fluorene-based host material is a secondary function having a negative slope And the concentration of the phosphorescent dopant material is in the form of a quadratic function with a negative slope. The organic light emitting display device of claim 1, wherein the hole transport material is a carbazole compound. The method of claim 13, wherein the carbazole compound is 1,3,5-tricarbazolylbenzene, 4,4'-biscarbazolylbiphenyl, polyvinylcarbazole, m-biscarbazolylphenyl, 4,4'- Biscarbazolyl-2,2'-dimethylbiphenyl, 4,4 ', 4 "-tri (N-carbazolyl) triphenylamine, 1,3,5-tri (2-carbazolylphenyl) benzene, 1, An organic light emitting display device, characterized in that at least one selected from the group consisting of 3,5-tris (2-carbazolyl-5-methoxyphenyl) benzene, and bis (4-carbazolylphenyl) silane. The organic light emitting diode of claim 1, wherein the electron transport material is at least one compound selected from organometallic complexes, spirofluorene compounds, oxadiazole compounds, phenanthroline compounds, triazine compounds, and triazole compounds. Display elements. The organometallic complex of claim 15 wherein the organometallic complex is a bis (8-hydroxyquinolato) biphenoxy metal, a bis (8-hydroxyquinolato) phenoxy metal, bis (2-methyl-8-hydroxy Quinolato) biphenoxy metal, bis (2-methyl-8-hydroxyquinolato) phenoxy metal) and bis (2- (2-hydroxyphenyl) quinolato) metal Above, the metal is Al, Zn, Be, or Ga, the organic light emitting display device characterized in that. The method of claim 15, wherein the spirofluorene-based compound is 2,5-disspirobifluorene-1,3,4-oxadiazole (2,5-Dispirobifluorene-1,3,4-oxadiazole), The oxadiazole compound is (4-biphenylyl) -5- (4-tertbutylphenyl) -1,3,4-oxadiazole, and the phenanthroline compound is 2,9-dimethyl-4,7-di Phenyl-9,10-phenanthroline, and the triazine-based compound is 2,4,6-tris (diarylamino) -1,3,5-triazine, 2,4,6-tris (diphenylamino) -1,3,5-triazine, 2,4,6-tricarbazolo-1,3,5-triazine, 2,4,6-tris (N-phenyl-2-naphthylamino) -1, 3,5-triazine, 2,4,6-tris (N-phenyl-1-naphthylamino) -1,3,5-triazine, and 2,4,6-trisbiphenyl-1,3, At least one selected from the group consisting of 5-triazines, and the triazole-based compound is 3-phenyl-4- (1'-naphthyl) -5-phenyl-1,2,4-triazole device. The organic light emitting diode display of claim 1, wherein the phosphorescent dopant is 5 to 15 parts by weight based on 100 parts by weight of the total weight of the light emitting layer forming material. 19. The phosphate dopant of claim 18, wherein the phosphorescent dopant is bisthienylpyridine acetylacetonate iridium, bis (benzothienylpyridine) acetylacetonate iridium, bis (2-phenylbenzothiazol) acetylacetonate iridium, bis (1-phenyl Isoquinoline) iridium acetylacetonate, tris (1-phenylisoquinoline) iridium, tris (phenylpyridine) iridium, tris (2-biphenylpyridine) iridium, tris (3-biphenylpyridine) iridium, tris (4-bi Phenylpyridine) iridium; at least one selected from the group consisting of iridium. The organic light emitting diode display as claimed in claim 1, further comprising a hole injection layer between the first electrode and the light emitting layer. The organic light emitting display device of claim 1, further comprising at least one selected from a hole blocking layer and an electron injection layer between the light emitting layer and the second electrode.

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