A multiple resonance thermally activated delayed fluorescence compound based on hexa-substituted phenyl as a core and a steric heavy atom effect, a preparation method and an organic electroluminescent device

Abstract

A compound with multiple resonance thermally activated delayed fluorescence based on a hexasubstituted phenyl core and the spatial heavy atom effect, its preparation method, and an organic electroluminescent device are disclosed. This compound belongs to the field of organic light-emitting materials. In this compound, structural units containing heavy atoms and multiple resonance thermally activated delayed fluorescence units are alternately connected to the central benzene ring. The molecular orbitals of the two interact spatially, promoting the anti-system crossing process of the multiple resonance thermally activated delayed fluorescence units, thereby reducing the delayed fluorescence lifetime and improving the device performance.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials technology, and particularly relates to organic electroluminescent materials, specifically a multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect. Background Technology

[0002] Organic light-emitting diodes (OLEDs) possess advantages such as vibrant colors, fast response speed, wide viewing angle, low driving voltage, energy efficiency, thinness, and flexible display capabilities. However, traditional OLED fluorescent materials are costly, highly toxic, and have low exciton utilization. The emergence of thermally activated delayed fluorescence (TADF) materials has driven the development of OLED technology. Typically, TADF materials employ a twisted donor-acceptor (DA) structure to reduce the overlap of leading molecular orbitals and lower the singlet (S1) to triplet (T1) energy level difference (ΔE). ST <0.3eV), promoting the anti-RISC process from T1 to S1, thereby achieving 100% exciton utilization. Here, the leading molecular orbitals refer to the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), i.e., the HOMO-LUMO energy level orbitals. However, DA-structured TADF materials exhibit strong intramolecular charge-transfer emission, leading to significant structural relaxation in their excited states. Furthermore, the strong vibrational coupling between the excited and ground states results in a broad emission spectrum with a full width at half maximum (FWHM) exceeding 70 nm. Therefore, poor color purity hinders its application in ultra-high-definition displays.

[0003] In 2016, Hatakeyama et al. proposed the design concept of multiresonance thermally activated delayed fluorescence (MR-TADF) materials. This involves embedding atoms or clusters with opposite electron effects (electron-withdrawing and electron-donating effects) into a planar polycyclic aromatic hydrocarbon (PAH) framework. Utilizing the opposite resonance effects of these atoms, HOMO and LUMO are alternately distributed on different atoms, reducing the overlap of leading molecular orbitals and generating the TADF effect. Importantly, MR-TADF based on a PAH framework possesses a rigid molecular structure, which can reduce structural relaxation in excited states. Furthermore, the alternating distribution of HOMO and LUMO on atoms effectively suppresses high-frequency vibrational coupling and spectral shoulder peaks caused by chemical bond stretching vibrations. Therefore, MR-TADF generally exhibits narrow spectral emission characteristics (FWHM < 40 nm), overcoming the problem of poor spectral color purity in traditional TADF materials.

[0004] Through rational molecular design and device structure optimization, MR-TADF OLED devices covering the entire visible light region have been reported, with external quantum efficiency (EQE) reaching 30%. Nevertheless, MR-TADF materials still face the following challenges:

[0005] Firstly, MR-TADF utilizes the resonance effect of electron-rich and electron-deficient atoms in the polycyclic aromatic hydrocarbon framework to regulate the distribution of HOMO and LUMO, making effective separation of HOMO and LUMO difficult to achieve. Therefore, MR-TADF typically exhibits a large ΔE. ST Low inter-system crossover rate (k RISC ~10 4 -10 5 s -1 ) and a longer fluorescence lifetime (τ) d >50µs), which leads to a severe roll-off in device efficiency;

[0006] Secondly, the planar molecular structure of MR-TADF itself is prone to strong intermolecular π-π interactions, which leads to the aggregation of light-emitting units in the doped film, resulting in aggregation quenching effect and phenomena such as broadening and redshift of the emission spectrum.

[0007] How to solve the above problems, further improve the performance of MR-TADF materials, and promote their commercial application is an urgent issue to be addressed. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention proposes a multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect, its preparation method, and an organic electroluminescent device. The compound contains a heavy atom unit (HAU) and an MR-TADF unit attached to the central benzene ring. The molecular orbitals of the two units can generate spatial interactions, which can effectively reduce the delayed fluorescence lifetime and improve device performance.

[0009] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0010] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect, the molecular formula of which is shown in formula (I) or formula (II):

[0011]

[0012] in:

[0013] It is a structural unit containing heavy atoms, wherein the atomic number of the heavy atoms is greater than 13.

[0014] It is a multiple resonance thermally activated delayed fluorescence unit.

[0015] In this invention, the unit containing heavy atoms is selected from any one of the following formulas: HAU-1 to HAU-8.

[0016]

[0017]

[0018] In this context, dashed lines indicate whether the lines are connected or not;

[0019] K is selected from B, N, and R3-P=O;

[0020] Q1, Q2, and Q3 are each independently selected from one of R4-Si-R5, R6-Ge-R7, S, Se, and Te;

[0021] R1 to R7 in formulas HAU-1 to HAU-8 are each independently selected from H, halogens, -CN, -NO2, substituted or unsubstituted C1 to C22 straight-chain alkyl, substituted or unsubstituted C1 to C22 branched alkyl, substituted or unsubstituted C1 to C22 cycloalkyl, substituted or unsubstituted C1 to C22 alkoxy chain, substituted or unsubstituted C6 to C20 aryl, substituted or unsubstituted C3 to C20 heteroaryl, groups formed by combinations of the above groups, or groups formed by fusion of the above groups; or R1 to R7 can be connected by chemical bonds to form a bridging structure.

[0022] Preferably, the unit containing heavy atoms is selected from any one of the following groups formed by lacking one hydrogen atom: HAU-1-1 to HAU-8-1.

[0023]

[0024]

[0025]

[0026] In this invention, the multiple resonance thermally activated delayed fluorescence unit is selected from any one of the following formulas: MR-1 to MR-4.

[0027]

[0028] Among them, G1 to G2 are each independently selected from non-keyed, single-keyed, and BR. 1 R 1 -CR 2 R 1 -Si-R 2 NR 1 PR 1 R 1 -P=O, C=O, S=O, O=S=O, O, S, Se or Te;

[0029] M1 to M4 are selected from BR 1 NR 1 PR 1 R 1 -P=O, C=O, S=O, O=S=O, O, S, Se or Te;

[0030] K1 to K2 are each independently selected from B, N, P, and P=O;

[0031] BR in G1~G2 and M1~M4 1 R 1 -CR 2 R 1 -Si-R2 NR 1 PR 1 With R 1 -P=O in R 1 and R 2 Each is independently selected from substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl; or the BR 1 R 1 -CR 2 R 1 -Si-R 2 NR 1 PR 1 With R 1 -P=O in R 1 and R 2 It is connected to one or two bonds of adjacent A1 to A5 via a connecting base or a single bond; or the BR 1 R 1 -CR 2 R 1 -Si-R 2 NR 1 PR 1 With R 1 -P=O in R 1 and R 2 A1 to A5 are each independently selected from aromatic rings of C6 to C60 or aromatic heterocyclic rings of C3 to C60, and are connected to one or two adjacent M1 to M4 via a linker or a single bond; A1 to A5 are each independently selected from aromatic rings of C6 to C60 or aromatic heterocyclic rings of C3 to C60.

[0032] In this context, A1 to A5 in the aforementioned multiple resonance thermally activated delayed fluorescence units are each independently selected from any one of the following formulas 1 to 53:

[0033]

[0034]

[0035] L1, L2, and L3 are each independently selected from: (i) H, halogen, -CN, -NO2, OH; (ii) a straight-chain, branched, cycloalkyl, or alkoxy chain containing 1 to 30 carbon atoms, wherein one or more non-adjacent carbon atoms may be substituted by O, S, Si, -CO-O-, and one or more hydrogen atoms may be substituted by halogen; (iii) substituted or unsubstituted C6-C60 aryl or C5-C60 heteroaryl; L1, L2, and L3 can be connected by chemical bonds to form a bridging structure.

[0036] Preferably, the above-mentioned multiple resonance thermally activated delayed fluorescence unit is selected from any one of the following formulas: MR-1-1 to MR-4-6.

[0037]

[0038]

[0039]

[0040]

[0041]

[0042] Among them, R1~R 12 Each group is independently selected from H, halogen, -CN, -NO2, substituted or unsubstituted C1-C22 straight-chain alkyl, substituted or unsubstituted C1-C22 branched alkyl, substituted or unsubstituted C1-C22 cycloalkyl, substituted or unsubstituted C1-C22 alkoxy chain, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C3-C20 heteroaryl, groups formed by combinations of the above groups, or groups formed by fusion of the above groups; or R1-R 12 They are connected by chemical bonds to form a bridging structure.

[0043] Furthermore, the aforementioned multiple resonance thermally activated delayed fluorescence unit is selected from any one of the following formulas: MR-1-1-1 to MR-4-5-1.

[0044]

[0045]

[0046]

[0047] Furthermore, the multiple resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is one of the following formulas (1)-(2):

[0048]

[0049]

[0050]

[0051]

[0052]

[0053] In this invention, the preparation method of the above-mentioned multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect specifically includes:

[0054]

[0055] In a protective gas atmosphere, the alkyne intermediate containing heavy atoms and multiple resonant thermally activated delayed fluorescence structural units shown in formula (III) undergoes a cyclotrimerization reaction to obtain the target compound shown in formula (II), or the alkyne intermediate shown in formula (III) and the compound shown in formula (IV) undergo a Diels-Alder reaction to obtain the target compound shown in formula (I).

[0056] The cyclotrimerization reaction is carried out at a temperature of 80–160°C for 20–60 h, and the catalyst used is Co2(CO)8; the Diels-Alder reaction is carried out at a temperature of 200–300°C for 3–20 h, and the solvent used is diphenyl ether.

[0057] In this invention, an organic electroluminescent device includes the above-mentioned multiple resonant thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and a spatial heavy atom effect, and uses it as the luminescent material of the organic electroluminescent device.

[0058] Furthermore, the organic electroluminescent device includes a substrate, an anode disposed on the substrate, an organic layer disposed on the anode, and a cathode disposed on the organic layer, wherein the organic layer has at least one layer, and at least one organic electroluminescent layer is disposed in the organic layer, the organic electroluminescent layer comprising one or more of the above-mentioned multiple resonance thermally activated delayed fluorescence compounds based on hexasubstituted phenyl as the core and spatial heavy atom effect.

[0059] Furthermore, the substrate is made of glass or plastic with a thickness of 0.3–0.7 mm; the anode is a hole-injection based material, a conductive metal or a conductive metal oxide, preferably indium tin oxide; the cathode is a metal, one of calcium, magnesium, barium, aluminum, and silver, preferably aluminum.

[0060] Furthermore, the organic layer between the anode and the organic electroluminescent layer includes a hole injection layer, a hole transport layer, and an electron blocking layer, and the organic layer between the organic electroluminescent layer and the cathode includes a hole blocking layer and an electron injection / transport layer.

[0061] In this invention, the method for preparing the above-mentioned organic electroluminescent device includes the following steps:

[0062] An anode is formed on the substrate;

[0063] One or more organic layers are formed on the anode, including an organic electroluminescent layer;

[0064] A cathode is formed on the organic layer.

[0065] The organic electroluminescent layer and the underlying organic layer can be formed on the anode by solution spin coating, inkjet printing, offset printing or stereolithography. After the organic electroluminescent layer is formed, a hole blocking layer and an electron injection / transport layer can be formed on its surface by vacuum evaporation or spin coating. The cathode can be formed by vacuum deposition, among other things.

[0066] Compared with existing technologies, this application employs a multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect as the luminescent material for organic electroluminescent devices. In this compound, HAU and MR-TADF structural units containing heavy atoms are alternately connected to the central benzene ring. Due to steric hindrance, the peripheral HAU and MR-TADF units are almost perpendicular to the central benzene ring. Therefore, adjacent HAU and MR-TADF units tend to form a face-to-face arrangement, spatially close together. Utilizing the spatial interaction between them, the heavy atom effect of HAU can be transferred to the MR-TADF unit through this spatial interaction, promoting the RISC process of MR-TADF. On the other hand, the hexasubstituted phenyl molecular backbone is propeller-shaped, which can increase the distance between luminescent units while suppressing intermolecular interactions and avoiding molecular aggregation. Therefore, this invention can provide a new approach for the development of high-performance MR-TADF materials. Detailed Implementation

[0067] The present invention will be further described below with reference to specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0068] Example 1

[0069] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structural formula (1) and the monomer used:

[0070]

[0071] Under a nitrogen atmosphere, 5 mmol of Mon-1 (including the (III) structure containing the HAU-3-6 unit and the MR-1-1-1 unit) and 1 mmol of C were added to a 100 ml Schlenk flask. O2 (CO)8 and 50 mL of anhydrous 1,4-dioxane were reacted at 120 °C for 48 hours. After cooling to room temperature, the reaction solution was poured into 200 mL of water, filtered to obtain a solid, dried under vacuum, and purified by silica gel column chromatography (petroleum ether / dichloromethane = 3:1) to obtain compound (1), a yellow solid with a yield of 38%. Elemental analysis structure (C 151 H 100 B3N9S E3Theoretical values: C: 78.52; H: 4.36; B: 1.40; N: 5.46; Measured values: C: 77.84; H: 4.56; B: 1.45; N: 5.21; MALDI-TOF mass spectrometry: Theoretical value 2309.9, Experimental value 2309.6 (M + ).

[0072] Example 2

[0073] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structure (2) and the monomer used:

[0074]

[0075] The preparation conditions and feed ratio of compound (2) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-2 (containing the structure of formula (III) with HAU-3-6 and MR-1-1-2 units). The resulting compound was a yellow solid with a yield of 33%. Elemental analysis of the structure (C 222 H 147 B3N 12 Se3): Theoretical value C: 81.99; H: 4.56; B: 1.00; N: 5.17; Measured value C: 82.38; H: 4.34; B: 0.94; N: 5.31; MALDI-TOF mass spectrometry: Theoretical value 3252.0, Experimental value 3252.0 (M + ).

[0076] Example 3

[0077] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structure (3) and the monomer used:

[0078]

[0079] The preparation conditions and feed ratio of compound (3) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-3 (including the structure of formula (III) consisting of HAU-3-6 and MR-1-1-3 units). The resulting compound was a yellow solid with a yield of 41%. Elemental analysis of the structure (C 150 H 84 B3N9Se3): Theoretical values: C: 78.96; H: 3.71; B: 1.42; N: 5.52; Measured values: C: 79.32; H: 3.63; B: 1.38; N: 5.38; MALDI-TOF mass spectrometry: Theoretical value 2281.7, Experimental value 2282.5 (M + ).

[0080] Example 4

[0081] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structure (4) and the monomer used:

[0082]

[0083] The preparation conditions and feed ratio of compound (4) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-4 (including the structure of formula (III) consisting of HAU-3-6 and MR-1-1-4 units). The resulting compound was a yellow solid with a yield of 43%. Elemental analysis of the structure (C 198 H 180 B3N9Se3): Theoretical values: C: 80.48; H: 6.14; B: 1.10; N: 4.27; Measured values: C: 79.68; H: 5.87; B: 1.16; N: 4.36; MALDI-TOF mass spectrometry: Theoretical value 2955.0, experimental value 2955.2 (M + ).

[0084] Example 5

[0085] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following diagram (5):

[0086]

[0087] The preparation conditions and feed ratio of compound (5) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-5 (including the structure of formula (III) consisting of HAU-4-9 and MR-1-1-4 units). The resulting compound was a yellow solid with a yield of 43%. Elemental analysis of the structure (C 207 H 192 B3N9Se3): Theoretical values: C: 80.85; H: 6.29; B: 1.05; N: 4.10; Measured values: C: 81.03; H: 6.18; B: 1.12; N: 4.02; MALDI-TOF mass spectrometry: Theoretical value 3075.2, experimental value 3074.3 (M + ).

[0088] Example 6

[0089] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following diagram (6):

[0090]

[0091] The preparation conditions and feed ratio of compound (6) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-6 (containing the structure of formula (III) with HAU-5-8 and MR-1-1-4 units). The resulting compound was a yellow solid with a yield of 37%. Elemental analysis of the structure (C 216 H 204 B3N9Se3): Theoretical values: C: 81.19; H: 6.64; B: 1.01; N: 3.95; Measured values: C: 81.33; H: 6.29; B: 1.13; N: 3.87; MALDI-TOF mass spectrometry: Theoretical value 3195.4, Experimental value 3195.4 (M + ).

[0092] Example 7

[0093] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following diagram (7):

[0094]

[0095] The preparation conditions and feed ratio of compound (7) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-7 (including the structure of formula (III) consisting of HAU-4-17 unit and MR-1-1-4 unit). The resulting compound was a yellow solid with a yield of 34%. Elemental analysis of the structure (C 198 H 174 B3N9O3Se3): Theoretical values: C: 79.35; H: 5.85; B: 1.08; N: 4.21; Measured values: C: 79.63; H: 5.67; B: 1.14; N: 3.97; MALDI-TOF mass spectrometry: Theoretical value 2998.1, experimental value 3197.2 (M + ).

[0096] Example 8

[0097] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structural formula (15) and the monomer used:

[0098]

[0099] The preparation conditions and feed ratio of compound (15) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-15 (containing the structure of formula (III) with HAU-7-2 and MR-1-1-4 units). The obtained compound was a yellow solid with a yield of 41%. Elemental analysis of the structure (C 180 H 165B3N6O6S3Se3): Theoretical values: C: 75.23; H: 5.79; B: 1.13; N: 2.92; Measured values: C: 75.57; H: 5.71; B: 1.16; N: 2.86; MALDI-TOF mass spectrometry: Theoretical value 2875.0, Experimental value 2875.0 (M + ).

[0100] Example 9

[0101] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structural formula (19) and the monomer used:

[0102]

[0103] The preparation conditions and feed ratio of compound (19) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-19 (containing the structure of formula (III) with HAU-6-4 and MR-1-1-4 units). The obtained compound was a yellow solid with a yield of 36%. Elemental analysis of the structure (C 183 H 165 B3N6O3Se3): Theoretical values: C: 79.47; H: 6.01; B: 1.17; N: 3.04; Measured values: C: 79.86; H: 5.89; B: 1.21; N: 2.97; MALDI-TOF mass spectrometry: Theoretical value 2765.7, Experimental value 2766.0 (M + ).

[0104] Example 10

[0105] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structural formula (31) and the monomer used:

[0106]

[0107] The preparation conditions and feed ratio of compound (31) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-31 (containing the structure of formula (III) with HAU-3-6 and MR-1-13-2 units). The obtained compound was a white solid with a yield of 43%. Elemental analysis of the structure (C 138 H 114 B3N3O6Se3): Theoretical values: C: 76.04; H: 5.27; B: 1.49; N: 1.93; Measured values: C: 76.52; H: 5.16; B: 1.53; N: 1.84; MALDI-TOF mass spectrometry: Theoretical value 2181.6, Experimental value 2181.6 (M + ).

[0108] Example 11

[0109] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structural formula (34) and the monomer used:

[0110]

[0111] The preparation conditions and feed ratio of compound (34) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-34 (containing the HAU-3-6 unit and the MR-1-24-1 unit of formula (III)). The resulting compound was a yellow solid with a yield of 38%. Elemental analysis of the structure (C 114 H 66 B3N3S6Se3): Theoretical values: C: 70.60; H: 3.43; B: 1.67; N: 2.17; Measured values: C: 71.26; H: 3.27; B: 1.72; N: 2.04; MALDI-TOF mass spectrometry: Theoretical value 1941.1, Experimental value 1940.1 (M + ).

[0112] Example 12

[0113] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structural formula (38) and the monomer used:

[0114]

[0115] The preparation conditions and feed ratio of compound (38) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-38 (containing the HAU-3-6 unit and the MR-1-48-2 unit of formula (III)). The resulting compound was a yellow solid with a yield of 41%. Elemental analysis of the structure (C 132 H 75 B3N3O6Se3): Theoretical values: C: 76.87; H: 3.67; B: 1.57; N: 4.07; Measured values: C: 77.26; H: 3.48; B: 1.66; N: 3.96; MALDI-TOF mass spectrometry: Theoretical value 2064.3, experimental value 2062.3 (M + ).

[0116] Example 13

[0117] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structural formula (39) and the monomer used:

[0118]

[0119] The preparation conditions and feed ratio of compound (39) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-39 (including the structure of formula (III) consisting of HAU-3-6 and MR-1-49-2 units). The resulting compound was a yellow solid with a yield of 32%. Elemental analysis of the structure (C 132 H 75 B3N6S3Se3): Theoretical values: C: 75.12; H: 3.58; B: 1.54; N: 3.98; Measured values: C: 76.47; H: 3.49; B: 1.61; N: 3.88; MALDI-TOF mass spectrometry: Theoretical value 2112.3, Experimental value 2110.3 (M + ).

[0120] Example 14

[0121] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following diagram (46):

[0122]

[0123] The preparation conditions and feed ratio of compound (46) were the same as those of compound (1), except that reactant Mon-1 was replaced with Mon-46 (containing the HAU-3-6 unit and the MR-1-51-1 unit of formula (III)). The resulting compound was a yellow solid with a yield of 41%. Elemental analysis of the structure (C 120 H 66 N₆O₆Se₃): Theoretical value C: 74.88; H: 3.46; N: 4.37; Measured value C: 75.31; H: 3.28; N: 4.52; MALDI-TOF mass spectrometry: Theoretical value 1926.2, Experimental value 1925.2 (M + ).

[0124] Example 15

[0125] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following diagram (50):

[0126]

[0127] Under a nitrogen atmosphere, 5 mmol Mon-1, 5 mmol of compound (IV), and 20 mL of diphenyl ether were added to a 50 mL Schlenk flask, and the mixture was heated to 260 °C and reacted for 48 h. After cooling to room temperature, the reaction system was purified by silica gel column chromatography (petroleum ether / dichloromethane = 4:1) to give compound (50), a yellow solid, yield: 74%. Elemental analysis of the structure (C...) 94 H 80 BN3Se): Theoretical values: C: 84.16; H: 6.01; B: 0.81; N: 3.13; Measured values: C: 84.53; H: 5.88; B: 0.94; N: 2.98; MALDI-TOF mass spectrometry: Theoretical value 1341.5, Experimental value 1342.5 (M + ).

[0128] Example 16

[0129] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect is shown in the following structural formula (53) and the monomer used:

[0130]

[0131] The preparation conditions and feed ratios of compound (53) were the same as those of compound (50), except that reactant Mon-1 was replaced with Mon-39 (containing the structure of formula (III) with units HAU-3-6 and MR-1-48-2). The resulting compound was a yellow solid with a yield of 72%. Elemental analysis of the structure (C...) 72 H 45B N2SSe): Theoretical value C: 91.58; H: 4.28; B: 1.02; N: 2.64; Measured value C: 81.92; H: 4.17; B: 1.09; N: 2.49; MALDI-TOF mass spectrometry: Theoretical value 1060.2, Experimental value 1060.2 (M + ).

[0132] Device Examples

[0133] The specific device structure used is ITO / PEDOT:PSS / EML (~50nm) / TSPO1 / TmPyPB / LiF / Al, where ITO, PEDOT:PSS, TSPO1, TmPyPB, LiF, and Al are the anode, hole injection layer, hole blocking layer, electron transport layer, electron injection layer, and cathode, respectively.

[0134]

[0135] The device fabrication process includes: spin-coating poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) (PEDOT:PSS) onto indium tin oxide supported on a glass substrate, annealing at 120°C for 30 min, incorporating the above compound into the host material mCBP at a certain ratio, dissolving it in toluene solution (8 mg / mL), and then spin-coating the above solution onto PEDOT:PSS to form a 40 nm light-emitting layer at a spin speed of 1500 rpm for 60 s, followed by annealing at 100°C for 30 min. Then, a 4 × 10⁻⁶ layer is formed. -4 Organic electroluminescent devices were obtained by sequentially depositing TSPO1, TmPyPB, and LiF / Al cathodes under a vacuum of Pa.

[0136] Comparative Example 1

[0137]

[0138] In Comparative Example 1, the device structure and fabrication process are the same as those in the device embodiment. The only difference is that the comparative compound Ctrl-1, which does not have a spatial heavy atom effect, is doped into the host material mCBP in a certain proportion to prepare the light-emitting layer.

[0139] Table 1. Performance parameters of organic electroluminescent devices obtained from device examples and comparative examples.

[0140]

[0141] Note: Half-width at half-maximum (WHM) is the peak width at half the peak height of the electroluminescence spectrum at room temperature; the turn-on voltage is the voltage at which the luminance is 1 cd / m². -2 The driving voltage of the device is given by the current-voltage curve and the maximum external quantum efficiency is obtained by calculation based on the device's current-voltage curve and electroluminescence spectrum according to the method described in the literature (Jpn.J.Appl.Phys.2001,40,L783).

[0142] As shown in Table 1, with a doping content of 2 wt%, the multi-resonance thermally activated delayed fluorescence compound based on the hexasubstituted phenyl core and spatial heavy atom effect provided by this invention achieves a fluorescence intensity of 1000 cd / m². 2 It still maintains a high external quantum efficiency (19-21%), while the comparative example has an external quantum efficiency of 1000 cd / m². 2 The external quantum efficiency decreased from 21% to 8%. This phenomenon can be attributed to the fact that the heavy atom-containing structural units in the compound provided by this invention can promote the anti-intersystem crossing process of the multiple resonant thermally activated delayed fluorescence units in the compound through spatial interactions, thereby reducing the delayed fluorescence lifetime and slowing down the device efficiency roll-off.

[0143] When the doping content increased from 2 wt% to 10 wt%, the electroluminescence spectrum and full width at half maximum (FWHM) of the compound provided by this invention did not change significantly, remaining at 481-483 nm and 21-23 nm, respectively, while the external quantum efficiency remained at 23-26%. However, with increasing doping content, a redshift and broadening of the electroluminescence spectrum were observed in the comparative example; the electroluminescence spectrum redshifted from 481 nm to 495 nm, and the FWHM broadened from 21 nm to 35 nm. These differences indicate that the hexasubstituted phenyl molecular skeleton of the compound provided by this invention can suppress the aggregation of luminescent units and has a wider doping window.

[0144] In summary, this invention provides a multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl core and the spatial heavy atom effect. Its heavy atom structural units can interact spatially with adjacent MR-TADF units, generating a spatial heavy atom effect, promoting the RISC process of triplet excitons, and suppressing the efficiency roll-off of the device. On the other hand, its propeller-shaped hexasubstituted phenyl molecular framework can suppress the aggregation of light-emitting units, avoiding the problems of luminescence quenching, spectral redshift, and luminescence spectrum broadening caused by excessive doping concentration. It can provide a new reference scheme for the development of high-performance MR-TADF materials.

[0145] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A multiple resonance thermally activated delayed fluorescence compound based on a hexa-substituted phenyl core and steric heavy atom effect, characterized in that: The compounds are compounds (4), (7), and (9), wherein compound (4) is: ； Compound (7) is: ； Compound (9) is: .

2. An organic electroluminescent device, characterized in that, This includes the multi-resonance thermally activated delayed fluorescence compound as described in claim 1, which is based on a hexasubstituted phenyl core and the spatial heavy atom effect.