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

[0001] This application is a divisional application of the patent application with application number 2025101055902. The application date of the original application is January 23, 2025. The name of the invention is green phosphorescent host materials and organic electroluminescent devices - applied to the divisional application. Technical Field

[0002] The invention belongs to the field of electroluminescent materials and relates to a green phosphorescent main material and an organic electroluminescent device. Background Art

[0003] Research on OLEDs (organic light-emitting diodes) has made significant progress. The first generation of OLEDs, 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 OLEDs, 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 OLEDs 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 at high currents, resulting in a serious roll-off in device efficiency. In recent years, in order to reduce device production costs and make OLEDs truly commercial and industrialized, the use of noble metal-doped phosphorescent materials in the light-emitting layer has been avoided.

[0004] OLED light-emitting devices rely on the recombination of charge carriers (electrons and holes) transported within organic semiconductor materials. Organic materials are known to have poor electrical conductivity, lacking continuous energy bands. Carrier transport is often described using hopping theory. To achieve breakthroughs in the application of organic electroluminescent devices, the poor charge injection and transport capabilities of organic materials must be overcome. Scientists have achieved this by adjusting device structure, for example by increasing the number of organic material layers and assigning different organic layers different roles. For example, some functional materials can facilitate electron injection from the cathode, others from the anode, while others promote charge transport and others block electron or hole transport. Of course, in OLED devices, the crucial requirement is that the various color-matching luminescent materials must be compatible with the adjacent functional materials. Therefore, efficient and long-lasting OLED light-emitting devices are often the result of an optimized combination of device structure and various organic materials. This presents significant opportunities and challenges for researchers to design and develop functional materials with diverse structures. Summary of the Invention

[0005] In response to the shortcomings of the prior art, the present invention aims 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 dibenzothiophene group as an intermediate bridging group, with a carbazole group and a triazine group connected to the 1- and 4-positions of the dibenzofuran group or dibenzothiophene group, respectively. This structure effectively improves the transport capacity of holes and electrons and achieves a state of equilibrium between holes and electrons, enabling the material device to maintain a low driving voltage while also having high luminous efficiency and service life.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In one aspect, the present invention provides a green phosphorescent host material, wherein the green phosphorescent host material has the general structural formula of Chemical Formula I:

[0008]

[0009] in,

[0010] X is selected from O, S;

[0011] R1 and R2 are each independently selected from deuterium;

[0012] R3 is independently selected from deuterium, phenyl;

[0013] n1 and n2 are each independently selected from 0, 1, 2, 3, 4, and 5;

[0014] n3 is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8;

[0015] 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.

[0016] More preferably, Ar1 and Ar2 are each independently selected from the following groups:

[0017]

[0018] Wherein, * represents the connection site;

[0019] R4-R 16 are each independently selected from hydrogen, deuterium, and deuterium-substituted or unsubstituted C1-C6 alkyl;

[0020] n4、n 11 Each independently selected from 0, 1, 2, 3, 4, 5;

[0021] n5 and n8 are each independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9;

[0022] n6、n 14 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13;

[0023] n7 and n9 are each independently selected from 0, 1, 2, 3, 4, 5, 6, and 7;

[0024] n 10 、n 16 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8;

[0025] n 12 Independently selected from 0, 1, 2, 3, 4;

[0026] n 13 、n 15 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11.

[0027] In the present invention, 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, phenanthrenyl, anthracenyl, indenyl, triphenylene, pyrenyl, yl, furyl, thienyl, pyrrolyl, pyridyl, benzofuranyl, benzothienyl, isobenzofuranyl, dibenzofuranyl, dibenzothienyl, benzimidazolyl, benzothiazolyl, benzisothiazolyl, benzisoxazolyl, benzoxazolyl, isoindolyl, indolyl, benzindolyl, indazolyl, benzothiadiazolyl, carbazolyl, benzocarbazolyl.

[0028] Furthermore, the green phosphorescent host material is selected from any one of the following compounds:

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042] The green phosphorescent host material of the present invention can be prepared by a synthesis method known to those skilled in the art.

[0043] The present invention provides a method for preparing the green phosphorescent host material as described above, the preparation method comprising the following steps:

[0044] (1) Raw material A reacts with raw material B to obtain intermediate 1. The reaction formula is as follows:

[0045]

[0046] (2) Intermediate 1 reacts with isopropyl borate to obtain intermediate 2. The reaction formula is as follows:

[0047]

[0048] (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:

[0049]

[0050] wherein X, R1, R2, R3, n1, n2, n3, Ar1, and Ar2 are as defined in claim 1, and Hal1 and Hal2 are each independently selected from chlorine or bromine.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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, and the reaction time is 4-20h, for example, 4h, 8h, 10h, 12h, 14h, 16h, 18h or 20h.

[0055] Preferably, the molar ratio of the intermediate 1 to isopropyl borate in step (2) is 1:1.5.

[0056] The reaction in step (2) is carried out in the presence of n-butyllithium.

[0057] In step (2), n-butyl lithium is added into the reaction system at -78°C.

[0058] The reaction in step (2) is carried out at room temperature for 1-2 hours.

[0059] The molar ratio of the intermediate 2 to the raw material C in step (3) is 1:1.0-1.3, for example 1:1.0, 1:1.1, 1:1.2 or 1:1.3.

[0060] 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.

[0061] The reaction in step (3) is carried out in a solvent, which is a mixed solution of toluene, ethanol and water.

[0062] The reaction temperature of 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.

[0063] As a preferred technical solution, the green phosphorescent host material of the present invention is prepared by the following reaction process:

[0064]

[0065] Specific preparation method:

[0066] Step 1 specifically includes the following processes:

[0067] Raw material A (1.0 eq), raw material B (1.0-1.2 eq) and sodium tert-butoxide (2.0-4.0 eq) were added to a reaction flask, followed by addition of anhydrous toluene. Tris(dibenzylideneacetone)dipalladium (0.01-0.05 eq) was added under nitrogen protection, the temperature was raised to 100-110° C., and the reaction was refluxed for 4-20 h. The reaction was detected by thin layer chromatography. After the reaction was completed, the temperature was slightly lowered, and the product was filtered through 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 the intermediate 1 was 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.

[0068] Step 2 specifically includes the following processes:

[0069] Under nitrogen protection, intermediate 1 (1.0 eq) was added to a reaction flask 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 monitored by thin layer chromatography. After the reaction was complete, the mixture was extracted with an aqueous ammonium chloride solution at room temperature, and the organic layer was dried over MgSO 4, concentrated, and recrystallized from ethyl acetate to obtain intermediate 2.

[0070] Step 3 specifically includes the following processes:

[0071] Intermediate 2 (1.0 eq), raw material C (1.0-1.3 eq) and potassium carbonate (2.0-4.0 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 (0.01-0.03 eq) was added under nitrogen protection. The temperature was raised to 80°C-95°C and refluxed for 4-20 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 salts and catalysts. 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 purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:4-1:10) to obtain Chemical Formula I.

[0072] In the above formula, X, R1, R2, R3, n1, n2, n3, Ar1, and Ar2 are as defined in the above chemical formula I, and Hal1 and Hal2 are each independently selected from chlorine or bromine.

[0073] 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.

[0074] 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 described above.

[0075] Preferably, the organic electroluminescent material layer further includes 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.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] The compound of the present invention effectively exhibits the characteristics of a phosphorescent host layer material. The compound structure uses a rigid dibenzofuran group or dibenzothiophene group as an intermediate bridging group, with a carbazole group and a triazine group connected to the 1-position and 4-position of the dibenzofuran group or dibenzothiophene group, respectively. The triazine acts as an electron acceptor unit with high carrier transport capability, and the carbazole group and the dibenzofuran group or dibenzothiophene group act as electron donor units with high carrier transport capability. This structure can effectively improve the transport capability of holes and electrons and achieve a state of equilibrium between holes and electrons, thereby increasing the luminous efficiency and service life of the organic electroluminescent device while maintaining a low driving voltage.

[0078] Among them, the carbazole group has a higher triplet energy level, which helps to effectively capture and transmit triplet excitons, prevent energy loss, and thus improve the phosphorescent luminescence efficiency of the material device. And the carbazole group is strong in rigidity and has better thermal stability. It can maintain the integrity of the structure at high temperatures, 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 the rigid dibenzofuran group or dibenzothiophene group increases the thermal stability of the material molecule and thus greatly improves the life of the device. A phenyl group (or deuterated phenyl) is connected to the dibenzofuran group or dibenzothiophene group, which can effectively increase the conjugated area, further improve the luminous efficiency, and can also balance the structure of the molecule, enhance the thermal stability and film-forming properties during its evaporation, and effectively improve the life of the device. Further connection with a triazine group with high electron affinity to improve the mobility of the organic molecule, wherein the N atom has good electron transport properties, 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 conductive properties of the material, and improving the overall performance of the device.

[0079] Moreover, the carbazole group and triazine group are located at the 1-position and 4-position of the dibenzofuran group or dibenzothiophene group, respectively, which can effectively reduce the quenching phenomenon caused by aggregation and form a more effective conjugated system, enhancing 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

[0080] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of compound 1 provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0081] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0082] Example 1

[0083]

[0084] Step 1 specifically includes the following processes:

[0085] 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 addition of anhydrous toluene, and tris(dibenzylideneacetone)dipalladium (0.02 eq) was added under nitrogen protection, the temperature was raised to 100° C., and the reaction was refluxed for 12 h; the reaction was detected by thin layer chromatography. After the reaction was completed, the temperature was slightly lowered, and the mixture was 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 a mixed solution of dichloromethane and petroleum ether (V:V=1:5) was purified by column chromatography to obtain intermediate 1 (yield: 75.6%).

[0086] Step 2 specifically includes the following processes:

[0087] Under nitrogen, Intermediate 1 (1.0 eq) was added to a reaction flask containing THF and dissolved. n-BuLi (1.5 eq) was slowly added dropwise at -78°C, and the mixture was stirred at room temperature for 1 hour. Isopropyl borate (i-PrO) 3B (1.5 eq) was added dropwise at -78°C to the reaction mixture, followed by stirring at room temperature for another 1 hour. The reaction was monitored by thin-layer chromatography. After completion of the reaction, the mixture was extracted with aqueous ammonium chloride at room temperature, and the organic layer was dried over MgSO 4 , concentrated, and recrystallized from ethyl acetate to obtain Intermediate 2 (yield: 64.8%).

[0088] Step 3 specifically includes the following processes:

[0089] 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 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. Compound 1 was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:4) to obtain compound 1 (yield: 80.1%).

[0090] The obtained compound 1 was tested and analyzed, and the results were as follows:

[0091] HPLC purity: >99.8%.

[0092] Mass spectrometry test: Waters XEVO TQD mass spectrometer, using ESI source.

[0093] Measured value (ESI, m / Z): [M+H] + ):716.49.

[0094] Elemental analysis:

[0095] Calculated values: C, 85.45; H, 4.50; N, 7.82; O, 2.23;

[0096] The test values are: C, 85.15; H, 4.62; N, 7.96; O, 2.36.

[0097] The H NMR spectrum of compound 1 is shown in Figure 1 shown.

[0098] Example 2

[0099]

[0100] Step 1 specifically includes the following processes:

[0101] 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 addition of anhydrous toluene. Tris(dibenzylideneacetone)dipalladium (0.02 eq) was added under nitrogen protection, the temperature was raised to 110° C., and the reaction was refluxed for 10 h. The reaction was detected by thin layer chromatography. After the reaction was completed, the temperature was slightly lowered and filtered through 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 a mixed solution of dichloromethane and petroleum ether (V:V=1:5) was used for purification by column chromatography to obtain intermediate 1 (yield: 75.8%).

[0102] Step 2 specifically includes the following processes:

[0103] Under nitrogen, Intermediate 1 (1.0 eq) was added to a reaction flask containing THF and dissolved. n-BuLi (1.5 eq) was slowly added dropwise at -78°C, and the mixture was stirred at room temperature for 1 hour. Isopropyl borate (i-PrO) 3B (1.5 eq) was added dropwise at -78°C to the reaction mixture, followed by stirring at room temperature for another 1 hour. The reaction was monitored by thin-layer chromatography. After completion of the reaction, the mixture was extracted with aqueous ammonium chloride at room temperature, and the organic layer was dried over MgSO 4 , concentrated, and recrystallized from ethyl acetate to obtain Intermediate 2 (yield: 65.7%).

[0104] Step 3 specifically includes the following processes:

[0105] 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). Tetrakis(triphenylphosphine)palladium (0.03 eq) was added under nitrogen protection, and the temperature was raised to 95°C, and the reaction was refluxed for 8 hours. The reaction was detected by thin layer chromatography. After the reaction was completed, the temperature was slightly lowered and the mixture was filtered through diatomaceous earth to remove salt and catalyst. After the filtrate was cooled to room temperature, it was extracted with dichloromethane and water, separated, and the organic phase was retained and concentrated. Compound 210 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%).

[0106] The obtained compound 210 was tested and analyzed, and the results were as follows:

[0107] HPLC purity: >99.7%.

[0108] Mass spectrometry test: Waters XEVO TQD mass spectrometer, using ESI source.

[0109] Measured value (ESI, m / Z): [M+H] + ):711.48;

[0110] Calculated values: C, 82.67; H, 4.95; N, 7.87; S, 4.50;

[0111] The test values are: C, 82.35; H, 5.08; N, 8.00; S, 4.64.

[0112] Example 3-44

[0113] The following compounds were synthesized with reference to the synthesis methods of Examples 1 and 2, and tested using a Waters XEVOTQD mass spectrometer, which has low precision. The ESI source was used for testing, and the mass spectrometry test values are shown in Table 1 below.

[0114] Table 1 Mass spectrometry test values of Examples 3-44

[0115]

[0116]

[0117] In addition, other compounds of the present invention can be obtained by referring to the synthesis methods of the above-mentioned examples, so they are not listed here one by one.

[0118] Device Example 1: Preparation of organic electroluminescent device

[0119] The structure of the prepared OLED device is: ITO anode / HIL / HTL / Prime / EML / HBL / ETL / EIL / cathode / CPL.

[0120] a. ITO anode: the coating thickness is The ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate 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 evaporated on it in sequence.

[0121] b. HIL (hole injection layer): The hole injection layer materials HT and P-dopant were vacuum evaporated at a deposition rate of 97:3, and the thickness was 10 nm.

[0122] c. HTL (hole transport layer): At a deposition rate of , 130 nm of HT was vacuum evaporated on the hole injection layer as a hole transport layer.

[0123] d. Prime (luminous auxiliary layer): At a deposition rate of , 50nm of Prime was vacuum evaporated on the hole transport layer as a light-emitting auxiliary layer.

[0124] e. EML (light-emitting layer): Then on the above-mentioned light-emitting auxiliary layer, The evaporation rate is 40 nm, and two main materials (compound 1 provided in the above embodiment as the first main compound and Host-2 as the second main compound) and the dopant material (Dopant) are vacuum evaporated as the light-emitting layer, with a total thickness of 40 nm, wherein the evaporation rate ratio of the first main compound, the second main compound and the dopant compound is 45:45:10.

[0125] f. HBL (hole blocking layer): The hole blocking layer HB with a thickness of 5 nm was vacuum-deposited at a deposition rate of .

[0126] g. ETL (Electron Transport Layer): ET and Liq were vacuum-deposited at a deposition rate of 50:50 to form an electron transport layer with a thickness of 30 nm.

[0127] h. EIL (electron injection layer): The evaporation rate is 1 nm, and a Yb film layer is evaporated to form an electron injection layer.

[0128] i. Cathode: The evaporation rate ratio of magnesium and silver was 13nm, and the evaporation rate ratio was 1:9 to obtain an OLED device.

[0129] j. CPL (covering layer): At a deposition rate of , CPL with a thickness of 65 nm was vacuum evaporated on the cathode as a covering layer.

[0130] k. The vapor-deposited substrate is then packaged. First, the cleaned cover is coated with UV glue using a glue coating device. The coated cover is then moved to the laminating section, where the vapor-deposited substrate is placed on top of the cover. Finally, the substrate and cover are laminated using a laminating device, and the UV glue is cured by light.

[0131] The structural formulas of HT, P-dopant, Prime, Host-2, Dopant, HB, ET, and CPL used in the device embodiment 1 are as follows:

[0132]

[0133] 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.

[0134] Device Comparison Examples 1-12:

[0135] Comparative Examples 1-12 of the Devices were prepared by referring to the method provided in Device Example 1, except that the host material (Compound 1) of the light-emitting layer in Device Example 1 was replaced by Comparative Compound a1 for evaporation, and these were respectively referred to as Comparative Examples 1-12. The chemical structure of Comparative Compound a1 is as follows:

[0136]

[0137] The driving voltage, luminous efficiency, and lifespan of the organic electroluminescent devices obtained from the above device examples 1-44 and device comparison examples 1-12 were characterized at a brightness of 15,000 (nits). The test results are shown in Table 2 below:

[0138] Table 2 Device test results

[0139]

[0140]

[0141] As can be seen from Table 2, compared with the devices prepared using the comparative compounds 1-12, the organic electroluminescent devices of Examples 1-44 prepared using the luminescent layer host material provided by the present invention have improved luminous efficiency and lifespan while maintaining a low driving voltage.

[0142]

[0143] Compounds a, b and compounds 244, 6 are parallel comparative examples, respectively. 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 the dibenzothiophene group and the dibenzofuran group in compounds 244 and 6 of the present invention are respectively connected to a phenyl group and a deuterated phenyl group as substituents, which effectively expands the conjugated system, enhances the conjugated effect, effectively improves the phosphorescence quantum efficiency, and avoids the localization of carrier migration, thereby increasing the migration rate, thereby reducing the voltage and increasing the luminous 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 improving the life of the device.

[0144]

[0145] Compound C and Compound 45 are parallel comparative examples. The difference between them is that in Compound C, the dibenzofuran group 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. It can maintain structural integrity at high temperatures, improve the thermal stability of the material, and make the material less likely to change its structure 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 efficiency of energy transfer, thereby improving the phosphorescent luminescence efficiency.

[0146]

[0147] Compounds d, e, f and compounds 42, 2, 204 are parallel comparative examples, and the difference between them is that the carbazole group and the triarylamine group in compounds d, e, and 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, and 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, thereby enhancing the charge transport 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.

[0148] The applicant declares that while the present invention uses the aforementioned embodiments to illustrate the green phosphorescent host material and organic electroluminescent device of the present invention, the present invention is not limited to the aforementioned embodiments, nor does it imply that the present invention must rely on the aforementioned embodiments in order to be implemented. Persons skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure 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 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: Wherein, * represents the connection site; R4-R 16 are each independently selected from hydrogen, deuterium, and deuterium-substituted or unsubstituted C1-C6 alkyl; n4、n 11 Each 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 more of the following substituents connected together: deuterium, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopentane, cyclohexane, phenyl, biphenyl, naphthyl, fluorenyl, dimethylfluorenyl, phenanthrenyl, anthracenyl, indenyl, triphenylene, pyrenyl, yl, furyl, 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 claim 1, 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, and Ar2 are as defined in claim 1, and Hal1 and 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, wherein 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, which is selected from toluene. The reaction temperature in step (1) is 100-110° C., and the reaction time is 4-20 h.

7. The preparation method according to claim 5, characterized in that The molar ratio of the intermediate 1 to isopropyl borate in step (2) is 1:1.5; The reaction in step (2) is carried out in the presence of n-butyl lithium; The n-butyl lithium in step (2) is added to 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 The molar ratio of the intermediate 2 to the raw material C in step (3) is 1:1.0-1.3; The reaction in step (3) is carried out in the presence of a catalyst, wherein 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 4-20 h.

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 according to any one of claims 1 to 4.

10. The organic electroluminescent device according to claim 9, characterized in that: The organic electroluminescent material layer further includes 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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