High-performance covering layer material and organic electroluminescent device

Abstract

The invention provides a high-performance covering layer material and an organic electroluminescent device. The covering layer material comprises a compound as shown in a formula (I) or a formula (II). When the compound provided by the invention is used as a covering layer material, the refractive index is high; the material has relatively large absorption under 400nm, and harmful blue light can be reduced; meanwhile, good stability is achieved, so that the covering layer material cannot be subjected to high-temperature decomposition in the long-time evaporation process; when the organic light emitting diode is applied to OLED devices, color cast is small, and efficiency is high. # imgabs0 #

Description

Technical Field

[0001] This application relates to the technical field of organic light-emitting devices, and particularly to a high-performance capping layer material and an organic electroluminescent device. Background Art

[0002] Display screens are constantly evolving towards high pixels, large color gamuts, and low power consumption. The obvious advantages of OLED (organic electroluminescent diode) flexible display screens compared to TFT-LCD (thin film transistor liquid crystal display) make flexible screens the trend of display screen development. The foldable and bendable properties of flexible screens are particularly favored by electronic device enthusiasts.

[0003] Currently used OLED devices mostly adopt a top-emitting device structure, using a reflective anode and a transparent cathode to enhance the light extraction efficiency through the microcavity effect. Blue light devices are still the focus of development. Due to the high energy of blue light, the lifespan needs to be improved, and at the same time, a lower voltage needs to be maintained to reduce power consumption. Introducing a capping layer (CPL) in the top-emitting device, through a higher refractive index, a combination of high and low refractive indices is formed above the cathode, thereby achieving a better light extraction effect and improving efficiency. However, the refractive index of existing CPL materials is not high enough, and the improvement in device efficiency is very small; the absorption intensity is small, and it cannot effectively absorb the harmful blue light of OLED devices, which is not conducive to protecting eyes from blue light; and the CPL material will decompose during long-term evaporation at high temperatures, easily causing the material to lose its original properties. Therefore, new CPL materials still need to be developed. Summary of the Invention

[0004] The purpose of this application is to provide a high-performance capping layer material and an organic electroluminescent device to increase the refractive index of the CPL material; have a large absorption at 400 nm, capable of reducing harmful blue light; and at the same time have good stability, so that the CPL material will not undergo high-temperature decomposition during long-term evaporation; when applied to OLED devices, the color deviation is small. The specific technical solutions are as follows:

[0005] The first aspect of this application provides a compound represented by formula (I) or formula (II):

[0006]

[0007] Wherein,

[0008] Ar 1 is selected from

[0009] Ar 2 is selected from

[0010] L is selected from a single bond or a phenylene group;

[0011] L1 and L 2 each independently selected from a single bond, C 6 -C 20 arylene or C 5 -C 20 heteroarylene;

[0012] X is selected from C 1 -C 6 alkyl, O or S;

[0013] Y 1 and Y 2 and Y 3 and Y 4 each independently selected from O or S;

[0014] Z is selected from CH or N;

[0015] The heteroatoms in the heteroarylene are selected from N, O or S.

[0016] In some embodiments of the present application, all hydrogens on the compound represented by formula (I) or the compound represented by formula (II) are optionally replaced by deuterium.

[0017] In some embodiments of the present application, in the compound represented by formula (I) or the compound represented by formula (II), L 1 and L 2 each independently selected from a single bond or C 6 -C 12 arylene.

[0018] In some embodiments of the present application, in the compound represented by formula (I) or the compound represented by formula (II), L 1 and L 2 each independently selected from a single bond or phenylene.

[0019] In some embodiments of the present application, in the compound represented by formula (I) or the compound represented by formula (II), X is selected from C 2 -C 3 alkyl, O or S; preferably, X is selected from -C(CH 3 ) 2 -, O or S.

[0020] In some embodiments of the present application, in the compound represented by formula (I) or the compound represented by formula (II), Ar 1 is selected from Ar 2 is selected from

[0021] In some embodiments of the present application, the compound represented by formula (I) or the compound represented by formula (II) is selected from the compounds represented by A1 - A62 as follows:

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029] The second aspect of the present application provides a cover layer material, which comprises at least one of the compounds described in the first aspect of the present application.

[0030] The third aspect of the present application provides an organic electroluminescent device, which comprises at least one of the compounds described in the first aspect of the present application or the cover layer material described in the second aspect of the present application.

[0031] The fourth aspect of the present application provides a display device, which comprises at least one of the compounds described in the first aspect of the present application, the cover layer material described in the second aspect of the present application, or the organic electroluminescent device described in the third aspect of the present application.

[0032] Advantages of the present application: When the compound provided by the present application is used as a cover layer material, it has a high refractive index; has a large absorption at 400 nm, which can reduce harmful blue light; and has good stability, so that the cover layer material will not undergo high-temperature decomposition during a long-term evaporation process; when it is applied to an OLED device, it has a small color deviation and high efficiency.

[0033] Of course, it is not necessary for any product or method implementing the present application to achieve all the above advantages simultaneously. Detailed Embodiments

[0034] Next, the technical solutions in the present application will be clearly and completely described in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0035] The first aspect of the present application provides a compound represented by formula (I) or formula (II):

[0036]

[0037] Among them,

[0038] Ar 1 is selected from

[0039] Ar 2 is selected from

[0040] L is selected from a single bond or a phenylene group;

[0041] L 1 and L 2 are each independently selected from a single bond, C 6 -C 20 arylene or C 5 -C 20 heteroarylene;

[0042] X is selected from C 1 -C 6 alkyl, O or S;

[0043] Y 1 and Y 2 and Y 3 and Y 4 are each independently selected from O or S;

[0044] Z is selected from CH or N;

[0045] The heteroatoms in the heteroarylene are selected from N, O or S.

[0046] The C 6 -C 20 arylene described in this application includes fused arylene; C 5 -C 20 heteroarylene includes fused heteroarylene.

[0047] In some embodiments of this application, all hydrogens on the compound represented by formula (I) or the compound represented by formula (II) are optionally replaced by deuterium.

[0048] In some embodiments of this application, in the compound represented by formula (I) or the compound represented by formula (II), L 1 and L 2 are each independently selected from a single bond or C 6 -C 12 arylene.

[0049] In some embodiments of this application, in the compound represented by formula (I) or the compound represented by formula (II), L 1 and L 2Each independently selected from a single bond or a phenylene group.

[0050] In some embodiments of the present application, in the compound represented by formula (I) or the compound represented by formula (II), X is selected from C 2 -C 3 alkyl, O or S; preferably, X is selected from -C(CH 3 ) 2 -, O or S.

[0051] In some embodiments of the present application, in the compound represented by formula (I) or the compound represented by formula (II), Ar 1 is selected from Ar 2 is selected from

[0052] In some embodiments of the present application, the compound represented by formula (I) or the compound represented by formula (II) is selected from the compounds shown as A1 - A62 below:

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060] When the compound provided by the present application is used as a cover layer material, it has a high refractive index; has a large absorption at 400 nm, can reduce harmful blue light; and at the same time has good stability, so that the cover layer material will not undergo thermal decomposition during a long - term evaporation process.

[0061] The second aspect of the present application provides a cover layer material, which comprises at least one of the compounds described in the first aspect of the present application.

[0062] The cover layer material is above the cathode, and its main function is to improve the light - emitting efficiency of the entire OLED device. Therefore, the refractive index is a very important parameter. Using at least one of the compounds described in the first aspect of the present application as the cover layer material has a high refractive index and high thermal stability, and thus an OLED device with a small color deviation and high efficiency can be obtained.

[0063] The third aspect of the present application provides an organic electroluminescent device, which comprises at least one of the compounds described in the first aspect of the present application or the covering layer material described in the second aspect of the present application.

[0064] By using at least one of the compounds described in the first aspect of the present application as the covering layer material, the obtained covering layer has a high refractive index and high thermal stability, and thus an OLED device with small color deviation and high efficiency is obtained.

[0065] In the present application, there is no particular limitation on the type and structure of the organic electroluminescent device, and it can be various types and structures of organic electroluminescent devices known in the art, as long as at least one of the covering layer materials provided by the present application can be used.

[0066] The organic electroluminescent device of the present application can be a top-emitting structure light-emitting device. For example, it sequentially includes a first electrode (anode), a hole injection layer (HIL), a hole transport layer (HTL), a light-emitting layer (EML), an electron transport layer (ETL), an electron injection layer (EIL), a second electrode (cathode), and a covering layer (CPL) on a substrate.

[0067] The organic electroluminescent device of the present application can also be a double-sided emitting structure light-emitting device. For example, it sequentially includes a first electrode (anode), a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a second electrode (cathode), and a covering layer on a substrate.

[0068] In addition, an electron blocking layer (EBL) can be provided between the hole transport layer and the light-emitting layer, and a hole blocking layer (HBL) can be provided between the light-emitting layer and the electron transport layer. However, the structure of the organic electroluminescent device of the present application is not limited to the above specific structures, and if necessary, the above-mentioned layers can be omitted or added.

[0069] The present application has no particular limitation on the thickness of the above-mentioned layers, as long as the object of the present application can be achieved. For example, the organic electroluminescent device can sequentially include a first electrode (anode) (50 nm to 100 nm) made of metal or metal oxide, a hole injection layer (5 nm to 40 nm), a hole transport layer (30 nm to 130 nm), an electron blocking layer (5 nm to 80 nm), a light-emitting layer (15 nm to 80 nm), a hole blocking layer (5 nm to 20 nm), an electron transport layer (5 nm to 60 nm), an electron injection layer (0.5 nm to 3 nm), a second electrode (cathode) (10 nm to 200 nm), and a covering layer (50 nm to 80 nm) on a substrate.

[0070] In the organic electroluminescent device of the present application, except that the covering layer contains the covering material provided by the present application, other layers can all use various materials for the layers in the prior art.

[0071] In this application, the material of the substrate is not particularly limited, and conventional substrates known in the art can be selected. For example, glass, polymer materials, and glass and polymer materials with thin-film transistor (TFT) components, etc.

[0072] In this application, the material of the first electrode (anode electrode) is not particularly limited, and transparent conductive materials known in the art such as indium tin oxide (ITO), indium zinc oxide (IZO), tin dioxide (SnO 2 ), zinc oxide (ZnO), low-temperature polycrystalline silicon (LTPS), etc. can be selected. Metal materials such as silver and its alloys, aluminum and its alloys, etc. can also be selected. Organic conductive materials such as poly(3,4-ethylenedioxythiophene) (PEDOT), etc. can also be selected, or a multi-layer structure of the above materials, etc.

[0073] In this application, the material of the hole injection layer is not particularly limited, and hole injection materials well-known in the art can be used. For example, hole injection materials well-known in the art: 1,4,5,8,9,11-hexaazatriphenylenehexanitrile (HATCN), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN), 4-bromo-4-phenyldiphenylamine (BPBPA), molybdenum trioxide (MoO 3 ) and at least one of the like can be used as the hole injection material.

[0074] In this application, the material of the hole transport layer is not particularly limited, and hole transport materials known in the art can be selected. For example, the hole transport material can be selected from at least one of 4-bromo-4-phenyldiphenylamine (BPBPA), 4-[1-[4-[bis(4-methylphenyl)amino]phenyl]cyclohexyl]-N-(3-methylphenyl)-N-(4-methylphenyl)aniline (TAPC), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), etc.

[0075] In this application, the material of the electron blocking layer is not particularly limited, and electron blocking materials known in the art can be selected. For example, the electron blocking material can be selected from at least one of 2-methyl-4-chlorobutyric acid (mCPB), tris(4-carbazol-9-ylphenyl)amine (TCTA), etc.

[0076] In this application, for the blue light-emitting layer, it can include a host material and a dopant (guest material), and the specific materials thereof are not particularly limited, and materials known in the art can be selected. For example, the host material (BH) can be The dopant (BD) can be 1,4-bis-[4-(N,N-diphenyl)amino]styrylbenzene (DSA-Ph).

[0077] For the red light-emitting layer, it may include a P-type host material for transporting holes, an N-type host material for transporting electrons, and a dopant (guest material). There are no particular limitations on the specific materials of the P-type host material for transporting holes and the N-type host material for transporting electrons, and materials known in the art can be selected. For example, the P-type host material (RH-P) for transporting holes can be The N-type host material (RH-N) for transporting electrons can be The dopant (guest material, RD) can be

[0078] For the green light-emitting layer, it may include a P-type host material for transporting holes, an N-type host material for transporting electrons, and a dopant (guest material). There are no particular limitations on the specific materials thereof, and materials known in the art can be selected. For example, the P-type host material (GH-P) for transporting holes can be The N-type host material (GH-N) for transporting electrons can be The dopant (guest material, GD) can be

[0079] In the present application, there are no particular limitations on the amounts of the host material, guest material, and dopant, and the amounts can be those well-known to those skilled in the art.

[0080] In the present application, there are no particular limitations on the material of the hole blocking layer, and a hole blocking layer material known in the art can be used. For example, the hole blocking material can be 1,3,5-tris(1-phenyl-1H-benzoimidazol-2-yl) (TPBi).

[0081] In the present application, there are no particular limitations on the material of the electron transport layer, and an electron transport material known in the art can be used. For example, the electron transport material can be selected from at least one of 1,10-benzophenanthroline (Bphen), 2-[4-(9,10-dinaphtho[2,1-a:2',1'-j]anthracen-2-yl)phenyl]-1-phenyl-1H-benzoimidazole (ZADN), 4,6-bis(3,5-di(4-pyridyl)phenyl)-2-methylpyrimidine (B4PyMPM), 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1'''-terphenyl]-3,3''-diyl]dipyridine (TmPyPb), etc.

[0082] In the present application, there are no particular limitations on the material of the electron injection layer, and an electron injection material well-known in the art can be used. For example, the electron injection material can be selected from at least one of materials such as Liq (lithium 8-hydroxyquinoline), LiF (lithium fluoride), cesium carbonate (CsCO 3 )), ytterbium metal (Yb), etc.

[0083] In the present application, the material of the second electrode (reflective cathode electrode) is not particularly limited, and an electron injection material well-known in the art can be used. For example, the material of the second electrode (reflective cathode electrode) can be selected from at least one of materials such as Al, Mg, Ag, Mg:Ag, etc.

[0084] Specifically, the structure of the white organic light-emitting device sequentially includes a first electrode, a hole injection layer (HIL), a hole transport layer (HTL), an electron blocking layer (EBL), a light-emitting layer (EML), a hole blocking layer (HBL), an electron transport layer (ETL), an electron injection layer (EIL), a second electrode, and a cover layer (CPL).

[0085] Red light: The material of the first electrode is ITO; the thickness of the HIL is 10 nm; the thickness of the HTL is 110 nm; the thickness of the EBL is 75 nm; the EML is composed of RH and RD, and the thickness of the evaporated coating layer of RD accounts for 2% of the total thickness of the light-emitting layer. The mass ratio of the P-type host material for hole transport and the N-type host material for electron transport in RH is 5:5. The thickness of the EML is 45 nm; the thickness of the HBL is 5 nm; the ETL is composed of an ETL material and Liq, and the thickness of the Liq layer accounts for 50% of the total thickness of the ETL. The thickness of the ETL is 30 nm; the thickness of the EIL is 1 nm; the material of the second electrode is Mg and Ag, and the thickness of the second electrode is 13 nm; the thickness of the CPL is 65 nm.

[0086] Green light: The material of the first electrode is ITO; the thickness of the HIL is 10 nm; the thickness of the HTL is 110 nm; the thickness of the EBL is 35 nm; the EML is composed of GH and GD, and the thickness of the evaporated coating layer of GD accounts for 8% of the total thickness of the light-emitting layer. The mass ratio of the P-type host material for hole transport and the N-type host material for electron transport in GH is 5:5. The thickness of the EML is 35 nm; the thickness of the HBL is 5 nm; the ETL is composed of an ETL material and Liq, and the thickness of the Liq layer accounts for 50% of the total thickness of the ETL. The thickness of the ETL is 30 nm; the thickness of the EIL is 1 nm; the material of the second electrode is Mg and Ag, and the thickness of the second electrode is 13 nm; the thickness of the CPL is 65 nm.

[0087] Blue light: The material of the first electrode is ITO; the thickness of the HIL is 10 nm; the thickness of the HTL is 110 nm; the thickness of the EBL is 5 nm; the EML is composed of BH and BD, and the thickness of the evaporated coating layer of BD accounts for 3% of the total thickness of the light-emitting layer. The thickness of the EML is 20 nm; the thickness of the HBL is 5 nm; the ETL is composed of an ETL material and Liq, and the thickness of the Liq layer accounts for 50% of the total thickness of the ETL. The thickness of the ETL is 30 nm; the thickness of the EIL is 1 nm; the material of the second electrode is Mg and Ag, and the thickness of the second electrode is 13 nm; the thickness of the CPL is 65 nm.

[0088] Specifically, the structure of the red organic electroluminescent device sequentially includes a first electrode, a hole injection layer (HIL), a hole transport layer (HTL), an electron blocking layer (EBL), a light-emitting layer (EML), a hole blocking layer (HBL), an electron transport layer (ETL), an electron injection layer (EIL), a second electrode, and a cover layer (CPL).

[0089] Red light: The material of the first electrode is ITO; the thickness of the HIL is 10 nm; the thickness of the HTL is 110 nm; the thickness of the EBL is 75 nm; the EML is composed of RH and RD, and the thickness of the evaporated coating layer of RD accounts for 2% of the total thickness of the light-emitting layer. The mass ratio of the P-type host material for hole transport and the N-type host material for electron transport in RH is 5:5. The thickness of the EML is 45 nm; the thickness of the HBL is 5 nm; the ETL is composed of an ETL material and Liq, and the thickness of the Liq layer accounts for 50% of the total thickness of the ETL. The thickness of the ETL is 30 nm; the thickness of the EIL is 1 nm; the material of the second electrode is Mg and Ag, and the thickness of the second electrode is 13 nm; the thickness of the CPL is 65 nm.

[0090] The present application does not particularly limit the preparation method of the organic electroluminescent device, and any method known in the art can be adopted. For example, it may include but is not limited to the following steps:

[0091] (1) Clean the substrate coated with the first electrode (anode electrode), and perform cleaning through a combination of one or several methods such as chemical washing, water washing, brush, high-pressure water washing, air knife, UV irradiation, nitrogen treatment, oxygen treatment, etc., and then perform heat treatment;

[0092] (2) Vacuum deposit a hole injection material on the first electrode (anode electrode) as the hole injection layer;

[0093] (3) Vacuum deposit a hole transport material on the hole injection layer as the hole transport layer;

[0094] (4) Vacuum deposit an electron blocking material on the hole transport layer as the electron blocking layer;

[0095] (5) Vacuum deposit a light-emitting layer on the electron blocking layer, and the light-emitting layer contains a host material and a guest material;

[0096] (6) Vacuum deposit a hole blocking material on the light-emitting layer as the hole blocking layer;

[0097] (7) Vacuum deposit an electron transport material on the hole blocking layer as the electron transport layer;

[0098] (8) Vacuum deposit an electron injection material on the electron transport layer as the electron injection layer;

[0099] (9) A cathode material is vacuum-evaporated on the electron injection layer as the second electrode (reflective cathode electrode).

[0100] The fourth aspect of the present application provides a display device, which includes at least one of the compounds described in the first aspect of the present application, the covering layer material described in the second aspect of the present application, or the organic electroluminescent device described in the third aspect of the present application.

[0101] The display device described in the present application includes, but is not limited to, a display, a television, a tablet computer, a mobile communication terminal, etc.

[0102] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments of the present application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0103] Synthesis Example 1: Synthesis of Compound A48

[0104]

[0105] In a 1,4-dioxane solution in the presence of nitrogen, 2-bromophenanthro[5,4-bcd]furan (40.67 g, 150 mmol), 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (32.86 g, 150 mmol), Pd(PPh 3 ) 2 Cl 2 (1.05 mg, 1.5 mmol) and sodium carbonate (0.32 g, 3 mmol) were added, and the mixture was stirred and reacted at 80 °C for 12 hours. After the reaction was completed, filtration was carried out to obtain Intermediate 48-1 (yield 74%).

[0106] Toluene solvent (150 mL) was added to the reaction flask, and then Intermediate 48-1 (28.33 g, 100 mmol), 2-bromophenanthrene (25.71 g, 100 mmol) and sodium tert-butoxide (14.42 g, 150 mmol) were added. After filling with nitrogen for protection, Pd 2 (dba) 3 (0.92 g, 1 mmol) was added, and then Sphos (2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl, 0.82 g, 2 mmol) was added. The mixture was refluxed under nitrogen for 2 hours. Filtration was carried out and the solid was washed with methanol to obtain a recrystallized solid, and Intermediate 48-2 (yield 91%) was obtained.

[0107] Add toluene solvent into the reaction flask, and then successively add intermediate 48-2 (36.76 g, 80 mmol), 3-bromobenzo[d]naphtho[3,2-b]furan (23.77 g, 80 mmol) and sodium tert-butoxide (11.53 g, 120 mmol). After filling with nitrogen, add Pd 2 (dba) 3 (0.73 g, 0.8 mmol), and then add Sphos (0.66 g, 1.6 mmol). Repeat the nitrogen filling process, and reflux for 2 hours. After the reaction is completed, cool to room temperature, and filter through diatomaceous earth to obtain the filtrate. Concentrate and heat, add a small amount of ethanol, let it stand to room temperature for recrystallization, filter by suction and wash with ethanol to obtain the recrystallized solid, and obtain compound 48 (A48), which is a pale yellow solid. Purity: 99.61%, yield: 92%, m / z: 675.83, and the identified molecular formula is C 50 H 29 NO 2 。

[0108] The synthesis of other compounds can all refer to the above synthesis process, and the raw materials in Table 1 below can be used as intermediates.

[0109] Table 1 Raw Materials

[0110]

[0111]

[0112]

[0113]

[0114] Example 1

[0115] Evaporate thin films of the compound of the present application and control compounds CP-1, CP-2, CP-3, CP-4, and CP-5 on the silicon wafer respectively, and obtain a CPL material thin film with a thickness of 50 nm by evaporation. The structural formulas of CP-1, CP-2, CP-3, CP-4, and CP-5 are as follows:

[0116]

[0117]

[0118] Use an ellipsometer to measure the absorption coefficient (k) and refractive index (n) of the evaporated CPL material thin film, and the instrument scanning range is 245 - 1000 nm.

[0119] Compare the refractive indices of the CPL material thin films prepared from different compounds at three common wavelengths of 460 nm, 530 nm, and 620 nm. The results are shown in Table 2.

[0120] To protect the OLED device from damage by ultraviolet light in the external environment, the CPL material needs to have strong absorption ability at about 400 nm to absorb the external ultraviolet light and prevent the device from aging. At the same time, it should not absorb the light emitted by the OLED device itself. Therefore, the absorption at 450 nm and later is required to be almost 0. The extinction coefficients (k) of the CPL material films prepared from different compounds are compared at two common wavelengths of 400 nm and 450 nm, and the results are shown in Table 2.

[0121] In addition, the glass transition temperature (Tg) is an important parameter to ensure the stability of the material during the evaporation process; the glass transition temperature is measured by DSC (differential scanning calorimeter), and the second heating process is selected to measure the glass transition temperature value during the temperature range from room temperature to 300 °C, and the results are shown in Table 2.

[0122] Result comparison in Table 2

[0123]

[0124]

[0125] It can be seen from the above results that the refractive indices of the CPL material films evaporated with the compounds of the present application are significantly higher than those of the CPL material films evaporated with the control compounds CP-1 to CP-5. In the wavelength range of 460 nm - 620 nm, the refractive indices are all greater than 2. At the same time, the CPL material films evaporated with the compounds of the present application have a relatively high extinction coefficient, with a high extinction coefficient at 400 nm, but 0 at 450 nm. Therefore, it can effectively reduce harmful blue light without affecting the normal blue light color.

[0126] Example 2

[0127] The stability of the material after long-term evaporation is judged through an ampoule experiment. The compounds of the present application and the control compounds CP-1 and CP-4 are placed in ampoules and stored at 300 °C for 100 h, and then the HPLC of each compound is tested, and the heat resistance of the material is judged from the reduction amplitude of the purity. The structural formulas of CP-1, CP-4, and CP-5 are the same as those in Example 1. The test results are shown in Table 3.

[0128] Purity results in Table 3

[0129] Compound HPLC (Initial) HPLC (After 100 h) HPLC Difference A2 99.95％ 99.84％ 0.11％ A3 99.96％ 99.78％ 0.18％ A8 99.93％ 99.72％ 0.21％ A9 99.94％ 99.79％ 0.15％ A30 99.92％ 99.83％ 0.09％ A31 99.95％ 99.82％ 0.13％ A48 99.94％ 99.80％ 0.14％ A62 99.97％ 99.85％ 0.12％ A64 99.97％ 99.90％ 0.07％ CP-1 99.96％ 97.93％ 2.03％ CP-4 99.97％ 98.31％ 1.66％

[0130] Note: The initial HPLC data are all the purities after sublimation.

[0131] As can be seen from the above results, the initial purity of all compounds is very high, meeting the requirements of the test. After storing at 300 °C for 100 h, the HPLC difference values of the compounds of the present application are all within 1%, and the purity after 100 h is above 99.5%, and the purity is still very high; while the purity of the control compounds CP-1 and CP-4 both decreased by more than 1.5%, the thermal stability of the materials is poor, and the stability in actual evaporation coating is poor, which may affect the efficiency of the final device.

[0132] Example 3

[0133] The ITO substrate was cleaned and dried; the HIL material, HTL material, and EBL material were sequentially evaporated on the anode; then the light-emitting layers RH and RD were evaporated; the HBL material, ETL material, and EIL material were evaporated on the light-emitting layer; then the cathode was evaporated; on top of the cathode, the CPL layer was evaporated. The structure of the red light device is: HIL(10 nm) / HTL(110 nm) / EBL(75 nm) / RH:RD(45 nm, 5:5, 2%) / HBL(5 nm) / ETL:LIQ(30 nm, 50%) / EIL(1 nm) / Mg:Ag 13 nm / CPL 65 nm, that is, the material of the first electrode is ITO; the thickness of HIL is 10 nm; the thickness of HTL is 110 nm; the thickness of EBL is 75 nm; the EML is composed of RH and RD, the thickness of the evaporated coating layer of RD accounts for 2% of the total thickness of the light-emitting layer, the mass ratio of the P-type host material (RH-P) for transporting holes and the N-type host material (RH-N) for transporting electrons in RH is 5:5, and the thickness of the EML is 45 nm; the thickness of HBL is 5 nm; the ETL is composed of the ETL material and Liq, the thickness of the Liq layer accounts for 50% of the total thickness of the ETL, and the thickness of the ETL is 30 nm; the thickness of EIL is 1 nm; the material of the second electrode is Mg and Ag, and the thickness of the second electrode is 13 nm; the thickness of CPL is 65 nm.

[0134] In all devices, the material of the hole injection layer (HIL) is selected as HATCN, the material of the hole transport layer (HTL) is selected as NPB, the material of the hole blocking layer (HBL) is selected as TPBi, the material of the electron transport layer (ETL) is selected as Bphen, the material of the electron blocking layer (EBL) is selected as TCTA, and the material of the electron injection layer (EIL) is selected as ytterbium metal (Yb). The specific structure is as follows. The P-type host material (RH-P) for transporting holes, the N-type host material (RH-N) for transporting electrons, and the dopant (RD) used in the light-emitting layer have the following structural formulas.

[0135]

[0136] The CPL materials selected for the devices in different groups are respectively Compound A3, A8, A30, A31, A48, A62 of the present application and the control compounds CP-2, CP-4, CP-5 described in Example 1. The devices in different groups are the same except for the CPL materials used.

[0137] Optoelectronic performance detection of the organic electroluminescent device: At the same brightness, use a digital source meter and a luminance meter to measure the driving voltage, current efficiency, and device lifetime of the organic electroluminescent devices prepared with different compounds. Specifically, increase the voltage at a rate of 0.1 V per second and measure the voltage when the brightness of the organic electroluminescent device reaches 1000 cd / m 2 That is, the driving voltage, and at the same time measure the current density at this time; the ratio of brightness to current density is the current efficiency. The lifetime test is as follows: Use a luminance meter at a brightness of 1000 cd / m 2 Brightness, keep a constant current, and measure the time it takes for the brightness of the organic electroluminescent device to decay from the initial value to 90%, with the unit of h. The detection results are shown in Table 4 below (using the data of Device D7 as 100% for comparison).

[0138] Table 4 Comparison of Optoelectronic Performance Results of Organic Electroluminescent Devices

[0139] Device CPL Layer Voltage Efficiency Lifetime D1 A3 98％ 105％ 100％ D2 A8 99％ 104％ 100％ D3 A30 99％ 105％ 100％ D4 A31 98％ 105％ 100％ D5 A48 97％ 107％ 100％ D6 A62 97％ 106％ 100％ D7 A64 97％ 107％ 100％ D8 CP-2 100％ 100％ 100％ D9 CP-4 100％ 100％ 100％ D10 CP-5 100％ 101％ 100％

[0140] It can be seen from the above results that by using the compounds provided in the present application, due to their high refractive index, the efficiency of the red light devices is improved to varying degrees, the voltage is slightly reduced, and the lifetime remains unchanged.

[0141] Example 4

[0142] Clean and dry the ITO substrate; sequentially deposit the HIL material, HTL material, and EBL material on the anode; then deposit the light-emitting layers RH and RD; deposit the HBL material, ETL material, and EIL material on the light-emitting layer; then deposit the cathode; above the cathode, deposit the CPL layer. The structure of the white light device (including devices of three colors, RGB) is:

[0143] Blue light: HIL(10nm) / HTL(110nm) / EBL(5nm) / BH: BD(20nm, 3%) / HBL(5nm) / ETL: LIQ(30nm, 50%) / EIL(1nm) / Mg: Ag 13nm / CPL 65nm; that is, the material of the first electrode is ITO; the thickness of HIL is 10nm; the thickness of HTL is 110nm; the thickness of EBL is 5nm; EML is composed of BH and BD. The mass ratio of the P-type host material for hole transport and the N-type host material for electron transport in BH is 5:5. The thickness of the evaporated coating layer of BD accounts for 3% of the total thickness of the light-emitting layer. The thickness of EML is 20nm; the thickness of HBL is 5nm; ETL is composed of ETL material and Liq. The thickness of the Liq layer accounts for 50% of the total thickness of ETL. The thickness of ETL is 30nm; the thickness of EIL is 1nm; the material of the second electrode is Mg and Ag. The thickness of the second electrode is 13nm; the thickness of CPL is 65nm.

[0144] Green light: HIL(10nm) / HTL(110nm) / EBL(35nm) / GH: GD(35nm, 5:5, 8%) / HBL(5nm) / ETL: LIQ(30nm, 50%) / EIL(1nm) / Mg: Ag 13nm / CPL 65nm; that is, the material of the first electrode is ITO; the thickness of HIL is 10nm; the thickness of HTL is 110nm; the thickness of EBL is 35nm; EML is composed of GH and GD. The thickness of the evaporated coating layer of GD accounts for 8% of the total thickness of the light-emitting layer. The mass ratio of the P-type host material for hole transport and the N-type host material for electron transport in GH is 5:5. The thickness of EML is 35nm; the thickness of HBL is 5nm; ETL is composed of ETL material and Liq. The thickness of the Liq layer accounts for 50% of the total thickness of ETL. The thickness of ETL is 30nm; the thickness of EIL is 1nm; the material of the second electrode is Mg and Ag. The thickness of the second electrode is 13nm; the thickness of CPL is 65nm.

[0145] Red light: HIL(10nm) / HTL(110nm) / EBL(75nm) / RH: RD(45nm, 5:5, 2%) / HBL(5nm) / ETL: LIQ(30nm, 50%) / EIL(1nm) / Mg:Ag 13nm / CPL 65nm; that is, the material of the first electrode is ITO; the thickness of HIL is 10nm; the thickness of HTL is 110nm; the thickness of EBL is 75nm; EML is composed of RH and RD, the thickness of the RD evaporation coating layer accounts for 2% of the total thickness of the light-emitting layer, the mass ratio of the P-type host material for hole transport and the N-type host material for electron transport in RH is 5:5, the thickness of EML is 45nm; the thickness of HBL is 5nm; ETL is composed of ETL material and Liq, the thickness of the Liq layer accounts for 50% of the total thickness of ETL, the thickness of ETL is 30nm; the thickness of EIL is 1nm; the material of the second electrode is Mg and Ag, the thickness of the second electrode is 13nm; the thickness of CPL is 65nm.

[0146] In all devices, the hole injection layer (HIL) material is selected as HATCN, the hole transport layer (HTL) material is selected as NPB, the hole blocking layer (HBL) material is selected as TPBi, the electron transport layer (ETL) material is selected as Bphen, the material of the electron blocking layer (EBL) is selected as TCTA, and the material of the electron injection layer (EIL) is selected as ytterbium metal (Yb). The specific structure is as shown in Example 3. The structural formulas of the P-type host material (RH-P) for hole transport and the N-type host material (RH-N) for electron transport used in the red light-emitting layer are as shown in Example 3; the host material (BH) used in the blue light-emitting layer is selected as ADN, and the structural formula is as shown below, and the guest material (BD) is selected as DSA-Ph, and the structural formula is as shown below; the structural formulas of the P-type host material (GH-P) for hole transport, the N-type host material (GH-N) for electron transport, and the guest material (GD) used in the green light-emitting layer are as shown below.

[0147]

[0148] The blue light-emitting layer and the green light-emitting layer of the devices in different groups are the same, only the red light-emitting layer part is replaced. Except for the different CPL materials used in the red light-emitting layer, which are Compound A2, A31, A48 of the present application and the control compounds CP-2 and CP-4 described in Example 1 respectively, the others are the same.

[0149] White light efficiency detection of the device: The efficiencies of red, green, and blue colors are respectively tested through the PR680 device, and the white light efficiency is synthesized. The test condition is to fix the current density at 10mA / cm 2 。

[0150] Detection of white light brightness attenuation (30°) of the device: The brightness changes of red, green, and blue colors at angles from -70° to 70° are measured respectively by the PR680 device, and the white light brightness change is synthesized. The brightness attenuation value at 30° is selected.

[0151] Detection of white light color deviation (JNCD) (30°) of the device: The detection direction of color deviation is the same as that of brightness attenuation. The color deviation is calculated by the offset value of the color coordinates, and the offset value at 30° is selected.

[0152] The detection results are shown in Table 5 below.

[0153] Table 5 Performance comparison of different devices

[0154] Device CPL Layer White Light Efficiency White Light Luminance Decay (30°) White Light Chromaticity Shift (JNCD) (30°) W1 A2 105％ 29.7％ 4.07 W2 A32 105％ 29.5％ 4.06 W3 A48 107％ 29.1％ 4.11 W4 A64 107％ 28.6％ 3.98 W-R1 CP-2 100％ 30.8％ 5.89 W-R2 CP-4 101％ 30.3％ 5.97

[0155] It can be seen from the above results that by using the compound provided in this application as the covering layer material, the white light efficiency is improved, the white light brightness attenuation (30°) is controlled at about 30%, and the color deviation is significantly improved.

[0156] The above are only the preferred embodiments of this application, and are not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the scope of protection of this application.

Claims

1. A compound represented by formula (I) or formula (II): in, Ar1 is selected from Ar2 is selected from L is selected from a single bond or a phenylene group; L1 and L2 are each independently selected from a single bond, a C6-C 20 Arylene or C5-C 20 heteroarylene; X is selected from C1-C6 alkyl, O or S; Y1, Y2, Y3 and Y4 are each independently selected from O or S; Z is selected from CH or N; The heteroatom in the heteroarylene group is selected from N, O or S.

2. The compound according to claim 1, wherein All hydrogen atoms in the compound represented by formula (I) or the compound represented by formula (II) are optionally replaced by deuterium.

3. The compound according to claim 1, wherein L1 and L2 are each independently selected from a single bond or a C6-C 12 Arylene.

4. The compound according to claim 1, wherein L1 and L2 are each independently selected from a single bond or a phenylene group.

5. The compound according to claim 1, wherein X is selected from C2-C3 alkyl, O or S; preferably, X is selected from -C(CH3)2-, O or S.

6. The compound according to claim 1, wherein Ar1 is selected from Ar2 is selected from 7. The compound according to claim 1, wherein The compound is selected from the following compounds A1-A62:

8. A covering material comprising at least one of the compounds according to any one of claims 1 to 7. 9 . An organic electroluminescent device comprising at least one of the compounds according to claim 1 or the covering layer material according to claim 8 . 10 . A display device comprising at least one of the compounds according to claim 1 , the covering layer material according to claim 8 , or the organic electroluminescent device according to claim 9 .

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