Phosphorescent host material and organic electroluminescent device

Abstract

The application provides a phosphorescent host material and an organic electroluminescent device, and belongs to the technical field of organic electroluminescent materials. The phosphorescent host material is specifically shown in the structure of formula 1. The phosphorescent host material is applied to the organic electroluminescent device, and has the characteristics of low driving voltage, high luminous efficiency and long service life. 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 phosphorescent host material and an organic electroluminescent device. Background Technology

[0002] Organic light-emitting diodes (OLEDs), as a new generation of display and lighting technology, have been widely used in the consumer electronics field due to their advantages such as self-illumination and flexibility. As display technology develops towards larger sizes, higher resolutions, and greater flexibility, the luminous efficiency, stability, and lifespan of OLEDs have become key limiting factors.

[0003] Phosphorescent OLEDs can theoretically achieve 100% internal quantum efficiency and represent an important development direction; however, their performance is highly dependent on the host material, especially the N-type host material. An ideal N-type host material needs to possess matched energy levels, high electron mobility, good exciton blocking ability, and excellent stability. Existing materials still suffer from problems such as high driving voltage, severe efficiency roll-off, and insufficient stability in practical applications, which restricts the development of high-performance devices.

[0004] Therefore, designing and developing novel N-type host materials with excellent overall performance is of great significance for improving the efficiency and lifespan of phosphorescent OLEDs and promoting their application in high-performance displays and lighting. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a phosphorescent host material and an organic electroluminescent device. The phosphorescent host material described in this invention, when applied to an organic electroluminescent device, exhibits characteristics of low driving voltage, high luminous efficiency, and long lifetime, resulting in excellent overall device performance.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a phosphorescent host material, wherein the phosphorescent host material has the structure shown in Formula 1 below:

[0008] ;

[0009] Where X is selected from O or S;

[0010] R is selected from deuterium, or from unsubstituted or deuterated phenyl groups;

[0011] p is 0, 1, 2, 3, 4, 5, 6, 7 or 8. When p is greater than 1, multiple Rs can be the same or different, and the total number of unsubstituted or deuterated phenyl groups R is 0, 1 or 2; that is, the total number of unsubstituted or deuterated phenyl groups R does not exceed 2.

[0012] R1, R2, and R3 are deuterium;

[0013] n, m, and q are independently 0, 1, 2, 3, 4, or 5;

[0014] Ar is 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.

[0015] Furthermore, the phosphorescent host material has any of the following structures:

[0016] ;

[0017] Furthermore, Ar is selected from the following groups that are unsubstituted or deuterated:

[0018] An asterisk indicates the junction between a group and a carbon atom on a ring.

[0019] In this invention, the term "unsubstituted or substituted" means substituted by one, two or more of the following groups, up to the maximum number of substitutable groups: deuterium, phenyl, phenyl fully or partially substituted with deuterium, or without any substituents.

[0020] In this invention, C6-C 24 It can be C6, C8, C10, C12, C14, C16, C18, C20, or C24, etc., C 12 -C 18 It can be C12, C13, C14, C15, C16, C17 or C18.

[0021] More specifically, the phosphorescent host material is selected from any one of the following compounds:

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041] The synthesis method of the phosphorescent host material shown in Formula 1 of this invention is as follows:

[0042]

[0043] 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 6-8 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.

[0044] Intermediate c (1.0 eq) and reactant d (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), 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.

[0045] in,

[0046] Hal and Hal1 are selected from F, Cl, Br, or I;

[0047] R, R1, R2, R3, X, n, m, p, q, and Ar have the definitions given above;

[0048] 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).

[0049] 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);

[0050] 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).

[0051] 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 light-emitting layer comprising the phosphorescent host material as described above.

[0052] Preferably, the organic layer further includes any one or a combination of at least two of the following: a hole injection layer, a light-emitting auxiliary layer, a hole blocking layer, an electron transport layer, or an electron injection layer.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] This invention provides a structure with a "carbazole-triazine-dibenzo[a]heterocyclic ring" as the parent core, wherein a triazine group is attached to the 4-position of the dibenzo[a]heterocyclic ring, and a phenyl group is substituted at the 1-position, forming a continuous and efficient electron transport channel, thus improving device efficiency. Simultaneously, the introduction of a phenyl group onto the benzene ring on the opposite side of the triazine-substituted dibenzo[a]heterocyclic ring enhances molecular stereochemistry, effectively preventing excessive π-π stacking between molecules, making the film more prone to forming a stable amorphous morphology, and extending device lifetime. When this phosphorescent host material is applied to a light-emitting device, it exhibits characteristics of low driving voltage, high luminous efficiency, and long lifetime, resulting in excellent overall device performance. Attached Figure Description

[0055] Figure 1 The above is the 1H NMR spectrum of compound 93 prepared in Example 1 of this invention. Detailed Implementation

[0056] 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.

[0057] Example 1:

[0058]

[0059] Reactants 93-a (1.0 eq, CAS No.: 1480589-64-7), 93-b (1.3 eq, CAS No.: 73183-34-3), 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 cooling the filtrate 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 93-c.

[0060] Intermediate 93-c (1.0 eq) and reactant 93-d (1.3 eq, CAS No.: 2933942-87-9) were added to a reaction flask, followed by a mixture of toluene, ethanol, and water (volume ratio 3:1:1), Pd(PPh3)4 (0.02 eq) and t-BuONa (2.0 eq). The mixture was heated to 120 °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 93 (yield: 74.1%).

[0061] Characterization:

[0062] HPLC purity: >99.8%.

[0063] Mass spectrometry test: Waters XEVO TQD mass spectrometer, using ESI source.

[0064] Test value (ESI, m / Z): [M+H]+: 645.48.

[0065] Elemental analysis:

[0066] Test values: C, 83.62; H, 5.19; N, 8.70; O, 2.52.

[0067] The proton NMR spectrum of compound 93 is as follows: Figure 1 As shown.

[0068] The synthesis methods for other compounds are similar to those in the above examples, and will not be described in detail here.

[0069] Device Example 1: Fabrication of Green Organic Light Emitting Device

[0070] 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 washed for 30 minutes, then repeatedly cleaned twice with distilled water, ultrasonically washed 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 deposition process is carried out using a vapor deposition machine, and other functional layers are sequentially deposited on it.

[0071] 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 96:4, and the thickness is 10 nm.

[0072] 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.

[0073] d. Prime (light-emitting auxiliary layer): A 35nm Prime layer was vacuum-deposited on the hole transport layer at a deposition rate of 0.5Å / s as a light-emitting auxiliary layer;

[0074] e. EML (Light Emitting Layer): Then, on the above-mentioned light-emitting auxiliary layer, a dual host material (compound 93 provided by this invention is the first host compound, and Host-2 is the second host compound) and a dopant material with a total thickness of 40 nm are vacuum-deposited at a deposition rate of 1 Å / s as the light-emitting layer, wherein the deposition rate ratio of the first host compound, the second host compound and the dopant compound is 45:45:10.

[0075] f. HB (hole blocking layer): HB with a thickness of 5.0 nm is vacuum-deposited at a deposition rate of 0.5 Å / s as a hole blocking layer.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] The material structure used in the above device is as follows:

[0082]

[0083] Device Examples 2-181: The first host material in Device Examples 2-181 in Table 1 can be replaced by compound 93 in Device Example 1.

[0084] Device Comparison Example 1 - Device Comparison Example 21:

[0085] Referring to the preparation method provided in Device Example 1 above, Comparative Compounds 1-21 were used to replace Compound 93 in Device Example 1, and were respectively referred to as Device Comparative Examples 1-21. The chemical structural formulas of Comparative Compounds 1-21 are as follows:

[0086]

[0087]

[0088]

[0089]

[0090] .

[0091] The driving voltage, luminous efficiency, and lifetime of the organic electroluminescent devices obtained in Examples 1-181 and Comparative Examples 1-21 were characterized at a brightness of 15000 nits. The test results are shown in Table 1 below.

[0092] Table 1 Device Test Results

[0093]

[0094]

[0095] As can be seen from Table 1, the organic electroluminescent devices 1-181 prepared using the light-emitting layer substrate provided by the present invention exhibit lower driving voltage, higher luminous efficiency, and longer lifetime compared with the devices prepared using comparative compounds 1-21, and the overall performance of the devices is superior.

[0096] Comparative compound 1 and compound 2 in this invention are parallel comparative examples. The difference is that in this invention, the triazine is bonded to a carbazole group, while in comparative compound 1, the triazine is bonded to a benzofuranocarbazole group. Because comparative compound 1 provides a larger rigid conjugated surface, the triplet state of the molecular structure is reduced, which is not conducive to preventing energy backflow and thus reduces the device efficiency.

[0097] The comparison compound 2 and compound 2 in this invention are parallel comparative examples, the difference being whether the dibenzofuran is further substituted by a phenyl group. The phenyl group introduced in compound 2 of this invention enhances molecular stereochemistry, effectively preventing excessive π-π stacking between molecules, making the thin film more prone to forming a stable amorphous state, and increasing device lifetime.

[0098] Comparative compound 3 and compound 2 of this invention are parallel comparative examples, differing only in the position of the phenyl group replacing the dibenzofuran and the number of substituted phenyl groups. In compound 2 of this invention, the triazine and phenyl group on one side of the dibenzofuran are in the para position, which is more conducive to electron transport. At the same time, the benzene ring on the other side of the dibenzofuran can also increase the stereochemistry of the molecule, ultimately resulting in a device with high efficiency and long lifespan. Similarly, there are comparative compounds 7 and compound 50 of this invention, comparative compounds 9 and compound 78 of this invention, comparative compounds 13 and compound 175 of this invention, comparative compounds 16 and compound 214 of this invention, comparative compounds 18 and compound 292 of this invention, comparative compounds 19 and compound 292 of this invention, comparative compounds 20 and compound 292 of this invention, and comparative compounds 21 and compound 356 of this invention.

[0099] Comparative compound 4 and compound 2 of this invention are parallel comparative examples, differing only in the substitution position of the triazine group on the dibenzofuran. The substitution position of the triazine group in compound 2, which conforms to the general formula of this invention, maximizes the efficiency of intramolecular charge transfer, thus improving device efficiency. Similarly, there are comparative compound 8 and compound 70 of this invention, and comparative compound 12 and compound 174 of this invention.

[0100] Compound 5 and Compound 4 of this invention are parallel comparative examples, differing only in the substituent groups on the triazine. Compound 4 of this invention, by introducing a carbazole group, achieves molecular bipolarity, balances exciton recombination, and thus improves device efficiency.

[0101] Comparative compound 6 and compound 4 in this invention are parallel comparative examples. Compared with compound 4 in this invention, the dibenzofuran in comparative compound 6 has one more phenyl substituted, which does not contribute much to the overall steric morphology of the molecule and increases the molecular weight, resulting in a higher evaporation temperature and affecting the device lifespan.

[0102] Comparative compound 10 and compound 89 of this invention are parallel comparative examples, differing only in the substitution positions of the groups on the benzene ring of the dibenzofuran. The connection method in the general formula of this invention enables the triazine and dibenzofuran to form the most efficient "push-pull" electron coupling, creating a continuous and efficient electron transport channel with a low electron injection barrier and high electron mobility. Similarly, there are comparative compound 11 and compound 146 of this invention, and comparative compound 17 and compound 290 of this invention.

[0103] Comparative compound 14 and compound 186 of this invention are parallel comparative examples, differing only in the phenyl substitution method on the dibenzofuran. In this invention, an additional phenyl group is introduced into the isotropic benzene ring of the triazine-substituted dibenzofuran, which can suppress close packing and aggregation between molecules, resulting in excellent and stable amorphous films and improving device lifetime. Similarly, there are comparative compound 15 and compound 204 of this invention.

[0104] The applicant declares that the above embodiments illustrate the phosphorescent host material and organic electroluminescent device of the present invention, 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, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A phosphorescent host material, characterized in that, The phosphorescent host material has the specific structure shown in Formula 1 below: ； Where X is selected from O or S; R is selected from deuterium, or from unsubstituted or deuterated phenyl groups; p is 0, 1, 2, 3, 4, 5, 6, 7 or 8. When p is greater than 1, multiple Rs can be the same or different, and the total number of unsubstituted or deuterated phenyl groups is 0, 1 or 2. R1, R2, and R3 are deuterium; n, m, and q are independently 0, 1, 2, 3, 4, or 5; Ar is 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 groups, unsubstituted or substituted 9,9-dimethylfluorenyl; "Unsubstituted or deuterated" means that the group is substituted by one, two or more, up to the maximum number of substituted groups, or has no substituents; "Unsubstituted or substituted" means that the group is substituted by one, two or more, up to the maximum number of substituted groups selected from the following groups: deuterium, phenyl, fully or partially deuterated phenyl, or has no substituents.

2. The phosphorescent host material according to claim 1, characterized in that, The phosphorescent host material has any of the following structures: 。 3. The phosphorescent host material according to claim 1 or 2, characterized in that, Ar is 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 phosphorescent host material according to claim 1, characterized in that, The phosphorescent host 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 light-emitting layer, the light-emitting layer including the phosphorescent host material according to any one of claims 1-4.

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

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