Blue light material based on dibenzofuran and preparation method and application thereof

Abstract

The application provides a kind of blue light material based on diphenyl furan and its preparation method and application, belong to organic electroluminescent material technical field.The blue light material provided by the application uses naphthalene group as π bridge, introduces diphenyl furan electron donor and spiroboron or diaryl boron derivative electron acceptor structure on naphthalene ring, forms D-π-A type molecular structure.In the blue light material, the central core of naphthalene group has a planar symmetric structure, and the electron acceptor has a non-planar rigid structure, which provides electron-withdrawing effect, conjugation effect and steric hindrance effect, and the two cooperate with diphenyl furan group to form D-π-A molecular structure with twisted structure, which is conducive to the realization of blue light emission of the material.At the same time, the conjugation effect is conducive to reducing the energy of the system and improving the thermal stability of the material;The conjugation effect and the steric hindrance effect can improve the rigidity of the molecular structure, inhibit the non-radiative transition caused by the interaction between molecules, and improve the fluorescence quantum yield of the material, thereby improving the luminous efficiency of the material.

Description

Technical Field

[0001] This invention relates to the field of electroluminescent materials technology, and in particular to a blue light-emitting material based on dibenzofuran, its preparation method, and its application. Background Technology

[0002] After more than 30 years of development, organic light-emitting diodes (OLEDs) have entered a stage of large-scale application in the display and lighting fields. Compared with traditional displays, they have advantages such as fast response, low power consumption, self-illumination, wide color gamut, ultra-thinness, foldability and flexibility, and the ability to manufacture large-size panels, making them the most ideal and promising new display technology for the future.

[0003] In OLED devices, the performance of the luminescent material is a crucial parameter determining the device's performance. Currently, blue light-emitting materials suffer from low luminous efficiency, concentration quenching, and poor stability, making it difficult to obtain high-efficiency and high-stability blue OLED devices, thus hindering commercial applications. From a molecular structure perspective, there are generally two design strategies for blue light molecules that form wide light bands. One strategy involves connecting aromatic conjugated groups such as phenyl, fluorenyl, naphthyl, and aryynyl groups, controlling the emission wavelength by regulating the conjugation length of these groups. However, these materials tend to accumulate in aggregated states, leading to fluorescence quenching. The other strategy involves connecting weak electron donors and acceptors through suitable conjugated π-bridge groups to form D-π-A type molecules. To achieve blue light emission, it is necessary to control the electron-donating and electron-withdrawing capabilities of the electron-donating and acceptor structures and the degree of conjugation of the π-bridge groups. Improper matching of electron donors, acceptors, and π-bridge groups can easily cause a redshift in emission and a decrease in quantum yield. Therefore, blue light-emitting materials with high luminous efficiency and good thermal stability remain a significant challenge. Summary of the Invention

[0004] The purpose of this invention is to provide a blue light material based on dibenzofuran, its preparation method and application. The dibenzofuran-based material provided by this invention can achieve blue light emission, has high luminous efficiency, and has good thermal stability.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solutions.

[0006] This invention provides a blue light-emitting material based on dibenzofuran, having the structure shown in Formula I:

[0007]

[0008] In equation I, R is... * indicates the location where the group is attached.

[0009] The specific synthetic route of a blue light-emitting material based on dibenzofuran is shown below:

[0010]

[0011] In the process of synthesizing C from A and B, the alkaline reagent is any one of Na2CO3, K2CO3, or Cs2CO3; the palladium catalyst is any one of Pd(PPh3)4, PdCl2, or Pd2(dba)3; the polar organic solvent M is any one of tetrahydrofuran, toluene, or N,N-dimethylformamide; the alcohol solvent is a low-carbon alcohol with fewer than 4 carbon atoms; and the volume ratio of the polar organic solvent M to the alcohol solvent is 20 to 10:1.

[0012] In the synthesis of E from D, a polar solvent with a strong base reagent is used, namely tetrahydrofuran, and the strong base reagent is bis(trimethylsilyl)aminopotassium. The ratio of the strong base reagent, the compound with the structure shown in D, to the solvent is 3–10 mmol: 1–2 mmol: 20–100 mL. The reaction temperature is 60–70 °C, and the reaction time is 6–10 h.

[0013] In the synthesis of F from E, a chloroalkane solvent is used, preferably dichloromethane, trichloromethane, carbon tetrachloride, or dichloroethane, and more preferably dichloromethane. The amounts of reactants and reagents satisfy the following ratio: compound with the structure shown in formula E: boron trichloride: dichloromethane solvent = 4–6 mol: 0.5–1 mL: 40–80 mL. The initial reaction temperature is -78°C, and then the reaction mixture is slowly heated to room temperature for 3–5 hours.

[0014] In the process of synthesizing I-1 from C and F, the ratio of the amount of the compound with the structure shown in formula C, the compound with the structure shown in formula F, and the tert-butyllithium initiator is 1-1.5 mol: 1-5 mol: 1.5-10 mol, the reaction temperature is -78℃ to room temperature, and the reaction time is 4-8 h.

[0015] Another specific synthetic route for blue light-emitting materials based on dibenzofuran is shown below:

[0016]

[0017] In the process of synthesizing C from A and B, the alkaline reagent is any one of Na2CO3, K2CO3, or Cs2CO3; the palladium catalyst is any one of Pd(PPh3)4, PdCl2, or Pd2(dba)3; the polar organic solvent M is any one of tetrahydrofuran, toluene, or N,N-dimethylformamide; the alcohol solvent is a low-carbon alcohol with fewer than 4 carbon atoms; and the volume ratio of the polar organic solvent M to the alcohol solvent is 20 to 10:1.

[0018] In the process of synthesizing I-2 from C and G, the ratio of the amount of the compound with the structure shown in formula C, the compound with the structure shown in formula G, and the tert-butyllithium initiator is 1-1.5 mol: 1-5 mol: 1.5-10 mol, the reaction temperature is -78℃ to room temperature, and the reaction time is 4-8 h.

[0019] The blue light material based on dibenzofuran provided by this invention can be used as a light-emitting layer material in organic electroluminescent devices and their preparation process.

[0020] The blue light-emitting material based on dibenzofuran, its preparation method, and its application provided by this invention represent a technological advancement over existing technologies in the following aspects:

[0021] (1) Compared with existing blue light materials, the blue light material based on dibenzofuran provided by this invention uses a naphthyl group as a π-bridge and spiroboridine or diarylborane derivatives as electron acceptors. A dibenzofuran electron donor and a suitable electron acceptor are introduced onto the naphthyl ring to form a D-π-A type molecule with a twisted structure. The naphthyl group central core provided by this invention has a planar symmetric structure and a suitable degree of conjugation, while the electron acceptor has a non-planar rigid structure and a weak electron-withdrawing ability. The naphthyl central core and the electron acceptor form a large electron-deficient conjugated system, providing a weak electron-withdrawing effect, a conjugation effect, and a steric hindrance effect. Combined with the weak electron donor dibenzofuran, this facilitates the material's blue light emission. Simultaneously, the conjugation effect helps reduce the system's energy and improve the material's thermal stability. The conjugation effect and steric hindrance effect can increase the rigidity of the molecular structure, suppress non-radiative transitions caused by intermolecular interactions, and increase the material's fluorescence quantum yield, thereby improving the material's luminescence efficiency and contributing to its performance in electroluminescent devices.

[0022] (2) The blue light material preparation method provided by the present invention has readily available starting materials, suitable reaction conditions, and simple operation steps, which helps to reduce preparation costs and realize commercial application. Attached Figure Description

[0023] Figure 1 The fluorescence spectrum of Example 1 in toluene solution;

[0024] Figure 2The fluorescence spectrum of Example 2 in toluene solution;

[0025] Figure 3 Thermogravimetric curve and differential scanning calorimetry curve of Example 1;

[0026] Figure 4 Thermogravimetric curve and differential scanning calorimetry curve of Example 2;

[0027] Figure 5 The electroluminescence spectrum of the undoped organic electroluminescent device in Example 1 is shown.

[0028] Figure 6 The electroluminescence spectrum of the undoped organic electroluminescent device in Example 2 is shown.

[0029] Figure 7 The graph shows the changes in brightness and current density of the organic electroluminescent device prepared in Example 1 as a function of voltage.

[0030] Figure 8 The graph shows the changes in brightness and current density of the organic electroluminescent device prepared in Example 2 as a function of voltage.

[0031] Figure 9 The graph shows the current efficiency and external quantum efficiency of the organic electroluminescent device prepared in Example 1 as a function of brightness.

[0032] Figure 10 The graph shows the changes in current efficiency and external quantum efficiency of the organic electroluminescent device prepared in Example 2 as a function of brightness. Detailed Implementation

[0033] This invention provides a blue light-emitting material based on dibenzofuran, having the structure shown in Formula I:

[0034]

[0035] In equation I, R is... * indicates the location where the group is attached.

[0036] Unless otherwise specified, all raw materials used in the specific synthetic routes of the compounds of this invention are commercially available products well known in the art.

[0037] The synthetic route of this invention is as follows.

[0038] The compound with the structure shown in Formula A, the compound with the structure shown in Formula B, a basic reagent, a palladium catalyst, a polar organic solvent, and an alcohol solvent are mixed and refluxed to obtain the compound with the structure shown in Formula C.

[0039] In one specific embodiment, the alcohol solvent is preferably anhydrous ethanol; the polar organic solvent is preferably toluene. The molar ratio of the compound with the structure shown in Formula A, the compound with the structure shown in Formula B, the basic reagent, and the palladium catalyst is 1–2 mol: 1–3 mol: 5–20 mol: 0.02–0.1 mol, more preferably 1 mol: 1 mol: 10 mol: 0.05 mol. The molar ratio of the compound with the structure shown in Formula A to the alcohol solvent is preferably 1–1.3 mmol: 2–5 mL, more preferably 1 mmol: 3 mL. This invention does not have special requirements for the mixing process of the compound with the structure shown in Formula A, the alcohol solvent, and the polar organic solvent; it is sufficient to ensure that the three are mixed evenly.

[0040] In one specific embodiment, the reflux temperature is preferably 70-90°C, more preferably 80°C; the reflux reaction time is determined by the completion of the reaction as monitored by thin-layer chromatography.

[0041] In this invention, the equation for the reflux reaction is as follows:

[0042]

[0043] After the reflux is complete, water is added to quench the reaction. Upon cooling, the crude product is collected by filtration and washed with water and ethanol. The product is then purified with dichloromethane or ethanol.

[0044] In this invention, a compound with the structure shown in Formula D, 5,5-dioxo-dibenzothiophene, a strong base reagent, and a polar organic solvent are mixed and subjected to a nucleophilic substitution reaction to obtain a compound with the structure shown in Formula E.

[0045] In one specific embodiment, the strong base reagent comprises bis(trimethylsilyl)aminopotassium; the polar organic solvent comprises tetrahydrofuran, and the ratio of the strong base reagent, the compound with structure D, and the solvent is 3–10 mmol: 1–2 mmol: 20–100 mL. In this invention, there are no special requirements for the mixing process of the compound with structure D, the polar organic solvent, and the strong base reagent; it is sufficient to ensure that the three are mixed evenly.

[0046] In this invention, in step (2), the temperature of the mixing reaction is 60-70°C and the reaction time is 6-10h.

[0047] In this invention, the equation for the mixed reaction is as follows:

[0048]

[0049] After the mixed reaction is complete, the reaction is preferably quenched with a saturated ammonium chloride aqueous solution. The organic phase is extracted with dichloromethane and dried with anhydrous sodium sulfate. After purification by silica gel column chromatography (eluent: dichloromethane), it is recrystallized from dichloromethane and petroleum ether to obtain the compound with the structure shown in E.

[0050] After obtaining the compound with the structure shown in formula E, the compound with the structure shown in formula E, boron trichloride, and a chloroalkane solvent are mixed to obtain the compound with the structure shown in formula F.

[0051] In a specific embodiment of the present invention, the ratio of the compound with the structure shown in Formula E, boron trichloride, and chloroalkane is 4-6 mol: 0.5-1 mL: 40-80 mL. The chloroalkane solvent is preferably dichloromethane, trichloromethane, carbon tetrachloride, or dichloroethane, more preferably dichloromethane. The mixing of the compound with the structure shown in Formula E, boron trichloride, and the chloroalkane solvent preferably comprises adding the compound with the structure shown in Formula E and boron trichloride to the chloroalkane solvent.

[0052] In a specific embodiment of the present invention, the initial temperature of the reaction is preferably -78°C, and then slowly raised to room temperature. The reaction time is preferably 3 to 5 hours. The reaction from E to F is preferably carried out under stirring conditions.

[0053] In this invention, the equation for the reaction is:

[0054]

[0055] After the reaction is complete, the present invention preferably removes excess boron trichloride and dichloromethane under vacuum, and then heats the residue to 100°C to remove the generated Me2SnCl2, thereby obtaining a compound with the structure shown in F.

[0056] After obtaining the compound with the F structure, the compound with the structure shown in Formula C, the compound with the F structure, and tert-butyllithium and tert-butylbenzene are mixed to obtain the target product with the structure shown in Formula I-1.

[0057] The compound with the structure shown in Formula C and the compound with the structure G are mixed with tert-butyllithium and tert-butylbenzene to obtain the target product with the structure shown in Formula I-2.

[0058] In a specific embodiment of the present invention, the ratio of the compound with the structure shown in Formula C, the compound with the structure shown in Formula F or Formula G, and the tert-butyllithium initiator is 1–1.5 mol: 1–5 mol: 1.5–10 mol. The initial reaction temperature is preferably -78°C, and then slowly raised to room temperature. The reaction time is preferably 4–6 hours.

[0059] In this invention, the reaction equation is:

[0060]

[0061] After the reaction is complete, the solvent is preferably removed under reduced pressure. Dichloromethane and water are added to the residue for extraction, and the organic phase is dried over anhydrous sodium sulfate. After purification by silica gel column chromatography (using a mixed solvent of dichloromethane and petroleum ether as eluent), the target product of formula I is obtained.

[0062] This invention provides the application of the dibenzofuran-based blue light material described in the above-described scheme or the dibenzofuran-based blue light material prepared by the above-described preparation method as an organic electroluminescent material.

[0063] The present invention provides an organic electroluminescent device, wherein at least one functional layer contains the blue light material based on dibenzofuran as described in the above-described scheme or the blue light material based on dibenzofuran prepared by the preparation method described in the above-described scheme.

[0064] The present invention preferably contains a blue light-emitting material based on dibenzofuran as described in the above-described scheme or a blue light-emitting material based on dibenzofuran prepared by the preparation method described in the above-described scheme in the light-emitting layer.

[0065] In this invention, the blue light material of dibenzofuran is preferably used as an undoped light-emitting layer material or a guest material of a doped light-emitting layer in an electroluminescent device.

[0066] The specific embodiments of the present invention will be described in more detail below.

[0067]

Example 1

[0068] This embodiment provides a blue light-emitting compound based on dibenzofuran, having the structure shown in Formula I-1 below:

[0069]

[0070] (1) Synthesis of compound C:

[0071]

[0072] 1,4-Dibromonaphthalene (2.86 g, 1.0 mol), 4-dibenzofuranboronic acid (2.12 g, 1 mol), Pd(PPh3)4 (57.8 mg, 0.05 mol), sodium carbonate (1.06 g, 10.0 mol), ethanol, and toluene were mixed in a flask. The mixture was refluxed for 8 hours. After the reaction was complete, water was added to quench the reaction. After cooling, the crude product was collected by filtration and washed with water and ethanol. The product was purified by recrystallization from dichloromethane or ethanol. Structural characterization data: 1¹H NMR (500MHz, CDCl₃, δ): 8.94 (dd, J = 7.8, 1.4Hz, 1H), 8.08 (dd, J = 7.9, 1.4Hz, 1H), 8.03 (d, J = 8.8Hz, 1H), 7.99 (dd, J = 7.8, 1.6Hz, 1H), 7.94 (dd, J = 7.8, 1.6Hz, 1H), 7.78–7.74 (m, 2H), 7.63 (d, J = 8.4Hz, 1H), 7.54–7.47 (m, 3H), 7.44–7.35 (m, 2H); The molecular ion mass determined by mass spectrometry is 372.75 (calculated value: 373.25); Theoretical elemental content (%) C 22 H 13 OBr; C 70.80, H 3.51; Measured elemental content (%): C 70.73, H 3.54.

[0073] (2) Synthesis of compound E:

[0074]

[0075] Potassium bis(trimethylsilyl)amino (KHMDS, 21.5 mL, 1 M THF) was slowly added to a 250 mL flask, followed by the addition of 5,5-dimethyl-5,10-dihydrodibenzotinamine (2.7 g, 8.6 mmol), 5,5-dioxo-dibenzothiophene (1.85 g, 8.6 mmol), and dry tetrahydrofuran (40 mL) at room temperature. The mixture was then heated to 65 °C and stirred for 8 hours. After cooling to room temperature, the reaction was quenched with a saturated aqueous solution of ammonium chloride. The organic phase was extracted with dichloromethane (3 × 30 mL). The resulting organic solution was dried over anhydrous sodium sulfate. Purification was performed by silica gel column chromatography (eluent: dichloromethane), and recrystallization from dichloromethane and petroleum ether gave compound E (white powder, 2.3 g, yield 58%). Structural characterization data: 1 ¹H NMR (400MHz, CDCl₃, δ): 7.80 (dd, J = 7.8, 1.8Hz, 2H), 7.66 (m, dd, J = 8.2, 1.8Hz, 2H), 7.39–7.32 (m, 6H), 7.20–7.14 (m, 3H), 7.11 (dd, J = 7.8, 2.0Hz, 1H), 6.93 (dd, J = 8.0, 1.8Hz, 2H), 0.55 (s, 6H); Mass spectrometry determined the molecular ion mass to be 465.26 (calculated value: 465.18); Theoretical elemental content (%) C 27 H 22 Sn: C 69.71, H 4.77; Measured element content (%): C 69.68, H 4.75.

[0076] (3). Synthesis of compound F:

[0077]

[0078] At -78°C, a 1M, 33.4 mL solution of boron trichloride in dichloromethane was slowly added to a 200 mL solution of compound E (3.1 g, 6.7 mmol) in dichloromethane. The reaction mixture was slowly heated to room temperature and stirred for 3 hours. Excess boron trichloride and dichloromethane were removed under vacuum, and the residue was then heated to 100°C and stored under vacuum for 3.5 hours to remove the generated Me₂SnCl₂. Since the resulting compound F is sensitive to moisture, no further purification is required for use. Structural characterization data: 1 ¹H NMR (400MHz, CDCl₃, δ): 7.85 (dd, J = 7.8, 1.8Hz, 2H), 7.61 (dd, J = 7.8, 1.8Hz, 2H), 7.39-7.32 (m, 6H), 7.27 (dd, J = 7.8, 2.0Hz, 2H), 7.16 (td, J = 7.8, 1.8Hz, 2H), 6.91 (dd, J = 8.0, 1.8Hz, 2H). The molecular ion mass determined by mass spectrometry is 361.60 (calculated value: 362.66); theoretical elemental content (%) C 25 H 16 BCl: C 82.80, H 4.45; Measured elemental content (%): C 82.71, H 4.47.

[0079] (4). Synthetic route of dibenzofuranyl blue light compound I-1 containing spirocyclic boronane structure:

[0080]

[0081] Tert-butyllithium (8.9 mL, 14.2 mmol) was slowly added at -78 °C to a 250 mL flask containing compound C (2.65 g, 7.1 mmol) and tert-butylbenzene (40 mL). The reaction mixture was then heated at room temperature for 2.5 hours. The temperature was lowered to 0 °C, and the mixture was slowly added to a solution of compound F (1.2 g, 3.34 mmol) in tert-butylbenzene (30 mL). The resulting mixture was then stirred overnight at room temperature. The solvent was removed under vacuum, and the residue was extracted with dichloromethane (3 × 30 mL) and water. The organic phase was dried over anhydrous sodium sulfate. Purification by silica gel column chromatography (eluent: dichloromethane / petroleum ether, volume ratio = 1 / 8) yielded dibenzofuranyl blue light compound I-1 (2.7 g, yield 65%) containing a spiral borane structure. Structural characterization data: 1¹H NMR (400MHz, CDCl₃, δ): 8.09–8.03 (m, 3H), 7.96 (d, J = 7.9 Hz, 1H), 7.89 (dd, J = 7.7, 1.6 Hz, 1H), 7.85 (dd, J = 7.8, 1.8 Hz, 2H), 7.75 (dd, J = 8.0, 1.6 Hz, 1H), 7.66–7.61 (m, 3H), 7.51–7.33 (m, 12H), 7.24 (dd, J = 7.6, 1.8 Hz, 1H), 7.17–7.11 (m, 3H), 6.91 (dd, J = 8.1, 1.8 Hz, 2H). The molecular ion mass determined by mass spectrometry was 620.81 (calculated value: 620.56). Theoretical elemental content (%) C 47 H 29 BO: C 90.97, H 4.71; Measured element content (%): C 90.86, H 4.69. Figure 1 Compound I-1 in toluene solution (concentration of 10) -5 The fluorescence spectrum of the sample (mol / L) shows an emission peak at 463 nm, which is blue light emission, and the fluorescence quantum yield is 59%. Figure 3 The thermogravimetric and differential scanning calorimetric curves of the compound show that the thermal decomposition temperature and glass transition temperature are 365℃ and 140℃, respectively, indicating that the material has good thermal stability.

[0082] The device structure described in this invention is ITO / HATCN (5nm) / NPB (40nm) / TCTA (5nm) / Ⅰ-1 (20nm) / TPBi (30nm) / LiF (1nm) / Al (100nm). ITO glass serves as the substrate, HATCN and NPB as hole transport layers, TCTA as an electron blocking layer, compound Ⅰ-1 as the light-emitting layer, TPBi as the electron transport layer, LiF as the electron injection layer, and Al as the cathode layer. The hole transport layer, electron blocking layer, light-emitting layer, electron transport layer, electron injection layer, and cathode layer are sequentially prepared on the surface of the anode layer by vacuum evaporation to obtain a blue OLED device.

[0083] Example test results are as follows Figure 5 As shown in Figures 7 and 9, the electroluminescence spectrum of an organic electroluminescent device using dibenzofuran-based blue light compound I-1 (with spiroboridine as the second substituent) as the emitting layer is shown. The emission peak is located at 466 nm, and the device exhibits blue light emission. The device has a turn-on voltage of 3.3 V, a maximum current efficiency of 12.5 cd / A, a power efficiency of 11.9 lm / W, and an external quantum efficiency of 2.7%.

[0084]

Example 2

[0085] Synthetic route of dibenzofuranyl blue light compound I-2 containing bis(2,4,6-trimethylphenyl)borane:

[0086]

[0087] The only difference from Example 1 was that compound F was replaced with chlorobis(2,4,6-trimethylphenyl)borane. Tert-butyllithium (8.9 mL, 1.6 M in n-hex, 14.2 mmol) was slowly added at -78 °C to a flask containing compound C (2.65 g, 7.1 mmol) and tert-butylbenzene (40 mL). The reaction mixture was then stirred at room temperature for 2.5 hours. The temperature was lowered to 0 °C, and the mixture was added to a solution of chlorobis(2,4,6-trimethylphenyl)borane (1.94 g, 6.8 mmol) in tert-butylbenzene (30 mL). The resulting mixture was then stirred overnight at room temperature. The solvent was removed under vacuum, and the residue was extracted with dichloromethane (3 × 30 mL) and water. The organic phase was dried over anhydrous Na₂SO₄, filtered, and the solvent was removed by vacuum evaporation. After purification by silica gel column chromatography (eluent: dichloromethane / petroleum ether, volume ratio = 1 / 10), the dibenzofuranyl blue light compound I-2 of bis(2,4,6-trimethylphenyl)borane was obtained (2.8 g, yield 58%). Structural characterization data: 1 ¹H NMR (400MHz, CDCl₃, δ): 8.09–8.06 (m, 2H), 8.03 (d, J = 8.0 Hz, 1H), 7.96 (d, J = 8.0 Hz, 1H), 7.88 (dd, J = 7.8, 1.8 Hz, 1H), 7.75 (dd, J = 8.0, 1.8 Hz, 1H), 7.72 (d, J = 8.0 Hz, 1H), 6.52–6.36 (m, 6H), 6.83 (s, 4H), 2.26 (s, 6H), 2.09 (s, 12H). The molecular ion mass determined by mass spectrometry was 542.81 (calculated value: 542.53). Theoretical elemental content (%) C 40 H 35 BO: C 88.56, H 6.50; Measured element content (%): C 88.67, H 6.56. Figure 2 Compound I-2 in toluene solution (concentration of 10) -5 The fluorescence spectrum of the sample (mol / L) shows an emission peak at 446 nm, which is blue light emission, and the fluorescence quantum yield is 41%. Figure 4 The thermogravimetric and differential scanning calorimetric curves of compound I-2 show that the thermal decomposition temperature and glass transition temperature are 370 and 147 °C, respectively, indicating that the material has good thermal stability.

[0088] The device structure described in this invention is ITO / HATCN (5nm) / NPB (40nm) / TCTA (5nm) / Ⅰ-2 (20nm) / TPBi (30nm) / LiF (1nm) / Al (100nm). ITO glass serves as the substrate, HATCN and NPB as hole transport layers, TCTA as an electron blocking layer, compound Ⅰ-2 as the light-emitting layer, TPBi as the electron transport layer, LiF as the electron injection layer, and Al as the cathode layer. The hole transport layer, electron blocking layer, light-emitting layer, electron transport layer, electron injection layer, and cathode layer are sequentially prepared on the surface of the anode layer by vacuum evaporation to obtain a blue OLED device.

[0089] Example test results are as follows Figure 6 As shown in Figures 8 and 10, an organic electroluminescent device using dibenzofuranyl blue light-emitting compound I-2 (with bis(2,4,6-trimethylphenyl)borane as the second substituent) as the emitting layer exhibits blue light emission with an emission peak at 444 nm. The device has a turn-on voltage of 3.3 V, a maximum current efficiency of 11.80 cd / A, a power efficiency of 11.6 lm / W, and an external quantum efficiency of 2.6%.

[0090] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A blue light-emitting material based on dibenzofuran, characterized in that, It has the structure shown in Equation I: ； Formula I; In formula I, R is or * indicates the location of the group connection.

2. The method for preparing the blue light-emitting material according to claim 1, characterized in that, Includes the following steps: (1) Mix the compound with the structure shown in Formula A, the compound with the structure shown in Formula B, the basic reagent, the palladium catalyst, the polar organic solvent M and the alcohol solvent, and reflux to obtain the compound with the structure shown in Formula C. (2) Mix the compound with the structure shown in Formula C, tert-butylbenzene, tert-butyllithium initiator and the compound with the structure shown in Formula F or Formula G, and carry out a nucleophilic substitution reaction to obtain a blue light material with the structure shown in Formula I. The structural formulas of the compounds represented by formulas A, B, C, F, and G are as follows: Formula A; Formula B; Formula C; Formula F; Formula G.

3. The method for preparing the blue light-emitting material according to claim 2, characterized in that, In step (1), the alkaline reagent is any one of Na2CO3, K2CO3, or Cs2CO3; the palladium catalyst is any one of Pd(PPh3)4, PdCl2, or Pd2(dba)3; the polar organic solvent M is any one of tetrahydrofuran, toluene, or N,N-dimethylformamide; the alcohol solvent is a low-carbon alcohol with less than 4 carbon atoms; and the volume ratio of the polar organic solvent M to the alcohol solvent is 20 to 10:

1.

4. The method for preparing the blue light-emitting material according to claim 2, characterized in that, In step (2), the ratio of the amount of the compound with the structure shown in formula C, the compound with the structure shown in formula F or formula G, and the tert-butyllithium initiator is 1~1.5 mol: 1~5 mol: 1.5~10 mol, the reaction temperature of the nucleophilic substitution reaction is -78 ℃ to room temperature, and the reaction time is 4~8 h.

5. The method for preparing the blue light-emitting material according to claim 2, characterized in that, The preparation method of the compound with the structure shown in Formula F is as follows: (1) The compound with the structure shown in formula D, 5,5-dioxo-dibenzothiophene, a strong base reagent and a polar organic solvent were mixed and subjected to a nucleophilic substitution reaction to obtain the compound with the structure shown in formula E. (2) The compound with the structure shown in formula E, boron trichloride and chloroalkane solvent are mixed and reacted to obtain the compound with the structure shown in formula F; The structural formulas of the compounds represented by formulas D and E are as follows: Formula D; Formula E.

6. The method for preparing blue light-emitting material according to claim 5, characterized in that, In step (1), the polar solvent is tetrahydrofuran, the strong base reagent is bis(trimethylsilyl)aminopotassium, and the ratio of the amount of the strong base reagent, the compound with structure D shown in the figure, to the solvent is 3~10 mmol : 1~2 mmol : 20~100 mL.

7. The method for preparing blue light-emitting material according to claim 5, characterized in that, In step (1), the temperature of the nucleophilic substitution reaction is 60~70 ℃ and the reaction time is 6~10 h.

8. The method for preparing blue light-emitting material according to claim 5, characterized in that, In step (2), the chloroalkane solvent is dichloromethane, trichloromethane, carbon tetrachloride, or dichloroethane; the ratio of the compound with the structure shown in Formula E, boron trichloride, and the chloroalkane solvent is 4~6 mol: 0.5~1 mL: 40~80 mL.

9. The method for preparing blue light-emitting material according to claim 5, characterized in that, In step (2), the initial temperature of the reaction is -78 °C, and then the reaction mixture is slowly heated to room temperature for 3 to 5 h.

10. The blue light-emitting material based on dibenzofuran as described in claim 1 is used as a light-emitting layer material in an organic electroluminescent device.

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