WO2020199325A1 - Thermally activated delayed fluorescent material and preparation method therefor, and electroluminescent device - Google Patents

Abstract

A thermally activated delayed fluorescent material, comprising a triazinyl nucleus, and an electron donor and an electron acceptor linked to the nucleus and capable of inhibiting a non-radiative transition rate. An electroluminescent device comprises the thermally activated delayed fluorescent material, and can effectively improve the light emitting efficiency.

Description

Thermally activated delayed fluorescent material, preparation method thereof, and electroluminescent device Technical field

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

Background technique

Organic light-emitting diodes (OLEDs), due to active light emission, large viewing angle, fast response speed, wide temperature adaptation range, low driving voltage, low power consumption, high brightness, simple production process, light and thin, and can The advantages of flexible display and other advantages have shown great application prospects in the field of OLED display and lighting, attracting the attention of scientific researchers and companies. At present, Samsung and LG have implemented OLEDs in mobile phones. In OLED, the pros and cons of light-emitting layer materials are decisive for the industrialization of OLED. The usual luminescent layer material consists of host and guest luminescent materials, and the luminous efficiency and lifetime of luminescent materials are two important indicators of the quality of luminescent materials. Early OLED light-emitting materials were traditional fluorescent materials. In OLED display devices, the ratio of singlet and triplet excitons is 1:3, while traditional fluorescent materials can only use singlet excitons to emit light. Therefore, traditional fluorescent The OLED theoretical internal quantum efficiency of the material is 25%. Due to the spin-orbit coupling effect of heavy atoms, metal complex phosphorescent materials can achieve 100% utilization of singlet excitons and triplet excitons; and are now also used in red and green OLED display devices . However, phosphorescent materials usually use heavy metals such as iridium, platinum, osmium and other precious metals, which are not only costly, but also highly toxic. In addition, efficient and long-life phosphorescent metal complex materials are still a great challenge.

technical problem

To solve the above technical problems: the present invention provides a thermally activated delayed fluorescent material and a preparation method thereof, and an electroluminescent device. The structure of the thermally activated delayed fluorescent material is DAA type, where D is an electron donor and A is an electron acceptor , Through the electron acceptor to increase the electron withdrawing ability and rigidity, can effectively inhibit the non-radiative transition rate, thereby increasing the molecular photoluminescence quantum yield; at the same time reduce the highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO) The electron clouds between the overlapped, so as to obtain a smaller triple energy level difference, in addition, you can also adjust the emission spectrum.

Technical solutions

The technical solution to solve the above problems is: the present invention provides a thermally activated delayed fluorescent material, which has the following general structural formula:

In the general structural formula, D is an electron donor, and A is an electron acceptor.

In an embodiment of the present invention, the electron donor includes one of the following structures:

In an embodiment of the present invention, the electron acceptor includes at least one of the following structures:

In an embodiment of the present invention, the method for preparing the thermally activated delayed fluorescent material includes the following steps: preparing a format reagent, and placing the format reagent in a first three-necked flask; placing the first reactant and tetrahydrofuran A first solution is obtained from the first reaction flask, wherein the first reactant has the structure of 4-bromophenyl and electron acceptor; the first solution is dropped into the first reaction flask to perform the Grignard reaction , Get the second solution, and stir at room temperature for 1-3 hours, then place the second solution in a dry ice/acetone bath; place trichlorotriazine and tetrahydrofuran in the second reaction flask to obtain the third solution; The second solution was added dropwise to the third solution, and reacted for 2 hours at a temperature of -78°C, then slowly raised to room temperature, and allowed to stand for 12 hours to 24 hours to obtain the fourth solution; the fourth solution was added to distilled water , And extract with dichloromethane several times, wash with distilled water after each extraction to obtain the first extract; dry the first extract with anhydrous sodium sulfate, filter, spin dry, and then use 200-300 mesh silica gel Perform column chromatography and rinse with eluent to obtain an intermediate; add the intermediate, pyridine-3-phenylboronic acid, toluene, and sodium carbonate aqueous solution into a second three-necked flask, and ventilate with argon. ; Add four (triphenylphosphorus) palladium to the second three-necked flask, reflux for 24h at a temperature of 75℃-85℃, and cool to room temperature to obtain the fifth solution; add the fifth solution to distilled water , And extract with dichloromethane for several times, wash with distilled water after each extraction to obtain the second extract; dry the second extract with anhydrous sodium sulfate, filter, spin dry, and then use 200-300 mesh silica gel Column chromatography is performed and eluted with eluent to obtain the thermally activated delayed fluorescent material.

In an embodiment of the present invention, the format reagent includes tetrahydrofuran, magnesium and iodine.

In an embodiment of the present invention, the step of performing the Grignard reaction includes heating the first three-necked flask to initiate the Grignard reaction at the beginning of the Grignard reaction. During the Grignard reaction, the first three The mouth flask was placed in an ice water bath to adjust the reaction temperature.

The present invention also provides an electroluminescent device, which includes the thermally activated delayed fluorescent material.

In an embodiment of the present invention, the electroluminescent device includes a first electrode; an electron injection layer provided on the first electrode; a hole transport layer provided on the electron injection layer; a light emitting layer, It is arranged on the hole transport layer, and the material used for the light emitting layer includes the thermally activated delayed fluorescent material; the electron transport layer is arranged on the light emitting layer; and the second electrode is arranged on the electron transport layer.

In an embodiment of the present invention, the first electrode is an anode, and the material used is indium tin oxide; the second electrode is a cathode, and the material used is one of lithium fluoride or aluminum.

In an embodiment of the present invention, the material used for the electron transport layer is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene The material used for the hole transport layer is 4,4'-cyclohexyl bis[N,N-bis(4-methylphenyl)aniline].

Beneficial effect

The thermally activated delayed fluorescent material of the present invention has an electron acceptor. The electron acceptor effectively increases the electron-withdrawing ability and rigidity of the thermally activated delayed fluorescent material, and can effectively inhibit the non-radiative transition rate, thereby improving the thermally activated delayed fluorescent material. Photoluminescence quantum yield (PLQY); at the same time, it can reduce the electron cloud overlap between the highest occupied molecular orbital (HOMO) and the lowest occupied molecular orbital (LUMO), so as to obtain a smaller minimum singlet and triplet energy level difference ( ΔEST), in addition, you can also adjust the emission spectrum of the molecule. The preparation method of the thermally activated delayed fluorescent material of the present invention can effectively improve the synthesis efficiency. The electroluminescent device of the present invention, which has the thermally activated delayed fluorescent material of the present invention, can effectively improve the luminous efficiency.

Description of the drawings

In order to more clearly describe the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

The present invention will be further explained below in conjunction with the drawings and embodiments.

Fig. 1 is a fluorescence spectrum diagram of a thermally activated delayed fluorescent material prepared by a preparation method in an embodiment of the present invention.

Fig. 2 is a structural diagram of an electroluminescent device in an embodiment of the present invention.

Reference signs:

10 Electroluminescent devices;

1 First electrode; 2 Electron injection layer;

3 Hole transport layer; 4 Light emitting layer;

5 Electronic transmission layer; 6 Second electrode.

Embodiments of the invention

The following describes the embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions. The following embodiments described with reference to the accompanying drawings are exemplary, and are only used to explain the present invention, and cannot be understood as a limitation to the present invention.

The description of the following embodiments refers to the attached drawings to illustrate specific embodiments in which the present invention can be implemented. The directional terms mentioned in the present invention, such as "up", "down", "front", "rear", "left", "right", "top", "bottom", etc., are only for reference to additional drawings direction. Therefore, the directional terms used are used to describe and understand the present invention, rather than to limit the present invention.

The thermally activated delayed fluorescent material of the present invention has the following general structural formula:

In the general structural formula, D is an electron donor, and A is an electron acceptor.

In this embodiment, the electron donor includes one of the following structures:

In this embodiment, the electron acceptor includes at least one of the following structures:

Through the arrangement and combination of electron donors and electron acceptors, there are always several (90 or more) thermally activated delayed fluorescent materials with different structures.

Taking the electron donor: 9,9-dimethylacridine as an example, the molecular structures of the thermally activated delayed fluorescent material in this embodiment are as follows:

In order to explain the present invention more clearly, the thermally activated delayed fluorescent material will be further explained below in conjunction with the preparation method of the thermally activated delayed fluorescent material of the present invention.

The preparation method of the thermally activated delayed fluorescent material includes the following steps:

Prepare the format reagent and place the format reagent in the first three-necked flask. The format reagent includes tetrahydrofuran, magnesium and iodine. In this step, the volume of tetrahydrofuran is 30 ml, and the amount of magnesium is 15 mmol.

The first reactant and tetrahydrofuran are placed in the first reaction flask to obtain the first solution, wherein the first reactant has the structure of 4-bromophenyl and electron acceptor. In this step, the volume of tetrahydrofuran is 30 ml, and the amount of the substance of the first reactant is 10 mmol; the structural formula of the first reactant is:

The first solution was added dropwise to the first reaction flask, and the Grignard reaction was performed to obtain the second solution, which was stirred at room temperature for 1-3 hours, and then the second solution was placed in a dry ice/acetone bath. During the Grignard reaction, if it is difficult to initiate the reaction at the beginning, the first three-necked flask can be heated at the beginning of the Grignard reaction to initiate the Grignard reaction. During the Grignard reaction, the first three-necked flask is placed Adjust the reaction temperature in an ice water bath.

Place trichlorotriazine and tetrahydrofuran in the second reaction flask to obtain a third solution. In this step, the amount of trichlorotriazine is 10 mmol, and the volume of tetrahydrofuran is 50 ml.

The second solution was added dropwise to the third solution and reacted for 2 hours at a temperature of -78°C, then slowly raised to room temperature, and allowed to stand for 12 hours to 24 hours to obtain a fourth solution.

The fourth solution was added to distilled water and extracted with dichloromethane several times. After each extraction, it was washed with distilled water to obtain the first extract; the first extract was dried with anhydrous sodium sulfate, filtered, and spin-dried. Then use 200-300 mesh silica gel for column chromatography, and rinse with eluent to obtain the intermediate. In this step, the volume of distilled water is 100ml. In this example, the yield of the intermediate is at least 78%.

The structural formula of the intermediate is as follows:

Add the intermediate, pyridine-3-phenylboronic acid, toluene, and sodium carbonate aqueous solution into the second three-necked flask, and ventilate with argon; add tetrakis(triphenylphosphorus) palladium to the second three-necked flask. In a mouth flask, the reaction was refluxed for 24 hours at a temperature of 75°C-85°C, and the fifth solution was obtained after cooling to room temperature. In this example, the amount of the intermediate substance is 5 mmol; the amount of pyridine-3-phenylboronic acid is 11 mmol; the volume of toluene is 8 ml; the amount of tetrakis(triphenylphosphorus) palladium is 0.2 mmol.

The fifth solution was added to distilled water, and extracted with dichloromethane several times, and washed with distilled water after each extraction to obtain a second extract.

The second extract was dried with anhydrous sodium sulfate, filtered, and spin-dried, and then column chromatography was performed with 200-300 mesh silica gel and eluted with eluent to obtain the thermally activated delayed fluorescent material. In this embodiment Among them, the production rate of the thermally activated delayed fluorescent material is at least 84%.

The structural formula of the thermally activated delayed fluorescent material is:

By preparing the thermally activated delayed fluorescent material by the preparation method of this embodiment, the thermally activated delayed fluorescent material can be effectively synthesized, and the synthesis efficiency can be improved.

In order to verify whether the characteristics of the thermally activated delayed fluorescent material of the present invention meet the requirements of electroluminescent devices, in this embodiment, the thermally activated delayed fluorescent material obtained by the preparation method of this embodiment is subjected to spectral experiments and photophysical data detection. Obtain the fluorescence spectrum shown in Figure 1 and the photophysical data shown in Table 1.

Table 1 shows the photophysical data of the thermally activated delayed fluorescent material of the present invention.

To	PL Peak(nm)	S 1 (eV)	T 1 (eV)	E ST (eV)	PLQY(%)
Thermally activated delayed fluorescent material	586	2.35	2.29	0.06	90

It can be seen from FIG. 1 that the effective wavelength range of the thermally activated delayed fluorescent material of the present invention is between 500-700, and therefore, the emission spectrum of the molecule can be adjusted within this range. It can be seen from Table 1 that the thermally activated delayed fluorescent material of the present invention has a smaller minimum singlet state and triplet energy difference (ΔE _ST ).

As shown in Figure 2, the present invention also provides an electroluminescent device, which includes the thermally activated delayed fluorescent material.

The electroluminescent device includes a first electrode 1, an electron injection layer 2, a hole transport layer 3, a light emitting layer 4, an electron transport layer 5, and a second electrode 6. Wherein, the electron injection layer 2 is provided on the first electrode 1; the hole transport layer 3 is provided on the electron injection layer 2; the light emitting layer 4 is provided on the hole transport layer 3 The material used for the light-emitting layer 4 includes the thermally activated delayed fluorescent material; the electron transport layer 5 is provided on the light-emitting layer 4; the second electrode 6 is provided on the electron transport layer 5.

In this embodiment, the first electrode 1 is an anode, and the material used is indium tin oxide; the second electrode 6 is a cathode, and the material used is one of lithium fluoride or aluminum. The material used for the electron transport layer 5 is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene; the hole transport layer 3 The material used is 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline].

The electroluminescent device 10 of the present invention adopts the thermally activated delayed fluorescent material in the luminescent layer 4, which effectively improves the luminous efficiency of the electroluminescent device 10.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. Inside.

Claims (10)

1. A thermally activated delayed fluorescent material, which has the following general structural formula:

   

   In the general structural formula, D is an electron donor, and A is an electron acceptor.
2. The thermally activated delayed fluorescent material according to claim 1, wherein the electron donor comprises one of the following structures:

   
3. The thermally activated delayed fluorescent material according to claim 1, wherein the electron acceptor comprises at least one of the following structures:

   
4. A preparation method for preparing the thermally activated delayed fluorescent material according to claim 1, wherein the preparation method comprises the following steps:

   Prepare the format reagent and place the format reagent in the first three-necked flask;

   Placing the first reactant and tetrahydrofuran in the first reaction flask to obtain a first solution, wherein the first reactant has a structure of 4-bromophenyl and an electron acceptor;

   Add the first solution dropwise to the first reaction flask, perform a Grignard reaction to obtain a second solution, and stir at room temperature for 1-3 hours, and then place the second solution in a dry ice/acetone bath;

   Place trichlorotriazine and tetrahydrofuran in the second reaction flask to obtain a third solution;

   Add the second solution dropwise to the third solution, and react at a temperature of -78°C for 2 hours, then slowly rise to room temperature, and let stand for 12 hours to 24 hours to obtain a fourth solution;

   Add the fourth solution to distilled water, and extract with dichloromethane several times, and wash with distilled water after each extraction to obtain the first extract;

   Drying the first extract with anhydrous sodium sulfate, filtering, spin-drying, and then performing column chromatography with 200-300 mesh silica gel and eluting with eluent to obtain an intermediate;

   Add the intermediate, pyridine-3-phenylboronic acid, toluene, and sodium carbonate aqueous solution into a second three-necked flask, and ventilate with argon;

   Add tetrakis(triphenylphosphonium) palladium to the second three-necked flask, reflux for 24 hours at a temperature of 75°C-85°C, and then cool to room temperature to obtain a fifth solution;

   Add the fifth solution to distilled water, and extract with dichloromethane several times, and wash with distilled water after each extraction to obtain a second extract;

   The second extract is dried with anhydrous sodium sulfate, filtered, and spin-dried, and then column chromatography is performed with 200-300 mesh silica gel and rinsed with an eluent to obtain the thermally activated delayed fluorescent material.
5. The preparation method according to claim 4, wherein the Grignard reagent includes tetrahydrofuran, magnesium and iodine.
6. The preparation method according to claim 4, wherein the step of performing the Grignard reaction includes heating the first three-necked flask to initiate the Grignard reaction at the beginning of the Grignard reaction, and in the Grignard reaction process, the The first three-necked flask was placed in an ice water bath to adjust the reaction temperature.
7. An electroluminescent device comprising the thermally activated delayed fluorescent material as claimed in claim 1.
8. The electroluminescent device according to claim 7, which comprises

   First electrode

   The electron injection layer is provided on the first electrode;

   The hole transport layer is provided on the electron injection layer;

   A light-emitting layer arranged on the hole transport layer, and the material used for the light-emitting layer includes the thermally activated delayed fluorescent material;

   The electron transport layer is located on the light-emitting layer;

   The second electrode is arranged on the electron transport layer.
9. The electroluminescent device according to claim 8, wherein the first electrode is an anode, and the material used is indium tin oxide; the second electrode is a cathode, and the material used is one of lithium fluoride or aluminum. Kind.
10. The electroluminescent device according to claim 8, wherein the material used for the electron transport layer is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12- Hexaazatriphenylene; the material used for the hole transport layer is 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline].

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