KR102326951B1 - Organic light emitting device - Google Patents

Abstract

The organic electroluminescent device according to an embodiment of the present invention is between an anode and a cathode, and in the organic electroluminescent device including a light emitting layer and an electron transport layer, the electron transport layer prevents the movement of holes from the light emitting layer to the electron transport layer A first electron transport material and a second electron transport material that helps the movement of electrons to the light emitting layer, wherein the first electron transport material has a triplet excitation energy level higher than that of the second electron transport material and has a low electron mobility characterized.

Description

Organic light emitting device {ORGANIC LIGHT EMITTING DEVICE}

The present invention relates to an organic electroluminescent device, and more particularly, to an organic electroluminescent device capable of reducing a driving voltage and improving luminous efficiency.

A video display device that implements various information on a screen is a key technology in the information and communication era, which is developing in the direction of thinner, lighter, more portable and high-performance. With the recent development of the information society, as the demand for various types of display devices increases, LCD (Liquid Crystal Display), PDP (Plasma Display Panel), ELD (Electro Luminescent Display), FED (Field Emission Display), OLED ( Research on display devices such as Organic Light Emitting Diode) is being actively conducted.

Among them, the organic light emitting device is a device that emits light while electrons and holes are paired and then disappear when electric charges are injected into the organic light emitting layer formed between the anode and the cathode. The organic electroluminescent device can be formed on a flexible transparent substrate such as plastic, and can be driven at a lower voltage than a plasma display panel or an inorganic electroluminescent (EL) display, and power consumption is relatively low. It has the advantage of being small and the color is excellent. In particular, the organic electroluminescent device for realizing white color is a device that is used for various purposes, such as a thin light source, a backlight of a liquid crystal display device, or a full-color display device employing a color filter as well as lighting.

The organic electroluminescent device may have a structure in which an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode are sequentially stacked. Therefore, the holes supplied from the anode and the electrons received from the cathode combine in the light emitting layer to form an exciton, a hole-electron pair, and emit light by energy generated as the exciton returns to the ground state.

However, when the electron transport layer has a high triplet excitation energy level among conventional organic light emitting devices, the driving voltage is increased due to low electron injection capability and low electron mobility. In addition, when the electron transport layer has high electron injection ability and electron affinity, charge balance is broken due to high electron mobility, and thus lifespan and efficiency are deteriorated.

The present invention provides an organic electroluminescent device capable of reducing a driving voltage and improving luminous efficiency.

In order to achieve the above object, the organic electroluminescent device according to an embodiment of the present invention is between an anode and a cathode, and in the organic electroluminescent device including a light emitting layer and an electron transport layer, the electron transport layer is the light emitting layer A first electron transport material that prevents the movement of holes to the electron transport layer and a second electron transport material that helps the electrons move to the light emitting layer, wherein the first electron transport material has a triplet excitation energy level than that of the second electron transport material It is characterized by high electron mobility and low electron mobility.

The electron transport layer is characterized in that it is a single layer.

The electron transport layer is characterized in that it consists of a single layer including three layers in which the first layer, the mixed layer, and the second layer are stacked.

The first layer includes the first electron transport material, the mixed layer includes the first electron transport material and the second electron transport material, and the second layer includes the second electron transport material characterized.

The triplet excitation energy level of the first electron transport material is 2.6 to 2.8 eV, and the triplet excitation energy level of the second electron transport material is 1.6 to 2.0 eV.

The electron mobility of the second electron transport material is 1×10 ^-3 to 1×10 ^-5 cm 2 /Vs.

With respect to the sum of the first electron transport material and the second electron transport material, the first electron transport material is characterized in that it comprises a ratio of 30 to 50%.

The ratio of the first electron transport material is equal to or smaller than the ratio of the second electron transport material.

The thickness of the electron transport layer is characterized in that 50 to 450 Å.

The thickness of each of the first layer and the second layer is 25 to 100% of the thickness of the mixed layer, and the thickness of the mixed layer is 150 to 200 Å.

The first electron transport material is located close to the light emitting layer, characterized in that it prevents the movement of the holes from the light emitting layer to the electron transport layer.

The second electron transport material is located close to the cathode, characterized in that it helps the electrons to move to the light emitting layer.

It is characterized in that the charge balance of the light emitting layer is controlled by the first electron transport material and the second electron transport material.

In addition, the organic electroluminescent device according to an embodiment of the present invention includes at least one light emitting part positioned between an anode and a cathode, and an electron transport layer positioned between the at least one light emitting part and the cathode, wherein the electron The transport layer is characterized in that it is composed of a single layer including the first electron transport material and the second electron transport material.

The single layer is three layers in which a first layer including a first electron transport material, a mixed layer including the first electron transport material and a second electron transport material, and a second layer including the second electron transport material are stacked. characterized in that it consists of

It is characterized in that the triplet excitation energy level or electron mobility of the first electron transport material and the second electron transport material are different from each other.

The triplet excitation energy level of the first electron transport material is higher than the triplet excitation energy level of the second electron transport material.

The triplet excitation energy level of the first electron transport material is 2.6 to 2.8 eV, and the triplet excitation energy level of the second electron transport material is 1.6 to 2.0 eV.

The electron mobility of the first electron transport material is characterized in that lower than the electron mobility of the second electron transport material.

The electron mobility of the second electron transport material is 1×10 ^-3 to 1×10 ^-5 cm 2 /Vs.

With respect to the sum of the first electron transport material and the second electron transport material, the first electron transport material is characterized in that it comprises a ratio of 30 to 50%.

The ratio of the first electron transport material is equal to or smaller than the ratio of the second electron transport material.

The thickness of the electron transport layer is characterized in that 50 to 450 Å.

The thickness of each of the first layer and the second layer is 25 to 100% of the thickness of the mixed layer, and the thickness of the mixed layer is 150 to 200 Å.

The organic electroluminescent device of the present invention forms an electron transport layer including a first electron transport material having a high triplet excitation energy level and a second electron transport material having a high electron mobility, thereby forming various energy levels in the electron transport layer. Thus, there is an advantage in that the driving voltage can be lowered by reducing the barrier of charges passing from the adjacent layer.

In addition, a first layer including a first electron transport material having a high triplet excitation energy level is provided to increase device efficiency, and a second layer including a second electron transport material having high electron mobility is provided. Accordingly, there is an advantage that the driving voltage can be lowered by further facilitating the movement of electrons.

1 is a view showing an organic electroluminescent device according to a first embodiment of the present invention.
2 is a view showing an organic electroluminescent device according to a second embodiment of the present invention.
3 is a view showing an organic electroluminescent device according to a third embodiment of the present invention.
4 is an energy band diagram of an organic light emitting diode according to an embodiment of the present invention.
5 is a view showing an organic electroluminescent device according to a fourth embodiment of the present invention.
6 is a view showing an organic electroluminescent device according to a fifth embodiment of the present invention.
7 is a view showing an organic electroluminescent device according to a sixth embodiment of the present invention.
8 is an energy band diagram of an organic electroluminescent device according to a fourth embodiment of the present invention.
9 is a diagram schematically illustrating a co-deposition method for manufacturing an electron transport layer of the organic electroluminescent device of the present invention.
10 is a graph showing the current density according to the driving voltage of the device manufactured according to Example 2 of the present invention.
11 is a graph showing the efficiency according to the luminance of the device manufactured according to Example 2 of the present invention.
12 is a graph showing the light emission intensity according to the wavelength of the device manufactured in Example 2 of the present invention in which the material mixing ratio of the electron transport layer is 7:3 and 3:7, respectively.
13 is a graph showing the emission intensity according to the wavelength of the device manufactured in Example 2 of the present invention in which the material mixing ratio of the electron transport layer is 1:1 and 3:7, respectively.
14 is a graph showing the current density according to the driving voltage of the organic light emitting diode manufactured according to Example 3 of the present invention.
15 is a graph showing the efficiency according to the luminance of the organic electroluminescent device manufactured according to Example 3 of the present invention.
16 is a graph showing the light emission intensity according to the wavelength of the organic electroluminescent device manufactured according to Example 3 of the present invention.
17 is a graph showing the current density according to the driving voltage of the organic light emitting device manufactured according to Examples 4 and 5 of the present invention.
18 is a graph showing the efficiency according to the luminance of the organic light emitting device manufactured according to Examples 4 and 5 of the present invention.
19 is a graph showing the intensity according to the wavelength of the organic light emitting device manufactured according to Examples 4 and 5 of the present invention.

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.

In the case of a description of a temporal relationship, for example, 'immediately' or 'directly' when a temporal relationship is described with 'after', 'following', 'after', 'before', etc. It may include cases that are not continuous unless this is used.

Although the first, second, etc. are used to describe various components, these components 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.

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

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

1 is a view showing an organic electroluminescent device according to a first embodiment of the present invention.

Referring to FIG. 1 , the organic electroluminescent device 10 according to the first embodiment of the present invention has an anode 20 , a hole injection layer 30 , a hole transport layer 40 , a light emitting layer 50 , and an electron transport layer 60 . ), the electron injection layer 70 and the cathode 80 may be included.

The anode 20 is an electrode for injecting holes and may be any one of indium tin oxide (ITO), indium zinc oxide (IZO), and zinc oxide (ZnO) having a high work function. In addition, when the anode 20 is a reflective electrode, the anode 20 includes a reflective layer made of any one of aluminum (Al), silver (Ag), or nickel (Ni) under the layer made of any one of ITO, IZO, and ZnO. may include more.

The hole injection layer 30 may serve to smoothly inject holes from the anode 20 to the light emitting layer 50 . The hole injection layer 30 includes copper phthalocyanine (CuPc), poly(3,4)-ethylenedioxythiophene (PEDOT), polyaniline (PANI), and N,N-bis(naphthalene-1-yl)-N,N'- It may consist of any one or more selected from the group consisting of bis(phenyl)-2,2'-dimethylbenzidine), but is not limited thereto. The hole injection layer 30 may have a thickness of 1 to 150 nm. Here, when the thickness of the hole injection layer 30 is 1 nm or more, there is an advantage in that the hole injection characteristics can be prevented from being deteriorated. If the thickness of the hole injection layer 30 is 150 nm or less, the thickness of the hole injection layer 30 is too thick, there is an advantage in that the driving voltage can be prevented from being increased to improve hole movement. The hole injection layer 30 or the electron injection layer 70 may not be included in the configuration of the organic light emitting diode depending on the structure or characteristics of the device.

The hole transport layer 40 serves to facilitate hole transport, and NPD (N,N-bis(naphthalene-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine) , TPD(N,N'-bis-(3-methylphenyl)-N,N'-bis-(phenyl)-benzidine), spiro-TAD(2,2',7,7'-tetrakis(N,N- diphenylamino)-9,9-spirofluorene) and MTDATA (4,4',4"-Tris(N-3-methylphenyl-N-phenylamino)-triphenylamine) The thickness of the hole transport layer 40 may be 1 to 150 nm. Here, if the thickness of the hole transport layer 40 is 1 nm or more, there is an advantage in that the hole transport properties can be prevented from being deteriorated. When the thickness of the transport layer 40 is 150 nm or less, there is an advantage in that the thickness of the hole transport layer 40 is too thick to prevent an increase in the driving voltage to improve hole movement.

The emission layer 50 may emit red (R), green (G), and blue (B) light, and may be made of a phosphorescent material or a fluorescent material.

When the light emitting layer 50 is red, it includes a host material such as CBP (4,4'-bis(carbazol-9-yl)biphenyl), and Ir(PIQ) ₂ (acac)(bis(1-phenylisoquinoline)acetylacetonate Iridium (III)), Ir (PIQ) ₃ (tris (1-phenylquinoline) iridium (III)) and PtOEP (octaethylporphine platinum) can be made of a phosphor containing a dopant comprising at least one selected from the group consisting of, and , alternatively, PBD:Eu(DBM) ₃ (Phen) or a fluorescent material including Perylene, but is not limited thereto.

When the light emitting layer 50 is green, it contains a host material such as CBP (4,4'-bis(carbazol-9-yl)biphenyl), and is a phosphor containing a dopant material containing an iridium series. Alternatively, it may be made of _{a fluorescent material including Alq 3} (tris(8-hydroxyquinolino)aluminum), but is not limited thereto.

When the light emitting layer 50 is blue, it contains a host material such as CBP (4,4'-bis(carbazol-9-yl)biphenyl), and a phosphorescent material including a dopant material including an iridium series. Alternatively, spiro-BDAVBi(2,7-bis)4-diphenylamino)styryl)-9,9-spirofluorene), spiro-CBP(2,2',7,7'-tetrakis(carbozol-9) -yl)-9,9-spirofluorene), distylbenzene (DSB), distrylarylene (DSA), a PFO-based polymer and a fluorescent material including any one selected from the group consisting of a PPV-based polymer. not limited

The electron transport layer 60 serves to facilitate the transport of electrons, and affects the lifespan and efficiency of the organic light emitting diode. Accordingly, the inventors of the present invention conducted various experiments in order to improve the characteristics of the electron transport layer to improve the lifespan or efficiency of the organic light emitting diode. In order to reduce the driving voltage, when the electron transport layer is composed of a single layer having a high triplet excitation energy level, it can be seen that the driving voltage is increased because electron injection is not smooth due to the low electron mobility. In addition, it was found that, in the case of a single layer having high electron mobility, electron injection is smooth, but the balance between electrons and holes in the light emitting layer is broken and the lifespan is reduced. Accordingly, when the electron transport layer is composed of two layers, the driving voltage is increased because the thickness of the device is increased. Accordingly, the inventors of the present invention mix two materials included in the electron transport layer to form the electron transport layer as a single layer, and organic electroluminescence according to the characteristics of the two materials included in the electron transport layer and the thickness or mixing ratio of the two materials A structure of an organic light emitting diode having a new structure capable of improving the device efficiency and reducing the driving voltage has been invented.

The electron transport layer 60 includes a first electron transport material and a second electron transport material. The first electron transport material has a higher triplet excitation energy level (T1 Level) and lower electron mobility than the second electron transport material. In addition, the second electron transport material has a lower triplet excitation energy level (T1 Level) and higher electron mobility than the first electron transport material. The first electron transport material and the second electron transport material may be formed by co-deposition.

In more detail, the first electron transport material has a high triplet excitation energy level (T1 Level), thereby blocking the passage of holes from the light emitting layer and maintaining the balance of electrons and holes in the light emitting layer to achieve a charge balance. can play a role in aligning Accordingly, the first electron transport material may be positioned adjacent to the emission layer 50 to prevent the movement of holes from the emission layer 50 to the electron transport layer 60 . The triplet excitation energy level (T1 Level) is 2.6 to 2.8 eV. In addition, the first electron transport material has a HOMO level of -5.9 to -6.3 eV and a LUMO level of -2.4 to -2.8 eV. The first electron transport material having the triplet excitation energy level, the HOMO level, and the LUMO level may be a compound such as a carbazole compound, an oxadiazole compound, or a triazole compound. For example, it may be a compound represented by the following formula (1).

[Formula 1]

In Formula 1, A ₁ to A ₁₃ are each independently a substituted or unsubstituted C6 to C50 aromatic ring, or at least one is a substituted or unsubstituted C5 to C549 S, N and O It is selected from a heterocyclic ring containing a (Heterocyclic Ring).

Since the second electron transport material has a high electron mobility, it may serve to improve electron injection and lower the driving voltage of the device. The electron mobility is 1×10 ⁻³ to 1×10 ⁻⁵ cm 2 /Vs. In addition, the second electron transport material has a HOMO level of -5.8 to -6.2 eV, a LUMO level of -2.8 to -3.2 eV, and a triplet excitation energy level of 1.6 to 2.0 eV. The second electron transport material is a quinoline compound, an anthracene compound, or the like, and may be, for example, a compound represented by Formula 2 below.

[Formula 2]

In Formula 2, A ₁ to A ₁₀ are each independently a substituted or unsubstituted C6 to C50 aromatic ring, or at least one is a substituted or unsubstituted C5 to C49 S, N and O It is selected from a heterocyclic ring containing a (Heterocyclic Ring).

According to the present invention, by providing an electron transport layer including materials having different properties, various energy levels are formed in the electron transport layer to reduce a barrier between charges passing from an adjacent layer. Accordingly, it is possible to maintain a balance of charges in the light emitting layer because the transfer of charges to the light emitting layer is easy, and there is an effect that the driving voltage can be lowered. In particular, in the present invention, the efficiency of the device is increased by including the first electron transport material having a high triplet excitation energy level (T1 Level). In addition, by including the second electron transport material having a high electron mobility, there is an effect that the driving voltage can be lowered by further facilitating the movement of electrons.

In order to lower the driving voltage and improve the efficiency of the organic light emitting diode, the electron transport layer 60 of the present invention includes a first electron transport material and a second electron transport material. Here, in the electron transport layer 60 , the first electron transport material accounts for 30 to 50% of the sum of the first electron transport material and the second electron transport material. If the ratio of the first electron transport material to the sum of the first electron transport material and the second electron transport material is less than 30%, the charge balance of the device is not met, and thus the efficiency is lowered. When the ratio of the first electron transport material to the sum of the first electron transport material and the second electron transport material exceeds 50%, the movement of electrons is not smooth, so that the driving voltage of the device is increased and the efficiency is lowered.

In addition, the electron transport layer 60 is made of a single layer including the first electron transport material and the second electron transport material, and has a thickness of 50 to 450 Å. Here, if the thickness of the electron transport layer 60 is less than 50 Å, it cannot function as an electron transport layer. cannot be maximized.

On the other hand, the electron injection layer 70 serves to facilitate the injection of electrons, and Alq ₃ (tris(8-hydroxy quinolinato)aluminum), PBD(2-(4-biphenyl)-5-(4-tert-) butylphenyl)-1,3,4-oxadiazole), TAZ(3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole), and BAlq(Bis(2-methyl- 8-quinolinolate)-4-(phenylphenolato)aluminum) may be used, but is not limited thereto. On the other hand, the electron injection layer 70 may be made of a metal compound, a metal compound, for example LiQ, LiF, NaF, KF, RbF, CsF, FrF, BeF _2, MgF _2, CaF _2, SrF _2, BaF ₂ And RaF _{2 It} may be any one or more selected from the group consisting of, but is not limited thereto. The electron injection layer 70 may have a thickness of 1 to 50 nm. Here, when the thickness of the electron injection layer 70 is 1 nm or more, it is possible to prevent the electron injection characteristic from being deteriorated. If the thickness of the electron injection layer 70 is 50 nm or less, the thickness of the electron injection layer 70 is too thick to prevent an increase in the driving voltage for improving electron movement. The electron injection layer 70 may not be included in the configuration of the organic light emitting device depending on the structure or characteristics of the device.

The cathode 80 is an electron injection electrode, and may be formed of magnesium (Mg), calcium (Ca), aluminum (Al), silver (Ag), or an alloy thereof having a low work function. Here, the cathode 80 may be formed to be thin enough to transmit light when the organic light emitting device has a front or double-sided light emitting structure, and when the organic light emitting device has a rear light emitting structure, it can reflect light. It can be formed as thick as possible.

As described above, the organic electroluminescent device of the present invention forms an electron transport layer including a first electron transport material having a high triplet excitation energy level and a second electron transport material having a high electron mobility, thereby forming an electron transport layer in the electron transport layer. There is an advantage in that the driving voltage can be lowered by forming several energy levels to reduce the barrier of charges passing from adjacent layers. In addition, the electron transport layer includes a first electron transport material having a high triplet excitation energy level to increase the efficiency of the device, and includes a second electron transport material having a high electron mobility to further facilitate the movement of electrons. There is an advantage that the driving voltage can be lowered.

2 is a view showing an organic electroluminescent device according to a second embodiment of the present invention. Hereinafter, descriptions of the same components as those of the above-described first embodiment will be briefly described.

Referring to FIG. 2 , the organic light emitting diode 100 according to the second embodiment of the present invention includes light emitting units ST1 and ST2 and light emitting units ST1 and ST2 positioned between an anode 110 and a cathode 220 . ) and a charge generation layer 160 positioned between them.

In more detail, the first light emitting unit ST1 constitutes one light emitting device unit and includes the first light emitting layer 140 . The first light emitting layer 140 may emit any one of red, green, and blue, and in the present embodiment may be a blue light emitting layer that emits blue. The blue light emitting layer may be one of a blue light emitting layer, a dark blue light emitting layer, or a sky blue light emitting layer. The first light emitting part ST1 further includes a first hole injection layer 120 and a first hole transport layer 130 on the anode 110 . In addition, the first light emitting part ST1 further includes a first electron transport layer 150 on the first light emitting layer 140 . And an electron injection layer may be further included on the first electron transport layer 150 . Accordingly, the first light emitting part ST1 including the first hole injection layer 120 , the first hole transport layer 130 , the first light emitting layer 140 , and the first electron transport layer 150 on the anode 110 is formed. make up The first hole injection layer 120 and the electron injection layer may not be included in the configuration of the first light emitting part ST1 depending on the structure or characteristics of the device.

A second light emitting part ST2 including a second light emitting layer 190 is positioned on the first light emitting part ST1 . The second light emitting layer 190 may emit one color among red, green, and blue, for example, a yellow-green light emitting layer or a green light emitting layer in this embodiment. The yellow green light emitting layer may be formed of a yellow light emitting layer or a multilayer structure of a yellow green light emitting layer and a green light emitting layer. The second light emitting part ST2 further includes a second hole injection layer 170 and a second hole transport layer 180 , and a second electron transport layer 200 and an electron injection layer on the second light emitting layer 190 ( 210) is further included. Accordingly, the second hole injection layer 170 , the second hole transport layer 180 , the yellow green light emitting layer 190 , the second electron transport layer 200 and the electron injection layer 210 are formed on the first light emitting part ST1 . The included second light emitting unit ST2 is formed. The second hole injection layer 170 and the electron injection layer 210 may not be included in the configuration of the second light emitting part ST2 depending on the structure or characteristics of the device.

A charge generation layer 160 is positioned between the first light emitting part ST1 and the second light emitting part ST2 . The charge generation layer 160 is a PN junction charge generation layer in which the N-type charge generation layer 160N and the P-type charge generation layer 160P are joined, and generates charges or separates them into holes and electrons to apply charges to each of the light emitting layers. inject That is, the N-type charge generation layer 160N supplies electrons to the first light-emitting layer 140 adjacent to the anode, and the P-type charge generation layer 160P supplies holes to the second light-emitting layer 190, so that a plurality of The luminous efficiency of the organic electroluminescent device including the light emitting layer can be further increased, and the driving voltage can also be lowered.

Here, the N-type charge generation layer 160N may be formed of a metal or an N-type doped organic material. Here, the metal may be one selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Sm, Eu, Tb, Dy and Yb. For example, the N-type dopant may be an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound. In detail, the N-type dopant may be one selected from the group consisting of Li, Be, Cs, K, Rb, Mg, Na, Ca, Sr, Eu, Fr, Ba, Ra and Yb. The host material may be, for example, _{one material selected from the group consisting of Alq 3} (tris(8-hydroxyquinolinato)aluminum), triazine derivatives, benzazole derivatives, and silole derivatives. .

Meanwhile, the P-type charge generation layer 160P may be formed of a metal or an organic material doped with a P-type. Here, the metal may be made of one or more alloys selected from the group consisting of Al, Cu, Fe, Pb, Zn, Au, Pt, W, In, Mo, Ni and Ti. In addition, as the P-type dopant and the host material used in the P-type doped organic material, a commonly used material may be used. For example, the P-type dopant is a group consisting _{of F 4} -TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane), iodine, FeCl ₃ , FeF ₃ and SbCl _{5 .} It may be one material selected from In addition, the host is NPB (N,N'-bis(naphthaen-1-yl)-N,N'-bis(phenyl)-benzidine), TPD (N,N'-bis(3-methylphenyl)N,N It may be one material selected from the group consisting of '-bis(phenyl)-benzidine) and TNB (N,N,N',N'-tetra-naphthalenyl-benzidine).

The cathode 220 is positioned on the second light emitting part ST2. The cathode 220 is an electron injection electrode, and may be made of magnesium (Mg), calcium (Ca), aluminum (Al), silver (Ag), or an alloy thereof having a low work function. Here, the cathode 220 may be formed to be thin enough to transmit light when the organic light emitting device has a front or double-sided light emitting structure, and when the organic light emitting device has a rear light emitting structure, it can reflect light. It can be formed as thick as possible.

Meanwhile, the first electron transport layer 150 located in the first light emitting part ST1 of the organic electroluminescent device 100 according to the second embodiment of the present invention serves to facilitate electron transport. In more detail, the first electron transport layer 150 includes a first electron transport material and a second electron transport material. The first electron transport material blocks passing of holes and serves to balance the charge balance, and has a triplet excitation energy level (T1 Level) of 2.6 to 2.8 eV. In addition, the first electron transport material has a HOMO level of -5.9 to -6.3 eV and a LUMO level of -2.4 to -2.8 eV. The second electron transport material serves to improve electron injection and lower the driving voltage of the device, and may have an electron mobility of 1×10 ⁻³ to 1×10 ⁻⁵ cm 2 /Vs. In addition, the second electron transport material has a HOMO level of -5.8 to -6.2 eV, a LUMO level of -2.8 to -3.2 eV, and a triplet excitation energy level (T1 Level) of 1.6 to 2.0 eV.

As described above, the organic electroluminescent device of the present invention comprises an electron transport layer including a first electron transport material having a high triplet excitation energy level (T1 Level) and a second electron transport material having a high electron mobility. , it is possible to lower the driving voltage by forming various energy levels in the electron transport layer to reduce the barrier of charges passing from the adjacent layer. In addition, the efficiency of the device is improved by including the first electron transport material having a high triplet excitation energy level (T1 Level), and the movement of electrons is made easier by including the second electron transport material having high electron mobility. Thus, the driving voltage can be lowered.

3 is a view showing an organic electroluminescent device according to a third embodiment of the present invention. Hereinafter, the same reference numerals are assigned to the same components as those of the above-described second embodiment, and descriptions thereof will be omitted.

Referring to FIG. 3 , the organic light emitting diode 100 according to the third embodiment of the present invention includes a plurality of light emitting units ST1 , ST2 , and ST3 positioned between an anode 110 and a cathode 220 , and a plurality of A first charge generation layer 160 and a second charge generation layer 230 are positioned between the light emitting units ST1 , ST2 , and ST3 . In the present embodiment, it has been illustrated and described that three light emitting units are positioned between the anode 110 and the cathode 220 , but the present invention is not limited thereto and four or more light emitting units are disposed between the anode 110 and the cathode 220 . may include

In more detail, the first light emitting unit ST1 constitutes one light emitting device unit and includes the first light emitting layer 140 . The first light emitting layer 140 may emit any one of red, green, and blue, and in the present embodiment may be a blue light emitting layer that emits blue. The blue light emitting layer may be one of a blue light emitting layer, a dark blue light emitting layer, or a sky blue light emitting layer.

The first light emitting part ST1 further includes a first hole injection layer 120 and a first hole transport layer 130 on the anode 110 . In addition, the first light emitting part ST1 further includes a first electron transport layer 150 on the first light emitting layer 140 . Accordingly, the first light emitting part ST1 including the first hole injection layer 120 , the first hole transport layer 130 , the first light emitting layer 140 , and the first electron transport layer 150 on the anode 110 is formed. make up In addition, an electron injection layer may be further included on the first electron transport layer 150 .

The first hole injection layer 120 and the electron injection layer may not be included in the configuration of the first light emitting part ST1 depending on the structure or characteristics of the device.

A second light emitting part ST2 is positioned on the first light emitting part ST1 . The second light emitting part ST2 includes a second light emitting layer 190 . The second light emitting layer 190 may emit one color among red, green, and blue, for example, a yellow-green light emitting layer or a green light emitting layer in this embodiment. The yellow green light emitting layer may be formed of a yellow light emitting layer or a multilayer structure of a yellow green light emitting layer and a green light emitting layer. The second light emitting part ST2 further includes a second hole injection layer 170 and a second hole transport layer 180 between the first charge generating layer 160 and the second light emitting layer 190 , and a second A second electron transport layer 200 is further included on the light emitting layer 190 . In addition, an electron injection layer may be further included on the second electron transport layer 200 . Accordingly, the second light emitting unit including the second hole injection layer 170 , the second hole transport layer 180 , the second emission layer 190 , and the second electron transport layer 200 on the first charge generation layer 160 . (ST2) is constructed. The second hole injection layer 170 and the electron injection layer may not be included in the configuration of the second light emitting part ST2 depending on the structure or characteristics of the device.

A first charge generation layer 160 is positioned between the first light emitting part ST1 and the second light emitting part ST2 . The first charge generation layer 160 is a PN junction charge generation layer in which an N-type charge generation layer 160N and a P-type charge generation layer 160P are joined, and generates charges or separates them into holes and electrons in each light emitting layer. inject an electric charge

In addition, the third light emitting part ST3 including the third light emitting layer 250 is positioned on the second light emitting part ST2 . The third light emitting layer 250 may emit one color among red, green, and blue, for example, a blue light emitting layer that emits blue in the present embodiment. The blue light emitting layer may be one of a blue light emitting layer, a dark blue light emitting layer, or a sky blue light emitting layer. The third light emitting part ST3 further includes a third hole transport layer 240 between the second charge generating layer 230 and the third light emitting layer 250 , and the third electrons on the third light emitting layer 250 . It further includes a transport layer 260 and an electron injection layer 210 . Accordingly, the third light emitting part ST3 including the third hole transport layer 240 , the third emission layer 250 , the third electron transport layer 260 , and the electron injection layer 210 on the second charge generation layer 230 . ) constitutes A cathode 220 is provided on the third light emitting part ST3 to configure the organic electroluminescent device according to the second embodiment of the present invention. The third hole transport layer 240 and the electron injection layer 210 may not be included in the configuration of the third light emitting unit ST3 depending on the structure or characteristics of the device.

A second charge generation layer 230 is positioned between the second light emitting part ST2 and the third light emitting part ST3 . The second charge generation layer 230 is a PN junction charge generation layer in which an N-type charge generation layer 230N and a P-type charge generation layer 230P are joined, and generates charges or separates them into holes and electrons in each of the light emitting layers. inject an electric charge

Meanwhile, the third electron transport layer 260 located in the third light emitting part ST3 of the organic electroluminescent device 100 according to the third embodiment of the present invention serves to facilitate electron transport. In more detail, the third electron transport layer 260 includes a first electron transport material and a second electron transport material. The first electron transport material blocks passing of holes and serves to balance the charge balance, and has a triplet excitation energy level (T1 Level) of 2.6 to 2.8 eV. In addition, the first electron transport material has a HOMO level of -5.9 to -6.3 eV and a LUMO level of -2.4 to -2.8 eV. The second electron transport material serves to improve electron injection and lower the driving voltage of the device, and may have an electron mobility of 1×10 ⁻³ to 1×10 ⁻⁵ cm 2 /Vs. In addition, the second electron transport material has a HOMO level of -5.8 to -6.2 eV, a LUMO level of -2.8 to -3.2 eV, and a triplet excitation energy level (T1 Level) of 1.6 to 2.0 eV.

In addition, the organic electroluminescent device 100 according to the third embodiment of the present invention includes the first electron transport layer 150 of the first light emitting part ST1 in addition to the third electron transport layer 260 of the third light emitting part ST3. may be configured in the same manner as the above-described third electron transport layer 260 . That is, the first electron transport layer 150 of the first light emitting part ST1 may include the above-described first electron transport material and the second electron transport material. The electron transport layer including the first electron transport material and the second electron transport material of the present invention may be applied to any light emitting part as long as it emits blue light.

As described above, the organic electroluminescent device of the present invention forms an electron transport layer including a first electron transport material having a high triplet excitation energy level and a second electron transport material having a high electron mobility, thereby forming an electron transport layer in the electron transport layer. By forming multiple energy levels, the driving voltage can be lowered by reducing the barrier of charges passing from adjacent layers. In addition, the efficiency of the device is increased by including the first electron transport material having a high triplet excitation energy level, and the driving voltage is increased by including the second electron transport material having high electron mobility to facilitate the movement of electrons. can be lowered

4 is an energy band diagram of an organic light emitting diode according to an embodiment of the present invention.

Referring to FIG. 4 , the organic electroluminescent device of the present invention has a hole transport layer (HTL), a light emitting layer (EML) including a host and a dopant, an electron transport layer (Mixed ETL) and an electron injection layer (EIL). includes The electron transport layer (Mixed ETL) is an electron transport layer in which the first electron transport material and the second electron transport material are mixed. In the electron transport layer (Mixed ETL), a first electron transport material having a high triplet excitation energy level forms one bandgap, and a second electron transport material having a high electron mobility forms another bandgap. do. Accordingly, two materials having different band gaps are mixed to reduce a barrier for moving carriers passing from an adjacent electron injection layer (EIL) or a cathode, thereby facilitating movement of carriers into the light emitting layer (EML). In addition, the first electron transport material having a high triplet excitation energy level (T1 Level) prevents holes from passing from the emission layer (EML) to the electron transport layer (Mixed ETL), thereby improving the efficiency of the emission layer (EML). . In addition, the ability to inject electrons into the light emitting layer EML may be improved due to the second electron transport material having high electron mobility, and thus the driving voltage of the device may be lowered.

In addition, the electron transport layer of the organic electroluminescent device of the present invention may have a three-layer structure of a first layer, a mixed layer, and a second layer. Hereinafter, embodiments in which the electron transport layer has the above-described three-layer structure are disclosed. However, the same reference numerals are attached to the same components as those of the above-described first to third embodiments to facilitate understanding and to simplify the description.

5 is a view showing an organic electroluminescent device according to a fourth embodiment of the present invention.

Referring to FIG. 5 , the organic electroluminescent device 10 according to the fourth embodiment of the present invention has an anode 20 , a hole injection layer 30 , a hole transport layer 40 , a light emitting layer 50 , and an electron transport layer 60 . ), the electron injection layer 70 and the cathode 80 may be included.

The anode 20 is an electrode for injecting holes into the light emitting layer 50 , and the hole injection layer 30 and the hole transport layer 40 serve to smoothly inject holes from the anode 20 to the light emitting layer 50 . do The hole injection layer 30 or the hole transport layer 40 may not be included in the configuration of the organic electroluminescent device depending on the structure or characteristics of the device. The emission layer 50 may emit red (R), green (G), and blue (B) light, and may be made of a phosphorescent material or a fluorescent material. The electron transport layer 60 is positioned on the light emitting layer 50 , and the electron injection layer 70 is positioned on the electron transport layer 60 to facilitate electron injection. A cathode 80 as an electrode for injecting electrons is positioned on the electron injection layer 70 .

On the other hand, the electron transport layer 60 serves to facilitate the transport of electrons, and affects the lifespan and efficiency of the organic light emitting diode. Accordingly, the inventors of the present invention conducted various experiments in order to improve the characteristics of the electron transport layer to improve the lifespan or efficiency of the organic light emitting diode. When a single layer having a high triplet excitation energy level was formed to reduce the driving voltage, it was found that the driving voltage was increased because electron injection was not smooth due to low electron mobility. In addition, it was found that, in the case of a single layer having high electron mobility, electron injection is smooth, but the balance between electrons and holes is broken and the lifespan is reduced. Accordingly, when the electron transport layer is composed of two layers, the driving voltage is increased because the thickness of the device is increased. Accordingly, the inventors of the present invention found that the first layer of the first electron transport material, the second layer of the second electron transport material, and the first electron transport material and the second electron transport material are mixed therebetween without increasing the thickness of the electron transport layer. It was composed of three layers of mixed layers. In addition, according to the characteristics, thickness, thickness of the mixed layer, and the mixing ratio of the first electron transport material and the second electron transport material included in the electron transport layer, the efficiency of the organic light emitting diode can be improved and the driving voltage can be reduced. Invented the structure of the organic electroluminescent device.

The electron transport layer 60 includes a first layer 61 adjacent to the light emitting layer 50 , a mixed layer 62 positioned on the first layer 61 , and a second layer 63 positioned on the mixed layer 62 . . The first layer 61 is a layer including the first electron transport material, and serves to buffer between the light emitting layer 50 and the mixed layer 62 . The first electron transport material included in the first layer 61 has a higher triplet excitation energy level (T1 Level) and lower electron mobility than the second electron transport material. The second layer 63 is a layer including the second electron transport material, and serves to buffer between the electron injection layer 70 or the cathode 80 and the mixed layer 62 . The second electron transport material included in the second layer 63 has a lower triplet excitation energy level (T1 Level) and higher electron mobility than the first electron transport material. The mixed layer 62 is located between the first layer 61 and the second layer 63 and is a layer in which the first electron transport material and the second electron transport material are mixed. The mixed layer 62 serves to facilitate charge transfer to the light emitting layer 50 .

In more detail, the first layer 61 of the electron transport layer 60 is positioned adjacent to the light emitting layer 60 . The first layer 61 includes a first electron transport material having a high triplet excitation energy level (T1 Level), thereby blocking the passing of holes from the hole transport layer 40 and electrons in the light emitting layer 50 It may play a role in balancing the charge balance by maintaining the balance of the holes. Accordingly, the first layer 61 of the electron transport layer 60 may be positioned adjacent to the emission layer 50 to prevent the movement of holes from the emission layer 50 to the electron transport layer 60 . The first electron transport material has a triplet excitation energy level (T1 Level) of 2.6 to 2.8 eV. In addition, the first electron transport material has a HOMO level of -5.9 to -6.3 eV and a LUMO level of -2.4 to -2.8 eV. The first electron transport material having the triplet excitation energy level, the HOMO level, and the LUMO level may be a compound such as a carbazole compound, an oxadiazole compound, or a triazole compound. For example, it may be a compound represented by Chemical Formula 1 described above.

The second layer 63 of the electron transport layer 60 is positioned adjacent to the electron injection layer 70 or the cathode 80 . The second layer 63 includes a second electron transport material having high electron mobility, thereby improving the injection of electrons injected from the electron injection layer 70 or the cathode 80 and lowering the driving voltage of the device. can play a role Accordingly, the second layer 63 of the electron transport layer 60 may be positioned adjacent to the electron injection layer 70 or the cathode 80 to help electrons move to the light emitting layer 50 . The second electron transport material may have an electron mobility in a range of 1×10 ⁻³ to 1×10 ⁻⁵ cm 2 /Vs. In addition, the second electron transport material has a HOMO level of -5.8 to -6.2 eV, a LUMO level of -2.8 to -3.2 eV, and a triplet excitation energy level of 1.6 to 2.0 eV. The second electron transport material is a quinoline compound, an anthracene compound, or the like, and may be, for example, a compound represented by Chemical Formula 2 described above.

The mixed layer 62 of the electron transport layer 60 is positioned between the first layer 61 and the second layer 62, and is a layer in which the aforementioned first electron transport material and the second electron transport material are mixed. The mixed layer 62 includes the first electron transport material, blocks the passing of holes from the hole transport layer 40 , and balances electrons and holes in the light emitting layer 50 to balance the charge. In addition, the mixed layer 62 includes the second electron transport material, improves electron injection and lowers the driving voltage of the device.

The electron transport layer 60 of the present invention includes a first layer 61 made of a first electron transport material, a mixed layer 62 made of a mixture of a first electron transport material and a second electron transport material, and a second electron transport material. By including the second layer 63, different energy levels are formed in the electron transport layer 60 to reduce the barrier of charges passing from the adjacent layer. Accordingly, there is an effect that the driving voltage can be lowered because electrons can easily move to the light emitting layer 50 .

In addition, the electron transport layer 60 of the present invention includes a first layer 61 including a first electron transport material having a high triplet excitation energy level (T1 Level), and the light emitting layer 50 in the mixed layer 62 . to increase the efficiency of the device to reach In addition, by providing the second layer 63 including the second electron transport material having high electron mobility, it is possible to reduce the driving voltage by further facilitating the movement of electrons.

In the mixed layer 62 of the electron transport layer 60 of the present invention, the first electron transport material and the second electron transport material are mixed. Here, in the electron transport layer 60, the first electron transport material accounts for 30 to 50% of the sum of the first electron transport material and the second electron transport material. If the ratio of the first electron transport material to the sum of the first electron transport material and the second electron transport material is less than 30%, the charge balance of the device is not met, and the efficiency is lowered, and the first electron transport material and the second electron transport material When the ratio of the first electron transport material to the sum of , the movement of electrons is not smooth, the driving voltage of the device is increased and the efficiency is lowered.

Meanwhile, the electron transport layer 60 in the fourth embodiment of the present invention includes the first layer 61 and the second layer 63 in addition to the mixed layer 62 in the electron transport layer 60 of the first to third embodiments described above. ) is further provided, but the overall thickness of the electron transport layer 60 is not increased.

Accordingly, the electron transport layer 60 is composed of three layers, and the total thickness of the three layers is 50 to 450 Å. Here, if the total thickness of the electron transport layer 60 is less than 50 Å, it cannot function as an electron transport layer, and if the total thickness of the electron transport layer 60 exceeds 450 Å, the thickness of the electron transport layer becomes thick, the driving voltage rises, and the The cavity effect cannot be maximized.

In addition, in the electron transport layer 60 , the thickness of the first layer 61 is 25% or more and 100% or less with respect to the thickness of the mixed layer 62 . Here, if the thickness of the first layer 61 is 25% or more with respect to the thickness of the mixed layer 62, the efficiency of the device can be improved by blocking the passing of holes from the hole transport layer, thereby balancing the charge balance of the light emitting layer, and the first When the thickness of the layer 61 is 100% or less with respect to the thickness of the mixed layer 62, the thickness of the mixed layer 62 is prevented from being relatively thin, thereby preventing a decrease in device efficiency.

In addition, the thickness of the second layer 63 in the electron transport layer 60 is 25% or more and 100% or less with respect to the thickness of the mixed layer 62 . Here, if the thickness of the second layer 63 is 25% or more with respect to the thickness of the mixed layer 62 , it is possible to reduce the charge barrier through which electrons pass from the electron injection layer 70 or the cathode 80 to improve the efficiency of the device. have. When the thickness of the second layer 63 is 100% or less with respect to the thickness of the mixed layer 62 , the thickness of the mixed layer 62 is prevented from being relatively thin, thereby preventing a decrease in device efficiency.

As described above, the organic electroluminescent device of the present invention forms an electron transport layer including a first electron transport material having a high triplet excitation energy level and a second electron transport material having a high electron mobility, thereby forming an electron transport layer in the electron transport layer. There is an advantage in that the driving voltage can be lowered by forming several energy levels to reduce the barrier of charges passing from adjacent layers. In addition, a first layer including a first electron transport material having a high triplet excitation energy level is provided to improve device efficiency, and a second layer including a second electron transport material having high electron mobility is provided. Accordingly, there is an advantage that the driving voltage can be lowered by further facilitating the movement of electrons.

6 is a view showing an organic electroluminescent device according to a fifth embodiment of the present invention. Hereinafter, descriptions of the same components as those of the above-described second embodiment will be briefly described.

Referring to FIG. 6 , the organic light emitting diode 100 according to the fifth embodiment of the present invention includes light emitting units ST1 and ST2 and light emitting units ST1 and ST2 positioned between an anode 110 and a cathode 220 . ) and a charge generation layer 160 positioned between them.

In more detail, the first light emitting unit ST1 constitutes one light emitting device unit and includes the first light emitting layer 140 . The first light emitting layer 140 may emit any one of red, green, and blue, and in the present embodiment may be a blue light emitting layer that emits blue. The blue light emitting layer may be one of a blue light emitting layer, a dark blue light emitting layer, or a sky blue light emitting layer. The first light emitting part ST1 further includes a first hole injection layer 120 and a first hole transport layer 130 between the anode 110 and the first light emitting layer 140 . In addition, the first light emitting part ST1 further includes a first electron transport layer 150 on the first light emitting layer 140 . An electron injection layer may be further included on the first electron transport layer 150 . Accordingly, the first light emitting part ST1 including the first hole injection layer 120 , the first hole transport layer 130 , the first light emitting layer 140 , and the first electron transport layer 150 on the anode 110 is formed. make up The first hole injection layer 120 and the electron injection layer may not be included in the configuration of the first light emitting part ST1 depending on the structure or characteristics of the device.

In addition, the second light emitting part ST2 including the second light emitting layer 190 is positioned on the first light emitting part ST1 . The second light emitting layer 190 may emit one color among red, green, and blue, for example, a yellow-green light emitting layer or a green light emitting layer in this embodiment. The yellow green light emitting layer may be formed of a yellow light emitting layer or a multilayer structure of a yellow green light emitting layer and a green light emitting layer. The second light emitting part ST2 further includes a second hole injection layer 170 and a second hole transport layer 180 , and a second electron transport layer 200 and an electron injection layer on the second light emitting layer 190 ( 210) is further included. Accordingly, the second hole injection layer 170 , the second hole transport layer 180 , the yellow green light emitting layer 190 , the second electron transport layer 200 , and the electron injection layer 210 on the first light emitting part ST1 ) constitutes the second light emitting part ST2 including The second hole injection layer 170 and the electron injection layer 210 may not be included in the configuration of the second light emitting unit ST2 depending on the structure or characteristics of the device.

A charge generation layer 160 is positioned between the first light emitting part ST1 and the second light emitting part ST2 . The charge generation layer 160 is a PN junction charge generation layer in which the N-type charge generation layer 160N and the P-type charge generation layer 160P are joined, and generates charges or separates them into holes and electrons to apply charges to each of the light emitting layers. inject That is, the N-type charge generation layer 160N supplies electrons to the first light-emitting layer 140 adjacent to the anode, and the P-type charge generation layer 160P is the second light-emitting layer 190 of the second light-emitting part ST2. By supplying holes to the light emitting layer, the luminous efficiency of the organic electroluminescent device including a plurality of light emitting layers can be further increased, and the driving voltage can also be lowered. In addition, the cathode 220 is positioned on the second light emitting part ST2.

In addition, the first electron transport layer 150 located in the first light emitting part ST1 of the organic electroluminescent device 100 according to the fifth embodiment of the present invention serves to facilitate electron transport. The first electron transport layer 150 includes a first layer 151 adjacent to the first light emitting layer 140 , a mixed layer 152 positioned on the first layer 151 , and a second layer 153 positioned on the mixed layer 152 . includes The first layer 151 includes a first electron transport material having a high triplet excitation energy level (T1 Level), thereby blocking the passing of holes from the hole transport layer 130 and in the first light emitting layer 140 . It may serve to balance the charge balance by maintaining the balance of electrons and holes. The first electron transport material has a triplet excitation energy level (T1 Level) of 2.6 to 2.8 eV. In addition, the first electron transport material has a HOMO level of -5.9 to -6.3 eV and a LUMO level of -2.4 to -2.8 eV. Since the second layer 153 includes a second electron transport material having high electron mobility, it may serve to improve the injection of electrons injected from the cathode 220 and lower the driving voltage of the device. The second electron transport material may have an electron mobility in a range of 1×10 ⁻³ to 1×10 ⁻⁵ cm 2 /Vs. In addition, the second electron transport material has a HOMO level of -5.8 to -6.2 eV, a LUMO level of -2.8 to -3.2 eV, and a triplet excitation energy level of 1.6 to 2.0 eV. The mixed layer 152 is located between the first layer 151 and the second layer 153, and is a layer in which the above-described first electron transport material and the second electron transport material are mixed. The mixed layer 152 may include a first electron transport material to block the passage of holes from the first light emitting layer 140 and balance the charge balance by maintaining the balance of electrons and holes in the first light emitting layer 140 . . In addition, the mixed layer 152 includes the second electron transport material, and may improve electron injection and lower the driving voltage of the device.

As described above, the organic electroluminescent device of the present invention forms an electron transport layer including a first electron transport material having a high triplet excitation energy level and a second electron transport material having a high electron mobility, thereby forming an electron transport layer in the electron transport layer. There is an advantage in that the driving voltage can be lowered by forming several energy levels to reduce the barrier of charges passing from adjacent layers. In addition, a first layer including a first electron transport material having a high triplet excitation energy level is provided to increase device efficiency, and a second layer including a second electron transport material having high electron mobility is provided. Accordingly, there is an advantage that the driving voltage can be lowered by further facilitating the movement of electrons.

7 is a view showing an organic electroluminescent device according to a sixth embodiment of the present invention. Hereinafter, the same reference numerals are given to the same components as those of the above-described fifth embodiment, and descriptions thereof will be omitted.

Referring to FIG. 7 , the organic light emitting diode 100 according to the sixth embodiment of the present invention includes a plurality of light emitting units ST1 , ST2 , and ST3 positioned between an anode 110 and a cathode 220 , and a plurality of A first charge generation layer 160 and a second charge generation layer 230 are positioned between the light emitting units ST1 , ST2 , and ST3 . In the present embodiment, it has been illustrated and described that three light emitting units are positioned between the anode 110 and the cathode 220 , but the present invention is not limited thereto and four or more light emitting units are disposed between the anode 110 and the cathode 220 . may include

In more detail, the first light emitting unit ST1 constitutes one light emitting device unit and includes the first light emitting layer 140 . The first light emitting layer 140 may emit any one of red, green, and blue, and in the present embodiment may be a blue light emitting layer that emits blue. The blue light emitting layer may be one of a blue light emitting layer, a dark blue light emitting layer, or a sky blue light emitting layer.

The first light emitting part ST1 further includes a first hole injection layer 120 and a first hole transport layer 130 between the anode 110 and the first light emitting layer 140 . In addition, the first light emitting part ST1 further includes a first electron transport layer 150 on the first light emitting layer 140 . An electron injection layer may be further included on the first electron transport layer 150 . Accordingly, the first light emitting part ST1 including the first hole injection layer 120 , the first hole transport layer 130 , the first light emitting layer 140 , and the first electron transport layer 150 on the anode 110 is formed. make up The first hole injection layer 120 and the electron transport layer may not be included in the configuration of the first light emitting part ST1 depending on the structure or characteristics of the device.

In addition, the second light emitting part ST2 including the second light emitting layer 190 is positioned on the first light emitting part ST1 . The second light emitting layer 190 may emit one color among red, green, and blue, and may be, for example, a yellow-green or green light emitting layer in the present embodiment. The yellow green light emitting layer may have a yellow light emitting layer or a multilayer structure of a yellow green light emitting layer and a green light emitting layer. The second light emitting part ST2 further includes a second hole injection layer 170 and a second hole transport layer 180 between the first charge generating layer 160 and the second light emitting layer 190 , and a second A second electron transport layer 200 is further included on the light emitting layer 190 . In addition, an electron injection layer may be further included on the second electron transport layer 200 . Accordingly, the second light emitting unit including a second hole injection layer 170 , a second hole transport layer 180 , a second light emitting layer 190 and a second electron transport layer 200 on the first light emitting unit ST1 ( ST2) is configured. The second hole injection layer 170 and the electron injection layer may not be included in the configuration of the second light emitting part ST2 depending on the structure or characteristics of the device.

A first charge generation layer 160 is positioned between the first light emitting part ST1 and the second light emitting part ST2 . The first charge generation layer 160 is a PN junction charge generation layer in which an N-type charge generation layer 160N and a P-type charge generation layer 160P are joined, and generates charges or separates them into holes and electrons in each light emitting layer. inject an electric charge

In addition, the third light emitting part ST3 including the third light emitting layer 250 is positioned on the second light emitting part ST2 . The third light-emitting layer 250 may emit one color among red, green, and blue, for example, a blue light-emitting layer that emits blue in the present embodiment. The blue light emitting layer may be one of a blue light emitting layer, a dark blue light emitting layer, or a sky blue light emitting layer. The third light emitting part ST3 further includes a third hole transport layer 240 between the second charge generating layer 230 and the third light emitting layer 250 , and the third electrons on the third light emitting layer 250 . It further includes a transport layer 260 and an electron injection layer 210 . In addition, a hole injection layer may be further included under the third hole transport layer 240 . Accordingly, the third light emitting part ST3 including the third hole transport layer 240 , the third emission layer 250 , the third electron transport layer 260 , and the electron injection layer 210 on the second charge generation layer 230 . ) constitutes A cathode 220 is provided on the third light emitting part ST3 to configure the organic electroluminescent device according to the second embodiment of the present invention. The hole injection layer and the electron injection layer 210 may not be included in the configuration of the third light emitting unit ST3 depending on the structure or characteristics of the device.

In addition, the third electron transport layer 260 located in the third light emitting part ST3 of the organic electroluminescent device 100 according to the sixth embodiment of the present invention serves to facilitate electron transport. The third electron transport layer 260 includes a first layer 261 adjacent to the third light emitting layer 250 , a mixed layer 262 positioned on the first layer 261 , and a second layer 263 positioned on the mixed layer 262 . includes The first layer 261 includes a first electron transport material having a high triplet excitation energy level (T1 Level), thereby blocking the passing of holes from the hole transport layer and maintaining the balance of electrons and holes in the light emitting layer. It can play a role in balancing the charge. The first electron transport material has a triplet excitation energy level (T1 Level) of 2.6 to 2.8 eV. In addition, the first electron transport material has a HOMO level of -5.9 to -6.3 eV and a LUMO level of -2.4 to -2.8 eV. Since the second layer 263 includes a second electron transport material having high electron mobility, it may serve to improve the injection of electrons injected from the cathode 220 and lower the driving voltage of the device. The second electron transport material may have an electron mobility in a range of 1×10 ⁻³ to 1×10 ⁻⁵ cm 2 /Vs. In addition, the second electron transport material has a HOMO level of -5.8 to -6.2 eV, a LUMO level of -2.8 to -3.2 eV, and a triplet excitation energy level of 1.6 to 2.0 eV. The mixed layer 262 is located between the first layer 261 and the second layer 262, and is a layer in which the above-described first electron transport material and the second electron transport material are mixed. The mixed layer 262 may include the first electron transport material to block the passage of holes from the third light emitting layer 250 and to balance the charge balance by balancing electrons and holes in the third light emitting layer 250 . . In addition, the mixed layer 262 includes the second electron transport material, and may improve electron injection and lower the driving voltage of the device.

In addition, the organic electroluminescent device 100 according to the sixth embodiment of the present invention includes the first electron transport layer 150 of the first light emitting part ST1 in addition to the third electron transport layer 260 of the third light emitting part ST3. may be configured in the same manner as the above-described third electron transport layer 260 . That is, the first electron transport layer 150 of the first light emitting unit ST1 includes a first layer including a first electron transport material, a mixed layer in which the first electron transport material and the second electron transport material are mixed, and a second electron transport layer. and a second layer comprising a material. In addition, the first electron transport layer 150 may be a single layer including a first layer, a mixed layer, and a second layer. The electron transport layer having a three-layer structure including the first electron transport material and the second electron transport material of the present invention may be applied to any light emitting part as long as it emits blue light.

As described above, the organic electroluminescent device of the present invention forms an electron transport layer including a first electron transport material having a high triplet excitation energy level and a second electron transport material having a high electron mobility, thereby forming an electron transport layer in the electron transport layer. There is an advantage in that the driving voltage can be lowered by forming several energy levels to reduce the barrier of charges passing from adjacent layers. In addition, a first layer including a first electron transport material having a high triplet excitation energy level is provided to increase device efficiency, and a second layer including a second electron transport material having high electron mobility is provided. Accordingly, there is an advantage that the driving voltage can be lowered by further facilitating the movement of electrons.

8 is an energy band diagram of an organic electroluminescent device according to a fourth embodiment of the present invention.

Referring to FIG. 8 , the organic electroluminescent device of the present invention includes a light emitting layer (EML), an electron transport layer (ETL) and an electron injection layer (EIL) including a host and a dopant. The electron transport layer (ETL) is a mixture of a first layer (ETL1) including a first electron transport material, a second layer (ETL2) including a second electron transport material, and a first electron transport material and a second electron transport material. Mixed ETL.

A first electron transport material having a high triplet excitation energy level in the first layer ETL1 forms one band gap, and a second electron transport material having a high electron mobility in the second layer ETL2 is another to form a band gap of In the mixed ETL, the first electron transport material and the second electron transport material form band gaps, respectively. Carriers injected from the adjacent electron injection layer EIL or the cathode may easily move to the second layer ETL2 beyond the band gap of the second electron transport material of the second layer ETL2 . Carriers reaching the second layer ETL2 easily move to the mixed ETL through the band gap of the same second electron transport material formed in the mixed ETL, or the first electron transport formed in the mixed ETL It can migrate across the bandgap of the material into the mixed ETL. And among the carriers that have reached the mixed ETL, carriers existing in the band gap of the second electron transport material cross the band gap of the first electron transport material formed in the first layer ETL1 to the first layer ETL1. Carriers moving or existing in the band gap of the first electron transport material may easily move to the first layer ETL1 through the band gap of the same first electron transport material. That is, by providing an electron transport layer including the first layer (ETL1), the mixed layer (Mixed ETL) and the second layer (ETL2), the barrier of carriers moving from the electron injection layer or the cathode to the light emitting layer is reduced to reduce the carrier movement. can do it smoothly. In addition, the first electron transport material having a high triplet excitation energy level (T1 Level) prevents holes from passing from the emission layer EML to the electron transport layer ETL, thereby improving efficiency. In addition, an electron injection ability is improved due to the second electron transport material having high electron mobility, and thus the driving voltage of the device may be lowered.

9 is a diagram schematically illustrating a co-deposition method for manufacturing an electron transport layer of an organic electroluminescent device of the present invention.

9, the electron transport layer of the organic light emitting device of the present invention is formed by a co-deposition method (co-deposition method). In more detail, the first deposition source S_ETL1 provided with the first electron transport material ETL1 and the second deposition source S_ETL2 provided with the second electron transport material ETL2 are provided at the bottom of the chamber, and the light emitting layer surface A substrate mounted to face these deposition sources is provided at the top of the chamber. When the substrate moves in one direction of the chamber, the first deposition source S_ETL1 and the second deposition source S_ETL2 start deposition of the first electron transport material and the second electron transport material. As the substrate moves, the first electron transport material ETL1 evaporated from the first deposition source S_ETL1 is deposited on the substrate to form a first layer, and then the first electron transport material ETL1 and the second electron The transport material ETL2 is simultaneously deposited to form a mixed layer, and finally, a second electron transport material ETL2 evaporated from the second deposition source S_ETL2 is deposited to form a second layer. Accordingly, the electron transport layers according to the fourth to sixth embodiments of the present invention are manufactured.

On the other hand, if the distance between the first deposition source S_ETL1 and the second deposition source S_ETL2 is reduced, both the first electron transport material and the second electron transport material may be simultaneously deposited on the substrate. Accordingly, the electron transport layer according to the first to third embodiments of the present invention can be manufactured. Therefore, in the present invention, the electron transport layer can be formed in various structures by adjusting the spacing between the deposition sources.

Hereinafter, an embodiment in which the organic electroluminescent device of the present invention is manufactured is disclosed. The following materials for the electron transport layer are not intended to limit the scope of the present invention.

Experiment 1: Characteristics of the device according to the mixed material compared to the single material of the electron transport layer

<Comparative Example 1>

A device including a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, a dry purple injection layer, and a cathode was constructed on a substrate. The light emitting layer was composed of a blue light emitting layer, and an oxadiazole compound was formed as the electron transport layer. The device was tested by constructing a mono device.

<Comparative Example 2>

In the same configuration as in Comparative Example 1 described above, an electron transport layer was formed with a quinoline compound to construct a device.

<Example 1>

In the same configuration as in Comparative Example 1, an electron transport layer was formed by mixing an oxadiazole compound and a quinoline compound to construct a device.

The materials of the electron transport layer in Comparative Examples 1 and 1 are not intended to limit the content of the present invention.

The driving voltage and luminous efficiency of the devices manufactured according to Comparative Example 1 and Example 1 are shown in Table 1 below, and the driving voltage and luminous efficiency of the devices manufactured according to Comparative Examples 2 and 1 are shown in Table 2 below. shown in In Table 1 below, the result value of Comparative Example 1 was reported as 100% and the result value of Example 1 was expressed as a percentage, and in Table 2, the result value of Comparative Example 2 was reported as 100% and the result of Example 1 accordingly Values are expressed as percentages.

Comparative Example 1 Example 1 Driving voltage (V) 100% 58% Luminous Efficiency 100% 172%

Comparative Example 2 Example 1 Driving voltage (V) 100% 110% Luminous Efficiency 100% 121%

Referring to Table 1, compared to Comparative Example 1 having an electron transport layer formed only of a material having a high triplet excitation energy level, the device of Example 1 in which a material with high charge mobility is further mixed has a lower driving voltage and The luminous efficiency was improved by 72%. In addition, referring to Table 2, compared to Comparative Example 2 having an electron transport layer formed only of a material having a high charge mobility, the device of Example 1 in which a material having a high triplet excitation energy level is further mixed has a driving voltage Although this increased slightly, the luminous efficiency was improved by 21%.

Experiment 2: of the electron transport layer Device properties as a function of material ratio

<Example 2>

Under the same process conditions as in Example 1, an electron transport layer was formed by mixing an oxadiazole compound and a quinoline compound in a ratio of 7:3, 1:1, and 3:7, respectively, to prepare a device.

The material of the electron transport layer in Example 2 does not limit the content of the present invention.

Table 3 below shows the driving voltage and luminous efficiency of the device according to the material mixing ratio of the electron transport layer according to Example 2 described above. In addition, the current density according to the driving voltage was measured and shown in FIG. 10, and the efficiency according to the luminance was measured and shown in FIG. 11 . In addition, according to Example 2, the material mixing ratio of the electron transport layer was 7:3 and 3:7, respectively. The emission intensity according to the wavelength of the device was measured and shown in FIG. 12, and the material of the electron transport layer according to Example 2 The light emission intensity according to the wavelength of the device prepared in the mixing ratio of 1:1 and 3:7, respectively, was measured and shown in FIG. 13 . In Table 3 below, the result value of the device mixed in the ratio of 1:1 was regarded as 100%, and the result value of the device mixed in the ratio of 7:3 and 3:7 was expressed as a percentage.

Mixing ratio of electron transport layer 7:3 1:1 3:7 Driving voltage (V) 141.3 100.0 89.1 Luminous Efficiency 70.9 100.0 100.0

10 and 11, referring to Table 3, the luminous efficiency showed the same mixing ratio of 1:1 and 3:7, and the driving voltage showed the lowest at the mixing ratio of 7:3, in particular, A high driving voltage and low luminous efficiency were exhibited at a mixing ratio of 7:3. Through this, it can be seen that in order to realize a device with a low voltage and high efficiency, a ratio of a material having high electron mobility should be mixed in a ratio of 1 or more compared to a material having a high triplet excitation energy level.

And, as shown in FIGS. 12 and 13 , it can be seen that the mixing ratio of 3:7 at a wavelength of 440 nm to 480 nm that emits blue light has an increase in emission intensity than the mixing ratio of 7:3. Therefore, it can be seen that the light emission intensity is increased when the ratio of the material with high electron mobility is high compared to the case of the material with high triplet excitation energy level.

Experiment 3: of the electron transport layer according to thickness organic light emitting device characteristic

<Example 3>

A first light emitting part including a blue light emitting layer, a charge generating layer, a second light emitting part including a yellow light emitting layer, a third light emitting part including a charge generating layer and a blue light emitting layer are formed on a substrate, and a cathode is formed to perform organic electroluminescence The device was fabricated. Here, the electron transport layer included in the third light emitting part was formed by mixing oxadiazole and a quinoline compound in a ratio of 3:2 to a thickness of 250 Å.

The material of the electron transport layer or the configuration of the light emitting layer in Example 3 does not limit the content of the present invention.

In the organic electroluminescent device according to Example 3, the thickness of the electron transport layer was changed to 250 and 300 Å, respectively, to fabricate the organic electroluminescent device, and the driving voltage and luminous efficiency thereof were measured, and is shown in Table 4 below. In addition, the current density according to the driving voltage was measured and shown in FIG. 14 , the efficiency according to the luminance was measured and shown in FIG. 15 , and the emission intensity according to the wavelength was measured and shown in FIG. 16 . In Table 4 below, the result value of the device in which the electron transport layer was formed to a thickness of 300 Å was expressed as 100%, and the resulting value of the device formed to the thickness of 250 Å was expressed as a percentage.

Electron transport layer thickness (Å) 250 300 Driving voltage (V) 94.3 100.0 Luminous Efficiency 97.4 100.0

Referring to FIGS. 14 and 15 and Table 4, as the thickness of the electron transport layer decreased from 300 Å to 250 Å, the driving voltage decreased and the luminous efficiency decreased somewhat. Through this, it was confirmed that when the thickness of the electron transport layer was reduced, it was excellent in terms of driving voltage.

And, as shown in FIG. 16, it can be seen that the luminescence intensity increased in the case of forming at 300 Å at a wavelength of 440 nm to 480 nm for emitting blue and 510 nm to 590 nm for emitting yellow-green light compared to the case of forming at 250 Å. can

Experiment 4: of the electron transport layer according to mixed material organic light emitting device characteristic

<Example 4>

In the same configuration as in Example 3, an organic electroluminescent device was manufactured by mixing an oxadiazole compound and a quinoline compound in a 1:1 ratio as an electron transport layer.

<Example 5>

In the same configuration as in Example 4, an organic electroluminescent device was manufactured by mixing a carbazole compound and a quinoline compound in a 1:1 ratio as an electron transport layer.

The materials of the electron transport layer or the configuration of the light emitting layer in Examples 4 and 5 do not limit the content of the present invention.

The driving voltage, R, G, B, and W color lifetimes, luminous efficiency, and quantum efficiency of the organic light emitting diodes manufactured according to Examples 4 and 5 were measured, and are shown in Table 5 below. In addition, the current density according to the driving voltage was measured and shown in FIG. 17 , the efficiency according to the luminance was measured and shown in FIG. 18 , and the emission intensity according to the wavelength was measured and shown in FIG. 19 . In Table 5 below, the device result value of Example 4 is shown as 100%, and the device result value of Example 5 is expressed as a percentage.

Example 4 Example 5 Driving voltage (%)
Vpeak 100 97.7 V(10mA/cm2) 100 98.3
Lifetime (T95)(%)

R 100 101.6 G 100 98.7 B 100 72.5 W 100 94.0 characteristic(%)
Luminous Efficiency (Cd/A) 100 100.2 Quantum efficiency (%) 100 100.3

Referring to FIGS. 17 and 18 and Table 5, the devices according to Examples 4 and 5 using materials having similar properties exhibited equal levels of lifetime and efficiency.

And, as shown in FIG. 19, it can be seen that the emission intensity is at the same level at a wavelength of 440 nm to 480 nm for emitting blue and 510 nm to 590 nm for emitting yellow-green.

Experiment 5: of the electron transport layer according to the thickness of each layer organic light emitting device characteristic

<Example 6>

In the same configuration as in Example 2, an organic electroluminescent device was manufactured by mixing an oxadiazole compound and a quinoline compound in a 1:1 ratio as an electron transport layer.

<Example 7>

In the same configuration as in Example 6, an oxadiazole compound was formed to a thickness of 50 Å as a first layer of the electron transport layer, and an oxadiazole and a quinoline compound were mixed 1:1 as a mixed layer of the electron transport layer to a thickness of 200 Å. was formed, and a quinoline compound was formed to a thickness of 50 Å as a second layer of the electron transport layer to fabricate an organic electroluminescent device.

<Example 8>

In the same configuration as in Example 7, an oxadiazole compound is formed to a thickness of 100 Å as a first layer of the electron transport layer, and an oxadiazole and a quinoline compound are mixed 1:1 as a mixed layer of the electron transport layer to a thickness of 100 Å. was formed, and a quinoline compound was formed to a thickness of 100 Å as a second layer of the electron transport layer to fabricate an organic electroluminescent device.

<Example 9>

In the same configuration as in Example 7, an oxadiazole compound was formed to a thickness of 50 Å as the first layer of the electron transport layer, and an oxadiazole and a quinoline compound were mixed 1:1 as a mixed layer of the electron transport layer to a thickness of 150 Å. was formed, and a quinoline compound was formed to a thickness of 100 Å as a second layer of the electron transport layer to fabricate an organic electroluminescent device.

<Example 10>

In the same configuration as in Example 7, an oxadiazole compound is formed to a thickness of 100 Å as a first layer of the electron transport layer, and an oxadiazole and a quinoline compound are mixed 1:1 as a mixed layer of the electron transport layer to a thickness of 150 Å. was formed, and a quinoline compound was formed to a thickness of 50 Å as a second layer of the electron transport layer to fabricate an organic electroluminescent device.

The driving voltage, luminous efficiency, and lifespan of the organic light emitting diodes manufactured according to Examples 6 and 10 were measured, and are shown in Table 6 below. In Table 6 below, the device result value of Example 6 is shown as 100%, and the device result value of Examples 7 to 10 is expressed as a percentage.

Example 6 Example 7 Example 8 Example 9 Example 10 Driving voltage (%) 100 95 100 91 98 efficiency(%) 100 103 95 105 104 life span(%) 100 102 90 118 105

Referring to Table 6, compared to Example 6 in which a mixed electron transport layer of 300 Å was formed as a single layer, Example 7 in which an electron transport layer was formed with a first layer of 50 Å, a mixed layer of 200 Å and a second layer of 50 Å was formed. The driving voltage was reduced by 5%, the efficiency was increased by 3%, and the service life was increased by 2%. Example 8, in which the electron transport layer was formed with the first layer of 100 Å, the mixed layer of 100 Å, and the second layer of 100 Å, had the same driving voltage, reduced efficiency by 5%, and reduced lifespan by 10%. In Example 9, in which the electron transport layer was formed with the first layer of 50 Å, the mixed layer of 150 Å, and the second layer of 100 Å, the driving voltage decreased by 9%, the efficiency increased by 5%, and the lifetime increased by 18%. In Example 10, in which the electron transport layer was formed with the first layer of 100 Å, the mixed layer of 150 Å, and the second layer of 50 Å, the driving voltage decreased by 2%, the efficiency increased by 4%, and the lifetime increased by 5%.

With the exception of Example 8, the driving voltage was reduced compared to Example 6, and the efficiency and lifespan of Examples 7, 9 and 10 were increased. From this result, it can be seen that when the mixed layer of the electron transport layer is 100 Å or less, the efficiency and lifespan of the device are reduced, and the mixed layer of the electron transport layer is preferably 150 Å or more. In addition, Example 9 exhibits excellent effects, and it can be seen that the electron transport layer comprising the first layer of 50 Å, the mixed layer of 150 Å and the second layer of 100 Å is most preferable.

As described above, the organic electroluminescent device of the present invention forms an electron transport layer including a first electron transport material having a high triplet excitation energy level and a second electron transport material having a high electron mobility, so that various There is an advantage in that the driving voltage can be lowered by forming an energy level to reduce a barrier of charges passing from an adjacent layer. In addition, a first layer including a first electron transport material having a high triplet excitation energy level is provided to increase device efficiency, and a second layer including a second electron transport material having high electron mobility is provided. Accordingly, there is an advantage that the driving voltage can be lowered by further facilitating the movement of electrons.

In addition, the driving voltage may be lowered by configuring the ratio of the second electron transport material having high electron mobility equal to or greater than the ratio of the first electron transport material having a high triplet excitation energy level.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical configuration of the present invention can be changed to other specific forms by those skilled in the art to which the present invention pertains without changing the technical spirit or essential features of the present invention. It will be appreciated that this may be practiced. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. In addition, the scope of the present invention is indicated by the claims to be described later rather than the above detailed description. In addition, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention.

10: organic light emitting device 20: anode
30: hole injection layer 40: hole transport layer
50: light emitting layer 60: electron transport layer
70: electron injection layer 80: cathode

Claims (28)

In the organic electroluminescent device between the anode and the cathode, comprising a light emitting layer and an electron transport layer,
The electron transport layer includes a first layer including a first electron transport material, a second layer including a second electron transport material, and located between the first layer and the second layer, and the first and second electron transport materials It has a three-layer structure of a mixed layer comprising
The first electron transport material has a triplet excitation energy level higher than that of the second electron transport material organic electroluminescent device, characterized in that the electron mobility is low. delete delete delete delete delete According to claim 1,
The organic electroluminescent device, characterized in that the first electron transport material comprises a ratio of 30 to 50% with respect to the sum of the first electron transport material and the second electron transport material. According to claim 1,
The ratio of the first electron transport material is an organic electroluminescent device, characterized in that less than or equal to the ratio of the second electron transport material. According to claim 1,
The thickness of the electron transport layer is an organic electroluminescent device, characterized in that 50 to 450 Å. According to claim 1,
The thickness of each of the first layer and the second layer is 25 to 100% of the thickness of the mixed layer, the organic electroluminescent device, characterized in that the thickness of the mixed layer is 150 to 200 Å. According to claim 1,
The first electron transport material is located close to the light emitting layer, the organic light emitting device, characterized in that to prevent movement of the holes from the light emitting layer to the electron transport layer. According to claim 1,
The second electron transport material is located close to the cathode, the organic electroluminescent device, characterized in that helping the electrons to the light emitting layer. According to claim 1,
The organic electroluminescent device, characterized in that the charge balance of the light emitting layer is adjusted by the first electron transport material and the second electron transport material. an anode and a cathode;
a first light emitting unit positioned between the anode and the cathode and including a first light emitting layer and a first electron transport layer;
and a second light emitting unit positioned between the first light emitting unit and the cathode and including a second light emitting layer and a second electron transport layer,
At least one of the first and second electron transport layers is located between a first layer including a first electron transport material, a second layer including a second electron transport material, and the first layer and the second layer. An organic electroluminescent device, characterized in that it has a three-layer structure of a mixed layer comprising a first and a second electron transport material. an anode and a cathode;
a first light emitting part positioned between the anode and the cathode and including a first light emitting layer and a first electron transport layer;
a second light emitting unit positioned on the first light emitting unit and including a second light emitting layer and a second electron transport layer;
It is positioned between the second light emitting unit and the cathode, and includes a third light emitting unit including a third light emitting layer and a third electron transport layer,
At least one of the first to third electron transport layers is located between a first layer including a first electron transport material, a second layer including a second electron transport material, and the first layer and the second layer. An organic electroluminescent device, characterized in that it has a three-layer structure of a mixed layer comprising a first and a second electron transport material. 16. The method of claim 14 or 15,
The organic electroluminescent device, characterized in that the triplet excitation energy level or electron mobility of the first electron transport material and the second electron transport material are different from each other. 17. The method of claim 16,
The triplet excitation energy level of the first electron transport material is higher than the triplet excitation energy level of the second electron transport material. delete 17. The method of claim 16,
The organic electroluminescent device, characterized in that the electron mobility of the first electron transport material is lower than the electron mobility of the second electron transport material. delete 16. The method of claim 14 or 15,
The organic electroluminescent device, characterized in that the first electron transport material comprises a ratio of 30 to 50% with respect to the sum of the first electron transport material and the second electron transport material. 16. The method of claim 14 or 15,
The ratio of the first electron transport material is an organic electroluminescent device, characterized in that less than or equal to the ratio of the second electron transport material. 16. The method of claim 15,
The thickness of at least one layer including the first layer, the second layer, and the mixed layer among the first to third electron transport layers is 50 to 450 Å. 16. The method of claim 14 or 15,
The thickness of each of the first layer and the second layer is 25 to 100% of the thickness of the mixed layer, the organic electroluminescent device, characterized in that the thickness of the mixed layer is 150 to 200 Å. 16. The method of claim 15,
The first light-emitting layer and the third light-emitting layer are a blue light-emitting layer, and the second light-emitting layer is an organic electroluminescent device, characterized in that a green light-emitting layer or a yellow-green light-emitting layer. 15. The method of claim 14,
At least one of the first and second light emitting layers is an organic electroluminescent device, characterized in that the blue light emitting layer. 15. The method of claim 14,
At least one layer including the first layer, the second layer, and the mixed layer among the first and second electron transport layers has a thickness of 50 to 450 Å. According to claim 1,
The light emitting layer is an organic light emitting device, characterized in that one of a red light emitting layer, a green light emitting layer, and a blue light emitting layer.

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