Phosphorescent host material, preparation method and organic electroluminescent device

Abstract

The invention belongs to the technical field of organic photoelectric materials, and discloses a phosphorescent host material, a preparation method and an organic electroluminescent device.The phosphorescent host material compound is subjected to carbazolyl and triazine group substitution at the first position and the second position of a dibenzoheterocycle, and a phenyl mother nucleus structure is introduced to the substituted same-side aromatic ring of the dibenzoheterocycle, so that the phosphorescent host material is obtained. Structural molecules conforming to the general formula (1) or the general formula (2) are low in symmetry, relatively high in structural rigidity and large in steric hindrance, so that the triplet state energy can be improved, the phenomenon of energy return can be avoided, and meanwhile, the energy loss in the molecules can be reduced, so that the overall performance of the device is more excellent; in addition, the structure conforming to the general formula is more beneficial to charge transfer, so that the driving voltage is reduced, and the luminous efficiency is enhanced.

Description

Technical Field

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

[0002] Organic electroluminescent (OLED) devices are self-luminous devices. Due to their low driving voltage, high brightness, fast response time, wide viewing angle, high resolution, simple process, flexibility and bendability, they have attracted much attention in the fields of new display technology and lighting technology.

[0003] Currently, organic electroluminescent device (OLED) display technology has been applied in smart phones, tablet computers and other fields, and will also expand to large-size application areas such as televisions. However, compared with actual product application requirements, OLED's luminous efficiency and service life and other performance still need to be further improved.

[0004] At present, the phosphorescent host materials used in OLED devices are mainly derivatives with triazine-carbazole as the parent core. Although the types of structures vary, improving the comprehensive performance of the device is still a major challenge. It is difficult to achieve a good balance between driving voltage, luminous efficiency and life. Therefore, developing stable and efficient host materials to improve the comprehensive performance of the device has very important practical application value and is also one of the technical problems that technicians in this field need to solve urgently. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a phosphorescent host material, a preparation method and an organic electroluminescent device. The phosphorescent host material is applied to the light-emitting device, which exhibits low driving voltage, high luminous efficiency and long life characteristics, and the overall performance of the obtained green light organic electroluminescent device is more excellent.

[0006] In order to solve the above problems, the present invention provides the following technical solutions: In a first aspect, the present invention provides a phosphorescent host material, wherein the phosphorescent host material has a compound structure shown in Formula 1 or Formula 2: ; wherein X is selected from O or S; R, R1, R2 are each independently selected from deuterium; n is taken from the values ​​0, 1, 2, 3, 4, 5, 6, 7, 8; Both m and p are 0, 1, 2, 3, 4, 5; q takes the value of 0, 1; Ar is unsubstituted or deuterium-substituted phenyl; Ar1 and Ar2 are independently selected from unsubstituted or deuterated C6-C 24 Aryl, unsubstituted or deuterated C containing one heteroatom of O, S or N 12 -C 18 The heteroaryl group.

[0007] In one embodiment of the present invention, the phosphorescent host material has any of the following structures:

[0008] .

[0009] In one embodiment of the present invention, Ar1 and Ar2 are independently selected from the following groups which are unsubstituted or substituted with deuterium:

[0010] The "*" indicates the attachment point of the group to a ring carbon.

[0011] 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.

[0012] In one embodiment of the present invention, the phosphorescent host material is selected from any one of the following compounds:

[0013]

[0014] .

[0015] The above are some specific structural forms of phosphorescent host material compounds, but they are not limited to the chemical structures listed. All compounds with simple changes of groups within the defined range based on the general structural formula as shown in formula (1) or formula (2) should be included.

[0016] In a second aspect, the present invention further provides a method for synthesizing the above-mentioned phosphorescent host material compound, comprising the following steps: The steps for synthesizing the compound of the structure shown in Formula 1 are as follows: ; The compound with the structure shown in Formula 2 can be synthesized by replacing the reactant 1-a in the above Formula 1 with 2-a; The steps for synthesizing the compound of the structure shown in Formula 2 are as follows: ; Wherein, Hal, Hal1, Hal2 are selected from F, Cl, Br, I; R, R1, R2, n, m, p, q, Ar, Ar1 and Ar2 have the meanings given above.

[0017] Specifically, the steps of synthesizing the compound represented by Formula 1 or Formula 2 include: After the reactant 1-a or 2-a (1.0 eq) and the reactant 1-b (0.8-1.0 eq) are dissolved in xylene, a palladium catalyst (0.01-0.05 eq), a phosphorus ligand (0.02-0.15 eq), and an alkaline salt (2.0-2.4 eq) are added; after the addition, the reaction temperature is slowly raised to 100-120° C., and the mixture is stirred for 8-12 hours; the reaction is detected by thin layer chromatography, and after the reaction is completed, water and dichloromethane are added for extraction and separation, the organic phases are combined and concentrated, and a mixed solution of dichloromethane and petroleum ether (V:V=1:4-1:8) is used for purification by column chromatography to obtain an intermediate 1-c or an intermediate 2-c.

[0018] Note: In this reaction step, the raw material 1-a or 2-a may have two halogens. On the one hand, the characteristics of the reaction activity I>Br>Cl are utilized, and on the other hand, the reaction site is controlled by controlling the reaction conditions, and the reaction is purified by column chromatography to obtain the target compound. Reference common knowledge is as follows: "Transition Metal Organic Chemistry" (Original Sixth Edition), Robert H. Crabtree, Publisher: Shanghai East China University of Science and Technology Press, Publication Date: 2017-09-00, ISBN: 978-7-5628-5111-0, page 388.

[0019] "Organic Chemistry and Optoelectronic Materials Experimental Tutorial", Chen Runfeng, Publisher: Southeast University Press, Publication Date: 2019-11-00, ISBN: 9787564184230, Page 174.

[0020] Dissolve intermediate 1-c or intermediate 2-c (1.0 eq), reactant intermediate 1-d (1.0-1.3 eq), palladium catalyst (0.01-0.02 eq) and potassium acetate (2.0-3.0 eq) in DMF, raise the temperature to 80-100°C, react for 6-8 hours, and remove the solvent using a rotary evaporator. Add dichloromethane to the residue, stir, filter, and purify by column chromatography to obtain intermediate 1-e or intermediate 2-e; The intermediate 1-e or intermediate 2-e (1.0eq) and the reactant 1-f (1.0-1.3eq) are added to the reaction bottle, followed by a mixed solution of toluene, ethanol and water (volume ratio of 3:1:1), a palladium catalyst (0.01-0.02eq) and an alkaline salt (2.0-3.0eq), and the temperature is raised to 100-120°C, and the reaction is refluxed for 6-18 hours. The mixture is filtered while hot using diatomaceous earth, 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 a compound of the structure shown in Formula 1 or Formula 2.

[0021] In one embodiment of the present invention, the alkaline salt is selected from one or more of K2CO3 (potassium carbonate), K3PO4 (potassium phosphate), Na2CO3 (sodium carbonate), CsF (cesium fluoride), Cs2CO3 (cesium carbonate) and t-BuONa (sodium tert-butoxide).

[0022] In one embodiment of the present invention, the palladium catalyst is selected from one or more of 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) and NiCl2(dppf) ((1,1'-bis(diphenylphosphino)ferrocene)nickel dichloride).

[0023] In one embodiment of the present invention, the phosphorus ligand is selected from one or more of P(t-Bu)3 (tri-tert-butylphosphine), X-phos (2-cyclohexylphosphine-2,4,6-triisopropylbiphenyl), PET3 (triethylphosphine), PMe3 (trimethylphosphine), PPh3 (triphenylphosphine), KPPh2 (potassium diphenylphosphonate) and P(t-Bu)2Cl (di-tert-butylphosphine chloride).

[0024] In a third aspect, the present invention further provides an organic electroluminescent device, comprising the above-mentioned phosphorescent host material.

[0025] In one embodiment of the present invention, the green light organic electroluminescent device includes an anode, a hole injection layer, a hole transport layer, a luminescence auxiliary layer, a luminescent layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode arranged in sequence; the luminescent layer contains the phosphorescent host material.

[0026] In one embodiment of the present invention, the light-emitting layer contains a phosphorescent host material as a first host compound, a second host compound Host-2 and a dopant material.

[0027] Beneficial technical effects of the present invention: The present invention provides a phosphorescent host material compound, wherein the 1-position and 2-position of a dibenzoheterocyclic ring are substituted with a carbazole group and a triazine group, and a phenyl core structure is introduced into the aromatic ring on the same side of the substituted dibenzoheterocyclic ring. The structure conforming to the general formula (1) and the general formula (2) of the present invention has low molecular symmetry, strong structural rigidity, and large steric hindrance, which is conducive to improving the energy of the triplet state and avoiding the phenomenon of energy backtransfer. At the same time, it can also reduce the energy loss inside the molecule, so that the overall performance of the device is more excellent. In addition, the structure conforming to the general formula of the present invention is more conducive to charge transmission, thereby reducing the driving voltage and enhancing the luminous efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the hydrogen nuclear magnetic resonance spectrum of compound 282 in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0030] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available.

[0031] Example 1 Preparation of compound 282: , After reactant 282-a (1.0 eq, CAS number: 2765550-02-3) and reactant 282-b (0.8 eq, CAS number: 86-74-8) were dissolved in xylene, Pd(PPh3)4 (0.02 eq), X-Phos (0.01 eq), and t-BuONa (2.0 eq) were added; after the addition, the reaction temperature was slowly raised to 100°C, and the mixture was stirred for 8 hours; the reaction was detected by thin layer chromatography, and after the reaction was completed, water and dichloromethane were added for extraction and separation, the organic phases were combined and concentrated, and the intermediate 282-c was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:4).

[0032] The intermediate 282-c (1.0 eq), the reactant intermediate 282-d (1.3 eq, CAS No.: 73183-34-3), Pd(PPh3)4 (0.01 eq) and potassium acetate (2.0 eq) were dissolved in DMF, heated to 90°C, reacted for 8 hours, and the solvent was removed by a rotary evaporator. The residue was added with dichloromethane, stirred, filtered, and purified by column chromatography to obtain the intermediate 282-e; The intermediate 282-e (1.0 eq) and the reactant 282-f (1.3 eq, 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 (0.01 eq) and t-BuONa (2.0 eq), and the temperature was raised to 120°C, and the reaction was refluxed for 10 hours. Celite was used for hot suction filtration, and the filtrate was cooled to room temperature, and then water was added to the filtrate for washing. After separation, the organic phase was retained, 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 282 (yield: 73.9%, test value MS (ESI, m / Z): [M+H]+ = 656.33).

[0033] The H NMR spectrum of compound 282 is as follows Figure 1 shown.

[0034] Characterization: HPLC purity: >99.8%.

[0035] Elemental Analysis: Theoretical values: C, 82.29; H, 4.30; N, 8.53; S, 4.88 Test values: C, 82.21; H, 4.33; N, 8.57; S, 4.96 Device Example 1 Preparation of green organic electroluminescent devices: a. ITO anode: Wash the ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate with a coating thickness of 150nm in distilled water twice, ultrasonically wash for 30 minutes, and then repeatedly wash it with distilled water twice, ultrasonically wash 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 this substrate as the anode, use an evaporation machine to perform the evaporation device process, and evaporate other functional layers on it in sequence.

[0036] b. HIL (hole injection layer): vacuum evaporation of hole injection layer materials HT and P-dopant at an evaporation rate of 1 angstrom / second, with the evaporation rate ratio of HT to P-dopant being 97:3 and the thickness being 10 nm; c. HTL (hole transport layer): 120 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): 35nm of Prime is vacuum-deposited on the hole transport layer at a deposition rate of 0.5 angstroms / second as a luminescence auxiliary layer; e. EML (light-emitting layer): Then, on the above-mentioned light-emitting auxiliary layer, a dual host material (compound 282 provided by the present invention is used as the first host compound, and Host-2 is used as the second host compound) and a dopant material (Dopant) with a total thickness of 30 nm are vacuum-deposited at a deposition rate of 1 Å / s as a light-emitting layer, wherein the deposition rate ratio of the first host compound, the second host compound and the dopant material is 44:44:12.

[0037] f. HB (hole blocking layer): HB with a thickness of 5.0 nm was vacuum-deposited at a deposition rate of 0.5 Å / s as a hole blocking layer.

[0038] g. ETL (electron transport layer): ET and Liq with a thickness of 30 nm were vacuum-deposited at a deposition rate of 1 angstrom / second as the electron transport layer. The deposition rate ratio of ET to Liq was 1:1.

[0039] h. EIL (electron injection layer): 1.0 nm of Yb film was evaporated at a deposition rate of 0.5 Å / s to form an electron injection layer.

[0040] i. Cathode: 13 nm of magnesium and silver were evaporated at an evaporation rate ratio of 1 angstrom / s, and the evaporation rate ratio was 1:9 to obtain an OLED device.

[0041] j. Light extraction layer: CPL with a thickness of 65 nm was vacuum-deposited on the cathode at a deposition rate of 1 angstrom / second to serve as the light extraction layer.

[0042] k. Package the substrate after evaporation. 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 evaporation-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.

[0043] The material structure used in the above device is as follows: .

[0044] Device Example 2-108: The first host material in device examples 2 - 108 in Table 1 can be substituted for compound 282 in device example 1.

[0045] Device Comparative Example 1-Device Comparative Example 23: Referring to the preparation method provided in the above device example 1, comparative compounds 1-23 are substituted for compound 282 in device example 1, and they are respectively recorded as device comparative examples 1-23, wherein the chemical structural formula of comparative compounds 1-23 is as follows:

[0046]

[0047]

[0048] .

[0049] The driving voltage, luminous efficiency and life of the organic electroluminescent devices obtained from the device embodiments 1-108 and the device comparison examples 1-23 were characterized at a brightness of 15000 (nits). The test results are shown in Table 1 below.

[0050] Table 1 Device test results

[0051]

[0052]

[0053]

[0054]

[0055]

[0056] As can be seen from Table 1, the organic electroluminescent device Examples 1-108 prepared using the phosphorescent host material provided by the present invention as the main body of the light-emitting layer exhibits the characteristics of low driving voltage, high luminous efficiency and long life compared with the device prepared using the comparative compound 1-23 as the main body of the light-emitting layer, and the overall performance of the device is more excellent.

[0057] Among them, comparison compound 2 and comparison compound 3 are parallel comparison examples with compound 246 of the present invention. Compared with compound 246, the introduction of a dibenzofuran group in comparison compound 2 on the aromatic ring of the parent nucleus dibenzofuran of the present invention not only reduces the asymmetry of the molecule, but also enhances the coupling between the structures to cause molecular stacking, increases the molecular crystallinity, and causes the device efficiency to roll off significantly and reduce the life span. Compared with the parent nucleus of the present invention, comparison compound 3 introduces one less phenyl, and the molecular weight is small, resulting in poor thermal stability, which makes the overall performance of the device poor. At the same time, the phenyl introduced by the present invention can also further improve the electron mobility and reduce the driving voltage of the device.

[0058] Comparative compound 6 and compound 329 of the present invention are parallel comparative examples, and the only difference between the two is the substitution position of the triazine group. From the device data in Table 1, it can be seen that the overall performance of the present invention is more excellent, because the molecular space provided by the present invention is more stereoscopic, the energy of the triplet state is increased, the phenomenon of energy back transmission is avoided, and the overall performance of the device is better. Comparative compound 8 and compound 334 of the present invention, comparative compound 9 and compound 335 of the present invention, comparative compound 10 and compound 337 of the present invention, comparative compound 11 and compound 338 of the present invention, comparative compound 12 and compound 277 of the present invention, comparative compound 13 and compound 369 of the present invention, comparative compound 16 and compound 1 of the present invention, comparative compound 19 and compound 2 of the present invention also have structural defects of poor molecular stereoscopic properties.

[0059] Comparative compound 18 and compound 1 of the present invention are parallel comparative examples, and the only difference is the group substituted at the 4-position of dibenzofuran. Compared with the carbazole group, the phenyl group has a smaller molecular weight and has less effect on the thermal stability of the molecule. Secondly, the phenyl group has better compatibility and can be mixed with many other organic materials (such as dopants), which helps to improve the overall performance of the device.

[0060] Comparative compound 15 is closer to compound 1 of the present invention. In comparative compound 15, triazine and dibenzofuran are connected by phenylene groups instead of direct bonding as in the present invention. The stereochemistry of the molecule is relatively small, and the phenylene groups in the middle will also cause rotation inside the molecule and lose energy, affecting the overall performance of the device.

[0061] Comparative compound 23 and compound 281 are parallel comparative examples. The substituent groups on one side of dibenzothiophene are the same but the substitution positions are different. From the device data, it can be seen that the compounds conforming to the general formula of the present invention perform better in terms of device voltage, luminous efficiency and life. The possible reason is that the connection method in the general formula of the present invention is more conducive to electron delocalization, so that the molecular structure can be stabilized, which is beneficial to charge transfer and improves electron mobility.

[0062] The specific embodiments described above have detailed descriptions of the objectives, technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A phosphorescent host material, characterized in that: The phosphorescent host material has a compound structure shown in Formula 1 or Formula 2: ； Wherein, X is selected from O or S; R, R1, R2 are each independently selected from deuterium; The values ​​of n are 0, 1, 2, 3, 4, 5, 6, 7, 8; The values ​​of m and p are 0, 1, 2, 3, 4, 5; q takes the value 0, 1; Ar is unsubstituted or deuterium-substituted phenyl; Ar1 and Ar2 are independently selected from unsubstituted or deuterated C6-C 24 Aryl, unsubstituted or deuterated C containing one heteroatom of O, S or N 12 -C 18 The heteroaryl group.

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: The Ar1 and Ar2 are independently selected from the following groups which are unsubstituted or substituted with deuterium: ， "*" indicates the attachment point of the group to a ring carbon.

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. A method for synthesizing the phosphorescent host material according to any one of claims 1 to 4, characterized in that: The following steps are involved: After reactant 1-a or reactant 2-a and reactant 1-b are dissolved in xylene, a palladium catalyst, a phosphorus ligand and a basic salt are added; Heat the reaction mixture to a temperature of 100-120°C and stir the mixture for 8-12h; After the reaction is completed, water and dichloromethane are added for extraction and separation, the organic phases are combined and concentrated, and a mixed solution of dichloromethane and petroleum ether is used for purification by column chromatography to obtain intermediate 1-c or 2-c; Dissolve intermediate 1-c or intermediate 2-c, reactant intermediate 1-d, palladium catalyst and potassium acetate in DMF, raise the temperature to 80-100° C., react for 6-8 hours, and remove the solvent using a rotary evaporator; The residue is added with dichloromethane, stirred, filtered, and purified by column chromatography to obtain intermediate 1-e or intermediate 2-e; Add intermediate 1-e or intermediate 2-e and reactant 1-f to a reaction flask, then add a mixed solution of toluene, ethanol and water, add a palladium catalyst and an alkaline salt, heat to 100-120° C., and reflux for 6-18 hours; Use diatomaceous earth to filter while hot, and after the filtrate is cooled to room temperature, water is added to the filtrate for washing, and after separation, the organic phase is retained, and the aqueous phase is extracted with ethyl acetate; Then, the combined organic layer is dried with magnesium sulfate, and purified by column chromatography to obtain a compound with a structure represented by Formula 1 or Formula 2; The reaction formula of the structural compound shown in the synthetic formula 1 is as follows: ； The reaction formula of the structural compound shown in the synthetic formula 2 is as follows: ； Wherein, Hal, Hal1, Hal2 are selected from F, Cl, Br or I; X is selected from O, or S; R, R1, R2 are each independently selected from deuterium; The values ​​of n are 0, 1, 2, 3, 4, 5, 6, 7, 8; Both m and p are 0, 1, 2, 3, 4, 5; q takes the value of 0, 1; Ar is unsubstituted or deuterium-substituted phenyl; Ar1 and Ar2 are each independently selected from unsubstituted or deuterated C6-C 24 Aryl, unsubstituted or deuterated C containing one heteroatom of O, S or N 12 -C 18 The heteroaryl group.

6. The synthesis method according to claim 5, characterized in that The alkaline salt is selected from one or more of potassium carbonate, potassium phosphate, sodium carbonate, cesium fluoride, cesium carbonate and sodium tert-butoxide; The palladium catalyst is selected from one or more of tris(dibenzylideneacetone)dipalladium, tetrakis(triphenylphosphine)palladium, palladium dichloride, [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride, palladium acetate, bis(triphenylphosphine)palladium dichloride and (1,1'-bis(diphenylphosphino)ferrocene)nickel dichloride; The phosphorus ligand is selected from one or more of tri-tert-butylphosphine, 2-cyclohexylphospho-2,4,6-triisopropylbiphenyl, triethylphosphine, trimethylphosphine, triphenylphosphine, potassium diphenylphosphine and di-tert-butylphosphine chloride.

7. An organic electroluminescent device, characterized in that: The phosphorescent host material comprises any one of claims 1 to 4.

8. The organic electroluminescent device according to claim 7, characterized in that: The organic electroluminescent device comprises an anode, a hole injection layer, a hole transport layer, a luminescence auxiliary layer, a luminescent layer, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode which are arranged in sequence; the luminescent layer contains the phosphorescent host material.

9. The organic electroluminescent device according to claim 8, characterized in that: The light emitting layer contains a phosphorescent host material as a first host compound, a second host compound, and a dopant material.

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