Blue phosphorescence luminescent material as well as preparation method and application thereof

Abstract

The invention discloses a blue phosphorescence luminescent material as well as a preparation method and application thereof, and belongs to the technical field of organic luminescent materials. The preparation method of the blue phosphorescence luminescent material comprises the following steps: sealing benzotripolycyanamide, and carrying out first calcination treatment to obtain a benzotripolycyanamide dimer; and mixing the benzotripolycyanamide and the benzotripolycyanamide dimer, sealing, and carrying out second calcination treatment to obtain the blue phosphorescence luminescent material. The blue phosphorescence luminescent material provided by the invention has relatively high luminescence quantum efficiency, and the blue light OLED device prepared from the blue phosphorescence luminescent material is beneficial to improving the efficiency of the blue light OLED device.

Description

Technical Field

[0001] The present invention relates to the technical field of organic luminescent materials, and in particular to a blue phosphorescent luminescent material and a preparation method and application thereof. Background Art

[0002] The development of blue phosphorescent materials is one of the core challenges in achieving breakthroughs in OLED technology. Currently, commercial OLEDs still rely on inefficient blue fluorescent materials, whose theoretical maximum exciton utilization in electroluminescence is only 25%, severely limiting the overall performance of the display. Second-generation blue OLED materials are phosphorescent, theoretically capable of 100% exciton utilization, but they suffer from challenges such as poor stability and insufficient color purity. As a result, current blue OLED materials are still fluorescent, and the development of blue phosphorescent OLED materials generally lags behind that of red and green light. Breaking through the technical bottlenecks of blue phosphorescent materials, optimizing their stability and color gamut, and driving the OLED industry towards higher performance remain pressing technical challenges for those skilled in the art. Summary of the Invention

[0003] The purpose of the present invention is to provide a blue phosphorescent material and a preparation method and application thereof, so as to solve the problems existing in the above-mentioned prior art.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention: a blue phosphorescent material, the structural formula of which is shown in formula (1):

[0006]

[0007] The second technical solution of the present invention is a method for preparing the above-mentioned blue phosphorescent material, comprising the following steps:

[0008] After sealing the benzoguanamine, a first calcination treatment is performed to obtain a benzoguanamine dimer;

[0009] The structure of the benzoguanamine dimer is:

[0010] The blue phosphorescent material (ie, the benzoguanamine trimer) is obtained by mixing benzoguanamine and the benzoguanamine dimer, sealing the mixture, and then performing a second calcination process.

[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 comprises purification after the first calcination treatment;

[0013] The purification comprises: adding the reaction system obtained after the first calcination treatment into a THF solution, collecting the filter residue and washing it with methanol to obtain benzoguanamine dimer.

[0014] Furthermore, the molar ratio of the benzoguanamine to the benzoguanamine 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 comprises purification after the second calcination treatment;

[0017] The purification comprises: adding the reaction system obtained after the second calcination treatment to a THF solution, collecting the filtrate, and then concentrating the filtrate until a precipitate just appears, and then adding methanol to obtain a solid product;

[0018] The solid product is dissolved in a THF solution, and then evaporated and recrystallized to obtain the blue phosphorescent luminescent material.

[0019] Furthermore, the temperature of the THF solution is 40-60°C.

[0020] The third technical solution of the present invention: an application of the above-mentioned blue phosphorescent material in the preparation of an organic light-emitting device.

[0021] The present invention discloses the following technical effects:

[0022] (1) The blue phosphorescent material of the present invention has a high luminous quantum efficiency (54%). Preparing it into a blue light OLED device is beneficial to improving the efficiency of the blue light device.

[0023] (2) The present invention uses phenylguanidine as a raw material, and connects it into a trimer molecular structure through oligomerization at high temperature to obtain a blue pure phosphorescent luminescent material.

[0024] (3) The present invention uses phenylguanidine as the initial structure and prepares the target molecule (blue phosphorescent material) for the first time through thermal condensation, and obtains a solvent purification method, which has the advantages of simple preparation method and easy large-scale preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is the hydrogen spectrum of the benzoguanamine dimer (product C2) prepared in Example 1;

[0027] Figure 2 This is the hydrogen spectrum of the blue phosphorescent material (product C3) prepared in Example 1;

[0028] Figure 3 This is the carbon spectrum of the blue phosphorescent material (product C3) prepared in Example 1;

[0029] Figure 4 1H-15N heteronuclear single quantum correlation (HSQC) NMR spectrum of the blue phosphorescent material (product C3) prepared in Example 1;

[0030] Figure 5 1H-15N heteronuclear multiple bond correlation (HMBC) NMR spectrum of the blue phosphorescent material (product C3) prepared in Example 1;

[0031] Figure 6 This is a single crystal structure diagram of the blue phosphorescent material (product C3) prepared in Example 1;

[0032] Figure 7 This is a high-resolution mass spectrum of the blue phosphorescent material (product C3) prepared in Example 1;

[0033] Figure 8 This is the absorption spectrum of the blue phosphorescent material (product C3) prepared in Example 1;

[0034] Figure 9 This is a luminescence spectrum of a THF solution of the blue phosphorescent material (product C3) prepared in Example 1;

[0035] Figure 10 Steady-state luminescence spectrum and delayed luminescence spectrum of a THF solution of the blue phosphorescent material (product C3) prepared in Example 1 at 77K;

[0036] Figure 11 The steady-state luminescence spectrum and delayed luminescence spectrum of the crystalline powder of the blue phosphorescent material (product C3) prepared in Example 1;

[0037] Figure 12 This is a photograph of the blue phosphorescent material (product C3) prepared in Example 1 under visible light and 365nm UV;

[0038] Figure 13 This is the CIE coordinate diagram of the luminescence of the blue phosphorescent material powder sample prepared in Example 1. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting 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 terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0041] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0042] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0044] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0045] Currently, the structure of an organic electroluminescent device (OLED) generally consists of an electron transport layer, a light-emitting layer, and a hole transport layer. For the light-emitting layer, using only heavy metal complexes as the phosphorescent emission layer in an OLED device can result in excessive exciton concentration, potentially leading to triplet-triplet quenching and loss of triplet excitons, thus reducing the efficiency of the OLED device. Therefore, the light-emitting layer of phosphorescent OLEDs typically utilizes a host-guest luminescence system, dispersing the guest luminescent material within a specific host material to improve the device's luminescence efficiency. This host-guest luminescence system has two luminescence mechanisms: energy transfer and carrier capture.

[0046] Energy transfer can be divided into two types: Energy transfer and Dexter energy transfer. Energy transfer is a process of transferring energy through dipole-dipole induction over a longer distance. If the emission of the main luminescent body and the absorption of the guest luminescent body can overlap, and the transition between the two is allowed, a rapid and non-luminescent energy transfer will occur between the main and guest luminescent bodies. Dexter energy transfer is a process of transferring energy through electron exchange over a shorter distance. Electron transfer needs to comply with the Wigner-Witmer selection rule, that is, the electron spin parameter remains unchanged before and after the transfer. Therefore, energy transfer only occurs between singlet-to-singlet and triplet-to-triplet states. Because this mechanism only acts on molecules that are closer, the transfer process is slower. In the light-emitting layer of a phosphorescent component, the energies of the singlet excited state and triplet excited state of the main luminescent body are respectively expressed by Energy transfer and Dexter energy transfer are transmitted to the singlet excited state and triplet excited state of the phosphorescent light-emitting body, and then the energy of the singlet excited state is transferred to the triplet excited state through rapid intersystem crossing inside the phosphorescent light-emitting body, thereby emitting phosphorescence. Therefore, the internal quantum efficiency can be close to 100%.

[0047] The triplet energy level, thermal stability, electrochemical, and photophysical properties of the host material are closely related to the molecular structure, which in turn affects the performance of PHOLEDs. To date, the chemical structures of almost all reported high-efficiency host materials are very simple. However, it is worth noting that although these high-efficiency host materials have simple structures, the synthesis from the starting materials to the target product often requires as many as 4 to 6 reaction steps, and also requires the use of precious metal catalysts, highly toxic phosphorus reagents, flammable and explosive reagents, or harsh conditions such as anhydrous and oxygen-free conditions and extremely low temperatures. Based on this, the development of organic host materials that are simple and efficient, designed and synthesized directly through one or two steps of green chemical reactions, can greatly reduce the cost of materials and will be of great significance to the commercialization of OLEDs.

[0048] To solve the above problems, the present invention provides the following technical solutions:

[0049] In a first aspect, the present invention provides a blue phosphorescent material having a structural formula as 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 guanamine (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 a tube furnace. Keep it at 350-420°C for 0.5-3 hours. 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 the unreacted C1 (guanamine) in the filter residue with methanol to obtain a crude product C2 (guanamine dimer) with a yield of 30-50%.

[0053] The chemical reaction equation is as follows:

[0054]

[0055] (2) C1 (phenylguanamine) and C2 (phenylguanamine dimer) are mixed uniformly in a molar ratio of 1:1. 1-5 g of the mixture is placed in an alumina crucible, sealed with aluminum foil, and placed in a muffle furnace or a tube furnace. The mixture is kept at 350-420°C for 0.5-3 h. After the reaction system cools to room temperature, the reaction system is placed in a THF solution and filtered to collect the residue and filtrate. The residue is washed with methanol to remove unreacted C1 to obtain a crude product C2, which is used as the raw material for step (2). The filtrate is distilled and concentrated until a precipitate is just beginning to form. The same volume of methanol as the filtrate is immediately added. Powder is observed to form. The mixture is immediately filtered to obtain a crude product C3 (content of 70-90%). The crude C3 product is then placed in a hot THF solution (temperature of 50-60°C) and then subjected to evaporation and recrystallization treatment to obtain a C3 molecule (i.e., a blue phosphorescent material, a benzoguanamine trimer) with a purity greater than 95% and a total yield of 20-30%.

[0056] The chemical reaction equation is as follows:

[0057]

[0058] In a third aspect, the present invention provides a use of the above-mentioned blue phosphorescent material in the preparation of an organic light-emitting device.

[0059] Example 1

[0060] A method for preparing a blue phosphorescent material:

[0061] (1) 1 g of compound C1 (benzoguanamine) was added to a 50 mL alumina crucible, sealed with aluminum foil, and placed in a muffle furnace. The mixture was kept at 350°C for 0.5 h. After the reaction system cooled to room temperature, the reaction system was placed in a THF solution and filtered to obtain a residue. The unreacted C1 in the residue was washed with methanol to obtain a crude product C2 (benzoguanamine dimer) with a yield of approximately 30%.

[0062] The structural formula of compound C1 is:

[0063] The structural formula of product C2 is:

[0064] The hydrogen spectrum of product C2 is shown in Figure 1 .

[0065] The proton spectrum data of product C2 are: 1H NMR (500 MHz, DMSO-d6) δ 9.86 (s, 1H), 8.41 (d, J = 7.2 Hz, 4H), 7.58 (t, J = 7.2 Hz, 2H), 7.51 (t, J = 7.6 Hz, 4H), 7.31 (d, J = 70.2 Hz, 5H).

[0066] (2) Weigh C1 and C2, mix them evenly in a molar ratio of 1:1 to obtain a mixture; take 1 g of the mixture into a 50 mL alumina crucible, seal it with aluminum foil, and place it in a tube furnace. Keep it warm at 350 ° C for 0.5 h. After the reaction system is cooled to room temperature, place the reaction system into THF solution, filter and collect the residue and filtrate respectively.

[0067] The filter residue is washed with methanol to remove unreacted C1 to obtain a crude product C2, which is used as the raw material for step (2).

[0068] The filtrate was concentrated by distillation until precipitation ceased. An equal volume of methanol was immediately added to the filtrate. Powder was observed to form, which was immediately filtered to obtain crude C3 (content of approximately 70%). The crude C3 was then placed in a hot THF solution (temperature 40°C) and then evaporated and recrystallized to obtain product C3 (blue phosphorescent material, benzoguanamine trimer) with a purity of >95% and an overall yield of approximately 20%.

[0069] The structural formula of the blue phosphorescent material (product C3) is:

[0070] The hydrogen spectrum of blue phosphorescent material is shown in Figure 2 , carbon spectrum see Figure 3 .

[0071] The hydrogen spectrum data of blue phosphorescent luminescent materials 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 in Figure 4 , 1H-15N heteronuclear multiple bond correlation (HMBC) NMR spectrum is shown in Figure 5 .

[0073] The single crystal structure of blue phosphorescent material is shown in Figure 6 .

[0074] High-resolution mass spectrometry of blue phosphorescent materials Figure 7 ; The absorption spectrum of blue phosphorescent material is shown in Figure 8 .

[0075] from Figure 7 It can be seen that the molecular weight after adding a proton is 528.2121, and the calculated relative molecular weight of the target molecule is 527.2051, which is consistent with the theoretical calculated value of 527.2043.

[0076] from Figure 8 It can be seen that the maximum absorption of the blue phosphorescent material prepared in this embodiment is at 260nm, and the molar extinction coefficient is 96700mol -1 cm -1 .

[0077] THF solution of blue phosphorescent material (concentration 10 -5 mol / L) is shown in the luminescence spectrum Figure 9 .

[0078] from Figure 9 It can be seen that the strongest emission position of the blue phosphorescent material is at 451nm.

[0079] THF solution of blue phosphorescent material (concentration 10 -5 mol / L) at 77K, see the steady-state luminescence spectrum and delayed luminescence spectrum. Figure 10 .

[0080] from Figure 10 As can be seen in the figure, the steady-state spectrum of the blue phosphorescent material has the strongest emission 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 example can emit pure blue phosphorescence at 77 K.

[0081] The steady-state luminescence spectrum and delayed luminescence spectrum of the crystal powder of blue phosphorescent luminescent material are shown in Figure 11 .

[0082] from Figure 11As can be seen in the figure, the blue phosphorescent material has a steady-state luminescence spectrum with the strongest emission at 460 nm, accompanied by a strong shoulder peak at 485 nm. The delayed luminescence spectrum peak overlaps with the steady-state luminescence spectrum, indicating that the blue phosphorescent material prepared in this example is primarily phosphorescent.

[0083] The photos of blue phosphorescent materials under visible light and 365nm UV are shown in Figure 12 .

[0084] from Figure 12 It can be seen that the blue phosphorescent material appears off-white under visible light and sky blue under 365nm UV.

[0085] Example 2

[0086] A method for preparing a blue phosphorescent material:

[0087] (1) 5 g of compound C1 (benzoguanamine) was added to a 50 mL alumina crucible, sealed with aluminum foil, and placed in a tube furnace. The mixture was kept at 420°C for 3.0 h. After the reaction system cooled to room temperature, the reaction system was placed in a THF solution and filtered to obtain a residue. The unreacted C1 in the residue was washed with methanol to obtain a crude product C2 (benzoguanamine dimer) with a yield of approximately 50%.

[0088] The structural formula of compound C1 is:

[0089] The structural formula of product C2 is:

[0090] (2) Weigh C1 and C2, mix them evenly in a molar ratio of 1:1 to obtain a mixture; take 5 g of the mixture into a 50 mL alumina crucible, seal it with aluminum foil, and place it in a tube furnace. Keep it warm at 420 ° C for 3.0 h. After the reaction system is cooled to room temperature, place the reaction system into THF solution, filter and collect the residue and filtrate respectively.

[0091] The filter residue is washed with methanol to remove unreacted C1 to obtain a crude product C2, which is used as the raw material for step (2).

[0092] The filtrate was concentrated by distillation until precipitation ceased. An equal volume of methanol was immediately added to the filtrate. Powder was observed to form, which was immediately filtered to obtain crude C3 (with a content of approximately 90%). The crude C3 was then placed in a hot THF solution (temperature 60°C) and evaporated and recrystallized to obtain product C3 (blue phosphorescent material, benzoguanamine trimer) with a purity greater than 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 performance of the blue phosphorescent material prepared in this example are the same as those in Example 1.

[0095] Comparative Example 1

[0096] A method for preparing a blue phosphorescent material:

[0097] (1) 3 g of compound C1 (benzoguanamine) was added to a 50 mL alumina crucible, sealed with aluminum foil, and placed in a tube furnace. The mixture was kept at 420°C for 3.0 h. After the reaction system cooled to room temperature, the reaction system was placed in a THF solution and filtered to obtain a residue. The unreacted C1 in the residue was washed with methanol to obtain a crude product C2 (benzoguanamine dimer) with a yield of approximately 40%.

[0098] The structural formula of compound C1 is:

[0099] The structural formula of product C2 is:

[0100] (2) Weigh C1 and C2, mix them evenly in a molar ratio of 1:1 to obtain a mixture; take 3 g of the mixture into a 50 mL alumina crucible, seal it with aluminum foil, and place it in a tube furnace. Keep it warm at 420 ° C for 3.0 h. After the reaction system is cooled to room temperature, place the reaction system into THF solution, filter and collect the residue and filtrate respectively.

[0101] The filter residue is washed with methanol to remove unreacted C1 to obtain a crude product C2, which is used as the raw material for step (2).

[0102] The same volume of methanol as the filtrate was directly added to the filtrate. Powder was observed to form and immediately filtered to obtain crude C3 (content of approximately 90%). The crude C3 was then placed in a hot THF solution (temperature of 60°C) and then evaporated and recrystallized to obtain product C3 (blue phosphorescent material, benzoguanamine trimer) with a purity of >95% and an overall yield of approximately 10%.

[0103] Comparative Example 2

[0104] A method for preparing a blue phosphorescent material:

[0105] (1) 3 g of compound C1 (benzoguanamine) was added to a 50 mL alumina crucible, sealed with aluminum foil, and placed in a tube furnace. The mixture was kept at 420°C for 3.0 h. After the reaction system cooled to room temperature, the reaction system was placed in a THF solution and filtered to obtain a residue. The unreacted C1 in the residue was washed with methanol to obtain a crude product C2 (benzoguanamine dimer) with a yield of approximately 40%.

[0106] The structural formula of compound C1 is:

[0107] The structural formula of product C2 is:

[0108] (2) Weigh C1 and C2, mix them evenly in a molar ratio of 1:2.0 to obtain a mixture; take 3 g of the mixture into a 50 mL alumina crucible, seal it with aluminum foil, and place it in a tube furnace. Keep it warm at 420 ° C for 3.0 h. After the reaction system is cooled to room temperature, place the reaction system into THF solution, filter and collect the residue and filtrate respectively.

[0109] The filter residue is washed with methanol to remove unreacted C1 to obtain a crude product C2, which is used as the raw material for step (2).

[0110] The filtrate was distilled and concentrated until the precipitation stopped, and an excess of methanol was immediately added. Powder was observed to be generated, which was immediately filtered to obtain a crude product, the main component of which was C2.

[0111] Effect Example 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., indicating high thermal stability.

[0113] The CIE coordinate diagram of the blue phosphorescent material powder sample prepared in Example 1 is shown in Figure 13 .

[0114] from Figure 13 It can be seen that the CIE coordinates of the blue phosphorescent material powder sample are: 0.1662, 0.2389.

[0115] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A blue phosphorescent material, characterized in that: The structural formula is shown in formula (1):

2. A method for preparing the blue phosphorescent material according to claim 1, characterized in that: The following steps are involved: After sealing the benzoguanamine, a first calcination treatment is performed to obtain a benzoguanamine dimer; The structure of the benzoguanamine dimer is: The blue phosphorescent material is obtained by mixing guanamine and the guanamine dimer, sealing the mixture, and then performing a second calcination process.

3. The preparation method according to claim 2, characterized in that The temperature of the first calcination treatment is 350-420° C., and the time is 0.5-3 hours.

4. The preparation method according to claim 2, characterized in that Also included is purification after the first calcination treatment; The purification comprises: adding the reaction system obtained after the first calcination treatment into a THF solution, collecting the filter residue and washing it with methanol to obtain benzoguanamine dimer.

5. The preparation method according to claim 2, characterized in that The molar ratio of the benzoguanamine to the benzoguanamine dimer is 1:(0.5-2.0).

6. The preparation method according to claim 2, characterized in that The temperature of the second calcination treatment is 350-420° C., and the time is 0.5-3 hours.

7. The preparation method according to claim 2, characterized in that Also comprising purifying after the second calcination treatment; The purification comprises: adding the reaction system obtained after the second calcination treatment to a THF solution, collecting the filtrate, and then concentrating the filtrate until a precipitate just appears, and then adding methanol to obtain a solid product; The solid product is dissolved in a THF solution, and then evaporated and recrystallized to obtain the blue phosphorescent luminescent material.

8. The preparation method according to claim 7, characterized in that The temperature of the THF solution is 40-60°C.

9. Use of the blue phosphorescent material according to claim 1 in the preparation of an organic light-emitting device.

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