An organic electroluminescent device

Abstract

An organic electroluminescence device comprises an anode, a cathode and an organic layer formed between the anode and the cathode, the organic layer comprising a hole injection layer, a hole transport region, an electron blocking layer, a light emitting region, an electron transport region; the hole transport region comprises a first material and a second material, the first material and the second material are sequentially evaporated to form two layers of hole transport layer, the first material is selected from the compound shown in formula 1; the second material is selected from the compound shown in formula 2. The first material with high refractive index is arranged as the first hole transport layer, the second material with low refractive index is arranged as the second hole transport layer, and the structure of the first material and the second material is limited respectively, through the comprehensive regulation of the material structure, the energy level and the refractive index of the double-layer hole transport layer, the limitations of single material or simple mixed material in the hole transport and the light emitting efficiency are overcome.

Description

Technical Field

[0001] This invention relates to the field of organic electroluminescence technology, and more specifically, to an organic electroluminescent device. Background Technology

[0002] Organic light-emitting diode (OLED) technology, as an emerging solid-state lighting and display technology, possesses advantages such as self-illumination, wide viewing angle, fast response speed, low heat generation, and ease of flexibility. It has shown enormous application potential in high-end displays and general lighting, and is considered the next generation of mainstream display technology after liquid crystal displays. Its basic working principle is as follows: Under the drive of an applied external electric field, electrons and holes are injected from the cathode and anode, respectively. After being transported through the electron transport layer and hole transport layer, they meet and recombine in the light-emitting layer to form excitons. The excitons then undergo radiative transitions and de-excitement, emitting photons.

[0003] To achieve high-efficiency, long-life OLED devices, their structure is typically designed as a multi-layer thin-film stack, including an anode, hole injection layer, hole transport layer, emissive layer, electron transport layer, electron injection layer, and cathode. Each of these functional layers has a specific function. The hole transport layer, located between the anode or hole injection layer and the emissive layer, has the core function of efficiently transporting holes from the anode to the emissive layer while simultaneously blocking electrons from migrating backward. This increases the recombination probability of holes and electrons in the emissive layer, which is crucial for reducing device driving voltage and improving luminous efficiency and stability.

[0004] Currently, research on OLEDs by those skilled in the art mainly focuses on how to further reduce driving voltage, improve luminous efficiency, and extend device lifespan. To achieve these performance breakthroughs, in addition to optimizing device structure and fabrication processes, developing novel high-performance organic functional materials is crucial.

[0005] In existing technologies, hole transport layers typically employ a single hole transport material. However, a single material often struggles to simultaneously meet all performance requirements. For instance, some materials with high hole mobility may have a highest occupied molecular orbital (HOMO) energy level that is mismatched with the energy levels of adjacent hole injection or emissive layer materials, leading to a hole injection barrier at the interface. The presence of this barrier causes a large accumulation of holes at the interface, not only increasing the device's driving voltage but also accelerating material aging due to interface polarization or Joule heating, severely impacting the device's lifespan.

[0006] To address the issue of poor energy level matching with single materials, existing technologies employ dual-material approaches. For example, patent CN110416422B discloses an organic electroluminescent device and a display including it. This approach involves co-evaporating two organic materials to form the hole transport layer of the organic electroluminescent device and defining the HOMO of the first and second organic materials. This reduces the potential barrier between the anode and the electron blocking layer interface, facilitating hole injection from the anode into the electron blocking layer. Furthermore, the organic film layer composed of two different materials effectively improves molecular arrangement and intermolecular interactions, resulting in higher film stability. However, the overall luminous efficiency of the hole transport layer as a combination of the two materials still needs improvement. Patent CN116761868A optimizes the light extraction efficiency of the organic electroluminescent device from the perspective of refractive index, but performance still needs further improvement. Therefore, there is an urgent need to develop more efficient and higher-performance hole transport layers and devices. Summary of the Invention

[0007] Based on existing technology, the present invention provides an organic electroluminescent device, including an anode, a cathode, and an organic layer formed between the anode and the cathode, wherein the organic layer includes a hole injection layer, a hole transport region, an electron blocking layer, a light-emitting region, and an electron transport region;

[0008] The hole transport region comprises a first material and a second material, which are sequentially vapor-deposited to form two hole transport layers. The first material is selected from the compound shown in Formula 1.

[0009] Where A, B, C, and D are each independently selected from substituted or unsubstituted C6-C30 aryl and substituted or unsubstituted C5-C30 heteroaryl groups, and the substituents are selected from: hydrogen, deuterium, fluorine, C1-C20 alkyl, C6-C12 aryl, and C5-C12 heteroaryl groups; the second material is selected from the compound shown in Formula 2.

[0010] R1-R31 are each independently selected from hydrogen, deuterium, fluorine, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C6-C12 aryl, substituted or unsubstituted C5-C12 heteroaryl, and the substituent is selected from hydrogen, deuterium, fluorine, and C1-C20 alkyl. R1-R9 are not all H at the same time.

[0011] As a preferred embodiment of the present invention, R1-R31 are each independently selected from H, D, methyl, deuterated methyl, and tert-butyl.

[0012] As a preferred embodiment of the present invention, A, B, C, and D are each independently selected from substituted or unsubstituted C6-C30 aryl groups, wherein the substituents are selected from hydrogen, deuterium, fluorine, C1-C20 alkyl, and C6-C12 aryl groups.

[0013] As a preferred embodiment of the present invention, A, B, C, and D are each independently selected from substituted or unsubstituted phenyl, naphthyl, biphenyl, anthraceneyl, and phenanthrene groups, wherein the substituents are selected from H, D, and phenyl.

[0014] As a preferred embodiment of the present invention, the first material is selected from compounds with the following structural formulas:

[0015] .

[0016] As a preferred embodiment of the present invention, the second material is selected from compounds with the following structural formulas:

[0017] .

[0018] In a preferred embodiment of the present invention, the first material is a diamine compound and the second material is a monoamine compound.

[0019] In a preferred embodiment of the present invention, the first material is a high-refractive-index hole transport material, and the first hole transport layer formed by the first material is disposed in close contact with the hole injection layer; the second material is a low-refractive-index hole transport material, and the second hole transport layer formed by the second material is disposed in close contact with the electron blocking layer.

[0020] As a preferred embodiment of the present invention, the refractive index of the first material is ≥1.9, and the refractive index of the second material is <1.9.

[0021] In a preferred embodiment of the present invention, the light-emitting region includes at least one light-emitting layer.

[0022] The beneficial effects of this invention are:

[0023] This invention employs a first material with a high refractive index as the first hole transport layer and a second material with a low refractive index as the second hole transport layer. The structures of both materials are specifically defined such that the energy levels of the second material satisfy the HOMO range of -5.3 eV to -5.6 eV, and the HOMO range of the first material is -5.4 eV to -5.7 eV, with |HOMO second material| < |HOMO first material|, thus constructing a stepped energy level structure. This design not only reduces the interfacial barrier between the anode and the hole transport layer, promoting effective hole injection, but also provides a smooth path for hole migration to the emitting layer through the stepped energy level transition, reducing hole accumulation and driving voltage between transport layers, thereby improving the device's luminous efficiency. By setting a first material layer with a high refractive index and a second material layer with a low refractive index, an effective refractive index gradient is formed within the device, optimizing the light distribution within the device, reducing total internal reflection losses, and significantly improving light extraction efficiency. At the same time, by combining the structural characteristics of two different host materials, the molecular arrangement and stacking of the organic film were improved through intermolecular synergy, based on the achievement of refractive index control. This enhanced the stability of the film layer and ensured that the electrical stability and lifetime of the device were improved simultaneously while the light extraction efficiency was increased. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the organic electroluminescent device provided by the present invention;

[0025] The numbers in the diagram represent: 1-anode, 2-hole injection layer, 3-first hole transport layer, 4-second hole transport layer, 5-electron blocking 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

[0026] Embodiments of various aspects are further illustrated and described below. It should be understood that the description herein 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 spirit and scope of this disclosure as defined by the appended claims.

[0027] As used herein, in the context of “substituted” or “unsubstituted”, the term “substituted” means that at least one hydrogen in the group is recoordinated with a deuterium, alkyl group, hydrocarbon derivative group, halogen, or cyano (-CN). The term “unsubstituted” means that at least one hydrogen in the group is not recoordinated with a deuterium, alkyl group, hydrocarbon derivative group, halogen, or cyano (-CN). Examples of alkyl or hydrocarbon derivative groups may include, but are not limited to, C1 to C30 alkyl, C2 to C30 alkenyl, C2 to C30 alkynyl, C6 to C30 aryl, C5 to C30 heteroaryl, C1 to C30 alkylamino, C6 to C30 aromaticamino, C6 to C30 heteroarylamino, C6 to C30 aryl heteroarylamino, etc.

[0028] In this invention, deuterium refers to a stable isotope of hydrogen, also known as heavy hydrogen, and its element symbol is D.

[0029] In this invention, an aromatic group refers to a monocyclic or fused polycyclic group with 6 to 30 carbon atoms, possessing a fully conjugated π-electron system. Non-limiting examples of aryl groups include phenyl, naphthyl, anthraceneyl, biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, benzo[1,12-bcd]furanyl, phenanthrene, etc.

[0030] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0031] Synthesis example 1:

[0032]

[0033] S1:

[0034] Procedure and post-treatment: Under nitrogen protection, compound 1-a (1 eq, 26.76 g, 267.55 g / mol, 0.1 mol), compound 1-b (1 eq, 16.92 g, 169.23 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 (1.83 eq, 8.1 ml, 915.7 g / mol, 0.002 mol), and toluene (300... 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 while hot through silica gel. Wash the filter cake with dichloromethane. Concentrate the filtrate under reduced pressure to dryness. Add ethanol (150 mL), heat to 80℃ and stir to dissolve. Cool to room temperature and crystallize for 5 hours. Filter to obtain a gray solid. Dry the solid at 85℃ to obtain compound 1-c (30.9 g, yield 86.8%). MS (EI): 356 (M+).

[0035] S2:

[0036] Procedure and post-treatment: Under nitrogen protection, compounds 1-c (1 eq, 30.9 g, 355.86 g / mol, 86.83 mmol), 1-b (1 eq, 14.69 g, 169.23 g / mol, 86.83 mmol), sodium tert-butoxide (1.5 eq, 12.52 g, 96.1 g / mol, 0.13 mol), XPhos (0.04 eq, 1.66 g, 476.72 g / mol, 3.4732 mmol), palladium acetate (0.39 eq, 8.1 ml, 224 g / mol, 1.7366 mmol), and toluene (300 mL) were dissolved in nitrogen. 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 through silica gel while hot. Wash the filter cake with dichloromethane. Concentrate the filtrate under reduced pressure to dryness. Add toluene (150ml) and heat to dissolve. Add ethanol (150ml) and cool to room temperature for 2 hours to crystallize. The filtered solid is recrystallized four times with toluene (150ml) + ethanol (150ml). The filtered solid is dried at 85℃ to obtain compound 1 (26.7 g, yield 62.93%). ESI-MS (m / z, [M+H]+): theoretical value 489.24, measured value 489.26. Elemental analysis results (molecular formula C36H28N2).

[0037] Synthesis example 2:

[0038]

[0039] S1:

[0040] S2:

[0041] The process and post-treatment were basically the same as in Example 1. The reaction yielded compound 2 (yield 61.83%). ESI-MS (m / z) ([M+H]+): theoretical value 641.30, measured value 641.29. Elemental analysis results (molecular formula C48H36N2).

[0042] Synthesis example 3:

[0043]

[0044] S1:

[0045] S2:

[0046] Process and post-processing: Basically the same as in Example 1, the reaction yielded compound 3 (yield 63%), ESI-MS (m / z) ([M+H]+): theoretical value 641.30, measured value 641.28, elemental analysis results (molecular formula C48H36N2).

[0047] Synthesis example 4:

[0048]

[0049] S1:

[0050] S2:

[0051] The process and post-treatment were basically the same as in Example 1. The reaction yielded compound 68 (yield 59.8%). ESI-MS (m / z) ([M+H]+): theoretical value 793.36, measured value 793.33. Elemental analysis results (molecular formula C60H44N2).

[0052] Synthesis example 5:

[0053]

[0054] S1:

[0055] S2:

[0056] The process and post-treatment were basically the same as in Example 1. The reaction yielded compound 5 (yield 61.5%). ESI-MS (m / z) ([M+H]+): theoretical value 589.27, measured value 589.26. Elemental analysis results (molecular formula C44H32N2).

[0057] Synthesis example 6:

[0058]

[0059] S1:

[0060] S2:

[0061] The process and post-treatment were basically the same as in Example 1. The reaction yielded compound 6 (yield 60.8%). ESI-MS (m / z) ([M+H]+): theoretical value 589.27, measured value 589.29. Elemental analysis results (molecular formula C44H32N2).

[0062] Synthesis example 7:

[0063]

[0064] S1:

[0065] S2:

[0066] The process and post-treatment were basically the same as in Example 1. The reaction yielded compound 7 (yield 61.3%). ESI-MS (m / z) ([M+H]+): theoretical value 639.28, measured value 639.26. Elemental analysis results (molecular formula C48H34N2).

[0067] Synthesis example 8:

[0068]

[0069] S1:

[0070] S2:

[0071] The process and post-treatment were basically the same as in Example 1. The reaction yielded compound 8 (yield 60.7%). ESI-MS (m / z) ([M+H]+): theoretical value 689.30, measured value 689.33. Elemental analysis results (molecular formula C52H36N2).

[0072] Synthesis example 9:

[0073]

[0074] S1:

[0075] S2:

[0076] The process and post-treatment were basically the same as in Example 1. The reaction yielded compound 9 (yield 61.2%). ESI-MS (m / z) ([M+H]+): theoretical value 589.27, measured value 589.30. Elemental analysis results (molecular formula C44H32N2).

[0077] Synthesis example 10:

[0078]

[0079] S1:

[0080] S2:

[0081] The process and post-treatment were basically the same as in Example 1. The reaction yielded compound 12 (yield 60.8%). ESI-MS (m / z) ([M+H]+): theoretical value 689.30, measured value 689.26. Elemental analysis results (molecular formula C52H36N2).

[0082] Synthesis example 11:

[0083]

[0084] S1:

[0085] Procedure and post-treatment: Under nitrogen protection, compound 101-a (1 eq, 27.32 g, 273.17 g / mol, 0.1 mol), compound 101-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), and tris(dibenzylacetone) palladium (0.02 eq, 1.83 g, 915.7 g / mol, 0.002 mol) were subjected to the following treatments: 1 mol) and toluene (300 mL) were added to the reaction flask. After the addition was complete, the temperature was raised to 110 °C and the mixture was stirred for 6 h. After the reaction was complete, the mixture was filtered through silica gel while hot. The filter cake was washed with dichloromethane. The filtrate was concentrated to dryness under reduced pressure. Ethanol (150 mL) was added and heated to 80 °C and stirred until dissolved. The mixture was then cooled to room temperature to crystallize for 5 h. The resulting gray solid was filtered and dried at 85 °C to give compound 1-c (28.5 g, yield 75.9%). MS (EI): 376 (M+).

[0086] S2:

[0087] Procedure and post-treatment: Under nitrogen protection, compound 1-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, 0.114 mol), 10% tri-tert-butylphosphine toluene solution (0.04 eq, 6.1 ml, 202.32 g / mol, 3.036 mmol), tris(dibenzylacetone)palladium (0.02 eq, 1.39 g, 915.7 g / mol, 1.518 mmol), and toluene (300 mL) were subjected to nitrogen treatment. 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 through silica gel while hot. 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 recrystallized twice with toluene (75 ml). The obtained solid is dried at 85℃ to obtain compound 101 (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 C53H39N).

[0088] Synthesis example 12:

[0089]

[0090] S1:

[0091] S2:

[0092] The process and post-treatment were basically the same as in Example 11. The reaction yielded compound 109 (yield 60.3%). ESI-MS (m / z) ([M+H]+): theoretical value 802.44, measured value 802.45. Elemental analysis results (molecular formula C61H55N).

[0093] Synthesis example 13:

[0094]

[0095] S1:

[0096] S2:

[0097] The process and post-treatment were basically the same as in Example 11. The reaction yielded compound 117 (yield 62%). ESI-MS (m / z) ([M+H]+): theoretical value 746.38, measured value 746.36. Elemental analysis results (molecular formula C57H47N).

[0098] Synthesis example 14:

[0099]

[0100] S1:

[0101] S2:

[0102] The process and post-treatment were basically the same as in Example 11. The reaction yielded compound 125 (yield 58.2%). ESI-MS (m / z) ([M+H]+): theoretical value 690.32, measured value 690.30. Elemental analysis results (molecular formula C53H39N).

[0103] Synthesis example 15:

[0104]

[0105] S1:

[0106] S2:

[0107] The process and post-treatment were basically the same as in Example 11. The reaction yielded compound 129 (yield 60.5%). ESI-MS (m / z) ([M+H]+): theoretical value 704.33, measured value 704.29. Elemental analysis results (molecular formula C54H41N).

[0108] Synthesis example 16:

[0109]

[0110] S1:

[0111] S2:

[0112] The process and post-treatment were basically the same as in Example 11. The reaction yielded compound 130 (yield 59.8%). ESI-MS (m / z) ([M+H]+): theoretical value 816.46, measured value 816.45. Elemental analysis results (molecular formula C62H57N).

[0113] Synthesis example 17:

[0114]

[0115] S1:

[0116] S2:

[0117] The process and post-treatment were basically the same as in Example 11. The reaction yielded compound 141 (yield 63.3%). ESI-MS (m / z) ([M+H]+): theoretical value 844.49, measured value 844.47. Elemental analysis results (molecular formula C64H61N).

[0118] Device performance testing:

[0119] Application Example 1:

[0120] 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.

[0121] A hole injection layer (HIL) is formed by depositing 10 nm of compound 1 of the present invention, doped with 3% NDP-9, on top of an ITO / Ag / ITO anode substrate.

[0122] A first hole transport layer (HTL1) is formed by vacuum evaporating 46 nm of the compound 1 of the present invention above the hole injection layer (HIL);

[0123] A second hole transport layer (HTL2) is formed by vacuum evaporating 52 nm of the compound 101 of the present invention above the first hole transport layer (HTL1);

[0124] EB-1 was vacuum-deposited above the second hole transport layer (HTL2) to form a hole blocking layer EBL with a thickness of 10 nm;

[0125] BH-1 was used as the main light-emitting material and BD-1 was used as the light-emitting dopant (BD-1 doping ratio 1%). They were co-deposited on the hole blocking layer EBL to form a first light-emitting layer (EML1) with a thickness of 5nm.

[0126] BH-2 was used as the main light-emitting material and BD-1 was used as the light-emitting dopant (BD-1 doping ratio 2%). They were co-deposited on the first light-emitting layer (EML1) to form a second light-emitting layer (EML2) with a thickness of 15nm.

[0127] HB-1 was deposited onto the second light-emitting layer (EML2) to obtain a hole blocking layer (HBL) with a thickness of 5 nm.

[0128] ET-1 and LiQ were co-deposited onto the hole blocking layer (HBL) in a 5:5 ratio to obtain an electron transport layer (ETL) with a thickness of 30 nm.

[0129] Ytterbium (Yb) is vapor-deposited onto a hole blocking layer (HBL) to form an electron injection layer (EIL) with a thickness of 1 nm;

[0130] Magnesium (Mg) and silver (Ag) are mixed in a 1:9 ratio and vapor-deposited onto the electron injection layer (EIL) to form a cathode with a thickness of 12 nm. A light extraction layer (CPL) with a thickness of 60 nm is then deposited on the cathode sealing layer. Finally, the device surface is sealed with a UV-curable adhesive and a sealing film containing a desiccant to protect the organic electroluminescent device from the influence of atmospheric oxygen or moisture. This completes the fabrication of the organic electroluminescent device.

[0131]

[0132] Comparative Example 1

[0133] The hole transport layer (98 nm) was prepared using compound 101 of this application to replace the first hole transport layer and the second hole transport layer in Application Example 1. At the same time, compound 1 of this application in the hole injection layer was replaced with compound 101 of this application, and an organic electroluminescent device was prepared accordingly to obtain Comparative Example 1.

[0134] Comparative Example 2

[0135] A hole transport layer (98 nm) was prepared using compound 1 of this application to replace the first and second hole transport layers in Application Example 1, and an organic electroluminescent device was prepared accordingly to obtain Comparative Example 2.

[0136] Comparative Example 3

[0137] Using HT-73 from CN116761868A as the first hole transport layer and HT-92 as the second hole transport layer, compound 1 in the hole injection layer was replaced with compound HT-73; and an organic electroluminescent device was prepared accordingly to obtain Comparative Example 3.

[0138] Comparative Example 4

[0139] Using HT-74 from CN116761868A as the first hole transport layer and HT-93 as the second hole transport layer, compound 1 in the hole injection layer was replaced with compound HT-74; and an organic electroluminescent device was prepared accordingly to obtain Comparative Example 4.

[0140] Comparative Example 5

[0141] Using HT-19 from CN116761868A as the first hole transport layer and HT-33 as the second hole transport layer, compound 1 in the hole injection layer was replaced with compound HT-19; and an organic electroluminescent device was prepared accordingly to obtain Comparative Example 5.

[0142] Comparative Example 6

[0143] The first hole transport layer (98 nm) was prepared by co-evaporation of HTⅠ-57 and HTⅡ-78 in CN110416422B at a ratio of 1:1, and the compound 1 in the hole injection layer was replaced with HTⅠ-57 and HTⅡ-78. Based on this, an organic electroluminescent device was prepared to obtain Comparative Example 6.

[0144] Application Example 2-10:

[0145] Compound 1 in the first hole transport layer and compound 1 in the hole injection layer of Application Example 1 were replaced with compounds 2, 3, 68, 5, 6, 7, 8, 9, and 12 of the present invention, respectively, and organic electroluminescent devices were prepared accordingly to obtain Application Examples 2-10.

[0146] Application Example 11-20:

[0147] Compound 109 of the present invention was used to replace compound 101 in the second hole transport layer in Application Example 1, and compounds 1, 2, 3, 68, 5, 6, 7, 8, 9, and 12 were used as part of the first hole transport layer and the hole injection layer, respectively, and organic electroluminescent devices were prepared accordingly to obtain Application Examples 11-20.

[0148] Application Examples 21-30:

[0149] Compound 117 of the present invention was used to replace compound 101 in the second hole transport layer in Application Example 1, and compounds 1, 2, 3, 68, 5, 6, 7, 8, 9, and 12 were used as part of the first hole transport layer and the hole injection layer, respectively, and organic electroluminescent devices were prepared accordingly to obtain Application Examples 21-30.

[0150] Application Examples 31-34:

[0151] Compound 101 in the second hole transport layer of Application Example 1 was replaced with compounds 125, 129, 130, and 141 of the present invention, respectively, and organic electroluminescent devices were prepared accordingly to obtain Application Examples 31-34.

[0152] Application Examples 35-38:

[0153] Compound 5 of the present invention was used to replace compound 1 in the first hole transport layer and the hole injection layer in Application Example 1, and compounds 125, 129, 130 and 141 of the present invention were used as the second hole transport layer, respectively, and organic electroluminescent devices were prepared accordingly to obtain Application Examples 35-38.

[0154] Application Examples 39-42:

[0155] Compound 8 of the present invention was used to replace compound 1 in the first hole transport layer and the hole injection layer in Application Example 1, and compounds 125, 129, 130 and 141 of the present invention were used as the second hole transport layer, respectively, and organic electroluminescent devices were prepared accordingly to obtain Application Examples 39-42.

[0156] Application examples 43-46:

[0157] Compound 12 of the present invention was used to replace compound 1 in the first hole transport layer and the hole injection layer in Application Example 1, and compounds 125, 129, 130 and 141 of the present invention were used as the second hole transport layer, respectively, and organic electroluminescent devices were prepared accordingly to obtain Application Examples 43-46.

[0158] Organic electroluminescent devices (OLEDs) prepared in Application Examples 1-46 and Control Examples 1-6 were tested respectively. Voltage, luminous efficiency, and luminous lifetime were measured for both. The luminous lifetime test yielded the luminous lifetime T97% data (the time it takes for the luminous brightness to decrease to 97% of its initial brightness). The testing equipment was a TEO OLED lifetime testing system. The test results are shown in Tables 1-1, 1-2, and 1-3.

[0159] Table 1-1

[0160]

[0161] Table 1-2

[0162]

[0163] Table 1-3

[0164]

[0165] As shown in Tables 1-1, 1-2, and 1-3 above, the present invention uses a first material with a high refractive index as the first hole transport layer and a second material with a low refractive index as the second hole transport layer. The structures of the first and second materials are also defined such that the energy levels of the second material satisfy the HOMO level of -5.3 eV to -5.6 eV, and the HOMO level of the first material is -5.4 eV to -5.7 eV, with |HOMO second material| < |HOMO first material|. This design not only reduces the interfacial barrier between the anode and the hole transport layer, promoting effective hole injection, but also provides a smooth path for hole migration to the light-emitting layer through the stepwise energy level change, reducing hole accumulation and driving voltage between the transport layers, thereby improving the device's luminous efficiency. By setting a first material layer with a high refractive index and a second material layer with a low refractive index, an effective refractive index gradient is formed inside the device, optimizing the light distribution inside the device, reducing total internal reflection loss, and significantly improving light extraction efficiency. Meanwhile, by combining the structural characteristics of two different host materials, and achieving refractive index control, the molecular arrangement and stacking of the organic film were improved through intermolecular synergy, enhancing film stability and ensuring that the electrical stability and lifetime of the device were simultaneously improved while light extraction efficiency was increased. This invention overcomes the limitations of single materials or simple mixtures of materials in terms of hole transport and luminous efficiency. The resulting organic electroluminescent device exhibits lower driving voltage, higher luminous efficiency (current efficiency and power efficiency), and longer lifespan, making it particularly suitable for high-performance, high-resolution display products.

Claims

1. An organic electroluminescent device, comprising an anode, a cathode, and an organic layer formed between the anode and the cathode, said organic layer comprising a hole injection layer, a hole transport region, an electron blocking layer, a light-emitting region, and an electron transport region; characterized in that, The hole transport region comprises a first material and a second material, which are sequentially vapor-deposited to form two hole transport layers. The first material is selected from the compound shown in Formula 1. wherein A, B, C, D are each independently selected from the group consisting of substituted or unsubstituted C6-C30aryl, substituted or unsubstituted C5-C30heteroaryl, the substituents being selected from the group consisting of hydrogen, deuterium, fluorine, C1-C20alkyl, C6-C12aryl, C5-C12heteroaryl; the second material is selected from the group consisting of compounds of formula 2: wherein R1-R31 are each independently selected from the group consisting of hydrogen, deuterium, fluorine, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C6-C12 aryl, substituted or unsubstituted C5-C12 heteroaryl, and the substituents are selected from the group consisting of hydrogen, deuterium, fluorine, C1-C20 alkyl, R1-R9 are not simultaneously H.

2. An organic electroluminescent device according to claim 1, characterized in that R1-R31 are each independently selected from H, D, methyl, deuterated methyl, and tert-butyl.

3. An organic electroluminescent device according to claim 1, wherein the organic electroluminescent device is a white light emitting device. A, B, C, and D are each independently selected from substituted or unsubstituted C6-C30 aryl groups, wherein the substituents are selected from hydrogen, deuterium, fluorine, C1-C20 alkyl, and C6-C12 aryl groups.

4. An organic electroluminescent device as described in claim 1, characterized in that, A, B, C, and D are each independently selected from substituted or unsubstituted phenyl, naphthyl, biphenyl, anthraceneyl, and phenanthrene groups, wherein the substituents are selected from H, D, and phenyl.

5. An organic electroluminescent device as described in claim 1, characterized in that, The first material is selected from compounds with the following structural formulas: 。 6. An organic electroluminescent device as described in claim 1, characterized in that, The second material is selected from compounds with the following structural formulas: 。 7. An organic electroluminescent device as described in claim 1, characterized in that, The first material is a diamine compound, and the second material is a monoamine compound.

8. An organic electroluminescent device as described in claim 1, characterized in that, The first material is a high-refractive-index hole transport material, and the first hole transport layer formed by the first material is disposed in close contact with the hole injection layer. The second material is a low-refractive-index hole transport material, and the second hole transport layer formed by the second material is disposed in close contact with the electron blocking layer.

9. An organic electroluminescent device as described in claim 1, characterized in that, The refractive index of the first material is ≥1.9, and the refractive index of the second material is <1.

9.

10. An organic electroluminescent device as described in claim 1, characterized in that, The luminescent region includes at least one luminescent layer.

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