An asymmetric heterocyclic compound, its preparation method, and an electroluminescent device thereof

Abstract

This invention belongs to the field of organic light-emitting materials and semiconductor technology, and provides an asymmetric heterocyclic compound, its preparation method, and an electroluminescent device. The structural formula of the asymmetric heterocyclic compound is as follows. Using the asymmetric heterocyclic compound provided by this invention as the host light-emitting material to prepare an electroluminescent device can effectively improve the luminous performance of the electroluminescent device and extend its service life.

Description

Technical Field

[0001] This invention belongs to the field of organic light-emitting materials and semiconductor technology, specifically relating to an asymmetric heterocyclic compound, its preparation method, and an electroluminescent device. Background Technology

[0002] In recent years, organic light-emitting diodes (OLEDs) have become a hot research topic in the lighting and display fields due to their excellent characteristics such as self-illumination, high brightness, high contrast, transparency, wearability, foldability, low energy consumption, wide viewing angle, and low temperature resistance.

[0003] OLED devices typically consist of functional layers such as an anode, cathode, hole transport layer (HTL), emission material layer (EML), and electron transport layer (ETL). The selection and combination of materials for the hole transport layer, emission material layer, and other functional layers have a significant impact on the current efficiency, driving voltage, emission color purity, emission brightness, and lifetime of OLED devices. Therefore, exploring functional layer materials with higher performance remains a key task in the current development of the OLED industry.

[0004] International patent application No. WO 2021 / 117809 A1 discloses a symmetrical naphthiazole and naphthiazole compound. This type of compound is used as an excellent blue light material in the OLED light-emitting layer. However, OLED devices based on this type of compound have insufficient stability and short lifespan.

[0005] Therefore, in order to meet people's higher requirements for OLED devices, there is an urgent need in this field to develop higher performance luminescent materials. Summary of the Invention

[0006] To address the problems of the prior art, this invention provides an asymmetric heterocyclic compound, its preparation method, and an electroluminescent device, thereby solving the problems of insufficient stability and lifespan of current electroluminescent devices.

[0007] This invention is achieved through the following technical solution: In a first aspect, the present invention provides an asymmetric heterocyclic compound, the structural formula of which is shown in formula (1):

[0008] R1 to R4 are independently selected from H, vinyl, C6 to C20 aryl, C6 to C20 heteroaryl and C1 to C10 alkyl, respectively, and R1 to R4 are independent of each other or bonded to each other; R5 is selected from substituted or unsubstituted C6-C40 aryl groups and substituted or unsubstituted C6-C40 heteroaryl groups; R5 is bonded to the host structure by a single bond; the heteroatom in the heteroaryl group includes at least one of O, S, Si, and N; the host structure is... .

[0009] Preferably, in the asymmetric heterocyclic compound, R5 is selected from one of the following groups A01 to A30:

[0010] Among the groups A01~A30, " "" indicates the position where R5 is bonded to the main structure, wherein groups A8, A10, A11, A14, A15, A17, A19, and A24~A28 are bonded by only one " "It is bonded to the main structure."

[0011] Preferably, R3 and R4 are H, and R1 and R2 are bonded to form a benzene ring; or, R1 and R4 are H, and R2 and R3 are bonded to form a benzene ring; or, R1 and R2 are H, and R3 and R4 are bonded to form a benzene ring; or, R1 and R2 are H, and R3 and R4 are bonded to form triphenylmethyl; or, R1 and R4 are H, and R2 and R3 are bonded to form cumene.

[0012] Preferably, the asymmetric heterocyclic compound is selected from one of the following compounds 1 to 135: .

[0013] Secondly, the present invention provides a method for preparing the asymmetric heterocyclic compound, comprising:

[0014] In the general reaction formula, X is Cl or Br; S1: It undergoes a digestion reaction with nitric acid (HNO3), acetic acid (AcOH), and acetic anhydride (Ac2O) to yield reactant b. n ; S2: Reactant b n It reacts with hydrazine hydrate to give intermediate Mn-1; S3: Intermediate Mn-1 reacts with tetrahydroxydiborane (B2(OH)4) under basic conditions of triethylamine (Et3N) to give intermediate Mn; S4: Intermediate Mn reacts with R5-X to obtain the asymmetric heterocyclic compound described in this invention; The reaction principle in S1 is as follows: nitric acid is activated by acetic anhydride and acetic acid to generate nitrate cations (NO2). + ), nitrocellulose as an electrophile and The reaction yields reactant b. n .

[0015] Preferably, S2 is: reactant b n Refluxing with hydrazine hydrate in ethanol, reactant b n Under the action of hydrazine hydrate, nitro reduction, intramolecular cyclization and dehydration / oxidation reactions occur to give intermediate Mn-1.

[0016] Preferably, S4 specifically comprises: intermediate Mn and R5-X (reactant a) n The asymmetric heterocyclic compound described in this invention undergoes a Buchwald-Hartwig cross-coupling reaction in the presence of Pd2(dba)3, Am-phos, sodium tert-butoxide, and toluene.

[0017] Thirdly, the present invention provides an electroluminescent device, comprising a cathode, an anode, and an organic layer located between the cathode and the anode, the organic layer comprising a hole transport layer, an emitting layer, and an electron transport layer, the hole transport layer being located between the anode and the emitting layer, and the electron transport layer being located between the cathode and the emitting layer; the emitting layer comprises an asymmetric heterocyclic compound as shown in formula (1).

[0018] Preferably, the components of the light-emitting layer include a host light-emitting material and a dopant light-emitting material; the host light-emitting material includes an asymmetric heterocyclic compound as shown in formula (1), and the dopant light-emitting material can be selected from high-performance compounds. , One of them.

[0019] Preferably, the mass fraction of the guest luminescent material in the present invention accounts for 1.0% to 3.0% of the total mass fraction of the luminescent layer.

[0020] Preferably, the electroluminescent device of the present invention further includes a hole injection layer (HIL), an electron blocking layer (EBL), a hole blocking layer (HBL), and an electron injection layer (EIL); the hole injection layer is located between the anode and the hole transport layer, the electron blocking layer is located between the hole transport layer and the light-emitting layer, the hole blocking layer is located between the light-emitting layer and the electron transport layer, and the electron injection layer is located between the electron transport layer and the cathode.

[0021] As the anode in an electroluminescent device, the anode material is preferably a material with a high work function in order to facilitate the injection of holes into the organic layer. Specific examples of anode materials that can be used in this invention include: metals such as vanadium, chromium, copper, zinc, and gold, or their alloys; oxides such as zinc oxide, aluminum oxide, or tin dioxide; and conductive polymers such as polypyrrole and polyaniline.

[0022] The hole injection layer, hole transport layer, electron blocking layer, hole blocking layer, electron transport layer and electron injection layer described in this invention are made of cost-effective materials in the industry. The compatibility between each layer needs to be determined through a series of tests and screening processes.

[0023] Preferably, the material of the hole injection layer in this invention is MoO3.

[0024] Preferably, the hole transport layer in this invention is selected from one of the following materials: .

[0025] Preferably, the material of the electron blocking layer in this invention is selected from one of the following materials: .

[0026] Preferably, the material of the hole-blocking layer in this invention is selected from one of the following materials: .

[0027] Preferably, the electron transport layer in this invention is selected from one of the following materials: .

[0028] As a cathode, the cathode material is preferably a material with a low work function in order to facilitate the injection of electrons into the organic layer. Specific examples of cathode materials that can be used in this invention include: metals such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, and lead, or alloys thereof.

[0029] The electroluminescent device of the present invention may further include a substrate on the outside of the anode and a covering protection layer (CPL) on the outside of the cathode.

[0030] As a substrate, it needs to have the characteristics of high mechanical strength, excellent thermal stability, excellent water resistance, and excellent transparency.

[0031] As a protective covering layer, it can improve the refractive index of the cathode surface and increase the light extraction rate; preferably... .

[0032] The hole injection layer, hole transport layer, electron blocking layer, light-emitting layer, hole blocking layer, electron transport layer, and electron injection layer can be prepared by various means or methods such as vacuum thermal evaporation, spin coating, and printing.

[0033] Fourthly, the present invention provides a method for fabricating the above-mentioned electroluminescent device. An anode is adhered to a substrate after pretreatment and cleaning. Then, under low-temperature conditions, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer of a predetermined thickness are sequentially vapor-deposited. A cathode and a protective layer are then sputtered at low temperature. Finally, the test device is packaged using conventional device testing and packaging methods to obtain the electroluminescent device.

[0034] Fifthly, the present invention provides a display panel, the display panel including the electroluminescent device as described above.

[0035] Compared with the prior art, the present invention has the following beneficial effects: The asymmetric heterocyclic compound provided by this invention In this invention, the triazole structure itself is thermally unstable. However, when it is cyclically combined with a multi-aryl aromatic ring to form a rigid fused-ring framework, its thermal instability can be significantly reduced or even eliminated. Simultaneously, this rigid fused-ring framework is connected to the R5 substituent, which has high conjugation properties, further enhancing the rigidity of the molecule. This effectively suppresses π-π stacking between molecules, reduces aggregation quenching, and improves device stability. Furthermore, the combination of the rigid fused ring of the asymmetric heterocyclic compound and the aromatic substituent R5 in this invention increases the glass transition temperature (Tg) of the molecule, enhancing the morphological stability of the film and extending the device's lifespan. In addition, the triazole structure in this invention is a typical electron transport group, while the R5-substituted aromatic ring can introduce hole transport capabilities, giving the molecule both electron and hole transport properties. This helps to balance the carrier concentration in the light-emitting layer, thereby improving luminous efficiency.

[0036] The electroluminescent device provided by this invention uses an asymmetric heterocyclic compound as the light-emitting layer material, which can effectively improve the light-emitting performance of the electroluminescent device and extend its service life. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the structure of the electroluminescent device described in an embodiment of the present invention; Figure 2 The NMR spectrum of compound 1 prepared in Example 1 of this invention; Figure 3 The NMR spectrum of compound 38 prepared in Example 2 of this invention; Figure 4 The NMR spectrum of compound 73 prepared in Example 3 of this invention; Figure 5 The NMR spectrum of compound 96 prepared in Example 4 of this invention; Figure 6 The NMR spectrum of compound 129 prepared in Example 5 of this invention; Figure 7 The NMR spectrum of compound 134 prepared in Example 6 of this invention.

[0039] Explanation of reference numerals in the attached figures: 1-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, 11-Covering protective layer. Detailed Implementation

[0040] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0041] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under standard conditions or as recommended by the manufacturer. All raw materials used in the following examples are commercially available products of conventional specifications in the art.

[0042] The reactants used in the embodiments of this invention are as follows:

[0043] Among them, b1, b3, b4, and b5 are commercially available products, while b2, b4, and b6 are obtained through chemical synthesis.

[0044] The synthesis process of the asymmetric heterocyclic compound described in this invention is as follows.

[0045] Preparation Example 1 (Synthesis of Compound 1):

[0046] Step 1: Procedure: Add reactant b1 (62.3 g, 0.3 mol), 80 wt% hydrazine hydrate (73 g, 1.2 mol), and 600 mL of ethanol to a 2 L three-necked flask. Start stirring and heat the reaction solution to 82 °C for 12 h. After the reaction is complete, remove the solvent by drying under reduced pressure. Recrystallize with an aqueous solution of ethanol (ethanol to water volume ratio of 1:1, 300 mL) to obtain intermediate M1-1, weighing 41.7 g, with a yield of 75.1% and an HPLC purity of 98%.

[0047] Step Two: Procedure: Add intermediate M1-1 (37.0 g, 0.2 mol), tetrahydroxydiboron (21.5 g, 0.24 mol), triethylamine (24.3 g, 0.24 mol), and 400 mL of acetonitrile to a 1 L three-necked flask. Start stirring and heat the reaction solution to 50 °C for 2 h. After the reaction is complete, remove the solvent by drying under reduced pressure to obtain the residue. Purify the residue by silica gel column chromatography (ethyl acetate: petroleum ether = 10:1) to obtain intermediate M1, weighing 32.2 g, with a yield of 95.3% and an HPLC purity of 98%.

[0048] Step 3: Under nitrogen protection, take a 100 mL three-necked flask, add intermediate M1 (1.7 g, 0.01 mol), reactant a4 (3.6 g, 0.01 mol), and 50 mL toluene, stir until the solution is clear, add Pd2(dba)3 (0.092 g, 0.1 mmol), Am-phos (0.08 g, 0.3 mmol), and sodium tert-butoxide (1.9 g, 0.02 mol), then heat to 110 °C and continue the reaction for 10 h; after the reaction is complete, filter with diatomaceous earth while hot, cool the filtrate to room temperature, add purified water for washing, separate the liquid and retain the organic phase, then extract the aqueous phase with ethyl acetate, combine the organic phases, dry and concentrate the organic phase with anhydrous magnesium sulfate, and then purify by silica gel column chromatography with dichloromethane / n-heptane at a volume ratio of 1:3 to obtain compound 1, weighing 3.6 g, yield 73.2%, HPLC purity 99%, LC-MS showed a molecular weight of 497.6.

[0049] The proton NMR data of compound 1 are as follows Figure 2 Shown: 1H NMR (500 MHz, CD3OD) δ 8.51 (s, 1H), 8.22 – 8.09 (m, 6H), 7.96 (s, 1H), 7.82 (s, 1H), 7.71 (q, J = 15.0 Hz, 5H), 7.61 (s, 2H), 7.53 – 7.38 (m, 7H).

[0050] Preparation Example 2 (Synthesis of Compound 73):

[0051] Step 1: Procedure: Add 200 mL of acetic acid and 100 mL of acetic anhydride to a 1 L three-necked flask, start stirring, and cool the reaction solution to 0 °C. Slowly add 102.4 g (0.632 mol) of 2-chloronaphthalene. After the reaction solution becomes clear, slowly add 150 mL of concentrated nitric acid dropwise at 0 °C. During the dropwise addition, control the temperature of the reaction system between 0 and 10 °C. After the dropwise addition is complete, raise the temperature of the system to 30 °C and react for 5 h. After the reaction is complete, pour the reaction solution into a 1 L ice-water mixture and stir. At this time, a large amount of solid precipitates out. Filter, wash the solid with water, and recrystallize (ethanol and water are mixed at a volume ratio of 1:1, using 500 mL) to obtain reactant b2, weighing 74.7 g, with a yield of 56.9% and an HPLC purity of 97%.

[0052] Step Two: Procedure: Referring to the synthesis process of intermediate M1-1, reactant b1 was replaced with reactant b2 (62.3g, 0.3mol) to obtain intermediate M2-1, weighing 41.1g, with a yield of 73.9% and HPLC purity of 98%.

[0053] Step 3: Procedure: Following the synthesis process of intermediate M1, intermediate M1-1 was replaced with intermediate M2-1 (37.0 g, 0.2 mol) to obtain intermediate M2, weighing 31.4 g, with a yield of 92.9% and an HPLC purity of 98%.

[0054] Step 4: Referring to the synthesis process of compound 1, replace intermediate M1 with intermediate M2 (1.7 g, 0.01 mol), and simultaneously replace reactant a4 with reactant a. 42 (4.3 g, 0.01 mol) yielded compound 73, weighing 3.5 g, with a yield of 68.4%, HPLC purity of 99%, and LC-MS showing a molecular weight of 515.6.

[0055] The 1H NMR data of compound 73 are as follows Figure 3 As shown: 1 H NMR (500 MHz, CD3OD) δ 8.51 (s,1H), 8.11 (s, 1H), 7.96 (s, 1H), 7.82 (s, 1H), 7.72 (s, 1H), 7.67 (s, 1H),7.54 (s, 1H), 7.32 (d, J = 5.0 Hz, 4H), 7.18 (d, J = 15.0 Hz, 7H), 7.00 (s, 3H).

[0056] Preparation Example 3 (Synthesis of Compound 38):

[0057] Step 1: Procedure: Referring to the synthesis process of intermediate M1-1, reactant b1 was replaced with reactant b3 (62.3g, 0.3mol) to obtain intermediate M3-1, weighing 42.5g, with a yield of 76.5% and HPLC purity of 98%.

[0058] Step Two: Procedure: Referring to the synthesis process of intermediate M1, intermediate M1-1 was replaced with intermediate M3-1 (37.0 g, 0.2 mol) to obtain intermediate M3, weighing 31.2 g, with a yield of 92.3% and HPLC purity of 98%.

[0059] Step 3: Referring to the synthesis process of compound 1, replace intermediate M1 with intermediate M3 (1.7 g, 0.01 mol), and simultaneously replace reactant a4 with reactant a. 15 (3.6 g, 0.01 mol) yielded compound 38, weighing 4.2 g, with a yield of 73.2%, HPLC purity of 99%, and LC-MS showing a molecular weight of 571.7.

[0060] The 1H NMR data of compound 38 are as follows Figure 4 As shown: 1 H NMR (500 MHz, CD3OD) δ 9.00 (s,2H), 8.59 (s, 1H), 8.34 (s, 1H), 8.25 (s, 1H), 7.82 (d, J = 20.0 Hz, 4H), 7.67 (d, J = 20.0 Hz, 5H), 7.59 – 7.37 (m, 9H), 7.27 (s, 2H).

[0061] Preparation Example 4 (Synthesis of Compound 96):

[0062] Step 1: Procedure: Referring to the synthesis process of intermediate M1-1, reactant b1 was replaced with reactant b4 (95.5g, 0.3mol) to obtain intermediate M4-1, weighing 59.5g, with a yield of 78.9% and HPLC purity of 98%.

[0063] Step Two: Procedure: Following the synthesis process of intermediate M1, intermediate M1-1 was replaced with intermediate M4-1 (50.3g, 0.2mol) to obtain intermediate M4, weighing 40.6g, with a yield of 86.2% and HPLC purity of 98%.

[0064] Step 3: Referring to the synthesis process of compound 1, intermediate M1 was replaced with intermediate M4 (2.4 g, 0.01 mol), and reactant a4 was replaced with reactant a9 (3.9 g, 0.01 mol), yielding compound 96, weighing 4.4 g, with a yield of 75.1%, HPLC purity of 99%, and LC-MS showing a molecular weight of 587.8.

[0065] The 1H NMR data of compound 96 are as follows Figure 5 As shown: 1 H NMR (500 MHz, CD3OD)δ 8.59 (s, 1H),8.41 (s, 1H), 8.33 (s, 1H), 8.24 (s, 1H), 7.96 (s, 2H), 7.80 (d, J = 5.0 Hz,6H), 7.69 (s, 1H), 7.61 – 7.31 (m, 10H), 1.69 (s, 6H).

[0066] Preparation Example 5 (Synthesis of Compound 129):

[0067] Step 1: Procedure: Referring to the synthesis process of intermediate M1-1, reactant b1 was replaced with reactant b5 (132.7g, 0.2mol) to obtain intermediate M5-1, weighing 80.3g, with a yield of 71.3% and HPLC purity of 98%.

[0068] Step Two: Procedure: Following the synthesis procedure of intermediate M1, intermediate M1-1 was replaced with intermediate M5-1 (75.1g, 0.2mol) to obtain intermediate M5, weighing 65.6g, with a yield of 91.3% and HPLC purity of 98%.

[0069] Step 3: Referring to the synthesis process of compound 1, replace intermediate M1 with intermediate M5 (3.6 g, 0.01 mol), and simultaneously replace reactant a4 with reactant a. 38 (2.7 g, 0.01 mol) yielded compound 129, weighing 3.7 g, with a yield of 66.5%, HPLC purity of 99%, and LC-MS showing a molecular weight of 551.7.

[0070] The 1H NMR data of compound 129 are as follows Figure 6 As shown: 1H NMR (500 MHz, CD3OD) δ 8.24 (d, J= 4.5 Hz, 2H), 8.03 (t, J = 10.1 Hz, 3H), 7.90 (d, J = 5.0 Hz, 3H), 7.64 (s,1H), 7.53 (d, J = 5.2 Hz, 2H), 7.45 (s, 1H), 7.34 (s, 1H), 7.26 (s, 4H), 7.18 (s, 2H), 7.10 (s, 4H), 1.69 (s, 6H).

[0071] Preparation Example 6 (Synthesis of Compound 134):

[0072] Step 1: Procedure: Referring to the synthesis process of reactant b2, 2-chloronaphthalene was replaced with 9-bromophenanthrene (77.1 g, 0.3 mol) to obtain reactant b5, weighing 51.8 g, with a yield of 57.2% and an HPLC purity of 98%.

[0073] Step Two: Procedure: Referring to the synthesis process of intermediate M1-1, reactant b1 was replaced with reactant b6 (60.4 g, 0.2 mol) to obtain intermediate M6-1, weighing 35.2 g, with a yield of 74.9% and an HPLC purity of 98%.

[0074] Step 3: Procedure: Following the synthesis procedure of intermediate M1, intermediate M1-1 was replaced with intermediate M6-1 (23.5g, 0.1mol) to obtain intermediate M6, weighing 20.7g, with a yield of 94.5% and HPLC purity of 98%.

[0075] Step 4: Referring to the synthesis process of compound 1, replace intermediate M1 with intermediate M6 (2.2 g, 0.01 mol), and simultaneously replace reactant a4 with reactant a. 18 (3.6 g, 0.01 mol) yielded compound 134, weighing 3.5 g, with a yield of 69.7%, HPLC purity of 99%, and LC-MS showing a molecular weight of 495.7.

[0076] The 1H NMR data of compound 134 are as follows Figure 7 As shown: 1H NMR (500 MHz, CD3OD) δ 8.98 (s,4H), 8.93 (s, 1H), 8.33 (s, 1H), 8.11 (s, 2H), 7.89 (t, J = 15.0 Hz, 4H), 7.66 (dd, J = 32.5, 7.5 Hz, 9H).

[0077] The synthesis of other compounds follows the same procedures as in Preparation Examples 1-6 above, using only the corresponding reactants a (a1-a2). 46 The reactants b and b6 can be replaced.

[0078] The electroluminescent devices of Examples 1-44 and Comparative Examples 1-5 were prepared according to the structural information of the light-emitting layer of the electroluminescent device given in Table 1.

[0079] Schematic diagrams of the electroluminescent devices in the various embodiments and comparative examples of this invention are shown below. Figure 1 As shown, it includes a substrate 1, an anode 2, a hole injection layer 3, a hole transport layer 4, an electron blocking layer 5, a light-emitting layer 6, a hole blocking layer 7, an electron transport layer 8, an electron injection layer 9, a cathode 10, and a protective cover layer 11.

[0080] Example 1: Electroluminescent device containing compound 1 This embodiment of the electroluminescent device containing compound 1 comprises, from anode to cathode, polyethylene terephthalate (PET) plastic, indium tin oxide (ITO) conductive glass, MoO3, HT-2, EB-2, a light-emitting layer, HB-1, ET-2, LiF, Al-Mg (Al:Mg=9:1), and CPL; the CPL is made of the following material: ; The light-emitting layer is composed of compound 1 and Ir(dfpypy)3 in a mass ratio of 99:1.

[0081] The method for preparing the electroluminescent device containing compound 1 includes the following steps: 1. Using 1.5mm PET plastic as substrate 1 and 0.15mm ITO conductive glass as anode 2, the substrate is washed in sequence by alkaline washing, pure water washing, drying, and ultraviolet-ozone washing to remove organic residues from the surfaces of the PET plastic and ITO conductive glass.

[0082] 2. A layer of ITO conductive glass is adhered to PET plastic. Using a vacuum evaporation apparatus, a 20nm thick MoO3 layer is deposited as a hole injection layer 3. Then, a 110nm thick HT-2 layer is deposited as a hole transport layer 4. Subsequently, a 30nm thick EB-2 layer is deposited as an electron blocking layer 5. On the EB-2 layer, a 60nm thick luminescent layer 6 is formed by compound 1 (host luminescent material) and Ir(dfpypy)3 (guest luminescent material) with a mass ratio of 99:1 is deposited. A 10 nm thick HB-1 layer is deposited on the light layer 6 as a hole blocking layer 7. Then, a 30 nm thick ET-2 layer is deposited as an electron transport layer 8. A 16 nm thick LiF layer is deposited on the electron transport layer 8 as an electron injection layer 9. After the electron injection layer 9 is deposited, a 10 nm thick Al-Mg (Al:Mg=9:1) alloy is sputtered at low temperature as a cathode 10. Finally, a 40 nm thick CPL layer is deposited on the cathode 10 as a protective cover layer 11.

[0083] 3. Vacuum encapsulation of MoO3, HT-2, EB-2, light-emitting layer 6, HB-1, ET-2 and LiF was performed to prepare an electroluminescent device.

[0084] Examples 2-3 The difference between Examples 2 and 3 and Example 1 is that the mass ratios of compound 1 and Ir(dfpypy)3 are 97:3 and 98:2, respectively.

[0085] Examples 4 to 38 The difference from Example 3 is that in Examples 4 to 38, compounds 2 to 29, 33, 62, 127 to 129, 132, and 133 were used as the main luminescent materials of the luminescent layer 6, respectively.

[0086] Comparative Example 1 The difference from Example 1 is that, in the light-emitting layer 6, the international patent application with publication number WO 2021 / 117809 A1 is used. As the main luminescent material.

[0087] The structure of the electroluminescent device in Comparative Example 1 is as follows: PET substrate / ITO / MoO3 (20nm) / HT-2 (110nm) / EB-2 (30nm) / db-1:Ir(dfpypy)3=99:1 (60nm) / HB-1 (10nm) / ET-2 (30nm) / LiF (16nm) / Al:Mg=9:1 (10nm) / CPL (40nm).

[0088] Comparative Example 2 The difference from Example 2 is that, in the light-emitting layer 6, the international patent application with publication number WO 2021 / 117809 A1 is used. As the main luminescent material.

[0089] The structure of the electroluminescent device in Comparative Example 2 is as follows: PET substrate / ITO / MoO3 (20nm) / HT-2 (110nm) / EB-2 (30nm) / db-2:Ir(dfpypy)3=97:3 (60nm) / HB-1 (10nm) / ET-2 (30nm) / LiF (16nm) / Al:Mg=9:1 (10nm) / CPL (40nm).

[0090] Comparative Example 3 The difference from Example 3 is that, in the light-emitting layer 6, the international patent application with publication number WO 2021 / 117809 A1 is used. As the main luminescent material.

[0091] The structure of the electroluminescent device in Comparative Example 3 is as follows: PET substrate / ITO / MoO3 (20nm) / HT-2 (110nm) / EB-2 (30nm) / db-3:Ir(dfpypy)3=98:2 (60nm) / HB-1 (10nm) / ET-2 (30nm) / LiF (16nm) / Al:Mg=9:1 (10nm) / CPL (40nm).

[0092] The electroluminescent devices from the above embodiments and comparative examples were fabricated into 30mm × 30mm samples. The anode and cathode were connected using an industry-known driving circuit, and various luminescence performance indicators were tested. The test results are shown in Table 1.

[0093] Table 1

[0094] Note: The current density during the test was 20 mA / cm². 2 Tg refers to the glass transition temperature of a material, and lifetime T95 refers to the time it takes for the brightness of a device to decay to 95% of its initial brightness.

[0095] As can be seen from the test results in Table 1, compared with Comparative Examples 1-3, the electroluminescent devices prepared using the preferred asymmetric heterocyclic compounds of this invention in Examples 1-38 have significant advantages in overall luminous efficiency, with current efficiency increased by about 2 times and lifespan (LT95) extended by about 2 times. This may be because the symmetry of the structure of the host luminescent material in Comparative Examples 1-3 causes intermolecular stacking, leading to aggregation quenching, which affects the stability and lifespan of the device. In contrast, the asymmetric heterocyclic compounds of this invention can effectively suppress intermolecular π-π stacking, reduce aggregation quenching, and improve device stability.

[0096] The data from the electroluminescent devices in Examples 1 to 3 show that when the mass of the guest light-emitting material in the light-emitting layer is in the range of 1% to 3%, the overall luminous efficiency of the electroluminescent devices is similar; when the mass of the guest light-emitting material is 2%, the luminous performance of the electroluminescent device prepared is slightly better than that in Examples 1 and 2.

[0097] As can be seen from the test results in Table 1, compared with Comparative Examples 1-3, the Tg of the compounds corresponding to Examples 1-38 is significantly improved, especially the Tg of Examples 5 (corresponding to compound 3), Examples 6 (corresponding to compound 4), Examples 11 (corresponding to compound 9), and Examples 33 (corresponding to compound 62), which are all above 150°C. This may be due to the large volume and rigid structure of the R5 substituent in compounds 3, 4, 9, and 62. In other words, the larger the volume of the R5 substituent, the stronger its rigidity. The greater the intramolecular rotational steric hindrance, the worse the overall conformational flexibility of the molecule, and the higher the activation energy of chain segment motion, thus the Tg of the compound increases significantly.

[0098] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. An asymmetric heterocyclic compound, characterized in that, The structural formula of the asymmetric heterocyclic compound is shown in formula (1): R1 to R4 are independently selected from H, vinyl, C6 to C20 aryl, C6 to C20 heteroaryl and C1 to C10 alkyl, respectively, and R1 to R4 are independent of each other or bonded to each other; R5 is selected from substituted or unsubstituted C6-C40 aryl groups and substituted or unsubstituted C6-C40 heteroaryl groups; R5 is bonded to the host structure by a single bond; the host structure is... .

2. The asymmetric heterocyclic compound according to claim 1, characterized in that, The heteroatom in the heteroaryl group includes at least one of O, S, Si, and N.

3. The asymmetric heterocyclic compound according to claim 1, characterized in that, R5 is selected from one of the following groups A01 to A30: Among the groups A01~A30, " "" indicates the position where R5 is bonded to the main structure, wherein groups A8, A10, A11, A14, A15, A17, A19, and A24~A28 are bonded together by only one " "It is bonded to the main structure." 4. The asymmetric heterocyclic compound according to claim 1, characterized in that, R3 and R4 are H, and R1 and R2 are bonded to form a benzene ring; or, R1 and R4 are H, and R2 and R3 are bonded to form a benzene ring; or, R1 and R2 are H, and R3 and R4 are bonded to form a benzene ring; or, R1 and R2 are H, and R3 and R4 are bonded to form triphenylmethyl; or, R1 and R4 are H, and R2 and R3 are bonded to form cumene.

5. The asymmetric heterocyclic compound according to claim 1, characterized in that, Selected from one of the following compounds: 1 to 135 。 6. A method for preparing the asymmetric heterocyclic compound according to any one of claims 1 to 5, characterized in that, include: Make reactant b n It reacts with hydrazine hydrate to give intermediate Mn-1; Intermediate Mn-1 was reacted with tetrahydroxydiborane (B2(OH)4) under alkaline conditions of triethylamine (Et3N) to obtain intermediate Mn; The intermediate Mn and R5-X were reacted to obtain the aforementioned asymmetric heterocyclic compound; in, X is either Cl or Br.

7. The method for preparing the asymmetric heterocyclic compound according to claim 6, characterized in that, The intermediate Mn and R5-X are reacted under the action of Pd2(dba)3, Am-phos, and sodium tert-butoxide to obtain the aforementioned asymmetric heterocyclic compound.

8. An electroluminescent device, characterized in that, It includes a cathode, an anode, and an organic layer located between the cathode and the anode. The organic layer includes a hole transport layer, a light-emitting layer, and an electron transport layer. The hole transport layer is located between the anode and the light-emitting layer, and the electron transport layer is located between the cathode and the light-emitting layer. The composition of the light-emitting layer includes an asymmetric heterocyclic compound as shown in formula (1).

9. The electroluminescent device according to claim 8, characterized in that, The components of the light-emitting layer include a host light-emitting material and a guest light-emitting material; the host light-emitting material includes an asymmetric heterocyclic compound as shown in formula (1).

10. The electroluminescent device according to claim 9, characterized in that, The object luminescent material is , One of them.

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