CN112397661B - 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 PDFInfo
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Abstract
The invention discloses a nano material, a preparation method thereof and a quantum dot light-emitting diode, wherein the nano material has a core-shell structure, the core material of the nano material comprises NiO nano particles, and the shell material of the nano material comprises MoS 2 Nanosheets. NiO nano-particles as core material, ultra-thin MoS grown on the surface of NiO nano-particles 2 The nanosheets serve as the shell material. MoS 2 The shell can protect the NiO core with relatively high activity and reduce the NiO surface defects, thereby inhibiting the capture of carriers by the surface defects; moS 2 The growth of the nano-sheet can enable the NiO nucleus to be better dispersed in the solvent, and the dispersibility is improved. Compared with MoS 2 NiO has better hole transmission performance and can ensure the fast transfer of holes. The nano material with the core-shell structure is used as a hole transport material, moS 2 And the hole transmission efficiency is improved under the synergistic action of NiO, so that the luminous efficiency of the quantum dot light-emitting diode is improved.
Description
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 semiconductor quantum dots have quantum size effect, people can realize the required light emission with specific wavelength by regulating and controlling the size of the quantum dots, and the tuning range of the light emission wavelength of the CdSe QDs can be from blue light to red light. In the 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 wide bandgap semiconductors can be accelerated under high electric fields to obtain high enough energy to strike QDs to cause it to emit light.
In recent years, inorganic semiconductors have been studied as a hole transport layer with relative heat. As a p-type semiconductor material, the nano NiO has adjustable band gaps (the band gap is 3.6-4.0 eV, the HOMO energy level is-5.4 eV to-5.0 eV, and the LUMO energy level is-1.6 eV), has higher light transmission performance in an ultraviolet light region, a visible light region and a near infrared light region, and has the advantages of excellent chemical stability, unique optical, electrical and magnetic properties and the like, and is widely applied to electrochromic devices, organic light-emitting diodes, gas-sensitive sensors, dye-sensitized solar cells and p-n heterojunction. MoS 2 As the most representative material in the two-dimensional transition metal sulfide layered nanometer material, the material can not only make up the defect of zero band gap of graphene and the like, but also overcome the defect of low layered carrier mobility due to the unique microstructure, the adjustable energy band gap (1.13 eV-1.87 eV) and the high carrier mobility, and is an ideal hole transport material. Molybdenum disulfide as a transition metal material has attracted attention of researchers at home and abroad due to its unique microstructure, adjustable energy band gap and high carrier mobility. However, composite materials composed of nickel oxide and molybdenum disulfide have been reported.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a nano material, a preparation method thereof and a quantum dot light-emitting diode, and aims to solve the problem that a NiO hole transport layer in the conventional quantum dot light-emitting diode is low in efficiency.
The technical scheme of the invention is as follows:
a nanomaterial having a core-shell structure, wherein a core material of the nanomaterial comprises NiO nanoparticles and a shell material of the nanomaterial comprises MoS 2 Nanosheets.
A method for preparing a nano material, comprising the following steps:
providing a mixed solution containing nickel salt and alkali, and reacting to obtain NiO nano-particles;
the NiO nano-particlesMixing the particles with thiomolybdate, and forming MoS on the surface of NiO nano particles through hydrothermal reaction 2 Nanosheets, resulting in a core material comprising NiO nanoparticles and a shell material comprising MoS 2 The core-shell structure nano material of the nano sheet.
A quantum dot light emitting diode comprising: the anode, the cathode, the quantum dot light emitting layer arranged between the anode and the cathode, and the hole transport layer arranged between the anode and the quantum dot light emitting layer, wherein the hole transport layer is made of the nano material; and/or the hole transport layer material is the nano material prepared by the preparation method.
Has the advantages that: the nano material has a core-shell structure, wherein NiO nano particles are used as a core material, and the ultra-thin MoS grows on the surfaces of the NiO nano particles 2 The nanosheets serve as the shell material. MoS as shell material 2 The NiO nucleus with relatively high activity can be protected to a certain extent, and the NiO surface defects are reduced, so that the capture of the surface defects on current carriers is inhibited; at the same time, moS 2 The growth of the nano-sheet can enable the NiO nucleus to be better dispersed in the solvent, and the dispersibility is improved. Compared with MoS 2 NiO has better hole transmission performance and can ensure the fast transfer of holes. NiO and MoS 2 The formed core-shell nano material is used as a hole transport material, moS 2 The hole transmission efficiency is improved by the synergistic effect of the nano-sheet and the NiO nano-particle core-shell structure, so that the luminous efficiency of the quantum dot light-emitting diode is improved.
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Fig. 1 is a schematic flow chart of a method for preparing a nanomaterial provided in an embodiment of the present 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
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 nano material which has a core-shell structure, wherein the core material of the nano material comprises NiO nano particles, and the shell material of the nano material comprises MoS 2 Nanosheets.
In one embodiment, the core material of the nanomaterial is NiO nanoparticles, and the shell material of the nanomaterial is MoS 2 Nanosheets.
In one embodiment, the NiO nanoparticles have a particle size of 5 to 10nm.
In a preferred embodiment, the MoS is a solid-state imaging device 2 The thickness of the nano-sheet is 3-5nm. Within this thickness range, the nanomaterial described in this example has better dispersibility in solvents.
In a preferred embodiment, the NiO nanoparticles are in contact with the MoS 2 The molar ratio of the nano-sheets is 1: (0.2-0.5). At this molar ratio, moS 2 The nano-sheets are uniformly distributed on the surface of the NiO core.
The nano material has a core-shell structure, wherein NiO nano particles are used as a core material, and the ultra-thin MoS grows on the surfaces of the NiO nano particles 2 The nanosheets serve as the shell material. MoS as shell material 2 NiO nuclei with relatively high activity can be protected to a certain extent, and NiO surface defects are reduced, so that the capture of carriers by the surface defects is inhibited; at the same time, moS 2 The growth of the nano-sheet can enable the NiO nucleus to be better dispersed in the solvent, and the dispersibility is improved. Compared with MoS 2 NiO has better hole transmission performance and can ensure the fast transfer of holes. NiO and MoS 2 The formed core-shell nano material is used as a hole transport material, moS 2 The hole transmission efficiency is improved by the synergistic effect of the nano-sheet and the NiO nano-particle core-shell structure, so that the luminous efficiency of the quantum dot light-emitting diode is improved.
Referring to fig. 1, an embodiment of the present invention provides a flow chart of a method for preparing a nano material, which includes the following steps:
s10, providing a mixed solution containing nickel salt and alkali, and reacting to obtain NiO nano particles;
s20, mixing the NiO nano particles with thiomolybdate, and forming MoS on the surfaces of the NiO nano particles through a hydrothermal reaction 2 Nanosheets, resulting in a core material comprising NiO nanoparticles and a shell material comprising MoS 2 The core-shell structure nano material of the nano sheet.
The invention utilizes a hydrothermal method to prepare the nano material with the core-shell structure, wherein NiO nano particles are used as the core material, and the ultra-thin MoS grows on the surfaces of the NiO nano particles 2 The nanosheets serve as the shell material. MoS as shell material 2 NiO nuclei with relatively high activity can be protected to a certain extent, and NiO surface defects are reduced, so that the capture of carriers by the surface defects is inhibited; at the same time, moS 2 The growth of the nano-sheet can enable the NiO nucleus to be better dispersed in the solvent, and the dispersibility is improved. Compared with MoS 2 NiO has better hole transmission performance and can ensure the fast transfer of holes. The nano material provided by the embodiment of the invention is used as a hole transport layer, moS 2 The synergistic effect of the nano-sheet and the NiO nano-particle core-shell structure improves the hole transmission efficiency, thereby improving the luminous efficiency and the performance of the quantum dot light-emitting diode.
In this embodiment, the step S10 specifically includes: dissolving nickel salt in an organic solvent, stirring and dissolving at constant temperature, adding alkali liquor, stirring and dissolving at constant temperature, cooling, separating out by using a precipitator, washing and drying to obtain the NiO nano-particles. In this example, alkali was added to the solution containing nickel salt, and the mixture was stirred at a constant temperature to dissolve the nickel salt, and reacted under an alkaline condition to obtain NiO nanoparticles. In the embodiment, the temperature for stirring and dissolving at constant temperature is lower than the boiling point temperature of alkali and organic solvent, generally 60-90 ℃, and the specific temperature is set according to the boiling point of the alkali; in order to fully stir and dissolve, the stirring time is preferably 2h-4h.
In this embodiment, the nickel salt is a soluble inorganic nickel salt or a soluble organic nickel salt. In one embodiment, the nickel salt includes one or more of nickel acetate, nickel nitrate, nickel chloride, nickel sulfate, nickel acetate tetrahydrate, and the like.
In one embodiment, the organic solvent comprises one or more of isopropanol, ethanol, propanol, butanol, pentanol, hexanol, and the like.
In this embodiment, the alkali solution is prepared by dissolving an alkali in an organic solvent, and the alkali is an inorganic alkali or an organic alkali. In one embodiment, the inorganic base comprises an alkali metal hydroxide and the organic base comprises an alcamines compound. In a particular embodiment, the alkali metal hydroxide comprises one or more of potassium hydroxide, sodium hydroxide, lithium hydroxide, and the like. The alcohol amine compound comprises one or more of ethanolamine, ethylene glycol, diethanolamine, triethanolamine, ethylenediamine and the like.
In this example, the precipitant is a weakly polar or non-polar solvent. In one embodiment, the precipitation agent comprises one or more of ethyl acetate, heptane, octane, and the like.
In a preferred embodiment, in the mixed solution comprising a nickel salt and a base, the molar ratio of the base to the nickel salt is (1.8-2.5): 1. when the ratio of alkali to nickel salt is less than 1.8:1, excessive nickel salt, wherein the added nickel salt can not completely react; greater than 2.5:1, too high a pH results in a slower polycondensation rate in the system. Preferably, the ratio of the molar amount of the base to the molar amount of the nickel ions is maintained between (1.8 and 2.5): 1, a compact and compact nickel oxide film can be obtained subsequently, and the particles on the surface of the film are uniformly distributed.
In one embodiment, the concentration of the nickel salt in the mixed solution comprising the nickel salt and the alkali is 0.2M to 1M.
In one embodiment, the mixed solution comprising a nickel salt and a base has a pH =12-13.
In this embodiment, the step S20 specifically includes: mixing the NiO nano particles with thiomolybdate, carrying out hydrothermal reaction, cooling, washing and drying to obtain a core material comprising NiO nano particles and a shell material comprising MoS 2 The core-shell structure nano material of the nano sheet.
In one embodiment, the thiomolybdate salt includes one or more of sodium thiomolybdate, potassium thiomolybdate, ammonium thiomolybdate, and the like.
In one embodiment, the temperature of the hydrothermal reaction is from 150 ℃ to 200 ℃.
In one embodiment, the hydrothermal reaction time is 20h to 24h.
In one embodiment, the temperature of the drying is from 150 ℃ to 200 ℃.
In a preferred embodiment, the molar ratio of the Ni element to the Mo element is 1: (0.2-0.5), mixing the NiO nanoparticles with thiomolybdate. Pure NiO is a particle structure with a smooth surface, the surface of a product after hydrothermal reaction becomes rough with the addition of thiomolybdate, and when the molar ratio of Ni element to Mo element is less than 1: at 0.2, the surface of the obtained product is mainly provided with tiny particles, and the surface becomes rough and uneven; when the molar ratio of the Ni element to the Mo element is about 1: (0.2-0.5), a large number of nano sheets grow on the surface of the NiO core and are uniformly distributed; when the molar ratio of the Ni element to the Mo element is more than 1: at 0.5, more and more nano-sheets are arranged on the surface of the NiO core, and as the reaction proceeds, flower balls assembled by sheets even appear on the surface. The occurrence of the flower ball can not form NiO and MoS well 2 The core-shell structure is formed. Therefore, the molar ratio of the Ni element to the Mo element is maintained at about 1: the most preferable range is 0.2 to 0.5.
The embodiment of the invention provides a quantum dot light-emitting diode, which comprises: the light-emitting diode comprises an anode, a cathode, a quantum dot light-emitting layer arranged between the anode and the cathode, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the hole transport layer is made of the nano material in the embodiment of the invention; and/or the hole transport layer material is the nano material prepared by the preparation method provided by the embodiment of the invention.
In this example, the nanomaterial, in which NiO nanoparticles are used as the core, was an ultra-thin MoS grown on the surface of the NiO nanoparticles 2 The nanosheets serve as the shell. MoS as shell material 2 NiO nuclei with relatively high activity can be protected to a certain extent, and NiO surface defects are reduced, so that the capture of carriers by the surface defects is inhibited; at the same time, moS 2 Nano-sheetThe NiO nuclei can be dispersed in the solvent better by the growth of (2), and the dispersibility is improved. Compared with MoS 2 NiO has better hole transmission performance and can ensure the fast transfer of holes. The nano material described in this example is used as a hole transport layer, moS 2 The synergistic effect of the nano-sheet and the NiO nano-particle core-shell structure improves the hole transmission efficiency, thereby improving the luminous efficiency and the performance of the quantum dot light-emitting diode.
In this embodiment, the quantum dot light emitting diode has various forms, and the quantum dot light emitting diode has a positive structure and an inverse structure, and this embodiment will be described in detail mainly by taking the quantum dot light emitting diode with the positive structure as shown in fig. 2 as an example. Specifically, as shown in fig. 2, the quantum dot light emitting diode includes a substrate 1, an anode 2, a hole transport layer 3, a quantum dot light emitting layer 4, an electron transport layer 5, and a cathode 6, which are stacked from bottom to top; the hole transport layer 3 is made of the nano material, and the nano material comprises NiO nano particles and MoS combined on the surfaces of the NiO nano particles 2 Nanosheets.
In a preferred embodiment, the hole transport layer has a thickness of 20 to 60nm. If the thickness of the hole transport layer is too thin, the transport performance of a current carrier cannot be ensured, so that holes 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 hole 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 material of the quantum dot light emitting layer may be an oil-soluble quantum dot, where the oil-soluble quantum dot includes one or more of binary phase, ternary phase, quaternary phase quantum dot, 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 thickness of the quantum dot light emitting layer is about 20nm to 60nm.
In this embodiment, the material of the electron transport layer may be selected from materials with good electron transport properties, for example, may include but is not limited to n-type ZnO, tiO 2 、Fe 2 O 3 、SnO 2 、Ta 2 O 3 One or more of AlZnO, znSnO, inSnO and the like. In this embodiment, the thickness of the electron transport layer is about 80nm.
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.
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.
The embodiment of the invention also provides a preparation method of the quantum dot light-emitting diode with the positive structure, wherein the preparation method comprises the following steps:
providing a substrate;
preparing a hole transport layer on a substrate;
preparing a quantum dot light emitting layer on the hole transport layer;
preparing an electron transport layer on the quantum dot light-emitting layer;
and 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 transport layer, the anode needs to be subjected to a pretreatment process. Wherein the pretreatment process specifically comprises: and cleaning the anode with a cleaning agent to primarily remove stains on the surface of the anode, then sequentially and respectively ultrasonically cleaning the anode in deionized water, acetone, absolute ethyl alcohol and deionized water for 20min to remove impurities on the surface, and finally drying the anode by using high-purity nitrogen to obtain the anode.
In a preferred 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.).
The method for producing the nanomaterial of the present invention is described in detail below with reference to examples.
Example 1
This example uses nickel chloride, ethanol, sodium hydroxide, ammonium molybdate sulfide as an example for detailed description:
1) Firstly, adding a proper amount of nickel chloride into 50ml of ethanol, stirring and dissolving at 70 ℃ to form a salt solution with the total concentration of 0.5M; weighing potassium hydroxide, and dissolving in 10ml ethanol to prepare potassium hydroxide solution; according to OH - And Ni 2+ In a molar ratio of 2:1 ofProportionally, adding a potassium hydroxide solution into a salt solution to form a mixed solution with the pH value of 12, and continuously stirring at 70 ℃ for 4 hours to obtain a uniform transparent solution; then, after the solution is cooled, ethyl acetate is used for precipitation, a small amount of ethanol is used for dissolution after centrifugation, the precipitation and dissolution steps are repeated for 3 times, and drying is carried out, so as to prepare NiO nano particles;
2) Ultrasonically dispersing the dried NiO nano particles into 20ml of a mixed solution of water and ethanol (the volume ratio of the water to the ethanol is 2; 0.3g of (NH) 4 ) 2 MoS 4 (ii) a Transferring the dispersion liquid into a hydrothermal reaction kettle, and reacting for 24 hours at 200 ℃; then cooling and washing (water washing 2 times, absolute ethyl alcohol washing 1 time) are carried out, and drying is carried out at 50 ℃ to obtain NiO/MoS 2 A core-shell nano material.
Example 2
This example uses nickel nitrate, methanol, ethanolamine, sodium thiomolybdate as an example for detailed description:
1) Firstly, adding a proper amount of nickel nitrate into 50ml of methanol, stirring and dissolving at 60 ℃ to form a salt solution with the total concentration of 0.5M; weighing ethanolamine, dissolving the ethanolamine in 10ml of methanol to prepare ethanolamine solution; adding ethanolamine solution into the salt solution to form a mixed solution with pH =12, and continuously stirring at 60 ℃ for 4h to obtain a uniform transparent solution; then, after the solution is cooled, octane is used for precipitation, a small amount of ethanol is used for dissolution after centrifugation, the precipitation and dissolution steps are repeated for 3 times, and drying is carried out to prepare NiO nano particles;
2) Ultrasonically dispersing the dried NiO nano particles into 20ml of a mixed solution of water and ethanol (the volume ratio of the water to the ethanol is 2; 0.3g of Na was added in a molar ratio of Ni to Mo of 1 2 MoS 4 (ii) a Transferring the dispersion liquid into a hydrothermal reaction kettle, and reacting for 24 hours at 200 ℃; then cooling and washing (water washing 2 times, absolute ethyl alcohol washing 1 time) are carried out, and drying is carried out at 50 ℃ to obtain NiO/MoS 2 A core-shell nano material.
Example 3
This example uses nickel sulfate, propanol, sodium hydroxide, potassium thiomolybdate as an example for detailed description:
1) Firstly, adding a proper amount of nickel sulfate into 50ml of propanol, stirring and dissolving at 70 ℃ to form a salt solution with the total concentration of 0.5M; weighing sodium hydroxide, and dissolving the sodium hydroxide in 10ml of propanol to prepare a sodium hydroxide solution; according to OH - And Ni 2+ In a molar ratio of 2:1, adding a sodium hydroxide solution into a salt solution to form a mixed solution with the pH of 12, and continuously stirring at 80 ℃ for 4 hours to obtain a uniform transparent solution; then, after the solution is cooled, using heptane for precipitation, after centrifugation, using a small amount of ethanol for dissolution, repeating the precipitation and dissolution steps for 3 times, and drying to prepare NiO nano particles;
2) Ultrasonically dispersing the dried NiO nano particles into 20ml of a mixed solution of water and ethanol (the volume ratio of the water to the ethanol is 2; 0.3g of K was added in a molar ratio of Ni to Mo of 1 2 MoS 4 (the dispersion is transferred to a hydrothermal reaction kettle and reacted for 24 hours at the temperature of 200 ℃), then cooling and washing are carried out (water washing is carried out for 2 times, absolute ethyl alcohol washing is carried out for 1 time), and drying is carried out at the temperature of 50 ℃ to obtain NiO/MoS 2 A core-shell nano material.
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. Wherein the substrate is made of glass sheet, the anode is made of ITO substrate, and the hole transport layer is made of NiO/MoS 2 The core-shell nano material is characterized in that the electron transport layer is made of ZnO, 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, depositing the precursor solution obtained in the method of embodiment 1 on the ITO substrate, and annealing to prepare a hole transport layer;
depositing a quantum dot light emitting layer on the hole transport layer;
depositing an electron transport layer over the quantum dot light emitting layer;
depositing 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, and the hole transport layer is made of NiO/MoS 2 The core-shell nano material is characterized in that the electron transport layer is made of ZnO, 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, depositing the precursor solution obtained in the method of the embodiment 2 on the ITO substrate, and annealing to prepare a hole transport layer;
depositing a quantum dot light emitting layer on the hole transport layer;
depositing 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, and the hole transport layer is made of NiO/MoS 2 The core-shell nano material is characterized in that the electron transport layer is made of ZnO, 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, depositing the precursor solution obtained in the method of embodiment 3 on the ITO substrate, and annealing to prepare a hole transport layer;
depositing a quantum dot emissive layer on the hole transport layer;
depositing an electron transport layer over the quantum dot light emitting layer;
depositing 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. Wherein the substrate is made of glass sheet, the cathode is made of ITO substrate, and the hole transport layer is made of NiO/MoS 2 The core-shell nano material is characterized in that the electron transport layer is made of ZnO, 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 depositing an electron transport layer on the cathode substrate;
preparing a quantum dot light-emitting layer on the electron transport layer, depositing the precursor solution obtained by the method in the embodiment 1 on the quantum dot light-emitting layer, and annealing to prepare a hole transport 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, and the hole transport layer is made of NiO/MoS 2 Core-shell nanomaterial, electron transport layerThe material is ZnO, and the material of the anode is Al.
The preparation method of the quantum dot light-emitting diode comprises the following steps:
providing a cathode substrate, and depositing an electron transport layer on the cathode substrate;
preparing a quantum dot light-emitting layer on the electron transport layer, depositing the precursor solution obtained by the method in the embodiment 2 on the quantum dot light-emitting layer, and annealing to prepare a hole transport 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, and the hole transport layer is made of NiO/MoS 2 The core-shell nano material is characterized in that the electron transport layer is made of ZnO, 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 depositing an electron transport layer on the cathode substrate;
preparing a quantum dot light-emitting layer on the electron transport layer, depositing the precursor solution obtained by the method in the embodiment 3 on the quantum dot light-emitting layer, and annealing to prepare a hole transport 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 anode is arranged on a substrate. Wherein the material of the substrateThe frit is a glass plate, the anode is made of an ITO substrate, and the hole transport layer is made of commercial MoS 2 The material (purchased from sigma company), the material of the electron transport layer is ZnO, and the material of the cathode is 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 anode 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 a commercial NiO material (purchased from sigma company), the electron transport layer is made of ZnO, and the cathode is made of Al.
The performance tests were performed on the hole transport films prepared in examples 1 to 3, the hole transport films in comparative examples 1 and 2, and the quantum dot light emitting diodes prepared in examples 4 to 9 and comparative examples 1 and 2, and the test indexes and test methods were as follows:
(1) Hole mobility: testing the current density (J) -voltage (V) of the hole transport film, drawing a curve relation graph, fitting a Space Charge Limited Current (SCLC) region in the relation graph, and then calculating the hole mobility according to a well-known Child, s law formula:
J＝(9/8)ε r ε 0 μ e V 2 /d 3
wherein J represents current density in mAcm -2 ；ε r Denotes the relative dielectric constant,. Epsilon 0 Represents the vacuum dielectric constant; mu.s e Denotes hole mobility in cm 2 V -1 s -1 (ii) a V represents the drive voltage, in units of V; d represents the film thickness in m.
(2) Resistivity: and measuring the resistivity of the hole transport film by using the same resistivity measuring instrument.
(3) External Quantum Efficiency (EQE): measured using an EQE optical test instrument.
Note: the hole mobility and resistivity were tested as single layer thin film structure devices, i.e.: cathode/hole transport film/anode. 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
As can be seen from Table 1 above, the materials provided in examples 1-3 of the present invention are NiO/MoS 2 The resistivity of the hole transport film made of the core-shell nano material is obviously lower than that of the hole transport films in the comparative examples 1 and 2, and the hole mobility is obviously higher than that of the hole transport films prepared in the comparative examples 1 and 2.
Quantum dot light-emitting diodes (NiO/MoS as hole transport layer material) provided in embodiments 4 to 9 of the present invention 2 Core-shell nanomaterial) is obviously higher than that of the quantum dot light-emitting diodes in comparative examples 1 and 2, which shows that the quantum dot light-emitting diodes obtained in the examples have better luminous efficiency.
It is noted that the embodiments provided by the present invention all use blue light quantum dots Cd X Zn 1-X S/ZnS is used as a material of a luminescent layer, is based on that a blue light luminescent system uses more systems (the blue light quantum dot luminescent diode has more reference value because high efficiency is difficult to achieve), and does not represent that the invention is only used for the blue light luminescent system.
In summary, the invention provides a nano material, a preparation method thereof and a quantum dot light emitting diode. In the invention, the nano material has a core-shell structure, wherein NiO nano particles are used as a core material, and the ultrathin MoS grows on the surfaces of the NiO nano particles 2 Nanosheet as shell materialAnd (4) feeding. MoS as shell material 2 NiO nuclei with relatively high activity can be protected to a certain extent, and NiO surface defects are reduced, so that the capture of carriers by the surface defects is inhibited; at the same time, moS 2 The growth of the nano-sheet can enable the NiO nucleus to be better dispersed in the solvent, and the dispersibility is improved. Compared with MoS 2 NiO has better hole transmission performance and can ensure the fast transfer of holes. The nano material with the core-shell structure is used as a hole transport material, moS 2 The hole transmission efficiency is improved under the synergistic effect of the nano sheets and the NiO nano particles, so that the luminous efficiency of the quantum dot light-emitting diode is improved.
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 (10)
1. A quantum dot light-emitting diode comprises a hole transport layer and is characterized in that the hole transport layer is made of a nano material, the nano material has a core-shell structure, the core material of the nano material comprises NiO nano particles, and the shell material of the nano material comprises MoS 2 Nanosheets.
2. The quantum dot light-emitting diode of claim 1, wherein the core material of the nanomaterial is NiO nanoparticles and the shell material of the nanomaterial is MoS 2 Nanosheets.
3. The quantum dot light-emitting diode of claim 1, wherein the MoS is 2 The thickness of the nano-sheet is 3-5nm.
4. The quantum dot light-emitting diode of claim 1, wherein the NiO nanoparticles and the MoS 2 The molar ratio of the nano-sheets is 1: (0.2-0.5).
5. The quantum dot light-emitting diode of claim 1, wherein the preparation method of the nano material comprises the following steps:
providing a mixed solution containing nickel salt and alkali, and reacting to obtain NiO nano-particles;
mixing the NiO nano particles with thiomolybdate, and forming MoS on the surfaces of the NiO nano particles through a hydrothermal reaction 2 Nanosheets, resulting in a core material comprising NiO nanoparticles and a shell material comprising MoS 2 A nano material with a nano sheet and a core-shell structure.
6. The quantum dot light-emitting diode of claim 5, wherein the nickel salt comprises one or more of nickel acetate, nickel nitrate, nickel chloride, nickel sulfate, and nickel acetate tetrahydrate; and/or
The base comprises one or more of potassium hydroxide, sodium hydroxide, lithium hydroxide, ethanolamine, ethylene glycol, diethanolamine, triethanolamine and ethylenediamine.
7. The quantum dot light-emitting diode of claim 5, wherein the mixed solution comprising the nickel salt and the alkali has a molar ratio of the alkali to the nickel salt of (1.8-2.5): 1; and/or
The mixed solution of the nickel salt and the alkali has a pH =12-13.
8. The quantum dot light-emitting diode of claim 5, wherein the molar ratio of the Ni element to the Mo element is 1: (0.2-0.5), mixing the NiO nanoparticles with thiomolybdate.
9. The quantum dot light-emitting diode of claim 5, wherein the temperature of the hydrothermal reaction is 150 ℃ o C-200 o C; and/or
The time of the hydrothermal reaction is 20-24 h.
10. The qd-led of any one of claims 1-9, wherein the qd-led further comprises: the hole transport layer is arranged between the anode and the quantum dot light-emitting layer.
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