An organic electroluminescent material and its application in optoelectronic devices

Abstract

Organic electroluminescent material, which is the compound with the structure of formula (I): where L for a single bond, substituted or unsubstituted phenylene, substituted or unsubstituted biphenyls, or substituted or unsubstituted pyridylene; Ar is one of the following groups: B is selected from O, S, Se; X1-X8 are independently selected from N or CR, and each six-membered ring contains at most one N atom, and R is independently selected from one of hydrogen, deuterium, halogen, alkyl, heteroalkyl, aryl, heteroaryl, or aryloxy.

Description

Technical field

[0001] The present invention relates to the field of organic electroluminescent materials, in particular a light-emitting material based on imidazole and indenopyrrole building blocks and an optoelectronic device thereof. Background of the technology

[0002] In recent years, organic light-emitting diodes (OLEDs) have attracted considerable attention in academia and industry as a lighting and display technology with very promising applications. OLED devices exhibit self-illumination, wide viewing angles, short response times, and potential applications in the fabrication of flexible devices, making them a strong competitor in the next generation of display and lighting technology. Currently, OLEDs still face challenges such as low efficiency and short lifespans, necessitating further research.

[0003] Since Forrest et al. reported electrophosphorescent devices (PHOLEDs) in 1998, PHOLEDs have attracted attention due to their highly efficient use of triplet and singlet excitons for light emission. High-efficiency PHOLED devices typically have a multilayer structure, and their advantage lies in the ease with which charge carrier injection, transport, and recombination can be controlled. The light-emitting layer usually employs host-guest doping technology. If the guest doping concentration is high, concentration quenching and T1-T1 annihilation occur, leading to a reduction in light yield. To overcome these problems, the guest material is commonly doped within the host material to "dilute" the guest material concentration.The excitons generated in the host are transferred to the guest via Förster and Dexter energy transfer, and the excited guest emits radiant light and returns to its ground state. Therefore, to obtain highly efficient PHOLED devices, it is particularly important to develop new, high-performance host materials.

[0004] The host material in the light-emitting layer can be divided into three types: hole-type, electron-type, and bipolar-type. Using only hole- or electron-type host material can easily lead to charge transport imbalances in the light-emitting layer and a reduction in efficiency. Furthermore, it narrows the recombination region of charge carriers, increasing the local exciton density and accelerating T1-T1 annilation, which does not improve device performance.The above-mentioned problems can be effectively solved with bipolar materials, not only by balancing holes and electrons in the device and expanding the recombination range of charge carriers, but also by simplifying the device's construction, which is of great importance for optimizing the performance of organic optoelectronic devices.

[0005] Organic electroluminescent materials are also known, for example, from the documents CN 104 557 875 A, WO 2014 / 058183 A1 and KR 10 2010 0 110 495 A. Content of the invention

[0006] The object of the present invention is to provide a bipolar organic electroluminescent material based on imidazole and indenopyrrole building blocks, wherein the spiro structure of the molecule is advantageous in preventing stacking between molecules. The organic electroluminescent material according to the invention exhibits improved thermal stability and balanced charge carrier transport performance, while simultaneously offering higher luminous efficacy and color purity.

[0007] Organic electroluminescent material is the compound with the structure of formula (I) : where L stands for a single bond, substituted or unsubstituted phenylene, substituted or unsubstituted biphenylene, or substituted or unsubstituted pyridylene; Ar is one of the following groups: B is selected from O, S, Se; X1-X8 are independently selected from N or CR, and each six-membered ring contains at most one N atom, and R is independently selected from one of hydrogen, deuterium, halogen, alkyl, heteroalkyl, aryl, heteroaryl, or aryloxy.

[0008] Preferably, L is a single bond or substituted or unsubstituted phenylene; Ar is one of the following groups: B is selected from O, S; X1-X8 are independently selected from N or CR, and each six-membered ring contains at most one N atom, and R is independently selected from one of hydrogen, deuterium, alkyl and aryl.

[0009] Preferably, L is a single bond or phenylene; Ar is one of the following groups: B is selected from O, S; One of X1-X8 is N, and the remainders are CH. L is more preferred as a single bond; Ar is one of the following groups: B is selected from O, S; One of X1-X8 is N, and the remainders are CH; L is more preferred as a single bond; Ar is one of the following groups: B is selected from O, S; X1-X8 are CH; Furthermore, the light-emitting materials of formula (I) according to the invention are preferably the following compounds 1-36, but are not limited to the structures listed: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

[0010] The synthesis procedure for the above compounds comprises the following steps: (1) the compound a and YL-Ar are available, Y is halogen; (2) Under nitrogen protection, compound a and compound YL-Ar, Pd (OAc)2, PPh3, K2CO3 and DMAc are heated to 150 °C and the compound represented by formula (I) is obtained by reaction.

[0011] The Y is either chlorine or bromine.

[0012] The manufacturing process for compound a is as follows: A) Compound a-1 is reacted with o-dihalopyrazine to obtain compound a-2; B) Compound a-2 is reacted with imidazole to obtain compound a-3; C) By completing the ring closure of the connection a-3, the connection a is obtained;

[0013] The reaction formula is shown as follows:

[0014] The above-mentioned compounds are used in organic electroluminescent devices, mechanoluminescent devices, organic field-effect transistors, organic solar cells, and chemical sensors.

[0015] The organic electroluminescence device in the present invention comprises a cathode, an anode and an organic layer, wherein the organic layer consists of one or more layers of a hole injection layer, a hole transport layer, a light-emitting layer, a hole-blocking layer, an electron injection layer and an electron transport layer, and each layer of this organic layer need not be present.

[0016] At least one of the hole injection layer, hole transport layer, hole blocking layer, light-emitting layer and / or electron transport layer contains the compound shown in formula (I).

[0017] Preferably, the layer in which the compound of structural formula (1) is located is a light-emitting layer or an electron transport layer.

[0018] The total thickness of the organic layer of the device of the present invention is 1-1000 nm, preferably 1-500 nm and more preferably 5-300 nm.

[0019] The organic layer can be formed into a thin film by vapor deposition or a solution process.

[0020] The test results show that, compared to the usual light-emitting material CBP, which can easily transport holes, the organic light-emitting material of the present invention has better thermal stability and a capacity to compensate for charge carrier transport, while at the same time improving light output and color purity, and may possibly be used in the field of organic electroluminescent devices. Description of the drawings Fig. Figure 1 is a structural diagram of the organic electroluminescence device of the present invention, wherein 10 represents a glass substrate, 20 an anode, 30 a hole injection layer, 40 a hole transport layer, 50 a light-emitting layer, 60 an electron transport layer, 70 an electron injection layer and 80 a cathode. Detailed designs

[0021] To further explain the present invention, the following examples are given, but are not limited to them.

[0022] Compounds 1-1 and 13-1, which are not specifically mentioned, are commercially available. Example 1: Synthesis of compound 1 Synthesis from intermediate a-2

[0023] Under nitrogen protection, the compounds α-1 (6.10 g, 20.0 mmol) (see synthesis in Org. Lett., 2010, 12, 296-299), o-dibromobenzene (9.44 g, 40.0 mmol), CuI (380 mg, 2.0 mmol), trans-1,2-cyclohexanediamine (456 mg, 4.0 mmol), K3PO4 (12.74 g, 60.0 mmol), and xylene (100 ml) were successively added to a Schlenk tube, heated to 90°C, and reacted for 24 hours. After cooling to room temperature, the reaction liquid was dissolved in water, extracted three times with dichloromethane, and the organic phases were combined. The organic phase was dried over anhydrous sodium sulfate, the solvent was removed by rotary evaporator, and the residue was separated by column chromatography. Then a white-grey solid is obtained (5.1g, yield 55%). Synthesis from intermediate a-3

[0024] Under nitrogen protection, the compounds α-2 (5.0 g, 10.9 mmol), imidazole (1.36 g, 20.0 mmol), CuI (380 mg, 2.0 mmol), K₂CO₃ (8.50 g, 40.0 mmol), and xylene (100 ml) were successively added to a Schlenk tube, heated to 90°C, and reacted for 24 hours. After cooling to room temperature, the reaction liquid was dissolved in water, extracted three times with dichloromethane, and the organic phases were combined. The organic phase was dried over anhydrous sodium sulfate, the solvent was removed by rotary evaporator, and the residue was separated by column chromatography. A pale yellow solid was then obtained (3.2 g, yield 66%). Synthesis from intermediate a

[0025] Under nitrogen protection, the compound α-3 (3.0 g, 6.7 mmol) is dissolved in tetrahydrofuran (30 mL) and cooled to -40°C. Sec-butyllithium, s-BuLi (1.2 eq.), is added dropwise and stirred for 30 minutes. Iodine (1.1 eq.) is then added and stirred for 30 minutes. The mixture is then warmed to room temperature and stirred for 1 hour. The reaction liquid is dissolved in water, extracted three times with dichloromethane, and the organic phases are combined. The organic phase is dried over anhydrous sodium sulfate, and the solvent is removed by rotary evaporation. A pale yellow solid is obtained. This solid is dissolved in tetrahydrofuran (20 mL). Dichloro-di-tert-butyl-(4-dimethylaminophenyl) phosphine palladium, PdCl2(AMPhos)2 (0.05 eq.) and aqueous solution of potassium carbonate (2M, 4ml) are added and the mixture is allowed to reflux overnight under nitrogen protection.After cooling to room temperature, the above reaction liquid is dissolved in water, extracted three times with dichloromethane, and the organic phases are combined. The organic phase is dried over anhydrous sodium sulfate, the solvent is removed by rotary evaporator, and the residue is separated by column chromatography. A pale yellow solid is then obtained (1.6 g, yield 53%). Synthesis of compound 1

[0026] Under nitrogen protection, compound a (2.1 g, 4.7 mmol), compound 1-1 (5.8 g, 23.4 mmol), Pd(OAc)₂ (105 mg, 0.47 mmol), PPh₃ (380 mg, 1.4 mmol), K₂CO₃ (1.38 g, 10 mmol), and DMAc (20 ml) were successively added to a Schlenk tube, heated to 150°C, and reacted for 24 hours. After cooling to room temperature, the reaction liquid was dissolved in water, extracted three times with dichloromethane, and the organic phases were combined. The organic phase was dried over anhydrous sodium sulfate, the solvent was removed by rotary evaporator, and the residue was separated by column chromatography. A pale yellow solid was then obtained (1.5 g, yield 52%). ESI-MS (m / z): 614.3 (M + 1). Example 2: Synthesis of compound 9

[0027] Under nitrogen protection, compound a (1.6 g, 3.6 mmol), compound 9-1 (3.7 g, 18.0 mmol) (see synthesis in patent CN102449107), Pd(OAc)₂ (80 mg, 0.36 mmol), PPh₃ (190 mg, 0.72 mmol), K₂CO₃ (1.38 g, 10 mmol), and DMAc (20 ml) are successively added to a Schlenk tube, heated to 150 °C, and reacted for 24 hours. After cooling to room temperature, the reaction liquid is dissolved in water, extracted three times with dichloromethane, and the organic phases are combined. The organic phase is dried over anhydrous sodium sulfate, the solvent is removed by rotary evaporation, and the residue is separated by column chromatography. A pale yellow solid (700 mg, yield 32%) is then obtained. ESI-MS (m / z): 615.0 (M+1). Example 3 Synthesis of compound 11

[0028] The intermediate 9-1 (see synthesis in Dyes Pigm., 2013, 99, 390-394) is replaced by intermediate 11-1, and compound 11 is prepared using the synthesis method of compound 9. This gives a pale yellow solid (700 mg, yield 33%). ESI-MS (m / z): 631.3 (M + 1). Example 4 Synthesis of compound 13

[0029] Intermediate 9-1 is replaced by intermediate 13-1, and compound 13 is prepared using the synthesis procedure for compound 9. This yields a pale yellow solid (1.1 g, yield 50%). ESI-MS (m / z): 630.0 (M + 1). Example 5 Synthesis of compound 22

[0030] Intermediate 9-1 is replaced by intermediate 22-1 (see synthesis in patent CN105585555). Compound 22 is prepared using the synthesis method for compound 9. This yields a light yellow solid (800 mg, yield 47%). ESI-MS (m / z): 690.0 (M + 1). Example 6 Synthesis of compound 27

[0031] Intermediate 9-1 is replaced by intermediate 27-1 (see synthesis in patent US2012 / 256169). Compound 27 is prepared using the synthesis method for compound 9. This yields a light yellow solid (600 mg, 50% yield). ESI-MS(m / z): 706.2(M+1). Example 7 Synthesis of compound 30

[0032] The intermediate 9-1 is replaced by the intermediate 30-1 (see synthesis in patent CN107686484). Compound 30 is prepared using the synthesis method for compound 9. This gives a light yellow solid (750 mg, yield 43%). ESI-MS(m / z): 689.3(M+1). Example 8 Synthesis of compound 36

[0033] Intermediate 9-1 is replaced by intermediate 36-1 (see synthesis in Chem. Mater., 2013, 25, 3758-3765). Compound 36 is prepared using the synthesis method for compound 9. This gives a pale yellow solid (660 mg, yield 52%). ESI-MS(m / z): 765.1(M+1). Examples 9-16

[0034] The organic light-emitting material of the present invention is used to manufacture an electroluminescent device. The structure of the device is in Fig. 1 shown.

[0035] First, a transparent conductive ITO glass substrate 10 (with the anode 20 on it) is successively washed with detergent solution, deionized water, ethanol, acetone and deionized water and treated with oxygen plasma for 30 seconds.

[0036] Then HATCN is vapor-deposited onto the ITO with a thickness of 10nm as the hole injection layer 30.

[0037] Then the compound TAPC is vapor-deposited to form a hole transport layer 40 with a thickness of 40 nm.

[0038] Then, a light-emitting layer 50 with a thickness of 30 nm is vapor-deposited onto the hole transport layer. The light-emitting layer consists of a doped composition of Ir(PPy)3 (10%) and the compound product (90%) in Examples 1 to 8.

[0039] Then TmPyPb is deposited with a thickness of 50nm on the light-emitting layer as the electron transport layer 60.

[0040] Finally, 1 nm LiF is used as the electron injection layer 70 and 100 nm Al as the device cathode 80. Comparative example

[0041] Using CBP instead of the above compound in the present invention, an organic light-emitting device is produced according to the same method.

[0042] The structural formulas in the device are listed below,

[0043] The efficiency of the organic electroluminescent devices in Examples 9-17 and the comparison example at a current density of 10 mA / cm² 2 is shown in the following table: Light-emitting device Connection External quantum yield Fluorescent paint 9 1 15.6 Green light 10 9 14.7 Green light 11 11 14.5 Green light 12 13 15.2 Green light 13 22 16.4 Green light 14 27 16.2 Green light 15 30 16.8 Green light 16 36 17.2 Green light Comparative example CBP 12.7 Green light

[0044] Under the same conditions, the efficiency of the organic electroluminescence device produced from the compound of the present invention is better than that of the comparison example.

[0045] The compound of the present invention exhibits improved stability, and the device produced from the compound of the present invention exhibits improved color purity and higher efficiency, which is of great importance for optimizing the performance of organic optoelectronic devices.

Claims

[1] Organic electroluminescent material, which is the compound with the structure of formula (I): where L for a single bond, substituted or unsubstituted phenylene, substituted or unsubstituted biphenyls, or substituted or unsubstituted pyridylene; Ar is one of the following groups: B is selected from O, S, Se; X1-X8 are independently selected from N or CR, and each six-membered ring contains at most one N atom, and R is independently selected from one of hydrogen, deuterium, halogen, alkyl, heteroalkyl, aryl, heteroaryl, or aryloxy. [2] Organic electroluminescent material according to claim 1, wherein L is a single bond or substituted or unsubstituted phenylene; Ar is one of the following groups: B is selected from O, S; X1-X8 are independently selected from N or CR, and each six-membered ring contains at most one N atom, and R is independently selected from hydrogen, deuterium, alkyl, aryl. [3] Organic electroluminescent material according to claim 2, wherein L is a single bond or phenylene; Ar is one of the following groups: B is selected from O, S; One of X1-X8 N is and the remainders are CH. [4] Organic electroluminescent material according to claim 3, wherein L is a single bond; Ar is one of the following groups: One of X1-X8 N is and the remainders are CH. [5] Organic electroluminescent material according to claim 2, wherein L is a single bond; Ar is one of the following groups: B is selected from O, S; X1-X8 CH are. [6] Organic electroluminescent material according to claim 1, comprising the following compound 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 [7] Method for the synthesis of an organic electroluminescent material according to any one of claims 1 to 6, wherein the method comprises the following steps: (1) the compound a and YL-Ar are available, Y is halogen; (2) Under nitrogen protection, compound a and compound YL-Ar, Pd(OAc)2, PPh3, K2CO3 and DMAc are heated to 150 °C and the compound represented by formula (I) is obtained by reaction. [8] Method according to claim 7, wherein Y is chlorine or bromine. [9] Method according to claim 7, wherein the manufacturing method of compound a is as follows: A) Compound a-1 is reacted with o-dihalopyrazine to obtain compound a-2; B) Compound a-2 is reacted with imidazole to obtain compound a-3; C) By completing the ring closure of the connection a-3, the connection a is obtained; [10] Method according to claim 9, wherein the o-dihalopyrazine is o-dibromopyrazine. [11] Method according to claim 10, wherein the reaction formula for the preparation of compound a is as follows. [12] Application of an organic electroluminescent material according to any one of claims 1 to 6 in organic electroluminescent devices, mechanoluminescent devices, organic field-effect transistors, organic solar cells and chemical sensors. [13] Organic electroluminescent device comprising a cathode, an anode and an organic layer, wherein the organic layer consists of one or more layers of a hole injection layer, a hole transport layer, a light-emitting layer, a hole-blocking layer, an electron injection layer and an electron transport layer, and wherein the organic layer contains an organic electroluminescent material according to any one of claims 1 to 6. [14] Organic electroluminescent device according to claim 13, wherein the organic layer in which the organic electroluminescent material according to any one of claims 1 to 6 is located is a light-emitting layer or an electron transport layer. [15] Organic electroluminescent device according to claim 13, wherein the total thickness of the organic layer in which the organic electroluminescent material according to any one of claims 1 to 6 is located is 1 to 1000 nm, and wherein the organic layer in which the organic electroluminescent material according to any one of claims 1 to 6 is located is formed into a thin film by vapor deposition or a solution process.

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