KR102271666B1 - Organic light emitting diode - Google Patents

Abstract

An organic light emitting device is provided. The organic light emitting device may include a first electrode, a first organic light emitting layer disposed on the first electrode, a connection laminate disposed on the first organic light emitting layer and including a plurality of intermediate connection layers, and a first organic light emitting layer disposed on the connection laminate. a second organic light-emitting layer and a second electrode disposed on the second organic light-emitting layer, wherein the connection stack includes a first intermediate connection layer disposed in contact with the first organic light-emitting layer and a second organic light-emitting layer disposed in contact with the second organic light-emitting layer 2 intermediate connection layers, wherein the LUMO level of the first intermediate connection layer is higher than the LUMO level of the first organic light emitting layer, and the LUMO level of the second intermediate connection layer is higher than the LUMO level of the second organic light emitting layer do. The organic light emitting device according to an embodiment of the present invention has improved lifespan of the device and excellent luminous efficiency.

Description

Organic light emitting device {ORGANIC LIGHT EMITTING DIODE}

The present invention relates to an organic light emitting device, and more particularly, to an organic light emitting device having excellent luminous efficiency and improved lifespan.

An organic light emitting diode display (OLED) is a self-emission type display device that injects electrons and holes from an electrode for electron injection and an electrode for hole injection into an organic light emitting layer, respectively. , a display device using an organic light emitting diode that emits light when excitons in which injected electrons and holes are combined fall from an excited state to a ground state.

The organic light emitting diode display includes a top emission type, a bottom emission type, a dual emission type, etc. depending on the direction in which light is emitted, and a passive matrix type according to a driving method. ) and active matrix type.

Unlike a liquid crystal display (LCD), the organic light emitting diode display does not require a separate light source, so it can be manufactured in a lightweight and thin form. In addition, the organic light emitting diode display is being studied as a next-generation display because it is advantageous in terms of power consumption due to low voltage driving and excellent color realization, response speed, viewing angle, and contrast ratio (CR).

Specifically, the organic light emitting device includes an anode, a hole injection layer (HIL), a hole transport layer (HTL), an organic light emitting layer (Emitting Layer; EML), and an electron transport layer (ETL). ), an electron injection layer (EIL) and a cathode.

As described above, although an organic light emitting device used in an organic light emitting display device may consist of a single organic light emitting layer, an organic light emitting device having a structure having a plurality of organic light emitting layers has been developed to improve light emitting ability.

An organic light emitting device including a plurality of organic light emitting layers includes a first organic light emitting layer and a second organic light emitting layer sequentially stacked between an anode and a cathode, and an n-type charge is generated between the first organic light emitting layer and the second organic light emitting layer and an inter connecting layer (ICL) in which the layer and the p-type charge generating layer are stacked. The n-type charge generation layer and the p-type charge generation layer control the balance of charges injected into the first organic emission layer and the second organic emission layer.

Specifically, charges are generated between the n-type charge generation layer and the p-type charge generation layer, and electrons move to the first organic light emitting layer adjacent to the n-type charge generation layer, combine with holes injected from the anode to form excitons. , and the holes move to the second organic light emitting layer adjacent to the p-type charge generation layer, combine with electrons injected from the cathode to form excitons, so that light is emitted from the first organic light emitting layer and the second organic light emitting layer at the same time can do.

FIG. 1 is a diagram illustrating an energy band diagram for an organic light emitting device including a conventional intermediate connection layer by way of example. In FIG. 1 , LUMO (Lowest) of a hole transport layer (HTL), a first organic light emitting layer (EML1), an intermediate connection layer (ICL), a second organic light emitting layer (EML2), and an electron transport layer (ETL) included in a conventional organic light emitting device Unoccupied Molecular Orbitals) levels and Highest Occupied Molecular Orbitals (HOMO) levels are shown.

In a conventional organic light emitting device having a plurality of organic light emitting layers showing an energy band diagram as shown in FIG. 1 , there is a problem in that luminous efficiency is reduced and lifespan is reduced.

Specifically, referring to FIG. 1 , when the LUMO level of the intermediate connection layer ICL is lower than that of the first organic emission layer EML1 and the second organic emission layer EML2, holes and electrons are formed in the first organic emission layer EML1. and a phenomenon in which excitons are formed by bonding in layers other than the second organic light emitting layer EML2. In addition, even in the case of excitons bonded in the first organic emission layer EML1 and the second organic emission layer EML2, there is a high probability that they exist at the interface of the intermediate layer ICL. Therefore, when the excitons fall from the excited state to the ground state, the organic There is a problem in that energy is transferred to a layer other than the light emitting layer.

In this case, although excitons fall from the excited state to the ground state, they do not emit a desired color, so that the luminous efficiency is reduced. As a result, an applied current is increased in the organic light emitting device, and electrical and thermal stress is increased inside the organic light emitting device, thereby increasing power consumption. Finally, the increased power consumption causes a problem in that the lifespan of the organic light emitting device is reduced.

[Related technical literature]

1. Organic light emitting display device (Patent Application No. 10-2011-0146325)

As described above, the inventors of the present invention, in the case of an organic light emitting device including a plurality of organic light emitting layers, according to the position of the LUMO level of the intermediate connection layer disposed in contact with the first organic light emitting layer and the second organic light emitting layer, It was found that the luminous efficiency and lifetime of the device may be reduced. Accordingly, the inventors of the present invention, in an organic light emitting device including a multi-layered organic light emitting layer, improve the luminous efficiency and lifespan of the organic light emitting device to have excellent reliability, an intermediate connection layer and an organic light emitting layer having a new LUMO level Invented an organic light emitting device comprising.

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic light emitting device capable of minimizing a decrease in luminous efficiency that occurs because recombination of electrons and holes does not occur at an appropriate position.

Another object to be solved by the present invention is to provide an organic light emitting device capable of minimizing a decrease in lifetime caused by an increase in current applied to the inside of the organic light emitting device.

An organic light emitting diode according to an embodiment of the present invention for achieving the above object includes a first electrode, a first organic light emitting layer disposed on the first electrode, and a plurality of intermediate connections disposed on the first organic light emitting layer A connection laminate including a layer, a second organic emission layer disposed on the connection laminate, and a second electrode disposed on the second organic emission layer, wherein the connection laminate is in contact with the first organic emission layer a first intermediate connection layer disposed in contact with the second intermediate connection layer and a second intermediate connection layer disposed in contact with the second organic emission layer, wherein a LUMO level of the first intermediate connection layer is higher than a LUMO level of the first organic emission layer, and the second intermediate connection layer The LUMO level of the connection layer is higher than the LUMO level of the second organic light emitting layer.

According to another feature of the present invention, the difference between the LUMO level of the first intermediate connection layer and the LUMO level of the first organic emission layer and the difference between the LUMO level of the second intermediate connection layer and the LUMO level of the second organic emission layer are 0.1 eV or more, respectively. characterized in that

According to another feature of the present invention, the first intermediate connection layer is an n-type charge generation layer, and the second intermediate connection layer is a p-type charge generation layer.

According to another feature of the present invention, the first intermediate connecting layer comprises at least one selected from the group consisting of phenanthroline derivatives, anthracene derivatives, naphthalene derivatives and biphenyl derivatives. .

According to another embodiment of the present invention, a third intermediate connecting layer and a fourth intermediate connecting layer are disposed between the first intermediate connecting layer and the second intermediate connecting layer, the fourth intermediate connecting layer being the third intermediate connecting layer. It is characterized in that it is disposed on a layer.

According to another feature of the present invention, the third intermediate connection layer is an n-type charge generation layer, and the fourth intermediate connection layer is a p-type charge generation layer.

According to another feature of the present invention, the first intermediate connection layer is an auxiliary electron transport layer, and the second intermediate connection layer is an auxiliary hole transport layer.

According to another feature of the present invention, the first intermediate connection layer and the third intermediate connection layer include the same host.

According to another feature of the present invention, the second intermediate connection layer and the fourth intermediate connection layer include the same host.

According to another feature of the present invention, the LUMO level of the intermediate connection layer including any one selected from the group consisting of the third intermediate connection layer and the fourth intermediate connection layer is the LUMO level of the first organic emission layer and the LUMO level of the second organic emission layer. It is characterized in that it is lower than the LUMO level of

According to another feature of the present invention, the LUMO level of the first organic light emitting layer and the LUMO level of the second organic light emitting layer are the same.

According to another feature of the present invention, the first organic emission layer and the second organic emission layer include the same host.

The details of other embodiments are included in the detailed description and drawings.

According to the present invention, in an organic light emitting device including a plurality of organic light emitting layers, by disposing an intermediate connection layer having a higher LUMO level than that of an adjacent organic light emitting layer, holes and electrons are recombined in each organic light emitting layer, so that luminous efficiency This decrease can be suppressed.

In addition, the present invention can improve the lifespan of the organic light emitting device by reducing electrical and thermal stress that may occur in the organic light emitting device.

The effect according to the present invention is not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a diagram showing an energy band diagram for a conventional organic light emitting device.
2A is a schematic cross-sectional view for explaining an organic light emitting device according to an embodiment of the present invention.
2B is a schematic cross-sectional view for explaining an organic light emitting diode according to another embodiment of the present invention.
3 is a diagram illustrating an energy band diagram of an organic light emitting diode according to an embodiment of the present invention.
4 is a diagram showing an energy band diagram of the organic light emitting device of Example 1. Referring to FIG.
5 is a diagram illustrating an energy band diagram of an organic light emitting diode according to Example 2;
6 is a diagram illustrating an energy band diagram of an organic light emitting diode of Comparative Example 2. Referring to FIG.
FIG. 7 is a view showing the decrease in luminance with time for the organic light emitting devices of Examples 1, 2, and Comparative Examples 1 and 2;

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims.

The shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, and thus the present invention is not limited to the illustrated matters. Like reference numerals refer to like elements throughout. In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the case in which the plural is included is included unless otherwise explicitly stated.

In interpreting the components, it is interpreted as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship of two parts is described as 'on', 'on', 'on', 'beside', etc., 'right' Alternatively, one or more other parts may be positioned between the two parts unless 'directly' is used.

Reference to a device or layer “on” another device or layer includes any intervening layer or other device directly on or in the middle of another device.

Although first, second, etc. are used to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the spirit of the present invention.

Like reference numerals refer to like elements throughout.

The size and thickness of each component shown in the drawings are illustrated for convenience of description, and the present invention is not necessarily limited to the size and thickness of the illustrated component.

Each feature of the various embodiments of the present invention may be partially or wholly combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments may be implemented independently of each other or may be implemented together in a related relationship. may be

In the present specification, the intermediate connecting layer (inter connecting layer) includes all intermediate layers that may exist between the plurality of organic light emitting layers, and according to the characteristics of the organic light emitting device including the plurality of organic light emitting layers, generally an n-type charge generating layer and and a p-type charge generation layer.

Also, in the present specification, the LUMO and HOMO levels of a specific layer mean the LUMO and HOMO levels of a host material constituting the layer.

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

The organic light emitting device of the present invention includes a first electrode, a first organic light emitting layer disposed on the first electrode, a connection laminate disposed on the first organic light emitting layer and including a plurality of intermediate connection layers, and a connection laminate on the connection laminate a second organic light emitting layer disposed on the second organic light emitting layer and a second electrode disposed on the second organic light emitting layer, wherein the connection stack is in contact with the first intermediate connecting layer and the second organic light emitting layer disposed in contact with the first organic light emitting layer It consists of a structure including a second intermediate connection layer disposed to be. In this case, the connection laminate including the plurality of intermediate connection layers is formed by stacking two intermediate connection layers or three or more intermediate connection layers.

2A and 2B are schematic cross-sectional views for explaining the organic light emitting diodes 100 and 200 according to an embodiment of the present invention. The organic light emitting devices 100 and 200 may be applied to a top emission type organic light emitting display device or a bottom emission type organic light emitting display device, respectively. The top emission type organic light emitting display device refers to a method in which light emitted from an organic light emitting layer is emitted toward the top surface of the organic light emitting display device, and in the bottom emission type organic light emitting display device, light emitted from the organic light emitting layer is emitted from the organic light emitting diode display. It refers to a method of emitting light in the direction of the lower surface of the light emitting display device.

The organic light emitting diode 100 illustrated in FIG. 2A is characterized in that it includes a connection stack including two intermediate connection layers. Referring to FIG. 2A , an organic light emitting diode 100 according to an embodiment of the present invention includes a first electrode 110 (anode), a hole injection layer (HIL), and a hole transport layer 130 (hole transporting). layer: HTL), a first organic light emitting layer 140 (emission layer: EML1), a first intermediate connecting layer (151, inter connecting layer: ICL1), a second intermediate connecting layer (152, inter connecting layer: ICL2), a second It includes an organic emission layer 160 (emission layer: EML2), an electron transporting layer (ETL), a second electrode 180 (cathode), and a capping layer (CPL).

The first electrode 110 (anode) is an anode, and includes tin oxide (TO), indium tin oxide (ITO), indium zinc oxide (IZO), and indium tin oxide (Indium Tin). It is formed of a transparent conductive material such as zinc oxide (ITZO). In addition, the reflective material layer such as silver (Ag) or a silver alloy (Ag alloy) may be included together.

The hole injection layer 120 may serve to facilitate hole injection, and may include HATCN (1,4,5,8,9,11-hexaazatriphenylene-hexanitrile) and CuPc (cupper phthalocyanine), PEDOT (poly(3) ,4)-ethylenedioxythiophene), PANI (polyaniline), and NPD (N,N-dinaphthyl-N,N'-diphenylbenzidine) may be made of any one or more selected from the group consisting of, but is not limited thereto.

The hole transport layer 130 is disposed on the hole injection layer 120 . The hole transport layer 130 serves to facilitate the transport of holes, NPD (N,N-dinaphthyl-N,N'-diphenylbenzidine), TPD (N,N'-bis-(3-methylphenyl)-N, Any one selected from the group consisting of N'-bis-(phenyl)-benzidine), s-TAD and MTDATA (4,4',4"-Tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine) It may be made as above, but is not limited thereto.

The first organic emission layer 140 is disposed on the hole transport layer 130 . The first organic light emitting layer may include a light emitting material emitting red, green, or blue light, and the light emitting material may be formed using a phosphorescent material or a fluorescent material.

More specifically, when the first organic emission layer 140 emits red light, it includes a host material including CBP (carbazole biphenyl) or mCP (1,3-bis (carbazol-9-yl)), and PIQIr (acac Any one selected from the group consisting of )(bis(1-phenylisoquinoline) acetylacetonate iridium), PQIr(acac)(bis(1-phenylquinoline) acetylacetonate iridium), PQIr(tris(1-phenylquinoline) iridium) and PtOEP(octaethylporphyrin platinum) It may be made of a phosphorescent material including a dopant including the above, and alternatively, it may be made of a fluorescent material including PBD:Eu(DBM)3(Phen) or Perylene, but is not limited thereto.

In addition, when the first organic light emitting layer 140 emits green light, it includes a host material including CBP or mCP, and an Ir complex including Ir(ppy)3 (fac tris(2-phenylpyridine)iridium). It may be formed of a phosphorescent material including a dopant material, and alternatively, may be formed of a fluorescent material including tris(8-hydroxyquinolino)aluminum (Alq3), but is not limited thereto.

In addition, when the first organic emission layer 140 emits blue light, it may be formed of a phosphorescent material including a host material including CBP or mCP and a dopant material including (4,6-F2ppy)2Irpic. . In addition, spiro-DPVBi, spiro-6P, distylbenzene (DSB), distrylarylene (DSA), may be made of a fluorescent material containing any one selected from the group consisting of PFO-based polymers and PPV-based polymers, but limited thereto doesn't happen

The connection stack 150 is disposed on the first organic light emitting layer 140 . The intermediate connection layer 150 is an intermediate layer including a conductive material disposed between the first organic emission layer 140 and the second organic emission layer 160 to be in contact with the first organic emission layer 140 and the second organic emission layer ( 160) plays a role in regulating the charge balance. The connection stack 150 generally includes an n-type charge generation layer and a p-type charge generation layer according to characteristics of an organic light-emitting device including a plurality of organic emission layers.

Specifically, according to FIG. 2A , the organic light-emitting device 100 includes a first intermediate connection layer 151 and a second intermediate connection layer 152 as a connection stack 150 . In this case, the first intermediate connection layer 151 is adjacent to the first organic emission layer 140 , and the second intermediate connection layer 152 is adjacent to the second organic emission layer 160 .

In this case, it is preferable that the first intermediate connection layer 151 is an n-type charge generation layer, and the second intermediate connection layer 152 is a p-type charge generation layer. That is, the first intermediate connection layer 151 serves as an n-type charge generating layer that helps injection of electrons into the first organic emission layer 140 , and the second intermediate connection layer 152 serves as the second organic emission layer 160 . It acts as a p-type charge generation layer that helps the injection of holes.

More specifically, the first intermediate connection layer 151, which is an n-type charge generating layer serving as an electron injection, may be formed of an alkali metal, an alkali metal compound, an organic material serving as an electron injection, or a compound thereof. In addition, the host material of the first intermediate connection layer 151 may include, for example, n-type (n) derivatives such as phenanthroline derivatives, anthracene derivatives, naphthalene derivatives, and biphenyl derivatives. -type) may be formed of a mixed layer in which an organic material is doped with a dopant such as lithium (Li), but is not limited thereto. In particular, considering the LUMO level of the first organic light emitting layer in contact, a phenanthroline derivative having a high LUMO level is more preferable.

The dopant may be made of a metal having excellent conductivity and a material having a low work function. More specifically, a single material made of an alkali metal or alkaline earth metal, an alloy material in which an alkali metal or alkaline earth metal is mixed, and an alkali metal or alkaline earth metal are used as the dopant. It may consist of any one of the included complex compounds. Although not limited thereto, for example, lithium (Li), sodium (Na), potassium (K), calcium (Ca), silver (Ag), gold (Au), copper (Cu), magnesium (Mg), It may be made of a single material of a metal such as aluminum (Al) or barium (Ba) or an alloy material thereof.

The second intermediate connection layer 152 is disposed on the first intermediate connection layer 151 . The second intermediate connection layer 152 , which is a p-type charge generating layer serving as a hole injection layer, may be formed of an organic material used as a material of the hole transport layer 130 . For example, it may be made of an organic material such as HAT-CN (Hexaazatriphenylene-hexacarbonitrile), F ₄ -TCNQ (tetrafluoro- Tetracyanoquinodimethane), or the like, or a _{metal material such as V 2} O ₅ , MoOx, WO ₃ and the like, but is not limited thereto.

1 , the LUMO level of the first intermediate connection layer 151 and the second intermediate connection layer 152 is the LUMO level of the first organic emission layer 140 or the LUMO level of the second organic emission layer 160 . In a lower case, a phenomenon in which holes and electrons are combined in a layer other than the organic light emitting layer to form excitons occurs. When excitons are formed in a layer other than the organic light emitting layer, it is difficult for the excitons to transfer energy to the organic light emitting layer, so that luminous efficiency is greatly limited. In addition, a significant amount of excitons formed inside the organic light emitting layer are located at the interface of the connection stack 150 , and energy can be transferred to other layers in contact with the organic light emitting layer, so that luminous efficiency is reduced.

However, referring to FIG. 3 , in the organic light emitting diode 100 of the present invention, the LUMO level of the first intermediate connection layer 151 is higher than the LUMO level of the first organic emission layer 140, and the second intermediate connection layer ( It can be seen that the LUMO level of 152 is higher than the LUMO level of the second organic emission layer 160 . In this case, holes and electrons may recombine in the first organic emission layer 140 and the second organic emission layer 160 to form excitons, and the phenomenon of transferring energy to another layer adjacent to the organic emission layer may be minimized.

More specifically, when the LUMO level as in the present invention is satisfied, electrons injected from the first intermediate connection layer 151 into the first organic emission layer 140 are transferred from the hole transport layer 130 to the first organic emission layer. Most of them recombine at (140) to form excitons. In this case, excitons generated in layers other than the first intermediate connection layer 151 are rapidly reduced, and excitons existing at the interface between the first intermediate connection layer 151 and the first organic emission layer 140 are also reduced.

In addition, most of the holes injected from the second intermediate connection layer 152 into the second organic emission layer 160 recombine with electrons injected from the electron transport layer 170 in the second organic emission layer 160 to form excitons. can In particular, the phenomenon that electrons injected from the second electrode do not combine with holes in the second organic light emitting layer 160 and flow into the second intermediate connection layer 152 having a low HOMO level is also greatly reduced, so that the light emission of the organic light emitting device is greatly reduced. A decrease in efficiency and lifespan can be minimized.

In this case, the difference between the LUMO level of the first intermediate connection layer 151 and the LUMO level of the first organic emission layer 140 and the LUMO level of the second intermediate connection layer 152 and the LUMO level of the second organic emission layer 160 Each of the differences is preferably 0.1 eV or more, and more preferably 0.2 eV or more. The difference between the LUMO level of the first intermediate connection layer 151 and the LUMO level of the first organic emission layer 140 and the difference between the LUMO level of the second intermediate connection layer 152 and the LUMO level of the second organic emission layer 160 This is because when the above range is satisfied, the formation of excitons in layers other than the first organic light emitting layer 140 and the second organic light emitting layer 160 is further suppressed, and the lifespan of the organic light emitting device is improved.

The organic light emitting diode 100 of the present invention may further include a diffusion barrier layer disposed between the first intermediate connection layer 151, which is an n-type charge generation layer, and the second intermediate connection layer 152, which is a p-type charge generation layer. have.

When the organic light emitting diode 100 is driven, the metal dopant included in the first intermediate connection layer 151 that is the n-type charge generation layer receives a driving force according to the pressure field, and thus the second intermediate connection layer that is the p-type charge generation layer. It can be diffused to (152). When the metal dopant diffuses into the second intermediate connection layer 152 , the metal dopant moves to the interface of the second organic light emitting layer 160 , and deterioration occurs and the driving voltage increases. Accordingly, by preventing the diffusion of the metal dopant by using the diffusion barrier layer, it is possible to prevent the reduction and deterioration of the lifespan of the organic light emitting diode 100 .

Meanwhile, the organic light emitting diode 100 of the present invention may further include a plurality of intermediate connection layers disposed between the first intermediate connection layer 151 and the second intermediate connection layer 152 .

More specifically, according to FIG. 2B , the connection stack 250 of the organic light emitting device 200 includes a third intermediate connection layer ( ) disposed between the first intermediate connection layer 251 and the second intermediate connection layer 252 . 253 ) and a fourth intermediate connecting layer 254 , wherein the fourth intermediate connecting layer 254 is disposed on the third intermediate connecting layer 253 .

In this case, it is preferable that the third intermediate connection layer 253 is an n-type charge generation layer, and the fourth intermediate connection layer 254 is a p-type charge generation layer. That is, the third intermediate connection layer 253 serves as an n-type charge generation layer that helps injection of electrons into the first organic emission layer 140 , and the fourth intermediate connection layer 254 serves as the second organic emission layer 160 . It acts as a p-type charge generation layer that helps the injection of holes.

The first intermediate connection layer 251 is adjacent to the first organic emission layer 140 , and the second intermediate connection layer 252 is adjacent to the second organic emission layer 160 .

In this case, it is preferable that the first intermediate connection layer 251 is an auxiliary electron transport layer, and the second intermediate connection layer 252 is an auxiliary hole transport layer.

The first intermediate connection layer 251 is an auxiliary electron transport layer, and from the third intermediate connection layer 253, which is an n-type charge generation layer, to the first organic light emitting layer 140, can play a role of injection and transport of electrons, The thickness of the third intermediate connection layer 253 may be adjusted in consideration of electron transport characteristics.

As an auxiliary electron transport layer, the first intermediate connection layer 251 serves to facilitate electron transport, and includes Alq3 (tris(8-hydroxyquinolino)aluminum), PBD(2-(4-biphenylyl)-5-(4) -tert-butylpheny)-1,3,4oxadiazole), TAZ, spiro-PBD, BAlq and SAlq may be made of any one or more selected from the group consisting of, but is not limited thereto.

The second intermediate connection layer 252 is an auxiliary hole transport layer, and serves to facilitate the transport of holes from the fourth intermediate connection layer 254, which is a p-type charge generation layer, to the second organic light emitting layer 160, and NPD ( N,N-dinaphthyl-N,N'-diphenylbenzidine), TPD (N,N'-bis-(3-methylphenyl)-N,N'-bis-(phenyl)-benzidine), s-TAD and MTDATA (4 ,4',4"-Tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine) may consist of any one or more selected from the group consisting of, but is not limited thereto.

Meanwhile, the first intermediate connecting layer 251 and the third intermediate connecting layer 253 include the same host, and the second intermediate connecting layer 252 and the fourth intermediate connecting layer 252 and the fourth intermediate connecting layer 251 and the third intermediate connecting layer 253 may further facilitate the transport of electrons and holes. More preferably, the connection layer 254 includes the same host.

Meanwhile, the LUMO level of the intermediate connection layer including any one selected from the group consisting of the third intermediate connection layer 253 and the fourth intermediate connection layer 254 is the LUMO level of the first organic emission layer 140 and the second organic emission layer 140 . It may be lower than the LUMO level of the emission layer 160 . A feature of the present invention is that the LUMO level of the first intermediate connection layer 251 and the second intermediate connection layer 252 disposed in contact with the first organic emission layer 140 and the second organic emission layer 160 is in contact. It is sufficient if it is higher than the LUMO level of the organic light emitting layer 140 and the second organic light emitting layer 160, and a third intermediate connecting layer ( 253) or the LUMO level of the fourth intermediate connection layer 254 may be lower than the LUMO level of the first organic emission layer 140 and the LUMO level of the second organic emission layer 160 .

A second organic emission layer 160 is disposed on the second intermediate connection layer 252 . The second organic light emitting layer 160 may include a light emitting material emitting red, green, or blue light, and the light emitting material may be formed using a phosphorescent material or a fluorescent material.

Since the content of the light emitting material emitting light of each color is the same as that described for the first organic light emitting layer 140 , a detailed description thereof will be omitted.

Preferably, the LUMO level of the first organic emission layer 140 and the LUMO level of the second organic emission layer 160 are the same. When the LUMO level of the first organic light emitting layer 140 and the LUMO level of the second organic light emitting layer 160 are different from each other, the energy wavelength of light generated from the first organic light emitting layer 140 and the second organic light emitting layer 160 is different from each other As a result, inter-wavelength interference occurs. As a result, a desired color may not be expressed, which may cause a problem in that color purity is lowered.

In order to make the LUMO level of the first organic light emitting layer 140 and the LUMO level of the second organic light emitting layer 160 the same, the host material of the first organic light emitting layer 140 and the second organic light emitting layer 160 is preferably the same. Do.

The electron transport layer 170 is disposed on the second organic emission layer 160 . The electron transport layer 170 may serve to transport and inject electrons, and the thickness of the electron transport layer 170 may be adjusted in consideration of electron transport characteristics.

The electron transport layer 170 serves to facilitate the transport of electrons, and includes Alq3 (tris(8-hydroxyquinolino)aluminum), PBD(2-(4-biphenylyl)-5-(4-tert-butylpheny)-1, Alq3(tris(8-hydroxyquinolino)aluminum), PBD(2-(4-biphenylyl)-5-(4-tert-butylpheny)-1, 3,4oxadiazole), TAZ, spiro-PBD, BAlq, and SAlq may consist of any one or more selected from the group consisting of, but is not limited thereto.

In addition, it is possible to additionally form an electron injection layer (EIL) on the electron transport layer 170 separately. The electron injection layer (EIL) is Alq3 (tris(8-hydroxyquinolino)aluminum), PBD(2-(4-biphenylyl)-5-(4-tert-butylpheny)-1,3,4oxadiazole), TAZ, spiro-PBD , BAlq or SAlq may be used, but is not limited thereto. In addition, it is possible to abbreviate|omit the electron injection layer EIL.

The second electrode 180 is disposed on the electron transport layer 170 or the electron injection layer. The second electrode 180 is a negative electrode, and at least one selected from the group consisting of an opaque conductive material such as magnesium (Mg), silver (Ag), aluminum (Al), calcium (Ca), etc. and alloys thereof having a low work function. may be made, but is not limited thereto. In particular, when the organic light emitting diode is applied to a top emission type organic light emitting display device, the second electrode 180 may have a transflective property so that light emitted from the organic light emitting layer can be transmitted, and the second electrode ( 180) may be made of an alloy of magnesium and silver (Mg:Ag).

The capping layer 190 is disposed on the second electrode 180 . The capping layer 190 is for increasing the light extraction effect of the organic light emitting device, and is not limited thereto, but may be made of an acrylic-based resin or an epoxy-based resin, and It may be formed of any one of a material for the transport layer 130 , a material for the electron transport layer 170 , and a host material for the first and second organic emission layers 140 and 160 . Also, the capping layer 190 may be omitted.

Hereinafter, the configuration and LUMO of the first intermediate connection layer ICL1, the second intermediate connection layer ICL2, the third intermediate connection layer ICL3, and the fourth intermediate connection layer ICL4 in order to examine the effects of the present invention. Organic light emitting devices of Comparative Example 1, Comparative Example 2, Example 1, and Example 2 having different levels were manufactured.

Example One

A hole injection layer (100 Å) made of HAT-CN is formed on a first electrode made of ITO (70 Å)/Ag (100 Å)/ITO (70 Å), and then a hole injection layer (100 Å) made of NPD is formed on the hole injection layer. A hole transport layer (300 Å) was formed. Thereafter, a first organic emission layer (200 Å) doped with an anthracene derivative and a pyrene derivative 5% as a host material was formed on the hole transport layer. A connection laminate was formed on the first organic light emitting layer. Thereafter, an electron transport layer (300 Å) made of Alq3 was formed, a second electrode (160 Å) including Ag:Mg in a 1:1 ratio was formed, and then a capping layer (650 Å) made of NPD was formed. .

At this time, the connection laminate is a first intermediate connection layer (ICL1, 125 Å) made of a phenanthroline derivative / a third intermediate connection layer (ICL3, 125 Å) formed by doping lithium (Li) in 2% of a phenantholline derivative (ICL3, 125 Å) / A fourth intermediate connection layer (ICL4, 100 Å) formed by doping F ₄ -TCNQ into NPD by 10% / a second intermediate connection layer (ICL2, 400 Å) made of NPD was formed.

Example 2

As a connecting laminate, a first intermediate connecting layer (ICL1, 125 Å) made of a phenanthroline derivative / a third intermediate connecting layer formed by doping an anthracene derivative with lithium (Li) 2% (ICL3, 125 Å) / F _{4 in NPD} - An organic light emitting diode was manufactured in the same manner as in Example 1, except that a fourth intermediate connection layer (ICL4, 100 Å) formed by doping 10% TCNQ / a second intermediate connection layer (ICL2, 400 Å) made of NPD was formed. prepared.

comparative example One

A hole injection layer (100 Å) made of HAT-CN is formed on a first electrode made of ITO (70 Å)/Ag (100 Å)/ITO (70 Å), and then a hole injection layer (100 Å) made of NPD is formed on the hole injection layer. A hole transport layer (1100 Å) was formed. Thereafter, an organic light emitting (200 Å) layer doped with 5% anthracene derivative and pyrene derivative as a host material was formed on the hole transport layer. After forming an electron transport layer (300 Å) made of Alq3 on the organic light emitting layer, a second electrode (160 Å) including Ag:Mg in a 1:1 ratio is formed, and then a capping layer made of NPD ( 650 Å) to prepare an organic light emitting device having a single organic light emitting layer.

comparative example 2

As a connecting laminate, a first intermediate connecting layer made of an anthracene derivative (ICL1, 125 Å) / a third intermediate connecting layer formed by doping an anthracene derivative with lithium (Li) 2% (ICL3, 125 Å) / F ₄ -TCNQ to NPD An organic light emitting diode was manufactured in the same manner as in Example 1, except that the fourth intermediate connection layer (ICL4, 100 Å) / second intermediate connection layer (ICL2, 400 Å) made of NPD was formed by doping with 10% .

Meanwhile, FIG. 4 is an energy band diagram of the organic light emitting device of Example 1, FIG. 5 is an energy band diagram of the organic light emitting device of Example 2, and FIG. 6 is an organic light emitting device of Comparative Example 2 The energy band diagram for

Referring to FIG. 4 , the LUMO levels of the first intermediate connection layer ICL1 and the second intermediate connection layer ICL2 of Example 1 are 2.68 and 2.5, respectively, so the first organic light emitting layer EML1 and the second intermediate connection layer EML1 disposed in contact with each other 2 It has a higher LUMO level than that of the organic light emitting layer EML2.

Referring to FIG. 5 , the LUMO levels of the first intermediate connection layer ICL1 and the second intermediate connection layer ICL2 of Example 2 are 2.68 and 2.5, respectively, so that the first organic light emitting layer EML1 and the second organic light emitting layer EML1 disposed in contact with each other are provided. 2 It has a higher LUMO level than that of the organic light emitting layer EML2.

Referring to FIG. 6 , since the LUMO level of the second intermediate connecting layer ICL2 of Comparative Example 2 is 2.5, it has a higher LUMO level than that of the second organic light emitting layer EML2 disposed in contact with the first intermediate connecting layer ( Since the LUMO level of ICL1 is 3.2, it has a lower LUMO level than that of the second organic light emitting layer EML2 disposed in contact with each other.

Table 1 below shows the results of evaluating the current efficiency of the organic light emitting diodes according to Examples 1, 2, and Comparative Examples 1 and 2 of the present invention.

division Luminous Efficiency
(cd/A) Example 1 14.3 Example 2 14.4 Comparative Example 1 6.8 Comparative Example 2 10.2

Referring to Table 1, Comparative Example 1 including a single-layered organic light emitting layer showed a result of 6.8 Cd/A, which was significantly lower than that of Examples 1 and 2. As a result, it was found that the current efficiency of the organic light emitting layer of the present invention was improved compared to the conventional single layer organic light emitting layer.

In addition, Comparative Example 2 showed a result of 10.2 Cd/A, but showed lower results compared to Examples 1 and 2 having result values of 14.3 Cd/A and 14.4 Cd/A. Referring to FIG. 6 , although Comparative Example 2 includes a plurality of organic light emitting layers as in Examples 1 and 2, the LUMO level of the first intermediate connection layer ICL1 is adjacent to the first organic light emitting layer ( It is low compared to the LUMO level of EML1). In contrast, in Examples 1 and 2, as can be seen in FIGS. 4 to 6 , the LUMO level of the first intermediate connection layer ICL1 is higher than the LUMO level of the adjacent first organic light emitting layer EML1, so the exciton A phenomenon in which light is generated or emitted in a layer other than the first organic light emitting layer EML1 may be suppressed, and current efficiency may be improved.

In addition, comparing Examples 1 and 2, the first intermediate connection layer ECL1 and the second intermediate connection layer ECL2 disposed in contact with the first organic emission layer EML1 and the second organic emission layer EML2 ) is higher than the LUMO level of the first organic light emitting layer EML1 and the second organic light emitting layer EML2, and the LUMO level of the third intermediate connection layer ECL2 and the fourth intermediate connection layer ECL4 is the first It can be seen that the LUMO level of the first organic light emitting layer EML1 and the second organic light emitting layer EML2 is not higher than the LUMO level.

7 is a graph showing the decrease in luminance with time for the organic light emitting devices of Examples 1, 2, Comparative Examples 1 and 2 of the present invention.

7 , the organic light emitting diodes of Examples 1 and 2 have a LUMO of the first organic light emitting layer EML1 adjacent to Comparative Example 1 having a single organic light emitting layer and the LUMO level of the first intermediate connection layer ICL1. Compared to Comparative Example 2, which was low compared to the level, it was confirmed that the luminance decrease rate with time was insufficient. That is, when the organic light emitting device according to the present invention and the conventional organic light emitting device were driven for the same time, the organic light emitting device of the present invention exhibited better luminance, and thus, the organic light emitting diode according to the embodiment of the present invention. It was confirmed that the lifetime of the device was long.

Taking the above results together, in the case of the organic light emitting device 100 according to the embodiment of the present invention and the organic light emitting device 200 according to another embodiment of the present invention, the first organic light emitting layer 140 and the second organic light emitting layer The LUMO levels of the first intermediate connection layers 151 and 251 and the second intermediate connection layers 152 and 252 disposed in contact with 160 are the LUMO levels of the first organic emission layer 140 and the second organic emission layer 160 . By adjusting the level to be higher than the level, luminous efficiency may be improved, and electrical and thermal stress in the organic light emitting devices 100 and 200 may be reduced, thereby improving lifespan.

Although the embodiments of the present invention have been described in more detail with reference to the accompanying drawings, the present invention is not necessarily limited to these embodiments, and various modifications may be made within the scope without departing from the technical spirit of the present invention. . Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the equivalent range should be construed as being included in the scope of the present invention.

100. 200: organic light emitting device
110: first electrode
120: hole injection layer
130: hole transport layer
140: first organic light emitting layer
150, 250: connecting laminate
151, 251: first intermediate connection layer
152, 252: second intermediate connection layer
253: third intermediate connection layer
254: fourth intermediate connection layer
160: second organic light emitting layer
170: electron transport layer
180: second electrode
190: capping layer

Claims (12)

a first electrode;
a first organic light emitting layer disposed on the first electrode;
a connection laminate disposed on the first organic light emitting layer and including a plurality of intermediate connection layers;
a second organic light emitting layer disposed on the connection laminate; and
a second electrode disposed on the second organic light emitting layer;
The connection laminate includes a first intermediate connection layer disposed in contact with the first organic light emitting layer, a third intermediate connection layer disposed on the first intermediate connection layer, and a fourth intermediate connection layer disposed on the third intermediate connection layer. a second intermediate connection layer disposed on the connection layer and the fourth intermediate connection layer and disposed in contact with the second organic light emitting layer;
The LUMO level of the first intermediate connection layer is higher than the LUMO level of the first organic light emitting layer, the LUMO level of the second intermediate connection layer is higher than the LUMO level of the second organic light emitting layer;
that the LUMO level of the intermediate connection layer including any one selected from the group constituting the third intermediate connection layer and the fourth intermediate connection layer is lower than the LUMO level of the first organic emission layer and the LUMO level of the second organic emission layer Characterized in the organic light emitting device. According to claim 1,
The difference between the LUMO level of the first intermediate connecting layer and the LUMO level of the first organic light emitting layer and the difference between the LUMO level of the second intermediate connecting layer and the LUMO level of the second organic light emitting layer are each 0.1 eV or more. light emitting element. According to claim 1,
The first intermediate connection layer is an n-type charge generation layer, the second intermediate connection layer is an organic light emitting device, characterized in that the p-type charge generation layer. According to claim 1,
The first intermediate connection layer comprises at least one selected from the group consisting of a phenanthroline derivative, an anthracene derivative, a naphthalene derivative, and a biphenyl derivative. delete According to claim 1,
The third intermediate connection layer is an n-type charge generation layer, and the fourth intermediate connection layer is a p-type charge generation layer, characterized in that the organic light emitting device. According to claim 1,
The first intermediate connection layer is an auxiliary electron transport layer, the second intermediate connection layer is an auxiliary hole transport layer, characterized in that the organic light emitting device. According to claim 1,
The first intermediate connection layer and the third intermediate connection layer are characterized in that they include the same host, the organic light emitting device. According to claim 1,
The second intermediate connection layer and the fourth intermediate connection layer are characterized in that they include the same host, the organic light emitting device. delete According to claim 1,
An organic light emitting device, characterized in that the LUMO level of the first organic light emitting layer and the LUMO level of the second organic light emitting layer are equal to each other. According to claim 1,
An organic light emitting device, characterized in that the first organic light emitting layer and the second organic light emitting layer include the same host.

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