CN113122241A - Quantum dot material and preparation method thereof, quantum dot light-emitting diode and light-emitting device - Google Patents

Quantum dot material and preparation method thereof, quantum dot light-emitting diode and light-emitting device Download PDF

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CN113122241A
CN113122241A CN201911391269.6A CN201911391269A CN113122241A CN 113122241 A CN113122241 A CN 113122241A CN 201911391269 A CN201911391269 A CN 201911391269A CN 113122241 A CN113122241 A CN 113122241A
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quantum dot
thiophenol
light
particles
zns
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何斯纳
吴龙佳
吴劲衡
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TCL Corp
TCL Research America Inc
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TCL Research America Inc
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/56—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing sulfur
    • C09K11/562—Chalcogenides
    • C09K11/565—Chalcogenides with zinc cadmium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/02—Use of particular materials as binders, particle coatings or suspension media therefor
    • C09K11/025—Use of particular materials as binders, particle coatings or suspension media therefor non-luminescent particle coatings or suspension media
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/115—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising active inorganic nanostructures, e.g. luminescent quantum dots

Abstract

The invention provides a quantum dot material, which comprises quantum dot particles and thiophenol organic matters combined on the surfaces of the quantum dot particles, wherein the thiophenol organic matters are bonded with the quantum dot particles through-SH. The quantum dots modified by thiophenols can improve the luminous efficiency of the quantum dots, thereby improving the luminous performance of the quantum dot light-emitting diode.

Description

Quantum dot material and preparation method thereof, quantum dot light-emitting diode and light-emitting device
Technical Field
The invention belongs to the technical field of quantum dot materials, and particularly relates to a quantum dot material and a preparation method thereof, a quantum dot light-emitting diode and a light-emitting device.
Background
LCD (Liquid Crystal Display) Display technology is the mainstream Display technology at present. Because the LCD needs a backlight source, the LCD has many limitations such as complex structure and process, high cost, high power consumption, etc. The research finds that: the Quantum Dots (QDs) are adopted to replace the traditional fluorescent powder, so that the color gamut of the display screen can be greatly improved. The application of the quantum dots in the backlight module shows that the color gamut of the display screen can be improved from 72% NTSC to 110% NTSC. However, when the quantum dot gets rid of the backlight technology and an active matrix quantum dot light emitting diode display device is utilized, compared with a traditional backlight LCD, the self-luminous QLED (quantum dot light emitting diode) has more prominent display effect, smaller power consumption and wider applicable temperature range under the scenes of black expression, high brightness and the like, and can be used for preparing a display screen with the color gamut of 130% NTSC.
The quantum dot has excellent optical properties, including continuously adjustable full-spectrum luminescence peak position, high color purity and good stability, and is an excellent luminescent and photoelectric material. The quantum dot display is a display technology which utilizes the special performance of quantum dots to realize high performance and low cost, the color gamut value can reach about 130% of NTSC color gamut, the coverage rate of the color gamut exceeds that of the traditional display technology, and the extremely-good image quality is shown, so that a picture is shown more naturally by primary colors. However, the quantum dot surface is coated with a longer oleic acid carbon chain to form a potential barrier to block the movement of a carrier, so that the carrier transport capacity in the device is low, and the application of the quantum dot on a photoelectronic device is limited.
Disclosure of Invention
The invention aims to provide a quantum dot material and a preparation method thereof, and aims to solve the problems that a potential barrier formed by a longer oleic acid carbon chain coated on the surface of a quantum dot hinders the movement of a current carrier and the transport capacity of the current carrier in a quantum dot light-emitting diode is reduced.
Another object of the present invention is to provide a quantum dot light emitting diode using the above quantum dot material as a material of a quantum dot light emitting layer, and a light emitting device including the above quantum dot light emitting diode.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a quantum dot material, which comprises quantum dot particles and thiophenol organic matters combined on the surfaces of the quantum dot particles, wherein the thiophenol organic matters are bonded with the quantum dot particles through-SH.
The invention provides a preparation method of a quantum dot material, which comprises the following steps:
providing an initial quantum dot solution and thiophenol organic matters, adding the thiophenol organic matters into the initial quantum dot solution, heating for reaction, and bonding quantum dot particles with-SH in the thiophenol organic matters to prepare the quantum dot material.
The invention provides a quantum dot light-emitting diode, which comprises a cathode and an anode which are oppositely arranged, and a quantum dot light-emitting layer arranged between the cathode and the anode, wherein the quantum dot light-emitting layer at least contains a quantum dot material, the quantum dot material comprises quantum dot particles and thiophenol organic matters combined on the surfaces of the quantum dot particles, and the thiophenol organic matters are combined with the quantum dot particles in a bonding way through-SH.
The invention provides a light-emitting device, which comprises the quantum dot light-emitting diode.
The quantum dot material provided by the invention comprises quantum dot particles and thiophenol organic matters, wherein-SH on molecules of the thiophenol organic matters and metal atoms on the surfaces of the quantum dot particles act as bonds, so that the surface modification of the quantum dot particles is realized. Specifically, benzene rings in thiophenol organic matters have strong electron density, and are used as electron supply groups to generate an electron transfer reaction with the surfaces of quantum dot particles, so that surrounding charges can be effectively attracted and transferred to the quantum dots, the interface loss between a quantum dot light-emitting layer and a functional layer is effectively counteracted, the effective recombination of electrons and holes in the quantum dots is promoted, the influence of exciton accumulation on the performance of the quantum dot light-emitting diode is reduced, the light-emitting efficiency of the quantum dots is improved, and the light-emitting performance of the quantum dot light-emitting diode is improved.
The quantum dot material prepared by the method is prepared by mixing the quantum dot particles and the thiophenol organic matters in a liquid phase medium and reacting the mixture to form-SH bonding combination quantum dot materials in the quantum dot particles and the thiophenol organic matters. The method is simple to operate, mild in condition, easy to control and beneficial to realizing large-scale production. More importantly, the quantum dot material prepared by the method is beneficial to offsetting the interface loss between the quantum dot light-emitting layer and the functional layer, promoting the effective recombination of electron-hole in the quantum dot, reducing the influence of exciton accumulation on the performance of the quantum dot light-emitting diode, improving the light-emitting efficiency of the quantum dot, and further improving the light-emitting performance of the quantum dot light-emitting diode.
According to the quantum dot light-emitting diode provided by the invention, the material of the quantum dot light-emitting layer contains the quantum dot material, so that the interface loss between the quantum dot light-emitting layer and the functional layer is reduced, the electron-hole recombination in the quantum dot is enhanced, the influence of exciton accumulation on the performance of the quantum dot light-emitting diode is reduced, the light-emitting efficiency of the quantum dot can be improved, and the light-emitting performance of the quantum dot light-emitting diode is improved.
The light-emitting device provided by the invention comprises the quantum dot light-emitting diode, and the material of the quantum dot light-emitting layer in the quantum dot light-emitting diode comprises the quantum dot material, so that the interface loss between the quantum dot light-emitting layer and the functional layer is reduced, the electron-hole recombination in the quantum dot is enhanced, the influence of exciton accumulation on the performance of the quantum dot light-emitting diode is reduced, the light-emitting efficiency of the quantum dot can be improved, and the light-emitting performance of the quantum dot light-emitting diode is improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a flow chart of a preparation process of a quantum dot material provided by an embodiment of the invention;
fig. 2 is a schematic structural diagram of a quantum dot light emitting diode according to an embodiment of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The weight of the related components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present invention as long as it is in accordance with the description of the embodiments of the present invention. Specifically, the weight described in the description of the embodiment of the present invention may be a unit of mass known in the chemical industry field, such as μ g, mg, g, and kg.
The first aspect of the embodiments of the present invention provides a quantum dot material, which includes quantum dot particles and thiophenol organic compounds bonded to the surfaces of the quantum dot particles, and the thiophenol organic compounds are bonded to the quantum dot particles through-SH.
The quantum dot material provided by the embodiment of the invention comprises quantum dot particles and thiophenol organic matters, wherein-SH on molecules of the thiophenol organic matters reacts with metal atoms on the surfaces of the quantum dot particles to form bonds, so that the surface modification of the quantum dot particles is realized. Specifically, benzene rings in thiophenol organic matters have strong electron density, and are used as electron supply groups to generate an electron transfer reaction with the surfaces of quantum dot particles, so that surrounding charges can be effectively attracted and transferred to the quantum dots, the interface loss between a quantum dot light-emitting layer and a functional layer is effectively counteracted, the effective recombination of electrons and holes in the quantum dots is promoted, the influence of exciton accumulation on the performance of the quantum dot light-emitting diode is reduced, the light-emitting efficiency of the quantum dots is improved, and the light-emitting performance of the quantum dot light-emitting diode is improved.
In the embodiment of the present application, the quantum dot particles refer to quantum dots that can be used as a light emitting layer material in a quantum dot light emitting diode. In some embodiments, the quantum dot particles are selected from CdSe, ZnSe, PbSe, CdTe, InP, GaN, GaP, AlP, InN, ZnTe, InAs, GaAs, CaF2、Cd1-xZnxS、Cd1-xZnxSe、CdSeyS1-y、PbSeyS1-y、ZnXCd1-XTe、CdS/ZnS、Cd1-xZnxS/ZnS、Cd1-xZnxSe/ZnSe、CdSe1-xSx/CdSeyS1-y/CdS、CdSe/Cd1-xZnxSe/CdyZn1-ySe/ZnSe、Cd1-xZnxSe/CdyZn1-ySe/ZnSe、CdS/Cd1-xZnxS/CdyZn1-yS/ZnS、NaYF4、NaCdF4、Cd1-xZnxSeyS1-y、CdSe/ZnS、Cd1-xZnxSe/ZnS、CdSe/CdS/ZnS、CdSe/ZnSe/ZnS、Cd1-xZnxSe/CdyZn1-yS/ZnS, InP/ZnS, but not limited thereto.
In some embodiments, the thiophenolic organic compound is selected from at least one of thiophenol, 4-methylthiophenol, 3-methylthiophenol, 2-ethylthiophenol, 3-ethylthiophenol, 4-tert-butylthiophenol, 2, 4-dimethylthiophenol, 2, 5-dimethylthiophenol, 2, 6-dimethylthiophenol. In the thiophenol organic compound provided by the embodiment of the invention, the structure is provided with only methyl, ethyl and tert-butyl as substituent groups except the phenol-sulfur functional skeleton, so that the strong electron density of benzene rings in thiophenol cannot be dispersed or transferred, and the substituent groups are used as short electron-donating groups, so that the electron density of the benzene rings in the thiophenol can be further improved.
In some embodiments, the quantum dot material has a molar ratio of the quantum dot particles to the thiophenols organic compound of 1:0.8 to 1: 2. At this time, the thiophenol organic compounds can be well modified on the surface of the quantum dot particles. Most preferably, when the molar ratio of the quantum dot particles to the thiophenol organic matters is 1:1, the combination of the thiophenol organic matters on the surfaces of the quantum dot particles tends to be saturated, and at the moment, the obtained quantum dot material can offset the interface loss between the quantum dot light-emitting layer and the functional layer to the maximum extent, promote the effective recombination of electron-hole in the quantum dot, reduce the influence of exciton accumulation on the performance of the quantum dot light-emitting diode, improve the light-emitting efficiency of the quantum dot, and thus improve the light-emitting performance of the quantum dot light-emitting diode. When the molar ratio of the thiophenols to the quantum dot particles is smaller, the electron transfer reaction between the thiophenols and the surfaces of the quantum dot nanoparticles is reduced, so that the ability of the thiophenols to attract surrounding charges and transfer the charges to the quantum dots is weakened, and accordingly, the function of offsetting the interface loss between the quantum dot light-emitting layer and the functional layer is reduced. When the molar ratio of the thiophenols to the quantum dot particles is as low as 0.8:1, the concentration of the thiophenols becomes smaller and smaller with the progress of the coordination reaction between the thiophenols and the quantum dot particles, the counter strain is very slow, and the thiophenols cannot be completely adsorbed on the surfaces of the quantum dot particles. If the molar ratio of the thiophenols to the quantum dot particles is too large and is higher than 2:1, the adsorption and desorption reactions between the thiophenols and the quantum dot particles are too fast, which easily causes uneven coating. In addition, the excessive addition amount of the thiophenol organic compound causes excessive thiophenol organic compound coated on the quantum dot particles, and the formed ligand layer is too thick. In the process of light emission of the quantum dot, light must be transmitted through the ligand layer, and the ligand can absorb part of light energy, so that when the ligand layer is too thick, the loss of the light energy can be increased, and the light emission efficiency of the quantum dot is reduced.
The quantum dot material provided by the embodiment of the invention can be prepared by the following method.
Accordingly, as shown in fig. 1, a second aspect of the embodiments of the present invention provides a method for preparing a quantum dot material, including the following steps:
s01, providing an initial quantum dot solution and thiophenol organic matters, adding the thiophenol organic matters into the initial quantum dot solution, heating for reaction, and bonding quantum dot particles with-SH in the thiophenol organic matters to prepare the quantum dot material.
According to the preparation method of the quantum dot material provided by the embodiment of the invention, the quantum dot particles and the thiophenol organic matters are mixed in a liquid phase medium to react to prepare the quantum dot material in which the quantum dot particles and-SH in the thiophenol organic matters are bonded. The method is simple to operate, mild in condition, easy to control and beneficial to realizing large-scale production. More importantly, the quantum dot material prepared by the method is beneficial to offsetting the interface loss between the quantum dot light-emitting layer and the functional layer, promoting the effective recombination of electron-hole in the quantum dot, reducing the influence of exciton accumulation on the performance of the quantum dot light-emitting diode, improving the light-emitting efficiency of the quantum dot, and further improving the light-emitting performance of the quantum dot light-emitting diode.
Specifically, in the embodiment of the invention, thiophenol organic matters are used as a modification material for improving the luminous efficiency of the quantum dot particles. In some embodiments, the thiophenolic organic compound is selected from at least one of thiophenol, 4-methylthiophenol, 3-methylthiophenol, 2-ethylthiophenol, 3-ethylthiophenol, 4-tert-butylthiophenol, 2, 4-dimethylthiophenol, 2, 5-dimethylthiophenol, 2, 6-dimethylthiophenol. In the thiophenol organic compound provided by the embodiment of the invention, the structure is provided with only methyl, ethyl and tert-butyl as substituent groups except the phenol-sulfur functional skeleton, so that the strong electron density of benzene rings in thiophenol cannot be dispersed or transferred, and the substituent groups are used as short electron-donating groups, so that the electron density of the benzene rings in the thiophenol can be further improved.
The initial quantum dots in the initial quantum dot solution are conventional quantum dots, can be commercially available quantum dot products, and can also be self-prepared quantum dots. Typically, the surface of the quantum dot will contain a ligand. In a subsequent step, the surface ligands in the initial quantum dots are provided with a strong chargeDisplacement of the daughter thiophenols by organics. It is to be understood that the quantum dot particles in the initial quantum dots are quantum dots referred to above that can be used as a light emitting layer material in a quantum dot light emitting diode. In some embodiments, the quantum dot particles are selected from CdSe, ZnSe, PbSe, CdTe, InP, GaN, GaP, AlP, InN, ZnTe, InAs, GaAs, CaF2、Cd1-xZnxS、Cd1-xZnxSe、CdSeyS1-y、PbSeyS1-y、ZnXCd1-XTe、CdS/ZnS、Cd1-xZnxS/ZnS、Cd1-xZnxSe/ZnSe、CdSe1-xSx/CdSeyS1-y/CdS、CdSe/Cd1-xZnxSe/CdyZn1-ySe/ZnSe、Cd1-xZnxSe/CdyZn1-ySe/ZnSe、CdS/Cd1-xZnxS/CdyZn1-yS/ZnS、NaYF4、NaCdF4、Cd1- xZnxSeyS1-y、CdSe/ZnS、Cd1-xZnxSe/ZnS、CdSe/CdS/ZnS、CdSe/ZnSe/ZnS、Cd1-xZnxSe/CdyZn1- yS/ZnS, InP/ZnS, but not limited thereto.
In some embodiments, the initial quantum dots in the initial quantum dot solution are quantum dot particles having organic ligands on their surfaces. In some embodiments, the initial quantum dots in the initial quantum dot solution are quantum dot particles having a surface comprising an organic amine ligand. When the initial quantum dot surface ligand is an organic amine ligand, as no other ligand is contained, the exchange between thiophenol organic matters and the surface ligand is relatively simple in the heating reaction process of the subsequent step, and the reaction temperature and the reaction time do not need to be adjusted according to the types of different ligands; and the exchange between thiophenols and organic amine ligands is more sufficient, which is beneficial to the thiophenols to fully replace the organic amine on the surface of the quantum dot.
In some embodiments, when the initial quantum dot surface ligand is an organic amine ligand, the initial quantum dot solution is prepared by: preparing a colloidal solution of quantum dot particles; and under an inert atmosphere, heating the colloidal solution of the quantum dot particles, adding oleylamine, and carrying out heat preservation reaction to prepare an initial quantum dot solution.
In some embodiments, the method for preparing the colloidal solution of quantum dot particles is as follows: and dispersing the quantum dot particles in an organic solvent A to obtain the quantum dot colloidal solution. The organic solvent A is selected from high-boiling-point olefin such as 1-Octadecene (ODE), 1-hexadecene, 1-eicosene and the like which have relatively good solubility to quantum dots, so that the organic solvent A can still be used as a good dispersion medium in the subsequent high-temperature reaction process.
In some embodiments, the concentration of quantum dot particles in the colloidal solution of quantum dot particles is 20mg/mL to 50 mg/mL. In the concentration range, the quantum dot particles are not easy to agglomerate in the organic solvent A, and a better dispersion effect can be obtained, so that the optimal contact area can be obtained during ligand exchange reaction. If the concentration of the quantum dots is too low, the dispersion degree in the organic solvent A is too large, the spacing among particles is too large, excessive grafting of a ligand is caused, and the performance of a luminescent layer of the quantum dots is influenced finally; if the concentration of the quantum dots is too high, an agglomerate is easily formed, and a good contact environment with the ligand cannot be formed.
Further, in order to avoid introducing a byproduct by reacting an oxygen-containing gas with a colloidal solution of quantum dot particles at a high temperature, in the embodiment of the invention, the colloidal solution of the quantum dot particles is heated under an inert atmosphere to make the colloidal solution of the quantum dot particles in a good solution state, and then oleylamine is added for a heat preservation reaction, so that an original ligand on the surface of the quantum dot particles is replaced by an oleylamine ligand. Wherein the inert atmosphere includes, but is not limited to, an argon atmosphere.
In some embodiments, the colloidal solution of the quantum dot particles is subjected to heating treatment, and is added into an oleylamine heat preservation reaction step, wherein the volume ratio of the quantum dot particles to the oleylamine is (100-120): 1, adding oleylamine into the colloidal solution of the quantum dot particles. In this range, the oleylamine may be well dispersed in the solvent, and may be sufficiently contacted with the quantum dot particles and attached at a suitable ratio on the surface of the quantum dot particles. If the dosage of the oleylamine is too small, and the volume ratio of the oleylamine to the quantum dot particles is less than 1:120, the quantum dot in the precursor colloidal solution formed by the quantum dot particles and the oleylamine cannot be fully wrapped; if the dosage of the oleylamine is excessive, and the volume ratio of the oleylamine to the quantum dot particles is larger than 1:100, in the process of ligand exchange with thiophenol organic matters, the thiophenol organic matters need to be greatly increased to initiate ligand exchange reaction, which is not beneficial to the balance of forward ligand exchange.
In some embodiments, the temperature of the incubation reaction is 200 ℃ to 250 ℃ and the reaction time is 0.5 hour to 1 hour. Under a high-temperature environment, oleylamine can coat the surfaces of quantum dot particles, and the amine groups and the quantum dot particles form coordinate bonds to form a quantum dot-oleylamine precursor colloidal solution, namely an initial quantum dot solution. The surface of the quantum dot particle is modified with oleylamine by the method, other impurity substances on the surface of the quantum dot particle are removed, and a favorable environment is provided for ligand exchange of thiophenol organic matters in the next step.
In the embodiment of the present invention, when the thiophenol organic compound is added to the initial quantum dot solution, the concentration of the initial quantum dots, that is, the quantum dot particles in the initial quantum dot solution is preferably 20mg/mL to 50 mg/mL. In the concentration range, the quantum dot particles are not easy to agglomerate, and a better dispersion effect can be obtained, so that the optimal contact area can be obtained during the exchange reaction of thiophenol organic matters and the initial quantum dot surface ligands. If the concentration of the quantum dot particles is too low, the dispersion degree of the quantum dot particles in a solution is too large, the distance between the particles is too large, excessive grafting of a ligand is caused, and the performance of a quantum dot light-emitting layer is finally affected (in the light-emitting process of the quantum dot, light transmission must pass through a ligand layer, and the ligand can absorb a part of light energy, so that the light-emitting efficiency is reduced); if the concentration of the quantum dot particles is too high, an agglomerate is easily formed, and a good contact environment with the ligand cannot be formed.
In some embodiments, in the step of adding the thiophenol organic in the initial quantum dot solution, the thiophenol organic is added in the initial quantum dot solution in a ratio of the molar ratio of the quantum dot particles to the thiophenol organic being 1:0.8 to 1: 2. At this time, the thiophenol organic compounds can be well exchanged with the initial ligands on the surface of the quantum dot particles to modify the surface of the quantum dot particles. Most preferably, when the molar ratio of the quantum dot particles to the thiophenol organic matters is 1:1, the combination of the thiophenol organic matters on the surfaces of the quantum dot particles tends to be saturated, and at this time, the obtained quantum dot material can counteract the interface loss between the quantum dot light-emitting layer and the functional layer to the maximum extent, promote the effective recombination of electrons and holes in QDs, reduce the influence of exciton accumulation on the performance of the quantum dot light-emitting diode, improve the light-emitting efficiency of the quantum dot, and thus improve the light-emitting performance of the quantum dot light-emitting diode. When the molar ratio of the thiophenols to the quantum dot particles is smaller, the electron transfer reaction between the thiophenols and the surfaces of the quantum dot nanoparticles is reduced, the ability of the thiophenols to attract surrounding charges and transfer the charges to the quantum dots is weakened, and accordingly, the function of offsetting the interface loss between the quantum dot light-emitting layer and the functional layer is reduced. When the molar ratio of the thiophenols to the quantum dot particles is as low as 0.8:1, the concentration of the thiophenols becomes smaller and smaller with the progress of the coordination reaction between the thiophenols and the quantum dot particles, the counter strain is very slow, and the thiophenols cannot be completely adsorbed on the surfaces of the quantum dot particles. If the molar ratio of the thiophenols to the quantum dot particles is too large and is higher than 2:1, the adsorption and desorption reactions between the thiophenols and the quantum dot particles are too fast, which easily causes uneven coating. In addition, the excessive addition amount of the thiophenol organic compound causes excessive thiophenol organic compound coated on the quantum dot particles, and the formed ligand layer is too thick. In the process of light emission of the quantum dot, light must be transmitted through the ligand layer, and the ligand can absorb part of light energy, so that when the ligand layer is too thick, the loss of the light energy can be increased, and the light emission efficiency of the quantum dot is reduced.
In some embodiments, the thiophenol organic is added to the initial quantum dot solution, and the heating reaction is carried out at a temperature of 200 ℃ to 250 ℃ so that the quantum dot particles are bonded with-SH bonds in the thiophenol organic for 0.5 hours to 1 hour. If the reaction temperature is too low or the reaction time is too short, the ligand replacement reaction is insufficient, and the function of thiophenol organic matters for enhancing the luminous efficiency of the quantum dot particles is reduced or even has no obvious function. If the reaction is too high and the reaction time is too long, the degradation or other miscellaneous side reactions of the surface ligand of the quantum dot can be caused, so that the purpose of modifying the quantum dots by thiophenol organic matters is lost.
Further, after the reaction is finished, the temperature of the reaction solution is reduced to room temperature, then ethyl acetate, ethanol and acetone are used for fractional precipitation and cleaning, and then the solution is re-dispersed in an organic solvent to prepare the thiophenol organic matter modified quantum dot solution. Wherein the organic solvent is selected from nonpolar solvents such as n-hexane, n-octane, n-decane, chloroform, ODE and the like.
As shown in fig. 2, a third aspect of the embodiments of the present invention provides a quantum dot light emitting diode, including a cathode and an anode that are oppositely disposed, and a quantum dot light emitting layer disposed between the cathode and the anode, where the quantum dot light emitting layer contains at least a quantum dot material, and the quantum dot material includes quantum dot particles and thiophenol organic matters bonded to the surfaces of the quantum dot particles, and the thiophenol organic matters are bonded to the quantum dot particles through-SH.
According to the quantum dot light-emitting diode provided by the embodiment of the invention, the material of the quantum dot light-emitting layer contains the quantum dot material, so that the formed quantum dot light-emitting diode has the advantages that the interface loss between the quantum dot light-emitting layer and the functional layer is reduced, the electron-hole recombination in the quantum dot is enhanced, the influence of exciton accumulation on the performance of the quantum dot light-emitting diode is reduced, the light-emitting efficiency of the quantum dot can be improved, and the light-emitting performance of the quantum dot light-emitting diode is improved.
In the embodiment of the present invention, the quantum dot material contained in the material of the electron transport layer is the above-mentioned quantum dot material. Specifically, the quantum dot material comprises quantum dot particles and thiophenol organic matters combined on the surfaces of the quantum dot particles, and the thiophenol organic matters are bonded with the quantum dot particles through-SH. The material of the quantum dot light-emitting layer contains the quantum dot material, so that in the formed quantum dot light-emitting diode, thiophenol organic matters are used as a strong electron donor to generate an electron transfer reaction with the surface of quantum dot nano particles, and can effectively attract surrounding charges and transfer the charges to quantum dots, so that the interface loss between the quantum dot light-emitting layer and the functional layer is effectively counteracted, and the light-emitting efficiency is improved.
In a preferred embodiment, the material of the quantum dot light-emitting layer is the quantum dot material, that is, the quantum dot light-emitting layer is made of the quantum dot material.
In some embodiments, the quantum dot material has a molar ratio of the quantum dot particles to the thiophenols organic compound of 1:0.8 to 1: 2. At this time, the thiophenol organic compounds can be well exchanged with the initial ligands on the surface of the quantum dot particles to modify the surface of the quantum dot particles. Most preferably, when the molar ratio of the quantum dot particles to the thiophenol organic matters is 1:1, the combination of the thiophenol organic matters on the surfaces of the quantum dot particles tends to be saturated, and at this time, the obtained quantum dot material can counteract the interface loss between the quantum dot light-emitting layer and the functional layer to the maximum extent, promote the effective recombination of electrons and holes in QDs, reduce the influence of exciton accumulation on the performance of the quantum dot light-emitting diode, improve the light-emitting efficiency of the quantum dot, and thus improve the light-emitting performance of the quantum dot light-emitting diode. When the molar ratio of the thiophenols to the quantum dot particles is smaller, the electron transfer reaction between the thiophenols and the surfaces of the quantum dot nanoparticles is reduced, the ability of the thiophenols to attract surrounding charges and transfer the charges to the quantum dots is weakened, and accordingly, the function of offsetting the interface loss between the quantum dot light-emitting layer and the functional layer is reduced. When the molar ratio of the thiophenols to the quantum dot particles is as low as 0.8:1, the concentration of the thiophenols becomes smaller and smaller with the progress of the coordination reaction between the thiophenols and the quantum dot particles, the counter strain is very slow, and the thiophenols cannot be completely adsorbed on the surfaces of the quantum dot particles. If the molar ratio of the thiophenols to the quantum dot particles is too large and is higher than 2:1, the adsorption and desorption reactions between the thiophenols and the quantum dot particles are too fast, which easily causes uneven coating. In addition, the excessive addition amount of the thiophenol organic compound causes excessive thiophenol organic compound coated on the quantum dot particles, and the formed ligand layer is too thick. In the process of light emission of the quantum dot, light must be transmitted through the ligand layer, and the ligand can absorb part of light energy, so that when the ligand layer is too thick, the loss of the light energy can be increased, and the light emission efficiency of the quantum dot is reduced.
In some embodiments, the thiophenolic organic compound is selected from at least one of thiophenol, 4-methylthiophenol, 3-methylthiophenol, 2-ethylthiophenol, 3-ethylthiophenol, 4-tert-butylthiophenol, 2, 4-dimethylthiophenol, 2, 5-dimethylthiophenol, 2, 6-dimethylthiophenol. In the thiophenol organic compound provided by the embodiment of the invention, the structure is provided with only methyl, ethyl and tert-butyl as substituent groups except the phenol-sulfur functional skeleton, so that the strong electron density of benzene rings in thiophenol cannot be dispersed or transferred, and the substituent groups are used as short electron-donating groups, so that the electron density of the benzene rings in the thiophenol can be further improved.
In the embodiment of the invention, the thickness of the quantum dot light-emitting layer is 20-60 nm.
Specifically, the quantum dot light emitting diode according to the embodiment of the present invention has a positive structure and an inversion structure.
In one embodiment, a positive structure quantum dot light emitting diode includes an anode and a cathode disposed opposite each other, a quantum dot light emitting layer disposed between the anode and the cathode, and the anode is disposed on a substrate. Furthermore, an electron functional layer such as an electron injection layer, an electron transport layer, a hole blocking layer and the like can be arranged between the cathode and the electron transport layer; and a hole functional layer such as a hole transport layer, a hole injection layer and an electron blocking layer can be arranged between the anode and the quantum dot light-emitting layer. In some embodiments of the positive-type structure device, the quantum dot light emitting diode includes a substrate, an anode disposed on a surface of the substrate, the hole injection layer disposed on a surface of the anode, a hole transport layer disposed on a surface of the hole injection layer, a quantum dot light emitting layer disposed on a surface of the hole transport layer, an electron transport layer disposed on a surface of the quantum dot light emitting layer, and a cathode disposed on a surface of the electron transport layer.
In one embodiment, an inverted structure quantum dot light emitting diode includes a stacked structure including an anode and a cathode disposed opposite each other, a quantum dot light emitting layer disposed between the anode and the cathode, and the cathode disposed on a substrate. Furthermore, an electron functional layer such as an electron injection layer, an electron transport layer, a hole blocking layer and the like can be arranged between the cathode and the electron transport layer; and a hole functional layer such as a hole transport layer, a hole injection layer and an electron blocking layer can be arranged between the anode and the quantum dot light-emitting layer. In some embodiments of the device with the inverted structure, the quantum dot light emitting diode includes a substrate, a cathode disposed on a surface of the substrate, an electron transport layer disposed on a surface of the cathode, a quantum dot light emitting layer disposed on a surface of the electron transport layer, a hole transport layer disposed on a surface of the quantum dot light emitting layer, a hole injection layer disposed on a surface of the hole transport layer, and an anode disposed on a surface of the hole injection layer.
Specifically, the selection of the anode is not limited strictly, and ITO may be selected, but is not limited thereto. The thickness of the anode is 15-30 nm.
The cathode can be made of conventional cathode materials, such as metal silver or metal aluminum, or a nano Ag wire or a nano Cu wire, and the materials have low resistance so that carriers can be injected smoothly. The thickness of the cathode is 15-30 nm.
The material of the hole transport layer can be made of a hole transport material which is conventional in the field, and can be TFB, PVK, Poly-TPD, TCTA, PEDOT: PSS, CBP, but not limited thereto.
The material of the electron transport layer can be made of electron transport materials conventional in the art, including but not limited to ZnO, Ca, Ba, CsF, LiF, CsCO3And Alq3One kind of (1).
In some embodiments, the qd-led may further comprise an encapsulation layer. The packaging layer can be arranged on the surface of a top electrode (an electrode far away from the substrate) and can also be arranged on the surface of the whole quantum dot light-emitting diode.
The quantum dot light-emitting diode provided by the embodiment of the invention can be prepared by the following method.
A fourth aspect of the embodiments of the present invention provides a method for manufacturing a quantum dot light emitting diode, including the steps of:
E01. providing a substrate;
E02. providing an initial quantum dot solution and thiophenol organic matters, adding the thiophenol organic matters into the initial quantum dot solution, heating for reaction, and bonding quantum dot particles with-SH in the thiophenol organic matters to prepare a quantum dot material;
E03. and depositing the quantum dot material on the surface of the substrate, and annealing to obtain the quantum dot light-emitting layer.
Specifically, in step E01, in the positive type structure quantum dot light emitting diode, the bottom electrode provided on the substrate is an anode, that is, the substrate at least includes an anode substrate. In some embodiments of the invention, the substrate is an anode substrate with an anode disposed on a substrate. In some embodiments of the present invention, the substrate may be a laminated substrate in which an anode is disposed on a substrate and a hole injection layer is disposed on a surface of the anode. In some embodiments of the present invention, the substrate may be a laminated substrate in which an anode is disposed on a substrate, a hole injection layer is disposed on a surface of the anode, and a hole transport layer is disposed on a surface of the hole injection layer. It should be understood that the present invention is not limited to the structures of the above-described embodiments.
For the quantum dot light emitting diode with the inversion structure, the bottom electrode arranged on the substrate is a cathode, namely, the substrate at least comprises a cathode substrate. In some embodiments of the invention, the substrate is a cathode substrate with a cathode disposed on a substrate. In still other embodiments of the present invention, the substrate may be a laminated substrate in which a cathode is provided on a substrate and an electron injection layer is provided on a surface of the cathode. In still other embodiments of the present invention, the substrate may be a laminated substrate in which a cathode is disposed on a substrate, an electron injection layer is disposed on a surface of the cathode, and an electron transport layer is disposed on a surface of the electron injection layer. It should be understood that the present invention is not limited to the structures of the above-described embodiments.
In the preparation method of the quantum dot light-emitting diode provided by the embodiment of the invention, before the functional layer is prepared on the surface of the anode substrate or the cathode substrate, the anode substrate or the cathode substrate is preferably subjected to pretreatment. In a preferred embodiment, the step of pre-treating comprises: cleaning the anode substrate or the cathode substrate with a cleaning agent to primarily remove stains on the surface, and then sequentially performing ultrasonic cleaning in deionized water, acetone, absolute ethyl alcohol and deionized water for 10-30 min, preferably 20min, to remove impurities on the surface; and finally, drying the anode substrate or the cathode substrate by using high-purity nitrogen to obtain the surface of the anode substrate or the cathode substrate.
In the step E02, the preparation of the quantum dot material is as described above, and is not repeated herein for brevity.
In the step E03, the quantum dot material is deposited on the surface of the substrate by using a conventional solution processing method, including but not limited to spin coating, inkjet printing, and the like. In some embodiments, the substrate is placed on a spin coater, a quantum dot material solution with a certain concentration is prepared to be spin-coated to form a film, the thickness of the light emitting layer is controlled by adjusting the concentration of the solution, the spin coating speed and the spin coating time, the thickness is about 20-60 nm, and the light emitting layer is dried at a proper temperature.
The functional layers (including but not limited to hole injection layer, hole transport layer, electron injection layer, electron transport layer, hole blocking layer, electron blocking layer) except the anode and the cathode of the embodiments of the present application can be prepared by conventional solution processing methods including but not limited to inkjet printing, spin coating, drop coating, dipping, coating, and evaporation. Similarly, the film thickness of each layer can be controlled by adjusting the concentration of the solution, the printing or spin coating speed and the deposition time; and thermal annealing treatment is carried out after the solution is deposited.
In some embodiments, the substrate is an anode substrate, and the method for preparing the hole transport layer comprises: placing the anode substrate on a spin coater, and spin-coating a prepared solution of the hole transport material to form a film; the film thickness is controlled by adjusting the concentration of the solution, the spin-coating speed and the spin-coating time, and then a thermal annealing process is performed at an appropriate temperature. In some embodiments, the preparation of the electron transport layer: and placing the cathode substrate or the anode substrate on which the quantum dot luminous layer is deposited in a vacuum evaporation chamber, and evaporating an electron transmission layer with the thickness of about 80nm at the evaporation speed of about 0.01-0.5 nm/s.
In some embodiments, the method further comprises performing packaging treatment on the obtained quantum dot light emitting diode. The packaging process can adopt common machine packaging or manual packaging. Preferably, the oxygen content and the water content in the packaging treatment environment are both lower than 0.1ppm so as to ensure the stability of the device.
A fifth aspect of the embodiments of the present invention provides a light emitting device, including the above-described quantum dot light emitting diode.
The light-emitting device provided by the embodiment of the invention comprises the quantum dot light-emitting diode, and the material of the quantum dot light-emitting layer in the quantum dot light-emitting diode comprises the quantum dot material, so that the interface loss between the quantum dot light-emitting layer and the functional layer of the formed quantum dot light-emitting diode is reduced, the electron-hole recombination in the quantum dot is enhanced, the influence of exciton accumulation on the performance of the quantum dot light-emitting diode is reduced, the light-emitting efficiency of the quantum dot can be improved, and the light-emitting performance of the quantum dot light-emitting diode is improved.
The following description will be given with reference to specific examples.
Example 1
A quantum dot material modified by thiophenol organic matters is prepared by the following steps:
1) an appropriate amount of CdS/ZnS was added to 20mL ODE to form a quantum dot colloidal solution with a total concentration of 20 mg/mL. Subsequently, the temperature is raised to 200 ℃ in an argon atmosphere, and then the ratio of the quantum dots to the oleylamine is increased according to the volume ratio of 100:1, and keeping the temperature for reaction for 30min to form a quantum dot solution.
2) Adding the thiophenol into the quantum dot solution according to the molar ratio of the quantum dot to the thiophenol of 1:1, and continuously stirring at 200 ℃ for 30 min. After the reaction is finished, after the reaction solution is cooled to room temperature, using a mixed solvent of ethyl acetate and ethanol and a mixed solvent of acetone and ethanol to perform fractional precipitation and cleaning, and then re-dispersing in n-hexane to prepare the thiophenol modified CdS/ZnS quantum dots.
Example 2
A4-methylphenylthiol organic matter modified quantum dot material is prepared by the following steps:
1) adding proper amount of Cd1-xZnxAnd adding the S into 20mL of 1-hexadecene to form a quantum dot colloidal solution with the total concentration of 30 mg/mL. Subsequently, the temperature is raised to 200 ℃ in an argon atmosphere, and then the ratio of the quantum dots to the oleylamine is increased to 120:1, and keeping the temperature for reaction for 30min to form a quantum dot solution.
2) Adding 4-methylthiophenol into the quantum dot solution according to the molar ratio of the quantum dot to the 4-methylthiophenol of 1:1.5, and continuously stirring for 1h at 200 ℃. After the reaction is finished, after the reaction solution is cooled to room temperature, using a mixed solvent of ethyl acetate and ethanol and a mixed solvent of acetone and ethanol to perform fractional precipitation and cleaning, and then re-dispersing in n-octane to prepare 4-methylthiophenol modified Cd1-xZnxAnd (4) S quantum dots.
Example 3
A quantum dot material modified by 2, 4-dimethyl thiophenol organic matters is prepared by the following steps:
1) adding proper amount of Cd1-xZnxS/ZnS is added into 20mL of 1-eicosene to form a quantum dot colloidal solution with a total concentration of 50 mg/mL. Subsequently, the temperature is raised to 250 ℃ in an argon atmosphere, and then the ratio of the quantum dots to the oleylamine is increased according to the volume ratio of 110: 1, and keeping the temperature for reaction for 30min to form a precursor solution A.
2) Adding 2, 4-dimethylthiophenol into the quantum dot solution according to the molar ratio of the quantum dot to the 2, 4-dimethylthiophenol of 1:2, and continuously stirring for 1h at 250 ℃. After the reaction is finished, the reaction solution is cooled down toAfter room temperature, using a mixed solvent of ethyl acetate and ethanol and a mixed solvent of acetone and ethanol to perform fractional precipitation and cleaning, and then re-dispersing in n-hexane to prepare 2, 4-dimethylthiophenol modified Cd1-xZnxAnd (3) S/ZnS quantum dots.
Example 4
A quantum dot light-emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the anode is arranged on a substrate. The substrate is made of a glass sheet, the anode is made of an ITO (indium tin oxide) base plate, the hole transport layer is made of TFB (tunneling glass), the electron transport layer is made of ZnO, the quantum dot material is a thiophenol modified CdS/ZnS quantum dot material, and the cathode is made of Al.
The preparation method of the quantum dot light-emitting diode comprises the following steps:
providing an ITO substrate, and preparing a hole transport layer on the ITO substrate;
depositing a quantum dot light-emitting layer on the hole transport layer, wherein the quantum dot light-emitting layer is the thiophenol modified CdS/ZnS quantum dot obtained by the method in the embodiment 1;
preparing an electron transport layer on the quantum dot light emitting layer;
preparing a cathode on the electron transport layer.
Example 5
A quantum dot light-emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the anode is arranged on a substrate. Wherein the substrate is made of glass sheet, the anode is made of ITO substrate, the hole transport layer is made of TFB, the electron transport layer is made of ZnO, and the quantum dot is made of 4-methylthiophenol modified Cd1-xZnxS quantum dot materialAnd the cathode is made of Al.
The preparation method of the quantum dot light-emitting diode comprises the following steps:
providing an ITO substrate, and preparing a hole transport layer on the ITO substrate;
depositing a quantum dot luminescent layer on the hole transport layer, wherein the quantum dot luminescent layer is the 4-methylthiophenol modified Cd obtained in the method of example 21-xZnxS quantum dots;
preparing an electron transport layer on the quantum dot light emitting layer;
preparing a cathode on the electron transport layer.
Example 6
A quantum dot light-emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the anode is arranged on a substrate. Wherein the substrate is made of glass sheet, the anode is made of ITO substrate, the hole transport layer is made of TFB, the electron transport layer is made of ZnO, and the quantum dot is made of 2, 4-dimethylthiophenol modified Cd1-xZnxThe cathode is made of Al and is made of S/ZnS quantum dot material.
The preparation method of the quantum dot light-emitting diode comprises the following steps:
providing an ITO substrate, and preparing a hole transport layer on the ITO substrate;
depositing a quantum dot light-emitting layer on the hole transport layer, wherein the quantum dot light-emitting layer is 2, 4-dimethylthiophenol modified Cd obtained in the method of example 31-xZnxS/ZnS quantum dots;
preparing an electron transport layer on the quantum dot light emitting layer;
preparing a cathode on the electron transport layer.
Example 7
A quantum dot light-emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the cathode is arranged on a substrate. The substrate is made of a glass sheet, the cathode is made of an ITO (indium tin oxide) base plate, the hole transport layer is made of TFB (polycrystalline silicon nitride), the electron transport layer is made of ZnO, the quantum dot material is a thiophenol modified CdS/ZnS quantum dot material, and the anode is made of Al.
The preparation method of the quantum dot light-emitting diode comprises the following steps:
providing a cathode substrate, and preparing an electron transport layer on the cathode substrate;
preparing a quantum dot light emitting layer on the electron transport layer, wherein the quantum dot light emitting layer is the thiophenol modified CdS/ZnS quantum dot obtained by the method in the embodiment 1;
preparing a hole transport layer on the quantum dot light emitting layer;
an anode is prepared on the hole transport layer.
Example 8
A quantum dot light-emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the cathode is arranged on a substrate. Wherein the substrate is made of glass sheet, the cathode is made of ITO substrate, the hole transport layer is made of TFB, the electron transport layer is made of ZnO, and the quantum dot is made of 4-methylthiophenol modified Cd1-xZnxThe material of the S quantum dot and the material of the anode are Al.
The preparation method of the quantum dot light-emitting diode comprises the following steps:
providing a cathode substrate, and preparing an electron transport layer on the cathode substrate;
preparing a quantum dot luminescent layer on the electron transport layer, wherein the quantum dot luminescent layer is the 4-methylthiophenol modified Cd obtained in the method described in example 21-xZnxS quantum dots;
preparing a hole transport layer on the quantum dot light emitting layer;
an anode is prepared on the hole transport layer.
Example 9
A quantum dot light-emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the cathode is arranged on a substrate. Wherein the substrate is made of glass sheet, the cathode is made of ITO substrate, the hole transport layer is made of TFB, the electron transport layer is made of ZnO, and the quantum dot is made of 2, 4-dimethylthiophenol modified Cd1-xZnxThe material of the S/ZnS quantum dot and the material of the anode are Al.
The preparation method of the quantum dot light-emitting diode comprises the following steps:
providing a cathode substrate, and preparing an electron transport layer on the cathode substrate;
preparing a quantum dot luminescent layer on the electron transport layer, wherein the quantum dot luminescent layer is 2, 4-dimethylthiophenol modified Cd obtained in the method in example 31-xZnxS/ZnS quantum dots;
preparing a hole transport layer on the quantum dot light emitting layer;
an anode is prepared on the hole transport layer.
Comparative example 1
A quantum dot light-emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the cathode is arranged on a substrate. The substrate is made of a glass sheet, the anode is made of an ITO (indium tin oxide) substrate, the hole transport layer is made of TFB, the electron transport layer is made of ZnO, the quantum dot material is CdS/ZnS quantum dot, and the cathode is made of Al.
Comparative example 2
A quantum dot light-emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the cathode is arranged on a substrate. The substrate is made of glass sheets, the anode is made of an ITO (indium tin oxide) substrate, the hole transport layer is made of TFB (thin film transistor), the electron transport layer is made of ZnO, and the quantum dot is made of Cd1-xZnxAnd the cathode is made of Al.
Comparative example 3
A quantum dot light-emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the cathode is arranged on a substrate. The substrate is made of glass sheets, the anode is made of an ITO (indium tin oxide) substrate, the hole transport layer is made of TFB (thin film transistor), the electron transport layer is made of ZnO, and the quantum dot is made of Cd1-xZnxS/ZnS quantum dots, and the cathode is made of Al.
The quantum dot light-emitting diodes prepared in examples 4 to 9 and comparative examples 1 to 3 were subjected to performance tests, and the test indexes and test methods were as follows:
(1) external Quantum Efficiency (EQE): measured using an EQE optical test instrument.
Note: the external quantum efficiency test is the QLED device, namely: anode/hole transport film/quantum dot/electron transport film/cathode, or cathode/electron transport film/quantum dot/hole transport film/anode.
The test results are shown in table 1 below:
TABLE 1
Figure BDA0002345039830000211
As can be seen from table 1 above, the external quantum efficiency of the quantum dot light emitting diodes provided in examples 4 to 9 of the present invention (the quantum dot material is a quantum dot material modified by thiophenol and homologs thereof) is significantly higher than that of the quantum dot light emitting diodes of the unmodified quantum dot materials in comparative examples 1 to 3, which indicates that the quantum dot light emitting diodes obtained in the examples have better light emitting efficiency.
It is noted that the specific examples provided by the invention all use blue light quantum dots (CdS/ZnS, Cd)1-xZnxS、Cd1-xZnxS/ZnS) is used as a material of a light emitting layer, and is based on that a blue light emitting system uses more systems (in addition, a light emitting diode based on blue quantum dots is relatively difficult to manufacture, and therefore has more reference value), and does not mean that the invention is only used for the blue light emitting system.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (18)

1. The quantum dot material is characterized by comprising quantum dot particles and thiophenol organic matters bound on the surfaces of the quantum dot particles, wherein the thiophenol organic matters are bound with the quantum dot particles through-SH.
2. The quantum dot material of claim 1, wherein the quantum dot material has a molar ratio of the quantum dot particles to the thiophenol organic compound of 1:0.8 to 1: 2.
3. The quantum dot material of claim 1 or 2, wherein the thiophenol organic is at least one selected from the group consisting of thiophenol, 4-methylphenylthiol, 3-methylphenylthiol, 2-ethylphenylphenol, 3-ethylphenylphenol, 4-tert-butylphenylthiol, 2, 4-dimethylphenylthiol, 2, 5-dimethylphenylthiol and 2, 6-dimethylphenylthiol.
4. A quantum dot material according to claim 1 or 2, wherein the quantum dot particles are selected from CdSe, ZnSe, PbSe, CdTe, InP, GaN, GaP, AlP, InN, ZnTe, InAs, GaAs, CaF2、Cd1-xZnxS、Cd1-xZnxSe、CdSeyS1-y、PbSeyS1-y、ZnXCd1-XTe、CdS/ZnS、Cd1-xZnxS/ZnS、Cd1-xZnxSe/ZnSe、CdSe1-xSx/CdSeyS1-y/CdS、CdSe/Cd1-xZnxSe/CdyZn1-ySe/ZnSe、Cd1-xZnxSe/CdyZn1-ySe/ZnSe、CdS/Cd1-xZnxS/CdyZn1-yS/ZnS、NaYF4、NaCdF4、Cd1-xZnxSeyS1-y、CdSe/ZnS、Cd1-xZnxSe/ZnS、CdSe/CdS/ZnS、CdSe/ZnSe/ZnS、Cd1-xZnxSe/CdyZn1-yS/ZnS、InP/ZnS。
5. The preparation method of the quantum dot material is characterized by comprising the following steps of:
providing an initial quantum dot solution and thiophenol organic matters, adding the thiophenol organic matters into the initial quantum dot solution, heating for reaction, and bonding quantum dot particles with-SH in the thiophenol organic matters to prepare the quantum dot material.
6. The method for preparing a quantum dot material according to claim 5, wherein in the step of adding the thiophenol organic compound to the initial quantum dot solution, the thiophenol organic compound is added to the initial quantum dot solution in a ratio of the molar ratio of the quantum dot particles to the thiophenol organic compound being 1:0.8 to 1: 2.
7. The method of claim 5 or 6, wherein the thiophenol organic compound is at least one selected from the group consisting of thiophenol, 4-methylphenthiophenol, 3-methylphenthiophenol, 2-ethylthiophenol, 3-ethylthiophenol, 4-tert-butylphenol, 2, 4-dimethylthiophenol, 2, 5-dimethylthiophenol, and 2, 6-dimethylthiophenol.
8. The method of claim 5 or 6, wherein the heating reaction is performed at a temperature of 200 ℃ to 250 ℃ for 0.5 hour to 1 hour.
9. The method of claim 5 or 6, wherein the initial quantum dots in the initial quantum dot solution are quantum dot particles having organic ligands on their surfaces.
10. The method for preparing a quantum dot material according to claim 9, wherein the initial quantum dots in the initial quantum dot solution are quantum dot particles having a surface containing an organic amine ligand.
11. The method of preparing a quantum dot material according to claim 10, wherein the initial quantum dot solution is prepared by: preparing a colloidal solution of quantum dot particles; and under an inert atmosphere, heating the colloidal solution of the quantum dot particles, adding oleylamine, and carrying out heat preservation reaction to prepare an initial quantum dot solution.
12. The preparation method of the quantum dot material according to claim 11, wherein in the step of heating the colloidal solution of the quantum dot particles and adding oleylamine for a heat preservation reaction, oleylamine is added to the colloidal solution of the quantum dot particles according to a volume ratio of the initial quantum dot to the oleylamine of 100:1 to 120: 1.
13. The method of preparing a quantum dot material of claim 5 or 6 or 10 or 11 or 12, wherein the concentration of the initial quantum dot solution is 20mg/mL to 50 mg/mL.
14. The quantum dot light-emitting diode is characterized by comprising a cathode and an anode which are oppositely arranged, and a quantum dot light-emitting layer arranged between the cathode and the anode, wherein the quantum dot light-emitting layer at least contains a quantum dot material, the quantum dot material comprises quantum dot particles and thiophenol organic matters combined on the surfaces of the quantum dot particles, and the thiophenol organic matters are bonded with the quantum dot particles through-SH.
15. The qd-led of claim 14, wherein the material of the qd-light layer is the qd material.
16. The quantum dot light-emitting diode of claim 14 or 15, wherein the quantum dot material has a molar ratio of the quantum dot particles to the thiophenols organic compound of 1:0.8 to 1: 2.
17. The qd-led of claim 14 or claim 15, wherein the thiophenol organic is selected from at least one of thiophenol, 4-methylthiophenol, 3-methylthiophenol, 2-ethylthiophenol, 3-ethylthiophenol, 4-tert-butylthiophenol, 2, 4-dimethylthiophenol, 2, 5-dimethylthiophenol, 2, 6-dimethylthiophenol.
18. A light emitting device comprising a qd-led according to any one of claims 14 to 17.
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