Carbazole compound, light extraction material and application thereof

Abstract

The invention discloses a carbazole compound, a light extraction material and application thereof, and belongs to the technical field of display. The embodiment of the invention provides a carbazole compound, which has a general formula as shown in any one of the following formulas (I) to (III): # imgabs0, according to the general formulas of the formulas (I) to (III), a carbazole group in the carbazole compound can form a conjugated structure with other groups, and the conjugated structure can reduce the refractive index sensitivity of the carbazole compound to a specific wavelength, so that the refractive index sensitivity of the carbazole compound to the specific wavelength can be reduced, and the refractive index sensitivity of the carbazole compound to the specific wavelength can be reduced. And the refractive index difference from blue light to red light is reduced, so that the white light efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of display technologies, and particularly to a carbazole compound, a light extraction material and their applications. Background Art

[0002] Organic Light Emission Diodes (OLED) are widely used in the fields of lighting and display. Currently, most of the OLED devices in use adopt a top-emitting device structure. In the top-emitting device, a light extraction (Capping Layer, CPL) layer is introduced. By means of a relatively high refractive index, a combination of high and low refractive indices is formed above the cathode, thereby achieving a better light extraction effect.

[0003] However, in related technologies, the refractive index of the light extraction material varies greatly from blue light to red light, which is not conducive to improving the white light efficiency. Summary of the Invention

[0004] Embodiments of this application provide a carbazole compound, a light extraction material and their applications, which can improve the white light efficiency. The technical solutions are as follows:

[0005] On the one hand, embodiments of this application provide a carbazole compound, which has a general formula as shown in any one of formulas (I) to (III):

[0006]

[0007]

[0008] Among them, Ar1 is selected from any one of the following groups:

[0009]

[0010] At least one of Ar2, Ar3, and Ar4 is: The rest are each independently selected from (1-a) to (1-g):

[0011]

[0012] Ar5 is selected from any one of the following groups:

[0013]

[0014] L1 to L5 are each independently selected from: a single bond, a phenylene group, a biphenylene group or a C6-C10 heteroarylene group;

[0015] X is selected from O or S.

[0016] In a possible implementation manner, the carbazole compound includes at least one deuterium substituent.

[0017] In another possible implementation, the carbazole compound is any one of Compounds 1 to 44:

[0018]

[0019]

[0020]

[0021]

[0022] On the other hand, an embodiment of the present application provides a light extraction material, and the light extraction material includes the carbazole compound described in any one of the above.

[0023] In one possible implementation, the refractive index of the light extraction material in the wavelength range of 460 nm to 620 nm is greater than 2.

[0024] In another possible implementation, the glass transition temperature of the light extraction material is greater than or equal to 115 °C.

[0025] In another possible implementation, the extinction coefficient of the light extraction material at 450 nm is 0.

[0026] On the other hand, an embodiment of the present application provides an organic electroluminescent device, and the organic electroluminescent device includes an anode, a light-emitting functional layer, a cathode, and a light extraction layer that are sequentially stacked, wherein the light extraction layer includes the light extraction material described in any one of the above.

[0027] In one possible implementation, the light-emitting functional layer includes a hole transport unit, a light-emitting layer, and an electron transport unit, and the hole transport unit, the light-emitting layer, and the electron transport unit are sequentially stacked in the direction from the anode to the cathode;

[0028] Wherein, the hole transport unit includes at least one of a hole injection layer, a hole transport layer, and an electron blocking layer;

[0029] The electron transport unit includes at least one of a hole blocking layer, an electron transport layer, and an electron injection layer.

[0030] On the other hand, an embodiment of the present application provides a display device, and the display device includes the organic electroluminescent device described in any one of the above.

[0031] An embodiment of the present application provides a carbazole compound. According to the general formulas of formulas (I) to (III), the carbazole group in the carbazole compound can form a conjugated structure with other groups, and this conjugated structure can reduce the refractive index sensitivity of the carbazole compound to a specific wavelength and reduce the refractive index difference from blue light to red light, thereby improving the white light efficiency. Detailed implementation manners

[0032] To make the technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below.

[0033] An embodiment of the present application provides a carbazole compound, and the carbazole compound has a general formula as described in any one of formulas (I) to (III) below:

[0034]

[0035] Wherein, Ar1 is selected from any one of the following groups:

[0036]

[0037] At least one of Ar2, Ar3, and Ar4 is: The rest are each independently selected from (1-a) to (1-g):

[0038]

[0039] Ar5 is selected from any one of the following groups:

[0040]

[0041] L1 to L5 are each independently selected from: a single bond, a phenylene group, a biphenylene group, or a C6-C10 heteroarylene group;

[0042] X is selected from O or S.

[0043] In the embodiment of the present application, the heteroatoms contained in the heteroarylene group may be O, S, N, etc., and the heteroarylene group may be a subunit of the following heteroaryl groups: benzofuranyl, naphthofuranyl, phenanthrofuranyl, dibenzofuranyl, benzo-dibenzofuranyl, benzothiophenyl, naphthothiophenyl, phenanthrothiophenyl, dibenzothiophenyl, benzo-dibenzothiophenyl, indolyl, naphthylindolyl, carbazolyl, benzocarbazolyl, benzodisulfide group, dihydroisobenzofuranyl, dihydrobenzofuranyl, dihydrobenzothiophenyl, dihydroisobenzothiophenyl, phenoxazinyl, phenothiazinyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, quinolinyl, etc.

[0044] The embodiments of the present application provide a carbazole compound. According to the general formulas of Formulas (I) to (III), the carbazole group in the carbazole compound can form a conjugated structure with other groups, and this conjugated structure can reduce the refractive index sensitivity of the carbazole compound to a specific wavelength and reduce the refractive index difference from blue light to red light, thereby improving the white light efficiency.

[0045] Moreover, the carbazole compound provided by the embodiments of the present application has a large absorption at 360 nm. When applied in an OLED device, it can absorb ultraviolet light in the external light and prevent the aging caused by the irradiation of ultraviolet light on the OLED device, especially for long-life OLED devices.

[0046] In a possible implementation manner, at least one of Ar2, Ar3, and Ar4 is The rest are each independently selected from (1-a) to (1-g):

[0047]

[0048] That is, if one of Ar2, Ar3, and Ar4 is Then the other two are each independently selected from (1-a) to (1-g). For example, Ar2 is Ar3 and Ar4 are both selected from (1-g), and X is S.

[0049] If two of Ar2, Ar3, and Ar4 are Then the third one is selected from (1-a) to (1-g). For example, Ar3 and Ar4 are both Ar2 is selected from (1-e). Or Ar2, Ar3, and Ar4 can also all be No specific limitation is made thereto.

[0050] In a possible implementation manner, the carbazole compound includes at least one deuterium substituent.

[0051] In this implementation manner, some of the hydrogens in the carbazole compound can be replaced by deuterium, or all of them can be replaced by deuterium. No specific limitation is made thereto.

[0052] In the embodiments of the present application, the bond energy of the chemical bond between carbon and deuterium is higher than that of the chemical bond between carbon and hydrogen. Therefore, after deuterium replaces hydrogen, the stability of the carbazole compound can be significantly improved.

[0053] Combined with the above-mentioned carbazole compound, some examples of the carbazole compound can be any one of Compounds 1 to 44:

[0054]

[0055]

[0056]

[0057]

[0058]

[0059] The embodiment of the present application also provides a preparation method of a carbazole compound, and the preparation method includes:

[0060] When the carbazole compound has the general formula of formula (I), it is prepared by the following method:

[0061] Step 1: Provide reactants A1, A2 and A3.

[0062] Among them, the general formulas of reactants A1 and A2 are shown as follows:

[0063]

[0064] The structural general formula of reactant A3 is Ar1-Y. Among them, Y represents a halogen. For example, Y is F, Cl, Br or I, etc.

[0065] Step 2: React reactants A1 and A2 to obtain a first intermediate.

[0066] The reaction process of reactants A1 and A2 is shown as follows:

[0067]

[0068] Step 3: React the first intermediate with reactant A3 to obtain the carbazole compound shown in formula (I).

[0069] The reaction process of the first intermediate and reactant A3 is shown as follows:

[0070]

[0071] In the embodiment of the present application, reactants A1 to A3 can be designed according to the chemical structure of the carbazole compound. Among them, reactants A1 to A3 can be obtained by purchasing known compound products or can be prepared by oneself, and no specific limitation is made thereto.

[0072] When the carbazole compound has the general formula of formula (II), it is prepared by the following method:

[0073] Step 1: Provide compound A1, compound B1, compound B2 and compound B3.

[0074] Among them, the general structural formula of compound B1 is: Ar2-L2-Y, the general structural formula of compound B2 is: Ar3-L3-Y, and the general structural formula of compound B3 is: Ar4-L4-Y.

[0075] Step 2: React compound A1 with compound B2 to obtain a second intermediate.

[0076] Step 3: React the second intermediate with compound B3 to obtain a third intermediate.

[0077] It should be noted that it is also possible to first react compound A1 with compound B3 to obtain a fourth intermediate, and then react the fourth intermediate with compound B2 to obtain a third intermediate, and no specific limitation is made thereto.

[0078] Step 4: React the third intermediate with compound B1 to obtain the carbazole compound shown in formula (II).

[0079] In the embodiments of the present application, reactants B1 to B3 can be designed according to the chemical structure of the carbazole compound. Among them, reactants B1 to B3 can be obtained by purchasing known compound products or can be prepared by oneself, and no specific limitation is made thereto.

[0080] When the carbazole compound has the general formula of formula (III), it is prepared by the following method:

[0081] Step 1: Provide compound C1 and compound C2.

[0082] Among them, the general structural formula of compound C1 is: Ar5-L5-Y, and the general structural formula of compound C2 is as follows:

[0083]

[0084] Step 2: React compound C1 and compound C2 to obtain the carbazole compound shown in formula (III).

[0085] The reaction process of compound C1 and compound C2 is as follows:

[0086]

[0087] In the embodiments of the present application, reactants C1 and C2 can be designed according to the chemical structure of the carbazole compound. Among them, reactants C1 and C2 can be obtained by purchasing known compound products or can be prepared by oneself, and no specific limitation is made thereto.

[0088] The embodiments of the present application also provide a light extraction material, and the light extraction material includes any one of the above-mentioned carbazole compounds. The light extraction material provided by the embodiments of the present application has all the advantages of the carbazole compound.

[0089] In some examples, the mass percentage of the carbazole compound in the light extraction material is 100%, that is, the light extraction material only includes the carbazole compound.

[0090] In some examples, the light extraction material includes a carbazole compound and an additive. According to actual requirements, the addition amount of the additive can be adaptively determined. For example, the mass percentage of the additive in the light extraction material can be 0.5% - 5%.

[0091] Among them, the additive can be selected from at least one of materials with a refractive index lower than that of the carbazole compound, a scattering agent, and a light stabilizer. For example, nano-silica, nano-titanium dioxide, nano-zinc oxide, hindered amine light stabilizer, etc.

[0092] The light extraction layer is above the cathode, and its main function is to improve the light extraction efficiency of the entire OLED device. Therefore, the refractive index of the light extraction material is a very important parameter. Based on the use of the carbazole compound provided in the embodiments of the present application, the refractive index of the light extraction material can be greater than 2 in the wavelength range of 460nm - 620nm, showing excellent light refraction effects. And the glass transition temperature of the light extraction material is greater than or equal to 115°C, showing excellent thermal stability.

[0093] In addition, the light extraction material has a strong absorption ability at about 400nm, which can protect the OLED device from being damaged by ultraviolet light in the external environment, absorb external ultraviolet light, prevent device aging. At the same time, the extinction coefficient of the light extraction material at 450nm is 0, that is, the light extraction material does not absorb the light emitted by the OLED device itself, which can maximize the blue light transmittance and improve the light extraction efficiency of the blue light device.

[0094] On the other hand, the embodiments of the present application also provide an organic electroluminescent device, wherein the organic electroluminescent device includes an anode, a light-emitting functional layer, a cathode, and a light extraction layer arranged in a stacked manner in sequence, and the light extraction layer includes any one of the above-mentioned light extraction materials. The organic electroluminescent device provided by the embodiments of the present application has all the advantages of the carbazole compound, so it has a high light extraction efficiency and device stability.

[0095] For example, the light-emitting functional layer includes a hole transport unit, a light-emitting layer, and an electron transport unit, and the hole transport unit, the light-emitting layer, and the electron transport unit are arranged in a stacked manner in sequence from the anode to the cathode. Among them, the hole transport unit includes at least one of a hole injection layer, a hole transport layer, and an electron blocking layer; the electron transport unit includes at least one of a hole blocking layer, an electron transport layer, and an electron injection layer.

[0096] In some examples, the hole transport unit includes a hole transport layer, wherein the anode, the hole transport layer, and the light-emitting layer are arranged in a stacked manner in sequence.

[0097] In some examples, the hole transport unit includes a hole injection layer and a hole transport layer, wherein the anode, the hole injection layer, the hole transport layer, and the light-emitting layer are sequentially stacked.

[0098] In some examples, the hole transport unit includes a hole transport layer and an electron blocking layer, wherein the anode, the hole transport layer, the electron blocking layer, and the light-emitting layer are sequentially stacked.

[0099] In some examples, the hole transport unit includes a hole transport layer, an electron blocking layer, and a hole injection layer, wherein the anode, the hole injection layer, the hole transport layer, the electron blocking layer, and the light-emitting layer are sequentially stacked.

[0100] In some examples, the electron transport unit includes an electron transport layer, wherein the cathode, the electron transport layer, and the light-emitting layer are sequentially stacked.

[0101] In some examples, the electron transport unit includes an electron transport layer and an electron injection layer, wherein the cathode, the electron injection layer, the electron transport layer, and the light-emitting layer are sequentially stacked.

[0102] In some examples, the electron transport unit includes an electron transport layer and a hole blocking layer, wherein the cathode, the electron transport layer, the hole blocking layer, and the light-emitting layer are sequentially stacked.

[0103] In some examples, the electron transport unit includes an electron transport layer, a hole blocking layer, and an electron injection layer, wherein the cathode, the electron injection layer, the electron transport layer, the hole blocking layer, and the light-emitting layer are sequentially stacked.

[0104] The hole transport unit, the electron transport unit, the anode, and the cathode can all adopt currently known related materials, which will not be elaborated here.

[0105] For example, the hole injection layer includes but is not limited to: inorganic oxides, p-type dopants of strong electron-withdrawing systems, and dopants of hole transport materials, such as hexacyanohaxazatriphenylene, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-p-benzoquinodimethane (F4TCNQ), 1,2,3-tris[(cyano)(4-cyano-2,3,5,6-tetrafluorophenyl)methylene]cyclopropane, etc.

[0106] The hole transport layer / electron blocking layer includes but is not limited to: arylamines with hole transport properties, dimethylfluorene, or carbazole materials and their derivatives.

[0107] The light-emitting layer is selected according to actual light-emitting requirements. Taking green light-emitting materials as an example, it can be selected from but is not limited to iridium complexes.

[0108] The hole blocking layer / electron transport layer includes, but is not limited to: aromatic heterocyclic compounds, which can be selected from, but are not limited to, at least one of benzimidazole, triazine, pyrimidine, pyridine, pyrazine, quinoxaline, quinoline, diazole, diazaphosphole, phosphine oxide, aromatic ketone, lactam, borane compounds and their derivatives.

[0109] The electron injection layer is generally an alkali metal or a metal, such as LiF, Yb, Mg, Ca or their compounds, etc.

[0110] On the other hand, an embodiment of the present application also provides a display device, which includes any one of the above-mentioned organic electroluminescent devices.

[0111] The display device provided by the embodiment of the present application has all the advantages of the organic electroluminescent device. Exemplarily, the display device includes, but is not limited to: OLED TVs, tablet computers, in-vehicle displays, MP3 players, smart watches, fitness bracelets, virtual reality (VR) helmets, augmented reality (AR) glasses, etc.

[0112] The exemplary embodiments of the present application will be described in more detail below. Although the exemplary embodiments of the present application are described below, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. For those without specific technical or conditions noted in the examples, the techniques or conditions described in the literature in the art or according to the product specifications are followed. Those reagents or instruments without the manufacturer noted are all conventional products that can be obtained through commercial purchase.

[0113] Example 1

[0114] In this example, a compound 1 was synthesized, and the synthesis route is as follows:

[0115]

[0116] Step 1: In the presence of nitrogen, in a 1,4-dioxane solution, 3,6-dibromocarbazole (32.5 g, 100 mmol), dibenzothiophene-3-boronic acid (45.6 g, 200 mmol), Pd[P(C6H5)3]4 (4.62 mg, 4 mmol) and potassium carbonate (41.46, 300 mmol) were added, and the mixture was stirred at 80 °C for 12 hours, and then filtered to obtain intermediate 1-1 (yield 83%).

[0117] Step 2: Add toluene solvent into the flask, and then successively add Intermediate 1-1 (42.54 g, 80 mmol), 2-bromophenanthrene (20.57 g, 80 mmol) and sodium tert-butoxide (11.53 g, 120 mmol). After filling with nitrogen, add Pd2(dba)3 (0.73 g, 0.8 mmol), and add (tBu3P)HBF4 (0.47 g, 1.6 mmol). Repeat the nitrogen filling process, and reflux for 6 hours. After the reaction is completed, cool to room temperature, filter to obtain a solid. Add a small amount of methanol, let it stand to room temperature for recrystallization, filter by suction and wash with ethanol to obtain the recrystallized solid, and obtain Compound 1.

[0118] Compound 1 is a pale yellow solid, purity: 99.97%, yield: 89%, m / z: 707.57; C 50 H 29 NS2.

[0119] Example 2

[0120] In this example, a compound 35 was synthesized, and the synthetic route is as follows:

[0121]

[0122] In the presence of nitrogen, add 9H,9H-3,3-bicarbazole (5.00 g, 15.04 mmol), 2-(4-bromophenyl)benzo[b]thiophene (9.57 g, 33.09 mmol), Pd2(dba)3 (0.69 g, 0.75 mmol), (tBu3P)HBF4 (0.44 g, 1.50 mmol) and sodium tert-butoxide (8.67 g, 90.25 mmol) into the toluene solution, and reflux at 110 °C for 7 hours.

[0123] After the reaction is completed, cool to room temperature, filter to obtain the crude product. Add dichloromethane for column chromatography, and spin-dry the solvent to obtain Compound 35.

[0124] Compound 35 is a pale yellow solid, purity: 99.91%, yield: 89%, m / z: 748.23; C 52 H 32 N2S2.

[0125] Referring to Table 1, the present application also synthesized Compound 3, Compound 4, Compound 6, Compound 8, Compound 14, Compound 15, Compound 21, Compound 29, Compound 38, Compound 40, Compound 42 and Compound 43. The raw materials used are shown in Table 1 respectively. The specific synthesis process is the same as that of Compound 1 or Compound 35, and will not be elaborated here.

[0126] Table 1

[0127]

[0128]

[0129]

[0130]

[0131] Comparative Example

[0132] Comparative Example 1 involves CP-1, Comparative Example 2 involves CP-2, Comparative Example 3 involves CP-3, Comparative Example 4 involves CP-4, Comparative Example 5 involves CP-5, Comparative Example 6 involves CP-6, Comparative Example 7 involves CP-7, and Comparative Example 8 involves CP-8. The structures of CP-1 to CP-8 are shown as follows:

[0133]

[0134] Test Example 1

[0135] The refractive index and extinction coefficient were measured using an ellipsometer: the instrument scanning range was 245 - 1000 nm, and a silicon wafer was coated with a thin film with a thickness of 50 nm.

[0136] The glass transition temperature is an important parameter to ensure the stability of the material during the evaporation process. The glass transition temperature was measured by DSC, and the second heating process was selected, with the temperature ranging from room temperature to 300 °C.

[0137] In this application, the refractive index, extinction coefficient, and glass transition temperature Tg of the compounds provided in the above examples and comparative examples were tested at different wavelengths. The test results are shown in Table 2.

[0138] Table 2

[0139]

[0140] It can be seen from Table 2 that the refractive indices of CP-1, CP-2, and CP-5 are all relatively low. The refractive indices of CP-3, CP-4, and CP-8 are relatively high in the blue light region, but very low in the red light region. The refractive index difference between the blue light region and the red light region is large, and the glass transition temperature is relatively low. The extinction coefficients of CP-6 and CP-7 are relatively low at 360 nm, and the glass transition temperature is relatively low.

[0141] However, the compounds prepared in the examples of this application have a refractive index greater than 2 in the wavelength range of 460 - 620 nm, showing a relatively high refractive index. Moreover, they have a relatively high extinction coefficient at 360 nm and an extinction coefficient of 0 at 450 nm, which does not affect the efficiency of blue light devices. At the same time, the glass transition temperatures are all greater than 115 °C, showing excellent thermal stability.

[0142] Test Example 2

[0143] Prepare multiple white light devices, and the preparation process is as follows:

[0144] Clean and dry the pre-prepared ITO substrate, and sequentially start evaporating HIL material, HTL material, EBL material, light-emitting layer material, HBL material, ETL material, and EIL material on the anode, and then evaporate the cathode. On top of the cathode, evaporate the CPL layer.

[0145] The device structure is:

[0146] 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;

[0147] Green light: HIL(10nm) / HTL(110nm) / EBL(35nm) / GH:GD(35nm, the mass fraction of GD is 8%) / HBL(5nm) / ETL:LIQ(30nm, 50%) / EIL(1nm) / Mg:Ag 13nm / CPL 65nm;

[0148] Red light: HIL(10nm) / HTL(110nm) / EBL(75nm) / RH:RD(45nm, the mass fraction of RD is 2%) / HBL(5nm) / ETL:LIQ(30nm, 50%) / EIL(1nm) / Mg:Ag 13nm / CPL 65nm.

[0149] It should be noted that GH includes compound GH-P and GH-N, and the mass ratio of GH-P to GH-N is 5:5. RH includes compound RH-P and RH-N, and the mass ratio of RH-P to RH-N is 5:5.

[0150] The material used for the EIL layer in the device is Yb, and the compounds used for other functional layers are as follows:

[0151]

[0152]

[0153] Device W1 (a device including RGB three colors): The CPL layer uses Compound 1; Device W2 (a device including RGB three colors): The CPL layer uses Compound 3; Device W3 (a device including RGB three colors): The CPL layer uses Compound 4; Device W4 (a device including RGB three colors): The CPL layer uses Compound 6; Device W5 (a device including RGB three colors): The CPL layer uses Compound 8; Device W6 (a device including RGB three colors): The CPL layer uses Compound 10; Device W7 (a device including RGB three colors): The CPL layer uses Compound 21; Device W8 (a device including RGB three colors): The CPL layer uses Compound 35; Device W9 (a device including RGB three colors): The CPL layer uses Compound 38; Device W10 (a device including RGB three colors): The CPL layer uses Compound 40; Device W11 (a device including RGB three colors): The CPL layer uses Compound 43; Device W-R1 (a device including RGB three colors): The CPL layer uses CP-1;

[0154] Device W-R2 (a device including RGB three colors): The CPL layer uses CP-4;

[0155] Device W-R3 (a device including RGB three colors): The CPL layer uses CP-5;

[0156] Device W-R4 (a device including RGB three colors): The CPL layer uses CP-8.

[0157] In the embodiments of the present application, the performance of the above devices was tested, and the test results are shown in Table 3.

[0158] Table 3

[0159]

[0160] Among them, taking the white light efficiency of CP-1 as 100%, the white light efficiencies of the remaining devices are all relative to the efficiency of W-R1. The white light brightness attenuation (30°) refers to the attenuation degree of the white light brightness of the device at a 30° viewing angle compared to the white light brightness at a 0° viewing angle.

[0161] In the compounds 1, 4, 6, and 8 provided by the embodiments of the present application, the substituents on the N of carbazole are all aryl groups without heteroatoms, and they have obvious advantages in terms of the attenuation of white light brightness. In compounds 3 and 10, a heteroatom is introduced into the substituents on the N of carbazole, which improves the white light efficiency and has a relatively large extinction coefficient, being beneficial to protecting the OLED device. The extinction coefficient of compound 21 is also relatively large, which is beneficial to protecting the OLED device. Compounds 35 and 38 have obvious advantages in terms of the attenuation of white light brightness. Compound 43 has the advantages of high white light efficiency and small white light attenuation.

[0162] However, in CP-4 and CP-8, since 2 heteroatoms are introduced into the substituents on the N of carbazole, the difference between blue light and red light is large. Although the refractive index is high, the improvement of the overall white light efficiency is small, and the attenuation of white light brightness is too large.

[0163] In summary, according to the general formulas (I) to (III), it can be seen that the carbazole group in the carbazole compounds provided by the present application can form a conjugated structure with other groups. This conjugated structure can reduce the refractive index sensitivity of the carbazole compound to a specific wavelength, reduce the refractive index difference from blue light to red light, and thus improve the white light efficiency.

[0164] The above description is only for the convenience of those skilled in the art to understand the technical solutions of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A carbazole compound, characterized in that, The carbazole compound has a general formula as described in any one of the following formulas (I) to (III): Wherein, Ar1 is selected from any one of the following groups: At least one of Ar2, Ar3, and Ar4 is: The rest are each independently selected from (1-a) to (1-g): Ar5 is selected from any one of the following groups: L1 to L5 are each independently selected from: a single bond, a phenylene group, a biphenylene group or a C6-C10 heteroarylene group; X is selected from O or S.

2. The carbazole compound according to claim 1, wherein The carbazole compound includes at least one deuterium substituent.

3. The carbazole compound according to claim 1, wherein The carbazole compound is any one of Compounds 1 to 44:

4. A light extraction material, characterized in that, The light extraction material includes the carbazole compound according to any one of Claims 1 to 3.

5. The light extraction material according to claim 4, wherein The refractive index of the light extraction material in the wavelength range of 460 nm to 620 nm is greater than 2.

6. The light extraction material according to claim 4, characterized in that, The glass transition temperature of the light extraction material is greater than or equal to 115 °C.

7. The light extraction material according to claim 4, wherein The extinction coefficient of the light extraction material at 450 nm is 0.

8. An organic electroluminescent device, characterized in that, The organic electroluminescent device includes an anode, a light-emitting functional layer, a cathode, and a light extraction layer which are sequentially stacked, wherein the light extraction layer includes the light extraction material according to any one of Claims 4 to 7.

9. The organic electroluminescent device according to claim 8, wherein, The light-emitting functional layer includes a hole transport unit, a light-emitting layer, and an electron transport unit, and the hole transport unit, the light-emitting layer, and the electron transport unit are sequentially stacked in the direction from the anode to the cathode; Wherein, the hole transport unit includes at least one of a hole injection layer, a hole transport layer, and an electron blocking layer; The electron transport unit includes at least one of a hole blocking layer, an electron transport layer, and an electron injection layer.

10. A display device, characterized in that, The display device includes the organic electroluminescent device according to any one of Claims 8 to 9.

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