CN113130779B - Nano material, preparation method thereof and quantum dot light-emitting diode - Google Patents

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

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CN113130779B
CN113130779B CN201911401405.5A CN201911401405A CN113130779B CN 113130779 B CN113130779 B CN 113130779B CN 201911401405 A CN201911401405 A CN 201911401405A CN 113130779 B CN113130779 B CN 113130779B
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nano material
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李龙基
刘文勇
杨一行
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TCL Technology Group Co Ltd
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    • 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
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Abstract

The invention discloses a nano material and a preparation method thereof and a quantum dot light-emitting diode, wherein the preparation method of the nano material comprises the following steps: and mixing a Zn source, phosphomolybdic acid and an organic solvent, reacting to generate ZnO crystal nuclei, and co-assembling the ZnO crystal nuclei and the phosphomolybdic acid to obtain the nano material with the sheet structure. Compared with the existing common ZnO nano material, the nano material has higher stability in solution and more uniform film formation, and common ZnO nano particles are unstable in solution and are easy to separate out; and the electron mobility is obviously higher, mainly because of the excellent structure of the two-dimensional hybrid ultrafine nanosheet; in addition, the energy levels of the shells of the nano material and the blue quantum dots are more matched, which is beneficial to the rapid injection and transmission of electrons, thereby effectively balancing the current carriers in the light emitting layer of the device and improving the optical performance of the device.

Description

Nano material, preparation method thereof and quantum dot light-emitting diode
Technical Field
The invention relates to the field of quantum dot light-emitting devices, in particular to a nano material, a preparation method thereof and a quantum dot light-emitting diode.
Background
The quantum dots have the advantages of high color purity, high luminous quantum efficiency, adjustable luminous color, high quantum yield and the like, and can be prepared by a printing process, so that the light-emitting diode (namely, the quantum dot light-emitting diode: QLED) based on the quantum dots is generally concerned by people recently, and the performance indexes of the device are rapidly developed. However, in the blue QLED device, the injection transport of electrons is weaker than that of holes, which results in more exciton-hole three-particle system, and the quenching effect of holes on excitons is usually stronger than that of electrons, so the blue device with insufficient electron injection is subject to severe exciton quenching, thereby severely limiting the performance of the QLED device. Because ZnO has the advantages of high transmittance, high electron mobility, low cost, environmental compatibility, simple preparation process and the like, and is widely used In an electron transport layer of an electroluminescent device, the problems of carrier imbalance and the like In the device still cannot be solved, at present, a great deal of literature reports on modifying ZnO to improve the injection transport performance of electrons are available, for example, Al-doped ZnO, In-doped ZnO and the like, but the performance of these doped materials cannot meet the requirements.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the above disadvantages of the prior art, an object of the present invention is to provide a nanomaterial, a method for preparing the nanomaterial, and a quantum dot light emitting diode, and to solve the problem of low electron transport efficiency of a ZnO electron transport layer in the conventional quantum dot light emitting diode.
The technical scheme of the invention is as follows:
a method for preparing a nano material, comprising the following steps:
and mixing a Zn source, phosphomolybdic acid and a solvent, reacting to generate ZnO crystal nuclei, and co-assembling the ZnO crystal nuclei and the phosphomolybdic acid to obtain the nano material with the sheet structure.
A nanomaterial, wherein the nanomaterial comprises: ZnO nanoparticles and phosphomolybdic acid combined with the ZnO nanoparticles, wherein the nano material is a nano sheet.
A quantum dot light emitting diode comprising: the cathode is arranged on the anode, the quantum dot light-emitting layer is arranged between the cathode and the anode, and the electron transport layer is arranged between the cathode and the quantum dot light-emitting layer, wherein the electron transport layer material comprises the nano material prepared by the preparation method; and/or the electron transport layer material comprises the nanomaterial of the present invention.
Has the advantages that: the invention realizes the controllable synthesis of the two-dimensional hybrid ZnO-PMA superfine nanosheet by introducing PMA to intervene nucleation in the ZnO nucleation stage and adopting a method of agglomeration and co-assembly of ZnO crystal nucleus and PMA. Compared with the existing common ZnO nano material, the nano material has higher stability in solution and more uniform film formation, and common ZnO nano particles are unstable in solution and are easy to separate out; and the electron mobility is obviously higher, mainly because of the excellent structure of the two-dimensional hybrid ultrafine nanosheet; in addition, the energy levels of the shells of the nano material and the blue quantum dots are more matched, which is beneficial to the rapid injection and transmission of electrons, thereby effectively balancing the current carriers in the light emitting layer of the device and improving the optical performance of the device.
Drawings
Fig. 1 is a schematic structural diagram of a quantum dot light emitting diode with a positive structure according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a quantum dot light emitting diode with an inversion structure according to an embodiment of the present invention.
Fig. 3 is a schematic flow chart of a method for manufacturing the quantum dot light-emitting diode with the structure of fig. 1.
Fig. 4 is a schematic flow chart of a method for manufacturing the quantum dot light-emitting diode with the structure of fig. 2.
Detailed Description
The invention provides a nano material, a preparation method thereof and a quantum dot light-emitting diode, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The embodiment of the invention provides a preparation method of a nano material, which comprises the following steps: and mixing a Zn source, phosphomolybdic acid and a solvent, reacting to generate ZnO crystal nuclei, and co-assembling the ZnO crystal nuclei and the phosphomolybdic acid to obtain the nano material with the sheet structure.
Phosphomolybdic acid (PMA) is a polyacid, a multimetal oxygen cluster composed of transition metal ions and oxygen, and belongs to a complex. And strong electrostatic interaction exists between the ZnO crystal nucleus and the polyacid, and at the initial stage of formation of the ZnO crystal nucleus, phosphomolybdic acid and the ZnO crystal nucleus are adsorbed on the surface of the ZnO crystal nucleus through electrostatic interaction to prevent the ZnO crystal nucleus from further growing, so that phosphomolybdic acid and ZnO are assembled into the two-dimensional hybridized nanosheet with very small size.
In this example, a Zn source and PMA are mixed in a solvent, the Zn source generates ZnO crystal nuclei through a hydrolysis reaction, the generated ZnO crystal nuclei are agglomerated and co-assembled with PMA, and a material having an ultra-fine nanostructure can be continuously grown and formed. In the embodiment, the controlled synthesis of the two-dimensional hybrid ZnO-PMA superfine nanosheet is realized by introducing PMA to intervene in nucleation at a ZnO nucleation stage and by a method of agglomeration and co-assembly of ZnO crystal nucleus and PMA. According to the embodiment, the nanosheet with the two-dimensional stable simple tetragonal configuration can be prepared by the method, the size distribution is uniform, the thickness is less than 2nm, the length is less than 5nm, and further the length is less than 2 nm. The smaller the prepared size is, the more excellent the performance is, and the more favorable the electron transmission is.
Compared with the existing common ZnO nano material, the nano material of the embodiment has higher stability in the solution and more uniform film formation, and common ZnO nano particles are unstable in the solution and are easy to separate out; compared with the existing common ZnO nano material, the two-dimensional hybridized superfine nano sheet has higher electron mobility. In addition, the energy levels of the shells of the nano material and the blue quantum dot are more matched, which is beneficial to the rapid injection and transmission of electrons, so that the current carriers in the light emitting layer of the device are effectively balanced, and the optical performance of the device is improved.
In one embodiment, the method for preparing the nanomaterial specifically comprises the following steps: mixing a Zn source, phosphomolybdic acid and a solvent, and continuously stirring; ZnO crystal nucleus is generated by reaction at a certain temperature, and the ZnO crystal nucleus and phosphomolybdic acid are assembled together; and centrifuging, washing and drying the obtained precipitate to prepare the two-dimensional hybridized ZnO-PMA nano material. And dispersing the prepared ZnO-PMA nano material into an alcohol solvent by an ultrasonic method, and preparing the ZnO-PMA nano material for preparing the quantum dot light-emitting diode. Wherein the alcohol solvent can be methanol, ethanol and the like, and the concentration of the nano material can be 10-100 mg/ml.
In one embodiment, the reaction temperature is 20-80 ℃, and the ZnO crystal nuclei have increased collision probability due to too high temperature, which may result in too large size. The reaction time is 2-48 h, the reaction time is too long, the collision probability of ZnO crystal nuclei is increased, and the size is possibly too large.
In one embodiment, in the step of mixing the Zn source, the phosphomolybdic acid and the solvent, the molar ratio of the Zn source to the phosphomolybdic acid is 1:1 to 1:5, so as to ensure that sufficient PMA is co-assembled with the ZnO during the initial stage of nucleation, and the hydrolysis reaction of the Zn source, i.e. the formation of ZnO nuclei, is not affected.
In one embodiment, the zinc salt is a soluble inorganic zinc salt or a soluble organic zinc salt. By way of example, the zinc salt includes zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, zinc acetate dihydrate, and the like, without limitation to one or more of these.
In one embodiment, the solvent includes one or more of deionized water, an alkaline solution, alcohols (e.g., methanol, ethanol, etc.), amines (e.g., ethanolamine, etc.), and the like, without limitation.
The embodiment of the invention provides a nano material, wherein the nano material comprises: ZnO nanoparticles and phosphomolybdic acid combined with the ZnO nanoparticles, wherein the nano material is a nano sheet.
In one embodiment, the nanomaterial is a nanosheet formed by self-assembly of ZnO nanoparticles and phosphomolybdic acid.
The nano material in the embodiment is a nano sheet formed by self-assembling ZnO nanoparticles and phosphomolybdic acid. Compared with the existing common ZnO nano material, the nano material of the embodiment has higher stability in the solution and more uniform film formation, and common ZnO nano particles are unstable in the solution and are easy to separate out; and the electron mobility is obviously higher, mainly because of the excellent structure of the two-dimensional hybrid ultrafine nanosheet; in addition, the energy levels of the shells of the nano material and the blue quantum dots are more matched, which is beneficial to the rapid injection and transmission of electrons, thereby effectively balancing the current carriers in the light emitting layer of the device and improving the optical performance of the device. The nano material of the embodiment is a two-dimensional stable nano sheet with a simple tetragonal configuration, and has uniform size distribution, a thickness of less than 2nm, a length of less than 5nm, and a further length of less than 2 nm.
The embodiment of the invention provides a quantum dot light-emitting diode, which comprises: the cathode comprises an anode, a cathode, a quantum dot light-emitting layer arranged between the anode and the cathode, and an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, wherein the electron transport layer comprises the nanomaterial prepared by the preparation method in the embodiment of the invention, and/or the electron transport layer comprises the nanomaterial in the embodiment of the invention.
In one embodiment, the electron transport layer material is a nanomaterial prepared by the preparation method described in the embodiment of the present invention; and/or the electron transport layer material is the nano material of the embodiment of the invention.
The electron transport layer material in this embodiment is a two-dimensional hybrid ZnO-PMA nanomaterial formed by self-assembling ZnO nanoparticles and phosphomolybdic acid, and the nanomaterial is a two-dimensional hybrid ultrafine nanosheet. Compared with the existing common ZnO electron transport material, the nano material of the embodiment has higher stability in a solution and more uniform film formation, and common ZnO nanoparticles are unstable in the solution and are easy to separate out; in addition, the two-dimensional hybridized superfine nanosheet structure can improve the electron mobility of the material; in addition, the energy levels of the shells of the nano material and the blue quantum dots are more matched, which is beneficial to the rapid injection and transmission of electrons, thereby effectively balancing the current carriers in the light emitting layer of the device and improving the optical performance of the device.
In this embodiment, the quantum dot light emitting diode has various forms, and the quantum dot light emitting diode has a positive type structure and a negative type structure, wherein the quantum dot light emitting diode with the positive type structure will be mainly described by taking the structure shown in fig. 1 as an example. Specifically, as shown in fig. 1, the quantum dot light emitting diode includes an anode-containing substrate 11, a hole injection layer 12, a hole transport layer 13, a quantum dot light emitting layer 14, an electron transport layer 15, and a cathode 16, which are stacked from bottom to top; the material of the electron transport layer 15 is the nano material described in this embodiment, and the nano material is a nano sheet formed by self-assembling ZnO nanoparticles and phosphomolybdic acid.
In one embodiment, the electron transport layer has a thickness of 20nm to 60 nm. If the thickness of the electron transport layer is too thin, the transport performance of a current carrier cannot be ensured, so that electrons cannot reach the quantum dot light emitting layer to cause hole-electron recombination of the transport layer, and quenching is caused; if the thickness of the electron transport layer is too thick, light transmittance of the film layer is reduced, and carrier permeability of the device is reduced, resulting in a reduction in the conductivity of the entire device.
In this embodiment, the substrate may be a rigid substrate, such as glass, or a flexible substrate, such as one of PET or PI.
In this embodiment, the anode may be selected from one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), and the like.
In this embodiment, the hole injection layer may be made of water-soluble PEDOT: PSS, or other materials with good hole injection performance, such as NiO and MoO 3 、WO 3 Or V 2 O 5 And the like. Further, PEDOT: PSS was chosen as the hole injection layer material. The thickness of the hole injection layer is 10-100 nm.
In the present embodiment, the material of the hole transport layer may be selected from materials having good hole transport properties, and may include, for example, but not limited to, Poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine) (TFB), Polyvinylcarbazole (PVK), Poly (N, N 'bis (4-butylphenyl) -N, N' -bis (phenyl) benzidine) (Poly-TPD), Poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-Phenylenediamine) (PFB), 4', 4 ″ -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), and the like. The thickness of the hole transport layer is 1-100 nm.
In this embodiment, the material of the quantum dot light emitting layer may be oil-soluble quantum dots, where the oil-soluble quantum dots include one or more of binary phase, ternary phase, quaternary phase quantum dots, and the like; the binary phase quantum dots comprise one or more of CdS, CdSe, CdTe, InP, AgS, PbS, PbSe, HgS and the like, the ternary phase quantum dots comprise one or more of ZnCdS, CuInS, ZnCdSe, ZnSeS, ZnCdTe, PbSeS and the like, and the quaternary phase quantum dots comprise one or more of ZnCdS/ZnSe, CuInS/ZnS, ZnCdSe/ZnS, CuInSeS, ZnCdTe/ZnS, PbSeS/ZnS and the like. The material of the quantum dot light-emitting layer can be any one of common red, green and blue quantum dots or other yellow light, and the quantum dots can contain cadmium or do not contain cadmium. 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 this embodiment, the cathode may be selected from one of an aluminum (Al) electrode, a silver (Ag) electrode, a gold (Au) electrode, and the like, and may also be selected from one of a nano aluminum wire, a nano silver wire, a nano gold wire, and the like. The material has smaller resistance, so that carriers can be smoothly injected. In this embodiment, the cathode has a thickness of about 60nm to about 120 nm.
It should be noted that the quantum dot light emitting diode of the present invention may further include one or more of the following functional layers: a hole injection layer arranged between the hole transport layer and the anode, and an electron injection layer arranged between the electron transport layer and the cathode.
In this embodiment, the quantum dot light emitting diode has various forms, and the quantum dot light emitting diode may be a positive type structure or an inversion type structure, where the quantum dot light emitting diode with the inversion type structure will be mainly described by taking the structure shown in fig. 2 as an example. Specifically, as shown in fig. 2, the quantum dot light emitting diode with the inversion structure includes a substrate 21 including a cathode, an electron transport layer 22, a quantum dot light emitting layer 23, a hole transport layer 24, a hole injection layer 25, and an anode 26, which are arranged in sequence from bottom to top; the material of the electron transport layer 22 is the nano material described in this embodiment, and the nano material is a nano sheet formed by self-assembling ZnO nanoparticles and phosphomolybdic acid.
In one embodiment, the cathode may be selected from one or more of indium doped tin oxide (ITO), fluorine doped tin oxide (FTO), antimony doped tin oxide (ATO), aluminum doped zinc oxide (AZO), and the like. Further, the cathode is indium-doped tin oxide (ITO).
In one embodiment, the anode may be selected from one of an aluminum (Al) electrode, a silver (Ag) electrode, a gold (Au) electrode, and the like, and may also be selected from one of a nano aluminum wire, a nano silver wire, a nano gold wire, and the like.
In the above device, the material selection of the remaining layers is described above and will not be described herein.
Referring to fig. 3, fig. 3 is a schematic flow chart of a method for manufacturing a quantum dot light emitting diode with a positive structure shown in fig. 1 according to an embodiment of the present invention, as shown in fig. 3, including the steps of:
s11, providing a substrate containing an anode;
s12, preparing a hole injection layer on the substrate containing the anode;
s13, preparing a hole transport layer on the hole injection layer;
s14, preparing a quantum dot light emitting layer on the hole transport layer;
s15, preparing an electron transport layer on the quantum dot light-emitting layer; the electron transport layer material is the nano material of the embodiment;
and S16, preparing a cathode on the electron transport layer to obtain the quantum dot light-emitting diode.
In this embodiment, in order to obtain a high-quality hole injection layer, the substrate including the anode needs to be subjected to a pretreatment process. Wherein the pretreatment process specifically comprises: the substrate containing the anode is washed by a cleaning agent to primarily remove stains existing on the surface of the substrate containing the anode, and then the clean substrate is treated by ultraviolet-ozone or oxygen plasma to further remove organic matters attached on the surface of the substrate and improve the work function of the substrate.
In one embodiment, the step of preparing a hole injection layer on a substrate includes: placing the substrate containing the anode on a spin coater, and spin-coating the substrate with a prepared solution of a hole injection 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 the hole injection layer is obtained by thermal annealing treatment at a proper temperature.
In one embodiment, the step of preparing a hole transport layer on the hole injection layer comprises: placing the substrate on a spin coater, and spin-coating the substrate with a prepared solution of a 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 the hole transport layer is obtained by thermal annealing treatment at a proper temperature.
In one embodiment, the step of preparing a quantum dot light emitting layer on a hole transport layer comprises: and placing the prepared substrate with the hole transport layer on a spin coater, spin-coating the prepared luminescent material solution with a certain concentration to form a film, controlling the thickness of the quantum dot luminescent layer by adjusting the concentration, the spin-coating speed and the spin-coating time of the solution, and finally drying at a proper temperature to obtain the quantum dot luminescent layer.
In one embodiment, the step of preparing an electron transport layer at the quantum dot light emitting layer comprises: the method comprises the steps of placing a substrate with a prepared quantum dot light emitting layer on a spin coater, carrying out spin coating on a prepared electron transmission material solution with a certain concentration to form a film, controlling the thickness of an electron transmission layer by adjusting the concentration of the solution, the spin coating speed (preferably, the rotating speed is 3000rpm-5000 rpm) and the spin coating time, and then annealing to form the film to obtain the electron transmission layer. The step can be annealing in air or in nitrogen atmosphere, and the annealing atmosphere is selected according to actual needs.
In one embodiment, the obtained quantum dot light emitting diode is subjected to an encapsulation process. 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.
In this embodiment, the preparation method of each layer may be a chemical method or a physical method, wherein the chemical method includes, but is not limited to, one or more of a chemical vapor deposition method, a continuous ion layer adsorption and reaction method, an anodic oxidation method, an electrolytic deposition method, and a coprecipitation method; the physical methods include, but are not limited to, one or more of solution methods (e.g., spin coating, printing, knife coating, dip-draw, dipping, spray coating, roll coating, casting, slot coating, or bar coating), evaporation (e.g., thermal evaporation, electron beam evaporation, magnetron sputtering, or multi-arc ion plating), deposition (e.g., physical vapor deposition, elemental layer deposition, pulsed laser deposition, etc.).
Referring to fig. 4, fig. 4 is a schematic flow chart of a method for manufacturing the quantum dot light emitting diode with the inversion structure shown in fig. 2 according to an embodiment of the present invention, as shown in fig. 4, including the steps of:
s21, providing a substrate containing a cathode;
s22, preparing an electron transport layer on the substrate containing the cathode; the electron transport layer material is the nano material of the embodiment;
s23, preparing a quantum dot light-emitting layer on the electron transport layer;
s24, preparing a hole transport layer on the quantum dot light emitting layer;
s25, preparing a hole injection layer on the hole transport layer;
and S26, preparing an anode on the hole injection layer to obtain the quantum dot light-emitting diode.
In the above-mentioned preparation method, the detailed preparation process of each layer is described above and is not described herein again.
The present embodiment will be described in detail with reference to specific examples.
Embodiment 1, the preparation method of the two-dimensional hybrid ZnO-PMA ultrafine nanosheet of the embodiment comprises the following specific steps:
1g of zinc acetate and 1.8g of phosphomolybdic acid are dissolved in 0.28g of ethanolamine and 10ml of ethylene glycol monomethyl ether and stirred continuously for 12 hours; then centrifuging, washing and drying the obtained precipitate to prepare a two-dimensional hybrid ZnO-PMA superfine nanosheet; and finally dispersing the prepared two-dimensional hybrid ZnO-PMA superfine nanosheet into an ethanol solution by an ultrasonic method, wherein the concentration is 30 mg/ml.
Embodiment 2, in combination with the schematic structural diagram 1 of the quantum dot light emitting diode device, the preparation steps of the quantum dot light emitting diode device are as follows:
firstly, placing a patterned ITO substrate in acetone, washing liquor, deionized water and isopropanol in sequence for ultrasonic cleaning, wherein each step of ultrasonic cleaning lasts for about 15 minutes. After the ultrasonic treatment is finished, the ITO substrate is placed in a clean oven to be dried for later use; after the ITO substrate is dried, treating the surface of the ITO substrate with ultraviolet ozone for 5 minutes to further remove organic matters attached to the surface of the ITO substrate and improve the work function of the ITO substrate;
then, spin-coating a layer of PEDOT, PSS, with the thickness of 30nm, on the surface of the processed ITO substrate, and heating the substrate on a heating table at 150 ℃ for 30 minutes to remove moisture, wherein the step needs to be completed in the air;
next, the dried substrate coated with the hole injection layer was placed in a nitrogen atmosphere, a layer of the hole transport layer material PVK was spin-coated, the thickness of this layer was 30nm, and the substrate was placed on a heating stage at 150 ℃ and heated for 30 minutes to remove the solvent;
after the wafer processed in the previous step is cooled, the blue quantum dot luminescent material is coated on the surface of the hole transport layer in a spinning mode, the thickness of the blue quantum dot luminescent material is 20nm, after the deposition in the previous step is finished, the wafer is placed on a heating table at the temperature of 80 ℃ to be heated for 10 minutes, and residual solvent is removed;
and then spin-coating a layer of two-dimensional hybrid ZnO-PMA nano material as an electron transport layer with the thickness of 30nm, placing the wafer on a heating table at 80 ℃ after deposition is finished, heating for 10 minutes, and removing residual solvent.
And finally, placing the sheet on which the functional layers are deposited in an evaporation bin, and thermally evaporating a layer of aluminum as a cathode through a mask plate, wherein the thickness of the aluminum is 100 nm. And completing the preparation of the device.
The test result shows that compared with a device using ZnO nanoparticles, a device using two-dimensional hybrid ZnO-PMA nanosheets has more uniform luminescence and no black spots, while a device using ZnO nanoparticles has a small amount of black spots, and the EQE is improved by about 30% and is improved to 12% from 9.2%. This is because the two-dimensional hybrid ZnO-PMA nanoplatelets have higher electron mobility compared to ZnO nanoparticles; in addition, the shell energy levels of the two-dimensional hybrid ZnO-PMA nanosheet and the blue quantum dot are more matched, so that the rapid injection and transmission of electrons are facilitated, carriers in a light emitting layer of the device are effectively balanced, and the optical performance of the device is improved.
Example 3: in combination with the provided schematic structural diagram 2 of the quantum dot light emitting diode device, the preparation steps of the quantum dot light emitting diode device are as follows:
firstly, placing a patterned ITO substrate in acetone, washing liquor, deionized water and isopropanol in sequence for ultrasonic cleaning, wherein each step of ultrasonic cleaning lasts for about 15 minutes. After the ultrasonic treatment is finished, placing the ITO in a clean oven for drying for later use; after the ITO substrate is dried, treating the surface of the ITO substrate with ultraviolet ozone for 5 minutes to further remove organic matters attached to the surface of the ITO substrate;
then, printing a layer of two-dimensional hybrid ZnO-PMA nano material on the surface of the processed ITO substrate to be used as an electron transmission layer, wherein the thickness of the electron transmission layer is 25nm, placing the wafer on a heating table at 80 ℃ after deposition is finished, heating for 10 minutes, and removing residual solvent;
after the wafer is cooled, printing the blue quantum dot luminescent material on the surface of the electron transport layer, wherein the thickness of the blue quantum dot luminescent material is 20nm, after the deposition in the step is finished, placing the wafer on a heating table at 80 ℃ for heating for 10 minutes, and removing the residual solvent;
evaporating a layer of hole transport layer material NPB, wherein the thickness of the layer is 10 nm;
then, a layer of hole injection layer material MoO is evaporated 3 The thickness of this layer is 30 nm;
and finally, placing the sheet on which the functional layers are deposited in an evaporation bin, and thermally evaporating a layer of silver as an anode through a mask plate, wherein the thickness of the silver is 80 nm. And completing the preparation of the device.
The test result shows that compared with a device using ZnO nanoparticles, a device using two-dimensional hybrid ZnO-PMA nanosheets has more uniform luminescence and no black spots, while a device using ZnO nanoparticles has a small amount of black spots, and the EQE is improved by about 30% and is improved from 7.8% to 10%.
In summary, the invention provides a nano material, a preparation method thereof and a quantum dot light emitting diode. The invention realizes the controllable synthesis of the two-dimensional hybrid ZnO-PMA superfine nanosheet by introducing PMA to intervene nucleation at the ZnO nucleation stage and adopting a method of agglomeration and co-assembly of ZnO crystal nucleus and PMA. Compared with the existing common ZnO nano material, the nano material has higher stability in solution and more uniform film formation, and common ZnO nano particles are unstable in solution and are easy to separate out; and the electron mobility is obviously higher, mainly because of the excellent structure of the two-dimensional hybrid ultrafine nanosheet; in addition, the energy levels of the shells of the nano material and the blue quantum dots are more matched, which is beneficial to the rapid injection and transmission of electrons, thereby effectively balancing the current carriers in the light emitting layer of the device and improving the optical performance of the device.
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. A method for preparing a nano material is characterized by comprising the following steps:
mixing a Zn source, phosphomolybdic acid and a solvent, reacting to generate ZnO crystal nuclei, and co-assembling the ZnO crystal nuclei and the phosphomolybdic acid to obtain the nano material with the sheet structure, wherein the nano material is a nano sheet formed by self-assembling ZnO nanoparticles and the phosphomolybdic acid, the thickness of the nano sheet is less than 2nm, and the length of the nano sheet is less than 5 nm.
2. The method according to claim 1, wherein in the step of mixing the Zn source, the phosphomolybdic acid and the solvent, the molar ratio of the Zn source to the phosphomolybdic acid is 1:1 to 1: 5.
3. The method for preparing the nano-material according to claim 1, wherein the reaction temperature is 20-80 ℃; and/or the reaction time is 2-48 h.
4. A nanomaterial, the nanomaterial comprising: the nano material is a nano sheet, wherein the nano material is a nano sheet formed by self-assembling ZnO nanoparticles and phosphomolybdic acid, the thickness of the nano sheet is less than 2nm, and the length of the nano sheet is less than 5 nm.
5. Nanomaterial according to claim 4, characterized in that the length of the nanoplatelets is less than 2 nm.
6. A quantum dot light emitting diode comprising: an anode, a cathode, a quantum dot light-emitting layer arranged between the anode and the cathode, and an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, wherein the electron transport layer comprises a nano material prepared by the preparation method of any one of claims 1 to 3; and/or the electron transport layer material comprises a nanomaterial according to any of claims 4 to 5.
7. The quantum dot light-emitting diode according to claim 6, wherein the electron transport layer material is a nanomaterial prepared by the preparation method according to any one of claims 1 to 3; and/or the electron transport layer material is a nanomaterial according to any one of claims 4 to 5.
8. The qd-led of claim 7, wherein the electron transport layer has a thickness of 10nm to 60 nm.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1772835A (en) * 2005-11-17 2006-05-17 复旦大学 Nanometer luminescent core-shell zinc oxide-polymer particle and its prepn
CN107591488A (en) * 2016-07-08 2018-01-16 中国科学院苏州纳米技术与纳米仿生研究所 Multi-metal oxygen cluster compound metal complex oxide, its preparation method and application
CN107793294A (en) * 2017-09-12 2018-03-13 沈阳化工大学 A kind of absolute ethyl alcohol, low-grade ethanol process for refining and purifying

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1772835A (en) * 2005-11-17 2006-05-17 复旦大学 Nanometer luminescent core-shell zinc oxide-polymer particle and its prepn
CN107591488A (en) * 2016-07-08 2018-01-16 中国科学院苏州纳米技术与纳米仿生研究所 Multi-metal oxygen cluster compound metal complex oxide, its preparation method and application
CN107793294A (en) * 2017-09-12 2018-03-13 沈阳化工大学 A kind of absolute ethyl alcohol, low-grade ethanol process for refining and purifying

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