Phosphorescent host material, preparation method and organic electroluminescent device

Abstract

The 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 structural general formula of the phosphorescent host material is shown in the specification. The phosphorescent host material provided by the invention is used as a material in a luminescent layer of an organic electroluminescent device, so that the luminous efficiency can be improved, the service life of the device can be remarkably prolonged, and the driving voltage can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of organic electroluminescent materials, and in particular relates to a phosphorescent host material, a preparation method 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] At present, in OLED devices made of phosphorescent materials, the main body of the light-emitting layer is mostly a type of derivative with triazine and polycyclic heteroaromatic rings as the parent core. Although the types of structural changes have been quite diverse, a type of material that can achieve a good balance between device voltage, luminous efficiency and life has not yet been found. Therefore, the development of stable and efficient main materials, so that the device can show excellent comprehensive performance in terms of driving voltage, luminous efficiency and life, 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 and an organic electroluminescent device. The phosphorescent host material of the present invention is applied to a specific light-emitting device, which has low driving voltage, high luminous efficiency and long service life.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: The first technical purpose of the present invention is to provide a phosphorescent host material, wherein 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, wherein the heteroatom contains one heteroatom selected from O, S and N.

[0006] Furthermore, the phosphorescent host material has any of the following structures: .

[0007] Further, Ar1, Ar2 are independently selected from the following groups which are unsubstituted or substituted with deuterium: , "*" indicates the connection point of the group to the carbon on the ring.

[0008] In the present invention, the term "unsubstituted or deuterium-substituted" means that the group is substituted with one, two or more deuteriums up to the maximum substitutable number, or has no substituent.

[0009] More specifically, the phosphorescent host material is selected from any one of the following compounds: .

[0010] Only some specific structural forms are listed above, but this series of phosphorescent host materials is not limited to the above molecular structures. Other specific molecular structures can be obtained by simple changes of some simple groups and their substituted groups and substitution positions, which will not be described one by one here.

[0011] The second object of the present invention is to provide a method for preparing the above phosphorescent host material. The phosphorescent host material of the present invention can be prepared by a synthetic method known to those skilled in the art. Alternatively, the following reaction process is preferably used for preparation.

[0012] (1) Synthesis formula 1: The reactant 1-a (1.0 eq), the reactant 1-b (1.0-1.5 eq) and potassium carbonate (4.5-5.5 eq) 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; The intermediate 1-c (1.0 eq) and the reactant 1-d (1.0-1.5 eq) are added to a reaction flask, followed by a mixed solution of toluene, ethanol and water (volume ratio of 3:1:1), 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), 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, and 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 given above.

[0013] Further, the base is selected from K2CO3 (potassium carbonate), K3PO4 (potassium phosphate), Na2CO3 (sodium carbonate), CsF (cesium fluoride), Cs2CO3 (cesium carbonate) or t-BuONa (sodium tert-butoxide); The palladium catalyst is selected from Pd2(dba)3 (tris(dibenzylideneacetone)dipalladium), Pd(PPh3)4 (tetrakis(triphenylphosphine)palladium), PdCl2 (palladium dichloride), PdCl2(dppf) ([1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride), Pd(OAc)2 (palladium acetate), Pd(PPh3)2Cl2 (bis(triphenylphosphine)palladium dichloride) or NiCl2(dppf) ((1,1'-bis(diphenylphosphino)ferrocene)nickel dichloride); The phosphine ligand is selected from P(t-Bu)3 (tri-tert-butylphosphine), X-phos (2-cyclohexylphospho-2,4,6-triisopropylbiphenyl), PET3 (triethylphosphine), PMe3 (trimethylphosphine), PPh3 (triphenylphosphine), KPPh2 (potassium diphenylphosphate) or P(t-Bu)2Cl (di-tert-butylphosphine chloride).

[0014] The third object of the present invention is to provide application of the above phosphorescent host material in an organic electroluminescent device.

[0015] An organic electroluminescent device comprises the phosphorescent host material.

[0016] 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 luminescence auxiliary layer, a luminescent layer, a hole blocking layer, an electron transport layer and an electron injection layer.

[0017] 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.

[0018] 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.

[0019] It should be noted that the light-emitting device containing the phosphorescent host material of 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.

[0020] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects: The invention provides a parent core structure in which positions 1 and 3 of a dibenzoheterocycle are substituted with carbazole and triazine groups, and the side not substituted with triazine is substituted with phenyl. The structural resonance system conforming to the general formula has an appropriate length and a high triplet state, thereby effectively preventing the doped triplet excited state energy level from being transmitted back to the triplet state energy level of the main body, thereby obtaining a high-efficiency device structure; the side not substituted with triazine is substituted with a phenyl group of appropriate molecular weight, which is beneficial to energy transfer and enhances the spatial stereoscopic property of the molecule to ensure a long device life; the electron-pushing group carbazole and the electron-withdrawing group triazine are placed on the same side, thereby reducing the molecular stacking phenomenon caused by the dipole-dipole force between molecules. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0022] Figure 1 It is the hydrogen nuclear magnetic resonance spectrum of compound 3 in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The embodiment of the present invention discloses a method for preparing a phosphorescent host material.

[0025] In addition, it should be noted that the numerical values ​​given in the following examples are as accurate as possible, but those skilled in the art understand that due to unavoidable measurement errors and experimental operation problems, each number should be understood as an approximate number rather than an absolutely accurate value.

[0026] Embodiment 1: ; The reactant 3-a (20 mmol, CAS No.: 2967684-81-5), the 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; when the solution temperature dropped to room temperature, it was poured into water and stirred, and the resulting precipitate was recovered by suction filtration, dissolved in CH2Cl2 and dried over MgSO4, the solvent was removed by distillation under reduced pressure, and the intermediate 3-c was obtained by recrystallization separation.

[0027] The intermediate 3-c (20 mmol) and the reactant 3-d (30 mmol, CAS No.: 3842-55-5) were added to the reaction flask, followed by a mixed solution of toluene, ethanol and water (volume ratio of 3:1:1), Pd(PPh3)4 (0.4 mmol), Na2CO3 (40 mmol), X-phos (3 mmol) and cesium carbonate (40 mmol), and the temperature was raised to 100°C, and the reaction was refluxed for 10 hours; diatomaceous earth was used for hot suction filtration, and the filtrate was cooled to room temperature, and then water was added to the filtrate for washing, and the organic phase was retained after separation, and the aqueous phase was extracted with ethyl acetate; the combined organic layer was then dried with magnesium sulfate and purified by column chromatography to obtain compound 3 (9.17 g, yield: 71.5%, test value MS (ESI, m / Z): [M+H] + = 641.03).

[0028] The H NMR spectrum of compound 3 is as follows Figure 1 shown.

[0029] Characterization: HPLC purity: >99.8%.

[0030] Elemental Analysis: Theoretical values: C, 84.35; H, 4.40; N, 8.74; O, 2.50 Measured values: C, 84.25; H, 4.51; N, 8.77; O, 2.53.

[0031] Device Example 1: Preparation of Green Organic Electroluminescent Device a. ITO anode: clean an ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate with a coating thickness of 150nm in distilled water twice, ultrasonically clean it for 30 minutes, then repeatedly clean it with distilled water twice, ultrasonically clean it for 10 minutes, and bake it in a vacuum oven at 220℃ for 2 hours. After baking, cool it down and it can be used; use the substrate as the anode, use an evaporation machine to carry out the evaporation device process, and evaporate other functional layers on it in sequence.

[0032] b. HIL (hole injection layer): vacuum evaporation of hole injection layer materials HT and P-dopant at an evaporation rate of 1Å / s, with the evaporation rate ratio of HT to P-dopant being 96:4 and the thickness being 10nm; c. HTL (hole transport layer): 125 nm of HT was vacuum-deposited on the hole injection layer at a deposition rate of 1.5 Å / s as the hole transport layer; d. Prime (luminescence auxiliary layer): 40nm of Prime was vacuum evaporated on the hole transport layer at a deposition rate of 0.5Å / s as a luminescence auxiliary layer; e. EML (light-emitting layer): At a deposition rate of 1Å / s, a dual host material (compound 3 provided by the present invention is the first host compound, Host-2 is the second host compound) and a dopant material (Dopant) with a total thickness of 35nm are vacuum-deposited on the light-emitting auxiliary layer 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.

[0033] f. HB (hole blocking layer): HB with a thickness of 5.0 nm was vacuum-deposited on the light-emitting layer at a deposition rate of 0.5 Å / s as a hole blocking layer.

[0034] g. ETL (electron transport layer): ET and Liq with a thickness of 30 nm were vacuum evaporated on the hole blocking layer at a deposition rate of 1Å / s, and the deposition rate ratio of ET and Liq was 1:1.

[0035] h. EIL (electron injection layer): A Yb film with a thickness of 1.0 nm was vacuum-deposited on the electron transport layer at a deposition rate of 0.5 Å / s to form an electron injection layer.

[0036] i. Cathode: Magnesium and silver with a thickness of 13 nm were vacuum evaporated on the electron injection layer at a deposition rate of 1Å / s. The deposition rate ratio of magnesium to silver was 1:9 to obtain a cathode.

[0037] j. Light extraction layer: CPL with a thickness of 60 nm was vacuum-deposited on the cathode at a deposition rate of 1Å / s as a light extraction layer.

[0038] k. Package the vapor-deposited substrate: first, use the glue coating equipment to coat the cleaned cover with UV glue, then move the coated cover to the pressing section, place the vapor-deposited substrate on the upper end of the cover, and finally bond the substrate and cover with the bonding equipment, and complete the light curing of the UV glue at the same time.

[0039] The material structure used in the above device is as follows: .

[0040] Device Example 2-Device Example 125: Referring to the preparation method provided in the above-mentioned Device Example 1, the first main material in Device Example 2 to Device Example 125 in Table 1 is substituted for Compound 3 in Device Example 1, and they are respectively recorded as Device Example 2 to Device Example 125.

[0041] Device Comparative Example 1-Device Comparative Example 32: Referring to the preparation method provided in the above device example 1, comparative compounds 1 to comparative compounds 32 are substituted for compound 3 in device example 1, and are respectively recorded as device comparative example 1 to device comparative example 32, wherein the chemical structures of comparative compounds 1 to comparative compounds 32 are as follows: .

[0042] The driving voltage, luminous efficiency and life of the organic electroluminescent devices obtained from the above-mentioned device examples 1 to 125 and device comparison examples 1 to 32 were characterized at a brightness of 15000 (nits). The test results are shown in Table 1 below.

[0043] Table 1 Device test results ; As can be seen from Table 1, the organic electroluminescent devices Example 1 to Device Example 125 prepared using the light-emitting layer main body provided by the present invention exhibit the characteristics of low driving voltage, high luminous efficiency and long life compared with the devices prepared using Comparative Compound 1 to Comparative Compound 32, and the overall performance of the devices is more excellent.

[0044] Among them, the comparison compound 1 and the compound 1 in the present invention, the comparison compound 6 and the compound 6 in the present invention, the comparison compound 27 and the compound 4 in the present invention, the comparison compound 31 and the compound 393 in the present invention, the comparison compound 5 and the compound 29 in the present invention, the comparison compound 20 and the compound 27 in the present invention, the comparison compound 14 and the compound 95 in the present invention, and the comparison compound 19 and the compound 348 in the present invention are parallel comparative examples, and the difference is only in the substitution position of carbazole and triazine on dibenzofuran. From the device data, it can be seen that only the compounds that conform to the general formula of the present invention perform well in luminous efficiency, because when the substitution position on the aromatic ring of dibenzofuran is as in the present invention, the resonance system of the compound is of appropriate length and the triplet state is high, so that the triplet excited state energy level of the doping can be effectively prevented from being transmitted back to the triplet state energy level of the host to obtain a high-efficiency device structure.

[0045] 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 parallel comparative examples, and the difference is only whether the group substituted on the aromatic ring of one side of dibenzofuran is phenyl. It can be seen from the device data that the compound conforming to the general formula of the present invention exhibits a long life in terms of device life, because the phenyl group has a smaller molecular weight than the substituent group in the existing structure, which makes the overall thermal stability of the molecule better.

[0046] 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 parallel comparative examples, and the only difference is whether the unbonded triazine side of the dibenzofuran ring is substituted with a phenyl group. It can be seen from the device data that the device efficiency of the compound conforming to the general formula of the present invention is higher and the driving voltage is lower, because the phenyl group substitution with an appropriate molecular weight is conducive to energy transfer, and at the same time, the molecular spatial stereoscopicity is enhanced to ensure the long life of the device.

[0047] Comparative compound 29 and compound 8 in the present invention are parallel comparative examples, and the only difference is the number of phenyl groups substituted on the unbonded triazine side of the dibenzofuran ring. From the above analysis, it can be seen that phenyl substitution with an appropriate molecular weight is beneficial to energy transfer and is more beneficial to the thermal stability of the molecule as a whole. Therefore, the molecular weight of comparative compound 29 is relatively large, and the evaporation temperature is high, which affects the device life and cannot prepare a device structure with excellent comprehensive performance.

[0048] Comparative compound 25 and compound 8 in the present invention are parallel comparative examples, and the only difference is whether the triazine group is substituted on the same side as carbazole. From the device structure, it can be seen that the compound device that conforms to the general formula of the present invention has a longer device life. The reason is that in the present invention, the electron-pushing group carbazole and the electron-withdrawing group triazine are on the same side, which can reduce the molecular stacking phenomenon caused by the intermolecular dipole-dipole force compared to the comparative compound where they are substituted on both sides.

[0049] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may 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 the 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, wherein 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 3, characterized in that: "Unsubstituted or deuterium-substituted" means that the group is substituted with one, two, or more, up to the maximum substitutable number of deuterium, or has no substituents.

5. 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:

6. 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.

7. The method for preparing the phosphorescent host material according to claim 6, characterized in that: 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.

8. 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.

9. The organic electroluminescent device according to claim 8, 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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