Self-healing stretchable thermally activated delayed fluorescent polymer and application thereof in electroluminescence

Abstract

The invention designs a self-healing stretchable thermally activated delayed fluorescent polymer, the material contains TADF molecules, so that the polymer has the performance of TADF, the polymer can be used for realizing an organic light-emitting diode (OLED) processed by a solution, and groups with hydrogen bond arrangement exist through copolymerization, so that the polymer has the self-healing stretchable performance. No precious metal is used in the synthesis process, and synthesis of the polymer is achieved through simple organic reaction. The polymer not only can be applied to future extension of organic light-emitting diodes, but also can realize breakthrough in the fields of medicine, machinery, environment, artificial intelligence and the like.

Description

Technical Field

[0001] The present invention specifically relates to the field of organic electroluminescent materials, and in particular to the molecular design of self-healing stretchable thermally activated delayed fluorescent polymer materials, belonging to the field of compound technology. Background Art

[0002] In 1961, Parker et al. observed the TADF phenomenon in tetrabromofluorescein and called it "E-type" delayed fluorescence (DF). In 2009, Adachi's research group prepared OLEDs for the first time, observed the TADF phenomenon under electrical excitation, and proposed the TADF mechanism. 1 and T 1 The energy level difference between the states is small enough (ΔE ST ) 1 The excitons in the S state can absorb the surrounding heat energy and reach the S state through the reverse intersystem crossing (RISC) process. 1 state, and then from S 1 The radiative transition from state to ground state (S 0 ) to emit light. Therefore, TADF materials make full use of triplet and singlet excitons, and theoretically can achieve 100% IQE. TADF materials are pure organic molecules, which not only make up for the high cost and environmental pollution of introducing heavy metals into phosphorescent materials, but also make full use of triplet excitons, becoming a hot research object for the new generation of organic light-emitting materials.

[0003] The work that really applied TADF materials to OLEDs was the PIC-TRZ pure organic molecule designed by Adachi et al. in 2011. By designing the molecular structure with electron donor (D) and electron acceptor (A) fragments from the perspective of quantum mechanics, such molecules usually present a distorted configuration. The overlap of the electron clouds of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) can be effectively reduced to obtain a smaller ΔEST, so that the triplet excitons can be upconverted to the singlet state, thereby achieving delayed luminescence. To date, the external quantum efficiency of TADF materials can reach 38%, which is comparable to phosphorescent materials. Therefore, TADF materials have become recognized as the third generation of organic light-emitting materials.

[0004] At present, conventional rigid electronics dominate current information technology and human life, while their rigid properties show an intrinsic mismatch with curved and deformable organisms, limiting their widespread application in various flexible scenarios. Flexible and stretchable electronics are the way forward, enabling sensing, display, and actuation of soft robots and artificial entities. Recently, great progress has been made in flexible and stretchable electronics for various emerging applications, including flexible displays, organic photovoltaics, deformable optoelectronics, stretchable circuits, and flexible energy storage devices. Although flexible displays have been commercialized, stretchable displays with reproducible stretchability and high flexibility remain to be explored. Organic light-emitting diodes (OLEDs) are becoming ideal components for stretchable displays because of their low driving voltage, high brightness, fast response time, long-term durability, and solution processing properties. To make OLEDs stretchable, several strategies have been reported, including geometric engineering and physical hybrid composites that embed organic light-emitting materials into an elastomeric matrix. Geometric engineering methods allow stretchability, but non-hybrid OLEDs fabricated in this way are limited by the stretchability of conventional electroluminescent materials, which have difficulty withstanding large mechanical deformations. To realize highly deformable OLEDs, the most common approach is to fabricate hybrid stretchable devices based on composites of conventional electroluminescent materials and soft elastic insulators. However, the introduction of soft elastic insulators to induce stretchability will sacrifice the optoelectronic performance of the device. To address this challenge, Bao et al. recently proposed a strategy to construct high-brightness stretchable OLEDs using a light-emitting layer of a nano-confined light-emitting polymer structure formed by spontaneous phase separation of soft elastomers. However, due to the obvious difference in the molecular structure of conjugated luminescent materials and non-conjugated elastomers, the compatibility and matching ability of the materials are limited. In addition, physically blended composites also require complex molecular combinations to obtain high elasticity, high stretchability, and high compatibility, which further limits the widespread application of such methods. Compared with physically blended composites, non-blended intrinsically stretchable electroluminescent elastomers (ISEEs) have become an attractive development direction due to their precisely controllable optoelectronic properties, relatively low tensile modulus, and solution processability for large-area printing. However, developing stretchable and even elastic electroluminescent elastomers without sacrificing performance is a desirable but difficult goal. Existing stretchable elastomers with luminescent properties are mainly realized by cross-linking to enhance the emission effect, which, however, poses great challenges to the construction of electroluminescent devices and is not conducive to the fabrication of non-hybrid stretchable OLEDs. In fact, the development of luminescent elastomers suitable for efficient stretchable OLEDs remains a huge challenge. Summary of the invention

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The purpose of the present invention is to provide a method for preparing a self-healing stretchable organic electroluminescent material based on heptazine ring and acrylic acid. The specific steps of the preparation process are as follows:

[0007] Heptazine ring derivatives, fluorenyl derivatives and K 2 CO 3 The solvents are mixed and reacted, and the obtained product is separated by column chromatography to obtain the intermediate product Q 1 .

[0008] Q 2 (Synthesis see below), intermediates and K 2 CO 3 The solvents are mixed and reacted, and the obtained product is separated by column chromatography to obtain product Q 3 .

[0009] Q 3 , Q 4 (Synthesis see below) and AIBN initiator were copolymerized, and the resulting product was separated by column chromatography to obtain the final product Z 1 The reaction needs to be protected in an argon environment, the reaction temperature is 65°C, and the reaction time is generally 24 hours.

[0010] Another object of the present invention is to use the self-healing stretchable organic electroluminescent material obtained by the preparation method of the self-healing stretchable organic electroluminescent material based on heptazine ring and acrylic acid in an electroluminescent device:

[0011] The self-healing stretchable organic electroluminescent material based on heptazine ring and acrylic acid is used as the light-emitting layer of the organic electroluminescent display in a non-doped manner.

[0012] The organic electroluminescent display further includes a cathode, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, an electron transport layer and an electron injection layer.

[0013] The organic electroluminescent display is manufactured in the following order: anode, hole injection layer, hole transport layer, electron blocking layer, light emitting layer, electron transport layer, electron injection layer and cathode.

[0014] The present invention has the following advantages and effects:

[0015] The present invention uses nucleophilic substitution and double bond polymerization, and the synthesis process is simple. No noble metal is used for catalysis during the synthesis process, and the cost is low. The polymer is composed of a TADF luminescent group as the main chain, and an acrylic acid group that can form a hydrogen bond effect as a side chain. The main chain is encapsulated and polymerized through the side chain, and multiple hydrogen bonds are formed between the molecular groups in the side chain. The polymerization forms a network structure connected by hydrogen bonds, so that the polymer has a self-healing and stretchable effect while achieving the luminescent effect. It is well known that optical electronic devices have a certain lifespan, and after use, certain waste will be generated, causing certain harm to the environment. The polymer in the present invention can achieve the characteristic of self-healing, and under certain circumstances, the service life of electronic devices can be extended. The side chain acrylic acid group formed by multiple hydrogen bonds realizes the stretchable effect of the polymer, which provides a feasible idea in many aspects such as artificial intelligence, medical treatment, environmental governance, biosensors, etc. in the future, and has broad commercial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is polymer Z 1 Infrared spectrum of .

[0017] Figure 2 These are the polymer stretching effects at different ratios.

[0018] Figure 3 It is the fluorescence spectra of polymers with different proportions.

[0019] Figure 4 It's Q 3 :30wt%Q 4 VL curve of the polymer.

[0020] Figure 5 It's Q 3 :30wt%Q 4 EL spectrum of the polymer. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings:

[0022] Self-healing, stretchable thermally activated delayed fluorescent macromolecular material. This material has the advantages of low cost, self-healing, stretchability, environmental friendliness, high utilization rate, wet device preparation, and simple synthesis. It is a TADF material with great development prospects for OLED devices in the future.

[0023] The self-healing, stretchable thermally activated delayed fluorescent polymer Z 1 Compounds with the following structure:

[0024] Example polymer Z 1 The synthesis process:

[0025]

[0026] Q 1 The synthesis is as follows:

[0027]

[0028] Q 2 The synthesis is as follows:

[0029]

[0030] Q 3 The synthesis is as follows:

[0031]

[0032] Q 4 The synthesis is as follows:

[0033]

[0034] Z 1 The synthesis is as follows:

[0035]

[0036] In an argon atmosphere, 10,10″-(2-(4-(2-(4-((4-vinylbenzyl)oxy)phenyl)propan-2-yl)phenoxy)-1,3,3a1,4,6,7,9-heptaazabenzene-5,8-diyl)bis(10H-spiroacridine-9,9′-fluorene]), 16-ethyl-18-(31-methyl-30-oxo-2,5,8,11,14,17,20,23,26,29-decaoxatriacontan-32-yl)-10-methylene- 1,15-dioxo-1-((2-oxo-2,3-dihydrobenzo[d]thiazol-5-yl)amino)-11,14-dioxa-2,9-diazanona-19-oic acid and initiator AIBN were dissolved in THF and argon was replaced by three passes for 5 minutes. The reaction bottle was sealed and frozen at -40°C for 15 minutes with continuous ventilation, then taken out and warmed to room temperature and reacted at 65°C for 24 hours. After the reaction was completed, a viscous liquid was obtained, which was purified by column chromatography to obtain a yellow viscoelastic polymer.

[0037] Testing and Characterization

[0038] 1. Fourier infrared spectroscopy test

[0039] The self-healing stretchable polymer Z was studied by FT-IR. 1 Infrared spectrum. Figure 1 As shown, at 1070cm -1 The OH bond stretching vibration peak of acrylic acid carboxyl (-COOH) is at 1600cm-1 The characteristic absorption peak of the C=O double bond on the carboxyl group of acrylic acid is at 2340 cm -1 The characteristic stretching vibration peak of the CH bond of the heptazine group is at 2930 cm -1 The characteristic absorption peak of the stretching vibration of the C=N double bond on the fluorene group is shown in Figure 2. Infrared spectroscopy can provide characteristic absorption information of different functional groups in polymers, which can help determine the chemical structure and composition of polymers, and assist in studying the changes of functional groups in molecular polymerization reactions, so as to determine the analysis of the chemical composition of polymers.

[0040] 2. Stress-strain test

[0041] The tensile strength of polymers with different polymerization ratios was tested by a universal tensile testing machine. Figure 2 As shown in the figure, with the increase of the polymerization ratio of the side chain acrylic derivatives, it can be clearly seen that the stretching ability of the polymer is constantly increasing, reflecting that the acrylic derivatives containing hydrogen bonding groups in the side chains can form elastic network structures connected by multiple hydrogen bonds after polymerization, which is the key to the polymer's ability to complete stretching. By precisely controlling the chain length and branching points of acrylic derivatives and defining the subtle interaction between structure and performance, the polymer can disperse stress during stretching, thereby improving its tensile properties.

[0042] 3. Fluorescence test

[0043] The fluorescence spectrometer was used to test the fluorescence spectra of self-healing stretchable polymers with different polymerization ratios. Figure 3 As shown in the figure, with the increase of the polymerization ratio of the side chain acrylic acid derivatives, it can be clearly seen that the fluorescence spectrum of the polymer has basically not changed, reflecting that after the acrylic acid derivatives containing hydrogen bonding groups on the side chain polymerize the TADF luminescent molecules, there will be no red shift or blue shift in the TADF luminescent molecules. This shows that after the side chain assembly of the TADF molecule by acrylic acid derivatives, the stretchable performance is achieved while maintaining a very stable luminescence ability.

[0044] 4. Electroluminescence performance test

[0045] In order to further study the luminescent properties of the self-healing stretchable polymer, we studied its electroluminescent properties. The organic electroluminescent device was prepared by solution method, the hole transport layer and the emission layer (EML) were prepared by spin coating, and the subsequent electron transport layer (ETL) TPBi was deposited by thermal evaporation. 30wt% Q 4 With Q 3 After polymerization, the emission layer (EML) is formed for device manufacturing. Figure 4 and Figure 5The voltage-luminance curve (VL) and EL spectrum of the polymer-based device clearly show typical blue light emission, which means that the acrylic acid group with hydrogen bonds in the side chain does not affect the light-emitting unit in terms of luminescence effect. This proves that the polymer not only has the characteristics of self-healing and stretchable, but also still shows a good level in electroluminescence, creating a new feasible way to realize the diversified OLED device manufacturing.

[0046] The above are all preferred embodiments of the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, various equivalent modifications to the present invention belong to the protection scope of the claims attached to this application.

Claims

1. A self-healing, stretchable, thermally activated delayed fluorescent polymer, characterized in that: The TADF luminescent group is modified by double bond polymerization, which plays a role in self-healing and stretching of the raw materials. Its general structural formula is: Wherein, X, Y are the degree of polymerization, and the degree of polymerization is an integer of 10-10000. are different groups, which are TADF light-emitting units in different forms and acrylic acid derivatives containing hydrogen bonds or multiple hydrogen bonds. It is a C=C double bond; Said The independent structure is CH2=CH2; The Any DA-type TADF light-emitting unit that can form a C=C double bond, including but not limited to the following structures formed by disordered combination of acceptors and donors: The TADF unit acceptor is one of benzonitrile, triazine, diphenyl sulfone, benzophenone, oxadiazole, pyrimidine, azaphenanthrene, cyanobenzene, etc.; The TADF unit donor is one of carbazole, aniline, triphenylamine, acridine, phenoxazine, diphenylacridine, 9,9-dimethylacridine, 5-phenylphenazine, etc. The It is an acrylic acid derivative containing hydrogen bonds or multiple hydrogen bonds, including but not limited to the following acrylic acid derivative structures: acrylic acid, methacrylic acid, hydroxypropyl acrylate, terephthalic acid, and 2-bromoacrylic acid.

2. The self-healing stretchable thermally activated delayed fluorescent polymer according to claim 1, characterized in that: Application of the polymer as a self-healing stretchable thermally activated delayed fluorescent material.

3. An electroluminescent device, comprising glass, a conductive glass substrate layer attached to the glass, a hole injection layer bonded to the conductive glass substrate layer, a hole transport layer bonded to the hole injection layer, a light-emitting layer bonded to the hole transport layer, a hole blocking layer bonded to the light-emitting layer, an electron transport layer bonded to the hole blocking layer, and a cathode layer bonded to the electron transport layer, characterized in that: The light-emitting layer is the self-healing stretchable polymer according to claim 1.

4. The electroluminescent device according to claim 3, characterized in that: The light-emitting layer of the device is composed solely of the self-healing stretchable polymer described in claim 1, and the device is manufactured without doping.

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