Organic light-emitting diode based on red phosphorescent material and preparation method thereof

Abstract

The invention discloses an organic light-emitting diode based on a red phosphorescent material and a preparation method of the organic light-emitting diode, and belongs to the field of organic light-emitting diodes. The device is composed of a transparent glass substrate, an anode layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer and a cathode layer, the light-emitting layer is formed by doping a thermally activated delayed fluorescent material 4CzTPN-Ph and a phosphorescent material PtOEP, and the device is prepared by adopting a solution method; under the driving of forward voltage, the device emits red light, the maximum external quantum efficiency can reach 19.21%, and the maximum brightness can reach 12698 cd / m < 2 >; the device is simple in preparation process, short in preparation time and low in cost, and meanwhile excellent performance of the device is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of electroluminescence, and particularly to an organic light-emitting diode based on a red phosphorescent material and a preparation method thereof. Background Art

[0002] As a typical representative of the new generation of display and solid-state lighting technologies, organic light-emitting diodes (OLEDs) have become a research hotspot in the past two decades. The structure of an OLED device is complex, and the emission layer composed of luminescent materials, as the core component of an OLED, is directly related to the electroluminescence efficiency. Fluorescent small molecule materials are simple to synthesize, easy to purify, and have a high quantum yield, and are the most common luminescent materials in OLED devices. However, organic small molecule fluorescent materials have an aggregation-induced quenching effect at a relatively high concentration, and only singlet excitons are generated during the luminescence process. For such a fluorescent material that emits light solely by radiative decay of singlet excitons, its maximum internal quantum efficiency is only 25%, so the efficiency of the device is relatively low. The luminescence principle of phosphorescent materials is different from that of fluorescent materials. During the luminescence process, when electrons and holes are injected from the cathode and anode respectively, not only singlet excitons are generated, but also triplet excitons are generated, and the formation probability of triplet excitons is theoretically three times that of singlet excitons. Therefore, the internal quantum efficiency of phosphorescent materials can theoretically reach 100%. Due to its good chemical stability, easily tunable wavelength, and high photoluminescence efficiency, Pt(II) complexes have attracted increasing attention and have been successfully used as phosphorescent dopants in the manufacture of high-efficiency OLEDs. Summary of the Invention

[0003] The purpose of the present invention is to design an organic light-emitting diode based on a red phosphorescent material and a preparation method thereof to solve the above problems.

[0004] The present invention achieves the above purpose through the following technical solutions: An organic light-emitting diode based on a red phosphorescent material, the red organic electroluminescent device is formed into a normal structure or an inverted structure; when the normal structure is set, from bottom to top, there are arranged a substrate, a conductive anode layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a conductive cathode in sequence; when the inverted structure is set, from bottom to top, there are a substrate, a conductive cathode layer, an electron transport layer, a light-emitting layer, a hole transport layer, and a conductive anode in sequence; wherein the light-emitting layer is made by doping a thermally activated delayed fluorescence material 4CzTPN-Ph and a phosphorescent material PtOEP, and the light-emitting layer is an organic thin film formed after spin coating and annealing by a dissolution method. The molecular formula of the thermally activated delayed fluorescence material 4CzTPN-Ph is: , The molecular formula of the phosphorescent material PtOEP is: 。

[0005] A preparation method of an organic light-emitting diode based on a red phosphorescent material, a preparation method of a normal structure, comprising the following steps: A1. Clean the ITO glass substrate composed of a transparent glass substrate and a transparent conductive anode ITO, and blow dry with nitrogen after cleaning; A2. Perform ultraviolet light irradiation treatment on the ITO glass substrate; A3. Spin-coat the prepared conductive polymer poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate solution onto the ITO glass substrate, and perform thermal annealing treatment on the spin-coated substrate to obtain a hole transport layer; A4. Spin-coat and prepare a light-emitting layer on the hole transport layer, and perform thermal annealing treatment on the spin-coated substrate. The light-emitting layer is prepared from a thermally activated delayed fluorescence material 4CzTPN-Ph doped with a phosphorescent material PtOEP; A5. Under the condition of a vacuum degree of 2x10 -4 Pa, evaporate and deposit an electron transport layer TPBi on the surface of the light-emitting layer; A6. Under the condition of a vacuum degree of 4x10 -3 Pa, evaporate and deposit an electron injection layer and a conductive cathode; A preparation method of an inverted structure, comprising the following steps: B1. Clean the ITO substrate composed of a transparent glass substrate and a transparent conductive cathode ITO, and blow dry with nitrogen after cleaning; B2. Spin-coat the prepared ZnO onto the ITO substrate, and perform thermal annealing treatment on the spin-coated substrate to obtain a ZnO electron transport layer; B3. Spin-coat and prepare a light-emitting layer on the electron transport layer, and perform thermal annealing treatment on the spin-coated substrate. The light-emitting layer is prepared from a thermally activated delayed fluorescence material 4CzTPN-Ph doped with a phosphorescent material PtOEP; B4. Under the condition of a vacuum degree of 2x10 -4 Pa, evaporate and deposit a hole transport layer CBP on the surface of the light-emitting layer; B5. Under the condition of a vacuum degree of 4x10 -3 Pa, evaporate and deposit a conductive anode Ag or Al.

[0006] The beneficial effects of the present invention are as follows: 1. Due to the material characteristics of 4CzTPN-Ph, it has good film-forming properties, can be applied to solution method preparation, and the material has aggregation-induced emission characteristics, effectively suppressing concentration quenching and improving the efficiency of the device; 2. The thermally activated delayed fluorescence material 4CzTPN-Ph has good solubility in chlorobenzene and is suitable for preparing the light-emitting layer by solution method. Compared with the thermal evaporation process, it reduces material loss, decreases the device preparation cost, can be prepared in large areas, and is applicable to processes such as roll-to-roll and inkjet printing. It is the trend of large-scale preparation of future OLED devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 are the current efficiency - luminance characteristic curves of the devices in Example 3 (normal type) and Example 8 (inverted type) provided by the present invention; Figure 2 are the external quantum efficiency - luminance characteristic curves of the devices in Example 3 (normal type) and Example 8 (inverted type) provided by the present invention; Figure 3 is the test curve graph of the emission spectrum of the device in Example 3 of the present invention; Figure 4 is the test curve graph of the emission spectrum of the device in Example 8 of the present invention; Figure 5 is the schematic structural diagram of the normal type structure in the present invention; Figure 6 is the schematic structural diagram of the inverted type structure in the present invention.

[0008] In the figure: 1 - substrate, 2 - conductive anode layer, 3 - hole transport layer, 4 - light-emitting layer, 5 - electron transport layer, 6 - electron injection layer, 7 - conductive cathode, 8 - conductive cathode layer, 9 - conductive anode. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0009] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0010] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0011] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0012] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "left", "right", etc. are based on the orientation or positional relationships shown in the drawings, or the orientation or positional relationships in which the inventive product is customarily placed during use, or the orientation or positional relationships commonly understood by those skilled in the art. These are merely for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention.

[0013] In addition, the terms "first", "second", etc. are only used for descriptive distinction and should not be construed as indicating or implying relative importance.

[0014] In the description of the present invention, it should also be noted that unless otherwise clearly specified and defined, terms such as "arrangement" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0015] The following will describe in detail the specific embodiments of the present invention with reference to the drawings.

[0016] An organic light-emitting diode based on a red phosphorescent material, and the red organic electroluminescent device is formed into a normal structure or an inverted structure; as Figure 5 shown, when the normal structure is arranged, from bottom to top, there are arranged a substrate 1, a conductive anode layer 2, a hole transport layer 3, a light-emitting layer 4, an electron transport layer 5, an electron injection layer 6, and a conductive cathode 7 in sequence; as Figure 6 shown, when the inverted structure is arranged, from bottom to top, there are a substrate 1, a conductive cathode layer 8, an electron transport layer 5, a light-emitting layer 4, a hole transport layer 3, and a conductive anode 9 in sequence; wherein the light-emitting layer is made by doping a thermally activated delayed fluorescence material 4CzTPN-Ph and a phosphorescent material PtOEP, and the light-emitting layer is an organic thin film formed after spin coating and annealing by the dissolution method; The molecular formula of the thermally activated delayed fluorescence material 4CzTPN-Ph is: , The molecular formula of the phosphorescent material PtOEP is: .

[0017] In some embodiments, the material used for the substrate is at least one of glass, transparent polymer flexible material, or biodegradable flexible material; wherein the transparent polymer flexible material is at least one of polyethylene, polymethyl methacrylate, polycarbonate, polyurethane, polyimide, vinyl chloride resin, or polyacrylic acid; the biodegradable flexible material is at least one of plant fiber, silk fibroin, gelatin, polylactic acid, glucose, viral cellulose, polylactic acid, poly(lactic-co-glycolic acid), polyvinyl alcohol, polyvinylpyrrolidone, polycaprolactone, polyhydroxyalkanoate, polysaccharide, polyglycolic acid and its copolymer, collagen gel, fibrin gel.

[0018] In some embodiments, the materials used for the conductive anode layer in the positive structure and the conductive cathode layer in the inverted structure are at least one of indium tin oxide (ITO), conductive polymer poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT:PSS), graphene, carbon nanotube, metal elemental nanowires, metal alloy nanowires, and metal heterojunction nanowires; wherein, the metal elemental nanowires are at least one of iron nanowires, copper nanowires, silver nanowires, gold nanowires, aluminum nanowires, nickel nanowires, cobalt nanowires, manganese nanowires, cadmium nanowires, indium nanowires, tin nanowires, tungsten nanowires, or platinum nanowires; the metal alloy nanowires are at least one of copper-iron alloy nanowires, silver-iron alloy nanowires, gold-iron alloy nanowires, aluminum-iron alloy nanowires, nickel-iron alloy nanowires, cobalt-iron alloy nanowires, manganese-iron alloy nanowires, cadmium-iron alloy nanowires, indium-iron alloy nanowires, tin-iron alloy nanowires, tungsten-iron alloy nanowires, platinum-iron alloy nanowires, silver-copper alloy nanowires, gold-copper alloy nanowires, aluminum-copper alloy nanowires, nickel-copper alloy nanowires, cobalt-copper alloy nanowires, manganese-copper alloy nanowires, cadmium-copper alloy nanowires, silver-copper alloy nanowires, tin-copper alloy nanowires, cadmium-manganese alloy nanowires, indium-manganese alloy nanowires, tin-manganese alloy nanowires, tungsten-manganese alloy nanowires, platinum-manganese alloy nanowires, indium-cadmium alloy nanowires, tin-cadmium alloy nanowires, tungsten-cadmium alloy nanowires, platinum-cadmium alloy nanowires, tin-indium alloy nanowires, tungsten-indium alloy nanowires, platinum-indium alloy nanowires, tungsten-tin alloy nanowires, platinum-tin alloy nanowires, or platinum-tungsten alloy nanowires;The metal heterojunction nanowires are at least one of copper-iron heterojunction nanowires, silver-iron heterojunction nanowires, gold-iron heterojunction nanowires, aluminum-iron heterojunction nanowires, nickel-iron heterojunction nanowires, cobalt-iron heterojunction nanowires, manganese-iron heterojunction nanowires, cadmium-iron heterojunction nanowires, indium-iron heterojunction nanowires, tin-iron heterojunction nanowires, tungsten-iron heterojunction nanowires, platinum-iron heterojunction nanowires, silver-copper heterojunction nanowires, gold-copper heterojunction nanowires, aluminum-copper heterojunction nanowires, nickel-copper heterojunction nanowires, cobalt-copper heterojunction nanowires, manganese-copper heterojunction nanowires, cadmium-copper heterojunction nanowires, silver-copper heterojunction nanowires, tin-copper heterojunction nanowires, tungsten-copper heterojunction nanowires, platinum-copper heterojunction nanowires, gold-silver heterojunction nanowires, aluminum-silver heterojunction nanowires, nickel-silver heterojunction nanowires, cobalt-silver heterojunction nanowires, manganese-silver heterojunction nanowires, cadmium-silver heterojunction nanowires, indium-silver heterojunction nanowires, tin-silver heterojunction nanowires, tungsten-silver heterojunction nanowires, platinum-silver heterojunction nanowires, aluminum-gold heterojunction nanowires, nickel-gold heterojunction nanowires, cobalt-gold heterojunction nanowires, manganese-gold heterojunction nanowires, cadmium-gold heterojunction nanowires, indium-gold heterojunction nanowires, tin-gold heterojunction nanowires, tungsten-gold heterojunction nanowires, cobalt-nickel heterojunction nanowires, manganese-nickel heterojunction nanowires, cadmium-nickel heterojunction nanowires, indium-nickel heterojunction nanowires, tin-nickel heterojunction nanowires, tungsten-nickel heterojunction nanowires, platinum-nickel heterojunction nanowires, cadmium-manganese heterojunction nanowires, indium-manganese heterojunction nanowires, tin-manganese heterojunction nanowires, tungsten-manganese heterojunction nanowires, platinum-manganese heterojunction nanowires, indium-cadmium heterojunction nanowires, tin-cadmium heterojunction nanowires, tungsten-cadmium heterojunction nanowires, platinum-cadmium heterojunction nanowires, tin-indium heterojunction nanowires, tungsten-indium heterojunction nanowires, platinum-indium heterojunction nanowires, tungsten-tin heterojunction nanowires, platinum-tin heterojunction nanowires or platinum-tungsten heterojunction nanowires.

[0019] In some embodiments, the hole transport layer material is any one of aromatic diamine compounds, aromatic triamine compounds, carbazole compounds, star-shaped triphenylamine compounds, furan compounds, spiral structure compounds, and polymer materials.

[0020] In some embodiments, the electron transport layer material is any one of metal oxides, metal complexes, oxadiazole compounds, quinoxaline compounds, nitrogen-containing heterocyclic compounds, anthracene compounds, organosilicon materials, organoboron materials, and organosulfur materials.

[0021] In some embodiments, the electron injection layer material in the n-type structure is LiF or Mg.

[0022] In some embodiments, the conductive cathode in the n-type structure and the conductive anode in the inverted structure are both metal thin films or alloy thin films. The metal thin film is a lithium or magnesium or calcium or strontium or aluminum or indium thin film, and the alloy thin film is an alloy of lithium or magnesium or calcium or strontium or aluminum or indium and copper or gold or silver.

[0023] In some embodiments, the thickness range of the light-emitting layer is 20 - 30 nm, the thickness of the electron injection layer in the n-type structure is 1 nm, the thickness range of the conductive cathode material in the n-type structure is 100 nm - 110 nm, and the thicknesses of the hole transport layer material and the electron transport layer material are 20 - 50 nm.

[0024] A method for preparing an organic light-emitting diode based on a red phosphorescent material, A1. Clean the substrate composed of a transparent glass substrate and a transparent conductive anode ITO, and blow it dry with nitrogen after cleaning; A2. Perform ultraviolet light irradiation treatment on the ITO glass substrate; A3. Spin-coat the prepared PEDOT:PSS solution onto the ITO substrate, and perform thermal annealing treatment on the spin-coated substrate to obtain a PEDOT:PSS hole transport layer; the thermal annealing temperature is 130 °C, and the time range is 30 min; A4. Spin-coat and prepare a light-emitting layer on the hole transport layer, and perform thermal annealing treatment on the spin-coated substrate. The light-emitting layer is prepared from a host material 4CzTPN-Ph doped with a guest material PtOEP; the thermal annealing temperature is 100 °C, and the time range is 20 min; A5. Under a vacuum of 2 x 10 -4 Pa, evaporate the electron transport layer TPBi on the surface of the light-emitting layer; A6. Under a vacuum of 4 x 10 -3 Pa, evaporate the electron injection layer and the conductive cathode; The preparation method of the inverted structure includes the following steps: B1. Clean the substrate composed of a transparent glass substrate and a transparent conductive cathode ITO, and blow it dry with nitrogen after cleaning; B2. Spin-coat the prepared ZnO onto the ITO substrate, and perform thermal annealing treatment on the spin-coated substrate to obtain a ZnO electron transport layer; the thermal annealing temperature is 130 °C, and the time range is 30 min; B3. Spin-coat and prepare a light-emitting layer on the electron transport layer, and perform thermal annealing treatment on the spin-coated substrate. The light-emitting layer is prepared from a host material 4CzTPN-Ph doped with a guest material PtOEP; the thermal annealing temperature is 100 °C, and the time range is 20 min; B4. Under a vacuum of 2 x 10-4 Pa, evaporate the hole transport layer CBP on the surface of the light-emitting layer; B5. Under a vacuum of 4 x 10-4 Pa, evaporate the conductive anode Ag or Al.

[0025] The above thermal annealing methods all adopt at least one of constant temperature hot stage heating, oven heating, far-infrared heating, and hot air heating.

[0026] Example 1: A substrate composed of a transparent glass substrate with a surface roughness less than 1 nm and a sheet resistance less than 15 Ω and a transparent conductive anode ITO was cleaned and dried with nitrogen after cleaning; the dried substrate was subjected to UV-ozone treatment for 10 min; the treated substrate was placed on the stage of a spin coater to prepare a hole transport layer PEDOT:PSS film layer. 60 μL of PEDOT:PSS solution was spin-coated on ITO, the rotation speed was set to 3000 rpm, and the time was 60 s. Then, the substrate was heat-treated at 130 °C for 30 min to form a 30-nm-thick PEDOT:PSS thin film. After the preparation of the hole transport layer was completed, the substrate was transferred into a glove box with a nitrogen atmosphere to spin-coat and prepare an organic light-emitting doped layer. The pre-prepared organic light-emitting doped layer solution was spin-coated with a spin coater to prepare a light-emitting layer, the rotation speed was set to 3000 rpm, the time was 60 s, the heat treatment temperature was 100 °C, and the time was 20 min. The organic light-emitting layer solution was an organic solution with a concentration of 15 mg / mL prepared by using 4CzTPN-Ph:PtOEP (wt%, 99:1) and chlorobenzene as an organic solvent. The substrate with the prepared light-emitting layer was transferred to an organic evaporation chamber through a transition chamber for vacuum thermal evaporation coating. The evaporation material TPBi was used as the electron transport layer with a thickness of 40 nm, and the vacuum degree of the vacuum environment was maintained at below 2×10 -4 Pa, and the material evaporation rate was controlled. Then, it was transferred to an inorganic chamber, and under the condition of a vacuum degree of 4×10 -3 Pa, 1 nm of LiF was evaporated as the electron transport layer and a metal cathode Al with a thickness of 100 nm. Under standard test conditions, the maximum current efficiency of the device was 33.26 cd / A, the maximum external quantum efficiency reached 17.84%, and the maximum brightness was 8562 cd / m 2 .

[0027] Example 2: The substrate composed of a transparent glass substrate with a surface roughness less than 1 nm and a sheet resistance less than 15 Ω and a transparent conductive anode ITO is cleaned, and after cleaning, it is dried with nitrogen; the dried substrate is subjected to UV-ozone treatment for 10 min; the treated substrate is placed on the stage of a spin coater to prepare a hole transport layer PEDOT:PSS film. 60 μL of PEDOT:PSS solution is spin-coated on ITO, the rotation speed is set at 3000 rpm, and the time is 60 s. Then, the substrate is heat-treated at 130 °C for 30 min to form a 30-nm-thick PEDOT:PSS thin film. After the preparation of the hole transport layer is completed, the substrate is transferred into a glove box under a nitrogen atmosphere to spin-coat and prepare an organic light-emitting doping layer. The pre-prepared organic light-emitting doping layer solution is spin-coated by a spin coater to prepare a light-emitting layer, the rotation speed is set at 3000 rpm, the time is 60 s, the heat treatment temperature is 100 °C, and the time is 20 min. The organic light-emitting layer solution is an organic solution with a concentration of 15 mg / mL prepared by using 4CzTPN-Ph:PtOEP (wt%, 97:3) with chlorobenzene as an organic solvent. The substrate with the prepared light-emitting layer is transferred to an organic evaporation chamber through a transition chamber for vacuum thermal evaporation coating. The evaporation material TPBi is used as an electron transport layer with a thickness of 40 nm, and the vacuum degree of the vacuum environment is maintained at 2×10 -4 Pa or less, and the evaporation rate of the material is controlled. Then, it is transferred to an inorganic chamber, and under the condition of a vacuum degree of 4×10 -3 Pa, 1 nm of LiF is evaporated as an electron transport layer and a metal cathode Al with a thickness of 100 nm. Under standard test conditions, the maximum current efficiency of the device is 37.59 cd / A, the maximum external quantum efficiency reaches 18.65%, and the maximum brightness is 11542 cd / m 2 .

[0028] Example 3: The substrate composed of a transparent glass substrate with a surface roughness less than 1 nm and a transparent conductive anode ITO with a sheet resistance less than 15 Ω is cleaned and blown dry with nitrogen after cleaning; the dried substrate is subjected to UV-ozone treatment for 10 min; the treated substrate is placed on the stage of a spin coater to prepare a hole transport layer PEDOT:PSS film. 60 μL of PEDOT:PSS solution is spin-coated on ITO, the rotation speed is set at 3000 rpm, and the time is 60 s. Then, the substrate is heat-treated at 130 °C for 30 min to form a 30-nm-thick PEDOT:PSS film. After the preparation of the hole transport layer is completed, the substrate is transferred into a glove box with a nitrogen atmosphere for spin-coating to prepare an organic light-emitting doping layer. The pre-prepared organic light-emitting doping layer solution is spin-coated with a spin coater to prepare a light-emitting layer, the rotation speed is set at 3000 rpm, the time is 60 s, the heat treatment temperature is 100 °C, and the time is 20 min. The organic light-emitting layer solution is an organic solution with a concentration of 15 mg / mL prepared by using 4CzTPN-Ph:PtOEP (wt%, 95:5) with chlorobenzene as the organic solvent. The substrate with the prepared light-emitting layer is transferred to an organic evaporation chamber through a transition chamber for vacuum thermal evaporation coating. The evaporation material TPBi is used as the electron transport layer with a thickness of 40 nm, and the vacuum degree of the vacuum environment is maintained below 2×10 -4 Pa. Then, the material evaporation rate is controlled and then transferred to an inorganic chamber. Under the condition of a vacuum degree of 4×10 -3 Pa, 1 nm of LiF is evaporated as the electron transport layer and the metal cathode Al with a thickness of 100 nm. Under standard test conditions, the maximum current efficiency of the device is 43.66 cd / A, the maximum external quantum efficiency reaches 19.21%, and the maximum brightness is 12698 cd / m 2 . Figure 3 The test curve graph of the light-emitting spectrum of the device in Example 3 is shown.

[0029] Example 4: The substrate composed of a transparent glass substrate with a surface roughness less than 1 nm and a sheet resistance less than 15 Ω and a transparent conductive anode ITO is cleaned, and after cleaning, it is dried with nitrogen; the dried substrate is subjected to UV-ozone treatment for 10 min; the treated substrate is placed on the stage of a spin coater to prepare a hole transport layer PEDOT:PSS film layer. 60 μL of PEDOT:PSS solution is spin-coated on ITO, the rotation speed is set at 3000 rpm, and the time is 60 s. Then, the substrate is heat-treated at 130 °C for 30 min to form a 30-nm-thick PEDOT:PSS thin film. After the preparation of the hole transport layer is completed, the substrate is transferred into a glove box with a nitrogen atmosphere to spin-coat and prepare an organic light-emitting doped layer. The pre-prepared organic light-emitting doped layer solution is spin-coated by a spin coater to prepare a light-emitting layer, the rotation speed is set at 3000 rpm, the time is 60 s, the heat treatment temperature is 100 °C, and the time is 20 min. The organic light-emitting layer solution is an organic solution with a concentration of 15 mg / mL prepared by using 4CzTPN-Ph:PtOEP (wt%, 93:7) with chlorobenzene as an organic solvent. The substrate with the prepared light-emitting layer is transferred to an organic evaporation chamber through a transition chamber for vacuum thermal evaporation coating. The evaporation material TPBi is used as an electron transport layer with a thickness of 40 nm, and the vacuum degree of the vacuum environment is maintained below 2×10 -4 Pa. Then, it is transferred to an inorganic chamber, and under the condition of a vacuum degree of 4×10 -3 Pa, 1 nm of LiF is evaporated as an electron transport layer and a metal cathode Al with a thickness of 100 nm. Under standard test conditions, the maximum current efficiency of the device is 42.15 cd / A, the highest external quantum efficiency reaches 18.44%, and the highest brightness is 10054 cd / m 2 .

[0030] Example 5: The substrate composed of a transparent glass substrate with a surface roughness less than 1 nm and a transparent conductive anode ITO with a sheet resistance less than 15 Ω is cleaned, and after cleaning, it is dried with nitrogen; the dried substrate is subjected to UV-ozone treatment for 10 min; the treated substrate is placed on the stage of a spin coater to prepare a hole transport layer PEDOT:PSS film. 60 μL of the PEDOT:PSS solution is spin-coated on the ITO, the rotation speed is set at 3000 rpm, and the time is 60 s. Then, the substrate is heat-treated at 130 °C for 30 min to form a 30-nm-thick PEDOT:PSS thin film. After the preparation of the hole transport layer is completed, the substrate is transferred into a glove box under a nitrogen atmosphere to spin-coat and prepare an organic light-emitting doping layer. The pre-prepared organic light-emitting doping layer solution is spin-coated using a spin coater to prepare a light-emitting layer, the rotation speed is set at 3000 rpm, the time is 60 s, the heat treatment temperature is 100 °C, and the time is 20 min. The organic light-emitting layer solution is an organic solution with a concentration of 15 mg / mL prepared by using 4CzTPN-Ph:PtOEP (wt%, 91:9) with chlorobenzene as the organic solvent. The substrate with the prepared light-emitting layer is transferred to an organic evaporation chamber through a transition chamber for vacuum thermal evaporation coating. The evaporation material TPBi is used as the electron transport layer with a thickness of 40 nm, and the vacuum degree of the vacuum environment is maintained below 2×10 -4 Pa. Then, it is transferred to an inorganic chamber, and under a vacuum degree of 4×10 -3 Pa, 1 nm of LiF is evaporated as the electron transport layer and a metal cathode Al with a thickness of 100 nm. Under standard test conditions, the maximum current efficiency of the device is 40.98 cd / A, the maximum external quantum efficiency reaches 17.86%, and the maximum brightness is 9548 cd / m 2 .

[0031] Example 6: The substrate composed of a transparent glass substrate with a surface roughness less than 1 nm and a sheet resistance less than 15 Ω and a transparent conductive anode ITO is cleaned, and after cleaning, it is dried with nitrogen; the dried substrate is subjected to UV-ozone treatment for 10 min; the treated substrate is placed on the stage of a spin coater to prepare the electron transport layer ZnO film. 60 μL of ZnO solution is spin-coated on ITO, the rotation speed is set to 3000 rpm, and the time is 60 s. Then, the substrate is heat-treated at 130 °C for 30 min to form a 30-nm-thick ZnO film. After the preparation of the electron transport layer is completed, the substrate is transferred into a glove box with a nitrogen atmosphere to spin-coat and prepare the organic light-emitting doped layer. The pre-prepared organic light-emitting doped layer solution is spin-coated by a spin coater to prepare the light-emitting layer, the rotation speed is set to 3000 rpm, the time is 60 s, the heat treatment temperature is 100 °C, and the time is 20 min. The organic light-emitting layer solution is prepared by using 4CzTPN-Ph:PtOEP (wt%, 99:1), and an organic solution with a concentration of 15 mg / mL is prepared by using chlorobenzene as an organic solvent. According to the host-guest doping ratio of 1%, the two solutions are then mixed in a volume ratio and stirred for 4 h. The substrate with the prepared light-emitting layer is transferred to the organic evaporation chamber through a transition chamber for vacuum thermal evaporation coating. The evaporation material CBP is used as the hole transport layer with a thickness of 40 nm, and the vacuum degree of the vacuum environment is maintained at 2×10 -4 Pa or less, and the evaporation rate of the material is controlled. Then it is transferred to the inorganic chamber, and under the condition of a vacuum degree of 4×10 -3 Pa, the metal cathode Al is evaporated with a thickness of 100 nm. Under standard test conditions, the maximum current efficiency of the device is 35.65 cd / A, the maximum external quantum efficiency reaches 16.51%, and the maximum brightness is 8574 cd / m 2 .

[0032] Example 7: The substrate composed of a transparent glass substrate with a surface roughness less than 1 nm and a transparent conductive anode ITO with a sheet resistance less than 15 Ω is cleaned, and after cleaning, it is dried with nitrogen; the dried substrate is subjected to UV-ozone treatment for 10 min; the treated substrate is placed on the stage of a spin coater to prepare the electron transport layer ZnO film. 60 μL of ZnO solution is spin-coated on ITO, the rotation speed is set at 3000 rpm, and the time is 60 s. Then, the substrate is heat-treated at 130 °C for 30 min to form a 30-nm-thick ZnO film. After the preparation of the electron transport layer is completed, the substrate is transferred into a glove box with a nitrogen atmosphere to spin-coat and prepare the organic light-emitting doped layer. The pre-prepared organic light-emitting doped layer solution is spin-coated with a spin coater to prepare the light-emitting layer, the rotation speed is set at 3000 rpm, the time is 60 s, the heat treatment temperature is 100 °C, and the time is 20 min. The organic light-emitting layer solution is prepared by using 4CzTPN-Ph:PtOEP (wt%, 97:3), and an organic solution with a concentration of 15 mg / mL is respectively prepared by using chlorobenzene as an organic solvent. According to the host-guest doping ratio of 1%, the two solutions are then mixed in a volume ratio to prepare a solution and stirred for 4 h. The substrate with the prepared light-emitting layer is transferred to an organic evaporation chamber through a transition chamber for vacuum thermal evaporation coating. The evaporation material CBP is used as the hole transport layer with a thickness of 40 nm, and the vacuum degree of the vacuum environment is maintained below 2×10 -4 Pa. Then, it is transferred to an inorganic chamber, and under the condition of a vacuum degree of 4×10 -3 Pa, the metal cathode Al is evaporated with a thickness of 100 nm. Under standard test conditions, the maximum current efficiency of the device is 38.25 cd / A, the maximum external quantum efficiency reaches 17.54%, and the maximum brightness is 9624 cd / m 2 .

[0033] Example 8: The substrate composed of a transparent glass substrate with a surface roughness less than 1 nm and a sheet resistance less than 15 Ω and a transparent conductive anode ITO is cleaned, and after cleaning, it is dried with nitrogen; the dried substrate is subjected to UV-ozone treatment for 10 min; the treated substrate is placed on the stage of a spin coater to prepare an electron transport layer ZnO film. 60 μL of ZnO solution is spin-coated on ITO, the rotation speed is set to 3000 rpm, and the time is 60 s. Then, the substrate is heat-treated at 130 °C for 30 min to form a 30-nm-thick ZnO film. After the preparation of the electron transport layer is completed, the substrate is transferred into a glove box with a nitrogen atmosphere to spin-coat and prepare an organic light-emitting doped layer. The previously prepared organic light-emitting doped layer solution is spin-coated by a spin coater to prepare a light-emitting layer, the rotation speed is set to 3000 rpm, the time is 60 s, the heat treatment temperature is 100 °C, and the time is 20 min. The organic light-emitting layer solution is prepared by using 4CzTPN-Ph:PtOEP (wt%, 95:5), and organic solutions with a concentration of 15 mg / mL are respectively prepared by using chlorobenzene as an organic solvent. According to the host-guest doping ratio of 1%, the two solutions are then mixed in a volume ratio to prepare a solution and stirred for 4 h. The substrate with the prepared light-emitting layer is transferred to an organic evaporation chamber through a transition chamber for vacuum thermal evaporation coating. The evaporation material CBP is used as a hole transport layer with a thickness of 40 nm, and the vacuum degree of the vacuum environment is maintained at 2×10 -4 Pa or less, and the material evaporation rate is controlled. Then it is transferred to an inorganic chamber, and under the condition of a vacuum degree of 4×10 -3 Pa, a metal cathode Al is evaporated with a thickness of 100 nm. Under standard test conditions, the maximum current efficiency of the device is 42.05 cd / A, the maximum external quantum efficiency reaches 18.56%, and the maximum brightness is 11487 cd / m 2 . Figure 1 Figure 1 shows the current efficiency-luminance characteristic curves of the devices in Example 3 (normal type) and Example 8 (inverted type). Figure 2 Figure 2 shows the external quantum efficiency-luminance characteristic curves of the devices in Example 3 (normal type) and Example 8 (inverted type). Figure 4 Figure 3 shows the test curve graph of the emission spectrum of the device in Example 8.

[0034] Example 9: The substrate composed of a transparent glass substrate with a surface roughness less than 1 nm and a sheet resistance less than 15 Ω and a transparent conductive anode ITO is cleaned, and after cleaning, it is dried with nitrogen; the dried substrate is subjected to UV-ozone treatment for 10 min; the treated substrate is placed on the stage of a spin coater to prepare an electron transport layer ZnO film. 60 μL of ZnO solution is spin-coated on ITO, the rotation speed is set at 3000 rpm, and the time is 60 s. Then, the substrate is heat-treated at 130 °C for 30 min to form a 30-nm-thick ZnO film. After the preparation of the electron transport layer is completed, the substrate is transferred into a glove box with a nitrogen atmosphere to spin-coat and prepare an organic light-emitting doped layer. The pre-prepared organic light-emitting doped layer solution is spin-coated by a spin coater to prepare a light-emitting layer, the rotation speed is set at 3000 rpm, the time is 60 s, the heat treatment temperature is 100 °C, and the time is 20 min. The organic light-emitting layer solution is prepared by using 4CzTPN-Ph:PtOEP (wt%, 93:7), and an organic solution with a concentration of 15 mg / mL is prepared by using chlorobenzene as an organic solvent. According to the host-guest doping ratio of 1%, the two solutions are then mixed in a volume ratio and stirred for 4 h. The substrate with the prepared light-emitting layer is transferred to an organic evaporation chamber through a transition chamber for vacuum thermal evaporation coating. The evaporation material CBP is used as a hole transport layer with a thickness of 40 nm, and the vacuum degree of the vacuum environment is maintained at 2×10 -4 Pa or less, and the evaporation rate of the material is controlled. Then, it is transferred to an inorganic chamber, and under the condition of a vacuum degree of 4×10 -3 Pa, a metal cathode Al is evaporated with a thickness of 100 nm. Under standard test conditions, the maximum current efficiency of the device is 41.18 cd / A, the maximum external quantum efficiency reaches 17.69%, and the maximum brightness is 10054 cd / m 2 .

[0035] Example 10: Clean a substrate composed of a transparent glass substrate with a surface roughness less than 1 nm and a sheet resistance less than 15 Ω and a transparent conductive anode ITO, and blow it dry with nitrogen after cleaning; perform UV-ozone treatment on the dried substrate for 10 min; place the treated substrate on the stage of a spin coater to prepare an electron transport layer ZnO film. Take 60 μL of ZnO solution and spin coat it on ITO, with the rotation speed set at 3000 rpm and the time at 60 s, and then perform heat treatment on the substrate at 130 °C for 30 min to form a 30-nm-thick ZnO film. After the preparation of the electron transport layer is completed, transfer the substrate into a glove box with a nitrogen atmosphere and spin coat to prepare an organic light-emitting doped layer. Spin coat the pre-prepared organic light-emitting doped layer solution with a spin coater to prepare a light-emitting layer, with the rotation speed set at 3000 rpm and the time at 60 s, the heat treatment temperature at 100 °C, and the time at 20 min. The organic light-emitting layer solution is prepared by using 4CzTPN-Ph:PtOEP (wt%, 91:9), and using chlorobenzene as an organic solvent to prepare organic solutions with concentrations of 15 mg / mL respectively. According to the host-guest doping ratio of 1%, then mix the two solutions in a volume ratio and prepare the solution and stir for 4 h. Transfer the substrate with the prepared light-emitting layer to an organic evaporation chamber through a transition chamber for vacuum thermal evaporation coating. The evaporation material CBP is used as a hole transport layer with a thickness of 40 nm, and the vacuum degree of the vacuum environment is maintained at 2×10 -4 Pa or less, and the evaporation rate of the material is controlled. Then transfer it to an inorganic chamber, and under the condition of a vacuum degree of 4×10 -3 Pa, evaporate the metal cathode Al with a thickness of 100 nm. Under standard test conditions, the maximum current efficiency of the device is 40.97 cd / A, the highest external quantum efficiency reaches 16.27%, and the highest brightness is 8896 cd / m 2 .

[0036] Maximum current efficiency (cd / A) Maximum external quantum efficiency (%) <![CDATA[Maximum brightness (cd / m 2 )]]> Example 1 33.26 17.84 8562 Example 2 37.59 18.65 11542 Example 3 43.66 19.21 12698 Example 4 42.15 18.44 10054 Example 5 40.98 17.86 9548 Example 6 35.65 16.51 8574 Example 7 38.25 17.54 9624 Example 8 42.05 18.56 11487 Example 9 41.18 17.69 10054 Example 10 40.97 16.27 8896 This shows the performance parameters of the organic light-emitting diodes corresponding to each embodiment.

[0037] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An organic light-emitting diode based on a red phosphorescent material, characterized in that, The red organic electroluminescent device is formed into a normal structure or an inverted structure; when the normal structure is set, it is set from bottom to top as a substrate, a conductive anode layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a conductive cathode in sequence; when the inverted structure is set, it is from bottom to top as a substrate, a conductive cathode layer, an electron transport layer, a light-emitting layer, a hole transport layer, and a conductive anode in sequence. Among them, the light-emitting layer is made by doping the thermally activated delayed fluorescence material 4CzTPN-Ph and the phosphorescent material PtOEP, and the light-emitting layer is an organic thin film formed after spin coating and annealing by the dissolution method. The molecular formula of the thermally activated delayed fluorescence material 4CzTPN-Ph is: ， The molecular formula of the phosphorescent material PtOEP is: 。 2. An organic light-emitting diode based on a red phosphorescent material according to claim 1, characterized in that, The material used for the substrate is at least one of glass, transparent polymer flexible material, or biodegradable flexible material; among them, the transparent polymer flexible material is at least one of polyethylene, polymethyl methacrylate, polycarbonate, polyurethane, polyimide, vinyl chloride resin, or polyacrylic acid; the biodegradable flexible material is at least one of plant fiber, silk fibroin, gelatin, polylactic acid, glucose, viral cellulose, polylactic acid, poly(lactic acid-glycolic acid) copolymer, polyvinyl alcohol, polyvinylpyrrolidone, polycaprolactone, polyhydroxyalkanoate, polysaccharide, polyglycolic acid and its copolymer, collagen gel, fibrin gel.

3. An organic light-emitting diode based on a red phosphorescent material according to claim 1, characterized in that, The materials used for the conductive anode layer in the normal structure and the conductive cathode layer in the inverted structure are at least one of indium tin oxide, conductive polymer poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate, graphene, carbon nanotubes, metal elemental nanowires, metal alloy nanowires, and metal heterojunction nanowires; among them, the metal elemental nanowires are at least one of iron nanowires, copper nanowires, silver nanowires, gold nanowires, aluminum nanowires, nickel nanowires, cobalt nanowires, manganese nanowires, cadmium nanowires, indium nanowires, tin nanowires, tungsten nanowires, or platinum nanowires; the metal alloy nanowires are at least one of copper-iron alloy nanowires, silver-iron alloy nanowires, gold-iron alloy nanowires, aluminum-iron alloy nanowires, nickel-iron alloy nanowires, cobalt-iron alloy nanowires, manganese-iron alloy nanowires, cadmium-iron alloy nanowires, indium-iron alloy nanowires, tin-iron alloy nanowires, tungsten-iron alloy nanowires, platinum-iron alloy nanowires, silver-copper alloy nanowires, gold-copper alloy nanowires, aluminum-copper alloy nanowires, nickel-copper alloy nanowires, cobalt-copper alloy nanowires, manganese-copper alloy nanowires, cadmium-copper alloy nanowires, silver-copper alloy nanowires, tin-copper alloy nanowires, cadmium-manganese alloy nanowires, indium-manganese alloy nanowires, tin-manganese alloy nanowires, tungsten-manganese alloy nanowires, platinum-manganese alloy nanowires, indium-cadmium alloy nanowires, tin-cadmium alloy nanowires, tungsten-cadmium alloy nanowires, platinum-cadmium alloy nanowires, tin-indium alloy nanowires, tungsten-indium alloy nanowires, platinum-indium alloy nanowires, tungsten-tin alloy nanowires, platinum-tin alloy nanowires, or platinum-tungsten alloy nanowires;The metal heterojunction nanowires are at least one of copper-iron heterojunction nanowires, silver-iron heterojunction nanowires, gold-iron heterojunction nanowires, aluminum-iron heterojunction nanowires, nickel-iron heterojunction nanowires, cobalt-iron heterojunction nanowires, manganese-iron heterojunction nanowires, cadmium-iron heterojunction nanowires, indium-iron heterojunction nanowires, tin-iron heterojunction nanowires, tungsten-iron heterojunction nanowires, platinum-iron heterojunction nanowires, silver-copper heterojunction nanowires, gold-copper heterojunction nanowires, aluminum-copper heterojunction nanowires, nickel-copper heterojunction nanowires, cobalt-copper heterojunction nanowires, manganese-copper heterojunction nanowires, cadmium-copper heterojunction nanowires, silver-copper heterojunction nanowires, tin-copper heterojunction nanowires, tungsten-copper heterojunction nanowires, platinum-copper heterojunction nanowires, gold-silver heterojunction nanowires, aluminum-silver heterojunction nanowires, nickel-silver heterojunction nanowires, cobalt-silver heterojunction nanowires, manganese-silver heterojunction nanowires, cadmium-silver heterojunction nanowires, indium-silver heterojunction nanowires, tin-silver heterojunction nanowires, tungsten-silver heterojunction nanowires, platinum-silver heterojunction nanowires, aluminum-gold heterojunction nanowires, nickel-gold heterojunction nanowires, cobalt-gold heterojunction nanowires, manganese-gold heterojunction nanowires, cadmium-gold heterojunction nanowires, indium-gold heterojunction nanowires, tin-gold heterojunction nanowires, tungsten-gold heterojunction nanowires, cobalt-nickel heterojunction nanowires, manganese-nickel heterojunction nanowires, cadmium-nickel heterojunction nanowires, indium-nickel heterojunction nanowires, tin-nickel heterojunction nanowires, tungsten-nickel heterojunction nanowires, platinum-nickel heterojunction nanowires, cadmium-manganese heterojunction nanowires, indium-manganese heterojunction nanowires, tin-manganese heterojunction nanowires, tungsten-manganese heterojunction nanowires, platinum-manganese heterojunction nanowires, indium-cadmium heterojunction nanowires, tin-cadmium heterojunction nanowires, tungsten-cadmium heterojunction nanowires, platinum-cadmium heterojunction nanowires, tin-indium heterojunction nanowires, tungsten-indium heterojunction nanowires, platinum-indium heterojunction nanowires, tungsten-tin heterojunction nanowires, platinum-tin heterojunction nanowires or platinum-tungsten heterojunction nanowires.

4. An organic light emitting diode based on a red phosphorescent material according to claim 1, characterized in that, The hole transport layer material is any one of aromatic diamine compounds, aromatic triamine compounds, carbazole compounds, star-shaped triphenylamine compounds, furan compounds, spiral structure compounds, and polymer materials.

5. An organic light-emitting diode based on a red phosphorescent material according to claim 1, wherein, The electron transport layer material is any one of metal oxides, metal complexes, oxadiazole compounds, quinoxaline compounds, nitrogen-containing heterocyclic compounds, anthracene compounds, organosilicon materials, organoboron materials, and organosulfur materials.

6. An organic light-emitting diode based on a red phosphorescent material according to claim 1, wherein In the normal structure, the electron injection layer material is LiF or Mg.

7. An organic light emitting diode based on a red phosphorescent material according to claim 1, wherein In the normal structure, the conductive cathode and in the inverted structure, the conductive anode are both metal thin films or alloy thin films. The metal thin film is a lithium or magnesium or calcium or strontium or aluminum or indium thin film, and the alloy thin film is an alloy of lithium or magnesium or calcium or strontium or aluminum or indium and copper or gold or silver.

8. An organic light emitting diode based on a red phosphorescent material according to claim 1, characterized in that, The thickness range of the light-emitting layer is 20 - 30 nm, the thickness of the electron injection layer in the normal structure is 1 nm, the thickness range of the conductive cathode material in the normal structure is 100 nm - 110 nm, and the thicknesses of the hole transport layer material and the electron transport layer material are 20 - 50 nm.

9. A method for preparing an organic light-emitting diode based on a red phosphorescent material according to any one of claims 1 - 8, characterized in that: The preparation method of the normal structure includes the following steps: A1. Clean the ITO glass substrate composed of a transparent glass substrate and a transparent conductive anode ITO, and blow it dry with nitrogen after cleaning. A2. Perform ultraviolet light irradiation treatment on the ITO glass substrate. A3. Spin coat the prepared conductive polymer poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate solution onto the ITO glass substrate, and perform thermal annealing treatment on the spin-coated substrate to obtain a hole transport layer. A4. Spin-coat a light-emitting layer on the hole transport layer, and perform thermal annealing on the spin-coated substrate. The light-emitting layer is prepared from a doped mixture of a thermally activated delayed fluorescence material 4CzTPN-Ph and a phosphorescent material PtOEP; A5. Under the condition of a vacuum degree of 2×10 -4 Pa, the electron transport layer TPBi is evaporated on the surface of the light-emitting layer; A6. Under the condition of a vacuum degree of 4x10 -3 Pa, evaporate and deposit an electron injection layer and a conductive cathode; The preparation method of the inverted structure includes the following steps: B1. Clean the ITO substrate composed of a transparent glass substrate and a transparent conductive cathode ITO, and dry it with nitrogen after cleaning; B2. Spin-coat the prepared ZnO onto the ITO substrate, and perform thermal annealing on the spin-coated substrate to obtain a ZnO electron transport layer; B3. Spin-coat a light-emitting layer on the electron transport layer, and perform thermal annealing on the spin-coated substrate. The light-emitting layer is prepared from a doped mixture of a thermally activated delayed fluorescence material 4CzTPN-Ph and a phosphorescent material PtOEP; B4. Under the condition of a vacuum degree of 2×10 -4 Pa, the hole transport layer CBP is evaporated and deposited on the surface of the light-emitting layer; B5. Under the condition of a vacuum degree of 4x10 -3 Pa, evaporate and deposit a conductive anode Ag or Al.

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