Multi-resonance thermally activated delayed fluorescence molecular light-emitting film, preparation method thereof and light-emitting diode

Abstract

The invention provides a multi-resonance thermally activated delayed fluorescence molecular light-emitting film, a preparation method thereof and a light-emitting diode, belongs to the technical field of light-emitting devices, and aims to reduce the preparation defects of the light-emitting film. The method comprises the following steps: dissolving a first host material, a second host material and a guest material in an organic solvent according to the concentration of 1-10mg / mL respectively, a first solution, a second solution and a third solution are obtained; wherein the guest material is a multi-resonance thermally activated delayed fluorescence material; mixing the first solution, the second solution and the third solution according to a mass ratio of 10: (1-3): (0.1-1) to obtain a mixed solution; the bottom of a culture dish is fully paved with water, and the mixed solution is dropwise added into the culture dish; when an organic thin film is formed in the culture dish, sucking the pretreated substrate by adopting a vacuum chuck, and dipping the organic thin film by adopting the substrate; and placing the substrate comprising the organic thin film on a heating platform, and annealing at the temperature of 70-90 DEG C for 10-25 minutes to obtain the multi-resonance thermal activation delayed fluorescence molecular light-emitting thin film.

Description

Technical Field

[0001] The invention relates to the technical field of light emitting diodes, and in particular to a multi-resonance thermally activated delayed fluorescence molecular light emitting film and a preparation method thereof, and a light emitting diode. Background Art

[0002] In recent years, organic electroluminescent devices (OLEDs) have attracted much attention in the display and lighting industries. Research on OLEDs has received extensive attention due to the advantages of organic semiconductor materials such as low cost, environmental protection, manufacturing through solution spin coating process, and the ability to make large-area flexible devices. OLEDs have the characteristics of active luminescence, fast response speed, high contrast, low energy consumption, and wide viewing angle, which give them broad application prospects. OLEDs are not only suitable for small-sized mobile phone screens, but also for large-area TV screens, and can be used to manufacture flexible screens and lighting sources.

[0003] At present, a solution method is usually used to prepare organic electroluminescent devices. Specifically, a cross-linking reaction can be used to bond a large number of small molecules to each other through thermal cross-linking or chemical cross-linking to form a high molecular polymer with a stable network structure, so as to improve the solubility resistance of the solute, thereby preventing the formed film layer from being destroyed by dissolving in the solvent of the next film layer. Alternatively, the solubility of the material in different solvents is different, and different solvents are used to dissolve the organic semiconductor materials of adjacent film layers to avoid the adjacent film layers from being destroyed. However, there are currently few materials available for cross-linking reactions, and the solubility of organic semiconductor materials in different solvents is not much different, which results in varying degrees of damage to the interface of the organic electroluminescent device currently prepared. Summary of the invention

[0004] In view of this, the present invention aims to provide a multi-resonance thermally activated delayed fluorescence molecular luminescent film and a preparation method thereof, and a light emitting diode.

[0005] The first aspect of the present invention provides a method for preparing a multi-resonance thermally activated delayed fluorescence molecular luminescent film, comprising: Dissolving the first host material, the second host material and the guest material in an organic solvent at a concentration of 1-10 mg / mL, respectively, to obtain a first solution, a second solution and a third solution; wherein the guest material is a multiple resonance thermally activated delayed fluorescent material; The first solution, the second solution and the third solution are mixed in a mass ratio of 10:(1-3):(0.1-1) to obtain a mixed solution; Spread water on the bottom of the culture dish, and drop the mixed solution into the culture dish; When the organic thin film is formed in the culture dish, the pre-treated substrate is sucked by a vacuum suction cup so as to dip the organic thin film by the substrate; The substrate including the organic film is placed on a heating platform and annealed at a temperature of 70-90° C. for 5-14 minutes to obtain the multi-resonance thermally activated delayed fluorescence molecular luminescent film.

[0006] Optionally, the substrate pretreatment method includes: Soaking the substrate in substrate detergent, deionized water, and anhydrous ethanol respectively, and cleaning the substrate with an ultrasonic cleaner after each soaking; After the cleaned substrate is blown dry with a nitrogen gun, the dried substrate is treated with oxygen plasma to obtain a pre-treated substrate.

[0007] Optionally, the first host material includes at least one bipolar small molecule, and the second host material includes at least one organic high molecular polymer material with a network structure.

[0008] Optionally, the first main material includes at least one of 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]bipyridine, 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene, 1,3,5-tri(p-pyridin-3-yl-phenyl)benzene, and bis[2-[(oxy)diphenylphosphino]phenyl]ether.

[0009] Optionally, the second main material includes one of poly(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene) or poly(9,9-bis(3'-((N,N-dimethyl)N-ethylammonium)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene).

[0010] Optionally, the guest material includes: one of V-DABNA, BN-1 or BN-3.

[0011] Optionally, the concentration of the first solution is 1-4 mg / mL, the concentration of the second solution is 1-8 mg / mL, and the concentration of the third solution is 1-5 mg / mL.

[0012] Optionally, the substrate is any one of glass, silicon dioxide, quartz, polyethylene terephthalate, polyethylene naphthalate or polyimide.

[0013] The second aspect of the present invention provides a multiple resonance thermally activated delayed fluorescence molecular luminescent film, which is prepared by the preparation method of the multiple resonance thermally activated delayed fluorescence molecular luminescent film described in the first aspect.

[0014] The third aspect of the present invention provides a light-emitting diode, comprising: a substrate, a first electrode, a light-emitting layer and a second electrode stacked in sequence, wherein the light-emitting layer is prepared by the preparation method of the multi-resonance thermally activated delayed fluorescence molecular light-emitting film described in the first aspect.

[0015] Beneficial effects: The preparation method of the multiple resonance thermally activated delayed fluorescence molecular luminescent film provided by the present invention comprises: dissolving a first main material, a second main material and a guest material in an organic solvent at a concentration of 1-10 mg / mL respectively to obtain a first solution, a second solution and a third solution; wherein the guest material is a multiple resonance thermally activated delayed fluorescence material; mixing the first solution, the second solution and the third solution at a mass ratio of 10:(1-3):(0.1-1) to obtain a mixed solution; spreading water on the bottom of a culture dish, and dropping the mixed solution into the culture dish; when an organic film is formed in the culture dish, using a vacuum suction cup to suck a pretreated substrate so as to dip the organic film with the substrate; placing the substrate including the organic film on a heating platform, and annealing at a temperature of 70-90°C for 10-25min to obtain the multiple resonance thermally activated delayed fluorescence molecular luminescent film; Therefore, the present invention forms a film by mixing solutions of the first main material, the second main material and the luminescent material in a culture dish, and then uses intermolecular forces to absorb the film onto the surface of the substrate, and finally performs heating annealing to obtain a multiple resonance thermally activated delayed fluorescence molecular luminescent film. In this way, when the film is formed in the culture dish, the solvent has evaporated, and the dipped film does not include the solvent, thereby reducing the problem of device interface damage caused by the similar solubility of organic semiconductor materials in organic solvents. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 A flow chart showing the steps of a method for preparing a multi-resonance thermally activated delayed fluorescence molecular light-emitting film provided by an embodiment of the present invention is shown; Figure 2 A fluorescence microscope image of a multi-resonance thermally activated delayed fluorescence molecular luminescent film provided by an embodiment of the present invention is shown; Figure 3 A schematic diagram of the structure of a light emitting diode provided by an embodiment of the present invention is shown; Figure 4 A schematic structural diagram of a light emitting diode provided by another embodiment of the present invention is shown; Figure 5The photoluminescence spectrum of the light-emitting film prepared in Example 1 is shown; Figure 6 The photoluminescence spectrum of the light-emitting film prepared in Example 2 is shown. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following is a detailed description of the embodiments of the present invention. The present embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments. If the specific experimental steps or conditions are not indicated in the embodiments, the operation or conditions of the conventional experimental steps described in the prior art in this field can be carried out. The reagents used and other instruments that do not indicate the manufacturer are all conventional reagent products that can be obtained commercially.

[0018] In the related art, organic electroluminescent devices usually adopt a solution method to prepare device film layers. However, each device film layer is obtained by dissolving organic semiconductor materials in organic solvents and then performing annealing treatment. Since organic semiconductor materials are soluble in organic solvents, when preparing adjacent film layers, part of the prepared film layers are dissolved by the organic solvent, thereby causing interface defects.

[0019] In addition, in organic electroluminescent devices, multi-resonance thermally activated delayed fluorescence (TADF) luminescent materials have the advantages of high fluorescence quantum yield and narrow-band luminescence, and have become a research hotspot in the field of organic optoelectronics in recent years. Most multi-resonance (MR) induced thermally activated delayed fluorescence (TADF) emitters usually exhibit strong aggregation and relatively poor solubility due to their rigid and planar molecular structure, which limits their large-scale application due to solubility, concentration quenching and other issues. The luminescent layer obtained by preparing multi-resonance thermally activated delayed fluorescence luminescent materials by solution method is not ideal.

[0020] In view of this, an embodiment of the present invention provides a method for preparing a multi-resonance thermally activated delayed fluorescence molecular luminescent film, by forming a mixed solution of organic semiconductor materials in a culture dish, and then using a substrate to dip the film after the solvent evaporates to form a film, and then heating and annealing to form a luminescent film, so that adjacent film layers will not contact the solvent of the luminescent film layer during the formation process, thereby reducing the interface defect problem caused by the dissolution of organic semiconductors.

[0021] The first aspect of the present invention provides a method for preparing a multi-resonance thermally activated delayed fluorescence molecular luminescent film, referring to Figure 1 , Figure 1 The flowchart of the steps of the method for preparing the multi-resonance thermally activated delayed fluorescence molecular luminescent film provided by the embodiment of the present invention is shown as follows: Figure 1 As shown, the preparation method specifically comprises: S101, dissolving a first host material, a second host material and a guest material in an organic solvent at a concentration of 1-10 mg / mL, respectively, to obtain a first solution, a second solution and a third solution; wherein the guest material is a multiple resonance thermally activated delayed fluorescent material.

[0022] In this embodiment, the first host material and the second host material are materials used for carrier transport in the light-emitting film, and the guest material is a material that plays a luminescent role in the light-emitting film. In the process of light-emitting film light-emitting, the first host material and the second host material transfer carriers to the guest material, so that the carriers recombine and emit light in the guest material; wherein the guest material is usually doped into the host material as a dopant.

[0023] In one example, the first host material and the second host material are functional materials, which, in addition to realizing the transport of carriers, can also be used to improve the film formation uniformity of the light-emitting film, so that the light-emitting film formed in the subsequent process is uniform. At this time, the first host material can be a bipolar small molecule and a derivative of a bipolar small molecule, and the second host material is a high molecular polymer. The interaction force between the bipolar small molecule and the high molecular polymer can make the two spread evenly during the film formation process.

[0024] Specifically, the first host material can be at least one of 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]bipyridine, 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene, 1,3,5-tri(p-pyridin-3-yl-phenyl)benzene, 1,3,5-tri(p-pyridin-3-yl-phenyl)benzene or bis[2-[(oxy)diphenylphosphino]phenyl]ether.

[0025] The second host material can be any one of poly(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene) or poly(9,9-bis(3'-((N,N-dimethyl)N-ethylammonium)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene).

[0026] The guest material may be any of V-DABNA, BN-1 or BN-3.

[0027] For example, the first host material is 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]bipyridine, the second host material is poly(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene), and the guest material is V-DABNA; The first host material is 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, the second host material is poly(9,9-bis(3'-((N,N-dimethyl)N-ethylammonium)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene), and the guest material is BN-1; The first host material is bis[2-[(oxy)diphenylphosphino]phenyl]ether, the second host material is poly(9,9-bis(3'-((N,N-dimethyl)N-ethylammonium)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene), and the guest material is BN-3.

[0028] The organic solvent may be chlorobenzene, toluene, etc., and this embodiment does not make any specific limitation.

[0029] In this embodiment, bipolar small molecules are used as the first main material and high molecular polymers are used as the second main material. Since high molecular polymers are high molecular weight compounds formed by repeated covalent bonds, they are easy to form films. In the process of forming the light-emitting film, high molecular polymers are used as the second main material so that the light-emitting film has better film-forming properties. In addition, since the high molecular polymers form a network structure when forming the film, the interface defect states can be reduced, which is beneficial to the dipole radiation luminescence.

[0030] The concentration of the first solution may be 1-10 mg / mL, specifically 1 mg / mL, 3 mg / mL, 5 mg / mL, 7 mg / mL or 10 mg / mL, etc.; The concentration of the second solution may be 1-10 mg / mL, specifically 1 mg / mL, 2 mg / mL, 4 mg / mL, 6 mg / mL or 8 mg / mL, etc.; The concentration of the third solution may be 1-10 mg / mL, specifically 1 mg / mL, 2 mg / mL, 5 mg / mL, 8 mg / mL or 10 mg / mL, etc.

[0031] In one example, the concentration of the first solution is 1-4 mg / mL, the concentration of the second solution is 1-8 mg / mL, and the concentration of the third solution is 1-5 mg / mL.

[0032] S102, mixing the first solution, the second solution and the third solution in a mass ratio of 10:(1-3):(0.1-1) to obtain a mixed solution.

[0033] Specifically, the mass ratio of the first solution, the second solution, and the third solution may be 10:1:0.1, 10:1:0.5, 10:1:1, 10:2:0.1, 10:2:0.5, 10:3:1, or the like.

[0034] The mixing process of the first solution, the second solution and the third solution may be specifically to mix the first solution, the second solution and the third solution according to a mass ratio, and stir for 10-12 hours under a nitrogen environment at room temperature to obtain a mixed solution. The concentration of the solute in the mixed solution may be adjusted by adding an organic solvent.

[0035] S103, spreading water on the bottom of the culture dish, and dropping the mixed solution into the culture dish.

[0036] In this embodiment, the mixed solution is added dropwise while water is spread on the bottom of the culture dish. Since the mixed solution and water are not miscible, the mixed solution is dispersed on the surface of the water after the addition. At this time, due to the effects of the first main material and the second main material, the solute in the mixed solution can be evenly dispersed in the culture dish. Among them, the size of the culture dish can be determined according to the size of the light-emitting film to be prepared. Of course, it is also possible to prepare a larger-sized light-emitting film first, and then cut the light-emitting film according to the required size. It should be noted that in the process of adding the mixed solution to the culture dish, it is necessary to pay attention to the dripping rate and maintain a uniform dripping speed to improve the dispersibility of the mixed solution and facilitate the film-forming process.

[0037] S104, when an organic thin film is formed in the culture dish, a vacuum suction cup is used to suck up the pre-treated substrate so as to dip the organic thin film into the substrate.

[0038] Specifically, after the solvent evaporates, the formed organic film is insoluble in water and will be formed on the water surface of the culture dish. Since the interaction between the organic film and water is small, a substrate can be used to dip the organic film. Specifically, a vacuum suction cup can be used to suck one side of the substrate and the other side of the substrate can be used to dip the organic film. Before using the substrate to dip the organic film, the substrate needs to be pretreated to keep the surface of the substrate clean so that the organic film can be dipped through the intermolecular force.

[0039] Among them, when the light-emitting film is used as the light-emitting layer of the organic electroluminescent device, the required film layers can be prepared in advance on the substrate. For example, the organic electroluminescent device includes a transparent electrode, a hole transport layer, a light-emitting layer, an electron transport layer and a metal electrode. The transparent electrode and the hole transport layer can be prepared on the substrate first, and then the substrate is pretreated. In this way, the light-emitting layer can be directly formed on the hole transport layer, making the preparation process of the organic electroluminescent device more convenient.

[0040] S105, placing the substrate including the organic film on a heating platform, and annealing at a temperature of 70-90°C for 10-25 minutes to obtain a multi-resonance thermally activated delayed fluorescence molecular luminescent film.

[0041] In this embodiment, after dipping the organic film, the organic film needs to be firmly formed on the substrate surface. Therefore, the substrate dipped in the organic film is placed on a heating platform for annealing to obtain a multiple resonance thermally activated delayed fluorescence molecular luminescent film.

[0042] In which, when the light-emitting film is used as an organic electroluminescent layer, the light-emitting layer may include a layer of light-emitting film, or may be composed of multiple layers of light-emitting films. In which, when the light-emitting layer is composed of multiple layers of light-emitting films, each preparation of the light-emitting film can be performed using the above steps S101-S105 until the required number of layers is reached.

[0043] The method for preparing a multiple resonance thermally activated delayed fluorescence molecular luminescent film provided in an embodiment of the present invention comprises the following steps: first dissolving a first main material, a second main material and a third main material in an organic solvent to obtain a solution, then mixing the solution to obtain a mixed solution, delivering the mixed solution to a culture dish with water at the bottom, and after the solvent evaporates to form a thin film, using a pretreated substrate to dip the organic film. In this way, in the process of preparing the luminescent film, the organic solvent will not contact other film layers, thus avoiding the situation where the adjacent film layers are partially dissolved due to the preparation of the luminescent film, resulting in defects at the film layer interface, and affecting the performance of the organic electroluminescent diode. In addition, since the first main material is a bipolar small molecule and the second main material is a high molecular polymer, the dispersibility of the multiple resonance thermally activated delayed fluorescence molecular luminescent material can be improved by using the first main material and the second main material, and since the high molecular polymer is used as the main material, the high molecular polymer has good film-forming properties because it includes repeated covalent bonds, so that the prepared luminescent film is uniform.

[0044] In one embodiment, the pretreatment method for the substrate specifically includes: first, soaking the substrate in substrate detergent, deionized water and anhydrous ethanol respectively, and cleaning the substrate with an ultrasonic cleaner after each soaking; then, blowing the cleaned substrate dry with a nitrogen gun, and treating the dried substrate with oxygen plasma to obtain a pretreated substrate.

[0045] In this embodiment, when the substrate is used to dip the organic film, the surface of the substrate needs to be clean. Therefore, before the substrate is used to dip the organic film, the substrate needs to be pretreated to keep the surface of the substrate clean. Before dipping the organic film, a film layer located before the light-emitting layer can be prepared according to the device structure of the organic electroluminescent device, and then the organic film can be dipped. After dipping the organic film, the light-emitting layer can be directly formed by heating and annealing without transfer, thereby improving the preparation efficiency of the light-emitting device.

[0046] For example, if the light-emitting layer of the organic electroluminescent device includes a transparent electrode before, the transparent electrode can be first formed on the substrate and then cleaned, and then the side of the transparent electrode away from the substrate is used to dip the thin film; if the light-emitting layer of the organic electroluminescent device is preceded by a substrate, a transparent electrode and a hole transport layer in sequence, the transparent electrode and the hole transport layer can be first formed on the substrate in sequence, and then the substrate including the transparent electrode and the hole transport layer is cleaned, and then the side of the hole transport layer away from the substrate is used to form a light-emitting thin film on the hole transport layer.

[0047] In one embodiment, the substrate may be a rigid substrate or a flexible substrate. The rigid substrate may be any one of silicon dioxide and quartz, and the flexible substrate may be any one of polyethylene terephthalate, polyethylene naphthalate or polyimide.

[0048] The method for preparing a multiple resonance thermally activated delayed fluorescence molecular luminescent film provided in an embodiment of the present invention comprises the following steps: dripping a mixed solution including a bipolar molecule, a high molecular polymer and a multiple resonance thermally activated delayed fluorescence material into a culture dish filled with water; due to the intermolecular forces between the bipolar molecules and the high molecular polymer, the dripped mixed solution can be evenly dispersed on the water surface, and then can form a uniform film after the solvent evaporates; and, since the solvent has evaporated when the film is transferred to the substrate, the already formed film layer will not be affected, thereby avoiding damage to the already formed film layer during the preparation process.

[0049] The second aspect of the present invention provides a multiple resonance thermally activated delayed fluorescence molecular luminescent film, which is prepared by the preparation method described in the first aspect.

[0050] In this embodiment, the prepared multi-resonance thermally activated delayed fluorescence molecular light-emitting film was observed using an electron scanning microscope, and the following Figure 2 The image shown, according to Figure 2 It can be seen that the microscopic surface of the prepared multiple resonance thermally activated delayed fluorescence molecular luminescent film is uniform and has no agglomeration phenomenon. Therefore, the multiple resonance thermally activated delayed fluorescence molecular luminescent film provided in this embodiment has uniform film formation and can be prepared over a large area.

[0051] The multiple resonance thermally activated delayed fluorescence molecular luminescent film provided by the embodiment of the present invention adopts bipolar molecules and their derivatives as the first main material and adopts high molecular polymers such as PFN-DOF or PFN-Br as the second main material. Since the first main material and the second main material have the characteristics of good mechanical processing and easy film formation, the prepared multiple resonance thermally activated delayed fluorescence molecular luminescent film has uniform film formation and can be prepared over a large area. Therefore, the problem that the multiple resonance thermally activated delayed fluorescence molecular luminescent film is difficult to prepare over a large area due to the low solubility and high aggregation of the multiple resonance thermally activated delayed fluorescence material is solved.

[0052] The third aspect of the present invention provides a light-emitting diode, comprising: a substrate, a first electrode, a light-emitting layer and a second electrode stacked in sequence, wherein the light-emitting layer is prepared by the preparation method of the multi-resonance thermally activated delayed fluorescence molecular light-emitting film described in the first aspect.

[0053] Specifically, Figure 3 For example, Figure 3 FIG. 4 shows a schematic diagram of the structure of a light emitting diode provided by an embodiment of the present invention. Figure 3 As shown, the light-emitting diode includes a substrate 11, a first electrode 12, a light-emitting layer 13 and a second electrode 14 stacked in sequence; wherein the substrate 11 is a transparent base, the first electrode 12 is a transparent electrode, the light-emitting layer 13 is a multi-resonance thermally activated delayed fluorescence molecular luminescent energy film, and the second electrode is a metal electrode.

[0054] The light-emitting layer 13 may include a layer of multi-resonance thermally activated delayed fluorescent molecular light-emitting film, or may include multiple layers, for example, Figure 4 For example, Figure 4 FIG. 4 shows a schematic diagram of the structure of a light emitting diode provided by another embodiment of the present invention. Figure 4 As shown, the light emitting diode may include n layers of multiple resonant thermally activated delayed luminescence thin films. In this case, each layer of the luminescent thin film may be prepared by the preparation method of the multiple resonant thermally activated delayed luminescence thin film described in the first aspect above.

[0055] In this embodiment, the light emitting diode may further include functional layers such as a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer, which may be added according to actual conditions and are not specifically limited in the present invention.

[0056] The light-emitting diode provided by the embodiment of the present invention has a light-emitting layer whose solvent is first evaporated to form a thin film during the preparation process and then transferred to the surface of the substrate to form a film layer. Therefore, the light-emitting layer will not cause damage to the already prepared film layer during the preparation process, thereby reducing interface defects in the prepared light-emitting diode and improving device performance.

[0057] In order to enable those skilled in the art to better understand the present invention, the preparation method of the multi-resonance thermally activated delayed fluorescence molecular luminescent film provided by the present invention is described below through a number of specific embodiments.

[0058] Example 1 Dissolve 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]bipyridine (TmPyPB) in chlorobenzene at a concentration of 8 mg / mL, and stir on a stirring platform for more than 4 hours to obtain a first solution; Dissolving poly(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene) (PFN-DOF) in chlorobenzene at a concentration of 2 mg / mL, and adding a magnetic stirrer for more than 4 hours to obtain a second solution; Dissolve V-DABNA in chlorobenzene at a concentration of 1 mg / mL, and add a magnetic stirrer for more than 4 hours to obtain a third solution; The first solution, the second solution and the third solution were mixed in a mass ratio of 10:0.5:1, and stirred at room temperature for 12 hours to prepare a mixed solution with a solute concentration of 6 mg / mL; Cover the bottom of the culture dish with water and drop 50 μL of the mixed solution into the dish; When the organic film is formed on the water surface after the solvent evaporates, a vacuum suction cup is used to suck one side of the pre-treated substrate so as to dip the organic film with the substrate; The substrate dipped with the organic film was placed on a heating platform and annealed at 80° C. for 20 minutes to obtain a multi-resonance thermally activated delayed fluorescence molecular luminescent film.

[0059] The obtained multiple resonance thermally activated delayed fluorescence molecular luminescent film was tested and the following results were obtained: Figure 5 The photoluminescence spectrum shown, Figure 5 As shown, the luminescence peak of the luminescent film is around 470nm.

[0060] Example 2 Dissolve 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]bipyridine (TmPyPB) in chlorobenzene at a concentration of 8 mg / mL, and stir on a stirring platform for more than 4 hours to obtain a first solution; Dissolving poly(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene) (PFN-DOF) in chlorobenzene at a concentration of 2 mg / mL, and adding a magnetic stirrer for more than 4 hours to obtain a second solution; Dissolve BN-1 in chlorobenzene at a concentration of 1 mg / mL, and add a magnetic stirrer for more than 4 hours to obtain a third solution; The first solution, the second solution and the third solution were mixed in a mass ratio of 10:0.5:1, and stirred at room temperature for 12 hours to prepare a mixed solution with a solute concentration of 6 mg / mL; Cover the bottom of the culture dish with water and drop 50 μL of the mixed solution into the dish; When the organic film is formed on the water surface after the solvent evaporates, a vacuum suction cup is used to suck one side of the pre-treated substrate so as to dip the organic film with the substrate; The substrate dipped with the organic film was placed on a heating platform and annealed at 80° C. for 20 minutes to obtain a multi-resonance thermally activated delayed fluorescence molecular luminescent film.

[0061] The obtained multiple resonance thermally activated delayed fluorescence molecular luminescent film was tested and the following results were obtained: Figure 6 The photoluminescence spectrum shown, Figure 6 As shown, the luminescence peak of the luminescent film is around 470nm.

[0062] Example 3 Dissolve 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]bipyridine (TmPyPB) in chlorobenzene at a concentration of 8 mg / mL, and stir on a stirring platform for more than 4 hours to obtain a first solution; Dissolving poly(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene) (PFN-DOF) in chlorobenzene at a concentration of 2 mg / mL, and adding a magnetic stirrer for more than 4 hours to obtain a second solution; Dissolve BN-3 in chlorobenzene at a concentration of 1 mg / mL, and add a magnetic stirrer for more than 4 hours to obtain a third solution; The first solution, the second solution and the third solution were mixed in a mass ratio of 10:0.5:1, and stirred at room temperature for 12 hours to prepare a mixed solution with a solute concentration of 6 mg / mL; Cover the bottom of the culture dish with water and drop 50 μL of the mixed solution into the dish; When the organic film is formed on the water surface after the solvent evaporates, a vacuum suction cup is used to suck one side of the pre-treated substrate so as to dip the organic film with the substrate; The substrate dipped with the organic film was placed on a heating platform and annealed at 80° C. for 20 minutes to obtain a multi-resonance thermally activated delayed fluorescence molecular luminescent film.

[0063] Example 4 Dissolve 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole in chlorobenzene at a concentration of 8 mg / mL, and stir on a stirring platform for more than 4 hours to obtain a first solution; Dissolve poly (9,9-bis (3'- ((N,N-dimethyl) N-ethylammonium) propyl) -2,7-fluorene) -2,7- (9,9-dioctylfluorene) in chlorobenzene at a concentration of 2 mg / mL, and stir with a magnetic stirrer for more than 4 hours to obtain a second solution; Dissolve BN-1 in chlorobenzene at a concentration of 1 mg / mL, and add a magnetic stirrer for more than 4 hours to obtain a third solution; The first solution, the second solution and the third solution were mixed in a mass ratio of 10:0.5:1, and stirred at room temperature for 12 hours to prepare a mixed solution with a solute concentration of 6 mg / mL; Cover the bottom of the culture dish with water and drop 50 μL of the mixed solution into the dish; When the organic film is formed on the water surface after the solvent evaporates, a vacuum suction cup is used to suck one side of the pre-treated substrate so as to dip the organic film with the substrate; The substrate dipped with the organic film was placed on a heating platform and annealed at 80° C. for 20 minutes to obtain a multi-resonance thermally activated delayed fluorescence molecular luminescent film.

[0064] Example 5 Dissolve 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene in chlorobenzene at a concentration of 8 mg / mL, and stir on a stirring platform for more than 4 hours to obtain a first solution; Dissolve poly (9,9-bis (3'- ((N,N-dimethyl) N-ethylammonium) propyl) -2,7-fluorene) -2,7- (9,9-dioctylfluorene) in chlorobenzene at a concentration of 2 mg / mL, and stir with a magnetic stirrer for more than 4 hours to obtain a second solution; Dissolve BN-1 in chlorobenzene at a concentration of 1 mg / mL, and add a magnetic stirrer for more than 4 hours to obtain a third solution; The first solution, the second solution and the third solution were mixed in a mass ratio of 10:0.5:1, and stirred at room temperature for 12 hours to prepare a mixed solution with a solute concentration of 6 mg / mL; Cover the bottom of the culture dish with water and drop 50 μL of the mixed solution into the dish; When the organic film is formed on the water surface after the solvent evaporates, a vacuum suction cup is used to suck one side of the pre-treated substrate so as to dip the organic film with the substrate; The substrate dipped with the organic film was placed on a heating platform and annealed at 80° C. for 20 minutes to obtain a multi-resonance thermally activated delayed fluorescence molecular luminescent film.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily required by the present invention.

[0066] The above is a detailed introduction to a multiple resonance thermally activated delayed fluorescence molecular luminescent film and its preparation method and light-emitting diode provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technicians in this field, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for preparing a multi-resonance thermally activated delayed fluorescence molecular luminescent film, characterized in that: The method comprises: Dissolving the first host material, the second host material and the guest material in an organic solvent at a concentration of 1-10 mg / mL, respectively, to obtain a first solution, a second solution and a third solution; wherein the guest material is a multiple resonance thermally activated delayed fluorescent material; The first solution, the second solution and the third solution are mixed in a mass ratio of 10:(1-3):(0.1-1) to obtain a mixed solution; Spread water on the bottom of the culture dish, and drop the mixed solution into the culture dish; When the organic film is formed in the culture dish, the pre-treated substrate is sucked by a vacuum suction cup so as to dip the organic film by the substrate; The substrate including the organic film is placed on a heating platform and annealed at a temperature of 70-90° C. for 10-25 minutes to obtain the multi-resonance thermally activated delayed fluorescence molecular luminescent film.

2. The preparation method according to claim 1, characterized in that: The substrate pretreatment method comprises: Soaking the substrate in substrate detergent, deionized water, and anhydrous ethanol respectively, and cleaning the substrate with an ultrasonic cleaner after each soaking; After the cleaned substrate is blown dry with a nitrogen gun, the dried substrate is treated with oxygen plasma to obtain a pre-treated substrate.

3. The preparation method according to claim 1, characterized in that: The first main material includes at least one bipolar small molecule, and the second main material includes at least one organic high molecular polymer material with a network structure.

4. The preparation method according to claim 3, characterized in that: The first host material includes at least one of 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]bipyridine, 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene, 1,3,5-tri(p-pyridin-3-yl-phenyl)benzene, 1,3,5-tri(p-pyridin-3-yl-phenyl)benzene or bis[2-[(oxy)diphenylphosphino]phenyl]ether.

5. The preparation method according to claim 3, characterized in that: The second host material includes one of poly(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene) or poly(9,9-bis(3'-((N,N-dimethyl)N-ethylammonium)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene).

6. The preparation method according to claim 1, characterized in that: The guest material includes: one of V-DABNA, BN-1 or BN-3.

7. The preparation method according to claim 1, characterized in that: The concentration of the first solution is 1-4 mg / mL, the concentration of the second solution is 1-8 mg / mL, and the concentration of the third solution is 1-5 mg / mL.

8. The preparation method according to claim 2, characterized in that: The substrate is any one of glass, silicon dioxide, quartz, polyethylene terephthalate, polyethylene naphthalate or polyimide.

9. A multi-resonance thermally activated delayed fluorescence molecular luminescent film, characterized in that: The film is prepared by the method for preparing the multi-resonance thermally activated delayed fluorescence molecular luminescent film according to any one of claims 1 to 8.

10. A light emitting diode, characterized in that: The invention comprises a substrate, a first electrode, a light-emitting layer and a second electrode which are stacked in sequence, wherein the light-emitting layer is prepared by the method for preparing the multi-resonance thermally activated delayed fluorescence molecular light-emitting film according to any one of claims 1 to 8.

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