CN108389982B

CN108389982B - LED device and display device

Info

Publication number: CN108389982B
Application number: CN201810093671.5A
Authority: CN
Inventors: 王允军
Original assignee: Suzhou Xingshuo Nanotech Co Ltd
Current assignee: Suzhou Xingshuo Nanotech Co Ltd
Priority date: 2016-08-23
Filing date: 2016-08-23
Publication date: 2020-03-27
Anticipated expiration: 2036-08-23
Also published as: CN108389982A; CN106356462A; WO2018035948A1

Abstract

The invention provides a light-emitting diode device which comprises a substrate, an anode, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode and is characterized in that the light-emitting layer is formed by combining quantum dots and energy transfer molecules, and the energy transfer molecules and the quantum dots are crosslinked through click chemistry. The energy transfer molecules as the dispersion medium of the quantum dots have high electron/hole carrier injection capability, can promote the generation of excitons in the energy transfer molecules, and realize the effective energy transfer from the energy transfer molecules to the fluorescent quantum dots. Under a certain voltage, the device can emit light in the wavelength range of 380-900nm, and the maximum emission peak value ranges from ultraviolet to deep red light. The invention also discloses a preparation method of the light-emitting diode device and electronic display equipment.

Description

Light emitting diode device and display device

Divisional application

The present application is a divisional application of chinese patent application "201610704608.1" entitled "light emitting diode device including quantum dots and energy transfer molecules, method of manufacturing the same, and display device", filed on 8/23/2016.

Technical Field

The application belongs to the field of display, and particularly relates to a light-emitting diode device and a display device.

Background

Quantum dots are semiconductor nanocrystals of nanometer size, with controllable surface chemical states and size-dependent optical properties. Quantum dots can be photoluminescent and electroluminescent. In display device applications, quantum dots are comparable to Organic Light Emitting Diodes (OLEDs) and have the following advantages: 1) the service life of the quantum dot is long, and the quantum dot is composed of inorganic cores and has potential long service life; 2) the color purity is high, the types of colors generated by the quantum dots are very many, and improved super visual experience is provided for an end user; 3) flexibility, the quantum dots are soluble in both water and non-aqueous solvents, which provides more options for making display devices of a wide variety of sizes and reduces production, operation and processing costs.

A typical QLED structure consists of a transparent anode on which is deposited an organic hole transport layer followed by a single layer of colloidal quantum dots, an organic electron transport layer, and a metal cathode. Two electroluminescent mechanisms have been proposed in QLEDs. The first mechanism is that the electron and hole carriers, transported through the organic charge transport layer, are injected directly into the quantum dots where they can form excited states capable of radiative recombination. The second mechanism is that the high-energy excited state formed in the organic molecules coated around the quantum dot film transfers the excited state energy resonance to the quantum dot, and then the quantum dot is made to emit light.

Despite advances in device assembly and high quality quantum dot synthesis, the mechanism of QLEDs remains the same: the quantum dot excited state is formed in the recombination of holes and electrons. Holes come from organic or polymeric layers and electrons also come from organic and polymeric layers. There are two major problems with this mechanism. First, a portion of the holes and/or electrons formed by the organic and polymeric layers recombine directly and cause emission from the host matrix. One way to overcome this problem is to create a hybrid organic/inorganic multilayer QLED structure with an external quantum efficiency of 0.5% by sandwiching a single layer of quantum dots between organic electron and hole transport layers by a phase separation process. Given that a thin quantum dot layer helps mitigate the effects of low quantum dot carrier mobility, the sandwich structure described above will help balance the carrier injection. However, even these devices may exhibit significant emission from organic matrices under high brightness conditions. The main drawback of the second type of QLED is its low internal quantum efficiency, which results from the presence of energy level barriers for the quantum dots, especially when they are coated with a layer of organic ligands, which is exacerbated by the problem of low quantum efficiency due to the low conductivity of the semiconductor nanocrystals, which makes it more difficult for carriers to be injected into the quantum dots.

Disclosure of Invention

In view of the above problems of the conventional QLED display device, the present invention provides a light emitting diode device capable of effectively improving the injection of charges into a light emitting layer.

The invention aims to provide a light-emitting diode device, which comprises:

a) a hole transport layer for injecting and transporting holes;

b) a light-emitting layer in contact with the hole transport layer;

c) an electron transport layer in contact with the light emitting layer for injecting and transporting electrons to the light emitting layer;

d) an anode and a cathode for a direct current voltage to cause a current to flow in the device and to emit radiation in the form of ultraviolet, visible or near infrared light to cause the light emitting diode device to emit light;

the light-emitting layer comprises quantum dots and energy transfer molecules, the energy transfer molecules are used as a dispersion medium of the quantum dots, have high electron and/or hole carrier injection capacity, and are crosslinked with the quantum dots through click chemistry.

The energy transfer molecule has the functions of quantum dot dispersing solvent and energy transfer. The QLED constructed by the method promotes the injection of charges in the quantum dots, especially the injection of electrons from the cathode to the quantum dots, from the energy transfer process of energy transfer molecules mixed near the surfaces of the quantum dots to the quantum dot cores.

Preferably, the light emitting diode device has electroluminescence with a wavelength in the range of 380-900nm when a direct voltage of 0-30V is applied between the cathode and the anode.

Preferably, the energy transfer molecules have high fluorescence quantum efficiency, reversible redox properties in the non-aqueous electrolyte, and a wider band gap than the quantum dots, thereby achieving efficient electron and/or hole carrier injection.

Preferably, the quantum dots are crosslinked with energy transfer molecules by click chemistry to form a composite layer, wherein the energy transfer molecules comprise one of an ethynyl or azido functional group, and the ligand terminal group of the quantum dots comprise either one of an ethynyl or azido; after heat treatment, the quantum dots and the energy transfer molecules complete cross-linking to form a composite layer.

Preferably, the energy transfer molecule is of the molecular, oligomeric or polymeric type, comprising at least one of the following groups of molecules or their derivatives:

wherein R is₁，R₂，R₃Is- (CH2) x- (CH ═ CH) y- (CH2) z-R; r is one of the following groups-H, -Cl, -Br, -I, -OH and-OCH₃、-OC₂H₅、-CHO、-COOCH₃、-COOH、-CONH₂、-COCl、 -COBr、-COI、-NH₂、-N⁺(CH₃)₃、-C(CH₃)₃、-CH＝CH₂、-CCH、-C₆H₅、-C₅H₅、 -N₃、-OCN、-NCO、-CN、-NC、-NO₂、-C₅H₄N、-SH、-S-S-H、-SOCH₃、-SO₂H、-SCN、-NCS、-CSH、-PH₂Phosphono, phospho, guanyl, cytosinyl, adenylyl, thyminyl. The energy transfer molecule having the above structure has two functional group sites, a P ═ O functional group is advantageous for injection of electrons into quantum dots, and a heterocyclic nitrogen functional group is advantageous for injection of holes.

The organic metal fluorescent emitter is hybridized with a wide three-line band gap substrate, and the QLED with high brightness is realized. Preferably, the energy transfer molecule is 2, 7-bis (diphenylphosphine oxide) -9, 9-octylfluorene (PO8), and the PO8 molecule has a long alkyl chain compound to bind the ligand on the surface of the quantum dot. The presence of PO8 can effectively promote electron injection into the quantum dot/PO 8 hybrid layer and block hole carriers from entering the hybrid layer, thus reducing current at the same applied voltage.

Preferably, the composite layer of the quantum dots and the PO8 is prepared by a method of spin coating a mixed solution.

Preferably, the substrate is glass or a flexible substrate.

Preferably, the anode material is a conductive metal oxide or a conductive polymer.

Preferably, the cathode material comprises any one of Al, Ca, Ba, Ca/Al, Ag.

Preferably, the hole transport layer comprises one of the following groups of molecules: tertiary arylamine, thiophene oligomer, thiophene polymer, pyrrole oligomer, vinylphenylene polymer, vinylcarbazole oligomer, vinylcarbazole polymer, fluorine oligomer, fluorine polymer, ethynylbenzene oligomer, ethynylbenzene polymer, phenylene oligomer, phenylene polymer, acetylene oligomer, acetylene polymer, phthalocyanine derivative, porphyrine, and porphyrine derivative.

Preferably, the electron transport layer comprises at least one of the following group of molecules: oxadiazole, oxadiazole derivative, oxazole derivative, isoxazole derivative, thiazole derivative, 1, 2, 3-triazole derivative, 1, 3, 5-triazine derivative, quinoxaline derivative, pyrrole oligomer, pyrrole polymer, vinylphenylene oligomer, vinylphenylene polymer, vinylcarbazole oligomer, vinylcarbazole polymer, fluorine oligomer, fluorine polymer, ethynylphenylene oligomer, ethynylphenylene polymer, phenylene oligomer, phenylene polymer, thiophene oligomer, thiophene polymer, acetylene oligomer, acetylene polymer, TiO polymer, and the like₂Nanoparticles, ZnO nanoparticles, SnO nanoparticles, gold nanoparticles, and silver nanoparticles.

Preferably, the quantum dot comprises one of the following structures:

a) ZnSe/ZnSeS/ZnS core/shell structure quantum dots with the size within the range of 1.5-9 nm;

b) ZnTe/ZnSe/ZnS core/shell structure quantum dots with the size within the range of 1.5-9 nm;

c) ZnTe/ZnTeS/ZnS core/shell structure quantum dots, the size is in the range of 1.5-9 nm;

d) the CdSe/CdSnS/ZnS core/shell structure quantum dots have the size within the range of 1.5-9 nm;

e) the CdSe/CdZnSe/ZnSe/ZnS core/shell structure quantum dots have the size within the range of 1.5-9 nm;

f) the CdTe/CdZnS/ZnS core/shell structure quantum dot has the size within the range of 1.5-9 nm;

g) the quantum dots have a CdS/ZnS core/shell structure, a CdS/ZnSe/ZnS core/shell structure or a CdZnS/ZnSe/ZnS core/shell structure, and have the size within the range of 1.5-10 nm;

h) CdTe/InP/ZnS core/shell structure quantum dot with size in 1.5-9 nm;

i) InP/ZnS core/shell structure quantum dots, the size is within the range of 1.5-9 nm;

j) mn as Mn-doped ZnSe²⁺ZnS core/Shell structured Quantum dots, ZnSe/ZnS Mn²⁺/ZnS core/shell structure quantum dot or ZnS: Mn²⁺The size of the/ZnS core/shell structure quantum dot is within the range of 1.5-9 nm;

k) copper doping ZnS: Cu⁺/ZnS core/shell structure quantum dot or ZnSe: Cu⁺The size of the/ZnS core/shell structure quantum dot is within the range of 1.5-10 nm;

l) ZnSe/InP/ZnS core/shell structure quantum dots, the size is in the range of 1.5-9 nm;

m) PbS/ZnS core/shell structure quantum dots, the size is in the range of 1.5-10 nm;

n) PbSe/ZnS core/shell structure quantum dots, the size is within the range of 1.5-10 nm;

o)CuInS₂quantum dots and core/shell structured CuInS₂The size of the/ZnS quantum dot is within the range of 1.5-10 nm;

p) CuS/ZnS core/shell structure quantum dots, the size is within the range of 1.5-10 nm;

q)AgInS₂quantum dots and AgInS₂The size of the/ZnS core-shell structure quantum dot is within the range of 1.5-10nm

Preferably, the quantum dots comprise ZnSe/ZnSeS/ZnS quantum dots with an electroluminescence peak value within the range of 380-450nm and a cadmium or mercury content of less than 0.001 mass percent; ZnTe/ZnSe/ZnS quantum dots, ZnTe/ZnTeSe/ZnSe quantum dots or ZnTe/ZnTeSe/ZnS quantum dots with the electroluminescent peak value within the range of 480-900nm and the cadmium or mercury content lower than 0.001 mass percent; the electroluminescent peak value is in the range of 500-700nm, and the content of cadmium or mercury is lower than 50 percent of CdSe/CdZnS/ZnS quantum dots or CdSe/CdZnSe/ZnSe/ZnS quantum dots.

Preferably, the molar ratio of quantum dots to energy transfer molecules is between 100000:1 and 1: 100000.

Another object of the present invention is to provide a method for manufacturing a light emitting diode device, comprising the steps of:

providing a substrate, and arranging an anode layer on the substrate;

then, a hole transport layer is arranged on the anode layer;

and then arranging a light-emitting layer on the hole transport layer, wherein the light-emitting layer is a composite layer formed by quantum dots and energy transfer molecules, and the preparation of the composite layer is selected from one of the following three steps:

a) mixing the solution of quantum dots with the solution of energy transfer molecules;

b) dissolving a powder of the quantum dots into a solution of the energy transfer molecules;

c) dissolving a solid or slurry of the energy transfer molecules into a solution of the quantum dots;

subsequently disposing an electron transport layer on the light emitting layer;

finally, a cathode layer is arranged on the electron transmission layer.

Another object of the present invention is to provide a display device including the above light emitting diode device, capable of outputting visual information or tactile information, operated by an electric signal as input information, the quantum dot light emitting diode device being used for a color display of a single color, two colors, three colors, four colors or more, wherein the three color display includes a combination of blue-violet, green and red colors, or a combination of blue, green and red colors; the four color display includes a combination of violet, green, yellow and red.

The display device of the present invention includes a gamut covering a plurality of colors, more than the 19762 ° gamut of the national committee on television systems based on the international commission on illumination (CIE).

The invention has the beneficial effects that: the quantum dots are simply dispersed in the energy transfer molecular main body, the energy transfer molecular has high electron and/or hole carrier injection capacity, the capability of the quantum dots for generating excitons is improved, and meanwhile, the energy transfer molecular can be well combined with ligand groups on the surfaces of the quantum dots due to the long alkyl chains of the energy transfer molecular, so that the energy transfer process between the quantum dots and the energy transfer molecular is more facilitated, high electroluminescent efficiency is obtained, and a new and effective method and thought are provided for the injection of the quantum dot holes/electrons at present, so that the performance of a quantum dot electroluminescent device can be improved. Furthermore, based on the good experimental results of the application of the invention to cadmium-free quantum dots or low-cadmium quantum dots, the invention has important significance for developing next-generation environment-friendly QLEDs, quantum dot applications and commercialization of quantum dot technology-related products.

Drawings

FIGS. 1 a-1 c show schematic diagrams of the multi-layer structure of a QLED device of the present invention;

fig. 2 shows chromaticity values and colors of 10 examples of QLED devices proposed by the present invention;

FIG. 3 shows the absorption and photoluminescence spectra of one energy transfer molecule (2, 7-bis (diphenylphosphine oxide) -9, 9-octylfluorene, PO8) and three quantum dot solutions (blue-violet emitting ZnSe/ZnSeS/ZnS quantum dots, green emitting CdSe/CdZnS/ZnS quantum dots, and red emitting CdSe/CdZnS/ZnS quantum dots) in one embodiment of the present invention;

fig. 4 shows a schematic diagram of the energy transfer process of a QLED in operation in one embodiment of the present invention. The hybrid layer comprises ZnSe/ZnSeS/ZnS quantum dots and energy transfer molecules PO 8;

fig. 5 shows an energy transfer process for a QLED having a multilayer structure as shown in fig. 1c, and a hybrid layer consisting of quantum dots and energy transfer molecules that can facilitate electron and hole injection into the quantum dots, in operation according to an embodiment of the present invention;

FIGS. 6 a-6 e show exemplary structures of the molecular species (FIGS. 6 a-6 d) and the oligomer/polymer species (FIG. 6e) of the energy transfer molecule in one embodiment of the invention;

FIGS. 7 a-7 b show the synthesis of two exemplary energy transfer molecules (FIGS. 6a and 6e) of FIGS. 6 a-6 e;

FIGS. 8 a-8 b show SEM images of quantum dots at two different magnifications in one embodiment of the invention, with ZnSe/ZnSeS/ZnS quantum dots having a core/shell structure having a dimension around 9nm and a photoluminescence peak wavelength at 440 nm;

FIG. 9 shows an example of energy levels of materials used in a QLED in an embodiment of the present invention;

FIGS. 10 a-10 c show the electroluminescent properties of a blue-violet emitting QLED in accordance with an embodiment of the present invention, the light emitting layer is comprised of ZnSe/ZnSeS/ZnS quantum dots and energy transfer molecules PO 8;

FIGS. 11 a-11 b show the J-V-I curve (FIG. 11a) and EQE and luminous efficacy curves (FIG. 11b) for a QLED emitting violet light in an embodiment of the invention, the light-emitting layer is composed of ZnSe/ZnSeS/ZnS quantum dots and energy transfer molecules PO 8;

FIGS. 12a to 12b show the effect of the molar ratio of quantum dots to energy transfer molecules PO8 on the device performance in an embodiment of the present invention, and FIGS. 12a and 12b are the effect of the emission luminance and EQE of a QLED constructed with ZnSe/ZnSeS/ZnS quantum dots, respectively, with the PO8 content;

FIG. 13 shows the stability of a QLED device in one embodiment of the invention, cycled 1200 times at an intermittent switch operating voltage of 0-6 v;

FIG. 14 shows a graph of the QLED device stability for purple-emitting ZnSe/ZnSeS/ZnS in an embodiment of the invention;

FIGS. 15 a-15 c show the electroluminescent properties of a green-emitting QLED in accordance with an embodiment of the present invention, the light-emitting layer is composed of CdSe/CdZnS/ZnS quantum dots and energy transfer molecules PO 8;

FIGS. 16 a-16 b show J-V-I curves (FIG. 16a) and EQE and luminous efficiency curves (FIG. 16b) for a green-emitting QLED in accordance with an embodiment of the present invention, the light-emitting layer is composed of CdSe/CdZnS/ZnS quantum dots and energy transfer molecules PO 8;

FIGS. 17a to 17c show the electroluminescent properties of a red-emitting QLED in an embodiment of the invention, the light-emitting layer is composed of CdSe/CdZnS/ZnS quantum dots and energy transfer molecules PO 8;

fig. 18 a-18 b show J-V-I curves (fig. 18a) and EQE and luminous efficacy curves (fig. 18b) for a red emitting QLED in an embodiment of the invention, the light emitting layer consisting of CdSe/CdZnS/ZnS quantum dots and energy transfer molecules PO 8.

In the drawings like parts are provided with the same reference numerals. The figures show embodiments of the application only schematically.

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.

Fig. 1a to 1c illustrate schematic diagrams of multilayer structures of a QLED device in an embodiment of the present invention, which sequentially include an anode, a hole transport layer, a hybrid layer of quantum dots and energy transfer molecules, an electron transport layer, and a cathode from bottom to top.

The anode material is used for connecting with the anode of an external power supply, and in a specific embodiment, the anode material is conductive metal oxide or conductive polymer, preferably Indium Tin Oxide (ITO). The thickness of the anode may be 10-1000nm, preferably 100-400 nm.

In a preferred embodiment, the anode surface is further provided with a conductive layer capable of injecting holes. In one particular embodiment, the conductive layer is preferably poly 3, 4-ethylenedioxythiophene in a 5:1 molar ratio: coatings of polystyrene sulfonate (PEDOT: PSS) PEDOT: PSS coatings can be 5-100nm thick, preferably 10-50nm thick. In a specific embodiment, the conductive layer is disposed on the anode by spin coating.

The hole transport layer mainly serves to transport holes to the light emitting layer. The hole transport layer may be selected from one of the following groups of molecules: tertiary arylamine, thiophene oligomer, thiophene polymer, pyrrole oligomer, vinylphenylene polymer, vinylcarbazole oligomer, vinylcarbazole polymer, fluorine oligomer, fluorine polymer, ethynylbenzene oligomer, ethynylbenzene polymer, phenylene oligomer, phenylene polymer, acetylene oligomer, acetylene polymer, phthalocyanine derivative, porphyrine, and porphyrine derivative. In a specific embodiment, the hole transport layer is a vinyl carbazole Polymer (PVK), the hole transport layer is disposed on the conductive layer by spin coating, and the hole transport layer may have a thickness of 20 to 600nm, preferably 50 to 200 nm.

The hybrid layer of quantum dots and energy transfer molecules is mainly used for light emission due to recombination of holes and electrons in the hole transport layer and the electron transport layer located above and below the hybrid layer. Depending on the structure and function of energy transfer of the energy transfer molecules, the hybrid layer has three modes, as shown in fig. 1 a: the energy transfer molecules are donor type and can promote electrons to be injected into the quantum dots; as shown in fig. 1 b: the energy transfer molecules are receptor type and can promote the injection of holes into the quantum dots; as shown in fig. 1 c: the energy transfer molecules are of a donor-acceptor type and can simultaneously promote the simultaneous injection of electrons and holes into the quantum dots. The energy transfer molecules may be of the molecular, oligomeric or polymeric type. In a preferred embodiment, the energy transfer molecules are easy to generate electrons or/and holes, and have a wider band gap than the quantum dots, and meanwhile, long alkyl chains of the energy transfer molecules can be well combined with the surfaces of the quantum dots to be crosslinked through click chemistry. The above mode leads to the injection of electrons or/and holes into the quantum dots, thereby solving the problem that excitons in the quantum dots are not easy to be injected. In a preferred embodiment, the quantum dot comprises one of the following structures:

h) CdTe/InP/ZnS core/shell structure quantum dot with size in 1.5-9 nm;

q)AgInS₂quantum dots and AgInS₂The size of the/ZnS core-shell structure quantum dot is within the range of 1.5-10 nm.

In a preferred embodiment, the quantum dots comprise ZnSe/ZnSeS/ZnS quantum dots having an electroluminescence peak in the range of 380-450nm and a cadmium or mercury content of less than 0.001 mass%; ZnTe/ZnSe/ZnS quantum dots, ZnTe/ZnTeSe/ZnSe quantum dots or ZnTe/ZnTeSe/ZnS quantum dots with the electroluminescent peak value within the range of 480-900nm and the cadmium or mercury content lower than 0.001 mass percent; the electroluminescent peak value is in the range of 500-700nm, and the content of cadmium or mercury is lower than 50 percent of CdSe/CdZnS/ZnS quantum dots or CdSe/CdZnSe/ZnSe/ZnS quantum dots. In a specific embodiment, the blue-violet emitting quantum dots are preferably ZnSe/ZnSeS/ZnS quantum dots; the green light-emitting quantum dots are preferably CdSe/CdZnS/ZnS quantum dots; the red-emitting quantum dots are preferably CdSe/CdZnS/ZnS quantum dots.

In a preferred embodiment, the energy transfer molecules are of the molecular, oligomeric or polymeric type (groups of molecules shown in figures 6a to 6e or their derivatives, wherein figures 6 a-6 d represent molecular-based structures and figure 6e represents oligomer/polymer-based structures, in a preferred embodiment, the energy transfer molecule has one of an ethynyl group or an azido group, and the ligand terminal group of the quantum dot has one of the ethynyl group or the azido group; after the heat treatment, the mixture is subjected to heat treatment, the quantum dots and energy transfer molecules complete the cross-linking to form a composite layer, hi one particular embodiment, the energy transfer molecule is po8. in a preferred embodiment, the molar ratio of quantum dots to energy transfer molecules is between 100000:1 and 1:100000, and the preparation of the composite layer is selected from one of the following three steps:

a) mixing a solution of quantum dots with a solution of energy transfer molecules;

b) dissolving a powder of quantum dots into a solution of energy transfer molecules;

c) a solid or slurry of energy transfer molecules is dissolved into a solution of quantum dots.

In a specific embodiment, the light-emitting layer is disposed on the hole transport layer by spin coating, and the light-emitting layer may have a thickness of 10 to 300nm, preferably 40 to 100 nm.

The electron transport layer is mainly used to transport electrons to the light emitting layer. The electron transport layer is selected from one of the following group of molecules: oxadiazole, oxadiazole derivative, oxazole derivative, isoxazole derivative, thiazole derivative, 1, 2, 3-triazole derivative, 1, 3, 5-triazine derivative, quinoxaline derivative, pyrrole oligomer, pyrrole polymer, vinylphenylene oligomer, vinylphenylene polymer, vinylcarbazole oligomer, vinylcarbazole polymer, fluorine oligomer, fluorine polymer, ethynylphenylene oligomer, ethynylphenylene polymer, phenylene oligomer, phenylene polymer, thiophene oligomer, thiophene polymer, acetylene oligomer, acetylene polymer, TiO polymer, and the like₂Nanoparticles, ZnO nanoparticles, SnO nanoparticles, gold nanoparticles, and silver nanoparticles. The thickness of the electron transport layer may be 20 to 600nm, preferably 50 to 200 nm. In a specific embodiment, the electron transport layer is disposed on the light emitting layer by spin coating.

The cathode material is used for connecting a negative electrode of an external power supply. In a preferred embodiment, the cathode material comprises any one or more of Al, Ca, Ba, Ca/Al, Ag. In a specific embodiment, the cathode material is Al. The thickness of the cathode material can be 10-600nm, and the preferred thickness is 50-200 nm. In a specific embodiment, the cathode material is disposed on the electron transport layer by evaporation, and the thickness of the cathode layer is 200 nm.

It should be understood that the manufacturing process of the embodiment of the present invention involves a specific deposition process for the anode, the hole transport layer, the light emitting layer, the electron transport layer, and the cathode, which may include, but is not limited to, one of spin coating, spray coating, printing, and vacuum evaporation.

Fig. 2 shows chromaticity values and colors (small white circles) of 10 examples of QLED devices proposed in the embodiments of the present invention. Chromaticity values and colors show 4 bluish violet QLEDs, three green QLEDs and three red QLEDs in the CIE 19762 ° color gamut. The experimental results in the figure show that in 10 devices, the color of 9 QLEDs is outside the NTSC standard color gamut (black triangle).

In a more specific embodiment, the anode is mainly made of ITO, the conducting layer is mainly made of PEDOT: PSS, the hole transport layer is mainly made of PVK, the light emitting layer is a composite layer of ZnSe/ZnS core-shell structure quantum dots and PO8, and the cathode is mainly made of Al. The energy level structure of the light emitting diode device in the specific embodiment of the present invention is shown in fig. 9.

Fig. 3 shows the absorption and photoluminescence spectra of the energy transfer molecule PO8 and three quantum dot solutions (blue-violet emitting ZnSe/ZnSeS s/ZnS quantum dots, green emitting CdSe/CdZnS/ZnS quantum dots, and red emitting CdSe/CdZnS/ZnS quantum dots) in a specific example. The absorption wavelength of PO8 is in the range of 270-330nm, and the photoluminescence wavelength thereof is in the range of 310-400nm, all of which fall into the absorption spectrum range of the three quantum dots, and the larger spectrum overlapping degree greatly increases the probability of energy transfer between the energy transfer molecules and the quantum dots, thereby providing reliable guarantee for the quantum yield of the device.

Fig. 4 shows the energy transfer process of a QLED in operation in a specific embodiment, in which the hybrid layers comprise ZnSe/ZnSeS s/ZnS quantum dots, and the energy transfer molecules PO8 are encapsulated. When the QLED is operated, the PO8 molecules can inject electrons from the cathode layer and transport them to the adjacent quantum dots. The injected electron-hole pair forms an excited state from which a photon is generated and emitted.

Fig. 5 shows the energy transfer process of a QLED in operation having a multilayer structure as shown in fig. 1c, the hybrid layer consisting of quantum dots and one specific energy transfer molecule, which can facilitate both electron and hole injection into the quantum dots.

The synthesis of two exemplary energy transfer molecules (fig. 6a and 6e) of fig. 6 a-6 e is shown in fig. 7 a-7 b, respectively.

Fig. 8a to 8b show scanning electron microscope images of quantum dots at high magnification and low magnification, respectively, in an example of the present invention. In one embodiment, the ZnSe/ZnSeS/ZnS quantum dots having a core/shell structure have a size dimension around 9 nm.

Fig. 10a to 10c show the electroluminescence properties of the QLED emitting blue-violet light in the example of the present invention, and the light emitting layer is composed of ZnSe/ZnSeS/ZnS quantum dots and energy transfer molecules PO 8. Fig. 10a, 10b show optical images of bright blue-violet light of the device in operation. The corresponding electroluminescence spectrum is shown in fig. 10c, and the results show that the emission peak wavelength of the QLED is around 440nm and has a very sharp half-peak width (14.6 nm).

FIGS. 11 a-11 b show the J-V-I curve (FIG. 11a), EQE and luminous efficiency curve (FIG. 11b) of a QLED with a luminescent layer consisting of ZnSe/ZnSeS/ZnS quantum dots and energy transfer molecules PO8, which emits violet light in a specific example of the present invention. As can be seen from the graph, the emission luminance was 38cd/m²When the emission efficiency is high, the maximum EQE is 3.4%, and the maximum emission efficiency is 23 lm/W.

FIGS. 12a to 12b show the effect of the molar ratio of quantum dots to energy transfer molecules PO8 on the device performance in the specific example of the present invention, and FIGS. 12a and 12b are the changes of the emission luminance and EQE of a QLED constructed with ZnSe/ZnSeS/ZnS quantum dots, respectively, with the content of PO8, and it can be seen that the emission luminance and EQE increase significantly with the increase of the molar ratio of quantum dots to PO8 molecules within a certain molar ratio range (1:0-1: 25).

Fig. 13 shows the stability of the QLED device in the specific embodiment of the present invention, and it can be seen that the luminance of the QLED device can maintain good stability after 1200 switching cycles at 0-6v of the intermittent operation voltage.

FIG. 14 shows a graph of the QLED device stability of ZnSe/ZnSeS/ZnS emitting violet light in the example of the present invention, and the experimental results show that at 10cd/m²The half-life of the QLED at light emission luminance was 133 hours.

Fig. 15a to 15c show the electroluminescent properties of a green-emitting QLED in the example of the present invention, the light-emitting layer is composed of CdSe/CdZnS/ZnS quantum dots and energy transfer molecules PO 8. Fig. 15a shows the electroluminescence spectrum of the device when operated at a voltage of 6-14V, and fig. 15b and 15c show optical images of bright green light of the device in operation.

FIGS. 16a to 16b show J-V-I curves (FIG. 16a), EQE and luminous efficiency curves (FIG. 16b) of a green light-emitting QLED according to an embodiment of the present invention, in which a light-emitting layer composed of CdSe/CdZnS/ZnS quantum dots and energy transfer molecules PO8, as seen in the graphs, has a maximum luminous luminance 3800cd/m²。

Fig. 17a to 17c show the electroluminescent properties of a red-emitting QLED in an example of the present invention, the light-emitting layer being composed of CdSe/CdZnS/ZnS quantum dots and energy transfer molecules PO 8. Figure 17a represents the electroluminescence spectrum of the device when operated at a voltage of 6-16V and figures 17b and 17c show optical images of bright red light of the device in operation.

FIGS. 18 a-18 b show J-V-I curves (FIG. 18a), EQE and luminous efficiency curves (FIG. 18b) for a red emitting QLED in an example of the present invention. The luminescent layer is made of CdSe/CdSnS/ZnSA sub-point and an energy transfer molecule PO 8. As can be seen in the figure, the maximum light-emission luminance was 6300cd/m²Corresponding to a wavelength of 625nm, a maximum EQE of 0.63%, and a light emission luminance of 68cd/m²To (3).

Example 1

Synthesis of P8 molecule:

under an argon atmosphere, 3.29g (6mmol) of 2, 7-dibromo-9, 9-dioctylfluorene were dissolved in 80ml of anhydrous tetrahydrofuran and cooled to-78 deg.C (dry ice-acetone bath). 5.1ml of n-butyllithium (2.5M in hexane; 12.75mmol) were slowly added dropwise to give a thick, bright yellow solution. Stirring was continued at-70 ℃ for 20min, and then the temperature of the reaction mixture was raised to 0 ℃. The temperature was then raised to normal temperature and 2.8g (12.75mmol) of diphenylphosphine chloride were added. The reaction was stirred at-70 ℃ for an additional 3 hours before quenching of 2ml of degassed methanol. The volatiles were removed under reduced pressure leaving an oily liquid. The crude material was purified by column chromatography on silica (Rf ═ 0.29) with chloroform/n-hexane (2:8) as the mobile phase, yielding finally 3.50g (77%) of chemically pure P8.

Example 2

Synthesis of PO8 molecule:

3.03g (4mmol) of P8, 50ml of methylene chloride and 10ml of 30% hydrogen peroxide solution were mixed and stirred overnight at ordinary temperature. The organic layer was separated and washed with water and brine in this order. The product was evaporated to dryness to give a white solid which was further purified by recrystallisation from toluene/n-hexane to give 2.7g (85%) of chemically pure PO 8.

Example 3

Pre-treatment and cleaning of pre-patterned ITO sheets:

12 pre-patterned ITO chips whose surfaces were covered with a polymer were placed on a glass substrate and immersed in a 5% aqueous solution of sodium hydroxide at 80 ℃ for 5 min. The above steps were repeated, and then the chip was washed with nano pure water, a 20% aqueous ethanolamine solution, and sonicated for 15min, followed by washing with sufficient nano pure water and drying. And finally, loading the ITO chip to a plasma cleaning chamber, and cleaning the surface of the ITO-coated equipment.

Example 4

Constructing a purple light QLED through high-quality ZnSe/ZnSeS/ZnS quantum dots:

the equipment chip with the precleaned ITO coating is coated with a conductive layer, and the experimental process comprises the following steps: an aqueous solution of PEDOT: PSS in a molar ratio of 5:1 of 200 microliter was applied to the surface using a spin coater at a spin speed of 1750rpm for a spin time of 60 s. The device was then vacuum dried in a 180 ℃ vessel for 20min, cooled to room temperature, and another layer of hole transport layer poly-4-butylbenzene-benzidine (molecular weight >50,000) was further coated on the device by spin coating with 100. mu.l wt 0.05% polymer in chlorobenzene dispersion at a spin speed of 2500rpm for a spin time of 60 s. The device was then dried in a vacuum vessel at 160 ℃ for 40 min. The device was cooled and the quantum dot hybrid layer and energy transfer molecules were spin coated thereon. The mixture of quantum dots and energy transfer molecules was prepared by dissolving the purified quantum dots in n-hexane/toluene, varying the concentration to adjust the absorbance at 400nm to about 1.0, and then adding 0.01% mass fraction of energy transfer molecules to the solution. The process of spin coating the mixed solution on the surface of the device piece is as follows: 100 microliters of the solution was added to the surface of the chip and spin-coated at a spin speed of 2000rpm for 60 seconds, and then the chip was dried under vacuum at 140 ℃ for 30 minutes and cooled to normal temperature. Then, a cathode layer of an aluminum layer having a thickness of 200nm was deposited by thermal deposition in a vacuum of 2X 10-6 Torr. The device was then closed, wrapped in epoxy and irradiated with a UV lamp for 10 min. The electrical and optical properties of QLEDs were tested in a system using the KEITHLEY series 2400 multifunctional source meter (with LabTracer 2.0 software) as the energy source, an Ossila OLED/OPV test platform, a NEWPORT 2835C multifunctional optical source, and a calibrated NEWPORT 818 optical detection probe, the output of the meter was collected by LabView 8.2 software, and QLEDs with a 1.5mm x 3 mm-4.5 x 10-6m2 light emitting area were tested.

Example 5

Through high-quality CdSe/CdSeS/ZnS quantum dots, a green light QLED is constructed:

the construction of the green CdSe/CdSeS/ZnS QLED was similar to the purple-emitting QLED of example 4 above, except that the ZnSe/ZnSeS/ZnS quantum dots were replaced with surface ligand-modified green CdSe/CdSeS/ZnS quantum dots.

Example 6

Constructing a red light QLED through high-quality CdSe/CdSeS/ZnS quantum dots:

construction of a red CdSe/CdSeS/ZnS QLED similar to the purple-emitting QLED described above in example 4, except that the ZnSe/ZnSeS/ZnS quantum dots were replaced with surface ligand-modified red CdSe/CdSeS/ZnS quantum dots.

And (3) testing results:

the device performance of QLEDs based on ZnSe/ZnSeS/ZnS quantum dots without cadmium, surface-modified with ligands and energy transfer molecules can be summarized as follows:

1) electroluminescence wavelength in the ultraviolet-violet range 380nm-450nm (fig. 10 c).

2) Maximum light emission luminance 620cd/m²(FIG. 11 a).

3) The maximum luminous efficiency is 23.22lm/W (FIG. 11 b).

4) The maximum EQE was 3.4%, the maximum light-emission luminance was 38cd/m2, and the emission peak was 440 nm.

5) The emission peak had a sharp line width (half-peak width 14.6nm) (fig. 10 c).

6) The starting voltage is only 2.8V (fig. 10 a).

7) The preservation time is more than 3 months.

8) The device half-life is greater than 130 hours when tested in air and ambient.

9) After 1200 cycles on and off, the device remained stable, showing no significant change in emission intensity (less than 5% deviation).

10) Three representative luminescence colors, 1976CIE L a b color gamut, chromaticity values (0.242, 0.051), (0.235, 0.075), and (0.224, 0.097) (fig. 2).

QLEDs based on CdSe/ZnS quantum dots and energy transfer molecules can be summarized as follows:

11) electroluminescence in the green-red range (480-700nm) of visible light.

12) The maximum brightness of the green light QLED reaches 3000cd/m²The emission peak was 525 nm.

13) The maximum brightness of the red light QLED reaches 6300cd/m²The emission peak was at 625 nm.

14) The maximum luminous efficiency is 4.57lm/W, and the luminous brightness is 41.4cd/m²To (3).

15) The turn-on voltage of the red QLED is as low as 1.9V, and the turn-on voltage of the green QLED is as low as 2.2V.

16) The maximum EQE is 0.7%, and the light-emitting brightness is 41.4cd/m²To (3).

17) The emission peak had a sharp line width (half-peak width 24 nm).

18) The shelf life is longer than 6 months.

19) In air and ambient environments, the half-life of the device is greater than 130 hours.

20) After cycling on and off 520 times, the device remained stable and showed no significant change in emission intensity (less than 5% deviation).

21) Three representative green emission colors, 1976CIE L a b color gamut, chromaticity values (0.102, 0.558), (0.092, 0.560), and (0.088, 0.562).

22) Three representative red emission colors, 1976CIE L a b color gamut, chromaticity values (0.478, 0.521), (0.482, 0.524), and (0.484, 0.525).

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

1. A light-emitting diode device, comprising:

a) a hole transport layer for injecting and transporting holes;

b) a light-emitting layer, in contact with the hole transport layer;

c) an electron transport layer in contact with the light-emitting layer for injecting and transporting electrons to the light-emitting layer;

d) an anode and a cathode for a DC voltage that allows current to flow in the device and emits radiation in the form of ultraviolet, visible or near-infrared light, causing the light-emitting diode device to emit light;

It is characterized in that, the light-emitting layer includes quantum dots and energy transfer molecules, and the energy transfer molecules, as the dispersion medium of the quantum dots, have high electron and/or hole carrier injection capability, and are compatible with the quantum dots. For cross-linking by click chemistry, the energy transfer molecules are molecules, oligomers or polymers, including at least one of the following molecular groups or their derivatives:

Wherein R ₁ , R ₂ , R ₃ are -(CH ₂ ) _x -(CH=CH) _y -(CH ₂ ) _z -R; R is one of the following groups -H, -Cl, -Br, -I, -OH, _-OCH3 , _-OC2H5 , -CHO, -COOCH3, -COOH, _-CONH2 , _-COCl , _-COBr , -COI, _-NH2 , -N ⁺ ( _CH3 ) ₃ , -C( _CH3 ) ₃ , -CH= _CH2 , _-CCH , _-C6H5 , _-C5H5 , _-N3 , _-OCN , -NCO, -CN, -NC, _-NO2 , _-C5H4N , -SH, -SSH, -SOCH3, -SO2H, _-SCN , _-NCS , _-CSH , _-PH2 , phosphono, phosphate, guanine, cytosine, Adenine and thymine.

2 . The light-emitting diode device according to claim 1 , wherein when a DC voltage of 0-30V is applied between the cathode and the anode, the light-emitting diode device has a wavelength in the range of 380-900 nm. 3 . Electroluminescence inside.

3. The light-emitting diode device of claim 1, wherein the energy transfer molecule has high fluorescence quantum efficiency, reversible redox properties in a non-aqueous electrolyte, and a wider band gap than the quantum dots, Thereby, efficient electron and/or hole carrier injection is obtained.

4 . The light-emitting diode device according to claim 1 , wherein the quantum dots and the energy transfer molecules are cross-linked by click chemistry to form a composite layer, wherein the energy transfer molecules comprise acetylene or azide functional groups. 5 . In one of the above, the ligand end group of the quantum dot includes either an acetylene group or an azide group; after heat treatment, the quantum dot and the energy transfer molecule are cross-linked to form a composite layer.

5. The light emitting diode device of claim 1, wherein the electron transport layer comprises at least one molecule from the group consisting of oxadiazoles, oxadiazole derivatives, oxazoles, oxadiazoles azole derivatives, isoxazoles, isoxazole derivatives, thiazoles, thiazole derivatives, 1,2,3-triazoles, 1,2,3-triazole derivatives, 1,3,5-triazines , 1,3,5-triazine derivatives, quinoxaline, quinoxaline derivatives, pyrrole oligomers, pyrrole polymers, vinyl phenylene oligomers, vinyl phenylene polymers, vinyl Carbazole oligomers, vinylcarbazole polymers, fluorooligomers, fluoropolymers, ethynyl phenylene oligomers, ethynyl phenylene polymers, phenylene oligomers, phenylene polymers, thiophene oligomers polymers, thiophene polymers, acetylene oligomers, acetylene polymers, _TiO nanoparticles, ZnO nanoparticles, SnO nanoparticles, gold nanoparticles, and silver nanoparticles.

6. The light emitting diode device of claim 1, wherein the hole transport layer comprises one of the following group of molecules: tertiary aromatic amines, thiophene oligomers, thiophene polymers, and pyrrole oligomers , vinyl phenylene oligomer, vinyl phenylene polymer, vinyl carbazole oligomer, vinyl carbazole polymer, fluoro oligomer, fluoropolymer, ethynyl phenylene oligomer, ethynyl Phenylene polymers, phenylene oligomers, phenylene polymers, acetylene oligomers, acetylene polymers, phthalocyanines, phthalocyanine derivatives, porphyrine and porphyrine derivatives.

7. The light-emitting diode device according to claim 1, wherein the quantum dots comprise one of the following quantum dots:

a) ZnSe/ZnSeS/ZnS core/shell/shell structured quantum dots with sizes in the range of 1.5-9 nm;

b) ZnTe/ZnSe/ZnS core/shell/shell structured quantum dots with sizes in the range of 1.5-9 nm;

c) ZnTe/ZnTeS/ZnS core/shell/shell structured quantum dots with sizes in the range of 1.5-9 nm;

d) CdSe/CdZnS/ZnS core/shell/shell structured quantum dots with sizes in the range of 1.5-9 nm;

e) CdSe/CdZnSe/ZnSe/ZnS core/shell/shell/shell structured quantum dots with sizes in the range of 1.5-9 nm;

f) CdTe/CdZnS/ZnS core/shell/shell structured quantum dots with sizes in the range of 1.5-9 nm;

g) CdS/ZnS core/shell structure, CdS/ZnSe/ZnS core/shell/shell structure or CdZnS/ZnSe/ZnS core/shell/shell structure quantum dots, the size is in the range of 1.5-10nm;

h) CdTe/InP/ZnS core/shell/shell structured quantum dots with sizes in the range of 1.5-9 nm;

i) InP/ZnS core/shell structured quantum dots with size in the range of 1.5-9 nm;

j) Manganese-doped ZnSe:Mn ²⁺ /ZnS core/shell quantum dots, ZnSe/ZnS:Mn ²⁺ /ZnS core/shell/shell quantum dots or ZnS:Mn ²⁺ /ZnS core/shell quantum dots , the size is in the range of 1.5-9nm;

k) Cu-doped ZnS:Cu ⁺ /ZnS core/shell quantum dots or ZnSe:Cu ⁺ /ZnS core/shell quantum dots, with a size in the range of 1.5-10 nm;

l) ZnSe/InP/ZnS core/shell/shell structure quantum dots, the size is in the range of 1.5-9nm;

m) PbS/ZnS core/shell structured quantum dots with size in the range of 1.5-10 nm;

n) PbSe/ZnS core/shell structured quantum dots with size in the range of 1.5-10 nm;

o) CuInS ₂ quantum dots and core/shell structured CuInS ₂ /ZnS quantum dots with sizes in the range of 1.5-10 nm;

p) CuS/ZnS core/shell structured quantum dots with size in the range of 1.5-10 nm;

q) AgInS ₂ quantum dots and AgInS ₂ /ZnS core-shell quantum dots, with sizes in the range of 1.5-10 nm.

8 . The light-emitting diode device according to claim 7 , wherein the quantum dots comprise ZnSe/ZnSeS/ZnS with an electroluminescence peak in the range of 380-450 nm and a cadmium or mercury content of less than 0.001% by mass. Quantum dots; ZnTe/ZnSe/ZnS quantum dots, ZnTe/ZnTeSe/ZnSe quantum dots or ZnTe/ZnTeSe/ZnS quantum dots with an electroluminescence peak in the range of 480-900nm and a cadmium or mercury content of less than 0.001% mass fraction; The luminescence peak is in the range of 500-700 nm, and CdSe/CdZnS/ZnS quantum dots or CdSe/CdZnSe/ZnSe/ZnS quantum dots with cadmium or mercury content less than 50%.

9 . The light-emitting diode device of claim 1 , wherein the molar ratio of the quantum dots to the energy transfer molecules in the light-emitting layer is between 100,000:1 and 1:100,000. 10 .

10. A preparation method of a light-emitting diode device, comprising the following steps:

providing a substrate on which an anode layer is provided;

then disposing a hole transport layer on the anode layer;

Then, a light-emitting layer is arranged on the hole transport layer, and the light-emitting layer is a composite layer composed of quantum dots and energy transfer molecules, and the preparation of the composite layer is selected from one of the following three steps:

b) dissolving the powder of the quantum dots into the solution of the energy transfer molecules;

c) dissolving the solid or slurry of the energy transfer molecules into the solution of the quantum dots;

then disposing an electron transport layer on the light emitting layer;

Finally, the cathode layer is arranged on the electron transport layer;

Wherein, the energy transfer molecules are molecules, oligomers or polymers, including at least one of the following molecular groups or their derivatives:

11. An electronic display device capable of outputting visual information or tactile information and operating as input information through electrical signals, the electronic display device comprising the light-emitting diode device according to any one of claims 1-9, the light-emitting diode The device can be used for single-color, two-color, three-color, four-color or more color display, wherein the three-color display includes a combination of blue-violet, green and red, or a combination of blue, green and red; four-color display includes A combination of violet blue, green, yellow and red.