Phosphorescent host material, preparation method and organic electroluminescent device

Abstract

The present invention belongs to the technical field of organic electroluminescent materials, and provides a phosphorescent host material, a preparation method and an organic electroluminescent device. The general structural formula of the phosphorescent host material in the present invention is shown in the specification. The phosphorescent host material provided by the present invention is used as a material in the light-emitting layer of an organic electroluminescent device, which can not only improve the luminous efficiency, but also significantly increase the life of the device and reduce the driving voltage.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic electroluminescent materials, and particularly relates to a phosphorescent host material, a preparation method thereof, and an organic electroluminescent device. Background Art

[0002] Organic electroluminescent (OLED) devices have the advantages of high brightness, fast response, wide viewing angle, simple process, and flexibility, and have attracted much attention in the fields of new display technology and new lighting technology.

[0003] Currently, in OLED devices prepared using phosphorescent materials, the host of the light-emitting layer is mostly a class of derivatives with triazine and polyheteroaromatic rings as the parent nucleus. Although the variety of structures has been relatively diverse, a class of materials that can well balance the device voltage, luminous efficiency, and lifespan has not been found yet. Therefore, developing stable and efficient host materials, so that the devices show excellent comprehensive performance in terms of driving voltage, luminous efficiency, and lifespan, has very important practical application value. Summary of the Invention

[0004] In view of this, the present invention provides a phosphorescent host material, a preparation method thereof, and an organic electroluminescent device. Applying the phosphorescent host material of the present invention to a specific light-emitting device has a low driving voltage, high luminous efficiency, and long service life.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The first technical object of the present invention is to provide a phosphorescent host material, and the phosphorescent host material has a structure shown in Formula 1 or Formula 2 as follows: Wherein,

[0007] X is selected from O or S;

[0008] R, R 1 , R 2 are independently selected from deuterium;

[0009] n is 0, 1, 2, 3, 4, 5, 6, 7, 8;

[0010] m, p are independently selected from 0, 1, 2, 3, 4, 5;

[0011] q is selected from 0, 1;

[0012] Ar is selected from an unsubstituted or deuterium-substituted phenyl group;

[0013] Ar 1 , Ar 2Independently selected from unsubstituted or deuterium-substituted C6-C24 aryl, unsubstituted or deuterium-substituted C12-C18 heteroaryl, the heteroatom containing one heteroatom of O, S, or N.

[0014] Furthermore, the phosphorescent host material has any one of the following structures: 。

[0015] Furthermore, Ar 1 ,Ar 2 are independently selected from the following unsubstituted or deuterium-substituted groups: ,“*” indicates the connection point of the group to the carbon on the ring.

[0016] In the present invention, the term "unsubstituted or deuterium-substituted" means that the group is substituted with one, two or more, up to the maximum number of substituents, of deuterium, or has no substituents.

[0017] More specifically, the phosphorescent host material is selected from any one of the following compounds: 。

[0018] Only some specific structural forms are listed above, but this series of phosphorescent host materials is not limited to the above molecular structures. Any simple transformation of some simple groups, their substituted groups, and substitution positions can obtain other specific molecular structures, which will not be elaborated one by one here.

[0019] The second object of the present invention is to provide a preparation method of the above-mentioned phosphorescent host material. The phosphorescent host material of the present invention can be prepared by synthetic methods known to those skilled in the art. Alternatively, the following reaction process is preferably used for preparation.

[0020] (1)Synthesize Formula 1:

[0021] Dissolve reactant 1-a (1.0 eq), reactant 1-b (1.0 - 1.5 eq) and potassium carbonate (4.5 - 5.5 eq) in anhydrous DMSO, and then stir at 140 - 160 °C for 6 - 8 hours; after the solution temperature is reduced to room temperature, pour water into it and stir. The resulting precipitate is recovered by suction filtration and dissolved in CH2 Cl 2 in and via MgSO 4 Dry, remove the solvent by distillation under reduced pressure, and isolate the intermediate 1-c by recrystallization;

[0022] Add the intermediate 1-c (1.0 eq) and the reactant 1-d (1.0 - 1.5 eq) to a reaction flask, then add a mixed solution of toluene, ethanol, and water (volume ratio 3:1:1), add a palladium catalyst (0.01 - 0.03 eq), a base (2.0 - 3.0 eq), a phosphine ligand (0.10 - 0.20 eq), and cesium carbonate (2.0 - 3.0 eq), heat up to 100 - 120 °C, and reflux for 6 - 18 hours; Filter while hot using diatomaceous earth, after the filtrate cools to room temperature, then add water to the filtrate for washing, retain the organic phase after liquid separation, and extract the aqueous phase with ethyl acetate; Then dry the combined organic layers using magnesium sulfate and purify by column chromatography to obtain Formula 1;

[0023] The specific synthesis route is as follows: ;

[0024] (2) Synthesis of Formula 2:

[0025] Obtained by replacing the reactant 1-a with 2-a according to the method for synthesizing Formula 1 above;

[0026] The specific synthesis route is as follows: ;

[0027] Wherein,

[0028] Hal, Hal 1 are selected from F, Cl, Br, I;

[0029] R' is or ;

[0030] R, R 1 , R 2 , n, m, p, q, Ar 1 and Ar 2 have the definitions given above.

[0031] Furthermore, the base is selected from K 2 CO 3 (potassium carbonate), K 3 PO 4 (potassium phosphate), Na 2 CO 3 (sodium carbonate), CsF (cesium fluoride), Cs 2 CO 3 (cesium carbonate) or t-BuONa (sodium tert-butoxide);

[0032] The palladium catalyst is selected from Pd 2 (dba) 3 (tris(dibenzylideneacetone)dipalladium), Pd(PPh 3 ) 4 (Tetrakis(triphenylphosphine)palladium), PdCl 2 (Palladium dichloride), PdCl 2 (dppf) ([1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride), Pd(OAc) 2 (palladium acetate), Pd(PPh 3 ) 2 Cl 2 (bis(triphenylphosphine)palladium dichloride) or NiCl 2 (dppf) ((1,1'-bis(diphenylphosphino)ferrocene) nickel dichloride);

[0033] The phosphine ligand is selected from P(t-Bu) 3 (tri-tert-butylphosphine), X-phos (2-cyclohexylphosphino-2,4,6-triisopropylbiphenyl), PET 3 (Triethylphosphine), PMe 3 (Trimethylphosphine), PPh 3 (Triphenylphosphine), KPPh 2 (potassium diphenyl phosphate) or P(t-Bu) 2 Cl (di-tert-butylphosphine chloride).

[0034] The third object of the present invention is to provide the application of the above-mentioned phosphorescent host material in an organic electroluminescent device.

[0035] An organic electroluminescent device, comprising the phosphorescent host material.

[0036] The organic electroluminescent device comprises a first electrode, a second electrode and an organic layer disposed between the two electrodes, wherein the organic layer comprises at least one or more of a hole injection layer, a hole transport layer, a light-emitting auxiliary layer, a light-emitting layer, a hole blocking layer, an electron transport layer and an electron injection layer.

[0037] Specifically, the organic electroluminescent device comprises a light-emitting layer, and the light-emitting layer contains the phosphorescent host material described in the present invention.

[0038] Furthermore, the light-emitting layer of the organic electroluminescent device comprises a host material and a doping material, and the host material comprises the phosphorescent host material described in the present invention.

[0039] It should be noted that the light-emitting device containing the phosphorescent host material described in the present invention exhibits the characteristics of low driving voltage, high luminous efficiency and long life, and the overall performance of the device is more excellent.

[0040] As can be seen from the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention provides a parent nucleus structure in which the 1- and 3-positions of a dibenzoheterocycle are substituted with carbazolyl and triazine groups, and the side unsubstituted by triazine is substituted with a phenyl group. The structural resonance system conforming to this general formula has an appropriate length, a relatively high triplet state, so that the energy level of the doped triplet excited state can be effectively prevented from returning to the triplet energy level of the host, obtaining a high-efficiency device structure; substituting the side unsubstituted by triazine with a phenyl group of an appropriate molecular weight is conducive to energy transfer, and at the same time enhances the molecular steric hindrance to ensure the long life of the device; placing the electron-donating group carbazole and the electron-withdrawing group triazine on the same side can reduce the molecular stacking phenomenon caused by the intermolecular dipole-dipole interaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0043] Figure 1 1H NMR spectrum of compound 3 in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0045] The embodiments of the present invention disclose a preparation method of a phosphorescent host material.

[0046] In addition, it should be noted that the values given in the following embodiments are as accurate as possible. However, those skilled in the art understand that due to inevitable measurement errors and experimental operation problems, each number should be understood as an approximate number, rather than an absolutely accurate value.

[0047] Example 1: ;

[0048] Reactant 3-a (20 mmol, CAS No.: 2967684-81-5), reactant 3-b (30 mmol, CAS No.: 86-74-8) and potassium carbonate (100 mmol) were dissolved in anhydrous DMSO, and then stirred at 150 °C for 6 hours; after the solution temperature was lowered to room temperature, water was poured into it and stirred, and the resulting precipitate was recovered by suction filtration, dissolved in CH 2 Cl 2 and dried over MgSO 4 . The solvent was removed by distillation under reduced pressure, and intermediate 3-c was obtained by separation through recrystallization.

[0049] Intermediate 3-c (20 mmol) and reactant 3-d (30 mmol, CAS No.: 3842-55-5) were added to a reaction flask, and then a mixed solution of toluene, ethanol, and water (volume ratio 3:1:1) was added, and Pd(PPh 3 ) 4 (0.4 mmol), Na 2 CO 3 (40 mmol), X-phos (3 mmol) and cesium carbonate (40 mmol) were added. The temperature was raised to 100 °C and the reaction was refluxed for 10 hours; it was filtered while hot using diatomaceous earth. After the filtrate was cooled to room temperature, water was then added to the filtrate for washing. After liquid separation, the organic phase was retained, and the aqueous phase was extracted with ethyl acetate; then the combined organic layer was dried over magnesium sulfate and purified by column chromatography to obtain compound 3 (9.17 g, yield: 71.5%, measured value MS (ESI, m / z): [M+H] + = 641.03).

[0050] The 1H NMR spectrum of compound 3 is as Figure 1 shown.

[0051] Characterization:

[0052] HPLC purity: > 99.8%.

[0053] Elemental analysis:

[0054] Theoretical values: C, 84.35; H, 4.40; N, 8.74; O, 2.50

[0055] Measured values: C, 84.25; H, 4.51; N, 8.77; O, 2.53.

[0056] Device Example 1: Preparation of green organic electroluminescent device

[0057] a, ITO anode: Clean the ITO (Indium Tin Oxide)-Ag-ITO (Indium Tin Oxide) glass substrate with a coating thickness of 150 nm twice in distilled water, wash it ultrasonically for 30 min, then wash it repeatedly twice with distilled water and ultrasonically for 10 min, and bake it in a vacuum oven at 220 °C for 2 hours. After baking, let it cool down and it can be used. Using this substrate as the anode, perform the evaporation device process with an evaporation coater, and evaporate other functional layers on it in sequence.

[0058] b, HIL (Hole Injection Layer): Vacuum evaporate the hole injection layer materials HT and P-dopant at an evaporation rate of 1 Å / s. The evaporation rate ratio of HT and P-dopant is 96:4, and the thickness is 10 nm.

[0059] c, HTL (Hole Transport Layer): Vacuum evaporate 125 nm of HT as the hole transport layer on the hole injection layer at an evaporation rate of 1.5 Å / s.

[0060] d, Prime (Luminescence-Assisting Layer): Vacuum evaporate 40 nm of Prime as the luminescence-assisting layer on the hole transport layer at an evaporation rate of 0.5 Å / s.

[0061] e, EML (Emitting Layer): Vacuum evaporate a total thickness of 35 nm of a double-host material (Compound 3 provided by the present invention is the first host compound, and Host-2 is the second host compound) and a doping material (Dopant) as the emitting layer on the luminescence-assisting layer at an evaporation rate of 1 Å / s. The evaporation rate ratio of the first host compound, the second host compound, and the doping compound is 45:45:10.

[0062] f, HB (Hole Blocking Layer): Vacuum evaporate 5.0 nm of HB as the hole blocking layer on the emitting layer at an evaporation rate of 0.5 Å / s.

[0063] g, ETL (Electron Transport Layer): Vacuum evaporate a thickness of 30 nm of ET and Liq as the electron transport layer on the hole blocking layer at an evaporation rate of 1 Å / s. The evaporation rate ratio of ET and Liq is 1:1.

[0064] h, EIL (Electron Injection Layer): Vacuum evaporate a 1.0 nm thick Yb film layer on the electron transport layer at an evaporation rate of 0.5 Å / s to form the electron injection layer.

[0065] i, Cathode: Vacuum evaporate a thickness of 13 nm of magnesium and silver on the electron injection layer at an evaporation rate of 1 Å / s. The evaporation rate ratio of magnesium and silver is 1:9 to obtain the cathode.

[0066] j. Light extraction layer: CPL with a thickness of 60 nm was vacuum-evaporated on the cathode at an evaporation rate of 1 Å / s as the light extraction layer.

[0067] k. Encapsulating the evaporated substrate: First, a coating device was used to coat the cleaned cover plate with UV glue. Then, the coated cover plate was moved to the lamination section, and the evaporated substrate was placed on top of the cover plate. Finally, the substrate and the cover plate were laminated under the action of a laminating device, and at the same time, the UV glue was cured by light irradiation.

[0068] The material structures used in the above devices are as follows: 。

[0069] Device Example 2 - Device Example 125:

[0070] Referring to the preparation method provided in Device Example 1 above, the first host material in Device Examples 2 - 125 in Table 1 was used to replace Compound 3 in Device Example 1, and they were respectively denoted as Device Examples 2 - 125.

[0071] Device Comparative Example 1 - Device Comparative Example 32:

[0072] Referring to the preparation method provided in Device Example 1 above, Comparative Compounds 1 - 32 were used to replace Compound 3 in Device Example 1, and they were respectively denoted as Device Comparative Examples 1 - 32. The chemical structural formulas of Comparative Compounds 1 - 32 are as follows: 。

[0073] The driving voltage, luminous efficiency, and lifetime of the organic electroluminescent devices obtained from Device Examples 1 - 125 and Device Comparative Examples 1 - 32 were characterized at a brightness of 15,000 (nits). The test results are shown in Table 1 below.

[0074] Table 1 Device Test Results

[0075] ;

[0076] As can be seen from Table 1, Examples 1 - 125 of the organic electroluminescent device prepared using the luminescent layer host provided by the present invention exhibit characteristics of low driving voltage, high luminous efficiency, and long lifespan compared with the devices prepared from Comparative Compounds 1 - 32. The comprehensive performance of the devices is more excellent.

[0077] Among them, Comparative Compound 1 and Compound 1 of the present invention, Comparative Compound 6 and Compound 6 of the present invention, Comparative Compound 27 and Compound 4 of the present invention, Comparative Compound 31 and Compound 393 of the present invention, Comparative Compound 5 and Compound 29 of the present invention, Comparative Compound 20 and Compound 27 of the present invention, Comparative Compound 14 and Compound 95 of the present invention, and Comparative Compound 19 and Compound 348 of the present invention are respectively parallel comparative examples, with the only difference being the substitution positions of carbazole and triazine on dibenzofuran. From the device data, it can be seen that only the compounds conforming to the general formula of the present invention show good performance in luminous efficiency. The reason is that when the substitution position on the aryl ring of dibenzofuran is as in the present invention, the resonance system of the compound is of appropriate length and the triplet state is relatively high, thus effectively preventing the triplet excited state energy level of the dopant from returning to the triplet state energy level of the host, so as to obtain a device structure with high efficiency.

[0078] Comparative Compound 2 and Compound 5 of the present invention, Comparative Compound 4 and Compound 13 of the present invention, Comparative Compound 3 and Compound 9 of the present invention, and Comparative Compound 18 and Compound 11 of the present invention are respectively parallel comparative examples, with the only difference being whether the group substituted on one aromatic ring of dibenzofuran is a phenyl group. From the device data, it can be seen that the compounds conforming to the general formula of the present invention show long lifespan in terms of device lifespan. The reason is that the phenyl group has a smaller molecular weight compared to the substituted groups in the existing structure, making the overall thermal stability of the molecule better.

[0079] Comparative Compound 10 and Compound 6 of the present invention, Comparative Compound 15 and Compound 106 of the present invention, and Comparative Compound 12 and Compound 398 of the present invention are respectively parallel comparative examples, with the only difference being whether there is a phenyl substitution on the side where the triazine is not bonded to the dibenzofuran ring. From the device data, it can be seen that the devices of the compounds conforming to the general formula of the present invention have higher efficiency and lower driving voltage. The reason is that the substitution of phenyl groups with appropriate molecular weight is beneficial to energy transfer and at the same time enhances the molecular steric hindrance to ensure the long lifespan of the device.

[0080] Comparative Compound 29 and Compound 8 of the present invention are parallel comparative examples, with the only difference being the number of phenyl substitutions on the side where the triazine is not bonded to the dibenzofuran ring. As can be seen from the foregoing analysis, the substitution of phenyl groups with appropriate molecular weight is beneficial to energy transfer and more beneficial to the overall thermal stability of the molecule. Therefore, the molecular weight of Comparative Compound 29 is relatively large and the evaporation temperature is relatively high, which affects the device lifespan and cannot prepare a device structure with excellent comprehensive performance.

[0081] Comparative compound 25 and compound 8 of the present invention are parallel comparative examples, and the only difference lies in whether the triazine group is substituted on the same side as the carbazole. From the device structure, it can be seen that the device life of the compound conforming to the general formula of the present invention is longer. The reason is that in the present invention, the electron-donating group carbazole and the electron-withdrawing group triazine are on the same side, as opposed to being substituted on both sides in the comparative compound, which can reduce the molecular stacking phenomenon caused by the intermolecular dipole-dipole force.

[0082] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A phosphorescent host material, characterized in that: The phosphorescent host material has a structure as shown in Formula 1 or Formula 2: ; in, X is selected from O or S; R, R1, R2 are independently selected from deuterium; n is 0, 1, 2, 3, 4, 5, 6, 7, 8; m, p are independently selected from 0, 1, 2, 3, 4, 5; q is selected from 0, 1; Ar is selected from unsubstituted or deuterium-substituted phenyl; Ar1 and Ar2 are independently selected from unsubstituted or deuterium-substituted C6-C24 aryl groups, and unsubstituted or deuterium-substituted C12-C18 heteroaryl groups, and the heteroatom contains one heteroatom selected from O, S, and N.

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: Ar1, Ar2 are independently selected from the following groups which are unsubstituted or substituted with deuterium: , "*" indicates the connection point between the group and the carbon on the ring.

4. The phosphorescent host material according to claim 1, characterized in that: The phosphorescent host material is selected from any one of the compounds shown in the following structural formulas: .

5. A method for preparing the phosphorescent host material as claimed in claim 1, characterized in that: The method specifically comprises the following steps: (1) Synthesis formula 1: 1.0 eq of reactant 1-a, 1.0-1.5 eq of reactant 1-b and 4.5-5.5 eq of potassium carbonate are dissolved in anhydrous DMSO, and then stirred at 140-160° C. for 6-8 hours; when the solution temperature is lowered to room temperature, it is poured into water and stirred, and the resulting precipitate is recovered by suction filtration, dissolved in CH2Cl2 and dried over MgSO4, the solvent is removed by distillation under reduced pressure, and the intermediate 1-c is separated by recrystallization; 1.0 eq of intermediate 1-c and 1.0-1.5 eq of reactant 1-d are added to a reaction flask, followed by a mixed solution of toluene, ethanol and water in a volume ratio of 3:1:1, 0.01-0.03 eq of palladium catalyst, 2.0-3.0 eq of base, 0.10-0.20 eq of phosphine ligand and 2.0-3.0 eq of cesium carbonate are added, the temperature is raised to 100-120° C., and the reaction is refluxed for 6-18 hours; diatomaceous earth is used for hot suction filtration, and after the filtrate is cooled to room temperature, water is then added to the filtrate for washing, the organic phase is retained after separation, and the aqueous phase is extracted with ethyl acetate; the combined organic layer is then dried with magnesium sulfate, and purified by column chromatography to obtain Formula 1; The specific synthetic route is as follows: ; (2) Synthesis formula 2: According to the method of the above-mentioned synthesis formula 1, the reactant 1-a is replaced by 2-a to obtain; The specific synthetic route is as follows: ; in, Hal, Hal1 are selected from F, Cl, Br, I; R' is or ; R, R1, R2, n, m, p, q, Ar1 and Ar2 have the meanings as given in claim 1; The base is selected from potassium carbonate K2CO3, potassium phosphate K3PO4, sodium carbonate Na2CO3, cesium fluoride CsF, cesium carbonate Cs2CO3 or sodium tert-butoxide t-BuONa; The palladium catalyst is selected from tris(dibenzylideneacetone)dipalladium Pd2(dba)3, tetrakis(triphenylphosphine)palladium Pd(PPh3)4, palladium dichloride PdCl2, [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium PdCl2(dppf), palladium acetate Pd(OAc)2, bis(triphenylphosphine)dichloropalladium Pd(PPh3)2Cl2 or (1,1'-bis(diphenylphosphino)ferrocene)dichloronickel NiCl2(dppf); The phosphine ligand is selected from tri-tert-butylphosphine P(t-Bu)3, 2-dicyclohexylphosphine-2,4,6-triisopropylbiphenyl X-phos, triethylphosphine PET3, trimethylphosphine PMe3, triphenylphosphine PPh3, potassium diphenylphosphate KPPh2 or di-tert-butylphosphine chloride P(t-Bu)2Cl.

6. An organic electroluminescent device, characterized in that: The organic electroluminescent device comprises a first electrode, a second electrode, and an organic layer disposed between the first electrode and the second electrode; The organic layer at least includes one or more of a hole injection layer, a hole transport layer, a luminescence auxiliary layer, a luminescent layer, a hole blocking layer, an electron transport layer, and an electron injection layer; The light-emitting layer comprises the phosphorescent host material as claimed in claim 1 .

7. The organic electroluminescent device according to claim 6, characterized in that: The light-emitting layer includes a main material and a doping material, and the main material includes the phosphorescent main material.

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