CN116143781A - A kind of organic electroluminescent compound and its preparation method and application - Google Patents

Abstract

The invention discloses an organic electroluminescent compound. When the organic electroluminescent compound is used as a hole transport material or other organic compound layer of an OLED light-emitting device, the high hole transport rate can reduce the initial voltage of the device and improve the effective The efficiency of the electroluminescent device can prolong the service life very well.

Description

An organic electroluminescent compound and its preparation method and application

Technical Field

The present invention relates to the technical field of optoelectronic materials, and more particularly to an organic electroluminescent compound and a preparation method and application thereof.

Background Art

With the advent of the information age, people's living standards have changed with each passing day, and the requirements for display technology are also constantly increasing. Among the existing technologies, OLED technology has the advantages of high contrast, flexibility, wide viewing angle, and fast response speed, which makes OLED technology have good potential to replace traditional display technology.

Usually, an OLED light-emitting device has a stacked structure, which is composed of a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer. The hole transport layer (HTL) is responsible for adjusting the injection speed and injection amount of holes, and the hole transport material directly affects the efficiency and life of the OLED. In the prior art, the commonly used compounds in the hole transport region include copper phthalocyanine (CuPc), 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), 4,4',4"-tris(3-methylphenylphenylamino)triphenylamine (MTDATA), etc.

However, OLEDs using these materials have problems with quantum efficiency and service life. This is because hole transport materials usually have low highest occupied molecular orbital (HOMO) values, and the excitons generated in the light-emitting layer diffuse to the hole transport layer interface or the hole transport layer side, ultimately leading to light emission at the interface within the light-emitting layer or charge imbalance within the light-emitting layer, thereby emitting light at the interface of the hole transport layer, reducing the color purity and efficiency of the organic electroluminescent device.

Therefore, how to provide a hole transport material with high luminous efficiency, good life and low voltage is a technical problem that technical personnel in this field need to solve urgently.

Summary of the invention

The purpose of the present invention is to provide an organic electroluminescent compound and a preparation method and application thereof, so as to solve the problems raised in the above background technology.

In order to achieve the above object, the present invention adopts the following technical solution:

An organic electroluminescent compound, characterized in that its general structural formula is as shown in Chemical Formula 1:

Among them, a and b are 0 or 1 respectively, and a and b cannot be 0 at the same time;

R ₁ , R ₄ and R ₅ are at any position of the ring, and the number of substituents of R ₁ , R ₄ and R ₅ is an integer of 0-4 respectively;

_R2 and _R3 are at any position of the ring, and the number of substituents of _R2 and _R3 is an integer of 0-3 respectively;

R ₁ -R ₅ are each independently selected from a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C6-C30 aryl group, or a substituted or unsubstituted C3-C30 heteroaryl group;

or,

Connected with adjacent substituents to form a monocyclic or polycyclic ring, specifically a C3-C30 alicyclic ring or an aromatic ring;

Ar ₁ -Ar ₄ are each independently selected from substituted or unsubstituted C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, substituted or unsubstituted C3-C30 cycloalkyl, substituted or unsubstituted C3-C30 heterocycloalkyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted 3-30 membered heteroaryl, substituted or unsubstituted 3-30 membered heteroarylamine, substituted or unsubstituted C6-C60 arylamine, C1-C30 alkoxy, C6-C60 aryloxy;

or,

Connected with adjacent substituents to form a monocyclic or polycyclic C3-C30 aliphatic ring or a 3 to 30-membered aromatic ring, wherein the carbon atoms of the ring may be replaced by at least one heteroatom selected from nitrogen, oxygen and sulfur;

_L1 and _L2 are each independently selected from a linking bond or a substituted or unsubstituted C6-C30 aryl group.

Preferably, the R ₁ -R ₅ are 0-1 substituents respectively, and the R ₁ -R ₅ are each independently selected from a substituted or unsubstituted C1-C30 alkyl group or a substituted or unsubstituted C6-C30 aryl group.

Preferably, the Ar ₁ -Ar ₄ are each independently selected from a substituted or unsubstituted C6-C20 aryl group, a substituted or unsubstituted C15-C26 heteroaryl group or a triarylamine group.

More preferably, the Ar ₁ -Ar ₄ are each independently selected from a substituted or unsubstituted C10-C14 aryl group, a substituted or unsubstituted C18-C22 heteroaryl group or a triphenylamine group.

Preferably, _L1 and _L2 are each independently selected from benzene or deuterated benzene.

Furthermore, the organic electroluminescent compound is one of formula H001 to formula H138:

The preparation method of the above-mentioned organic electroluminescent compound has the following synthesis path:

In the above formula, R ₁ to R ₅ , Ar ₁ -Ar ₄ , L ₁ and L ₂ and a, b are identical to those in the above Chemical Formula 1, and c is 1 or 2; wherein, Chemical Formula 2 indicates that L ₁ and L ₂ in Chemical Formula 1 are both connecting bonds;

The specific preparation method is:

Step 1, preparation of intermediate 1

The raw material 2 was dissolved in THF, and then ventilated 3 times, cooled to -78°C, n-BuLi was added, and the reaction was continued for 2 hours. Then, the raw material 1 was added under the protection of _N2 , and the temperature was raised to 25°C, and stirred for 10 hours to prepare the intermediate 1;

Step 2, preparation of intermediate 2

Add intermediate 1 to a reaction flask, add glacial acetic acid, raise the temperature to 80°C, and drop concentrated sulfuric acid to prepare intermediate 2;

Step 3, preparation of chemical formula 1

The intermediate 2 and the raw material 3 were added to a mixed solution of toluene, ethanol and water, and then ventilated 3 times. A palladium catalyst and potassium carbonate were added under nitrogen protection, and the mixture was stirred evenly. The mixture was heated to 95° C. and reacted for 10 hours to prepare the chemical formula 1.

or,

Preparation of Chemical Formula 2

The intermediate 2 and the raw material 4 were added to the toluene solution, followed by venting 3 times, and palladium catalyst, tri-tert-butylphosphine and sodium tert-butoxide were added under nitrogen protection, stirred evenly, heated to 110° C., reacted for 8 hours, and the chemical formula 2 was prepared.

Preferably, the above step 1 specifically includes:

The raw material 2 was dissolved in THF, then ventilated 3 times, cooled to -70 to -80°C, n-BuLi was slowly added, and the reaction was continued for 1-3h. The raw material 1 was added under _N2 protection, and the temperature was slowly raised to 20-30°C. The mixture was stirred for 8-10h. Then, distilled water was slowly added to the reaction solution to quench the reaction, and the reaction solution was extracted with DCM. The extracted organic layer was then dried with magnesium sulfate, and the solvent was removed with a rotary evaporator. The solid was precipitated with DCM and PE (1:6) to obtain the intermediate 1.

Preferably, the above step 2 specifically includes:

Add intermediate 1 to a reaction bottle, add 10 times the volume of glacial acetic acid and heat to 80°C, slowly add concentrated sulfuric acid (1 times the volume) dropwise, and the reaction is complete. Then add distilled water 20 times the volume of concentrated sulfuric acid, and all solids precipitate, filter and dry to obtain intermediate 2.

Preferably, the above step 3 specifically includes:

Preparation of Chemical Formula 1

Intermediate 2 and raw material 3 are added to a mixed solution of toluene ethanol and water, followed by venting 3 times, adding palladium catalyst and potassium carbonate under nitrogen protection, stirring evenly, heating to 95°C, reacting for 10 hours, and then extracting the mixture with dichloromethane and water; then drying the extracted organic layer with sodium sulfate, and removing the solvent with a rotary evaporator; purifying the remaining substance with column chromatography to obtain the compound shown in Chemical Formula 1.

or,

Preparation of Chemical Formula 2

The intermediate 2 and the raw material 4 were added to the toluene solution, followed by venting 3 times, and palladium catalyst, tri-tert-butylphosphine and sodium tert-butoxide were added under nitrogen protection, stirred evenly, heated to 110°C, reacted for 10 hours, and then the mixture was extracted with dichloromethane and water; the extracted organic layer was then dried with sodium sulfate, and the solvent was removed with a rotary evaporator; the remaining substance was purified by column chromatography to obtain the compound shown in Chemical Formula 2.

Another object of the present invention is to provide an organic electroluminescent device containing the above-mentioned organic electroluminescent compound, comprising: a first electrode, a second electrode, and one or more organic compound layers disposed between the first electrode and the second electrode;

The organic compound layer includes a hole transport layer, and the hole transport layer includes the above-mentioned organic electroluminescent compound.

The hole transport material is a material that can receive holes from the anode or the hole injection layer and transport the holes to the light emitting layer, and has high hole mobility.

Preferably, it also includes one or more layers of a hole injection layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer.

Preferably, the first electrode serves as an anode, which preferably comprises a material having a high work function, such as indium tin oxide (ITO) or indium zinc oxide (IZO). Since the lifetime of the device of the invention is shortened in the presence of water and/or air, the device is appropriately (depending on the application) structured, provided with contacts and finally sealed.

The electron blocking layer may be disposed between the hole transport layer and the light emitting layer. As the electron blocking layer, materials known in the art, such as arylamine-based organic materials, may be used.

The material of the light emitting layer is a material that can emit visible light by receiving holes and electrons from the hole transport layer and the electron transport layer, respectively, and combining the received holes and electrons.

The light-emitting layer comprises a host material and a doping material;

The mass ratio of the main material to the doping material is 90-99.5:0.5-10;

The host material includes a fluorescent host and a phosphorescent host;

Doping materials include fluorescent doping and phosphorescent doping;

The hole blocking layer material may be any compound known in the prior art that has a hole blocking effect, for example, phenanthroline derivatives such as bathocuproine (BCP), oxazole derivatives, triazole derivatives, triazine derivatives, etc., but is not limited thereto.

The electron transport layer can promote electron transport. Compounds with electron transport function known in the prior art can be used, for example, Al complexes of 8-hydroxyquinoline; complexes containing Alq3; organic free radical compounds; hydroxyflavone-metal complexes, etc.

The electron injection layer can promote electron injection. It has the ability to transfer electrons and prevent the excitons generated in the light-emitting layer from migrating to the hole injection layer. The electron injection materials used in the present invention include fluorenone, anthraquinone dimethane, diphenoquinone, thiopyran dioxide, azole, diazole, triazole, imidazole, perylene tetracarboxylic acid, fluorenyl methane, anthrone, etc. and their derivatives, metal complexes, nitrogen-containing five-membered ring derivatives, etc., but are not limited thereto.

The second electrode is used as a cathode, and is usually preferably made of a material with a small work function so that electrons can be smoothly injected into the organic material layer, such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin and lead, or alloys thereof.

It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

The π conjugation effect in the organic electroluminescent compound gives it a strong hole transport ability; when the organic electroluminescent compound is used as a hole transport material or other organic compound layer of an OLED light-emitting device, the high hole transport rate can reduce the starting voltage of the device, improve the efficiency of the organic electroluminescent device, and can greatly extend the service life.

DETAILED DESCRIPTION

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

Example 1

A method for preparing an organic electroluminescent compound, using the above-mentioned synthesis route, comprises the following steps:

Add raw material 2 (44.6 mmol) and 100 ml THF to the reaction vessel, ventilate 3 times and cool to -78 ° C, add 2.5 mol / L n-BuLi (17.8 ml, 44.6 mmol) under nitrogen atmosphere and stir for 2 hours, add raw material 1 (37 mmol) and heat to 25 ° C, stir for 10 hours, and the reaction is completed. Then distilled water is added to the reaction solution to quench the reaction, and the reaction solution is extracted with DCM. Then, the extracted organic layer is dried with magnesium sulfate, and the solvent is removed by a rotary evaporator, and the solid is precipitated with DCM and PE (1: 6) to obtain intermediate 1 (12.8 g, yield 75.7%, MW: 457.91).

Add intermediate 1 (26.2 mmol) into a reaction bottle, add 240 ml of glacial acetic acid, raise the temperature to 80°C, add 12 ml of concentrated sulfuric acid dropwise, and the reaction is completed when the addition is complete. Then add 240 ml of distilled water, solid precipitates, and dry to obtain intermediate 2 (8.9 g, yield 77.23%, MW: 439.88).

The intermediate 2 (18.1 mmol) and the raw material 3 (21.8 mmol) were added to 300 ml of toluene solution, and then ventilated 3 times. Palladium catalyst (0.181 mmol), tri-tert-butylphosphine (0.905 mmol) and sodium tert-butoxide (36.2 mmol) were added under nitrogen protection, stirred evenly, heated to 110° C., reacted for 10 h, and then the mixture was extracted with dichloromethane and water; then the extracted organic layer was dried with sodium sulfate, and the solvent was removed with a rotary evaporator; the remaining substance was purified by column chromatography (the volume ratio of DCM to PE was 1:11) to obtain an organic electrogenic compound, see formula H048 (9.88 g, yield 71.3%, MW: 764.97), the reaction route is as follows:

Example 2

A method for preparing an organic electroluminescent compound, using the above-mentioned synthesis route, comprises the following steps:

Add raw material 2 (44.6 mmol) and 100 ml THF to the reaction vessel, ventilate 3 times and cool to -78 ° C, add 2.5 mol / L n-BuLi (17.8 ml, 44.6 mmol) under nitrogen atmosphere and stir for 2 hours, add raw material 1 (37 mmol) and heat to 25 ° C, stir for 10 hours, and the reaction is completed. Then distilled water is added to the reaction solution to quench the reaction, and the reaction solution is extracted with DCM. Then, the extracted organic layer is dried with magnesium sulfate, and the solvent is removed by a rotary evaporator, and the solid is precipitated with DCM and PE (1: 6) to obtain intermediate 1 (12.4 g, yield 73.4%, MW: 457.92).

Add intermediate 1 (26.2 mmol) into a reaction bottle, add 240 ml of glacial acetic acid, raise the temperature to 80°C, add 12 ml of concentrated sulfuric acid dropwise, and the reaction is completed when the addition is complete. Then add 240 ml of distilled water, and the solid precipitates. Dry to obtain intermediate 2 (8.4 g, yield 72.8%, MW: 439.89).

Intermediate 2 (18.1 mmol) and raw material 3 (21.8 mmol) were added to a mixed solution of toluene (180 ml), ethanol (60 ml), and water (60 ml), and then ventilated 3 times, palladium catalyst (0.181 mmol), potassium carbonate (54.3 mmol), stirred evenly, heated to 100 ° C, reacted for 10 hours, and then the mixture was extracted with dichloromethane and water; then the extracted organic layer was dried with sodium sulfate, and the solvent was removed by a rotary evaporator; the remaining substance was purified by column chromatography (the volume ratio of DCM to PE was 1:11) to obtain an organic electrogenic compound, see formula H033 (10.1 g, yield 69.8%, MW: 801.05), the reaction route is as follows:

Example 3

A method for preparing an organic electroluminescent compound, using the above-mentioned synthesis route, comprises the following steps:

Add raw material 2 (44.6 mmol) and 100 ml THF to the reaction vessel, ventilate 3 times and cool to -78 ° C, add 2.5 mol / L n-BuLi (17.8 ml, 44.6 mmol) under nitrogen atmosphere and stir for 2 hours, add raw material 1 (37 mmol) and heat to 25 ° C, stir for 10 hours, and the reaction is completed. Then distilled water is added to the reaction solution to quench the reaction, and the reaction solution is extracted with DCM. Then, the extracted organic layer is dried with magnesium sulfate, and the solvent is removed by a rotary evaporator, and the solid is precipitated with DCM and PE (1: 6) to obtain intermediate 1 (14.3 g, yield 72.4%, MW: 536.11).

Add intermediate 1 (26.2 mmol) into a reaction bottle, add 240 ml of glacial acetic acid, raise the temperature to 80°C, add 12 ml of concentrated sulfuric acid dropwise, and the reaction is completed when the addition is complete. Then add 240 ml of distilled water, and the solid precipitates. Dry to obtain intermediate 2 (10.4 g, yield 76.5%, MW: 518.10).

The intermediate 2 (18.1 mmol) and the raw material 3 (21.8 mmol) were added to 300 ml of toluene solution, and then ventilated 3 times. Palladium catalyst (0.181 mmol), tri-tert-butylphosphine (0.905 mmol) and sodium tert-butoxide (36.2 mmol) were added under nitrogen protection, stirred evenly, heated to 110° C., reacted for 10 h, and then the mixture was extracted with dichloromethane and water; then the extracted organic layer was dried with sodium sulfate, and the solvent was removed with a rotary evaporator; the remaining substance was purified by column chromatography (the volume ratio of DCM to PE was 1:11) to obtain an organic electrogenic compound, see formula H067 (11.2 g, yield 70.1%, MW: 883.18), the reaction route is as follows:

Example 4

A method for preparing an organic electroluminescent compound, using the above-mentioned synthesis route, comprises the following steps:

Add raw material 2 (44.6 mmol) and 100 ml THF to the reaction vessel, ventilate 3 times and cool to -78 ° C, add 2.5 mol / L n-BuLi (17.8 ml, 44.6 mmol) under nitrogen atmosphere and stir for 2 hours, add raw material 1 (37 mmol) and heat to 25 ° C, stir for 10 hours, and the reaction is completed. Then distilled water is added to the reaction solution to quench the reaction, and the reaction solution is extracted with DCM. Then, the extracted organic layer is dried with magnesium sulfate, and the solvent is removed by a rotary evaporator, and the solid is precipitated with DCM and PE (1: 6) to obtain intermediate 1 (14.2 g, yield 75.5%, MW: 508.05).

Add intermediate 1 (26.2 mmol) into a reaction bottle, add 240 ml of glacial acetic acid, raise the temperature to 80°C, add 12 ml of concentrated sulfuric acid dropwise, and the reaction is completed when the addition is complete. Then add 240 ml of distilled water, and the solid precipitates. Dry to obtain intermediate 2 (9.8 g, yield 76.1%, MW: 490.08).

The intermediate 2 (18.1 mmol) and the raw material 3 (21.8 mmol) were added to 300 ml of toluene solution, and then ventilated 3 times. Palladium catalyst (0.181 mmol), tri-tert-butylphosphine (0.905 mmol) and sodium tert-butoxide (36.2 mmol) were added under nitrogen protection, stirred evenly, heated to 110° C., reacted for 10 h, and then the mixture was extracted with dichloromethane and water; then the extracted organic layer was dried with sodium sulfate, and the solvent was removed with a rotary evaporator; the remaining substance was purified by column chromatography (the volume ratio of DCM to PE was 1:11) to obtain an organic electrogenic compound, see formula H093 (10.7 g, yield 71.1%, MW: 829.08), the reaction route is as follows:

Example 5-20

Compounds 2, 6, 11, 18, 26, 47, 60, 70, 76, 82, 85, 92, 95, 100, 105, and 123 were synthesized by referring to the synthesis method of Example 1. The mass spectra, molecular formulas, and yields of Examples 5-20 are shown in Table 1. In addition, it should be noted that other compounds of the present application can be obtained by referring to the synthesis methods of the above-listed examples.

Table 1

Application Example 1

An organic electroluminescent device is prepared by the following method:

的ITO(氧化铟锡)-Ag-ITO(氧化铟锡)玻璃基板在蒸馏水中清洗2次，超声波洗涤30min，再用蒸馏水反复清洗2次，超声波洗涤10min，洗涤结束后，用甲醇、丙酮、异丙醇依次超声波洗涤(每次洗涤5min)，干燥，然后转移至等离子体清洗机内洗涤5min，再送至蒸镀机中，以该基板为阳极，在其上依次蒸镀其它功能层。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 cleaned for 30 minutes, and then repeatedly cleaned twice with distilled water, ultrasonically cleaned for 10 minutes. After washing, it was ultrasonically cleaned 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 thereon in sequence.

的蒸镀速率，真空蒸镀空穴注入层材料HT(本发明实施例1中所提供的化合物)和P-dopant，所述HT和P-dopant的蒸镀速率比为98：2，厚度为10nm；b. HIL (hole injection layer):

The hole injection layer material HT (the compound provided in Example 1 of the present invention) and P-dopant are vacuum-deposited at a deposition rate of 98:2, and the thickness is 10 nm;

的蒸镀速率，在空穴注入层上面真空蒸镀120nm的本发明实施例1中所提供的化合物作为空穴传输层；c. HTL (hole transport layer):

At a deposition rate of , vacuum-deposit 120 nm of the compound provided in Example 1 of the present invention on the hole injection layer as a hole transport layer;

的蒸镀速率，真空蒸镀厚度为25nm的主体材料(Host)和掺杂材料(Dopant)作为发光层，其Host和Dopant的化学式如下所示。其中Host和Dopant的蒸镀速率比为97：3。d. EML (light-emitting layer): Then on the hole transport layer,

The host material (Host) and dopant material (Dopant) with a thickness of 25nm are vacuum-deposited as the light-emitting layer. The chemical formulas of Host and Dopant are shown below. The evaporation rate ratio of Host to Dopant is 97:3.

的蒸镀速率，真空蒸镀厚度为35nm的ET和Liq作为电子传输层，其ET的化学式如下所示。其中ET和Liq的蒸镀速率比为50：50。e. ETL (Electron Transport Layer):

ET and Liq were vacuum-deposited at a deposition rate of 35 nm as an electron transport layer, and the chemical formula of ET is shown below. The deposition rate ratio of ET to Liq is 50:50.

的蒸镀速率，蒸镀Yb膜层1.0nm，形成电子注入层。f. EIL (electron injection layer):

At a evaporation rate of , a 1.0 nm Yb film layer was evaporated to form an electron injection layer.

的蒸镀速率比，蒸镀镁和银18nm，其蒸镀速率比为1:9，得到OLED器件。g. Cathode:

The evaporation rate ratio is 1:9, and magnesium and silver are evaporated at 18nm, and the evaporation rate ratio is 1:9 to obtain an OLED device.

的蒸镀速率，在阴极上真空蒸镀厚度为70nm的CPL，作为光取出层。h. Light extraction layer:

At a deposition rate of , CPL with a thickness of 70 nm was vacuum-deposited on the cathode as a light extraction layer.

i. Package the substrate after evaporation. First, use the glue coating equipment to coat the cleaned cover with UV glue, then move the coated cover to the pressing section, place the evaporation-deposited substrate on the upper end of the cover, and finally bond the substrate and cover with the bonding equipment, and complete the light curing of the UV glue.

Comparative Example 1

According to the method of Application Example 1, the material of the hole transport layer is replaced by the compound in Application Example 1 with chemical A. The structural formula of compound A is as follows:

Comparative Example 2

According to the method of Application Example 1, the material of the hole transport layer is replaced by the compound in Application Example 1 with chemical B, and the structural formula of compound B is as follows:

The driving voltage, luminous efficiency, BI value and life of the organic electroluminescent device obtained from the above device embodiment and device comparison example were characterized at a brightness of 1000 (nits). The test results are shown in Table 2 below:

Table 2

As can be seen from Table 2, the π conjugation effect in the organic electroluminescent compound proposed by the present invention enables it to have a strong hole transport ability. By introducing the aromatic amine side chain, the overall structure of the compound is made radial, so that the distance between molecules becomes larger, which is beneficial to reduce the cohesion between molecules and reduce the possibility of crystallization. When the organic electroluminescent compound is used as a hole transport material or other organic compound layer of an OLED light-emitting device, the high hole transport rate can reduce the starting voltage of the device, improve the efficiency of the organic electroluminescent device, and can well extend the service life.

In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims (7)

1. An organic electroluminescent compound, characterized in that its general structural formula is as shown in Chemical Formula 1:

Among them, a and b are 0 or 1 respectively, and a and b cannot be 0 at the same time; R ₁ , R ₄ and R ₅ are at any position of the ring, and the number of substituents of R ₁ , R ₄ and R ₅ is an integer of 0-4 respectively; _R2 and _R3 are at any position of the ring, and the number of substituents of _R2 and _R3 is an integer of 0-3 respectively; R ₁ -R ₅ are each independently selected from a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C6-C30 aryl group, or a substituted or unsubstituted C3-C30 heteroaryl group; or, Connecting with adjacent substituents to form a single ring or multiple rings; Ar ₁ -Ar ₄ are each independently selected from substituted or unsubstituted C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, substituted or unsubstituted C3-C30 cycloalkyl, substituted or unsubstituted C3-C30 heterocycloalkyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted 3-30 membered heteroaryl, substituted or unsubstituted 3-30 membered heteroarylamine, substituted or unsubstituted C6-C60 arylamine, C1-C30 alkoxy, C6-C60 aryloxy; or, Connected with adjacent substituents to form a monocyclic or polycyclic ring, and the carbon atoms thereof may be replaced by at least one heteroatom selected from nitrogen, oxygen and sulfur; _L1 and _L2 are each independently selected from a linking bond or a substituted or unsubstituted C6-C30 aryl group. 2 . The organic electroluminescent compound according to claim 1 , wherein the Ar ₁ -Ar ₄ are each independently selected from a substituted or unsubstituted C6-C20 aryl group, a substituted or unsubstituted C15-C26 heteroaryl group or a triarylamine group. 3 . The organic electroluminescent compound according to claim 1 , wherein L ₁ and L ₂ are independently selected from benzene or deuterated benzene. 4. The organic electroluminescent compound according to claim 1, characterized in that the organic electroluminescent compound is one of formula H001 to formula H138:

5. A method for preparing an organic electroluminescent compound according to any one of claims 1 to 4, characterized in that the synthesis route is as follows:

In the above formula, R ₁ to R ₅ , Ar ₁ -Ar ₄ , L ₁ and L ₂ and a, b are identical to the same parts as those in any one of the chemical formulas 1 to 3, and c is 1 or 2; wherein, chemical formula 2 indicates that L ₁ and L ₂ in chemical formula 1 are both connecting bonds; The specific preparation method is: Step 1, preparation of intermediate 1 The raw material 2 was dissolved in THF, and then ventilated 3 times, cooled to -70--80°C, n-BuLi was added, and the reaction was continued for 1-3 hours. Then, the raw material 1 was added under the protection of _N2 , and the temperature was raised to 20-30°C, and stirred for 8-10 hours to prepare the intermediate 1; Step 2, preparation of intermediate 2 Add intermediate 1 to a reaction flask, add glacial acetic acid, raise the temperature to 60-80°C, and drop concentrated sulfuric acid to prepare intermediate 2; Step 3, preparation of chemical formula 1 The intermediate 2 and the raw material 3 are added to a mixed solution of toluene, ethanol and water, and then the mixture is ventilated three times. A palladium catalyst and potassium carbonate are added under nitrogen protection, and the mixture is stirred evenly. The mixture is heated to 90-100° C. and reacted for 8-10 hours to prepare the chemical formula 1. or, Preparation of Chemical Formula 2 The intermediate 2 and the raw material 4 are added to the toluene solution, followed by venting 3 times, and palladium catalyst, tri-tert-butylphosphine and sodium tert-butoxide are added under nitrogen protection, stirred evenly, heated to 100-110° C., reacted for 7-10 hours, and the chemical formula 2 is prepared. 6. A hole transport layer in an organic electroluminescent device, characterized in that the hole transport layer in the organic electroluminescent device comprises the organic electroluminescent compound according to any one of claims 1 to 4 or the organic electroluminescent compound prepared by the preparation method according to claim 5. 7. An organic electroluminescent device, characterized by comprising the hole transport layer according to claim 6.