Organometallic compound and organic electroluminescent device

Abstract

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

Description

Technical Field

[0001] The invention belongs to the technical field of organic electroluminescence and relates to an organic metal compound and an organic electroluminescent device. Background Art

[0002] Organic electroluminescence (OLED) and related research began as early as 1963, when Pope et al. first discovered the electroluminescence phenomenon of single-crystal anthracene, an organic compound. In 1987, Kodak in the United States produced an amorphous device using the vapor deposition of small organic molecules, reducing the driving voltage to less than 20V. OLEDs are dual-hole and electron injection light-emitting devices, converting electrical energy directly into light energy from organic semiconductor molecules. Compared to traditional display devices such as CRTs (crystal ray tubes), LCDs (liquid crystal displays), and PDPs (plasma display panels), OLEDs combine all the advantages of existing displays while offering unique advantages. They offer high brightness, high contrast, high definition, wide viewing angles, and a wide color gamut for high-quality images. Furthermore, they are ultra-thin, ultra-light, with low driving voltage, low power consumption, and a wide operating temperature range, meeting the requirements of portable devices for portability, power efficiency, and outdoor operation. Furthermore, OLED displays offer unique characteristics such as self-luminescence, high luminous efficiency, short response time, transparency, and flexibility. Consequently, OLEDs have been widely researched, developed, and used.

[0003] In 1998, Forrest et al. at Princeton University discovered that by doping the phosphorescent dye octaethylporphyrin platinum into a host luminescent material, they could produce a light-emitting device with an external quantum efficiency of 4% and an internal quantum efficiency of 23%. This pioneered the field of phosphorescent electroluminescence, and in the following years, organic electrophosphorescence research saw rapid development. As phosphorescent materials, noble metal complexes fully utilize both singlet and triplet excitons. Compared to fluorescent materials, which only utilize singlet excitons, the effective utilization of triplet excitons, up to 75%, enables phosphorescent organic light-emitting diodes (PhOLEDs), which achieve 100% internal quantum efficiency. Therefore, the development of high-efficiency phosphorescent organic electroluminescent devices has provided a significant impetus for the development of the flat-panel and portable display industries.

[0004] Iridium's high atomic number allows for strong spin-orbit coupling in complexes, favoring phosphorescence. The large d-orbital energy level splitting within the iridium metal ion prevents interaction with the complex's MLCT (triplet metal-to-ligand charge transfer) states, which could reduce phosphorescence efficiency. Iridium's trivalent ions form highly stable neutral molecules with ligands, facilitating device fabrication via vacuum evaporation or solution processing. Furthermore, the complex's emission color spans the entire visible spectrum, and its excellent stability meets the requirements of electroluminescent materials, making iridium complexes a research priority for organic electroluminescent and phosphorescent materials.

[0005] However, due to the narrow energy gap of red iridium complexes, energy level matching between the red light-emitting material and the carrier transport layer is difficult, and concentration quenching is prone to occur, resulting in suboptimal overall performance of red light-emitting devices and affecting the color saturation of the entire device. Therefore, research on red iridium complexes and devices is particularly important for device performance (such as efficiency, voltage, and lifetime). Summary of the Invention

[0006] In response to the shortcomings of the prior art, the present invention provides an organometallic compound and an organic electroluminescent device. The organometallic compound of the present invention is an iridium complex. By adjusting the structural combination of the primary ligand and the auxiliary ligand, the color saturation (red saturation), luminous efficiency, and device life of the device are improved.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In one aspect, the present invention provides an organometallic compound having a structure represented by Formula I:

[0009]

[0010] Among them, 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, trimethylsilyl, trimethylgermanium, 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, tert-butyl or isopropyl;

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

[0013] In the present invention, 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 is independently selected from hydrogen, deuterium, tritium, fluorine, cyano, -CH3, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, phenyl, -CD3 or any one of the groups represented by the following structural formula:

[0015]

[0016] Wherein, * represents the attachment position of the group.

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

[0018] The substituents in the substituted groups as described above are selected from hydrogen, deuterium, tritium, fluorine, cyano, -CH3, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-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] Where D is deuterium and TMS is trimethylsilyl.

[0023] Only some specific structural formulas are listed above, but the series of organometallic compounds protected by the present invention are not limited to the above molecular structures. Any simple transformation of the groups and substitution positions disclosed in the present invention can obtain other specific molecular structures, which will not be described one by one here, and they should all fall within the scope of protection of the present application.

[0024] In the present invention, the preparation process of the organic electroluminescent material is as follows:

[0025]

[0026] The definitions of the groups in the above formula are the same as above and will not be repeated here.

[0027] The specific synthesis steps are as follows:

[0028] 1. Under nitrogen protection, a compound of formula LA and IrCl3·3H2O were placed in a reaction system. A mixed solution of ethylene glycol ethyl ether and purified water was added. The mixture was refluxed under nitrogen protection and then cooled to room temperature. A precipitate was precipitated. The precipitate was filtered, rinsed with water, anhydrous ethanol, and petroleum ether in that order, and dried. The bridging ligand compound shown in LB was obtained.

[0029] 2. Weigh the intermediate LB compound and anhydrous potassium carbonate, add ethylene glycol ether, then add the ligand LC. Under nitrogen protection, reflux the reaction, filter, wash with alcohol, and dry. Use dichloromethane as the solvent and perform silica gel column chromatography. Concentrate the filtrate to precipitate a solid to obtain the final product of the compound represented by Formula I.

[0030] In another aspect, the present invention provides an organic electroluminescent device comprising an anode, a cathode, and an organic material layer disposed between the anode and the cathode, wherein the organic material layer comprises at least one of the organometallic compounds described above.

[0031] Preferably, the organic material layer includes a light-emitting layer, the light-emitting layer includes a host material and a doping material, and the doping material includes at least one of the organic metal compounds described above.

[0032] Preferably, the organic material layer further includes 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.

[0033] 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 which are arranged in sequence.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The organometallic compound of the present invention can improve the color saturation (red saturation), luminous efficiency and device life of an organic electroluminescent device. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the H NMR spectrum of compound L-8. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0038] Example 1 Preparation of organometallic compound L-8

[0039]

[0040] Step 1: Under nitrogen, weigh 1 eq of raw materials A-8 (CAS: 2177237-24-8), 1.1 eq of sodium thiomethoxide (CAS: 5188-07-8), and 20 eq of DMF (N,N-dimethylformamide). Replace the atmosphere with nitrogen twice, raise the temperature to 80°C, and react for 48 hours. Water is then added to the system, followed by separation with ethyl acetate. The mixture is then spin-dried and purified by column chromatography to obtain B-8 (yield: 32.0%).

[0041]

[0042] Step 2: Under nitrogen, weigh 1.1 eq of B-8, 1 eq of C-8 (CAS 884494-53-5), 3 eq of potassium carbonate, 20 eq of toluene, 10 eq of ethanol, and 10 eq of water. The atmosphere was replaced with nitrogen twice. 3% eq of tetrakistriphenylphosphine palladium was added under nitrogen and reacted at 70°C for 24 h. After completion of the reaction, the mixture was cooled to room temperature, separated into ethyl acetate, dried by spin drying, and purified by column chromatography to obtain D-8 (yield: 46.4%).

[0043]

[0044] Step 3: Under nitrogen, 1 eq of intermediate D-8, 3 eq of potassium carbonate, and 20 eq of DMF were added sequentially to the reaction system, followed by heating and stirring at 100°C for 12 h. After completion of the reaction, the mixture was cooled and filtered through celite. The organic phase was washed with saturated brine, extracted twice with ethyl acetate, dried over anhydrous magnesium sulfate, and filtered under reduced pressure to obtain E-8 (yield: 33.2%).

[0045]

[0046] Step 4: Under nitrogen, weigh 1 eq of E-8, 1.1 eq of F-8 (CAS 2217657-10-6), 3 eq of potassium carbonate, 20 eq of toluene, 10 eq of ethanol, and 10 eq of water. The atmosphere was replaced with nitrogen twice. 3% eq of tetrakistriphenylphosphine palladium was added under nitrogen and reacted at 100°C for 24 h. After completion of the reaction, the mixture was cooled to room temperature, separated into ethyl acetate, and dried by spin column chromatography using petroleum ether and ethyl acetate as the developing solvents. This gave intermediate G-8 (yield: 65.4%).

[0047]

[0048] Step 5: Weigh 2.5 eq of intermediate G-8 and 1 eq of iridium trichloride trihydrate and add them to the reaction system. Then, add 18 eq of ethylene glycol ether and 6 eq of water. Replace the reaction mixture with nitrogen twice, raise the temperature to 120°C, and react for 48 hours. After completion, cool the temperature to 30°C, filter, and rinse the filter cake with ethanol and petroleum ether, drying it to obtain the bridged ligand H-8 (yield: 70.1%).

[0049]

[0050] Step 6: Weigh 1 eq of bridging ligand H-8, 2 eq of potassium carbonate, and 12 eq of ethylene glycol ethyl ether and add them sequentially to the reaction system. The atmosphere is purged twice with nitrogen. Then, under nitrogen, add 2 eq of 3,7-diethyl-3,7-dimethylnonane-4,6-dione (CAS: 865193-73-3). Heat to 120°C and react for 36 h. After completion of the reaction, filter the mixture, pass it through a silica gel funnel, and spin dry to obtain the organometallic compound L-8 (yield: 67.7%).

[0051] HPLC purity: ≥99%.

[0052] Mass spectrum: Test value 1396.63.

[0053] Elemental analysis: Calculated: C, 71.36%; H, 5.99%; N, 2.01%; O, 2.29%; S 4.59%; Found: C, 71.44%; H, 6.03%; N, 2.11%; O, 2.32%, S 4.62.

[0054] The H NMR spectrum of compound L-8 is shown in Figure 1 shown.

[0055] The synthesis methods of other organometallic 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 those in the above embodiments and are not described here one by one. The molecular formula and mass spectrum of the synthesized organometallic iridium complexes are shown in Table 1 below.

[0056] Table 1

[0057]

[0058] Device Examples

[0059] The organic electroluminescent device is prepared using the organometallic compound formula L-8. The specific process is as follows:

[0060] An ITO glass substrate with a coating thickness of 1500Å was washed twice in distilled water, ultrasonically washed for 30 minutes, and repeatedly washed twice with distilled water, ultrasonically washed for 10 minutes. After the distilled water washing, it was ultrasonically washed in isopropyl alcohol, acetone, and methanol solvents in sequence (once each, and each washing for 10 minutes). After drying, it was transferred to a plasma cleaner, washed for 5 minutes, and then sent to an evaporator. Using ITO as the anode, the hole injection layer material CuPc (200Å) was first evaporated on it, followed by the hole transport layer material NPB (400Å) and the main material of the light-emitting layer 4,4'-N,N'-biphenyldicarbazole ("CBP") evaporated in sequence. Finally, the light-emitting layer dopant material compound L-8 was evaporated at a weight ratio of 95:5, the electron transport layer "Alq3" (300Å), the electron injection layer LiF (5Å), and the cathode Al (1000Å), to prepare the organic electroluminescent device D-8.

[0061] Then, according to the above preparation scheme, formula L-8 was replaced with 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 in sequence to obtain the 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.

[0062] Comparative Examples 1-4

[0063] An organic electroluminescent device was prepared according to the same preparation scheme as in Example 1, wherein the organometallic compound L-8 doped in the light-emitting layer was replaced by the compound of Comparative Example 1-4.

[0064] The structures of the compounds of Comparative Examples 1-4 are as follows:

[0065]

[0066] Comparative Examples 1-4 prepared corresponding comparative devices E, F, G, and H.

[0067] The structural formulas of the compounds copper (II) phthalocyanine (CuPc), NPB, Alq3 and CBP used in the device embodiment of the present invention are as follows:

[0068]

[0069] .

[0070] The luminescence 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 at a brightness of 3000 nits to characterize the driving voltage, current efficiency, and phosphorescence lifetime of the devices. The specific test results are shown in Table 2 below.

[0071] Table 2

[0072]

[0073] From Table 2 we can see that:

[0074] By comparison with Comparative Examples 1-4, it can be found that under the same diketone ligand conditions, the compound of the present invention has a higher rigidity and thermal decomposition temperature than the dibenzofuran structure due to its 9,9-dimethylfluorene structure, which can better adapt to the high temperature requirements of the OLED evaporation process. At the same time, 9,9-dimethylfluorene can adjust the HOMO-LUMO energy level through alkylation modification, and has electron blocking ability, thereby improving the exciton recombination efficiency. The dimethyl substitution at the 9th position of 9,9-dimethylfluorene provides a steric hindrance effect, reducing intermolecular interactions. At the same time, due to its high bond dissociation energy and resistance to concentration quenching, it can significantly extend the life of OLED devices. At the same time, the rigid planar biphenyl structure and orthogonal configuration of 9,9-dimethylfluorene give the molecule a highly rigid skeleton, significantly increasing the glass transition temperature of the material and inhibiting the tendency to crystallize. In the evaporation process, this group increases the molecular distance, reduces molecular stacking and association, and improves film uniformity and device yield.

[0075] The applicant states that while the present invention illustrates the organometallic compound and organic electroluminescent device through the aforementioned embodiments, the present invention is not limited to these embodiments. This does not necessarily mean that the present invention must rely on these embodiments in order to be implemented. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. An organometallic compound, characterized in that The organometallic compound has a structure represented by general formula I: ； Among them, 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, trimethylsilyl, trimethylgermanium, 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; X is any one of O, S, Se, NR'Si R'R'', Ge R'R'', C R'R'', wherein R' and R'' are independently selected from -F, -CN, -CD3, methyl, ethyl, tert-butyl or isopropyl; S1 is selected from substituted or unsubstituted 9,9-dimethylfluorene, wherein 9,9-dimethylfluorene is fused to the five-membered ring, and the fusion position is Hit 1, 2, 2, 3, 3, 4, 5, 6, 6, 7 or 7, 8.

2. The organometallic compound according to claim 1, characterized in that R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is 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, and substituted or unsubstituted 5-10 membered heteroaryl.

3. The organometallic compound according to claim 1 or 2, characterized in that R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is independently selected from hydrogen, deuterium, tritium, fluorine, cyano, -CH3, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, phenyl, -CD3 or any one of the groups represented by the following structural formula: ； Wherein, * represents the attachment position of the group.

4. The organometallic compound according to claim 1, characterized in that The substituents in the substituted groups are selected from hydrogen, deuterium, tritium, fluorine, cyano, -CH3, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, phenyl or -CD3.

5. The organometallic compound according to claim 1, characterized in that The organometallic compound is selected from any one of the following L-1 to L-630: ； Where D is deuterium and TMS is trimethylsilyl.

6. An organic electroluminescent device, characterized in that: The organic electroluminescent device comprises an anode, a cathode, and an organic material layer disposed between the anode and the cathode, wherein the organic material layer comprises at least one of the organometallic compounds according to any one of claims 1 to 5.

7. The organic electroluminescent device according to claim 6, characterized in that: The organic material layer includes a light-emitting layer, the light-emitting layer includes a host material and a doping material, and the doping material includes at least one of the organic metal compounds according to any one of claims 1 to 5.

8. The organic electroluminescent device according to claim 6, 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.

9. The organic electroluminescent device according to claim 6, 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 which are arranged in sequence.

Images