An organic electroluminescent device

Abstract

The invention discloses an organic electroluminescent device, which is provided with a substrate, a first electrode, an organic layer and a second electrode in sequence from bottom to top, wherein the organic layer comprises: a hole transport region, a light-emitting layer and an electron transport region, wherein the electron transport region comprises a first electron transport layer comprising a first electron transport compound and a second electron transport layer comprising a second electron transport compound, wherein the LUMO energy level of the first electron transport compound is between 3.2-3.5 eV, the LUMO energy level of the second electron transport compound is between 2.5-2.8 eV, and [LUMO (first electron transport compound) + LUMO (second electron transport compound)] / 2 is between 2.85-3.15 eV.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic devices, and in particular to an organic electroluminescent device, especially an organic electroluminescent device including a specific electron transport layer, as well as a preparation method thereof and a display device including the same. Background Art

[0002] In recent years, organic electroluminescent devices have attracted much attention as the next generation of full-color flat panel displays and are being actively studied. In order to promote the practical application and industrialization of OLEDs, the reduction of device driving voltage and long life are indispensable elements. In order to achieve these elements, new electron transport layer materials have been developed. In particular, low voltage and long life must be achieved in blue light devices. Patent documents CN102414179B, CN106661024A, CN107431141A, CN108352449A, etc. disclose that derivatives such as triazine, pyridine, pyrimidine, imidazole, oxadiazole, triazole, phenanthroline, anthracene, etc. are used as electron transport layer materials, which have relatively excellent electron transmission speeds. At present, they are also the most basic materials used for electron transport layer materials. But in fact, the application of such materials to reduce the voltage of devices and extend the life of devices still has certain limitations.

[0003] In addition, patents such as CN107108504A involve hole blocking layer materials, which have the characteristic of significantly improving device life, but this phenomenon is unpredictable in reducing device voltage. Summary of the invention

[0004] In order to achieve a certain balance between reducing device voltage and increasing device life, the present invention provides a material combination as an electron injection and transport layer of the device.

[0005] In addition, the present invention also aims to provide an organic electroluminescent device, which is provided with a substrate and an anode, an organic layer and a cathode in sequence, wherein the substrate can be arranged on the anode side or the cathode side, and the organic layer includes a hole transport region, a light-emitting layer, and an electron transport region, wherein

[0006] a light-emitting layer, located between the cathode and the anode, and comprising a host material and a guest material;

[0007] The hole transport region is located between the anode and the light-emitting layer;

[0008] The electron transport region, located between the cathode and the light-emitting layer;

[0009] Characterized in that the electron transport layer includes a first electron transport layer and a second electron transport layer, wherein the second electron transport layer is located between the first electron transport layer and the light-emitting layer;

[0010] The first electron transport layer comprises a first electron transport compound, wherein the LUMO energy level of the first electron transport compound (ETM1) is between 3.2-3.5 eV;

[0011] The second electron transport layer comprises or consists of a second electron transport compound, and the LUMO energy level of the second electron transport compound (ETM2) is between 2.5 and 2.8 eV;

[0012] And [LUMO (first electron transport layer) + LUMO (second electron transport layer)] / 2 is between 2.85 and 3.15 eV.

[0013] Another object of the present invention is to provide a method for preparing the organic electroluminescent device according to the present invention.

[0014] Another object of the present invention is to provide a display device comprising the organic electroluminescent device according to the invention.

[0015] Technical Effects

[0016] In the present invention, when two electron transport layers are selected and these two electron transport layers meet certain conditions, the prepared organic electroluminescent device has unexpected technical effects. Specifically, when a specific first electron transport compound according to the present invention is used as the first electron transport layer and a specific second electron transport compound according to the present invention is used as the second electron transport layer, the energy level difference between the two compounds can adjust the amount of electrons injected into the light-emitting layer and the ease of electron injection, while making the recombination area in the light-emitting layer located at the best recombination position. It is beneficial to reduce the driving voltage of the device, generally improve the stability of the device, and extend the life of the device. For example, its LT90 (that is, the time consumed when the brightness of the organic electroluminescent device decays to 90% of its initial brightness) even exceeds the T90 obtained when using only one electron transport compound as the electron transport layer, and when other types of energy level combinations are used, there will only be an increase in life, and the voltage is not improved or even increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The energy levels represented by the first electron transport compound (ETM1) and the second electron transport compound (ETM2), wherein EM represents the light-emitting layer, and the figure shows the energy level relationship and corresponding positions of the first transport layer and the second transport layer in the present invention.

[0018] Figure 2The cross-sectional structure diagram of an organic electroluminescent device provided by the present invention, wherein the organic electroluminescent device comprises a substrate layer 100, and a first electrode layer anode layer 200, an organic light-emitting functional layer 300, a second electrode layer cathode layer 400 and a cover layer 500 sequentially formed on the substrate layer 100

[0019] Figure 3 A schematic diagram of the cross-sectional structure of an organic light-emitting functional layer in an organic electroluminescent device provided by the present invention. The organic light-emitting functional layer 300 may include a light-emitting layer 340 (EML), and a hole transport region may be formed between the EML and the first electrode layer 200, and an electron transport region may be formed between the EML and the second electrode layer 400. The hole transport region may include at least one of a hole injection layer 310 (HIL), a hole transport layer 320 (HTL), and an electron blocking layer 330 (EBL). The electron transport region may include at least one of a hole blocking layer (i.e., a second electron transport layer) 350 (ETM2), a first electron transport layer 360 (ETM1), and an electron injection layer 370 (EIL). Therefore, the organic light-emitting functional layer 300 includes at least two combinations of a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer, and an electron injection layer.

[0020] Figure 4-5 Schematic diagram of the combination of different luminescent materials in the luminescent layer, where EM1 is the red luminescent layer, EM2 is the green luminescent layer, and EM3 is the blue luminescent layer.

[0021] Figure 6-7 A schematic diagram of the structural connection of a light-emitting layer including two or more organic light-emitting functional layers

[0022] Hereinafter, each layer in the present invention will be described in more detail. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present invention are described in detail. However, these embodiments are illustrative, the present invention is not limited thereto and the present invention is defined by the specification of the claims.

[0024] In the present invention, unless otherwise stated, all operations are carried out at room temperature and normal pressure.

[0025] In this article, the term “C1-C 20 The term "alkyl" refers to a straight or branched alkyl group having 1 to 20 carbon atoms, examples of which are methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, isobutyl, sec-butyl, pentyl, isopentyl, octyl or heptyl, etc., but are not limited thereto. "C1-C 20 The term "alkylene" refers to a straight or branched chain alkylene group having 1 to 20 carbon atoms, examples of which include, but are not limited to, divalent groups of the above groups.

[0026] In this article, the term “C5-C 60 The term "aryl" refers to a monovalent group of a fully unsaturated monocyclic, polycyclic or fused polycyclic (i.e., rings sharing a pair of adjacent carbon atoms) system having 5 to 30 ring carbon atoms, examples of which include, but are not limited to, phenyl, naphthyl, anthracenyl, phenanthrenyl, fused tetraphenyl, pyrenyl, biphenyl, p-terphenyl, m-terphenyl, anthracenyl, 1,1-diphenylene, 1,1-diphenylene, 1,1-diphenylene, 1,1-diphenylene, 1,1-diphenylene, 1,1-diphenylene, 1,1-diphenylene, etc. "C5-C 30 The term "arylene" refers to a divalent radical of a fully unsaturated monocyclic, polycyclic or fused polycyclic (i.e., rings sharing a pair of adjacent carbon atoms) system having 5 to 30 ring carbon atoms, examples of which include but are not limited to the divalent radicals of the above groups.

[0027] In this article, the term “C2-C 60 The term "heteroaryl" refers to an aromatic monovalent group having 2 to 59 ring carbon atoms and at least one heteroatom selected from N, O and S. Examples thereof include, but are not limited to, furyl, thienyl, pyrrolyl, pyrazolyl, imidazolyl, triazolyl, oxazolyl, thiazolyl, oxadiazolyl, thiadiazolyl, pyridyl, pyrimidinyl, pyrazinyl, triazinyl, benzofuranyl, benzothienyl, benzimidazolyl, indolyl, quinolyl, isoquinolyl, quinazolinyl, quinoxalinyl, naphthyridinyl, benzoxazinyl, benzothiazinyl, acridinyl, phenazinyl, phenathiazinyl, phenoxazinyl, dibenzofuranyl, dibenzothienyl, carbazolyl, and the like. It also includes aromatic combination groups with heteroatoms, for example etc. "C2-C 60 The term "heteroarylene" refers to an aromatic divalent group having 2 to 59 ring carbon atoms and at least one heteroatom selected from N, O and S, examples of which include but are not limited to the divalent groups of the above groups.

[0028] It will be understood that the use of the terms “include” and / or “comprises” specifies the presence of stated features or components, but does not preclude the presence or addition of one or more other features or components.

[0029] As used herein, the term "organic functional material layer" refers to a single layer and / or multiple layers located between a first electrode and a second electrode in an organic electroluminescent device. The material included in the organic functional material layer is not limited to an organic material.

[0030] As used herein, the prefix "substituted or unsubstituted" before a group means that the group is optionally selected from cyano, halogen, C 1-20 Alkyl, C 2-20 Alkenyl, C 6-30 Aryl, C2-30 At least one group in the heteroaryl group is substituted; or it is unsubstituted. The heteroatom in the heteroaryl group and the heteroarylene group is optionally selected from at least one of an oxygen atom, a sulfur atom or a nitrogen atom, and examples of the substituent include, but are not limited to, phenyl, biphenyl, anthracenyl, naphthyl, pyridyl, triazolyl, methyl, dimethylfluorenyl, fluorenyl, diphenylfluorenyl, N-phenylbenzimidazolyl, N-phenylcarbazolyl, spirobifluorenyl, dibenzofuran, benzimidazolyl, etc.

[0031] Any numerical range listed herein is intended to include all sub-ranges with the same numerical precision included in the listed range. For example, "1.0 to 10.0" means all sub-ranges (and including 1.0 and 10.0) included between the listed minimum value 1.0 and the listed maximum value 10.0, that is, all sub-ranges with a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0. Any maximum numerical limit listed herein is intended to include all smaller numerical limits included in this article, and any minimum numerical limit listed herein is intended to include all larger numerical limits included in this article. Therefore, the applicant reserves the right to modify the claims and the specification to clearly describe any sub-ranges falling within the scope clearly described herein.

[0032] Hereinafter, the organic electroluminescent device of the present invention is described according to specific embodiments, but it should be noted that the specific embodiments do not limit the present invention.

[0033] In one embodiment of the present invention, an organic electroluminescent device is provided, wherein:

[0034] The first electron transport compound may include one or more compounds having structures represented by general formula (1-1) to general formula (1-3)

[0035]

[0036] The second electron transport compound may include compounds having structures represented by general formula (2-1) and general formula (2-2), or may be composed of one or more of them.

[0037]

[0038] In the general formula,

[0039] X1-X9 can be independently represented by CR or N atoms;

[0040] Z1-Z8 can be independently represented by CR or N atoms;

[0041] Y can be represented by a single bond, -O-, -S-, -CR 10 R 11-or-NR 12 ;

[0042] L1-L4 are independently represented by a single bond, C1-C 20 Alkylene, substituted or unsubstituted C5-C 60 arylene, or substituted or unsubstituted C2-C 60 The heteroarylene group is preferably a phenylene group, a biphenylene group, or a terphenylene group;

[0043] Ar1-Ar8 can be independently represented by substituted or unsubstituted C5-C 60 aryl, or substituted or unsubstituted C2-C 60 Heteroaryl, preferably phenyl, naphthyl, biphenyl, terphenyl, anthracenyl, phenanthryl, pyridyl, pyrimidinyl, furanyl, benzofuranyl, dibenzofuranyl, imidazolyl, benzimidazolyl, indolyl, benzindolyl, carbazolyl, N-phenylcarbazolyl,

[0044] Cy can be represented by substituted or unsubstituted C2-C 60 Preferably, pyridyl, pyrimidinyl, triazine, imidazolyl, benzimidazolyl, indolyl, benzindolyl, carbazolyl, N-phenylcarbazolyl, furyl, benzofuranyl, dibenzofuranyl, quinolyl, isoquinolyl or

[0045] R represents a hydrogen atom, a substituted or unsubstituted phenyl group, a naphthyl group, a biphenyl group, or a pyridyl group, and the substituted substituent group may be one or more of a phenyl group, a methyl group, an ethyl group, a propyl group, and a butyl group;

[0046] R1-R7 can be independently represented by hydrogen, substituted or unsubstituted C5-C 60 Aryl, or substituted or unsubstituted C2-C 60 Heteroaryl, preferably naphthyl, anthracenyl, phenanthrenyl, pyrenyl,

[0047] R8-R9 are independently substituted or unsubstituted C5-C 60 Aryl, or the structure represented by general formula (3)

[0048]

[0049] R 10 -R 12 Each is independently represented by C 1-20 Alkyl, substituted or unsubstituted C 5-60 aryl or substituted or unsubstituted C2-C 60 heteroaryl;

[0050] Where R 13 , R 14 are independently halogen atoms, substituted or unsubstituted C1-C 20 Alkyl, substituted or unsubstituted C5-C 60 aryl, or substituted or unsubstituted C2-C 60 The heteroaryl group, and R 13 and R 14 Can be connected by single bonds to form 5-7 membered rings;

[0051] R 15 , R 16 can be independently represented by hydrogen atom, halogen atom, cyano group,

[0052] The general formula (3-1), the general formula (3-2), and the general formula (3-3) are connected to form a ring with the general formula (3) through "*",

[0053] R8-R9 are preferably

[0054] Wherein Y1-Y3 are independently represented by -O-, -S-, -CR 17 R 18 - or NR 19 ;

[0055] R 17 -R 19 Definition and R 10 -R 12 The definition scope is consistent.

[0056] In a preferred embodiment of the organic electroluminescent device of the present invention, the first electron transport compound may include one or more of the following compounds:

[0057]

[0058]

[0059]

[0060]

[0061] In a preferred embodiment of the organic electroluminescent device of the present invention, the second electron transport compound may include one or more of the following compounds or consist of one or more thereof:

[0062]

[0063]

[0064]

[0065] In a preferred embodiment of the organic electroluminescent device of the present invention, the hole transport region includes a hole injection layer, a hole transport layer and an electron blocking layer in sequence, wherein the hole injection layer is located between the anode and the hole transport layer, the hole transport layer is located between the hole injection layer and the electron blocking layer, and the electron blocking layer is located between the light-emitting layer and the hole transport layer.

[0066] In a preferred embodiment of the organic electroluminescent device of the present invention, the electron transport region further comprises an electron injection layer, and the electron injection layer is located between the first electron transport layer and the cathode layer.

[0067] In a preferred embodiment of the organic electroluminescent device of the present invention, the first electron transport layer is doped with the first electron transport compound and other compounds conventionally used for electron transport layers, preferably, the first electron transport compound and Liq (8-hydroxyquinoline lithium).

[0068] In a preferred embodiment of the organic electroluminescent device of the present invention, the second electron transport layer is composed of one or more compounds selected from second electron transport compounds, preferably composed of one second electron transport compound.

[0069] In a more preferred embodiment of the organic electroluminescent device of the present invention, the weight ratio of the first electron transport compound to Liq ranges from about 1:10 to 10:1, preferably from about 1:9 to 9:1, and more preferably from about 2:8 to about 8:2.

[0070] Preferably, other structures in the organic electroluminescent device of the present invention are described in detail below.

[0071] refer to Figure 2 An organic electroluminescent device of the present invention includes a substrate layer 100 , an anode layer 200 , an organic light-emitting functional layer 300 , a cathode layer 400 and a covering layer 500 .

[0072] Substrate layer

[0073] The substrate may be any substrate commonly used in organic electroluminescent devices. For example, the substrate may be a glass substrate or a transparent plastic substrate having good mechanical strength, thermal stability, transparency, surface flatness, handling convenience and water resistance, but is not limited thereto.

[0074] Anode layer

[0075] According to the organic electroluminescent device of the present invention, an anode may be disposed on the substrate. Alternatively, the anode may not be disposed on the substrate, but the cathode may be disposed on the substrate.

[0076] In a preferred embodiment of the organic electroluminescent device of the present invention, the anode material is preferably a material with a high work function so that holes are easily injected into the organic functional material layer. Non-limiting examples of the first electrode material include, but are not limited to, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO2), zinc oxide (ZnO), magnesium (Mg), aluminum (Al), silver (Ag), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In) and magnesium-silver (Mg-Ag). The first electrode 2 can have a single-layer structure or a multilayer structure including two or more layers. For example, the first electrode 2 can have a three-layer structure of ITO / Ag / ITO, but is not limited thereto. In addition, the thickness of the first electrode depends on the material used, typically 50-500nm, preferably 70-300nm and more preferably 100-200nm.

[0077] Hole transport region

[0078] The organic electroluminescent device according to the present invention may be provided with a hole transport region, which may sequentially include, but is not limited to, for example, a hole injection layer 310, a hole transport layer 320, and an electron blocking layer 330. The hole transport region may have a single-layer structure formed of a single material, a single-layer structure formed of a plurality of different materials, or a multi-layer structure having a plurality of layers formed of a plurality of different materials.

[0079] When the hole transport region includes a hole transport layer, the material of the hole transport layer is preferably a material having a high hole mobility, which enables holes to be transferred from the anode or the hole injection layer to the light emitting layer. The hole transport material may include the following compounds HT1 to HT25, but is not limited thereto:

[0080]

[0081]

[0082] According to the present invention, HT23 is preferably used as the hole transport layer material. The thickness of the hole transport layer of the present invention may be 5-200 nm, preferably 10-180 nm and more preferably 20-150 nm.

[0083] In addition to the above materials, the hole injection layer and / or the hole transport layer may also include a charge generating material to improve the conductive properties. The charge generating material may be uniformly or non-uniformly dispersed in the hole injection layer and / or the hole transport layer. The charge generating material may be, for example, a P dopant. The P-type doping material is mainly used for hole injection. The P-type doping material is incorporated into the hole transport host to form a charge transfer state with the hole transport host material, so that the holes are more easily injected into the organic material layer. In a preferred embodiment of the present invention, the P-type doping material used is selected from one of the following organic compounds:

[0084]

[0085]

[0086] In addition to the hole injection layer and the hole transport layer, the hole transport region may also include a buffer layer, an electron blocking layer, or a combination thereof. The buffer layer may compensate for the optical resonance distance according to the wavelength of the light emitted from the light emitting layer, thereby improving the luminous efficiency of the organic electroluminescent device. The electron blocking layer may prevent electrons from being injected from the electron transport region. In a specific embodiment, the electron blocking layer compound may be selected from the following compounds EB1 to EB7, but is not limited thereto:

[0087]

[0088] The thickness of the electron blocking layer of the present invention may be 1-200 nm, preferably 5-150 nm, and more preferably 10-100 nm.

[0089] Luminescent layer

[0090] The organic electroluminescent device according to the present invention is provided with a light emitting layer, wherein the material of the light emitting layer is a material capable of emitting visible light by receiving holes from a hole transport region and electrons from an electron transport region respectively and combining the received holes and electrons.

[0091] In a preferred embodiment of the present invention, the host material of the light-emitting layer is selected from one or more combinations of the following EMH-1 to EMH-22:

[0092]

[0093]

[0094] In addition, in order to improve the fluorescence or phosphorescence properties, the light-emitting layer guest material may also include phosphorescent or fluorescent materials. Phosphorescent materials include phosphorescent materials such as metal complexes of iridium, platinum, etc. For example, green phosphorescent materials such as Ir(ppy)3[fac-tri(2-phenylpyridine)iridium], blue phosphorescent materials such as FIrpic, FIr6, and red phosphorescent materials such as Btp2Ir(acac) can be used. For fluorescent materials, those commonly used in the art can be used. In a preferred embodiment of the present invention, the light-emitting layer guest material used is selected from one of the following EMD-1 to EMD-23:

[0095]

[0096]

[0097] In the light-emitting layer of the present invention, the ratio of the host material to the guest material used is 99:1-70:30, preferably 99:1-85:15 and more preferably 97:3-87:13, based on mass.

[0098] In addition, in order to obtain a high-efficiency organic electroluminescent unit, in addition to the fluorescent or phosphorescent host-guest materials used above, the light-emitting layer may also use another guest material, or use multiple guest materials. The guest material may be a simple fluorescent material, a delayed fluorescent (TADF) material or a phosphorescent material, or a combination of different fluorescent materials, TADF materials, and phosphorescent materials. The light-emitting layer may be a single light-emitting layer material, or a composite light-emitting layer material stacked together horizontally or vertically. The light-emitting layer constituting the above-mentioned organic electroluminescent device has the following multiple structures:

[0099] (1) Single organic light-emitting layer material;

[0100] (2) Any combination of blue organic light-emitting layer materials and green, yellow or red light-emitting layer materials, regardless of the order of precedence, such as Figure 4 As shown;

[0101] (3) Any combination of blue organic light-emitting layer materials and green, yellow or red light-emitting layer materials, regardless of the order of precedence, such as Figure 5 As shown;

[0102] (4) A combination of a blue organic light-emitting layer material and a green, yellow or red light-emitting layer material, and charge transfer through a connecting layer to form a two-layer device structure, such as Figure 6 As shown;

[0103] (5) A combination of any two of a blue organic light-emitting layer material and a green, yellow or red light-emitting layer material, and charge transfer through a connecting layer to form a three-layer device structure, such as Figure 7 shown.

[0104] Preferably, the organic light-emitting functional layer comprises a light-emitting layer comprising one or a combination of at least two of blue, green, red and yellow organic light-emitting layer materials.

[0105] exist Figure 6 and 7 In the figure, 300 represents an organic light-emitting functional layer, 610, 620 and 630 represent connecting layers, and the connecting layer material combination can be any one of the following types: (1) n-type doped organic layer / inorganic metal oxide, such as Bphen:Li / MoO3, Alq3:Mg / WO3, BCP:Li / V2O5 and BCP:Cs / V2O5; (2) n-type doped organic layer / organic layer, such as Alq3:Li / HAT-CN; (3) n-type doped organic layer / p-type doped organic layer, such as BPhen:Cs / NPB:F4-TCNQ, Alq3:Li / NPB:FeCl3, TPBi:Li / NPB:FeCl3 and Alq3:Mg / m-MTDATA:F4-TCNQ; (4) non-doped type, such as F16CuPc / CuPc and Al / WO3 / Au.

[0106] In order to adjust the effective combination of carrier charges in the light-emitting layer, the film thickness of the light-emitting layer 340 constituting the OLED light-emitting body can be adjusted arbitrarily as needed, or light-emitting layers of different colors can be alternately superimposed and combined as needed, and charge blocking layers with different functional purposes can be added to the organic layer adjacent to the light-emitting layer.

[0107] The thickness of the light-emitting layer of the present invention may be, for example, 5-60 nm, preferably 10-50 nm, and more preferably 20-45 nm.

[0108] Electron transport region

[0109] The organic electroluminescent device according to the present invention is provided with an electron transport region, which is arranged between the light-emitting layer and the cathode, and may include a first electron transport layer, a second electron transport layer, and an electron injection layer, wherein the first electron transport compound (ETM1) is a material that easily receives electrons from the cathode and transfers the received electrons to the second electron transport layer. Preferably, the first electron transport layer is located between the light-emitting layer and the electron injection layer, and the second electron transport layer is also called a hole blocking layer, which is located between the first electron transport layer and the light-emitting layer.

[0110] The details of the compounds of the first electron transport layer and the second electron transport layer are as described above.

[0111] The first electron transport compound of the present invention, alone or in combination with other conventional materials for electron transport, preferably in combination with Liq, is used as the first electron transport layer, preferably using one or more of the above-mentioned specific compounds 1-1, 1-8, 1-17, 1-29, 1-38, 1-44, 1-58, 1-63, 1-64, 1-72.

[0112] The first electron transport layer of the present invention may have a thickness of 10-80 nm, preferably 20-60 nm, and more preferably 25-45 nm.

[0113] The second electron transport compound (ETM2) also has a high electron transport rate.

[0114] As the second electron transport layer material of the present invention, it is preferred to use one or more of the above-mentioned specific compounds 2-1, 2-8, 2-28, 2-40, 2-43, 2-54, 2-63, and 2-72, and it is more preferred to use one of them.

[0115] The second electron transport layer (ETM2) of the present invention may have a thickness of 5-60 nm, preferably 5-30 nm, and more preferably 5-20 nm.

[0116] In a preferred embodiment of the organic electroluminescent device of the present invention, the electron injection layer material preferably has a material with a low work function, so that electrons are easily injected into the organic functional material layer. As the electron injection layer material of the present invention, the electron injection layer material for organic electroluminescent devices known in the prior art can be used, for example, lithium; lithium salts, such as 8-hydroxyquinoline lithium, lithium fluoride LiF, lithium carbonate or lithium azide; or cesium salts, cesium fluoride, cesium carbonate or cesium azide; or ytterbium. The thickness of the electron injection layer of the present invention can be 0.1-5nm, preferably 0.5-3nm, and more preferably 0.8-1.5nm.

[0117] cathode

[0118] Organic electroluminescent device of the present invention is provided with cathode.The material for forming cathode can be a material with low work function, such as metal, alloy, conductive compound or their mixture.Non-limiting examples of second electrode can include lithium (Li), ytterbium (Yb), magnesium (Mg), aluminum (Al), calcium (Ca), and aluminum-lithium (Al-Li), magnesium-indium (Mg-In) and magnesium-silver (Mg-Ag).The thickness of second electrode depends on the material used, is generally 5-100nm, preferably 7-50nm and more preferably 10-25nm.

[0119] Light extraction layer (cover layer)

[0120] In order to improve the light extraction efficiency of the organic electroluminescent device, a light extraction layer, i.e., a cover layer 500 (CPL layer) may be added on the second electrode (i.e., cathode) of the device. According to the optical absorption and refraction principle, the refractive index of the CPL cover layer material should be as high as possible, and the absorption coefficient should be as small as possible. Any material known in the art can be used as the CPL layer material, such as Alq3, CP-1

[0121]

[0122] The thickness of the CPL cover layer is typically 5-300 nm, preferably 20-100 nm and more preferably 40-80 nm.

[0123] The organic electroluminescent device may further include an encapsulation structure. The encapsulation structure may be a protective structure that prevents foreign substances such as moisture and oxygen from entering the organic layer of the organic electroluminescent device. The encapsulation structure may be, for example, a can, such as a glass can or a metal can; or a thin film covering the entire surface of the organic layer.

[0124] Method for preparing organic electroluminescent device

[0125] The present invention also relates to a method for preparing the above-mentioned organic electroluminescent device, which comprises laminating an anode, an organic layer and a cathode according to the present invention on a substrate in sequence, or laminating a cathode, an organic layer and an anode according to the present invention in sequence. Preferably, the organic layer is formed by laminating a hole transport region, a light-emitting layer and an electron transport region on the anode in sequence, and the hole transport region is formed by laminating a hole injection layer, a hole transport layer and an electron blocking layer on the anode in sequence. Preferably, the electron transport region is formed by laminating a hole blocking layer, an electron transport layer and an electron injection layer on the light-emitting layer in sequence. In addition, a CPL layer can also be laminated on the electrode on the light-emitting side to improve the light extraction efficiency of the organic electroluminescent device.

[0126] For lamination, vacuum deposition, vacuum evaporation, spin coating, casting, LB method, inkjet printing, laser printing or LITI methods may be used, but are not limited thereto. Vacuum evaporation means heating and coating a material onto a substrate in a vacuum environment.

[0127] In the present invention, the various layers are preferably formed by vacuum evaporation, wherein the layers can be formed at a temperature of about 100-500° C. and at a temperature of about 10 -8 -10 -2 Torr vacuum and approx. Preferably, the temperature is 200-400°C, more preferably 250-300°C. The vacuum degree is preferably 10 -6 -10 -2 Torr, more preferably 10 -5 -10 -3The rate is about More preferably, about

[0128] In addition, it should be noted that the materials used to form each layer described in the present invention can be formed into a film alone and used as a single layer, or can be mixed with other materials to form a film and used as a single layer. It can also be a stacked structure between layers formed into films alone, a stacked structure between layers formed into films after mixing, or a stacked structure of layers formed into films alone and layers formed into films after mixing.

[0129] The present invention also relates to a display device including an organic electroluminescent device according to the present invention, in particular a flat panel display device. In a preferred embodiment, the display device may include one or more of the above-mentioned organic electroluminescent devices, and in the case of including a plurality of devices, the devices are stacked and combined laterally or longitudinally. Preferably, the display device includes devices each having an organic light-emitting material layer of three colors of blue, green and red, each of the devices having an electron blocking layer of the same or different film thickness, and the materials of the electron blocking layer are the same or different. The display device may also include at least one thin film transistor. The thin film transistor may include a gate electrode, a source electrode and a drain electrode, a gate insulating layer and an active layer, wherein one of the source electrode and the drain electrode may be electrically connected to the first electrode of the organic electroluminescent device. The active layer may include crystalline silicon, amorphous silicon, an organic semiconductor or an oxide semiconductor, but is not limited thereto.

[0130] Exemplary embodiments have been disclosed herein, and although specific terms are used therein, these terms are used and interpreted only as general and descriptive meanings, and not for limiting purposes. In some cases, as will be apparent to those of ordinary skill in the art with the filing of this application, unless specifically indicated, the features, characteristics, and / or elements described in conjunction with a particular embodiment may be used alone or in combination with the features, characteristics, and / or elements described in conjunction with other embodiments. Accordingly, it will be understood by those skilled in the art that various changes may be made in form and detail without departing from the spirit and scope of the invention.

[0131] The following examples are intended to better explain the present invention, but the scope of the present invention is not limited thereto.

[0132] Example

[0133] I. Compound Preparation Examples

[0134] Preparation of a first electron transport compound and a second electron transport compound

[0135] (1) Synthesis of compounds 1-1, 1-8, 1-17, 1-29, 1-38, 1-44, 1-58, 1-63, 1-64, 1-72 (ETM1)

[0136] The synthesis methods of compounds 1-1, 1-8, 1-17, 1-29, 1-38, 1-44, 1-58, 1-63, 1-64, and 1-72 can be directly synthesized by referring to the methods of patents KR2014094408A, KR2017003502A, KR2017065317, CN102471679, etc., or directly purchased through commercial channels.

[0137] (2) Synthesis of compounds 2-1, 2-8, 2-23, 2-28, 2-40, 2-43, 2-54, 2-63, 2-72 (ETM2)

[0138] The synthesis of compounds 2-1, 2-8, 2-23, 2-28, 2-40, 2-43, 2-54, 2-63, and 2-72 can be directly synthesized by referring to the synthesis methods in CN109748899A, EP3312895, and WO2016105141.

[0139] II. Compound Testing Examples

[0140] The compounds prepared in 1 were tested.

[0141] There are many methods for directly testing the HOMO energy level of OLED materials, including CV method, UPS method, IPS method, AC method, etc. The HOMO energy level of OLED materials can also be predicted by quantitative calculation. Among the above-mentioned measurement methods, the CV method is greatly affected by the solvent and the operation method, and the measured values ​​are often quite different. When the AC method is measured, the sample needs to be placed in a dry air environment. When high-energy ultraviolet monochromatic light acts on the surface of the sample, the escaped electrons need to combine with oxygen in the air, and the detector can obtain a signal. Therefore, the sample material is greatly affected by the oxygen element in the environment, and the HOMO energy level test of some materials with deep HOMO energy levels (such as P-doped materials) is inaccurate.

[0142] Whether it is the UPS method or the IPS method, both can be used to test the photoelectron energy spectrum of OLED materials under a high vacuum environment, so that the adverse environmental influences can be eliminated to the maximum extent, close to the preparation environment atmosphere of OLED light-emitting devices, and the concept of in-situ measurement to the maximum extent. Therefore, from the perspective of the measurement method, it has a higher numerical accuracy than other measurement methods. Even so, it is still necessary to emphasize that the HOMO energy level test of different materials has the significance of absolute comparison only when the consistency of equipment and methods is achieved and the influence of the test environment is avoided. The HOMO energy levels of all materials involved in the present invention are the measurement means of IPS.

[0143] The specific measurement method is as follows:

[0144] HOMO energy level: Using vacuum evaporation equipment, under vacuum pressure of 1.0E-5Pa, the evaporation rate is controlled to The material was evaporated onto an ITO substrate with a film thickness of 60-80 nm. The HOMO energy level of the sample film was then measured using an IPS3 measuring device in a measurement environment of 10 -2 Vacuum environment below Pa.

[0145] Eg energy level: Draw a tangent line between the ultraviolet spectrophotometry (UV absorption) baseline of a single film of the material and the rising side of the first absorption peak, and calculate it using the numerical value of the intersection of the tangent line and the baseline.

[0146] LUMO energy level: calculated based on the difference between the aforementioned HOMO energy level and the Eg energy level.

[0147] Table 1 shows the energy level test results of the luminescent host materials (EMH-1, EMH-10, EMH-11 and EMH-13), the guest materials (EMD-1, EMD-8 and EMD-13), the first electron transport compound (compounds of formula (1-1) to (1-3)) and the second electron transport compound (compounds of formula (2-1) to (2-2)).

[0148] Table 1

[0149]

[0150]

[0151] It can be seen from the results in Table 1 that the HOMO energy level of the first electron transport compound in the present invention is 6.2-6.75 eV, and the LUMO energy level is 3.2-3.45 eV;

[0152] The HOMO energy level of the second electron transport compound is 5.9-6.2 eV, and the LUMO energy level is 2.6-2.8 eV.

[0153] When the first electron transport compound and the second electron transport compound of the present invention are used to prepare an organic electroluminescent device, the LUMO energy levels of the first electron transport compound and the second electron transport compound need to satisfy:

[0154] The value of [LUMO(first electron transport compound)+LUMO(second electron transport compound)] / 2 is in the range of 2.85-3.15 eV, preferably in the range of 2.9-3.12 eV.

[0155] Unless otherwise specified, various materials used in the following examples and comparative examples are commercially available or can be obtained by methods known to those skilled in the art.

[0156] III. Device Preparation Example

[0157] The compounds prepared in I are used as the first electron transport compound and the second electron transport compound to prepare Prepare organic electroluminescent devices.

[0158] The structures of compounds HT23, P1, CP-1, EB6, EB7, EMH-1, EMD-1, EMH-13, EMD-14, EMH-10, EMH-11, etc. used in the examples are shown above.

[0159] The vacuum deposition was carried out under the following conditions: using an OLED ChusterDeposition System (model: 1504-10117-01_0) vacuum deposition device (manufacturer: CHOSHU INDUSTRY Co. LTD.) at a vacuum degree of 1.0×10 -7 When only one material is used to form a layer, the evaporation rate is controlled to If two or more materials are used in the same layer, the several materials used are placed in a separate evaporation source, and their evaporation rates are set separately so that the ratio of the evaporation rates is equal to their mass ratio. For example, when the first and second host materials and the doping material are used in the light-emitting layer, the three materials are placed in three evaporation sources respectively. When their mass ratio is 50:50:6, their evaporation rates are controlled to be respectively and

[0160] Device Example B-1 (BLUE)

[0161] a) A transparent PI film is used as the substrate layer 100, which is washed, that is, washed with a cleaning agent (SemiCleanM-L20), washed with pure water, dried, and then washed with ultraviolet-ozone to remove organic residues on the surface of the anode layer. Ag (150nm) is evaporated on the washed substrate layer 100 to serve as the anode layer 2.

[0162] b) On the anode layer 200, HT23 and P1 are placed in two evaporation sources, and the evaporation rates are controlled to be and The obtained layer served as the hole injection layer 310 and had a film thickness of 10 nm.

[0163] c) On the hole injection layer 310, HT23 was evaporated as the hole transport layer 320 with a film thickness of 130 nm.

[0164] d) On the hole transport layer 320, EB6 is evaporated as the electron blocking layer 330 with a film thickness of 20 nm.

[0165] e) On the electron blocking layer 330, the main compound EMH-1 and the doping material EMD-1 are placed in two evaporation sources respectively, and the evaporation rates thereof are controlled to be The obtained layer was used as the light-emitting layer 340 and had a thickness of 20 nm.

[0166] f) Compound 2-8 was evaporated on the light-emitting layer 340 to form the second electron transport layer 350 with a film thickness of 5 nm.

[0167] g) On the second electron transport layer 350, the electron transport compound 1-1 and the electron transport compound Liq are placed in two evaporation sources, and the evaporation rates are controlled to be and The obtained layer served as the first electron transport layer 360 and had a film thickness of 30 nm.

[0168] h) Yb was evaporated on the first electron transport layer 360 to form the electron injection layer 370 with a film thickness of 1 nm.

[0169] i) On the electron injection layer 370, Mg and Ag are placed in two evaporation sources, and the evaporation rates are controlled to be and The obtained layer was used as the cathode layer 400 and had a film thickness of 15 nm.

[0170] j) CP-1 was evaporated on the cathode layer 400 as a cover layer 500 with a film thickness of 70 nm.

[0171] Device Example R-1 (RED)

[0172] a) A transparent PI film is used as the substrate layer 100, which is washed, that is, washed with a cleaning agent (SemiCleanM-L20), washed with pure water, dried, and then washed with ultraviolet-ozone to remove organic residues on the surface of the anode layer. Ag (150nm) is evaporated on the washed substrate layer 100 to serve as the anode layer 200.

[0173] b) On the anode layer 2, HT23 and P1 were placed in two evaporation sources, and the evaporation rates were controlled to be and The obtained layer served as the hole injection layer 310 and had a film thickness of 10 nm.

[0174] c) On the hole injection layer 310, HT23 was evaporated as the hole transport layer 320 with a film thickness of 130 nm.

[0175] d) EB7 was evaporated on the hole transport layer 320 as the electron blocking layer 330 with a film thickness of 40 nm.

[0176] e) On the electron blocking layer 330, the main compound EMH-13 and the doping material EMD-14 are placed in two evaporation sources respectively, and the evaporation rates are controlled to be The obtained layer was used as the light-emitting layer 340 and had a thickness of 40 nm.

[0177] f) Compound 2-8 was evaporated on the light-emitting layer 340 to form the second electron transport layer 350 with a film thickness of 5 nm.

[0178] g) On the second electron transport layer 350, the electron transport compound 1-1 and the electron transport compound Liq are placed in two evaporation sources, and the evaporation rates are controlled to be and The obtained layer served as the first electron transport layer 360 and had a film thickness of 30 nm.

[0179] h) Yb was evaporated on the second electron transport layer 360 to form the electron injection layer 370 with a film thickness of 1 nm.

[0180] i) On the electron injection layer 370, Mg and Ag are placed in two evaporation sources, and the evaporation rates are controlled to be and The obtained layer was used as the cathode layer 400 and had a film thickness of 15 nm.

[0181] j) CP-1 was evaporated on the cathode layer 400 as a cover layer 500 with a film thickness of 70 nm.

[0182] Device Example G-1 (GREEN)

[0183] a) A transparent PI film is used as the substrate layer 100, which is washed, that is, washed with a cleaning agent (SemiCleanM-L20), washed with pure water, dried, and then washed with ultraviolet-ozone to remove organic residues on the surface of the anode layer. Ag (150nm) is evaporated on the washed substrate layer 100 to serve as the anode layer 200.

[0184] b) On the anode layer 200, HT23 and P1 are placed in two evaporation sources, and the evaporation rates are controlled to be and The obtained layer served as the hole injection layer 310 and had a film thickness of 10 nm.

[0185] c) On the hole injection layer 310, HT23 was evaporated as the hole transport layer 320 with a film thickness of 130 nm.

[0186] d) EB6 was evaporated on the hole transport layer 320 as the electron blocking layer 330 with a film thickness of 40 nm.

[0187] e) On the electron blocking layer 330, the main compound EMH-10, the main compound EMH-11 and the doping material EMD-13 are placed in three evaporation sources respectively, and the evaporation rates thereof are controlled to be and The obtained layer was used as the light-emitting layer 340 and had a thickness of 40 nm.

[0188] f) Compound 2-1 was evaporated on the light-emitting layer 340 to form the second electron transport layer 350 with a film thickness of 5 nm.

[0189] g) On the second electron transport layer 350, the electron transport compound 1-1 and the electron transport compound Liq are placed in two evaporation sources, and the evaporation rates are controlled to be and The obtained layer served as the first electron transport layer 360 and had a film thickness of 30 nm.

[0190] h) Yb was evaporated on the first electron transport layer 360 to form the electron injection layer 370 with a film thickness of 1 nm.

[0191] i) On the electron injection layer 370, Mg and Ag are placed in two evaporation sources, and the evaporation rates are controlled to be and The obtained layer was used as the cathode layer 400 and had a film thickness of 15 nm.

[0192] j) CP-1 was evaporated on the cathode layer 400 as a cover layer 500 with a film thickness of 70 nm.

[0193] Example R-2 to Example R-11

[0194] An organic electroluminescent device was prepared in the same manner as in device example R-1, except that in step f), the compounds shown in Table 2 were used to form ETM2 of examples 2 to 16, and in step g), the compounds shown in Table 2 were used to form ETM1 of examples 2 to 16, wherein when the ratio of ETM1 to Liq was 50:50, the evaporation rate was controlled to be and The specific compounds used in ETM2 and ETM1 are shown in Table 2.

[0195] Device Comparative Example R-1

[0196] An organic electroluminescent device was prepared in the same manner as in device example R-1, except that step f) was omitted, and step g used compound 1-1 as ETM1, wherein the ratio of compound 1-1 to Liq was 50:50, and the controller evaporation rate was and And the thickness of this layer is 35nm.

[0197] Device Comparative Example R-2

[0198] An organic electroluminescent device was prepared according to the same idea as that of device example R-1, except that in step f), compound 2-23 shown in Table 2 was used to form ETM2 of device comparison example R-2, and in step g), compound Alq3 shown in Table 2 was used to form ETM1 of device comparison example R-2, wherein when the ratio of Alq3 to Liq was 50:50, the evaporation rate was controlled to be and The specific compounds used in ETM2 and ETM1 are shown in Table 2.

[0199] Device Examples G-2 to G-11 and Comparative Examples G-1 and G-2

[0200] An organic electroluminescent device was prepared in the same manner as in Device Example G-1, except that the first electron transport layer ETM1 and the second electron transport layer ETM2 used the compounds shown in Table 3, respectively.

[0201] Device Examples B-2 to B-11 and Comparative Examples B-1 and B-2

[0202] An organic electroluminescent device was prepared in the same manner as in Device Example B-1, except that the first electron transport layer ETM1 and the second electron transport layer ETM2 used the compounds shown in Table 4, respectively.

[0203] IV. Device Testing Examples

[0204] All devices prepared in III were tested. The test method is as follows:

[0205] The driving voltage and current efficiency are both 10mA / cm 2 The voltage, current efficiency and color coordinates were tested using an IVL (current-voltage-luminance) test system (Suzhou Foster Scientific Instrument Co., Ltd.).

[0206] LT95 refers to the time taken for the device brightness to decay to 95% of the original brightness when the brightness is 10,000 nits. The life test system is the EAS-62C OLED device life tester produced by Japan System Technology Co., Ltd.

[0207] The test results are shown in Tables 2 to 4 below.

[0208] Table 2: Organic electroluminescent devices prepared in device preparation examples R-1 to R-12 and device comparison examples R-1 and R-2

[0209]

[0210]

[0211] Table 3 Organic electroluminescent devices prepared in device preparation examples G-1 to G-12 and comparative examples G-1 and G-2

[0212]

[0213]

[0214] Table 4: Organic electroluminescent devices prepared in device preparation examples B-1 to B-12 and device comparison examples B-1 and B-2

[0215]

[0216] It can be seen from the device data results in Tables 2 to 4 that in red, green, and blue light-emitting devices, compared with the device comparison examples R-1, G-1, and B-1 that do not use the second electron transport layer and use the compound described in this application as the first electron transport compound, and the device comparison examples R-2, G-2, and B-2 that use the prior art material Alq3: Liq (1: 1) as the first electron transport layer and the compound described in this application as the first electron transport compound, the invention embodiments R-1 to R-12, G-1 to G-12, and B-1 to B-12 have achieved better results, for example, lower driving voltage, longer LT95 life, and higher current efficiency. In particular, the red light-emitting devices and green light-emitting devices prepared using the first electron transport layer and the second electron transport layer of the present invention have achieved significantly better technical effects than the prior art. For red light-emitting devices, compared with the comparative example, the current efficiency of the invention embodiment is equivalent, but the driving voltage is significantly reduced and the life is significantly extended.

[0217] From the above, it can be seen that by using the first electron transport compound for the first electron transport layer and the second electron transport compound for the second electron transport layer that meet the following conditions as described in the present application:

[0218] The LUMO energy level of the first electron transport compound (ETM1) is between 3.2-3.5 eV;

[0219] The LUMO energy level of the second electron transport compound (ETM2) is between 2.5 and 2.8 eV;

[0220] And [LUMO (first electron transport compound) + LUMO (second electron transport compound)] / 2 is between 2.85-3.15 eV,

[0221] The prepared blue, green and red organic electroluminescent devices all achieve better technical effects. In particular, the combination of the electron transport layer described in the present application is more suitable for red light-emitting devices and green light-emitting devices, especially red light-emitting devices.

Claims

1. An organic electroluminescent device, which is provided with a substrate and an anode, an organic layer and a cathode in sequence, wherein the substrate is arranged on the anode side or on the cathode side, the organic layer includes a hole transport region, a light emitting layer, and an electron transport region, wherein a light-emitting layer, located between the cathode and the anode, and comprising a host material and a guest material; The hole transport region is located between the anode and the light-emitting layer; The electron transport region, located between the cathode and the light-emitting layer; Characterized in that the electron transport region includes a first electron transport layer and a second electron transport layer, wherein the second electron transport layer is located between the first electron transport layer and the light-emitting layer; The first electron transport layer comprises a first electron transport compound, wherein the LUMO energy level of the first electron transport compound (ETM1) is between 3.2-3.5 eV; The second electron transport layer comprises or consists of a second electron transport compound, and the LUMO energy level of the second electron transport compound (ETM2) is between 2.5 and 2.8 eV; and [LUMO (first electron transport layer) + LUMO (second electron transport layer)] / 2 is between 2.85 and 3.15 eV; The first electron transport compound includes one or more compounds having structures shown in general formula (1-1) to general formula (1-3). The second electron transport compound includes compounds having structures represented by general formula (2-1) and general formula (2-2), or is composed of one or more of them. In the general formula, X1-X9 are independently represented by CR or N atoms; Z1-Z8 are independently represented by CR or N atoms; Y represents a single bond, -O-, -S-, -CR 10 R 11 -or-NR 12 ; L1-L4 are independently represented by a single bond, C1-C 20 Alkylene, substituted or unsubstituted C5-C 60 arylene, or substituted or unsubstituted C2-C 60 Heteroarylene; Ar1-Ar8 are independently substituted or unsubstituted C5-C 60 aryl, or substituted or unsubstituted C2-C 60 heteroaryl; Cy represents substituted or unsubstituted C2-C 60 R represents a hydrogen atom, a substituted or unsubstituted phenyl, naphthyl, biphenyl, or pyridyl group, and the substituted substituent represents one or more of a phenyl, methyl, ethyl, propyl, and butyl group; R1-R7 are independently hydrogen, substituted or unsubstituted C5-C 60 Aryl, or substituted or unsubstituted C2-C 60 Heteroaryl; R8 represents a substituted terphenyl group, or a structure represented by general formula (3) R9 is represented by the structure shown in general formula (3); R 10 -R 12 Each is independently represented by C 1-20 Alkyl, substituted or unsubstituted C 5-60 aryl or substituted or unsubstituted C2-C 60 heteroaryl; Where R 13 , R 14 are independently halogen atoms, substituted or unsubstituted C1-C 20 Alkyl, substituted or unsubstituted C5-C 60 aryl, or substituted or unsubstituted C2-C 60 and optionally R 13 and R 14 Connected by single bonds to form 5-7 membered rings; R 15 , R 16 Each independently represents a hydrogen atom, a halogen atom, a cyano group, The general formula (3-1), the general formula (3-2), and the general formula (3-3) are connected to form a ring with the general formula (3) through "*", Wherein Y1-Y3 are independently represented by -O-, -S-, -CR 17 R 18 - or NR 19 ; R 17 -R 19 Definition and R 10 -R 12 The definition scope is consistent; The prefix "substituted or unsubstituted" used before a group, if not specified, means that the group is optionally selected from cyano, halogen, C 1-20 Alkyl, C 2-20 Alkenyl, C 6-30 Aryl, C 2-30 At least one of the heteroaryl groups is substituted; or is unsubstituted.

2. The electroluminescent device according to claim 1, wherein In the general formula, L1 to L4 are independently phenylene, biphenylene or terphenylene.

3. The electroluminescent device according to claim 1, wherein In the general formula, Ar1-Ar8 are independently phenyl, naphthyl, biphenyl, terphenyl, anthracenyl, phenanthryl, pyridyl, pyrimidinyl, furanyl, benzofuranyl, dibenzofuranyl, imidazolyl, benzimidazolyl, indolyl, benzindolyl, carbazolyl, N-phenylcarbazolyl, 4. The electroluminescent device according to claim 1, wherein In the general formula, Cy represents a pyridyl group, a pyrimidyl group, a triazine group, an imidazolyl group, a benzimidazolyl group, an indolyl group, a benzindolyl group, a carbazolyl group, an N-phenylcarbazolyl group, a furyl group, a benzofuranyl group, a dibenzofuranyl group, a quinolyl group, an isoquinolyl group or 5. The electroluminescent device according to claim 1, wherein In the general formula, R1-R7 are independently naphthyl, anthracenyl, phenanthrenyl, pyrenyl, 6. The electroluminescent device according to claim 1, wherein In the general formula, R8 is 7. The electroluminescent device according to claim 1, wherein: In the general formula, R9 is 8. The organic electroluminescent device according to claim 1, characterized in that: The first electron transport compound includes a compound having the following structure:

9. The organic electroluminescent device according to claim 1, wherein the second electron transport compound comprises or consists of a compound having the following structure:

10. The organic electroluminescent device according to claim 1, wherein: The hole transport region includes a hole injection layer, a hole transport layer and an electron blocking layer in sequence, wherein the hole injection layer is located between the anode and the hole transport layer, the hole transport layer is located between the hole injection layer and the electron blocking layer, and the electron blocking layer is located between the light-emitting layer and the hole transport layer.

11. The organic electroluminescent device according to claim 1, wherein: The electron transport region further includes an electron injection layer, which is located between the first electron transport layer and the cathode layer.

12. The organic electroluminescent device according to claim 1, wherein: The first electron transport layer is doped with a first electron transport compound and Liq. 13 . The organic electroluminescent device according to claim 1 , wherein the second electron transport layer is composed of one or more compounds selected from the second electron transport compound. 14 . The organic electroluminescent device according to claim 1 , wherein the second electron transport layer is composed of a compound selected from the second electron transport compound.

15. The organic electroluminescent device according to claim 12, wherein: The weight ratio of the first electron transport compound to Liq ranges from 1:10 to 10:

1.

16. The organic electroluminescent device according to claim 15, wherein: The weight ratio of the first electron transport compound to Liq ranges from 1:9 to 9:

1.

17. The organic electroluminescent device according to claim 16, wherein: The weight ratio of the first electron transport compound to Liq ranges from 2:8 to 8:

2.

18. A method for preparing an organic electroluminescent device according to any one of claims 1 to 17, comprising laminating the anode, organic layer and cathode of claims 1 to 17, or laminating the cathode, organic layer and anode of claims 1 to 17, on a substrate in succession, wherein the lamination is performed by vacuum evaporation at a temperature of 100 to 500° C. at a temperature of 10 -8 -10 -2 Torr vacuum and at a rate of .

19. A display device comprising the organic electroluminescent device according to any one of claims 1 to 17.

20. The display device according to claim 19, characterized in that In the case of comprising a plurality of devices, the devices are stacked and combined laterally or vertically.

21. The display device according to claim 20, wherein the display device comprises devices each having an organic light-emitting material layer of three colors: blue, green and red, each of the devices having an electron blocking layer of the same or different film thickness, and the materials of the electron blocking layers are the same or different.

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