A pyrene-based compound, a preparation method and application thereof

Abstract

This invention provides a pyrene-based compound, its preparation method, and its applications, belonging to the technical field of organic electroluminescent materials. The pyrene-based compound provided by this invention has the structural formula shown in Formula 1, wherein R1 and R2 are each independently selected from substituted or unsubstituted methyl, tert-butyl, phenyl, carbazole, diphenylamino, and dibenzofuranyl. The pyrene-based organic electroluminescent material provided by this invention can be applied in solution-processed OLED technology as a narrow-spectrum luminescent material, effectively improving the aggregation-induced fluorescence quenching effect and the broadening of the full width at half maximum (FWHM) caused by the rigid planar structure of boron-nitrogen fused rings. It reduces the FWHM, ensuring that the luminescent performance and color purity of the device are not only not reduced during the luminescence process but are also significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent materials technology, and particularly relates to a pyrene-based compound, its preparation method, and its application. Background Technology

[0002] Organic electroluminescent materials and devices have broad application prospects in flat panel displays and solid-state lighting. Among them, the boron-nitrogen (BN)-based multi-resonance thermally activated delayed fluorescence molecule is an organic light-emitting material with narrow spectral luminescence characteristics and high efficiency. This type of organic light-emitting material has important application value in the future ultra-high-definition display field.

[0003] While vacuum evaporation is a relatively mature method for preparing boron-nitrogen organic light-emitting materials, the availability of boron-nitrogen materials suitable for solution processing is still limited and warrants further research. This is primarily because boron-nitrogen light-emitting materials generally possess a rigid molecular structure. This rigidity hinders their dissolution and solution processing for film formation and easily leads to strong molecular aggregation, resulting in a redshift and broadening of their emission spectra. In the field of organic electroluminescence, the light-emitting material is a key factor determining the performance of OLED devices. Currently, solution-processable MR-TADF light-emitting materials are scarce, and further breakthroughs are urgently needed.

[0004] In solution-processed OLED devices, the hole injection layer, hole transport layer, and emissive layer are typically formed sequentially onto the anode via spin coating or inkjet printing, while the hole blocking layer, electron transport layer, electron injection layer, and cathode are generally deposited via vapor deposition. The emissive layer typically comprises a host material and a luminescent material. Luminescent materials suitable for solution-processed OLEDs, or those applicable to both vacuum deposition and solution processing, need to have good solubility in organic solvents. Furthermore, to reduce device efficiency roll-off and suppress emission redshift and spectral broadening, the luminescent material must not accumulate excessively during thin film formation. However, there are relatively few solution-processed MR-TADF luminescent materials that meet these requirements, and related organic electroluminescent materials and devices require further attention and in-depth research. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a pyrene-based compound, its preparation method, and its application. The pyrene-based organic electroluminescent material of this invention can be used as a narrow-spectrum luminescent material in solution-processed OLED technology. It effectively improves the aggregation-induced fluorescence quenching effect caused by the rigid planar structure of boron-nitrogen fused rings and the deficiency of aggregation-induced broadening of the full width at half maximum (FWHM), reducing the FWHM. Therefore, during the luminescence process, the luminescent performance and color purity of the device are not only not reduced but are also significantly improved. To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a pyrene-based compound having the structural formula shown in Formula 1: R1 and R2 are each independently selected from substituted or unsubstituted methyl, tert-butyl, phenyl, carbazolyl, diphenylamino, and dibenzofuranyl.

[0006] Preferably, the pyrene compound is selected from any one of the compounds shown in the following structural formulas: .

[0007] This invention also provides a method for preparing the above-mentioned pyrene compound, wherein the preparation method is carried out according to the following synthetic route: .

[0008] Preferably, the preparation method includes: taking raw material 1 through a boronization reaction to generate intermediate 1; and then taking intermediate 1 and raw material 2 through a Suzuki coupling reaction to generate the above-mentioned pyrene compound.

[0009] The present invention also provides an organic electroluminescent composition comprising the pyrene compound described above.

[0010] The present invention also provides an organic electroluminescent device, comprising an anode, a cathode, and an organic thin film layer disposed between the anode and the cathode; the organic thin film layer comprises a light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer; the light-emitting layer comprises the pyrene compound described above.

[0011] This invention also provides the application of the above-mentioned organic electroluminescent devices in the fabrication of organic light-emitting diodes, organic photovoltaic cells, organic light-emitting cells, organic field-effect transistors, organic light-emitting field-effect transistors, organic lasers, organic spintronic devices, organic sensors, and organic plasma-emitting diodes.

[0012] The pyrene-based compound provided by this invention, by connecting multiple BN luminescent backbone core units to pyrene groups, gives the pyrene-based compound a special twisted molecular structure. The twisted structure of the pyrene-based compound molecule can, on the one hand, improve the solubility of organic materials in organic solvents, thus enabling its application in solution processing; on the other hand, it helps to suppress the accumulation of luminescent molecules, thereby reducing the efficiency roll-off of the device and the spectral redshift and spectral broadening caused by molecular accumulation.

[0013] The pyrene-based compound provided by this invention has a BN molecular core framework and exhibits narrow-band luminescence, which can effectively improve the color purity of the device.

[0014] The pyrene-based TADF material provided by this invention exhibits excellent thermal stability, with a glass transition temperature greater than 120°C and a thermal decomposition temperature greater than 500°C. Furthermore, it can be used to prepare blue light-emitting devices through spin coating, expanding the processing methods of TADF materials. Therefore, the novel TADF material provided by this invention has broad market application prospects and is easily applicable to large-scale industrial production.

[0015] This invention applies pyrene compounds to organic electroluminescent devices, achieving high photoelectric conversion efficiency, long service life, and reduced costs.

[0016] The pyrene compounds provided by this invention are easy to modify, can control the overall molecular weight, and can be applied to the spin-coating process for OLED fabrication.

[0017] The pyrene compounds provided by this invention can be used as narrow-spectrum luminescent materials in solution-processed OLED technology. They can effectively improve the aggregation-induced fluorescence quenching effect and the broadening of the full width at half maximum (FWHM) caused by the rigid planar structure of boron-nitrogen fused rings, thereby reducing the FWHM. As a result, the luminescence performance and color purity of the device are not only not reduced during the luminescence process, but are also greatly improved. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the organic electroluminescent device of the present invention. In the figure, 1-transparent substrate layer; 2-transparent anode electrode layer; 3-hole transport layer; 4-light emission layer; 5-electron transport layer; 6-electron injection layer. Detailed Implementation

[0019] This invention provides a pyrene-based compound having the structural formula shown in Formula 1: R1 and R2 are each independently selected from substituted or unsubstituted methyl, tert-butyl, phenyl, carbazolyl, diphenylamino, and dibenzofuranyl.

[0020] In this invention, the pyrene compound is preferably selected from any one of the compounds shown in the following structural formulas: .

[0021] This invention also provides a method for preparing the above-mentioned pyrene compound, wherein the preparation method preferably follows the synthetic route described below: .

[0022] In this invention, the preparation method preferably includes: taking raw material 1 through a boronization reaction to generate intermediate 1; and then taking intermediate 1 and raw material 2 through a Suzuki coupling reaction to generate the above-mentioned pyrene compound.

[0023] The present invention also provides an organic electroluminescent device, comprising an anode, a cathode, and an organic thin film layer disposed between the anode and the cathode; the organic thin film layer comprises a light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer; the light-emitting layer comprises the pyrene compound described above.

[0024] In this invention, the light-emitting layer comprises a host material and a light-emitting material. The light-emitting layer, hole injection layer, and hole transport layer are preferably prepared using a spin coating process or an inkjet printing process, while the electron transport layer, electron injection layer, and cathode are preferably prepared using a vacuum evaporation process.

[0025] In this invention, the organic electroluminescent device may further include an optional hole blocking layer, an optional electron blocking layer, and an optional capping layer, etc.

[0026] In this invention, the pyrene compound can be used as a light-emitting guest material in the light-emitting layer of an organic electroluminescent device, wherein the organic electroluminescent device contains a hole injection layer, optionally contains a hole transport layer, contains one or more electron transport layers, and a light-emitting layer.

[0027] In this invention, when the pyrene compound is used as a guest luminescent material in the luminescent layer, the mass ratio of the pyrene compound in the luminescent layer is preferably 0.1 to 20%.

[0028] This invention applies the pyrene compound as an organic electroluminescent material in solution-processed OLED technology as a narrow-spectrum light-emitting material, resulting in a significant improvement in color purity for the corresponding solution-processed organic electroluminescent devices.

[0029] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0030] Example 1 A method for preparing a pyrene compound includes: performing a boronization reaction on a raw material 1 to generate an intermediate 1, as shown in the following reaction formula:

[0031] Intermediate 1 and starting material 2 undergo a Suzuki coupling reaction to produce the final product, formula 1, as shown in the following reaction formula: ; The reaction conditions for synthesizing intermediate 1 are as follows: The catalyst [Ir(COD)(OCH3)]2 (0.01 eq), 4,4-di-tert-butylbipyridine (dtbpy) (0.02 eq), feedstock 1 (1.0 eq), and bis(pinacol)diboron (B2Pin) (1.0 eq) were added to ultra-dry tetrahydrofuran solvent, bubbled with nitrogen for 5 minutes, heated under reflux and stirred for 24 hours under a nitrogen atmosphere, cooled to room temperature, and purified by column chromatography to obtain intermediate 1.

[0032] The reaction conditions for synthesis formula 1 are: Intermediate 1 (2.2 eq), raw material 2 (1.0 eq), appropriate amounts of tetrabutylammonium bromide and tetra(triphenylphosphine)palladium were added to potassium carbonate aqueous solution and tetrahydrofuran. The mixture was heated under reflux for 8 hours in a nitrogen atmosphere, and after extraction, column chromatography was used to separate the final product, formula 1.

[0033] Example 2 Taking pyrene compound structure 2 as an example, the synthetic route of the pyrene compound of the present invention is described, and the specific steps are as follows: (1) Catalyst [Ir(COD)(OCH3)]2 (43.1 mg, 0.065 mmol), 4,4-di-tert-butylbipyridine (dtbpy) (34.9 mg, 0.13 mmol), starting material 1-2 (4.69 g, 6.5 mmol), and bis(pinacol)diboron (B2Pin) (1.68 g, 6.6 mmol) were added to a 250 mL double-necked flask. Then, 60 mL of ultra-dry tetrahydrofuran was added. The mixture was bubbled under nitrogen for 5 minutes, heated under reflux and stirred for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the reaction solution was concentrated under reduced pressure and purified by column chromatography using dichloromethane and petroleum ether to obtain intermediate 1-2 (4.8 g), with a yield of 87%. MS (MALDI-TOFMS): m / z 848.37 ([M+H]+).

[0034] (2) The catalyst tetra-triphenylphosphine palladium (350 mg, 0.3 mmol), tetrabutylammonium bromide (0.1 mg, 0.3 mmol), the above intermediates 1-2 (14.93 g, 17.6 mmol), raw material 2 (3.1 g, 8 mmol) and 50 mL of potassium carbonate aqueous solution with a concentration of 1 mol / L were added to a 250 mL double-necked flask, and then 50 mL of ultra-dry tetrahydrofuran was added. The mixture was heated under reflux and stirred for 8 hours under a nitrogen atmosphere. After cooling to room temperature, the reaction solution was extracted and concentrated under reduced pressure. The solution was purified by column chromatography using dichloromethane and petroleum ether to obtain the final product with structural formula 2 (10.1 g), with a yield of 72%.

[0035]

[0036] The following compounds were prepared using the same synthetic method as that used in structural formula 2. The specific elemental analysis (percentage of C, H and N in the compounds) and mass spectrometry molecular weight data of the raw materials and products are shown in Table 1.

[0037] Table 1. Raw material preparation and product analysis ; Example 3 The organic solvent solubility test of this invention includes the following: Take 1 mL of solvent and add the corresponding mass of pyrene compound to it. Heat at 80 °C for 2 h and observe whether the solution is clear and transparent. If the solution is clear and transparent, it is considered to be completely dissolved; otherwise, it is considered not to be completely dissolved.

[0038] The solubility of pyrene compounds 2, 16, and BN from this invention was compared. Two commonly used organic solvents in solution processing (chlorobenzene and methyl benzoate) were selected. These solvents include low-boiling-point solvents (boiling point less than 180℃) and high-boiling-point solvents (boiling point greater than or equal to 180℃), respectively, and are representative of their properties. The test results are shown in Table 2.

[0039]

[0040] The structural formula of compound BN is as follows:

[0041] Table 2 Comparison of organic solvent solubility tests for compounds 2, 16, 20, and BN ; In this embodiment of the invention, pyrene compounds link multiple BN luminescent backbone core units together via pyrene groups to obtain pyrene compounds with a distorted molecular structure. Compared to unlinked pyrene compounds (e.g., BN), the solubility of pyrene compounds with a distorted molecular structure (e.g., 2, 16, 20) in this embodiment of the invention is significantly improved.

[0042] Example 4 The pre-fabricated ITO glass was ultrasonically cleaned with cleaning solution, deionized water, and isopropanol for 15 minutes in sequence and then dried in a 70°C oven. The dried ITO glass was then treated with an ultraviolet ozone cleaner for 15 minutes. After that, 200 μL of PEDOT:PSS solution was dropped onto the ITO glass and spin-coated at 2000 rpm / min for 40 seconds. Then, it was annealed and dried at 150°C for 15 minutes to form a hole injection layer with a thickness of 40 nm. Compound α was selected as the host material, and the aforementioned luminescent material structural formula 1 was selected as the luminescent guest. They were dissolved in chlorobenzene solvent at a certain mass ratio to form a first mixture with a concentration of 15 mg / ml. This first mixture was filtered through a PTFE membrane with a 0.22-micron filter diameter to form a second mixture. 100 μL of the second mixture was dropped onto the hole injection layer and spin-coated at 1500 rpm / min for 30 seconds. The mixture was then annealed and dried at 80°C for 60 minutes to form a 40 nm thick luminescent layer. The unfinished device was then transferred to a vapor deposition chamber and dried at 3 × 10⁻⁶ ppm. -5 Under a vacuum atmosphere of Pa, an electron transport layer with a thickness of 30 nm was formed at a rate of 0.05 nm / s, using TmPyPB as the electron transport layer material; an electron injection layer with a thickness of 2 nm was formed at a rate of 0.01 nm / s, using lithium (8-hydroxyquinoline) as the electron injection layer material; and a cathode layer was formed at a rate of 0.02 nm / s, using metallic aluminum as the cathode layer. An organic electroluminescent device was thus obtained.

[0043]

[0044] The main material of the light-emitting layer of the electroluminescent device is compound 1, 2, 5, 16, 18, 20 of this invention.

[0045] Table 3. Performance test results of organic electroluminescent devices in the device and comparative example BN. ; By comparing the device performance of the examples and comparative examples in Table 3, the following conclusions can be drawn: When the pyrene compound of this invention is used as a light-emitting guest material for solution-processed OLED devices, it has better solubility than the comparative material BN. The organic electroluminescent device achieves higher maximum efficiency and maintains better color (half-maximum width at half maximum). At the same time, it maintains higher efficiency at higher brightness and can effectively suppress spectral broadening caused by increasing doping concentration. This is beneficial for expanding the process window of the material in device fabrication and makes it more applicable.

[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A pyrene-based compound, characterized in that, The pyrene compound has the structural formula shown in Formula 1: R1 and R2 are each independently selected from substituted or unsubstituted methyl, tert-butyl, phenyl, carbazolyl, diphenylamino, and dibenzofuranyl.

2. The pyrene-based compound according to claim 1, characterized in that, The pyrene compound is selected from any one of the compounds shown in the following structural formulas: 。 3. A method for preparing a pyrene compound according to claim 1 or 2, characterized in that, The preparation method follows the synthetic route described below: 。 4. The method for preparing a pyrene compound according to claim 3, characterized in that, The preparation method includes: passing raw material 1 through a boronization reaction to generate intermediate 1; and then passing intermediate 1 and raw material 2 through a Suzuki coupling reaction to generate the pyrene compound shown in Formula 1 of claim 1.

5. An organic electroluminescent composition, characterized in that, Includes the pyrene-based compound as described in claim 1.

6. An organic electroluminescent device, characterized in that, It includes an anode, a cathode, and an organic thin film layer disposed between the anode and the cathode; the organic thin film layer includes a light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer; the light-emitting layer includes the pyrene compound as described in claim 1.

7. The application of the organic electroluminescent device according to claim 6 in the fabrication of organic light-emitting diodes, organic photovoltaic cells, organic light-emitting cells, organic field-effect transistors, organic light-emitting field-effect transistors, organic lasers, organic spintronic devices, organic sensors, and organic plasma-emitting diodes.

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