Phosphorescent host material and organic electroluminescent device

Abstract

The invention provides a phosphorescent host material and an organic electroluminescent device, and belongs to the technical field of organic electroluminescent materials, the phosphorescent host material has a structure as shown in a formula I. The phosphorescent host material is applied to the organic electroluminescent device, shows the characteristics of low driving voltage, high luminous efficiency and long service life, and can be applied to the organic electroluminescent device. And the comprehensive performance of the device is excellent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic electroluminescent materials, and particularly relates to a phosphorescent host material and an organic electroluminescent device. BACKGROUND

[0002] As a new generation of display and lighting technology, organic electroluminescent diodes (OLEDs) have been widely used in consumer electronics due to their self-luminescence and flexibility. With the development of display technology towards large size, high resolution and flexibility, the luminous efficiency, stability and service life of OLEDs have become key factors.

[0003] Phosphorescent OLEDs can theoretically achieve 100% internal quantum efficiency, which is 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 should have matching energy levels, high electron mobility, good exciton blocking ability and excellent stability. The existing materials still have problems such as high driving voltage, serious efficiency roll-off and insufficient stability in practical application, which restricts the development of high-performance devices.

[0004] Therefore, it is of great significance to design and develop N-type host materials with novel structure and excellent comprehensive performance for improving the efficiency and lifetime of phosphorescent OLEDs and promoting their application in the field of high-performance display and lighting. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a phosphorescent host material and an organic electroluminescent device. The phosphorescent host material according to the present application applied to an organic electroluminescent device exhibits low driving voltage, high luminous efficiency and long lifetime, and the comprehensive performance of the device is excellent.

[0006] To achieve this purpose, the present application adopts the following technical solutions:

[0007] On the one hand, the present application provides a phosphorescent host material, which is specifically shown as the structure of formula 1:

[0008] ;

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

[0010] R is selected from deuterium, phenyl unsubstituted or substituted with deuterium;

[0011] p is 0, 1, 2, 3, 4, 5, 6, 7 or 8, when p is greater than 1, multiple R can be the same or different, and the total number of R which is phenyl unsubstituted or substituted with deuterium is 0 or 1 or 2; that is, the total number of R which is phenyl unsubstituted or substituted with deuterium does not exceed 2;

[0012] R1, R2 and R3 are deuterium;

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

[0014] Ar is selected from the group consisting of unsubstituted or substituted C6-C 24 aryl, unsubstituted or substituted C 12 -C 18 heteroaryl, unsubstituted or substituted 9,9-dimethylfluorenyl.

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

[0016] ;

[0017] Further, Ar is selected from the group consisting of unsubstituted or deuterium- substituted:

[0018] , the asterisk indicates the connection of the group to the carbon on the ring;

[0019] In the present invention, the term "unsubstituted or substituted" means substituted by one, two or more, up to the maximum number of substituents, selected from the group consisting of deuterium, phenyl, fully or partially deuterium-substituted phenyl, or without any substituents.

[0020] In the present invention, C6-C 24 may be C6, C8, C10, C12, C14, C16, C18, C20 or C24, etc., C 12 -C 18 may 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 the present application is as follows:

[0042]

[0043] The reactant a (1.0 eq), the reactant b (1.0-1.3 eq), potassium acetate (2.0-3.0 eq) are added into a reaction bottle, then 1,4-dioxane is added, the gas is exchanged for three times, the palladium catalyst (0.02-0.15 eq) and the phosphine ligand (0.1-0.2 eq) are added under the protection of nitrogen, the temperature is increased to 80-100 DEG C, and the reaction is carried out for 6-8 h. The hot diatomite is used to filter, the filtrate is cooled to room temperature, then water is added into the filtrate to wash, the organic phase is reserved after the separation, the water phase is extracted by ethyl acetate; then the combined organic layer is dried by magnesium sulfate, and is purified by column chromatography to obtain the intermediate c;

[0044] The intermediate c (1.0 eq) and the reactant d (1.0-1.3 eq) are added into a reaction bottle, then the mixed solution of toluene, ethanol and water (volume ratio is 3:1:1) is added, the palladium catalyst (0.01-0.02 eq) and the base (2.0-3.0 eq) are added, the temperature is increased to 80-120 DEG C, and the reaction is carried out for 6-18 h. The hot diatomite is used to filter, the filtrate is cooled to room temperature, then water is added into the filtrate to wash, the organic phase is reserved after the separation, the water phase is extracted by ethyl acetate; then the combined organic layer is dried by magnesium sulfate, and is purified by column chromatography to obtain Formula 1.

[0045] wherein,

[0046] Hal, Hal1is selected from F, Cl, Br or I;

[0047] R, R1, R2, R3, X, n, m, p, q and Ar have the meanings as 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] The palladium catalyst can be Pd2(dba)3 (tris(dibenzylideneacetone)dipalladium), Pd(PPh3)4 (tetrakis(triphenylphosphine)palladium), PdCl2 (palladium dichloride), PdCl2(dppf) ([1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium), Pd(OAc)2 (palladium acetate), Pd(PPh3)2Cl2 (bis(triphenylphosphine)palladium dichloride);

[0050] The phosphine ligand 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 diphenylphosphinate) or P(t-Bu)2Cl (di-tert-butylchlorophosphine).

[0051] In another aspect, the present application provides an organic electroluminescent device, comprising an anode, a cathode and an organic layer disposed between the anode and the cathode, wherein the organic layer comprises a light-emitting layer, and the light-emitting layer comprises the phosphorescent host material as described above.

[0052] Preferably, the organic layer further comprises any one or a combination of at least two of 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 application has the following beneficial effects:

[0054] The application provides a structure with a "carbazole-triazine-dibenzoheterocycle" as a mother nucleus, wherein the 4-position of the dibenzoheterocycle is connected with the triazine group, and the 1-position is substituted with a phenyl group, forming a continuous and efficient electron transport channel to improve device efficiency; meanwhile, a phenyl group is introduced on the para-position of the triazine-substituted dibenzoheterocycle, which can enhance the molecular stereospecificity and effectively prevent excessive π-π stacking between molecules, so that the thin film is more inclined to form a stable amorphous state, and the device life is prolonged. The phosphorescent host material is applied to a light-emitting device, and the device has the characteristics of low driving voltage, high luminous efficiency and long service life, and has excellent comprehensive performance. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 The nuclear magnetic resonance hydrogen spectrum of the compound 93 prepared in Example 1 of the application is shown. DETAILED DESCRIPTION

[0056] The technical solutions of the application will be further described through specific embodiments. It should be understood by those skilled in the art that the embodiments are only used to help understand the application and should not be regarded as specific limitations on the application.

[0057] Example 1:

[0058]

[0059] The reactant 93-a (1.0 eq, CAS No.: 1480589-64-7), the reactant 93-b (1.3 eq, CAS No.: 73183-34-3) and potassium acetate (2.0 eq) were added to a reaction bottle, then 1,4-dioxane was added, the gas was exchanged for three times, Pd(PPh3)4 (0.02 eq) and X-phos (0.1 eq) were added under nitrogen protection, the temperature was increased to 90°C, and the reaction was carried out for 6 hours. The hot diatomite was used for suction filtration, the filtrate was cooled to room temperature, then water was added to the filtrate for washing, the organic phase was retained after separation, the water phase was extracted with ethyl acetate; then the combined organic layer was dried with magnesium sulfate, and purified by column chromatography to obtain the intermediate 93-c;

[0060] The intermediate 93-c (1.0 eq) and the reactant 93-d (1.3 eq, CAS No.: 2933942-87-9) were added to a reaction bottle, then a mixed solution of toluene, ethanol and water (volume ratio 3:1:1) was added, Pd(PPh3)4 (0.02 eq) and t-BuONa (2.0 eq) were added, the temperature was increased to 120°C, and the reaction was carried out for 8 hours. The hot diatomite was used for suction filtration, the filtrate was cooled to room temperature, then water was added to the filtrate for washing, the organic phase was retained after separation, the water phase was extracted with ethyl acetate; then the combined organic layer was dried with magnesium sulfate, and purified by column chromatography to obtain the compound 93 (yield: 74.1%).

[0061] Characterization:

[0062] HPLC purity: >99.8%.

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

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

[0065] Elemental analysis:

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

[0067] The nuclear magnetic resonance hydrogen spectrum of compound 93 is shown in Figure 1 .

[0068] The synthesis methods of other compounds are similar to the above examples, which are not described one by one here.

[0069] Device Example 1: Preparation of a green organic electroluminescent device

[0070] a, ITO anode: ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate with a coating thickness of 150 nm is cleaned twice in distilled water, ultrasonic washing for 30 min, and then repeatedly cleaned twice with distilled water, ultrasonic washing for 10 min, and then baked in a vacuum oven at 220°C for 2 hours. After baking, it is cooled and ready for use. The substrate is used as an anode, and a deposition machine is used to perform device deposition process, and other functional layers are sequentially deposited thereon.

[0071] b, HIL (hole injection layer): The hole injection layer materials HT and P-dopant are vacuum deposited at a deposition rate of 1 A / s, and the deposition rate ratio of the HT and P-dopant is 96:4, and the thickness is 10 nm;

[0072] c, HTL (hole transport layer): The HT as a hole transport layer is vacuum deposited on the hole injection layer at a deposition rate of 1.5 A / s, and the thickness is 130 nm;

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

[0074] e、EML (Emission Layer): Then, on the above-mentioned light-emitting auxiliary layer, a double-host material (compound 93 provided by the present application as the first host compound, and Host-2 as the second host compound) and a dopant material (Dopant) were vacuum evaporated at a rate of 1 A / s to a total thickness of 40 nm as the light-emitting layer, wherein the evaporation rate ratio of the first host compound, the second host compound and the dopant compound was 45:45:10.

[0075] f、HB (Hole Blocking Layer): HB was vacuum evaporated at a rate of 0.5 A / s to a thickness of 5.0 nm as a hole blocking layer.

[0076] g、ETL (Electron Transport Layer): ET and Liq were vacuum evaporated at a rate of 1 A / s to a thickness of 30 nm as an electron transport layer. The evaporation rate ratio of ET and Liq was 1:1.

[0077] h、EIL (Electron Injection Layer): Yb film layer was evaporated at a rate of 0.5 A / s to 1.0 nm to form an electron injection layer.

[0078] i、Cathode: Magnesium and silver were evaporated at a rate of 1 A / s to 13 nm, and the evaporation rate ratio was 1:9 to obtain an OLED device.

[0079] j、Light Extraction Layer: CPL was vacuum evaporated at a rate of 1 A / s to a thickness of 60 nm on the cathode as a light extraction layer.

[0080] k、The substrate after evaporation was packaged. First, the cleaned cover plate was coated with UV glue using a gluing device, then the coated cover plate was moved to the pressing section, the substrate after evaporation was placed on the end of the cover plate, and finally the substrate and the cover plate were bonded under the action of the bonding device, and the UV glue was cured by light.

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

[0082]

[0083] Device Example 2-Device Example 181: Use the first host material in device examples 2-181 in Table 1 to replace compound 93 in device example 1.

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

[0085] Referring to the preparation method provided in device example 1 above, comparative compounds 1-21 are used to replace compound 93 in device example 1, respectively denoted as device comparative examples 1-21, wherein 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 from the above device examples 1-181 and device comparative examples 1-21 were characterized under a brightness of 15000 (nits), and 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 prepared using the host of the light-emitting layer provided by the present application, examples 1-181, exhibit low driving voltage, high luminous efficiency and long lifetime compared with the devices prepared using comparative compounds 1-21, and the comprehensive performance of the devices is more excellent.

[0096] Comparative compound 1 and compound 2 in the present application are parallel comparative examples, the difference is that the triazine bond in the present application is bonded to a carbazole group, and the triazine bond in comparative compound 1 is bonded to a benzofuranocarbazole group. Since comparative compound 1 provides a larger rigid conjugated plane, the triplet state of the molecular structure is reduced, which is not conducive to preventing energy backflow, resulting in a decrease in device efficiency.

[0097] Comparative compound 2 and compound 2 in the present application are parallel comparative examples, the difference is whether the benzofuran is further substituted by a phenyl group. The introduction of a phenyl group in compound 2 in the present application can enhance the stereospecificity of the molecule, effectively prevent π-π excessive stacking between molecules, and make the thin film more inclined to form a stable amorphous state, thereby increasing the lifetime of the device.

[0098] Comparative compound 3 and compound 2 in the present application are parallel examples, the difference is the position of phenyl substituted dibenzofuran and the number of substituted phenyl. In the compound 2 of the present application, the phenyl on one side of the dibenzofuran triazine and phenyl are para, which is more conducive to the transmission of electrons, and the benzene ring on the other side of the dibenzofuran can also increase the stereospecificity of the molecule, ultimately obtaining a device with high efficiency and long life. Similarly, there are comparative compound 7 and compound 50 in the present application, comparative compound 9 and compound 78 in the present application, comparative compound 13 and compound 175 in the present application, comparative compound 16 and compound 214 in the present application, comparative compound 18 and compound 292 in the present application, comparative compound 19 and compound 292 in the present application, comparative compound 20 and compound 292 in the present application, comparative compound 21 and compound 356 in the present application.

[0099] Comparative compound 4 and compound 2 in the present application are parallel examples, the difference is the substitution position of the triazine group on the dibenzofuran. The substitution position of the triazine group in compound 2 of the present application maximizes the efficiency of intramolecular charge transfer, providing device efficiency. Similarly, there are comparative compound 8 and compound 70 in the present application, comparative compound 12 and compound 174 in the present application.

[0100] Comparative compound 5 and compound 4 in the present application are parallel examples, the difference is the substitution group on the triazine. The introduction of a carbazole group in compound 4 in the present application can achieve the bipolarity of the molecule, balance the exciton recombination, and improve the efficiency of the device.

[0101] Comparative compound 6 and compound 4 in the present application are parallel examples, and the dibenzofuran of comparative compound 6 is substituted with one more phenyl than compound 4 in the present application, which does not contribute much to the overall stereospecificity of the molecule and increases the molecular weight, resulting in a higher evaporation temperature and affecting the device life.

[0102] Comparative compound 10 and compound 89 in the present application are parallel examples, the difference is the substitution position of the group on the benzene ring of dibenzofuran. The connection mode in the general formula of the present application makes the triazine and dibenzofuran form the most effective "push-pull" electronic coupling, forming a continuous and efficient electron transport channel, with small electron injection barrier and high electron mobility. Similarly, there are comparative compound 11 and compound 146 in the present application, comparative compound 17 and compound 290 in the present application.

[0103] Comparative compound 14 and compound 186 in the present application are parallel examples, the difference is the way of phenyl substitution on dibenzofuran. In the present application, one phenyl is introduced to the meta-phenyl of triazine-substituted dibenzofuran, which can inhibit the close packing and aggregation between molecules, obtain excellent and stable amorphous thin film, and improve the device lifetime. Similarly, there are comparative compound 15 and compound 204 in the present application.

[0104] The applicant declares that the phosphorescent host material and the organic electroluminescent device of the present application are illustrated by the above examples, but the present application is not limited to the above examples, that is, it does not mean that the present application must rely on the above examples to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of the raw materials selected by the present application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the protection scope and disclosure scope of the present application.

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 p 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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