A viscous flow state fluorene-phenyl blue-violet light-emitting material, a preparation method and an organic electroluminescent device

Abstract

This invention provides a class of fluorene-phenyl blue-violet luminescent materials with a viscous flow state, a preparation method, and an organic electroluminescent device. The general structural formula of the luminescent material is shown in Formula I: In the formula: R 1 R1 is a straight-chain or branched alkyl chain with 1 to 12 hydrogen atoms or carbon atoms; R2 is a straight-chain or branched alkyl chain with 6 to 12 carbon atoms. The luminescent material prepared by this invention has a regular structure, good structural extensibility, good solubility, and good luminous efficiency and viscous flow properties, thus it has a promising application prospect in the field of OLED displays.

Description

A viscous fluorene-phenyl blue-violet light-emitting material, its preparation method, and an organic electroluminescent device. Technical Field

[0001] This invention belongs to the field of OLED display technology, specifically relating to a fluorene-phenyl blue-violet light-emitting material with a viscous flow state, its preparation method, and an organic electroluminescent device. Background Technology

[0002] Organic light-emitting diodes (OLEDs) are used in information displays, wearable electronics, and medical devices, and are currently a major research focus and direction in academia and industry. The controllable preparation of high-performance red, green, and blue primary color emitting materials is one of the prerequisites for realizing full-color OLED displays. High-performance red, green, and blue emitting materials are the core elements of OLED emitting materials. Compared to red and green organic molecules, wide-bandgap organic blue-violet emitting molecules have shorter wavelengths, higher energy, lower color purity, poor stability, and significant quantum efficiency decay, which are significant bottlenecks limiting the application of organic blue-violet emitting materials in information displays.

[0003] Organic blue-violet luminescent materials mainly include fluorene, benzene, anthracene, indene-pyrazine, phenanthrene-imidazolium, triphenylamine-imidazolium, pyrene, and multiple resonance nitrogen-boron compounds. Compared with many luminescent frameworks, the fluorene-based unit framework structure has multi-dimensional and multifunctional sites, allowing the introduction of modifying groups at positions 9, 2, and 4 to optimize the material structure and improve luminous efficiency and conductivity. Therefore, fluorene-based organic blue light-emitting materials exhibit high luminous quantum efficiency, blue light emission, and high mobility, and are widely used in OLEDs, lasers, and field-effect light-emitting transistors, making them one of the most studied materials in the field of blue OLEDs. However, fluorene-based blue light-emitting molecules also exhibit complex electronic transition orders, vibrational relaxation, conformational transitions, and aggregation behaviors, resulting in broad-band, multi-peak, long-baseline, and long-wavelength emission, which reduces the color purity and stability of blue light. Therefore, designing and fabricating high-performance, high-color-purity fluorene-based blue-violet light-emitting molecules is an important strategy for realizing the fabrication of high-performance narrow-band OLED devices. Summary of the Invention

[0004] The purpose of this invention is to provide a class of fluorene-phenyl blue-violet luminescent materials exhibiting a viscous flow state, which display viscous flow and semiconductor properties, have a regular structure, and possess excellent and stable blue light emission characteristics. Another purpose of this invention is to provide a method for preparing this class of viscous flow fluorene-phenyl blue-violet luminescent materials. The final objective of this invention is to provide an organic electroluminescent device comprising this luminescent material.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a fluorene-phenyl blue-violet light-emitting material having a viscous flow state, the general structural formula of which is shown in Formula I:

[0007]

[0008] In the formula: R1 is a straight-chain or branched alkyl chain with 1 to 12 hydrogen atoms or carbon atoms; R2 is a straight-chain or branched alkyl chain with 6 to 12 carbon atoms.

[0009] Secondly, the present invention provides a method for preparing a fluorene-phenyl blue-violet luminescent material with a viscous flow state. When R1 is an alkyl chain, the synthesis method of Formula I is as follows:

[0010] Will Sodium carbonate and tetraphenylphosphine palladium were added to a reaction flask, followed by ethanol and ethylene glycol dimethyl ether (after removing peroxide). The mixture was reacted at 85°C for 12 hours under a nitrogen atmosphere, and the resulting product was purified to obtain compound 1.

[0011] Furthermore, when R1 is an alkyl chain, the synthetic route of formula I is as follows:

[0012]

[0013] Furthermore, The molar ratio of sodium carbonate to tetraphenylphosphine palladium is 1:3:8:0.16, and the volume ratio of ethanol to ethylene glycol is 4:3.

[0014] Furthermore, the preparation method of the fluorene-phenyl blue-violet luminescent material with a viscous flow state further includes:

[0015] Compound 1 and dried dichloromethane were added to a reaction flask and dissolved completely. BBr3 was dissolved in dried dichloromethane. The dichloromethane solution containing BBr3 was added dropwise to the reaction flask in an ice-water bath. The ice-water bath was removed, and the reaction was stirred at room temperature under a nitrogen atmosphere for 3 hours. The neutralization reaction was quenched with water, and the mixture was purified to obtain compound 2.

[0016]

[0017] Furthermore, the molar ratio of compound 1 to BBr3 is 1:10.

[0018] Thirdly, the present invention provides an organic electroluminescent device, comprising an anode, a cathode, and an organic thin film layer located between the anode and the cathode, wherein the organic thin film layer contains the fluorene-phenyl blue-violet luminescent material having a viscous flow state as described in the first aspect.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] (1) The viscous flow fluorene-phenyl blue-violet light luminescent material of the present invention is prepared by Suzuki and BBr3 demethylation reaction, which has the advantages of simple preparation, mild reaction conditions, high yield, high selectivity and simple post-processing.

[0021] (2) The viscous flow fluorene-phenyl blue-violet light-emitting material prepared by the present invention has a regular structure, good structural extensibility and good solubility, and exhibits special viscous flow physicochemical properties;

[0022] (3) The viscous flow fluorene-phenyl blue-violet light-emitting material of the present invention has good luminous efficiency, and therefore has good application prospects in the field of blue-violet OLED. Attached Figure Description

[0023] Figure 1 is the proton nuclear magnetic resonance spectrum of DMeOphFO in Example 1 of the present invention;

[0024] Figure 2 shows the absorption and emission spectra of the DMeOphFO toluene solution in Example 1 of the present invention;

[0025] Figure 3 is the 1H NMR spectrum of DOHphFO in Example 2 of the present invention;

[0026] Figure 4 shows the absorption and emission spectra of the DOHphFO toluene solution in Example 2 of the present invention;

[0027] Figure 5 is a fluorescence image of the viscous flow state of DMeOphFO in Example 1 of the present invention;

[0028] Figure 6 is a fluorescence image of the DOHphFO viscous flow state in Example 2 of the present invention;

[0029] Figure 7 is the DSC spectrum of DMeOphFO in Example 1 of the present invention;

[0030] Figure 8 is the DSC spectrum of DOHphFO in Example 2 of the present invention;

[0031] Figure 9 is the TGA spectrum of DMeOphFO in Example 1 of the present invention;

[0032] Figure 10 is the TGA spectrum of DOHphFO in Example 2 of the present invention;

[0033] Figure 11 is the CV spectrum of DMeOphFO in Embodiment 1 of the present invention;

[0034] Figure 12 is the CV spectrum of DOHphFO in Example 2 of the present invention;

[0035] Figure 13 shows the voltage-brightness versus current density curves of the OLED device fabricated based on DMeOphFO in Example 1 (CD: current density, Lum: luminous brightness).

[0036] Figure 14 shows the electroluminescence spectrum of the OLED device fabricated based on DMeOphFO in Example 1;

[0037] Figure 15 shows the voltage-brightness versus current density curves of the OLED device fabricated based on DOHphFO in Example 2 (CD: current density, Lum: luminous brightness).

[0038] Figure 16 shows the electroluminescence spectrum of the OLED device prepared based on DOHphFO in Example 2. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. These embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0040] As mentioned earlier, fluorene-based blue light molecules exhibit complex electronic transition sequences, vibrational relaxation, conformational transitions, and aggregation behaviors, resulting in broad-band, multi-peak, long-baseline, and long-wavelength emission, which reduces the color purity and stability of blue light. By employing steric hindrance and molecular encapsulation strategies to suppress π-electron coupling between conjugated backbones, it is possible to achieve excited-state behavior of a single molecular state, narrow the emission spectrum, and improve color purity and efficiency.

[0041] The fluorene-based unit itself has a λ at 302 nm. PL The fluorene group exhibits a spectral density that, through chemical modification, can easily achieve a redshift in emission, thus enabling efficient blue-violet light emission. Compared to solid-state blue-violet light-emitting materials, viscous flow-state luminescent molecules possess transparency and intrinsic flexibility, exhibiting excellent and stable blue light emission characteristics. Furthermore, they can be used for plasticizing effects to enhance the intrinsic flexibility of luminescent materials, showing broad application prospects in the field of flexible OLED display technology. The multi-site functionalization of the fluorene molecular unit itself provides an effective molecular design strategy for constructing viscous flow-state fluorene-based luminescent molecules.

[0042] This invention relates to a class of fluorene-phenyl blue-violet luminescent materials exhibiting a viscous flow state. The main blue-violet luminescent framework is obtained by connecting two phenyl groups at the 2 and 7 positions of fluorene, followed by flexible chain modification at the 9 position of fluorene and the 2 and 6 positions of benzene. Its core feature is the acquisition of viscous flow behavior and semiconductor properties. Its general structural formula is shown in Formula I.

[0043]

[0044] In the formula: R1 is a straight-chain or branched alkyl chain with 1 to 12 hydrogen atoms or carbon atoms; R2 is a straight-chain or branched alkyl chain with 6 to 12 carbon atoms.

[0045] Example 1:

[0046]

[0047] The synthesis method of DMeOphFO is as follows:

[0048]

[0049] Add FO (2.74 g, 5 mmol), dimethylphenylboronic acid (2.73 g, 15 mmol), sodium carbonate (4.24 g, 40 mmol), and tetrakis(triphenylphosphine)palladium (0.92 g, 0.8 mmol) to a reaction flask. Add 20 mL of deoxygenated ethanol and 15 mL of ethylene glycol dimethyl ether to the reaction flask and heat to 85°C. React under nitrogen protection for 12 hours until the substrate is completely reacted. After the reaction, cool to room temperature and extract with dichloromethane. Combine the dichloromethane extracts of the organic phases, dry with anhydrous sodium sulfate, filter to remove the drying agent and solvent, and purify the crude product by silica gel column chromatography to obtain a viscous liquid DMeOphFO (2.1 g, 63%).

[0050] Figure 1 shows the 1H NMR spectrum of DMeOphFO prepared in Example 1 of this invention. 1H NMR (400MHz, Chloroform-d) δ 7.64 (dd, J = 7.7, 0.7Hz, 2H), 7.28–7.24 (m, 4H), 7.20 (s, 2H), 6.62 (d, J = 8.4Hz, 4H), 3.66 (s, 12H), 1.93–1.81 (m, 4H).

[0051] Example 2:

[0052]

[0053] The synthesis method of DOHphFO is as follows:

[0054]

[0055] Add DMeOphFO (1 g, 1.7 mmol) to the reaction flask, then add 50 mL of dried dichloromethane to dissolve it completely. Next, dissolve BBr3 (4.04 g, 17 mmol) completely in a constant-pressure dropping funnel containing 10 mL of dried dichloromethane. Add the solution dropwise to the reaction flask while maintaining an ice-water bath. After the solution in the constant-pressure dropping funnel has been completely added, remove the ice-water bath and stir the reaction at room temperature under nitrogen protection for 3 hours until the substrate has completely reacted. Quench the reaction with water. Extract with dichloromethane, combine the organic phase dichloromethane extracts, dry with anhydrous sodium sulfate, filter to remove the drying agent and solvent, and purify the crude product by silica gel column chromatography to obtain a red waxy solid, DOHphFO (0.74 g, 71%).

[0056] Figure 3 shows the 1H NMR spectrum of DOHphFO prepared in Example 2 of this invention. 1H NMR (400MHz, Chloroform-d) δ 7.98–7.92 (m, 2H), 7.49–7.41 (m, 4H), 7.19 (t, J = 8.2 Hz, 2H), 6.63 (d, J = 8.2 Hz, 4H), 4.91 (s, 4H), 2.06–1.92 (m, 4H).

[0057] Material property testing

[0058] 1. Absorption and emission spectroscopic properties of DMeOphFO and DOHphFO:

[0059] The DMeOphFO prepared in Example 1 was dissolved in toluene solution to obtain DMeOphFO toluene solutions with concentrations of 5 mg / mL, 10 mg / mL and 20 mg / mL, respectively. The absorption and emission spectra are shown in Figure 2.

[0060] The DOHphFO prepared in Example 2 was dissolved in toluene solution to obtain DOHphFO toluene solutions with concentrations of 5 mg / mL, 10 mg / mL and 20 mg / mL, respectively. The absorption and emission spectra are shown in Figure 4.

[0061] As can be seen from Figures 2 and 4, the films of DMeOphFO and DOHphFO exhibit similar absorption and emission characteristics. The maximum absorption and emission wavelengths of the films are 330 nm and 360 nm, respectively, and they exhibit good blue-violet light emission with luminescence quantum efficiencies of 50% and 36%, respectively.

[0062] 2. Viscous Flow Test

[0063] Figure 5 shows a fluorescence image of the viscous flow state of DMeOphFO in Example 1 of the present invention, and Figure 6 shows a fluorescence image of the viscous flow state of DOHphFO in Example 2 of the present invention. As can be seen from the figures, both DMeOphFO and DOHphFO exhibit excellent viscous flow behavior.

[0064] 3. Thermal stability test

[0065] The thermogravimetric temperature T of DMeOphFO and DOHphFO was tested. d and glass transition temperature T g The test results are shown in Figures 7 to 10.

[0066] As can be seen from Figures 9 and 10, the thermogravimetric temperature T of DMeOphFO is... d The thermogravimetric temperature T of DOHphFO is 307.5℃. d The temperature was 324.16℃. This data shows that the DMeOphFO and DOHphFO prepared in this invention possess excellent thermal stability, meeting the requirements for use in organic electroluminescent materials.

[0067] Figures 7 and 8 show the DSC spectra of DMeOphFO and DOHphFO, respectively. The DSC tests reveal that the glass transition temperatures of both DMeOphFO and DOHphFO are less than 0°C, further demonstrating that these materials exhibit viscous flow physical properties at room temperature.

[0068] 4. Energy level structure testing

[0069] Figures 11 and 12 show the CV spectra of DMeOphFO and DOHphFO, respectively. Based on the CV measurements of the two materials, the corresponding HOMO and LUMO energy level values ​​can be obtained. The HOMO and LUMO energy levels of DOHphFO are -6.20 eV and -2.10 eV, respectively, and those of DMeOphFO are -6.23 eV and -2.01 eV, respectively. The band gap values ​​(E0) of the two luminescent materials are also shown. g The values ​​were 4.1 eV and 4.22 eV, respectively, indicating that the material exhibits blue-violet light emission, proving that the compound of the present invention can be used to prepare blue-violet organic electroluminescent devices.

[0070] Device fabrication and testing

[0071] Example 3

[0072] The ITO substrate was sequentially ultrasonically cleaned with detergent, acetone, isopropanol, and deionized water, dried in an oven at 120°C for 2 hours, and treated with ultraviolet ozone for 10 minutes before spin coating. First, a 40 nm thick PEDOT:PSS layer was prepared at a spin speed of 1500 rpm and annealed at 120°C for 30 minutes. Then, the viscous luminescent material DMeOphFO prepared in Example 1 of this invention was dissolved in a 20 mg / mL toluene solution, and a luminescent layer was spin-coated at a spin speed of 1500 rpm and annealed at 120°C for 20 minutes in a nitrogen atmosphere. The thickness of the spin-coated film of the viscous luminescent material was approximately 50 nm. Finally, the coating was annealed at a temperature below 1 × 10⁻⁶. -5 Organic electroluminescent devices with an area of ​​2 mm × 2 mm were prepared by thermal evaporation under a pressure of mbar, consisting of 25 nm TPBI, 0.8 nm LiF, and 100 nm Al.

[0073] Example 4

[0074] The organic electroluminescent device of Example 4 was prepared by replacing the DMeOphFO spin-coating layer with the viscous flow luminescent material DOHphFO prepared in Example 2 of the present invention, and keeping the other parts the same as in Example 3.

[0075] The characteristics of the organic electroluminescent devices prepared in Examples 3 and 4 were measured, and all device parameters were measured in an air environment.

[0076] Figures 13 and 14 show the voltage-brightness versus current density curves and electroluminescence spectra of the OLED device fabricated from DMeOphFO, respectively. Figures 15 and 16 show the voltage-brightness versus current density curves and electroluminescence spectra of the OLED device fabricated from DOHphFO, respectively. As can be seen from the figures, the viscous fluorene-phenyl blue-violet luminescent material of this invention, when applied to organic electroluminescent devices, can achieve good blue-violet luminescence intensity.

[0077] The present invention has been disclosed above with reference to preferred embodiments, but it is not intended to limit the present invention. All technical solutions obtained by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the present invention.

Claims

1. A fluorene-phenyl blue-violet luminescent material exhibiting a viscous flow state, characterized in that, Its general structural formula is shown in Formula I: In the formula: R1 is a hydrogen atom or a methyl group; R2 is a straight-chain or branched alkyl chain with 6 to 12 carbon atoms.

2. The method for preparing the fluorene-phenyl blue-violet luminescent material with a viscous flow state according to claim 1, characterized in that, When R1 is a methyl group, the synthesis method of formula I is as follows: 、 Sodium carbonate and tetraphenylphosphine palladium were added to a reaction flask, followed by deoxygenated ethanol and ethylene glycol dimethyl ether. The reaction was carried out at 85°C for 12 h under a nitrogen atmosphere, and the mixture was purified to obtain compound 1. The synthetic route of formula I is as follows: 。 3. The method for preparing the fluorene-phenyl blue-violet luminescent material with a viscous flow state according to claim 2, characterized in that, 、 The molar ratio of sodium carbonate and tetraphenylphosphine palladium is 1:3:8:0.16, and the volume ratio of ethanol and ethylene glycol dimethyl ether is 4:

3.

4. The method for preparing the fluorene-phenyl blue-violet luminescent material with a viscous flow state according to claim 2, characterized in that, Also includes: Compound 1 and dried dichloromethane were added to a reaction flask and dissolved thoroughly. BBr3 was dissolved in dried dichloromethane. The dichloromethane solution containing dissolved BBr3 was added dropwise to the reaction flask in an ice-water bath. The ice-water bath was removed, and the reaction was stirred at room temperature under a nitrogen atmosphere for 3 hours. The neutralization reaction was quenched with water, and the mixture was purified to obtain compound 2. Compound 2 is the compound with the general structural formula I when R1 is a hydrogen atom. The synthetic route of compound 2 is as follows: 。 5. The method for preparing the fluorene-phenyl blue-violet luminescent material with a viscous flow state according to claim 4, characterized in that, The molar ratio of compound 1 to BBr3 is 1:

10.

6. An organic electroluminescent device, characterized in that, It includes an anode, a cathode, and an organic thin film layer located between the anode and the cathode, wherein the organic thin film layer contains the fluorene-phenyl blue-violet light-emitting material with a viscous flow state as described in claim 1.

Images