Spirobifluorene-based compounds, methods of making and using the same

Abstract

The application provides a compound based on spirobifluorene shown in formula (1) and a preparation method and application thereof. The compound is produced by introducing a rigid spirobifluorene as a structural center, and is directly connected with a donor-acceptor (D / A) to produce effective face-to-face stacking to improve carrier mobility, and to help the formation of a hybrid local-charge transfer excited state. The introduction of the spirobifluorene bridge can effectively regulate the CT state component, improve blue purity and high photoluminescence quantum efficiency (PLQY) in terms of the excited state characteristics of the molecules involved. In addition, the high rigidity of the molecules is conducive to inhibiting intramolecular and intermolecular vibration and rotational relaxation, thereby improving the luminescent efficiency. From the aspect of the molecular structure, the planar configuration can ensure the thermal stability of the molecules, effectively inhibit the deformation of the molecules in the excited state and inhibit non-radiative inactivation, thereby further improving the PLQY of the material and the efficiency and stability of the electroluminescent device.

Description

Technical Field

[0001] This invention relates to a spirodifluorene-based compound, its preparation method, and its application, belonging to the field of organic electroluminescent display technology. Background Technology

[0002] Organic light-emitting diodes (OLEDs) offer numerous irreplaceable advantages over traditional inorganic LEDs. The development of organic light-emitting materials has progressed through three generations: first-generation traditional fluorescent materials, second-generation noble metal phosphorescent materials, and third-generation pure organic light-emitting materials with high exciton utilization. Traditional fluorescent materials, due to spin statistical limitations, can only achieve an exciton utilization of 25%. While phosphorescent materials based on noble metal complexes can achieve 100% exciton utilization, they are more expensive and have longer excited-state lifetimes, resulting in generally shorter lifespans for blue light-emitting devices. Developing a new generation of efficient, stable, and low-cost pure organic light-emitting materials is beneficial for the long-term development of the OLED industry.

[0003] Thermally activated delayed fluorescence (TADF) materials have a small minimum singlet-triplet excited-state bandgap (ΔE). ST Triplet excitons can be converted into singlet excitons through anti-system crossing to emit light, achieving a quantum efficiency of up to 100% within the device. This makes it a low-cost, high-efficiency organic electroluminescent material. After more than a decade of rapid development, the performance of green and red light devices using TADF materials is now comparable to that of noble metal phosphorescence. However, in the blue light band, both phosphorescence and TADF materials suffer from poor stability. Therefore, given the excellent stability of fluorescent materials, currently commercially available blue light materials are still first-generation fluorescent materials. Against this backdrop, Professor Ma Yuguang and his colleagues designed and synthesized molecules with hybridized localized charge-transfer states (HLCT), which can recover triplet excitons through high-energy triplet anti-system crossing, achieving 100% exciton utilization. Furthermore, these molecules have short excited-state lifetimes (nanosecond-level) and good thermal stability, making them more conducive to obtaining efficient and stable blue light devices.

[0004] In recent years, thermal exciton materials have seen significant development. High-performance thermal exciton materials are obtained primarily by employing heteroatom-containing donor (D) and acceptor (A) combinations to modulate excited-state properties, resulting in simple structures that can be mass-produced. However, despite some expansion and extension of donor / acceptor (D / A)-based thermal exciton materials, high-performance materials remain scarce, with low external quantum efficiencies (less than 8%). Therefore, developing more efficient and high-mobility electroluminescent devices based on thermal exciton materials is of great importance. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a spirodifluorene-based compound as shown in formula (1), its preparation method, and its applications. By changing the acceptor type and bonding position, a series of highly efficient and high-mobility blue light-emitting molecules were synthesized. High external quantum efficiency and high brightness electroluminescent devices can be obtained with the aid of simple device structures, significantly saving device fabrication time and costs.

[0006] The following compound is based on spirodifluorene, as shown in equation (1).

[0007]

[0008] R1 and R2 may be the same or different, and are independently selected from H, unsubstituted groups, or groups substituted by one, two, or more Ra groups, including the following groups: C 6-20 Aryl, 5-22 heteroaryl, -N(C 6-20 aryl)2, -N(5-22 heteroaryl)2, -Si(C 6-20 aryl)3, -Si(5-22 heteroaryl)3;

[0009] Ra is selected from =O, CN, C 1-12 Alkyl, C 1-12 Alkoxy, halogenated C 1-12 Alkyl, -N(C) 6-20 aryl)2, -N(5-22-membered heteroaryl)2, unsubstituted or substituted by one, two, or more Rb groups as follows: C 6-20 Aryl, 5-22 heteroaryl;

[0010] Rb is selected from =O, CN, C 1-12 Alkyl, C 1-12 Alkoxy, halogenated C 1-12 Alkyl, -N(C) 6-20 aryl)2,-N(5-22 heteroaryl)2,C 6-20 Aryl or 5-22 heteroaryl groups;

[0011] The condition is that R1 and R2 are not 1-position and 8-position substituents.

[0012] According to an embodiment of the present invention, R1 and R2 are substituents at positions 2 and 7, respectively, i.e., formula (1) is selected from the following structures:

[0013]

[0014] According to embodiments of the present invention, R1 and R2 may be the same or different, and are independently selected from -5-22 heteroaryl groups; and are affected by one, two or more C groups. 1-12 Alkyl-substituted 5-14-membered heteroaryl groups; with one, two or more carbon atoms. 1-12Alkoxy-substituted 5-14-membered heteroaryl groups; -5-14-membered heteroaryl groups (C 6-14 Aryl)2,-C 6-14 Aryl-N(C) 6-14 aryl)2, -N(C 6-14 Aryl)2,-C 6-14 aryl-5-14-membered heteroaryl, -5-16-membered heteroaryl-C 6-14 Aryl, -C 6-14 aryl-5-16 heteroaryl-cyano-substituted C 6-14 Aryl, -C 6-14 aryl-5-16 heteroaryl-C 6-14 Aryl, -C 6-14 aryl-5-14 heteroaryl (C 6-14 aryl)2, -5-14 heteroaryl (C 6-14 aryl)2, -5-22-membered heteroaryl (C 1-12 Alkyl)2,-5-22-membered heteroaryl (halogenated C) 1-12 Alkyl)2, -C 6-14 aryl-5-14 heteroaryl (C 1-12 alkyl)2,-5-14-membered heteroaryl (C 1-12 alkyl)2,-5-14-membered heteroaryl (C 6-14 Aryl)2,-C 6-14 Aryl-Si-(C 6-14 aryl)3,-Si-(C 6-14 Aryl)3, C 6-14 The spirocyclic group formed by the linkage of aryl and 5-14 heteroaryl groups, with C atoms replaced by one or two =O atoms. 6-14 Spirocyclic groups formed by aryl groups linked to 5-14 heteroaryl groups, and 5-22 heteroaryl groups substituted with =O.

[0015] According to embodiments of the present invention, R1 and R2 may be the same or different, and are independently selected from carbazole groups, surrounded by 2 or 4 C atoms. 1-6 Alkyl-substituted carbazole group, with 2 Cs 1-6 Alkoxy-substituted carbazolyl, carbazolyl substituted with two phenyl groups, -phenyl-N(phenyl)2, -N(phenyl)2, -phenyl-carbazolyl, -carbazolyl-phenyl, -phenyl-triazinyl(phenyl)2, -triazinyl(phenyl)2, -phenyl-1,3,4-oxadiazole-phenyl, -phenyl-1,3,4-triazole(phenyl)2, -phenyl-Si(phenyl)3, -Si(phenyl)3, or the following groups:

[0016]

[0017] According to embodiments of the present invention, R1 and R2 may be the same or different, and are independently selected from the following groups:

[0018]

[0019]

[0020] According to an embodiment of the present invention, R1 and R2 have different structures, that is, the compound based on spirodifluorene shown in formula (1) has an asymmetric structure.

[0021] In some specific embodiments of the present invention, the spirodifluorene-based compound shown in formula (1) is selected from one of the following structures:

[0022]

[0023]

[0024]

[0025] According to an embodiment of the present invention, the spirodifluorene-based compound shown in formula (1) is a thermal exciton material.

[0026] The present invention also provides a method for preparing the spirodifluorene-based compound shown in formula (1) above, comprising the following steps:

[0027]

[0028] Compound 1a reacts with compound L1-R1 to give compound 1b; compound 1b then reacts with compound L2-R2 to give the compound shown in formula (1);

[0029] Wherein, R1 and R2 have the definitions described above; L1 is *-B(OH)2, L2 is In compound 1a, the two bromine groups are not substituents at positions 1 and 8.

[0030] The present invention also provides the use of the spirodifluorene-based compound shown in formula (1) as a thermal exciton material in the preparation of organic electronic devices, preferably in the preparation of organic electroluminescent devices.

[0031] According to an embodiment of the present invention, the spirodifluorene-based compound exhibits photoluminescence or electroluminescence properties and can emit blue light. Preferably, the spirodifluorene-based compound is a thermal exciton material.

[0032] The present invention also provides an organic electroluminescent device comprising two electrodes and an organic layer located between the electrodes, wherein the organic layer comprises a spirodifluorene-based compound as shown in formula (1) above.

[0033] Preferably, the organic layer is one, two, or more of the following: an injection layer, a transport layer, a light-emitting layer, and a blocking layer.

[0034] Preferably, the spirodifluorene-based compound shown in formula (1) is located in the luminescent layer.

[0035] According to an embodiment of the present invention, in the organic electroluminescent device, indium tin oxide (ITO) is used as the anode, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzophenanthrene (HAT-CN) is used as the hole injection material, 4-[1-[4-[bis(4-methylphenyl)amino]phenyl]cyclohexyl]-N-(3-methylphenyl)-N-(4-methylphenyl)aniline (TAPC) is used as the hole transport material, 4,4',4”-tris(carbazole-9-yl)triphenylamine (TCTA) is used as the electron blocking material, 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1”-terphenyl]-3,3”-diyl]dipyridine (TmPyPB) is used as the electron transport material, 8-hydroxyquinoline-lithium (Liq) is used as the electron injection material, and metallic aluminum (Al) is used as the cathode material.

[0036] In some embodiments of the present invention, the organic electroluminescent device comprises: ITO / HAT-CN (8 nm) / TAPC (50 nm) / TCTA (10 nm) / compound represented by formula (1) / TmPyPB (30 nm) / Liq (1 nm) / Al (100 nm).

[0037] According to an embodiment of the present invention, the organic electroluminescent device is a doped device or an undoped device.

[0038] According to an embodiment of the present invention, when the organic electroluminescent device is a doped device, Ir(pq)2acac or Ir(dmppy-ph)2tmd is doped into the compound shown in formula (1) as a light-emitting layer.

[0039] According to an embodiment of the present invention, the weight of Ir(pq)2acac or Ir(dmppy-ph)2tmd in the luminescent layer accounts for 5 to 12%, for example 7 to 9%, such as 8%, of the compound shown in formula (1).

[0040] The present invention also provides a method for fabricating the organic electroluminescent device as described above, comprising the following steps: sequentially forming an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode on a substrate.

[0041] Preferably, the anode, hole injection layer, hole transport layer, electron blocking layer, light-emitting layer, hole blocking layer, electron transport layer, electron injection layer and cathode are formed by vapor deposition, spin coating or inkjet printing, for example by vapor deposition.

[0042] More preferably, the vapor deposition is performed under vacuum conditions, for example, at a vacuum level below 2 × 10⁻⁶. -5 The deposition is carried out under the condition of Pa. More preferably, the deposition rate of the hole injection layer is 0.05 nm / s, the deposition rate of the electron injection layer is 0.01 nm / s, and the deposition rate of the other functional layers and the light-emitting layer is 0.1 nm / s.

[0043] Beneficial effects

[0044] 1. This invention provides a class of compounds based on spirodifluorene. The material uses rigid spirodifluorene as the structural center, has a suitable band gap (greater than 2.9 eV), can suppress self-aggregation, and enhance bond dissociation energy. It can be applied in the field of electroluminescence, mainly emitting blue light and deep blue light.

[0045] 2. Using the compound provided by this invention as the light-emitting layer in an electroluminescent device, the resulting electroluminescent device exhibits excellent device performance, with the following specific advantages:

[0046] (1) This invention introduces rigid spirofluorene as a structural center, which directly connects to the donor / acceptor (D / A) to generate effective face-to-face stacking, improving carrier mobility and facilitating the formation of hybridized local charge-transfer excited states. Regarding the excited-state characteristics of the involved molecules, the introduction of the spirofluorene bridge can effectively regulate the CT state composition, improving blue purity and high photoluminescence quantum efficiency (PLQY). Furthermore, the high rigidity of these molecules helps suppress intramolecular and intermolecular vibrations and rotational relaxation, thereby improving luminescence efficiency. From a molecular structure perspective, the planar configuration ensures the thermal stability of the molecules, effectively suppressing molecular deformation in the excited state while inhibiting non-radiative deactivation, thus further improving the PLQY of the material and the efficiency and stability of the electroluminescent device.

[0047] (2) Compared with the commercial iridium complex Flrpic, the electroluminescent device prepared using the thermal exciton material based on spirodifluorene described in this invention has excellent performance (stable emission color, high luminous efficiency and small device efficiency roll-off, i.e. better stability).

[0048] (3) The present invention is based on the simple preparation process of thermal exciton material of spirodifluorene, and the raw materials used in the synthesis are cheap and readily available. This type of material has good application effect in electroluminescent devices and has industrialization and industrialization prospects.

[0049] Terminology Definitions and Explanations

[0050] In this invention, the substituents marked with an asterisk (*) indicate connection sites.

[0051] The term "halogen" refers to F, Cl, Br, and I. In other words, F, Cl, Br, and I can be described as "halogens" in this specification. "Halogenated" means replaced by one, two, three, or more of the aforementioned "halogens".

[0052] Term "C" 1-12 "alkyl" should be understood to refer to a straight-chain or branched saturated monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably C12. 1-10 Alkyl group. "C" 1-10 "Alkyl" should be understood to mean a straight-chain or branched saturated monovalent hydrocarbon group having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl, or 1,2-dimethylbutyl, etc., or isomers thereof. In particular, the group has 1, 2, 3, 4, 5, 6, or 10 carbon atoms ("C"). 1-6 Alkyl groups, such as methyl, ethyl, propyl, butyl, isopropyl, isobutyl, sec-butyl, tert-butyl, and more particularly, the groups having 1, 2, or 3 carbon atoms (“C”). 1-3 Alkyl), such as methyl, ethyl, n-propyl or isopropyl.

[0053] Term "C" 6-20 "Aryl" should be understood as representing a monocyclic, bicyclic, or tricyclic hydrocarbon ring with 6 to 60 carbon atoms that is monovalent and partially aromatic, preferably "C". 6-14 "Aromatic". The term "C" 6-14 "Aryl" should be understood as representing a monovalent aromatic or partially aromatic monocyclic, bicyclic, or tricyclic hydrocarbon ring ("C") having 6, 7, 8, 9, 10, 11, 12, 13, or 14 carbon atoms. 6-14 Aryl), particularly a ring with 6 carbon atoms (“C6 aryl”), such as phenyl; or biphenyl, or a ring with 9 carbon atoms (“C9 aryl”), such as indenyl or indenyl, or a ring with 10 carbon atoms (“C9 aryl”). 10 Aryl groups, such as tetrahydronaphthyl, dihydronaphthyl, or naphthyl, or rings with 13 carbon atoms (“C”). 13 Aryl groups, such as fluorene groups, or rings with 14 carbon atoms (“C”). 14 Aryl), for example, anthracene.

[0054] The term "5-22-membered heteroaryl" should be understood to include monovalent monocyclic, bicyclic, or tricyclic aromatic ring systems having 5 to 22 ring atoms and containing 1 to 5 heteroatoms independently selected from N, O, and S, for example, "5-14-membered heteroaryl". The term "5-14-membered heteroaryl" should also be understood to include monovalent monocyclic, bicyclic, or tricyclic aromatic ring systems having 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 ring atoms, particularly 5, 6, 9, or 10 carbon atoms, and containing 1 to 5, preferably 1 to 3, heteroatoms independently selected from N, O, and S, and in each case, may be benzofused. Specifically, the heteroaryl group is selected from thienyl, furanyl, pyrroleyl, oxazolyl, thiazolyl, imidazoleyl, pyrazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, thiadiazolyl, thia-4H-pyrazolyl, and their benzo[derivatives], such as benzofuranyl, benzothienyl, benzooxazolyl, benzoisooxazolyl, benzoimidazolyl, benzotriazolyl, indazole, indolyl, isindolyl, etc.; or pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, and their benzo[derivatives], such as quinolinyl, quinazolinyl, isoquinolinyl, etc.; or acrylinyl, inazinyl, purinyl, and their benzo[derivatives]; or terpenolyl, phthalazinyl, quinazolinyl, quinoxolinyl, naphridinyl, pteridinyl, carbazolyl, acridineyl, phenazinyl, phenothiazinyl, phenothiazinyl, etc.

[0055] Unless otherwise stated, heterocyclic, heteroaryl, or heteroaryl groups include all their possible isomers, such as their positional isomers. Thus, for some illustrative, non-limiting examples, pyridyl or pyridylene includes pyridin-2-yl, pyridin-2-yl, pyridin-3-yl, pyridin-3-yl, pyridin-4-yl, and pyridin-4-yl; thiophenyl or thiophene includes thiophene-2-yl, thiophene-2-yl, thiophene-3-yl, and thiophene-3-yl.

[0056] The above refers to the term "C" 1-12 The definition of "alkyl" also applies to compounds containing "C". 1-12 Other terms for "alkyl", such as the term "C 1-12 Alkoxy, halogenated C 1-12 Alkyl groups, etc. Attached Figure Description

[0057] Figure 1 The steady-state photoluminescence spectra of compounds 1-4 and 1-15 prepared in Examples 3 and 6 of this invention as luminescent materials (pure films) are shown.

[0058] Figure 2 The transient decay spectra (at room temperature) of compounds 1-4 and 1-15 prepared in Examples 3 and 6 of this invention as luminescent materials (pure films).

[0059] Figure 3 Thermogravimetric analysis (TGA) curves of compounds 1-4 and 1-15 prepared in Examples 3 and 6 of this invention are shown. The thermal decomposition temperatures of compounds 1-4 and 1-15 are 479℃ and 520℃, respectively, indicating that the compounds have good thermal stability.

[0060] Figure 4 Differential scanning calorimetry (DSC) curves of compounds 1-4 and 1-15 prepared in Examples 3 and 6 of this invention are shown. The dissolution temperatures of compounds 1-4 and 1-15 are 348℃ and 400℃, respectively. No obvious glass transition temperature was observed, indicating that the compounds have good film-forming properties.

[0061] Figure 5 The spectrum of the undoped organic electroluminescent device in Example 9 of the present invention is shown under different voltages. Its spectrum shows almost no change under different driving voltages, demonstrating good spectral stability.

[0062] Figure 6 The spectrum of the undoped organic electroluminescent device in Example 12 of the present invention is shown under different voltages. The spectrum shows almost no change under different driving voltages, indicating good spectral stability.

[0063] Figure 7 The figures show the external quantum efficiency-luminescence curves of the undoped organic electroluminescent devices in Examples 9 and 12 of this invention. Analysis of the curves reveals that the electroluminescent devices corresponding to the compounds prepared in Examples 3 and 6 exhibit high and stable luminous efficiencies, with almost no roll-off at 1000 nits, and even at 10000 nits, the roll-off is minimal.

[0064] Figure 8 The figures show the current density-voltage-brightness curves of the undoped organic electroluminescent devices in Examples 9 and 12 of this invention. Analysis of the curves reveals that the electroluminescent devices corresponding to the compounds prepared in Examples 3 and 6 have high brightness and low start-up voltages, achieving the device's operating conditions at relatively low voltages, thus contributing to energy conservation and consumption reduction.

[0065] Figure 9 This is a structural diagram of an organic electroluminescent device fabricated using the compounds of this invention.

[0066] Among them, 1-transparent glass substrate, 2-anode, 3-hole injection layer, 4-hole transport layer, 5-electron blocking layer, 6-light emitting layer, 7-hole blocking layer, 8-electron transport layer, 9-electron injection layer, 10-cathode.

[0067] Figure 10 This diagram illustrates the energy transfer mechanism of the spirodifluorene-based compound as the main complex in this invention.

[0068] Among them, FRET: Energy transfer; DET: Dexter energy transfer; ISC: intergap jump; IC: internal conversion; hRISC: anti-intergap jump of high-energy triplet state; F: fluorescence; P: phosphorescence; S0 and S1: ground state and singlet state; T1, T2 and T3: the first, second and third excited states of triplet state. Detailed Implementation

[0069] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0070] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0071] The synthetic methods for compounds based on spirodifluorene are as follows:

[0072]

[0073] Example 1: Synthesis of Compounds 1-2

[0074] 4-(9H-carbazole-9-yl)phenylboronic acid (0.74 g, 2.6 mmol), 2,7-dibromo-9,9'-spirodifluorene (0.94 g, 2.0 mmol), and potassium carbonate (0.42 g, 3.0 mmol) were mixed. Then, tetrahydrofuran (40 mL) and deionized water (8 mL) were added to a 100 mL round-bottom flask. The mixture was purged with nitrogen three times, heated to 90 °C, and tetra(triphenylphosphine)palladium (80 mg, 0.07 mmol) was added. After reflux for 24 hours, the mixture was cooled to room temperature, and the solvent was removed under vacuum. The mixture was extracted three times with CH₂Cl₂, and the organic phase was collected and dried over anhydrous sodium sulfate. The solvent was removed to obtain the crude product. The crude product was purified by silica gel column chromatography using a mixture of petroleum ether and dichloromethane as eluent. After vacuum drying, the final intermediate product was obtained as a white solid (1.0 g, 1.6 mmol). The intermediate was then mixed with 2,4-diphenyl-6-[4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl]-1,3,5-triazine (0.87 g, 2.0 mmol), and then tetrahydrofuran (30 mL) and deionized water (6 mL) were added to a 100 mL round-bottom flask. The mixture was purged with nitrogen three times, heated to 90 °C, and tetra(triphenylphosphine)palladium (64 mg, 0.06 mmol) was added. After reflux for 24 hours, the mixture was cooled to room temperature, and the solvent was removed under vacuum. The mixture was extracted three times with CH₂Cl₂, and the organic phase was collected, dried over anhydrous sodium sulfate, and the solvent was removed to obtain the crude product. The crude product was purified by silica gel column chromatography using a mixture of petroleum ether and dichloromethane as eluent, and finally dried under vacuum to obtain the intermediate product as a white solid (1.0 g).

[0075] MS(EI): m / z 864.3253 [M] + Combustion-based elemental analysis: C 60 H 40 Calculated N4 (%): C 88.86; H 4.66; N 6.48; Measured: C 88.88; H 4.64; N 6.46.

[0076] Example 2 Synthesis of compounds 1-3

[0077] Except for replacing 4-(9H-carbazole-9-yl)phenylboronic acid (0.74 g, 2.6 mmol) with N-phenyl-3-carbazoleboronic acid (0.75 g, 2.6 mmol), the remaining steps were the same as those for the synthesis of compounds 1-2, and the final product was a white solid (0.97 g).

[0078] MS(EI): m / z 864.3253 [M] + Combustion-based elemental analysis: C 60 H 40Calculated N4 (%): C 88.86; H 4.66; N 6.48; Measured: C 88.85; H 4.68; N 6.50.

[0079] Example 3 Synthesis of compounds 1-4

[0080] Except for replacing 4-(9H-carbazole-9-yl)phenylboronic acid (0.74 g, 2.6 mmol) with 4-boronic acid triphenylamine (0.75 g, 2.6 mmol) and 2-phenyl-5-(4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)-1,3,4-oxadiazole (CAS No.: 1145663-98-4, 0.95 g, 2.0 mmol) with 2,4-diphenyl-6-[4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl]-1,3,5-triazine (0.87 g, 2.0 mmol), the remaining steps were the same as those for the synthesis of compounds 1-2, finally yielding a white solid (0.91 g).

[0081] MS(EI): m / z 779.9430 [M] + Combustion-based elemental analysis: C 57 H 37 Calculated N3O (%): C 87.78; H 4.78; N 5.39; O 2.05; Measured: C 87.76, H 4.75, N 5.41, O 2.08.

[0082] Example 4 Synthesis of compounds 1-10

[0083] Synthesis of compound BO-B

[0084]

[0085] BO-Br (1.74 g, 5.0 mmol), pinacol diborate (1.78 g, 7.0 mmol), tetrakis(triphenylphosphine)palladium (40 mg, 0.04 mmol), and potassium acetate (0.7 g, 7.0 mmol) were dissolved in N,N-dimethylformamide (DMF). The mixture was purged with nitrogen three times, heated to 120 °C, and cooled to room temperature after 12 hours. The mixture was extracted three times with CH₂Cl₂, and the organic phase was collected, dried over anhydrous sodium sulfate, and the solvent was removed to obtain the crude product. The crude product was purified by silica gel column chromatography using a mixture of petroleum ether and dichloromethane as eluent, and dried under vacuum to give BO-B as a white solid (1.2 g).

[0086] Following the preparation process of compounds 1-4, BO-B (0.79 g, 2.0 mmol) was substituted for 2-phenyl-5-(4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)-1,3,4-oxadiazole (0.95 g, 2.0 mmol), finally yielding a white solid (1.08 g).

[0087] MS(EI): m / z 827.7900 [M] + Combustion-based elemental analysis: C 61 H 38 BNO2 (%) Calculated values: C 88.51; H 4.63; B 1.31; N 1.69; O 3.87; Measured values: C 88.53; H 4.65; B 1.34; N 1.70; O 3.85.

[0088] Example 5 Synthesis of compounds 1-11

[0089] Except for replacing 4-(9H-carbazole-9-yl)phenylboronic acid (0.74 g, 2.6 mmol) with 7-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)benzo[5,6][1,4]oxazino[2,3,4-KL]phenoxazine (1.04 g, 2.6 mmol) and 2,4-diphenyl-6-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)phenyl]-1,3,5-triazine (0.87 g, 2.0 mmol) with BO-B (0.79 g, 2.0 mmol), the remaining steps were the same as those for the synthesis of compound 1-1, finally yielding a white solid (0.75 g).

[0090] MS(EI): m / z 855.2581 [M] + Combustion-based elemental analysis: C 61 H 34 BNO4 (%) Calculated values: C 85.62; H 4.00; B 1.26; N 1.64; O 7.48; Measured values: C 85.60; H 4.01; B 1.25; N 1.66; O 7.47.

[0091] Example 6 Synthesis of compounds 1-15

[0092] Except for replacing 2-phenyl-5-(4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentane-2-yl)phenyl)-1H-phenanthro[9,10-D]imidazole (9.93 g, 2.0 mmol) with 1-phenyl-2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentane-2-yl)phenyl)-1,3,4-oxadiazole (0.95 g, 2.0 mmol), the remaining steps were the same as those for the synthesis of compounds 1-4, ultimately yielding a white solid (1.16 g).

[0093] MS(EI): m / z 928.1510 [M] + Combustion-based elemental analysis: C 70 H 45 Calculated N3 (%): C 90.59; H 4.89; N 4.53; Measured: C 90.56; H 4.88; N 4.55.

[0094] The complex FIrpic of Comparative Example A, Ir(pq)2acac of Example 13, and Ir(dmppy-ph)2tmd of Example 14 were obtained directly from commercial channels.

[0095] The structures of compounds in comparative examples B and C are as follows:

[0096]

[0097] Synthesis of Compound S1 in Comparative Example B

[0098] Except for replacing 2,7-dibromo-9,9-dipropylfluorene (0.82 g, 2.0 mmol) with 2,7-dibromo-9,9'-spirodifluorene (0.94 g, 2.0 mmol), the remaining steps were the same as those for the synthesis of compounds 1-3, and the final product was a white solid (0.85 g).

[0099] MS(EI): m / z 799.0340 [M] + Combustion-based elemental analysis: C 58 H 46 Calculated N4 (%): C 87.19; H 5.80; N 7.01; Measured: C 87.18; H 5.82; N 7.03.

[0100] Synthesis of Compound S2 (Comparative Example C)

[0101] Except for replacing 2,7-dibromo-9,9-dipropylfluorene (0.82 g, 2.0 mmol) with 2,7-dibromo-9,9'-spirodifluorene (0.94 g, 2.0 mmol), the remaining steps were the same as those for the synthesis of compounds 1-4, and the final product was a white solid (0.95 g).

[0102] MS(EI): m / z 713.9250 [M] + Combustion-based elemental analysis: C 51 H 43 Calculated N3O (%): C 85.80; H 6.07; N 5.89; O 2.24; Measured: C 85.81; H 6.05; N 5.90; O 2.26.

[0103] Example 7 Fabrication of Organic Electroluminescent Device 1 (OLED-1)

[0104] In this embodiment, compounds 1-2 prepared in Example 1 were used as luminescent materials, indium tin oxide (ITO) as the anode, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzophenanthrene (HAT-CN) as the hole injection material, 4-[1-[4-[bis(4-methylphenyl)amino]phenyl]cyclohexyl]-N-(3-methylphenyl)-N-(4-methylphenyl)aniline (TAPC) as the hole transport material, and 4,4',4”-tris(carbazole-9-yl)triphenylamine (TCTA) as the electron transport material. The blocking material is 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1”-terphenyl]-3,3”-diyl]dipyridine (TmPyPB), used as the electron transport material; 8-hydroxyquinoline-lithium (Liq) is used as the electron injection material; and metallic aluminum (Al) is used as the cathode material. The device structure is: ITO / HAT-CN (8 nm) / TAPC (50 nm) / TCTA (10 nm) / compound 1-2 (20 nm) / TmPyPB (30 nm) / Liq (1 nm) / Al (100 nm).

[0105] Specifically, the device fabrication process is as follows: A transparent conductive glass substrate with an anode ITO is cleaned multiple times with a cleaning agent and rinsed thoroughly with deionized water. It is then sequentially placed in deionized water, acetone, and isopropanol solvents, and sonicated for at least 15 minutes each. After cleaning, the substrate is dried in a high-purity argon atmosphere, and then treated in an ultraviolet ozone generator for 15 minutes. The cleaned ITO is carefully placed into the vacuum deposition chamber of the device, and the vacuum is evacuated to below 2 × 10⁻⁶. -5After Pa, the deposition of functional layers begins: First, HAT-CN is deposited on the glass substrate at a rate of 0.05 nm / s to 8 nm as a hole injection layer; then TAPC is deposited at a rate of 0.1 nm / s to 50 nm as a hole transport layer; then TCTA is deposited at a rate of 0.1 nm / s to 10 nm as an electron blocking layer; then compound is deposited at a rate of 0.1 nm / s to 1-2 nm to 20 nm as a light-emitting layer; then TmPyPB is deposited at a rate of 0.1 nm / s to 30 nm as an electron transport layer; then Liq is deposited at a rate of 0.01 nm / s to 1 nm as an electron injection layer; finally, Al is deposited at a rate of 0.5 nm / s to 100 nm as a cathode. The structure of the organic electroluminescent device is as follows. Figure 9 As shown.

[0106] Fabrication of organic light-emitting devices (OLED-2, OLED-3, OLED-4, OLED-5, and OLED-6) in Examples 8, 9, 10, 11, and 12

[0107] Except for using compounds 1-3, 1-4, 1-10, 1-11 and 1-15 as emitting layer materials instead of compound 1-2, the other preparation conditions are the same as those for OLED-1.

[0108] The energy transfer mechanism utilizing the spirodifluorene-based compounds of this invention as the main complex host is as follows: Figure 10 As shown.

[0109] Depend on Figure 10 It can be seen that the thermal exciton material based on spirodifluorene in this invention is mainly obtained from T n (n≥2) to S m The high-energy triplet state anti-gap crossover (hRISC) process (m≥1) recovers triplet excitons, and then through... Energy is transferred to the singlet state of the emitter, and then undergoes inter-gap crossover (ISC) to the triplet state of the emitter for radiative emission. The fast hRISC process shortens the lifetime of triplet excitons to the nanosecond level, significantly avoiding triplet exciton aggregation. This allows the spirodifluorene-based thermal exciton material of this invention to be used for OLED fabrication using undoped techniques. Due to these advantages and excellent carrier transport capability and stability, the spirodifluorene-based compound of this invention is also very suitable as a host material and can effectively recycle excitons. Furthermore, compared to traditional ternary systems with thermal activation sensitization and phosphorescence sensitization, the binary doped system containing the spirodifluorene-based compound of this invention helps reduce the possibility of dexter energy transfer, thereby improving device efficiency. Therefore, the spirodifluorene-based compound of this invention is a promising host material.

[0110] Fabrication of doped devices (OLED-7 and OLED-8) in Examples 13 and 14

[0111] Except for using complexes Ir(pq)₂acac and Ir(dmppy-ph)₂tmd as the final emitter dopants (doping ratio: 8 wt% of compounds 1-4, wt% represents weight percentage) to replace compounds 1-2 in compounds 1-4, the other preparation conditions were the same as for OLED-1. The device obtained by replacing compounds 1-2 with Ir(pq)₂acac and Ir(dmppy-ph)₂tmd as the emissive layer is OLED-7. The device obtained by replacing compounds 1-2 with Ir(dmppy-ph)₂tmd and Ir(dmppy-ph)₂tmd as the emissive layer is OLED-8.

[0112] Fabrication of Comparative Examples A, B, and C Organic Light Emitting Devices (OLED-A, OLED-B, and OLED-C)

[0113] Except for using complexes FIrpic, S1, and S2 as the emitting layer materials instead of compounds 1-2, the preparation conditions were the same as for OLED-1. Specifically, OLED-A was prepared using FIrpic, OLED-B was prepared using complex S1, and OLED-C was prepared using complex S2.

[0114] Fabrication of D and E-doped devices (OLED-D and OLED-E) in Example

[0115] To demonstrate the superiority of the spirodifluorene-based compound as the host of this invention, for comparison, except that the bipolar host 26DCzPPy was used instead of compounds 1-4, the other preparation conditions were the same as those for OLED-7 and OLED-8.

[0116] The structures of the functional layers and coordination compounds FIrpic, Ir(pq)2acac and Ir(dmppy-ph)2tmd used in Examples 7-14 and Comparative Example AE are as follows:

[0117]

[0118] Table 1. Performance Comparison of Undoped Devices in Examples 7-12 and Comparative Examples A, B, and C with Doped Devices in Examples 13 and 14 and Comparative Examples D and E

[0119]

[0120] Analysis of device characterization test results shows that, compared with undoped OLEDs prepared using compounds 1-2, 1-3, 1-4, 1-10, 1-11 and 1-15 prepared in this invention as emitting layer materials, undoped OLEDs prepared with these compounds as emitting layer materials exhibit certain improvements in brightness and external quantum efficiency. Furthermore, the devices have lower turn-on voltages, and the efficiency roll-off at 1000 nits is significantly mitigated.

[0121] Compounds 1-4 prepared in this invention were used as the main components of the complexes Ir(pq)2acac (OLED-7) and Ir(dmppy-ph)2tmd (OLED-8), respectively. Compared with doped devices (OLED-D and OLED-E) prepared using the traditional bipolar main component 26DCzPPy, the performance of these compounds was significantly improved in all aspects, especially in terms of efficiency roll-off and device brightness. The spirodifluorene-based compounds of this invention possess good stability and carrier transport rate, with hole and electron transport rates reaching 10-1. -5 cm 2 V -1 s -1 It is relatively balanced and can be compared with a carrier transport rate of 26 DCzPPy (approximately 2 × 10⁻⁶). -5 cm 2 V -1 s -1 In addition to being comparable to, it can also achieve the effect of triplet exciton recycling, further improving exciton utilization and thus enhancing device performance.

[0122] As can be seen from the above comparison, the spirodifluorene-based compounds of this invention can effectively improve the performance of materials and devices, and have a low preparation cost.

[0123] The steady-state photoluminescence spectra of undoped thin films of compounds 1-4 and 1-15 in Examples 3 and 6 of this invention, respectively, as luminescent materials, are shown below. Figure 1 As shown. By Figure 1 It can be seen that both compounds exhibit efficient blue light emission in undoped thin films.

[0124] The transient decay spectra of compounds 1-4 and 1-15 in Examples 3 and 6 of this invention as undoped thin films of luminescent materials are shown below. Figure 2 As shown (at room temperature). From Figure 2 It is known that compounds 1-4 and 1-15 have shorter fluorescence lifetimes at room temperature (2.2 nanoseconds and 2.6 nanoseconds, respectively), which is beneficial for obtaining a smaller device efficiency roll-off.

[0125] Thermogravimetric analysis (TGA) curves of compounds 1-4 and 1-15 in Examples 3 and 6 of this invention are as follows: Figure 3 As shown. By Figure 3 It can be seen that the thermal decomposition temperatures of compounds 1-4 and 1-15 are 479℃ and 520℃, respectively, indicating that the compounds have good thermal stability.

[0126] The differential scanning calorimetry (DSC) curves of compounds 1-4 and 1-15 in Examples 3 and 6 of this invention are as follows: Figure 4 As shown. By Figure 4 It can be seen that the thermal decomposition temperatures of compounds 1-4 and 1-15 are 348℃ and 400℃, respectively, and no obvious glass transition temperature was observed, indicating that the compounds have good film-forming properties.

[0127] The spectra of the undoped organic electroluminescent devices of Examples 9 and 12 of this invention (containing compounds 1-4 and 1-15, respectively) at different voltages (3-10 volts) are as follows: Figure 5 and Figure 6 As shown. By Figure 5 and Figure 6 It can be seen that its spectrum changes only slightly under different driving voltages, demonstrating good spectral stability.

[0128] The external quantum efficiency-luminescence curves of the undoped organic electroluminescent devices of Examples 9 and 12 of this invention (containing compounds 1-4 prepared in Example 3 and compounds 1-15 prepared in Example 6, respectively) are as follows: Figure 7 As shown in the figure. The curve analysis shows that the electroluminescent devices corresponding to the compounds prepared in Examples 3 and 6 have high and stable luminous efficiency, and there is almost no roll-off (0%) at 1000 nits, and even at 10000 nits the roll-off is very small.

[0129] The current density-voltage-luminescence curves of the undoped organic electroluminescent devices of Examples 9 and 12 of this invention (containing compounds 1-4 prepared in Example 3 and 1-15 prepared in Example 6, respectively) are shown below. Figure 8 As shown in the figure. Analysis of the curves reveals that the electroluminescent devices corresponding to the compounds prepared in Examples 3 and 6 exhibit high brightness (55900 nits and 21300 nits, respectively) and low start-up voltages (2.5 volts and 2.6 volts, respectively). These low voltages allow the devices to operate at relatively low voltages, contributing to energy conservation and reduced power consumption.

[0130] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention, such as material substitutions and device improvements, should be included within the protection scope of the present invention.

Claims

1. As shown in equation (1), a compound based on spirodifluorene, （1） in, R1 is selected from , ; R2 is selected from , , ; R1 and R2 are substituents at positions 2 and 7, respectively.

2. The compound according to claim 1, characterized in that, The spirodifluorene-based compound shown in formula (1) is selected from one of the following structures:

3. A method for preparing the compound according to claim 1 or 2, characterized in that, Includes the following steps: Compound 1a reacts with compound L1-R1 to give compound 1b; compound 1b then reacts with compound L2-R2 to give the compound shown in formula (1); Wherein, R1 and R2 have the definition as described in claim 1; L1 is L2 is In compound 1a, the two bromine groups are substituents at positions 2 and 7.

4. Use of the spirodifluorene-based compound of formula (1) as described in claim 1 or 2 as a thermal exciton material in the fabrication of organic electronic devices.

5. The use according to claim 4, wherein, The compound based on spirodifluorene shown in Equation (1) is used as a thermal exciton material to prepare organic electroluminescent devices.

6. An organic electroluminescent device, characterized in that, It includes two electrodes and an organic layer located between the electrodes, the organic layer comprising a spirodifluorene-based compound as shown in formula (1) of claim 1 or 2.

7. The organic electroluminescent device according to claim 6, characterized in that, The organic layer comprises an injection layer, a transport layer, a light-emitting layer, and a blocking layer.

8. The organic electroluminescent device according to claim 7, characterized in that, The spirodifluorene-based compound shown in formula (1) is located in the luminescent layer.

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