CN113185526A - Green light thermal activation delayed fluorescent material and preparation method thereof - Google Patents

Green light thermal activation delayed fluorescent material and preparation method thereof Download PDF

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CN113185526A
CN113185526A CN202110524488.8A CN202110524488A CN113185526A CN 113185526 A CN113185526 A CN 113185526A CN 202110524488 A CN202110524488 A CN 202110524488A CN 113185526 A CN113185526 A CN 113185526A
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formula
fluorescent material
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delayed fluorescent
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方一文
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Nanchang Wanji Technology Co ltd
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    • C07D491/02—Heterocyclic compounds containing in the condensed ring system both one or more rings having oxygen atoms as the only ring hetero atoms and one or more rings having nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D451/00 - C07D459/00, C07D463/00, C07D477/00 or C07D489/00 in which the condensed system contains two hetero rings
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Abstract

The invention belongs to the technical field of photoelectric display devices, and particularly relates to a green light thermal activation delayed fluorescent material and a preparation method thereof. The invention provides a green light thermal activation delayed fluorescent material, which has a structural formula shown as a formula (I). The invention also provides a preparation method of the green-light thermal-activation delayed fluorescent material, which comprises the step of carrying out substitution reaction on 2-bromo-7- (pyranyl-1-yl) -9H-thioxanthone-9-10, 10-dioxide and a compound shown in a formula (II) to prepare the compound shown in the formula (I). The invention provides a green-light thermally-activated delayed fluorescent material and a preparation method thereof, and solves the technical problems that the existing green-light TADF material is difficult to synthesize and the device efficiency is low.

Description

Green light thermal activation delayed fluorescent material and preparation method thereof
Technical Field
The invention belongs to the technical field of photoelectric display devices, and particularly relates to a green light thermal activation delayed fluorescent material and a preparation method thereof.
Background
In recent years, due to the low efficiency of conventional fluorescent organic light emitting diodes and the high cost of phosphorescent organic light emitting diodes, scientists have been interested in developing a new generation of delayed organic electroluminescent materials based on the conversion of triplet excitons into singlet excitons, such as novel organic electroluminescent materials having a triplet-triplet delayed fluorescence effect and a thermally activated delayed fluorescence effect. Among them, TADF materials are the fastest growing. Among electroluminescent three-primary-color materials, the molecular synthesis of the TADF material is difficult due to the green light. Therefore, the green molecular species are relatively few and the device efficiency is not high.
Disclosure of Invention
The invention provides a green-light thermally-activated delayed fluorescent material and a preparation method thereof, and solves the technical problems that the existing green-light TADF material is difficult to synthesize and the device efficiency is low.
The invention provides a green light thermal activation delayed fluorescent material, which has a structural formula shown as a formula (I):
Figure BDA0003065299480000011
the invention also provides a preparation method of the green light thermal activation delayed fluorescent material, which comprises the steps of carrying out substitution reaction on the compound shown in the formula (III) and the compound shown in the formula (II) to prepare the compound shown in the formula (I);
Figure BDA0003065299480000021
preferably, the time of the substitution reaction is 8 to 20 hours.
Preferably, the time of the substitution reaction is 20 h.
The invention has the following beneficial effects:
the TADF material prepared by the embodiment of the invention has the absorption wavelength of about 500nm and the emission wavelength of 550nm-600nm, is green light emission, has obvious red shift of the emission spectrum along with the increase of the reaction time, and can be attributed to ICT effect in a molecular structure. The fluorescence quantum yield of the TADF material prepared by the embodiment of the invention is more than 85%, and the transient decay lifetime tau p (ns) of the TADF material is smaller, which shows that the electroluminescent efficiency roll-off of the TADF material is smaller. The brightness of the prepared compound is improved along with the increase of the reaction time in the embodiment of the invention, which is from 14268cd/m2Increased to 15723cd/m2The maximum external quantum efficiency can reach 21.3%, and the external quantum efficiency of the TADF material prepared by the embodiment of the invention is more than 15%.
Drawings
FIG. 1 is a UV-VIS absorption spectrum of the compound obtained in examples 6 and 7 of the present invention;
FIG. 2 is a PL spectrum of a compound prepared in examples 6 and 7 of the present invention;
FIG. 3 is a current density-voltage-luminance curve of examples 6 and 7 of the present invention;
FIG. 4 is a graph of external quantum efficiency versus current density for examples 6 and 7 of the present invention;
wherein the reference numbers are as follows:
1. example 6; 2. example 7.
Detailed Description
The present invention will be described in further detail with reference to specific examples, which are not intended to limit the present invention in any manner. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.
Example 1
Pyrene (2.02g, 10mmol) was dissolved in 50ml of hydrogen peroxide, and hydrogen bromide (1.21g, 15mmol), a mixed solution of ether and methanol (volume ratio ═ 1:2) was added to the above solution, stirred at 0 ℃ for 8h, and the resulting product was recrystallized in ethanol to give the product 1-bromopyrene (2.38g, yield 85%) whose chemical reaction equation was:
Figure BDA0003065299480000031
example 2
1-bromopyrene (2.81g, 10mmol), 2- (dimethyl-13-oxoalkyl) -4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane (3.46g,20mmol), 100ml of anhydrous tetrahydrofuran and butyllithium (40mmol) were added to a 250ml three-necked flask, and after introducing argon gas for 10min, the temperature was lowered to-78 ℃ to carry out a reaction for 28 hours, and after completion of the reaction, extraction purification treatment was carried out to obtain 4,4,5, 5-tetramethyl-2- (pyran-1-yl) -1,3, 2-dioxaborane (2.33g, yield 71%) as a product, the chemical reaction equation of which was:
Figure BDA0003065299480000041
example 3
To a 250mL dry single neck flask, 9H-thioxanthone (2.12g, 10mmol) and CCl were added4(20mL), slowly adding dropwise at room temperature to dissolve in CCl4After dropwise addition of (10mL) liquid bromine (1.55mL, 30mmol), the mixture was refluxed for 8h while being heated, and after TLC monitoring reaction, the mixture was cooled and evaporated to dryness to obtain a pale yellow crude product. The crude product was dissolved in 30ml of THF and Et dissolved in 10ml of THF was added dropwise under ice bath3N (50mL, 9.1mmol), after the addition was complete, the ice bath was removed and the mixture was stirred at room temperature for 4 h. After the reaction is finished, evaporating the solvent to dryness, adding ethyl acetate for extraction (30mL), combining organic phases, adding a saturated sodium chloride solution for backwashing, drying the mixture by anhydrous magnesium sulfate, carrying out rotary evaporation concentration, and carrying out column chromatography (V petroleum ether: V dichloromethane is 3: 1) to obtain a product 2, 7-dibromo 9H-thioxanthene (3.03g, the yield is 82%) with a chemical reaction equation:
Figure BDA0003065299480000042
example 4
4-tert-butylaniline (1.25g, 10mmol), 2, 7-dibromo 9H-thioxanthene (3.7g, 10mmol) and glacial acetic acid (50mL) were added to a 100mL round-bottomed flask and stirred well. Placing the round-bottom flask in a 110 ℃ oil bath kettle, refluxing, heating and stirring for 24 hours, pouring the whole reaction system into 150mL of ice water after the reaction is finished, standing for a few minutes, and filtering to obtain a crude product after the product is separated out. The crude product was dried in a desiccator for 12 hours and transferred to a rotary bottle to which a mixed solvent of methylene chloride and ethanol and 3g of silica gel powder were added and rotary-distilled. Column chromatography purification using dichloromethane as eluent gave the final product of the compound of formula (IV) (3.40g, 70% yield) according to the chemical reaction equation:
Figure BDA0003065299480000051
example 5
4,4,5, 5-tetramethyl-2- (pyran-1-yl) -1,3, 2-dioxaborane (0.656g, 2mmol), the compound represented by the formula (IV) (2.43g, 5mmol), anhydrous potassium carbonate (1.6g, 11.6mmol), 80mL of toluene, 40mL of tetrahydrofuran, and 40mL of deionized distilled water were charged into a 250mL round-bottomed flask, stirred uniformly, degassed under nitrogen and liquid nitrogen atmosphere20 minutes, the catalyst Pd (PPh) is added after the degassing is successful3)4(135mg,0.12mmol), degassed twice again to remove all oxygen from the system and finally placed the round bottom flask in an 85 ℃ oil bath for reflux heating for 30 hours. After the reaction is finished, cooling to room temperature, adding deionized water and dichloromethane, stirring and extracting. Adding the extracted organic phase and a proper amount of silica gel powder into a rotary bottle for spin-drying. And finally, mixing petroleum ether: 1-dichloromethane: 2 column chromatography purification with developing solvent to obtain the product of the compound of formula (III) (1.01g, 83% yield), which has the chemical reaction formula:
Figure BDA0003065299480000061
example 6
To a suspension of the compound represented by the formula (III) (6.06g, 10mmol) in anhydrous THF (120mL) was added dropwise n-butyllithium (6.4mL, 12.8mmol, 2.0M in cyclohexane) under a nitrogen atmosphere at-78 ℃. Stirring was continued for 3h, then the compound of formula (II) (6.254g, 18mmol) was added, the mixture was warmed to 80 ℃ and after stirring for 8h, the reaction was monitored by TLC, the organic compound obtained was extracted with dichloromethane, the residue obtained was dissolved in dichloromethane (50ml) and after stirring for 6 h at room temperature, the organic phase was Na2SO4And (4) extracting. The crude product obtained was subjected to silica gel column chromatography (using petroleum ether: dichloromethane (1: 3) as an eluent) to obtain the compound represented by the formula (I) (6.8g, yield 78%) whose chemical reaction equation is:
Figure BDA0003065299480000062
example 7
The difference between this example and example 6 is: the reaction time of example 6 was 8h and that of example 7 was 20h, to finally obtain compound 2(5.98g, yield 81%).
In conclusion, the ultraviolet-visible absorption spectrum test is carried out by adopting a Lamabda35 ultraviolet-visible spectrophotometer of Perkinelmer company in USA; performing PL spectrum test by a Fluoromax-4 fluorescence spectrometer of HORIBA company; testing the fluorescence quantum yield by a HAMAMATSU C11347 fluorescence quantum tester; TADF material was tested for brightness, ignition voltage, etc. using a Keithley236 instrument and calibrated with a silicon photodiode. Transient lifetime testing and delayed lifetime were determined using an EdinburghInsumentsFLS 980 spectrometer. Outside the nitrogen glove box, the color coordinates CIE were determined with a PhotoResearchPR705 type optical analyzer after the device was encapsulated.
The preparation process of the device comprises the following steps:
the preparation of the organic electroluminescent diode needs the following processes:
1) and putting the film developing frame with the ITO glass substrate in acetone, isopropanol, a washing solution and deionized water, and ultrasonically treating the possibly residual stains, such as photoresist and the like, on the surface of the ITO glass substrate by using an ultrasonic device and improving interface contact. Then drying in a vacuum oven;
2) placing the ITO in an oxygen Plasma etching instrument, continuously bombarding the ITO for 30 minutes by using O2Plasma, and completely removing possible residual organic matters on the surface of the ITO glass substrate;
3) HAT-CN was spin-coated on the ITO to a thickness of 10nm, and functions to reduce the influence of leakage current while increasing hole injection. Then drying the mixture in a vacuum oven for 12 hours at a temperature of 75 ℃;
4) in a glove box under nitrogen atmosphere, α -NPD was spin-coated on the HAT-CN layer to a thickness of about 40nm and heated at 100 ℃ for 30 minutes to remove the residual solvent.
5) And a layer of luminous organic matter film is spin-coated on the alpha-NPD layer, and the thickness is 80 nm. Heating and annealing for 20 minutes at the temperature of 80 ℃ on a heating table to remove residual solvent and improve the appearance of the luminescent layer film;
6) in the vacuum evaporation chamber, a layer of lithium fluoride (LiF) which is helpful for electron injection is firstly evaporated on the luminescent layer, and the thickness is 1.5 nm. Then, a layer of aluminum (Al) cathode is evaporated, and the thickness is 150 nm.
The effective area of the device is 0.18cm2. The thickness of the organic layer was measured by a quartz crystal monitoring thickness gauge.The device is prepared by polar curing and encapsulating in ultraviolet light with epoxy resin and thin-layer glass.
In summary, FIG. 1 is a diagram of the UV-VIS absorption spectrum of the compound prepared in the example of the present invention. Fig. 2 shows PL spectra of examples 6 and 7 of the present invention, and as can be seen from fig. 1, the TADF material prepared by the example of the present invention has an absorption wavelength of about 500nm and an emission wavelength of between 550nm and 600nm, and is green light emission, and the emission spectrum has a significant red shift with increasing reaction time, and is attributable to ICT effect in the molecular structure. In particular, the photophysical data for the novel TADF materials obtained in examples 6-7 of the present invention are shown in Table 1,
TABLE 1 photophysical data for TADF materials obtained according to examples 6 and 7 of the present invention
Figure BDA0003065299480000081
As can be seen from table 1, the color coordinates of the TADF materials obtained in examples 6 and 7 of the present invention show green emission, the fluorescence quantum yield of the TADF materials obtained in examples 6 and 7 of the present invention is above 85%, and the transient decay lifetime τ p (ns) of the present invention is relatively small, indicating that the roll-off of the electroluminescence efficiency of the present invention is relatively small.
The invention uses ITO (120nm)/HAT-CN (10 nm)/alpha-NPD (40nm)/emitter (80nm)/LiF (1.5nm)/Al (150nm) as a device, TADF materials prepared in examples 6 and 7 are used as a light-emitting layer, wherein HAT-CN and alpha-NPD respectively refer to 1,4,5,8,9, 12-hexaazatriphenylene hexacyano-nitrile and 4,4' -bis (N- (naphthalene-1-yl) -N-phenylamino) biphenyl, wherein, FIG. 3 is a current density-voltage-luminance curve of examples 6 and 7 of the invention, and FIG. 4 is an external quantum efficiency-current density curve of examples 6 and 7 of the invention; specific electroluminescent property data are shown in table 2.
Table 2 electroluminescent property data for examples 6 and 7
Examples Von L(cd/m2) EQE(％)
Example 6 4.0 14268 15.2
Example 7 4.3 15723 21.3
As is clear from Table 2, the luminance of the compound obtained in the examples of the present invention was improved as the reaction time was increased, from 14268cd/m2Increased to 15723cd/m2The external quantum efficiency can reach 21.3% at most, and the external quantum efficiency of the TADF material prepared by the embodiment of the invention is more than 15%, which shows that reverse system jump of T1-S1 exists in the molecular structure, and the current efficiency is remarkably improved along with the rise of voltage in the embodiment of the invention, which shows that the TADF material prepared by the embodiment of the invention has smaller resistance and better carrier transmission efficiency.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (4)

1. A green light thermal activation delayed fluorescence material is characterized in that the structural formula is shown as the formula (I):
Figure FDA0003065299470000011
2. a preparation method of a green-light thermally-activated delayed fluorescent material is characterized by comprising the steps of carrying out substitution reaction on a compound shown as a formula (III) and a compound shown as a formula (II) to prepare a compound shown as a formula (I);
Figure FDA0003065299470000012
3. the method of claim 2, wherein the time of the substitution reaction is 8-20 h.
4. The method of claim 2, wherein the time of the substitution reaction is 20 h.
CN202110524488.8A 2021-05-13 2021-05-13 Green light thermal activation delayed fluorescent material and preparation method thereof Withdrawn CN113185526A (en)

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Application publication date: 20210730