Axial chirality luminescent material with double luminescent center and preparation method and application thereof

Abstract

The application belongs to the field of organic light-emitting materials, and relates to a new type of chiral light-emitting material containing double light-emitting centers as well as a synthesis method and application thereof. Compared with existing fluorescent materials, the double light-emitting center material has the advantages of high light-emitting efficiency, stable chemical properties, easy sublimation purification and the like. In addition, due to the introduction of octahydrobinaphthyl structure, on the one hand, the material has large steric hindrance on the periphery, effectively inhibits molecular accumulation and improves light-emitting efficiency; on the other hand, due to the chiral characteristics brought by the octahydrobinaphthyl skeleton, the material has circularly polarized light-emitting performance. In addition, through modification of the conjugated nitrogen heterocyclic structure, the light-emitting position and light-emitting efficiency of the material can be adjusted in the visible light wavelength range, which provides convenience for the design and production of organic electroluminescent displays and lighting sources. Meanwhile, the synthesis method of the series of double light-emitting center chiral materials introduced in the application is simple, the yield is high, and the structural chemical modification is flexible.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic light-emitting materials and organic electroluminescent devices, and particularly relates to an axially chiral light-emitting material with double light-emitting centers, which has the characteristics of axial chirality, high light-emitting efficiency and circularly polarized emission; when applied to an organic electroluminescent device, a high-efficiency circularly polarized electroluminescent device can be obtained. BACKGROUND

[0002] As a research hotspot in the field of organic electronics, the development of new OLED materials is still in full swing, especially the urgent development of next-generation new light-emitting materials and special-purpose OLED devices. Among them, OLED devices prepared by taking chiral light-emitting materials as light-emitting centers can directly emit circularly polarized electroluminescence (Circularly Polarized Electroluminescence, CPEL), namely circularly polarized organic light-emitting diode (CP-OLED), which avoids complex filtering structure and loss of brightness efficiency, and has great application prospects in the fields of 3D display and optoelectronic communication, and also provides a new research direction for the development of next-generation OLED materials and devices.

[0003] Chiral light-emitting materials can generally be divided into conjugated high molecular polymers, phosphorescent metal complexes and organic small molecules. Among them, circularly polarized-thermally activated delayed fluorescence (CP-TADF) materials are considered to be new light-emitting materials with great development potential due to their circularly polarized emission and 100% light utilization characteristics, and have important applications in optical storage, optical anti-counterfeiting, 3D display and other aspects. At present, most CP-TADF molecules adopt the "chiral perturbation" strategy, that is, through chiral sources such as covalent linkage carbon chirality, axial chirality or face chirality, circularly polarized emission is realized. However, these "chiral perturbation" CP-TADF molecules have their shortcomings: the chiral source does not participate in the electronic arrangement of the molecular frontier orbital, resulting in that the material asymmetry factor (g) is generally very small. Therefore, it is crucial to develop high-efficiency light-emitting materials with excellent circularly polarized emission properties and their devices. SUMMARY

[0004] The purpose of the present application is to provide a kind of axially chiral light-emitting material with double light-emitting centers and a preparation method thereof, which can be used as a light-emitting center in organic electroluminescent devices.

[0005] 1. An axially chiral light-emitting material with double light-emitting centers, characterized in that the chemical structure of the light-emitting material is as follows,

[0006] wherein the red part is an axially chiral octahydrobinaphthyl anthrone structure, and X is O or S; the yellow part is a conjugated nitrogen heterocyclic structure, which can be a nitrogen heterocyclic ring, a fused aromatic ring and a fused aromatic heterocyclic ring, etc.

[0007] 2. The luminescent material according to claim 1, characterized in that the axially chiral octahydrobinaphthylanthracene structure is selected from any one of the following:

[0008]

[0009] the conjugated nitrogen heterocyclic structure is selected from any one of the following:

[0010]

[0011] 3. The double-luminescent-center axially chiral luminescent material according to claim 2, characterized in that the material has one of the following structures:

[0012]

[0013]

[0014]

[0015]

[0016] The application also provides a preparation method of the double-luminescent-center axially chiral luminescent material, characterized in that octahydrobinaphthylphenol (thiophenol) and methyl 2-fluoro-4-bromobenzoate are used as starting materials, an octahydrobinaphthylanthracene intermediate is obtained through continuous substitution, alkaline hydrolysis and cyclization reaction, and then the octahydrobinaphthylanthracene intermediate is coupled with a conjugated nitrogen heterocyclic ring to obtain the target compound. The molar ratio of the octahydrobinaphthylanthracene intermediate to the conjugated nitrogen heterocyclic ring is 1:2-1:8.

[0017] The application also provides application of the double-luminescent-center axially chiral luminescent material in preparation of an organic electroluminescent device.

[0018] The double-luminescent-center axially chiral luminescent material provided by the application not only has the advantages of high luminescent efficiency, stable chemical properties and easy sublimation purification, but also has the following advantages due to the introduction of the octahydrobinaphthyl structure: on the one hand, the material has large steric hindrance at the periphery, effectively inhibits molecular stacking and improves luminescent efficiency; on the other hand, the axially chiral feature brought by the octahydrobinaphthyl skeleton enables the material to have circularly polarized luminescence performance. In addition, through modification of the conjugated nitrogen heterocyclic structure, the luminescent position and luminescent efficiency of the material can be adjusted in the visible light wavelength range, which provides convenience for design and production of organic electroluminescent display devices and lighting sources. Meanwhile, the synthesis method of the series of novel double-luminescent-center axially chiral materials introduced by the application is simple, has high yield and is flexible in terms of structural chemical modification. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The electroluminescent spectrum of the double-luminescent-center axially chiral luminescent material OBN-2 provided by the application for an organic electroluminescent device is shown in the following figure:

[0020] Figure 2 The double luminescent center axis chiral luminescent material OBN-2 provided by the present application is used for the photoelectric performance of an organic electroluminescent device.

[0021] Figure 3 The double luminescent center axis chiral luminescent material OBN-2 provided by the present application is used for the photoelectric performance of an organic electroluminescent device.

[0022] Figure 4 The double luminescent center axis chiral luminescent material OBN-2 provided by the present application is used for the photoelectric performance of an organic electroluminescent device.

[0023] Figure 5 An isomer (S)-OBN-2 of the double luminescent center axis chiral luminescent material OBN-2 provided by the present application is used for circularly polarized electroluminescent spectrum of an organic electroluminescent device.

DETAILED DESCRIPTION

[0024] The present application will be further described in detail below in conjunction with the accompanying drawings and examples. The terms used in the present application have the meanings generally understood by those of ordinary skill in the art, unless otherwise specified.

[0025] The double luminescent center axis chiral luminescent material of the present application uses octahydrobinaphthol (thiophenol), carbazole, t-butyl carbazole, diphenylamine, indole carbazole derivatives, bis (dibenzalacetone) palladium, etc. in the synthesis process. The following examples will help further understand the present application, but do not limit the content of the present application.

[0026] Synthesis method of OBN-2

[0027]

[0028] A (400 mg, 0.62 mmol), 4,4'-di-t-butylcarbazole (452 mg, 2.47 mmol), sodium t-butoxide (712 mg, 7.40 mmol), bis (dibenzalacetone) palladium (105 mg, 0.18 mmol) and tri-t-butyl phosphine (0.87 mL, 0.36 mmol) were dissolved in 20 mL of toluene and stirred at 110°C for 36 hours. The solvent was removed by rotary evaporation, further purified by column chromatography (petroleum ether / dichloromethane / ethyl acetate = 40:10:1), and yellowish OBN-2 solid (426 mg, 81%) was collected.

[0029] OBN-2: 1 H NMR (400 MHz, CDCl3) δ 8.55 (d, J = 8.5 Hz, 1H), 8.22 (s,

[0030] 1H), 8.10 (s, 2H), 7.61 (dd, J = 8.5, 1.7 Hz, 1H), 7.49 - 7.35 (m, 5H), 3.14 - 2.91 (m, 2H), 2.50 (dt, J = 13.3, 6.4 Hz, 1H), 2.35 (dt, J = 17.5, 5.7 Hz, 1H), 1.80 (ddt, J = 24.9, 20.8, 7.3 Hz, 4H), 1.44 (s, 18H).

[0031] 13 C NMR (101 MHz, CDC13) δ 176.63 (s), 157.20 (s), 151.66 (s), 144.94 (s), 144.00 (d, J = 2.7 Hz), 138.22 (s), 134.46 (s), 128.41 (s), 126.51 (s), 124.00 (d, J = 11.6 Hz), 123.48 (s), 121.64 (s), 120.05 (s), 119.83 (s), 116.51 (s), 114.44 (s), 109.27 (s), 34.80 (s), 31.95 (s), 29.54 (s), 28.21 (s), 22.61 (d, J = 2.5 Hz).

[0032] EI [M] calcd for C 75 H 76 N2O4, 1068.58; found 1068.80.

[0033] The synthesis method of the series of double light-emitting center axial chiral light-emitting materials introduced in the application is simple, the yield is high, and the structural chemical modification is flexible. In addition to the advantages of high light-emitting efficiency, stable chemical properties, and easy sublimation purification, due to the introduction of the binaphthyl structure, on the one hand, the material periphery has large steric hindrance, effectively inhibits molecular accumulation, and improves the light-emitting efficiency; on the other hand, due to the axial chirality characteristics brought by the octahydrobinaphthyl skeleton, the material has circularly polarized light emission performance. In addition, by modifying the conjugated nitrogen heterocyclic structure, the light-emitting position and light-emitting efficiency of the material can be adjusted in the visible light wavelength range, which provides convenience for the design and production of organic electroluminescent display and lighting sources.

[0034] Preparation of an organic electroluminescent device

[0035] An organic electroluminescent device is prepared by using OBN-2 as a light-emitting material.

[0036] The classic structure of an OLED device is: substrate / anode / hole transport layer / organic light-emitting layer / electron transport layer / cathode.

[0037] In the device manufacturing of the present application, the substrate is glass, the anode material is indium tin oxide (ITO); the hole transport layer uses 4,4'-cyclohexyl di[N,N-di(4-methylphenyl) aniline (TAPC), the electron transport layer material uses 3,3'-(5'-(3-(pyridine-3-yl) phenyl)-[1,1':3',1"-triphenyl]-3,3"-diyl) dipyrrole (TmPyPB), the thickness is 60 nm, and the evaporation rate is 0.05 nm / s; the cathode uses LiF / Al, the thickness of LiF is 1 nm, the evaporation rate is 0.01 nm / s, the thickness of Al is 100 nm, and the evaporation rate is 0.2 nm / s. The organic light-emitting layer uses a doping structure, the host material is 26DCzPPy, the selected light-emitting material is OBN-2, the thickness is 25 nm, the evaporation rate is 0.05 nm / s, and the mass fraction of OBN-2 is 10%.

[0038] The structures of several materials used in the present application are as follows:

[0039]

[0040] The present application selects a double-emitting center axis chiral light-emitting material OBN-2 to prepare an organic electroluminescent device. Please refer to Figure 1 、 Figure 2 、 Figure 3 and Figure 4 , Figure 1 The electroluminescent spectrum of the double-emitting center axis chiral material OBN-2 provided by the present application for the organic electroluminescent device, Figure 2 The optoelectronic performance of the double-emitting center axis chiral material OBN-2 provided by the present application for the organic electroluminescent device, Figure 3 The optoelectronic performance of the double-emitting center axis chiral material OBN-2 provided by the present application for the organic electroluminescent device, Figure 4 The optoelectronic performance of the double-emitting center axis chiral material OBN-2 provided by the present application for the organic electroluminescent device. As Figures 1-4 shown, the maximum emission wavelength of the organic electroluminescent device is 450 nm, the starting voltage is 3.8 V, the maximum current efficiency and power efficiency are 6.0 cd A -1 and 3.8 lm W -1 , respectively. When the applied voltage of the organic electroluminescent device is 11.0 V, the maximum brightness reaches 10000 cd m -2 . The device prepared by using one isomer (S)-OBN-2 of OBN-2 split as a light-emitting center shows a circularly polarized electroluminescent signal Figure 5 , and the asymmetry factor is +0.0018.

[0041] By studying photoelectric properties, it is shown that the chiral luminescent material with double luminescent centers has good electroluminescent device performance.

[0042] Therefore, development of new double luminescent center chiral molecules based on binaphthyl structure can effectively synthesize chiral luminescent materials with high luminescent performance and different colors, and show good device performance, and the device shows good circularly polarized electroluminescent signal, which shows that the material has practical application value in the fields of display and lighting.

[0043] The double luminescent center chiral luminescent material provided by the application can be applied to the emission layer of circularly polarized organic light-emitting diodes CP-OLEDs as a luminescent center, by designing binaphthyl or conjugated nitrogen heterocyclic structure, and by modifying the chemical substituent group of the skeleton, the purpose of regulating the luminescent color and efficiency of the chiral luminescent material is achieved.

[0044] The above only describes the embodiments of the application, and it should be pointed out that, for those skilled in the art, improvements can be made without departing from the inventive concept, and these all belong to the protection scope of the application.

Claims

1. A bis-luminescent center chiral luminescent material, characterized in that, The chemical structure of the luminescent material is shown below, wherein the red part is an axially chiral octahydrodipyrenylanthracene structure and the yellow part is a conjugated heterocyclic structure, characterized in that the axially chiral octahydrodipyrenylanthracene structure is selected from any one of the following: The conjugated heterocyclic structure is selected from any one of the following:

2. The bis-lumicenter chiral luminescent material according to claim 1, characterized in that The material has one of the following structures:

3. An electroluminescent device using the double-luminescent-center axially chiral luminescent material according to any one of claims 1-2, comprising a glass substrate, indium tin oxide, a hole injection layer, a hole transport layer, a luminescent layer, an electron transport layer, an electron injection layer and LiF / Al.

Images