A hole-blocking layer material, its preparation method and application

Abstract

This invention provides a hole blocking layer material, its preparation method, and its application. This invention belongs to the field of organic electroluminescent materials technology. The hole blocking layer material has the structure shown in Formula 1 or Formula 2. When the hole blocking layer material is applied to a light-emitting device, it exhibits the characteristics of low driving voltage, high luminous efficiency, and long lifetime, resulting in superior overall device performance.

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] Since its inception, organic light-emitting diodes (OLEDs) have become the most popular technology in the flat panel display and lighting fields due to their numerous advantages such as low cost, low power consumption, high brightness, and wide viewing angle. In a typical stacked device structure, the hole blocking layer, located between the light-emitting 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 recombine efficiently in the light-emitting 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 an organic electroluminescent device. When the described hole-blocking layer material is applied to a light-emitting device, 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 adopts the following technical solution:

[0006] On one hand, the present invention provides a hole-blocking layer material, specifically with the structure shown in Formula 1 or Formula 2 below:

[0007] ;

[0008] in,

[0009] R and R' are each independently selected from the following groups, either unsubstituted or deuterated:

[0010] ;

[0011] An asterisk (*) represents a linking site of a functional group.

[0012] a can be 0, 1, or 2. When a is 2, multiple Rs can be the same or different.

[0013] b can be 0, 1, or 2. When b is 2, multiple R's can be the same or different.

[0014] D mThe number of times the structure within the square brackets is deuterated is m, where m is an integer from 0 to 41 (e.g., 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, or 41, etc.).

[0015] D n This indicates that the number of deuterated substitutions performed on the structure within the square brackets is n, where n is an integer from 0 to 41 (e.g., 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, or 41, etc.).

[0016] Ar, Ar1, Ar2, and Ar3 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.

[0017] Furthermore, the hole-blocking layer material has any of the following structures:

[0018] .

[0019] Furthermore, Ar, Ar1, Ar2, and Ar3 are independently selected from the following groups, either unsubstituted or deuterated:

[0020] An asterisk (*) indicates the junction between a group and a carbon atom on a ring.

[0021] 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.

[0022] More specifically, the hole-blocking layer material is selected from any one of the following compounds:

[0023]

[0024] .

[0025] Synthesis method:

[0026]

[0027] 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.

[0028] 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.

[0029]

[0030] The synthesis method of compound formula 2 is similar to that of formula 1, except that reactant a in the above reaction is replaced with reactant a' and reactant d is replaced with reactant d'.

[0031] in,

[0032] D m1 The number of times the structure within the square brackets is deuterated is m1, where m1 is an integer from 0 to 31 (e.g., 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, or 31, etc.).

[0033] 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.).

[0034] D n1 The number of times the structure within the square brackets is deuterated is n1, where n1 is an integer from 0 to 31 (e.g., 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, or 31, etc.).

[0035] D n2 This indicates that the number of deuterated substitutions performed on the structure within the square brackets is n2, where n2 is an integer from 0 to 10 (e.g., 0, 1, 2, 3, 4, 5, 6, 7, 8, or 10, etc.).

[0036] Hal, Hal1, Hal2, and Hal3 are selected from F, Cl, Br, and I;

[0037] R, R', a, b, D m D n Ar, Ar1, Ar2 and Ar3 have the definitions given above;

[0038] 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).

[0039] 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);

[0040] 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).

[0041] 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.

[0042] 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.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] This invention provides a core structure with "benzene-naphthalene" as the bridging group between triazine and fluorene. The introduction of "benzene-naphthalene" prolongs the conjugated system of the molecule, which is beneficial to enhancing electron mobility. At the same time, the HOMO energy level of the molecule can be finely tuned, thereby regulating the molecule's ability to block holes, enhancing the exciton recombination rate, and improving the luminescence efficiency of the device. Secondly, the methyl and phenyl groups at the 9-position of the fluorene ring in the molecule maintain effective steric hindrance and enable efficient electron transfer between molecules, ultimately resulting in excellent overall performance of the fabricated device. Attached Figure Description

[0045] Figure 1 This is the 1H NMR spectrum of compound 6 in Example 1 of the present invention. Detailed Implementation

[0046] 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.

[0047] Example 1:

[0048]

[0049] Reactant 6-a (1.0 eq, CAS No.: 3063530-78-6), 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 6-c.

[0050] Reactant 6-d (1.0 eq, CAS No.: 3091378-79-6) and intermediate 6-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 6 (yield: 78.7%).

[0051] Characterization:

[0052] HPLC purity: >99.8%.

[0053] Mass spectrometry test: Waters XEVO TQD mass spectrometer, using ESI source.

[0054] Test value (ESI, m / Z): [M+H]+: 689.42.

[0055] Elemental analysis:

[0056] Test values: C, 88.77; H, 5.15; N, 6.11.

[0057] The proton NMR spectrum of compound 6 is as follows: Figure 1 As shown.

[0058] 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.

[0059] Device Example 1: Fabrication of Green Organic Light Emitting Device

[0060] 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.

[0061] 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 95:5, and the thickness is 10 nm.

[0062] c. HTL (Hole Transport Layer): A 125nm HT is vacuum-deposited on the hole injection layer at a deposition rate of 1.5Å / s as a hole transport layer.

[0063] 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;

[0064] 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 95:5.

[0065] f. HB (hole blocking layer): Compound 6 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.

[0066] 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.

[0067] 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;

[0068] 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.

[0069] j. Optical extraction layer: A CPL with a thickness of 60 nm is vacuum-deposited on the cathode at a deposition rate of 1 Å / s as the optical extraction layer.

[0070] 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.

[0071] The material structure used in the above device is as follows:

[0072] .

[0073] Device Examples 2-240: Replace compound 6 in Device Example 1 with the materials in Device Examples 2-240 in Table 1.

[0074] Device Comparison Examples 1-11:

[0075] Referring to the preparation method provided in Device Example 1 above, Comparative Compounds 1-11 were used to replace Compound 6 in Device Example 1, and were respectively referred to as Device Comparative Examples 1-11. The chemical structural formulas of Comparative Compounds 1-11 are as follows:

[0076]

[0077]

[0078] .

[0079] The driving voltage, luminous efficiency, and lifetime of the organic electroluminescent devices obtained in Examples 1-240 and Comparative Examples 1-11 were characterized at a brightness of 1000 nits. The test results are shown in Table 1 below.

[0080] Table 1 Device Test Results

[0081]

[0082] 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.

[0083] As can be seen from Table 1, the organic electroluminescent devices 1-240 prepared using the light-emitting layer substrate provided by the present invention exhibit lower driving voltage (below 3.50V), higher luminous efficiency (above 8.6 cd / A), and longer lifetime (T95 above 470h) compared with the devices prepared using comparative compounds 1-6, and the overall performance of the devices is superior.

[0084] In this study, Comparative Compound 1 and Compound 5 of the present invention are parallel comparative examples, differing only in the linking group between the phenylene and fluorene groups. Comparative Compound 1 uses a phenylene ring, while Compound 5 of the present invention uses a naphthalene ring. Naphthalene itself is a rigid, planar, fused-ring aromatic hydrocarbon, which inherently provides steric hindrance, restricting the free rotation and vibration of the molecule. In contrast, the molecular conformation of Comparative Compound 1 is more flexible, with relatively weaker overall rigidity and steric hindrance. Therefore, Compound 5 of the present invention has a higher glass transition temperature, is less prone to crystallization or morphological changes due to heat, and is more stable in device operation, resulting in a longer device lifespan.

[0085] Comparative compound 2 and compound 24 of this invention are parallel comparative examples, differing only in the substituent group at the 9-position of the fluorene ring. In comparative compound 2, the substituent is phenyl, while in compound 24 of this invention, it is methyl, phenyl. Compound 24 of this invention disrupts the symmetry at the 9-position of the fluorene ring through the methyl group, reducing the overall tendency for molecular crystallization; simultaneously, the methyl group also induces steric hindrance, inhibiting recrystallization in the thin film state, ultimately increasing device lifetime. Similarly, there are comparative compounds 3 and 34 of this invention, 4 and 30 of this invention, 5 and 31 of this invention, 6 and 32 of this invention, 7 and 33 of this invention, and 8 and 36 of this invention.

[0086] Compound 9 and Compound 68 of this invention are parallel comparative examples, differing only in the linking group between the naphthalene ring and the triazine group. The introduction of phenylene into Compound 68 of this invention prolongs the π-conjugated system of the entire molecule, improving the overall luminous efficiency of the device. Simultaneously, it fine-tunes the HOMO energy level, making it deeper, thereby exhibiting stronger hole blocking ability, increasing exciton recombination rate, and enhancing the luminous efficiency of the device.

[0087] Comparative compound 10 and compound 166 of this invention are parallel comparative examples. The main difference lies in the linking group between the fluorene ring and the triazine group; this invention introduces a "benzene-naphthalene ring." Comparative compound 10 has a smaller overall molecule, limited conjugation system, and low electron mobility, which is unfavorable for fabricating high-efficiency luminescent devices. Meanwhile, the introduction of the "benzene-naphthalene ring" in this invention results in a relatively deeper HOMO energy level, thereby exhibiting stronger hole-blocking ability, increasing exciton recombination rate, and enhancing device luminescent efficiency.

[0088] Comparative examples 11 and 210 of this invention are parallel comparative examples. The main difference lies in the linking group between the fluorene ring and the triazine group. Compound 210 of this invention introduces an additional naphthalene ring, which not only fine-tunes the HOMO energy level but also enhances the overall stereochemistry of the molecule. Furthermore, the increased molecular conjugation results in superior overall performance of the fabricated device.

[0089] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments 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, 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 specific structure shown in Formula 1 or Formula 2: ； in, R and R' are each independently selected from the following groups, either unsubstituted or deuterated: ； An asterisk (*) represents a linking site of a functional group. a can be 0, 1, or 2. When a is 2, multiple Rs can be the same or different. b can be 0, 1, or 2. When b is 2, multiple R's 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 41; D n This indicates that n is the number of times the structure within the square brackets is deuterated, where n is an integer from 0 to 41; Ar, Ar1, Ar2, and Ar3 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.

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, The hole-blocking layer material is selected from any one of the following compounds: 。 4. 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 1-3.

5. The organic electroluminescent device according to claim 4, 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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