Multi-resonance thermal activation delayed fluorescence compound based on hexa-substituted phenyl as core and space heavy atom effect, preparation method and organic electroluminescent device

Abstract

The invention relates to a multi-resonance thermal activation delayed fluorescence compound based on hexa-substituted phenyl as a core and a space heavy atom effect, a preparation method and an organic electroluminescent device, and belongs to the field of organic luminescent materials, in the compound, a heavy atom-containing structural unit and a multi-resonance thermal activation delayed fluorescence unit are alternately connected to a central benzene ring, molecular orbits of the two are subjected to spatial interaction to promote the anti-intersystem crossing process of the multi-resonance thermal activation delayed fluorescence unit, so that the delayed fluorescence lifetime is shortened, and the device performance is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of luminescent materials, and in particular relates to an organic electroluminescent material, specifically a multi-resonance thermally activated delayed fluorescence compound based on hexasubstituted phenyl as the core and spatial heavy atom effect. Background Art

[0002] Organic light-emitting diodes (OLEDs) have the advantages of bright colors, fast response speed, wide viewing angle, low driving voltage, energy saving, thinness, and flexible display. The fluorescent materials of traditional OLEDs are expensive, toxic, and have low exciton utilization. The emergence of thermally activated delayed fluorescence (TADF) materials has promoted the development of OLED technology. Generally, TADF materials use a twisted donor-acceptor (DA) structure to weaken the overlap of frontier molecular orbitals and reduce the singlet (S1)-triplet (T1) energy level difference (ΔE ST <0.3eV), promoting the reverse intersystem crossing (RISC) process from T1 to S1, and then achieving 100% exciton utilization, where the frontier molecular orbital refers to the highest occupied molecular orbital (Highest Occupied Molecular Orbital, HOMO) and the lowest unoccupied molecular orbital (Lowest Unoccupied Molecular Orbital, LUMO), that is, the HOMO-LUMO energy level orbital. However, DA-structured TADF materials exhibit strong intramolecular charge transfer emission, resulting in large structural relaxation in their excited states. In addition, the vibration coupling between the excited state and the ground state is strong, resulting in a wide luminescence spectrum with a spectral half-width (Full Width at HalfMaximum, FWHM) exceeding 70nm. Therefore, poor color purity hinders its application in ultra-high-definition displays.

[0003] In 2016, Hatakeyama et al. proposed the design idea of ​​multiresonance thermally activated delayed fluorescence (MR-TADF) materials, embedding atoms or groups with opposite electronic effects (electron-withdrawing effect and electron-pushing effect) in the planar polycyclic aromatic hydrocarbon skeleton, and using the opposite resonance effect of the above atoms to make HOMO and LUMO alternately distributed on different atoms, weakening the overlap of frontier molecular orbitals and producing TADF effect. Importantly, MR-TADF based on polycyclic aromatic hydrocarbon skeleton has a rigid molecular structure, which can reduce the structural relaxation of the excited state. In addition, the alternating distribution of its HOMO and LUMO on atoms can effectively suppress the high-frequency vibration coupling and spectral shoulder peak caused by chemical bond stretching vibration. Therefore, MR-TADF generally exhibits narrow spectral emission (FWHM < 40nm), overcoming the problem of poor spectral color purity of traditional TADF materials.

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

[0005] First, MR-TADF uses the resonance effect of electron-rich atoms and electron-deficient atoms in the polycyclic aromatic hydrocarbon skeleton to regulate the distribution of HOMO and LUMO, which makes it difficult to achieve effective separation of HOMO and LUMO. Therefore, MR-TADF usually exhibits a large ΔE ST , low intersystem crossing rate (k RISC ~10 4 -10 5 s -1 ) and a longer fluorescence lifetime (τ d >50us), which leads to serious device efficiency roll-off;

[0006] Second, the planar molecular structure of MR-TADF itself is prone to strong intermolecular π-π interactions, which in turn leads to the aggregation of luminescent units in the doped film, resulting in aggregation quenching effects, broadening of the luminescent spectrum, and red shift.

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

[0008] In order to address the deficiencies in the prior art, the present invention proposes a multiple resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl group as the core and a spatial heavy atom effect, a preparation method and an organic electroluminescent device. The compound contains a heavy atom structural unit (Heavy Atom Unit, HAU) and a MR-TADF unit connected to the central benzene ring. The molecular orbitals between the two can produce 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 solutions:

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

[0011]

[0012] in:

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

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

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

[0016]

[0017]

[0018] Among them, the dotted line indicates bonding or non-bonding;

[0019] K is selected from one of 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, Te;

[0021] R1 to R7 in formulas HAU-1 to HAU-8 are each independently selected from H, halogen, -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, a group formed by a combination of the above groups, or a group formed by a condensation of the above groups; or R1 to R7 can be connected by chemical bonds to form a bridge structure.

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

[0023]

[0024]

[0025]

[0026] In the present 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] Wherein, G1 to G2 are each independently selected from non-bonded, single-bonded, 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~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-K2 are each independently selected from B, N, P, 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=R in O 1 and R 2 are each independently selected from substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl; or said BR 1 , R 1 -CR 2 , R 1 -Si-R 2 NR 1 , PR 1 With R 1 -P=R in O 1 and R 2 is connected to one or two of the adjacent A1 to A5 via a linker 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=R in O 1 and R 2 It is bonded to one or two adjacent M1-M4 via a linking group or a single bond; A1-A5 are each independently selected from a C6-C60 aromatic ring or a C3-C60 aromatic heterocyclic ring.

[0032] Wherein, A1 to A5 in the above-mentioned multiple resonance thermally activated delayed fluorescence unit are each independently selected from any one of the following formulas 1 to 53:

[0033]

[0034]

[0035] Wherein, L1, L2 and L3 are each independently selected from: (i) H, halogen, -CN, -NO2, OH; (ii) a straight chain, branched chain or 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) a substituted or unsubstituted C6~C60 aryl group or C5~C60 heteroaryl group; L1, L2 and L3 may be connected by chemical bonds to form a bridge 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 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, a group formed by a combination of the above groups, or a group formed by a fusion of the above groups; or R1-R 12 They are connected by chemical bonds to form a bridge structure.

[0043] Furthermore, the above-mentioned 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 multi-resonance thermally activated delayed fluorescence compound based on the hexasubstituted phenyl group as the core and the spatial heavy atom effect is one of the following formulas (1)-(2):

[0048]

[0049]

[0050]

[0051]

[0052]

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

[0054]

[0055] In a protective gas atmosphere, an acetylene intermediate containing a heavy atom structural unit and a multiple resonance thermally activated delayed fluorescence structural unit of formula (III) is subjected to a cyclotrimerization reaction to obtain a target compound of formula (II), or an acetylene intermediate of formula (III) and a compound of formula (IV) are subjected to a Diels-Alder reaction to obtain a target compound of formula (I).

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

[0057] In the present invention, an organic electroluminescent device includes the above-mentioned multi-resonance thermally activated delayed fluorescence compound based on hexasubstituted phenyl as the core and 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 arranged on the substrate, an organic layer arranged on the anode, and a cathode arranged on the organic layer, wherein there is at least one organic layer, and at least one organic electroluminescent layer in the organic layer, and the organic electroluminescent layer includes 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 to 0.7 mm; the anode is a material based on hole injection, 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 the present invention, the method for preparing the above-mentioned organic electroluminescent device comprises the following steps:

[0062] forming an anode on the substrate;

[0063] forming one or more organic layers on the anode, including an organic electroluminescent layer;

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

[0065] Among them, the organic electroluminescent layer and the organic layers below it can be formed on the anode by solution spin coating, inkjet printing, offset printing or stereo printing. 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 formation method of the cathode includes but is not limited to vacuum deposition.

[0066] Compared with the prior art, the present application adopts a multi-resonance thermally activated delayed fluorescence compound based on hexasubstituted phenyl as the core and spatial heavy atom effect as the luminescent material of the organic electroluminescent device. In the compound, the structural units HAU and MR-TADF units containing heavy atoms are alternately connected to the central benzene ring. Due to the steric effect, the peripheral HAU and MR-TADF units are almost perpendicular to the central benzene ring. Therefore, the adjacent HAU and MR-TADF units tend to produce a face-to-face arrangement and are arranged closely in space. The two are used to produce spatial interaction. The heavy atom effect of HAU can be transmitted to the MR-TADF unit through this spatial interaction, promoting the RISC process of MR-TADF; on the other hand, the molecular skeleton of the hexasubstituted phenyl is propeller-shaped, which can expand the distance between the luminescent units, while inhibiting the interaction between molecules and avoiding molecular aggregation. Therefore, the present invention can provide a new way to develop high-performance MR-TADF materials. DETAILED DESCRIPTION

[0067] The present invention is further described below in conjunction with specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0068] Example 1

[0069] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl group as the core and a spatial heavy atom effect, the structural formula (1) and the monomers used are as follows:

[0070]

[0071] In a nitrogen atmosphere, 5 mmol Mon-1 (comprising HAU-3-6 units and MR-1-1-1 units of formula (III)), 1 mmol C O2 (CO)8 and 50 mL of anhydrous 1,4-dioxane, heated to 120°C, reacted for 48 hours; after cooling to room temperature, the reaction solution was poured into 200 mL of water, filtered to obtain a solid, vacuum dried, 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 E3): Theoretical value C: 78.52; H: 4.36; B: 1.40; N: 5.46; Test value C: 77.84; H: 4.56; B: 1.45; N: 5.21; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (2) and the monomers used are shown below:

[0074]

[0075] The preparation conditions and feed ratio of compound (2) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-2 (structure of formula (III) including HAU-3-6 units and MR-1-1-2 units). The obtained compound is a yellow solid with a yield of 33%. Elemental analysis structure (C 222 H 147 B3N 12 Se3): theoretical value C: 81.99; H: 4.56; B: 1.00; N: 5.17; test value C: 82.38; H: 4.34; B: 0.94; N: 5.31; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (3) and the monomers used are as follows:

[0078]

[0079] The preparation conditions and feed ratio of compound (3) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-3 (structure of formula (III) including HAU-3-6 unit and MR-1-1-3 unit). The obtained compound is a yellow solid with a yield of 41%. Elemental analysis structure (C 150 H 84 B3N9Se3): theoretical value C: 78.96; H: 3.71; B: 1.42; N: 5.52; test value C: 79.32; H: 3.63; B: 1.38; N: 5.38; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (4) and the monomers used are shown below:

[0082]

[0083] The preparation conditions and feed ratio of compound (4) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-4 (structure of formula (III) including HAU-3-6 units and MR-1-1-4 units). The obtained compound is a yellow solid with a yield of 43%. Elemental analysis structure (C 198 H 180 B3N9Se3): theoretical value C: 80.48; H: 6.14; B: 1.10; N: 4.27; test value C: 79.68; H: 5.87; B: 1.16; N: 4.36; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (5) and the monomers used are as follows:

[0086]

[0087] The preparation conditions and feed ratio of compound (5) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-5 (structure of formula (III) including HAU-4-9 unit and MR-1-1-4 unit). The obtained compound is a yellow solid with a yield of 43%. Elemental analysis structure (C 207 H 192 B3N9Se3): theoretical value C: 80.85; H: 6.29; B: 1.05; N: 4.10; test value C: 81.03; H: 6.18; B: 1.12; N: 4.02; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (6) and the monomers used are shown below:

[0090]

[0091] The preparation conditions and feed ratio of compound (6) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-6 (structure of formula (III) including HAU-5-8 units and MR-1-1-4 units). The obtained compound is a yellow solid with a yield of 37%. Elemental analysis structure (C 216 H 204 B3N9Se3): theoretical value C: 81.19; H: 6.64; B: 1.01; N: 3.95; test value C: 81.33; H: 6.29; B: 1.13; N: 3.87; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (7) and the monomers used are as follows:

[0094]

[0095] The preparation conditions and feed ratio of compound (7) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-7 (structure of formula (III) including HAU-4-17 unit and MR-1-1-4 unit). The obtained compound is a yellow solid with a yield of 34%. Elemental analysis structure (C 198 H 174 B3N9O3Se3): theoretical value C: 79.35; H: 5.85; B: 1.08; N: 4.21; test value C: 79.63; H: 5.67; B: 1.14; N: 3.97; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (15) and the monomers used are as follows:

[0098]

[0099] The preparation conditions and feed ratio of compound (15) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-15 (structure of formula (III) including HAU-7-2 unit and MR-1-1-4 unit). The obtained compound is a yellow solid with a yield of 41%. Elemental analysis structure (C 180 H 165B3N6O6S3Se3): theoretical value C: 75.23; H: 5.79; B: 1.13; N: 2.92; test value C: 75.57; H: 5.71; B: 1.16; N: 2.86; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (19) and the monomers used are as follows:

[0102]

[0103] The preparation conditions and feed ratio of compound (19) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-19 (structure of formula (III) including HAU-6-4 unit and MR-1-1-4 unit). The obtained compound is a yellow solid with a yield of 36%. Elemental analysis structure (C 183 H 165 B3N6O3Se3): theoretical value C: 79.47; H: 6.01; B: 1.17; N: 3.04; test value C: 79.86; H: 5.89; B: 1.21; N: 2.97; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (31) and the monomers used are shown below:

[0106]

[0107] The preparation conditions and feed ratio of compound (31) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-31 (structure of formula (III) including HAU-3-6 units and MR-1-13-2 units). The obtained compound is a white solid with a yield of 43%. Elemental analysis structure (C 138 H 114 B3N3O6Se3): theoretical value C: 76.04; H: 5.27; B: 1.49; N: 1.93; test value C: 76.52; H: 5.16; B: 1.53; N: 1.84; MALDI-TOF mass spectrum: theoretical value 2181.6, experimental value 2181.6 (M + ).

[0108] Embodiment 11

[0109] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl group as the core and a spatial heavy atom effect, the structural formula (34) and the monomers used are shown below:

[0110]

[0111] The preparation conditions and feed ratio of compound (34) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-34 (structure of formula (III) including HAU-3-6 unit and MR-1-24-1 unit). The obtained compound is a yellow solid with a yield of 38%. Elemental analysis structure (C 114 H 66 B3N3S6Se3): theoretical value C: 70.60; H: 3.43; B: 1.67; N: 2.17; measured value C: 71.26; H: 3.27; B: 1.72; N: 2.04; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (38) and the monomers used are shown below:

[0114]

[0115] The preparation conditions and feed ratio of compound (38) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-38 (structure of formula (III) including HAU-3-6 unit and MR-1-48-2 unit). The obtained compound is a yellow solid with a yield of 41%. Elemental analysis structure (C 132 H 75 B3N3O6Se3): theoretical value C: 76.87; H: 3.67; B: 1.57; N: 4.07; test value C: 77.26; H: 3.48; B: 1.66; N: 3.96; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (39) and the monomers used are shown below:

[0118]

[0119] The preparation conditions and feed ratio of compound (39) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-39 (structure of formula (III) including HAU-3-6 unit and MR-1-49-2 unit). The obtained compound is a yellow solid with a yield of 32%. Elemental analysis structure (C 132 H 75 B3N6S3Se3): theoretical value C: 75.12; H: 3.58; B: 1.54; N: 3.98; test value C: 76.47; H: 3.49; B: 1.61; N: 3.88; MALDI-TOF mass spectrum: theoretical value 2112.3, experimental value 2110.3 (M + ).

[0120] Embodiment 14

[0121] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl group as the core and a spatial heavy atom effect, the structural formula (46) and the monomers used are shown below:

[0122]

[0123] The preparation conditions and feed ratio of compound (46) are the same as those of compound (1), and the reactant Mon-1 is replaced by Mon-46 (structure of formula (III) including HAU-3-6 unit and MR-1-51-1 unit). The obtained compound is a yellow solid with a yield of 41%. Elemental analysis 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 spectrum: theoretical value 1926.2, experimental value 1925.2 (M + ).

[0124] Embodiment 15

[0125] A multi-resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl group as the core and a spatial heavy atom effect, the structural formula (50) and the monomers used are shown below:

[0126]

[0127] Under nitrogen atmosphere, 5 mmol Mon-1, 5 mmol compound (IV) and 20 mL diphenyl ether were added to a 50 mL Schlenk bottle, the temperature was raised to 260°C, and the reaction was carried out for 48 hours. After cooling to room temperature, the reaction system was separated and purified by silica gel column chromatography (petroleum ether / dichloromethane = 4:1) to obtain compound (50) as a yellow solid with a yield of 74%. Elemental analysis structure (C 94 H 80 BN3Se): theoretical value C: 84.16; H: 6.01; B: 0.81; N: 3.13; measured value C: 84.53; H: 5.88; B: 0.94; N: 2.98; MALDI-TOF mass spectrum: 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 group as the core and a spatial heavy atom effect, the structural formula (53) and the monomers used are shown below:

[0130]

[0131] The preparation conditions and feed ratio of compound (53) are the same as those of compound (50), and the reactant Mon-1 is replaced by Mon-39 (structure of formula (III) including HAU-3-6 unit and MR-1-48-2 unit). The obtained compound is a yellow solid with a yield of 72%. Elemental analysis structure (C 72 H 45B N2SSe): theoretical value C: 91.58; H: 4.28; B: 1.02; N: 2.64; test value C: 81.92; H: 4.17; B: 1.09; N: 2.49; MALDI-TOF mass spectrum: theoretical value 1060.2, experimental value 1060.2 (M + ).

[0132] Device Embodiment

[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 anode, hole injection layer, hole blocking layer, electron transport layer, electron injection layer, and cathode, respectively.

[0134]

[0135] The device preparation process includes: spin coating poly (3,4-ethylenedioxythiophene) - poly (styrene sulfonic acid) (PEDOT:PSS) on indium tin oxide supported on a glass substrate, annealing at 120 ° C for 30 minutes, adding the above compounds to the host material mCBP in a certain proportion, dissolving in a toluene solution (8mg / mL), and then spin coating the above solution on PEDOT:PSS to form a 40nm light-emitting layer at a speed of 1500rpm, a spin coating time of 60s, and annealing at 100 ° C for 30 minutes. Then, at 4×10 -4 TSPO1, TmPyPB and LiF / Al cathode were deposited in sequence under a vacuum degree of Pa to obtain an organic electroluminescent device.

[0136] Comparative Example 1

[0137]

[0138] In Comparative Example 1, the device structure and preparation process are the same as those of the device embodiment, and only the comparative compound Ctrl-1 without the spatial heavy atom effect is doped into the main 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-peak width is the peak width at half the peak height of the electroluminescence spectrum at room temperature; Turn-on voltage is the value at which the brightness is 1 cd m -2 The maximum external quantum efficiency is obtained according to the current-voltage curve and electroluminescence spectrum of the device according to the calculation method described in the literature (Jpn. J. Appl. Phys. 2001, 40, L783).

[0142] From the data shown in Table 1, it can be seen that at a doping content of 2 wt%, the multiple resonance thermally activated delayed fluorescence compound based on the hexasubstituted phenyl core and the spatial heavy atom effect provided by the present invention has a fluorescence intensity of 1000 cd / m 2 The external quantum efficiency is still high (19-21%), while the comparative example is 1000cd / m 2 The external quantum efficiency under the condition of attenuation was reduced from 21% to 8%. The above phenomenon can be attributed to the fact that the structural unit containing heavy atoms in the compound provided by the present invention can promote the reverse intersystem crossing process of the multiple resonance thermally activated delayed fluorescence unit in the compound through spatial interaction, reduce the delayed fluorescence lifetime, and slow down the roll-off of the device efficiency.

[0143] When the doping content is increased from 2wt% to 10wt%, the electroluminescence spectrum and the spectrum half-peak width of the compound provided by the present invention have no obvious changes, which are respectively 481-483nm and 21-23nm, and the external quantum efficiency is still maintained at 23-26%. The difference is that as the doping content increases, the electroluminescence spectrum of the comparative example appears to be red-shifted and the spectrum is broadened. Its electroluminescence spectrum is red-shifted from 481nm to 495nm, and the spectrum half-peak width is widened from 21nm to 35nm. The above differences show that the hexasubstituted phenyl molecular skeleton of the compound provided by the present invention can inhibit the aggregation of the light-emitting unit and has a wider doping window.

[0144] In summary, the present invention provides a multiple resonance thermally activated delayed fluorescence compound based on a hexasubstituted phenyl group as the core and a spatial heavy atom effect. Its heavy atom structural unit can spatially interact with adjacent MR-TADF units to produce a spatial heavy atom effect, promote the RISC process of triplet excitons, and inhibit the efficiency roll-off of the device; on the other hand, its propeller-shaped hexasubstituted phenyl molecular skeleton can inhibit the aggregation of light-emitting units, avoid the problems of luminescence quenching, spectral red shift and luminescence spectrum broadening caused by excessive doping concentration, and can provide a new reference scheme for the development of high-performance MR-TADF materials.

[0145] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A multi-resonance thermally activated delayed fluorescence compound based on hexasubstituted phenyl as the core and spatial heavy atom effect, characterized in that: The structural formula of the compound is shown in formula (I) or formula (II): in: is a structural unit containing a heavy atom, wherein the atomic number of the heavy atom is greater than 13, It is a multiple resonance thermally activated delayed fluorescence unit.

2. The compound according to claim 1, characterized in that: The unit containing heavy atoms is selected from any one of the following formulas HAU-1 to HAU-8: Among them, the dotted line indicates bonding or non-bonding; K is selected from one of B, N, and R3-P=O; Q1, Q2 and Q3 are each independently selected from one of R4-Si-R5, R6-Ge-R7, S, Se, Te; R1 to R7 in formulas HAU-1 to HAU-8 are each independently selected from H, halogen, -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, a group formed by a combination of the above groups, or a group formed by a condensation of the above groups; or R1 to R7 can be connected by chemical bonds to form a bridge structure.

3. The compound according to claim 2, characterized in that: The unit containing a heavy atom is selected from any one of the groups formed by lacking a hydrogen atom in the following formulas HAU-1-1 to HAU-8-1:

4. The compound according to claim 1, characterized in that: The multiple resonance thermally activated delayed fluorescence unit is selected from any one of the following formulas MR-1 to MR-4: Wherein, G1 to G2 are each independently selected from non-bonded, single-bonded, 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; M1~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; K1-K2 are each independently selected from B, N, P, P=O; BR in G1~G2 and M1~M4 1 , R 1 -CR 2 , R 1 -Si-R 2 NR 1 , PR 1 With R 1 -P=R in O 1 and R 2 are each independently selected from substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl; or said BR 1 , R 1 -CR 2 , R 1 -Si-R 2 NR 1 , PR 1 With R 1 -P=R in O 1 and R 2 It is connected to one or two of the adjacent A1 to A5 via a linker 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=R in O 1 and R 2 It is bonded to one or two adjacent M1-M4 via a linking group or a single bond; A1-A5 are each independently selected from a C6-C60 aromatic ring or a C3-C60 aromatic heterocyclic ring.

5. The compound according to claim 4, characterized in that: A1 to A5 in the multiple resonance thermally activated delayed fluorescence unit are each independently selected from any one of the following formulas 1 to 53: Wherein, L1, L2 and L3 are each independently selected from: (i) H, halogen, -CN, -NO2, OH; (ii) a straight chain, branched chain or 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) a substituted or unsubstituted C6~C60 aryl group or C5~C60 heteroaryl group; L1, L2 and L3 may be connected by chemical bonds to form a bridge structure.

6. The compound according to claim 1, characterized in that: The multiple resonance thermally activated delayed fluorescence unit is selected from any one of the following formulas MR-1-1 to MR-4-6: Among them, R1~R 12 Each 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, a group formed by a combination of the above groups, or a group formed by a fusion of the above groups; or R1-R 12 They are connected by chemical bonds to form a bridge structure.

7. The compound according to claim 6, characterized in that: The 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:

8. The multiple resonance thermally activated delayed fluorescence compound based on hexasubstituted phenyl as the core and spatial heavy atom effect according to any one of claims 1 to 7, characterized in that: The preparation method comprises: In a protective gas atmosphere, an acetylene intermediate containing a heavy atom structural unit and a multiple resonance thermally activated delayed fluorescence structural unit of formula (III) is subjected to a cyclotrimerization reaction to obtain a target compound of formula (II), or an acetylene intermediate of formula (III) and a compound of formula (IV) are subjected to a Diels-Alder reaction to obtain a target compound of formula (I).

9. An organic electroluminescent device, comprising the multiple resonance thermally activated delayed fluorescence compound based on hexasubstituted phenyl as the core and the spatial heavy atom effect as claimed in any one of claims 1 to 7, or the multiple resonance thermally activated delayed fluorescence compound based on hexasubstituted phenyl as the core and the spatial heavy atom effect obtained by the preparation method of claim 8, characterized in that: The compound is used as a luminescent material of an organic electroluminescent device.

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