A fused heterocyclic compound and an organic electroluminescence device comprising the same

Abstract

The application discloses a fused heterocyclic compound and an organic electroluminescent device containing the same. By introducing a semi-conjugated (six-membered ring) spiro structure into a boron-nitrogen structure molecule, stability of a steric hindering group is improved while ensuring required blue light emission, thereby improving stability of the device and increasing the service life of the device.

Description

Technical Field

[0001] This invention relates to the field of organic electroluminescence technology, and in particular to a novel organic compound and its applications, as well as an organic electroluminescent device containing the compound. Background Technology

[0002] Organic light-emitting devices (OLEDs) are current-driven thin-film devices with a sandwich-like structure, consisting of one or more layers of organic functional materials sandwiched between the anode and cathode. OLEDs are characterized by self-emission, wide viewing angle, wide color gamut, short response time, high luminous efficiency, low operating voltage, low cost, and simple manufacturing process. They are currently widely used in display products such as televisions, smartphones, tablets, automotive displays, and lighting, and will be further applied in creative display products such as large-size displays and flexible screens.

[0003] Organic optoelectronic materials used in OLED devices can be divided into light-emitting layer materials and auxiliary functional layer materials. Among them, light-emitting layer materials include guest materials (also known as light-emitting materials or doped materials) and host materials (also known as matrix materials). Light-emitting materials are divided into fluorescent materials, phosphorescent materials and thermally activated delayed fluorescence materials according to different energy transfer methods. Auxiliary functional layer materials are further divided into electron injection materials, electron transport materials, hole blocking materials, and hole injection materials according to different electron or hole transport speeds.

[0004] The luminescent dopants used in the luminescent layer have a decisive influence on the color, efficiency, and stability of electroluminescent devices. However, luminescent dopant materials with high efficiency and narrow emission are still in short supply. Current blue luminescent dopants suffer from low efficiency, short lifetime, and insufficient color purity. For example, the boron-nitrogen compounds in Chinese Patent Publication No. 107851724 and literature (Adv. Mater. 2016, 28, 2777–2781) can achieve a narrow half-maximum width at half maximum (WHM) due to the multiple resonance effect of the boron-nitrogen structure. However, their molecular structure results in low luminescence efficiency and they are prone to intermolecular aggregation, leading to reduced efficiency and lifetime.

[0005] Therefore, there is an urgent need in this field to develop a class of OLED luminescent materials that possess high luminous efficiency and a narrow emission spectrum, while effectively suppressing intermolecular aggregation. Such materials offer advantages such as high efficiency, long lifetime, and high color purity when applied in organic electroluminescent devices.

[0006] Existing technical documents

[0007] Patent Document 1: Chinese Patent Publication No. 107851724

[0008] Non-patent literature 1: Adv. Mater. 2016, 28, 2777–2781 Summary of the Invention

[0009] Organic light-emitting materials based on the (boron-nitrogen) (BN) structure possess high efficiency and narrow spectral density; this narrow spectral density is particularly crucial for the production of commercial OLED products. Therefore, researchers have invested significant resources in developing BN-structured organic light-emitting materials to continuously improve product performance. The narrow spectral density and high efficiency of BN molecules primarily stem from their rigid planar molecular structure. However, the double-edged sword of BN structures also exists: the rigid planar molecular structure leads to significant intermolecular forces, affecting the emission spectrum and stability of the device, thus degrading its efficiency and lifespan. Therefore, researchers have achieved some success by adding sterically hindered groups such as tert-butyl, adamantane, and spirofluorene to suppress aggregation and improve device stability. However, tert-butyl and other alkyl-based sterically hindered structures have poor rigidity, and the steric hindrance effect changes with atomic vibrations, affecting device stability. Meanwhile, aromatic structures such as spirofluorene groups exhibit strong conjugation, causing changes in the molecular spectrum emission, making it difficult to achieve the desired blue light emission.

[0010] The inventors aimed to solve the aforementioned technical problems. Through in-depth research, they discovered that introducing a semi-conjugated (six-membered ring) spirocyclic structure into the BN molecule not only ensures the required blue light emission but also improves the stability of steric hindrance groups, thereby enhancing device stability and increasing device lifetime. Furthermore, the O, S, and N heteroatoms in the semi-conjugated (six-membered ring) spirocyclic structure are located at the para-position of B. The introduction of these para-position heteroatoms effectively reduces the full width at half maximum (FWHM) of the spectrum, narrowing the spectrum and thus improving device efficiency.

[0011] Specifically, the present invention provides: 1) a fused heterocyclic compound, characterized in that the fused heterocyclic compound is represented by the following general formula (1):

[0012]

[0013] Where X represents O and S; Y represents O, S, and NR. 11 Z represents a single bond, CR 21 R 22 O, S, NR 23 ;

[0014] R1, R2, R 11 R 21 R 22 R 23 R 31 R 32 R 33Each of the following independently represents an alkyl group with 1 to 50 substituted or unsubstituted carbon atoms, an alkoxy group with 1 to 50 substituted or unsubstituted carbon atoms, an aryl group with 6 to 50 substituted or unsubstituted carbon atoms, or a heteroaryl group with 2 to 50 substituted or unsubstituted carbon atoms; wherein m, n, and p are the same or different from each other, and each is an integer from 0 to 4 independently. When m, n, and p are each 2 or more, each R... 31 R 32 R 33 They may be the same or different; among which R 11 It can form a ring with the adjacent phenyl group;

[0015] R3 and R4 represent hydrogen, alkyl with 1 to 50 substituted or unsubstituted carbon atoms, alkoxy with 1 to 50 substituted or unsubstituted carbon atoms, aryl with 6 to 50 substituted or unsubstituted carbon atoms, heteroaryl with 2 to 50 substituted or unsubstituted carbon atoms, alkylsilyl with 1 to 30 substituted or unsubstituted carbon atoms, and arylsilyl with 5 to 30 substituted or unsubstituted carbon atoms.

[0016] 2) The fused heterocyclic compound according to 1), characterized in that the fused heterocyclic compound is represented by the following general formula (2):

[0017]

[0018] Wherein, X, Y, R1, R2, R3, R 12 As defined in 1).

[0019] 3) The fused heterocyclic compound according to 1) or 2), characterized in that R1 and R2 are each independently selected from: aryl groups with 6 to 30 carbon atoms (substituted or unsubstituted), heteroaryl groups with 2 to 30 carbon atoms (substituted or unsubstituted); preferably selected from phenyl groups (substituted or unsubstituted), benzofuranyl groups (substituted or unsubstituted), benzothiophenyl groups (substituted or unsubstituted); more preferably selected, for example, from the following groups:

[0020]

[0021] The R3 is selected from: hydrogen, methyl, tert-butyl, tert-butylphenyl, biphenyl, phenyl, naphthyl, adamantyl, cyclopentyl, trimethylsilyl, triphenylsilyl, carbazole, diphenylamino, tert-butyldiphenylamino.

[0022] 4) The fused heterocyclic compound according to 1) or 2), characterized in that the R 11 Selected from: alkyl groups with 1 to 10 carbon atoms (substituted or unsubstituted), and aryl groups with 6 to 30 carbon atoms (substituted or unsubstituted).

[0023] 5) The fused heterocyclic compound according to claim 1, characterized in that the fused heterocyclic compound is selected from the following structures:

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037] 6) An organic electroluminescent device, the organic electroluminescent device comprising an anode, a cathode and at least one organic thin film located between the anode and the cathode, the organic thin film containing any one of the compounds in 1) to 5).

[0038] 7) The organic electroluminescent device according to 6) wherein the organic thin film comprises any one or at least two combinations of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an exciton blocking layer, a hole blocking layer, an electron transport layer, and an electron injection layer, and at least one of the light-emitting layers contains any one of the compounds in 1) to 5).

[0039] 8) According to the organic electroluminescent device described in 7), the compound is used as a luminescent material in the organic electroluminescent device.

[0040] Compared with existing technologies, the beneficial effects of this invention are: while ensuring the required blue light emission, it improves the stability of steric hindrance groups, thereby improving device stability and increasing device lifespan. Simultaneously, it effectively reduces the full width at half maximum (FWHM) of the spectrum and narrows the spectrum, thereby improving device efficiency. Attached Figure Description

[0041] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0042] Figure 1 The diagram below shows the structure of an organic electroluminescent device using the compounds of this invention. The meanings of each layer in the device are as follows:

[0043] 1. Transparent substrate layer, 2. ITO anode layer, 3. Hole injection layer, 4. Hole transport layer A, 5. Hole transport layer B (or electron blocking layer), 6. Light-emitting layer, 7. Electron transport layer B (or hole blocking layer), 8. Electron transport layer A, 9. Electron injection layer, 10. Cathode reflective electrode layer. Detailed Implementation

[0044] The principles and features of the present invention will be further illustrated below with several synthetic embodiments. The embodiments are only used to explain the present invention, but are not intended to limit the scope of the present invention.

[0045] The following describes the synthetic methods for the specific compounds of formula (1). The specific synthetic steps are as follows:

[0046] Synthesis Example 1

[0047] Synthesis of intermediate M002-1 :

[0048]

[0049] The following raw materials were used: RM-1 (16.40 g, 40 mmol), aniline (RM-2, 3.91 g, 42 mmol), tris(dibenzylacetone)palladium (0.72 g, 0.80 mmol), and sodium tert-butoxide (5.76 g, 60 mmol). The reaction system was purged three times under nitrogen protection. Then, (3.2 mL, 3.20 mmol) of a toluene solution of tri-tert-butylphosphine (1 mol / L) and 100 mL of toluene were added via syringe. The mixture was heated and stirred at 100 °C for 12 h under nitrogen protection. The reaction was stopped, cooled to room temperature, and 100 mL of deionized water was added. The reaction solution was transferred to a separatory funnel and extracted. The extract was dried over anhydrous magnesium sulfate and concentrated. The sample was purified by silica gel column chromatography to obtain product M002-1, 12.86 g of white solid, yield 76%; the molecular weight was determined to be m / z = 423 by liquid chromatography-mass spectrometry.

[0050] Synthesis of intermediate M002-2:

[0051]

[0052] The following raw materials were used: RM-3 (8.48 g, 40 mmol), p-tert-butylaniline (RM-2, 3.91 g, 42 mmol), tris(dibenzylacetone)palladium (0.72 g, 0.80 mmol), and sodium tert-butoxide (5.76 g, 60 mmol). The reaction system was purged three times under nitrogen protection. Then, (3.2 mL, 3.20 mmol) of a toluene solution of tri-tert-butylphosphine (1 mol / L) and 100 mL of toluene were added via syringe. The mixture was heated and stirred at 100 °C for 12 h under nitrogen protection. The reaction was stopped, cooled to room temperature, and 100 mL of deionized water was added. The reaction solution was transferred to a separatory funnel and extracted. The extract was dried over anhydrous magnesium sulfate and concentrated. The sample was purified by silica gel column chromatography to obtain product M002-2, 6.03 g of light red solid, yield 67%; the molecular weight was determined to be m / z = 337 by liquid chromatography-mass spectrometry.

[0053] Synthesis of intermediate M002-3:

[0054]

[0055] The following raw materials were prepared: RM-4 (6.72 g, 30 mmol), M002-1 (12.69 g, 30 mmol), tris(dibenzylacetone)palladium (0.55 g, 0.60 mmol), and sodium tert-butoxide (5.76 g, 60 mmol). The reaction system was purged three times under nitrogen protection. Then, 2.4 mL (2.40 mmol) of a toluene solution of tri-tert-butylphosphine (1 mol / L) and 100 mL of toluene were added via syringe. Under nitrogen protection, the mixture was heated and stirred, and refluxed at 115 °C for 12 h. The reaction was stopped, cooled to room temperature, and 100 mL of deionized water was added. The reaction solution was transferred to a separatory funnel and extracted. The extract was dried over anhydrous magnesium sulfate and concentrated. The sample was purified by silica gel column chromatography to obtain product M002-3, 12.59 g of white solid, yield 74%; the molecular weight was determined to be m / z = 567 by liquid chromatography-mass spectrometry.

[0056] Synthesis of intermediate M002-4:

[0057]

[0058] Intermediate M002-3 (11.34 g, 20 mmol), M002-1 (4.50 g, 20 mmol), tris(dibenzylacetone)dipalladium (0.55 g, 0.60 mmol), and sodium tert-butoxide (5.76 g, 60 mmol) were prepared. The reaction system was purged three times under nitrogen protection. Then, (2.4 mL, 2.40 mmol) of a toluene solution of tri-tert-butylphosphine (1 mol / L) and 100 mL of xylene were added via syringe. Under nitrogen protection, the mixture was heated and stirred at 140 °C for 12 h. The reaction was stopped, cooled to room temperature, and 100 mL of deionized water was added. The reaction solution was transferred to a separatory funnel and extracted. The extract was dried over anhydrous magnesium sulfate and concentrated. The sample was purified by silica gel column chromatography to obtain product M002-4, 9.37 g of white solid, yield 62%; the molecular weight was determined to be m / z = 756 by liquid chromatography-mass spectrometry.

[0059] Synthesis of product BD002:

[0060]

[0061] Under nitrogen protection, intermediate M002-4 (7.56 g, 10 mmol) was added to 40 mL of tert-butylbenzene, and n-butyllithium (6 mL, 15 mmol, 2.5 M) was added dropwise at -78 °C. After the addition was complete, the mixture was stirred at 60 °C for 3 hours. Boron tribromide (5.02 g, 20 mmol) was added dropwise at -78 °C, and the resulting mixture was stirred at room temperature for 1 hour. N,N-diisopropylethylamine (3.96 g, 30 mmol) was added dropwise at 0 °C. After the addition was complete, the mixture was stirred at 120 °C for 2 hours. The reaction was stopped, cooled to room temperature, 100 mL of deionized water was added, and the reaction solution was transferred to a separatory funnel for extraction. The extract was dried and concentrated with anhydrous magnesium sulfate, and the sample was purified by silica gel column chromatography to obtain product BD002, 1.31 g of yellow solid, with a yield of 18%; the molecular weight was determined by liquid chromatography-mass spectrometry to be m / z = 730.

[0062] Similar reactions can be used to prepare the following compounds:

[0063] Table 1

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070] Device Examples: Fabrication of Organic Electroluminescent Devices Used as Electron Blocking Layer Materials

[0071] A 30mm × 30mm × 1.1mm thick glass substrate with an indium tin oxide (ITO) transparent electrode (anode) was ultrasonically cleaned in isopropanol for 5 minutes, followed by ultraviolet (UV)-ozone cleaning for 30 minutes. The cleaned glass substrate was then mounted on the substrate holder of a vacuum evaporation apparatus, and a vacuum of 1 × 10⁻⁶ was applied. -5 ~1×10 -6 Pa, a HATCN hole injection layer (HIL) with a thickness of 15 nm is deposited on an ITO transparent electrode. HT as a hole transport layer (HTL) with a thickness of 60 nm is then deposited on the hole injection layer. Subsequently, EB as an electron blocking layer (EBL) with a thickness of 10 nm is deposited on the hole transport layer. Next, an emissive layer (EML) with a thickness of 20 nm is co-deposited on the electron blocking layer; the EML uses a multi-source co-deposition method to deposit the host material and luminescent material (BH and BD014), with the luminescent material having a doping concentration of 2% wt. Then, HB as a hole blocking layer (HBL) with a thickness of 5 nm is deposited on the emissive layer. Then, electron transport material (ET) and lithium 8-hydroxyquinoline (Liq) are co-deposited in a 1:1 ratio on the hole blocking layer as an electron transport layer (ETL) with a thickness of 30 nm. Finally, Liq as an electron injection layer (EIL) with a thickness of 1 nm is deposited on the ETL. Then, an aluminum (Al) metal cathode with a film thickness of 100 nm is deposited on top of the EIL. The organic electroluminescent device structure of Example 1 is as follows. Figure 1 As shown, Figure 1 It also shows the stacking order and function of each functional layer.

[0072] The OLED, in principle, has the following layer structure: ITO substrate / hole injection layer (HIL) / hole transport layer (HTL) / electron blocking layer (EBL) / emitting layer (EML) / hole blocking layer (HBL) / electron transport layer (ETL) / electron injection layer (EIL) and finally, a cathode. The cathode is formed of an aluminum layer with a thickness of 100 nm. The exact structure of the OLED is shown in Table 2.

[0073] Table 2 Materials used in OLEDs

[0074]

[0075]

[0076] Device Example 1:

[0077] ITO(130) / HATCN(15) / HT(60) / EB(10) / BH:BD014(20,2%wt) / HB(5) / ET:Liq(30,50%wt) / Liq(1) / Al(100)

[0078] The only difference between Device Examples 2-37 and Device Example 1 is that the BD014 of the present invention used in the light-emitting layer is replaced with other compounds of the present invention. The performance test data of the resulting devices are shown in Table 3.

[0079] Comparative Examples 1-4:

[0080] The difference between this comparative example and device example 1 is that BD014 in the organic electroluminescent device is replaced by BD-1, BD-2, BD-3, and BD-4, which are well-known in the industry and have been commercially applied. The device performance test data are shown in Table 3.

[0081] The OLED was characterized using standard methods. For this purpose, the electroluminescence spectrum, current efficiency (measured in cd / A), power efficiency (measured in lm / W), and external quantum efficiency (EQE, measured as a percentage) were determined, calculated as a function of luminous density from the current / voltage / luminous density characteristic line (IUL characteristic line) exhibiting Lambertian emission characteristics. EQE1000 represents 1000 cd / m². 2 The external quantum efficiency at operating brightness, T95 indicates the device's efficiency at 1000 cd / m². 2 The operating time when the device brightness decreases to 95% from the initial brightness, Peak and FWHM values ​​indicate the device's operating time at 1000 cd / m². 2 The emission peak and spectral half-width are shown. The device performance of Examples 1-37 and Comparative Examples 1-4 of the present invention is summarized in Table 3.

[0082] Table 3 Device Performance

[0083]

[0084]

[0085] As can be seen from Table 3, compared with the prior art, using the materials of Examples 1-35 of the present invention can improve device lifetime while narrowing the spectrum and increasing device efficiency. Compared with Comparative Example 4 with an amine group on the periphery, the FWHM of BD059 in Device Example 10 is narrowed by 3 nm, resulting in a 10% increase in efficiency and a 28.9% increase in lifetime. Compared with Comparative Example 2 with a benzothiophene luminescent core, the FWHM of BD116 in Device Example 16 with a benzothiophene luminescent core is narrowed by 4 nm, resulting in an 11.2% increase in efficiency and a 49.5% increase in lifetime; while the FWHM of BD170 in Device Example 22 with a benzofuran luminescent core is narrowed by 3 nm, resulting in an 8.6% increase in efficiency and a 16.2% increase in lifetime.

[0086] Therefore, this invention introduces a semi-conjugated (six-membered ring) spirocyclic structure into the BN molecule, which improves the stability of steric hindrance groups while ensuring the required blue light emission, thereby enhancing device stability and increasing device lifetime. Furthermore, the O, S, and N heteroatoms in the semi-conjugated (six-membered ring) spirocyclic structure are located at the para-position of B. The introduction of these para-position heteroatoms effectively reduces the full width at half maximum (FWHM) of the spectrum, narrowing the spectrum and thus improving device efficiency.

Claims

1. A fused heterocyclic compound, characterized in that, The fused heterocyclic compounds are represented by the following general formula (2): General formula (2) Where X represents O and S; Y represents O, S, and NR. 11 ; R1 and R2 are each independently selected from: unsubstituted phenyl, , , ; R3 is selected from: hydrogen, methyl, tert-butyl, tert-butylphenyl, biphenyl, phenyl, naphthyl, adamantyl, cyclopentyl, trimethylsilyl, triphenylsilyl, carbazole, diphenylamino, tert-butyldiphenylamino; 11 Selected from: phenyl, tert-butylphenyl.

2. A fused heterocyclic compound, characterized in that, The fused heterocyclic compounds are selected from the following structures: 。 3. An organic electroluminescent device, characterized in that, The organic electroluminescent device includes an anode, a cathode, and at least one organic thin film located between the anode and the cathode, wherein the organic thin film contains the compound of claim 1 or 2.

4. The organic electroluminescent device according to claim 3, characterized in that, The organic thin film includes any one or at least two combinations of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an exciton blocking layer, a hole blocking layer, an electron transport layer, and an electron injection layer, and at least one of the light-emitting layers contains the compound described in claim 1 or 2.

5. The organic electroluminescent device according to claim 4, characterized in that, The compound is used as a luminescent material in organic electroluminescent devices.

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