Red and near-infrared luminescent materials with thermally activated delayed fluorescence and applications thereof

Abstract

The application belongs to the technical field of organic electroluminescent materials, and specifically discloses a kind of red and near-infrared luminescent material with thermal activated delayed fluorescence characteristics and application thereof.Taking pyrene as a conjugated skeleton center, an unsymmetrical acceptor of pyrazine is constructed, and t-butyl triphenylamine or dendritic t-butyl triphenylamine is used as an electron donor.A kind of red and near-infrared luminescent material with thermal activated delayed fluorescence characteristics is synthesized through oxidation, NBS bromination, Suzuki-Miyaura and Schiff base condensation reaction.The material has obvious thermal activated delayed fluorescence characteristics, which is beneficial to reducing the energy gap difference of singlet and triplet states, and improving the luminescent efficiency of the material.The application explores the relationship between molecular structure and performance, and has important significance for constructing new red and near-infrared luminescent materials.

Description

Technical Field

[0001] The invention belongs to the technical field of organic electroluminescent materials, and specifically discloses a class of red and near-infrared luminescent materials with thermally activated delayed fluorescence characteristics and applications thereof. Background Art

[0002] In recent years, red and near-infrared luminescent materials have made significant progress in various fields, including bioimaging, night vision devices, telecommunications, and catalytic organic reactions. For example, near-infrared (NIR) is beneficial for biomedicine and biosensing because biological tissue has weak absorption and autofluorescence in the NIR region. In addition, the 700-1000nm wavelength is contained in the "semi-transparent window" of biological tissue. Therefore, based on blood circulation enhancement or photoactivation of certain substances, near-infrared light-emitting diodes (LEDs) have the potential to be integrated into photodynamic therapy, near-infrared photomedicine, and bioimaging applications. Due to the penetration and independent transmission of infrared light, it exhibits anti-interference, security, high speed, and invisible characteristics, which make near-infrared devices suitable for integration into space optical communication applications. In addition, NIR LEDs are also used in biometrics, such as finger vein and iris recognition, as well as night-vision readable displays, chiral sensing, bioresponsive imaging, asymmetric synthesis, and chiral materials, and have broad application prospects.

[0003] In addition to the red applications mentioned above, CP-PLEDs (CPELs) have seen rapid development. However, due to a theoretical internal quantum efficiency (IQE) of 25%, conventional fluorescent materials cannot achieve satisfactory performance in OLED devices. To achieve more efficient EL, phosphorescent complexes with a theoretical IQE of 100% are used as the luminescent materials of the corresponding devices. However, phosphorescent materials still face problems such as high cost, environmental issues, and unstable coordination bonds.

[0004] As the third generation of light-emitting materials, thermally activated delayed fluorescence (TADF) emission materials with pure organic molecular structures can achieve the same 100% theoretical IQE as phosphorescent emission materials and are considered to be promising pure organic materials for the manufacture of organic light-emitting diodes (OLEDs). Unlike traditional fluorescent emission materials, TADF emission materials always have a sufficiently small singlet-triplet energy gap (ΔE) due to the sufficient separation of the distribution of the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs). ST ), which is less than 0.3 eV. Therefore, triplet excitons can be fully utilized through upconversion via the reverse intersystem crossing (RISC) process without the need for additional energy supply, thus improving the exciton utilization rate.

[0005] TADF luminescent materials can achieve 100% internal quantum efficiency like phosphorescent materials and can easily overcome the disadvantages of phosphorescent materials such as high cost, need for rare materials and environmental sustainability. The luminescent materials used in TADF OLEDs play a key role in controlling important device parameters such as efficiency, lifetime and color purity of the device. In the design of efficient TADF luminescent materials, it is necessary to balance two conflicting requirements, namely high photoluminescence quantum yield (PLQY) and a small energy gap (ΔE) between the lowest singlet (S1) and triplet (T1) excited states. ST ). Although highly efficient blue and green TADF OLEDs with external quantum efficiencies (EQEs) exceeding 30% have been recently reported, the design of efficient pure red emitters is challenging due to the limitations of the energy gap law. In particular, when designing pure red TADF molecules with emission wavelengths above 600nm, according to the energy gap law, the internal conversion (IC) (non-radiative decay) of singlet excitons competes with radiative decay. An effective design strategy to reduce the impact of the IC process is to introduce a more rigid molecular structure. Rigid donor-acceptor molecular design can be used to minimize non-radiative loss processes caused by the vibration and rotational motion of flexible structures, thereby realizing efficient long-wavelength TADF emitters. Several high-EQE orange and red TADF OLEDs have been reported to be fabricated using TADF emitters with such highly planar and rigid acceptors. However, due to the large dihedral angle between the donor and acceptor units in the red TADF emission (600–650nm), its oscillator strength (f) value is reduced, resulting in a lower PLQY and therefore a lower EQE value. In addition, the more rigid and planar aromatic backbones of red TADF emitters favor the formation of π-π stacking, but they induce severe exciton quenching and thus the efficiency drops drastically. Summary of the Invention

[0006] In order to further reduce ΔE ST , in order to obtain more efficient TADF materials. The present invention uses pyrene as the conjugated skeleton center, constructs a type of red and near-infrared materials with thermally activated delayed fluorescence properties, using pyrazine as an asymmetric acceptor, tert-butyltriphenylamine and dendritic tert-butyltriphenylamine as electron donors, and synthesizes them through oxidation, NBS bromination, Suzuki-Miyaura, and Schiff base condensation reactions. The relationship between molecular structure and performance was explored in detail, and how to construct an asymmetric acceptor with strong electron-withdrawing ability as the acceptor core of TADF was systematically studied; the influence of donors with different electron-donating abilities on the overall molecular performance was studied; it has important significance for the construction of new red and near-infrared luminescent materials.

[0007] Another object of the present invention is to provide a novel asymmetric acceptor red and near-infrared luminescent material for use as a light-emitting layer material for an organic electroluminescent diode, thereby obtaining a solution-processed organic electroluminescent device with excellent luminescent properties.

[0008] To achieve the above technical objectives, the present invention synthesized a class of red and near-infrared luminescent materials with thermally activated delayed fluorescence properties, using pyrene as the conjugated backbone center, a pyrazine-based asymmetric acceptor, and tert-butyltriphenylamine or dendritic tert-butyltriphenylamine as the electron donor. These materials have the following structure:

[0009]

[0010] Formula 1. Molecular structure

[0011] A pyrazine-based asymmetric acceptor was constructed with pyrene as the conjugated backbone, and tert-butyltriphenylamine or a dendrimer-type tert-butyltriphenylamine as the electron donor. The asymmetric acceptor core provides both strong electron-withdrawing capacity and partially inert groups, enhancing solubility while inhibiting planar stacking of the acceptor segments. Based on this acceptor structure, two TADF molecules were designed, and their photophysical and structural relationships, as well as their applications, were investigated.

[0012] The red and near-infrared luminescent materials with thermally activated delayed fluorescence properties are used as doping materials for the luminescent layer of an organic light-emitting diode, wherein the main material of the luminescent layer is 26DCzPPy or DtBuCzB.

[0013] The technical advantages of this patent are:

[0014] 1. Using the highly conjugated pyrene core as the central conjugated skeleton, which is easy to modify and has excellent thermal stability and high fluorescence quantum yield, a series of new red and near-infrared luminescent materials with asymmetric receptor cores are constructed;

[0015] 2. Using asymmetric pyrenopyrazine as a strong electron acceptor and tert-butyltriphenylamine or dendritic tert-butyltriphenylamine as a strong electron donor, the combination of the two is conducive to the separation of the highest occupied molecular orbital (HOMO) and the lowest occupied molecular orbital (LUMO), which is conducive to reducing ΔE ST , it is easy to obtain TADF materials and can improve the luminous efficiency of the materials;

[0016] 3. The effects of different electron-donating donors on the overall molecular performance were systematically studied, which is of great significance for the construction of new red and near-infrared luminescent materials.

[0017] The advantages of the present invention are:

[0018] A class of red-emitting materials with thermally activated delayed fluorescence (TADF) properties has been constructed and their applications. Using pyrene as the conjugated backbone, a pyrazine-based asymmetric acceptor was constructed, and tert-butyltriphenylamine or dendrimer-type tert-butyltriphenylamine was used as the electron donor. Through oxidation, NBS bromination, Suzuki-Miyaura, and Schiff base condensation reactions, a class of red and near-infrared luminescent materials with thermally activated delayed fluorescence properties was synthesized. The method of constructing asymmetric acceptors with strong electron-withdrawing ability as the acceptor core of TADF was systematically investigated, and the influence of different electron-donating donors on the overall molecular properties was studied. BRIEF DESCRIPTION OF THE DRAWINGS

[0019]

Figure 1

[0020]

Figure 2

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Figure 3

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Figure 4

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Figure 5

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Figure 6

[0025]

Figure 7

[0026]

Figure 8

[0027] The following specific implementation cases are intended to further illustrate the present invention, but these specific implementation cases do not limit the scope of protection of the present invention in any way.

[0028] Example 1

[0029] The synthesis scheme of the red and near-infrared luminescent materials based on the present invention is as follows:

[0030]

[0031]

[0032] Synthesis of compound M1:

[0033] At room temperature, a 500 mL two-necked flask was charged with 4.0 g, 19.8 mmol, pyrene, 492 mg, 2.3 mmol, 80 mL of acetonitrile (CH3CN), 80 mL of dichloromethane (CH2Cl2), 100 mL of H2O, and magnetite. Sodium periodate (NaIO4) (33.8 g, 158.2 mmol) was added in three portions to yield a dark brown suspension. The dark brown suspension was allowed to react at 30-40°C overnight. The reaction mixture was poured into 200 mL of H2O and filtered to remove the solid. The filtrate was extracted three times with CH2Cl2 (3 × 100 mL), washed three times with water (3 × 100 mL), dried over anhydrous magnesium sulfate, and filtered to yield a dark orange solution. The solvent was removed by vacuum distillation to yield a dark orange powder. Column chromatography was performed using pure CH2Cl2 as the eluent to obtain 1.1 g of the pure product M1 (pyrene-4,5,9,10-tetraone) as an orange solid, with a yield of 21%. 1 H NMR (400MHz, CDCl3) δ (ppm) 8.52 (d, J = 7.6 Hz, 4H), 7.73 (t, J = 7.6 Hz, 2H).

[0034] Synthesis of compound M2:

[0035] To a 100 mL two-necked flask, 1.0 g of pyrene-4,5,9,10-tetraone (M1) (3.8 mmol) and 10 mL of concentrated H2SO4 were added. The flask was placed in a thermostatic magnetic stirrer and N-bromosuccinimide (NBS) (1.7 g, 9.5 mmol) was added three times over 15 minutes at room temperature. The temperature was then raised to 60°C and allowed to react overnight. After the reaction, the mixture was cooled to room temperature and slowly added dropwise to ice water. The mixture was stirred for 30 minutes, filtered, and the filter cake was rinsed with boiling water to obtain a yellow cake. The mixture was then recrystallized from CH2Cl2 and methanol (CH3OH) to obtain 1.4 g of yellow powder M2 (2,7-dibromopyrene-4,5,9,10-tetraone) in a 90% yield. 1 H NMR (400MHz, DMSO) δ (ppm) 8.36 (s, 4H).

[0036] Synthesis of compound M3:

[0037] To a 500 mL two-necked flask were added p-bromoaniline (5.0 g, 29.0 mmol), tert-butyl iodobenzene (16.6 g, 63.9 mmol), CuI (2.2 g, 11.6 mmol), anhydrous 1,10-phenanthroline (2.1 g, 11.6 mmol), potassium hydroxide (KOH) (12.7 g, 226.0 mmol), and 120 mL of anhydrous toluene. The mixture was evacuated under nitrogen and allowed to react overnight. The mixture was cooled to room temperature and the organic solvent was removed by distillation under reduced pressure. The organic phases were then extracted with 150 mL of CH2Cl2 and saturated brine. The combined organic phases were dried over anhydrous magnesium sulfate, filtered, and the solvent was removed by distillation under reduced pressure. Column chromatography using pure petroleum ether (PE) as the eluent yielded 7.6 g of M3 (4'.4'-di-tert-butyl-4-bromotriphenylamine) as a white solid after CH3OH precipitation. The yield was 60%. 1 H NMR (400MHz, CD2Cl2) δ (ppm) 7.20 (d, J = 8.6 Hz, 6H), 6.91 (d, J = 8.6 Hz, 4H), 6.80 (d, J = 8.9 Hz, 2H), 1.22 (s, 18H).

[0038] Synthesis of compound M4:

[0039] A 500 mL single-necked flask was charged with 4'.4'-di-tert-butyl-4-bromotriphenylamine (M3) (5.0 g, 11.4 mmol), bis(pinacol borate) (3.5 g, 13.7 mmol), potassium acetate (AcOK) (6.7 g, 68.7 mmol), Pd(dppf)Cl2 (670.0 mg, 0.9 mmol), and 150 mL of dioxane. The mixture was reacted at 110°C under nitrogen for 24 h. After completion of the reaction, the organic solvent was removed by distillation under reduced pressure, and the mixture was extracted with CH2Cl2 and water. The organic phases were combined and the organic solvent was removed by distillation under reduced pressure. The mixture was separated by column chromatography using PE and CH2Cl2 (volume ratio = 4:1) as eluents to obtain a white solid. This solid was further recrystallized from a mixture of CH2Cl2 and CH3OH to obtain 4.8 g of M4 (4'.4'-di-tert-butyl-4-boronic acid pinacol triphenylamine) as a white solid in an 86% yield. 1 HNMR (400MHz, CD2Cl2) δ (ppm) 7.49-7.45 (m, 2H), 7.24-7.19 (m, 4H), 6.96-6.91 (m, 4H), 6.87-6.83 (m, 2H), 1.23 (d, J = 2.6Hz, 30H).

[0040] Synthesis of compound M5:

[0041] Compound M2 (1.0 g, 23.7 mmol), M4 (2.9 g, 5.9 mmol), Pd(PPh3)4 (220.0 mg, 0.2 mmol), a 2.0 mol / L aqueous solution of K2CO3 (10 mL, 2.0 mol / L), and 80.0 mL of N,N-dimethylformamide (DMF) were added to a 250 mL single-necked flask and reacted at 130°C under argon for 24 h. After completion of the reaction, the mixture was cooled to room temperature and 200 mL of H2O was added to precipitate a black solid. The solid was filtered, and the filter cake was rinsed with CH2Cl2. The filtrate was collected and the organic solvent was removed by distillation under reduced pressure. The solid was separated by column chromatography using CH2Cl2 and PE (volume ratio = 1:1) as eluents to obtain a blue powder. This was further recrystallized from CH2Cl2 and CH3OH to obtain 694.0 mg of a bluish-black powder, M5, in a 30% yield. 1 H NMR (400MHz, CDCl3) δ (ppm) 8.63 (s, 4H), 7.58 (d, J = 8.8Hz, 4H), 7.34-7.30 (m, 8H), 7.13 (d, J = 8.8Hz, 4H), 7.11-7.07 (m, 8H), 1.34 (s, 36H).

[0042] Synthesis of compound M6:

[0043] A 250 mL single-necked flask was charged with 4-tert-butylphenylboronic acid (2.0 g, 11.3 mmol), 4,5-dibromo-o-phenylenediamine (1.5 g, 3.5 mmol), Pd(PPh3)4 (347 mg, 0.3 mmol), a 2 mol / L aqueous K2CO3 solution, and 120 mL of 1,4-Dioxane. The mixture was evacuated and placed in a thermostatic magnetic stirrer. Stirring was continued at 110°C under argon for 24 h. After the reaction was completed, the mixture was cooled to room temperature, and the organic solvent was removed by distillation under reduced pressure. The mixture was then extracted with CH2Cl2. The combined organic phases were dried over anhydrous magnesium sulfate, and separated by column chromatography using pure CH2Cl2 as the eluent to afford a gray solid. This solid was recrystallized from CH2Cl2 and CH3OH to give 980.0 mg of the product, M6, as a white powder in a 70% yield. 1 H NMR (400MHz, CDCl3) δ (ppm) 7.17 (d, J = 8.3 Hz, 4H), 7.01 (d, J = 8.3 Hz, 4H), 6.78 (s, 2H), 3.46 (s, 4H), 1.28 (s, 18H).

[0044] Synthesis of compound M7:

[0045] Compound M5 (200.0 mg, 0.2 mmol), diaminomaleonitrile (26.0 mg, 0.3 mmol), 60 mL of CH2Cl3, and 15 mL of acetic acid were added to a 100 mL single-necked flask. The mixture was evacuated and placed in a thermostatic magnetic stirrer. Stirring was continued at 85°C under argon for 8 h. After the reaction was completed, the mixture was cooled to room temperature and 200 mL of water was added. A purple-black solid precipitated and filtered. The filter cake was rinsed with CH2Cl2 and the filtrate was collected. The organic solvent was removed by vacuum rotary evaporation. Column chromatography using PE and CH2Cl2 as eluents (volume ratio = 1:1) was used to separate the purple-black solid. The solid was further recrystallized from CH2Cl2 and CH3OH to obtain 161.0 mg of purple-black powder M7 in a 77% yield. 1 H NMR (400MHz, CDCl3) δ (ppm) 9.50 (s, 2H), 8.86 (s, 2H), 7.71 (d, J = 8.6Hz, 4H), 7. 34(d,J=8.5Hz,8H),7.21(d,J=8.6Hz,4H),7.13(d,J=8.5Hz,8H),1.35(s,36H).

[0046] Synthesis of compound PBCNT:

[0047] M7 (150.0 mg, 0.2 mmol), M6 (80.0 mg, 0.2 mmol), and 20 mL of acetic acid were added to a 100 mL single-necked flask, and the mixture was evacuated and reacted at 130°C under argon for 24 h. After the reaction was completed, the mixture was cooled to room temperature and 200 mL of water was added. A yellow solid precipitated, which was filtered and the filter cake rinsed with CH2Cl2. The filtrate was collected and the organic solvent removed by vacuum rotary evaporation. Column chromatography was performed using PE and CH2Cl2 as eluents (volume ratio = 2:1). The desired solution was collected and vacuum distilled to obtain an orange-yellow solid. This was further recrystallized from CH2Cl2 and CH3OH to obtain 90.0 mg of orange-red PBCNT powder with a yield of 47%. 1 HNMR (400MHz, CDCl3) δ (ppm) 8.97 (s, 2H), 8.60 (s, 2H), 8.23 ​​(s, 2H), 7.40 (d, J = 1 6.1Hz, 10H), 7.31 (d, J = 8.3Hz, 10H), 7.14 (d, J = 8.1Hz, 12H), 1.42-1.30 (m, 54H).

[0048] Preparation of compound M8:

[0049] To a 100mL two-necked flask, add compound M2 (500mg, 1.2mmol), 17mL of ethylene glycol, p-toluenesulfonic acid (230mg, 1.2mmol), and 40mL of toluene. Install a water trap at the side of the flask and place the device in a thermostatic magnetic stirrer. Stir at 125°C under argon for 24 hours. After the reaction, cool to room temperature, add methanol, and filter and dry the precipitated solid before proceeding to the next step. 1 H NMR (400MHz, CDCl3) δ (ppm) 7.89 (s, 4H), 4.21 (s, 8H), 3.67 (s, 8H).

[0050] Preparation of compounds M9, M10, and M11:

[0051] The synthesis methods are similar to those of compounds M3, M4, and M5, respectively.

[0052] For example, compound M9 was prepared according to the synthesis method of compound M3, except that the reaction substrate p-bromoaniline was replaced with dendritic diphenylamine, and the equivalent ratio of dendritic diphenylamine to p-bromoiodobenzene was 1:1.5. Other reaction conditions remained unchanged, and the post-reaction treatment method was similar. Finally, pure sample M9 was purified by column chromatography.

[0053] Preparation of compound M12:

[0054] M11 and 10 mL of water were added to a 100 mL two-necked flask, and then 50 mL of trifluoroacetic acid was added dropwise using a constant pressure dropping funnel under N2 protection. The reaction was allowed to proceed to room temperature for 48 h. After the reaction stopped, 100 mL of water was added, and the precipitated solid was filtered to obtain a black powder. After drying, the next step of the reaction was carried out.

[0055] Synthesis of compound M13:

[0056] Its synthesis method is similar to that of M7.

[0057] For example, compound M13 was prepared according to the synthesis method of compound M7, except that the reaction substrate M5 was replaced by 12, and the reaction conditions remained unchanged.

[0058] Synthesis of compound PBCN-TTPA:

[0059] Its synthesis method is similar to that of PBCNT.

[0060] For example, the compound PBCN-TTPA is prepared according to the synthesis method of the compound PBCNT, except that the reaction substrate M7 is replaced by M13, and the reaction conditions remain unchanged.

[0061] Example 2

[0062] The compound PBCNT in Example 1 was dissolved in toluene to prepare 10 -5 M solution, test its fluorescence and phosphorus spectra at 77K. Figure 1 (a) It can be seen that at 77K and vacuum conditions, 1) without delay: the maximum fluorescence emission peak of compound PBCNT in dilute toluene solution is at 664nm. 2) with a delay of 0.2ms: the maximum phosphorescence emission peak of compound PBCNT in dilute toluene solution is at 678nm. In comparison, the phosphorescence emission is red-shifted by 14nm compared to the fluorescence emission. The ΔE of compound PBCNT can be calculated. ST About 0.04eV.

[0063] Example 3

[0064] The compound PBCNT in Example 1 was dissolved in toluene to prepare 10 -5 M solution, and test its UV-visible absorption and photoluminescence spectrum. Figure 1 (b) It can be seen that the UV-visible absorption spectrum of the compound PBCNT in solution has two absorption peaks: the absorption peak at a short wavelength (380nm) is mainly attributed to the π-π* transition absorption of the molecule; the absorption peak at a long wavelength (490nm) is attributed to the charge transfer (ICT) transition absorption peak from the donor unit to the acceptor unit within the molecule. Figure 1As shown in (b), the maximum emission peak of the compound PBCNT is 664nm, in the deep red light region. Figure 2 (a) is the photoluminescence spectrum of the 1wt% doped 26DCzPPy film. The maximum emission peak of the compound PBCNT is 626nm, in the red region. The photoluminescence spectrum of the 1wt% doped DtBuCzB film. The maximum emission peak of the compound PBCNT is 612nm, in the red region. Figure 2 (b) shown.

[0065] Example 4

[0066] The fluorescence lifetime of the compound PBCNT in Example 1 in a 1 wt% doped PMMA film was tested under vacuum. Figure 3 As shown in (a), the delayed lifetime of PBCNT is 13.5μs after fitting.

[0067] Example 5

[0068] The compound PBCNT in Example 1 was tested in a vacuum atmosphere to obtain a temperature-dependent lifetime spectrum in a 1 wt% doped PMMA film. Figure 3 As shown in (b), the delayed component gradually increases with increasing temperature, which further proves the TADF characteristics of PBCNT.

[0069] Example 6

[0070] The fluorescence lifetime of the compound PBCNT in Example 1 in a 1 wt% doped 26DCzPPy film was tested under vacuum atmosphere. Figure 4 As shown in the figure, the delayed lifetime of PBCNT is 16.7μs after fitting.

[0071] Example 7

[0072] The fluorescence lifetime of the compound PBCNT in Example 1 in a 1 wt% doped DtBuCzB film was tested under a nitrogen atmosphere. Figure 5 As shown in (a), the transient lifetime of PBCNT is 44.6ns after fitting.

[0073] Example 8

[0074] The fluorescence lifetime of the compound PBCNT in Example 1 in a 1 wt% doped DtBuCzB film was tested under a nitrogen atmosphere. Figure 5 As shown in (b), the delayed lifetime of PBCNT is 10.2μs after fitting.

[0075] Example 9

[0076] The application of the compound PBCNT in Example 1 in organic electroluminescent devices. The compound is used as a dopant in the device light-emitting layer to prepare an organic electroluminescent diode of ITO / PEDOT:PSS (35nm) / PVK (30nm) / EML (25nm) / DPEPO (4.5nm) / TmPyPB (48nm) / LiF (0.5nm) / Al (100nm). Among them, PEDOT:PSS is a hole injection layer; PVK is a hole transport layer; DPEPO is a hole blocking layer; TmPyPB is an electron transport layer; LiF / Al is a cathode. EML is a light-emitting layer, including 26DCzPPy (light-emitting layer main material) and PBCNT (light-emitting layer dopant), and the dopant concentration is 0.5, 1, and 3 wt%. Figure 6 (a) shows the electroluminescence spectrum of the device with this doping ratio. The maximum external quantum efficiency of the device with compound PBCNT doped at 0.5, 1, and 3 wt% is 5.1%, 6.1%, and 1.2%, respectively. Figure 6 (b) is shown. The molecular structure of compound 26DCzPPy is as follows Figure 6 (c) shown.

[0077] Example 10

[0078] The application of the compound PBCNT in Example 1 in organic electroluminescent devices. In order to further improve the performance of the device, the compound DtBuCzB was selected as the main material of the light-emitting layer, and excellent device performance was achieved. ITO / PEDOT:PSS (35nm) / PVK / EML (25nm) / DPEPO / TmPyPB (48nm) / LiF (0.5nm) / Al (100nm) was prepared using the compound PBCNT as the light-emitting layer dopant of the device. Among them, PEDOT:PSS is the hole injection layer; PVK is the hole transport layer; DPEPO is the hole blocking layer; TmPyPB is the electron transport layer, and LiF / Al is the cathode. EML is the light-emitting layer, including DtBuCzB (light-emitting layer main material) and PBCNT (light-emitting layer dopant); the dopant concentration is 0.5, 1, 3, and 5wt%. Figure 7 As shown in (a), the electroluminescence spectra of devices with different doping ratios are shown. As the dopant concentration increases, the spectrum gradually red-shifts. The device with 1wt% doping of the compound PBCNT achieves a maximum external quantum efficiency of 28.5%, while the efficiency of the device with 0.5, 3, and 5wt% doping is 20.8%, 19.9%, and 18.7%, respectively. Figure 7 (b) is shown. The molecular structure of the compound DtBuCzB is as follows Figure 7 (c) shown.

[0079] Example 11

[0080] The H NMR spectrum of the compound PBCNT in Example 1 is as follows: Figure 8 .

[0081] Although the present invention has been described in conjunction with the preferred embodiments, the present invention is not limited to the above embodiments, and it should be understood that the appended claims summarize the scope of the present invention. Under the guidance of the inventive concept, those skilled in the art should appreciate that certain changes made to the various embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention.

Claims

1. A red and near-infrared luminescent material with thermally activated delayed fluorescence, characterized in that: The luminescent material uses pyrene as the central skeleton, an asymmetric pyrazine derivative as an electron acceptor, and tert-butyltriphenylamine and dendritic tert-butyltriphenylamine as electron donors to construct a series of red and near-infrared luminescent materials with thermally activated delayed fluorescence effect; The molecular structure of the luminescent material is shown below: 。 2. The red and near-infrared luminescent material having thermally activated delayed fluorescence properties according to claim 1, wherein: The preparation method of the luminescent material comprises the following steps: using pyrene as a central skeleton, an asymmetric pyrazine derivative as an electron acceptor, and tert-butyltriphenylamine or a dendritic tert-butyltriphenylamine as an electron donor, and synthesizing a red and near-infrared luminescent material with thermally activated delayed fluorescence characteristics through oxidation, NBS bromination, Suzuki-Miyaura, and Schiff base condensation reactions.

3. A use of the red and near-infrared luminescent material having thermally activated delayed fluorescence properties as claimed in claim 1, characterized in that: The red and near-infrared light-emitting materials having thermally activated delayed fluorescence characteristics are used as doping materials for the light-emitting layer of an organic light-emitting diode.

4. The use of the red and near-infrared luminescent material having thermally activated delayed fluorescence properties as claimed in claim 3, characterized in that: The main material of the light-emitting layer is 26DCzPPy or DtBuCzB.

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