Green organic light-emitting device based on Pt (II) complex and preparation method of green organic light-emitting device

Abstract

The invention discloses a Pt (II) complex-based green organic light-emitting device and a preparation method thereof, an organic light-emitting diode provided by the invention is of a common bottom emission structure, and the device is composed of a transparent substrate, an anode layer, a hole injection layer, a hole transport layer, an exciton barrier layer, a light-emitting layer, an electron transport layer, an electron injection layer and a cathode layer, wherein the luminescent layer takes a thermally activated delayed fluorescent material TCz-pMTrz as a sensitization subject and a green phosphorescent material Pt-SOPy as an object, efficient FRET and DET energy transfer exists between the subject and the object, and meanwhile, an exciton blocking structure is introduced, so that the utilization rate of excitons is greatly improved; under voltage driving, the device emits green light, the maximum external quantum efficiency can reach 24.70%, and the maximum brightness can reach 6530 cd / m < 2 >; according to the invention, a new scheme is provided for the preparation of a high-performance doped OLED by developing an efficient OLED luminescent material based on a subject-object sensitization strategy.

Description

Technical Field

[0001] The present invention relates to the technical field of organic light-emitting diodes, and particularly to a green organic electroluminescent device based on a Pt(II) complex and a preparation method thereof. Background Art

[0002] An organic light-emitting diode (OLED) is a device that uses organic materials to emit light under the excitation of an electric field or current. Due to its high-definition pixel quality and color contrast, rapid response time, and wide viewing angle, it has witnessed tremendous development in the past 25 years. Compared with the mature liquid crystal display technology (LCD), OLED does not require a backlight, and the display screen is thinner, lighter, and can achieve a true "black". In addition, the flexible advantages of OLED, such as "foldable and rollable", have also opened a new chapter in flexible display technology. In recent years, the commercial application of OLED has appeared in all aspects of daily life, such as smartphones, televisions, commercial lighting, and flat panel displays.

[0003] The internal quantum efficiency of OLED devices has also increased from less than 25% of the initial fluorescent materials to 100% of the current metal complex phosphorescent materials, further promoting the development of the entire industry and driving the upgrade of products. However, with the rapid development of China's OLED industry in recent years, many problems of a serious lack of self-luminous materials have gradually emerged. Although the current iridium(III)-based phosphorescent complexes have been widely used in OLEDs, their scarcity has limited the sustainable development of the organic display industry to a certain extent.

[0004] Therefore, it is urgent to develop efficient phosphorescent materials to achieve high-efficiency, high-stability, and highly adjustable organic electroluminescent devices and their preparation methods to solve the current problems. Summary of the Invention

[0005] The purpose of the present invention is to design a green organic electroluminescent device based on a Pt(II) complex and a preparation method thereof to solve the above problems.

[0006] The present invention achieves the above purpose through the following technical solutions: For the green organic electroluminescent device based on a Pt(II) complex, the device is formed into a bottom-emitting structure, and is sequentially provided with a transparent substrate, an anode layer, a hole injection layer, a hole transport layer, an exciton blocking layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode layer from bottom to top; wherein the light-emitting layer uses a thermally activated delayed fluorescence material TCz-pMTrz as a sensitizing host and a green phosphorescent material Pt-SOPy as a guest; The structural formula of the thermally activated delayed fluorescence material TCz-pMTrz is: , The structural formula of the green phosphorescent material Pt-SOPy is as follows: .

[0007] A method for preparing a green organic light-emitting device based on a Pt(II) complex includes the following steps: S1. Clean the substrate composed of a transparent substrate and an anode layer, and dry it with nitrogen after cleaning; S2. Treat the substrate by ultraviolet light irradiation; S3. Place the treated substrate in an evaporation chamber with a vacuum degree of 3×10 -3 Pa, and start to prepare the organic thin film. Evaporate the hole injection layer, hole transport layer, exciton blocking layer, light-emitting layer, and electron transport layer in sequence according to the device structure; the doping mass ratio of the green phosphorescent material Pt-SOPy in the light-emitting layer is regulated by the evaporation rates of two independent evaporation sources; S4. In an evaporation chamber with a vacuum degree of 2×10 -4 Pa, evaporate the electron injection layer and the metal cathode.

[0008] The beneficial effects of the present invention are as follows: 1. The metal-carbon bond with covalent properties in the green phosphorescent material Pt-SOPy increases the mixing of metal orbitals and ligand orbitals, thereby improving the stability of the compound; the mixing of metal d orbitals and ligand orbitals can enhance the influence of the metal center on the excited state of the ligand itself, enhance the spin-orbit coupling effect, thereby increasing the quantum yield of the triplet state and promoting efficient phosphorescent radiative relaxation.

[0009] 2. In the thermally activated delayed fluorescence material TADF, the ligand with a triplet excited state of higher energy in the host material TCz-pMTrz results in a large energy difference between the excited state of the ligand and the excited state of lower energy, effectively reducing the influence of the excited state on the luminescence efficiency.

[0010] 3. Using the green Pt(II) complex phosphorescent material as the guest and introducing the thermally activated delayed fluorescence material TCz-pMTrz as the sensitizing host, through efficient FRET and DET energy transfer between the host and the guest, greatly promotes the reverse intersystem crossing process of the triplet excitons of the TADF host, and then inhibits the TTA and TPQ processes, and further inhibits the efficiency roll-off at high current densities, greatly improving the efficiency of the device.

[0011] 4. By strategically designing the exciton blocking layer, adjusting the exciton recombination region, restricting the excitons in the light-emitting layer, higher exciton utilization rate can be obtained, thereby improving the luminescence performance. Description of the Drawings

[0012] Figure 1 Schematic diagram of the structure of a green OLED device according to the present invention; Figure 2 Graph of current efficiency - luminance characteristics of the devices described in Example 1 and Example 4 provided by the present invention; Figure 3 Graph of external quantum efficiency - luminance characteristics of the devices described in Example 1 and Example 4 provided by the present invention; Figure 4 Test curve graph of the emission spectrum of the device described in Example 4 of the present invention.

[0013] In the figure: 1 - transparent substrate; 2 - anode layer; 3 - hole injection layer; 4 - hole transport layer; 5 - exciton blocking layer; 6 - light - emitting layer; 7 - electron transport layer; 8 - electron injection layer; 9 - cathode layer. Detailed implementation manners

[0014] 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. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0015] Therefore, the following detailed description of the embodiments of the present invention provided in the 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.

[0016] It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0017] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is usually placed during use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only 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 to the present invention.

[0018] In addition, the terms "first", "second", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0019] In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, 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 components. 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.

[0020] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings.

[0021] As Figure 1 shown, for the green organic light-emitting device based on the Pt(II) complex, the device is formed into a bottom-emission structure, and is sequentially arranged from bottom to top as a transparent substrate, an anode layer, a hole injection layer, a hole transport layer, an exciton blocking layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode layer; wherein the light-emitting layer uses the thermally activated delayed fluorescence material TCz-pMTrz as the sensitizing host and the green phosphorescent material Pt-SOPy as the guest. The structural formula of the thermally activated delayed fluorescence material TCz-pMTrz is: ,

[0022] The structural formula of the green phosphorescent material Pt-SOPy is: .

[0023] The light-emitting layer is an organic thin film formed by co-evaporating the thermally activated delayed fluorescence material TCz-pMTrz and the green phosphorescent material Pt-SOPy under vacuum, and the doping mass ratio of the green phosphorescent material Pt-SOPy is 1% or 3% or 5% or 7% or 9%.

[0024] In the present invention, the transparent substrate 1 serves as the support for the electrode and the organic thin film layer. It has good light transmittance in the visible light region, has a certain ability to prevent water vapor and oxygen from permeating, and has good surface flatness. The preparation materials of the transparent substrate are at least one of glass, transparent polymer flexible materials, or biodegradable flexible materials; wherein the transparent polymer flexible materials are at least one of polyethylene, polymethyl methacrylate, polycarbonate, polyurethane, polyimide, vinyl chloride resin, and polyacrylic acid; the biodegradable flexible materials are at least one of plant fibers, silk fibroin, gelatin, polylactic acid, glucose, virus cellulose, polylactic acid, poly(lactic acid-glycolic acid) copolymer, polyvinyl alcohol, polyvinylpyrrolidone, polycaprolactone, polyhydroxyalkanoates, polysaccharides, polyglycolic acid and its copolymers, collagen gel, and fibrin gel.

[0025] In the present invention, the anode layer 2 serves as the connection layer between the device and the externally applied bias voltage, and it is required to have good electrical conductivity, visible light transparency, and a relatively high work function. The materials for preparing the anode layer include at least one of indium tin oxide (ITO), conductive polymer poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonate) (PEDOT:PSS), graphene, carbon nanotube, metal single crystal nanowire, metal alloy nanowire, and metal heterojunction nanowire; among them, the metal single crystal nanowire is at least one of iron nanowire, copper nanowire, silver nanowire, gold nanowire, aluminum nanowire, nickel nanowire, cobalt nanowire, manganese nanowire, cadmium nanowire, indium nanowire, tin nanowire, tungsten nanowire, or platinum nanowire; the metal alloy nanowire is at least one of copper-iron alloy nanowire, silver-iron alloy nanowire, gold-iron alloy nanowire, aluminum-iron alloy nanowire, nickel-iron alloy nanowire, cobalt-iron alloy nanowire, manganese-iron alloy nanowire, cadmium-iron alloy nanowire, indium-iron alloy nanowire, tin-iron alloy nanowire, tungsten-iron alloy nanowire, platinum-iron alloy nanowire, silver-copper alloy nanowire, gold-copper alloy nanowire, aluminum-copper alloy nanowire, nickel-copper alloy nanowire, cobalt-copper alloy nanowire, manganese-copper alloy nanowire, cadmium-copper alloy nanowire, silver-copper alloy nanowire, tin-copper alloy nanowire, tungsten-copper alloy nanowire, platinum-copper alloy nanowire, gold-silver alloy nanowire, aluminum-silver alloy nanowire, nickel-silver alloy nanowire, cobalt-silver alloy nanowire, manganese-silver alloy nanowire, cadmium-silver alloy nanowire, indium-silver alloy nanowire, tin-silver alloy nanowire, tungsten-silver alloy nanowire, platinum-silver alloy nanowire, aluminum-gold alloy nanowire, nickel-gold alloy nanowire, cobalt-gold alloy nanowire, manganese-gold alloy nanowire, cadmium-gold alloy nanowire, indium-gold alloy nanowire, tin-gold alloy nanowire, tungsten-gold alloy nanowire, cobalt-nickel alloy nanowire, manganese-nickel alloy nanowire, cadmium-nickel alloy nanowire, indium-nickel alloy nanowire, tin-nickel alloy nanowire, tungsten-nickel alloy nanowire, platinum-nickel alloy nanowire, cadmium-manganese alloy nanowire, indium-manganese alloy nanowire, tin-manganese alloy nanowire, tungsten-manganese alloy nanowire, platinum-manganese alloy nanowire, indium-cadmium alloy nanowire, tin-cadmium alloy nanowire, tungsten-cadmium alloy nanowire, platinum-cadmium alloy nanowire, tin-indium alloy nanowire, tungsten-indium alloy nanowire, platinum-indium alloy nanowire, tungsten-tin alloy nanowire, platinum-tin alloy nanowire, or platinum-tungsten alloy nanowire;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.

[0026] In the present invention, the hole injection layer 3 is a buffer layer to reduce the injection barrier. The material of the hole injection layer is MoO3.

[0027] In the present invention, the hole transport layer 4 serves as a connection layer between the hole injection layer and the organic active layer. It is required to have good hole transport ability; the preparation material of the hole transport layer is any one of aromatic diamine compounds, aromatic triamine compounds, carbazole compounds, star-shaped triphenylamine compounds, furan compounds, spiral structure compounds, and polymer materials.

[0028] The preparation material of the exciton blocking layer is the triphenylamine compound TCTA. It has a high triplet energy level, a high electron mobility, and a high thermal stability.

[0029] The electron transport layer 7 serves as the connection layer between the organic active layer and the electron injection layer, and it is required to have good electron transport ability. The materials for preparing the electron transport layer are any one of metal oxides, metal complexes, oxadiazole compounds, quinoxaline compounds, nitrogen-containing heterocyclic compounds, anthracene compounds, organosilicon materials, organoboron materials, and organosulfur materials.

[0030] In the present invention, the electron injection layer 8 serves as a material buffer layer to reduce the injection barrier. The material of the electron injection layer is LiF.

[0031] In the present invention, the cathode layer 9 serves as the connection layer between the device and the applied bias voltage, and it is required to have good electrical conductivity and a low work function. The cathode layer is a metal thin film or an alloy thin film. The metal thin film is a lithium, magnesium, calcium, strontium, aluminum, or indium thin film, and the alloy thin film is an alloy of lithium, magnesium, calcium, strontium, aluminum, or indium and copper, gold, or silver.

[0032] The thickness range of the light-emitting layer is 20 - 30 nm, the thickness of the electron injection layer is 1 nm, the thickness of the cathode layer is 100 nm, the thicknesses of the hole transport layer and the electron transport layer are 20 - 50 nm, and the exciton blocking layer is 5 - 10 nm.

[0033] A method for preparing a green organic light-emitting device based on a Pt(II) complex, and a method for preparing a bottom-emission structure, comprising the following steps: S1. Clean the substrate composed of a transparent substrate and an anode layer ITO, and blow it dry with nitrogen after cleaning; S2. Treat the substrate by ultraviolet light irradiation; S3. Place the treated substrate in an evaporation chamber with a vacuum degree of 3×10 -3 Pa, and start to prepare the organic thin film. Evaporate the hole injection layer MoO3, TAPC, exciton blocking layer TCTA, light-emitting layer, and electron transport layer TPBI in sequence according to the device structure; the doping mass ratio of the green phosphorescent material Pt-SOPy in the light-emitting layer is regulated by the evaporation rates of two independent evaporation sources; S4. In an evaporation chamber with a vacuum degree of 2×10 -4 Pa, evaporate LiF as the electron injection layer and Al as the metal cathode.

[0034] In some embodiments, the overall structure of the green OLED device provided by the present invention: transparent substrate / ITO(100nm) / MoO3(5 nm) / TAPC(30 nm) / TCTA(10 nm) / EML(25 nm) / TPBi(30 nm) / LiF(1 nm) / Al(100 nm). The above structure is shown in the appendix Figure 1 , and the structure of the EML light-emitting layer is designed.

[0035] The following are specific embodiments of the present invention: Example 1 (control group) The hole injection layer of the device is MoO3, the hole transport layer is TAPC, the exciton blocking layer is TCTA, the light-emitting layer is the green phosphorescent material Pt-SOPy, the electron transport layer is TPBi, and the cathode layer is Al. The device structure is: transparent substrate / ITO (100 nm) / MoO3 (5 nm) / TAPC (30 nm) / TCTA (10 nm) / Pt-SOPy (25 nm) / TPBi (30 nm) / LiF (1 nm) / Al (100 nm).

[0036] Preparation method: The transparent conductive substrate ITO glass is ultrasonically cleaned with detergent, acetone solution, deionized water and isopropyl alcohol solution, and the cleaning time for each time is 15 minutes. After cleaning, it is dried with dry nitrogen. The ITO film on the transparent substrate serves as the anode layer of the device, and the film thickness is 100 nm. The ITO glass substrate is treated by ultraviolet irradiation. The petri dish containing the glass substrate is placed inside for 30 minutes of ultraviolet treatment. The treated substrate is in an evaporation chamber with a vacuum degree of 3×10 -3 Pa. First, MoO3 is evaporated with a thickness of 5 nm, and then organic functional layer thin films are evaporated. According to the device structure described above, the materials TAPC layer of 30 nm, TCTA layer of 10 nm, light-emitting layer of 25 nm, and TPBi layer of 30 nm are evaporated in sequence. The light-emitting layer is the green phosphorescent material Pt-SOPy, and the evaporation rate of each organic layer is 0.5 Å / s. After the evaporation of the organic layer, the metal electrode is prepared. In an evaporation chamber with a vacuum degree of 2×10 -4 Pa, the evaporation rates of LiF and Al are controlled at 2.0 Å / s, and the film layer thicknesses are 1 nm and 100 nm respectively.

[0037] The above evaporation rates and thicknesses are monitored by a film thickness meter. Under standard test conditions, the maximum current efficiency of the device is 26.43 cd / A, the highest external quantum efficiency reaches 4.98%, and the highest brightness is 4198 cd / m 2 . Its current efficiency-brightness characteristic curve is as Figure 2 shown, and the external quantum efficiency-brightness characteristic curve is as Figure 3 shown.

[0038] Example 2: The hole injection layer of the device is MoO3, the hole transport layer is TAPC, the exciton blocking layer is TCTA, the light-emitting layer is an organic thin film formed by doping a thermally activated delayed fluorescence material with a green phosphorescent material, and the doping ratio is TCz-pMTrz: 1 wt% Pt-SOPy. The electron transport layer is TPBi, and the cathode layer is Al. The device structure is: transparent substrate / ITO (100 nm) / MoO3 (5 nm) / TAPC (30 nm) / TCTA (10 nm) / TCz-pMTrz: 1 wt% Pt-SOPy (25 nm) / TPBi (30 nm) / LiF (1 nm) / Al (100 nm).

[0039] Preparation method: The transparent conductive substrate ITO glass is ultrasonically cleaned with detergent, acetone solution, deionized water, and isopropyl alcohol solution, and the cleaning time for each time is 15 minutes. After cleaning, it is dried with dry nitrogen. The ITO film on the transparent substrate serves as the anode layer of the device, and the film thickness is 100 nm. The ITO glass substrate is treated by ultraviolet irradiation. The petri dish containing the glass substrate is placed inside for 30 minutes of ultraviolet treatment. The treated substrate is placed in an evaporation chamber with a vacuum of 3×10 -3 Pa. First, MoO3 is evaporated with a thickness of 5 nm, and then the organic functional layer thin film is evaporated. The materials are evaporated in sequence according to the device structure described above: 30 nm of the TAPC layer, 10 nm of the TCTA layer, 25 nm of the light-emitting layer, and 30 nm of the TPBi layer. The light-emitting layer is TCz-pMTrz: 1 wt% Pt-SOPy. The evaporation rate of each of the remaining organic layers is 0.5 Å / s. After the evaporation of the organic layer is completed, the metal electrode is prepared. In an evaporation chamber with a vacuum of 2×10 -4 Pa, the evaporation rates of LiF and Al are controlled at 2.0 Å / s, and the film layer thicknesses are 1 nm and 100 nm respectively.

[0040] The above evaporation rates and thicknesses are monitored by a film thickness meter. Under standard test conditions, the maximum current efficiency of the device is 56.36 cd / A, the highest external quantum efficiency reaches 18.01%, and the highest brightness is 4110 cd / m 2 .

[0041] Example 3: The hole injection layer of the device is MoO3, the hole transport layer is TAPC, the exciton blocking layer is TCTA, the light-emitting layer is an organic thin film formed by doping a thermally activated delayed fluorescence material with a green phosphorescent material, and the doping ratio is TCz-pMTrz: 3 wt% Pt-SOPy. The electron transport layer is TPBi, and the cathode layer is Al. The device structure is: transparent substrate / ITO (100 nm) / MoO3 (5 nm) / TAPC (30 nm) / TCTA (10 nm) / TCz-pMTrz: 3 wt% Pt-SOPy (25 nm) / TPBi (30 nm) / LiF (1 nm) / Al (100 nm).

[0042] Preparation method: The transparent conductive substrate ITO glass is ultrasonically cleaned with detergent, acetone solution, deionized water, and isopropyl alcohol solution, and the cleaning time for each time is 15 minutes. After cleaning, it is dried with dry nitrogen. The ITO film on the transparent substrate serves as the anode layer of the device, and the film thickness is 100 nm. The ITO glass substrate is treated by ultraviolet irradiation. The petri dish containing the glass substrate is placed inside for 30 minutes of ultraviolet treatment. The treated substrate is placed in an evaporation chamber with a vacuum degree of 3×10 -3 Pa. First, MoO3 is evaporated with a thickness of 5 nm, and then the organic functional layer thin film is evaporated. The materials are evaporated in sequence according to the device structure described above, including a 30 nm TAPC layer, a 10 nm TCTA layer, a 25 nm light-emitting layer, and a 30 nm TPBi layer. The light-emitting layer is TCz-pMTrz: 1 wt% Pt-SOPy. The evaporation rate of each of the remaining organic layers is 0.5 Å / s. After the evaporation of the organic layer, the metal electrode is prepared. In an evaporation chamber with a vacuum degree of 2×10 -4 Pa, the evaporation rates of LiF and Al are controlled at 2.0 Å / s, and the film layer thicknesses are 1 nm and 100 nm respectively.

[0043] The above evaporation rates and thicknesses are monitored by a film thickness meter. Under standard test conditions, the maximum current efficiency of the device is 77.25 cd / A, the highest external quantum efficiency reaches 20.67%, and the highest brightness is 5600 cd / m 2 .

[0044] Example 4: The hole injection layer of the device is MoO3, the hole transport layer is TAPC, the exciton blocking layer is TCTA, the light-emitting layer is an organic thin film formed by doping a thermally activated delayed fluorescence material with a green phosphorescent material, and the doping ratio is TCz-pMTrz: 5 wt% Pt-SOPy. The electron transport layer is TPBi, and the cathode layer is Al. The device structure is: transparent substrate / ITO (100 nm) / MoO3 (5 nm) / TAPC (30 nm) / TCTA (10 nm) / TCz-pMTrz: 5 wt% Pt-SOPy (25 nm) / TPBi (30 nm) / LiF (1 nm) / Al (100 nm).

[0045] Preparation method: The transparent conductive substrate ITO glass is ultrasonically cleaned with detergent, acetone solution, deionized water, and isopropyl alcohol solution, and the cleaning time for each time is 15 minutes. After cleaning, it is dried with dry nitrogen. The ITO film on the transparent substrate serves as the anode layer of the device, and the film thickness is 100 nm. The ITO glass substrate is treated by ultraviolet irradiation. The petri dish containing the glass substrate is placed inside for 30 minutes of ultraviolet treatment. The treated substrate is in an evaporation chamber with a vacuum of 3×10 -3 Pa. First, MoO3 is evaporated with a thickness of 5 nm, and then the organic functional layer thin film is evaporated. The materials are evaporated in sequence according to the device structure described above, with a TAPC layer of 30 nm, a TCTA layer of 10 nm, a light-emitting layer of 25 nm, and a TPBi layer of 30 nm. The light-emitting layer is TCz-pMTrz: 5 wt% Pt-SOPy. The evaporation rate of each of the remaining organic layers is 0.5 Å / s. After the evaporation of the organic layer is completed, the metal electrode is prepared. In an evaporation chamber with a vacuum of 2×10 -4 Pa, the evaporation rates of LiF and Al are controlled at 2.0 Å / s, and the film layer thicknesses are 1 nm and 100 nm respectively.

[0046] The above evaporation rates and thicknesses are monitored by a film thickness gauge. Under standard test conditions, the maximum current efficiency of the device is 81.40 cd / A, the highest external quantum efficiency reaches 24.70%, and the highest brightness is 6530 cd / m 2 . Its current efficiency-brightness characteristic curve is as shown in Figure 2 , the external quantum efficiency-brightness characteristic curve is as shown in Figure 3 , and the test curve of the emission spectrum is as shown in Figure 4 .

[0047] Example 5: The hole injection layer of the device is MoO3, the hole transport layer is TAPC, the exciton regulation layer is TCTA, the light-emitting layer is an organic thin film formed by doping a thermally activated delayed fluorescence material with a green phosphorescent material, and the doping ratio is TCz-pMTrz: 7 wt% Pt-SOPy. The electron transport layer is TPBi, and the cathode layer is Al. The device structure is: transparent substrate / ITO (100 nm) / MoO3 (5 nm) / TAPC (30 nm) / TCTA (10 nm) / TCz-pMTrz: 7 wt% Pt-SOPy (25 nm) / TPBi (30 nm) / LiF (1 nm) / Al (100 nm).

[0048] Preparation method: The transparent conductive substrate ITO glass is ultrasonically cleaned with detergent, acetone solution, deionized water and isopropanol solution, and the cleaning time for each time is 15 minutes. After cleaning, it is dried with dry nitrogen. The ITO film on the transparent substrate serves as the anode layer of the device, and the film thickness is 100 nm. The ITO glass substrate is treated by ultraviolet irradiation. The petri dish containing the glass substrate is placed inside for 30 minutes of ultraviolet treatment. The treated substrate is placed in an evaporation chamber with a vacuum degree of 3×10 -3 Pa. First, MoO3 is evaporated with a thickness of 5 nm, and then the organic functional layer thin film is evaporated. The materials are evaporated successively according to the device structure described above, with a TAPC layer of 30 nm, a TCTA layer of 10 nm, a light-emitting layer of 25 nm, and a TPBi layer of 30 nm. The light-emitting layer is TCz-pMTrz: 1 wt% Pt-SOPy. The evaporation rate of each of the remaining organic layers is 0.5 Å / s. After the evaporation of the organic layer is completed, the metal electrode is prepared. In an evaporation chamber with a vacuum degree of 2×10 -4 Pa, the evaporation rates of LiF and Al are controlled at 2.0 Å / s, and the film layer thicknesses are 1 nm and 100 nm respectively.

[0049] The above evaporation rates and thicknesses are monitored by a film thickness meter. Under standard test conditions, the maximum current efficiency of the device is 74.47 cd / A, the maximum external quantum efficiency reaches 21.71%, and the maximum brightness is 6830 cd / m 2 .

[0050] Example 6: The hole injection layer of the device is MoO3, the hole transport layer is TAPC, the exciton regulation layer is TCTA, the light-emitting layer is an organic thin film formed by doping a thermally activated delayed fluorescence material with a green phosphorescent material, and the doping ratio is TCz-pMTrz: 9 wt% Pt-SOPy. The electron transport layer is TPBi, and the cathode layer is Al. The device structure is: transparent substrate / ITO (100 nm) / MoO3 (5 nm) / TAPC (30 nm) / TCTA (10 nm) / TCz-pMTrz: 9 wt% Pt-SOPy (25 nm) / TPBi (30 nm) / LiF (1 nm) / Al (100 nm).

[0051] Preparation method: The transparent conductive substrate ITO glass is ultrasonically cleaned with detergent, acetone solution, deionized water and isopropyl alcohol solution, and the cleaning time for each time is 15 minutes. After cleaning, it is dried with dry nitrogen. The ITO film on the transparent substrate serves as the anode layer of the device, and the film thickness is 100 nm. The ITO glass substrate is treated by ultraviolet irradiation. The petri dish containing the glass substrate is placed inside and subjected to ultraviolet treatment for 30 minutes. The treated substrate is placed in an evaporation chamber with a vacuum of 3×10 -3 Pa. First, MoO3 is evaporated with a thickness of 5 nm, and then the organic functional layer thin film is evaporated. According to the device structure described above, the materials TAPC layer of 30 nm, TCTA layer of 10 nm, light-emitting layer of 25 nm, and TPBi layer of 30 nm are evaporated in sequence. The light-emitting layer is TCz-pMTrz: 9 wt% Pt-SOPy. The evaporation rate of each of the remaining organic layers is 0.5 Å / s. After the evaporation of the organic layer is completed, the metal electrode is prepared. In an evaporation chamber with a vacuum of 2×10 -4 Pa, the evaporation rates of LiF and Al are controlled at 2.0 Å / s, and the film layer thicknesses are 1 nm and 100 nm respectively.

[0052] The above evaporation rates and thicknesses are monitored by a film thickness meter. Under standard test conditions, the maximum current efficiency of the device is 52.63 cd / A, the highest external quantum efficiency reaches 16.89%, and the highest brightness is 7220 cd / m 2 .

[0053] Maximum current efficiency (cd / A) Maximum external quantum efficiency (%) <![CDATA[Maximum brightness (cd / m 2 )]]> Example 1 26.43 4.98 4198 Example 2 56.36 18.01 4110 Example 3 77.25 20.67 5600 Example 4 81.40 24.70 6530 Example 5 74.47 21.71 6830 Example 6 52.63 16.89 7220 Table 1 Performance parameters of organic light-emitting diodes It can be seen that: with the green Pt(II) complex phosphorescent material as the guest and the thermally activated delayed fluorescence material TCz-pMTrz as the sensitizing host (i.e., the organic light-emitting diode prepared in Examples 2-6), compared with the organic light-emitting diode with the pure green Pt(II) phosphorescent material as the light-emitting layer (i.e., the organic light-emitting diode prepared in Example 1), the device luminous efficiency and luminous brightness are significantly improved. Repeated experiments show that when the doping concentration of the green Pt(II) phosphorescent material as the light-emitting layer guest is 5%, the maximum EQE of 24.70% is obtained. This is because of the efficient FRET and DET energy transfer between the host and the guest, which greatly promotes the reverse intersystem crossing of the triplet excitons of the TADF host, thereby inhibiting the TTA and TPQ processes, and further inhibiting the efficiency roll-off at high current densities, greatly improving the efficiency of the device. In addition, the exciton blocking layer is strategically designed to adjust the exciton recombination region, confine the excitons in the light-emitting layer, and obtain higher exciton utilization rate, thereby improving the luminous performance. The above strategies not only solve the common problem of low PLQY of traditional phosphorescent materials, but also further reduce the exciton loss, providing a new and desirable strategy for the preparation of high-performance doped OLEDs.

[0054] The above are only the preferred embodiments of the present invention. It should be pointed out 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. A green organic electroluminescent device based on a Pt(II) complex, characterized in that: The device is formed into a bottom emission structure, which is sequentially provided from bottom to top with a transparent substrate, an anode layer, a hole injection layer, a hole transport layer, an exciton blocking layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode layer; The light-emitting layer is composed of the thermally activated delayed fluorescent material TCz-pMTrz as the sensitized host and the green phosphorescent material Pt-SOPy as the guest; The structural formula of the thermally activated delayed fluorescent material TCz-pMTrz is: ， The structural formula of the green phosphorescent material Pt-SOPy is: 。 2. The green organic electroluminescent device based on the Pt(II) complex according to claim 1, characterized in that: The light-emitting layer is an organic thin film formed by co-evaporation of thermally activated delayed fluorescent material TCz-pMTrz and green phosphorescent material Pt-SOPy under vacuum, wherein the doping mass ratio of the green phosphorescent material Pt-SOPy is 1% or 3% or 5% or 7% or 9%.

3. The green organic electroluminescent device based on Pt(II) complex according to claim 1, characterized in that: The transparent substrate is prepared from 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, chloroacetic resin and polyacrylic acid; the biodegradable flexible material is at least one of plant fiber, silk fibroin, gelatin, polylactic acid, glucose, viral cellulose, polylactic acid, polylactic acid-glycolic acid copolymer, polyvinyl alcohol, polyvinyl pyrrolidone, polycaprolactone, polyhydroxyalkanoate, polysaccharide, polyalcohol acid and copolymers thereof, collagen gel and fibrin gel.

4. The green organic electroluminescent device based on Pt(II) complex according to claim 1, characterized in that: The preparation material of the anode layer is at least one of indium tin oxide, conductive polymer poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate, graphene, carbon nanotubes, metal single substance nanowires, metal alloy nanowires, and metal heterojunction nanowires; wherein the metal single substance 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, and platinum nanowires; the metal alloy nanowires are Copper-iron alloy nanowire, silver-iron alloy nanowire, gold-iron alloy nanowire, aluminum-iron alloy nanowire, nickel-iron alloy nanowire, cobalt-iron alloy nanowire, manganese-iron alloy nanowire, cadmium-iron alloy nanowire, indium-iron alloy nanowire, tin-iron alloy nanowire, tungsten-iron alloy nanowire, platinum-iron alloy nanowire, silver-copper alloy nanowire, gold-copper alloy nanowire, aluminum-copper alloy nanowire, nickel-copper alloy nanowire, cobalt-copper alloy nanowire, manganese-copper alloy nanowire, cadmium-copper alloy nanowire, silver-copper alloy nanowire, tin-copper alloy nanowire, tungsten-copper Alloy nanowires, platinum-copper alloy nanowires, gold-silver alloy nanowires, aluminum-silver alloy nanowires, nickel-silver alloy nanowires, cobalt-silver alloy nanowires, manganese-silver alloy nanowires, cadmium-silver alloy nanowires, indium-silver alloy nanowires, tin-silver alloy nanowires, tungsten-silver alloy nanowires, platinum-silver alloy nanowires, aluminum-gold alloy nanowires, nickel-gold alloy nanowires, cobalt-gold alloy nanowires, manganese-gold alloy nanowires, cadmium-gold alloy nanowires, indium-gold alloy nanowires, tin-gold alloy nanowires, tungsten-gold alloy nanowires, cobalt-nickel alloy nanowires, manganese-nickel alloy At least one of nanowires, cadmium-nickel alloy nanowires, indium-nickel alloy nanowires, tin-nickel alloy nanowires, tungsten-nickel alloy nanowires, platinum-nickel 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 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 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 At least one of 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. ; 5. A green organic electroluminescent device based on a Pt(II) complex according to claim 1, characterized in that: The preparation material of the hole transport layer is any one of aromatic diamine compounds, aromatic triamine compounds, carbazole compounds, star-shaped triphenylamine compounds, furan compounds, spiro-structured compounds and polymer materials.

6. The green organic electroluminescent device based on Pt(II) complex according to claim 1, characterized in that: The material for preparing the exciton blocking layer is triphenylamine compound TCTA.

7. The green organic electroluminescent device based on Pt(II) complex according to claim 1, characterized in that: The preparation material of the electron transport layer is any one of metal oxides, metal complexes, oxadiazole compounds, quinoxaline compounds, nitrogen-containing heterocyclic compounds, anthracene compounds, organic silicon materials, organic boron materials, and organic sulfur materials.

8. The green organic electroluminescent device based on Pt(II) complex according to claim 1, characterized in that: The cathode layer is a metal film or an alloy film, the metal film is a lithium or magnesium or calcium or strontium or aluminum or indium film, and the alloy film is an alloy of lithium or magnesium or calcium or strontium or aluminum or indium and copper or gold or silver.

9. The green organic electroluminescent device based on Pt(II) complex according to claim 1, characterized in that: The thickness of the light-emitting layer ranges from 20 to 30 nm, the thickness of the electron injection layer is 1 nm, the thickness of the cathode layer is 100 nm, the thickness of the hole transport layer and the electron transport layer is 20 to 50 nm, and the thickness of the exciton blocking layer is 5 to 10 nm.

10. The method for preparing a green organic electroluminescent device based on a Pt(II) complex according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, cleaning the substrate composed of the transparent substrate and the anode layer, and drying it with nitrogen after cleaning; S2, treating the substrate by ultraviolet light irradiation; S3, the treated substrate is placed in a vacuum of 3×10 -3 In the evaporation chamber of Pa, the preparation of organic thin films began. The hole injection layer, hole transport layer, exciton blocking layer, light-emitting layer and electron transport layer were sequentially deposited according to the device structure. The doping mass ratio of the green phosphorescent material Pt-SOPy in the light-emitting layer was regulated by the evaporation rate of two independent evaporation sources. S4, at a vacuum degree of 2×10 -4 Pa in the evaporation chamber, the electron injection layer and the metal cathode are evaporated.

Images