Organometallic compound and organic electroluminescent device

Abstract

The application provides an organic metal compound and an organic electroluminescent device, the organic metal compound has a structure represented by general formula I, and the organic metal compound is an iridium complex. By adjusting the structural combination of a main ligand and an auxiliary ligand, the color saturation, the luminous efficiency and the device life of the device are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of organic electroluminescence, and relates to an organic metal compound and an organic electroluminescent device. BACKGROUND

[0002] Organic electroluminescence (OLED for short) and related research began in 1963 when Pope et al. first discovered the electroluminescence phenomenon of single-crystal anthracene. In 1987, Kodak in the United States used the method of evaporating small organic molecules to make a non-crystalline device, and the driving voltage was reduced to within 20V. OLED is a hole and electron double injection type light-emitting device that directly converts electrical energy into light energy of organic semiconductor molecules. Compared with traditional CRT (crystal ray tube), LCD (liquid crystal display), PDP (plasma display) and other display devices, OLED has all the advantages of existing displays, while also having its own unique advantages, such as high brightness, high contrast, high definition, wide viewing angle, wide color gamut, etc. to achieve high-quality images, and ultra-thin, ultra-light, low driving voltage, low power consumption, wide temperature, etc. to meet the needs of portable devices for lightness, power saving, and outdoor operation. In addition, self-luminescence, high luminous efficiency, short response time, transparency, flexibility, etc. are also unique characteristics of OLED display. Therefore, OLED has been widely researched, developed and used.

[0003] In 1998, Forrest et al. of Princeton University in the United States found that doping phosphorescent dye octaethylporphyrin platinum into the host light-emitting material produced a light-emitting device with an external quantum efficiency of 4% and an internal quantum efficiency of 23%. This opened up a new field of phosphorescent electroluminescence, and in the following years, research on organic electrophosphorescence has developed rapidly. As phosphorescent materials, noble metal complexes make full use of singlet and triplet excitons, and the effective use of triplet excitons, which is 75% of the proportion of singlet excitons, makes PhOLED based on phosphorescent materials achieve 100% internal quantum efficiency. Therefore, the research on high-efficiency phosphorescent organic electroluminescent devices provides an important driving force for the development of flat-panel and portable display industries.

[0004] Iridium has a large atomic number, which can produce strong spin-orbital coupling for the complex, which is conducive to phosphorescent emission; the d orbital level of iridium metal ions is split large, which avoids the interaction with the MLCT state (triplet state metal to ligand charge transfer) of the complex to reduce the phosphorescent emission efficiency; the trivalent ion of iridium can form a very stable neutral molecule with the ligand, which is conducive to the use of vacuum evaporation or solution processing to prepare devices. In addition, the emission color of the complex can cover the entire visible spectrum, and the stability is good, etc. It meets the requirements of electroluminescent materials, so that iridium complexes have become the research focus of organic electroluminescent phosphorescent materials.

[0005] However, due to the narrow energy gap of the red iridium complex, it is difficult to match the energy level between the red light material and the carrier transport layer, and concentration quenching is easy to occur, resulting in unsatisfactory comprehensive performance of the red light device, which affects the color saturation of the entire device. Therefore, the research on the red iridium complex and the device is particularly important for the performance of the device (such as in efficiency, voltage, life, etc.). SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide an organometallic compound and an organic electroluminescent device. The organometallic compound of the present application is an iridium complex. By adjusting the structural combination of the main ligand and the auxiliary ligand, the color saturation (red saturation), the luminous efficiency and the device life of the device are improved.

[0007] To achieve this purpose of the application, the following technical solutions are adopted:

[0008] In one aspect, the present application provides an organometallic compound, which has a structure represented by general formula I:

[0009]

[0010] wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 each independently selected from any one of hydrogen, deuterium, halogen, cyano, -CH2F, -CHF2, -CF3, trimethylsilane, trimethylgermane, substituted or unsubstituted C1-C30 alkyl, substituted or unsubstituted C3-C30 cycloalkyl, substituted or unsubstituted 5-30 membered heterocyclyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted 5-30 membered heteroaryl, and combinations thereof;

[0011] X is any one of O, S, Se, NR'Si R'R'', Ge R'R'', CR'R'' wherein R' and R'' are independently selected from -F, -CN, -CD3, methyl, ethyl, t-butyl or i-propyl;

[0012] S1 is selected from substituted or unsubstituted 9,9-dimethylfluorene, wherein the 9,9-dimethylfluorene is fused to the five-membered ring at positions 1, 2, positions 2, 3, positions 3, 4, positions 5, 6, positions 6, 7 or positions 7, 8.

[0013] In the present application, D represents deuterium.

[0014] Preferably, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10each independently selected from any one or a combination of at least two of hydrogen, deuterium, halogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C3-C12 cycloalkyl, substituted or unsubstituted 5-18 membered heterocyclyl, substituted or unsubstituted C6-C18 aryl, substituted or unsubstituted 5-10 membered heteroaryl; further preferably, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 each independently selected from any one or a combination of at least two of hydrogen, deuterium, tritium, fluorine, cyano, -CH3, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, phenyl, -CD3, or a group represented by the following structural formula:

[0015]

[0016] wherein * represents a connecting position of a group.

[0017] Further, in the above technical solution, "substituted" means that a hydrogen atom bonded to a carbon atom of a compound is changed into another substituent, and the position of substitution is not limited as long as the position is a position where a hydrogen atom is substituted (i.e., a position where a substituent can be substituted), and when there are two or more substituents, the two or more substituents can be the same as or different from each other.

[0018] The substituent in the group substituted as described above is selected from hydrogen, deuterium, tritium, fluorine, cyano, -CH3, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, phenyl, or -CD3.

[0019] Preferably, the organometallic compound is selected from any one of the following L-1 to L-630:

[0020]

[0021]

[0022] ;

[0023] wherein D is deuterium, and TMS is trimethylsilyl.

[0024] The above only lists some specific structural formulas, but the series of organic metal compounds claimed in the present application are not limited to the above molecular structures, and other specific molecular structures can be obtained by simple transformation of the groups disclosed in the present application and their substitution positions, which will not be described one by one, and should all fall within the protection scope of the present application.

[0025] In the present application, the preparation process of the organic electroluminescent material is as follows:

[0026]

[0027] wherein the definition of the groups in the above formula is consistent with the above, and will not be described again.

[0028] The specific synthesis steps are as follows:

[0029] 1. Under nitrogen protection, the compound of formula LA is put into the reaction system with IrCl3·3H2O, a mixed solution of ethylene glycol ethyl ether and pure water is added, and the reaction is refluxed under nitrogen protection, and then cooled to room temperature. Precipitate is precipitated, the precipitate is suction filtered, washed with water, anhydrous ethanol and petroleum ether in sequence, and dried. The bridged ligand compound of L-B is obtained.

[0030] 2. Take intermediate L-B compound and anhydrous potassium carbonate, add ethylene glycol ether, then add ligand L-C, reflux under nitrogen protection, filter, wash with alcohol, and dry. Use dichloromethane as solvent, and use silica gel column chromatography. Concentrate the filtrate to obtain solid, and then obtain the final product of the compound shown in formula I.

[0031] In another aspect, the present application provides an organic electroluminescent device, which comprises an anode, a cathode, and an organic material layer disposed between the anode and the cathode, the organic material layer comprising at least one of the organic metal compounds as described above.

[0032] Preferably, the organic material layer comprises a light-emitting layer, the light-emitting layer comprising a host material and a dopant material, the dopant material comprising at least one of the organic metal compounds as described above.

[0033] Preferably, the organic material layer further comprises at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an electron transport layer, or an electron injection layer.

[0034] Preferably, the organic electroluminescent device comprises an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode disposed in sequence.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] The organic metal compound of the present application can improve the color saturation (red saturation), luminous efficiency, and device lifetime of the organic electroluminescent device. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 NMR hydrogen spectrum of compound L-8. DETAILED DESCRIPTION

[0038] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application, and should not be regarded as specific limitations on the present application.

[0039] Example 1 Preparation of organic metal compound L-8

[0040]

[0041] First step: Under nitrogen condition, take A-8 (CAS: 2177237-24-8) 1 eq, sodium thiomethoxide (CAS: 5188-07-8) 1.1 eq, DMF (N,N-dimethylformamide) 20 eq. Replace nitrogen twice, heat to 80℃, after 48h reaction, add water to the system, separate with ethyl acetate, spin dry column chromatography to get B-8 (yield: 32.0%).

[0042]

[0043] Second step: Under nitrogen condition, take B-8 1.1 eq, C-8 (CAS 884494-53-5) 1 eq, potassium carbonate 3 eq, toluene 20 eq, ethanol 10 eq, water 10 eq, replace nitrogen twice, add palladium 3% eq under nitrogen condition, 70℃ reaction for 24h. After the reaction is completed, cool to room temperature, separate with ethyl acetate, spin dry, column chromatography to get D-8 (yield: 46.4%).

[0044]

[0045] Third step: Under nitrogen protection, add intermediate D-8 1 eq, potassium carbonate 3 eq and DMF 20 eq to the reaction system in turn, then heat and stir at 100℃ for 12h. After the reaction is completed, cool, filter with diatomite, wash the organic phase with saturated brine, extract twice with ethyl acetate, dry with anhydrous magnesium sulfate, and filter under reduced pressure to get E-8 (yield: 33.2%).

[0046]

[0047] Fourth step: Under nitrogen condition, take E-8 1 eq, F-8 (CAS 2217657-10-6) 1.1 eq, potassium carbonate 3 eq, toluene 20 eq, ethanol 10 eq, water 10 eq. Replace nitrogen twice, add palladium 3% eq under nitrogen condition, 100℃ reaction for 24h. After the reaction is completed, cool to room temperature, separate with ethyl acetate, spin dry, column chromatography, develop with petroleum ether and ethyl acetate. Spin dry to get intermediate G-8 (yield: 65.4%).

[0048]

[0049] Fifth step: First, take intermediate G-8 2.5 eq, iridium trichloride trihydrate 1 eq, add to the reaction system, then add ethylene glycol ether 18 eq, water 6 eq. Replace nitrogen twice, heat to 120℃, react for 48h. After the reaction is completed, cool to 30℃, filter, wash the filter cake with ethanol and petroleum ether, and dry to get bridged ligand H-8 (yield: 70.1%).

[0050]

[0051] Step 6: The bridging ligand H-8 1 eq, potassium carbonate 2 eq, ethylene glycol ether 12 eq were added into the reaction system in turn, and nitrogen was replaced twice. Then 3,7-diethyl-3,7-dimethylnonane-4,6-dione (CAS: 865193-73-3) 2 eq was added under the condition of nitrogen. The temperature was raised to 120°C and reacted for 36 h. After the reaction was completed, the reaction system was filtered, and the organic metal compound L-8 was obtained by rotary evaporation (yield: 67.7%).

[0052] HPLC purity: ≥ 99%.

[0053] Mass spectrum: test value 1396.63.

[0054] Elemental analysis: calculated value C, 71.36%; H, 5.99%; N, 2.01%; O, 2.29%; S 4.59%; measured value C, 71.44%; H, 6.03%; N, 2.11%; O, 2.32%, S 4.62.

[0055] The nuclear magnetic resonance hydrogen spectrum of compound L-8 is shown in Figure 1 .

[0056] The synthesis methods of other organic metal iridium complexes L-19, L-20, L-29, L-34, L-37, L-50, L-92, L-134, L-176, L-218, L-260, and L-321 are the same as the above-mentioned examples, which will not be repeated here. The molecular formula and mass spectrum of the synthesized organic metal iridium complexes are shown in Table 1 below.

[0057] Table 1

[0058]

[0059] Device Example

[0060] An organic electroluminescent device was prepared using the organic metal compound L-8, and the specific process was as follows:

[0061] An ITO glass substrate with a coating thickness of 1500 angstroms was cleaned in distilled water for 2 times, ultrasonic washing for 30 min, and repeated cleaning with distilled water for 2 times, ultrasonic washing for 10 min. After the distilled water cleaning, the substrate was dried by ultrasonic washing with isopropyl alcohol, acetone, and methanol solvents in sequence (each once, and each for 10 min). The substrate was then transferred into a plasma cleaning machine, washed for 5 min, and sent to an evaporation machine. With ITO as an anode, a hole injection layer material CuPc (200 angstroms) was first evaporated on the substrate, followed by sequentially evaporating a hole transport layer material NPB (400 angstroms), and a light-emitting layer host material 4,4'-N,N'-diphenylbiscarbazole ("CBP"), and finally evaporating a light-emitting layer doped material compound L-8 with a weight ratio of 95:5, an electron transport layer "Alq3" (300 angstroms), an electron injection layer LiF (5 angstroms), and a cathode Al (1000 angstroms), to prepare an organic electroluminescent device D-8.

[0062] Then, according to the preparation scheme described above, the compound L-8 was replaced by L-19, L-20, L-29, L-34, L-37, L-50, L-92, L-134, L-176, L-218, L-260, and L-321, respectively, to prepare corresponding organic electroluminescent devices D-19, D-20, D-29, D-34, D-37, D-50, D-92, D-134, D-176, D-218, D-260, and D-321.

[0063] Comparative Examples 1-4

[0064] The organic electroluminescent devices were prepared according to the same preparation scheme as in Example 1, wherein the light-emitting layer doped organic metal compound L-8 was replaced by the compounds of Comparative Examples 1-4.

[0065] The structures of the compounds of Comparative Examples 1-4 are as follows:

[0066]

[0067] Comparative Examples 1-4 prepared corresponding comparative devices E, F, G, and H.

[0068] The structures of the compounds used in the device embodiments of the present application, copper (II) phthalocyanine (CuPc), NPB, Alq3, and CBP, are as follows:

[0069]

[0070] .

[0071] The light emission characteristics of the devices obtained in the examples and comparative examples were tested using a KEITHLEY 2400 source measurement unit and a CS-2000 spectroradiometer. The driving voltage, current efficiency, and phosphorescence lifetime of the devices were characterized at a brightness of 3000 nits. The specific test results are shown in Table 2 below.

[0072] Table 2

[0073]

[0074] As can be seen from Table 2:

[0075] A comparison with Comparative Examples 1-4 reveals that, with the same diketone ligand, the compound of this invention, due to its 9,9-dimethylfluorene structure, exhibits higher rigidity and thermal decomposition temperature compared to the dibenzofuran structure, thus better meeting the high-temperature requirements of OLED evaporation processes. Furthermore, alkylation modification of 9,9-dimethylfluorene can adjust the HOMO-LUMO energy levels and provides electron blocking capabilities, enhancing exciton recombination efficiency. The dimethyl substitution at position 9 of 9,9-dimethylfluorene provides steric hindrance, reducing intermolecular interactions, and its high bond dissociation energy and resistance to concentration quenching significantly extend the lifetime of OLED devices. Simultaneously, the rigid planar biphenyl structure and orthorhombic configuration of 9,9-dimethylfluorene endow the molecule with a highly rigid framework, significantly increasing the glass transition temperature and suppressing crystallization tendency. In the evaporation process, this group increases the intermolecular distance, reducing molecular stacking and association, thereby improving film uniformity and device yield.

[0076] The applicant declares that the present invention is illustrated by the above embodiments to demonstrate the organometallic compounds and organic electroluminescent devices of the present invention, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An organometallic compound, characterized in that, The organometallic compound has a structure represented by general formula I: ； Wherein R2 is hydrogen, R1 and R3 are independently selected from substituted or unsubstituted C1-C6 alkyl groups, wherein the substituent in the substituted C1-C6 alkyl groups is fluorine, and R4, R5, R6, R7, and R9 are hydrogen; R8 is selected from substituted or unsubstituted tert-butyl groups, wherein the substituent in the substituted tert-butyl groups is deuterium; R 10 Selected from hydrogen, -CH3, and isopropyl; X is S; S1 is selected from substituted or unsubstituted 9,9-dimethylfluorene, wherein the 9,9-dimethylfluorene is fused with the five-membered ring, and the fusion position shown is... In the substituted 9,9-dimethylfluorene, the substituents at positions 1, 2, 2, 3, 3, 4, 5, 6, 6, 7, or 7, 8 are selected from deuterium, -CH3, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl.

2. The organometallic compound according to claim 1, characterized in that, R1 and R3 are each independently selected from -CH3, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc. , , * represents the connection position of the group.

3. An organometallic compound, characterized in that, The organometallic compound is selected from any one of the following compounds: ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； Where D represents deuterium.

4. An organic electroluminescent device, characterized in that, The organic electroluminescent device includes an anode, a cathode, and an organic material layer disposed between the anode and the cathode, wherein the organic material layer includes at least one of the organometallic compounds as described in any one of claims 1-3.

5. The organic electroluminescent device according to claim 4, characterized in that, The organic material layer includes a light-emitting layer, which comprises a host material and a dopant material, wherein the dopant material comprises at least one organometallic compound as described in any one of claims 1-3.

6. The organic electroluminescent device according to claim 4, characterized in that, The organic material layer further includes at least one of a hole injection layer, a hole transport layer, an electron blocking layer, an electron transport layer, or an electron injection layer.

7. The organic electroluminescent device according to claim 4, characterized in that, The organic electroluminescent device comprises an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode arranged sequentially.

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