CN115312670A - Quantum dot electroluminescent diode and light-emitting device - Google Patents
Quantum dot electroluminescent diode and light-emitting device Download PDFInfo
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Abstract
The application provides a quantum dot electroluminescent diode, which comprises a cathode, an electron transport layer, a first electroluminescent layer, an nth electroluminescent layer, a hole transport layer and an anode which are sequentially stacked, wherein n is an integer and is more than or equal to 2; wherein at least one of the first to nth electroluminescent layers comprises first quantum dots comprising a core, znS 1‑x O x The surface shell layer, x is more than 0 and less than or equal to 1; the first quantum dot can effectively improve the current efficiency, the brightness and the external quantum efficiency of the quantum dot electroluminescent diode, and can enable the quantum dot electroluminescent diode to obtain a longer service life.
Description
Technical Field
The application belongs to the technical field of display, and particularly relates to a quantum dot electroluminescent diode and a light-emitting device.
Background
Quantum dots (also called semiconductor nanocrystals) are a new type of semiconductor nanomaterial with a size of 1-10nm. They have unique Photoluminescent (PL) and Electroluminescent (EL) properties due to quantum size effects and dielectric confinement effects. Compared with the traditional organic fluorescent dye, the quantum dot has excellent optical characteristics of high quantum efficiency, high photochemical stability, difficult photolysis, wide excitation, narrow emission, high color purity, adjustable luminous color through controlling the size of the quantum dot and the like, and has wide application prospect in the technical field of display.
A Quantum dot light-emitting diode (QLED) is a device that electrically excites Quantum dot to emit light. Compared with the traditional Organic Light Emitting Diode (OLED), the QLED has the characteristics of more excellent color purity, brightness, visual angle and the like. The quantum dots can be dispersed in an organic solvent to prepare ink, and the luminescent film is manufactured by adopting methods such as ink-jet printing, spin coating, blade coating and the like, and is particularly suitable for preparing large-area devices by a solution method. Therefore, the QLED has very good market prospect.
The conventional QLED device generally adopts a structure that an anode, a hole transport layer, a quantum dot electroluminescent layer, an electron transport layer and a cathode are sequentially arranged from bottom to top, and through the improvement of quantum dot materials and the continuous optimization of the structure of the QLED device, the luminous performance of the conventional QLED device is greatly improved, but some performances still cannot meet the requirements, and especially the service life of the device and the requirements of industrial production have a certain difference. Therefore, there is a need to continuously optimize the structure of the quantum dot electroluminescent diode and improve the performance thereof, so as to promote the faster commercialization of the quantum dot electroluminescent diode.
Disclosure of Invention
In order to solve the technical problems, the application provides a quantum dot electroluminescent diode which comprises a cathode, an electron transport layer, a first electroluminescent layer, an nth electroluminescent layer, a hole transport layer and an anode which are sequentially stacked, wherein n is an integer and is more than or equal to 2;
wherein at least one of the first to nth electroluminescent layers comprises first quantum dots comprising a core, znS 1-x O x The surface shell layer, x is more than 0 and less than or equal to 1.
Furthermore, each of the first electroluminescent layer to the nth electroluminescent layer includes the first quantum dot, and in 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 gradually increases layer by layer.
Further, in the first electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dot is gradually increased layer by layer.
Further, the thickness of the first electroluminescent layer is 5-20 nm.
Further, the first electroluminescent layer comprises second quantum dots, the second quantum dots comprise the core body and a ZnS surface shell layer, each of the second electroluminescent layer to the nth electroluminescent layer comprises the first quantum dots, and the x of the first quantum dots is the same or gradually increases from layer to layer in any two adjacent layers in the direction from the second electroluminescent layer to the nth electroluminescent layer.
Further, in the second electroluminescent layer to the nth electroluminescent layer, the x of the first quantum dot is gradually increased layer by layer.
Further, the thickness of the second electroluminescent layer is 5-20 nm.
Further, the sum of the thicknesses of the first electroluminescent layer and the nth electroluminescent layer is 20-60 nm.
Further, the nucleus includes at least one of a group II-VI compound, a group III-V compound, a group IV-VI compound, a group I-III-VI compound, and a group I-II-IV-VI compound.
The application also provides a light-emitting device comprising the quantum dot electroluminescent diode.
Has the beneficial effects that: the quantum dot electroluminescent diode comprises a cathode, an electron transport layer, a first electroluminescent layer, an nth electroluminescent layer, a hole transport layer and an anode which are sequentially stacked, wherein n is an integer and is more than or equal to 2; wherein at least one of the first through nth electroluminescent layers comprises first quantum dots comprising a core, znS 1-x O x The surface shell layer, x is more than 0 and less than or equal to 1; this applicationThe surface shell layer in the first quantum dot is obtained by partially oxidizing the ZnS shell layer, so that the energy levels of the quantum dots in the electroluminescent layers can be stably changed, thereby avoiding huge energy level difference caused by using a single layer of quantum dots. In addition, because the quantum dots with different oxidation degrees have different conductive capacities, the conductive capacity of the electroluminescent layer can be controlled and adjusted more effectively under the laminated design, so that the current efficiency, the brightness and the external quantum efficiency of the quantum dot electroluminescent diode can be effectively improved, and the quantum dot electroluminescent diode can have a longer service life.
Drawings
Fig. 1 is a schematic structural diagram of a quantum dot electroluminescent diode according to an embodiment of the present disclosure;
FIG. 2 shows InP/ZnS in the second electroluminescent layer of the quantum dot electroluminescent diode of example 1 0.56 O 0.44 A surface energy spectrum analysis chart of the red light quantum dots;
FIG. 3 shows InP/ZnS in the second electroluminescent layer of the quantum dot electroluminescent diode of example 1 0.56 O 0.44 Scanning electron microscope images of red light quantum dots;
FIG. 4 is a voltage-luminance comparison graph of quantum dot electroluminescent diodes of example 1 and comparative example 1 of the present application;
fig. 5 is a graph comparing voltage-external quantum efficiency of quantum dot electroluminescent diodes of example 1 and comparative example 1 of the present application.
Detailed Description
The technical solutions in the examples of the present application will be described in detail below with reference to the embodiments of the present application. It should be noted that the described embodiments are only some embodiments of the present application, and not all embodiments. Unless otherwise defined, all terms (including technical and scientific terms) in the specification may be defined as commonly understood by one of ordinary skill in the art. Unless clearly defined, terms defined in a general dictionary may be undesirably or exaggeratedly explained. Furthermore, unless explicitly described to the contrary, the word "comprise" and variations such as "comprises" or "comprising", will be understood to imply the inclusion of stated elements (components) but not the exclusion of any other elements (components).
In the drawings, the thickness of layers, films, panels, regions, etc. are exaggerated for clarity. Like reference numerals refer to like elements throughout the specification.
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, there are no intervening elements present.
Furthermore, the singular includes the plural unless otherwise mentioned. As used herein, at least one of the terms "a", "an", "the" and "\8230; \8230, do not denote a limitation of quantity, but are intended to include both the singular and the plural, unless the context clearly indicates otherwise. For example, "an element" has the same meaning as "at least one element" unless the context clearly dictates otherwise. "at least one" is not to be construed as limiting "a" or "an". "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 be further understood that the terms "comprises" and/or "comprising," or variations thereof, when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.
It will be understood that, although the terms "first," "second," "third," etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section.
As mentioned in the background, the existing QLED still has some performance that can not meet the application requirements, especially the service life has a certain gap with the requirement of industrial production. The inventor finds that the current quantum dot electroluminescent layer is a quantum dot layer, the conductivity and the energy level of the quantum dot layer are fixed and cannot be adjusted, and the electrical properties of the QLED such as the service life, the current density and the brightness are limited to a certain extent.
Based on the above, the present application provides a quantum dot electroluminescent diode, as shown in fig. 1, comprising a cathode 10, an electron transport layer 20, first to nth electroluminescent layers 1 to N, a hole transport layer 40 and an anode 50, which are sequentially stacked, wherein N is an integer and is greater than or equal to 2; wherein at least one of the first to nth electroluminescent layers comprises first quantum dots comprising a core, znS 1-x O x The surface shell layer, x is more than 0 and less than or equal to 1. The inventors have found that ZnS on the first quantum dot in this application 1-x O x The existence of the surface shell layer can effectively adjust the conductivity of the first quantum dot, regulate and control the current density of the quantum dot electroluminescent diode and improve the brightness and quantum efficiency of the quantum dot electroluminescent diode, and electrons and holes can be compounded on the electroluminescent layer with gently-transitioned energy levels, so that the service life of the quantum dot electroluminescent diode is greatly prolonged.
In a first embodiment of the present application, each of the first electroluminescent layer to the nth electroluminescent layer includes the first quantum dot, and in any two adjacent layers in a direction from the first electroluminescent layer to the nth electroluminescent layer, x of the first quantum dot is the same or gradually increases from layer to layer, so as to better regulate and control current density in the electroluminescent diode and improve light emitting performance thereof.
In a preferred embodiment, each of the first to nth electroluminescent layers contains the first quantum dot, and x in the first electroluminescent layer is not greater than x in any of the second to nth electroluminescent layers, that is, x in the first electroluminescent layer on the side close to the electron transport layer is the smallest in each electroluminescent layer. In fact, x may represent the oxidation degree of the surface shell layer, and the inventors found that the oxidation degree of the first electroluminescent layer close to the electron transport layer is lower than that of the surface shell layer of the first quantum dot 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 electroluminescent diode with only one quantum dot electroluminescent layer, the multilayer electroluminescent layer improves the brightness, quantum efficiency and service life of the quantum dot electroluminescent diode.
In a further second embodiment, the x of the first quantum dots increases from layer to layer in the first electroluminescent layer to the nth electroluminescent layer. By controlling the gradual change rule among the multiple electroluminescent layers, the recombination efficiency of holes and electrons in the electroluminescent layers can be controlled more easily, so that the external quantum efficiency of the quantum dot electroluminescent diode is improved, and the service life of the quantum dot electroluminescent diode is prolonged.
In a further third embodiment, the thickness of the first electroluminescent layer is 5 to 20nm, that is, the first electroluminescent layer with the minimum oxidation degree near the electron transport layer is kept in a certain thickness range, so that the transport speed of electrons in the first electroluminescent layer is proper, the recombination speed of electrons and holes in the first electroluminescent layer is balanced, and the external quantum efficiency and the service life of the quantum dot electroluminescent diode are further improved, and more preferably, the thickness of the first electroluminescent layer is preferably 10 to 15nm.
In a fourth embodiment of the present application, the first electroluminescent layer includes second quantum dots, the second quantum dots include a core body and a ZnS surface shell layer, each of the second electroluminescent layer to the nth electroluminescent layer includes the first quantum dots, and in any two adjacent layers in the direction from the second electroluminescent layer to the nth electroluminescent layer, x of the first quantum dots is the same or gradually increases from layer to layer, so as to better regulate and control current density in the electroluminescent diode and improve the light emitting performance of the electroluminescent diode.
In a preferred embodiment, the electroluminescent layer is present in the second to the first layerIn the n electroluminescent layers, x of the first quantum dots in the second electroluminescent layer is the smallest. Specifically, the first electroluminescent layer contains second quantum dots comprising a ZnS shell layer, the second electroluminescent layer contains first quantum dots comprising ZnS 1-x O x And (5) surface shell layer. The arrangement ensures that the running speed of electrons transferred from the electron transport layer in the first electroluminescent layer and the second electroluminescent layer is controllable, the recombination efficiency of electrons and holes in each electroluminescent layer is easier to control, and the external quantum efficiency and the service life of the quantum dot electroluminescent diode are improved.
In a further fifth embodiment, the x of the first quantum dot increases from layer to layer in the second to nth electroluminescent layers. The gradual change rule between the second electroluminescent layer and the nth electroluminescent layer is controlled, so that the recombination efficiency of holes and electrons in the electroluminescent layer can be controlled more easily, the external quantum efficiency of the quantum dot electroluminescent diode is improved, and the service life of the quantum dot electroluminescent diode is prolonged.
In a further sixth embodiment, the second electroluminescent layer has a thickness of 5 to 20nm. Because the running speed of electrons at the first electroluminescent layer close to one side of the electron transport layer is lower, and the transmission rate of holes in quantum dots with higher oxidation degree is higher, the defect that the electron transfer rate is far greater than the hole transmission rate in a single-layer device is just made up, so that the recombination speed of electrons and holes in each electroluminescent layer tends to be balanced, the external quantum efficiency of the quantum dot electroluminescent diode is improved, and the service life of the quantum dot electroluminescent diode is prolonged. Preferably, the thickness of the second electroluminescent layer is preferably from 10 to 15nm.
In a seventh embodiment of the present application, the sum of the thicknesses of the first electroluminescent layer to the nth electroluminescent layer is 20 to 60nm, so that the total recombination efficiency of electrons and holes in each electroluminescent layer is higher, and the external quantum efficiency and brightness of the cold quantum dot electroluminescent diode are improved. Because the oxidation degrees of the quantum dots between the layers have regular difference, the running speeds of electrons and holes in the electroluminescent layer tend to be more consistent, and the service life of the quantum dot electroluminescent diode is obviously prolonged. The sum of the thicknesses of the first electroluminescent layer to the n-th electroluminescent layer is preferably 20 to 40nm.
In an eighth embodiment of the present application, the nucleus comprises a group II-VI compound, a group III-V compound, a group IV-VI compound, a group I-III-VI compound, a group I-II-IV-VI compound, or a combination thereof. For example, the group II-VI compounds may include: cdSe, cdTe, znS, znSe, znTe, znO, hgS, hgSe, hgTe, mgSe, mgS, cdSeS, cdSeTe, cdSSte, 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, hgZnSnZnSTe, or combinations thereof. The II-VI compound can further include a group III metal. The group III-V compounds may include: gaN, gaP, gaAs, gaSb, alN, alP, alAs, alSb, inN, inP, inAs, inSb, gaNP, gaNAs, gaNSb, gaAs, gaSb, alNP, alNAs, alNSb, alPAs, alPSb, inNP, inNAs, inNSb, inPAs, inPSb, znP, gaAlNP, gaAlNAs, gaAlNSb, gaAlPAs, gaAlPSb, gaInNP, gaInNAs, gaInNSb, gaInPAs, gaInPSb, inInInInInInNP, inAlNAs, inNSb, inAlPAs, inAlPSb, or combinations thereof. The III-V compound may further include a group II metal (e.g., inZnP). The group IV-VI compounds 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 group I-III-VI compounds may include CuInSe 2 、CuInS 2 CuInGaSe, and CuInGaS, but are not limited thereto. Examples of the group I-II-IV-VI compounds may include, but are not limited to, cuZnSnSe and CuZnSnS.
In the first quantum dot and the second quantum dot of the present application, a plurality of shell layers may be included between the core body and the outer shell layer, and adjacent shell layers may have different compositions from each other. When having a multi-layer shell, each layer may have a single composition. Several shells may have alloys. In the case of a multi-layer shell, the nanocrystals of the respective layers are selected to have appropriate band gap energies, thereby effectively exhibiting a quantum confinement effect.
In addition, the particle size of the first quantum dot, the second quantum dot of the present application may have a size of about 1nm to about 100 nm. For example, the quantum dots may have a particle size of about 1nm to about 50nm, such as from 2nm to 35 nm. The shape of the quantum dot of the present application is a shape generally used in the art, and is not particularly limited, and the corresponding shape may be selected according to actual needs.
In the present application, znS in the first quantum dot 1-x O x The surface shell layer is formed by partially oxidizing second quantum dots containing ZnS in the surface shell layer to different degrees, the surface shell layer of the first quantum dots contains ZnS and ZnO, when x is more than or equal to 0.1 and less than or equal to 0.9, the first quantum dots can better adjust the conductivity of the electroluminescent layer, so that a proper amount of electrons are compounded with holes in the electroluminescent layer and are not migrated to the hole transport layer for compounding consumption, x representing the degree of oxidation is more preferably more than or equal to 0.1 and less than or equal to 0.5, and the compounding efficiency of the holes and the electrons in the electroluminescent layer is higher at the moment.
The material of the hole transport layer 40 in the present application may be selected from organic materials having a hole transport ability, including, but not limited to, one or more of 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 ″ -tris (carbazol-9-yl) triphenylamine (TCTA), 4' -bis (9-Carbazole) Biphenyl (CBP), N '-diphenyl-N, N' -bis (3-methylphenyl) -1,1 '-biphenyl-4, 4' -diamine (TPD), N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine (NPB), doped graphene, non-doped graphene, C60. The hole transport layer 204 may also be selected from inorganic materials with hole transport capabilities including, but not limited to, doped or undoped MoOx, VOx, WOx, crOx, cuO, moS 2 、MoSe 2 、WS 2 、WSe 2 And CuS, but exemplary embodiments of the present application are not limited thereto.
Materials of the electron transport layer 20 of the present application include, but are not limited to, znO, tiO 2 、SnO 2 、Ta 2 O 3 、InSnO、Alq 3 、Ca、Ba、CsF、LiF、CsCO 3 But the exemplary embodiments of the present application are not limited thereto. Preferably, the electron transport material is a metal-doped ZnO nanoparticle, such as Mg, al, li, W, ti, ni, sn, mgO, al 2 O 3 、Li 2 O、W 2 O 3 、TiO 2 、NiO、SnO 2 Etc. doped ZnO nanoparticles.
The cathode 10 and the anode 50 are made of at least one material selected from one-dimensional or two-dimensional nano materials, metal materials and conductive metal oxide materials. More specifically, the materials of the cathode 10 and the anode 50 are independently selected from one or more of nano silver wire, nano copper wire, silver, graphene, indium tin oxide, carbon nanotube, 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.
The quantum dot electroluminescent diode structure of the present application may further include a hole injection layer, an electron injection layer, and other structures besides the above structures, and 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 may be selected according to actual situations.
The application also provides a light-emitting device, which comprises the quantum dot electroluminescent diode, the light-emitting device can be a display device and can also be a lighting device, the display device comprises devices or components such as but not limited to a mobile phone, a computer, a vehicle-mounted display, an AR display, a VR display, an intelligent watch, a display screen, a display panel and the like, and the components can be electroluminescent devices such as QLED devices, OLED devices, PLED devices, micro-LED devices, mini-LED devices and the like. The display device of the present application may be a top emission display device, a bottom emission display device, or a transparent display device. By adopting the quantum dot electroluminescent diode, the current density, the brightness, the external quantum efficiency and the service life of the light-emitting device are greatly improved.
Quantum dot compositions, display devices, 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.
Example 1
The quantum dot electroluminescent diodes in this embodiment are sequentially stacked:
a cathode (Al) which is a cathode,
an electron transport layer (ZnO),
a first electroluminescent layer (InP/ZnS red quantum dots, thickness about 15 nm),
second electroluminescent layer (InP/ZnS) 0.56 O 0.44 Red light quantum dots, which are obtained by oxidizing InP/ZnS red light quantum dots in the first electroluminescent layer and have the thickness of about 15 nm),
a hole transport layer (TFB),
a hole injection layer (PEDOT: PSS),
anode (ITO).
Example 2
The remaining layers are the same as in example 1, with the following modifications only in the electroluminescent layer:
first electroluminescent layer (InP/ZnS) 0.56 O 0.44 Red light quantum dots with thickness of about 15 nm),
second electroluminescent layer (InP/ZnS) 0.10 O 0.90 Red light quantum dots, which are obtained by oxidizing InP/ZnS red light quantum dots and have the thickness of about 15 nm).
Example 3 (varying the thickness of the first electroluminescent layer to 5 nm)
The remaining layers were the same as in example 1, except that the electroluminescent layer was changed as follows:
a first electroluminescent layer (InP/ZnS red quantum dots, thickness about 5 nm),
second electroluminescent layer (InP/ZnS) 0.56 O 0.44 Red light quantum dots oxidized from quantum dots in the first electroluminescent layer and having a thickness of about 15 nm).
Example 4
The remaining layers were the same as in example 1, except that the electroluminescent layer was changed as follows:
a first electroluminescent layer (InP/ZnS red quantum dots, thickness about 20 nm),
second electroluminescent layer (InP/ZnS) 0.56 O 0.44 Red light quantum dots, which are obtained by oxidizing InP/ZnS red light quantum dots in the first electroluminescent layer and have the thickness of about 15 nm).
Example 5
The remaining layers were the same as in example 1, except that the electroluminescent layer was changed as follows:
a first electroluminescent layer (InP/ZnS red quantum dots, thickness about 15 nm),
second electroluminescent layer (InP/ZnS) 0.56 O 0.44 Red light quantum dots obtained by oxidizing InP/ZnS red light quantum dots in the first electroluminescent layer and having a thickness of about 10 nm),
third electroluminescent layer (InP/ZnS) 0.10 O 0.90 Red light quantum dots, which are obtained by oxidizing InP/ZnS red light quantum dots in the first electroluminescent layer and have the thickness of about 10 nm).
Example 6
The remaining layers are the same as in example 1, with the following modifications only in the electroluminescent layer:
first electroluminescent layer (InP/ZnS) 0.89 O 0.11 Red light quantum dots with thickness of about 15 nm),
second electroluminescent layer (InP/ZnS) 0.56 O 0.44 Red light quantum dots obtained by oxidizing InP/ZnS red light quantum dots with a thickness of about 10 nm),
third electroluminescent layer (InP/ZnS) 0.10 O 0.90 Red light quantum dots, which are obtained by oxidizing InP/ZnS red light quantum dots and have the thickness of about 10 nm).
Example 7
The remaining layers are the same as in example 1, with the following modifications only in the electroluminescent layer:
a first electroluminescent layer (InP/ZnS green quantum dots, thickness about 15 nm),
second electroluminescent layer (InP/ZnS) 0.51 O 0.49 Green quantum dots oxidized from InP/ZnS green quantum dots in the first electroluminescent layer to a thickness of about 15 nm).
Example 8
The remaining layers were the same as in example 1, except that the electroluminescent layer was changed as follows:
a first electroluminescent layer (ZnSe/ZnS blue quantum dots, thickness about 15 nm),
second electroluminescent layer (ZnSe/ZnS) 0.51 O 0.49 Blue light quantum dots, wherein the blue light quantum dots are obtained by oxidizing ZnSe/ZnS in the first electroluminescent layer and have the thickness of about 15 nm).
Example 9
The remaining layers were the same as in example 1, except that the electroluminescent layer was changed as follows:
a first electroluminescent layer (CdSe/ZnS red quantum dots with thickness of about 15 nm),
second electroluminescent layer (CdSe/ZnS) 0.56 O 0.44 Red light quantum dots, wherein the red light quantum dots are obtained by oxidizing CdSe/ZnS red light quantum dots in the first electroluminescent layer, and the thickness of the red light quantum dots is about 15 nm).
Comparative example 1
The remaining layers are the same as in example 1, with the following modifications only in the electroluminescent layer:
an electroluminescent layer (InP/ZnS red quantum dots, thickness about 25 nm).
Comparative example 2
The remaining layers are the same as in example 1, with the following modifications only in the electroluminescent layer:
an electroluminescent layer (ZnSe/ZnS blue quantum dots, thickness about 25 nm).
Comparative example 3
The remaining layers are the same as in example 1, with the following modifications only in the electroluminescent layer:
an electroluminescent layer (CdSe/ZnS red quantum dots, thickness about 25 nm).
The quantum dots of examples 1 to 9 and comparative examples 1 to 3 were tested for electroluminescenceThe brightness, external Quantum Efficiency (EQE) and lifetime of the photodiode, and the electrical performance parameters are shown in tables 1-3, and InP/ZnS in the second electroluminescent layer of example 1 0.56 O 0.44 The surface energy spectrum analysis chart of the red light quantum dot is shown in fig. 2, and it can be known that the quantum dot comprises a surface shell layer of ZnS 0.56 O 0.44 (ii) a InP/ZnS in the second electroluminescent layer of example 1 0.56 O 0.44 The scanning electron micrograph of the red light quantum dot is shown in fig. 3, from which it can be seen that the particle size of the quantum dot is about 8 nm; comparative graphs of voltage-luminance and voltage-external quantum efficiency of example 1 and comparative example 1 are shown in fig. 4 to 5.
TABLE 1 TABLE OF ELECTRICAL PROPERTIES OF QUANTUM-POINT ELECTROLUMINESCENT DIODES COMPRISING QUANTUM POINTS WITH INP CORES IN EXAMPLES 1 TO 7 AND COMPARATIVE EXAMPLE 1
| Numbering | 3V luminance (nits) | EQE(％) | Life time 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 |
TABLE 2 TABLE 8 COMPARATIVE EXAMPLE 2 TABLE OF ELECTRICAL PROPERTIES OF QUANTUM-DOPED-POINT ELECTROLUMINESCENT DIODES COMPRISING QUANTUM DONTS HAVING ZnSe CORES
| Numbering | 3V Brightness (nits) | EQE(％) | Life T 50 @1000nits(h) |
| Example 8 | 285 | 9.37 | 8 |
| Comparative example 2 | 3 | 6.44 | 2 |
TABLE 3 COMPARATIVE TABLE OF ELECTRICAL PERFORMANCES OF QUANTUM-DOED ELECTROLUMINESCENT DIODES COMPRISING QUANTUM DONTS HAVING CdSE CORES IN EXAMPLE 9 AND COMPARATIVE EXAMPLE 3
| Number of | 3V Brightness (nits) | EQE(％) | Life T 50 @1000nits(h) |
| Example 9 | 14430 | 14.06 | 12000 |
| Comparative example 3 | 8260 | 11.02 | 5600 |
As can be seen from tables 1 to 3 and fig. 4 to 5, the quantum dot electroluminescent diodes of examples 1 to 9 of the present application have excellent electrical properties, and significantly improved current efficiency, luminance, EQE and lifespan, as compared to comparative examples 1 to 3.
Although the present disclosure has been described and illustrated in greater detail by the inventors, it should be understood that modifications and/or alterations to the above-described embodiments, or equivalent substitutions, will be apparent to those skilled in the art without departing from the spirit of the disclosure, and that no limitations to the present disclosure are intended or should be inferred therefrom.
Claims (10)
1. A quantum dot electroluminescent diode is characterized by comprising a cathode, an electron transport layer, a first electroluminescent layer to an nth electroluminescent layer, a hole transport layer and an anode which are sequentially stacked, wherein n is an integer and is more than or equal to 2;
wherein at least one of the first through nth electroluminescent layers comprises first quantum dots comprising a core, znS 1-x O x The surface shell layer, x is more than 0 and less than or equal to 1.
2. The quantum dot electroluminescent diode of claim 1, wherein each of the first electroluminescent layer to the nth electroluminescent layer comprises the first quantum dot, and x of the first quantum dot is the same or increases from layer to layer in any two adjacent layers from the first electroluminescent layer to the nth electroluminescent layer.
3. The quantum dot electroluminescent diode of claim 1, wherein x of the first quantum dot increases from layer to layer in the first to nth electroluminescent layers.
4. The quantum dot electroluminescent diode of claim 2, wherein the first electroluminescent layer has a thickness of 5 to 20nm.
5. The quantum dot electroluminescent diode of claim 1, wherein the first electroluminescent layer comprises second quantum dots, the second quantum dots comprise the core and a ZnS surface shell layer, each of the second to nth electroluminescent layers comprises the first quantum dots, and x of the first quantum dots is the same or increases from layer to layer in any two adjacent layers in a direction from the second to nth electroluminescent layers.
6. The quantum dot electroluminescent diode of claim 5, wherein the x of the first quantum dot increases from layer to layer in the second to nth electroluminescent layers.
7. The quantum dot electroluminescent diode of claim 5, wherein the second electroluminescent layer has a thickness of 5 to 20nm.
8. The quantum dot electroluminescent diode of any one of claims 1 to 7, wherein the sum of the thicknesses of the first electroluminescent layer to the nth electroluminescent layer is 20 to 60nm.
9. The quantum dot electroluminescent diode of claim 1, wherein the core body comprises at least one of a group II-VI compound, a group III-V compound, a group IV-VI compound, a group I-III-VI compound, and a group I-II-IV-VI compound.
10. A light-emitting device comprising the quantum dot electroluminescent diode according to any one of claims 1 to 9.
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| CN115322767A (en) * | 2021-05-10 | 2022-11-11 | 苏州星烁纳米科技有限公司 | Core-shell structure quantum dot for electroluminescent device, preparation method of core-shell structure quantum dot, and electroluminescent device |
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| CN115322767A (en) * | 2021-05-10 | 2022-11-11 | 苏州星烁纳米科技有限公司 | Core-shell structure quantum dot for electroluminescent device, preparation method of core-shell structure quantum dot, and electroluminescent device |
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