KR20160043891A - Organic light emitting device - Google Patents

Abstract

An organic electroluminescent device according to an embodiment of the present invention includes an emitting layer and an electron transporting layer between an anode and a cathode, wherein the electron transporting layer includes a hole transporting layer for preventing hole transport from the light emitting layer to the electron transporting layer Wherein the first electron transport material has a higher triplet excitation energy level and a lower electron mobility than the second electron transport material, wherein the first electron transport material comprises a first electron transport material and a second electron transport material that facilitates transfer of electrons to the light emitting layer, .

Description

TECHNICAL FIELD [0001] The present invention relates to an organic electroluminescent device,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic electroluminescent device, and more particularly, to an organic electroluminescent device capable of reducing driving voltage and improving luminous efficiency.

The image display device that realizes various information on the screen is a core technology of the information communication age and it is becoming thinner, lighter, more portable and higher performance. (LCD), a plasma display panel (PDP), an electro luminescent display (ELD), a field emission display (FED), and an organic light emitting diode (OLED) display device, Organic Light Emitting Diode) are being actively studied.

Among these organic electroluminescent devices, electrons and holes are paired when an electric charge is injected into the organic light emitting layer formed between the anode and the cathode, and then the light is emitted while disappearing. The organic electroluminescent device can be formed not only on a flexible transparent substrate such as a plastic but also can be driven at a lower voltage than a plasma display panel (plasma display panel) or an inorganic electroluminescence (EL) display, It has the advantage of being excellent in color. In particular, an organic electroluminescent device that implements white light 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.

The organic electroluminescent device may have a structure in which an anode, a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, an electron injecting 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, which is a pair of electron-hole pairs, and emit light due to energy generated when the excitons return to the ground state.

However, when the electron transport layer of the conventional organic electroluminescent device has a high triplet excitation energy level, the driving voltage increases due to low electron injection ability and low electron mobility. Further, when the electron transporting layer has a high electron injecting ability and an electron affinity, there is a problem that the charge balance is collapsed due to a high electron mobility and the lifetime and efficiency are lowered.

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

In order to achieve the above-mentioned object, an organic electroluminescent device according to an embodiment of the present invention includes an emitting layer and an electron transporting layer between an anode and a cathode, A first electron transporting material for blocking the movement of holes to the electron transporting layer and a second electron transporting material for facilitating the transfer of electrons to the light emitting layer, wherein the first electron transporting material has a triplet excitation energy level Is high and the electron mobility is low.

And the electron transport layer is a single layer.

The electron transport layer is formed of a single layer including three layers in which a first layer, a mixed layer and a second layer are stacked.

Wherein the first layer comprises the first electron transport material and the mixed layer comprises the first electron transport material and the second electron transport material and the second layer comprises the second electron transport material .

Wherein the triplet excitation energy level of the first electron transporting material is 2.6 to 2.8 eV and the triplet excitation energy level of the second electron transporting material is 1.6 to 2.0 eV.

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

And the first electron transporting material is composed of 30 to 50% of the sum of the first electron transporting material and the second electron transporting material.

The ratio of the first electron transporting material is less than or equal to the ratio of the second electron transporting material.

And the thickness of the electron transporting layer is 50 to 450 ANGSTROM.

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 ANGSTROM.

And the first electron transporting material is located close to the light emitting layer to prevent movement of the holes from the light emitting layer to the electron transporting layer.

And the second electron transporting material is located close to the cathode to facilitate movement of the electrons to the light emitting layer.

And the charge balance of the light emitting layer is controlled by the first electron transporting material and the second electron transporting material.

The organic electroluminescent device according to an embodiment of the present invention includes at least one light emitting portion positioned between an anode and a cathode, and an electron transporting layer disposed between the at least one light emitting portion and the cathode, And the transport layer is composed of a single layer containing the first electron transporting material and the second electron transporting material.

Wherein the single layer comprises a first layer comprising a first electron transporting material, a third layer comprising a mixture of the first electron transporting material and a second electron transporting material and a second layer comprising the second electron transporting material, .

And the triplet excitation energy level or electron mobility of the first electron transporting material and the second electron transporting material are different from each other.

Wherein the triplet excitation energy level of the first electron transporting material is higher than the triplet excitation energy level of the second electron transporting material.

Wherein the triplet excitation energy level of the first electron transporting material is 2.6 to 2.8 eV and the triplet excitation energy level of the second electron transporting material is 1.6 to 2.0 eV.

And the electron mobility of the first electron transporting material is lower than the electron mobility of the second electron transporting material.

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

And the first electron transporting material is composed of 30 to 50% of the sum of the first electron transporting material and the second electron transporting material.

The ratio of the first electron transporting material is less than or equal to the ratio of the second electron transporting material.

And the thickness of the electron transporting layer is 50 to 450 ANGSTROM.

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 ANGSTROM.

The organic electroluminescent device of the present invention forms an electron transporting layer including a first electron transporting material having a high triplet excitation energy level and a second electron transporting material having a high electron mobility to form various energy levels in the electron transporting layer Thereby reducing the barrier of the electric charges flowing from the adjacent layer and lowering the driving voltage.

It is also possible to provide a first layer comprising a first electron transporting material having a high triplet excitation energy level to increase the efficiency of the device and to have a second layer comprising a second electron transporting material having a high electron mobility Thereby making it easier to move the electrons and lower the driving voltage.

1 is a view illustrating an organic electroluminescent device according to a first embodiment of the present invention.
2 is a view illustrating an organic electroluminescent device according to a second embodiment of the present invention.
3 is a view illustrating an organic electroluminescent device according to a third embodiment of the present invention.
4 is an energy band diagram of an organic electroluminescent device according to an embodiment of the present invention.
5 is a view illustrating an organic electroluminescent device according to a fourth embodiment of the present invention.
6 is a view illustrating an organic electroluminescent device according to a fifth embodiment of the present invention.
7 is a view illustrating 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 schematic view of a co-deposition method for producing an electron transport layer of an organic electroluminescent device of the present invention.
10 is a graph showing a current density according to a driving voltage of an element manufactured according to Embodiment 2 of the present invention.
11 is a graph showing efficiency according to luminance of an element manufactured according to Embodiment 2 of the present invention.
12 is a graph showing emission intensities according to wavelengths of devices in which material mixing ratios of electron transporting layers are 7: 3 and 3: 7, respectively, according to Example 2 of the present invention.
FIG. 13 is a graph showing emission intensities according to wavelengths of devices in which material mixing ratios of electron transporting layers are 1: 1 and 3: 7, respectively, according to Example 2 of the present invention.
14 is a graph showing a current density according to a driving voltage of an organic electroluminescent device manufactured according to Example 3 of the present invention.
FIG. 15 is a graph showing efficiency according to luminance of an organic electroluminescent device manufactured according to Example 3 of the present invention. FIG.
16 is a graph showing the intensity of light emission according to wavelength of an organic electroluminescent device manufactured according to Embodiment 3 of the present invention.
17 is a graph showing current densities according to driving voltages of an organic electroluminescent device manufactured according to Embodiments 4 and 5 of the present invention.
18 is a graph showing efficiency according to luminance of an organic electroluminescent device manufactured according to Embodiments 4 and 5 of the present invention.
19 is a graph showing the intensities of organic electroluminescent devices manufactured according to Examples 4 and 5 according to wavelengths according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, and the like disclosed in the drawings for describing the embodiments of the present invention are illustrative, and thus the present invention is not limited thereto. Like reference numerals refer to like elements throughout the specification. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. In the case where the word 'includes', 'having', 'done', etc. are used in this specification, other parts can be added unless '~ only' is used. Unless the context clearly dictates otherwise, including the plural unless the context clearly dictates otherwise.

In interpreting the constituent elements, it is construed to include the error range even if there is no separate description.

In the case of a description of the positional relationship, for example, if the positional relationship between two parts is described as 'on', 'on top', 'under', and 'next to' Or " direct " is not used, one or more other portions may be located between the two portions.

In the case of a description of a temporal relationship, for example, if the temporal relationship is described by 'after', 'after', 'after', 'before', etc., May not be continuous unless they are not used.

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

It is to be understood that each of the features of the various embodiments of the present invention may be combined or combined with each other, partially or wholly, technically various interlocking and driving, and that the embodiments may be practiced independently of each other, It is possible.

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

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

1, an organic electroluminescent device 10 according to a first embodiment of the present invention includes an anode 20, a hole injecting layer 30, a hole transporting layer 40, a light emitting layer 50, an electron transporting layer 60 ), An electron injection layer (70), and a cathode (80).

The anode 20 may be any one of ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), and ZnO (Zinc Oxide) having high work function as an electrode for injecting holes. When the anode 20 is a reflective electrode, the anode 20 may have a reflective layer made of any one of aluminum (Al), silver (Ag), and nickel (Ni) under the layer made of any one of ITO, IZO, .

The hole injection layer 30 may function to smoothly inject holes from the anode 20 into the light emitting layer 50. The hole injection layer 30 may be formed of at least one selected from the group consisting of CuPc (copper phthalocyanine), PEDOT (poly (3,4) -ethylenedioxythiophene), PANI (polyaniline) and NPD (naphthalene- bis (phenyl) -2,2'-dimethylbenzidine), but the present invention is not limited thereto. The thickness of the hole injection layer 30 may be 1 to 150 nm. Here, if the thickness of the hole injection layer 30 is 1 nm or more, there is an advantage that the hole injection characteristics can be prevented from being lowered. When the thickness of the hole injection layer 30 is 150 nm or less, the thickness of the hole injection layer 30 is too thick, which is advantageous in preventing the driving voltage from rising to improve the movement of holes. The hole injecting layer 30 and the electron injecting layer 70 may not be included in the organic electroluminescent device depending on the structure and characteristics of the device.

The hole transport layer 40 serves to smooth the transport of holes, and NPD (N, N-bis (naphthalene-1-yl) -N, N'-bis (phenyl) , TPD (N, N'-bis- (3-methylphenyl) -N, N'-bis- (phenyl) benzidine), spiro-TAD (2,2 ', 7,7'- 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 in the range of 1 to 150 nm. When the thickness of the hole transport layer 40 is 1 nm or more, there is an advantage that the hole transport property can be prevented from being degraded. When the thickness of the transport layer 40 is 150 nm or less, the thickness of the hole transport layer 40 is too thick, which is advantageous in preventing the drive voltage from rising to improve the movement of the holes.

The light emitting layer 50 may emit red (R), green (G), or blue (B) light, and may be formed of a phosphor 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 includes Ir (PIQ) ₂ (acac) (bis (1-phenylisoquinoline) acetylacetonate a phosphorescent material containing a dopant including at least one selected from the group consisting of iridium (III), Ir (PIQ) ₃ , and PtOEP (octaethylporphine platinum) , Or a fluorescent material including PBD: Eu (DBM) ₃ (Phen) or Perylene, but not limited thereto.

When the light emitting layer 50 is green, a phosphorescent material containing a host material such as CBP (4,4'-bis (carbazol-9-yl) biphenyl) and containing a dopant material including 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, a phosphorescent material containing a host material such as CBP (4,4'-bis (carbazol-9-yl) biphenyl) and containing a dopant material including an iridium series (2,7-bis) 4-diphenylamino) styryl) -9,9-spirofluorene), spiro-CBP (2,2 ', 7,7'- tetrakis (carbozol-9 -yl) -9,9-spirofluorene, distyrylbenzene (DSB), distyrylarylene (DSA), PFO-based polymer, and PPV-based polymer. It is not limited.

The electron transport layer 60 plays a role of facilitating transport of electrons, and affects the lifetime and efficiency of the organic electroluminescent device. The inventors of the present invention have conducted various experiments to improve the lifetime and efficiency of the organic electroluminescent device by improving the characteristics of the electron transporting layer. When the electron transport layer is composed of one layer having a high triplet excitation energy level in order to reduce the driving voltage, the electron injection is not smooth due to the low electron mobility and the driving voltage is increased. In the case of a single layer having a high electron mobility, although the electron injection is smooth, the balance between electrons and holes in the light emitting layer is broken and the lifetime is reduced. Therefore, when the electron transport layer is composed of two layers, the driving voltage increases because the thickness of the device increases. Therefore, the inventors of the present invention have found out that the electron transporting layer is composed of a single layer by mixing the materials contained in the electron transporting layer in two, and the organic electroluminescent layer is formed in accordance with the characteristics of the two materials included in the electron transporting layer, The inventors have invented a structure of an organic electroluminescent device having a novel structure capable of improving the efficiency of the device and reducing the driving voltage.

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

More specifically, the first electron transporting material has a high triplet excitation energy level (T1 level), thereby blocking holes from the light emitting layer and maintaining a balance of electrons and holes in the light emitting layer, Can play a role. Accordingly, the first electron transporting material may be positioned adjacent to the light emitting layer 50 to prevent the movement of holes from the light emitting layer 50 to the electron transporting layer 60. The triplet excitation energy level (T1 Level) is 2.6 to 2.8 eV. The first electron transporting 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 transporting 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, May be a compound represented by the following formula (1).

[Chemical Formula 1]

In Formula 1, A ₁ to A ₁₃ each independently represent a substituted or unsubstituted aromatic ring having 6 to 50 carbon atoms, or at least one of the substituted or unsubstituted 5 to 49 carbon atoms selected from the group consisting of S, N, and O (Heterocyclic Ring). ≪ / RTI >

The second electron transporting material has a high electron mobility, thereby improving the injection of electrons and lowering 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 transporting material may be a quinoline compound, an anthracene compound or the like, and may be, for example, a compound represented by the following formula (2).

(2)

In Formula 2, A ₁ to A ₁₀ each independently represents a substituted or unsubstituted aromatic ring having 6 to 50 carbon atoms, or at least one is substituted or unsubstituted C 5 to S 49 S, N, and O (Heterocyclic Ring). ≪ / RTI >

The present invention includes an electron transport layer containing materials having different properties, thereby forming various energy levels in the electron transport layer to reduce the barrier of charges from adjacent layers. Thus, the charge can be easily transferred to the light emitting layer, so that the charge balance in the light emitting layer can be maintained and the driving voltage can be lowered. In particular, the present invention includes a first electron transport material having a high triplet excitation energy level (T1 level) to increase the efficiency of the device. Further, the second electron transporting material having a high electron mobility can facilitate the movement of electrons, thereby lowering the driving voltage.

In order to lower the driving voltage of the organic electroluminescent device and improve the efficiency, the electron transport layer 60 of the present invention includes the first electron transporting material and the second electron transporting material. Here, the electron transporting layer 60 accounts for 30 to 50% of the first electron transporting material with respect to the sum of the first electron transporting material and the second electron transporting material. If the ratio of the first electron transporting material to the sum of the first electron transporting material and the second electron transporting material is less than 30%, the charge balance of the device is not matched and the efficiency is lowered. If the ratio of the first electron transporting material to the sum of the first electron transporting material and the second electron transporting material is more than 50%, the movement of the electrons is not smooth and the driving voltage of the device is increased and the efficiency is lowered.

The electron transport layer 60 is formed of a single layer containing a first electron transporting material and a second electron transporting material and has a thickness of 50 to 450 ANGSTROM. If the thickness of the electron transporting layer 60 is less than 50 angstroms, the electron transporting layer 60 will not act as an electron transporting layer. When the thickness of the electron transporting layer 60 exceeds 450 angstroms, Can not be maximized.

On the other hand, the electron injection layer 70 serves to smoothly inject electrons, and Alq ₃ (tris (8-hydroxy quinolinato) aluminum), PBD 2- (4- butylphenyl-1,3,4-oxadiazole), TAZ (3- (4-biphenyl) -4-phenyl-5-tert- 8-quinolinolate) -4- (phenylphenolato) aluminum). 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 , but the present invention is not limited thereto. The thickness of the electron injection layer 70 may be 1 to 50 nm. Here, when the thickness of the electron injection layer 70 is 1 nm or more, the electron injection characteristics can be prevented from being lowered. When 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 drive voltage for improving the movement of electrons. The electron injection layer 70 may not be included in the organic electroluminescent device depending on the structure and characteristics of the device.

The cathode 80 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, when the organic electroluminescent device is a front or both-side light emitting structure, the cathode 80 may be formed to have a thickness thin enough to transmit light, and when the organic electroluminescent device is a back light emitting structure, It can be formed thick enough.

As described above, the organic electroluminescent device of the present invention forms an electron transporting layer containing a first electron transporting material having a high triplet excitation energy level and a second electron transporting material having a high electron mobility, There is an advantage in that the driving voltage can be lowered by forming a plurality of energy levels, thereby reducing the barrier of the charges from the adjacent layer. In addition, the electron transport layer may include a first electron transport material having a high triplet excitation energy level to increase the efficiency of the device, and may include a second electron transport material having a high electron mobility to further facilitate electron transport There is an advantage that the driving voltage can be lowered.

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

2, the organic electroluminescent device 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 the anode 110 and the cathode 220, And a charge generation layer 160 interposed between the charge generation layer 160 and the charge generation layer 160.

In more detail, the first light emitting portion ST1 constitutes one light emitting element unit and includes a first light emitting layer 140. [ The first light emitting layer 140 may emit light of any one of red, green, and blue. In this embodiment, the first light emitting layer 140 may be a blue light emitting layer emitting blue light. The light emitting layer for emitting blue light 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 portion ST1 further includes a first hole injection layer 120 and a first hole transport layer 130 on the anode 110. [ The first light emitting portion ST1 further includes a first electron transport layer 150 on the first light emitting layer 140. [ The first electron transport layer 150 may further include an electron injection layer. Accordingly, the first light emitting portion 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 is formed on the anode 110 . The first hole injection layer 120 and the electron injection layer may not be included in the first light emitting portion ST1 depending on the structure and characteristics of the device.

The second light emitting portion ST2 including the second light emitting layer 190 is located on the first light emitting portion ST1. The second light emitting layer 190 may emit light of one of red, green, and blue, and may be, for example, a yellow-green light emitting layer or a green light emitting layer in this embodiment. The yellow-emitting layer may have a multilayer structure of a light-emitting layer for emitting yellow light or a light-emitting layer for emitting green light. The second light emitting portion ST2 may further include a second hole injection layer 170 and a second hole transport layer 180. The second light emitting portion ST2 may include a second electron transport layer 200 and an electron injection layer 210). Therefore, the second hole injection layer 170, the second hole transport layer 180, the yellow organic light emitting layer 190, the second electron transport layer 200, and the electron injection layer 210 are formed on the first light emitting portion ST1 And the second light emitting portion ST2. The second hole injection layer 170 and the electron injection layer 210 may not be included in the second light emitting portion ST2 depending on the structure and characteristics of the device.

A charge generating layer 160 is positioned between the first light emitting portion ST1 and the second light emitting portion ST2. The 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 bonded to each other to generate charges or separate them into holes and electrons, 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, 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 made of an organic material doped with metal or N-type. 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 selected from the group consisting of Li, Be, Cs, K, Rb, Mg, Na, Ca, Sr, Eu, Fr, Ba, The host material may be, for example, a material selected from the group consisting of Alq ₃ (tris (8-hydroxyquinolinato) aluminum), triazine derivatives, benzazole derivatives and silole derivatives .

On the other hand, the P-type charge generation layer 160P may be formed of a metal or a P-type doped organic material. The metal may be one or more selected from the group consisting of Al, Cu, Fe, Pb, Zn, Au, Pt, W, In, Mo, Ni and Ti. The P-type dopant and the host material used for the organic material doped with P-type may be a conventionally used material. For example, the P-type dopant is _{F 4 -TCNQ (2,3,5,6-tetrafluoro-} 7,7,8,8-tetracyano-quinodimethane), iodine, FeCl _3, FeF _3, and the group consisting of SbCl ₅ ≪ / RTI > In addition, the host may be selected from the group consisting of NPB (N, N'-bis (naphthaen-1-yl) -N, N'- -bis (phenyl) -benzidine) and TNB (N, N, N ', N'-tetra-naphthalenyl-benzidine).

And the cathode 220 is positioned on the second light emitting portion 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, when the organic electroluminescent device is a front or both-side light emitting structure, the cathode 220 may be formed to have a thickness thin enough to transmit light, and when the organic electroluminescent device is a back light emitting structure, It can be formed thick enough.

Meanwhile, the first electron transport layer 150 located in the first light emitting portion ST1 of the organic electroluminescent device 100 according to the second embodiment of the present invention plays a role of facilitating transport of electrons. More specifically, the first electron transporting layer 150 includes a first electron transporting material and a second electron transporting material. The first electron transporting material serves to block the holes from reaching and to balance the charge, and the triplet excitation energy level (T1 level) is 2.6 to 2.8 eV. The first electron transporting 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 transporting material enhances the injection of electrons and lowers the driving voltage of the device, and the electron mobility may be in the range of 1 × 10 ^-3 to 1 × 10 ^-5 cm 2 / Vs. The second electron transporting 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 can form an electron transporting layer including a first electron transporting material having a high triplet excitation energy level (T1 level) and a second electron transporting material having a high electron mobility , It is possible to lower the driving voltage by forming various energy levels in the electron transporting layer to reduce the barrier of the charges from the adjacent layer. In addition, it includes a first electron transport material having a high triplet excitation energy level (T1 level) to improve the efficiency of the device, and includes a second electron transport material having a high electron mobility, So that the driving voltage can be lowered.

3 is a view illustrating an organic electroluminescent device according to a third embodiment of the present invention. In the following description, the same constituent elements as those of the second embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

3, an organic electroluminescent device 100 according to a third embodiment of the present invention includes a plurality of light emitting units ST1, ST2, and ST3 disposed between an anode 110 and a cathode 220, And a first charge generation layer 160 and a second charge generation layer 230 located between the light emitting portions ST1, ST2, and ST3. In the present embodiment, three light emitting portions are positioned between the anode 110 and the cathode 220. However, the present invention is not limited to this, and four or more light emitting portions may be provided between the anode 110 and the cathode 220 .

In more detail, the first light emitting portion ST1 constitutes one light emitting element unit and includes a first light emitting layer 140. [ The first light emitting layer 140 may emit light of any one of red, green, and blue. In this embodiment, the first light emitting layer 140 may be a blue light emitting layer emitting blue light. The light emitting layer for emitting blue light 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 portion ST1 further includes a first hole injection layer 120 and a first hole transport layer 130 on the anode 110. [ The first light emitting portion ST1 further includes a first electron transport layer 150 on the first light emitting layer 140. [ Accordingly, the first light emitting portion 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 is formed on the anode 110 . Further, the first electron transport layer 150 may further include an electron injection layer.

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

And the second light emitting portion ST2 is located on the first light emitting portion ST1. And the second light emitting portion ST2 includes a second light emitting layer 190. [ The second light emitting layer 190 may emit light of one of red, green, and blue, and may be, for example, a yellow-green light emitting layer or a green light emitting layer in this embodiment. The yellow-emitting layer may have a multilayer structure of a light-emitting layer for emitting yellow light or a light-emitting layer for emitting green light. The second light emitting portion ST2 further includes a second hole injection layer 170 and a second hole transport layer 180 between the first charge generation layer 160 and the second light emitting layer 190, And a second electron transport layer 200 on the light emitting layer 190. Further, the second electron transport layer 200 may further include an electron injection layer. Emitting layer 190 including the second hole injection layer 170, the second hole transport layer 180, the second light emitting layer 190, and the second electron transport layer 200 is formed on the first charge generation layer 160, (ST2). The second hole injection layer 170 and the electron injection layer may not be included in the second light emitting portion ST2 depending on the structure and characteristics of the device.

A first charge generating layer 160 is positioned between the first light emitting portion ST1 and the second light emitting portion ST2. The first charge generating layer 160 is a PN junction charge generating layer in which an N-type charge generating layer 160N and a P-type charge generating layer 160P are bonded to each other. Charges are generated or separated into holes and electrons, Charge the charge.

A third light emitting portion ST3 including a third light emitting layer 250 is disposed on the second light emitting portion ST2. The third light emitting layer 250 may emit one of red, green, and blue colors. For example, the third light emitting layer 250 may be a blue light emitting layer that emits blue light in this embodiment. The light emitting layer for emitting blue light 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 portion ST3 further includes a third hole transporting layer 240 between the second charge generating layer 230 and the third light emitting layer 250, Transport layer 260 and an electron injection layer 210. [ A third light emitting portion ST3 including a third hole transporting layer 240, a third light emitting layer 250, a third electron transporting layer 260, and an electron injection layer 210 is formed on the second charge generating layer 230, ). And a cathode 220 is provided on the third light emitting portion ST3 to constitute an 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 structure of the third light emitting portion ST3 depending on the structure and characteristics of the device.

A second charge generating layer 230 is positioned between the second light emitting portion ST2 and the third light emitting portion ST3. The second charge generating layer 230 is a PN junction charge generating layer in which an N-type charge generating layer 230N and a P-type charge generating layer 230P are bonded to each other. Charge is generated or separated into holes and electrons, Charge the charge.

Meanwhile, the third electron transport layer 260 located in the third light emitting portion ST3 of the organic light emitting device 100 according to the third embodiment of the present invention plays a role of facilitating transport of electrons. More specifically, the third electron transporting layer 260 includes a first electron transporting material and a second electron transporting material. The first electron transporting material serves to block the holes from reaching and to balance the charge, and the triplet excitation energy level (T1 level) is 2.6 to 2.8 eV. The first electron transporting 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 transporting material enhances the injection of electrons and lowers the driving voltage of the device, and the electron mobility may be in the range of 1 × 10 ^-3 to 1 × 10 ^-5 cm 2 / Vs. The second electron transporting 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.

The organic electroluminescent device 100 according to the third embodiment of the present invention may further include a first electron transport layer 150 of the first light emitting portion ST1 in addition to the third electron transport layer 260 of the third light emitting portion ST3. Can be configured in the same manner as the third electron transporting layer 260 described above. That is, the first electron transporting layer 150 of the first light emitting portion ST1 may include the first electron transporting material and the second electron transporting material described above. The electron transporting layer comprising the first electron transporting material and the second electron transporting material of the present invention can be applied to any light emitting portion as long as it emits blue light.

As described above, the organic electroluminescent device of the present invention forms an electron transporting layer containing a first electron transporting material having a high triplet excitation energy level and a second electron transporting material having a high electron mobility, By forming multiple energy levels, the driving voltage can be lowered by reducing the barrier of charges from adjacent layers. It also includes a first electron transport material having a high triplet excitation energy level to increase the efficiency of the device and further includes a second electron transport material having a high electron mobility to facilitate movement of electrons, Can be lowered.

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

4, the organic electroluminescent device of the present invention includes a hole transport layer (HTL), a light emitting layer (EML) including a host and a dopant, an electron transport layer (ETL), and an electron injection layer (EIL) . 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. The ETL may be formed by forming a bandgap of a first electron transporting material having a high triplet excitation energy level and forming a bandgap of a second electron transporting material having a high electron mobility do. Therefore, it is possible to facilitate the movement of the carriers to the light emitting layer (EML) by mixing two materials having different band gaps and reducing the barrier for moving the carriers from the adjacent electron injection layer (EIL) or the cathode. In addition, the efficiency of the light emitting layer (EML) can be improved by preventing the holes from flowing from the light emitting layer (EML) to the electron transporting layer (Mixed ETL) due to the first electron transporting material having a high triplet excitation energy level . In addition, the second electron transporting material having a high electron mobility improves the injection ability of electrons into the light emitting layer (EML), thereby lowering the driving voltage of the device.

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. The following describes embodiments in which the electron transporting layer has the three-layer structure described above. However, the same components as those of the first to third embodiments described above are denoted by the same reference numerals and their explanation will be simplified.

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

5, an organic electroluminescent device 10 according to a fourth embodiment of the present invention includes an anode 20, a hole injecting layer 30, a hole transporting layer 40, a light emitting layer 50, an electron transporting layer 60 ), An electron injection layer (70), and a cathode (80).

The anode 20 is an electrode for injecting holes into the light emitting layer 50 and the hole injecting layer 30 and the hole transporting layer 40 serve to smoothly inject holes from the anode 20 into the light emitting layer 50 . The hole injection layer 30 or the hole transport layer 40 may not be included in the organic electroluminescent device depending on the structure and characteristics of the device. The light emitting layer 50 may emit red (R), green (G), or blue (B) light, and may be formed of a phosphor 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 smoothly inject electrons. A cathode 80, which is an electrode for injecting electrons, is located on the electron injection layer 70.

On the other hand, the electron transport layer 60 plays a role of facilitating transport of electrons, and affects the lifetime and efficiency of the organic electroluminescent device. The inventors of the present invention have conducted various experiments to improve the lifetime and efficiency of the organic electroluminescent device by improving the characteristics of the electron transporting layer. It was found that the electron injection is not smooth due to the low electron mobility and the driving voltage is increased when the layer is formed as one layer having a high triplet excitation energy level in order to reduce the driving voltage. In the case of a single layer having a high electron mobility, the electron injection is smooth but the balance between electrons and holes is broken and the lifetime is reduced. Therefore, when the electron transport layer is composed of two layers, the driving voltage increases because the thickness of the device increases. Accordingly, the inventors of the present invention have found that the first layer of the first electron transporting material, the second layer of the second electron transporting material, and the first electron transporting material and the second electron transporting material are mixed with each other without increasing the thickness of the electron transporting layer Which is composed of three layers. A new structure capable of improving the efficiency of the organic electroluminescent device and reducing the driving voltage according to characteristics, thickness, mixed layer thickness, and mixing ratio of the first electron transporting material and the second electron transporting material included in the electron transporting layer Of the organic electroluminescent device of the present invention.

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

More specifically, the first layer 61 of the electron transporting layer 60 is located adjacent to the light emitting layer 60. The first layer 61 includes a first electron transporting material having a high triplet excitation energy level (T1 level), thereby blocking holes from the hole transporting layer 40, It can play a role of maintaining the charge balance by maintaining the hole balance. The first layer 61 of the electron transport layer 60 may be positioned adjacent to the luminescent layer 50 to prevent the movement of holes from the luminescent layer 50 to the electron transport layer 60. [ The first electron transporting material has a triplet excitation energy level (T1 Level) of 2.6 to 2.8 eV. In addition, the first electron transporting 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 transporting 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, May be a compound represented by the above-mentioned formula (1).

The second layer 63 of the electron transporting layer 60 is located adjacent to the electron injection layer 70 or the cathode 80. [ The second layer 63 includes a second electron transporting material having a high electron mobility to improve the injection of electrons injected from the electron injection layer 70 or the cathode 80 and to lower the driving voltage of the device Can play a role. Therefore, the second layer 63 of the electron transport layer 60 can be positioned adjacent to the electron injection layer 70 or the cathode 80 to help the electrons migrate to the emission layer 50. The second electron transporting material may have electron mobility in the 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 transporting material may be a quinoline compound, an anthracene compound or the like, and may be, for example, a compound represented by the above-mentioned formula (2).

The mixed layer 62 of the electron transporting layer 60 is located between the first layer 61 and the second layer 62 and is a layer in which the first electron transporting material and the second electron transporting material are mixed. The mixed layer 62 includes a first electron transporting material, blocks holes from passing through the hole transporting layer 40, and maintains a balance between electrons and holes in the light emitting layer 50, thereby adjusting the charge balance. In addition, the mixed layer 62 includes a second electron transporting material, which improves the injection of electrons 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 transporting material, a mixed layer 62 made of a mixture of a first electron transporting material and a second electron transporting material, and a second electron transporting material By including the second layer 63, various energy levels can be formed in the electron transport layer 60 to reduce the barrier of charges from adjacent layers. Accordingly, electrons can be easily transferred to the light emitting layer 50, and the driving voltage can be lowered.

The electron transport layer 60 of the present invention also includes a first layer 61 including a first electron transport material having a high triplet excitation energy level (T1 level) Lt; RTI ID = 0.0 > of < / RTI > And a second layer 63 including a second electron transporting material having a high electron mobility, thereby facilitating the movement of electrons and lowering the driving voltage.

The mixed layer (62) of the electron transport layer (60) of the present invention is mixed with the first electron transport material and the second electron transport material. Here, the electron transporting layer 60 accounts for 30 to 50% of the first electron transporting material with respect to the sum of the first electron transporting material and the second electron transporting material. If the ratio of the first electron transporting material to the sum of the first electron transporting material and the second electron transporting material is less than 30%, the charge balance of the device may be inadequate and the efficiency may deteriorate, and the first electron transporting material and the second electron transporting material The ratio of the first electron transporting material to the sum of the first electron transporting material and the second electron transporting material is more than 50%, the movement of the electrons is not smooth and the driving voltage of the device is increased and the efficiency is lowered.

The electron transport layer 60 in the fourth embodiment of the present invention has 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. ), But the total thickness of the electron transport layer 60 is not increased.

Therefore, the electron transport layer 60 is composed of three layers, and the total thickness of the three layers is 50 to 450 ANGSTROM. If the total thickness of the electron transporting layer 60 is less than 50 angstroms, the electron transporting layer 60 will not function. If the total thickness of the electron transporting layer 60 exceeds 450 angstroms, the thickness of the electron transporting layer becomes thick, The cavity effect can not be maximized.

The thickness of the first layer 61 in the electron transporting layer 60 is set to 25% or more and 100% or less of the thickness of the mixed layer 62. Here, if the thickness of the first layer 61 is 25% or more of the thickness of the mixed layer 62, blocking of holes from the hole transport layer can be blocked to adjust the charge balance of the light emitting layer to improve the efficiency of the device, When the thickness of the layer 61 is 100% or less of the thickness of the mixed layer 62, it is possible to prevent the thickness of the mixed layer 62 from becoming relatively thin, thereby preventing the efficiency of the device from being lowered.

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 of the thickness of the mixed layer 62, the efficiency of the device can be improved by reducing the charge barrier that electrons pass from the electron injection layer 70 or the cathode 80 have. When the thickness of the second layer 63 is 100% or less of the thickness of the mixed layer 62, it is possible to prevent the thickness of the mixed layer 62 from becoming relatively thin, thereby preventing the efficiency of the device from being lowered.

As described above, the organic electroluminescent device of the present invention forms an electron transporting layer containing a first electron transporting material having a high triplet excitation energy level and a second electron transporting material having a high electron mobility, There is an advantage in that the driving voltage can be lowered by forming a plurality of energy levels, thereby reducing the barrier of the charges from the adjacent layer. It is also possible to provide a second layer comprising a first electron transporting material having a high triplet excitation energy level to improve the efficiency of the device and to include a second electron transporting material having a high electron mobility Thereby making it easier to move the electrons and lower the driving voltage.

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

6, the organic light emitting display 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 interposed between the charge generation layer 160 and the charge generation layer 160.

In more detail, the first light emitting portion ST1 constitutes one light emitting element unit and includes a first light emitting layer 140. [ The first light emitting layer 140 may emit light of any one of red, green, and blue. In this embodiment, the first light emitting layer 140 may be a blue light emitting layer emitting blue light. The light emitting layer for emitting blue light 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 portion 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. [ The first light emitting portion 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 portion 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 is formed on the anode 110 . The first hole injection layer 120 and the electron injection layer may not be included in the first light emitting portion ST1 depending on the structure and characteristics of the device.

The second light emitting portion ST2 including the second light emitting layer 190 is located on the first light emitting portion ST1. The second light emitting layer 190 may emit light of one of red, green, and blue, and may be, for example, a yellow-green light emitting layer or a green light emitting layer in this embodiment. The yellow-emitting layer may have a multilayer structure of a light-emitting layer for emitting yellow light or a light-emitting layer for emitting green light. The second light emitting portion ST2 may further include a second hole injection layer 170 and a second hole transport layer 180. The second light emitting portion ST2 may include a second electron transport layer 200 and an electron injection layer 210). The second hole transport layer 180, the yellow organic light emitting layer 190, the second electron transport layer 200, and the electron injection layer 210 are formed on the first light emitting portion ST1. And the second light emitting portion ST2. The second hole injection layer 170 and the electron injection layer 210 may not be included in the second light emitting portion ST2 depending on the structure and characteristics of the device.

A charge generating layer 160 is positioned between the first light emitting portion ST1 and the second light emitting portion ST2. The 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 bonded to each other to generate charges or separate them into holes and electrons, 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 electrons to the second light emitting layer 190 of the second light emitting portion ST2. The luminous efficiency of the organic electroluminescent device having a plurality of light emitting layers can be further increased and the driving voltage can also be lowered. The cathode 220 is positioned on the second light emitting portion ST2.

The first electron transport layer 150 located in the first light emitting portion ST1 of the organic electroluminescent device 100 according to the fifth embodiment of the present invention plays a role of facilitating transport of electrons. The first electron transporting layer 150 includes a first layer 151 adjacent to the first emitting layer 140, a mixed layer 152 located on the first layer 151 and a second layer 153 located on the mixed layer 152, . The first layer 151 includes a first electron transporting material having a high triplet excitation energy level (T1 level), thereby blocking holes from the hole transporting layer 130 and blocking the holes from the first emitting layer 140 It can play a role of maintaining charge balance between electrons and holes. The first electron transporting material has a triplet excitation energy level (T1 Level) of 2.6 to 2.8 eV. In addition, the first electron transporting 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 layer 153 includes a second electron transporting material having a high electron mobility, thereby enhancing the injection of electrons injected from the cathode 220 and lowering the driving voltage of the device. The second electron transporting material may have electron mobility in the 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 first electron transporting material and the second electron transporting material are mixed. The mixed layer 152 may include a first electron transporting material to block electrons from passing through the first light emitting layer 140 and balance electrons and holes in the first light emitting layer 140 to balance the charge . In addition, the mixed layer 152 includes a second electron transport material, which can improve the injection of electrons and lower the driving voltage of the device.

As described above, the organic electroluminescent device of the present invention forms an electron transporting layer containing a first electron transporting material having a high triplet excitation energy level and a second electron transporting material having a high electron mobility, There is an advantage in that the driving voltage can be lowered by forming a plurality of energy levels, thereby reducing the barrier of the charges from the adjacent layer. It is also possible to provide a first layer comprising a first electron transporting material having a high triplet excitation energy level to increase the efficiency of the device and to have a second layer comprising a second electron transporting material having a high electron mobility Thereby making it easier to move the electrons and lower the driving voltage.

7 is a view illustrating an organic electroluminescent device according to a sixth embodiment of the present invention. In the following, the same constituent elements as those of the above-described fifth embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

7, an organic electroluminescent device 100 according to a 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 first charge generation layer 160 and a second charge generation layer 230 located between the light emitting portions ST1, ST2, and ST3. In the present embodiment, three light emitting portions are positioned between the anode 110 and the cathode 220. However, the present invention is not limited to this, and four or more light emitting portions may be provided between the anode 110 and the cathode 220 .

In more detail, the first light emitting portion ST1 constitutes one light emitting element unit and includes a first light emitting layer 140. [ The first light emitting layer 140 may emit light of any one of red, green, and blue. In this embodiment, the first light emitting layer 140 may be a blue light emitting layer emitting blue light. The light emitting layer for emitting blue light 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 portion 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. [ The first light emitting portion 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 portion 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 is formed on the anode 110 . The first hole injection layer 120 and the electron transport layer may not be included in the structure of the first light emitting portion ST1 depending on the structure and characteristics of the device.

The second light emitting portion ST2 including the second light emitting layer 190 is located on the first light emitting portion ST1. The second light emitting layer 190 may emit light of one of red, green, and blue, and may be a yellow-green or green light emitting layer in this embodiment. The yellow-emitting layer may have a multilayer structure of a light-emitting layer for emitting yellow light or a light-emitting layer for emitting green light. The second light emitting portion ST2 further includes a second hole injection layer 170 and a second hole transport layer 180 between the first charge generation layer 160 and the second light emitting layer 190, And a second electron transport layer 200 on the light emitting layer 190. Further, an electron injection layer may be further included on the second electron transport layer 200. Therefore, the second light emitting portion (second light emitting portion) including the second hole injection layer 170, the second hole transport layer 180, the second light emitting layer 190, and the second electron transport layer 200 is formed on the first light emitting portion ST1 ST2). The second hole injection layer 170 and the electron injection layer may not be included in the second light emitting portion ST2 depending on the structure and characteristics of the device.

A first charge generating layer 160 is positioned between the first light emitting portion ST1 and the second light emitting portion ST2. The first charge generating layer 160 is a PN junction charge generating layer in which an N-type charge generating layer 160N and a P-type charge generating layer 160P are bonded to each other. Charges are generated or separated into holes and electrons, Charge the charge.

A third light emitting portion ST3 including a third light emitting layer 250 is disposed on the second light emitting portion ST2. The third light emitting layer 250 may emit one of red, green, and blue colors. For example, the third light emitting layer 250 may be a blue light emitting layer that emits blue light in this embodiment. The light emitting layer for emitting blue light 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 portion ST3 further includes a third hole transporting layer 240 between the second charge generating layer 230 and the third light emitting layer 250, Transport layer 260 and an electron injection layer 210. [ Further, a hole injection layer may be further included under the third hole transport layer 240. A third light emitting portion ST3 including a third hole transporting layer 240, a third light emitting layer 250, a third electron transporting layer 260, and an electron injection layer 210 is formed on the second charge generating layer 230, ). And a cathode 220 is provided on the third light emitting portion ST3 to constitute an 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 third light emitting portion ST3 depending on the structure and characteristics of the device.

The third electron transport layer 260 located in the third light emitting portion ST3 of the organic electroluminescent device 100 according to the sixth embodiment of the present invention plays a role in facilitating transport of electrons. The third electron transporting layer 260 includes a first layer 261 adjacent to the third light emitting layer 250, a mixed layer 262 located on the first layer 261, and a second layer 263 located on the mixed layer 262. [ . The first layer 261 includes a first electron transporting material having a high triplet excitation energy level (T1 level), thereby blocking holes from the hole transporting layer and maintaining the balance of electrons and holes in the light emitting layer It can play a role of adjusting charge balance. The first electron transporting material has a triplet excitation energy level (T1 Level) of 2.6 to 2.8 eV. In addition, the first electron transporting 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 layer 263 includes a second electron transporting material having a high electron mobility, thereby improving the injection of electrons injected from the cathode 220 and lowering the driving voltage of the device. The second electron transporting material may have electron mobility in the 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 first electron transporting material and the second electron transporting material are mixed. The mixed layer 262 may include a first electron transporting material to block the holes from reaching the third light emitting layer 250 and balance electrons and holes in the third light emitting layer 250 to balance the charge . In addition, the mixed layer 262 includes a second electron transport material, which can enhance the injection of electrons and lower the driving voltage of the device.

The organic electroluminescent device 100 according to the sixth embodiment of the present invention includes a first electron transport layer 150 of the first light emitting portion ST1 in addition to the third electron transport layer 260 of the third light emitting portion ST3, Can be configured in the same manner as the third electron transporting layer 260 described above. That is, the first electron transporting layer 150 of the first light emitting portion ST1 includes a first layer containing a first electron transporting material, a mixed layer of a first electron transporting material and a second electron transporting material, And a second layer comprising a material. The first electron transport layer 150 may be a single layer including a first layer, a mixed layer, and a second layer. The electron transporting layer having a three-layer structure including the first electron transporting material and the second electron transporting material of the present invention can be applied to any light emitting portion that emits blue light.

As described above, the organic electroluminescent device of the present invention forms an electron transporting layer containing a first electron transporting material having a high triplet excitation energy level and a second electron transporting material having a high electron mobility, There is an advantage in that the driving voltage can be lowered by forming a plurality of energy levels, thereby reducing the barrier of the charges from the adjacent layer. It is also possible to provide a first layer comprising a first electron transporting material having a high triplet excitation energy level to increase the efficiency of the device and to have a second layer comprising a second electron transporting material having a high electron mobility Thereby making it easier to move the electrons and lower the driving voltage.

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) including a host and a dopant, an electron transport layer (ETL), and an electron injection layer (EIL). The electron transport layer (ETL) comprises a first layer (ETL1) comprising a first electron transporting material and a second layer (ETL2) comprising a second electron transporting material and a second layer (ETL2) comprising a first electron transporting material and a second electron transporting material And a mixed layer (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) Thereby forming a band gap. In the mixed ETL, the first electron transporting material and the second electron transporting material form band gaps, respectively. Carriers injected from the adjacent electron injection layer (EIL) or the cathode can easily move to the second layer ETL2 beyond the bandgap of the second electron transporting material of the second layer ETL2. The carriers reaching the second layer ETL2 can easily migrate to the mixed layer by taking the bandgap of the same second layer of the electron transport material formed in the mixed layer ETL, It can move to the mixed layer (ETL) beyond the bandgap of the material. The carriers existing in the bandgap of the second electron transporting material among the carriers reaching the mixed ETL extend beyond the bandgap of the first electron transporting material formed in the first layer ETL1 to the first layer ETL1 Or the carriers present in the bandgap of the first electron transporting material can easily migrate to the first layer ETL1 on the same bandgap of the first electron transporting material. That is, by providing the electron transport layer including the first layer ETL1, the mixed layer ETL and the second layer ETL2, the barrier of the carriers moving from the electron injection layer or the cathode to the light emitting layer is reduced, You can do it smoothly. Further, the first electron transporting material having a high triplet excitation energy level (T1 level) can prevent the holes from migrating from the light emitting layer (EML) to the electron transporting layer (ETL), thereby improving the efficiency. Further, the second electron transporting material having a high electron mobility improves the injection ability of electrons, so that the driving voltage of the device can be lowered.

9 is a schematic view of a co-deposition method for producing an electron transport layer of an organic electroluminescent device of the present invention.

Referring to FIG. 9, the electron transport layer of the organic electroluminescent device of the present invention is formed by a co-deposition method. In more detail, a second evaporation source S_ETL2 provided with a first evaporation source S_ETL1 provided with a first electron transport material ETL1 and a second evaporation source STL2 provided with a second electron transport material ETL2 is provided at the bottom of the chamber, A substrate mounted to face these evaporation sources is provided at the top of the chamber. When the substrate moves in one direction of the chamber, the first evaporation source S_ETL1 and the second evaporation source S_ETL2 start deposition of the first electron transporting material and the second electron transporting material. As the substrate moves, a first electron transport material ETL1 evaporated in the first evaporation source S_ETL1 is deposited on the substrate to form a first layer, and then a first electron transport material ETL1 and a second electron The transporting material ETL2 is simultaneously deposited to form a mixed layer, and finally the second electron transporting material ETL2 is evaporated in the second evaporation source S_ETL2 to form a second layer. Therefore, the electron transporting layer according to the fourth to sixth embodiments of the present invention is produced.

On the other hand, if the interval between the first evaporation source S_ETL1 and the second evaporation source S_ETL2 is reduced, both the first electron transporting material and the second electron transporting material can be simultaneously deposited on the substrate. Accordingly, the electron transporting 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 into various structures by adjusting the spacing of the evaporation sources.

Hereinafter, embodiments in which the organic electroluminescent device of the present invention is manufactured are disclosed. The material of the electron transporting layer or the like does not limit the scope of the present invention.

Experiment 1: Characteristic of the device according to the mixed material of single material and electron transport layer

≪ Comparative Example 1 &

A device including a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, a dry bulking layer, and a cathode was formed on a substrate. A blue light emitting layer as the light emitting layer, and an oxadiazole compound as the electron transporting layer. The device was constructed as a mono device and tested.

≪ Comparative Example 2 &

An electron transporting layer was formed of a quinoline compound with the same structure as that of Comparative Example 1 described above to constitute a device.

≪ Example 1 >

An element was constituted by mixing an oxadiazole compound and a quinoline compound to form an electron transport layer with the same constitution as that of Comparative Example 1 described above.

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

The driving voltage and the luminous efficiency of the device manufactured according to Comparative Example 1 and Example 1 are shown in Table 1 below and the driving voltage and luminous efficiency of the device manufactured according to Comparative Example 2 and Example 1 are shown in Table 2 Respectively. In Table 1, the results of Comparative Example 1 were taken as 100%, and the results of Example 1 were expressed as percentages. The results of Comparative Example 2 were taken as 100%, and the results of Example 1 The values are expressed in percent.

Comparative Example 1 Example 1 The driving voltage (V) 100% 58% Luminous efficiency 100% 172%

Comparative Example 2 Example 1 The driving voltage (V) 100% 110% Luminous efficiency 100% 121%

Referring to Table 1, in the device of Example 1 in which a material having a high charge mobility was further mixed as compared with Comparative Example 1 having an electron transport layer formed only of a material having a high triplet excitation energy level, the driving voltage was lowered The luminous efficiency was improved by 72%. Referring to Table 2, the device of Example 1, in which a material having a higher triplet excitation energy level was further mixed, as compared with Comparative Example 2 having an electron transport layer formed only of a material having a high charge mobility, But the luminous efficiency was improved by 21%.

Experiment 2: Electron transport layer  Characteristics of device by material ratio

≪ Example 2 >

An oxadiazole compound and a quinoline compound were mixed at different ratios of 7: 3, 1: 1, and 3: 7, respectively, under the same process conditions as in Example 1 to form an electron transport layer.

The material of the electron transporting layer in Embodiment 2 does not limit the content of the present invention.

Table 3 shows the driving voltage and luminous efficiency of the device according to the material mixing ratio of the electron transport layer according to the second embodiment. In addition, the current density according to the driving voltage is measured, and the efficiency according to the luminance is shown in FIG. 10 and shown in FIG. In addition, the luminescence intensity according to the wavelength of the device manufactured with the material mixture ratio of the electron transporting layer of 7: 3 and 3: 7 according to Example 2 was measured and shown in FIG. 12, and the material of the electron transporting layer The luminescence intensities according to the wavelengths of the devices prepared with the mixing ratios of 1: 1 and 3: 7 were measured and shown in Fig. In the following Table 3, the results of the devices mixed at the ratio of 1: 1 were regarded as 100%, and the results of the devices mixed at the ratios of 7: 3 and 3: 7 were expressed as percentages.

The mixing ratio of the electron transporting layer 7: 3 1: 1 3: 7 The driving voltage (V) 141.3 100.0 89.1 Luminous efficiency 70.9 100.0 100.0

Referring to FIG. 10 and FIG. 11 and Table 3, the luminescent efficiencies of 1: 1 and 3: 7 were the same, and the driving voltage was lowest at the mixing ratio of 7: 3. High driving voltage and low luminous efficiency were obtained at the mixing ratio of 7: 3. As a result, it can be seen that, in order to realize devices with low voltage and high efficiency, the proportion of materials having a high electron mobility should be mixed at a ratio of 1 or more as compared with materials having a high triplet excitation energy level.

As shown in FIGS. 12 and 13, it can be seen that the mixing ratio of 3: 7 at a wavelength of 440 to 480 nm, which emits blue light, has a luminescence intensity higher than a mixing ratio of 7: 3. Therefore, it can be seen that the luminescence intensity is higher in the case of a material having a high electron mobility than in a material having a high triplet excitation energy level.

Experiment 3: Electron transport layer  Thickness The organic electroluminescent device  characteristic

≪ Example 3 >

A first light emitting portion including a blue light emitting layer, a second light emitting portion including a charge generation layer, a yellow light emitting layer, and a third light emitting portion including a charge generation layer and a blue light emitting layer are formed on a substrate, Device. Here, the electron transport layer included in the third light emitting portion was formed by mixing oxadiazole and a quinoline compound in a ratio of 3: 2 to a thickness of 250 ANGSTROM.

The material of the electron transporting layer and the structure of the light emitting layer in the third embodiment do not limit the content of the present invention.

In the organic EL device according to Example 3, the thicknesses of the electron transporting layers were changed to 250 and 300 Å, respectively, and the driving voltage and the luminous efficiency of the organic EL devices were measured. The current density according to the driving voltage was measured to measure the efficiency according to the luminance shown in FIG. 14, and FIG. 15 shows the efficiency according to the luminance. The emission intensity according to the wavelength was measured and shown in FIG. In Table 4, the result of the device in which the electron transporting layer is formed to a thickness of 300 angstroms is represented by 100%, and the resulting value of the device formed by the thickness of 250 angstroms is expressed as a percentage.

The thickness (A) of the electron transporting layer 250 300 The 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 transporting layer was reduced from 300 ANGSTROM to 250 ANGSTROM, the driving voltage was decreased and the luminous efficiency was decreased. As a result, it was confirmed that when the thickness of the electron transporting layer is reduced, it is superior in terms of driving voltage.

As shown in FIG. 16, it was found that the luminescence intensity was increased compared with the case of forming 300 Å at a wavelength of 440-480 nm for emitting blue light and 510-590 nm for emitting yellow-green at 250 Å .

Experiment 4: Electron transport layer  Depending on the mixed material The organic electroluminescent device  characteristic

<Example 4>

An organic electroluminescent device was fabricated by mixing the oxadiazole compound and the quinoline compound as an electron transport layer at a ratio of 1: 1 with the same structure as that of Example 3 described above.

&Lt; Example 5 >

In the same manner as in Example 4 described above, a carbazole compound and a quinoline compound were mixed as an electron transport layer at a ratio of 1: 1 to prepare an organic electroluminescent device.

The materials of the electron transporting layer and the constitution of the light emitting layer in the fourth and fifth embodiments do not limit the content of the present invention.

The driving voltage, lifetime, luminous efficiency and quantum efficiency of the R, G, B, and W colors of the organic electroluminescent device manufactured according to Examples 4 and 5 were measured and shown in Table 5 below. In addition, the current density according to the driving voltage is measured, and the efficiency is measured according to the luminance shown in FIG. 17, and the luminous intensity according to the wavelength is shown in FIG. In Table 5, the device result value of Example 4 is expressed as 100%, and the device result value of Example 5 corresponding thereto is expressed as a percentage.

Example 4 Example 5 Driving voltage (%)
Vpeak 100 97.7 V (10 mA / cm 2) 100 98.3
Life (T95) (%)

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

Referring to FIGS. 17 and 18 and Table 5 above, the devices according to Examples 4 and 5 using materials having similar characteristics showed equivalent lifetime and efficiency.

As shown in FIG. 19, it can be seen that the emission intensity at the wavelength of 440-480 nm which emits blue light and the emission intensity at the wavelength of 510-590 nm which emit yellow-green are the same level.

Experiment 5: Electron transport layer  Depending on the thickness of each layer The organic electroluminescent device  characteristic

&Lt; Example 6 >

An organic electroluminescent device was fabricated by mixing the oxadiazole compound and the quinoline compound as an electron transport layer at a ratio of 1: 1 with the same constitution as in Example 2 described above.

&Lt; Example 7 >

An oxadiazole compound was formed to a thickness of 50 angstroms as the first layer of the electron transporting layer and a mixture of oxadiazole and quinoline compound was mixed as a mixed layer of the electron transporting layer at a ratio of 1: And a quinoline compound was formed to a thickness of 50 Å as a second layer of the electron transport layer, thereby preparing an organic electroluminescent device.

&Lt; Example 8 >

An oxadiazole compound was formed to a thickness of 100 Å as a first layer of the electron transport layer and a mixture of oxadiazole and a quinoline compound was mixed as a mixed layer of the electron transport layer at a ratio of 1: And a quinoline compound as a second layer of the electron transporting layer was formed to a thickness of 100 Å to prepare an organic electroluminescent device.

&Lt; Example 9 >

An oxadiazole compound was formed to a thickness of 50 angstroms as the first layer of the electron transporting layer and a mixture of oxadiazole and quinoline compound was mixed as a mixed layer of the electron transporting layer at a ratio of 1: And a quinoline compound as a second layer of the electron transporting layer was formed to a thickness of 100 Å to prepare an organic electroluminescent device.

&Lt; Example 10 >

An oxadiazole compound was formed to a thickness of 100 Å as the first layer of the electron transporting layer and a mixed layer of the electron transporting layer was mixed with the oxadiazole and the quinoline compound at a ratio of 1: And a quinoline compound was formed to a thickness of 50 Å as a second layer of the electron transport layer, thereby preparing an organic electroluminescent device.

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

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, Example 7, in which an electron transport layer is formed of a first layer of 50 angstroms, a mixed layer of 200 angstroms, and a second layer of 50 angstroms, compared to Example 6 in which an electron transporting layer mixed with a single layer of 300 angstroms is formed, The driving voltage decreased by 5%, the efficiency increased by 3%, and the lifetime increased by 2%. In Example 8 in which the electron transport layer was formed of the first layer of 100 ANGSTROM, the mixed layer of 100 ANGSTROM and the second layer of 100 ANGSTROM, the driving voltage was equal, the efficiency decreased by 5%, and the lifetime decreased by 10%. In Example 9 in which the electron transport layer was formed of the first layer of 50 Å, the mixture layer of 150 Å and the second layer of 100 Å, the driving voltage was decreased by 9%, the efficiency was increased by 5%, and the lifetime was increased by 18%. Example 10 in which the electron transport layer was formed of the first layer of 100 Å, the mixture layer of 150 Å and the second layer of 50 Å reduced the driving voltage by 2%, the efficiency by 4%, and the lifetime by 5%.

Except for Example 8, the driving voltage was reduced as compared to Example 6, and the efficiency and lifetime of Example 7, Example 9, and Example 10 were increased. As a result, it can be seen that the efficiency and lifetime of the device are reduced when the mixed layer of the electron transporting layer is 100 Å or less, and that the mixed layer of the electron transporting layer is preferably 150 Å or more. In addition, Example 9 exhibits excellent effects, and it is found that an electron transporting layer composed of a first layer of 50 angstroms, a mixed layer of 150 angstroms and a second layer of 100 angstroms is most preferable.

As described above, the organic electroluminescent device of the present invention forms an electron transporting layer including a first electron transporting material having a high triplet excitation energy level and a second electron transporting material having a high electron mobility, There is an advantage in that the driving voltage can be lowered by forming an energy level and reducing the barrier of the electric charges passing from the adjacent layer. It is also possible to provide a first layer comprising a first electron transporting material having a high triplet excitation energy level to increase the efficiency of the device and to have a second layer comprising a second electron transporting material having a high electron mobility Thereby making it easier to move the electrons and lower the driving voltage.

Further, the driving voltage can be lowered by configuring the ratio of the second electron transporting material having a high electron mobility to be equal to or larger than the ratio of the first electron transporting material having a high triplet excitation energy level.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

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

Claims (24)

An organic electroluminescent device comprising a light emitting layer and an electron transporting layer between an anode and a cathode,
Wherein the electron transporting layer comprises a first electron transporting material for blocking the movement of holes from the light emitting layer to the electron transporting layer and a second electron transporting material for assisting movement of electrons to the light emitting layer, Wherein the triplet excitation energy level is higher than the transporting material and the electron mobility is lower than that of the transporting material. The method according to claim 1,
Wherein the electron transport layer is a single layer. The method according to claim 1,
Wherein the electron transport layer comprises a single layer including three layers in which a first layer, a mixed layer, and a second layer are stacked. The method of claim 3,
Wherein the first layer comprises the first electron transport material and the mixed layer comprises the first electron transport material and the second electron transport material and the second layer comprises the second electron transport material Wherein the organic electroluminescent device comprises: The method according to claim 2 or 4,
Wherein 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 method according to claim 2 or 4,
And the electron mobility of the second electron transporting material is in the range of 1 × 10 ^-3 to 1 × 10 ^-5 cm 2 / Vs. The method according to claim 2 or 4,
Wherein the ratio of the first electron transporting material to the sum of the first electron transporting material and the second electron transporting material is 30 to 50%. The method according to claim 2 or 4,
Wherein the ratio of the first electron transporting material is less than or equal to the ratio of the second electron transporting material. The method according to claim 1,
Wherein the thickness of the electron transporting layer is 50 to 450 ANGSTROM. 5. The method of claim 4,
Wherein a thickness of each of the first layer and the second layer is 25 to 100% of a thickness of the mixed layer, and a thickness of the mixed layer is 150 to 200 ANGSTROM. The method according to claim 1,
Wherein the first electron transporting material is located close to the light emitting layer to prevent the movement of the hole from the light emitting layer to the electron transporting layer. The method according to claim 1,
Wherein the second electron transporting material is located close to the cathode to assist the movement of the electrons to the light emitting layer. The method according to claim 1,
Wherein the charge balance of the light emitting layer is controlled by the first electron transporting material and the second electron transporting material. At least one light emitting portion positioned between the anode and the cathode; And
And an electron transport layer positioned between the at least one light emitting portion and the cathode,
Wherein the electron transport layer comprises a single layer comprising a first electron transport material and a second electron transport material. 15. The method of claim 14,
Wherein the single layer comprises a first layer comprising a first electron transporting material, a third layer comprising a mixture of the first electron transporting material and a second electron transporting material and a second layer comprising the second electron transporting material, Wherein the organic electroluminescent device comprises: 16. The method of claim 15,
Wherein the first electron transporting material and the second electron transporting material have different triplet excitation energy levels or electron mobility. 17. The method of claim 16,
Wherein the triplet excitation energy level of the first electron transporting material is higher than the triplet excitation energy level of the second electron transporting material. 18. The method of claim 17,
Wherein 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. 17. The method of claim 16,
Wherein the electron mobility of the first electron transporting material is lower than the electron mobility of the second electron transporting material. 20. The method of claim 19,
And the electron mobility of the second electron transporting material is in the range of 1 × 10 ^-3 to 1 × 10 ^-5 cm 2 / Vs. 16. The method of claim 15,
Wherein the ratio of the first electron transporting material to the sum of the first electron transporting material and the second electron transporting material is 30 to 50%. 16. The method of claim 15,
Wherein the ratio of the first electron transporting material is less than or equal to the ratio of the second electron transporting material. 16. The method of claim 15,
Wherein the thickness of the electron transporting layer is 50 to 450 ANGSTROM. 24. The method of claim 23,
Wherein a thickness of each of the first layer and the second layer is 25 to 100% of a thickness of the mixed layer, and a thickness of the mixed layer is 150 to 200 ANGSTROM.

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