High-color-purity near-ultraviolet heat exciton compound with circular polarization property and application of high-color-purity near-ultraviolet heat exciton compound in preparation of circular polarization organic electroluminescent device

Abstract

The invention discloses a high-color-purity near ultraviolet heat exciton compound with circular polarization property and application thereof in preparation of a circular polarization organic electroluminescent device, and belongs to the technical field of organic photoelectric materials. The electroluminescent material disclosed by the invention is a high-color-purity near ultraviolet heat exciton compound with circular polarization property, and two pairs of near ultraviolet enantiomers are successfully designed and synthesized by combining a chiral group binaphthol, a weak donor dibenzothiophene, dibenzofuran and an acceptor cyanophenyl; the compounds show obvious circular polarization luminescence property and high fluorescence quantum yield. The electroluminescent devices prepared based on the enantiomers all show near ultraviolet emission, CIE coordinates are respectively (0.168, 0.040) and (0.166, 0.040), and the external quantum efficiencies are respectively 4.3% and 3.4%. According to the near ultraviolet heat exciton material, a new visual angle is provided for developing the near ultraviolet heat exciton material with circular polarization luminescence and high color purity at the same time, and 3D and wide color gamut display can be directly achieved in the future.

Description

Technical Field

[0001] The invention belongs to the technical field of organic photoelectric materials, and in particular relates to a near-ultraviolet thermoexciton compound with high color purity and circular polarization property and application in preparing circular polarization organic electroluminescent devices. Background Art

[0002] Circularly polarized organic light-emitting diodes (CP-OLEDs) have broad application prospects in 3D display, circularly polarized light detection field effect transistor devices (FET) and personalized diagnosis and treatment. Currently reported materials that can be used to prepare CP-OLEDs devices include polymers, metal complexes and organic small molecules. Among them, polymer materials and metal complex materials can show obvious circularly polarized electroluminescence signals (CPEL), but have problems such as low device efficiency, high manufacturing cost and serious environmental pollution. In contrast, chiral organic small molecules have the advantages of low synthesis cost, adjustable luminescence properties and low toxicity. Therefore, constructing a variety of chiral organic small molecules will be the most direct and effective way to achieve CP-OLEDs with high device efficiency, high circularly polarized luminescence properties and low efficiency roll-off.

[0003] After decades of development, CP-OLEDs materials have achieved breakthroughs in efficiency and color purity in the red, green, blue and infrared regions. However, research on near-ultraviolet emitting CP-OLEDs materials is still in its infancy. In order to broaden the color gamut and promote technological innovation of near-ultraviolet light sources, it is of great significance to develop near-ultraviolet emitting CP-OLEDs materials with high efficiency and high color purity. Traditional fluorescent materials are limited to 25% exciton utilization, and the external quantum efficiency is usually difficult to break through the theoretical upper limit of 5%. Therefore, improving the utilization of triplet excitons has become the key to improving the efficiency of near-ultraviolet devices. Up to now, the mechanisms of organic fluorescent devices utilizing triplet excitons mainly include: triplet-triplet annihilation (TTA), thermally activated delayed fluorescence (TADF) and hot exciton mechanism. Among them, the upper limit of TTA material exciton utilization is 62.5%, and the device efficiency is still not ideal; although TADF materials can theoretically achieve 100% exciton utilization, it requires the separation of HOMO and LUMO orbits to achieve a smaller single-triplet energy difference (△E ST ), the S1 energy level is usually a strong charge transfer (CT) excited state, which is not conducive to the construction of near-ultraviolet materials.

[0004] Thermoexciton materials can be generated by high-energy triplet states (T m , m≥2) to the singlet state (S n, n≥1) utilizes triplet excitons to achieve the separation of triplet exciton conversion and radiative transition channels. Therefore, the properties of the S1 excited state of the hot exciton material will not have a significant effect on the hRISC process. In addition, due to the short lifetime of high-energy excited state excitons, the hRISC process rate is fast enough to effectively alleviate the problem of exciton annihilation of triplet excitons at high current density, which is conducive to obtaining near-ultraviolet emitting circularly polarized materials with high efficiency and low efficiency roll-off. The present application proposes to develop new circularly polarized luminescent hot exciton near-ultraviolet materials and devices by combining molecular design with chemical synthesis, taking into account the dual advantages of circularly polarized luminescence and high color purity, which is conducive to the direct realization of 3D and wide color gamut display in the future. Summary of the invention

[0005] The purpose of the present invention is to provide a near-ultraviolet thermoexciton compound with high color purity and circular polarization properties and its application in the preparation of circularly polarized organic electroluminescent devices. The present invention uses a near-ultraviolet thermoexciton compound with high color purity as a light-emitting layer to prepare a high-efficiency, high-color-purity deep blue light circularly polarized OLED device, which has the potential for practical application.

[0006] The present invention discloses a near-ultraviolet thermoexciton compound with high color purity and circular polarization property, and its general structural formula is shown in (1):

[0007]

[0008] X is cyano (CN);

[0009] L m for Wherein * indicates the connection position with R and the benzene ring; m is 0 or 1;

[0010] R is * indicates the same as L m Or the attachment position of the benzene ring.

[0011] Furthermore, the present invention discloses a near-ultraviolet thermoexciton compound with high color purity and circular polarization property, and its structural formula is shown as one of the following:

[0012]

[0013] The above-mentioned near-ultraviolet thermoexciton material with circular polarization property provided by the present invention integrates high solid-state luminescence efficiency, significant circular polarization property and excellent electroluminescent performance, and can be used as a doping material for preparing the light-emitting layer of a circularly polarized organic electroluminescent device, wherein the main material is CBP, and the mass doping concentration of the near-ultraviolet thermoexciton compound is 5-20wt%. In the circularly polarized organic electroluminescent device, the organic functional layer other than the light-emitting layer is one or more of a hole injection layer, a hole transport layer, an exciton blocking layer, an electron transport layer and an electron injection layer. The circularly polarized organic electroluminescent device can be used to prepare a near-ultraviolet circularly polarized organic electroluminescent display or an organic electroluminescent lighting source.

[0014] The principle of the present invention is to use dibenzothiophene and dibenzofuran as weak donors and benzonitrile as acceptors to construct luminescent molecules. The ortho-connected cyano group helps to reduce the lowest unoccupied orbital (LUMO) and the carrier injection barrier, thereby reducing the charge transfer within the molecule. At the same time, binaphthol is directly combined with the luminescent molecule as a chiral group, which helps to obtain near-ultraviolet emitting CP-OLEDs materials. Based on this, two pairs of near-ultraviolet emitting enantiomers, namely R / S-OBN-CN-DBF and R / S-OBN-CN-DBT, were successfully designed and synthesized. They have high solid-state luminescence efficiency and obvious circularly polarized luminescence properties. The asymmetry factors in the non-doped film are +7.27×10 -4 / -8.37×10 -4 and +4.68×10 -4 / -5.65×10 -4 The electroluminescent devices prepared based on the enantiomers R / S-OBN-CN-DBF and R / S-OBN-CN-DBT all exhibited near-ultraviolet emission, with CIE coordinates of (0.168, 0.040) and (0.166, 0.040), and external quantum efficiencies of 4.3% and 3.4%, respectively. This work provides a new perspective for the development of near-ultraviolet hot exciton materials with both circularly polarized luminescence and high color purity, which is conducive to the direct realization of 3D and wide color gamut displays in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 : A schematic diagram of the structure of the organic electroluminescent device prepared by the present invention, in which 1 is a transparent glass substrate, 2 is an ITO conductive film anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is an exciton blocking layer, 6 is an organic light-emitting layer, 7 is an electron transport layer, and 8 is a cathode;

[0016] Figure 2The absorption and emission spectra of R-OBN-CN-DBF in doped thin films are shown in Figure 1. The main absorption peaks are located at 300nm and 329nm respectively; the main emission peak is located at 381nm, which is near-ultraviolet emission. It can be used as an organic near-ultraviolet material to prepare electroluminescent devices.

[0017] Figure 3 The absorption and emission spectra of R-OBN-CN-DBT in doped thin films are shown in Figure 2. The main absorption peaks are located at 299nm and 330nm respectively; the main emission peak is located at 381nm, which is near-ultraviolet emission. It can be used as an organic near-ultraviolet material to prepare electroluminescent devices.

[0018] Figure 4 is the circularly polarized photoluminescence spectrum of R / S-OBN-CN-DBF in the undoped thin film state, and the photoluminescence asymmetry factor is +7.27×10 -4 / -8.37×10 -4 .

[0019] Figure 5 This is the circularly polarized photoluminescence spectrum of R / S-OBN-CN-DBT in the undoped thin film state. The photoluminescence asymmetry factor is +4.68×10 -4 / -5.65×10 -4 .

[0020] Figure 6 It is the external quantum efficiency curve of the R / S-OBN-CN-DBF circularly polarized electroluminescent device prepared in Example 3, and the maximum external quantum efficiency is 4.3%; the inset is the electroluminescent spectrum, and the main peak of the spectrum is at 396nm.

[0021] Figure 7 It is the external quantum efficiency curve of the R / S-OBN-CN-DBT circularly polarized electroluminescent device prepared in Example 4, and the maximum external quantum efficiency is 3.4%; the inset is the electroluminescent spectrum, and the main peak of the spectrum is located at 400nm. DETAILED DESCRIPTION

[0022] Example 1: The preparation of R / S-OBN-CN-DMF in this example is as follows:

[0023] Synthesis of R / S-OBN-CN: 2-bromo-4,5-difluorobenzonitrile (305.2 mg, 1.4 mmol), R / S-binaphthol (400.4 mg, 1.4 mmol) and K2CO3 (483 mg, 3.5 mmol) were mixed, and 20 mL of anhydrous DMF was added, heated to 120 ° C and stirred for 12 hours. After cooling to room temperature, the reaction mixture was poured into water (100 mL), extracted with dichloromethane and water three times, and the combined organic layers were condensed in vacuo and purified by column chromatography with a mixed eluent of dichloromethane / petroleum ether (volume ratio 1:4) to obtain a white solid (422 mg) with a yield of 65%. Mass spectrum MALDI-TOF (m / z) [M + ]: The measured value is 464.12 and the theoretical value is 464.01.

[0024]

[0025] Synthesis of R / S-OBN-CN-DBF: R / S-OBN-CN (464 mg, 1 mmol), DBFBin (276 mg, 1.3 mmol), K2CO3 (1.11 g, 5 mmol), Pd(PPh3)4 (70 mg, 0.06 mmol) were mixed and added to a 100 mL flask, and then 20 mL toluene and 10 mL water were added, heated to 90 ° C and stirred for 24 hours. After cooling to room temperature, the reaction mixture was poured into water (50 mL), and the reaction mixture was extracted three times with dichloromethane and water, and the combined organic layers were condensed in vacuo and purified by column chromatography with a mixed eluent of dichloromethane / petroleum ether (volume ratio 1:4) to obtain a white solid (436 mg) with a yield of 79%. R-OBN-CN-DBF: 1 H NMR(500MHz,CD2Cl2)δ8.17–8.12(m,2H),8.12–8.07(m,2H),8.05(d,J=8.1Hz,2H),7.83(d,J=6.1Hz,2H), 7.68(s,1H),7.66(s,1H),7.63–7.60(m,2H),7.59–7.53(m,6H),7.48–7.43(m,3H).MALDI-TOF(m / z):Calcd for C 39 H 21 NO3,551.60;Found:551.51[M + ].S-OBN-CN-DBF: 1H NMR(500MHz,DMSO)δ8.33(d,J=8.1Hz,1H),8.24(d,J=9.9Hz,3H),8.15(s,2H),8.14 (s,1H),8.06(s,1H),7.79(d,J=6.4Hz,2H),7.77(d,J=3.7Hz,1H),7.75(s,1H),7.71 (d,J=7.9Hz,1H),7.61(t,J=5.8Hz,2H),7.59(d,J=6.9Hz,1H),7.52(d,J=8.3Hz,1H ),7.50(s,1H),7.47(d,J=7.8Hz,1H),7.44–7.38(m,2H).MALDI-TOF(m / z):Calcdfor C 39 H 21 NO3:551.60;Found:551.15[M + ].

[0026]

[0027] Example 2: The preparation of R / S-OBN-CN-DBT in this example is as follows:

[0028] Synthesis of R / S-OBN-CN-DBT: R / S-OBN-CN (464 mg, 1 mmol), DBTBin (296 mg, 1.3 mmol), K2CO3 (1.11 g, 5 mmol), Pd(PPh3)4 (70 mg, 0.06 mmol) were mixed and added to a 100 mL flask, and then 20 mL toluene and 10 mL water were added, heated to 90 ° C and stirred for 24 hours. After cooling to room temperature, the reaction mixture was poured into water (50 mL), extracted with dichloromethane and water three times, and the combined organic layers were condensed in vacuo and purified by column chromatography with a mixed eluent of dichloromethane / petroleum ether (volume ratio 1:4) to obtain a white solid (403 mg) with a yield of 71%. R-OBN-CN-DBT: 1 H NMR (500MHz, CD2Cl2) δ8.35(d,J=8.2Hz,1H),8.31–8.26(m,1H),8.13(s,1H),8.11(d,J=7.1Hz,2H),8.05(d,J=8.4Hz,2H),7.98–7. 93(m,1H),7.82(s,1H),7.73(d,J=8.2Hz,1H),7.59(d,J=8.3Hz,3H),7.58–7.52(m,6H),7.48–7.43(m,2H).MALDI-TOF(m / z):Calcd for C 39H 21 NO2S:567.66;Found:567.44[M + ].S-OBN-CN-DBF: 1 H NMR (500MHz, DMSO) δ8.55(d,J=8.3Hz,1H),8.48(d,J=8.5Hz,1H),8.36(s,1H),8.25(d ,J=2.9Hz,1H),8.23(d,J=2.9Hz,1H),8.18–8.13(m,3H),8.10(d,J=8.7Hz,1H),7.82(d ,J=4.4Hz,1H),7.81–7.78(m,2H),7.77(d,J=6.2Hz,1H),7.75(s,1H),7.62(d,J=7.4Hz ,1H),7.60–7.57(m,2H),7.54–7.49(m,2H),7.43–7.38(m,2H).MALDI-TOF(m / z):Calcd for C 39 H 21 NO2S:567.66;Found:567.32[M + ].

[0029]

[0030] Example 3

[0031] A circularly polarized organic electroluminescent device uses an organic blue light emitting small molecule with a molecular structure of R-OBN-CN-DBF as a light emitting layer material (emitters). The structure of the organic electroluminescent device R-OBN-CN-DBF is as follows: ITO / HATCN (6nm) / TAPC (25nm) / TCTA (15nm) / 5wt% emitters: CBP (20nm) / TmPyPB / LiF (1nm) / Al (120nm).

[0032] The device preparation process is as follows: Preparation of the substrate indium tin oxide (ITO) conductive glass: The substrate is cleaned in ultrasonic bath with deionized water, isopropanol, acetone, toluene, acetone, and isopropanol for 20 minutes each, and then dried in an oven for use. After the surface of the ITO conductive glass is treated in a UV ozone cleaner for 40 minutes, it is moved into a vacuum evaporation device (the pressure in the chamber is less than 2×10 -4Pa); on the anode ITO conductive glass, a hole injection layer HATCN is vacuum-deposited with a thickness of 5 nm; on HATCN, a hole transport layer TAPC is vacuum-deposited with a thickness of 25 nm: on TAPC, an exciton blocking layer TCTA is evaporated with a thickness of 15 nm; on TCTA, a light-emitting layer CBP:R-OBN-CN-DBF (mass doping concentration is 5wt%) is evaporated with a thickness of 20 nm; on the light-emitting layer, an electron transport layer TmPyPB is evaporated with a thickness of 40 nm; on TmPyPB, an electron transport layer LiF is evaporated with a thickness of 1 nm; on LiF, a cathode Al is evaporated with a thickness of 100 nm.

[0033] In this example, CBP:R-OBN-CN-DBF (doping concentration of 5 wt%) is used as the light-emitting layer material to prepare a circularly polarized organic electroluminescent device. Figure 6 The detailed electroluminescent performance data of the device are listed in Table 1, which shows that the prepared device has high color purity and significant circularly polarized electroluminescent signal.

[0034] Table 1: Relevant data parameters of the device prepared in Example 3

[0035]

[0036] Example 4

[0037] A circularly polarized organic electroluminescent device, using an organic blue light emitting small molecule with a molecular structure of R-OBN-CN-DBT as a light emitting layer material (emitters), wherein the structure of the organic electroluminescent device R-OBN-CN-DBT is as follows: ITO / HATCN (6nm) / TAPC (25nm) / TCTA (15nm) / 5wt% emitters: CBP (20nm) / TmPyPB / LiF (1nm) / Al (120nm). The preparation process of the device is similar to that of Example 3. Among them, the external quantum efficiency curve of the circularly polarized organic electroluminescent device prepared with CBP: R-OBN-CN-DBT (mass doping concentration of 5wt%) as the light emitting layer material is as shown in FIG. Figure 7 The detailed electroluminescent performance data of the device are listed in Table 2, which shows that the prepared device has high color purity and significant circularly polarized electroluminescent signal.

[0038] Table 2: Relevant data parameters of the device prepared in Example 4

[0039]

[0040] The structural formulas of the materials used in the organic electroluminescent devices of Examples 3-4 are as follows, and all of them are commercially available:

[0041]

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A near-ultraviolet thermoexciton compound with high color purity and circular polarization properties, the structural formula of which is shown in (1): X is cyano (CN); L m for Wherein * indicates the connection position with R and the benzene ring; m is 0 or 1; R is * indicates the same as L m Or the attachment position of the benzene ring.

2. A near-ultraviolet thermoexciton compound with high color purity and circular polarization properties as claimed in claim 1, wherein the structural formula is as shown in one of the following:

3. Use of a near-ultraviolet thermoexciton compound with high color purity and circular polarization properties as claimed in claim 1 or 2 in the preparation of a circularly polarized organic electroluminescent device, characterized in that: The near-ultraviolet thermoexciton compound is used as a doping material for preparing a light-emitting layer of a circularly polarized organic electroluminescent device. The main material is CBP, and the mass doping concentration of the near-ultraviolet thermoexciton compound is 5-20wt%.

4. The use of a near-ultraviolet thermoexciton compound with high color purity and circular polarization property in the preparation of a circularly polarized organic electroluminescent device as claimed in claim 3, characterized in that: The organic functional layer of the circularly polarized organic electroluminescent device other than the light-emitting layer is one or more of a hole injection layer, a hole transport layer, an exciton blocking layer, an electron transport layer and an electron injection layer.

5. The use of a near-ultraviolet thermoexciton compound with high color purity and circular polarization property in the preparation of a circularly polarized organic electroluminescent device as claimed in claim 4, characterized in that: The circularly polarized organic electroluminescent device is used for preparing a near-ultraviolet circularly polarized organic electroluminescent display or an organic electroluminescent lighting source.

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