Blue phosphorescent light-emitting material, preparation method and application thereof
By synthesizing a blue phosphorescent material with a trimer molecular structure through high-temperature oligomerization, the problems of low exciton utilization and poor stability of existing blue OLED materials have been solved, thus achieving a significant performance improvement in high-efficiency blue OLED devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- THE CHINESE UNIV OF HONG KONG (SHENZHEN)
- Filing Date
- 2025-07-07
- Publication Date
- 2026-07-21
AI Technical Summary
Existing blue OLED materials suffer from low exciton utilization, poor stability, and insufficient color purity, causing the development of blue OLED materials to lag behind that of red and green OLEDs, thus limiting the overall performance improvement of the OLED industry.
Using benzomelamine as raw material, a trimer molecular structure was synthesized through high-temperature oligomerization, and then purified by thermal shrinkage and solvent methods to prepare a highly efficient blue phosphorescent material.
A high luminescence quantum efficiency (54%) of blue phosphorescent luminescent material was achieved, which improved the efficiency of blue OLED devices and has the advantage of being simple and easy to fabricate on a large scale.
Smart Images
Figure CN120665024B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of organic light-emitting materials technology, and in particular to a blue phosphorescent material, its preparation method, and its application. Background Technology
[0002] The development of blue phosphorescent materials is one of the core challenges for breakthroughs in OLED technology. Currently, commercial OLEDs still rely on inefficient blue fluorescent materials, with a theoretical maximum exciton utilization rate of only 25% in electroluminescence, severely limiting the overall performance of displays. Second-generation blue OLED materials are phosphorescent materials, theoretically capable of achieving 100% exciton utilization, but they suffer from poor stability and insufficient color purity, resulting in current blue OLED materials still being fluorescent materials. The development of blue phosphorescent OLED materials generally lags behind that of red and green light. How to overcome the technical bottlenecks of blue phosphorescent materials, optimize their stability and color gamut performance, and drive the OLED industry towards higher performance remains a critical technical challenge that needs to be addressed by those skilled in the art. Summary of the Invention
[0003] The purpose of this invention is to provide a blue phosphorescent material, its preparation method, and its application, in order to solve the problems existing in the prior art.
[0004] To achieve the above objectives, the present invention provides the following solution:
[0005] One of the technical solutions of the present invention is a blue phosphorescent material, the structural formula of which is shown in formula (1):
[0006]
[0007] The second technical solution of the present invention: a method for preparing the above-mentioned blue phosphorescent material, comprising the following steps:
[0008] After sealing, benzomelamine was subjected to a first calcination treatment to obtain benzomelamine dimer;
[0009] The structure of the phenylcyanuric acid dimer is as follows:
[0010] The benzomelamine and the benzomelamine dimer are mixed, sealed, and then subjected to a second calcination treatment to obtain the blue phosphorescent material (i.e., benzomelamine trimer).
[0011] Furthermore, the temperature of the first calcination treatment is 350–420°C, and the time is 0.5–3 hours.
[0012] Furthermore, the preparation method further includes purification after the first calcination treatment;
[0013] The purification process includes: adding the reaction system obtained after the first calcination treatment to a THF solution, collecting the filter residue and washing it with methanol to obtain benzoic melamine dimer.
[0014] Furthermore, the molar ratio of the benzomelamine and the benzomelamine dimer is 1:(0.5-2.0).
[0015] Furthermore, the temperature of the second calcination treatment is 350–420°C, and the time is 0.5–3 hours.
[0016] Furthermore, the preparation method further includes purification after the second calcination treatment;
[0017] The purification process includes: adding the reaction system obtained after the second calcination treatment to a THF solution, collecting the filtrate, concentrating the filtrate until just as precipitates appear, and then adding methanol to obtain a solid product.
[0018] The solid product was dissolved in a THF solution, evaporated, and recrystallized to obtain the blue phosphorescent material.
[0019] Furthermore, the temperature of the THF solution is 40–60°C.
[0020] The third technical solution of the present invention: the application of the above-mentioned blue phosphorescent material in the preparation of organic light-emitting devices.
[0021] The present invention discloses the following technical effects:
[0022] (1) The blue phosphorescent material of the present invention has a high quantum efficiency of light emission (54%). It can be used to prepare blue OLED devices, which is beneficial to improve the efficiency of blue devices.
[0023] (2) The present invention uses phenyl melamine as raw material and connects them into a trimer molecular structure by oligomerization at high temperature to obtain a blue pure phosphorescent material.
[0024] (3) This invention uses benzotricyanamide as the initial structure and prepares the target molecule (blue phosphorescent material) for the first time by thermal shrinkage method, and obtains a solvent purification method, which has the advantages of simple preparation method and easy large-scale preparation. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 The hydrogen spectrum of the benzotricyanamide dimer (product C2) prepared in Example 1;
[0027] Figure 2 The hydrogen spectrum of the blue phosphorescent material (product C3) prepared in Example 1;
[0028] Figure 3 The carbon spectrum of the blue phosphorescent material (product C3) prepared in Example 1;
[0029] Figure 4 The 1H-15N heteronuclear single quantum correlation (HSQC) NMR spectrum of the blue phosphorescent material (product C3) prepared in Example 1;
[0030] Figure 5 The 1H-15N heteronuclear multibond correlation (HMBC) NMR spectrum of the blue phosphorescent material (product C3) prepared in Example 1;
[0031] Figure 6 The single-crystal structure diagram of the blue phosphorescent material (product C3) prepared in Example 1 is shown.
[0032] Figure 7 The high-resolution mass spectrum of the blue phosphorescent material (product C3) prepared in Example 1;
[0033] Figure 8 The absorption spectrum of the blue phosphorescent material (product C3) prepared in Example 1 is shown.
[0034] Figure 9 The emission spectrum of the THF solution of the blue phosphorescent material (product C3) prepared in Example 1 is shown.
[0035] Figure 10 Steady-state emission spectrum and delayed emission spectrum of the THF solution of the blue phosphorescent material (product C3) prepared in Example 1 at 77K;
[0036] Figure 11 Steady-state emission spectrum and delayed emission spectrum of the blue phosphorescent material (product C3) crystal powder prepared in Example 1;
[0037] Figure 12 Photographs of the blue phosphorescent material (product C3) prepared in Example 1 under visible light and 365nm UV light;
[0038] Figure 13 The image shows the CIE coordinates of the blue phosphorescent material powder sample prepared in Example 1. Detailed Implementation
[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0040] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0041] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0042] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.
[0043] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0044] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.
[0045] Currently, the structure of organic light-emitting diodes (OLEDs) generally includes an electron transport layer, an emissive layer, and a hole transport layer. For the emissive layer, using only heavy metal complexes as the phosphorescent emitting layer in OLED devices results in excessively high exciton concentrations, potentially leading to triplet-triplet quenching, loss of triplet excitons, and reduced OLED device efficiency. Therefore, phosphorescent OLEDs typically employ a host-guest emission system, dispersing the guest luminescent material within a host material to improve the device's luminous efficiency. This host-guest emission system has two emission mechanisms: energy transfer and carrier trapping.
[0046] Energy transfer methods can be divided into two types, namely Energy transfer and Dexter energy transfer. Energy transfer occurs via a relatively long dipole-dipole induction mechanism. If the emission of the host emitting electron and the absorption of the guest emitting electron overlap and their transitions are permitted, a rapid, non-luminescent energy transfer will occur between the host and guest emitting electrons. Dexter energy transfer, on the other hand, occurs via a shorter-distance electron exchange mechanism. This electron transfer must obey the Wigner-Witmer selection rule, meaning the electron spin parameter remains unchanged before and after the transfer. Therefore, it only occurs between singlet-to-singlet and triplet-to-triplet states. Because this mechanism only interacts with nearby molecules, the transfer process is relatively slow. In the emitting layer of a phosphorescent component, the energies of the singlet and triplet excited states of the host emitting electron are respectively determined by… Energy transfer and Dexter energy transfer are transferred to the singlet and triplet excited states of the phosphorescent luminescent body. Then, through rapid intersystem crossings within the phosphorescent luminescent body, the energy of the singlet excited state is transferred to the triplet excited state, thereby emitting phosphorescence. Therefore, the internal quantum efficiency can approach 100%.
[0047] The triplet energy levels, thermal stability, electrochemical and photophysical properties of the host material are closely related to its molecular structure, thus affecting the performance of PHOLEDs. To date, almost all reported high-efficiency host materials have very simple chemical structures. However, it is worth noting that although these high-efficiency host materials have simple structures, their synthesis from starting materials to the target product often requires as many as 4 to 6 reaction steps, and necessitates harsh conditions such as precious metal catalysts, highly toxic phosphorus reagents, flammable and explosive reagents, or anhydrous and oxygen-free environments and extremely low temperatures. Therefore, developing organic host materials that can be designed and synthesized directly through one or two green chemical reactions, resulting in simple and efficient structures, can significantly reduce material costs and will be of great significance to the commercialization of OLEDs.
[0048] To address the above problems, the present invention provides the following technical solution:
[0049] In a first aspect, the present invention provides a blue phosphorescent material with the structural formula shown in formula (1):
[0050]
[0051] In a second aspect, the present invention provides a method for preparing the above-mentioned blue phosphorescent material, comprising the following steps:
[0052] (1) Place benzomelamine (i.e., 2,4-diamino-6-phenyl-1,3,5-triazine, C1) in an alumina crucible, seal it with aluminum foil, and place it in a muffle furnace or tube furnace. Keep it at 350-420℃ for 0.5-3h. After the reaction system cools to room temperature, place the reaction system in a THF (tetrahydrofuran) solution, filter to obtain a filter residue, and wash away the unreacted C1 (benzomelamine) in the filter residue with methanol to obtain crude product C2 (benzomelamine dimer) with a yield of 30-50%.
[0053] The chemical reaction equation is as follows:
[0054]
[0055] (2) Mix C1 (benzomelamine) and C2 (benzomelamine dimer) in a 1:1 molar ratio until homogeneous. Take 1-5g and place it in an alumina crucible. Seal it with aluminum foil and place it in a muffle furnace or tube furnace. Keep it at 350-420℃ for 0.5-3h. After the reaction system cools to room temperature, place the reaction system in THF solution and filter to collect the residue and filtrate. Wash the residue with methanol to remove unreacted C1, and obtain crude product C2, which is used as the raw material for step (2). Distill and concentrate the filtrate until the precipitate is just visible. Immediately add the same volume of methanol as the filtrate. Powder will be generated. Filter immediately to obtain crude product C3 (content of 70-90%). The crude C3 product is then placed in a hot THF solution (temperature 50-60℃) and subjected to evaporation and recrystallization to obtain C3 molecules with a purity >95% (i.e., blue phosphorescent material, benzoic acid diamine trimer), with a total yield of 20-30%.
[0056] The chemical reaction equation is as follows:
[0057]
[0058] In a third aspect, the present invention provides an application of the above-mentioned blue phosphorescent material in the fabrication of organic light-emitting devices.
[0059] Example 1
[0060] A method for preparing a blue phosphorescent material:
[0061] (1) Add 1g of compound C1 (phenyl melamine) to a 50mL alumina crucible, seal it with aluminum foil, place it in a muffle furnace, keep it at 350℃ for 0.5h, and after the reaction system cools to room temperature, place the reaction system in THF solution, filter to obtain filter residue, wash away unreacted C1 in the filter residue with methanol to obtain crude product C2 (phenyl melamine dimer), with a yield of about 30%.
[0062] The structural formula of compound C1 is:
[0063] The structural formula of product C2 is:
[0064] The proton NMR spectrum of product C2 is shown below. Figure 1 .
[0065] The 1H NMR data for product C2 are as follows: 1H NMR (500MHz, DMSO-d6) δ 9.86 (s, 1H), 8.41 (d, J = 7.2Hz, 4H), 7.58 (t, J = 7.2Hz, 2H), 7.51 (t, J = 7.6Hz, 4H), 7.31 (d, J = 70.2Hz, 5H).
[0066] (2) Weigh C1 and C2 and mix them evenly in a molar ratio of 1:1 to obtain a mixture. Take 1g of the mixture into a 50mL alumina crucible, seal it with aluminum foil, and place it in a tube furnace. Keep it at 350℃ for 0.5h. After the reaction system cools to room temperature, place the reaction system into a THF solution and filter to collect the residue and filtrate.
[0067] The filter residue was washed with methanol to remove unreacted C1, yielding crude product C2, which was used as the raw material for step (2).
[0068] The filtrate was concentrated by distillation until the precipitate was just beginning to appear. Immediately, an equal volume of methanol was added to the filtrate, resulting in powder formation. This was then filtered to obtain crude C3 product (approximately 70% purity). The crude C3 product was then placed in a hot THF solution (40°C) and subjected to evaporation and recrystallization to obtain product C3 (blue phosphorescent material, phenyl melamine trimer) with a purity >95%, with an overall yield of approximately 20%.
[0069] The structural formula of the blue phosphorescent material (product C3) is:
[0070] The hydrogen spectrum of the blue phosphorescent material is shown below. Figure 2 The carbon spectrum can be found here. Figure 3 .
[0071] The proton spectrum data of the blue phosphorescent material are: 1 H NMR (500MHz, DMSO-d6) δ10.30(s,1H),8.57(d,J=7.4Hz,1H),8.40(d,J=7.3Hz,2H),7.64(t,J=7.3Hz,1H),7.53(dq,J=31.8,7.4Hz,5H),7.34(s,1H).
[0072] The 1H-15N heteronuclear single quantum correlation (HSQC) NMR spectrum of the blue phosphorescent material is shown below. Figure 4 The 1H-15N heteronuclear multibond correlation (HMBC) NMR spectrum is shown below. Figure 5 .
[0073] See the single-crystal structure diagram of the blue phosphorescent material. Figure 6 .
[0074] High-resolution mass spectra of blue phosphorescent materials are shown in [the image]. Figure 7 The absorption spectrum of the blue phosphorescent material is shown below. Figure 8 .
[0075] from Figure 7 As can be seen, its molecular weight after adding a proton is 528.2121, and the calculated relative molecular weight of the target molecule is 527.2051, which matches the theoretical value of 527.2043.
[0076] from Figure 8 As can be seen from the data, the maximum absorption of the blue phosphorescent material prepared in this embodiment is at 260 nm, and the molar extinction coefficient is 96700 mol. -1 cm -1 .
[0077] THF solution of blue phosphorescent material (concentration is 10) -5 The emission spectrum of (mol / L) is shown in the figure. Figure 9 .
[0078] from Figure 9 As can be seen, the strongest emission position of the blue phosphorescent material is at 451nm.
[0079] THF solution of blue phosphorescent material (concentration is 10) -5 The steady-state emission spectrum and delayed emission spectrum of (mol / L) at 77 K are shown in the figure. Figure 10 .
[0080] from Figure 10 As can be seen, the strongest emission position of the steady-state spectrum of the blue phosphorescent material is at 424 nm, accompanied by two shoulder peaks (399 nm and 450 nm). The delayed spectrum almost overlaps with the steady-state spectrum, indicating that the blue phosphorescent material prepared in this embodiment can emit pure blue phosphorescence at 77 K.
[0081] The steady-state emission spectrum and delayed emission spectrum of the blue phosphorescent crystalline powder are shown below. Figure 11 .
[0082] from Figure 11As can be seen, the strongest emission position in the steady-state emission spectrum of the blue phosphorescent material is at 460 nm, accompanied by a strong shoulder peak at 485 nm. The overlap between the delayed emission spectrum peak and the steady-state emission spectrum indicates that the luminescence of the blue phosphorescent material prepared in this embodiment is mainly phosphorescence.
[0083] Photos of the blue phosphorescent material under visible light and 365nm UV light are shown below. Figure 12 .
[0084] from Figure 12 As can be seen, the blue phosphorescent material appears off-white under visible light, but emits a sky-blue light under 365nm UV.
[0085] Example 2
[0086] A method for preparing a blue phosphorescent material:
[0087] (1) Add 5g of compound C1 (phenyl melamine) to a 50mL alumina crucible, seal it with aluminum foil, place it in a tube furnace, and keep it at 420℃ for 3.0h. After the reaction system cools to room temperature, place the reaction system in THF solution, filter to obtain filter residue, wash away unreacted C1 in the filter residue with methanol, and obtain crude product C2 (phenyl melamine dimer) with a yield of about 50%.
[0088] The structural formula of compound C1 is:
[0089] The structural formula of product C2 is:
[0090] (2) Weigh C1 and C2 and mix them evenly in a molar ratio of 1:1 to obtain a mixture. Take 5g of the mixture into a 50mL alumina crucible, seal it with aluminum foil, and place it in a tube furnace. Keep it at 420℃ for 3.0h. After the reaction system cools to room temperature, place the reaction system into a THF solution and filter to collect the residue and filtrate.
[0091] The filter residue was washed with methanol to remove unreacted C1, yielding crude product C2, which was used as the raw material for step (2).
[0092] The filtrate was concentrated by distillation until the precipitate was just beginning to appear. Immediately, an equal volume of methanol was added to the filtrate, resulting in powder formation. This was then filtered to obtain crude C3 product (approximately 90% purity). The crude C3 product was then placed in a hot THF solution (60°C) and subjected to evaporation and recrystallization to obtain product C3 (blue phosphorescent material, phenyl melamine trimer) with a purity >95%, with an overall yield of approximately 30%.
[0093] The structural formula of the blue phosphorescent material (product C3) is:
[0094] The characterization results and properties of the blue phosphorescent material prepared in this embodiment are the same as those in Example 1.
[0095] Comparative Example 1
[0096] A method for preparing a blue phosphorescent material:
[0097] (1) Add 3g of compound C1 (phenyl melamine) to a 50mL alumina crucible, seal it with aluminum foil, place it in a tube furnace, and keep it at 420℃ for 3.0h. After the reaction system cools to room temperature, place the reaction system in THF solution, filter to obtain filter residue, wash away unreacted C1 in the filter residue with methanol, and obtain crude product C2 (phenyl melamine dimer) with a yield of about 40%.
[0098] The structural formula of compound C1 is:
[0099] The structural formula of product C2 is:
[0100] (2) Weigh C1 and C2 and mix them evenly in a molar ratio of 1:1 to obtain a mixture. Take 3g of the mixture into a 50mL alumina crucible, seal it with aluminum foil, and place it in a tube furnace. Keep it at 420℃ for 3.0h. After the reaction system cools to room temperature, place the reaction system into a THF solution and filter to collect the residue and filtrate.
[0101] The filter residue was washed with methanol to remove unreacted C1, yielding crude product C2, which was used as the raw material for step (2).
[0102] Adding an equal volume of methanol to the filtrate directly results in powder formation. Immediate filtration yields crude C3 product (approximately 90% purity). The crude C3 product is then placed in a hot THF solution (60°C) and subjected to evaporation and recrystallization to obtain product C3 (blue phosphorescent material, phenyl melamine trimer) with a purity >95%, with an overall yield of approximately 10%.
[0103] Comparative Example 2
[0104] A method for preparing a blue phosphorescent material:
[0105] (1) Add 3g of compound C1 (phenyl melamine) to a 50mL alumina crucible, seal it with aluminum foil, place it in a tube furnace, and keep it at 420℃ for 3.0h. After the reaction system cools to room temperature, place the reaction system in THF solution, filter to obtain filter residue, wash away unreacted C1 in the filter residue with methanol, and obtain crude product C2 (phenyl melamine dimer) with a yield of about 40%.
[0106] The structural formula of compound C1 is:
[0107] The structural formula of product C2 is:
[0108] (2) Weigh C1 and C2 and mix them evenly in a molar ratio of 1:2.0 to obtain a mixture. Take 3g of the mixture into a 50mL alumina crucible, seal it with aluminum foil, place it in a tube furnace, and keep it at 420℃ for 3.0h. After the reaction system cools to room temperature, place the reaction system into a THF solution, filter and collect the residue and filtrate respectively.
[0109] The filter residue was washed with methanol to remove unreacted C1, yielding crude product C2, which was used as the raw material for step (2).
[0110] The filtrate was concentrated by distillation until the precipitate was just beginning to appear. Then, excess methanol was immediately added, and powder was observed to form. The product was then filtered immediately to obtain the crude product, whose main component was C2.
[0111] Example of effect 1
[0112] The blue phosphorescent material powder sample prepared in Example 1 has an IQE of 54% and a melting point of 345–347 °C, exhibiting high thermal stability.
[0113] The CIE coordinate diagram of the blue phosphorescent material powder sample prepared in Example 1 is shown below. Figure 13 .
[0114] from Figure 13 As can be seen, the CIE coordinates of the blue phosphorescent material powder sample are 0.1662 and 0.2389.
[0115] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A blue phosphorescent luminescent material, characterized in that, The structural formula is shown in equation (1): Equation (1).
2. A method for preparing the blue phosphorescent material according to claim 1, characterized in that, Includes the following steps: After sealing, benzomelamine was subjected to a first calcination treatment to obtain benzomelamine dimer; The structure of the phenylcyanuric acid dimer is as follows: ; The benzomelamine and the benzomelamine dimer were mixed, sealed, and then subjected to a second calcination treatment to obtain the blue phosphorescent material. The temperature of the first calcination treatment is 350~420℃, and the time is 0.5~3h; The second calcination treatment is carried out at a temperature of 350~420℃ for a time of 0.5~3h.
3. The preparation method according to claim 2, characterized in that, It also includes purification after the first calcination treatment; The purification process includes: adding the reaction system obtained after the first calcination treatment to a THF solution, collecting the filter residue and washing it with methanol to obtain benzoic melamine dimer.
4. The preparation method according to claim 2, characterized in that, The molar ratio of the benzomelamine and the benzomelamine dimer is 1:(0.5~2.0).
5. The preparation method according to claim 2, characterized in that, It also includes purification after the second calcination treatment; The purification process includes: adding the reaction system obtained after the second calcination treatment to a THF solution, collecting the filtrate, concentrating the filtrate until just as precipitates appear, and then adding methanol to obtain a solid product. The solid product was dissolved in a THF solution, evaporated, and recrystallized to obtain the blue phosphorescent material.
6. The preparation method according to claim 5, characterized in that, The temperature of the THF solution is 40~60℃.
7. The application of the blue phosphorescent material of claim 1 in the fabrication of organic light-emitting devices.