Organic light-emitting device, preparation method thereof and display device

Abstract

The invention belongs to the technical field of organic photoelectric materials and devices, and discloses an organic electroluminescent device, a preparation method thereof and a display device. The device sequentially comprises an anode layer, a hole transport layer, a light-emitting layer, a second electron transport layer, a first electron transport layer and a cathode layer, wherein the first electron transport layer is composed of an n-type dopant and a first electron transport material. According to the adopted electron transmission structure, small electron injection barriers are arranged between the second electron transmission layer and the first electron transmission layer and between the second electron transmission layer and the main body material, and the organic light-emitting device prepared through the electron transmission structure achieves good voltage stability in the aging process; therefore, the problem of power consumption increase of the organic light-emitting device in the aging process is solved. And a relatively small electron injection barrier can reduce the driving voltage of the device, so that the organic light-emitting device with low driving voltage, long service life and stable voltage is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic photoelectric materials and devices, and in particular relates to an organic electroluminescent device and a preparation method thereof, and a display device. Background Art

[0002] Organic Light-emitting Diode (OLED) technology is a technology that uses an organic semiconductor thin film to emit light under an applied voltage. It has many advantages such as flexibility, self-luminescence, lightness, and low power consumption. It has been widely used in smart phones, wearable devices, and car displays. Furthermore, OLED technology can also be used in indoor and outdoor lighting, medical lighting, and car lighting. For the OLED technology industry chain, organic light-emitting materials, as a key part of the OLED technology industry chain, are one of the links of the technical barrier. It is of great significance to explore OLED light-emitting materials that meet the needs of display panels.

[0003] With the increasing development and iteration of OLED technology, OLED devices are required to have properties such as low driving voltage, high luminous efficiency, long working life, and high color purity. In addition to the luminous efficiency and spectral half-width of OLED materials, which have received much attention in recent years, obtaining low driving voltage and long-life device performance is also the key to achieving high-performance OLED devices. Since the hole mobility is generally higher than the electron mobility, it is necessary to solve the voltage drop loaded on the electron transport layer to reduce the driving voltage of the device; on the other hand, it is also very important to ensure the life stability of the electron transport layer, which determines the working life of the entire device. In order to achieve the above electron transport layer design goals, the following material and device structure design strategies are usually adopted: 1) Using n-doped electron transport materials to replace traditional nitrogen heterocyclic electron transport materials. Due to the charge transfer effect between the n-dopant and the electron transport material, the electron mobility is significantly improved, reducing the voltage drop of the device in the electron transport layer; 2) Using an energy level-matched electron injection layer structure, the electron injection without energy level barrier is realized between the cathode and the electron transport layer, reducing the voltage drop at the cathode end, and at the same time improving the working life of the device. However, most of the current patents or research work focuses on the electron injection barrier between the electron transport material and the cathode or the electron mobility of the electron transport material itself, but rarely pays attention to the electron injection barrier between the electron transport layer and the hole blocking layer and the hole blocking layer and the light-emitting layer. At the same time, during the constant current aging process of OLED devices, not only does the brightness decay, but it is also accompanied by a rise in the device driving voltage, resulting in an increase in device power consumption. There are almost no relevant patents and papers reporting on the device voltage stability problem caused by device aging, and this aspect needs further research. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the prior art and provide an organic electroluminescent device including an electron transport structure, which can reduce the driving voltage of the OLED device and solve the driving voltage stability problem during the device aging process, thereby achieving low driving voltage, high efficiency, and stable life OLED device performance. Based on this, the first aspect of the present invention provides an organic electroluminescent device, which includes, from bottom to top, an anode layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode layer;

[0005] The light-emitting layer comprises a binary blend composition or a ternary blend composition, wherein the binary blend composition is a host material and a light-emitting guest material, and the ternary blend composition is a host material, a light-emitting guest material and a sensitizer;

[0006] The electron transport layer includes a second electron transport layer and a first electron transport layer from bottom to top; the first electron transport layer is composed of an n-type dopant and a first electron transport material; the second electron transport layer is composed of a second electron transport material; the difference between the LUMO energy level of the second electron transport layer and the LUMO energy level of the first electron transport layer is less than or equal to 0.10 eV, and the difference between the LUMO energy level of the main material or the sensitizer and the LUMO energy level of the second electron transport layer is less than or equal to 0.15 eV.

[0007] Among them, the electron transport structure requires that there is a small minimum occupied molecular orbital energy level difference between the electron transport material and the hole blocking layer, and between the hole blocking layer and the light-emitting layer, so that the organic electroluminescent device has a low driving voltage characteristic, and reduces the voltage rise change during the aging process of the device, so that the device power consumption remains stable during the aging process, and obtains an organic electroluminescent device with high efficiency, low driving voltage and high life stability.

[0008] In some implementations, in order to further enhance the hole blocking effect of the hole blocking layer, the HOMO energy level of the second electron transport material is at least 0.4 eV deeper than the HOMO energy level of the host material.

[0009] In some implementations, the structure of the second electron transport material is as shown in formula (1):

[0010]

[0011] Wherein, X and Y are independently selected from carbon or nitrogen atoms, and at least one of X and Y is a nitrogen atom; R1 and R2 are independently selected from weak electron-withdrawing groups, and the weak electron-withdrawing groups include benzocyano and its derivatives, fluorophenyl and its derivatives, benzothiophene and its derivatives, benzofuran and its derivatives, and fluorenyl and its derivatives.

[0012] Preferably, the structure of the second electron transport material is as shown in formula (2), formula (3) or formula (4):

[0013]

[0014] Wherein, X and Y are independently selected from carbon or nitrogen atoms, and at least one of X and Y is a nitrogen atom; R2 and R3 are independently selected from weak electron-withdrawing groups, and the weak electron-withdrawing groups include benzocyano and its derivatives, fluorophenyl and its derivatives, benzothiophene and its derivatives, benzofuran and its derivatives, and fluorenyl and its derivatives.

[0015] Further preferably, the structure of the second electron transport material is any one of Compound 4-1 to Compound 4-64:

[0016]

[0017]

[0018]

[0019]

[0020] In some implementations, since the LUMO energy level matching between the first electron transport layer and the second electron transport layer is particularly important for achieving the goals of low driving voltage and high voltage stability, and the first electron transport layer is also required to have a higher electron mobility characteristic to achieve good electron transport performance, the n-type dopant is preferably Li, Na, K, Rb, Cs, Yb, Ag, Mg, Zn, Au, Cs2CO3, Li2CO3; the structure of the first electron transport material is preferably any one of compounds 5-1 to 5-44:

[0021]

[0022]

[0023]

[0024] At the same time, in order to obtain the first electron transport layer with high electron mobility and avoid the n-type dopant from causing luminescence quenching to the light-emitting layer, the doping concentration of the n-type dopant is preferably 0.5 mass %-20 mass %;

[0025] In some implementations, the LUMO energy level matching between the second electron transport layer and the light-emitting layer is particularly important for achieving low driving voltage and high voltage stability. Therefore, the structure of the host material is preferably any one of Compounds 7-1 to 7-76:

[0026]

[0027]

[0028]

[0029]

[0030] Meanwhile, the structure of the sensitizer is preferably any one of Compound 6-1 to Compound 6-50:

[0031]

[0032]

[0033]

[0034]

[0035] Among them, the main function of the anode layer in the above-mentioned organic electroluminescent device is to inject holes into the hole transport layer or the light-emitting layer, and the anode layer material with a work function of 4.5eV or more is preferably used. Specific examples of anode layer materials are preferably indium tin oxide alloy (ITO), tin oxide (NESA), indium gallium zinc oxide (IGZO), silver, etc. The anode layer can be formed into an anode layer thin film by thermal evaporation, sputtering, etc. It is preferred that the light transmittance of the visible area of ​​the anode is greater than 80%. In addition, the square resistance of the anode layer is preferably 500Ω / cm -1 Hereinafter, the film thickness is preferably 10 nm to 200 nm.

[0036] The cathode layer in the above-mentioned organic electroluminescent device mainly functions to inject electrons into the electron injection layer, the electron transport layer or the light-emitting layer, and preferably the material with small work function. The cathode material is not particularly limited, and is preferably selected from aluminum, magnesium, silver, magnesium-silver alloy, magnesium-aluminum alloy, aluminum-lithium alloy, etc. The cathode layer can also be formed into a cathode layer thin film by thermal evaporation, sputtering, etc., similarly to the anode layer, and the cathode layer film thickness is preferably 10nm-200nm. In addition, luminescence can also be extracted from the cathode side as needed.

[0037] The hole transport layer in the above-mentioned organic electroluminescent device is an organic layer formed between the light-emitting layer and the anode layer (or hole injection layer), and its main function is to transport holes from the anode to the light-emitting layer. The hole transport layer may be composed of two layers of organic layer materials, the side close to the anode is defined as the hole injection layer, and the side close to the light-emitting layer is defined as the first hole transport layer; it may also be composed of three layers of organic layer materials, from the side close to the anode layer to the side close to the light-emitting layer, the hole injection layer, the first hole transport layer and the second hole transport layer. The film thickness of the hole transport layer is not particularly limited, and is preferably 20nm-200nm. Among them, when the hole transport layer of the organic electroluminescent device is composed of the first hole transport layer, the film thickness of the first hole transport layer is preferably 20nm-200nm; when the hole transport layer of the organic electroluminescent device is composed of the first hole transport layer and the second hole transport layer, the film thickness of the first hole transport layer is preferably 19nm-150nm, and the film thickness of the second hole transport layer is preferably 1nm-50nm. As the hole transport material used in the hole transport layer, an aromatic amine compound, for example, an aromatic amine derivative represented by the following formula (70) is preferably used.

[0038]

[0039] In the above formula (70), Ar1-Ar4 represent a substituted or unsubstituted aromatic hydrocarbon group having 6-50 (preferably 6-30, more preferably 6-20, and further preferably 6-12) ring carbon atoms, or a fused aromatic hydrocarbon group having 6-50 (preferably 6-30, more preferably 6-20, and further preferably 6-12) ring carbon atoms which may have a substituent, a substituted or unsubstituted aromatic heterocyclic group having 5-50 (preferably 5-30, more preferably 5-20, and further preferably 5-12) ring atoms, or a substituted or unsubstituted fused aromatic heterocyclic group having 5-50 (preferably 5-30, more preferably 5-20, and further preferably 5-12) ring atoms, or a group formed by bonding these aromatic hydrocarbon groups or fused aromatic hydrocarbon groups to aromatic heterocyclic groups or fused aromatic heterocyclic groups.

[0040] A ring may be formed between Ar1 and Ar2, and between Ar3 and Ar4. In the above formula (70), L represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 50 (preferably 6 to 30, more preferably 6 to 20, and further preferably 6 to 12) ring carbon atoms, or a fused aromatic hydrocarbon group having 6 to 50 (preferably 6 to 30, more preferably 6 to 20, and further preferably 6 to 12) ring carbon atoms which may have a substituent, or a substituted or unsubstituted aromatic heterocyclic group having 5 to 50 (preferably 5 to 30, more preferably 5 to 20, and further preferably 5 to 12) ring atoms, or a substituted or unsubstituted fused aromatic heterocyclic group having 5 to 50 (preferably 5 to 30, more preferably 5 to 20, and further preferably 5 to 12) ring atoms.

[0041] Alternatively, an aromatic amine compound represented by the following formula (71) is used:

[0042]

[0043] In the above formula (71), the definitions of Ar1 to Ar3 are the same as those of Ar1 to Ar4 in formula (70).

[0044] According to the above formula (70) and formula (71), the hole transport material can be preferably selected from any one of the following structures:

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051] The organic electroluminescent device of the present invention is preferably provided with a hole injection layer between the anode layer and the hole transport layer (or light-emitting layer). The main function of the hole injection layer is to promote the injection of holes from the anode layer into the hole transport layer or the light-emitting layer, thereby reducing the driving voltage of the organic electroluminescent device, and improving the luminous brightness and device life. Here, the hole injection layer is composed of a p-type dopant material (deep LUMO energy level), or is composed of a blend of a p-type dopant material and a hole transport material. As a specific example, the hole transport material is preferably selected from HT-1-HT-63 compounds. As a specific example, the p-type dopant material can be preferably selected from HATCN, F4TCNQ, HI-3, etc., and the doping concentration of the p-type dopant is preferably 0.1 mass % to 50.0 mass %. The film thickness of the hole injection layer is not particularly limited, and is preferably selected within the range of 1nm-50nm.

[0052] The structural formulas of p-type dopant materials HATCN, F3-TCNQ, and HI-3 are as follows:

[0053]

[0054] The organic electroluminescent device of the present invention preferably has an electron injection layer composed of an n-type dopant between the electron transport layer and the cathode layer. Here, as specific examples, the n-type dopant may preferably be Li, Cs, Ba, Yb, CsF, BaO, Liq, Naq, Libpp, Bepq2, Bepp2, LiF, CsCO3, ZnO, etc., and the doping concentration of the n-type dopant is preferably 1.0 mass%-90.0 mass%. The structural formulas of the n-type dopant materials Liq, Naq, Libpp, Bepq2, Bepp2 are as follows:

[0055]

[0056]

[0057] The second aspect of the present invention provides a method for preparing the above-mentioned organic electroluminescent device, comprising the following steps: forming the hole transport layer, the light-emitting layer, the electron transport layer and the cathode layer by sequentially evaporating on the anode layer.

[0058] A third aspect of the present invention provides an organic electroluminescent display device comprising the above organic electroluminescent device.

[0059] The beneficial effects of the present invention are as follows: 1) Thanks to the n-doped electron transport layer and the hole blocking layer, there is a small electron injection barrier between the hole blocking layer and the light-emitting layer, so that the voltage rise problem during the aging process of the organic electroluminescent device is effectively solved, and a small driving voltage rise change is achieved, thereby reducing the power consumption rise problem of the organic electroluminescent device during the aging process. And the small electron injection barrier can reduce the driving voltage of the device, and obtain an organic electroluminescent device with long life, high voltage stability and low driving voltage; 2) By preferably using triazine or pyrimidine compounds as the hole blocking layer, further introducing weakly electrically attractive units on the above compounds, adjusting the electron injection barrier between the electron transport layer and the light-emitting layer, thereby achieving a small electron injection barrier, reducing the device driving voltage, and obtaining a significant improvement in power efficiency performance. And the triazine derivative has good chemical stability, so that the working life of the device is extended; 3) The n-doped electron transport layer is used to replace the traditional nitrogen heterocyclic electron transport material. Due to the significant charge transfer effect between the n dopant and the electron transport material, the electron mobility of the electron transport layer is greatly improved, so that the voltage drop in the electron transport layer is significantly reduced. Thereby, low driving voltage and high efficiency device luminescence performance are obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1The figure shows a schematic diagram of the structure of an organic electroluminescent device, wherein 10: anode layer; 11: hole injection layer; 12: first hole transport layer; 13: second hole transport layer; 14: light emitting layer; 15: second electron transport layer; 16: first electron transport layer; 17: electron injection layer; 18: cathode layer. DETAILED DESCRIPTION

[0061] The following will be combined with the embodiments and drawings to clearly and completely describe the concept, specific structure and technical effects of the present invention, so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0062] The structures of compound HATCN, compound HT-48, compound HT-65, host material 7-60, sensitizer 6-27, host material 7-66, sensitizer 6-15, and sensitizer 6-18 are shown below:

[0063]

[0064] Among them, the structures of compounds 4-1 to 4-64 are shown below:

[0065]

[0066]

[0067]

[0068]

[0069] The structures of compounds 5-1 to 5-44 are shown below:

[0070]

[0071]

[0072]

[0073] An organic electroluminescent device, the structural schematic diagram of which is as follows Figure 1 As shown, the preparation method thereof comprises the following steps:

[0074] A 30mm×30mm×0.7mm thick glass substrate with an ITO / Ag / ITO reflective anode (anode layer 10, ITO film thickness of 10nm, Ag thickness of 150nm) was ultrasonically cleaned in isopropanol, and the cleaned ITO glass substrate was placed in an oven at 100°C for 3 hours; the baked ITO glass substrate was subjected to an ultraviolet lamp irradiation and ozone cleaning treatment for 3 minutes.

[0075] The glass substrate after UV irradiation was mounted on a substrate holder of a vacuum deposition device, and the compound HATCN was first deposited on the surface on which the transparent electrode lines were formed so as to cover the transparent electrode, thereby forming a hole injection layer 11 with a thickness of 10 nm.

[0076] Compound HT-48 was deposited on the hole injection layer 11 to form a first hole transport layer 12 having a film thickness of 135 nm.

[0077] Next, compound HT-65 was vapor-deposited on the first hole transport layer to form a second hole transport layer 13 having a film thickness of 10 nm.

[0078] Subsequently, a ternary blend composition consisting of a main material 7-60, a sensitizer 6-27 and a luminescent guest material 1 is co-evaporated on the second hole transport layer, wherein the doping concentration of the sensitizer 6-27 is 30% by mass and the doping concentration of the luminescent guest material 1 is 0.5% by mass, to form a luminescent layer 14 with a film thickness of 30 nm.

[0079] The chemical structure of the luminescent guest material 1 is as follows:

[0080]

[0081] Next, a second electron transport layer 15 with a film thickness of 15 nm was deposited on the light emitting layer 14 .

[0082] Next, the first electron transport layer 16 was evaporated on the second electron transport layer 15 to a thickness of 25 nm.

[0083] Furthermore, Yb was vapor-deposited on the first electron transport layer 16 to form an electron injection layer 17 having a film thickness of 1 nm.

[0084] Then, metal Ag was vapor-deposited on the electron injection layer to form a cathode layer 18 having a film thickness of 20 nm.

[0085] Examples 1-6 are formed by adjusting the material combination of the second electron transport layer 15 and the first electron transport layer, as shown in Table 1.

[0086] Table 1

[0087]

[0088] While keeping other aspects of Example 2 unchanged, the host material and the sensitizer in the light-emitting layer were adjusted to form Examples 7-9, as shown in Table 2.

[0089] Table 2

[0090] Example Main material Sensitizer Object material 7 7-60 6-15 Luminescent guest material 1 8 7-60 6-18 Luminescent guest material 1 9 7-66 6-27 Luminescent guest material 1

[0091] Thin films of 1 mass % Ag: 5-6, 1 mass % Yb: 5-6, comparative compound 1 and comparative compound 2 were formed on the above conductive substrates, respectively, as Examples 10-13, and the thin films obtained in Examples 10-13 were measured by time-of-flight method at 300 (V / cm) 1 / 2 Electron mobility under electric field strength. For comparison of the electron transport capability when using n-doped electron transport material as the first electron transport layer, the electron mobility results measured in Examples 10-13 are shown in Table 3.

[0092] Table 3

[0093]

[0094] The comparative compounds 1 and 2 have the following structural formulas:

[0095]

[0096] The combination of the second electron transport layer 15 and the first electron transport layer 16 of the organic electroluminescent devices prepared in Comparative Examples 20-27 is changed to be shown in Table 4 below.

[0097] Table 4

[0098]

[0099] The comparative compound 3 has the following structural formula:

[0100]

[0101] Performance evaluation of organic electroluminescent devices

[0102] The performance of the organic electroluminescent devices prepared in Examples 1-6, Examples 7-9 and Comparative Examples 20-27 of the present application was measured using a spectroradiometer CS-2000 (Konica Minolta) and a digital source meter 2420 (Keithley) at 1000 cd / m 2 Current efficiency at brightness, measured at 10 mA / cm 2 Driving voltage at current density. Using OLED device life test system at 10mA / cm 2 The lifetime of the device when it decays to 95% of the initial brightness and the driving voltage change when the device decays to 90% of the initial brightness are measured by constant current driving at current density. 第二电-第一电 E is defined as the difference between the LUMO energy level of the second electron transport layer and the LUMO energy level of the first electron transport layer. 敏-第二电 It is defined as the difference between the LUMO energy level of the sensitizer and the LUMO energy level of the second electron transport layer.

[0103] The device performance results of Examples 1-6, Examples 7-9 and Comparative Examples 20-27 are shown in Table 5.

[0104] Table 5

[0105]

[0106] From the device performance results of Examples 1-6 and Comparative Examples 20-22 and Comparative Example 26 in Comparative Table 5, it can be seen that when other materials in the structure of the organic electroluminescent device are the same, for the electron transport structure described in the present application, when the LUMO energy level difference between the second electron transport layer and the first electron transport layer and the LUMO energy level difference between the second electron transport layer and the main material or sensitizer material of the light-emitting layer are relatively small, the increase in the driving voltage during the aging process of the device is significantly smaller, and the driving voltage of the device decreases, thereby suppressing the problem of increased power consumption of the light-emitting device during the aging process, and obtaining an organic electroluminescent device with long life, high voltage stability and low driving voltage. From the electron mobility results measured in Examples 10-13, it can be seen that the electron mobility of the n-doped electron transport layer is significantly superior to that of the traditional nitrogen heterocyclic electron transport material, and the injection barrier for electrons injected from the cathode to the electron transport layer is small, thereby significantly reducing the driving voltage of the device. Therefore, by comparing the device performance results of Example 2 and Comparative Examples 24 and 25 in Table 5, it can be seen that the driving voltage of Example 2, which uses an n-doped electron transport layer to replace the traditional nitrogen heterocyclic electron transport material, is significantly lower than that of Comparative Examples 24 and 25.

[0107] The above experimental data show that the novel organic material of the present application is an organic light-emitting functional material with good performance as a light-emitting object of an organic electroluminescent device and is expected to be promoted for commercial application.

[0108] The above is only a preferred embodiment of the present invention. The present invention is not limited to the above implementation. As long as the technical effect of the present invention is achieved by the same means, it should belong to the protection scope of the present invention. Within the protection scope of the present invention, its technical scheme and / or implementation method can have various modifications and changes.

Claims

1. An organic electroluminescent device, characterized in that: From bottom to top, it includes an anode layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode layer; The light-emitting layer comprises a binary blend composition or a ternary blend composition, wherein the binary blend composition is a host material and a light-emitting guest material, and the ternary blend composition is a host material, a light-emitting guest material and a sensitizer; The electron transport layer includes a second electron transport layer and a first electron transport layer from bottom to top; the first electron transport layer is composed of an n-type dopant and a first electron transport material; the second electron transport layer is composed of a second electron transport material; the difference between the LUMO energy level of the second electron transport layer and the LUMO energy level of the first electron transport layer is less than or equal to 0.10 eV, and the difference between the LUMO energy level of the main material or the sensitizer and the LUMO energy level of the second electron transport layer is less than or equal to 0.15 eV.

2. The organic electroluminescent device according to claim 1, characterized in that: The HOMO energy level of the second electron transport material is at least 0.4 eV deeper than the HOMO energy level of the host material.

3. The organic electroluminescent device according to claim 1, characterized in that: The structure of the second electron transport material is shown in formula (1): Wherein, X and Y are independently selected from carbon or nitrogen atoms, and at least one of X and Y is a nitrogen atom; R1 and R2 are independently selected from weak electron-withdrawing groups, and the weak electron-withdrawing groups include benzocyano and its derivatives, fluorophenyl and its derivatives, benzothiophene and its derivatives, benzofuran and its derivatives, and fluorenyl and its derivatives.

4. The organic electroluminescent device according to claim 3, characterized in that: The structure of the second electron transport material is shown in formula (2), formula (3) or formula (4): Wherein, X and Y are independently selected from carbon or nitrogen atoms, and at least one of X and Y is a nitrogen atom; R2 and R3 are independently selected from weak electron-withdrawing groups, and the weak electron-withdrawing groups include benzocyano and its derivatives, fluorophenyl and its derivatives, benzothiophene and its derivatives, benzofuran and its derivatives, and fluorenyl and its derivatives.

5. The organic electroluminescent device according to claim 4, characterized in that: The structure of the second electron transport material is any one of Compounds 4-1 to 4-64:

6. The organic electroluminescent device according to claim 1, characterized in that: The n-type dopant is Li, Na, K, Rb, Cs, Yb, Ag, Mg, Zn, Au, Cs2CO3, Li2CO3; and / or, the doping concentration of the n-type dopant is 0.5 mass%-20 mass%; and / or, the structure of the first electron transport material is any one of compounds 5-1 to 5-44:

7. The organic electroluminescent device according to claim 1, characterized in that: The structure of the host material is any one of Compound 7-1 to Compound 7-76:

8. The organic electroluminescent device according to claim 1, characterized in that: The structure of the sensitizer is any one of Compound 6-1 to Compound 6-50:

9. A method for preparing an organic electroluminescent device according to any one of claims 1 to 8, characterized in that: The following steps are involved: The hole transport layer, the light emitting layer, the electron transport layer and the cathode layer are sequentially formed by vapor deposition on the anode layer.

10. An organic electroluminescent display device, characterized in that: An organic electroluminescent device comprising any one of claims 1 to 8.

Images