WO2020237885A1

WO2020237885A1 - Dark blue thermal activation delayed fluorescent material and preparation method therefor, and electroluminescent device

Info

Publication number: WO2020237885A1
Application number: PCT/CN2019/103503
Authority: WO
Inventors: 罗佳佳; 张曲
Original assignee: 武汉华星光电半导体显示技术有限公司
Priority date: 2019-05-24
Filing date: 2019-08-30
Publication date: 2020-12-03
Also published as: CN110079305A

Abstract

A dark blue thermal activation delayed fluorescent material and a preparation method therefor, and an electroluminescent device. According to the present invention, a series of dark blue TADF materials with high yield and high PLQY are synthesized by means of ingenious molecular design. The dark blue TADF material has high yield and is synthesized by simple steps. In addition, the dark blue TADF material is used as an object of a luminescent layer of the electroluminescent device, a series of electroluminescent devices with high luminance, high production efficiency and long service life are developed.

Description

Dark blue thermally activated delayed fluorescent material and its preparation method, electroluminescent device

Technical field

The invention relates to a display field technology, in particular to a dark blue thermally activated delayed fluorescent material, a preparation method thereof, and an electroluminescent device.

Background technique

Organic light-emitting diodes (OLEDs) do not require a backlight for active light emission, have high luminous efficiency, large viewing angle, fast response speed, large temperature adaptation range, relatively simple production and processing technology, and low driving voltage. , Low energy consumption, lighter and thinner, flexible display and other advantages and huge application prospects have attracted the attention of many researchers. In OLED, the light-emitting guest material is very important. The light-emitting guest materials used in early OLEDs were fluorescent materials. Since the ratio of singlet and triplet excitons in OLEDs is 1:3, the theoretical internal quantum efficiency (IQE) of OLEDs based on fluorescent materials is only It can reach 25%, which greatly limits the application of fluorescent electroluminescent devices. Due to the spin-orbit coupling of heavy atoms, heavy metal complex phosphorescent materials can simultaneously utilize singlet and triplet excitons to achieve 100% IQE. However, the commonly used heavy metals are all precious metals such as Ir and Pt, which are expensive, and phosphorescent luminescent materials still need a breakthrough in blue light materials. Organic thermally activated delayed fluorescence (TADF) materials, through clever molecular design, make the molecules have a small minimum single triplet energy difference (ΔE _ST ), so that the triplet excitons can cross through the reverse system (reverse intersystem crossing, RISC) returns to the singlet state, and then emits light through the radiation transition to the ground state, thereby simultaneously using singlet and triplet excitons to achieve 100% IQE.

technical problem

For TADF materials, fast reverse intersystem crossing constant (k _RISC ) and high photoluminescence quantum yield (PLQY) are necessary conditions for the preparation of high-efficiency OLEDs. At present, TADF materials with the above conditions are still relatively scarce compared to phosphorescent heavy metal complex materials. In the dark blue field where phosphorescent heavy metal complex materials need to be broken, TADF materials are even rarer.

Technical solutions

In view of the shortcomings of the existing technology, the present invention synthesizes a series of dark blue TADF materials with high yield and high PLQY through clever molecular design, which can effectively reduce the highest occupied molecular orbital (HOMO) and the lowest potential. Occupy the molecular orbital (lowest occupied molecular orbital, LUMO) degree of overlap, thereby obtaining a small ΔE _ST , thereby improving the efficiency of the device. Their structures were confirmed by NMR and carbon spectroscopy, and then their photophysical properties were studied in detail. Finally, a series of high-performance dark blue TADF OLEDs were prepared based on these luminescent materials.

In order to solve the above problems, the present invention conducts in-depth research on the hot thermally activated delayed fluorescent materials currently studied, and designs and synthesizes molecular systems of D1-A-D2 structures with different electron donors, in which D1 is the first The electron group, D2 is the second electron donating group, and A is the electron acceptor. The present invention provides a dark blue thermally activated delayed fluorescent material. The dark blue thermally activated delayed fluorescent material consists of a first electron-donating group, a second electron-donating group, and 2,-6-dibromo-4-methylpyridine Combined with nitrogen oxides, its general structural formula is:

Wherein, in the general structural formula, D1 is the first electron-donating group, D2 is the second electron-donating group, and the first electron-donating group is different from the second electron-donating group. Specifically, the first electron donating group is selected from one of the following materials:

Specifically, the second electron donating group is selected from one of the following materials:

The present invention also provides a method for synthesizing dark blue thermally activated delayed fluorescent material, which includes the following steps:

In the first mixed solution preparation step, the raw materials of the first electron-donating group, the electron acceptor, and the catalyst are placed in a reaction vessel to fully react to obtain a first mixed solution. The first mixed solution includes the first electron-donating group. The raw materials of the cluster and the intermediates generated by the electron acceptor reaction;

In the first extraction step, the first mixed solution is cooled to room temperature, the mixed solution is extracted to obtain the first compound, and the first compound is combined and purified to obtain the intermediate;

In the second mixed solution preparation step, the raw materials of the second electron donating group, the intermediate and the catalyst are placed in a reaction vessel to obtain a second mixed solution, and the second mixed solution includes the intermediate and the The raw material of the second electron donating group;

In the second extraction step, the second mixed solution is cooled to room temperature, the mixed solution is extracted to obtain a second compound, and the second compound is combined and purified to obtain a dark blue thermally activated delayed fluorescent material.

Specifically, the raw material of the first electron-donating group is selected from 4-carbazole phenylboronic acid, 4-(3,6-dimethylcarbazole)-phenylboronic acid, 4-(3,6-diphenylcarbazole) Azole)-a kind of phenylboronic acid.

Specifically, the electron acceptor is 2,-6-dibromo-4-methylpyridine oxynitride.

Specifically, the raw material of the second electron donating group is 4-(9,10-dihydro-9,9-diphenylacridine)-phenylboronic acid.

Specifically, the catalyst used in the first mixing configuration step includes K ₂ CO ₃ and Pd(PPh ₃ ) ₄ .

Specifically, the catalyst used in the second mixing configuration step includes K2CO3 and Pd(PPh3)4.

Specifically, the molar ratio of the electron acceptor to the raw material of the first electron donating group is 1:1 to 1:5.

Specifically, the molar ratio of the intermediate to the raw material of the second electron donating group is 1:1 to 1:5.

Specifically, the reaction temperature of the first mixed solution preparation step is 80-90 degrees Celsius, and the reaction time is at least 12 hours.

Specifically, the reaction temperature of the second mixed solution preparation step is 80-90 degrees Celsius, and the reaction time is at least 12 hours.

Specifically, the step of preparing the first mixed solution includes combining the raw material of the first electron-donating group, 2,-6-dibromo-4-methylpyridine oxynitride, K ₂ CO ₃ and Pd(PPh ₃ ) ₄ Placed together in the reaction vessel, pumped through three times, then placed the reaction vessel in an argon atmosphere, and added deoxygenated glycol dimethyl ether to the reaction vessel at 80°C. Perform reflux reaction at 90 degrees for at least 12 hours and then cool to room temperature to obtain a first mixed solution.

Specifically, the step of preparing the second mixed solution includes placing the raw material of the second electron donating group, the intermediate, K ₂ CO ₃ and Pd(PPh ₃ ) ₄ together in the reaction vessel, and pumping Pass three times, then place the reaction vessel in an argon atmosphere, add deoxygenated ethylene glycol dimethyl ether to the reaction vessel, reflux for at least 12 hours at 80-90 degrees Celsius, and then cool to room temperature , To obtain the second mixed solution.

Specifically, the first extraction step includes pouring the first mixed solution into ice water, using dichloromethane for multiple extractions, and combining the organic phases to obtain the first compound; using a developing agent, passing through a silica gel column The first compound is purified by chromatography to obtain the intermediate.

Specifically, the developing agent in the silica gel column chromatography method comprises dichloromethane and n-hexane, and the volume ratio of the dichloromethane and the n-hexane is 1:3.

Specifically, the second extraction step includes pouring the second mixed solution into ice water, using dichloromethane for multiple extractions, and combining the organic phases to obtain the second compound; using a developing agent, passing through a silica gel column The chromatographic method is used to purify the second compound for the first time to obtain the initial purified product, and the initial purified product is purified using a sublimation apparatus, and finally the dark blue thermally activated delayed fluorescent material is obtained.

Specifically, the developing agent in the silica gel column chromatography method comprises dichloromethane and n-hexane, and the volume ratio of the dichloromethane and the n-hexane is 1:1.

The present invention also provides an electroluminescent device, including:

A substrate layer; a hole transport and injection layer disposed on the substrate layer; a light emitting layer disposed on the hole transport and injection layer; an electron transport layer disposed on the light emitting layer ; And a cathode layer disposed on the electron transport layer;

Specifically, the luminescent material of the luminescent layer has a general structural formula as follows:

Specifically, in the general structural formula, D1 is a first electron-donating group, D2 is a second electron-donating group, and the first electron-donating group is different from the second electron-donating group.

Specifically, the first electron donating group is selected from one of the following materials:

Beneficial effect

By screening different electron donor units, the present invention adjusts the torsion angle between the electron donor and the electron acceptor and the charge transfer characteristics, so as to achieve the purpose of reducing the lowest single triplet energy level difference and deep blue emission of molecules. Make the molecules have excellent luminescence properties. The electroluminescent device made based on the dark blue TADF material provided by the present invention achieves very high luminous efficiency.

Description of the drawings

The present invention will be further described below with reference to the drawings and embodiments.

Figure 1 is a photoluminescence spectrum of a dark blue thermally activated delayed fluorescent material synthesized in an embodiment of the present invention in a toluene solution at room temperature;

Figure 2 is a schematic diagram of the structure of the electroluminescent device described in the embodiment of the present invention.

Embodiments of the invention

In order to further explain the technical means adopted by the present invention and its effects, the following describes in detail the preferred embodiments of the present invention and the accompanying drawings.

The present invention provides a dark blue thermally activated delayed fluorescent material. The dark blue thermally activated delayed fluorescent material consists of a first electron donating group, a second electron donating group, and 2,-6-dibromo-4-methylpyridine Combined with nitrogen oxides, its general structural formula is:

Wherein, in the general structural formula, D1 is the first electron-donating group, D2 is the second electron-donating group, and the first electron-donating group is different from the second electron-donating group.

Preferably, the first electron donating group is selected from one of the following materials:

Preferably, the second electron donating group is selected from one of the following materials:

The present invention also provides a method for synthesizing dark blue thermally activated delayed fluorescence. In order to make the description clearer, the following specific descriptions are given through Examples 1-3.

Example 1

The specific steps for synthesizing the dark blue thermally activated delayed fluorescent material of formula (1) are as follows:

The first mixed solution preparation step, wherein, in this implementation, the raw material of the first electron-donating group (4-carbazole phenylboronic acid, 2.87 g, 10 mmol) and 2,-6-dibromo-4-methylpyridine nitrogen oxide (2.67g, 10mmol) and the catalyst (K2CO3, 2.76g, 20mmol and Pd(PPh3)4, 0.575g, 0.5mmol) were placed in the reaction vessel, pumped three times, and injected the previously deoxygenated ethyl acetate under an argon atmosphere. Glycol dimethyl ether (100ml), followed by reflux reaction at 85 degrees Celsius for 12 hours to obtain a first mixed solution. The first mixed solution includes 4-carbazole phenylboronic acid and 2,-6-dibromo- Intermediate produced by the reaction of 4-picoline nitrogen oxide (2-bromo-4-methyl-6-(4-carbazolephenyl)-pyridine nitrogen oxide).

In the first extraction step, the first mixed solution is cooled to room temperature and poured into ice water (200ml), and extracted three times (100ml of methylene chloride is added each time), and the organic phases are combined to obtain compound 1; Using a developing solvent, the compound 1 was first purified by silica gel column chromatography to obtain 3.17 g of the intermediate with a yield of 74%.

Wherein, the developing agent is made by dichloromethane and n-hexane in a volume ratio of 1:3.

Wherein, the intermediate is a white powder, and the white powder is analyzed according to the detection requirements by the detection equipment. The analysis results are: 1H NMR (300MHz, CD2Cl2, δ): 1H NMR (300MHz, CD2Cl2, δ): 8.56 (d, J = 4.5 Hz, 1H), 8.19 (d, J = 4.5 Hz, 1H), 7.91-7.94 (m, 5H), 7.53-7.58 (m, 3H) , 7.35 (m, 1H), 7.16-7.20 (m, 3H), 2.45 (s, 3H).

In the second mixed solution preparation step, the raw material for the second electron donating group (4-(9,10-dihydro-9,9-diphenylacridine)-phenylboronic acid, 2.7g, 6mmol) and the intermediate Body (2-bromo-4-methyl-6-(4-carbazolephenyl)-pyridine nitrogen oxide, 2.15g, 5mmol) and catalyst (K2CO3, 1.38g, 10mmol and Pd(PPh3) 4, 0.29g) , 0.25mmol) was placed in the reaction vessel, pumped three times, injected in the previously deoxygenated ethylene glycol dimethyl ether (100ml) under an argon atmosphere, and then refluxed at 85 degrees Celsius for 12 hours to obtain the second A mixed solution, the second mixed solution includes the intermediate (2-bromo-4-methyl-6-(4-carbazolephenyl)-pyridine oxynitride) and 4-(9,10-bis Hydro-9,9-diphenylacridine)-phenylboronic acid.

The second extraction step is to cool the second mixed solution to room temperature and pour it into ice water (200ml), perform three extractions (add 100ml of dichloromethane each time), combine the organic phases to obtain compound 2; use The developing solvent was used to purify the compound 2 for the first time by silica gel column chromatography to obtain 2.28 g of the first initial purified product with a yield of 60%. Finally, the first initial purified product 1 was purified using a sublimation apparatus to obtain 1.3g of the deep blue thermally activated delayed fluorescent material of formula (1).

Wherein, the developing agent is made by dichloromethane and n-hexane with a volume ratio of 1:1.

Wherein, the dark blue thermally activated delayed fluorescent material of formula (1) is a white powder, and the white powder is analyzed by a detection device according to the detection requirements. The analysis result is: the results of the nuclear magnetic hydrogen spectrum and the carbon spectrum are: 1H NMR (300MHz, CD2Cl2, δ): 8.56 (d, J = 4.5 Hz, 1H), 8.19 (d, J = 4.5 Hz, 1H), 7.91-7.94 (m, 5H), 7.73 (m, 2H), 7.50 -7.58 (m, 2H), 7.15-7.37 (m, 21H), 6.95 (m, 4H), 2.45 (s, 3H).

The chemical reaction process of Example 1 is as follows:

In this embodiment, through the combination of different functional groups, a dark blue thermally activated delayed fluorescent material with high synthesis yield and high photoluminescence efficiency is designed.

Example 2

The specific steps for synthesizing the dark blue thermally activated delayed fluorescent material of formula (2) are as follows:

The first mixed solution preparation step, wherein, in this implementation, the raw material of the first electron donating group (4-(3,6-dimethylcarbazole)-phenylboronic acid, 3.15g, 10mmol) and 2,-6-di Bromo-4-methylpyridine nitrogen oxide (2.67g, 10mmol) and catalyst (K2CO3, 2.76g, 20mmol and Pd(PPh3)4, 0.575g, 0.5mmol) were placed in the reaction vessel, pumped three times, Glycol dimethyl ether (100ml) deoxygenated in advance was injected in an air atmosphere, and then refluxed at 85 degrees Celsius for 12 hours to obtain a first mixed solution. The first mixed solution contained 4-(3, The intermediate (2-bromo-4-methyl-6-(4-(3) produced by the reaction of 6-dimethylcarbazole)-phenylboronic acid and 2,-6-dibromo-4-methylpyridine nitrogen oxide ,6-Dimethylcarbazole)-phenyl)-pyridine oxynitride).

In the first extraction step, the first mixed solution is cooled to room temperature and poured into ice water (200ml), and extracted three times (each time adding 100ml of dichloromethane), and the organic phases are combined to obtain compound 3; Using a developing solvent, the compound 3 was first purified by silica gel column chromatography to obtain 3.01 g of the intermediate with a yield of 66%.

Wherein, the intermediate is a white powder, and the white powder is analyzed by testing equipment according to the testing requirements. The analysis results are: 1H NMR (300MHz, CD2Cl2, δ): 8.80 (s, 1H), 8.03 (s, 1H), 7.89-7.92 (m, 5H), 7.53 (m, 2H), 7.38 (m, 1H), 7.19 (s, 1H), 6.96 (m, 1H), 2.45(s, 3H). In the second mixed solution preparation step, the raw material for the second electron donating group (4-(9,10-dihydro-9,9-diphenylacridine)-phenylboronic acid, 2.7g, 6mmol) and the intermediate Body (2-bromo-4-methyl-6-(4-(3,6-dimethylcarbazole)-phenyl)-pyridine nitrogen oxide, 2.28g, 5mmol) and catalyst (K2CO3, 1.38g, 10mmol and Pd(PPh3)4, 0.29g, 0.25mmol) were placed in the reaction vessel, pumped through three times, injected in ethylene glycol dimethyl ether (50ml) deoxygenated in an argon atmosphere, and then heated at 85°C The reflux reaction was continued for 12 hours to obtain a second mixed solution, the second mixed solution including the intermediate (2-bromo-4-methyl-6-(4-(3,6-dimethylcarbazole) )-Phenyl) and 4-(9,10-dihydro-9,9-diphenylacridine)-phenylboronic acid.

In the second extraction step, the second mixed solution is cooled to room temperature and poured into ice water (200ml), and extracted three times (each time adding 100ml of dichloromethane), and the organic phases are combined to obtain compound 4; The compound 4 was first purified by silica gel column chromatography using a developing solvent to obtain 2.20 g of the initial purified product 2 with a yield of 56%. Finally, the initial purified product 2 was purified using a sublimation apparatus to obtain 1.1 g The dark blue thermally activated delayed fluorescent material of formula (2).

Wherein, the compound is a white powder. The white powder is analyzed by the detection equipment according to the detection requirements. The analysis results are: 1H NMR (300MHz, CD2Cl2, δ): 8.80( s, 1H), 8.03 (s, 1H), 7.89-7.92 (m, 5H), 7.73 (m, 2H), 7.53 (m, 1H), 7.38 (m, 3H), 7.19-7.26 (m, 16H) , 6.96 (m, 5H), 2.46 (s, 6H), 2.45 (s, 3H).

The chemical reaction process of Example 2 is as follows:

Example 3

The specific steps for synthesizing the dark blue thermally activated delayed fluorescent material of formula (3) are as follows:

The first mixed solution preparation step, wherein, in this implementation, the raw material of the first electron donating group (4-(3,6-diphenylcarbazole)-phenylboronic acid, 4.39g, 10mmol) and 2,-6-di Bromo-4-methylpyridine nitrogen oxide (2.67g, 10mmol) and catalyst (K2CO3, 2.76g, 20mmol and Pd(PPh3)4, 0.575g, 0.5mmol) were placed in the reaction vessel, pumped three times, Glycol dimethyl ether (100ml) deoxygenated in advance was injected in an air atmosphere, and then refluxed at 85 degrees Celsius for 12 hours to obtain a first mixed solution. The first mixed solution contained 4-(3, 6-Diphenylcarbazole)-phenylboronic acid and 2,-6-dibromo-4-methylpyridine nitrogen oxide reaction intermediate (2-bromo-4-methyl-6-(4-(3 ,6-Dimethylcarbazole)-phenyl)-pyridine oxynitride).

In the first extraction step, the first mixed solution was cooled to room temperature and poured into ice water (200ml), and extracted three times (each time adding 100ml of dichloromethane), and the organic phases were combined to obtain compound 5; Using a developing solvent, the compound 5 was first purified by silica gel column chromatography to obtain 3.60 g of the intermediate with a yield of 62%.

Wherein, the intermediate is a white powder, and the obtained white powder is analyzed by testing equipment according to the testing requirements. The results of the analysis are: 1H NMR (300MHz, CD2Cl2, δ): 8.30 (m, 1H), 8.13 (m, 1H), 7.89-7.99 (m, 7H), 7.75-7.77 (m, 5H), 7.49-7.53 (m, 7H), 7.19 (s, 1H) ,2.45(s,3H).

In the second mixed solution preparation step, the raw material for the second electron donating group (4-(9,10-dihydro-9,9-diphenylacridine)-phenylboronic acid, 2.7g, 6mmol) and the intermediate Body (2-bromo-4-methyl-6-(4-(3,6-dimethylcarbazole)-phenyl)-pyridine nitrogen oxide, 2.90g, 5mmol) and catalyst (K2CO3, 1.38g, 10mmol and Pd(PPh3)4, 0.29g, 0.25mmol) were placed in the reaction vessel, pumped through three times, injected in ethylene glycol dimethyl ether (50ml) deoxygenated in an argon atmosphere, and then heated at 85°C The reflux reaction was continued for 12 hours to obtain a second mixed solution, the second mixed solution including the intermediate (2-bromo-4-methyl-6-(4-(3,6-dimethylcarbazole) )-Phenyl)-pyridine oxynitride) and 4-(9,10-dihydro-9,9-diphenylacridine)-phenylboronic acid;

In the second extraction step, cool the second mixed solution to room temperature and pour it into ice water (200ml), and perform three extractions (each adding 100ml of dichloromethane), and combine the organic phases to obtain compound 6; The initial purification of the compound 6 was performed by silica gel column chromatography using a developing solvent to obtain 2.05 g of the initial purified product 3 with a yield of 45%. Finally, the initial purified product 3 was purified using a sublimation apparatus to obtain 1.0 g is the dark blue thermally activated delayed fluorescent material of formula (3).

Wherein, the compound 3 is a white powder, and the obtained white powder is analyzed by the detection equipment according to the detection requirements. The analysis results are: 1H NMR (300MHz, CD2Cl2, δ): 8.30 (m, 1H), 8.13 (m, 1H), 7.89-7.99 (m, 7H), 7.75-7.77 (m, 7H), 7.37-7.49 (m, 8H), 7.19-7.26 (m, 16H), 6.95 (m, 2H), 2.45 (s, 3H).

The chemical reaction process of Example 3 is as follows:

The following is a parameter analysis of the dark blue thermally activated delayed fluorescent materials synthesized in Example 1, Example 2 and Example 3. The analysis data is shown in Table (1) below.

Table 1)

The photoluminescence spectra of the dark blue thermally activated delayed fluorescent materials synthesized in Example 1, Example 2 and Example 3 in a toluene solution at room temperature are shown in FIG. 1.

The present invention also provides an electroluminescent device. In order to make the description clearer, the following specific descriptions are given through Examples 4-6.

Example 4

As shown in FIG. 2, the present invention also provides a first electroluminescent device, comprising: a substrate layer 1; a hole transport and injection layer 2 disposed on the substrate layer 1; and a light emitting layer 3, It is provided on the hole transport and injection layer 2; an electron transport layer 4 is provided on the light-emitting layer 3; and a cathode layer 5 is provided on the electron transport layer 4.

Furthermore, the material of the substrate layer 1 includes glass and conductive glass (ITO), and a layer of 50nm poly 3,4-ethylenedioxythiophene: polystyrene sulfonate is spin-coated on the substrate layer 1 after cleaning. Acid salt (PEDOT:PSS) to form the hole transport and injection layer 2; under vacuum conditions, a 40nm deep blue thermally activated fluorescent material is evaporated on the hole transport and injection layer 2 to form Light-emitting layer 3; under vacuum conditions, a 40nm layer of 1,3,5-tris(3-(3-pyridyl)phenyl)benzene (Tm3PyPB) is evaporated on the light-emitting layer 3 to form an electron transport Layer 4; under vacuum conditions, a layer of 1nm of lithium fluoride and 100nm of aluminum are evaporated on the electron transport layer 4 to obtain a cathode layer 5, and finally the first electroluminescent device is made, wherein, The material of the light-emitting layer 3 is the dark blue thermally activated fluorescent material synthesized in Example 1.

Example 5

Furthermore, the material of the substrate layer 1 includes glass and conductive glass (ITO), and a layer of 50nm poly 3,4-ethylenedioxythiophene: polystyrene sulfonate is spin-coated on the substrate layer 1 after cleaning. Acid salt (PEDOT:PSS) to form the hole transport and injection layer 2; under vacuum conditions, a 40nm deep blue thermally activated fluorescent material is evaporated on the hole transport and injection layer 2 to form Light-emitting layer 3; under vacuum conditions, a 40nm layer of 1,3,5-tris(3-(3-pyridyl)phenyl)benzene (Tm3PyPB) is evaporated on the light-emitting layer 3 to form an electron transport Layer 4; Under vacuum conditions, a layer of 1nm of lithium fluoride and 100nm of aluminum are evaporated on the electron transport layer 4 to obtain a cathode layer 5, and finally the second electroluminescent device is made, wherein, The material of the light-emitting layer 3 is the deep blue thermally activated fluorescent material synthesized in Example 2.

Example 6

As shown in FIG. 2, the present invention also provides a third electroluminescent device, including: a substrate layer 1; a hole transport and injection layer 2 disposed on the substrate layer 1, and a light emitting layer 3, It is provided on the hole transport and injection layer 2; an electron transport layer 4 is provided on the light-emitting layer 3; and a cathode layer 5 is provided on the electron transport layer 4.

Furthermore, the material of the substrate layer 1 includes glass and conductive glass (ITO), and a layer of 50nm poly 3,4-ethylenedioxythiophene: polystyrene sulfonate is spin-coated on the substrate layer 1 after cleaning. Acid salt (PEDOT:PSS) to form the hole transport and injection layer 2; under vacuum conditions, a 40nm deep blue thermally activated fluorescent material is evaporated on the hole transport and injection layer 2 to form Light-emitting layer 3; under vacuum conditions, a 40nm layer of 1,3,5-tris(3-(3-pyridyl)phenyl)benzene (Tm3PyPB) is evaporated on the light-emitting layer 3 to form an electron transport Layer 4; under vacuum conditions, a layer of 1nm lithium fluoride and 100nm aluminum are evaporated on the electron transport layer 4 to obtain a cathode layer 5, and finally the third electroluminescent device is made, wherein, The material of the light-emitting layer 3 is the dark blue thermally activated fluorescent material synthesized in Example 3.

The current-brightness-voltage characteristics of the first electroluminescent device, the second electroluminescent device, and the third electroluminescent device are measured by a Keithley source measurement system with a calibrated silicon photodiode (Keithley 2400 Sourcemeter, Keithley 2000 Currentmeter), the electroluminescence spectrum was measured by the French JY company SPEX CCD3000 spectrometer, all measurements were done in the atmosphere at room temperature.

The performance data of the first electroluminescent device, the second electroluminescent device and the third electroluminescent device are shown in the following table (2):

Table 2)

The electroluminescent device manufactured by using the dark blue thermally activated delayed fluorescent material provided by the present invention has higher luminous brightness, high manufacturing efficiency and long service life.

In summary, although the present invention has been disclosed as above in preferred embodiments, the above-mentioned preferred embodiments are not intended to limit the present invention. Those of ordinary skill in the art can make various modifications without departing from the spirit and scope of the present invention. Such changes and modifications, therefore, the protection scope of the present invention is subject to the scope defined by the claims.

Claims

A dark blue thermally activated delayed fluorescent material, the material has a general structural formula as follows:

Wherein, in the general structural formula, D1 is a first electron-donating group, D2 is a second electron-donating group, and the first electron-donating group is different from the second electron-donating group.
The thermally activated delayed fluorescent material according to claim 1, wherein the first electron donating group is selected from one of the following materials:

Wherein, the second electron donating group is selected from one of the following materials:
A method for synthesizing dark blue thermally activated delayed fluorescent material, including the following steps:

In the first mixed solution preparation step, the raw materials of the first electron-donating group, the electron acceptor, and the catalyst are placed in a reaction vessel to fully react to obtain a first mixed solution, and the first mixed solution includes the first donor The raw material of the electron group and the intermediate produced by the electron acceptor reaction;

In the first extraction step, the first mixed solution is cooled to room temperature, the first mixed solution is extracted and the organic phases are combined to obtain the first compound, and the first compound is purified to obtain the intermediate;

In the second mixed solution preparation step, the raw materials of the second electron donating group, the intermediate and the catalyst are placed in a reaction vessel to obtain a second mixed solution, and the second mixed solution includes the intermediate and the The raw material of the second electron donating group;

In the second extraction step, the second mixed solution is cooled to room temperature, the second mixed solution is extracted and the organic phases are combined to obtain a second compound, and the second compound is purified to obtain a dark blue thermally activated delayed fluorescent material.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 3, wherein the raw material of the first electron donating group is selected from 4-carbazole phenylboronic acid, 4-(3,6-dimethylcarbazole) -One of phenylboronic acid and 4-(3,6-diphenylcarbazole)-phenylboronic acid.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 3, wherein the electron acceptor is 2,-6-dibromo-4-methylpyridine oxynitride.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 3, wherein the raw material of the second electron donating group is 4-(9,10-dihydro-9,9-diphenylacridine)- Phenylboronic acid.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 3, wherein the catalyst used in the first mixing configuration step includes K 2 CO 3 and Pd(PPh 3 ) 4 .
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 3, wherein the catalyst used in the second mixing configuration step includes K2CO3 and Pd(PPh3) 4 .
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 3, wherein the molar ratio of the raw material of the electron acceptor to the first electron donating group is 1:1 to 1:5.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 3, wherein the molar ratio of the intermediate to the raw material of the second electron-donating group is 1:1-1:5.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 3, wherein the reaction temperature of the first mixed solution preparation step is 80-90 degrees Celsius, and the reaction time is at least 12 hours.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 3, wherein the reaction temperature of the second mixed solution preparation step is 80-90 degrees Celsius, and the reaction time is at least 12 hours.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 4, wherein the step of preparing the first mixed solution comprises combining the raw material of the first electron donating group, 2,-6-dibromo-4- The picoline nitroxide, K 2 CO 3 and Pd(PPh 3 ) 4 are placed in the reaction vessel together, pumped three times, and then the reaction vessel is placed in an argon atmosphere and sent to the reaction vessel Add ethylene glycol dimethyl ether for deoxygenation, reflux reaction at 80-90 degrees Celsius for at least 12 hours, and then cool to room temperature to obtain a first mixed solution.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 6, wherein the step of preparing the second mixed solution comprises combining the raw material of the second electron donating group, the intermediate, K 2 CO 3 and Pd(PPh 3 ) 4 is placed in the reaction vessel together, and pumped three times, then the reaction vessel is placed in an argon atmosphere, and oxygen-depleted glycol dimethyl ether is added to the reaction vessel, The reflux reaction is performed at 80-90 degrees Celsius for at least 12 hours and then cooled to room temperature to obtain a second mixed solution.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 4, wherein the first extraction step includes pouring the first mixed solution into ice water, and using dichloromethane for multiple extractions to combine the organic Phase to obtain the first compound; using a developing solvent to perform primary purification of the first compound by silica gel column chromatography to obtain the intermediate.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 15, wherein the developing agent in the silica gel column chromatography method comprises dichloromethane and n-hexane, and the dichloromethane and the normal hexane The volume ratio of alkanes is 1:3.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 4, wherein the second extraction step includes pouring the second mixed solution into ice water, and using dichloromethane for multiple extractions to combine the organic Phase to obtain the second compound; using a developing solvent to purify the second compound for the first time by silica gel column chromatography to obtain the initial purified product, and use a sublimation apparatus to purify the initial purified product, and finally obtain the The dark blue thermally activated delayed fluorescent material.
The method for synthesizing a dark blue thermally activated delayed fluorescent material according to claim 17, wherein the developing agent in the silica gel column chromatography method comprises dichloromethane and n-hexane, and the dichloromethane and the normal hexane The volume ratio of alkanes is 1:1.
An electroluminescent device, including:

A substrate layer;

A hole transport and injection layer disposed on the substrate layer;

A light-emitting layer disposed on the hole transport and injection layer;

An electron transport layer disposed on the light-emitting layer; and

A cathode layer disposed on the electron transport layer;

Wherein, the light-emitting material of the light-emitting layer has a general structural formula as follows:

Wherein, in the general structural formula, D1 is a first electron-donating group, D2 is a second electron-donating group, and the first electron-donating group is different from the second electron-donating group.
The luminescent material according to claim 19, wherein the first electron donating group is selected from one of the following materials:

Wherein, the second electron donating group is selected from one of the following materials: