Preparation process of blue light OLED (Organic Light Emitting Diode) organic small molecule material

Abstract

The invention relates to the technical field of organic electroluminescence, and discloses a preparation process of a blue light OLED (Organic Light Emitting Diode) organic small molecule material, which comprises the following steps: S1, one-pot cascade reaction synthesis: carrying out Suzuki coupling reaction on spirofluorene borate and bromotriazine raw materials under the action of a palladium catalyst to generate an intermediate; then adding a diphenylamine derivative and a copper catalyst, and directly carrying out Buchwald-Hartwisting amination reaction in the same reaction system to finish side chain modification; s2, microwave-assisted purification: putting the reaction mixture in the step S1 into a microwave reactor. According to the preparation process of the blue light OLED small organic molecule material, in order to improve the synthesis efficiency and reduce the loss of an intermediate product, a one-pot cascade reaction is adopted, a Suzuki coupling reaction is firstly carried out to generate an intermediate, and then a Buchwald-Hartwisting amination reaction is directly carried out in the same reaction system to complete side chain modification, so that the reaction steps are shortened, and the operation process is simplified.

Description

Technical Field

[0001] The present invention relates to the technical field of organic electroluminescence, and in particular to a preparation process of a blue light OLED organic small molecule material. Background Art

[0002] OLED (organic light-emitting diode) is a display technology based on the emission of light by organic materials under electric field excitation. It has the advantages of self-luminescence, high contrast, and flexibility. It is widely used in the fields of display and lighting. Its core structure includes anode, hole transport layer, light-emitting layer, electron transport layer and cathode. Among them, blue light material is the key technical bottleneck in the three primary colors of OLED (red, green and blue), because its luminous efficiency, color purity and stability directly affect the performance and life of the display device.

[0003] Early blue light materials were mainly based on fluorescent systems (such as anthracene derivatives), but their internal quantum efficiency was limited by the utilization rate of singlet excitons (theoretical limit 25%), resulting in low luminous efficiency. Phosphorescent materials: Phosphorescent materials using heavy metal complexes (such as iridium and platinum) can achieve 100% exciton utilization, but blue light phosphorescent materials are prone to non-radiative transitions due to their large energy gap, and heavy metal atoms can easily lead to poor material stability and short device life. Thermally activated delayed fluorescence (TADF) materials: The utilization rate of excitons is improved through reverse intersystem crossing (RISC), but the design of blue light TADF materials is difficult and prone to efficiency roll-off and color shift problems.

[0004] Existing preparation processes for blue light materials include: vacuum evaporation method: depositing an organic layer through vacuum high-temperature sublimation, but the thermal stability of the material is extremely high, and the process is complex, costly, and the material utilization rate is low (<30%); solution processing method: suitable for soluble materials (such as polymers or small molecule precursors), but blue light small molecule materials have poor solubility, insufficient film uniformity, and solvent residues can easily cause device defects; synthesis route: the existing blue light small molecule synthesis often involves multi-step reactions (such as Suzuki coupling and Buchwald-Hartwig amination), which have problems such as harsh reaction conditions (high temperature / anhydrous and oxygen-free), many by-products, and low yield (<50%).

[0005] The above existing methods often cannot effectively shorten the reaction steps and simplify the operation process by adopting a one-pot cascade reaction, first performing a Suzuki coupling reaction to generate an intermediate, and then directly performing a Buchwald-Hartwig amination reaction in the same reaction system to complete the side chain modification. In view of this, we proposed a preparation process for blue light OLED organic small molecule materials. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation process of a blue light OLED organic small molecule material to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A preparation process of a blue light OLED organic small molecule material comprises the following steps:

[0009] S1, one-pot tandem reaction synthesis:

[0010] S11. Raw material preparation:

[0011] Spirofluorene borate: as one of the main raw materials for the reaction;

[0012] Bromotriazine: Another key raw material for Suzuki coupling reaction with spirofluorene borate;

[0013] Palladium catalyst: Pd(PPh3)4 was selected as the palladium catalyst in an amount of 2.0 mol% of the reactant molar amount (selected within the range of 1.5 mol%-2.5 mol% to optimize the reaction effect);

[0014] Diphenylamine derivatives: Used in the subsequent Buchwald-Hartwig amination reaction to complete side chain modification, avoiding the tedious separation steps of traditional step-by-step synthesis, shortening the reaction cycle, reducing solvent consumption and product loss, and further optimizing reaction efficiency by dynamically adjusting the palladium catalyst dosage;

[0015] Copper catalyst: The copper catalyst is a CuI / 1,10-phenanthroline complex, and the molar ratio of CuI to the reactant is 1:20-1:30;

[0016] S12, Suzuki coupling reaction: In a reaction flask protected by nitrogen, add spirofluorene borate, bromotriazine and palladium catalyst, heat the reaction system to 80 ° C (in the range of 75-85 ° C), stir and react for 4 hours (in the range of 3-5 hours),

[0017] In one embodiment of the present invention, after the reaction is completed, the reaction yield is monitored by liquid chromatography. If the yield is lower than 90%, the amount of palladium catalyst is adjusted to 3.0 mol%, and the reaction is repeated.

[0018] S2. Microwave-assisted purification: The reaction mixture from step S1 is placed in a microwave reactor, and by-products are removed at 100-150°C and 200-400W of power to obtain a target product with a purity of ≥99%. Microwave energy can selectively heat by-products and rapidly destroy impurity structures by utilizing polarity differences. Compared with traditional recrystallization or column chromatography purification, this method significantly shortens purification time and reduces reagent consumption. Furthermore, the purification process can be precisely controlled to ensure a target product purity of ≥99%, providing high-purity raw materials for subsequent membrane formation processes.

[0019] S3. Solution preparation and film formation: dissolving the product obtained in step S2 in a mixed solvent of cyclopentyl methyl ether and ethylene glycol diethyl ether, and spin coating the solution under a nitrogen atmosphere to form a film;

[0020] S4, gradient annealing treatment: the membrane obtained in step S3 is subjected to stepwise temperature annealing in sequence to eliminate solvent residues and interface defects;

[0021] S5. Host-guest co-evaporation: co-evaporating the thin film obtained in step S4 with the carbazole-benzimidazole host material to form a uniform doping layer to obtain a blue light OLED organic small molecule material.

[0022] In a further embodiment, the palladium catalyst for the Suzuki coupling reaction in step S1 is Pd(PPh3)4, the amount of which is 1.5 mol%-2.5 mol% of the molar amount of the reactants, the reaction temperature is 75-85°C, and the reaction time is 3-5 hours.

[0023] In a further embodiment, the copper catalyst for the Buchwald-Hartwig amination reaction in step S1 is a CuI / 1,10-phenanthroline complex, the molar ratio of CuI to reactant is 1:20-1:30, the reaction temperature is 105-115° C., and the reaction time is 6-8 hours.

[0024] In a further embodiment, if the yield of the Suzuki coupling reaction is lower than 90%, the amount of the Pd(PPh3)4 palladium catalyst is adjusted to between 2.5 mol% and 3.5 mol%, and the reaction is repeated to achieve a better reaction effect.

[0025] In a further embodiment, the power of the microwave reaction in step S2 is 250-350 W, the reaction time is 20-40 minutes, and the microwave frequency is 2.45 GHz ± 5%.

[0026] In a further embodiment, the mixed solvent in step S3 is composed of cyclopentyl methyl ether and ethylene glycol diethyl ether in a volume ratio of 6.5:3.5 to 7.5:2.5, the dissolution temperature is 50-70° C., and the dissolution concentration is 15-25 mg / mL.

[0027] In a further solution, the spin coating process has a rotation speed of 2800-3200 rpm, a film thickness of 20-40 nm, and a surface roughness Ra≤1.2 nm after film formation, thereby improving the uniformity and density of the film layer and laying a good foundation for the subsequent co-evaporation process.

[0028] In a further embodiment, the gradient annealing in step S4 is divided into three stages:

[0029] S41: Keep warm at 75-85°C for 8-12 minutes;

[0030] S42: Raise the temperature to 115-125°C and keep warm for 15-25 minutes;

[0031] S43: Heat to 145-155°C and keep warm for 8-12 minutes at a heating rate of 2-5°C / min.

[0032] In a further solution, after the gradient annealing film forming process, if the film roughness is greater than 1 nm, the annealing temperature is adjusted, the S41 annealing temperature is adjusted to 85-95°C, the S42 annealing temperature is adjusted to 125-135°C, and the S43 annealing temperature is adjusted to 155-165°C, and gradient annealing is performed again to better eliminate solvent residues and interface defects.

[0033] In a further embodiment, in step S5, the HOMO energy level of the host material is -5.7 to -5.9 eV, the LUMO energy level is -2.5 to -2.7 eV, and the HOMO energy level difference between the host and guest materials is ΔHOMO = 0.15-0.25 eV, and the LUMO energy level difference is ΔLUMO = 0.15-0.25 eV.

[0034] Compared with the prior art, the present invention provides a preparation process for blue light OLED organic small molecule materials, which has the following beneficial effects:

[0035] 1. The preparation process of the blue light OLED organic small molecule material is to improve the synthesis efficiency, simplify the operation process, and reduce the loss of intermediate product separation: by adopting a one-pot cascade reaction technology, first, under nitrogen protection, a spirocyclic fluorene borate and bromotriazine are reacted in the presence of a palladium catalyst [Pd(PPh3)4, the amount of which is 1.5%-2.5% of the molar amount of the reactants] at 75-85°C for 3-5 hours to produce an intermediate; then, without isolating the intermediate, a diphenylamine derivative and a copper catalyst (CuI / 1,10-phenanthroline complex, the molar ratio of CuI to reactant is 1:20-1:30) are directly added to the same reaction system, and the temperature is raised to 105-115°C for 6-8 hours to carry out a Buchwald-Hartwig amination reaction to complete the side chain modification. This method avoids the tedious separation steps of traditional step-by-step synthesis, shortens the reaction cycle, reduces solvent consumption and product loss, and further optimizes the reaction efficiency by dynamically adjusting the amount of palladium catalyst.

[0036] 2. The preparation process of the blue light OLED organic small molecule material, in order to efficiently remove by-products and improve the purity of the target product: through microwave-assisted purification technology, the reaction mixture is placed in a microwave reactor and treated at 100-150°C and 250-350W power (microwave frequency 2.45GHz±5%) for 20-40 minutes. Microwave energy can selectively heat by-products and use polarity differences to quickly destroy the impurity structure. Compared with traditional recrystallization or column chromatography purification, it significantly shortens the purification time and reduces reagent consumption. It can also accurately control the purification process to ensure that the purity of the target product is ≥99%, providing high-purity raw materials for subsequent film-forming processes.

[0037] 3. The preparation process of the blue light OLED organic small molecule material, in order to eliminate solvent residues, interface defects and optimize the surface quality of the film: the spin-coated film is treated by a three-stage gradient annealing process: first, the temperature is kept at 75-85℃ for 8-12 minutes (S41) to initially volatilize the low-boiling point solvent; then the temperature is increased at a rate of 2-5℃ / min to 115-125℃ and kept for 15-25 minutes (S42) to remove the medium-boiling point solvent and initially repair the interface defects; finally, the temperature is increased to 145-155℃ and kept for 8-1 2 minutes (S43) to eliminate high-boiling-point solvent residues and further smooth the film layer. If the film roughness Ra is greater than 1nm after annealing, the solvent residue can be effectively reduced (for example, the residual amount after optimization is reduced from 0.8% to 0.05%) by increasing the annealing temperature at each stage (S41 is adjusted to 85-95℃, S42 is 125-135℃, and S43 is 155-165℃). The roughness of the film is controlled at Ra≤1.2nm, thereby improving the uniformity and density of the film layer and laying a good foundation for the subsequent co-evaporation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1Flow chart of the overall method of the present invention;

[0039] Figure 2 This is a flow chart of the one-pot tandem reaction synthesis steps of S1 of the present invention;

[0040] Figure 3 This is a flow chart of the microwave-assisted purification step S2 of the present invention;

[0041] Figure 4 Flow chart of the preparation and film-forming steps of the S3 solution of the present invention;

[0042] Figure 5 This is a flow chart of the S4 gradient annealing process steps of the present invention;

[0043] Figure 6 This is a flow chart of the S5 host-guest co-evaporation step of the present invention. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] In this application, the term "upper" indicates an orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. This is primarily for the purpose of better describing this application and its embodiments, and is not intended to limit the indicated devices, elements, or components to a specific orientation, or to be constructed and operated in a specific orientation. Furthermore, the term "upper" may also be used in certain circumstances to indicate a dependency or connection relationship. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0046] In addition, the terms "comprises" and "comprising" and any variations thereof are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, product, or apparatus.

[0047] See also Figures 1-6 , the present invention provides a technical solution:

[0048] A preparation process of a blue light OLED organic small molecule material comprises the following steps:

[0049] S1, one-pot tandem reaction synthesis:

[0050] S11. Raw material preparation:

[0051] Spirofluorene borate: as one of the main raw materials for the reaction;

[0052] Bromotriazine: Another key raw material for Suzuki coupling reaction with spirofluorene borate;

[0053] Palladium catalyst: Pd(PPh3)4 was selected as the palladium catalyst in an amount of 2.0 mol% of the reactant molar amount (selected within the range of 1.5 mol%-2.5 mol% to optimize the reaction effect);

[0054] Diphenylamine derivatives: Used in the subsequent Buchwald-Hartwig amination reaction to complete side chain modification, avoiding the tedious separation steps of traditional step-by-step synthesis, shortening the reaction cycle, reducing solvent consumption and product loss, and further optimizing reaction efficiency by dynamically adjusting the palladium catalyst dosage;

[0055] Copper catalyst: The copper catalyst is a CuI / 1,10-phenanthroline complex, and the molar ratio of CuI to the reactant is 1:20-1:30;

[0056] S12, Suzuki coupling reaction: In a reaction flask protected by nitrogen, add spirofluorene borate, bromotriazine and palladium catalyst, heat the reaction system to 80 ° C (in the range of 75-85 ° C), stir and react for 4 hours (in the range of 3-5 hours),

[0057] In one embodiment of the present invention, after the reaction is completed, the reaction yield is monitored by liquid chromatography. If the yield is less than 90%, the amount of palladium catalyst is adjusted to 3.0 mol%, and the reaction is repeated, referring to Table 1:

[0058]

[0059] Table 1: Suzuki coupling reaction conditions and yields

[0060] S13, Buchwald-Hartwig amination reaction: After the Suzuki coupling reaction is completed, a diphenylamine derivative and a copper catalyst are added to the reaction system, the reaction system is heated to 110° C. (within the range of 105-115° C.), and the reaction is continued with stirring for 7 hours (within the range of 6-8 hours).

[0061] S14. After the reaction is completed, the product structure is confirmed by liquid chromatography-mass spectrometry.

[0062] S2. Microwave-assisted purification: The reaction mixture of step S1 is placed in a microwave reactor, and the by-products are removed at 100-150°C and a power of 200-400W to obtain a target product with a purity ≥99%. The power of the microwave reaction is 250-350W, the reaction time is 20-40 minutes, and the microwave frequency is 2.45GHz±5%. Microwave energy can selectively heat by-products and use polarity differences to quickly destroy the impurity structure. Compared with traditional recrystallization or column chromatography purification, it significantly shortens the purification time, reduces reagent consumption, and can accurately control the purification process to ensure that the purity of the target product is ≥99%, providing high-purity raw materials for subsequent film-forming processes.

[0063] S3. Solution preparation and film formation: The product obtained in step S2 is dissolved in a mixed solvent of cyclopentyl methyl ether and ethylene glycol diethyl ether, and spin-coated under a nitrogen atmosphere to form a film, wherein the mixed solvent is composed of cyclopentyl methyl ether and ethylene glycol diethyl ether in a volume ratio of 6.5:3.5 to 7.5:2.5, the dissolution temperature is 50-70° C., and the dissolution concentration is 15-25 mg / mL;

[0064] In one embodiment of the present invention, the rotation speed of the spin coating process is 2800-3200 rpm, and the film thickness is 20-40 nm, so that the surface roughness Ra after film formation is ≤1.2 nm, thereby improving the uniformity and density of the film layer, laying a good foundation for the subsequent co-evaporation process, otherwise repeat step S3.

[0065] S4, gradient annealing treatment: The film obtained in step S3 is subjected to step-by-step temperature annealing in order to eliminate solvent residues and interface defects. The gradient annealing in step S4 is divided into three stages:

[0066] S41: Keep warm at 75-85℃ for 8 to 12 minutes.

[0067] S42: Raise the temperature to 115-125°C and keep warm for 15-25 minutes;

[0068] S43: Heat to 145-155°C and hold for 8-12 minutes at a heating rate of 2-5°C / min;

[0069] In one embodiment of the present invention, after the gradient annealing film forming process, if the film roughness is greater than 1 nm, the annealing temperature is adjusted:

[0070] Adjust the S41 annealing temperature to 85-95°C;

[0071] S42 annealing temperature is adjusted to 125-135°C;

[0072] S43 annealing temperature is adjusted to 155-165°C;

[0073] Re-perform gradient annealing,

[0074] Refer to Table 2:

[0075]

[0076] Table 2: Effect of gradient annealing temperature on film roughness

[0077] S5. Host-guest co-evaporation: The thin film obtained in step S4 is co-evaporated with the carbazole-benzimidazole host material to form a uniformly doped layer to obtain a blue light OLED organic small molecule material. In addition, the HOMO energy level of the host material is -5.7 to -5.9 eV, the LUMO energy level is -2.5 to -2.7 eV, and the HOMO energy level difference between the host and guest materials is ΔHOMO = 0.15-0.25 eV, and the LUMO energy level difference is ΔLUMO = 0.15-0.25 eV.

[0078] While the present invention has been generally described above, modifications and improvements are readily apparent to those skilled in the art. Therefore, modifications and improvements that do not depart from the spirit of the present invention are intended to be within the scope of the present invention.

Claims

1. A preparation process of a blue light OLED organic small molecule material, characterized in that: The following steps are involved: S1. One-pot cascade reaction synthesis: A Suzuki coupling reaction of spirofluorene borate and bromotriazine starting material in the presence of palladium catalyst generates an intermediate. Subsequently, a diphenylamine derivative and copper catalyst are added to directly carry out a Buchwald-Hartwig amination reaction in the same reaction system to complete the side chain modification. S2. Microwave-assisted purification: Place the reaction mixture from step S1 in a microwave reactor and remove by-products at 100-150°C and 200-400W to obtain the target product with a purity of ≥99%; S3. Solution preparation and film formation: dissolving the product obtained in step S2 in a mixed solvent of cyclopentyl methyl ether and ethylene glycol diethyl ether, and spin coating the solution under a nitrogen atmosphere to form a film; S4, gradient annealing treatment: the membrane obtained in step S3 is subjected to stepwise temperature annealing in sequence to eliminate solvent residues and interface defects; S5. Host-guest co-evaporation: co-evaporating the thin film obtained in step S4 with the carbazole-benzimidazole host material to form a uniform doping layer to obtain a blue light OLED organic small molecule material.

2. The process for preparing a blue light OLED organic small molecule material according to claim 1, characterized in that: The palladium catalyst for the Suzuki coupling reaction in step S1 is Pd(PPh3)4, and its usage is 1.5mol%-2.5mol% of the molar weight of the reactants. The reaction temperature is 75-85°C, and the reaction time is 3-5 hours.

3. The process for preparing a blue light OLED organic small molecule material according to claim 2, characterized in that: The copper catalyst for the Buchwald-Hartwig amination reaction in step S1 is a CuI / 1,10-phenanthroline complex, the molar ratio of CuI to reactant is 1:20-1:30, the reaction temperature is 105-115° C., and the reaction time is 6-8 hours.

4. The process for preparing a blue light OLED organic small molecule material according to claim 3, characterized in that: If the yield of the Suzuki coupling reaction is lower than 90%, the amount of Pd(PPh3)4 palladium catalyst is adjusted to between 2.5mol% and 3.5mol% and the reaction is repeated.

5. The process for preparing a blue light OLED organic small molecule material according to claim 1, characterized in that: The power of the microwave reaction in step S2 is 250-350 W, the reaction time is 20-40 minutes, and the microwave frequency is 2.45 GHz ± 5%.

6. The process for preparing a blue light OLED organic small molecule material according to claim 1, characterized in that: In step S3, the mixed solvent is composed of cyclopentyl methyl ether and ethylene glycol diethyl ether in a volume ratio of 6.5:3.5 to 7.5:2.5, the dissolution temperature is 50-70° C., and the dissolution concentration is 15-25 mg / mL.

7. The process for preparing a blue light OLED organic small molecule material according to claim 1, characterized in that: The rotation speed of the spin coating process is 2800-3200 rpm, the film thickness is 20-40 nm, and the surface roughness Ra after film formation is ≤1.2 nm.

8. The process for preparing a blue light OLED organic small molecule material according to claim 1, characterized in that: The gradient annealing in step S4 is divided into three stages: S41: Keep warm at 75-85°C for 8-12 minutes; S42: Raise the temperature to 115-125°C and keep warm for 15-25 minutes; S43: Heat to 145-155°C and keep warm for 8-12 minutes at a heating rate of 2-5°C / min.

9. The process for preparing a blue light OLED organic small molecule material according to claim 8, characterized in that: After the gradient annealing film forming process, if the film roughness is greater than 1 nm, the annealing temperature is adjusted, the S41 annealing temperature is adjusted to 85-95°C, the S42 annealing temperature is adjusted to 125-135°C, the S43 annealing temperature is adjusted to 155-165°C, and gradient annealing is performed again.

10. The process for preparing a blue light OLED organic small molecule material according to claim 1, characterized in that: In step S5, the HOMO energy level of the host material is -5.7 to -5.9 eV, the LUMO energy level is -2.5 to -2.7 eV, and the HOMO energy level difference between the host and guest materials is ΔHOMO=0.15-0.25 eV, and the LUMO energy level difference is ΔLUMO=0.15-0.25 eV.

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