WO2020215439A1 - Red thermally activated delayed fluorescent material and preparation method therefor, and electroluminescent device - Google Patents

Abstract

A red thermally activated delayed fluorescent material and a preparation method therefor, and an electroluminescent device. The red thermally activated delayed fluorescent material comprises an electron donor and an electron acceptor, and the electron acceptor comprises an anthrylimide structure. The anthrylimide structure in the electron acceptor enables red thermally activated delayed fluorescent molecules to have rigid and large planar characteristics, and can effectively inhibit the reduction of radiation transition rate caused by the energy gap law; moreover, the carbonyl in the anthrylimide structure can increase the radiation transition rate of the molecules; thus, high photoluminescence quantum yield (PLQY) can be obtained.

Description

Red 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 red 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.

For red thermally activated delayed fluorescent materials (TADF), a small minimum singlet and triplet energy difference (ΔEST) and high photoluminescence quantum yield (PLQY) are necessary conditions for preparing high-efficiency OLEDs. At present, green and sky blue red thermally activated delayed fluorescent materials have achieved an external quantum efficiency (EQE) of more than 30%; however, red and deep red thermally activated delayed fluorescent materials cannot achieve excellent results due to the energy gap law. Device performance.

technical problem

In order to solve the above technical problem: the present invention provides a red thermally activated delayed fluorescent material, a preparation method thereof, and an electroluminescent device. The red thermally activated delayed fluorescent molecules have rigid and large planar properties, which can effectively inhibit the reduction of the radiation transition rate due to the energy gap regulation. At the same time, the carbonyl group in the anthrylimide structure can increase the radiation transition rate of the molecule to obtain high Photoluminescence quantum yield (PLQY).

Technical solutions

The technical solution for solving the above-mentioned problems is: the present invention provides a red thermally activated delayed fluorescent material, including an electron donor and an electron acceptor, wherein the electron acceptor contains an anthrylimide structure.

In an embodiment of the present invention, the structure of the red thermally activated delayed fluorescent material is as follows:

In the general structural formula, the group R includes one of an alkyl group, an alkoxy group, and an aromatic group; and the group D is an electron donor.

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

The present invention also provides a preparation method for preparing the red thermally activated delayed fluorescent material. The preparation method includes the following steps: preparing an intermediate including an electron acceptor and an electron acceptor connected to the intermediate. The bromo group on the; the electron acceptor has an anthrylimide structure; the intermediate and the organic acid with the electron donor, the sodium tetrahydrofuran carbon solution are added to the three-necked flask, and carried out with argon Ventilate; add tetrakis(triphenylphosphorus) palladium to the three-necked flask, reflux for 24h at a temperature of 75°C-85°C, and cool to room temperature to obtain a mixed solution; use the mixed solution Dichloromethane was extracted several times, and washed with distilled water after each extraction to obtain an extract; the extract was dried with anhydrous sodium sulfate, filtered, spin-dried, and then column chromatography was performed with 200-300 mesh silica gel and used The eluent is rinsed to obtain the red thermally activated delayed fluorescent material.

In an embodiment of the present invention, the step of preparing the intermediate includes adding 7-bromophenylisobenzopyran-1,3-dione, an organic amine with an R group, and ethanol to the application. In the Ranke flask, the group R includes one of an alkyl group, an alkoxy group, and an aromatic group; argon is passed into the Schranke flask, and the Schranke flask is heated under the protection of argon. The reflux reaction is carried out, and the reaction time is 12-24 hours to obtain the first mixed solution; the first mixed solution is extracted with dichloromethane several times, and each extraction is washed with distilled water to obtain the first extract; The first extract is dried with anhydrous sodium sulfate, filtered, and spin-dried, and then column chromatography is performed with 200-300 mesh silica gel and eluted with eluent to obtain the intermediate.

The present invention also provides an electroluminescent device, which includes the red 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 , Arranged on the hole transport layer, the material used for the light emitting layer includes the red thermally activated delayed fluorescent material; an electron transport layer, arranged on the light emitting layer; a second electrode, arranged on the electron transport layer.

In an embodiment of the present invention, the light-emitting layer further includes 4,4'-N,N'-dicarbazole biphenyl.

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 injection layer is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene The material used for the electron transport layer is 1,3,5-tris (3-(3-pyridyl) phenyl) benzene; the material used for the hole transport layer is 4,4'-cyclohexyl two [N, N-bis(4-methylphenyl)aniline].

Beneficial effect

In the red thermally activated delayed fluorescent material of the present invention, the electron acceptor is an anthracene nucleus acceptor, that is, the electron acceptor contains an anthrylimide structure, so that the red thermally activated delayed fluorescent molecule has rigid and large plane characteristics, and can effectively inhibit the The energy gap rule reduces the radiation transition rate, and the carbonyl group in the anthrylimide structure can increase the radiation transition rate of the molecule to obtain high photoluminescence quantum yield (PLQY). The preparation method of the red thermally activated delayed fluorescent material of the present invention can effectively improve the synthesis efficiency. The electroluminescent device of the present invention has the red thermally activated delayed fluorescent material of the present invention. Since the anthracene itself has a P-type delayed fluorescence characteristic in the anthrylimide structure, it can effectively suppress the efficiency roll-off of the device, thereby improving the electrical The efficiency of the electroluminescent device 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 red 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, wherein 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 red thermally activated delayed fluorescent material of the present invention includes an electron donor and an electron acceptor, wherein the electron acceptor contains an anthrylimide structure. The red thermally activated delayed fluorescent material has the following general structural formula:

In the general structural formula, the group R includes one of an alkyl group, an alkoxy group, and an aromatic group; and the group D is an electron donor.

The structure of the electron donor includes one of the following structures;

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

In an embodiment of the present invention, the preparation of the target compound 1 (a red thermally activated delayed fluorescent material of the present invention) is taken as an example to illustrate the preparation method of the red thermally activated delayed fluorescent material of the present invention in detail. The general structure of the target compound is as follows:

The synthetic route of target compound one is as follows:

Referring to the synthetic route of the target compound 1, the preparation method of the red thermally activated delayed fluorescent material of the present invention includes the following steps:

An intermediate is prepared, the intermediate includes an electron acceptor and a bromo group connected to the electron acceptor; the electron acceptor has an anthrylimide structure; and the step of preparing the intermediate includes 7 -Bromophenylisobenzopyran-1,3-dione, organic amine with R group and ethanol are added to Schlenk bottle, said group R includes alkyl group, alkoxy group and aromatic group In one of them, in the preparation of target compound one, the organic amine of the R group is tert-butylamine. Pour argon gas into the Schlenk flask, and heat the Schrank flask under the protection of argon to perform reflux reaction. The reaction time is 12-24 hours to obtain a first mixed solution; 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 Column chromatography and elution with eluent to obtain the intermediate: 7-bromo-2-tert-butyl-diphenylisoquinoline-1,3-dione.

The general structural formula of the intermediate is as follows:

The intermediate, the organic acid with the electron donor, and the sodium tetrahydrofuran carbon solution were added to a three-necked flask, and argon was used for pumping. In the preparation of target compound 1, the organic acid with electron donor is 4-(9,9-dimethylacridine)-phenylboronic acid.

Tetrakis(triphenylphosphorus) palladium was added to the three-necked flask, and the reaction was refluxed at a temperature of 75° C.-85° C. for 24 hours, and a mixed solution was obtained after cooling to room temperature.

The mixed solution is extracted with dichloromethane several times, and washed with distilled water after each extraction to obtain an extract.

The extract is dried with anhydrous sodium sulfate, filtered, and spin-dried, and then column chromatography is performed with 200-300 mesh silica gel and eluted with eluent to obtain the target compound one, which is a red color of the present invention. The thermally activated delayed fluorescent material has a yield of 85%.

In another embodiment of the present invention, taking the preparation of target compound two (a red thermally activated delayed fluorescent material of the present invention) as an example, the preparation method of the red thermally activated delayed fluorescent material of the present invention is described in detail. The general structure of the target compound is as follows:

The synthetic route of target compound one is as follows:

Referring to the synthetic route of the target compound 1, the preparation method of the red thermally activated delayed fluorescent material of the present invention includes the following steps:

An intermediate is prepared, the intermediate includes an electron acceptor and a bromo group connected to the electron acceptor; the electron acceptor has an anthrylimide structure; and the step of preparing the intermediate includes 7 -Bromophenylisobenzopyran-1,3-dione, organic amine with R group and ethanol are added to Schlenk bottle, said group R includes alkyl group, alkoxy group and aromatic group In one of them, in the preparation of the second target compound, the organic amine of the R group is p-tert-butylaniline. Pour argon gas into the Schlenk flask, and heat the Schrank flask under the protection of argon to perform reflux reaction. The reaction time is 12-24 hours to obtain a first mixed solution; 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 Column chromatography and elution with eluent to obtain the intermediate: 7-bromo-2-tert-butyl-diphenylisoquinoline-1,3-dione.

The general structural formula of the intermediate is as follows:

The intermediate, the organic acid with the electron donor, and the sodium tetrahydrofuran carbon solution were added to a three-necked flask, and argon was used for pumping. In the preparation of target compound 1, the organic acid with electron donor is 4-(9,9-dimethylacridine)-phenylboronic acid.

Tetrakis(triphenylphosphorus) palladium was added to the three-necked flask, and the reaction was refluxed at a temperature of 75° C.-85° C. for 24 hours, and a mixed solution was obtained after cooling to room temperature.

The mixed solution is extracted with dichloromethane several times, and washed with distilled water after each extraction to obtain an extract.

The extract is dried with anhydrous sodium sulfate, filtered, and spin-dried, and then column chromatography is performed with 200-300 mesh silica gel and eluted with eluent to obtain the target compound one, which is a red color of the present invention. Thermally activated delayed fluorescent material with a yield of 88%

By preparing the red thermally activated delayed fluorescent material by the preparation method of this embodiment, the red 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 red thermally activated delayed fluorescent material of the present invention meet the requirements of electroluminescent devices, in this embodiment, the red 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 red thermally activated delayed fluorescent material of the present invention.

	PL Peak(nm)	S 1 (eV)	T 1 (eV)	E ST (eV)	PLQY(%)
Target compound one	721	2.35	2.16	0.19	75
Target compound two	763	2.11	1.96	0.15	68

It can be seen from FIG. 1 that the effective wavelength range of the target compound 1 of the present invention is between 680-800 nm, and the effective wavelength range of the target compound 2 is between 700-850 nm. Therefore, the emission spectrum of the molecule can be adjusted within this range. It can be seen from Table 1 that the red 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 red thermally activated delayed fluorescent material.

Specifically, 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 red thermally activated delayed fluorescent material and 4,4'-N,N'-dicarbazole biphenyl, 4,4'-N,N'-dicarbazole biphenyl is The host molecule is doped with the red 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 1,3,5-tris(3-(3-pyridyl)phenyl)benzene; the material used for the hole transport layer 3 is 4,4'-cyclohexylbis[N ,N-bis(4-methylphenyl)aniline], the material used for the electron injection layer 2 is 2,3,6,7,10,11-hexacyano-1,4,5,8,9, 12-hexaazatriphenylene.

Table 2 is a performance data table of the electroluminescent device 10 using target compound one or using target compound two.

In the electroluminescent device 10 of the present invention, the red thermally activated delayed fluorescent material is used in the light-emitting layer 4 to effectively manufacture a red electroluminescent device and improve the luminous efficiency of the red electroluminescent device.

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 red thermally activated delayed fluorescent material includes an electron donor and an electron acceptor, wherein the electron acceptor contains an anthrylimide structure.
2. The red thermally activated delayed fluorescent material according to claim 1, wherein the general structural formula is as follows:

   

   In the general structural formula, the group R includes one of an alkyl group, an alkoxy group, and an aromatic group; and the group D is an electron donor.
3. The red thermally activated delayed fluorescent material according to claim 1, wherein the structure of the electron donor includes one of the following structures;

   

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

   Preparing an intermediate, the intermediate including an electron acceptor and a bromo group connected to the electron acceptor; the electron acceptor has an anthrylimide structure;

   Add the intermediate, the organic acid with the electron donor, and the sodium tetrahydrofuran carbon solution into a three-necked flask, and ventilate with argon;

   Adding tetrakis(triphenylphosphorus) palladium to the three-necked flask, refluxing reaction at a temperature of 75°C-85°C for 24 hours, and cooling to room temperature to obtain a mixed solution;

   Extract the mixed solution with dichloromethane several times, and wash with distilled water after each extraction to obtain an extract;

   The extract is dried with anhydrous sodium sulfate, filtered, and spin-dried, and then column chromatography is performed with 200-300 mesh silica gel and eluted with an eluent to obtain the red thermally activated delayed fluorescent material.
5. The preparation method according to claim 4, wherein:

   In the step of preparing the intermediate, it includes

   Add 7-bromophenylisobenzopyran-1,3-dione, an organic amine with R group and ethanol into the Schlenk bottle. The group R includes alkyl, alkoxy, One of the aromatic groups; argon is passed into the Schrank flask, and the Schrank flask is heated under the protection of argon to perform reflux reaction. The reaction time is 12-24 hours to obtain the first mixed solution;

   Extracting the first mixed solution with dichloromethane several times, washing with distilled water after each extraction, to obtain a first extract;

   The first extract is dried with anhydrous sodium sulfate, filtered, and spin-dried, and then column chromatography is performed with 200-300 mesh silica gel and eluted with an eluent to obtain the intermediate.
6. An electroluminescent device comprising the red thermally activated delayed fluorescent material according to claim 1.
7. The electroluminescent device according to claim 6, 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 red 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.
8. The electroluminescent device according to claim 7, wherein the light-emitting layer further comprises 4,4'-N,N'-dicarbazole biphenyl.
9. The electroluminescent device according to claim 7, 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 injection layer is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene;

    The material used for the electron transport layer is 1,3,5-tris(3-(3-pyridyl)phenyl)benzene;

    The material used for the hole transport layer is 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline].

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