Light-emitting device, preparation method thereof and display device

Abstract

The invention belongs to the technical field of display, and relates to a light-emitting device, a preparation method thereof and a display device. The light-emitting device comprises a first electrode, a first light-emitting unit, a charge generation unit, a second light-emitting unit and a second electrode which are sequentially arranged in a stacked mode. The charge generation unit comprises a carrier injection layer and a carrier generation layer, the carrier injection layer is arranged close to the first light emitting unit, and the carrier generation layer is arranged close to the second light emitting unit; and the material of the carrier injection layer comprises n-type graphene. By adopting the n-type graphene, the carrier injection layer can be prevented from being damaged by the hole injection material, and a charge generation unit with good charge separation and injection performance is obtained, so that the luminous efficiency of the light-emitting device is improved, and the service life of the light-emitting device is prolonged.

Description

Technical Field

[0001] The present application relates to the field of display technology, and more specifically, to a light-emitting device and a method for preparing the same, and a display apparatus. Background Art

[0002] The stacked light-emitting device connects at least two light-emitting units in series to reduce the current density required by the device at the same brightness, thereby increasing the life of the device. Therefore, it is an important direction for improving the life of the current light-emitting device. In the stacked light-emitting device, part of the carriers are provided by the driving voltage, and the other part of the carriers are generated in the charge generation layer. The current mainstream charge generation layer usually uses metal oxides as carrier injection layers, but they have poor stability. When other film layers are prepared using the solution method, they are prone to chemical reactions, causing their electrical properties to change, thereby affecting device performance. Summary of the invention

[0003] Based on this, the embodiments of the present application provide a light emitting device and a method for manufacturing the same, as well as a display device.

[0004] In order to solve the above technical problems, the embodiment of the present application provides a light emitting device, which adopts the following technical solution:

[0005] A light-emitting device comprises a first electrode, a first light-emitting unit, a charge generating unit, a second light-emitting unit and a second electrode which are sequentially stacked;

[0006] The charge generation unit includes a carrier injection layer and a carrier generation layer which are stacked, wherein the carrier injection layer is arranged close to the first light-emitting unit, and the carrier generation layer is arranged close to the second light-emitting unit;

[0007] The material of the carrier injection layer includes n-type graphene.

[0008] Further, the n-type graphene is n-type graphene quantum dots; and / or

[0009] The average particle size of the n-type graphene is less than 20 nm; and / or

[0010] The light transmittance of the carrier generation layer is greater than 70%; and / or

[0011] The light transmittance of the carrier injection layer is greater than 70%; and / or

[0012] The thickness ratio of the carrier injection layer to the carrier generation layer is (5-50):(10-150).

[0013] Furthermore, the peak wavelength of the light that can be transmitted through the carrier generation layer is 380 to 780 nm; and / or

[0014] The peak wavelength of the light that can be transmitted through the carrier injection layer is 440 to 650 nm; and / or

[0015] The n-type graphene quantum dots include at least one of n-type graphene quantum dots and doped n-type graphene quantum dots; the doped n-type graphene quantum dots include at least one of n-type graphene quantum dots doped with N atoms and n-type graphene quantum dots doped with S atoms;

[0016] In the n-type graphene quantum dots doped with N atoms, the mass ratio of the N atoms to the n-type graphene quantum dots is (1:20) to (1:100); and / or

[0017] In the n-type graphene quantum dots doped with S atoms, the mass ratio of the S atoms to the n-type graphene quantum dots is (1:20) to (1:100).

[0018] Furthermore, the material of the carrier injection layer also includes a modifier.

[0019] Further, the mass ratio of the n-type graphene to the modifier is selected from 1:0 to 1:1; and / or

[0020] The modifier is a fatty amine modifier, and the fatty amine modifier is selected from at least one of polyethylene imine, polyethoxyethylene imine, and polyether amine; and / or

[0021] The mass average molecular weight Mw of the modifier is >1000.

[0022] Furthermore, the material of the carrier generation layer is a p-type semiconductor material or an n-type semiconductor material;

[0023] When the material of the carrier generation layer is a p-type semiconductor material, a PN heterojunction is formed between the carrier generation layer and the carrier injection layer; or

[0024] When the material of the carrier generation layer is an n-type semiconductor material, a PN heterojunction is formed between the carrier generation layer and the second light emitting unit.

[0025] Furthermore, the p-type semiconductor material includes a host material and a guest material, wherein the host material is selected from at least one of PEDOT, TFB, Poly-TPD, VNPB, PTAA, 1F-PTAA, VB-FNPD, QUPD, OTPD, CuSCN, and NiO; and the guest material is selected from MoO 3 Nanoparticles, WO 3Nanoparticles, molybdenum ethoxide, tungsten ethoxide, phosphomolybdic acid, phosphotungstic acid, ammonium metavanadate, ammonium metatungstate, ammonium molybdate, sulfuric acid, benzenesulfonic acid, pentafluorobenzenesulfonic acid, polystyrenesulfonic acid, FeCl 3 、AsCl 3 、SbCl 5 、AuCl 3 , BCF, Magic-blue, HATCN, F6TCNQ, CN6-CP, NDP-9, Mo(tfd)3, Mo(tfd-COCF3)3, Mo(tfd-CO2Me)3; or,

[0026] The n-type semiconductor material is selected from MoO 3 Nanoparticles, WO 3 One of nanoparticles, molybdenum ethoxide, tungsten ethoxide, phosphomolybdic acid, phosphotungstic acid, ammonium metavanadate, ammonium metatungstate, ammonium molybdate, HATCN, F6TCNQ, CN6-CP, and NDP-9; and / or

[0027] The absolute value of the LUMO energy level of the n-type semiconductor material is ≥4.5 eV.

[0028] Furthermore, the first light-emitting unit includes a first light-emitting layer, one side of the first light-emitting layer is close to the first electrode, and the other side of the first light-emitting layer is close to the carrier injection layer; and / or

[0029] The second light-emitting unit comprises a second light-emitting layer, one side of the second light-emitting layer is close to the carrier generation layer, and the other side is close to the second electrode; and / or

[0030] The first light-emitting unit further includes a first hole functional layer and / or a first electron functional layer, the first hole functional layer is arranged between the first electrode and the light-emitting layer, and the first electron functional layer is arranged between the light-emitting layer and the carrier injection layer; and / or

[0031] The second light-emitting unit further includes a second hole functional layer and / or a second electron functional layer, wherein the second hole functional layer is disposed between the carrier generating layer and the second light-emitting layer, and the second electron functional layer is disposed between the second light-emitting layer and the second electrode.

[0032] In order to solve the above technical problems, the present application provides a method for preparing a light-emitting device, which adopts the following technical solution:

[0033] A method for preparing a light emitting device comprises the following steps:

[0034] Providing a light-emitting device preform, wherein the light-emitting device preform comprises a first electrode and a first light-emitting unit arranged in sequence;

[0035] Placing a carrier injection material solution on the first light-emitting unit to prepare a carrier injection layer;

[0036] preparing a carrier generation layer on the carrier injection layer;

[0037] Sequentially preparing a second light-emitting unit and a second electrode on the carrier generation layer to obtain a light-emitting device;

[0038] Wherein, the carrier injection material solution includes a carrier injection material, and the carrier injection material includes n-type graphene.

[0039] Furthermore, the step of providing a carrier injection material solution on the first light-emitting unit to prepare a carrier injection layer specifically includes:

[0040] Placing a carrier injection material solution on the first light-emitting unit to obtain a first precursor film;

[0041] performing a first annealing treatment on the first precursor film to obtain the carrier injection layer; and / or

[0042] The step of preparing a carrier generation layer on the carrier injection layer specifically includes:

[0043] placing a carrier generating material solution on the carrier injection layer to obtain a second precursor film;

[0044] The second precursor film is subjected to a second annealing treatment to obtain the carrier generation layer.

[0045] Further, the n-type graphene is n-type graphene quantum dots; and / or

[0046] The average particle size of the n-type graphene is less than 20 nm; and / or

[0047] The light transmittance of the carrier generation layer is greater than 70%; and / or

[0048] The light transmittance of the carrier injection layer is greater than 70%; and / or

[0049] The thickness ratio of the carrier injection layer to the carrier generation layer is (5-50):(10-150).

[0050] Furthermore, the peak wavelength of the light that can be transmitted through the carrier generation layer is 400 to 600 nm; and / or

[0051] The peak wavelength of the light that can be transmitted through the carrier injection layer is 440 to 650 nm; and / or

[0052] The n-type graphene quantum dots include at least one of n-type graphene quantum dots and doped n-type graphene quantum dots; the doped n-type graphene quantum dots include at least one of n-type graphene quantum dots doped with N atoms and n-type graphene quantum dots doped with S atoms;

[0053] In the n-type graphene quantum dots doped with N atoms, the mass ratio of the N atoms to the n-type graphene quantum dots is (1:20) to (1:100); and / or

[0054] In the n-type graphene quantum dots doped with S atoms, the mass ratio of the S atoms to the n-type graphene quantum dots is (1:20) to (1:100).

[0055] Furthermore, the carrier injection material solution further comprises a first solvent, wherein the first solvent is selected from at least one of an alcohol solvent, an ether solvent and a ketone solvent; and / or

[0056] The first solvent is selected from at least one of n-butanol, n-pentanol, n-hexanol, n-heptanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, cyclohexanone and methyl ethyl ketone; and / or

[0057] The mass concentration of the carrier injection material solution is 1% to 10%; and / or

[0058] The carrier injection material solution further includes a modifier; and / or

[0059] The mass ratio of the n-type graphene to the modifier is selected from 1:0 to 1:1.

[0060] Further, the carrier generating material solution comprises a carrier generating material and a second solvent, wherein the carrier generating material comprises a p-type semiconductor material or an n-type semiconductor material; and / or

[0061] The second solvent is selected from at least one of an alcohol solvent and a nitrile solvent; and / or

[0062] The second solvent is selected from at least one of ethanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, acetonitrile, propionitrile, benzonitrile, xylene, chlorobenzene, cyclohexylbenzene and tetralin;

[0063] The mass concentration of the carrier generating material solution is 1% to 10%.

[0064] Further, the temperature of the first annealing treatment is 100-200° C.; and / or

[0065] The first annealing treatment lasts for 5 to 60 minutes; and / or

[0066] The temperature of the second annealing treatment is 100-200° C.; and / or

[0067] The second annealing treatment lasts for 5 to 60 minutes.

[0068] In order to solve the above technical problems, the present application provides a display device, which adopts the following technical solution:

[0069] A display device includes the light-emitting device as described above, or includes a light-emitting device manufactured using the manufacturing method as described above.

[0070] Compared with the prior art, the embodiments of the present application have the following beneficial effects: the present application adopts n-type graphene as the carrier injection layer, and the carrier injection layer can prevent being destroyed by the hole injection material to obtain a charge generation unit with charge separation and better injection performance, thereby improving the luminous efficiency and service life of the light-emitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] In order to more clearly illustrate the scheme of the present application, a brief introduction is given below to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0072] Figure 1 is a schematic diagram of a charge generation layer provided in an embodiment of the present application;

[0073] Figure 2 is a flow chart of a method for preparing a charge generation layer provided in an embodiment of the present application;

[0074] Figure 3 It is a schematic diagram of a light-emitting device provided in an embodiment of the present application.

[0075] Figure numerals: 1, first electrode; 2, first light-emitting unit; 3, charge generating unit; 31, carrier injection layer; 32, carrier generating layer; 4, second light-emitting unit; 5, second electrode; 6, hole injection layer; 7, electron injection layer. DETAILED DESCRIPTION

[0076] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0077] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0078] For ease of understanding, the terms mentioned in the specific implementation are first explained below:

[0079] Transmittance: Light enters from one side of the film layer and passes through the film layer and exits from the other side. The light intensity before the light enters one side of the film layer is defined as l0, and the light intensity exiting from the other side of the film layer is defined as lt. The transmittance is lt / l0.

[0080] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings.

[0081] The present application provides a light emitting device, such as Figure 1 and Figure 2 As shown, the light-emitting device includes a first electrode 1, a first light-emitting unit 2, a charge generating unit 3, a second light-emitting unit 4 and a second electrode 5 which are stacked in sequence; the charge generating unit 3 includes a carrier injection layer 31 and a carrier generating layer 32 which are stacked, the carrier injection layer 31 is arranged close to the first light-emitting unit 2, and the carrier generating layer 32 is arranged close to the second light-emitting unit 4; the material of the carrier injection layer 31 includes n-type graphene.

[0082] In this embodiment, the charge generation layer 3 is arranged between the first light-emitting unit 2 and the second light-emitting unit 4, wherein the n-type graphene is acid- and alkali-resistant. The present application adopts the n-type graphene as the carrier injection layer 31, so that when the carrier injection layer 31 and the carrier generation layer 32 are stacked, they can prevent being damaged by the hole injection material and generate charges, so as to obtain a charge generation unit 3 with good electrical transmission performance. In this embodiment, the charge generation unit 3 has good charge separation and injection performance, so that it has improved performance in the light-emitting device, thereby improving the luminous efficiency and service life of the light-emitting device; and the charge generation unit 3 has a simple structure, which can simplify the preparation process of the solution method.

[0083] Furthermore, the light-emitting device may further include a third light-emitting unit, etc., and a charge generating unit is disposed between the second light-emitting unit and the third light-emitting unit; further, the light-emitting device may further include a fourth light-emitting unit, etc., and a charge generating unit is disposed between the third light-emitting unit and the fourth light-emitting unit. Multiple light-emitting units may be disposed according to actual needs, and a charge generating unit may be disposed between adjacent light-emitting units, and this application does not limit this.

[0084] Furthermore, the n-type graphene is n-type graphene quantum dots.

[0085] In this embodiment, the n-type graphene quantum dots can be regarded as cut-out fragments of graphene in terms of structure, and have abundant functional groups and surface states, as well as relatively good carrier concentration.

[0086] In this embodiment, the unique structural characteristics of n-type graphene quantum dots, such as rich functional groups and surface states, as well as relatively excellent carrier concentration, are utilized to improve the potential distribution of the contact interface when the n-type graphene quantum dots and the carrier generation layer 32 are in contact (adjacent), thereby reducing the electron transfer resistance of the carrier generation layer 32, so that the electrons generated in the PN heterojunction can be injected into the first light-emitting unit 2 through the n-type graphene quantum dots.

[0087] In this embodiment, the n-type graphene quantum dots have a flake structure, good film morphology, and more surface states. Compared with ordinary quantum dots, the n-type graphene quantum dots have better electrical transmission performance.

[0088] Furthermore, the average particle size of the n-type graphene is less than 20 nm.

[0089] In this embodiment, the average particle size of n-type graphene is less than 20 nm, so that it can be applied to the solution method, and the film quality can be guaranteed without affecting the energy level structure of the material.

[0090] In some optional implementations of this embodiment, the average particle size of the n-type graphene is any one of 1 nm, 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, etc., or a range between any two of them.

[0091] Further, the n-type graphene quantum dots include at least one of n-type graphene quantum dots and doped n-type graphene quantum dots; the doped n-type graphene quantum dots include at least one of n-type graphene quantum dots doped with N atoms and n-type graphene quantum dots doped with S atoms;

[0092] In the n-type graphene quantum dots doped with N atoms, the mass ratio of the N atoms to the n-type graphene quantum dots is (1:20) to (1:100); and / or

[0093] In the n-type graphene quantum dots doped with S atoms, the mass ratio of the S atoms to the n-type graphene quantum dots is (1:20) to (1:100).

[0094] In this embodiment, the doping of N atoms and S atoms belongs to N-type doping, and the energy level, defect state energy level and mobility of n-type graphene quantum dots can be adjusted after doping. The doping of S atoms and N atoms will affect the energy level and mobility of n-type graphene quantum dots. The material selection can be carried out according to actual needs, and this application is not limited here.

[0095] Furthermore, the mass ratio of the N atoms to the n-type graphene quantum dots is (1:20) to (1:100).

[0096] In some optional implementations of this embodiment, the mass ratio of the N atoms to the n-type graphene quantum dots is any one of 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, etc., or a range between any two of them.

[0097] Furthermore, the mass ratio of the S atoms to the n-type graphene quantum dots is (1:20) to (1:100).

[0098] In some optional implementations of this embodiment, the mass ratio of the S atoms to the n-type graphene quantum dots is any one of 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, etc., or a range between any two of them.

[0099] Furthermore, the light transmittance of the carrier generation layer 32 is greater than 70%.

[0100] In this embodiment, the light transmittance of the carrier generating layer is greater than 70%, which is easy to improve the light emitting efficiency of the light emitting device.

[0101] Furthermore, the peak wavelength of the light that can be transmitted through the carrier generation layer 32 is 380-780 nm.

[0102] In this embodiment, the peak wavelength of 380-780 nm is the wavelength range of visible light. The carrier generation layer 32 has a transmittance greater than 70% at the peak wavelength of 380-780 nm, which can easily improve the luminous efficiency of the light-emitting device.

[0103] Furthermore, the light transmittance of the carrier injection layer 31 is greater than 70%.

[0104] In this embodiment, the light transmittance of the carrier injection layer 31 is greater than 70%, which is easy to improve the light emitting efficiency of the light emitting device.

[0105] Furthermore, the peak wavelength of the light that can be transmitted through the carrier injection layer 31 is 440-650 nm.

[0106] In this embodiment, the peak wavelength of 440-650 nm is the wavelength range of visible light. The carrier injection layer 31 has a light transmittance greater than 70% at the peak wavelength of 440-650 nm, which is easy to improve the light emitting efficiency of the light emitting device.

[0107] It can be understood that the light transmittance is the ability of light to pass through a medium, specifically the ratio of the light flux passing through the medium to the incident light flux. In this embodiment, the light intensity before passing through the carrier injection layer 31 or the carrier generation layer 32 is defined as l 0 , the light intensity after passing through the carrier injection layer 31 or the carrier generation layer 32 is l t , then the light transmittance is l t / l 0 .

[0108] Furthermore, the thickness ratio of the carrier injection layer 31 to the carrier generation layer 32 is (5-50):(10-150).

[0109] In some optional implementations of this embodiment, the thickness ratio of the carrier injection layer 31 to the carrier generation layer 32 is in the range of any one of 5:10, 5:50, 5:100, 5:150, 10:10, 10:50, 10:100, 10:150, 20:10, 20:50, 20:100, 20:150, 30:10, 30:50, 30:100, 30:150, 40:10, 40:50, 40:100, 40:150, 50:10, 50:50, 50:100, 50:150, etc., or in the range of any two thereof.

[0110] Furthermore, the carrier generation layer 32 has a thickness of 10-150 nm.

[0111] In some optional implementations of this embodiment, the thickness of the carrier generation layer 32 is any one of 10 nm, 30 nm, 50 nm, 70 nm, 90 nm, 110 nm, 130 nm, 150 nm, etc., or in the range between any two of them.

[0112] Furthermore, the carrier injection layer 31 has a thickness of 5-50 nm.

[0113] In some optional implementations of this embodiment, the thickness of the carrier injection layer 31 is any one of 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc., or in a range between any two of them.

[0114] Furthermore, the material of the carrier injection layer 31 also includes a modifier.

[0115] In this embodiment, the modifier can inject the electrons generated by the charge generation layer 3 into the light-emitting layer of the first light-emitting unit 2 (the structure of the first light-emitting unit is described below) through the n-type graphene.

[0116] Furthermore, the mass ratio of the n-type graphene to the modifier is selected from 1:0 to 1:1.

[0117] In some optional implementations of this embodiment, the mass ratio of the n-type graphene to the modifier is any one of 1:0, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, etc., or a range between any two of them.

[0118] Preferably, the mass ratio of the n-type graphene to the modifier is 1:0.2.

[0119] In this embodiment, the mass ratio of the n-type graphene to the modifier is less than 1:1, which can prevent the n-type graphene from being too high and ensure the injection of electrons into the first light-emitting unit; the mass ratio of the n-type graphene to the modifier is greater than 1:0, which can ensure that the n-type graphene content is prevented from being too low, so as to avoid the situation that is not conducive to the transfer of charges due to the high resistance of the modifier itself.

[0120] Furthermore, the modifier is a fatty amine modifier, and the fatty amine modifier is selected from at least one of polyethylene imine, polyethoxyethylene imine, polyether amine

[0121] In this embodiment, the aliphatic amine modifier mainly utilizes the electrons on its N atoms and can be used as an N-type dopant for doping. Specifically, the aliphatic amine can react with the surface groups of n-type graphene to increase the electron electrostatic potential and improve the injection of electrons.

[0122] Furthermore, the mass average molecular weight Mw of the modifier is >1000.

[0123] In this embodiment, the mass average molecular weight Mw of the modifier is greater than 1000, so that the molecule has good stability as a polymer and prevents the molecule from volatilizing or being solvent-intolerant.

[0124] Further, the material of the carrier generation layer 32 is a p-type semiconductor material or an n-type semiconductor material;

[0125] When the material of the carrier generation layer 32 is a p-type semiconductor material, a PN heterojunction is formed between the carrier generation layer 32 and the carrier injection layer 31; or

[0126] When the material of the carrier generation layer 32 is an n-type semiconductor material, a PN heterojunction is formed between the carrier generation layer 32 and the second light emitting unit 4 .

[0127] It can be understood that the PN heterojunction is an interface region formed by the contact of two semiconductor materials of different conductivity types. In the present embodiment, the carrier injection layer 31 is an n-type graphene semiconductor material. When the carrier generation layer 32 is a p-type semiconductor material, a PN heterojunction is formed between the carrier generation layer 32 and the carrier injection layer 31; the carrier injection layer 31 is an n-type graphene semiconductor material. When the carrier generation layer 32 is an n-type semiconductor material, a PN heterojunction is formed between the carrier generation layer 32 and the second light-emitting unit 4, specifically, a PN heterojunction is formed between the carrier generation layer 32 and the second hole functional layer.

[0128] In this embodiment, for the doped PN heterojunction, the n-type graphene quantum dots can be structurally regarded as cut fragments of graphene, with rich functional groups and surface states, and relatively good carrier concentration, so that a charge generation unit with good electrical transmission performance can be obtained.

[0129] In the present embodiment, for the undoped accumulation-type PN heterojunction, since the n-type carrier generation layer and the light-emitting layer (or electron transport layer) of the first light-emitting unit 2 have a large LUMO energy level difference, the generated electrons are difficult to be effectively injected into the first light-emitting unit 2. Here, since the n-type graphene quantum dots have rich surface states, when the carrier injection layer 31 and the n-type carrier generation layer are in contact, the potential distribution of the contact interface can be improved, thereby reducing the electron transfer resistance.

[0130] Furthermore, the absolute value of the LUMO energy level of the n-type semiconductor material is ≥4.5 eV.

[0131] In this embodiment, the absolute value of the LUMO energy level of the n-type semiconductor material ≥4.5 eV is helpful to improve the charge generation efficiency.

[0132] Further, the p-type semiconductor material includes a host material and a guest material, and the host material is selected from PEDOT (poly 3,4-ethylenedioxythiophene), TFB (poly [(9,9-dioctylfluorenyl-2,7-diyl)-CO-(4,4'-(N-(p-butylphenyl))biphenyl), Poly-TPD (polytriphenylamine), VNPB (N4, N4'-di(naphthalen-1-yl)-N4, N4'-bis(4-vinylphenyl)biphenyl 1-4,4'-diamine), PTAA (poly [bis(4-phenyl)(2,4,6-trimethylphenyl)amine]), 1F-PTAA (poly(bis(4-phenyl)(4-fluoro-2-methylphenyl)amine), VB- At least one of FNPD (9,9-bis[4-[(4-vinylphenyl 1) methoxy] phenyl 1]-N2, N7-di-1-naphthyl 1-N2, N7-diphenyl 1-9H-F-fluorene-2,7-diamine), QUPD (N4, N4'-bis(4-(6-(3-ethylloracetam-3-ylmethoxy)hexyloxy)phenyl 1)-N4, N4'-bis(4-methoxyphenyl 1)biphenyl 1-4, 4'-diamine), OTPD (N4, N4'-bis(4-(6-((3-ethylloracetam-3-ylmethoxy)hexyl)phenyl)-N4, N4'-diphenylbiphenyl 1-4, 4'-diamine), CuSCN, and NiO; the guest material is selected from MoO 3 Nanoparticles, WO 3 Nanoparticles, molybdenum ethoxide, tungsten ethoxide, phosphomolybdic acid, phosphotungstic acid, ammonium metavanadate, ammonium metatungstate, ammonium molybdate, sulfuric acid, benzenesulfonic acid, pentafluorobenzenesulfonic acid, polystyrenesulfonic acid, FeCl 3 、AsCl 3 、SbCl 5 、AuCl 3 , BCF, Magic-blue, HATCN, F6TCNQ, CN6-CP, NDP-9, Mo(tfd)3, Mo(tfd-COCF3)3, Mo(tfd-CO2Me)3, etc.

[0133] In this embodiment, the carrier injection layer 31 has a large carrier concentration. After the carrier generation layer is prepared using the above-mentioned main material and guest material, when the carrier injection layer 31 contacts the carrier generation layer containing p-type semiconductor material, the depletion region generated is narrow and has a lower resistance, so that the device has better charge generation capability and lower interface resistance.

[0134] Furthermore, the n-type semiconductor material is selected from MoO 3 Nanoparticles, WO 3 One of nanoparticles, ethoxide molybdenum, ethoxide tungsten, phosphomolybdic acid, phosphotungstic acid, ammonium metavanadate, ammonium metatungstate, ammonium molybdate, HATCN, F6TCNQ, CN6-CP, NDP-9, etc.

[0135] In this embodiment, the carrier injection layer 31 has a large carrier concentration. After the carrier generation layer is prepared using the above-mentioned material, when the carrier injection layer 31 contacts the carrier generation layer containing n-type semiconductor material, the depletion region generated is narrow and has a lower resistance, so that the device has better charge generation capability and lower interface resistance.

[0136] Further, the first light-emitting unit 2 includes a first light-emitting layer, one side of the first light-emitting layer is close to the first electrode, and the other side of the first light-emitting layer is close to the carrier injection layer; and / or

[0137] The second light-emitting unit 4 includes a second light-emitting layer, one side of the second light-emitting layer is close to the carrier generating layer, and the other side is close to the second electrode; and / or

[0138] The first light-emitting unit 2 further includes a first hole functional layer and / or a first electron functional layer, wherein the first hole functional layer is disposed between the first electrode and the light-emitting layer, and the first electron functional layer is disposed between the light-emitting layer and the carrier injection layer; and / or

[0139] The second light-emitting unit 4 further includes a second hole functional layer and / or a second electron functional layer, wherein the second hole functional layer is disposed between the carrier generating layer and the second light-emitting layer, and the second electron functional layer is disposed between the second light-emitting layer and the second electrode.

[0140] In this embodiment, when the material of the carrier generation layer 32 is an n-type semiconductor material, a PN heterojunction is formed between the carrier generation layer 32 and the second hole functional layer.

[0141] Further, the first electronic functional layer and the second electronic functional layer independently include an electron transport layer, and the material of the electron transport layer includes an inorganic material and / or an organic material; the inorganic material is selected from one or more of doped or undoped zinc oxide, barium oxide, aluminum oxide, titanium oxide, tin oxide, tantalum oxide, zirconium oxide, nickel oxide, lithium titanium oxide, zinc aluminum oxide, zinc manganese oxide, zinc tin oxide, lithium zinc oxide, indium tin oxide, cadmium sulfide, zinc sulfide, molybdenum sulfide, tungsten sulfide, copper sulfide, zinc tin, indium phosphide, gallium phosphide, copper indium sulfide, copper gallium sulfide, and barium titanate, and the doped elements include one or more of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium.

[0142] Further, the first hole functional layer and the second hole functional layer independently include a hole transport layer, the material of the hole transport layer includes at least one of an organic hole transport material and an inorganic hole transport material, and the organic material having hole transport capability includes poly(9,9-dioctylfluorene-co-N-(4-butylphenyl) diphenylamine) (TFB), polyvinylcarbazole (PVK), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl) benzidine) (poly-TPD), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1, At least one of: 4-phenylenediamine (PFB), 4,4',4"-tri(carbazole-9-yl)triphenylamine (TCATA), 4,4'-di(9-carbazole)biphenyl (CBP), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), doped graphene, undoped graphene and C60, wherein the inorganic material having hole transport capability comprises doped or undoped NiO, WO 3 、MoO 3 and at least one of CuO.

[0143] Further, the first light-emitting layer and the second light-emitting layer independently include a quantum dot light-emitting layer or an organic light-emitting layer; the material of the quantum dot light-emitting layer includes at least one of a single structure quantum dot and a core-shell structure quantum dot, and the material of the single structure quantum dot is selected from at least one of a II-VI group compound, a IV-VI group compound, a III-V group compound and a I-III-VI group compound, wherein the II-VI group compound is selected from CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, C At least one of dSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe and HgZnSTe, wherein the IV-VI group compound is selected from Sn At least one of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe and SnPbSTe, and the III-V group compound is selected from GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, G At least one of aPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs or InAlPSb, wherein the I-III-VI group compound is selected from CuInS 2 、CuInSe 2 AgInS 2 At least one of; and / or

[0144] The core of the core-shell structure quantum dot includes any one of the single structure quantum dots, and the shell material of the core-shell structure quantum dot includes at least one of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS and the single structure quantum dots; the material of the organic light-emitting layer includes at least one of 4,4'-bis(N-carbazole)-1,1'-biphenyl:tris[2-(p-tolyl)pyridine-C2,N)iridium(III), 4,4',4"-tri(carbazole-9-yl)triphenylamine:tris[2-(p-tolyl)pyridine-C2,N)iridium, diaromatic anthracene derivatives, distyrene aromatic derivatives, pyrene derivatives, fluorene derivatives, TBPe fluorescent materials, TTPX fluorescent materials, TBRb fluorescent materials and DBP fluorescent materials, polyacetylene and its derivatives, polyparaphenylene and its derivatives, polythiophene and its derivatives, polyfluorene and its derivatives.

[0145] Further, the materials of the first electrode 1 and the second electrode 5 independently include one or more of metal, carbon material and metal oxide, the metal includes one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, Yb and Mg; the carbon material includes one or more of graphite, carbon nanotubes, graphene and carbon fiber; the metal oxide includes doped or undoped metal oxide, including one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO and AMO, or includes a composite electrode in which a metal is sandwiched between doped or undoped transparent metal oxides, and the composite electrode includes AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO 2 / Ag / TiO 2 and TiO 2 / Al / TiO 2 One or more of .

[0146] Furthermore, a hole injection layer 6 is provided between the first electrode 1 and the first light-emitting unit 2 .

[0147] The material of the hole injection layer 6 includes at least one of TFB, CuPc, PVK, Poly-TPD, PFB, DNTPD, TCATA, TCCA, CBP, TPD, NPB, NPD, PEDOT:PSS, T·APC, MCC, F4-TCNQ, HATCN, 4,4',4'-tris(N-3-methylphenyl-Nphenylamino)triphenylamine, polyaniline, transition metal oxides, transition metal sulfides, transition metal tinides, doped graphene, undoped graphene and C60.

[0148] Furthermore, an electron injection layer 7 is provided between the second electrode 5 and the second light-emitting unit 4 .

[0149] The material of the electron injection layer 7 includes inorganic materials and / or organic materials; the inorganic material is selected from one or more of doped or undoped zinc oxide, barium oxide, aluminum oxide, titanium oxide, tin oxide, tantalum oxide, zirconium oxide, nickel oxide, lithium titanium oxide, zinc aluminum oxide, zinc manganese oxide, zinc tin oxide, lithium zinc oxide, indium tin oxide, cadmium sulfide, zinc sulfide, molybdenum sulfide, tungsten sulfide, copper sulfide, zinc tin, indium phosphide, gallium phosphide, copper indium sulfide, copper gallium sulfide, and barium titanate, and the doped elements include one or more of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium.

[0150] The present application also provides a method for preparing a charge generating unit. Figure 3 As shown, the method comprises the following steps:

[0151] S11, providing a light-emitting device preform, wherein the light-emitting device preform comprises a first electrode and a first light-emitting unit which are arranged in sequence;

[0152] S12, placing a carrier injection material solution on the first light-emitting unit to prepare a carrier injection layer;

[0153] S13, preparing a carrier generation layer on the carrier injection layer;

[0154] S14, preparing a second light-emitting unit and a second electrode on the carrier generating layer to obtain a light-emitting device;

[0155] Wherein, the carrier injection material solution includes a carrier injection material, and the carrier injection material includes n-type graphene.

[0156] In this embodiment, n-type graphene is resistant to acid and alkali. The present application adopts n-type graphene quantum dots as the carrier injection layer, so that when the carrier injection layer and the carrier generation layer are stacked, it can not only prevent being destroyed by the hole injection material, but also generate charges, so as to obtain a charge generation unit (i.e., carrier injection layer + carrier generation layer) with better electrical transmission performance, thereby improving the luminous efficiency and service life of the light-emitting device.

[0157] Furthermore, the step S12, arranging a carrier injection material solution on the first light-emitting unit to prepare a carrier injection layer, specifically includes:

[0158] Placing a carrier injection material solution on the first light-emitting unit to obtain a first precursor film;

[0159] The first precursor film is annealed to obtain the carrier injection layer.

[0160] Furthermore, the carrier injection material solution also includes a first solvent, and the first solvent is selected from at least one of alcohols, ethers, and ketones.

[0161] Specifically, the first solvent is selected from n-butanol, n-pentanol, n-hexanol, n-heptanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, cyclohexanone, methyl ethyl ketone and the like.

[0162] Furthermore, the mass concentration of the carrier injection material solution is 1% to 10%.

[0163] In some optional implementations of this embodiment, the mass concentration of the carrier injection material solution is any one of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., or a range between any two of them.

[0164] In this embodiment, the temperature of the first annealing treatment is 100-200° C., and the time is 5-60 minutes.

[0165] In some optional implementations of this embodiment, the temperature of the first annealing treatment is any one of 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, etc., or a range between any two of them.

[0166] In some optional implementations of this embodiment, the time of the first annealing treatment is any one of 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, etc., or a range between any two of them.

[0167] Furthermore, the carrier injection material solution also includes a modifier.

[0168] Furthermore, the step S13, the step of preparing a carrier generation layer on the carrier injection layer, specifically comprises:

[0169] placing a carrier generating material solution on the carrier injection layer to obtain a second precursor film;

[0170] The second precursor film is subjected to a second annealing treatment to obtain the carrier generation layer.

[0171] Furthermore, the carrier generating material solution includes a second solvent, and the second solvent is selected from at least one of alcohols and nitriles.

[0172] Specifically, the second solvent is selected from at least one of ethanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, acetonitrile, propionitrile, benzonitrile, xylene, chlorobenzene, cyclohexylbenzene and tetralin.

[0173] Furthermore, the mass concentration of the carrier generating material solution is 1% to 10%.

[0174] In some optional implementations of this embodiment, the mass concentration of the carrier generating material solution is any one of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., or a range between any two of them.

[0175] In this embodiment, the temperature of the second annealing treatment is 100-200° C., and the time is 5-60 minutes.

[0176] In some optional implementations of this embodiment, the temperature of the second annealing treatment is any one of 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, etc., or a range between any two of them.

[0177] In some optional implementations of this embodiment, the time of the second annealing treatment is any one of 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, etc., or a range between any two of them.

[0178] Furthermore, the n-type graphene is n-type graphene quantum dots.

[0179] In this embodiment, the n-type graphene quantum dots can be regarded as cut-out fragments of graphene in terms of structure, and have abundant functional groups and surface states, as well as relatively good carrier concentration.

[0180] In this embodiment, the unique structural characteristics of n-type graphene quantum dots, such as rich functional groups and surface states, as well as relatively excellent carrier concentration, are utilized to improve the potential distribution of the contact interface when the n-type graphene quantum dots are in contact (adjacent) with the carrier generation layer using hole injection material, thereby reducing the electron transfer resistance of the carrier generation layer, so that the electrons generated in the PN heterojunction can be injected into the first light-emitting unit through the n-type graphene quantum dots.

[0181] In this embodiment, the n-type graphene quantum dots have a flake structure, good film morphology, and more surface states. Compared with ordinary quantum dots, the n-type graphene quantum dots have better electrical transmission performance.

[0182] Furthermore, the average particle size of the n-type graphene is less than 20 nm.

[0183] In this embodiment, the average particle size of n-type graphene is less than 20 nm, so that it can be applied to the solution method, and the film quality can be guaranteed without affecting the energy level structure of the material.

[0184] In some optional implementations of this embodiment, the average particle size of the n-type graphene is any one of 1 nm, 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, etc., or a range between any two of them.

[0185] Further, the n-type graphene quantum dots include at least one of n-type graphene quantum dots and doped n-type graphene quantum dots; the doped n-type graphene quantum dots include at least one of n-type graphene quantum dots doped with N atoms and n-type graphene quantum dots doped with S atoms;

[0186] In the n-type graphene quantum dots doped with N atoms, the mass ratio of the N atoms to the n-type graphene quantum dots is (1:20) to (1:100); and / or

[0187] In the n-type graphene quantum dots doped with S atoms, the mass ratio of the S atoms to the n-type graphene quantum dots is (1:20) to (1:100).

[0188] In this embodiment, the doping of N atoms and S atoms belongs to N-type doping, and the energy level, defect state energy level and mobility of n-type graphene quantum dots can be adjusted after doping. The doping of S atoms and N atoms will affect the energy level and mobility of n-type graphene quantum dots. The material selection can be carried out according to actual needs, and this application is not limited here.

[0189] Furthermore, the mass ratio of the N atoms to the n-type graphene quantum dots is (1:20) to (1:100).

[0190] In some optional implementations of this embodiment, the mass ratio of the N atoms to the n-type graphene quantum dots is any one of 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, etc., or a range between any two of them.

[0191] Furthermore, the mass ratio of the S atoms to the n-type graphene quantum dots is (1:20) to (1:100).

[0192] In some optional implementations of this embodiment, the mass ratio of the S atoms to the n-type graphene quantum dots is any one of 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, etc., or a range between any two of them.

[0193] Furthermore, the light transmittance of the carrier generation layer is greater than 70%.

[0194] In this embodiment, the light transmittance of the carrier generating layer is greater than 70%, which is easy to improve the light emitting efficiency of the light emitting device.

[0195] Furthermore, the peak wavelength of the light that can be transmitted through the carrier generation layer is 380-780 nm.

[0196] In this embodiment, the peak wavelength of 380-780 nm is the wavelength range of visible light, and the carrier generation layer has a transmittance greater than 70% at the peak wavelength of 380-780 nm, which can easily improve the luminous efficiency of the light-emitting device.

[0197] Furthermore, the light transmittance of the carrier injection layer is greater than 70%.

[0198] In this embodiment, the light transmittance of the carrier injection layer is greater than 70%, which is easy to improve the light emitting efficiency of the light emitting device.

[0199] Furthermore, the peak wavelength of the light that can be transmitted through the carrier injection layer is 440-650 nm.

[0200] In this embodiment, the peak wavelength of 440 to 650 nm is the wavelength range of visible light, and the carrier generation layer has a transmittance greater than 70% at the peak wavelength of 440 to 650 nm, which can easily improve the luminous efficiency of the light-emitting device.

[0201] It can be understood that the light transmittance is the ability of light to pass through a medium, specifically the ratio of the light flux passing through the medium to the incident light flux. In this embodiment, the light intensity before passing through the carrier injection layer 31 or the carrier generation layer 32 is defined as l 0, the light intensity after passing through the carrier injection layer 31 or the carrier generation layer 32 is l t , then the light transmittance is l t / l 0 .

[0202] Furthermore, the thickness ratio of the carrier injection layer to the carrier generation layer is (5-50):(10-150).

[0203] In some optional implementations of this embodiment, the thickness ratio of the carrier injection layer to the carrier generation layer is 5:10, 5:50, 5:100, 5:150, 10:10, 10:50, 10:100, 10:150, 20:10, 20:50, 20:100, 20:150, 30:10, 30:50, 30:100, 30:150, 40:10, 40:50, 40:100, 40:150, 50:10, 50:50, 50:100, 50:150, etc., or a range between any two of them.

[0204] Furthermore, the carrier generation layer has a thickness of 10 to 150 nm.

[0205] In some optional implementations of this embodiment, the thickness of the carrier generation layer 12 is any one of 10 nm, 30 nm, 50 nm, 70 nm, 90 nm, 110 nm, 130 nm, 150 nm, etc., or in the range between any two of them.

[0206] Furthermore, the carrier injection layer has a thickness of 5 to 50 nm.

[0207] In some optional implementations of this embodiment, the thickness of the carrier injection layer is any one of 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc., or in the range between any two of them.

[0208] An embodiment of the present application further provides a display device, which includes the light-emitting device as described above, or includes a light-emitting device manufactured using the manufacturing method as described above.

[0209] In this embodiment, n-type graphene quantum dots are used as the carrier injection layer, which can prevent the carrier injection layer from being destroyed by the hole injection material to obtain a charge generation unit with charge separation and better injection performance, thereby improving the luminous efficiency and service life of the light-emitting device.

[0210] The above scheme is further described below in conjunction with specific implementation examples. The preferred embodiments of the present invention are described in detail as follows:

[0211] Example 1

[0212] Preparation of graphene: 1.35 g of polyethyleneimine (PEI) was thoroughly mixed with deionized water (3.5 mL), and then 2.30 g of glucosamine was added and dissolved by ultrasound at a frequency of 25 kHz for 5 min, and kept at 40 °C for 1 h. It was then poured into a PTFE cup and sealed in a Par acid digestion container and treated in a microwave oven at a power of 700 W for 7 s. The reaction container was then cooled at 4 °C for 30 min to obtain a brown solution of GQDs, which was then dispersed in methanol after reduced pressure drying.

[0213] Device preparation: The ITO anode substrate was cleaned and then treated under UV conditions for 15 minutes to increase its work function and wettability; then, a 30nm thick PEDOT:PSS was spin-coated on the treated ITO substrate and baked at 150°C for 20 minutes in an air atmosphere; then, TFB was spin-coated on the PEDOT:PSS substrate to form a first hole functional layer (hole transport layer) with a thickness of 30nm, and then baked at 180°C for 60 minutes in a nitrogen environment; then, a 60nm thick polymer light-emitting layer F8BT was spin-coated on the substrate as the first light-emitting layer, and baked at 150°C for 10 minutes; then, a carrier injection material solution was spin-coated on the first light-emitting layer, and annealed at 120°C for 10 minutes to form a 10nm thick carrier injection layer, and component 1 in the carrier generation material solution was n-type with a particle size of 5nm. Type graphene, component 2 modifier is PEI (Mw10000), the mass ratio of component 1 to component 2 is 1:0.2, and the concentration is 15 mg / mL; then a carrier generating material solution is spin-coated thereon, and annealed at 120°C for 20 min to obtain a 10 nm thick carrier generating layer, wherein in the carrier generating material solution, the carrier generating material is phosphomolybdic acid (n-type semiconductor material) with a concentration of 15 mg / mL; then TFB is spin-coated to form a second hole transport layer with a thickness of 30 nm, and baked at 180°C for 60 min; then a 60 nm thick polymer light-emitting layer F8BT is spin-coated on the substrate as the second light-emitting layer, and baked at 150°C for 10 min; finally, 1 nm of LiF is vacuum evaporated as the second electron transport layer and a 100 nm thick Al electrode is packaged and annealed at 80°C for 30 min.

[0214] Embodiment 2:

[0215] The difference from Example 1 is that the mass ratio of component 1 to component 2 is 1.5:1.

[0216] Embodiment 3:

[0217] The difference from Example 1 is that the mass ratio of component 1 to component 2 is 1:1.5.

[0218] Embodiment 4:

[0219] The difference from Example 1 is that phosphomolybdic acid is replaced by PEDOT:PSS (p-type semiconductor material).

[0220] Example 5 :

[0221] The difference from Example 1 is that the proportion of component 2 is 0.

[0222] Comparative Example 1:

[0223] The difference from Example 1 is that the carrier injection layer is replaced by ZnO.

[0224] Embodiment 6:

[0225] The preparation of graphene is the same as in Example 1;

[0226] Device preparation process: the ITO anode substrate is cleaned and then treated under UV conditions for 15 minutes to increase its work function and wettability; then, a 50nm thick PEDOT:PSS is spin-coated on the treated ITO substrate and baked at 150°C for 20 minutes in an air atmosphere; then, TFB is spin-coated on the PEDOT:PSS substrate to form a first hole functional layer (hole transport layer) with a thickness of 30nm, and then baked at 160°C for 30 minutes in a nitrogen environment; then, a 20nm thick green light QDs ink is spin-coated on the substrate and baked at 100°C for 10 minutes to form a first light-emitting layer; then, a carrier injection material solution is spin-coated on the first light-emitting layer and annealed at 120°C for 10 minutes to form a 20nm thick carrier injection layer, in which component 1 of the carrier generation material solution is n-type graphene with a particle size of 5nm, and component 2 is a modifier The method comprises the following steps: the first step is to prepare a PEI film having a Mw of 10,000 and a mass ratio of component 1 to component 2 of 1:0.2 and a concentration of 15 mg / mL; the second step is to spin-coat a carrier generating material solution and anneal at 120°C for 20 min to obtain a 20 nm thick carrier generating layer, wherein the carrier generating material in the carrier generating material solution is phosphomolybdic acid (n-type semiconductor material) and the concentration is 15 mg / mL; the second step is to spin-coat a 30 nm thick TFB and bake at 120°C for 30 min to form a second hole functional layer (hole transport layer); the second step is to spin-coat a 20 nm thick green light QDs ink and bake at 100°C for 15 min to form a second light-emitting layer; the second step is to spin-coat a 30 nm thick ZnO as a second electron transport layer and anneal at 100°C for 10 min; the second step is to vacuum-evaporate a 100 nm thick Al electrode, and finally encapsulate and anneal at 100°C for 30 min.

[0227] Embodiment 7:

[0228] The difference from Example 6 is that the mass ratio of component 1 to component 2 is 1.5:1.

[0229] Embodiment 8:

[0230] The difference from Example 6 is that the mass ratio of component 1 to component 2 is 1:1.5.

[0231] Embodiment 9:

[0232] The difference from Example 6 is that phosphomolybdic acid is replaced by PEDOT:PSS (p-type semiconductor material).

[0233] Embodiment 10:

[0234] The difference from Example 6 is that the proportion of component 2 is 0.

[0235] Comparative Example 2:

[0236] The difference from Example 6 is that the carrier injection layer is replaced by ZnO.

[0237] Experimental test analysis: The light emitting devices prepared in Examples 1 to 10 and Comparative Examples 1 to 2 were subjected to experimental test analysis. The analysis results are shown in Table 1.

[0238] Table 1

[0239]

[0240]

[0241] Among them, the voltage when the current density is 10mA / cm2 (J10) is used as the driving voltage index, the current efficiency when the brightness is 1000nit is used as the efficiency index, and the time when the brightness decays to 95% under constant current conditions from the initial brightness of 1000nit is used as the life evaluation index.

[0242] It can be seen from Examples 1 to 3 and Example 5 in Table 1 that in the OLED light-emitting device, when the mass ratio of n-type graphene to the modifier is 1:0.2, the driving voltage of the light-emitting device is the lowest, which means that the charge generation unit can efficiently inject the charge generated by the charge generation layer into the light-emitting units on both sides. At the same time, it can be seen from Examples 6 to 8 and Example 10 in Table 1 that in the QLED light-emitting device, controlling the amount of modifier added can make the device have better performance, which also reflects that the electrons in the QLED system have a smaller injection barrier than the OLED.

[0243] It can be seen from Example 4 and Comparative Example 1 in Table 1 that in the OLED light-emitting device, even when the carrier generation layer is a p-type carrier generation layer, the driving voltage of the light-emitting device in Example 4 is still lower than that in Comparative Example 1, which means that the charge generation unit can efficiently inject the charge generated by the charge generation layer into the light-emitting units on both sides. At the same time, it can be seen from Example 9 and Comparative Example 2 in Table 1 that in the QLED light-emitting device, even when the carrier generation layer is a p-type carrier generation layer, the driving voltage of the light-emitting device is still lower than that in Comparative Example 2, which means that the charge generation unit can efficiently inject the charge generated by the charge generation layer into the light-emitting units on both sides.

[0244] It can be seen from Example 1 and Comparative Example 1 in Table 1 that in the OLED light-emitting device, only metal oxide is used as the carrier injection layer, resulting in the driving voltage of the light-emitting device in Comparative Example 1 being higher than the driving voltage of Example 1, and the current efficiency and service life of Comparative Example 1 being much lower than those of Example 1; indicating that the use of a carrier injection layer containing n-type graphene has improved performance in the light-emitting device. At the same time, it can be seen from Example 6 and Comparative Example 2 in Table 1 that in the QLED light-emitting device, only metal oxide is used as the carrier injection layer, resulting in the driving voltage of the light-emitting device in Comparative Example 2 being higher than the driving voltage of Example 6, and the current efficiency and service life of Comparative Example 2 being much lower than those of Example 6; indicating that the use of a carrier injection layer containing n-type graphene has improved performance in the light-emitting device.

[0245] Obviously, the embodiments described above are only some embodiments of the present application, rather than all embodiments. The preferred embodiments of the present application are given in the accompanying drawings, but they do not limit the patent scope of the present application. The present application can be implemented in many different forms. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive. Although the present application is described in detail with reference to the aforementioned embodiments, for those skilled in the art, it is still possible to modify the technical solutions recorded in the aforementioned specific implementation methods, or to perform equivalent replacement of some of the technical features therein. Any equivalent structure made using the contents of the specification and drawings of this application, directly or indirectly used in other related technical fields, is similarly within the scope of patent protection of this application.

Claims

1. A light emitting device, characterized in that: It includes a first electrode, a first light-emitting unit, a charge generating unit, a second light-emitting unit and a second electrode which are sequentially stacked; The charge generation unit includes a carrier injection layer and a carrier generation layer which are stacked, wherein the carrier injection layer is arranged close to the first light-emitting unit, and the carrier generation layer is arranged close to the second light-emitting unit; The material of the carrier injection layer includes n-type graphene.

2. The light emitting device according to claim 1, characterized in that: The n-type graphene is n-type graphene quantum dots; and / or The average particle size of the n-type graphene is less than 20 nm; and / or The light transmittance of the carrier generation layer is greater than 70%; and / or The light transmittance of the carrier injection layer is greater than 70%; and / or The thickness ratio of the carrier injection layer to the carrier generation layer is (5-50):(10-150).

3. The light emitting device according to claim 2, characterized in that: The peak wavelength of the light that can be transmitted through the carrier generation layer is 380 to 780 nm; and / or The peak wavelength of the light that can be transmitted through the carrier injection layer is 440 to 650 nm; and / or The n-type graphene quantum dots include at least one of n-type graphene quantum dots and doped n-type graphene quantum dots; the doped n-type graphene quantum dots include at least one of n-type graphene quantum dots doped with N atoms and n-type graphene quantum dots doped with S atoms; In the n-type graphene quantum dots doped with N atoms, the mass ratio of the N atoms to the n-type graphene quantum dots is (1:20) to (1:100); and / or In the n-type graphene quantum dots doped with S atoms, the mass ratio of the S atoms to the n-type graphene quantum dots is (1:20) to (1:100).

4. The light emitting device according to claim 1, characterized in that: The material of the carrier injection layer also includes a modifier.

5. The light emitting device according to claim 4, characterized in that: The mass ratio of the n-type graphene to the modifier is selected from 1:0 to 1:1; and / or The modifier is a fatty amine modifier, and the fatty amine modifier is selected from at least one of polyethylene imine, polyethoxyethylene imine, and polyether amine; and / or The mass average molecular weight Mw of the modifier is >1000.

6. The light emitting device according to claim 1, characterized in that: The material of the carrier generation layer is a p-type semiconductor material or an n-type semiconductor material; When the material of the carrier generation layer is a p-type semiconductor material, a PN heterojunction is formed between the carrier generation layer and the carrier injection layer; or When the material of the carrier generation layer is an n-type semiconductor material, a PN heterojunction is formed between the carrier generation layer and the second light-emitting unit.

7. The light emitting device according to claim 6, characterized in that: The p-type semiconductor material includes a host material and a guest material, wherein the host material is selected from at least one of PEDOT, TFB, Poly-TPD, VNPB, PTAA, 1F-PTAA, VB-FNPD, QUPD, OTPD, CuSCN, and NiO; the guest material is selected from at least one of MoO3 nanoparticles, WO3 nanoparticles, ethoxide molybdenum, ethoxide tungsten, phosphomolybdic acid, phosphotungstic acid, ammonium metavanadate, ammonium metatungstate, ammonium molybdate, sulfuric acid, benzenesulfonic acid, pentafluorobenzenesulfonic acid, polystyrenesulfonic acid, FeCl3, AsCl3, SbCl5, AuCl3, BCF, Magic-blue, HATCN, F6TCNQ, CN6-CP, NDP-9, Mo(tfd)3, Mo(tfd-COCF3)3, and Mo(tfd-CO2Me)3; or, The n-type semiconductor material is selected from one of MoO3 nanoparticles, WO3 nanoparticles, molybdenum ethoxide, tungsten ethoxide, phosphomolybdic acid, phosphotungstic acid, ammonium metavanadate, ammonium metatungstate, ammonium molybdate, HATCN, F6TCNQ, CN6-CP, and NDP-9; and / or The absolute value of the LUMO energy level of the n-type semiconductor material is ≥4.5 eV.

8. The light emitting device according to claim 1, characterized in that: The first light-emitting unit includes a first light-emitting layer, one side of the first light-emitting layer is close to the first electrode, and the other side of the first light-emitting layer is close to the carrier injection layer; and / or The second light-emitting unit comprises a second light-emitting layer, one side of the second light-emitting layer is close to the carrier generation layer, and the other side is close to the second electrode; and / or The first light-emitting unit further includes a first hole functional layer and / or a first electron functional layer, the first hole functional layer is arranged between the first electrode and the light-emitting layer, and the first electron functional layer is arranged between the light-emitting layer and the carrier injection layer; and / or The second light-emitting unit further includes a second hole functional layer and / or a second electron functional layer, wherein the second hole functional layer is disposed between the carrier generating layer and the second light-emitting layer, and the second electron functional layer is disposed between the second light-emitting layer and the second electrode.

9. A method for preparing a light emitting device, characterized in that: The following steps are involved: Providing a light-emitting device preform, wherein the light-emitting device preform comprises a first electrode and a first light-emitting unit arranged in sequence; Placing a carrier injection material solution on the first light-emitting unit to prepare a carrier injection layer; preparing a carrier generation layer on the carrier injection layer; Sequentially preparing a second light-emitting unit and a second electrode on the carrier generation layer to obtain a light-emitting device; Wherein, the carrier injection material solution includes a carrier injection material, and the carrier injection material includes n-type graphene.

10. The method for preparing a light emitting device according to claim 9, characterized in that: The step of providing a carrier injection material solution on the first light-emitting unit to prepare a carrier injection layer specifically includes: Placing a carrier injection material solution on the first light-emitting unit to obtain a first precursor film; performing a first annealing treatment on the first precursor film to obtain the carrier injection layer; and / or The step of preparing a carrier generation layer on the carrier injection layer specifically includes: placing a carrier generating material solution on the carrier injection layer to obtain a second precursor film; The second precursor film is subjected to a second annealing treatment to obtain the carrier generation layer.

11. The method for preparing a light emitting device according to claim 9, characterized in that: The n-type graphene is n-type graphene quantum dots; and / or The average particle size of the n-type graphene is less than 20 nm; and / or The light transmittance of the carrier generation layer is greater than 70%; and / or The light transmittance of the carrier injection layer is greater than 70%; and / or The thickness ratio of the carrier injection layer to the carrier generation layer is (5-50):(10-150).

12. The method for preparing a light emitting device according to claim 11, characterized in that: The peak wavelength of the light that can be transmitted through the carrier generation layer is 380 to 780 nm; and / or The peak wavelength of the light that can be transmitted through the carrier injection layer is 440 to 650 nm; and / or The n-type graphene quantum dots include at least one of n-type graphene quantum dots and doped n-type graphene quantum dots; the doped n-type graphene quantum dots include at least one of n-type graphene quantum dots doped with N atoms and n-type graphene quantum dots doped with S atoms; In the n-type graphene quantum dots doped with N atoms, the mass ratio of the N atoms to the n-type graphene quantum dots is (1:20) to (1:100); and / or In the n-type graphene quantum dots doped with S atoms, the mass ratio of the S atoms to the n-type graphene quantum dots is (1:20) to (1:100).

13. The method for preparing a light emitting device according to claim 10, characterized in that: The carrier injection material solution further comprises a first solvent, wherein the first solvent is selected from at least one of an alcohol solvent, an ether solvent and a ketone solvent; and / or The first solvent is selected from at least one of n-butanol, n-pentanol, n-hexanol, n-heptanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, cyclohexanone and methyl ethyl ketone; and / or The mass concentration of the carrier injection material solution is 1% to 10%; and / or The carrier injection material solution further includes a modifier; and / or The mass ratio of the n-type graphene to the modifier is selected from 1:0 to 1:

1.

14. The method for preparing a light emitting device according to claim 10, characterized in that: The carrier generating material solution includes a carrier generating material and a second solvent, wherein the carrier generating material includes a p-type semiconductor material or an n-type semiconductor material; and / or The second solvent is selected from at least one of an alcohol solvent and a nitrile solvent; and / or The second solvent is selected from at least one of ethanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, acetonitrile, propionitrile, benzonitrile, xylene, chlorobenzene, cyclohexylbenzene and tetralin; The mass concentration of the carrier generating material solution is 1% to 10%.

15. The method for preparing a light emitting device according to claim 10, characterized in that: The temperature of the first annealing treatment is 100-200° C.; and / or The first annealing treatment lasts for 5 to 60 minutes; and / or The temperature of the second annealing treatment is 100-200° C.; and / or The second annealing treatment lasts for 5 to 60 minutes.

16. A display device, characterized in that: The invention comprises a light-emitting device as claimed in any one of claims 1 to 8, or comprises a light-emitting device manufactured by the manufacturing method as claimed in any one of claims 9 to 15.

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