A quantum dot light-emitting diode, a light-emitting device

Abstract

The present application provides a quantum dot light-emitting diode, which includes a cathode, an electron transport layer, a first electroluminescent layer to an nth electroluminescent layer, a hole transport layer, and an anode that are sequentially stacked. n is an integer and n≥2. At least one of the first electroluminescent layer to the nth electroluminescent layer contains a first quantum dot, and the first quantum dot includes a core body and ZnS 1‑x O x a surface shell layer, where 0<x≤1. The first quantum dot of the present application can not only effectively improve the current efficiency, brightness, and external quantum efficiency of the quantum dot light-emitting diode, but also enable the quantum dot light-emitting diode to have a long service life.

Description

Technical Field

[0001] This application belongs to the field of display technology, and particularly relates to a quantum dot light-emitting diode and a light-emitting device. Background Art

[0002] Quantum dots, also known as semiconductor nanocrystals, are a new type of semiconductor nanomaterial with a size of 1 - 10 nm. Due to the quantum size effect and dielectric confinement effect, they have unique photoluminescence (PL) and electroluminescence (EL) properties. Compared with traditional organic fluorescent dyes, quantum dots have excellent optical properties such as high quantum efficiency, high photochemical stability, not easily photolyzed, wide excitation, narrow emission, high color purity, and the emission color can be adjusted by controlling the size of quantum dots, and thus have broad application prospects in the field of display technology.

[0003] A quantum dot light-emitting diode (QLED) is a device that electrically excites quantum dots to emit light. Compared with traditional organic light-emitting diodes (OLEDs), QLEDs have more excellent characteristics such as color purity, brightness, and viewing angle. Quantum dots can be dispersed in organic solvents to form inks, and light-emitting films can be fabricated by methods such as inkjet printing, spin coating, and blade coating, which are particularly suitable for preparing large-area devices by solution methods. Therefore, the market prospect of QLEDs is very promising.

[0004] Common QLED devices generally adopt a structure with an anode, a hole transport layer, a quantum dot electroluminescent layer, an electron transport layer, and a cathode stacked in sequence from bottom to top. Through the improvement of quantum dot materials and the continuous optimization of the QLED device structure, the luminescence performance of existing QLED devices has been greatly improved, but there are still some performances that do not meet the requirements, especially there is still a certain gap between the device lifetime and the requirements of industrial production. Therefore, it is urgent to continue to optimize the structure of quantum dot light-emitting diodes and improve the performance to promote the faster commercialization of quantum dot light-emitting diodes. Summary of the Invention

[0005] In view of the above technical problems, this application provides a quantum dot light-emitting diode, which includes a cathode, an electron transport layer, a first to an nth electroluminescent layer, a hole transport layer, and an anode stacked in sequence, where n is an integer and n≥2;

[0006] Among them, at least one of the first to the nth electroluminescent layers contains a first quantum dot, and the first quantum dot includes a core and a ZnS 1-x O x surface shell layer, 0 < x ≤ 1.

[0007] Further, each layer from the first electroluminescent layer to the nth electroluminescent layer contains the first quantum dots, and in any two adjacent layers in the direction from the first electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots is the same or increases layer by layer.

[0008] Further, in the first electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots increases layer by layer.

[0009] Further, the thickness of the first electroluminescent layer is 5 - 20 nm.

[0010] Further, the first electroluminescent layer contains second quantum dots, the second quantum dots contain the core and a ZnS surface shell layer, each layer from the second electroluminescent layer to the nth electroluminescent layer contains the first quantum dots, and in any two adjacent layers in the direction from the second electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots is the same or increases layer by layer.

[0011] Further, in the second electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots increases layer by layer.

[0012] Further, the thickness of the second electroluminescent layer is 5 - 20 nm.

[0013] Further, the sum of the thicknesses of the first electroluminescent layer to the nth electroluminescent layer is 20 - 60 nm.

[0014] Further, the core includes at least one of II-VI group compounds, III-V group compounds, IV-VI group compounds, I-III-VI group compounds, and I-II-IV-VI group compounds.

[0015] This application also provides a light-emitting device including the above-mentioned quantum dot light-emitting diode.

[0016] Beneficial effects: The quantum dot light-emitting diode of this application includes a cathode, an electron transport layer, the first electroluminescent layer to the nth electroluminescent layer, a hole transport layer, and an anode that are sequentially stacked, where n is an integer and n ≥ 2; among them, at least one layer from the first electroluminescent layer to the nth electroluminescent layer contains first quantum dots, and the first quantum dots contain a core and ZnS 1-x O xSurface shell, 0 < x ≤ 1; The surface shell in the first quantum dots of the present application is obtained by partially oxidizing the ZnS shell, enabling the energy levels of the quantum dots in each electroluminescent layer to change smoothly, thereby avoiding the large energy level drop caused by using a single layer of quantum dots. Moreover, since the conductivity of quantum dots with different oxidation degrees also varies, the conductivity of the electroluminescent layer can be more effectively controlled and adjusted under the stacked layer design. Therefore, the present application can not only effectively improve the current efficiency, brightness, and external quantum efficiency of the quantum dot light-emitting diode, but also enable the quantum dot light-emitting diode to have a longer service life. Description of the Drawings

[0017] Figure 1 Schematic structural diagram of a quantum dot light-emitting diode in an embodiment of the present application;

[0018] Figure 2 InP / ZnS in the second electroluminescent layer of the quantum dot light-emitting diode in Example 1 of the present application 0.56 O 0.44 Surface energy spectrum analysis diagram of red light quantum dots;

[0019] Figure 3 InP / ZnS in the second electroluminescent layer of the quantum dot light-emitting diode in Example 1 of the present application 0.56 O 0.44 Scanning electron microscope image of red light quantum dots;

[0020] Figure 4 Voltage-brightness comparison diagram of the quantum dot light-emitting diodes in Example 1 of the present application and Comparative Example 1;

[0021] Figure 5 Voltage-external quantum efficiency comparison diagram of the quantum dot light-emitting diodes in Example 1 of the present application and Comparative Example 1. Detailed Description of the Embodiments

[0022] Next, the technical solutions in the embodiments of the present application will be described in detail in combination with the embodiments of the present application. It should be noted that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. If not otherwise defined, all terms (including technical terms and scientific terms) in the specification can be defined as those commonly understood by those skilled in the art. Unless clearly defined, the terms defined in the general dictionary can be interpreted neither idealistically nor exaggeratedly. In addition, unless explicitly described to the contrary, the word "comprising" and variants such as "including" or "containing" will be understood to mean including the stated elements (features), but not excluding any other elements (features).

[0023] In the drawings, for clarity, the thicknesses of layers, films, panels, regions, etc. are exaggerated. Throughout the specification, like reference numerals denote like elements.

[0024] It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, no intervening elements are present.

[0025] Furthermore, unless otherwise noted, the singular includes the plural. As used herein, "a", "one", "the", and "at least one" do not denote a limitation of quantity, but are intended to include both the singular and the plural, unless the context clearly dictates otherwise. For example, unless the context clearly dictates otherwise, "element" has the same meaning as "at least one element". "At least one" is not to be construed as limiting "a" or "one". "Or" means "and / or". As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. It will also be understood that when the terms "comprises" and / or "comprising" or variations thereof are used in this specification, they specify the presence of the stated features, regions, wholes, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or groups thereof.

[0026] It will be understood that although the terms "first", "second", "third", etc. are used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part.

[0027] As described in the background art, some performances of existing QLEDs still cannot meet the application requirements, especially there is still a certain gap between the service life and the requirements of industrial production. The inventors have found that currently the quantum dot electroluminescent layer is a single quantum dot layer, whose conductivity and energy levels are fixed and cannot be adjusted, which to a certain extent limits the electrical performances such as the life, current density, and brightness of QLEDs.

[0028] Based on this, the present application provides a quantum dot light emitting diode, as Figure 1As shown, it includes a cathode 10, an electron transport layer 20, a first electroluminescent layer to an nth electroluminescent layer N stacked in sequence, a hole transport layer 40, and an anode 50, where n is an integer and n≥2; among them, at least one layer of the first electroluminescent layer to the nth electroluminescent layer contains a first quantum dot, and the first quantum dot includes a core and ZnS 1-x O x a surface shell layer, 0<x≤1. The inventor found that the presence of the ZnS 1-x O x surface shell layer on the first quantum dot in this application can effectively regulate the conductivity of the first quantum dot, control the current density of the quantum dot light-emitting diode, and improve the brightness and quantum efficiency of the quantum dot light-emitting diode. Since electrons and holes can recombine on the electroluminescent layer with a gentle energy level transition, the lifespan of the quantum dot light-emitting diode is greatly improved.

[0029] In the first specific embodiment of this application, each layer of the first electroluminescent layer to the nth electroluminescent layer contains the first quantum dot. Among any two adjacent layers from the first electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dot is the same or increases layer by layer, so as to better control the current density in the electroluminescent diode and improve its light-emitting performance.

[0030] In a preferred embodiment, each layer of the first electroluminescent layer to the nth electroluminescent layer contains the first quantum dot, and the x in the first electroluminescent layer is not greater than the x of any layer in the second electroluminescent layer to the nth electroluminescent layer, that is, among each electroluminescent layer, the x of the first electroluminescent layer close to the electron transport layer is the smallest. In fact, x can represent the oxidation degree of the surface shell layer. The inventor found that the oxidation degree of the surface shell layer of the first quantum dot in the first electroluminescent layer close to the electron transport layer is lower than that in other electroluminescent layers, so that the injection speeds of electrons and holes in the electroluminescent layer are more balanced and the recombination efficiency is better. Therefore, compared with a quantum dot light-emitting diode with only one layer of quantum dot electroluminescent layer, the multi-layer electroluminescent layer of this application improves the brightness, quantum efficiency and service life of the quantum dot light-emitting diode.

[0031] In a further second specific embodiment, among the first electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dot increases layer by layer. By controlling the above gradually changing law between the multi-layer electroluminescent layers in this application, it is easier to control the recombination efficiency of holes and electrons in the electroluminescent layer, thereby improving the external quantum efficiency of the quantum dot light-emitting diode and extending the service life of the quantum dot light-emitting diode.

[0032] In a further third specific embodiment, the thickness of the first electroluminescent layer is 5 to 20 nm, that is, the first electroluminescent layer with the smallest degree of oxidation on the side close to the electron transport layer is maintained within a certain thickness range, so that the transport speed of electrons in the first electroluminescent layer is appropriate, and the recombination speed of electrons and holes in the first electroluminescent layer reaches equilibrium, thereby further improving the external quantum efficiency and service life of the quantum dot light-emitting diode. More preferably, the thickness of the first electroluminescent layer is preferably 10 to 15 nm.

[0033] In a fourth specific embodiment of the present application, the first electroluminescent layer contains second quantum dots, the second quantum dots include a core and a ZnS surface shell layer, and each layer from the second electroluminescent layer to the nth electroluminescent layer contains the first quantum dots. In any two adjacent layers in the direction from the second electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots is the same or increases layer by layer, so as to better control the current density in the light-emitting diode and improve its light-emitting performance.

[0034] In a preferred embodiment, among the second electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots in the second electroluminescent layer is the smallest. Specifically, the first electroluminescent layer contains second quantum dots, the second quantum dots include a ZnS outer shell layer, the second electroluminescent layer contains first quantum dots, and the first quantum dots include ZnS 1-x O x Surface shell layer. Such a setting makes the running speed of electrons migrating from the electron transport layer in the first electroluminescent layer and the second electroluminescent layer controllable, and it is easier to control the recombination efficiency of electrons and holes in each electroluminescent layer, improving the external quantum efficiency and service life of the quantum dot light-emitting diode.

[0035] In a further fifth specific embodiment, in the second electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots increases layer by layer. Controlling the above-mentioned gradually changing rule between the second electroluminescent layer and the nth electroluminescent layer can more easily control the recombination efficiency of holes and electrons in the electroluminescent layer, thereby improving the external quantum efficiency of the quantum dot light-emitting diode and extending the service life of the quantum dot light-emitting diode.

[0036] In a further sixth specific embodiment, the thickness of the second electroluminescent layer is 5 to 20 nm. Since the running speed of electrons in the first electroluminescent layer close to the electron transport layer is slower, and the transport rate of holes in the more oxidized quantum dots is faster, it just makes up for the defect that the electron migration rate in the single-layer device is much greater than the hole transport rate. Thus, the recombination speed of electrons and holes in each electroluminescent layer of this application will tend to be balanced, thereby improving the external quantum efficiency and service life of the quantum dot light-emitting diode. Preferably, the thickness of the second electroluminescent layer is preferably 10 to 15 nm.

[0037] In a seventh specific embodiment of this application, the sum of the thicknesses of the first electroluminescent layer to the nth electroluminescent layer is 20 to 60 nm, so that the overall recombination efficiency of electrons and holes in each electroluminescent layer is higher, improving the external quantum efficiency and brightness of the cold quantum dot light-emitting diode. Due to the regular differences in the oxidation degree of the quantum dots between the layers, the running speeds of electrons and holes in the electroluminescent layer are more consistent, thus significantly improving the service life of the quantum dot light-emitting diode. The sum of the thicknesses of the first electroluminescent layer to the nth electroluminescent layer is preferably 20 to 40 nm.

[0038] In the eighth specific embodiment of the present application, the core includes a II-VI compound, a III-V compound, a IV-VI compound, a I-III-VI compound, a I-II-IV-VI compound, or a combination thereof. For example, the II-VI compound may include: CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or a combination thereof. The II-VI compound may further include a Group III metal. The III-V compound may include: GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, InZnP, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or a combination thereof. The III-V compound may further include a Group II metal (e.g., InZnP). The IV-VI compound may include: SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe, or a combination thereof. Examples of the I-III-VI compound may include, but are not limited to, CuInSe2, CuInS2, CuInGaSe, and CuInGaS. Examples of the I-II-IV-VI compound may include, but are not limited to, CuZnSnSe and CuZnSnS.

[0039] In the first quantum dots and second quantum dots of the present application, several shells may be included between the core and the shell layer, and adjacent shell layers may have different compositions from each other. When there are multiple shells, each layer may have a single composition. Several shell layers may have alloys. In the case of multiple shells, the nanocrystals of each layer are selected to have appropriate bandgap energies, thereby effectively exhibiting the quantum confinement effect.

[0040] In addition, the particle sizes of the first quantum dots and second quantum dots of the present application may have dimensions of about 1 nm to about 100 nm. For example, the quantum dots may have a particle size of about 1 nm to about 50 nm, such as from 2 nm to 35 nm. The shapes of the quantum dots of the present application are the shapes commonly used in the art and are not particularly limited, and corresponding shapes can be selected according to actual needs.

[0041] In the present application, ZnS in the first quantum dots 1-x O x The surface shell layer is formed by partially oxidizing the second quantum dots with a surface shell layer of ZnS to different degrees. The surface shell layer of the first quantum dots contains both ZnS and ZnO. When 0.1 ≤ x ≤ 0.9, the first quantum dots can better adjust the conductivity of the electroluminescent layer, enabling an appropriate amount of electrons to recombine with holes in the electroluminescent layer, rather than migrating to the hole transport layer for recombination and consumption. The x characterizing the degree of oxidation is more preferably 0.1 ≤ x ≤ 0.5, and at this time, the recombination efficiency of holes and electrons in the electroluminescent layer is higher.

[0042] In the present application, the material of the hole transport layer 40 may be selected from organic materials having hole transport ability, including but not limited to 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-1,4-phenylenediamine) (PFB), 4,4’,4”-tris(carbazol-9-yl)triphenylamine (TCTA), 4,4'-bis(9-carbazolyl)biphenyl (CBP), N,N’-diphenyl-N,N’-bis(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, C60, or one or more of them. The hole transport layer 204 may also be selected from inorganic materials having hole transport ability, including but not limited to one or more of doped or undoped MoOx, VOx, WOx, CrOx, CuO, MoS2, MoSe2, WS2, WSe2, CuS, but the exemplary embodiments of the present application are not limited thereto.

[0043] The materials of the electron transport layer 20 of the present application include, but are not limited to, one or more of ZnO, TiO2, SnO2, Ta2O3, InSnO, Alq3, Ca, Ba, CsF, LiF, CsCO3. However, the exemplary embodiments of the present application are not limited thereto. Preferably, the electron transport material is metal-doped ZnO nanoparticles, such as ZnO nanoparticles doped with Mg, Al, Li, W, Ti, Ni, Sn, MgO, Al2O3, Li2O, W2O3, TiO2, NiO, SnO2, etc.

[0044] The materials of the cathode 10 and the anode 50 of the present application are each independently selected from at least one of one-dimensional or two-dimensional nanomaterials, metal materials, and conductive metal oxide materials. More specifically, the materials of the cathode 10 and the anode 50 are each independently selected from one or more of nanosilver wires, nanocopper wires, silver, graphene, indium tin oxide, carbon nanotubes, fluorine-doped tin oxide, indium zinc oxide, aluminum-doped zinc oxide, antimony-doped zinc oxide, gallium-doped zinc oxide, cadmium-doped zinc oxide, copper indium oxide, tin oxide, zirconium oxide, aluminum, calcium, barium, etc., but are not limited thereto.

[0045] In addition to the above structure, the quantum dot light-emitting diode structure of the present application may further include a hole injection layer, an electron injection layer, etc. The materials of the hole injection layer and the electron injection layer are not particularly limited, and any known hole injection and electron injection materials in the art can be used and can be selected according to actual situations.

[0046] The present application also provides a light-emitting device, including the above-mentioned quantum dot light-emitting diode. The light-emitting device of the present application can be a display device or a lighting device. The display device includes, but is not limited to, devices or components such as mobile phones, computers, in-vehicle displays, AR displays, VR displays, smart watches, display screens, display panels, etc. Components such as QLED devices, OLED devices, PLED devices, Micro-LED devices, Mini-LED devices, etc. can be electroluminescent devices. The display device of the present application can be a top-emitting display device, a bottom-emitting display device, or a transparent display device. By using the quantum dot light-emitting diode of the present application, the current density, luminous brightness, external quantum efficiency, and lifespan of the light-emitting device will all be greatly improved.

[0047] The quantum dot composition and display device according to some exemplary embodiments of the present application are described in more detail below; however, the exemplary embodiments of the present application are not limited thereto.

[0048] Example 1

[0049] The quantum dot light-emitting diodes in this example are stacked in sequence as follows:

[0050] Cathode (Al),

[0051] Electron transport layer (ZnO),

[0052] The first electroluminescent layer (InP / ZnS red quantum dots, with a thickness of about 15 nm),

[0053] The second electroluminescent layer (InP / ZnS 0.56 O 0.44 red quantum dots, which are obtained by oxidizing the InP / ZnS red quantum dots in the first electroluminescent layer, with a thickness of about 15 nm),

[0054] Hole transport layer (TFB),

[0055] Hole injection layer (PEDOT:PSS),

[0056] Anode (ITO).

[0057] Example 2

[0058] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0059] The first electroluminescent layer (InP / ZnS 0.56 O 0.44 red quantum dots, with a thickness of about 15 nm),

[0060] The second electroluminescent layer (InP / ZnS 0.10 O 0.90 red quantum dots, which are obtained by oxidizing the InP / ZnS red quantum dots, with a thickness of about 15 nm).

[0061] Example 3 (changing the thickness of the first electroluminescent layer to 5 nm)

[0062] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0063] The first electroluminescent layer (InP / ZnS red quantum dots, with a thickness of about 5 nm),

[0064] The second electroluminescent layer (InP / ZnS 0.56 O 0.44 red quantum dots, which are obtained by oxidizing the quantum dots in the first electroluminescent layer, with a thickness of about 15 nm).

[0065] Example 4

[0066] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0067] The first electroluminescent layer (InP / ZnS red quantum dots, with a thickness of about 20 nm),

[0068] The second electroluminescent layer (InP / ZnS 0.56 O 0.44 red quantum dots, which are obtained by oxidizing the InP / ZnS red quantum dots in the first electroluminescent layer and have a thickness of about 15 nm).

[0069] Example 5

[0070] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0071] The first electroluminescent layer (InP / ZnS red quantum dots, with a thickness of about 15 nm),

[0072] The second electroluminescent layer (InP / ZnS 0.56 O 0.44 red quantum dots, which are obtained by oxidizing the InP / ZnS red quantum dots in the first electroluminescent layer and have a thickness of about 10 nm),

[0073] The third electroluminescent layer (InP / ZnS 0.10 O 0.90 red quantum dots, which are obtained by oxidizing the InP / ZnS red quantum dots in the first electroluminescent layer and have a thickness of about 10 nm).

[0074] Example 6

[0075] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0076] The first electroluminescent layer (InP / ZnS 0.89 O 0.11 red quantum dots, with a thickness of about 15 nm),

[0077] The second electroluminescent layer (InP / ZnS 0.56 O 0.44 red quantum dots, which are obtained by oxidizing the InP / ZnS red quantum dots and have a thickness of about 10 nm),

[0078] The third electroluminescent layer (InP / ZnS 0.10 O 0.90 red quantum dots, which are obtained by oxidizing the InP / ZnS red quantum dots and have a thickness of about 10 nm).

[0079] Example 7

[0080] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0081] The first electroluminescent layer (InP / ZnS green quantum dots, with a thickness of about 15 nm),

[0082] The second electroluminescent layer (InP / ZnS 0.51 O 0.49 green quantum dots, which are obtained by oxidizing the InP / ZnS green quantum dots in the first electroluminescent layer and have a thickness of about 15 nm).

[0083] Example 8

[0084] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0085] The first electroluminescent layer (ZnSe / ZnS blue quantum dots, with a thickness of about 15 nm),

[0086] The second electroluminescent layer (ZnSe / ZnS 0.51 O 0.49 blue quantum dots, which are obtained by oxidizing the ZnSe / ZnS blue quantum dots in the first electroluminescent layer and have a thickness of about 15 nm).

[0087] Example 9

[0088] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0089] The first electroluminescent layer (CdSe / ZnS red quantum dots, with a thickness of about 15 nm),

[0090] The second electroluminescent layer (CdSe / ZnS 0.56 O 0.44 red quantum dots, which are obtained by oxidizing the CdSe / ZnS red quantum dots in the first electroluminescent layer and have a thickness of about 15 nm).

[0091] Comparative Example 1

[0092] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0093] Electroluminescent layer (InP / ZnS red quantum dots, with a thickness of about 25 nm).

[0094] Comparative Example 2

[0095] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0096] Electroluminescent layer (ZnSe / ZnS blue quantum dots, with a thickness of about 25 nm).

[0097] Comparative Example 3

[0098] The other layers are the same as those in Example 1, except for the following changes in the electroluminescent layer:

[0099] Electroluminescent layer (CdSe / ZnS red quantum dots, with a thickness of about 25 nm).

[0100] Test the brightness, external quantum efficiency (EQE), and service life of the quantum dot light-emitting diodes in Examples 1-9 and Comparative Examples 1-3 above. The specific electrical performance parameters are shown in Tables 1-3. In the second electroluminescent layer of Example 1, InP / ZnS 0.56 O 0.44 The surface energy spectrum analysis diagram of the red quantum dots is as Figure 2 , from which it can be seen that the surface shell layer contained in the quantum dots is ZnS 0.56 O 0.44 ; In the second electroluminescent layer of Example 1, InP / ZnS 0.56 O 0.44 The scanning electron microscope diagram of the red quantum dots is as Figure 3 , from which it can be seen that the particle size of the quantum dots is about 8 nm; The comparison diagrams of voltage-brightness and voltage-external quantum efficiency of Example 1 and Comparative Example 1 are as Figures 4 - 5 shown.

[0101] Table 1 Electrical performance parameter table of quantum dot light-emitting diodes containing InP-core quantum dots in Examples 1-7 and Comparative Example 1

[0102] Number 3V Luminance (nits) EQE (%) <![CDATA[Lifetime T 50 @1000nits(h)]]> Example 1 1420 15.08 380 Example 2 1347 12.02 368 Example 3 1914 10.79 365 Example 4 2259 19.26 574 Example 5 1522 16.19 520 Example 6 1433 17.26 536 Example 7 985 11.2 20 Comparative Example 1 556 9.64 20

[0103] Table 2 Electrical performance parameter table of quantum dot light-emitting diodes containing ZnSe-core quantum dots in Example 8 and Comparative Example 2

[0104] Number 3V Luminance (nits) EQE (%) <![CDATA[Lifetime T 50 @1000nits(h)]]> Example 8 285 9.37 8 Comparative Example 2 3 6.44 2

[0105] Table 3 Comparative table of electrical performance of quantum dot light-emitting diodes containing CdSe-core quantum dots in Example 9 and Comparative Example 3

[0106] Number 3V Luminance (nits) EQE (%) <![CDATA[Lifetime T 50 @1000nits(h)]]> Example 9 14430 14.06 12000 Comparative Example 3 8260 11.02 5600

[0107] From Tables 1-3, Figures 4 - 5 it can be seen that compared with Comparative Examples 1-3, the quantum dot light-emitting diodes of Examples 1-9 of the present application have excellent electrical performance, and the current efficiency, brightness, EQE, and service life have all been significantly improved.

[0108] Although the inventors have elaborated and listed the technical solutions of the present application in detail, it should be understood that for those skilled in the art, it is obvious to make modifications and / or adaptations to the above embodiments or adopt equivalent alternative solutions, and none of them can deviate from the essence of the spirit of the present application. The terms appearing in the present application are used to elaborate and understand the technical solutions of the present application and do not constitute a limitation to the present application.

Claims

1. A quantum dot light-emitting diode, characterized in that, It includes a cathode, an electron transport layer, a first electroluminescent layer to an nth electroluminescent layer, a hole transport layer, and an anode that are sequentially stacked, where n is an integer and n ≥ 2; Among them, at least one of the first to nth electroluminescent layers contains a first quantum dot, and the first quantum dot includes a core and ZnS 1-x O x a surface shell, where 0 < x < 1; ZnS in the first quantum dot 1-x O x The surface shell is formed by partially oxidizing the second quantum dot with a surface shell of ZnS to different degrees.

2. The quantum dot light-emitting diode according to claim 1, characterized in that Each layer among the first electroluminescent layer to the nth electroluminescent layer contains the first quantum dots. In any two adjacent layers in the direction from the first electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots is the same or increases layer by layer.

3. The quantum dot light emitting diode according to claim 1, wherein In the first electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots increases layer by layer.

4. The quantum dot light emitting diode according to claim 2, characterized in that, The thickness of the first electroluminescent layer is 5 - 20 nm.

5. The quantum dot light-emitting diode according to claim 1, wherein The first electroluminescent layer contains second quantum dots. The second quantum dots contain the core and a ZnS surface shell layer. Each layer among the second electroluminescent layer to the nth electroluminescent layer contains the first quantum dots. In any two adjacent layers in the direction from the second electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots is the same or increases layer by layer.

6. The quantum dot light emitting diode according to claim 5, wherein, In the second electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dots increases layer by layer.

7. The quantum dot light emitting diode according to claim 5, wherein The thickness of the second electroluminescent layer is 5 - 20 nm.

8. The quantum dot light-emitting diode according to any one of claims 1-7, characterized in that, The sum of the thicknesses of the first electroluminescent layer to the nth electroluminescent layer is 20 - 60 nm.

9. The quantum dot light emitting diode according to claim 1, wherein, The core includes at least one of II-VI group compounds, III-V group compounds, IV-VI group compounds, I-III-VI group compounds, and I-II-IV-VI group compounds.

10. A light-emitting device, characterized in that, It includes the quantum dot electroluminescent diode according to any one of claims 1 to 9.

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