Cover layer material and method of preparation, organic electroluminescent device and display device

Abstract

The application relates to a benzocarbazole capping layer material and a preparation method, an organic electroluminescent device and a display device, and belongs to the technical field of organic luminescent materials. The structural general formula of the capping layer material is general formula 1: The organic EL element of the application uses an organic EL element material with high refractive index, good thin film stability and excellent durability as the material of the cap layer, so that the light extraction efficiency is greatly improved compared with the known organic EL element, and the technical effects of high efficiency and long service life are achieved.

Description

Technical Field

[0001] This invention relates to the field of organic light-emitting materials technology, specifically to benzocarbazole-based capping layer materials and their preparation methods, organic electroluminescent devices, and display devices. Background Technology

[0002] Organic light emission diodes (OLEDs) can be used to replace liquid crystal displays and fluorescent lighting in the manufacture of display devices and lighting products. Specifically, OLED devices can be widely used in smartphones, tablets, and televisions.

[0003] Existing OLED devices generally include an anode, a cathode, an organic layer between the anode and cathode, and a capping layer (CPL) outside the cathode; the organic layer includes functional structures such as an emissive layer. The capping layer improves light extraction efficiency, thereby enhancing the device's luminous efficiency. To date, many improvements have been made to facilitate the practical application of organic EL (electroluminescent) devices, with each function becoming more subdivided. On the substrate, the following functional layers are sequentially arranged: anode, hole injection layer, hole transport layer, emissive layer, electron transport layer, electron injection layer, and cathode. In organic electroluminescent devices, high efficiency and durability can be achieved through bottom-emitting structures.

[0004] As a coating layer to adjust the refractive index, aluminum trioxide (8-hydroxyquinoline) (hereinafter referred to as Alq3) is known to be used. Alq3 is often used as a green light-emitting material or an electron transport material, but it exhibits weak absorption around 450 nm, which is used in blue light-emitting elements. Therefore, in the case of blue light-emitting elements, there is a problem of reduced color purity and decreased light extraction efficiency.

[0005] Existing CPL materials have improved light extraction efficiency to some extent. However, the refractive index of existing CPL materials is generally below 1.9, which does not meet the requirements for high refractive index, and their luminous efficiency is relatively low. To improve the characteristics of organic EL devices, especially to significantly improve light extraction efficiency, it is necessary to develop a material with a high refractive index to improve light extraction efficiency and solve the luminous efficiency problem. Regarding capping layer materials, materials with high refractive index and excellent film stability or durability are needed. Summary of the Invention

[0006] The purpose of this invention is to provide a capping layer material and its preparation method, an organic electroluminescent device, and a display device to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A capping layer material, wherein the structural formula of the capping layer material is general formula 1:

[0009]

[0010] In the formula, X1, X2, and X3 may be the same or different from each other, and X1, X2, and X3 are selected from O or S respectively;

[0011] L1, L2, and L3 may be the same as or different from each other, and are independently any one of the following: a connecting bond, a substituted or unsubstituted C3-C60 cycloalkyl group, a substituted or unsubstituted 3-30 heterocycloalkyl group, a substituted or unsubstituted C6-C60 arylene group, or a substituted or unsubstituted 3-30 heteroarylene group, wherein the heteroatom is selected from oxygen, nitrogen, or sulfur.

[0012] As a further technical solution of the present invention, L1, L2, and L3 may be the same or different from each other, and are independently any one of the following: a connecting bond, a substituted or unsubstituted C6-C30 arylene, or a substituted or unsubstituted 3-15 member heteroarylene, wherein the heteroatom is selected from oxygen, nitrogen, or sulfur.

[0013] As a further technical solution of the present invention, L1, L2, and L3 may be the same as or different from each other, and are independently a connecting key or one of the following structural formulas:

[0014]

[0015] In this context, * represents a connection point.

[0016] As a further technical solution of the present invention, the sealing layer material is one of the following structural formulas CP1-CP30:

[0017]

[0018]

[0019] A method for preparing a capping layer material includes the following steps:

[0020] Preparation of intermediate 1: Under nitrogen protection, raw material A and raw material B were dissolved in DMF solution, cesium carbonate was added, the temperature was raised and the reaction was refluxed to prepare intermediate 1;

[0021] Preparation of intermediate 2: Under nitrogen protection, intermediate 1 and raw material C were dissolved in a mixed solution of toluene, ethanol and water, potassium carbonate and palladium catalyst were added, the mixture was stirred evenly, heated and refluxed to prepare intermediate 2.

[0022] Preparation of capping layer material: Under nitrogen protection, intermediate 2 and raw material D were dissolved in a mixed solution of toluene, ethanol and water in 280.00 ml. Cesium carbonate, palladium catalyst and phosphine ligand were added, stirred evenly, heated and refluxed to prepare the capping layer material.

[0023] The structural formulas of raw material A, raw material B, raw material C, raw material D, intermediate 1, and intermediate 2 are as follows:

[0024]

[0025] The specific preparation method is as follows:

[0026] Under nitrogen protection, starting materials A (20.00 mmol) and B (22.00 mmol) were dissolved in 280.00 ml of DMF solution, and cesium carbonate (40.00 mmol) was added. The mixture was heated to 150 °C and refluxed for 5 h. After the reaction was completed, the mixture was cooled to room temperature, and 300 ml of pure water was slowly added with stirring until the product was completely precipitated. The product was then filtered. The filter cake was recrystallized from toluene to give intermediate 1 (6.09 g, yield: 85.64%).

[0027] Under nitrogen protection, intermediate 1 (17.10 mmol) and starting material C (17.10 mmol) were dissolved in 280.00 ml of a mixed solution of toluene, ethanol, and water. Potassium carbonate (34.20 mmol) and tetraphenylphosphine palladium (0.34 mmol) were added, and the mixture was stirred until homogeneous. The mixture was heated to 80 °C and refluxed for 6 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered through diatomaceous earth to remove salts and catalysts. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator to obtain a solid organic compound. The solid organic compound was completely dissolved in a small amount of dichloromethane and then slowly added dropwise to a petroleum ether solution. After stirring until homogeneous, a precipitate formed. The precipitate was filtered to obtain a solid, which was washed successively with anhydrous ethanol and petroleum ether, and dried to obtain intermediate 2 (5.95 g, yield: 81.32%).

[0028] Under nitrogen protection, intermediate 2 (13.89 mmol) and starting material D (27.78 mmol) were dissolved in 280.00 ml of a mixed solution of toluene, ethanol and water. Cesium carbonate (55.56 mmol), palladium acetate (1.38 mmol), and X-Phos (1.38 mmol) were added and stirred until homogeneous. The mixture was heated to 100 °C and refluxed for 10 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered with diatomaceous earth to remove salts and catalysts. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with ethyl acetate. The organic phases were combined and dried with anhydrous magnesium sulfate. The solvent was removed using a rotary evaporator. The remaining substances were purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:12) to obtain the compound, which is the capping material.

[0029] An organic electroluminescent device includes an anode, a cathode, and at least one organic layer disposed between the anode and the cathode, wherein a capping layer is provided on the side of the cathode away from the organic layer; the capping layer comprises the capping layer material as described above.

[0030] A display device includes a substrate and an organic electroluminescent device as described above disposed on the substrate.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. The organic EL element of the present invention uses an organic EL element material with high refractive index, good film stability and excellent durability as the material of the capping layer. Therefore, compared with known organic EL elements, the light extraction efficiency is greatly improved, thereby achieving a high-efficiency and long-life organic EL element.

[0033] 2. The organic compound of the present invention has a structure based on carbazole as the parent nucleus, and introduces rigid groups such as benzofuran, benzothiophene and their derivatives to improve structural stability. In addition, in terms of spatial structure, the three substituent groups introduced into the parent carbazole nucleus tend to be coplanar with the parent nucleus, thereby increasing density and improving refractive index. At the same time, the compound of the present invention has a high Tg, generally above 130°C, and a low vapor deposition temperature, generally less than 240°C under vacuum. This ensures that the organic compound of the present invention does not decompose during long-term vapor deposition of the material during mass production, and also reduces the influence of thermal radiation from the vapor deposition temperature on the deformation of the vapor-deposited mask. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0035] Figure 1 The image shows the 1H NMR spectrum of the capping material prepared in Example 1.

[0036] Figure 2 The image shows the 1H NMR spectrum of the capping material prepared in Example 2.

[0037] Figure 3 This is a comparison chart of refractive index n values.

[0038] Figure 4 This is a comparison chart of extinction coefficient k values. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] A method for preparing a capping layer material, the synthesis route of which is as follows:

[0042]

[0043] The specific preparation method is as follows:

[0044] Under nitrogen protection, starting materials A-1 (CAS No.: 6825-20-3; 20.00 mmol) and B-1 (CAS No.: 352-33-0; 22.00 mmol) were dissolved in 280.00 ml of DMF solution, and cesium carbonate (CAS No.: 534-17-8; 40.00 mmol) was added. The mixture was heated to 150 °C and refluxed for 5 h. After the reaction was completed, the mixture was cooled to room temperature, and 300 ml of pure water was slowly added with stirring until the product was completely precipitated. The mixture was then filtered. The filter cake was recrystallized from toluene to give intermediate 1 (6.09 g, yield: 85.64%).

[0045] Under nitrogen protection, intermediate 1 (17.10 mmol) and starting material C-1 (CAS No.: 1357926-66-9; 17.10 mmol) were dissolved in 280.00 ml of a mixed solution of toluene, ethanol and water. Potassium carbonate (CAS No.: 584-08-7; 34.20 mmol) and tetraphenylphosphine palladium (CAS No.: 14221-01-3; 0.34 mmol) were added, stirred until homogeneous, heated to 80 °C, and refluxed for 6 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered with diatomaceous earth to remove salts and catalysts. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator to obtain a solid organic compound. The solid organic matter was completely dissolved in a small amount of dichloromethane and then slowly added dropwise to a petroleum ether solution. After stirring until homogeneous, a precipitate formed. The solid was obtained by filtration and washed successively with anhydrous ethanol and petroleum ether, and then dried to obtain intermediate 2 (5.95 g, yield: 81.32%).

[0046] Under nitrogen protection, intermediate 2 (13.89 mmol) and starting material D-1 (CAS No.: 98437-24-2; 27.78 mmol) were dissolved in 280.00 ml of a mixed solution of toluene, ethanol, and water. Cesium carbonate (CAS No.: 534-17-8; 55.56 mmol), palladium acetate (CAS No.: 3375-31-3; 1.38 mmol), and X-Phos (CAS No.: 564483-18-7; 1.38 mmol) were added and stirred until homogeneous. The mixture was then heated to 100 °C and refluxed. The reaction was carried out for 10 hours. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered with diatomaceous earth to remove salts and catalysts. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The remaining substance was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:12) to obtain compound CP1 (8.62 g, yield: 83.50%, Mw: 743.86; please refer to the 1H NMR spectrum). Figure 1 ).

[0047] The obtained compound CP1 was analyzed, and the results are as follows:

[0048] HPLC purity: >99.6%;

[0049] Mass spectrometry test: theoretical value 743.86; test value 743.69;

[0050] Elemental analysis:

[0051] The calculated values ​​are: C, 87.19; H, 4.47; N, 1.88; O, 6.45.

[0052] The test values ​​were: C, 86.88; H, 4.76; N, 1.96; O, 6.47.

[0053] Example 2

[0054] A method for preparing a capping layer material, the synthesis route of which is as follows:

[0055]

[0056] The specific preparation method is as follows:

[0057] Under nitrogen protection, starting materials A-17 (CAS No.: 6825-20-3; 20.00 mmol) and B-17 (CAS No.: 352-33-0; 22.00 mmol) were dissolved in 280.00 ml of DMF solution, and cesium carbonate (CAS No.: 534-17-8; 40.00 mmol) was added. The mixture was heated to 150 °C and refluxed for 5 h. After the reaction was completed, the mixture was cooled to room temperature, and 300 ml of pure water was slowly added with stirring until the product was completely precipitated. The mixture was then filtered. The filter cake was recrystallized from toluene to give intermediate 1 (6.16 g, yield: 86.59%).

[0058] Under nitrogen protection, intermediate 1 (17.30 mmol) and starting material C-17 (CAS No.: 98437-24-2; 17.30 mmol) were dissolved in 280.00 ml of a mixed solution of toluene, ethanol and water. Potassium carbonate (CAS No.: 584-08-7; 34.60 mmol) and tetraphenylphosphine palladium (CAS No.: 14221-01-3; 0.34 mmol) were added, stirred until homogeneous, heated to 80 °C, and refluxed for 6 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered with diatomaceous earth to remove salts and catalysts. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator to obtain a solid organic compound. The solid organic matter was completely dissolved in a small amount of dichloromethane and then slowly added dropwise to a petroleum ether solution. After stirring until homogeneous, a precipitate formed. The solid was filtered off and washed successively with anhydrous ethanol and petroleum ether, and then dried to obtain intermediate 2 (6.26 g, yield: 84.60%).

[0059] Under nitrogen protection, intermediate 2 (14.61 mmol) and starting material D-17 (CAS No.: 98437-24-2; 29.22 mmol) were dissolved in 280.00 ml of a mixed solution of toluene, ethanol, and water. Cesium carbonate (CAS No.: 534-17-8; 58.44 mmol), palladium acetate (CAS No.: 3375-31-3; 1.46 mmol), and X-Phos (CAS No.: 564483-18-7; 1.46 mmol) were added and stirred until homogeneous. The mixture was then heated to 100 °C and refluxed. The reaction was carried out for 10 hours. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered with diatomaceous earth to remove salts and catalysts. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The remaining substance was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:12) to obtain compound CP17 (7.12 g, yield: 82.50%, Mw: 591.67; please refer to the 1H NMR spectrum). Figure 2 ).

[0060] The obtained compound CP17 was analyzed, and the results are as follows:

[0061] HPLC purity: >99.5%;

[0062] Mass spectrometry test: theoretical value 591.67; test value 591.35;

[0063] Elemental analysis:

[0064] The calculated values ​​are: C, 85.26; H, 4.26; N, 2.37; O, 8.11.

[0065] The test values ​​were: C, 84.87; H, 4.57; N, 2.49; O, 8.23.

[0066] Example 3

[0067] A method for preparing a capping layer material, the synthesis route of which is as follows:

[0068]

[0069] The specific preparation method is as follows:

[0070] Under nitrogen protection, starting materials A-20 (CAS No.: 6825-20-3; 20.00 mmol) and B-20 (CAS No.: 352-33-0; 22.00 mmol) were dissolved in 280.00 ml of DMF solution, and cesium carbonate (CAS No.: 534-17-8; 40.00 mmol) was added. The mixture was heated to 150 °C and refluxed for 5 h. After the reaction was completed, the mixture was cooled to room temperature, and 300 ml of pure water was slowly added with stirring until the product was completely precipitated. The mixture was then filtered. The filter cake was recrystallized from toluene to give intermediate 1 (6.06 g, yield: 85.13%).

[0071] Under nitrogen protection, intermediate 1 (17.02 mmol) and starting material C-20 (CAS No.: 98437-23-1; 17.02 mmol) were dissolved in 280.00 ml of a mixed solution of toluene, ethanol and water. Potassium carbonate (CAS No.: 584-08-7; 34.04 mmol) and tetraphenylphosphine palladium (CAS No.: 14221-01-3; 0.34 mmol) were added, stirred until homogeneous, heated to 80 °C, and refluxed for 6 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered with diatomaceous earth to remove salts and catalysts. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator to obtain a solid organic compound. The solid organic matter was completely dissolved in a small amount of dichloromethane and then slowly added dropwise to a petroleum ether solution. After stirring until homogeneous, a precipitate formed. The solid was obtained by filtration and washed successively with anhydrous ethanol and petroleum ether, and then dried to obtain intermediate 2 (6.50 g, yield: 86.05%).

[0072] Under nitrogen protection, intermediate 2 (14.62 mmol) and starting material D-20 (CAS No.: 98437-23-1; 29.24 mmol) were dissolved in 280.00 ml of a mixed solution of toluene, ethanol, and water. Cesium carbonate (CAS No.: 534-17-8; 58.48 mmol), palladium acetate (CAS No.: 3375-31-3; 1.46 mmol), and X-Phos (CAS No.: 564483-18-7; 1.46 mmol) were added and stirred until homogeneous. The mixture was then heated to 1... The reaction was refluxed at 00℃ for 10 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered with diatomaceous earth to remove salts and catalysts. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The remaining substance was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:12) to obtain compound CP20 (7.71 g, yield: 82.50%, Mw: 639.85).

[0073] The obtained compound CP20 was analyzed, and the results are as follows:

[0074] HPLC purity: >99.5%;

[0075] Mass spectrometry test: theoretical value 639.85; test value 639.57;

[0076] Elemental analysis:

[0077] The calculated values ​​are: C, 78.84; H, 3.94; N, 2.19; S, 8.11.

[0078] The test values ​​are: C, 78.59; H, 4.21; N, 2.34; S, 8.17.

[0079] Since the synthetic routes and principles for preparing other carbazole compounds with the general formula 1 in the invention are the same as those in Examples 1-3 listed above, it is only necessary to replace the reactants with the reactants corresponding to the target product and adjust the amount of reactants according to the corresponding stoichiometric ratio to obtain the corresponding carbazole compounds. Therefore, they will not be listed exhaustively here. The embodiments of the present invention refer to the preparation methods of Examples 1-3 to complete the synthesis of carbazole compounds with the general formula 1 in the invention. Their mass spectra, molecular formulas and yields are shown in Table 1 below.

[0080] Table 1

[0081]

[0082]

[0083] In addition, a 50 nm thick vapor-deposited film was fabricated on a substrate using the carbazole compounds provided in the embodiments of the present invention. The refractive index n and extinction coefficient k at 460 nm, 530 nm, and 620 nm were measured using a spectrophotometer. For comparison, measurements were performed on comparative compounds 1-1 and 1-2 as shown in the figure below. The test results are shown in Table 2. Figure 3 , Figure 4 .

[0084]

[0085] Table 2

[0086]

[0087] From Table 2 and Figure 3 , Figure 4It can be seen that for visible light with wavelengths of 460-620nm, the refractive indices of the carbazole compounds provided in the embodiments of the present invention are all greater than 2.0, and are all higher than the refractive indices of comparative compounds 1-1 and 1-2; they meet the refractive index requirements of the capping layer for light-emitting devices, and the extinction coefficient k value is almost 0 after the blue light wavelength of 430nm, which will not affect the light emission of the light-emitting layer material in the blue light region; therefore, the carbazole compounds provided in the embodiments of the present invention can bring higher luminous efficiency; in addition, it can be found in Table 2 that the glass transition temperatures of the compounds are all higher than 130℃, which indicates that the thin film is stable in the compounds of the present invention.

[0088] Application Example 1 (Red Light Device)

[0089] An organic electroluminescent device has the following structure: ITO anode / HIL / HTL / EML / ETL / EIL / cathode / light extraction layer. Its fabrication method includes the following steps:

[0090] a. ITO Anode: An ITO (Indium Tin Oxide)-Ag-ITO (Indium Tin Oxide) glass substrate with a coating thickness of 150nm is cleaned twice with distilled water, ultrasonically cleaned for 30 minutes, then repeatedly cleaned twice with distilled water, ultrasonically cleaned for 10 minutes. After cleaning, it is transferred to a spin dryer for spin drying, and finally baked in a vacuum oven at 220℃ for 2 hours. After baking, it is cooled before use. Using this substrate as the anode, a vapor deposition process is performed on it, and other functional layers are sequentially vapor deposited on it.

[0091] b. HIL (Hole Injection Layer): The evaporation rate of the vacuum evaporation hole injection layer material HT-1 and P-dopant is as follows, and the evaporation rate ratio of HT-1 and P-dopant is 97:3, with a thickness of 10nm.

[0092] c. HTL (Hole Transport Layer): At the evaporation rate, HT-1 of 130 nm was vacuum-deposited on the hole injection layer as a hole transport layer.

[0093] d. Light-emitting auxiliary layer: with At a certain evaporation rate, 95nm EB-1 was vacuum-deposited on the hole transport layer as a light-emitting auxiliary layer.

[0094] e. EML (Emitting Layer): Then, on the above-mentioned emitting auxiliary layer, with... The evaporation rate is such that a host material and a dopant material with a thickness of 40 nm are vacuum-evaporated as the light-emitting layer. The chemical formulas of the host and the dopant are shown below, and the evaporation rate ratio of the host to the dopant is 97:3.

[0095] f. HBL (Hole Blocking Layer): The evaporation rate was such that HB-1 with a thickness of 5.0 nm was vacuum-deposited as a hole-blocking layer.

[0096] g. ETL (Electron Transport Layer): The evaporation rate was determined, and ET-1 and Liq with a thickness of 35 nm were vacuum-deposited as electron transport layers, with the evaporation rate ratio of ET-1 to Liq being 50:50.

[0097] h, EIL (Electron Injection Layer): with The evaporation rate was such that a Yb film layer of 1.0 nm was deposited to form an electron injection layer;

[0098] i. Cathode: with The evaporation rate ratio of magnesium and silver at 18nm was 1:9, resulting in an OLED device.

[0099] j. Optical extraction layer: with The above-described embodiment provides compound 1 with a thickness of 70 nm is vacuum-deposited on the cathode at a high evaporation rate as a light extraction layer.

[0100] k. Subsequently, the vapor-deposited substrate is encapsulated. First, the cleaned cover plate is coated with UV adhesive using an adhesive coating equipment. Then, the coated cover plate is moved to the lamination section, and the vapor-deposited substrate is placed on the top of the cover plate. Finally, the substrate and cover plate are laminated under the action of the lamination equipment, while the UV adhesive is cured by light.

[0101] The chemical structural formulas of the corresponding compounds used in the above applications are shown below:

[0102]

[0103] Application Example 2-6

[0104] Following the method of Application Example 1, the cathode capping layer material was replaced with compounds CP3, CP10, CP15, CP17, and CP20, respectively, to fabricate organic electroluminescent devices, which are referred to as Application Examples 2-6.

[0105] Comparative Examples 1-2

[0106] Organic electroluminescent devices, Comparative Examples 1 and 2, were prepared according to the method of Application Example 1, except that the CPL layer material compound was replaced with comparative compound a and comparative compound b, while other light-emitting layer materials remained the same; the structural formulas of comparative compound a and comparative compound b are shown below:

[0107]

[0108] The driving voltage, luminous efficiency, and lifetime of the organic electroluminescent devices obtained in Application Examples 1-6 and Comparative Examples 1-2 were characterized at a brightness of 6000 nits. The test results are shown in Table 3 below.

[0109] Table 3

[0110]

[0111] Application Example 7 (Green Light Device)

[0112] An organic electroluminescent device has the following structure: ITO anode / HIL / HTL / EML / ETL / EIL / cathode / light extraction layer. Its fabrication method includes the following steps:

[0113] a. ITO anode: An ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate with a coating thickness of 150nm is cleaned twice in distilled water, ultrasonically washed for 30 minutes, then repeatedly cleaned twice in distilled water, ultrasonically washed for 10 minutes. After washing, it is transferred to a spin dryer for spin drying, and finally baked in a vacuum oven at 220℃ for 2 hours. After baking, it is cooled down before use. Using this substrate as the anode, the device process is carried out by vapor deposition, and other functional layers are sequentially vapor deposited on it.

[0114] b. HIL (Hole Injection Layer): The evaporation rate of the vacuum evaporation hole injection layer material HT-1 and P-dopant is as follows; the evaporation rate ratio of HT-1 and P-dopant is 97:3, and the thickness is 10nm.

[0115] c. HTL (Hole Transport Layer): At the evaporation rate, HT-1 of 130 nm was vacuum-deposited on the hole injection layer as a hole transport layer.

[0116] d. Light-emitting auxiliary layer: At a certain evaporation rate, 45 nm EB-2 was vacuum-deposited on the hole transport layer as a light-emitting auxiliary layer.

[0117] e. EML (Emitting Layer): Then, on the above-mentioned emitting auxiliary layer, with... The evaporation rate was determined by vacuum evaporation of a host material (Host1 and Host2) and a dopant material (Dopant) with a thickness of 40 nm as the light-emitting layer. The chemical formulas of the Host and Dopant are shown below. The evaporation rate ratio of Host1, Host2, and Dopant is 47:47:6.

[0118] f. HBL (Hole Blocking Layer): with The evaporation rate was such that HB-1 with a thickness of 5.0 nm was vacuum-deposited as a hole-blocking layer.

[0119] g. ETL (Electron Transport Layer): The evaporation rate was determined, and ET-1 and Liq layers with a thickness of 35 nm were vacuum-deposited as electron transport layers. The evaporation rate ratio of ET-2 to Liq was 50:50.

[0120] h, EIL (Electron Injection Layer): with The evaporation rate was such that a Yb film layer of 1.0 nm was deposited to form an electron injection layer;

[0121] i. Cathode: with The evaporation rate ratio of magnesium and silver at 18nm was 1:9, resulting in an OLED device.

[0122] j. Optical extraction layer: with The above-described embodiment provides compound 1 with a thickness of 70 nm is vacuum-deposited on the cathode at a high evaporation rate as a light extraction layer.

[0123] k. Subsequently, the vapor-deposited substrate is encapsulated. First, the cleaned cover plate is coated with UV adhesive using an adhesive coating equipment. Then, the coated cover plate is moved to the lamination section, and the vapor-deposited substrate is placed on the top of the cover plate. Finally, the substrate and cover plate are laminated under the action of the lamination equipment, while the UV adhesive is cured by light.

[0124] The chemical structural formulas of the corresponding compounds used in the above applications are shown below:

[0125]

[0126] Application Example 8-12

[0127] Following the method of Application Example 7, the cathode capping layer material was replaced with compounds CP3, CP10, CP15, CP17, and CP20, respectively, to fabricate organic electroluminescent devices, which are referred to as Application Examples 8-12.

[0128] Comparative Examples 3-4

[0129] Organic electroluminescent devices were prepared according to the method of Application Example 7 in Comparative Examples 3 and 4, except that the CPL layer material compound was replaced with Comparative Compound a and Comparative Compound b, while other aspects such as the light-emitting layer material remained the same. Organic electroluminescent devices prepared with Comparative Compound a and Comparative Compound b are designated as Comparative Example 3 and Comparative Example 4, respectively. The structural formulas of Comparative Compound a and Comparative Compound b are shown below:

[0130]

[0131] The driving voltage, luminous efficiency, and lifetime of the organic electroluminescent devices obtained in Application Examples 7-12 and Comparative Examples 3-4 were characterized at a brightness of 15000 nits. The test results are shown in Table 4 below.

[0132] Table 4

[0133]

[0134]

[0135] Application Example 13 (Blue Light Device)

[0136] An organic electroluminescent device has the following structure: ITO anode / HIL / HTL / EML / ETL / EIL / cathode / light extraction layer. Its fabrication method includes the following steps:

[0137] a. ITO anode: An ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate with a coating thickness of 150nm is cleaned twice in distilled water, ultrasonically washed for 30 minutes, then repeatedly cleaned twice in distilled water, ultrasonically washed for 10 minutes. After washing, it is transferred to a spin dryer for spin drying, and finally baked in a vacuum oven at 220℃ for 2 hours. After baking, it is cooled down before use. Using this substrate as the anode, the device process is carried out by vapor deposition, and other functional layers are sequentially vapor deposited on it.

[0138] b. HIL (Hole Injection Layer): The evaporation rate was determined by vacuum evaporation of hole-injection layer materials HT-1 and P-dopant. The evaporation rate ratio of HT-1 to P-dopant was 97:3, and the thickness was 10 nm.

[0139] c. HTL (Hole Transport Layer): At the evaporation rate, HT-1 of 130 nm was vacuum-deposited on the hole injection layer as a hole transport layer.

[0140] d. Light-emitting auxiliary layer: At a high evaporation rate, 5 nm of EB-3 was vacuum-deposited on the hole transport layer as a light-emitting auxiliary layer.

[0141] e. EML (Emitting Layer): Then, on the above-mentioned emitting auxiliary layer, with... The evaporation rate was set at a certain value, and a host material and a dopant material with a thickness of 20 nm were vacuum-deposited as the light-emitting layer. The evaporation rate ratio of the host to the dopant was 98:2.

[0142] f. ETL (Electron Transport Layer): The evaporation rate was determined, and ET-3 and Liq with a thickness of 35 nm were vacuum-deposited as electron transport layers. The chemical formula of ET-3 is shown below. The evaporation rate ratio of ET-3 to Liq is 50:50.

[0143] g. EIL (Electron Injection Layer): with The evaporation rate was such that a Yb film layer of 1.0 nm was deposited to form an electron injection layer;

[0144] h, Cathode: with The evaporation rate ratio of magnesium and silver at 18nm was 1:9, resulting in an OLED device.

[0145] i. Optical extraction layer: with The above-described embodiment provides compound 1 with a thickness of 70 nm is vacuum-deposited on the cathode at a high evaporation rate as a light extraction layer.

[0146] j. Subsequently, the vapor-deposited substrate is encapsulated. First, the cleaned cover plate is coated with UV adhesive using an adhesive coating equipment. Then, the coated cover plate is moved to the lamination section, and the vapor-deposited substrate is placed on the top of the cover plate. Finally, the substrate and cover plate are laminated under the action of the lamination equipment, while the UV adhesive is cured by light.

[0147] The chemical structural formulas of the corresponding compounds used in the above applications are shown below:

[0148]

[0149] Application Example 14-18

[0150] Following the method of Application Example 13, the cathode capping layer material was replaced with CP3, CP10, CP15, CP17, and CP20 respectively to fabricate organic electroluminescent devices, which are referred to as Application Examples 14-18 respectively.

[0151] Comparative Examples 5-6

[0152] Organic electroluminescent devices were prepared according to the method of Application Example 13, specifically in Comparative Examples 5 and 6, except that the CPL layer material compound was replaced with comparative compounds a and b, while other aspects, such as the light-emitting layer material, remained the same. The organic electroluminescent devices fabricated were designated as Comparative Examples 5 and 6, respectively. The structural formulas of comparative compounds a and b are shown below:

[0153]

[0154] The driving voltage, luminous efficiency, and lifetime of the organic electroluminescent devices obtained in Application Examples 13-18 and Comparative Examples 5-6 were characterized at a brightness of 1000 nits. The test results are shown in Table 5 below.

[0155] Table 5

[0156]

[0157] As can be seen from Tables 3-5 above, when red, green, and blue light devices were prepared using the compounds of the present invention, compared with Comparative Examples 1-6, the luminous efficiency of the devices using the compounds of the present invention as CPL materials was significantly improved. This indicates that by containing compounds with high refractive index in the capping layer, the light extraction efficiency can be greatly improved. Due to their high absorption coefficient and high refractive index, the compounds of the present invention can significantly improve the light extraction efficiency and have a stable thin film state, making them excellent compounds for organic EL devices. Organic EL devices prepared using these compounds can improve the luminous efficiency of the devices and are ideal CPL materials.

[0158] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0159] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A capping layer material, characterized in that, The structural formula of the capping layer material is Formula 1: ； The general formula 1 is one of the following structural formulas: ; 。 2. An organic electroluminescent device, comprising an anode, a cathode, and at least one organic layer disposed between the anode and the cathode, characterized in that, The cathode is provided with a capping layer on the side away from the organic layer; the capping layer comprises the capping layer material as described in claim 1.

3. A display device, comprising a substrate, characterized in that, It also includes the organic electroluminescent device as described in claim 2 disposed on the substrate.

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