Organic luminescent material containing phosphine oxide group and organic electroluminescent device thereof

Abstract

The invention discloses an organic light-emitting material containing phosphinoxyl and an organic electroluminescent device thereof, the organic light-emitting material containing phosphinoxyl is a compound with a structure shown in a formula I: # imgabs0 #, R1, R2, R3 and R4 are respectively and independently hydrogen, deuterium, halogen, substituted or unsubstituted alkyl with 1-20 carbon atoms, substituted or substituted naphthenic base with 3-20 ring atoms, and R1, R2, R3 and R4 are respectively and independently hydrogen, deuterium, halogen, substituted or unsubstituted alkyl with 1-20 carbon atoms and substituted or substituted cycloalkyl with 3-20 ring atoms. A substituted or unsubstituted heteroalkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted heterocyclic group having 3 to 20 ring atoms, a substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, or a substituted or unsubstituted heteroalkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted heteroalkyl group having 3 to 20 ring atoms, or a substituted or unsubstituted heteroalkyl group having 3 to 20 ring atoms, or a substituted or unsubstituted heteroalkyl group having 3 to 20 ring atoms, or a substituted or unsubstituted heteroalkyl group having 3 to 20 ring atoms. A substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and a substituted or unsubstituted heteroaryl group having 3 to 30 carbon atoms. The OLED device provided by the invention is high in efficiency and relatively small in efficiency roll-off degree, and also has a good film-forming characteristic.

Description

Technical Field

[0001] The invention relates to the field of organic electroluminescent devices, and in particular to a luminescent material and an electroluminescent device thereof. Background Art

[0002] At present, with the improvement of people's viewing needs and visual enjoyment, the existing display technology cannot meet people's increasingly high requirements for display devices. Finding new high-efficiency and lower-cost display devices has become people's pursuit. Organic electroluminescent diodes have excellent performance in display, such as low power consumption, easy bending, fast response speed, wide viewing angle, large-area display and full range of luminous colors, as well as their broad application prospects in solid-state lighting, making OLEDs widely concerned by academia and industry.

[0003] As a new type of organic light-emitting diode (OLED) material, TADF material has many potential advantages, but there are also some challenges and problems. TADF material still faces challenges in achieving high color purity blue light emission; when TADF material works at high brightness, efficiency roll-off may occur, that is, as the brightness increases, the luminous efficiency of the device decreases; the stability of TADF material is another key issue. Including the chemical stability of the material itself and the stability during the operation of the device. Improving the stability of TADF material and extending its working life are crucial to achieving commercial applications.

[0004] Due to the nature of the phosphorus atom itself, 5 covalent bonds can be formed, so the phosphine oxygen functional group is very easy to connect with other groups to form a derivative with it as the core. Since the oxygen atom has a strong electronegativity, this makes the phosphine oxygen structure highly polarized and has a strong electron-withdrawing property. The triphenylphosphine oxygen unit formed by the electron-withdrawing phosphine oxygen group connecting the benzene ring also has a strong electron-withdrawing property, which will also have a significant impact on the energy level structure of the formed compound. Due to the influence of the conjugation effect, the core of many molecules will reduce the triplet energy level when the molecular chain length is extended, and the triphenylphosphine oxygen group of the spatial tetrahedral structure will not extend the conjugation, thereby ensuring that the triplet energy level is not reduced. However, because the unique spatial configuration of the triphenylphosphine oxygen derivative suppresses the molecular stacking effect, this is conducive to maintaining the morphological stability of the material. Summary of the invention

[0005] The present invention aims to address the defects and shortcomings of the above-mentioned prior art and provide an organic light-emitting material and an organic electroluminescent device with a phosphine-oxy group as the central skeleton, which have good photoelectric properties and low efficiency roll-off characteristics. Specifically, it includes: an organic light-emitting material containing a phosphine-oxy group, a compound having a structure shown in formula I:

[0006]

[0007] wherein R1, R2, R3 and R4 are each independently hydrogen, deuterium, halogen, substituted or unsubstituted alkyl having 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl having 3 to 20 ring atoms, substituted or unsubstituted heteroalkyl having 1 to 20 carbon atoms, substituted or unsubstituted heterocyclyl having 3 to 20 ring atoms, substituted or unsubstituted aralkyl having 7 to 30 carbon atoms, substituted or unsubstituted alkoxy having 1 to 20 carbon atoms, substituted or unsubstituted aryloxy having 6 to 30 carbon atoms, substituted or unsubstituted alkenyl having 2 to 20 carbon atoms , substituted or unsubstituted aryl groups having 6-30 carbon atoms, substituted or unsubstituted heteroaryl groups having 3-30 carbon atoms, substituted or unsubstituted silyl groups having 3-20 carbon atoms, substituted or unsubstituted arylsilyl groups having 6-20 carbon atoms, substituted or unsubstituted alkylgermanyl groups having 3-20 carbon atoms, substituted or unsubstituted arylgermanyl groups having 6-20 carbon atoms, substituted or unsubstituted amino groups having 0-30 carbon atoms, acyl groups, carbonyl groups, carboxylic acid groups, ester groups, cyano groups, isocyano groups, hydroxyl groups, sulfenyl groups, sulfinyl groups, sulfonyl groups, phosphino groups, and combinations thereof;

[0008] The organic electroluminescent device is as follows:

[0009] ITO / HAT-CN / NPB / mCBP: Organic light-emitting materials / TPBi / LiF / Al

[0010] The organic electroluminescent material is selected from but not limited to one of the following compounds:

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017] Furthermore, the organic light-emitting material containing phosphine oxygen group of the present invention is applied to organic electroluminescent device.

[0018] Furthermore, the organic electroluminescent device of the present invention comprises a first electrode, a second electrode, and one or more organic layers disposed between the first electrode and the second electrode; and the organic layers comprise one of a hole injection layer, a hole transport layer, an electron blocking layer, a luminescence auxiliary layer, a luminescent layer, a hole blocking layer, an electron transport layer and an electron injection layer; and the hole transport layer comprises the organic light-emitting material containing a phosphine radical.

[0019] Furthermore, the organic electroluminescent device of the present invention is applied to an organic electroluminescent device. The organic electroluminescent device includes a flat panel display, a computer display, a medical monitor, a television, a billboard, a lamp for lighting or signaling, a head-up display, a fully transparent or partially transparent display, a flexible display, a laser printer, a telephone, a mobile phone, a photo album, a personal digital assistant (PDA), a wearable device, a laptop computer, a digital camera, a video camera, a three-dimensional display, a virtual reality or augmented reality display, a vehicle, a video wall including multiple displays tiled together, a theater or venue screen, a light therapy device and a sign.

[0020] Beneficial effects:

[0021] 1. The present invention has good photoelectric performance and a low efficiency roll-off characteristic.

[0022] 2. The OLED device of the present invention has high efficiency, low starting voltage, can maintain high device efficiency at high brightness, and also has good film-forming properties. DETAILED DESCRIPTION

[0023] The general synthetic formula of the compound of the present invention is as follows:

[0024]

[0025]

[0026] The present invention takes the preparation of compound 1 as an example:

[0027] Preparation of intermediate A (R2 = R3 = H): Under low temperature conditions of -78°C, [(5-bromo-3-fluorophenyl)phenylamino]methane acid-2-methylpropane-2-yl ester (1 equiv.) was dissolved in tetrahydrofuran, and then n-butyl lithium (3 equiv.) was slowly added and stirred for 1 hour, and then (2-bromophenyl) dichlorophosphine (2 equiv.) was added and stirred for 30 minutes. The mixture was returned to room temperature and stirred overnight. After 12 hours, water was added to quench the reaction, and the mixture was extracted and washed with dichloromethane and saturated brine. The organic phase was recovered and dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The crude product was then separated and purified by column chromatography to obtain intermediate A with a yield of 53%;

[0028] Preparation of intermediate B (R2 = R3 = R4 = H): Under nitrogen atmosphere, intermediate A (1 equivalent), aniline (1 equivalent), sodium tert-butoxide (1 equivalent), tri-tert-butylphosphine (1.0M toluene solution, 0.4 equivalent) and tris (dibenzylidene ethyl ketone) palladium (0) (0.01 equivalent) were dissolved in toluene solution. After stirring at 120 ° C for 12 hours, petroleum ether / ethyl acetate was used as eluent and purified by column chromatography to obtain a white solid product intermediate B with a yield of 71%.

[0029] Preparation of intermediate C (R2 = R3 = R4 = H): 3,6-bis (2-methylpropane-2-yl) -9H-carbazole (1 equiv.), bromobenzene (2.5 equiv.), KOH (3 equiv.) and solvent DMSO were added to a Shrek tube in sequence under a nitrogen atmosphere. The Shrek tube was then sealed and stirred in an oil bath at 135 ° C for 48 h. After the solvent was removed under reduced pressure, it was purified by flash column chromatography with petroleum ether / ethyl acetate (gradient mixture ratio of 100:0 to 85:15) as the eluent to obtain intermediate C with a yield of 67%.

[0030] Preparation of intermediate D (R1 = R2 = R3 = R4 = H): 3,6-bis(2-methylpropane-2-yl)-9H-carbazole (1 equiv.), iodobenzene (2 equiv.), KOH (3 equiv.) and solvent DMSO were added to a Shrek tube in sequence under a nitrogen atmosphere. The Shrek tube was then sealed and stirred in an oil bath at 135°C for 48 h. After the solvent was removed under reduced pressure, it was purified by flash column chromatography using petroleum ether / ethyl acetate (gradient mixture ratio of 100:0 to 80:10) as the eluent to obtain intermediate D with a yield of 59%.

[0031] Preparation of compound 1 (R1 = R2 = R3 = R4 = H): The intermediate D (1 equiv.) was dissolved in toluene, and 30% hydrogen peroxide (5 equiv.) was added respectively, and the reaction was carried out at room temperature for 12 hours to obtain a phosphine-containing intermediate, and trifluoroacetic acid (3 mL) was added respectively to react for 5 hours, and then extracted and washed with dichloromethane and saturated brine, and the organic phase was recovered and dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure, and then the crude product was separated and purified by column chromatography to generate compound 1, with a yield of 78%, MS (ESI): 733.323. The compounds of the formula I structure can all be synthesized by referring to the synthesis route of compound 1 to obtain the corresponding compounds.

[0032] Those skilled in the art should know that the above-mentioned preparation method is only an illustrative example, and those skilled in the art can obtain other compound structures of the present invention by improving it. It should be understood that the various embodiments described here are only examples and are not intended to limit the scope of the present invention. Therefore, as will be apparent to those skilled in the art, the claimed invention may include variations of the specific embodiments and preferred embodiments described herein. Many of the materials and structures described herein can be replaced with other materials and structures without departing from the spirit of the present invention. It should be understood that the various theories about why the present invention works are not intended to be restrictive. The light-emitting layer of the organic electroluminescent device of the present invention and the organic electroluminescent device are described below.

[0033] The compounds of the present invention can be used as doping materials for the light-emitting layer. The thermal properties and singlet-triplet energy level difference of the compounds of the present invention (the example compounds are compounds 1 to 38) and the existing material TADF1 were measured respectively. The test results are shown in Table 1.

[0034] Table 1: Material properties

[0035]

[0036]

[0037]

[0038] Note: Thermogravimetric loss temperature Td is the temperature at which the weight loss is 1% in a nitrogen atmosphere, and is measured on a TGA-50H thermogravimetric analyzer from Shimadzu Corporation, Japan, with a nitrogen flow rate of 20 mL / min; PL is the fluorescence emission wavelength of the sample solution, measured using a Japanese Topcon SR-3 spectroradiometer.

[0039] Cyclic voltammetric stability is determined by observing the redox properties of the material using cyclic voltammetry.

[0040] Test conditions: The test sample was dissolved in a mixed solvent of dichloromethane and acetonitrile with a volume ratio of 2:1, with a concentration of 1 mg / mL. The electrolyte was an organic solution of 0.1 M tetrabutylammonium tetrafluoroborate or tetrabutylammonium hexafluorophosphate. The reference electrode was an Ag / Ag+ electrode, the counter electrode was a titanium plate, the working electrode was an ITO electrode, and the number of cycles was 20.

[0041] It can be seen from the data in the above table that the compounds of the present invention have a higher pyrolysis temperature and better thermal stability, which provides the possibility for application in devices; at the same time, the smaller singlet-triplet energy level difference improves the efficiency and life of OLED devices using the compounds of the present invention as doping materials.

[0042] Controlled trials:

[0043] Example: Compound 1-38

[0044] The structure of the organic electroluminescent device of the present invention comprises, from bottom to top, a base layer, an anode layer, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer / hole blocking layer, an electron injection layer, and a cathode electrode layer.

[0045] The base layer can use the substrate in the conventional organic light-emitting organic electroluminescent device, such as glass or plastic. The anode layer material can use transparent high-conductivity materials, such as indium tin oxide (ITO), indium zinc oxide (IZO), tin dioxide (SnO2), zinc oxide (ZnO), etc. In the production of the organic electroluminescent device in the embodiment of the present invention, a glass substrate is selected and ITO is used as the anode material.

[0046] The hole transport region can be a single-layer structure formed by a single material, a single-layer structure formed by multiple different materials, or a multi-layer structure formed by multiple different materials, among which NPB is a commonly used hole transport material. The hole transport material selected in the preparation of the organic electroluminescent device in the embodiment of the present invention is NPB.

[0047] The structure of the organic electroluminescent device can be a single light-emitting layer or a multi-light-emitting layer structure.

[0048] The structure of a single light-emitting layer is adopted. The light-emitting layer of the organic electroluminescent device of the present invention comprises a main material and a doping material.

[0049] The main material can be composed of a single material or a mixture of multiple materials with different structures; the doping material is an organic compound with acridone as the core in the embodiment of the present invention, and the difference between its singlet and triplet energy levels is not more than 0.2eV, and the singlet and triplet energy levels of the main material are higher than those of the doping material; among them, it is preferred that the difference between the singlet and triplet energy levels of the main material film phase with the lowest luminous energy is not more than 0.15eV; among them, it is preferred that the main material of the luminescent layer is composed of a single material, and the mass doping concentration of the doping material is 3% to 30%, preferably 6%.

[0050] The electron transport region includes one or more of a hole blocking layer, an electron transport layer and an electron injection layer; for example, the electron transport region can have a structure of an electron transport layer / electron injection layer, a structure of a hole blocking layer / electron transport layer / electron injection layer, but is not limited thereto; the electron transport layer uses Alq3 or TAZ or TPBi or a combination of any two of these three materials.

[0051] In the manufacture of the organic electroluminescent device in the embodiment of the present invention, the cathode material selected is LiF / Al.

[0052] The specific structures of several materials used in the present invention are shown below:

[0053]

[0054] The specific preparation process of device 1-30 is as follows:

[0055] The ITO anode layer on the transparent glass substrate layer was cleaned by ultrasonic cleaning with deionized water, acetone, and ethanol for 15 minutes each, and then treated in a plasma cleaner for 2 minutes;

[0056] On the ITO anode layer, HAT-CN was evaporated with a thickness of 10 nm, which served as a hole injection layer. Then, NPB was evaporated with a thickness of 50 nm, which served as a hole transport layer.

[0057] Next, a 40 nm light-emitting layer was evaporated: wherein mCBP was used as the main material, compounds 1-29 were used as doping materials, and the doping mass concentration was 6%, and elements 1-30 were made respectively;

[0058] On top of the light-emitting layer, TPBi is vacuum-deposited with a thickness of 35 nm. This layer of organic material serves as a hole blocking / electron transport layer. On top of the hole blocking / electron transport layer, an electron injection layer LiF is vacuum-deposited with a thickness of 1 nm. This layer is the electron injection layer. On top of the electron injection layer, cathode Al (80 nm) is vacuum-deposited. This layer is the cathode electrode layer.

[0059] Comparative Example 1

[0060] Preparation of organic light emitting element 31: The difference between the organic light emitting element 1-30 prepared in Example 1-30 is that:

[0061] In the light-emitting layer of the organic light-emitting element 31, DSA-ph is used as the doping material, and the doping mass concentration is 6%, and the rest is the same.

[0062] The structure of the organic light emitting element 31 prepared in Comparative Example 1 is:

[0063] ITO / HAT-CN / NPB / mCBP:DSA-ph / TPBi / LiF / Al.

[0064] Comparative Example 2

[0065] Preparation of organic light-emitting element 32: The difference between the organic light-emitting element 1-30 prepared in Example 1-30 is that TADF-1 is used as the doping material in the light-emitting layer of the organic light-emitting element 32, and the doping mass concentration is 6%, and the rest is the same.

[0066] The structure of the organic light emitting element 32 prepared in Comparative Example 2 is:

[0067] ITO / HAT-CN / NPB / mCBP:TADF-1 / TPBi / LiF / Al.

[0068] The device structures of the compounds of the embodiments of the present invention and the comparative examples are shown in Table 2 below:

[0069] Table 2: Device structure table

[0070]

[0071] The performance test of the present invention includes the following:

[0072] The organic light-emitting elements 1-30 prepared in Examples 1-30 of the present invention and the elements 31 and 32 prepared in Comparative Examples 1 and 2 were subjected to the following performance tests. The performance test results are shown in Table 3.

[0073] Table 3: Performance test results

[0074]

[0075]

[0076] From the performance data in Table 3, it can be seen that the compounds provided by the embodiments of the present invention can fully utilize triplet energy compared to traditional fluorescent materials, thereby greatly improving device efficiency. Compared with known TADF materials, the half-peak width of the spectrum is significantly reduced, and its color purity is significantly improved; the device efficiency roll-off phenomenon is significantly suppressed, and the device life is significantly improved.

[0077] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art of the present invention, several simple deductions or substitutions made without departing from the concept of the present invention should be deemed to fall within the scope of protection of the present invention.

Claims

1. An organic light-emitting material containing a phosphine radical, characterized in that: A compound having the structure shown in Formula I: wherein R1, R2, R3 and R4 are each independently hydrogen, deuterium, halogen, substituted or unsubstituted alkyl having 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl having 3 to 20 ring atoms, substituted or unsubstituted heteroalkyl having 1 to 20 carbon atoms, substituted or unsubstituted heterocyclyl having 3 to 20 ring atoms, substituted or unsubstituted aralkyl having 7 to 30 carbon atoms, substituted or unsubstituted alkoxy having 1 to 20 carbon atoms, substituted or unsubstituted aryloxy having 6 to 30 carbon atoms, substituted or unsubstituted alkenyl having 2 to 20 carbon atoms , substituted or unsubstituted aryl having 6-30 carbon atoms, substituted or unsubstituted heteroaryl having 3-30 carbon atoms, substituted or unsubstituted silyl having 3-20 carbon atoms, substituted or unsubstituted arylsilyl having 6-20 carbon atoms, substituted or unsubstituted alkylgermanyl having 3-20 carbon atoms, substituted or unsubstituted arylgermanyl having 6-20 carbon atoms, substituted or unsubstituted amino having 0-30 carbon atoms, acyl, carbonyl, carboxylic acid, ester, cyano, isocyano, hydroxyl, thiol, sulfinyl, sulfonyl, phosphino, and combinations thereof.

2. The organic light-emitting material containing phosphine oxygen group according to claim 1, characterized in that: The fluorescent compound of the organic light-emitting material is selected from, but not limited to, the following structures:

3. An application of an organic light-emitting material containing a phosphine radical as claimed in any one of claims 1 and 2, characterized in that: The organic light-emitting material containing phosphine oxygen group is applied to organic electroluminescent device.

4. The use of an organic light-emitting material containing a phosphine oxygen group according to claim 3, characterized in that: The organic electroluminescent device comprises a first electrode, a second electrode, and one or more organic layers disposed between the first electrode and the second electrode; and the organic layers comprise one of a hole injection layer, a hole transport layer, an electron blocking layer, a luminescence auxiliary layer, a luminescent layer, a hole blocking layer, an electron transport layer and an electron injection layer; and the hole transport layer comprises the organic luminescent material containing a phosphine radical.

5. An organic electroluminescent device as claimed in claim 1, used in an organic electroluminescent device; The organic electroluminescent devices include flat panel displays, computer monitors, a medical monitor, a television, a billboard, a lamp for lighting or signaling, a head-up display, a fully transparent or partially transparent display, a flexible display, a laser printer, a telephone, a mobile phone, a photo album, a personal digital assistant (PDA), a wearable device, a laptop computer, a digital camera, a video camera, a three-dimensional display, a virtual reality or augmented reality display, a vehicle, a video wall including multiple displays tiled together, a theater or venue screen, a light therapy device and a sign.

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