Green phosphorescent host material and organic electroluminescent device

Abstract

The invention provides a green phosphorescent host material and an organic electroluminescent device, and belongs to the field of electroluminescent materials, the structural general formula of the green phosphorescent host material is a chemical formula I. The green phosphorescent host material provided by the invention takes a rigid dibenzofuran group or dibenzothiophene group as an intermediate bridging group; a carbazole group and a triazine group are respectively connected to the first position and the fourth position of a dibenzofuran group or a dibenzothiophene group, and the structure can effectively improve the hole and electron transmission capability, enables holes and electrons to reach a balance state, enables a material device to maintain low driving voltage, and has high luminous efficiency and long service life.

Description

Technical Field

[0001] The invention belongs to the field of electroluminescent materials and relates to a green phosphorescent main material and an organic electroluminescent device. Background Art

[0002] At present, the research on OLED (organic light-emitting diode) has made significant progress. The first generation of OLED based on the use of fluorescent materials in the light-emitting layer only uses singlet excitons to emit light, and its internal quantum efficiency (IQE) is only 25%. The second generation of OLED based on the use of transition metal phosphorescent materials in the light-emitting layer makes the radiation of triplet excitons possible through spin-orbit coupling, and the theoretical IQE can reach 100%. However, the second generation of OLED based on phosphorescent materials still faces many problems: (1) The high price of transition metals such as Os, Ir, and Pt commonly used in the light-emitting layer is not conducive to the mass production of high-efficiency OLED devices; (2) Triplet-triplet excitons are prone to quenching under high current, resulting in a serious roll-off of device efficiency. In recent years, in order to reduce the production cost of devices and make OLED truly commercialized and industrialized, the use of phosphorescent materials doped with precious metals in the light-emitting layer has been avoided.

[0003] OLED light-emitting devices rely on the recombination of carriers (electrons and holes) transported in organic semiconductor materials. As we all know, organic materials have poor conductivity, there is no continuous energy band in organic semiconductors, and the transport of carriers is often described by jumping theory. In order to achieve a breakthrough in the application of organic electroluminescent devices, the difficulty of poor charge injection and transport capabilities of organic materials must be overcome. Scientists adjust the device structure, such as increasing the number of organic material layers in the device, and making different organic layers play different device layers. For example, some functional materials can promote the injection of electrons from the cathode, some functional materials can promote the injection of holes from the anode, some materials can promote the transport of charges, and some materials can play the role of blocking the transport of electrons or holes. Of course, in OLED light-emitting devices, the most important thing is that the light-emitting materials of various colors must also achieve the purpose of matching with adjacent functional materials. Therefore, OLED light-emitting devices with good efficiency and long life are usually the result of optimized matching of device structure and various organic materials, which provides great opportunities and challenges for researchers to design and develop functional materials of various structures. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a green phosphorescent host material and an organic electroluminescent device. The green phosphorescent host material of the present invention uses a rigid dibenzofuran group or a dibenzothiophene group as an intermediate bridging group, and the 1-position and 4-position on the dibenzofuran group or the dibenzothiophene group are respectively connected to a carbazole group and a triazine group. This structure can effectively improve the transmission capacity of holes and electrons, and make holes and electrons reach a balanced state, so that the material device maintains a low driving voltage, and has a high luminous efficiency and service life.

[0005] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0006] In one aspect, the present invention provides a green phosphorescent host material, wherein the green phosphorescent host material has a general structural formula of Chemical Formula I:

[0007]

[0008] in,

[0009] X is selected from O, S;

[0010] R1 and R2 are each independently selected from deuterium;

[0011] R3 is independently selected from deuterium, phenyl;

[0012] n1 and n2 are each independently selected from 0, 1, 2, 3, 4, and 5;

[0013] n3 is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8;

[0014] Ar1 and Ar2 are each independently selected from a substituted or unsubstituted C6-C24 aryl group, a substituted or unsubstituted C3-C24 heteroaryl group, and the heteroatom thereof contains at least one of O, S, N, Si or Se.

[0015] More preferably, Ar1 and Ar2 are each independently selected from the following groups:

[0016]

[0017] In the formula, * represents the connection site;

[0018] R4-R 16 Each is independently selected from hydrogen, deuterium, and C1-C6 alkyl substituted or unsubstituted by deuterium;

[0019] n4、n 11 Each is independently selected from 0, 1, 2, 3, 4, 5;

[0020] n5 and n8 are each independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9;

[0021] n6、n 14 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13;

[0022] n7 and n9 are each independently selected from 0, 1, 2, 3, 4, 5, 6, and 7;

[0023] n 10 、n 16 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8;

[0024] n 12 Independently selected from 0, 1, 2, 3, 4;

[0025] n 13 、n 15 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11.

[0026] In the present invention, the term "substituted" in the term "substituted or unsubstituted" means a substituent connected by one, two or more substituents selected from the following: deuterium, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopentane, cyclohexane, phenyl, biphenyl, naphthyl, fluorenyl, dimethylfluorenyl, phenanthryl, anthracenyl, indenyl, triphenylene, pyrenyl, chrysyl, furanyl, thienyl, pyrrolyl, pyridyl, benzofuranyl, benzothienyl, isobenzofuranyl, dibenzofuranyl, dibenzothienyl, benzimidazolyl, benzothiazolyl, benzisothiazolyl, benzisoxazolyl, benzoxazolyl, isoindolyl, indolyl, benzindolyl, indazolyl, benzothiadiazolyl, carbazolyl, benzocarbazolyl.

[0027] Furthermore, the green phosphorescent host material is selected from any one of the following compounds:

[0028]

[0029] .

[0030] The green phosphorescent host material of the present invention can be prepared by a synthesis method known to those skilled in the art.

[0031] The present invention provides a method for preparing the green phosphorescent host material as described above, the method comprising the following steps:

[0032] (1) Raw material A reacts with raw material B to obtain intermediate 1. The reaction formula is as follows:

[0033] ;

[0034] (2) Intermediate 1 reacts with isopropyl borate to obtain intermediate 2. The reaction formula is as follows:

[0035] ;

[0036] (3) Intermediate 2 reacts with raw material C to obtain a green phosphorescent host material represented by chemical formula I. The reaction formula is as follows:

[0037] ;

[0038] Wherein, X, R1, R2, R3, n1, n2, n3, Ar1, Ar2 are as defined in claim 1, and Hal1, Hal2 are each independently selected from chlorine or bromine.

[0039] Preferably, the molar ratio of raw material A to raw material B in step (1) is 1:1.0-1.2; for example, 1:1.0, 1:1.1, 1:1.15 or 1:1.2.

[0040] The reaction in step (1) is carried out in the presence of an alkaline substance, wherein the alkaline substance is selected from sodium tert-butoxide and / or potassium tert-butoxide; the molar ratio of the alkaline substance to the raw material A is 2.0-4.0:1, for example, 2.0:1, 2.3:1, 2.5:1, 2.8:1, 3:1, 3.5:1, 3.8:1 or 4.0:1, etc.

[0041] The reaction in step (1) is carried out in the presence of a catalyst, the catalyst is selected from tris(dibenzylideneacetone)dipalladium, and the molar ratio of the catalyst to the raw material A is 0.01-0.05:1; for example, 0.01:1, 0.02:1, 0.03:1, 0.04:1 or 0.05:1.

[0042] The reaction in step (1) is carried out in an organic solvent selected from toluene. The reaction temperature in step (1) is 100-110°C, for example, 100°C, 105°C, 108°C or 110°C. The reaction time is 4-20h, for example, 4h, 8h, 10h, 12h, 14h, 16h, 18h or 20h.

[0043] Preferably, in step (2), the molar ratio of the intermediate 1 to isopropyl borate is 1:1.5.

[0044] The reaction in step (2) is carried out in the presence of n-butyllithium.

[0045] In step (2), n-butyl lithium is added into the reaction system at -78°C.

[0046] The reaction in step (2) is carried out at room temperature for 1-2 hours.

[0047] In step (3), the molar ratio of the intermediate 2 to the raw material C is 1:1.0-1.3, for example, 1:1.0, 1:1.1, 1:1.2 or 1:1.3.

[0048] The reaction in step (3) is carried out in the presence of a catalyst, the catalyst is selected from tetrakis(triphenylphosphine)palladium, and the molar ratio of the catalyst to the intermediate 2 is 0.01-0.03:1, for example 0.01:1, 0.02:1 or 0.03:1.

[0049] The reaction in step (3) is carried out in a solvent, which is a mixed solution of toluene, ethanol and water.

[0050] The reaction temperature in step (3) is 80°C-95°C, for example 80°C, 82°C, 85°C, 88°C, 90°C, 92°C or 95°C, and the reaction time is 4-20h, for example 4h, 8h, 10h, 12h, 14h, 16h, 18h or 20h.

[0051] As a preferred technical solution, the green phosphorescent host material of the present invention is prepared by the following reaction process:

[0052]

[0053] Specific preparation method:

[0054] Step 1 specifically includes the following processes:

[0055] Raw material A (1.0 eq), raw material B (1.0-1.2 eq) and sodium tert-butoxide (2.0-4.0 eq) are added to a reaction flask, followed by anhydrous toluene. Tri(dibenzylideneacetone)dipalladium (0.01-0.05 eq) is added under nitrogen protection, the temperature is raised to 100-110°C, and the reaction is refluxed for 4-20 hours. The reaction is detected by thin layer chromatography. After the reaction is completed, the temperature is slightly lowered, and diatomaceous earth is used for filtration to remove salt and catalyst. After the filtrate is cooled to room temperature, dichloromethane and water are added for extraction and separation. The organic phase is retained and concentrated, and intermediate 1 is purified by column chromatography using petroleum ether or a mixed solution of dichloromethane and petroleum ether (V:V=1:4-1:10) to obtain intermediate 1.

[0056] Step 2 specifically includes the following processes:

[0057] Under nitrogen protection, intermediate 1 (1.0 eq) was added to a reaction bottle containing THF to dissolve, and n-butyl lithium (n-BuLi, 1.5 eq) was slowly added dropwise at -78°C, and the mixture was stirred at room temperature for 1-2 h. Isopropyl borate (i-PrO) 3B (1.5 eq) was added dropwise to the reaction mixture at -78°C, and then stirred at room temperature for 1-2 h. The reaction was detected by thin layer chromatography. After the reaction was completed, the mixture was extracted with aqueous ammonium chloride at room temperature, and the organic layer was dried over MgSO4, concentrated, and recrystallized from ethyl acetate to obtain intermediate 2.

[0058] Step 3 specifically includes the following processes:

[0059] The intermediate 2 (1.0 eq), the raw material C (1.0-1.3 eq) and potassium carbonate (2.0-4.0 eq) were added to a reaction flask, and then a mixed solution of toluene, ethanol and water (V:V:V = 3:1:1) was added, and tetrakis(triphenylphosphine)palladium (0.01-0.03 eq) was added under nitrogen protection, and the temperature was raised to 80°C-95°C, and the reaction was refluxed for 4-20 hours; the reaction was detected by thin layer chromatography, and after the reaction was completed, the temperature was slightly lowered, and diatomaceous earth was used for filtering to remove salt and catalyst. After the filtrate was cooled to room temperature, dichloromethane and water were added for extraction and separation, and the organic phase was retained and concentrated, and a mixed solution of dichloromethane and petroleum ether (V:V=1:4-1:10) was used for purification by column chromatography to obtain chemical formula I.

[0060] In the above formula, X, R1, R2, R3, n1, n2, n3, Ar1, Ar2 are as defined in the above chemical formula I, and Hal1 and Hal2 are each independently selected from chlorine or bromine.

[0061] In particular, for complex raw materials that have not been disclosed before, the classic Suzuki coupling reaction and Buchwald–Hartwig coupling reaction are used for synthesis and applied to the present invention.

[0062] On the other hand, the present invention provides an organic electroluminescent device, which includes a first electrode, an organic electroluminescent material layer, and a second electrode; the organic electroluminescent material layer includes a light-emitting layer, and the light-emitting layer includes the green phosphorescent host material as described above.

[0063] Preferably, the organic electroluminescent material layer further comprises at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer and an electron injection layer.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] The compound of the present invention effectively presents the characteristics of the phosphorescent main layer material. The compound structure uses a rigid dibenzofuran group or a dibenzothiophene group as an intermediate bridging group, and the 1-position and 4-position of the dibenzofuran group or the dibenzothiophene group are respectively connected to a carbazole group and a triazine group, wherein the triazine serves as an electron acceptor unit with high carrier transport capability, and the carbazole group and the dibenzofuran group or the dibenzothiophene group serve as electron donor units with high carrier transport capability. The structure can effectively improve the transport capability of holes and electrons, and make holes and electrons reach a balanced state, so as to improve the luminous efficiency and service life of the organic electroluminescent device, while maintaining a low driving voltage.

[0066] Among them, the carbazole group has a higher triplet energy level, which helps to effectively capture and transfer triplet excitons, prevent energy loss, and thus improve the phosphorescent luminescence efficiency of the material device. In addition, the carbazole group has strong rigidity and better thermal stability, can maintain the integrity of the structure at high temperature, improve the thermal stability of the material, make the material structure less likely to change during high-temperature evaporation, and effectively extend the service life of the device. In addition, the introduction of rigid dibenzofuran group or dibenzothiophene group increases the thermal stability of the material molecule and greatly improves the life of the device. Connecting a phenyl group (or deuterated phenyl group) to the dibenzofuran group or dibenzothiophene group can effectively increase the conjugated area and further improve the luminescence efficiency. At the same time, it can also balance the structure of the molecule, enhance its thermal stability and film-forming properties during evaporation, and effectively improve the life of the device. Further connecting a triazine group with high electron affinity to improve the mobility of the organic molecule, the N atom in which has good electron transport performance, can lower the ability of the molecule LUMO energy level, and also has excellent energy level matching characteristics, which is conducive to matching with high work function electrodes, enhancing the conductivity of the material, and improving the overall performance of the device.

[0067] Moreover, the carbazole group and the triazine group are located at the 1-position and 4-position of the dibenzofuran group or the dibenzothiophene group, respectively, which can effectively reduce the quenching phenomenon caused by aggregation and form a more effective conjugated system to enhance the charge transfer and energy transfer within the molecule, which helps to improve the phosphorescence quantum efficiency of the material and thus improve the luminescence efficiency of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of compound 1 provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0069] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0070] Example 1

[0071]

[0072] Step 1 specifically includes the following processes:

[0073] Raw material A-1 (1.0 eq, CAS number: 1821235-55-5), raw material B-1 (1.0 eq, CAS number: 34479-78-2) and sodium tert-butoxide (2.0 eq) were added to a reaction flask, followed by anhydrous toluene. Tris(dibenzylideneacetone)dipalladium (0.02 eq) was added under nitrogen protection, the temperature was raised to 100°C, and the mixture was refluxed for 12 hours. The reaction was detected by thin layer chromatography. After the reaction was completed, the temperature was slightly lowered, and diatomaceous earth was used for filtration to remove salt and catalyst. After the filtrate was cooled to room temperature, dichloromethane and water were added for extraction and separation. The organic phase was retained and concentrated. The intermediate 1 was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:5) to obtain the intermediate 1 (yield: 75.6%).

[0074] Step 2 specifically includes the following processes:

[0075] Under nitrogen protection, intermediate 1 (1.0 eq) was added to a reaction bottle containing THF to dissolve, n-BuLi (1.5 eq) was slowly added dropwise at -78°C, and the mixture was stirred at room temperature for 1 h. Isopropyl borate (i-PrO)3B (1.5 eq) was added dropwise to the reaction mixture at -78°C, and then stirred at room temperature for another 1 h. The reaction was monitored by thin layer chromatography. After the reaction was completed, the mixture was extracted with aqueous ammonium chloride at room temperature, and the organic layer was dried over MgSO4, concentrated, and recrystallized from ethyl acetate to obtain intermediate 2 (yield: 64.8%).

[0076] Step 3 specifically includes the following processes:

[0077] Intermediate 2 (1.0 eq), raw material C-1 (1.0 eq, CAS number: 1472062-94-4) and potassium carbonate (3.0 eq) were added to a reaction flask, followed by a mixed solution of toluene, ethanol and water (V:V:V = 3:1:1), and tetrakis(triphenylphosphine)palladium (0.03 eq) was added under nitrogen protection. The temperature was raised to 95°C and refluxed for 12 hours. The reaction was detected by thin layer chromatography. After the reaction was completed, the temperature was slightly lowered, and diatomaceous earth was used for filtration to remove salt and catalyst. After the filtrate was cooled to room temperature, dichloromethane and water were added for extraction and separation. The organic phase was retained and concentrated, and a mixed solution of dichloromethane and petroleum ether (V:V=1:4) was used for purification by column chromatography to obtain compound 1 (yield: 80.1%).

[0078] The obtained compound 1 was tested and analyzed, and the results were as follows:

[0079] HPLC purity: >99.8%.

[0080] Mass spectrometry test: The model is Waters XEVO TQD mass spectrometer, using ESI source.

[0081] Test value (ESI, m / Z): [M+H] + ):716.49.

[0082] Elemental Analysis:

[0083] Calculated values: C, 85.45; H, 4.50; N, 7.82; O, 2.23;

[0084] Analytical values: C, 85.15; H, 4.62; N, 7.96; O, 2.36.

[0085] The H NMR spectrum of compound 1 is shown in Figure 1 shown.

[0086] Example 2

[0087]

[0088] Step 1 specifically includes the following processes:

[0089] Raw material A-210 (1.0 eq, CAS number: 2419887-92-4), raw material B-210 (1.0 eq, CAS number: 34479-78-2) and sodium tert-butoxide (2.0 eq) were added to a reaction flask, followed by anhydrous toluene. Tris(dibenzylideneacetone)dipalladium (0.02 eq) was added under nitrogen protection, the temperature was raised to 110°C, and the mixture was refluxed for 10 hours. The reaction was detected by thin layer chromatography. After the reaction was completed, the temperature was slightly lowered, and diatomaceous earth was used for filtration to remove salt and catalyst. After the filtrate was cooled to room temperature, dichloromethane and water were added for extraction and separation. The organic phase was retained and concentrated. The intermediate 1 was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:5) (yield: 75.8%).

[0090] Step 2 specifically includes the following processes:

[0091] Under nitrogen protection, intermediate 1 (1.0 eq) was added to a reaction bottle containing THF to dissolve, n-BuLi (1.5 eq) was slowly added dropwise at -78°C, and the mixture was stirred at room temperature for 1 h. Isopropyl borate (i-PrO)3B (1.5 eq) was added dropwise to the reaction mixture at -78°C, and then stirred at room temperature for 1 h. The reaction was monitored by thin layer chromatography. After the reaction was completed, the mixture was extracted with aqueous ammonium chloride at room temperature, and the organic layer was dried over MgSO4, concentrated, and recrystallized from ethyl acetate to obtain intermediate 2 (yield: 65.7%).

[0092] Step 3 specifically includes the following processes:

[0093] Intermediate 2 (1.0 eq), raw material C-210 (1.0 eq, CAS number: 2767642-32-8) and potassium carbonate (3.0 eq) were added to a reaction flask, followed by a mixed solution of toluene, ethanol and water (V:V:V = 3:1:1), and tetrakis(triphenylphosphine)palladium (0.03 eq) was added under nitrogen protection. The temperature was raised to 95°C and refluxed for 8 hours. The reaction was detected by thin layer chromatography. After the reaction was completed, the temperature was slightly lowered and filtered using diatomaceous earth to remove salt and catalyst. After the filtrate was cooled to room temperature, dichloromethane and water were added for extraction and separation. The organic phase was retained and concentrated, and compound 210 (yield: 81.3%) was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:5) to obtain compound 210 (yield: 81.3%).

[0094] The obtained compound 210 was tested and analyzed, and the results were as follows:

[0095] HPLC purity: >99.7%.

[0096] Mass spectrometry test: The model is Waters XEVO TQD mass spectrometer, using ESI source.

[0097] Test value (ESI, m / Z): [M+H] + ):711.48;

[0098] Calculated values: C, 82.67; H, 4.95; N, 7.87; S, 4.50;

[0099] The test values ​​are: C, 82.35; H, 5.08; N, 8.00; S, 4.64.

[0100] Example 3-44

[0101] The following compounds were synthesized by referring to the synthesis methods of Examples 1 to 2, and tested using a Waters XEVOTQD mass spectrometer with low precision. The ESI source was used for testing, and the mass spectrometry test values ​​are shown in Table 1 below.

[0102] Table 1 Mass spectrometry test values ​​of Examples 3-44

[0103]

[0104]

[0105] In addition, other compounds of the present invention can be obtained by referring to the synthesis methods of the above-mentioned embodiments, so they are not listed one by one here.

[0106] Device Example 1: Preparation of organic electroluminescent device

[0107] The structure of the prepared OLED device is: ITO anode / HIL / HTL / Prime / EML / HBL / ETL / EIL / cathode / CPL.

[0108] a. ITO anode: The ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate with a coating thickness of 1500Å was cleaned twice in distilled water, ultrasonically washed for 30 minutes, and then repeatedly cleaned twice with distilled water, ultrasonically washed for 10 minutes. After washing, it was ultrasonically washed with methanol, acetone, and isopropanol in sequence (5 minutes each time), dried, and then transferred to a plasma cleaning machine for washing for 5 minutes. It was then sent to a vapor deposition machine, and the substrate was used as the anode, and other functional layers were deposited on it in sequence.

[0109] b. HIL (hole injection layer): Hole injection layer materials HT and P-dopant were vacuum evaporated at an evaporation rate of 1Å / s. The evaporation rate ratio of HT to P-dopant was 97:3, and the thickness was 10nm.

[0110] c. HTL (hole transport layer): 130nm HT was vacuum-deposited on the hole injection layer at a deposition rate of 1.5Å / s as the hole transport layer.

[0111] d. Prime (luminescence auxiliary layer): 50nm of Prime was vacuum-deposited on the hole transport layer at a deposition rate of 0.5Å / s as a luminescence auxiliary layer.

[0112] e. EML (light-emitting layer): Then, on the above-mentioned light-emitting auxiliary layer, a dual host material (compound 1 provided in the above embodiment as the first host compound and Host-2 as the second host compound) and a dopant material (Dopant) are vacuum evaporated at a deposition rate of 1Å / s as a light-emitting layer, with a total thickness of 40nm, wherein the evaporation rate ratio of the first host compound, the second host compound and the dopant compound is 45:45:10.

[0113] f. HBL (hole blocking layer): A hole blocking layer HB with a thickness of 5 nm was vacuum-deposited at a deposition rate of 0.5 Å / s.

[0114] g. ETL (electron transport layer): ET and Liq were vacuum evaporated to a thickness of 30 nm at an evaporation rate of 1 Å / s as the electron transport layer. The evaporation rate ratio of ET to Liq was 50:50.

[0115] h. EIL (electron injection layer): 1 nm of Yb film was evaporated at a deposition rate of 0.5 Å / s to form an electron injection layer.

[0116] i. Cathode: 13 nm of magnesium and silver were evaporated at an evaporation rate ratio of 1 Å / s, and the evaporation rate ratio was 1:9 to obtain an OLED device.

[0117] j. CPL (covering layer): CPL with a thickness of 65 nm was vacuum-deposited on the cathode at a deposition rate of 1 Å / s as a covering layer.

[0118] k. Then the vapor-deposited substrate is packaged. First, the cleaned cover is coated with UV glue using glue coating equipment, and then the coated cover is moved to the pressing section, the vapor-deposited substrate is placed on the upper end of the cover, and finally the substrate and cover are bonded by bonding equipment, and the UV glue is cured by light.

[0119] The structural formulas of HT, P-dopant, Prime, Host-2, Dopant, HB, ET, and CPL used in the device embodiment 1 are as follows:

[0120] .

[0121] Referring to the method provided in the above device embodiment 1, the corresponding compounds in Table 2 were selected to replace compound 1, and the main material of the light-emitting layer was evaporated to prepare the corresponding organic electroluminescent devices, which were respectively recorded as device embodiments 2-44.

[0122] Device Comparison Examples 1-12:

[0123] Device Comparative Examples 1-12 Referring to the method provided in the above device embodiment 1, comparative compound a1 is used to replace the host material (compound 1) of the light-emitting layer in the above device embodiment 1 for evaporation, and are respectively recorded as device comparative examples 1-12, wherein the chemical structure of comparative compound a1 is as follows:

[0124]

[0125] The driving voltage, luminous efficiency and life of the organic electroluminescent devices obtained from the above device embodiments 1-44 and device comparative examples 1-12 were characterized at a brightness of 15000 (nits). The test results are shown in Table 2 below:

[0126] Table 2 Device test results

[0127]

[0128]

[0129] It can be seen from Table 2 that, compared with the devices prepared using the comparative compounds 1-12, the organic electroluminescent device embodiments 1-44 prepared using the luminescent layer host material provided by the present invention can improve the luminous efficiency and lifespan while maintaining a low driving voltage.

[0130]

[0131] Compounds a, b and compounds 244, 6 are parallel comparative examples, respectively, and the difference between them is that there are no other substituents on the outer benzene rings of the dibenzothiophene group and the dibenzofuran group in compounds a and b, while in the compounds 244 and 6 of the present invention, a phenyl group and a deuterated phenyl group are connected to the dibenzothiophene group and the dibenzofuran group, respectively, as substituents, which effectively expands the conjugated system, enhances the conjugated effect, and effectively improves the phosphorescence quantum efficiency, while avoiding the localization of carrier migration and increasing the migration rate, thereby reducing the voltage and increasing the luminescence efficiency of the device. At the same time, the substituted phenyl group (deuterated phenyl) on the dibenzothiophene group and the dibenzofuran rigid group balances the molecular structure while making it have higher thermal stability and film-forming properties when the device is evaporated, which is beneficial to increasing the life of the device.

[0132]

[0133] Compound C and Compound 45 are parallel comparative examples, the difference between which is that the dibenzofuran group in Compound C is connected to a phenyl group below, while the corresponding position in Compound 45 of the present invention is a carbazole group. The carbazole group is more rigid and has better thermal stability, and can maintain the integrity of the structure at high temperatures, improve the thermal stability of the material, and make the structure of the material less likely to change during high-temperature evaporation, effectively extending the service life of the device. In addition, the introduction of the carbazole group can enhance the triplet energy level of the material, improve the formation of triplet excitons and the energy transfer efficiency, thereby improving the phosphorescent luminescence efficiency.

[0134]

[0135] Compounds d, e, f and compounds 42, 2, 204 are parallel comparative examples, respectively, and the difference between them is that the carbazole group and the triarylamine group in compounds d, e, f are respectively connected to the 1- and 2-positions and the 2- and 4-positions on the dibenzofuran group (or dibenzothiophene group), while the carbazole group and the triarylamine group in compounds 42, 2, 204 of the present invention are respectively connected to the 1- and 4-positions on the dibenzofuran group (or dibenzothiophene group), and are distributed at the two sites farthest from the dibenzofuran group / dibenzothiophene group, which can effectively reduce the quenching phenomenon caused by aggregation, and also form a more effective conjugated system, enhance the charge transfer and energy transfer within the molecule, which helps to improve the phosphorescence quantum efficiency of the material, thereby improving the luminescence efficiency of the device.

[0136] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the green phosphorescent host material and the organic electroluminescent device of the present invention, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A green phosphorescent host material, characterized in that: The general structural formula of the green phosphorescent host material is Chemical Formula I: ； in, X is selected from O, S; R1 and R2 are each independently selected from deuterium; R3 is independently selected from deuterium, phenyl; n1 and n2 are each independently selected from 0, 1, 2, 3, 4, and 5; n3 is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8; Ar1 and Ar2 are each independently selected from a substituted or unsubstituted C6-C24 aryl group, a substituted or unsubstituted C3-C24 heteroaryl group, and the heteroatom thereof contains at least one of O, S, N, Si or Se.

2. The green phosphorescent host material according to claim 1, characterized in that: Ar1 and Ar2 are each independently selected from the following groups: ； In the formula, * represents the connection site; R4-R 16 Each is independently selected from hydrogen, deuterium, and C1-C6 alkyl substituted or unsubstituted by deuterium; n4、n 11 Each is independently selected from 0, 1, 2, 3, 4, 5; n5 and n8 are each independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9; n6、n 14 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13; n7 and n9 are each independently selected from 0, 1, 2, 3, 4, 5, 6, and 7; n 10 、n 16 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8; n 12 Independently selected from 0, 1, 2, 3, 4; n 13 、n 15 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11.

3. The green phosphorescent host material according to claim 1, characterized in that: The substituents in the substituted group are selected from one or two or more substituents connected to each other: deuterium, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopentane, cyclohexane, phenyl, biphenyl, naphthyl, fluorenyl, dimethylfluorenyl, phenanthryl, anthracenyl, indenyl, triphenylene, pyrenyl, chrysene, furanyl, thienyl, pyrrolyl, pyridyl, benzofuranyl, benzothienyl, isobenzofuranyl, dibenzofuranyl, dibenzothienyl, benzimidazolyl, benzothiazolyl, benzisothiazolyl, benzisoxazolyl, benzoxazolyl, isoindolyl, indolyl, benzindolyl, indazolyl, benzothiadiazolyl, carbazolyl, benzocarbazolyl.

4. The green phosphorescent host material according to claim 1, characterized in that: The green phosphorescent host material is selected from any one of the following compounds: ； Where D stands for deuterium.

5. A method for preparing a green phosphorescent host material according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) Raw material A reacts with raw material B to obtain intermediate 1. The reaction formula is as follows: ； (2) Intermediate 1 reacts with isopropyl borate to obtain intermediate 2. The reaction formula is as follows: ； (3) Intermediate 2 reacts with raw material C to obtain a green phosphorescent host material represented by chemical formula I. The reaction formula is as follows: ； Wherein, X, R1, R2, R3, n1, n2, n3, Ar1, Ar2 are as defined in claim 1, and Hal1, Hal2 are each independently selected from chlorine or bromine.

6. The preparation method according to claim 5, characterized in that: The molar ratio of raw material A to raw material B in step (1) is 1.0:1.0-1.2; The reaction in step (1) is carried out in the presence of an alkaline substance, wherein the alkaline substance is selected from sodium tert-butoxide and / or potassium tert-butoxide; the molar ratio of the alkaline substance to the raw material A is 2.0-4.0:1; The reaction in step (1) is carried out in the presence of a catalyst, the catalyst is selected from tris(dibenzylideneacetone)dipalladium, and the molar ratio of the catalyst to the raw material A is 0.01-0.05:1; The reaction in step (1) is carried out in an organic solvent, and the organic solvent is selected from toluene. The reaction temperature in step (1) is 100-110° C., and the reaction time is 4-20 hours.

7. The preparation method according to claim 5, characterized in that: In step (2), the molar ratio of the intermediate 1 to isopropyl borate is 1:1.5; The reaction in step (2) is carried out in the presence of n-butyl lithium; In step (2), n-butyl lithium is added into the reaction system at -78°C; The reaction in step (2) is carried out at room temperature for 1-2 hours.

8. The preparation method according to claim 5, characterized in that: In step (3), the molar ratio of the intermediate 2 to the raw material C is 1:1.0-1.3; The reaction in step (3) is carried out in the presence of a catalyst, the catalyst is selected from tetrakis(triphenylphosphine)palladium, and the molar ratio of the catalyst to the intermediate 2 is 0.01-0.03:1; The reaction in step (3) is carried out in a solvent, which is a mixed solution of toluene, ethanol and water; The reaction temperature in step (3) is 80°C-95°C, and the reaction time is 4-20h.

9. An organic electroluminescent device, characterized in that: The organic electroluminescent device comprises a first electrode, an organic electroluminescent material layer, and a second electrode; the organic electroluminescent material layer comprises a light-emitting layer, and the light-emitting layer comprises the green phosphorescent host material as claimed in claims 1-4.

10. The organic electroluminescent device according to claim 9, characterized in that: The organic electroluminescent material layer further comprises at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer and an electron injection layer.

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