CN108219779A - A kind of thermal activation delayed fluorescence material and application - Google Patents

Abstract

The invention belongs to field of organic electroluminescence more particularly to a kind of thermal activation delayed fluorescence material and applications.The present invention provides a kind of new small molecule electroluminescent organic material with double spiral shell type structures, such material has the triaromatic amine structural unit of the anthrone structural unit for drawing electronics and supplied for electronic simultaneously, with D A types molecular structures and very small triplet excited state singlet excited energy level difference Δ Est, with larger steric hindrance and excellent thin film stability, with appropriate molecular mass and excellent thermal stability, it is suitble to the vapor deposition processing procedure of small molecule organic electroluminescence device.Organic electroluminescence device using the material of the present invention as the luminescent layer making of organic electroluminescence device, illustrates preferable efficiency, 6350 7640cd/m2 of maximum brightness of device, 27.2 30.2cd/A of maximum current efficiency, and device efficiency is excellent.

Description

A thermally activated delayed fluorescent material and its application

technical field

The invention belongs to the field of organic electroluminescence, in particular to a thermally activated delayed fluorescent material and its application.

Background technique

Organic electroluminescent diode (OLED) was produced in the 1980s. It has many advantages such as self-illumination, wide viewing angle, fast response speed, wide color gamut, and flexible display. After 30 years of continuous development, the OLED The technology has gradually matured. At present, organic electroluminescence technology has been widely used in many products such as smart phones, flat-panel TVs, and virtual reality.

Organic electroluminescent devices are current-driven light-emitting devices, which can be divided into fluorescent devices and phosphorescent devices according to different light-emitting mechanisms. When charges are injected into the device from the electrodes, due to the randomness of the electron spin direction, the proportion of singlet excitons is only 25%, and the other 75% are triplet excitons. In general, fluorescent devices can only use singlet excited state excitons to emit light, while phosphorescent devices can simultaneously use the energy of singlet excitons and triplet excitons. Therefore, the efficiency of phosphorescent devices is much greater than that of fluorescent devices.

Although the efficiency of phosphorescent devices is higher than that of fluorescent devices, phosphorescent devices also have their shortcomings. For example, phosphorescent materials are mainly complexes containing noble metals, especially metal iridium and platinum complexes. Since metal iridium and platinum are expensive, Therefore, the price of phosphorescent materials is extremely expensive, which limits the application space of phosphorescent materials.

Therefore, the development of OLED devices that use fluorescent materials as light-emitting molecules and can achieve high-efficiency light emission is very attractive.

In 2012, C. Adachi published a paper in Nature (Nature., 2012, 492, 234), and reported for the first time a fluorescent device based on a thermally activated delayed fluorescence (TADF) mechanism to achieve high-efficiency light emission. Since this type of material can simultaneously The energy of singlet excitons and triplet excitons is used to emit light, so its device efficiency is much higher than that of traditional fluorescent materials. In theory, its luminous efficiency is equivalent to that of phosphorescent materials. Therefore, the development of new TADF materials is for high efficiency. The production of fluorescent devices has brought a new direction.

In order to realize TADF luminescence, organic materials need to have a very small triplet excited state-singlet excited state energy level difference (ΔEst), so as to ensure that the triplet excitons can undergo anti-intersystem crossing under excited conditions, thereby achieving thermal activation. Delayed fluorescence emission. In terms of molecular structure, TADF materials often need to have an electron donor structural unit (abbreviated as D) and an electron acceptor structural unit (abbreviated as A). The D-A molecular structure composed of this is conducive to the realization of thermally activated delayed fluorescence emission.

Contents of the invention

The technical problem to be solved by the present invention is to provide a thermally activated delayed fluorescent material and its application.

The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a thermally activated delayed fluorescent material, its structural formula is as follows:

Wherein, R ₁ and R ₂ are each independently an H atom, an F atom, a methyl group, an ethyl group or a tert-butyl group.

Compounds C01-C08 listed in the figure below are representative structures conforming to the spirit and principle of the present invention. It should be understood that the following compound structures are listed only to better explain the present invention, not to limit the present invention.

The third object of the present invention is to provide the application of the above thermally activated delayed fluorescent material as a light-emitting layer material in the field of manufacturing organic electroluminescent devices.

During application, the prepared organic electroluminescence device generally comprises the ITO conductive glass substrate (anode), the hole injection layer (HAT-CN), the hole transport layer (TAPC), the light-emitting layer (in the present invention) stacked successively. The material +CBP), electron transport layer (TpPyPB), electron injection layer (LiF) and cathode layer (Al). All functional layers are made by vacuum evaporation process. The molecular structural formulas of the organic compounds used in this type of device are shown below.

The beneficial effects of the present invention are:

1. The present invention provides a class of novel small-molecule organic electroluminescent materials with a double-helical structure. Structurally, this type of material has both an electron-drawing anthrone structural unit and an electron-donating triarylamine structural unit, which makes the material With a D-A molecular structure and a very small triplet excited state-singlet excited state energy gap ΔEst, the material can realize thermally activated delayed fluorescence emission. This type of material can be used as the light-emitting layer of small molecule organic electroluminescent devices, especially green organic The light-emitting layer of an electromechanical luminescence device is applied in the field of organic electroluminescence.

2. The material of the present invention has relatively large steric hindrance and excellent film stability. The molecular mass of this type of material is 710-830, has appropriate molecular mass and excellent thermal stability, and is suitable for small molecule organic electroluminescent devices evaporation process.

3. The organic electroluminescent device made by using the material of the present invention as the light-emitting layer of the organic electroluminescent device shows better performance, the maximum brightness of the device is 6350-7640cd/m2, and the maximum current efficiency is 27.2-30.2cd/A , excellent device efficiency.

Description of drawings

Fig. 1 is the structural representation of organic electroluminescence device of the present invention;

In the figure, 101, ITO conductive glass substrate; 102, hole injection layer; 103, hole transport layer; 104, light emitting layer; 105, electron transport layer; 106, electron injection layer; 107, cathode layer.

Detailed ways

The principles and features of the present invention are described below, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention.

The preparation of embodiment 1 compound C01

(1) Preparation of compound A01: In a 500mL three-necked flask, add compound 5,10-bis(2-bromobenzene)-5,10-dihydrophenazine (19.7g, 0.04mol), tetrahydrofuran (180g), and cool down To -78°C, add n-butyllithium in n-hexane solution (2.2mol/L, 36.5mL, 0.08mol) dropwise, after 1h the dropwise addition was completed, keep at -78°C for 1.5h, and add 9-anthrone (15.5g, 0.08 mol) was dissolved in 80g of tetrahydrofuran, slowly dripped into the reaction bottle, and the dropwise addition was completed in 1 hour. The temperature was kept at -78°C for 3 hours, and the reaction bottle was moved into a water bath, and the temperature was naturally raised to 0°C. The reaction was quenched with hydrochloric acid, stirred for 0.5 h, separated, the organic phase was collected, and the solvent was removed under reduced pressure to obtain 29.6 g of the crude product A01, which was directly put into the next reaction without further refining;

(2) Preparation of Compound B01: In a 500mL three-neck flask, add 29.6g of the crude product of Compound A01 prepared in the previous step, add 180g of glacial acetic acid, 0.5g of concentrated hydrochloric acid with a mass concentration of 37%, heat up to 105°C, stir for 3h, and naturally The temperature was lowered to 40°C, solids were precipitated, filtered by suction, rinsed with 300g of absolute ethanol, the crude product was collected, purified by silica gel column chromatography, the eluent was n-hexane: dichloromethane = 1:1 (v/v), Further use toluene as solvent for recrystallization to obtain 8.6g of the target product B01 fine product, yield 31.3%, high resolution mass spectrum, positive ion mode, molecular formula C ₅₂ H ₃₄ N ₂ , theoretical value 686.2722, test value 686.2728;

(3) Preparation of compound C01: In a 500mL three-necked flask, add compound B01 (8.23g, 0.012mol), dichloromethane (280mL), manganese dioxide (2.6g, 0.03mol), heat up to 30-32°C, Insulate for 32 hours, cool down to 20°C, filter with suction, rinse the filter cake with 500g of tetrahydrofuran, collect the filtrate, remove the solvent under reduced pressure, and use silica gel column chromatography to refine the obtained crude product. The eluent is n-hexane: dichloromethane = 1:2 (v/v), the obtained target C01 crude product was further sublimated and purified by chemical vapor deposition system, the sublimation temperature was 355°C, and 2.3g target C01 fine product was obtained, the yield was 26.8%, high-resolution mass spectrometry, positive ion mode, molecular formula C ₅₂ H ₃₀ N ₂ O ₂ , theoretical value 714.2307, test value 714.2309, elemental analysis (C ₅₂ H ₃₀ N ₂ O ₂ ), theoretical value C: 87.37, H: 4.23, N: 3.92, O: 4.48, found value C: 87.34, H: 4.23, N: 3.91, O: 4.52.

The preparation of embodiment 2 compound C02

Referring to Example 1, using 5,10-bis(2-bromo-5-methylbenzene)-5,10-dihydrophenazine as raw material, compound C02 was prepared to obtain 1.7 g of the target object, high-resolution mass spectrum, positive ion Pattern, molecular formula C ₅₄ H ₃₄ N ₂ O ₂ , theoretical value 742.2620, found value 742.2627, elemental analysis (C ₅₄ H ₃₄ N ₂ O ₂ ), theoretical value C: 87.31, H: 4.61, N: 3.77, O: 4.31 , Found C: 87.33, H: 4.60, N: 3.75, O: 4.32.

The preparation of embodiment 3 compound C03

Referring to Example 1, using 5,10-bis(2-bromo-4-methylbenzene)-5,10-dihydrophenazine as raw material, compound C03 was prepared to obtain 1.4 g of the target object, high-resolution mass spectrum, positive ion Pattern, molecular formula C ₅₄ H ₃₄ N ₂ O ₂ , theoretical value 742.2620, found value 742.2625, elemental analysis (C ₅₄ H ₃₄ N ₂ O ₂ ), theoretical value C: 87.31, H: 4.61, N: 3.77, O: 4.31 , found values C: 87.31, H: 4.63, N: 3.76, O: 4.30.

The preparation of embodiment 4 compound C04

Referring to Example 1, using 5,10-bis(2-bromo-4,5-dimethylbenzene)-5,10-dihydrophenazine as raw material, compound C04 was prepared to obtain 2.0 g of the target substance, high-resolution mass spectrum , positive ion mode, molecular formula C ₅₆ H ₃₈ N ₂ O ₂ , theoretical value 770.2933, test value 770.2938, elemental analysis (C ₅₆ H ₃₈ N ₂ O ₂ ), theoretical value C: 87.25, H: 4.97, N: 3.63, O: 4.15, Found C: 87.26, H: 4.96, N: 3.60, O: 4.18.

The preparation of embodiment 5 compound C05

Referring to Example 1, using 5,10-bis(2-bromo-4-ethylbenzene)-5,10-dihydrophenazine as raw material, compound C05 was prepared to obtain 1.9 g of the target object, high-resolution mass spectrum, positive ion Pattern, molecular formula C ₅₆ H ₃₈ N ₂ O ₂ , theoretical value 770.2933, found value 770.2936, elemental analysis (C ₅₆ H ₃₈ N ₂ O ₂ ), theoretical value C: 87.25, H: 4.97, N: 3.63, O: 4.15 , found C: 87.23, H: 4.99, N: 3.61, O: 4.17.

The preparation of embodiment 6 compound C06

Referring to Example 1, using 5,10-bis(2-bromo-4-tert-butylbenzene)-5,10-dihydrophenazine as raw material, compound C06 was prepared to obtain 1.5 g of the target substance, high-resolution mass spectrum, positive Ion mode, molecular formula C ₆₀ H ₄₆ N ₂ O ₂ , theoretical value 826.3559, test value 826.3556, elemental analysis (C ₆₀ H ₄₆ N ₂ O ₂ ), theoretical value C: 87.14, H: 5.61, N: 3.39, O: 3.87, found values C: 87.13, H: 5.60, N: 3.42, O: 3.85.

The preparation of embodiment 7 compound C07

Referring to Example 1, using 5,10-bis(2-bromo-4-fluorobenzene)-5,10-dihydrophenazine as a raw material, compound C07 was prepared to obtain 1.2 g of the target product, high-resolution mass spectrum, positive ion mode , molecular formula C ₅₂ H ₂₈ F ₂ N ₂ O ₂ , theoretical value 750.2119, test value 750.2116, elemental analysis (C ₅₂ H ₂₈ F ₂ N ₂ O ₂ ), theoretical value C: 83.19, H: 3.76, F: 5.06, N: 3.73, O: 4.26, Found C: 83.16, H: 3.75, F: 5.07, N: 3.75, O: 4.27.

The preparation of embodiment 8 compound C08

Referring to Example 1, using 5,10-bis(2-bromo-5-fluorobenzene)-5,10-dihydrophenazine as a raw material, compound C08 was prepared to obtain 1.3 g of the target product, high-resolution mass spectrum, positive ion mode , molecular formula C ₅₂ H ₂₈ F ₂ N ₂ O ₂ , theoretical value 750.2119, test value 750.2117, elemental analysis (C ₅₂ H ₂₈ F ₂ N ₂ O ₂ ), theoretical value C: 83.19, H: 3.76, F: 5.06, N: 3.73, O: 4.26, Found C: 83.17, H: 3.75, F: 5.09, N: 3.74, O: 4.25.

In the present invention, compound C01, compound C02, compound C03, compound C04, and compound C07 are selected as light-emitting layers to produce organic electroluminescent devices.

It should be understood that the device implementation process and results are only for better explaining the present invention, not limiting the present invention.

Application example 1

Application of Compound C01 in Organic Electroluminescent Devices:

a) Cleaning ITO (indium tin oxide) glass: ultrasonically clean the ITO glass with deionized water, acetone, and ethanol for 30 minutes each, and then treat it in a plasma cleaner for 5 minutes;

b) Vacuum evaporation of the hole injection layer HAT-CN on the anode ITO glass with a thickness of 10nm;

c) On the hole injection layer HAT-CN, a hole transport layer TAPC is vacuum evaporated with a thickness of 30nm;

d) On top of the hole transport layer TAPC, the light-emitting layer material CBP and compound C01 are mixed and evaporated in vacuum, wherein the mass ratio of CBP to compound C01 is 95:5, and the thickness is 30nm;

e) On the light-emitting layer, an electron transport layer TpPYPB is vacuum-evaporated with a thickness of 40 nm;

f) On top of the electron transport layer, an electron injection layer LiF is vacuum evaporated with a thickness of 1 nm;

g) On the electron injection layer, a cathode Al is vacuum-evaporated to a thickness of 100 nm.

The structure of device 1 is ITO/HAT-CN(10nm)/TAPC(30nm)/CBP+compound C01 (mass ratio 95:5, 30nm)/TpPYPB(40nm)/LiF(1nm)/Al(100nm), vacuum evaporation During the process, the pressure was <1.0X 10 ^-3 Pa, and the optoelectronic data such as the turn-on voltage, maximum brightness, maximum current efficiency, and luminescent color of device 1 are shown in Table 1.

For the light-emitting layer of application examples 2-5, compound C01 in application example 1 was replaced with compound C02, compound C03, compound C04, and compound C07, respectively, and devices 2 to 5 were prepared. The photoelectric performance is shown in Table 1.

comparative example

Replace compound C01 in application example 1 with compound C-545T to obtain device 6;

The structure of device six is ITO/HAT-CN(10nm)/TAPC(30nm)/CBP+C-545T (mass ratio 95:5, 30nm)/TpPYPB(40nm)/LiF(1nm)/Al(100nm); The photoelectric performance of the device is shown in Table 1.

Table 1

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (3)

1. A thermally activated delayed fluorescent material, characterized in that its structural formula is as follows: Wherein, R ₁ and R ₂ are each independently an H atom, an F atom, a methyl group, an ethyl group or a tert-butyl group. 2. The thermally activated delayed fluorescent material according to claim 1, wherein its structural formula is any one of the following structures: 3. A thermally activated delayed fluorescent material according to claim 1 or 2 is used as a light-emitting layer material in the field of making organic electroluminescent devices.