A solution-processable thermally activated delayed fluorescent red light material and its preparation method and application

Abstract

The present application discloses a solution-processable thermally activated delayed fluorescence red light material, a preparation method, and an application thereof, belonging to the technical field of organic light-emitting diodes. A phenanthropyrazine receptor is used as a first receptor, a methyl benzoate group is used as a second receptor, and phenoxazine is connected to synthesize two thermally activated delayed fluorescence (TADF) red light materials, and a corresponding organic electroluminescent device is provided based on the two red light TADF materials. The red light TADF material obtained in the present application has a small ΔEst, which is conducive to improving anti-intersystem crossing and exhibiting good TADF characteristics. The phenanthropyrazine structural unit has a certain rigidity and can well suppress non-radiative transitions. In addition, the introduction of a second receptor and the change of the connection site of the second receptor can, on the one hand, change the light color; on the other hand, increase the molecular solubility and facilitate the preparation of solution-processed devices. At the same time, the energy level regulation based on the excited state on the receptor is realized, and ultimately the efficiency of the red light device in solution processing is improved. The present application has broad application prospects and is expected to be widely used in fields such as flat panel displays and solid-state lighting.

Description

Technical Field

[0001] The present application relates to the technical field of organic electroluminescent materials, and more specifically, to a solution-processable thermally activated delayed fluorescent red light material, a preparation method thereof, and applications thereof. Background Art

[0002] Organic light-emitting diodes (OLEDs) are also known as organic electroluminescent diodes. Organic electroluminescence refers to a luminescence phenomenon in which organic small molecules, metal-organic complex molecules, or polymer molecules convert electrical energy directly into light energy under the action of a forward bias electric field. OLEDs are not only self-luminous, do not require a backlight, and are energy-efficient, but also have the characteristics of fast response speed, low driving voltage, high luminous efficiency, high resolution, wide viewing angle, and high contrast. OLEDs use cheap glass, metal, or even flexible plastic as substrates, and have the advantages of low cost, simple production process, and large-scale production. They have become a new generation of full-color display and lighting technology, with broad application prospects in mobile phones, computers, televisions, digital cameras, GPS, bendable and foldable electronic products, and lighting, and have received widespread attention from academia and industry.

[0003] The ratio of singlet and triplet excitons generated in OLEDs is 1:3. In conventional fluorescent OLEDs, only singlet excitons can be utilized for photon generation, resulting in a theoretical internal quantum efficiency (IQE) of only 25%. Phosphorescent OLEDs, by introducing phosphorescent materials containing heavy metals, can simultaneously utilize both singlet and triplet excitons, theoretically achieving an IQE of 100%. However, the scarcity of heavy metals makes them unsuitable for further application in phosphorescent OLEDs. In the past few years, an emerging technology based on the thermally activated delayed fluorescence (TADF) mechanism has attracted significant interest from academia and industry due to its potential to fully utilize excitons in metal-free emitters, and is considered the next generation of OLEDs. In TADF emitters, a small energy difference (ΔEst) between the lowest excited singlet (S1) and triplet (T1) states is essential for achieving reverse intersystem crossing (RISC) from triplet to singlet excitons. Therefore, effective separation between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) is crucial. Connecting the electron donor (D) unit to the electron acceptor (A) unit via a highly twisted bridge to disrupt their conjugation effectively reduces ΔEst. However, the weakened DA connection also reduces the oscillation intensity (f) and reduces radiative decay. Among the three primary colors, blue and green have larger energy gaps Eg, resulting in smaller non-radiative transitions for blue and green light relative to red light, resulting in far higher device efficiency in solution-processable devices than red materials. Therefore, to address the above issues, improving the anti-intersystem crossing efficiency of red light materials is a key approach to achieving high device efficiency.

[0004] Patent application content

[0005] To overcome one of the problems existing in the aforementioned prior art, the primary objective of this application is to provide a solution-processable thermally activated delayed fluorescent red material. This solution-processable thermally activated delayed fluorescent red material can be used in the preparation of solution-processed red OLED devices, achieving performance comparable to that of blue / green TADF devices, thereby potentially achieving higher external quantum efficiency.

[0006] Another object of the present application is to provide a method for preparing the above-mentioned solution-processable thermally activated delayed fluorescent red light material.

[0007] Another object of the present application is to provide an application of the above-mentioned solution-processable thermally activated delayed fluorescent red light material in an organic light-emitting device.

[0008] The above-mentioned purpose of this application is achieved through the following technical solutions:

[0009] A solution-processable heat-activated delayed fluorescent red light material, wherein the structural formula of the solution-processable heat-activated delayed fluorescent red light material has the following molecular structure:

[0010]

[0011] Wherein, R1 and R2 are H or 2-(methoxycarbonyl)phenyl; when R1 is H, R2 is 2-(methoxycarbonyl)phenyl; when R2 is H, R1 is 2-(methoxycarbonyl)phenyl, wherein the molecular structure of the 2-(methoxycarbonyl)phenyl is as follows:

[0012]

[0013] Preferably, the molecular structure of the solution-processable thermally activated delayed fluorescent red light material is as follows:

[0014]

[0015] The present application also provides a method for preparing the above-mentioned solution-processable thermally activated delayed fluorescent red light material, comprising the following steps:

[0016] S1. Preparation of Intermediate A

[0017] 3,6-dibromo-9,10-phenanthrenequinone, phenoxazine, tris(dibenzylideneacetone)dipalladium, cesium carbonate, and tri-tert-butylphosphine tetrafluoroborate are added to anhydrous toluene in a molar ratio of 1:(2.3-3):(0.04-0.1):(2.25-3):(0.1-0.2) under nitrogen protection to obtain a mixed solution A having a concentration of 3,6-dibromo-9,10-phenanthrenequinone of 0.03-0.05 mmol / ml. The solution is heated to 100-120° C. and stirred for reaction. After the 3,6-dibromo-9,10-phenanthrenequinone is completely reacted, the palladium salt and cesium carbonate precipitated during the reaction are filtered and distilled to obtain a crude product A. The crude product A is purified using a chromatographic column, and then the remaining phenoxazine and by-products are removed with an eluent. After recrystallization, filtration, and high-temperature sublimation, an intermediate A is obtained.

[0018] S2. Preparation of intermediate product B1 or B2

[0019] Intermediate A and 4-bromobenzene-1,2-diamine or 3-bromobenzene-1,2-diamine are added to glacial acetic acid at a molar ratio of 1:(1.2-2) under nitrogen protection to obtain a mixed solution B having a concentration of intermediate A of 0.03-0.05 mmol / ml. The solution is heated to 100-130° C. and stirred for reaction. After the intermediate A is completely reacted, the solution is cooled to room temperature, poured into the prepared deionized water, filtered, and recrystallized from ethanol to obtain intermediate product B1 or B2.

[0020] S3. Preparation of target product m-DBPP or o-DBPP

[0021] The intermediate product B1 or B2, (2-(methoxycarbonyl)phenyl)boric acid, tetrakistriphenylphosphine palladium and 2M potassium carbonate are added to 1,4-dioxane in a molar ratio of 1:(1.5-2):(0.04-0.1):(2-4.5) under nitrogen protection to obtain a mixed solution C with a concentration of 0.03-0.05 mmol / ml of the intermediate product B1. The solution is heated to 100-105° C. and stirred for reaction. After the intermediate product is completely reacted, the solution is cooled to room temperature and extracted with ethyl acetate EA and saturated brine for 1-2 times. The organic phase is dried on a rotary evaporator, separated and purified by column separation using a mixed eluent of petroleum ether and dichloromethane, and further recrystallized to obtain the target product m-DBPP or o-DBPP.

[0022] Preferably, the eluents in step S1 are petroleum ether and dichloromethane, and the volume ratio of the eluents is 1:1.

[0023] Preferably, the eluents in step S3 are petroleum ether and dichloromethane, and the volume ratio of the eluents is 2:1.

[0024] The present application also provides an organic electroluminescent device, which includes a light-emitting layer formed by mixing a host material and the above-mentioned solution-processable thermally activated delayed fluorescent red light material.

[0025] Preferably, the mass proportion of the organic thermally activated delayed fluorescent material in the light-emitting layer is 0.4 to 20%.

[0026] More preferably, the organic electroluminescent device further comprises a substrate, an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode electrode arranged in sequence from bottom to top, and the thickness of the light-emitting layer is 20 to 40 nm.

[0027] More preferably, the anode electrode is ITO; the hole transport layer is PEDOT:PSS; the electron transport layer is TmPyPB; and the cathode electrode is LiF / Al.

[0028] More preferably, the main material is TCTA, and the substrate and anode electrodes are both ITO conductive glass.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. The present invention proposes a solution-processable, heat-activated delayed fluorescent red light material. Two heat-activated delayed fluorescent materials are synthesized using an electrophilic phenanthropyrazine structural unit as the receptor core. These materials exhibit low ΔEst and good TADF properties. Furthermore, the pyrazinophenanthrene structural unit possesses a certain degree of rigidity, which effectively suppresses nonradiative transitions and improves red light emission efficiency. Furthermore, the introduction of methyl benzoate significantly increases the solubility of the molecule, providing advantages for solution-processed device preparation.

[0031] 2. Application: Organic electroluminescent devices containing solution-processable thermally activated delayed fluorescent red light materials can be used for red light emission, with an external quantum efficiency (EQE) of up to 17%. They have excellent luminescence performance and broad application prospects, and are expected to be widely used in fields such as flat panel displays and solid-state lighting. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the hydrogen spectrum of the compound m-DBPP prepared in Example 1 of the present application measured by a Bruker 400 MHz superconducting nuclear magnetic resonance instrument.

[0033] Figure 2 This is the hydrogen spectrum of the compound o-DBPP prepared in Example 2 of the present application measured by a Bruker 400 MHz superconducting nuclear magnetic resonance instrument.

[0034] Figure 3 This is the absorption-emission (Abs-FL) spectrum of the m-DBPP thermally activated delayed fluorescent material obtained in Example 1 of the present application at room temperature.

[0035] Figure 4 Thermogravimetric analysis curves of organic thermally activated delayed fluorescent materials m-DBPP and o-DBPP.

[0036] Figure 5 This is a graph showing the redox potential of the organic thermally activated delayed fluorescent material molecule m-DBPP according to Example 1 of the present application.

[0037] Figure 6 This is a photoluminescence decay curve of the transient lifetime of 5% m-DBPP, an organic thermally activated delayed fluorescent material molecule doped in CBP according to Example 1 of the present application.

[0038] Figure 7 This is a photoluminescence decay curve diagram of the organic thermally activated delayed fluorescent material molecule 5% m-DBPP doped in CBP for measuring the long life span according to Example 1 of the present application.

[0039] Figure 8 This is an electroluminescence spectrum of an organic electroluminescent device containing the thermally activated delayed fluorescent material m-DBPP obtained in Example 1 of the present application.

[0040] Figure 9 This is a current density-voltage-luminescence intensity curve of an organic electroluminescent device containing the thermally activated delayed fluorescent material m-DBPP obtained in Example 1 of the present application.

[0041] Figure 10 This is a graph of the external quantum efficiency (EQE) of an organic electroluminescent device containing the thermally activated delayed fluorescent material m-DBPP obtained in Example 1 of the present application.

[0042] Figure 11 This is the absorption-emission (Abs-FL) spectrum of the thermally activated delayed fluorescent material molecule o-DBPP obtained in Example 2 of the present application.

[0043] Figure 12 This is a graph showing the redox potential of the thermally activated delayed fluorescent material molecule o-DBPP obtained in Example 2 of the present application.

[0044] Figure 13 This is a photoluminescence decay curve diagram of the transient lifetime measured by 5% o-DBPP, a thermally activated delayed fluorescent material molecule obtained in Example 2 of the present application, doped in CBP.

[0045] Figure 14 This is a photoluminescence decay curve diagram of the measured lifetime of 5% o-DBPP, an organic thermally activated delayed fluorescent material molecule obtained in Example 2 of the present application, doped in CBP.

[0046] Figure 15This is an electroluminescence spectrum of an organic electroluminescent device containing the thermally activated delayed fluorescent material o-DBPP obtained in Example 2 of the present application.

[0047] Figure 16 This is the current density-voltage-luminescence intensity curve of the organic electroluminescent device containing the thermally activated delayed fluorescent material o-DBPP obtained in Example 2 of the present application.

[0048] Figure 17 This is a graph of the external quantum efficiency (EQE) of an organic electroluminescent device containing the thermally activated delayed fluorescent material o-DBPP obtained in Example 2 of the present application.

[0049] Figure 18 The fluorescence and phosphorescence spectra of the thermally activated delayed fluorescent material m-DBPP obtained in Example 1 of the present application at 77K.

[0050] Figure 19 This is the fluorescence and phosphorescence spectra of the thermally activated delayed fluorescent material o-DBPP obtained in Example 2 of the present application at 77K. DETAILED DESCRIPTION

[0051] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0052] It should be noted that:

[0053] In this application, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0054] In this application, unless otherwise specified, percentages (%) or parts refer to percentages or parts by weight relative to the composition.

[0055] In this application, unless otherwise specified, the components involved or their preferred components can be combined with each other to form a new technical solution.

[0056] In this application, unless otherwise specified, the numerical range "a-b" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "1-5" indicates that all real numbers between "1-5" are listed herein, and "1-5" is merely an abbreviation for these numerical combinations.

[0057] The "ranges" disclosed in this application are in the form of lower limits and upper limits, which can be one or more lower limits, and one or more upper limits, respectively.

[0058] In this application, unless otherwise stated, each reaction or operation step can be carried out sequentially or in a sequential manner. Preferably, the reaction method herein is carried out sequentially.

[0059] Unless otherwise specified, the professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods or materials similar or equivalent to those described herein may also be applied to this application. This application provides a solution-processable heat-activated delayed fluorescent red light material, the structural formula of which has the following molecular structure:

[0060]

[0061] Wherein, R1 and R2 are H or 2-(methoxycarbonyl)phenyl; when R1 is H, R2 is 2-(methoxycarbonyl)phenyl; when R2 is H, R1 is 2-(methoxycarbonyl)phenyl, wherein the molecular structure of the 2-(methoxycarbonyl)phenyl is as follows:

[0062]

[0063] In some preferred embodiments, the molecular structure of the solution-processable thermally activated delayed fluorescent red light material is as follows:

[0064]

[0065] The present application also provides a method for preparing the above-mentioned solution-processable thermally activated delayed fluorescent red light material. The method comprises the following steps:

[0066] S1. Preparation of Intermediate A

[0067] 3,6-dibromo-9,10-phenanthrenequinone, phenoxazine, tris(dibenzylideneacetone)dipalladium, cesium carbonate, and tri-tert-butylphosphine tetrafluoroborate are added to anhydrous toluene in a molar ratio of 1:(2.3-3):(0.04-0.1):(2.25-3):(0.1-0.2) under nitrogen protection to obtain a mixed solution A having a concentration of 3,6-dibromo-9,10-phenanthrenequinone of 0.03-0.05 mmol / ml. The solution is heated to 100-120° C. and stirred for reaction. After the 3,6-dibromo-9,10-phenanthrenequinone is completely reacted, the palladium salt and cesium carbonate precipitated during the reaction are filtered and distilled to obtain a crude product A. The crude product A is purified using a chromatographic column, and then the remaining phenoxazine and by-products are removed with an eluent. After recrystallization, filtration, and high-temperature sublimation, an intermediate A is obtained.

[0068] S2. Preparation of intermediate product B1 or B2

[0069] Intermediate A and 4-bromobenzene-1,2-diamine or 3-bromobenzene-1,2-diamine are added to glacial acetic acid at a molar ratio of 1:(1.2-2) under nitrogen protection to obtain a mixed solution B having a concentration of intermediate A of 0.03-0.05 mmol / ml. The solution is heated to 100-130° C. and stirred for reaction. After the intermediate A is completely reacted, the solution is cooled to room temperature, poured into the prepared deionized water, filtered, and recrystallized from ethanol to obtain intermediate product B1 or B2.

[0070] S3. Preparation of target product m-DBPP or o-DBPP

[0071] The intermediate product B1 or B2, (2-(methoxycarbonyl)phenyl)boric acid, tetrakistriphenylphosphine palladium and 2M potassium carbonate are added to 1,4-dioxane in a molar ratio of 1:(1.5-2):(0.04-0.1):(2-4.5) under nitrogen protection to obtain a mixed solution C with a concentration of 0.03-0.05 mmol / ml of the intermediate product B1. The solution is heated to 100-105° C. and stirred for reaction. After the intermediate product is completely reacted, the solution is cooled to room temperature and extracted with ethyl acetate EA and saturated brine for 1-2 times. The organic phase is dried on a rotary evaporator, separated and purified by column separation using a mixed eluent of petroleum ether and dichloromethane, and further recrystallized to obtain the target product m-DBPP or o-DBPP.

[0072] In the preparation method described in the present application, the eluents in step S1 are petroleum ether and dichloromethane, and the volume ratio of the eluents is 1:1.

[0073] In the preparation method described in the present application, the eluents in step S3 are petroleum ether and dichloromethane, and the volume ratio of the eluents is 2:1.

[0074] The present application also provides an organic electroluminescent device, which includes a light-emitting layer formed by mixing a host material and the above-mentioned solution-processable thermally activated delayed fluorescent red light material.

[0075] In some preferred embodiments of the present application, the mass proportion of the organic thermally activated delayed fluorescent material in the light-emitting layer is 0.4 to 20%.

[0076] In some more preferred embodiments of the present application, the organic electroluminescent device further comprises a substrate, an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode electrode arranged in sequence from bottom to top, and the thickness of the light-emitting layer is 20 to 40 nm.

[0077] In some more preferred embodiments of the present application, the anode electrode is ITO; the hole transport layer is PEDOT:PSS; the electron transport layer is TmPyPB; and the cathode electrode is LiF / Al.

[0078] In some more preferred embodiments of the present application, the main material is TCTA, and the substrate and anode electrodes are both ITO conductive glass.

[0079] The following is a detailed description of the preparation method of the solution-processable thermally activated delayed fluorescent red light material compounds o-DBPP and m-DBPP.

[0080] Example 1

[0081] This embodiment proposes a solution-processable thermally activated delayed fluorescent red light material, the molecular structure of which is m-DBPP as shown below:

[0082]

[0083] The main synthetic route is as follows:

[0084]

[0085] The preparation method of the solution-processable thermally activated delayed fluorescent red light material m-DBPP specifically comprises the following steps:

[0086] S11. Preparation of Intermediate A

[0087] To a 100 mL two-necked round-bottom flask with a magnetic rod, 3,6-dibromo-9,10-phenanthrenequinone (0.726 g, 2 mmol), phenoxazine (1.1 g, 5.6 mmol), tris(dibenzylideneacetone)dipalladium (0.0915 g, 0.1 mmol), cesium carbonate (2.6 g, 8 mmol) and tri-tert-butylphosphine tetrafluoroborate (0.087 g, 0.3 mmol) were added in sequence, and nitrogen was replaced three times. Under nitrogen protection, 30 mL of anhydrous toluene was extracted with a 50 mL syringe and added to the round-bottom flask, and the reaction was stirred at an oil bath temperature of 110 ° C for 24 h; thin layer chromatography (TCL) spot plate detection was used. After 3,6-dibromo-9,10-phenanthrenequinone was completely reacted, it was cooled to room temperature, saturated brine and dichloromethane (DCM) were added for extraction, the liquid was separated to obtain the organic phase, and the aqueous phase was extracted twice with DCM. The organic phase was dried over anhydrous magnesium sulfate and filtered. The solvent in the resulting filtrate was removed under reduced pressure. The product was then purified on a silica gel column using petroleum ether and dichloromethane (PE / DCM = 1:1) as eluents to obtain a black solid (1.5 g, 2.6 mmol) in a yield of 73%.

[0088] The chemical reaction equation in this preparation method is as follows:

[0089]

[0090] The obtained intermediate was subjected to 400 MHz chromatographic analysis by a Bruker 400 MHz instrument. 1 HMNR spectrum test detection, obtained 1 HMNR (400 Mhz, CDCl3) δ 8.46 (d, J = 8.3 Hz, 1 H), 7.95 (d, J = 1.9 Hz, 1 H), 6.74 (qd, J = 7.9, 1.8 Hz, 4 H), 6.65 (ddd, J = 8.0, 6.8, 2.1 Hz, 2 H), 6.12 (dd, J = 7.9, 1.3 Hz, 2 H), indicating that intermediate A was obtained.

[0091] S12. Preparation of intermediate product B1

[0092] To a 100mL two-necked round-bottom flask equipped with a magnetic rod, add Intermediate A (1.14g, 2mmol) and 4-bromobenzene-1,2-diamine (0.372g, 2mmol) sequentially. The nitrogen atmosphere was purged three times. Under nitrogen protection, 50mL of glacial acetic acid was drawn into the round-bottom flask using a 20mL syringe. The reaction was stirred in an oil bath at 120°C for 12 hours. Thin-layer chromatography (TLC) was used for spot plate analysis. After Intermediate A had reacted completely, the reaction mixture was immediately removed and the product was poured into 200mL of deionized water. The resulting solid was filtered, washed with water, and then washed again with anhydrous ethanol to obtain a reddish-brown solid B1. This was then dried and used directly in the next reaction without column chromatography.

[0093] The chemical reaction equation in this preparation method is as follows:

[0094]

[0095] S13. Preparation of target product m-DBPP

[0096] To a 100 mL two-necked round-bottom flask with a magnetic rod was added B1 (1.44 g, 2 mmol), (2-(methoxycarbonyl)phenyl)boric acid (0.54 g, 3 mmol), tetrakistriphenylphosphine palladium (0.12 g, 0.1 mmol), and 2MK2CO35 ml. The nitrogen atmosphere was replaced three times. Under nitrogen protection, 50 mL of 1,4-dioxane was extracted with a 50 mL syringe and added to the round-bottom flask. The reaction was stirred in an oil bath at 100 ° C for 12 h; after B1 was completely reacted, it was cooled to room temperature and extracted with EA and saturated brine. The organic phase was spin-dried and purified by column chromatography using petroleum ether and dichloromethane (PE / DCM = 2:1) as eluent to obtain the red target product m-DBPP (2.1 g 2.7 mmol) in a yield of 71%.

[0097] The chemical reaction equation in this preparation method is as follows:

[0098]

[0099] Example 2

[0100] This embodiment proposes a solution-processable thermally activated delayed fluorescent red light material, the molecular structure of which is o-DBPP as shown below:

[0101]

[0102] The main synthetic route is as follows:

[0103]

[0104] The preparation method of the solution-processable thermally activated delayed fluorescent red light material m-DBPP specifically comprises the following steps:

[0105] S21. Preparation of Intermediate A

[0106] The synthesis route and synthesis method steps of step S21 here are exactly the same as those of step S11 in Example 1. For specific operations, please refer to the method and steps of step S11 in Example 1.

[0107] S22. Preparation of intermediate product B2

[0108] To a 100mL two-necked round-bottom flask with a magnetic rod, add intermediate A (1.14g, 2mmol) and 3-bromobenzene-1,2-diamine (0.372g, 2mmol) in sequence, replace nitrogen three times, and under nitrogen protection, use a 20mL syringe to extract 50mL of glacial acetic acid and add it to the round-bottom flask. Stir and react for 12h at an oil bath temperature of 120℃. Use thin layer chromatography (TCL) spot plate detection. After the intermediate A is completely reacted, immediately remove the reaction and pour the reaction product into 200ml of deionized water. Filter and wash the obtained solid with water and then wash it again with anhydrous ethanol to obtain a reddish-brown solid B2, which is dried and used directly in the next step without column chromatography. The chemical reaction equation in this preparation method is as follows:

[0109]

[0110] S23. Preparation of target product o-DBPP

[0111] To a 100 mL two-necked round-bottom flask with a magnetic electron, B2 (1.44 g, 2 mmol), (2-(methoxycarbonyl)phenyl)boric acid (0.54 g, 3 mmol), tetrakistriphenylphosphine palladium (0.12 g, 0.1 mmol), and 2MK2CO35 ml were added in sequence. The nitrogen was exchanged three times. Under nitrogen protection, 50 mL of 1,4-dioxane was extracted with a 50 mL syringe and added to the round-bottom flask. The reaction was stirred in an oil bath at 100 ° C for 12 h; thin layer chromatography (TCL) spot plate detection was used. After B2 was completely reacted, it was cooled to room temperature and extracted with EA and saturated brine. The organic phase was spin-dried and purified by chromatographic column using petroleum ether and dichloromethane (PE / DCM = 2:1) as eluent to obtain the red target product o-DBPP (1.9 g 2.7 mmol) in a yield of 70%.

[0112] The chemical reaction equation in this preparation method is as follows:

[0113]

[0114] Characterization and performance testing

[0115] The compounds prepared in Examples 1 and 2 were characterized and tested for their properties. Figures 1 to 11 shown.

[0116] Figure 1 The compound m-DBPP prepared in Example 1 of the present application was tested for hydrogen spectrum by a Bruker 400MHz superconducting nuclear magnetic resonance instrument, and the solvent was deuterated chloroform. The intermediate obtained was tested by a Bruker 500MHz instrument. 1 HMNR spectrum test detection, obtained 1H NMR(500MHz,Chloroform-d)δ9.71(t,J=8.5Hz,2H),8.49(d,J=2.1Hz,2H),8.44–8.37(m,2H),8.04(dd,J=7.8 ,1.3Hz,1H),7.88(dd,J=8.7,1.9Hz,1H),7.78(ddd,J=8.4,6.4,1.9Hz,2H),7.68(td,J=7.4,1.4Hz,1H),7.60( The integrated values ​​of the H NMR spectrum (1H NMR, dd, J = 7.8, 1.4 Hz, 1H), 7.56 (td, J = 7.6, 1.3 Hz, 1H), 6.72 (dt, J = 8.0, 1.7 Hz, 4H), 6.65 (s, 4H), 6.61–6.54 (m, 4H), 6.04 (dd, J = 8.3, 3.6 Hz, 4H), and 3.69 (s, 3H) are generally consistent with the theoretical values ​​of the target luminescent molecule, confirming the preparation of the solution-processable thermally activated delayed fluorescent red material m-DBPP. Furthermore, the peaks in the H NMR spectrum correspond one-to-one with the hydrogen atoms of the m-DBPP molecule, and the number of peaks is reasonable, indicating that m-DBPP has been synthesized with a single structure and high purity.

[0117] Figure 2 The compound o-DBPP prepared in Example 2 of this application was tested for hydrogen spectrum by a Bruker 400MHz superconducting nuclear magnetic resonance instrument, and the solvent was deuterated chloroform. 1 HMNR spectrum test detection, obtained 1H NMR(500MHz,Chloroform-d)δ9.72(d,J=8.5Hz,1H),9.22(d,J=8.5Hz,1H),8.48–8.40(m,3H),8.18–8.12(m,1H),8.02(dd,J=8. 5,7.0Hz,1H),7.96(dd,J=7.0,1.4Hz,1H),7.77(dd,J=8.5,1.9Hz,1H),7.72(td,J=7.5,1.5Hz,1H),7.66(dd,J=8.5,1.9Hz,1H) ,7.61(td,J=8.5,8.0,1.3Hz,2H),6.71(td,J=7.9,1.5Hz,4H),6.68–6.60(m,4H),6.55(dtd,J=15.5,7.7,1.6Hz,4H),6.03(dd,J=8.0,1.4Hz,2H),5.96(dd,J=8.0,1.4Hz,2H),3.23(s,3H). The integral values ​​of the H NMR spectrum are basically consistent with the theoretical values ​​of the target luminescent molecule, confirming that the solution-processable thermally activated delayed fluorescent red material o-DBPP has been obtained. Moreover, the peaks in the above H NMR spectrum can correspond one-to-one with the hydrogen atoms of the o-DBPP molecule, and the number is reasonable, indicating that o-DBPP has been synthesized with a single structure and high purity.

[0118] Figure 3 The figure in the figure shows the normalized absorption spectrum of the ultraviolet absorption and emission spectra of the compound m-DBPP in toluene solvent measured by a Shimadzu UV-2700 UV-visible spectrophotometer. The organic thermally activated delayed fluorescent material with the molecular structure of m-DBPP obtained in Example 1 was prepared in toluene with a concentration of 10-5 mol / L. The absorption and emission (Abs-FL) spectra were measured at room temperature. Figure 3 As shown, it can be seen that the absorption peak of the organic thermally activated delayed fluorescent material with the molecular structure of m-DBPP is at 459 nm, indicating that it has a good TADF charge transfer state, and the emission peak is at 620 nm, indicating that it can achieve red light emission.

[0119] Figure 4 Thermogravimetric analysis curves of organic thermally activated delayed fluorescent materials m-DBPP and o-DBPP. Figure 4 It can be seen that the thermal decomposition temperatures of m-DBPP and o-DBPP are 445℃ and 458℃, respectively, indicating that both have good thermal stability.

[0120] This application also applies the solution-processable phenanthropyrazine receptor-based organic thermally activated delayed fluorescent material m-DBPP prepared in Example 1 to an organic electroluminescent device. Specifically, the OLED structure includes, from bottom to top, a glass substrate, an ITO anode electrode, a 40nm-thick PEDOT:PSS hole transport layer, a 40nm-thick TCTA:m-DBPP luminescent layer, a 40nm-thick TmPyPB electron transport layer, and a LiF / Al cathode electrode. The TCTA:m-DBPP luminescent layer is a hybrid film composed of a main material TCTA and an organic thermally activated delayed fluorescent material with the molecular structure of m-DBPP.

[0121] like Figure 5 As shown, by testing the redox potential curve of the organic thermally activated delayed fluorescent material with a molecular structure of m-DBPP, it can be seen that its oxidation potential is -5.21eV and its reduction potential is -3.11eV, which can well match the energy level of the main material TCTA.

[0122] like Figure 6 and Figure 7 As shown in the figure, the luminescence decay curve of the organic thermally activated delayed fluorescence material with the tested molecular structure of m-DBPP in the TCTA:m-DBPP light-emitting layer shows that the transient lifetime of the thermally activated delayed fluorescence material with the molecular structure of m-DBPP is 76.1ns and the delayed lifetime is 5.8μs, indicating that it has significant TADF characteristics.

[0123] In Example 1 of the present application, a light-emitting layer of a thermally activated delayed fluorescent material was prepared. By testing the luminescence performance of an organic electroluminescent device containing a solution-processable phenanthropyrazine acceptor organic thermally activated delayed fluorescent material m-DBPP, the following results were obtained: Figure 8 The electroluminescence spectrum shown in the figure shows that the EL emission peak is 640nm, which is significantly red-shifted compared to 620nm in toluene solution. This may be attributed to the strong intermolecular interaction between the host and the guest, resulting in strong charge transfer. Figure 9 The current density-voltage-luminous intensity curve shown in FIG1 shows that the change trend of current density-voltage-luminous intensity matches that of the selected device structure. Figure 10 The external quantum efficiency (EQE) diagram shown in the figure shows that when the device of organic thermally activated delayed fluorescent material is at the maximum EQE, 100cd.m -2 and 1000cd.m -2 The device efficiency achieved high efficiencies close to 16.2%, 16.1% and 12.3%.

[0124] The organic thermally activated delayed fluorescent material with the molecular structure of o-DBPP obtained in Example 2 was prepared at a concentration of 10 -5 mol / L toluene, the absorption emission (Abs-FL) spectrum measured at room temperature, such as Figure 11 As shown, it can be seen that the absorption peak of the organic thermally activated delayed fluorescent material with the molecular structure of o-DBPP is at 463nm, indicating that it has a good TADF charge transfer state, and the emission peak is at 625nm, indicating that it can achieve red light emission.

[0125] This application also applies the solution-processable phenanthropyrazine receptor-based organic thermally activated delayed fluorescent material o-DBPP prepared in Example 2 to an organic electroluminescent device. Specifically, the OLED structure includes, from bottom to top, a glass substrate, an ITO anode electrode, a 40nm-thick PEDOT:PSS hole transport layer, a 40nm-thick TCTA:o-DBPP luminescent layer, a 40nm-thick TmPyPB electron transport layer, and a LiF / Al cathode electrode. The TCTA:o-DBPP luminescent layer is a hybrid film composed of a main material TCTA and an organic thermally activated delayed fluorescent material with the molecular structure of o-DBPP.

[0126] like Figure 12 As shown in the figure, the redox potential curve of the organic thermally activated delayed fluorescent material with the molecular structure of o-DBPP was tested. The redox potential curve of the organic thermally activated delayed fluorescent material with the molecular structure of o-DBPP was tested, and it was found that its oxidation potential was -5.22eV and its reduction potential was -3.09eV, which can well match the energy level of the host material TCTA.

[0127] like Figure 13 and Figure 14 As shown in the figure, the luminescence decay curve of the organic thermally activated delayed fluorescence material with the tested molecular structure of o-DBPP in the TCTA:o-DBPP light-emitting layer shows that the transient lifetime of the organic thermally activated delayed fluorescence material with the molecular structure of o-DBPP is 74.1ns and the delayed lifetime is 6.8μs, indicating that it has significant TADF characteristics.

[0128] In Example 2 of the present application, a light-emitting layer of an organic thermally activated delayed fluorescent material was prepared. By testing the luminescence performance of an organic electroluminescent device containing an organic thermally activated delayed fluorescent material (o-DBPP) based on a solution-processable pyrazinophenanthrene acceptor, the following results were obtained: Figure 15 The electroluminescence spectrum shown in the figure shows that the EL emission peak is 644nm, which is significantly red-shifted compared to 625nm in toluene solution. This may be attributed to the strong intermolecular interaction between the host and the guest, resulting in strong charge transfer. Figure 16 The current density-voltage-luminous intensity curve shown in FIG1 shows that the change trend of current density-voltage-luminous intensity matches that of the selected device structure. Figure 17 The external quantum efficiency (EQE) diagram shown in the figure shows that when the device of organic thermally activated delayed fluorescent material is at the maximum EQE, 100cd.m -2 and 1000cd.m -2 The device efficiency achieved high efficiencies close to 14.4%, 14.2% and 11%.

[0129] This application proposes a solution-processable thermally activated delayed fluorescent red light material and its preparation method and application. Two thermally activated delayed fluorescent materials are synthesized with electrophilic phenanthropyrazine structural units as receptor cores, with small ΔEst (from Figure 18 and Figure 19 It can be seen that the pyrazinophenanthrene structural unit has good TADF properties, and the pyrazinophenanthrene structural unit has a certain rigidity, which can effectively suppress non-radiative transitions and improve the red light emission efficiency. In addition, the introduction of methyl benzoate greatly increases the solubility of the molecule, providing favorable conditions for solution processing and device preparation, as shown in the following table:

[0130] Table 1

[0131]

[0132] This application also applies the prepared solution-processable thermally activated delayed fluorescent red light material to organic electroluminescent devices for red light emission, with an external quantum efficiency (EQE) of up to 17%, excellent luminescence performance, and broad application prospects. It is expected to be widely used in fields such as flat panel displays and solid-state lighting.

[0133] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0134] Although several embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and purpose of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A solution-processable thermally activated delayed fluorescent red light material, characterized in that: The molecular structure of the solution-processable thermally activated delayed fluorescent red light material is as follows: ； m-DBPP o-DBPP.

2. The method for preparing the solution-processable thermally activated delayed fluorescent red light material according to claim 1, characterized in that: The following steps are involved: S1. Preparation of Intermediate A 3,6-dibromo-9,10-phenanthrenequinone, phenoxazine, tris(dibenzylideneacetone)dipalladium, cesium carbonate, and tri-tert-butylphosphine tetrafluoroborate are added to anhydrous toluene in a molar ratio of 1:(2.3-3):(0.04-0.1):(2.25-3):(0.1-0.2) under nitrogen protection to obtain a mixed solution A having a concentration of 0.03-0.05 mmol / ml of 3,6-dibromo-9,10-phenanthrenequinone. The solution is heated to 100-120° C. and stirred for reaction. After the 3,6-dibromo-9,10-phenanthrenequinone is completely reacted, the palladium salt and cesium carbonate precipitated during the reaction are filtered and distilled to obtain a crude product A. The crude product A is purified using a chromatographic column, and then the remaining phenoxazine and by-products are removed with an eluent. After recrystallization, filtration, and high-temperature sublimation, an intermediate A is obtained. S2. Preparation of intermediate product B1 or B2 Add intermediate A and 4-bromobenzene-1,2-diamine or 3-bromobenzene-1,2-diamine in a molar ratio of 1:(1.2-2) to glacial acetic acid under nitrogen protection to obtain a mixed solution B with a concentration of intermediate A of 0.03-0.05 mmol / ml, heat to 100-130°C and stir to react. After intermediate A is completely reacted, cool to room temperature, pour into prepared deionized water, filter with suction, and then recrystallize from ethanol to obtain intermediate product B1 or B2; S3. Preparation of target product m-DBPP or o-DBPP The intermediate product B1 or B2, (2-(methoxycarbonyl)phenyl)boric acid, tetrakistriphenylphosphine palladium and 2M potassium carbonate are added to 1,4-dioxane in a molar ratio of 1:(1.5-2):(0.04-0.1):(2-4.5) under nitrogen protection to obtain a mixed solution C with a concentration of 0.03-0.05 mmol / ml of the intermediate product B1. The solution is heated to 100-105° C. and stirred for reaction. After the intermediate product is completely reacted, the solution is cooled to room temperature and extracted with ethyl acetate EA and saturated brine 1-2 times. The organic phase is dried on a rotary evaporator and purified by column separation using a mixed eluent of petroleum ether and dichloromethane. The target product m-DBPP or o-DBPP is further recrystallized. The structural formulas of the intermediate A, intermediate products B1 and B2 are as follows: 、 、 。 3. The method for preparing the solution-processable thermally activated delayed fluorescent red light material according to claim 2, characterized in that: The eluents in step S1 are petroleum ether and dichloromethane, and the volume ratio of the two is 1:

1.

4. The method for preparing the solution-processable thermally activated delayed fluorescent red light material according to claim 2, characterized in that: The eluents in step S3 are petroleum ether and dichloromethane, and the volume ratio of the eluents is 2:

1.

5. An organic electroluminescent device, characterized in that: The invention comprises a light-emitting layer formed by mixing a main material and the solution-processable thermally activated delayed fluorescent red light material according to claim 1 or 2.

6. The organic electroluminescent device according to claim 5, wherein: The mass proportion of the organic thermally activated delayed fluorescent material in the light-emitting layer is 0.4-20%.

7. The organic electroluminescent device according to claim 6, wherein: The organic electroluminescent device further comprises a substrate, an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode electrode which are sequentially arranged from bottom to top, and the thickness of the light-emitting layer is 20-40 nm.

8. The organic electroluminescent device according to claim 7, wherein: The anode electrode is ITO; the hole transport layer is PEDOT:PSS; the electron transport layer is TmPyPB; and the cathode electrode is LiF / Al.

9. The organic electroluminescent device according to claim 8, wherein: The main material is TCTA, and the substrate and anode electrodes are both ITO conductive glass.

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