A green phosphorescent host material and an organic electroluminescent device

Abstract

The invention provides a green phosphorescent host material and an organic electroluminescent device. The invention belongs to the field of electroluminescent materials. The general structural formula of the green phosphorescent host material is chemical formula I. The green phosphorescent host material of the 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. The 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.

Description

Technical Field

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

[0002] Nowadays, significant progress has been made in the research on OLEDs (organic light-emitting diodes). The first-generation OLEDs with all-fluorescent materials in the light-emitting layer only utilize singlet excitons for luminescence, and their internal quantum efficiency (IQE) is only 25%. The second-generation OLEDs with transition-metal phosphorescent materials in the light-emitting layer enable the radiation of triplet excitons through spin-orbit coupling, and the theoretical IQE can reach 100%. However, the second-generation OLEDs based on phosphorescent materials still face many problems: (1) Transition metals commonly used in the light-emitting layer, such as Os, Ir, Pt, etc., are expensive, which 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 serious device efficiency roll-off. In recent years, in order to reduce the production cost of devices and make OLEDs truly commercialized and industrialized, the use of noble-metal-doped phosphorescent materials 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 is well known, the conductivity of organic materials is very poor, and there is no continuous energy band in organic semiconductors. The transport of carriers is usually described by the hopping theory. In order to achieve a breakthrough in the application of organic electroluminescent devices, it is necessary to overcome the difficulty of poor charge injection and transport ability of organic materials. Scientists have adjusted 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 electron injection from the cathode, some functional materials can promote hole injection from the anode, some materials can promote charge transport, and some materials can play a role in blocking electron or hole transport. Of course, in OLED light-emitting devices, the most important luminescent materials of various colors also need to match the adjacent functional materials. Therefore, OLED light-emitting devices with good efficiency and long lifespan are usually the result of the optimal combination of the device structure and various organic materials, which provides great opportunities and challenges for researchers to design and develop functional materials with various structures. Summary of the Invention

[0004] Aiming at the deficiencies 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 dibenzothiophene group as the middle bridging group, and a carbazole group and a triazine group are respectively connected to the 1-position and 4-position of the dibenzofuran group or dibenzothiophene group. This structure can effectively improve the hole and electron transport capabilities, and make the holes and electrons reach a balanced state, enabling the material device to maintain a low driving voltage, while having high luminous efficiency and service life.

[0005] To achieve the purpose of this invention, the following technical solutions are adopted in the present invention:

[0006] On the one hand, the present invention provides a green phosphorescent host material, and the structural general formula of the green phosphorescent host material is Chemical Formula I:

[0007]

[0008] Wherein,

[0009] X is selected from O, S;

[0010] R 1 、R 2 Each independently is selected from deuterium;

[0011] R 3 Independently is selected from deuterium, phenyl;

[0012] n 1 、n 2 Each independently is selected from 0, 1, 2, 3, 4, 5;

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

[0014] Ar 1 、Ar 2 Each independently is selected from one of a substituted or unsubstituted C6-C24 aryl group, a substituted or unsubstituted C3-C24 heteroaryl group, and its heteroatoms contain at least one of O, S, N, Si or Se.

[0015] Further preferably, Ar 1 、Ar 2 Each independently is selected from the following groups:

[0016]

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

[0018] R 4 -R 16Each independently selected from hydrogen, deuterium, deuterium-substituted or unsubstituted C1-C6 alkyl;

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

[0020] n 5 and n 8 Each independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9;

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

[0022] n 7 and n 9 Each independently selected from 0, 1, 2, 3, 4, 5, 6, 7;

[0023] n 10 and n 16 Each 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 and n 15 Each independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11.

[0026] In the present invention, the "substitution" in the term "substituted or unsubstituted" means being substituted 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, anthryl, indenyl, triphenylenyl, pyrenyl, chrysenyl, furyl, thienyl, pyrrolyl, pyridyl, benzofuryl, benzothienyl, isobenzofuryl, dibenzofuryl, dibenzothienyl, benzimidazolyl, benzothiazolyl, benzisothiazolyl, benzisoxazolyl, benzoxazolyl, isoindolyl, indolyl, benzindolyl, indazolyl, benzothiadiazolyl, carbazolyl, benzocarbazolyl.

[0027] Furthermore, among the above-mentioned green phosphorescent host materials, any one selected from 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, and the preparation method includes the following steps:

[0032] (1) React raw material A with raw material B to obtain intermediate 1, and the reaction formula is as follows:

[0033] ;

[0034] (2) React intermediate 1 with isopropyl borate to obtain intermediate 2, and the reaction formula is as follows:

[0035] ;

[0036] (3) React intermediate 2 with raw material C to obtain the green phosphorescent host material shown in Chemical Formula I, and the reaction formula is as follows:

[0037] ;

[0038] Wherein, X, R 1 , R 2 , R 3 , n 1 , n 2 , n 3 , Ar 1 , Ar 2 are defined as in claim 1, Hal 1 , Hal 2 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 described in step (1) is carried out in the presence of a basic substance, and the basic substance is selected from sodium tert-butoxide and / or potassium tert-butoxide; the molar ratio of the basic substance to raw material A is 2.0 - 4.0:1, such as 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 described in step (1) is carried out in the presence of a catalyst, and the catalyst is selected from tris(dibenzylideneacetone)dipalladium, and the molar ratio of the catalyst to raw material A is 0.01 - 0.05:1; such as 0.01:1, 0.02:1, 0.03:1, 0.04:1 or 0.05:1.

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

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

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

[0045] The n-butyllithium in step (2) is added to the reaction system at -78 °C.

[0046] The reaction described in step (2) is carried out at room temperature, and the reaction time is 1 - 2 h.

[0047] The molar ratio of intermediate 2 to raw material C in step (3) is 1:1.0 - 1.3, such as 1:1.0, 1:1.1, 1:1.2 or 1:1.3.

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

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

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

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

[0052]

[0053] Specific preparation method:

[0054] Step 1 specifically includes the following processes:

[0055] Add raw material A (1.0 eq), raw material B (1.0 - 1.2 eq) and sodium tert-butoxide (2.0 - 4.0 eq) into a reaction flask, then add anhydrous toluene, add tris(dibenzylideneacetone)dipalladium(0) (0.01 - 0.05 eq) under nitrogen protection, heat up to 100 - 110 °C, and reflux for 4 - 20 h; detect the reaction by thin-layer chromatography. After the reaction is completed, slightly lower the temperature, filter using diatomaceous earth to remove salts and catalysts. After the filtrate is cooled to room temperature, add dichloromethane and water for extraction and liquid separation. After retaining the organic phase, concentrate it, and purify it 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, add intermediate 1 (1.0 eq) to a reaction flask containing THF and dissolve it. Slowly add n-butyllithium (n-BuLi, 1.5 eq) dropwise at -78 °C, and stir the mixture at room temperature for 1 - 2 h. Add isopropyl borate (i-PrO) 3 B (1.5 eq) dropwise to the reaction mixture at -78 °C, and then stir at room temperature for 1 - 2 h. Detect the reaction by thin-layer chromatography. After the reaction is completed, extract the mixture with an aqueous ammonium chloride solution at room temperature, and dry and concentrate the organic layer with MgSO 4 Dry, concentrate, and recrystallize with ethyl acetate to obtain intermediate 2.

[0058] Step 3 specifically includes the following processes:

[0059] 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. Subsequently, a mixed solution of toluene, ethanol, and water (V:V:V = 3:1:1) was added. Under nitrogen protection, tetrakis(triphenylphosphine)palladium (0.01 - 0.03 eq) was added, and the temperature was raised to 80 °C - 95 °C, followed by refluxing for 4 - 20 h. The reaction was monitored by thin-layer chromatography. After the reaction was completed, the temperature was slightly lowered, and filtration was carried out using diatomaceous earth to remove salts and the catalyst. After the filtrate was cooled to room temperature, dichloromethane and water were added for extraction and liquid 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.

[0060] In the above formula, X, R 1 、R 2 、R 3 、n 1 、n 2 、n 3 、Ar 1 、Ar 2 As defined in Chemical Formula I above, Hal 1 、Hal 2 each independently selected from chlorine or bromine.

[0061] In particular, for complex raw materials that have not been disclosed, they were synthesized using classical Suzuki coupling reaction and Buchwald–Hartwig coupling reaction 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 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.

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

[0065] The compounds of the present invention effectively exhibit the characteristics of a phosphorescent host layer material. The compound structure uses a rigid dibenzofuran group or dibenzothiophene group as the intermediate bridging group, and a carbazole group and a triazine group are respectively connected to the 1-position and 4-position of the dibenzofuran group or dibenzothiophene group. Among them, triazine is an electron acceptor unit with high carrier transport ability, and the carbazole group and the dibenzofuran group or dibenzothiophene group are electron donor units with high carrier transport ability. This structure can effectively improve the transport ability of holes and electrons, and make the holes and electrons reach an equilibrium state, so as to improve the luminous efficiency and service life of the organic light-emitting device, while maintaining a low driving voltage.

[0066] Among them, the carbazole group has a relatively high triplet energy level, which helps to effectively capture and transfer triplet excitons, prevent energy loss, and thus improve the phosphorescent luminous efficiency of the material device. Moreover, the carbazole group has strong rigidity and better thermal stability, can maintain the integrity of the structure at high temperatures, improve the thermal stability of the material, and make the structure of the material not easily change during the high-temperature evaporation process, effectively extending the service life of the device. In addition, the introduction of a rigid dibenzofuran group or dibenzothiophene group increases the thermal stability of the material molecules and thus 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 conjugation area, further improve the luminous efficiency, and at the same time balance the structure of the molecule, enhance its thermal stability and film-forming property during the evaporation process, and effectively improve the life of the device. Further connecting a triazine group with high electron affinity to improve the mobility of organic molecules. The N atom therein has good electron transport performance, can lower the ability of the molecular LUMO energy level, and also has excellent energy level matching characteristics, which is beneficial to matching with the high-work function electrode, enhancing the conductivity of the material, and improving the overall performance of the device.

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

[0068] Figure 1 It is the nuclear magnetic resonance hydrogen spectrum of Compound 1 provided in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0069] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0070] Example 1

[0071]

[0072] Step 1 specifically includes the following process:

[0073] Add raw material A-1 (1.0 eq, CAS No.: 1821235-55-5), raw material B-1 (1.0 eq, CAS No.: 34479-78-2) and sodium tert-butoxide (2.0 eq) into a reaction flask, then add anhydrous toluene, add tris(dibenzylideneacetone)dipalladium(0) (0.02 eq) under nitrogen protection, heat up to 100 °C, and reflux for 12 h; detect the reaction by thin-layer chromatography. After the reaction is completed, slightly lower the temperature, filter using diatomaceous earth to remove salts and the catalyst. After the filtrate is cooled to room temperature, add dichloromethane and water for extraction and liquid separation. Retain the organic phase and concentrate it. Purify it by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:5) to obtain intermediate 1 (yield: 75.6%).

[0074] Step 2 specifically includes the following process:

[0075] Under nitrogen protection, add intermediate 1 (1.0 eq) to a reaction flask containing THF and dissolve it. Slowly add n-BuLi (1.5 eq) dropwise at -78 °C, and stir the mixture at room temperature for 1 h. Add isopropyl borate (i-PrO) 3 B (1.5 eq) dropwise to the reaction mixture at -78 °C, and then stir at room temperature for 1 h. Detect the reaction by thin-layer chromatography. After the reaction is completed, extract the mixture with aqueous ammonium chloride solution at room temperature, and dry and concentrate the organic layer with MgSO 4 Dry, concentrate, and recrystallize with ethyl acetate to obtain intermediate 2 (yield: 64.8%).

[0076] Step 3 specifically includes the following process:

[0077] Add intermediate 2 (1.0 eq), raw material C-1 (1.0 eq, CAS No.: 1472062-94-4) and potassium carbonate (3.0 eq) into a reaction flask, then add a mixed solution of toluene, ethanol and water (V:V:V = 3:1:1). Add tetrakis(triphenylphosphine)palladium(0) (0.03 eq) under nitrogen protection, heat up to 95 °C, and reflux for 12 h; detect the reaction by thin-layer chromatography. After the reaction is completed, slightly lower the temperature, filter using diatomaceous earth to remove salts and the catalyst. After the filtrate is cooled to room temperature, add dichloromethane and water for extraction and liquid separation. Retain the organic phase and concentrate it. Purify it by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:4) to obtain compound 1 (yield: 80.1%).

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

[0079] HPLC purity: >99.8%.

[0080] Mass spectrometry test: A mass spectrometer of model Waters XEVO TQD was used, with an 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] Test values: C, 85.15; H, 4.62; N, 7.96; O, 2.36.

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

[0086] Example 2

[0087]

[0088] Step 1 specifically includes the following process:

[0089] Raw material A-210 (1.0 eq, CAS No.: 2419887-92-4), raw material B-210 (1.0 eq, CAS No.: 34479-78-2) and sodium tert-butoxide (2.0 eq) were added to a reaction flask, and then anhydrous toluene was added. Under nitrogen protection, tris(dibenzylideneacetone)dipalladium(0) (0.02 eq) was added, and the temperature was raised to 110 °C and refluxed for 10 h. 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 salts and the catalyst. After the filtrate was cooled to room temperature, dichloromethane and water were added for extraction and liquid separation. After retaining the organic phase, it was concentrated, and purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:5) to obtain intermediate 1 (yield: 75.8%).

[0090] Step 2 specifically includes the following process:

[0091] Under nitrogen protection, 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 h. Isopropyl borate (i-PrO) was added dropwise to the reaction mixture at -78 °C 3B (1.5 eq), 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 solution at room temperature, and the organic layer was dried over MgSO 4 and concentrated, and recrystallized from ethyl acetate to obtain Intermediate 2 (yield: 65.7%).

[0092] Step 3 specifically includes the following process:

[0093] Intermediate 2 (1.0 eq), starting material C-210 (1.0 eq, CAS No.: 2767642-32-8), and potassium carbonate (3.0 eq) were added to a reaction flask, followed by adding a mixed solution of toluene, ethanol, and water (V:V:V = 3:1:1). Under nitrogen protection, tetrakis(triphenylphosphine)palladium(0) (0.03 eq) was added, and the temperature was raised to 95 °C and refluxed for 8 h. The reaction was monitored by thin-layer chromatography. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered through diatomaceous earth to remove salts and the catalyst. After the filtrate was cooled to room temperature, it was extracted with dichloromethane and water and separated. The organic phase was retained and concentrated, and 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 are as follows:

[0095] HPLC purity: >99.7%.

[0096] Mass spectrometry test: A mass spectrometer of model Waters XEVO TQD was used, and the ESI source was adopted.

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

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

[0099] Measured value: C, 82.35; H, 5.08; N, 8.00; S, 4.64.

[0100] Example 3 - 44

[0101] Referring to the synthesis methods of Examples 1 to 2, the synthesis of the following compounds was completed. A mass spectrometer of model Waters XEVO TQD was used for testing, 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-listed examples, so they will not be 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 1500 Å was washed twice in distilled water, ultrasonically washed for 30 min, then repeatedly washed twice with distilled water and ultrasonically washed for 10 min. After washing, it was ultrasonically washed with methanol, acetone, and isopropanol in sequence (each washing for 5 min), dried, then transferred to a plasma cleaner for washing for 5 min, and then sent to an evaporation coater. Using this substrate as the anode, other functional layers were evaporated thereon in sequence.

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

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

[0111] d. Prime (luminescence assisting layer): Prime with a thickness of 50 nm was vacuum-evaporated on the hole transport layer at an evaporation rate of 0.5 Å / s as the luminescence assisting layer.

[0112] e. EML (emitting layer): Then, on the above-mentioned luminescence assisting layer, a double-host material (Compound 1 provided in the above example as the first host compound and Host-2 as the second host compound) and a doping material (Dopant) were vacuum-evaporated at an evaporation rate of 1 Å / s as the emitting layer, with a total thickness of 40 nm. The evaporation rate ratio of the first host compound, the second host compound, and the doping compound was 45:45:10.

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

[0114] g, ETL (Electron Transport Layer): Using an evaporation rate of 1 Å / s, vacuum evaporate ET and Liq with a thickness of 30 nm as the electron transport layer. The evaporation rate ratio of ET and Liq is 50:50.

[0115] h, EIL (Electron Injection Layer): Using an evaporation rate of 0.5 Å / s, evaporate a 1-nm Yb film layer to form the electron injection layer.

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

[0117] j, CPL (Cover Layer): Using an evaporation rate of 1 Å / s, vacuum evaporate a 65-nm CPL on the cathode as the cover layer.

[0118] k. Subsequently, encapsulate the substrate after evaporation. First, use a gluing device to coat the cleaned cover plate with UV glue, then move the coated cover plate to the lamination section, place the substrate after evaporation on the upper end of the cover plate, and finally laminate the substrate and the cover plate under the action of a laminating device, while completing the photo-curing of the UV glue.

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

[0120] 。

[0121] Referring to the method provided in the above Device Example 1, respectively select the corresponding compounds in Table 2 to replace Compound 1 for the evaporation of the host material of the light-emitting layer, and prepare the corresponding organic electroluminescent devices, which are respectively denoted as Device Examples 2 - 44.

[0122] Device Comparative Examples 1 - 12:

[0123] Device Comparative Examples 1 - 12 refer to the method provided in the above Device Example 1, and respectively evaporate the comparative compounds a - l to replace the host material (Compound 1) of the light-emitting layer in the above Device Example 1, which are respectively denoted as Device Comparative Examples 1 - 12. Among them, the chemical structural formulas of the comparative compounds a - l are as follows:

[0124]

[0125] Characterize the driving voltage, luminous efficiency, and lifetime of the organic electroluminescent devices obtained from the above Device Examples 1 - 44 and Device Comparative Examples 1 - 12 at a brightness of 15000 (nits). The test results are shown in Table 2 below:

[0126] Table 2 Device Test Results

[0127]

[0128]

[0129] As can be seen from Table 2, compared with the devices prepared from Comparative Compounds 1-12, for Examples 1-44 of the organic electroluminescent devices prepared using the host material for the light-emitting layer provided by the present invention, while maintaining a low driving voltage, both the luminous efficiency and the lifetime can be improved.

[0130]

[0131] Compounds a, b and Compounds 244, 6 are parallel comparative examples. The difference is that there are no other substituents on the outer benzene rings of the dibenzothiophene group and the dibenzofuran group in Compounds a, b, while in Compound 244, 6 of the present invention, a phenyl group and a deuterated phenyl group are respectively connected to the dibenzothiophene group and the dibenzofuran group as substituents, effectively expanding the conjugated system, enhancing the conjugation effect, effectively improving the phosphorescence quantum efficiency, while avoiding the localization of carrier migration and enhancing the migration rate, thereby reducing the voltage and improving the luminous efficiency of the device. At the same time, the substituted phenyl group (deuterated phenyl group) on the rigid groups of the dibenzothiophene group and the dibenzofuran group balances the molecular structure and also has higher thermal stability and film-forming properties during the evaporation of the device, which is beneficial to improving the lifetime of the device.

[0132]

[0133] Compounds c and Compound 45 are parallel comparative examples. The difference is that a phenyl group is connected below the dibenzofuran group in Compound c, while in Compound 45 of the present invention, a carbazole group is at the corresponding position. The carbazole group has stronger rigidity and better thermal stability, can maintain the structural integrity at high temperatures, improve the thermal stability of the material, and make the structure of the material not easily change during the high-temperature evaporation process, 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 and energy transfer efficiency of triplet excitons, thereby improving the phosphorescent luminous efficiency.

[0134]

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

[0136] The applicant declares that the present invention uses the above 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 embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A phosphorescent host material, characterized in that: The general structural formula of the phosphorescent host material is Chemical Formula I: ； in, X is selected from O; 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 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.

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

3. A method for preparing the phosphorescent host material according to any one of claims 1 to 2, 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 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.

4. The preparation method according to claim 3, 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.

5. The preparation method according to claim 3, 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.

6. The preparation method according to claim 3, 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.

7. 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 phosphorescent host material as claimed in claim 1 or 2.

8. The organic electroluminescent device according to claim 7, 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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