CN113120952B - Zinc sulfide nano material and preparation method thereof, zinc sulfide thin film and quantum dot light-emitting diode - Google Patents
Zinc sulfide nano material and preparation method thereof, zinc sulfide thin film and quantum dot light-emitting diode Download PDFInfo
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Abstract
The invention discloses a zinc sulfide nano material and a preparation method thereof, a zinc sulfide film and a quantum dot light-emitting diode, wherein the preparation method of the zinc sulfide nano material comprises the following steps: dispersing zinc salt and a sulfur source in an organic solvent, and reacting to obtain a zinc sulfide precursor solution; and adding an aromatic ring bidentate ligand solution into the zinc sulfide precursor solution to prepare the zinc sulfide nano material. According to the invention, the aromatic ring bidentate ligand and the zinc sulfide nano particles are assembled to form the grafting structure, so that the quality of the zinc sulfide nano particles is improved, the conductive capacity of the zinc sulfide nano material is improved, the contact interface between the zinc sulfide material and an active layer when the zinc sulfide material is used as an electron transport layer is improved, and the electron transport performance and the stability of the zinc sulfide nano material are improved.
Description
Technical Field
The invention relates to the field of quantum dot light-emitting diodes, in particular to a zinc sulfide nano material and a preparation method thereof, a zinc sulfide film and a quantum dot light-emitting diode.
Background
Quantum dots have been rapidly developed in application to quantum dot light-emitting diodes (QLEDs) because of their excellent light-emitting characteristics. Quantum dots have a variety of properties including: (1) the emission spectrum can be adjusted by varying the particle size; (2) The excitation spectrum is wide, the emission spectrum is narrow, and the absorptivity is strong; (3) the light stability is good; (4) long fluorescence lifetime, etc. In a conventional inorganic electroluminescent device, electrons and holes are injected from a cathode and an anode, respectively, and then recombined in a light emitting layer to form excitons for light emission. Conduction band electrons in the wide-bandgap semiconductor can be accelerated under a high electric field to obtain enough high energy to impact the QDs so as to enable the QDs to emit light; the semiconductor quantum dot material has important commercial application value as a novel inorganic semiconductor fluorescent material.
In recent years, inorganic semiconductors have been studied as an electron transport layer in a relatively hot manner. Zinc oxide is an important inorganic semiconductor with a direct broadband (3.37 eV), and has the advantages of good stability, high transparency, safety, no toxicity and the like, so that the zinc oxide can be used as a commonly used electron transport layer material. Meanwhile, zinc sulfide (ZnS) is a II-VI semiconductor material, has two different structures of sphalerite and wurtzite, and has stable chemical property of forbidden bandwidth (3.62 eV), abundant resources and low price. However, zinc sulfide alone has been reported as an electron transport layer.
Disclosure of Invention
The inventor finds that ZnS particles are easy to gather and have certain defects on the surface, so that the ZnS film is easy to have obvious surface defects, has poor interface contact with an active layer, causes serious carrier recombination, limits the electron transmission performance of the ZnS film, has poor stability and is easy to be influenced by external conditions such as water vapor and the like.
The invention aims to provide a zinc sulfide nano material and a preparation method thereof, a zinc sulfide film and a quantum dot light-emitting diode, and aims to solve the problems of poor electron transmission performance and poor stability caused by surface defects of the existing zinc sulfide nano particles.
The technical scheme of the invention is as follows:
a zinc sulfide nano material comprises zinc sulfide nano particles and aromatic ring bidentate ligands combined on the surfaces of the zinc sulfide nano particles.
The zinc sulfide nano material is characterized in that the aromatic ring bidentate ligand is one or more of catechol, dopamine and protoporphyrin.
A preparation method of a zinc sulfide nano material comprises the following steps:
dispersing zinc salt and a sulfur source in an organic solvent, and reacting to obtain a zinc sulfide precursor solution;
and adding an aromatic ring bidentate ligand solution into the zinc sulfide precursor solution to prepare the zinc sulfide nano material.
In the step of adding the aromatic ring bidentate ligand solution into the zinc sulfide precursor solution, the molar ratio of the aromatic ring bidentate ligand in the aromatic ring bidentate ligand solution to the zinc sulfide precursor in the zinc sulfide precursor solution is 1-20.
The preparation method of the zinc sulfide nanometer material comprises the step of preparing an aromatic ring bidentate ligand solution, wherein the aromatic ring bidentate ligand solution comprises an organic solvent and an aromatic ring bidentate ligand dispersed in the organic solvent, and the concentration of the aromatic ring bidentate ligand solution is 0.01-0.05M.
The preparation method of the zinc sulfide nano material comprises the step of preparing a zinc salt, wherein the zinc salt is one or more of zinc acetate, zinc nitrate, zinc chloride and zinc acetate dihydrate.
The preparation method of the zinc sulfide nano material comprises the following step of preparing a sulfur source, wherein the sulfur source is one or more of thiourea, thioacetamide, sodium sulfide and L-cysteine.
The preparation method of the zinc sulfide nanometer material comprises the following steps of:
adding an aromatic ring bidentate ligand solution into the zinc sulfide precursor solution, and stirring for 2-4 hours at 50-80 ℃ to enable the aromatic ring bidentate ligand to be combined on the surface of the zinc sulfide nano particles, thereby preparing the zinc sulfide nano material.
The zinc sulfide thin film is made of the zinc sulfide nanometer material.
A quantum dot light emitting diode comprises an electron transport layer, and is characterized in that the electron transport layer is the zinc sulfide thin film.
Has the advantages that: according to the invention, the aromatic ring bidentate ligand and the zinc sulfide nanoparticles are assembled to form the zinc sulfide nano material, so that the quality of the existing zinc sulfide nanoparticles is improved, the conductivity of the zinc sulfide film is improved, the contact interface of the zinc sulfide film and the active layer is improved, and the electron transmission performance and stability of the zinc sulfide film are improved. In addition, the preparation method of the zinc sulfide nano material provided by the invention is simple to operate and suitable for large-area and large-scale preparation.
Drawings
Fig. 1 is a flow chart of a method for preparing a zinc sulfide nano material according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of zinc sulfide nanoparticles with catechol grafted on the surface.
Fig. 3 is a flow chart of a method for preparing a zinc sulfide thin film according to an embodiment of the present invention.
Fig. 4 is a schematic structural diagram of a quantum dot light emitting diode with a front-mounted structure according to an embodiment of the present invention.
Fig. 5 is a schematic structural diagram of a quantum dot light emitting diode with a flip-chip structure according to an embodiment of the present invention.
Detailed Description
The invention provides a zinc sulfide nano material and a preparation method thereof, a zinc sulfide film and a quantum dot light-emitting diode, and the invention is further explained in detail below in order to make the purpose, technical scheme and effect of the invention clearer and more clear. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
Referring to fig. 1, fig. 1 is a flow chart of a preferred embodiment of a method for preparing a zinc sulfide nano material according to the present invention, as shown in the figure, the method includes the steps of:
s10, dispersing zinc salt and a sulfur source in an organic solvent, and reacting to obtain a zinc sulfide precursor solution;
s20, adding an aromatic ring bidentate ligand solution into the zinc sulfide precursor solution to enable the aromatic ring bidentate ligand to be combined to the surface of the zinc sulfide nano particles, and obtaining the zinc sulfide nano material.
In the embodiment, the aromatic ring bidentate ligand and the zinc sulfide nanoparticles are assembled to form the grafting structure, so that the quality of the zinc sulfide nanoparticles is improved, the conductivity of the zinc sulfide nanoparticles is improved, the contact interface between the zinc sulfide nanoparticles and an active layer when the zinc sulfide nanoparticles are used as an electron transport layer is improved, and the electron transport performance and the stability of the zinc sulfide nanoparticles are improved. In addition, the preparation method of the zinc sulfide nano material provided by the embodiment is very simple and is suitable for large-area and large-scale preparation.
In this embodiment, the aromatic ring bidentate ligand can effectively passivate hydroxyl groups and defects on the surface of the zinc sulfide nanoparticle, so that an interface between the zinc sulfide nanoparticle material and an active functional layer when the zinc sulfide nanoparticle material is used as an electron transport layer is modified, electrons are promoted to enter a quantum dot light emitting region from the electron transport layer, and the recombination efficiency of electron-holes in the quantum dot light emitting region is improved.
In this embodiment, the aromatic ring structure grafted on the aromatic ring bidentate ligand on the surface of the zinc sulfide nanoparticle may generate a conjugation effect, so as to adjust the electronic structure on the surface of the zinc sulfide nanoparticle, so that the fermi level of the electronic structure is closer to the bottom of the conduction band, and thus the conductivity of the zinc sulfide nanomaterial may be improved.
In this embodiment, the aromatic ring bidentate ligand can be bound on the surface of the zinc sulfide nanoparticle in a hydrogen bonding manner, and compared with a traditional monodentate ligand, the aromatic ring bidentate ligand can effectively improve the binding energy of the ligand to form a stable coordination structure, so that the water vapor diffusion can be inhibited, the zinc sulfide film has stronger hydrophobicity, and the stability of a quantum dot light-emitting diode using the zinc sulfide film as an electron transport layer is improved.
In some embodiments, the zinc salt and the sulfur source are dispersed in an organic alcohol solvent and reacted to obtain a zinc sulfide precursor solution. In this embodiment, the zinc salt is a soluble organic zinc salt or a soluble inorganic zinc salt, and the zinc salt may be one or more of zinc acetate, zinc nitrate, zinc chloride, and zinc acetate dihydrate, but is not limited thereto; in this embodiment, the sulfur source may be one or more of thiourea, thioacetamide, sodium sulfide, and L-cysteine, but is not limited thereto; the organic alcohol solvent may be one or more of methanol, ethanol, butanol and isopropanol, but is not limited thereto.
In some specific embodiments, adding zinc salt into an organic alcohol solvent, stirring at 60-80 ℃ to dissolve the zinc salt to obtain a zinc salt solution, adding a sulfur source alcohol solution into the zinc salt solution, and continuously stirring for 0.5-2h to react to obtain a zinc sulfide precursor solution.
In some embodiments, adding the aromatic ring bidentate ligand solution into the zinc sulfide precursor solution, stirring for 2-4 hours at 50-80 ℃, and reacting to obtain the zinc sulfide nanoparticle solution with the aromatic ring bidentate ligand grafted on the surface. In this embodiment, the aromatic ring bidentate ligand can bind to two sites on the surface of the zinc sulfide nanoparticle, and the aromatic ring bidentate ligand can effectively improve the binding energy of the ligand to form a stable coordination structure.
In some embodiments, the molar ratio of the aromatic ring bidentate ligand in the aromatic ring bidentate ligand solution to the zinc sulfide precursor in the zinc sulfide precursor solution is from 1. In this embodiment, if the molar ratio of the aromatic ring bidentate ligand to the zinc sulfide precursor is greater than 1; if the molar ratio of the aromatic ring bidentate ligand to the zinc sulfide precursor is less than 1 20, the dosage of the aromatic ring bidentate ligand is too small, and the aromatic ring bidentate ligand cannot be effectively grafted to the surface of the zinc sulfide nanoparticles in the reaction process, so that the zinc sulfide nanoparticles are easy to agglomerate, and the stability of the zinc sulfide nanoparticles is reduced.
In some specific embodiments, the molar ratio of the aromatic ring bidentate ligand to the zinc sulfide precursor is from 1. Within the proportion range, the aromatic ring bidentate ligand can be effectively grafted to the surface of the zinc sulfide nano particles, and the growth of zinc sulfide crystals can not be influenced.
In some embodiments, the solution of the aromatic ring bidentate ligand comprises an organic alcohol solvent and the aromatic ring bidentate ligand dispersed in the organic alcohol solvent, and the concentration of the solution of the aromatic ring bidentate ligand is between 0.05M and 0.01M. In this embodiment, the bidentate aryl ring ligand is one or more of catechol, dopamine, and protoporphyrin, but is not limited thereto; the organic alcohol solvent is one or more of methanol, ethanol, butanol and isopropanol, but is not limited thereto.
In some specific embodiments, when the bidentate ligand on the aromatic ring is catechol, the catechol solution is added into the zinc sulfide precursor solution, and after reaction, the catechol can be grafted on the surface of the zinc sulfide nanoparticles, as shown in fig. 2, the catechol has two hydroxyl groups and can be simultaneously bonded with the surface of the zinc sulfide in a hydrogen bond manner, so that the catechol is modified on the surface of the zinc sulfide nanoparticles.
In some embodiments, there is also provided a zinc sulfide nanomaterial comprising a zinc sulfide nanoparticle and an aromatic ring bidentate ligand bound to the surface of the zinc sulfide nanoparticle.
In some embodiments, there is also provided a method of preparing a zinc sulfide thin film, as shown in fig. 3, comprising the steps of:
s100, dispersing zinc salt and a sulfur source in an organic alcohol solvent, and reacting to obtain a zinc sulfide precursor solution;
s200, adding an aromatic ring bidentate ligand solution into the zinc sulfide precursor solution, and reacting to obtain a zinc sulfide nanoparticle solution with the surface grafted with the aromatic ring bidentate ligand;
s300, preparing the zinc sulfide nano particle solution with the surface grafted with the aromatic ring bidentate ligand into a film, and obtaining the zinc sulfide film.
In the embodiment, the aromatic ring bidentate ligand and the zinc sulfide nanoparticles are assembled to form the grafting structure, so that the quality of the zinc sulfide nanoparticles is improved, the conductivity of the zinc sulfide film is improved, the contact interface of the zinc sulfide film and the active layer is improved, and the electron transmission performance and the stability of the zinc sulfide film are improved. In addition, the preparation method of the zinc sulfide film provided by the embodiment is very simple and is suitable for large-area and large-scale preparation; the aromatic ring bidentate ligand can effectively passivate hydroxyl and defects on the surface of zinc sulfide nano particles, so that an interface between a zinc sulfide film serving as an electron transport layer and an active functional layer is modified, electrons are promoted to enter a quantum dot light emitting region from the zinc sulfide film, and the recombination efficiency of electrons and holes in the quantum dot light emitting region is improved; the aromatic ring structure grafted on the aromatic ring bidentate ligand on the surface of the zinc sulfide nano particle can generate a conjugate effect, so that the electronic structure on the surface of the zinc sulfide nano particle is adjusted, the Fermi level of the zinc sulfide nano particle is closer to the bottom of a conduction band, and the conductivity of the zinc sulfide film can be improved.
In this embodiment, the aromatic ring bidentate ligand can be bound on the surface of the zinc sulfide nanoparticle in a hydrogen bonding manner, and compared with a traditional monodentate ligand, the aromatic ring bidentate ligand can effectively improve the binding energy of the ligand to form a stable coordination structure, so that the water vapor diffusion can be inhibited, the zinc sulfide film has stronger hydrophobicity, and the stability of a quantum dot light-emitting diode using the zinc sulfide film as an electron transport layer is improved.
In some embodiments, a zinc sulfide thin film is also provided, which is prepared by the preparation method of the zinc sulfide thin film.
The following examples are provided to describe the preparation of the zinc sulfide thin film in detail.
Example 1
The following description will be made in detail by taking zinc chloride, thiourea and catechol as examples:
1. weighing a proper amount of zinc chloride, adding the zinc chloride into 50mL of ethanol to form a solution with the concentration of 0.5M, stirring and dissolving the solution at 60 ℃, adding a thiourea ethanol solution with the concentration of 0.55M, and continuously stirring for 0.5 hour to obtain a mixed solution;
2. adding 0.05M catechol alcohol solution into the mixed solution, continuously stirring for 2 hours at 60 ℃ to obtain a clear transparent solution, and spin-coating the clear transparent solution on the treated ITO by a spin coater and annealing to obtain the zinc sulfide film.
Example 2
The following details are given by way of example of zinc nitrate hexahydrate, thioacetamide, dopamine:
1. weighing a proper amount of zinc nitrate, and adding the zinc nitrate into 50mL of ethanol to form a solution with the concentration of 0.5M; stirring at 60 deg.C for dissolving, adding thioacetamide ethanol solution with concentration of 0.55M, and stirring for 0.5 hr to obtain mixed solution;
2. adding 0.05M of dopamine alcohol solution into the mixed solution, continuously stirring for 2 hours at 60 ℃ to obtain a clear transparent solution, spin-coating the clear transparent solution on the treated ITO by using a spin coater, and annealing to obtain the zinc sulfide film.
Example 3
The following details are given by taking zinc acetate dihydrate, sodium sulfide and protoporphyrin as examples:
1. weighing a proper amount of zinc acetate, and adding the zinc acetate into 50mL of ethanol to form a solution with the concentration of 0.5M; stirring and dissolving at 60 ℃, adding a sodium sulfide ethanol solution with the concentration of 0.55M, and continuously stirring for 0.5 hour to obtain a mixed solution;
2. adding 0.03M of dopamine solution into the mixed solution, continuously stirring for 2 hours at 60 ℃ to obtain a clear transparent solution, spin-coating the clear transparent solution on the treated ITO by using a spin coater, and annealing to obtain the zinc sulfide film.
The preparation method of the zinc sulfide film provided by the invention has the following advantages:
1. the aromatic ring bidentate ligand can effectively passivate the surface hydroxyl and defects of ZnS nanoparticles, modify the interface of the zinc sulfide film serving as an electron transport layer and an active functional layer, promote electrons to enter a quantum dot light emitting region from the transport layer, and improve the recombination efficiency of electron-holes in a quantum dot light emitting diode;
2. the aromatic ring bidentate ligand has an aromatic ring structure, can generate a conjugate effect, and adjusts the electronic structure on the surface of the zinc sulfide nano particle to enable the Fermi level of the zinc sulfide nano particle to be closer to the bottom of a conduction band, so that the conductivity of the zinc sulfide film is improved;
3. the aromatic ring bidentate ligand can be combined with two sites on the surface of the zinc sulfide nano particle, compared with the traditional monodentate ligand, the aromatic ring bidentate ligand can effectively improve the combination energy of the ligand to form a stable coordination structure, thereby inhibiting the water vapor diffusion, enabling the zinc sulfide film to have stronger hydrophobicity and improving the stability of a quantum dot light-emitting diode taking the zinc sulfide film as an electron transport layer;
4. the preparation method of the zinc sulfide film provided by the invention is simple to operate and suitable for large-area and large-scale preparation.
In some embodiments, the invention further provides a zinc sulfide thin film prepared by the preparation method.
In some embodiments, there is also provided a quantum dot light emitting diode comprising an electron transport layer, wherein the electron transport layer is the zinc sulfide thin film of the present invention.
In some embodiments, the quantum dot light emitting diode comprises an anode, a quantum dot light emitting layer, an electron transport layer and a cathode, which are stacked, wherein the electron transport layer is the zinc sulfide thin film of the present invention.
In some specific embodiments, the quantum dot light emitting diode includes an anode, a hole transport layer, a quantum dot light emitting layer, an electron transport layer, and a cathode, which are stacked, wherein the electron transport layer is the zinc sulfide thin film of the present invention.
It should be noted that the present invention is not limited to the quantum dot light emitting diode with the above structure, and may further include an interface function layer or an interface modification layer, including but not limited to one or more of an electron blocking layer, a hole blocking layer, an electrode modification layer, and an isolation protection layer. The quantum dot light emitting diode can be partially packaged, fully packaged or not packaged.
The following describes the quantum dot light emitting diode including the electron transport layer and the method for manufacturing the same in detail:
the quantum dot light emitting diode can be divided into a quantum dot light emitting diode with a forward mounting structure and a quantum dot light emitting diode with an inverted mounting structure according to different light emitting types of the quantum dot light emitting diode.
As one embodiment, when the quantum dot light emitting diode is a forward-mounted structure, as shown in fig. 4, the QLED device includes an anode 2 (the anode 2 is stacked on a substrate 1), a hole transport layer 3, a quantum dot light emitting layer 4, an electron transport layer 5, and a cathode 6, where the electron transport layer 5 is a zinc sulfide thin film according to the present invention.
In another embodiment, when the quantum dot light emitting diode is a flip-chip structure, as shown in fig. 5, the QLED device includes a cathode 6 (the cathode 6 is stacked on a substrate 1), an electron transport layer 5, a quantum dot light emitting layer 4, a hole transport layer 3, and an anode 2, wherein the electron transport layer 5 is the zinc sulfide thin film of the present invention.
In some embodiments, the material of the anode is selected from doped metal oxides; wherein the doped metal oxide includes, but is not limited to, one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO), and aluminum-doped magnesium oxide (AMO).
In some embodiments, the material of the hole transport layer is selected from organic materials having good hole transport ability, such as one or more of Poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine) (TFB), polyvinylcarbazole (PVK), poly (N, N '-bis (4-butylphenyl) -N, N' -bis (phenyl) benzidine) (Poly-TPD), poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-Phenylenediamine) (PFB), 4',4 ″ -tris (carbazol-9-yl) triphenylamine (TCTA), 4' -bis (9-Carbazole) Biphenyl (CBP), N '-diphenyl-N, N' -bis (3-methylphenyl) -1,1 '-biphenyl-4, 4' -diamine (TPD), N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine (NPB), doped graphene, non-doped graphene, C60, copper oxide, nickel oxide, and tungsten oxide.
In some embodiments, the material of the quantum dot light emitting layer is selected from one or more of red quantum dots, green quantum dots, blue quantum dots, and may also be selected from yellow quantum dots. Specifically, the material of the quantum dot light emitting layer is selected from one or more of CdS, cdSe, cdTe, znO, znS, znSe, znTe, gaAs, gaP, gaSb, hgS, hgSe, hgTe, inAs, inP, inSb, alAs, alP, cuInS, cuInSe and various core-shell structure quantum dots or alloy structure quantum dots. The quantum dots of the present invention may be selected from cadmium-containing or cadmium-free quantum dots. The quantum dot light emitting layer of the material has the characteristics of wide and continuous excitation spectrum distribution, high emission spectrum stability and the like.
In some embodiments, the material of the cathode is selected from one or more of a conductive carbon material, a conductive metal oxide material, and a metallic material; wherein the conductive carbon material includes, but is not limited to, one or more of doped or undoped carbon nanotubes, doped or undoped graphene oxide, C60, graphite, carbon fibers, and porous carbon; the conductive metal oxide material includes, but is not limited to, one or more of ITO, FTO, ATO, and AZO; metallic materials include, but are not limited to, al, ag, cu, mo, au, or alloys thereof; wherein, the metal material has a form including but not limited to one or more of a compact film, a nanowire, a nanosphere, a nanorod, a nanocone and a hollow nanosphere.
The invention also provides a preparation method of the quantum dot light-emitting diode with the forward mounting structure, which comprises the following steps:
providing a substrate containing an anode, and preparing a hole transport layer on the anode;
preparing a quantum dot light-emitting layer on the hole transport layer;
preparing an electron transport layer on the quantum dot light-emitting layer, wherein the electron transport layer is the zinc sulfide film;
and preparing a cathode on the electron transport layer to obtain the quantum dot light-emitting diode.
As one embodiment, taking ITO conductive glass as an example of a substrate, in order to obtain a high-quality thin film, the ITO conductive glass needs to undergo a pretreatment process, and the basic specific processing steps include: etching the ITO conductive glass into narrow bands, sequentially and respectively carrying out ultrasonic cleaning in deionized water, acetone, absolute ethyl alcohol and deionized water to remove impurities on the surfaces, drying, and then cleaning by using an ultraviolet cleaning machine to obtain the ITO anode.
As one embodiment, the prepared solution of the hole transport material is coated on the ITO by spinning to form a film; controlling the film thickness by adjusting the concentration of the solution, the spin-coating speed and the spin-coating time, and then carrying out thermal annealing treatment at a proper temperature to obtain a hole transport layer; spin-coating the prepared solution of the hole transport material on ITO to form a film; and (2) carrying out spin coating on the prepared quantum dot solution with a certain concentration on the hole transport layer to form a film, controlling the thickness of the quantum dot light-emitting layer to be about 20-60 nm by adjusting the concentration, the spin coating speed and the spin coating time of the solution, and drying at a proper temperature.
As one embodiment, the step of preparing the electron transport layer on the quantum dot light emitting layer specifically includes: the method comprises the steps of spin-coating a prepared zinc sulfide nanoparticle solution with a certain concentration and the surface grafted with an aromatic ring bidentate ligand on the quantum dot light-emitting layer to form a film, controlling the thickness of an electron transport layer to be about 20-60 nm by adjusting the concentration, the spin-coating speed and the spin-coating time of the zinc sulfide nanoparticle solution with the surface grafted with the aromatic ring bidentate ligand, and then annealing to form the film.
In some embodiments, the spin speed is 3000 to 5000rpm.
As one embodiment, the step of preparing the cathode on the electron transport layer specifically includes: the substrate deposited with the functional layers is placed in an evaporation bin, a layer of 15-30nm metal silver or aluminum and the like is thermally evaporated through a mask plate to be used as a cathode, or a nano Ag wire or a Cu wire and the like are used, and the materials have low resistance so that carriers can be smoothly injected.
The invention also provides a preparation method of the quantum dot light-emitting diode with the inverted structure, which comprises the following steps:
providing a substrate containing a cathode, and preparing an electron transport layer on the cathode, wherein the electron transport layer is the zinc sulfide thin film;
preparing a quantum dot light-emitting layer on the electron transport layer;
preparing a hole transport layer on the quantum dot light emitting layer;
and preparing an anode on the hole transport layer to obtain the quantum dot light-emitting diode.
As one embodiment, the step of preparing the electron transport layer on the cathode specifically includes: the method comprises the steps of spin-coating a prepared zinc sulfide nanoparticle solution with a certain concentration and the surface grafted with an aromatic ring bidentate ligand on the quantum dot light-emitting layer to form a film, controlling the thickness of an electron transport layer to be about 20-60 nm by adjusting the concentration, the spin-coating speed and the spin-coating time of the zinc sulfide nanoparticle solution with the surface grafted with the aromatic ring bidentate ligand, and then annealing to form the film.
The invention also comprises the following steps: and carrying out packaging treatment on the obtained quantum dot light-emitting diode, wherein the packaging treatment can adopt a common machine for packaging and can also adopt manual packaging. Preferably, in the environment of the packaging treatment, the oxygen content and the water content are both lower than 0.1ppm so as to ensure the stability of the quantum dot light-emitting diode.
The preparation method of each layer can be a chemical method or a physical method, wherein the chemical method comprises one or more of but not limited to a chemical vapor deposition method, a continuous ionic layer adsorption and reaction method, an anodic oxidation method, an electrolytic deposition method and a coprecipitation method; physical methods include, but are not limited to, physical coating methods or solution methods, wherein solution methods include, but are not limited to, spin coating, printing, knife coating, dip-coating, dipping, spraying, roll coating, casting, slot coating, bar coating; physical coating methods include, but are not limited to, one or more of thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, pulsed laser deposition.
In conclusion, the invention adopts the aromatic ring bidentate ligand and the zinc sulfide nano particles to assemble to form a grafting structure, thereby preparing the zinc sulfide film. According to the invention, the aromatic ring bidentate ligand can effectively passivate hydroxyl and defects on the surface of the zinc sulfide nanoparticle, so that an interface between a zinc sulfide film serving as an electron transport layer and an active functional layer is modified, electrons are promoted to enter a quantum dot light emitting region from the zinc sulfide film, and the recombination efficiency of electron-holes in the quantum dot light emitting region is improved; the aromatic ring structure grafted on the aromatic ring bidentate ligand on the surface of the zinc sulfide nano particle can generate a conjugate effect, so that the electronic structure on the surface of the zinc sulfide nano particle is adjusted, the Fermi level of the zinc sulfide nano particle is closer to the bottom of a conduction band, and the conductivity of the zinc sulfide film can be improved; compared with the traditional monodentate ligand, the aromatic ring bidentate ligand can effectively improve the binding energy of the ligand and form a stable coordination structure, thereby inhibiting the diffusion of water vapor, enabling the zinc sulfide film to have stronger hydrophobicity and improving the stability of a quantum dot light-emitting diode taking the zinc sulfide film as an electron transport layer.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (8)
1. The zinc sulfide nano material is characterized by comprising zinc sulfide nano particles and aromatic ring bidentate ligands combined on the surfaces of the zinc sulfide nano particles, wherein the aromatic ring bidentate ligands are one or more of dopamine or protoporphyrin; wherein, when the zinc sulfide nano material is prepared, the molar ratio of the aromatic ring bidentate ligand in the aromatic ring bidentate ligand solution to the zinc sulfide precursor in the zinc sulfide precursor solution is 1-20.
2. A preparation method of a zinc sulfide nano material is characterized by comprising the following steps:
dispersing zinc salt and a sulfur source in an organic solvent, and reacting to obtain a zinc sulfide precursor solution;
adding an aromatic ring bidentate ligand solution into the zinc sulfide precursor solution, wherein the molar ratio of the aromatic ring bidentate ligand in the aromatic ring bidentate ligand solution to the zinc sulfide precursor in the zinc sulfide precursor solution is 1.
3. The preparation method of the zinc sulfide nanometer material according to the claim 2, characterized in that the aromatic ring bidentate ligand solution comprises an organic solvent and aromatic ring bidentate ligand dispersed in the organic solvent, and the concentration of the aromatic ring bidentate ligand solution is 0.01-0.05M.
4. The method for preparing the zinc sulfide nano material according to any one of claims 2 to 3, wherein the zinc salt is one or more of zinc acetate, zinc nitrate, zinc chloride and zinc acetate dihydrate.
5. The method for preparing zinc sulfide nano-materials according to any one of claims 2 to 3, wherein the sulfur source is one or more of thiourea, thioacetamide, sodium sulfide and L-cysteine.
6. The method for preparing the zinc sulfide nano material according to claim 2, wherein the step of adding an aromatic ring bidentate ligand solution into the zinc sulfide precursor solution to prepare the zinc sulfide nano material comprises the following steps:
adding an aromatic ring bidentate ligand solution into the zinc sulfide precursor solution, and stirring for 2-4 hours at 50-80 ℃ to enable the aromatic ring bidentate ligand to be combined on the surface of the zinc sulfide nano particles, thereby preparing the zinc sulfide nano material.
7. A zinc sulfide thin film, wherein the material of the zinc sulfide thin film is the zinc sulfide nanomaterial of claim 1.
8. A quantum dot light emitting diode comprising an electron transport layer, wherein the electron transport layer is the zinc sulfide thin film of claim 7.
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