Hole blocking layer material and preparation method and application thereof

Abstract

The invention provides a hole blocking layer material and a preparation method and application thereof, and belongs to the technical field of organic electroluminescent materials, the hole blocking layer material has a structure as shown in a formula 1, and the hole blocking layer material is applied to an organic electroluminescent device. The characteristics of low driving voltage, high luminous efficiency and long service life are shown, and the comprehensive performance of the device is excellent.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent materials technology, specifically relating to a hole blocking layer material, its preparation method, and its application. Background Technology

[0002] Organic light-emitting diodes (OLEDs), as core components of next-generation flat panel displays and solid-state lighting technologies, fundamentally depend on the precise balance of carrier injection, transport, and recombination processes within the device for key performance characteristics such as luminous efficiency, lifespan, and color purity. In a typical multilayer device structure, the hole blocking layer, located between the emissive layer and the electron transport layer, plays a crucial role. Its core function is to prevent holes from diffusing towards the electron transport layer or the cathode, thereby enabling electrons and holes to efficiently recombine in the emissive layer to form excitons, thus ensuring the device's high luminous efficiency, low driving voltage, and long lifespan.

[0003] However, most current research on hole-blocking materials focuses on optimizing single performance parameters, failing to achieve synergistic breakthroughs in multi-dimensional properties. Therefore, developing a hole-blocking material that achieves synergistic breakthroughs in multi-dimensional properties is particularly important. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a hole-blocking layer material, its preparation method, and its application. When this hole-blocking layer material is applied to organic electroluminescent devices, it exhibits characteristics such as low driving voltage, high luminous efficiency, and long lifetime, resulting in superior overall device performance.

[0005] To achieve this objective, the present invention employs the following technical solution: On one hand, the present invention provides a hole-blocking layer material having the structure shown in Formula 1: ; in, R is selected from the following groups: unsubstituted or deuterated groups: ; An asterisk (*) indicates the connection position of a functional group. n can be 0, 1, or 2. When n is 2, the two Rs can be the same or different. D m The number of times the structure within the square brackets is deuterated is m, where m is an integer from 0 to 45 (e.g., 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 40, 42, or 45, etc.). Ar and Ar1 are independently selected from unsubstituted or substituted C6-C. 24aryl, unsubstituted or substituted C containing one heteroatom of O, S or N. 12 -C 18 Heteroaryl, unsubstituted or substituted 9,9-dimethylfluorenyl.

[0006] In this invention, the C 12 -C 18 It can be C 12 C 13 C 15 C 16 Or C 18 wait.

[0007] Furthermore, the hole-blocking layer material has any of the following structures: .

[0008] Furthermore, Ar and Ar1 are independently selected from the following groups that are unsubstituted or deuterated: , An asterisk indicates the junction between a group and a carbon atom on a ring.

[0009] In this invention, the term "unsubstituted or substituted" means substituted by one, two or more groups selected from the following, up to the maximum number of substitutable groups: deuterium, phenyl, phenyl fully or partially substituted with deuterium, or without any substituents; "unsubstituted or deuterated" means that the group is substituted by one, two or more, up to the maximum number of substitutable groups of deuterium, or without any substituents.

[0010] More specifically, the hole-blocking layer material is selected from any one of the following compounds: .

[0011] Synthesis method: Reactant a (1.0 eq), reactant b (1.0-1.3 eq), and potassium acetate (2.0-3.0 eq) were added to a reaction flask, followed by the addition of 1,4-dioxane. The mixture was purged three times. Under nitrogen protection, palladium catalyst (0.02-0.15 eq) and phosphine ligand (0.1-0.2 eq) were added, and the mixture was heated to 80-100 °C and reacted for 6-10 h. The mixture was filtered hot using diatomaceous earth. After the filtrate cooled to room temperature, water was added to wash the filtrate. The organic phase was separated, and the aqueous phase was extracted with ethyl acetate. The combined organic layers were then dried with magnesium sulfate and purified by column chromatography to obtain intermediate c. Reactant d (1.0 eq) and intermediate c (1.0-1.3 eq) were added to a reaction flask, followed by a mixed solution of toluene, ethanol, and water (volume ratio 3:1:1), then palladium catalyst (0.01-0.02 eq) and base (2.0-3.0 eq). The mixture was heated to 80-120 °C and refluxed for 6-18 hours. The mixture was filtered while hot using diatomaceous earth. After the filtrate was cooled to room temperature, water was added to wash the filtrate. The organic phase was separated, and the aqueous phase was extracted with ethyl acetate. The combined organic layers were then dried with magnesium sulfate and purified by column chromatography to obtain Formula 1.

[0012] in, D m1 The number of deuterated substitutions performed on the structure within the square brackets is m1, where m1 is an integer from 0 to 35 (e.g., 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 30, 33, or 35, etc.). D m2 The number of times the structure within the square brackets is deuterated is m2, where m2 is an integer from 0 to 10 (e.g., 0, 1, 2, 3, 4, 5, 6, 7, 8, or 10, etc.). Hal and Hal1 are selected from F, Cl, Br, and I; R, n, D m Ar and Ar1 have the definitions given above; The base can be: K2CO3 (potassium carbonate), K3PO4 (potassium phosphate), Na2CO3 (sodium carbonate), CsF (cesium fluoride), Cs2CO3 (cesium carbonate) or t-BuONa (sodium tert-butoxide). Palladium catalysts can be: Pd2(dba)3 (tris(dibenzylacetone)palladium), Pd(PPh3)4 (tetra(triphenylphosphine)palladium), PdCl2 (palladium dichloride), PdCl2(dppf) ([1,1'-bis(diphenylphosphine)ferrocene]palladium dichloride), Pd(OAc)2 (palladium acetate), Pd(PPh3)2Cl2 (bis(triphenylphosphine)palladium dichloride); Phosphine ligands can be: P(t-Bu)3 (tri-tert-butylphosphine), X-phos (2-cyclohexylphosphine-2,4,6-triisopropylbiphenyl), PET3 (triethylphosphine), PMe3 (trimethylphosphine), PPh3 (triphenylphosphine), KPPh2 (potassium diphenylphosphate) or P(t-Bu)2Cl (di-tert-butylphosphine chloride).

[0013] On the other hand, the present invention provides an organic electroluminescent device, the organic electroluminescent device comprising an anode, a cathode and an organic layer disposed between the anode and the cathode, the organic layer comprising a hole blocking layer comprising the hole blocking layer material as described above.

[0014] Preferably, the organic layer further includes at least one of a hole injection layer, a hole transport layer, a light-emitting auxiliary layer, a light-emitting layer, an electron transport layer, or an electron injection layer.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a core structure with "benzene-naphthalene-benzene" as the bridging group between triazine and fluorene, wherein the substitution positions on the naphthalene ring are fixed at positions 1 and 8, which enhances the stericity of the molecule, making the formed film less prone to crystallization and maintaining a uniform, amorphous state. The resulting device can operate stably for extended periods, extending its lifespan. The appropriately sized conjugated molecular units conforming to the general formula of this invention can effectively transfer electrons, reducing the driving voltage; simultaneously, they possess good hole-blocking capabilities, enhancing exciton recombination rates and improving the luminous efficiency of the device. Attached Figure Description

[0016] Figure 1 This is the 1H NMR spectrum of compound 3 in Example 1 of the present invention. Detailed Implementation

[0017] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0018] Example 1: Reactant 3-a (1.0 eq, CAS No.: 2750379-74-7), reactant b (1.1 eq), and potassium acetate (2.0 eq) were added to a reaction flask, followed by the addition of 1,4-dioxane. The mixture was purged three times, and under nitrogen protection, Pd(PPh3)4 (0.02 eq) and X-Phos (0.1 eq) were added. The mixture was heated to 90 °C and reacted for 6 h. The mixture was filtered hot using diatomaceous earth. After the filtrate cooled to room temperature, water was added to wash the filtrate. The organic phase was separated, and the aqueous phase was extracted with ethyl acetate. The combined organic layers were then dried with magnesium sulfate and purified by column chromatography to obtain intermediate 3-c. Reactant 3-d (1.0 eq, CAS No.: 3091378-79-6) and intermediate 3-c (1.2 eq) were added to a reaction flask, followed by a mixed solution of toluene, ethanol, and water (volume ratio 3:1:1), Pd(PPh3)4 (0.01 eq) and t-BuONa (2.0 eq). The mixture was heated to 90 °C and refluxed for 8 hours. The mixture was filtered while hot using diatomaceous earth. After the filtrate was cooled to room temperature, water was added to wash the filtrate. The organic phase was separated and the aqueous phase was extracted with ethyl acetate. The combined organic layers were then dried with magnesium sulfate and purified by column chromatography to obtain compound 3 (yield: 73.4%).

[0019] Characterization: HPLC purity: >99.8%.

[0020] Mass spectrometry test: Waters XEVO TQD mass spectrometer, using ESI source.

[0021] Test value (ESI, m / Z): [M+H] + : 765.45.

[0022] Elemental analysis: Test values: C, 89.34; H, 5.17; N, 5.51.

[0023] The proton NMR spectrum of compound 3 is as follows: Figure 1 As shown.

[0024] Other compounds in this application can be obtained by referring to the synthesis methods of the synthesis examples listed above, so they will not be listed one by one here.

[0025] Device Example 1: Fabrication of Green Organic Light Emitting Device a. ITO Anode: An ITO (Indium Tin Oxide)-Ag-ITO (Indium Tin Oxide) glass substrate with a coating thickness of 150nm is cleaned twice in distilled water, ultrasonically cleaned for 30 minutes, then repeatedly cleaned twice with distilled water, ultrasonically cleaned for 10 minutes, and baked in a vacuum oven at 220℃ for 2 hours. After baking, it is cooled before use. Using this substrate as the anode, the device is deposited using a vapor deposition machine, and other functional layers are deposited sequentially on it. b. HIL (hole injection layer): Hole injection layer materials HT and P-dopant are vacuum-deposited at a deposition rate of 1 Å / s, wherein the deposition rate ratio of HT and P-dopant is 97:3, and the thickness is 10 nm. c. HTL (Hole Transport Layer): A 130 nm HT layer is vacuum-deposited on the hole injection layer at a deposition rate of 1.5 Å / s as a hole transport layer. d. Prime (light-emitting auxiliary layer): A 5nm Prime layer is vacuum-deposited on the hole transport layer at a deposition rate of 0.5Å / s as a light-emitting auxiliary layer; e. EML (Light Emitting Layer): Then, on the above-mentioned light-emitting auxiliary layer, a host material and a dopant material with a total thickness of 30 nm are vacuum-deposited at a deposition rate of 1 Å / s as the light-emitting layer, wherein the deposition rate ratio of the host to the dopant is 97:3. f. HB (hole blocking layer): Compound 3 of the present invention with a thickness of 5.0 nm was vacuum-deposited at a deposition rate of 0.5 Å / s as a hole blocking layer. g. ETL (Electron Transport Layer): ET and Liq layers with a thickness of 30 nm were vacuum-deposited at a deposition rate of 1 Å / s. The deposition rate ratio of ET to Liq was 1:1. h. EIL (Electron Injection Layer): A 1.0 nm Yb film is deposited at a deposition rate of 0.5 Å / s to form an electron injection layer; i. Cathode: Magnesium and silver are deposited at a deposition rate of 1 Å / s for 13 nm, with a deposition rate ratio of 1:9, to obtain the OLED device.

[0026] j. Optical extraction layer: A CPL with a thickness of 65 nm is vacuum-deposited on the cathode at a deposition rate of 1 Å / s as the optical extraction layer.

[0027] k. Encapsulate the vapor-deposited substrate. First, use a coating equipment to coat the cleaned cover plate with UV adhesive. Then, move the coated cover plate to the lamination section, place the vapor-deposited substrate on the top of the cover plate, and finally, laminate the substrate and cover plate together using a bonding equipment, while simultaneously curing the UV adhesive by light.

[0028] The material structure used in the above device is as follows: .

[0029] Device Examples 2-102: Replace compound 3 in Device Example 1 with the materials in Device Examples 2-102 in Table 1.

[0030] Device Comparison Examples 1-16: Referring to the preparation method provided in Device Example 1 above, Comparative Compounds 1-16 were used to replace Compound 3 in Device Example 1, and were respectively referred to as Device Comparative Examples 1-16. The chemical structural formulas of Comparative Compounds 1-16 are as follows: The driving voltage, luminous efficiency, and lifetime of the organic electroluminescent devices obtained in Examples 1-102 and Comparative Examples 1-16 were characterized at a brightness of 1000 nits. The test results are shown in Table 1 below.

[0031] Table 1 Device Test Results Note: In blue top-emitting devices, current efficiency is greatly affected by chromaticity. Therefore, the influence of chromaticity on efficiency is taken into account, and the ratio of luminous efficiency to CIEy is defined as the BI value, i.e., BI = (cd / A) / CIEy.

[0032] As can be seen from Table 1, the organic electroluminescent devices prepared using the light-emitting layer substrate provided by the present invention in Examples 1-102 exhibit lower driving voltage (below 3.42V), higher luminous efficiency (above 8.4 cd / A), and longer lifetime (T95 above 450h) compared with the devices prepared using comparative compounds 1-16, and the overall performance of the devices is superior.

[0033] Among them, Comparative Compound 1 and Compound 1 of the present invention are parallel comparative examples. In the present invention, the naphthalene is substituted at positions 1 and 8, which enhances the stereochemistry of the molecule, resulting in a higher glass transition temperature. The formed film is less prone to crystallization and can maintain a uniform, amorphous state. The prepared device can operate stably for a long time and has a longer service life. Similarly, there are Comparative Compound 3 and Compound 12 of the present invention, Comparative Compound 5 and Compound 23 of the present invention, Comparative Compound 8 and Compound 35 of the present invention, Comparative Compound 10 and Compound 39 of the present invention, Comparative Compound 13 and Compound 39 of the present invention, Comparative Compound 14 and Compound 59 of the present invention, and Comparative Compound 16 and Compound 100 of the present invention.

[0034] Comparative compound 2 and compound 1 of this invention are parallel comparative examples, differing only in the group attached to the phenylene group on one side of the compound; in comparative compound 2, it is benzonaphthofuran, while in this invention, it is 9-methyl-9-phenylfluorene. Compared to the large planar structure of benzonaphthofuran, the fluorene at the 9-position in this invention introduces a steric hindrance effect through the methyl and phenyl groups, which can suppress recrystallization of the molecule in the thin film state, ultimately increasing the device lifetime. Similarly, there are comparative compound 6 compared to compound 35 of this invention, comparative compound 9 compared to compound 36 of this invention, and comparative compound 15 compared to compound 87 of this invention.

[0035] Comparative compound 4 and compound 23 in this invention are parallel comparative examples. Compared with the substitution of the naphthalene ring at positions 1 and 8 in this invention, the naphthalene ring substitution in comparative compound 4 has less steric hindrance. At the same time, the overall molecule has two more phenyl groups than compound 23 in this invention, resulting in a larger overall molecular weight, higher evaporation temperature, poorer molecular stability, and shorter device life.

[0036] Comparative compound 7 and compound 35 of this invention are parallel comparative examples, the only difference being that in comparative compound 7, a carbazole group is used to replace the phenylene group, while in this invention, a 9-methyl-9-phenylfluorene group is used to replace the phenylene group. The structural conjugated units conforming to the general formula of this invention are more elongated, which is more conducive to electron transport and improves device efficiency.

[0037] Comparative compound 11 and compound 39 of this invention are parallel comparative examples. The main difference is that this invention uses "benzene-naphthalene-benzene" as the bridging group, while comparative compound 11 uses "benzene-anthracene-anthracene" as the bridging group. The excessively large planar conjugated units in comparative compound 11 result in a shallower HOMO energy level, which is detrimental to blocking holes from the luminescent layer and to exciton recombination, thereby reducing the luminous efficiency of the device. Similarly, there are comparative compound 12 and compound 39 of this invention.

[0038] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A hole-blocking layer material, characterized in that, The hole-blocking layer material has the structure shown in Formula 1: ； in, R is selected from the following groups: unsubstituted or deuterated groups: ； An asterisk (*) indicates the connection position of a functional group. n can be 0, 1, or 2. When n is 2, the two Rs can be the same or different. D m The number of deuterated substitutions performed on the structure within the square brackets is m, where m is an integer from 0 to 45; Ar and Ar1 are independently selected from unsubstituted or substituted C6-C. 24 aryl, unsubstituted or substituted C containing one heteroatom of O, S or N. 12 -C 18 Heteroaryl, unsubstituted or substituted 9,9-dimethylfluorenyl; The term "substituted" means substituted by one, two or more groups selected from the following, up to the maximum number of substituted groups: deuterium, phenyl, and phenyl that is fully or partially substituted by deuterium.

2. The hole-blocking layer material according to claim 1, characterized in that, The hole-blocking layer material has any of the following structures: 。 3. The hole-blocking layer material according to claim 1 or 2, characterized in that, Ar and Ar1 are independently selected from the following groups, either unsubstituted or deuterated: ， An asterisk indicates the junction between a group and a carbon atom on a ring.

4. The hole-blocking layer material according to claim 1 or 2, characterized in that, The hole-blocking layer material is selected from any one of the following compounds: 。 5. An organic electroluminescent device, characterized in that, The organic electroluminescent device includes an anode, a cathode, and an organic layer disposed between the anode and the cathode, the organic layer including a hole blocking layer, the hole blocking layer including the hole blocking layer material of any one of claims 1-4.

6. The organic electroluminescent device according to claim 5, characterized in that, The organic layer further includes at least one of a hole injection layer, a hole transport layer, a light-emitting auxiliary layer, a light-emitting layer, an electron transport layer, or an electron injection layer.

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