Thermally-induced delayed fluorescence red light material containing naphthalimide, and preparation method and application thereof

Abstract

The invention belongs to the field of organic light-emitting materials, and discloses a thermally-induced delayed fluorescence red-light-emitting material containing an imide structure and a synthesis method and application of the thermally-induced delayed fluorescence red-light-emitting material. The synthesis method disclosed by the invention is simple in process and easy to purify, and the synthesized luminescent material is suitable for preparing a luminescent layer in an organic electroluminescent device. The organic light-emitting material can also be used as a light-emitting material and an electron transport material in an organic light-emitting diode at the same time, the two layers in a classical OLED structure are combined into one layer, and the OLED device structure and the preparation process are simplified.

Description

Technical Field

[0001] The invention relates to the field of organic luminescent materials, and in particular to a thermally delayed fluorescent red light material containing naphthaleneimide and a preparation method and application thereof. Background Art

[0002] The development of organic light-emitting materials has gradually expanded from the initial anthracene single crystal to organic small molecules and polymer light-emitting materials. Not only has the material performance been continuously improved, but the preparation process has also become increasingly mature, such as the solution method and vacuum evaporation method, which can realize the preparation of large-area devices. In 1987, Tang and Vanslyke (CWTang, SAVanslyke. Appl. Phys. Lett. 1987, 51, 913) pioneered the field of OLED. After decades of rapid development, OLED has been widely used in solid-state light-emitting devices such as smart phones and flat-panel displays. Compared with traditional displays, OLED devices based on these materials have many advantages such as low driving voltage, fast response speed, bendability, wide viewing angle and active luminescence. However, traditional fluorescent devices can only use 25% of the singlet excitons generated by power-on, which seriously limits the performance and application of OLED devices.

[0003] In order to improve the luminous efficiency of OLED, it is necessary to make full use of the 75% triplet excitons generated by power supply. et al. used heavy metal-containing organometallic complexes to enhance spin-orbit coupling, overcome transition inhibition, and allow triplet excitons to return to the ground state through radiative transitions and emit phosphorescence (MA Baldo, DFO'Brien, Y. You, A. Shoustikov, S. Sibley, METhompson, SR Nature 1998,395,151). This method effectively utilizes triplet excitons, making the theoretical internal quantum efficiency of the device close to 100%. By selecting appropriate host materials, OLED devices prepared using this phosphorescent metal complex show high external quantum efficiency. However, the limited resources and high cost of precious metals limit their large-scale production applications. Therefore, researchers began to explore other methods that can utilize triplet states, including TTA (double triplet annihilation), HLCT (hybridized localized-charge transfer excited state) and TADF (thermally activated delayed fluorescence).

[0004] TADF involves the process of reverse intersystem crossing (RISC). Materials with TADF properties have a small energy level difference between the first excited triplet state (T1) and the first excited singlet state (S1). Under the action of thermal energy, the excitons can transition from T1 to S1 and return to the ground state through radiation transition to generate photons. In this way, triplet excitons can be fully utilized, improving the efficiency of OLED devices. At present, there have been many reports on high-efficiency blue, green and yellow TADF materials, and OLED devices with excellent performance have been obtained through device parameter optimization. However, there are fewer reports on red light TADF materials, mainly because there is non-radiative internal conversion in red light materials, resulting in low luminous efficiency.

[0005] To this end, the inventor has conducted useful explorations and attempts and found a solution to the above-mentioned problem. The solution to be introduced below is produced under this background. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a thermally delayed fluorescent red light material and a preparation method and application thereof in view of the deficiencies and defects of the prior art.

[0007] The technical problem solved by the present invention can be achieved by adopting the following technical solutions:

[0008] A thermally delayed fluorescent red light material containing a naphthaleneimide structure, characterized in that the material has a compound of the following structural formula (1).

[0009]

[0010] A method for preparing the thermally delayed fluorescent red light material containing a naphthaleneimide structure as claimed in claim 1, characterized in that it comprises the following steps:

[0011] S1, 4-bromonaphthalene anhydride and glacial acetic acid are mixed and stirred, nitroaniline is added dropwise, and the mixture is heated under reflux to react, thereby preparing an intermediate product, the structural formula of which is as follows:

[0012]

[0013] S2, mixing and stirring the intermediate product with a toluene solution, then adding phenoxazine, heating and refluxing for reaction, then adding potassium carbonate, palladium acetate and tri-tert-butylphosphine as catalysts, stirring and refluxing, and then cooling the solution; using a mixture of dichloromethane and n-hexane as an eluent for column chromatography separation and purification, to obtain the target product compound of structural formula (1).

[0014] In a preferred embodiment of the present invention, in S1, specifically, 4-bromonaphthalene anhydride (2.77 g, 10 mmol) is added to a 250 mL three-necked bottle, 100 mL of glacial acetic acid is added and stirred, and then p-nitroaniline (2.06 g, 12 mmol) is added, and the solvent is heated to reflux and reacted overnight; after cooling, the reactant is poured into 500 mL of water, filtered and washed with water 3 times to obtain an intermediate product with a mass of 3.88 g.

[0015] In a preferred embodiment of the present invention, in S2, specifically, the intermediate product (1 g, 2.32 mmol) is added to a three-necked flask, 100 mL of toluene solution is added, and then phenoxazine (1.39 g, 6.96 mmol) is added, heated to reflux of the solvent, and potassium carbonate (0.6 g, 4.26 mmol), palladium acetate and tri-tert-butylphosphine are added as catalysts, and the reaction solution is cooled after stirring and reflux for 24 hours.

[0016] In a preferred embodiment of the present invention, the volume ratio of dichloromethane to n-hexane in the eluent is 1:3.

[0017] In an embodiment of a light-emitting application device, the light-emitting device is prepared by applying the compound of structural formula (1) to the electron transport layer and the light-emitting material of the light-emitting application device.

[0018] The light-emitting application device in the embodiment of the present invention includes an OLED light-emitting device.

[0019] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0020] (1) The synthesis method of the present invention is simple in process and easy to purify, and is suitable for preparing the light-emitting layer in an organic electroluminescent device.

[0021] (2) Although the OLED device prepared by using this phosphorescent metal complex exhibits a high external quantum efficiency, the precious metal resources are limited and the cost is high. The synthesized material of the present invention is cheap and easy to obtain, which can reduce the cost of OLED light-emitting materials.

[0022] (3) Red organic light-emitting devices can be prepared using the material described in the present invention as the light-emitting layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 Schematic diagram of the chemical reaction formula for preparing the intermediate product of Example 1.

[0025] Figure 2 The chemical reaction diagram for preparing the target product (1) in Example 1.

[0026] Figure 3 This is the hydrogen nuclear magnetic resonance spectrum of the product of formula (1) in Example 1.

[0027] Figure 4 Schematic diagram of the device structure of Example 2.

[0028] Figure 5 The organic electroluminescence spectrum of Example 2

[0029] Figure 6 Schematic diagram of the device structure of Example 3.

[0030] Figure 7 This is the organic electroluminescence spectrum of Example 3. DETAILED DESCRIPTION

[0031] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below.

[0032] The embodiment of the present invention requires first obtaining an intermediate product through chemical synthesis, obtaining a target product of formula (1) through chemical synthesis of the intermediate product, and then preparing a light-emitting application device through the target product.

[0033] Example 1: Preparation of intermediate products and target products.

[0034] 4-Bromonaphthyl anhydride (2.77 g, 10 mmol) was added to a 250 mL three-necked flask, 100 mL of glacial acetic acid was added, and then p-nitroaniline (2.06 g, 12 mmol) was added, and the mixture was heated to reflux and reacted overnight. After cooling, the reactant was poured into 500 mL of water, filtered and washed with water 3 times to obtain an intermediate product with a mass of 3.88 g. The structural formula of the intermediate product is as follows, and its chemical reaction formula is shown in Figure 1 shown.

[0035]

[0036] The intermediate product (1 g, 2.32 mmol) was added to a three-necked flask, and 100 mL of toluene solution was added, followed by phenoxazine (1.39 g, 6.96 mmol), and the solvent was heated to reflux. Potassium carbonate (0.6 g, 4.26 mmol), palladium acetate and tri-tert-butylphosphine were added as catalysts, and the reaction solution was cooled after stirring and refluxing for 24 hours. The chemical reaction formula is shown in Figure 2 shown.

[0037] The product was extracted with dichloromethane and purified by silica gel column chromatography, with the eluent being a mixed solution of dichloromethane and n-hexane in a volume ratio of 1:3. The pure product was obtained with a mass of 0.93 g and a yield of 60%. The target product obtained is a naphthaleneimide thermal delayed fluorescent red light material, with a structural formula as shown in formula (1). The H NMR spectrum of the target product is shown in Figure 3 shown.

[0038]

[0039] Example 2: Preparation of organic light-emitting device A.

[0040] The target product prepared in Example 1 was used as the light-emitting layer to prepare an organic light-emitting device A, the structure of which is as follows: Figure 4 As shown. The device structure is ITO / PEDOT:PSS (40nm) / mCP: target product (60nm) / TPBi (40nm) / LiF (1nm) / Al (120nm). In this structure, PEDOT:PSS is poly (3,4-ethylenedioxythiophene): polystyrene sulfonate, which is used as a hole injection layer; the target product is the light-emitting material obtained in Example 1 above; LiF (lithium fluoride) is used as an electron injection layer; TPBi is 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene, which is used as an electron transport layer material. The luminescence spectrum of the organic light-emitting device prepared is shown as follows: Figure 5 As shown, in Example 2, an organic electroluminescent device emitting red light was obtained, and the maximum emission wavelength of electroluminescence was 700 nm.

[0041] Example 3 Preparation of organic light-emitting device B.

[0042] The target product compound prepared in Example 1 was used as the electron transport layer and the light-emitting layer to prepare an organic light-emitting device B, the device structure of which is as follows: Figure 6 As shown. The device structure is ITO / PEDOT:PSS (40nm) / target product (60nm) / LiF (1nm) / Al (120nm). In this structure, PEDOT:PSS is poly (3,4-ethylenedioxythiophene): polystyrene sulfonate, which is used as a hole injection layer; the target product is the electron transport layer and the light-emitting layer; LiF (lithium fluoride) is used as an electron injection layer. The luminescence spectrum of the organic light-emitting device prepared is shown in Figure 7 In Example 3, an organic electroluminescent device emitting red light was obtained, and the maximum emission wavelength of electroluminescence was 650nm.

[0043] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A red light material containing naphthaleneimide thermal delayed fluorescent light, characterized in that: The material is a compound having the following structural formula (1).

2. A method for preparing the thermally delayed fluorescent red light material containing a naphthaleneimide structure as claimed in claim 1, characterized in that: The steps include: S1, 4-bromonaphthalene anhydride and glacial acetic acid are mixed and stirred, nitroaniline is added dropwise, and the mixture is heated under reflux to react, thereby preparing an intermediate product, the structural formula of which is as follows: S2, mixing and stirring the intermediate product with a toluene solution, then adding phenoxazine, heating and refluxing for reaction, then adding potassium carbonate, palladium acetate and tri-tert-butylphosphine as catalysts, stirring and refluxing, and then cooling the solution; using a mixture of dichloromethane and n-hexane as an eluent for column chromatography separation and purification, to obtain the target product compound of structural formula (1).

3. The method for preparing a thermally delayed fluorescent red light material containing a naphthaleneimide structure according to claim 2, characterized in that: In S1, specifically, 4-bromonaphthalene anhydride (2.77 g, 10 mmol) was added to a 250 mL three-necked bottle, 100 mL of glacial acetic acid was added and stirred, and then p-nitroaniline (2.06 g, 12 mmol) was added, and the solvent was heated to reflux and reacted overnight; after cooling, the reactant was poured into 500 mL of water, filtered and washed with water 3 times to obtain an intermediate product with a mass of 3.88 g.

4. The method for preparing a thermally delayed fluorescent red light material containing a naphthaleneimide structure according to claim 3, characterized in that: In S2, specifically, the intermediate product (1 g, 2.32 mmol) was added to a three-necked flask, 100 mL of toluene solution was added, and then phenoxazine (1.39 g, 6.96 mmol) was added, and the solvent was heated to reflux, and potassium carbonate (0.6 g, 4.26 mmol), palladium acetate and tri-tert-butylphosphine were added as catalysts, and the reaction solution was cooled after stirring and refluxing for 24 hours.

5. The method for preparing a thermally delayed fluorescent red light material containing a naphthaleneimide structure according to claim 2, characterized in that: In S2, the volume ratio of dichloromethane to n-hexane in the eluent is 1:

3.

6. A light-emitting application device, wherein the light-emitting device is prepared by applying the compound of structural formula (1) according to claim 1 to the electron transport layer and the light-emitting material of the light-emitting application device.

7. A light-emitting application device according to claim 6, characterized in that: Including OLED light-emitting devices.

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