A novel organic electroluminescent device

Abstract

This invention provides a novel organic electroluminescent device, comprising an anode, a cathode, and a light-emitting layer formed between the anode and the cathode. A hole injection layer and a hole transport region are provided between the anode and the light-emitting layer closest to the anode. The hole transport region comprises a first hole transport layer and a second hole transport layer. The material of the first hole transport layer is selected from compounds shown in Formula 1, and the material of the second hole transport layer is selected from compounds shown in Formula 2. Furthermore, the refractive index of the first hole transport layer material is greater than that of the second hole transport layer material. This invention optimizes the overall performance of the device by replacing the material of the first hole transport layer with a material of higher refractive index. Based on this, further defining the structural characteristics of the high-refractive-index material achieves lower power consumption and a longer device lifetime.

Description

Technical Field

[0001] This invention belongs to the field of electroluminescence technology, specifically a novel organic electroluminescent device. Background Technology

[0002] Organic electroluminescent devices consist of a cathode, an anode, and multiple organic film layers disposed between them, such as a hole injection layer, a hole transport layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer. In devices containing these film layers, when a voltage is applied between the two electrodes, holes are injected into the organic layer from the anode, and electrons are injected into the organic layer from the cathode. When holes and electrons meet, excitons are formed, and when the excitons re-transition to the ground state, light is emitted.

[0003] In the field of organic electroluminescence technology, the luminous efficiency of light-emitting devices has always been a focus of industry attention. The luminous efficiency of these devices is affected by various electrical and optical factors, such as: electrical factors including exciton generation efficiency, carrier injection, transport, and balance design; and optical factors including material spectral properties, optical microcavity structure, and photon extraction efficiency. Furthermore, in organic electroluminescence devices, due to the presence of organic layers and metal electrodes, photons generated by the light-emitting layer are easily confined within the organic layer, forming waveguide modes, or coupled to the metal / organic interface to excite surface plasmon polaritons, resulting in energy loss as heat dissipation and making it difficult to effectively extract energy from the device.

[0004] The above factors collectively affect the luminous efficiency of organic electroluminescent devices. Changes in device materials or structure may have either positive or negative effects on these factors. Therefore, achieving a comprehensive improvement in device performance through material selection and structural design is challenging. Invention document CN121968890A discloses a novel device structure and configuration; however, the sublimation temperature of its high-refractive-index material during the evaporation process failed to reach the ideal state, resulting in the device's performance not reaching its optimal level. Summary of the Invention

[0005] The technical objective of this invention is to design an improved scheme to optimize the material combination and structural composition of organic electroluminescent devices in order to improve device performance.

[0006] The technical solution provided by this invention includes the following aspects: In a first aspect, the present invention provides a novel organic electroluminescent device, comprising an anode, a cathode, and a light-emitting layer formed between the anode and the cathode, wherein a hole injection layer and a hole transport region are provided between the anode and the light-emitting layer closest to the anode, characterized in that: the hole transport region comprises a first hole transport layer and a second hole transport layer, wherein the material of the first hole transport layer is selected from the compound shown in Formula 1, the material of the second hole transport layer is selected from the compound shown in Formula 2, and the refractive index of the material of the first hole transport layer is greater than the refractive index of the material of the second hole transport layer; Formula 1 Formula 2 In Formula 1, Ar1, Ar2, and Ar3 are each independently selected from substituted or unsubstituted C6-C20 aryl groups; Ar4, Ar5, and Ar6 are each independently selected from H, D, substituted or unsubstituted C6-C20 aryl groups, wherein the C6-C20 aryl group includes phenyl, biphenyl, and fused ring groups formed by the fusion of no more than 3 cyclic groups, and the substituents of the C6-C20 aryl group are selected from one or more of deuterium, phenyl, and naphthyl; x, y, and z are each independently selected from integers from 0 to 7, and Ar7, Ar8, and Ar9 are each independently H or D; when Ar4, Ar5, Ar6, Ar7, Ar8, and Ar9 are all H, Ar1, Ar2, and Ar3 are not simultaneously phenyl or naphthyl. In Formula 2, R1-R31 are each independently selected from hydrogen, deuterium, deuterated or unsubstituted C1-C4 alkyl groups, and the number of groups selected from deuterated or unsubstituted C1-C4 alkyl groups in R1-R9 is ≤3; R 10 -R 24 The number of groups selected from C1-C4 alkyl groups, whether deuterated or unsubstituted, is ≤4; R 25 -R 31 The number of groups selected from C1-C4 alkyl groups that are either deuterated or unsubstituted is ≤3.

[0007] As an alternative embodiment of the present invention, R1-R9 contain at least one C1-C4 alkyl group that is either deuterated or unsubstituted.

[0008] As an optional embodiment of the present invention, the material of the hole injection layer comprises a first compound and a second compound with different structures, wherein the first compound is selected from compounds shown in Formula 1 or Formula 2, and the second compound is a dopant with a mass less than 5% of the mass of the first compound.

[0009] As an optional embodiment of the present invention, the first compound of the hole injection layer is the same as the compound selected by the first hole transport layer or the second hole transport layer.

[0010] As an optional embodiment of the present invention, Ar1, Ar2, and Ar3 are each independently selected from phenyl, deuterated phenyl, naphthyl-substituted phenyl, deuterated naphthyl-substituted phenyl, biphenyl, deuterated biphenyl, naphthyl, deuterated naphthyl, phenyl-substituted naphthyl, and deuterated phenyl-substituted naphthyl; Ar4, Ar5, and Ar6 are each independently selected from D, H, phenyl, and naphthyl; when Ar4, Ar5, and Ar6 are all H, Ar1, Ar2, and Ar3 are not simultaneously phenyl or naphthyl.

[0011] As an alternative embodiment of the present invention, Ar1, Ar2, and Ar3 are each independently selected from the following groups: When Ar4, Ar5, and Ar6 are all H, Ar1, Ar2, and Ar3 are not simultaneously phenyl or naphthyl.

[0012] As an alternative to the present invention, the compound represented by Formula 1 is selected from any of the following compounds: .

[0013] As an optional embodiment of the present invention, in Formula 2, the C1-C4 alkyl group that is deuterated or unsubstituted includes methyl, isopropyl, tert-butyl and deuterated methyl; in R1-R9, R1-R9 are all hydrogen, or 1 to 2 of R1-R3, R5 and R9 are selected from the C1-C4 alkyl group that is deuterated or unsubstituted, and the rest are hydrogen; R 10 -R 24 In the middle, R 10 -R 24 All are hydrogen, or R 10 -R 18 R 21 -R 24 One to four of them are selected from C1-C4 alkyl groups that are substituted with deuterium or unsubstituted, and the remainder are hydrogen or deuterium; R 25 -R 31 In the middle, R 25 -R 31 All are hydrogen, or R 25 R28 R 30 R 31 One or two of them are selected from C1-C4 alkyl groups that are substituted with deuterium or not, and the rest are hydrogen.

[0014] As an alternative to the present invention, the compound shown in Formula 2 is selected from any of the following compounds: .

[0015] As an optional embodiment of the present invention, a hole injection layer, a first hole transport layer, a second hole transport layer, a third hole transport layer, one or more light-emitting layers, a hole blocking layer, an electron transport layer and an electron injection layer are arranged sequentially between the anode and the cathode.

[0016] The beneficial effects of this invention are as follows: This invention optimizes the overall performance of the device by replacing the first hole transport layer material with a material of higher refractive index. Furthermore, the structural characteristics of the high-refractive-index material are further defined: each of the three diarylamine groups attached to the central benzene ring has an α-naphthyl group attached to it; and when Ar4, Ar5, and Ar6 are all H, Ar1, Ar2, and Ar3 are not simultaneously phenyl or naphthyl, meaning at least one of the three diarylamine groups has a transition group (i.e., avoiding direct attachment of all three N atoms to terminal groups). The high-refractive-index material achieves an ideal sublimation temperature during the evaporation process, resulting in better device performance. This novel device achieves lower power consumption and longer device lifetime. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the organic electroluminescent device provided by the present invention; Figure 2 This is the HPLC chromatogram of compound 2 synthesized in this invention; Figure 3 This is the NMR spectrum of compound 2 of the present invention; Figure 4 The TGA spectrum of compound 2 of this invention is shown below. Figure 4 It can be seen that the Td value of compound 2 is 467.98℃; Figure 5 The DSC spectrum of compound 2 of this invention is shown below. Figure 5 It can be seen that the Tm value of compound 2 is 276.37℃; Figure 6 This is the HPLC chromatogram of compound 61 of the present invention; Figure 7 This is the HPLC chromatogram of compound 69 of the present invention; Figure 1 The reference numerals in the figures represent: 1-anode, 2-hole injection layer, 3-first hole transport layer, 4-second hole transport layer, 5-third hole transport layer, 6-first light-emitting layer, 7-second light-emitting layer, 8-hole blocking layer, 9-electron transport layer, 10-electron injection layer, 11-cathode, 12-light extraction layer. Detailed Implementation

[0018] Embodiments of various aspects of the invention are further described and illustrated below. It should be understood that the following description is not intended to limit the claims to the specific aspects described. Rather, it is intended to cover substitutions, modifications, and equivalents that may be included within the scope defined by the appended claims. The term "substituted or unsubstituted" as used herein means that at least one hydrogen atom of a group is replaced by a substituent group such as deuterium, alkyl, or aryl. "Aryl" refers to a group containing one or more aromatic rings, which, unless otherwise specified, includes, but is not limited to, benzene, naphthalene, phenanthrene, fluorene, and acenaphthene.

[0019] The terms C6-C20 and C1-C4 in the text indicate that the modified group contains 6-18 and 1-4 carbon atoms, respectively. If the corresponding group can be substituted, the terms C6-C20 and C1-C4 do not need to include the number of carbon atoms of the substituent.

[0020] In this invention, "deuterium" refers to an isotope of hydrogen (H), also known as heavy hydrogen, with the element symbol D. The following describes the implementation scheme of this invention and verifies the advancement of the design scheme in more detail, combining material synthesis and testing. In the corresponding embodiments, unless specific conditions are specified, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0021] Synthesis example 1 Synthesis of Compound 1: Synthesis route: .

[0022] Process and post-processing: S1: Under nitrogen protection, compounds 1-a (1 eq, 20.44 g, 408.8 g / mol, 0.05 mol), 1-b (2.02 eq, 29.83 g, 295.39 g / mol, 0.101 mol), sodium tert-butoxide (2 eq, 9.61 g, 96.1 g / mol, 0.1 mol), DPPF (0.04 eq, 1.11 g, 554.38 g / mol, 0.002 mol), tris(dibenzylacetone)palladium (0.02 eq, 0.92 g, 915.7 g / mol, 0.001 mol), and toluene (300... The solution was added to the reaction flask in mL. After the addition was complete, the temperature was raised to 110℃ and the mixture was stirred for 18 h. After the reaction was complete, the mixture was filtered through silica gel while hot. The filter cake was washed with dichloromethane, and the filtrate was concentrated to dryness under reduced pressure. The solution was purified by recrystallization from toluene / ethanol to obtain compound 1-c (33.92 g, yield 91.2%). ESI-MS (m / z, [M+H]+): theoretical value 743.21, measured value 744.28.

[0023] S2: Under nitrogen protection, compound 1-c (1 eq, 32 g, 743.75 g / mol, 43 mmol), compound 1-d (1.02 eq, 9.62 g, 219.29 g / mol, 43.9 mmol), sodium tert-butoxide (2 eq, 8.26 g, 96.1 g / mol, 86 mmol), 10% tri-tert-butylphosphine toluene solution (0.04 eq, 3.5 ml, 202.32 g / mol, 1.72 mmol), tris(dibenzylacetone)palladium (0.02 eq, 0.79 g, 915.7 g / mol, 0.86 mmol), and toluene (300 mL) were added to a reaction flask. After the addition was complete, the temperature was raised to 110 °C and the reaction was stirred for 5 h. After the reaction was complete, ethanol (300 mL) and water (50 mL) were added. The solution was cooled to room temperature and stirred for 2 hours to induce crystallization. The mixture was then filtered, and the filter cake was recrystallized four times with o-dichlorobenzene. After filtration and drying, compound 1 (18.7 g, yield 49.3%) was obtained. ESI-MS (m / z, [M+H]+): theoretical value 882.38, measured value 882.31. Elemental analysis results (molecular formula C...)... 66 H 47 N3): Theoretical values: C, 89.87; H, 5.37; N, 4.76; Measured values: C, 89.86; H, 5.36; N, 4.78.

[0024] Synthesis example 2 Synthesis of Compound 2 Synthesis route: .

[0025] Process and post-processing: The preparation method was basically the same as that of Synthesis Example 1, and the reaction yielded compound 2 (yield 51.3%). ESI-MS (m / z, [M+H]+): theoretical value 958.42, measured value 958.41. Elemental analysis results (molecular formula C...) 72 H 51 N3): Theoretical values: C, 90.25; H, 5.36; N, 4.39; Measured values: C, 90.26; H, 5.37; N, 4.37.

[0026] Synthesis example 3 Synthesis of Compound 73 Synthesis route: .

[0027] Process and post-processing: S1: Under nitrogen protection, compound 73-a (1 eq, 27.32 g, 273.17 g / mol, 0.1 mol), compound 73-b (1 eq, 18.33 g, 183.25 g / mol, 0.1 mol), sodium tert-butoxide (1.5 eq, 14.42 g, 96.1 g / mol, 0.15 mol), 10% tri-tert-butylphosphine toluene solution (0.04 eq, 8.1 ml, 202.32 g / mol, 0.004 mol), tris(dibenzylacetone)palladium (0.02 eq, 1.83 g, 915.7 g / mol, 0.002 mol), and toluene (300 mL) were mixed. Add mL of the solution to the reaction flask. After the addition is complete, heat to 110℃ and stir for 6 hours. After the reaction is complete, filter the solution through silica gel while hot. Wash the filter cake with dichloromethane. Concentrate the filtrate under reduced pressure to dryness. Add ethanol (150 mL) and heat to 80℃. Stir until dissolved. Cool to room temperature and crystallize for 5 hours. Filter to obtain a gray solid. Dry the solid at 85℃ to obtain compound 73-c (28.5 g, yield 75.9%). MS (m / z): 376.21 ([M+H]+).

[0028] S2: Under nitrogen protection, compound 73-c (1 eq, 28.5 g, 375.51 g / mol, 75.9 mmol), compound 1-b (1 eq, 30 g, 395.3 g / mol, 75.9 mmol), sodium tert-butoxide (1.5 eq, 10.94 g, 96.1 g / mol, 0.11 mol), 10% tritert-tert-butylphosphine toluene solution (0.04 eq, 6.1 ml, 202.32 g / mol, 3.04 mmol), tris(dibenzylacetone)palladium (0.02 eq, 1.39 g, 915.7 g / mol, 1.52 mmol), and toluene (300 mL) were mixed. Add mL) to the reaction flask. After the addition is complete, heat to 110℃ and stir for 6 hours. After the reaction is complete, filter the mixture while hot through silica gel. Wash the filter cake with dichloromethane. Concentrate the filtrate under reduced pressure to dryness. Add toluene (150 ml) and heat to dissolve. Add ethanol (150 ml) and cool to room temperature to crystallize for 2 hours. The filtered solid is recrystallized twice with toluene (150 ml) + ethanol (150 ml). The filtered solid is then recrystallized twice with toluene (75 ml). The resulting solid is dried at 85℃ to give compound 73 (31.2 g, yield 59.6%). ESI-MS (m / z, [M+H]+): theoretical value 690.32, measured value 690.33. Elemental analysis results (molecular formula C) 53 H 39N): Theoretical value C, 92.27; N, 2.03; H, 5.70; Measured value C, 92.29; N, 2.02; H, 5.69.

[0029] Synthesis example 4 Synthesis of Compound 81 Synthesis route: .

[0030] Process and post-processing: The preparation method was basically the same as that of Synthesis Example 3. The reaction yielded compound 81 (yield 60.3%). ESI-MS (m / z) ([M+H]+): theoretical value 802.44, measured value 802.45. Elemental analysis results (molecular formula C) 61 H 55 Theoretical values: C, 91.34; H, 6.91; N, 1.75; Measured values: C, 91.32; H, 6.92; N, 1.76.

[0031] Synthesis example 5 Synthesis of Compound 89 Synthesis route: .

[0032] Process and post-processing: The preparation method was basically the same as that of Synthesis Example 3. The reaction yielded compound 89 (yield 62%). ESI-MS (m / z) ([M+H]+): theoretical value 746.38, measured value 746.36. Elemental analysis results (molecular formula C) 57 H 47 N): Theoretical values ​​C, 91.77; H, 6.35; N, 1.88; Measured values ​​C, 91.75; H, 6.36; N, 1.89.

[0033] Synthesis example 6 Synthesis of Compound 97 Synthesis route: .

[0034] Process and post-processing: The preparation method was basically the same as that of Synthesis Example 3. The reaction yielded compound 97 (yield 58.2%). ESI-MS (m / z) ([M+H]+): theoretical value 690.32, measured value 690.30. Elemental analysis results (molecular formula C) 53 H 39 Theoretical values: C, 92.27; H, 5.70; N, 2.03; Measured values: C, 92.25; H, 5.73; N, 2.02.

[0035] Synthesis Example 7 Synthesis of Compound 101 Synthesis route: .

[0036] Process and post-processing: The preparation method was basically the same as in Synthesis Example 3. The reaction yielded compound 101 (yield 60.5%). ESI-MS (m / z) ([M+H]+): theoretical value 704.33, measured value 704.29. Elemental analysis results (molecular formula C) 54 H 41 N): Theoretical values ​​C, 92.14; H, 5.87; N, 1.99; Measured values ​​C, 92.11; H, 5.88; N, 2.01.

[0037] Synthesis example 8 Synthesis of Compound 105 Synthesis route: .

[0038] Process and post-processing: The preparation method was basically the same as that in Synthesis Example 3. The reaction yielded compound 105 (yield 59.8%). ESI-MS (m / z) ([M+H]+): theoretical value 816.46, measured value 816.45. Elemental analysis results (molecular formula C) 62 H 57 N): Theoretical values ​​C, 91.24; H, 7.04; N, 1.72; Measured values ​​C, 91.17; H, 7.07; N, 1.76.

[0039] Synthesis example 9 Synthesis of Compound 113 Synthesis route: .

[0040] Process and post-processing: The preparation method was basically the same as that in Synthesis Example 3. The reaction yielded compound 113 (yield 63.3%). ESI-MS (m / z) ([M+H]+): theoretical value 844.49, measured value 844.47. Elemental analysis results (molecular formula C) 64 H 61 N): Theoretical value C, 91.06; H, 7.28; N, 1.66; Measured value C, 91.09; H, 7.30; N, 1.61.

[0041] Material property testing Thermogravimetric temperature (Td) and melting point (Tm) of compound 2 prepared by synthesis example 2 of this invention were tested. Td was measured at a mass loss of 5% under nitrogen atmosphere using a TGAN-1000 thermogravimetric analyzer at a nitrogen flow rate of 10 mL / min. The melting point (Tm) was determined by differential scanning calorimetry (DSC, Shinco DSCN-650) at a heating rate of 10 °C / min. The test results are as follows: Figure 4 , Figure 5 As shown, compound 2 has a melting point Tm of 276.37℃ and a thermogravimetric temperature Td of 467.98℃. The test results indicate that the compound prepared in the synthesis example of this invention has a high Td value and a suitable melting point. Therefore, the compound of this invention exhibits excellent thermal stability, meeting the requirements for vapor deposition and use as an organic electroluminescent compound.

[0042] Application Example 1 ITO / Ag / ITO was used as the anode substrate material for the reflective layer, and its surface was treated sequentially with water, acetone, and N2 ions. A 10 nm thick compound 1 doped with 3% NDP-9 is deposited on top of an ITO / Ag / ITO anode substrate to form a hole injection layer (HIL). A first hole transport layer (HTL1) is formed by vacuum evaporating 46 nm of compound 1 above the hole injection layer (HIL); A second hole transport layer (HTL2) is formed by vacuum evaporating 52 nm of compound 73 above the first hole transport layer (HTL1); EB-1 was vacuum-deposited above the second hole transport layer (HTL2) to form a third hole transport layer EBL with a thickness of 10 nm. BH-1 was used as the host material for luminescence, and BD-1 was used as the dopant material for luminescence (the doping ratio of BD-1 was 1% of the mass of the host material BH-1). They were co-deposited to form a first luminescent layer (EML1) with a thickness of 5 nm on the third hole transport layer (EBL). BH-2 was used as the main luminescent material and BD-1 was used as the luminescent dopant (BD-1 was doped at 2% of the mass of the main material BH-2) and were co-deposited to form a second luminescent layer (EML2) with a thickness of 15 nm on the first luminescent layer (EML1). HB-1 was deposited onto the second light-emitting layer (EML2) to obtain a hole blocking layer (HBL) with a thickness of 5 nm. ET-1 and LiQ were co-deposited onto the hole blocking layer (HBL) at a mass ratio of 5:5 to obtain an electron transport layer (ETL) with a thickness of 30 nm; ytterbium (Yb) was deposited onto the electron transport layer (ETL) to form an electron injection layer (EIL) with a thickness of 1 nm. Magnesium (Mg) and silver (Ag) are mixed in a 1:9 mass ratio and vapor-deposited onto the electron injection layer (EIL) to form a 12 nm thick cathode. A 60 nm thick CP-2 layer is deposited at the cathode sealing layer to form a light extraction layer (CPL). Finally, the device surface is sealed with a UV-curable adhesive and a sealing cap containing a desiccant to protect the organic electroluminescent device from atmospheric oxygen or moisture. This completes the fabrication of the organic electroluminescent device.

[0043] Table 1

[0044] Application Example 2-7 Based on Application Example 1, the organic electroluminescent devices of Application Examples 2-7 were prepared by replacing compound 73 of the second hole transport layer with compounds 81, 89, 97, 101, 105, and 113, respectively, under the same preparation conditions as Application Example 1.

[0045] Application Example 8 Based on Application Example 1, compound 1 in the hole injection layer and the first hole transport layer was replaced with compound 2, and the organic electroluminescent device of Application Example 8 was prepared under the same preparation conditions as Application Example 1.

[0046] Application Example 9-14 Based on Application Example 8, the organic electroluminescent devices of Application Examples 9-14 were prepared by replacing compound 73 of the second hole transport layer with compounds 81, 89, 97, 101, 105, and 113, respectively, under the same preparation conditions as Application Example 8.

[0047] Comparative Examples 1-5 Based on Application Example 1, compound 1 in the hole injection layer and the first hole transport layer was replaced with compounds D1, D2, D3, D4, and D5, respectively. Under the same preparation conditions as Application Example 1, organic electroluminescent devices of Comparative Examples 1-5 were prepared.

[0048] Comparative Examples 6-10 Based on Application Example 1, compound 1 in the hole injection layer and the first hole transport layer was replaced with compounds D1, D2, D3, D4, and D5, and compound 73 in the second hole transport layer was replaced with compound 81. Under the same preparation conditions as Application Example 1, organic electroluminescent devices of Comparative Examples 6-10 were prepared respectively.

[0049] Comparative Examples 11-15 Based on Application Example 1, compound 1 in the hole injection layer and the first hole transport layer was replaced with compounds D1, D2, D3, D4, and D5, and compound 73 in the second hole transport layer was replaced with compound 101. Under the same preparation conditions as Application Example 1, organic electroluminescent devices of Comparative Examples 11-15 were prepared respectively.

[0050] Comparative Example 16 Based on Application Example 1, compound 1 in the hole injection layer was replaced with compound D1, and a hole transport layer with a thickness of 98 nm was deposited using compound 73 to replace the first hole transport layer (HTL1) and the second hole transport layer (HTL2) in Application Example 1. Under the same conditions as Application Example 1, an organic electroluminescent device of Comparative Example 16 was prepared.

[0051]

[0052] Device Testing The characteristics of the organic electroluminescent devices prepared in Comparative Examples 1-16 and Application Examples 1-14 were tested respectively, including the start-up voltage, luminous efficiency and luminous lifetime. The luminous lifetime was T97% data (the relative time ratio of the device luminous brightness to 97% of the initial brightness, with Comparative Example 16 as the reference).

[0053] The test results are shown in Tables 2-1 and 2-2 below: Table 2-1

[0054] Table 2-2 Based on the test data above, it can be seen that, within the scope of compounds defined in this invention, compared with Comparative Example 16, this invention can effectively improve hole injection and transport capabilities and reduce device startup voltage by replacing the first hole transport layer material with a material with a higher refractive index, thereby significantly reducing power consumption; at the same time, the luminous efficiency is significantly improved, and the device operating life also shows an extended trend, thus achieving optimization of the overall device performance.

[0055] Building upon this, the structural characteristics of the high-refractive-index material are further defined: each of the three diarylamine groups attached to the central benzene ring is linked to an α-naphthyl group, and at least one of the three diarylamine groups has a transition group (i.e., avoiding direct connection of all three N atoms to the terminal group). This structural design, on the one hand, utilizes the large conjugated planarity of the α-naphthyl group to enhance intermolecular packing and hole mobility; on the other hand, by introducing a transition group, it regulates the spatial configuration and energy level distribution of the molecule, suppressing excessive aggregation or crystallization, and improving film morphology and interfacial contact performance. The high-refractive-index material achieves an ideal sublimation temperature during the evaporation process, thus exhibiting better device performance, thereby further improving luminous efficiency, reducing start-up voltage, achieving lower power consumption, and longer device lifetime. Compared with materials not employing this specific structure (such as Comparative Examples 1-15), the devices in Application Examples 1-14 of this invention exhibit superior overall performance in terms of efficiency, voltage, power consumption, and lifetime.

[0056] In this invention, the NDP-9 content in the hole injection layer can generally be controlled to be below 5% of the mass of the hole injection layer bulk material, preferably a doping ratio of 1%-3%.

[0057] In the structural design of the hole transport layer (HTL) of this invention, the refractive index of the first hole transport layer is higher than that of the second hole transport layer. In the above test, the refractive index is the value at a wavelength of 460 nm. As a more preferred embodiment of this invention, specific compound combinations can be matched according to the scheme of "refractive index of the first hole transport layer - refractive index of the second hole transport layer ≥ 0.06".

[0058] This invention effectively controls the optical field distribution inside the device by optimizing the combination of hole transport layer materials and optical structure without affecting carrier transport performance and material stability, thereby reducing ineffective photon loss, improving the overall light extraction efficiency of the device, and giving the device a lower start-up voltage and better luminescence lifetime.

[0059] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A novel organic electroluminescent device, comprising an anode, a cathode, and a light-emitting layer formed between the anode and the cathode, wherein a hole injection layer and a hole transport region are provided between the anode and the light-emitting layer closest to the anode, characterized in that: The hole transport region includes a first hole transport layer and a second hole transport layer. The material of the first hole transport layer is selected from the compound shown in Formula 1, and the material of the second hole transport layer is selected from the compound shown in Formula 2. The refractive index of the material of the first hole transport layer is greater than the refractive index of the material of the second hole transport layer. Formula 1 Formula 2 In Formula 1, Ar1, Ar2, and Ar3 are each independently selected from substituted or unsubstituted C6-C20 aryl groups; Ar4, Ar5, and Ar6 are each independently selected from H, D, substituted or unsubstituted C6-C20 aryl groups, wherein the C6-C20 aryl group includes phenyl, biphenyl, and fused ring groups formed by the fusion of no more than 3 cyclic groups, and the substituents of the C6-C20 aryl group are selected from one or more of deuterium, phenyl, and naphthyl; x, y, and z are each independently selected from integers from 0 to 7, and Ar7, Ar8, and Ar9 are each independently H or D; when Ar4, Ar5, Ar6, Ar7, Ar8, and Ar9 are all H, Ar1, Ar2, and Ar3 are not simultaneously phenyl or naphthyl. In Equation 2, R1-R 31 Each group is independently selected from hydrogen, deuterium, deuterated or unsubstituted C1-C4 alkyl groups, and the number of groups selected from deuterated or unsubstituted C1-C4 alkyl groups in R1-R9 is ≤3; R 10 -R 24 The number of groups selected from C1-C4 alkyl groups, whether deuterated or unsubstituted, is ≤4; R 25 -R 31 The number of groups selected from C1-C4 alkyl groups that are either deuterated or unsubstituted is ≤3.

2. The novel organic electroluminescent device as described in claim 1, characterized in that, R1-R9 contain at least one C1-C4 alkyl group that is either deuterated or unsubstituted.

3. The novel organic electroluminescent device as described in claim 1, characterized in that, The hole injection layer is made of a first compound and a second compound with different structures, wherein the first compound is selected from compounds shown in Formula 1 or Formula 2, and the second compound is a dopant with a mass less than 5% of the mass of the first compound.

4. A novel organic electroluminescent device as described in claim 1, characterized in that, The first compound of the hole injection layer is the same as the compound selected for the first hole transport layer or the second hole transport layer.

5. A novel organic electroluminescent device as described in claim 1, characterized in that, Ar1, Ar2, and Ar3 are each independently selected from phenyl, deuterated phenyl, naphthyl-substituted phenyl, deuterated naphthyl-substituted phenyl, biphenyl, deuterated biphenyl, naphthyl, deuterated naphthyl, phenyl-substituted naphthyl, and deuterated phenyl-substituted naphthyl; Ar4, Ar5, and Ar6 are each independently selected from D, H, phenyl, and naphthyl; when Ar4, Ar5, and Ar6 are all H, Ar1, Ar2, and Ar3 are not simultaneously phenyl or naphthyl.

6. A novel organic electroluminescent device as described in claim 1, characterized in that, Ar1, Ar2, and Ar3 are each independently selected from the following groups: When Ar4, Ar5, and Ar6 are all H, Ar1, Ar2, and Ar3 are not simultaneously phenyl or naphthyl.

7. A novel organic electroluminescent device as described in claim 1, characterized in that, The compound shown in Formula 1 is selected from any one of the following compounds: 。 8. A novel organic electroluminescent device as described in claim 1, characterized in that, In Formula 2, the C1-C4 alkyl group that is substituted or unsubstituted with deuterium includes methyl, isopropyl, tert-butyl and deuterated methyl; in R1-R9, R1-R9 are all hydrogen, or 1 to 2 of R1-R3, R5 and R9 are selected from the C1-C4 alkyl group that is substituted or unsubstituted with deuterium, and the rest are hydrogen. R 10 -R 24 In the middle, R 10 -R 24 All are hydrogen, or R 10 -R 18 R 21 -R 24 One to four of them are selected from C1-C4 alkyl groups that are substituted with deuterium or unsubstituted, and the remainder are hydrogen or deuterium; R 25 -R 31 In the middle, R 25 -R 31 All are hydrogen, or R 25 R 28 R 30 R 31 One or two of them are selected from C1-C4 alkyl groups that are substituted with deuterium or not, and the rest are hydrogen.

9. A novel organic electroluminescent device as described in claim 1, characterized in that, The compound shown in Formula 2 is selected from any one of the following compounds: 。 10. A novel organic electroluminescent device according to any one of claims 1-9, characterized in that, Between the anode and the cathode are arranged sequentially a hole injection layer, a first hole transport layer, a second hole transport layer, a third hole transport layer, one or more light-emitting layers, a hole blocking layer, an electron transport layer, and an electron injection layer.

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