High efficiency organic electroluminescent device and preparation method thereof

Abstract

The application relates to a high-efficiency organic electroluminescent device and a preparation method thereof, which comprises sequentially preparing a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, a cathode on an anode to obtain the organic electroluminescent device, wherein the light-emitting layer comprises a compound with a structure of formula I. The application adopts a new thermally activated delayed fluorescence material, thereby having excellent light-emitting performance, and meanwhile, high efficiency and low roll-off can be realized, which will bring huge application prospects and economic values.

Description

Technical Field

[0001] This invention relates to an organic electroluminescent device, which has a novel structure of luminescent material. Background Technology

[0002] Organic light-emitting diodes (OLEDs) are current-driven light-emitting devices that use organic materials as active materials. They have a sandwich-like structure, consisting of positive and negative electrode layers and organic functional materials sandwiched between them. To fabricate OLEDs with lower driving voltages, better luminous efficiency, and longer lifespans, and to continuously improve OLED performance, innovation in OLED device structure and fabrication processes is necessary, along with ongoing research and innovation in the optoelectronic functional materials used in OLEDs to develop higher-performance functional materials. Unlike inorganic materials, organic materials are characterized by low synthesis costs, tunable functionality, flexibility, and good film-forming properties. Furthermore, devices based on organic materials typically have simple fabrication processes, are easy to mass-produce, are environmentally friendly, and can be fabricated using low-temperature thin-film methods, thus offering advantages in low manufacturing costs and possessing enormous application potential, attracting widespread attention and research from scholars both domestically and internationally over the past 30 years. Currently, lighting and display devices based on OLED technology are commercialized. However, the luminous performance of the light-emitting layer materials in existing devices still needs improvement. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide an electroluminescent device that employs a novel thermally activated delayed fluorescence material, thereby exhibiting excellent luminescence performance while achieving high efficiency and low roll-off, which will bring significant application prospects and economic value.

[0004] The present invention adopts the following technical solution:

[0005] An organic electroluminescent device includes an anode, a cathode, and a light-emitting layer inserted between the anode and the cathode, wherein the light-emitting layer comprises a compound of formula I.

[0006]

[0007] In the formula: R1, R2, R3 and R4 are independently selected from one of the following groups: hydrogen, methyl, tert-butyl, cyclohexyl, phenyl, 4-tert-butylphenyl, diphenylamino, nitrogen-containing aromatic ring (such as carbazole group); X1 and / or X2 are unsubstituted, or X1 and X2 are independently selected from single bond, double bond, O, S, S(=O)2, CR′R″ or Se; X1 and / or X2 are unsubstituted means that X1 and / or X2 are not present; A is selected from C6 to C60 aromatic amines or heteroaryl groups.

[0008] Furthermore, in CR′R″, R′ and R″ are selected from one of the following groups, substituted or unsubstituted: C1-C10 alkyl groups, C6-C30 monocyclic aromatic or fused-ring aromatic groups, and C5-C30 monocyclic heteroaromatic or fused-ring heteroaromatic groups. Preferably, the substituent is selected from one of deuterium, trifluoromethyl, cyano, halogen, C1-C10 alkyl or cycloalkyl groups, C6-C30 aryl groups, and C3-C30 heteroaryl groups.

[0009] In this invention, heteroatoms generally refer to atoms or groups of atoms selected from N, O, S, P, Si and Se, with N, O and S being preferred.

[0010] The organic electroluminescent device of the present invention includes an anode, a hole injection layer (HIL), a hole transport layer (HTL), an electron blocking layer (EBL), an emissive layer (EML), a hole blocking layer (HBL), an electron transport layer (ETL), an electron injection layer (EIL), and a cathode; the specific fabrication process of each layer of the organic electroluminescent device is a conventional technique, which is prepared by vacuum evaporation. Preferably, the organic electroluminescent device based on the above-mentioned compound of Formula I has the following specific structure: indium tin oxide (ITO) is used as the anode, bispyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexanonitrile (HATCN) is used as the hole injection layer (HIL), 4,4'-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline) (TAPC) is used as the hole transport layer (HTL), 4,4′,4”-tris(carbazole-9-yl)triphenylamine (TCTA) and 3,3′-bis(9H-carbazole-9-yl)-1,1′-biphenyl (mCBP) are used as the electron / exciton blocking layer (EBL), and the structure of Formula I is as follows: Compounds of formula I are used as guest materials, and 2,8-bis(diphenylphospho)dibenzo[B,D]furan (PPF) is used as the host material to form the light-emitting layer (EML). Alternatively, compounds of formula I are used as the light-emitting layer (EML), 2,8-bis(diphenylphospho)dibenzo[B,D]furan (PPF) is used as the hole blocking layer (HBL), 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (TmPyPB) is used as the electron transport layer (ETL), lithium octahydroxyquinoline (Liq) is used as the electron injection layer (EIL), and aluminum (Al) is used as the cathode. The specifications of each layer of the organic electroluminescent device are conventionally designed, such as ITO / HATCN. (10 nm) / TAPC (40 nm) / TCTA (10 nm) / mCBP (8 nm) / PPF: Guest material (20 wt%) (20 nm) / PPF (8 nm)TmPyPB (40 nm) / Liq (3 nm) / Al (100 nm). The specific preparation process is a conventional technique, using vacuum evaporation.

[0011] This invention discloses the application of the above-mentioned organic electroluminescent device in the preparation of organic electroluminescent apparatus.

[0012] This invention uses novel organic compounds to prepare organic electroluminescent devices, which are preferably used as luminescent layer materials, luminescent dyes and / or sensitizers; the prepared OLED devices have low turn-on voltage, high luminous efficiency, high color purity and better lifespan. Attached Figure Description

[0013] Figure 1 This is the specific chemical structural formula of the compound with structure I of this invention.

[0014] Figure 2 This is the specific chemical structural formula of the compound with structure I of this invention.

[0015] Figure 3 This is the specific chemical structural formula of the compound with structure I of this invention.

[0016] Figure 4 This is the specific chemical structural formula of the compound with structure I of this invention.

[0017] Figure 5 The diagram shows the device efficiency of device D1 prepared according to an embodiment of the present invention.

[0018] Figure 6 The electroluminescence spectrum of device D1 prepared according to an embodiment of the present invention is shown.

[0019] Figure 7 The proton NMR spectrum of compound 2PXZ2TRZ prepared in an embodiment of the present invention.

[0020] Figure 8 Mass spectra of compound 2PXZ2TRZ prepared in the embodiments of the present invention. Detailed Implementation

[0021] This invention uses compounds of Formula I as the light-emitting layer or light-emitting layer doping material of the device, enabling the OLED device to have low turn-on voltage, high luminous efficiency, high color purity and better lifespan.

[0022]

[0023] In the formula: R1, R2, R3 and R4 are independently selected from one of the following groups: hydrogen, methyl, tert-butyl, cyclohexyl, phenyl, 4-tert-butylphenyl, diphenylamino, nitrogen-containing aromatic ring (such as carbazole group); X1 and / or X2 are unsubstituted, or X1 and X2 are independently selected from single bond, double bond, O, S, S(=O)2, CR′R″ or Se; X1 and / or X2 are unsubstituted means that X1 and / or X2 are not present; A is selected from C6 to C60 aromatic amines or heteroaryl groups.

[0024] Furthermore, in CR′R″, R′ and R″ are selected from one of the following groups, substituted or unsubstituted: C1-C10 alkyl groups, C6-C30 monocyclic aromatic or fused-ring aromatic groups, and C5-C30 monocyclic heteroaromatic or fused-ring heteroaromatic groups. Preferably, the substituent is selected from one of deuterium, trifluoromethyl, cyano, halogen, C1-C10 alkyl or cycloalkyl groups, C6-C30 aryl groups, and C3-C30 heteroaryl groups.

[0025] In this invention, heteroatoms generally refer to atoms or groups of atoms selected from N, O, S, P, Si and Se, with N, O and S being preferred.

[0026] This invention discloses a method for preparing compounds with the structure of Formula I described above, illustrated below:

[0027]

[0028] In the raw materials, the substituents are the same as those in the compounds with the structure of Formula I above, and Y is a halogen, such as Cl, Br or I.

[0029] The specific chemical structural formula of the compound of Formula I of this invention is shown in [reference needed]. Figures 1 to 4 .

[0030] The specific preparation methods of the novel compounds of the present invention will be described in detail below using several synthetic examples, but the preparation methods of the present invention are not limited to these synthetic examples. All raw materials of the present invention are existing products, and the specific preparation methods and testing methods are conventional techniques, such as vacuum evaporation with a vacuum degree ≤2×10⁻⁶. -4 The deposition rate of the functional layer was 2 Å / s, the deposition rate of the host material was 1 Å / s, the deposition rate of the Liq layer was 0.1 Å / s, and the deposition rate of Al was 8 Å / s. The inventive aspect of this invention lies in providing a novel compound-doped host material as the luminescent layer for an organic electroluminescent device. A direct current was applied to the fabricated organic electroluminescent device, and its luminescent performance was evaluated using a PhotoResearch PR655 luminance meter; the current-voltage characteristics were measured using a computer-controlled Keithley 2400 digital source meter. The luminescent properties of the organic electroluminescent device were determined under varying applied DC voltage.

[0031] This invention discloses a novel structural compound used as a guest material to dope the host material as a light-emitting layer, or directly as a light-emitting layer, for the fabrication of organic electroluminescent devices. Furthermore, when the compound is used as both the guest and host materials as a light-emitting layer, the doping concentration of the compound is 15–25 wt%, preferably 20 wt%. The doping concentration refers to the percentage of the guest material relative to the combined mass of the guest and host materials.

[0032] Example 1

[0033] The organic electroluminescent device has the following structure: indium tin oxide (ITO) is used as the anode; bispyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexanonitrile (HATCN) is used as the hole injection layer (HIL); 4,4'-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline) (TAPC) is used as the hole transport layer (HTL); and 4,4′,4”-tris(carbazole-9-yl)triphenylamine (TCTA) and 3,3′-bis(9H-carbazole-9-yl)-1,1′-biphenyl (mCBP) are used as the electron blocking layer (E). BL), with 2,8-bis(diphenylphospho)dibenzo[B,D]furan (PPF) as the host material, are used together as the light-emitting layer (EML); 2,8-bis(diphenylphospho)dibenzo[B,D]furan (PPF) is used as the hole-blocking layer (HBL); 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (TmPyPB) is used as the electron transport layer (ETL); lithium octahydroxyquinoline (Liq) is used as the electron injection layer (EIL); and aluminum (Al) is used as the cathode; the specifications of each layer of the organic electroluminescent device are: ITO / HATCN. (10 nm) / TAPC (40 nm) / TCTA (10 nm) / mCBP (8 nm) / PPF: Guest material (20 wt%) (20 nm) / PPF (8 nm)TmPyPB (40 nm) / Liq (3 nm) / Al (100 nm). The specific preparation process is a conventional technique, using vacuum evaporation.

[0034] The specific performance data of the organic electroluminescent devices based on the above compounds are detailed in Table 1, and the specific testing methods are existing technologies.

[0035]

[0036] The experimental data above demonstrate that the novel TADF material provided by this invention, when applied to organic electroluminescent devices, achieves both high luminous efficiency and low efficiency roll-off, while also realizing ultra-high brightness. Therefore, this type of novel compound is a high-performance organic light-emitting functional material with promising prospects for commercial application. Figure 5 The device efficiency diagram for device D1; Figure 6 This is the electroluminescence spectrum of device D1.

[0037] The preparation method of the compound used as a guest material is as follows.

[0038] Synthesis of Compound 2PXZ-TRZ in Example 1

[0039]

[0040] Under a nitrogen atmosphere, n-butyllithium (2.0 M, 3.00 mL) was added dropwise to a tetrahydrofuran solution of raw material A1 (1.00 g, 1.67 mmol) at a low temperature (-78 °C). After stirring at -78 °C for 1 hour, raw material B1 (2.40 g, 4.92 mmol) dissolved in tetrahydrofuran solution was added. The mixture was then stirred at room temperature for 12 hours, and the solvent was removed under reduced pressure. Acetic acid (40 mL) and hydrochloric acid (36%, 1 mL) were then added, and the mixture was reacted at 120 °C for 15 hours. After the reaction was completed, the reaction solution was poured into water and filtered under reduced pressure. The residue was purified by silica gel column chromatography (developing solvent: dichloromethane:petroleum ether = 1:1, v / v) to give compound 2PXZ2TRZ (1.26 g, yield: 55%), a white powder, which was the main product. MALDI-TOF-MS results: molecular ion peak 1378.797. Figure 7 The hydrogen spectrum of compound 2PXZ2TRZ; Figure 8 Mass spectra of compound 2PXZ2TRZ were obtained. A byproduct, 2PXZTRZ (0.35 g, yield: 21%), was also obtained as a white powder. MALDI-TOF-MS results showed a molecular ion peak at 988.945.

[0041] Based on the synthesis example 1, other compounds can be obtained by changing the starting materials; the reactions are as follows.

[0042]

[0043]

[0044]

[0045]

[0046] Although the present invention has been described in conjunction with embodiments, the present invention is not limited to the above embodiments. It should be understood that, guided by the concept of the present invention, various modifications and improvements can be made by those skilled in the art, and all such modifications and improvements should fall within the protection scope of the appended claims.

Claims

1. An organic electroluminescent device, comprising an anode, a cathode, and a light-emitting layer inserted between the anode and the cathode, characterized in that, The light-emitting layer comprises compounds with the following structure: ； ； ； 。 2. The organic electroluminescent device according to claim 1, characterized in that, The organic electroluminescent device includes an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode.

3. The organic electroluminescent device according to claim 2, characterized in that, Each layer of the organic electroluminescent device is prepared by vacuum evaporation.

4. The organic electroluminescent device according to claim 1, characterized in that, The luminescent layer is the compound.

5. The organic electroluminescent device according to claim 1, characterized in that, The compound-doped host material serves as the luminescent layer.

6. The organic electroluminescent device according to claim 5, characterized in that, The doping concentration of the compound is 15–25 wt%.

7. The method for preparing the organic electroluminescent device according to claim 1, characterized in that, An organic electroluminescent device is obtained by sequentially fabricating a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode on the anode.

8. An organic electroluminescent device, characterized in that, Includes the organic electroluminescent device as described in claim 1.

9. The application of the organic electroluminescent device according to claim 1 in the preparation of organic electroluminescent devices.

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