CN113054145B - Composite material, preparation method and application thereof, light-emitting diode and preparation method thereof - Google Patents

Composite material, preparation method and application thereof, light-emitting diode and preparation method thereof Download PDF

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CN113054145B
CN113054145B CN201911383743.0A CN201911383743A CN113054145B CN 113054145 B CN113054145 B CN 113054145B CN 201911383743 A CN201911383743 A CN 201911383743A CN 113054145 B CN113054145 B CN 113054145B
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composite material
cerium
niobium
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nitrogen
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CN113054145A (en
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何斯纳
吴龙佳
吴劲衡
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TCL Technology Group Co Ltd
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14—Carrier transporting layers
    • H10K50/16—Electron transporting layers
    • H10K50/165—Electron transporting layers comprising dopants
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
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    • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
    • H10K71/10—Deposition of organic active material
    • H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating
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Abstract

The invention belongs to the technical field of nano materials, and particularly relates to a composite material, a preparation method and application thereof, a light-emitting diode and a preparation method thereof. The composite material comprises cerium dioxide nano particles and nitrogen element and niobium element doped in the cerium dioxide nano particles. Co-doping of N-Nb to make CeO 2 The medium electron fermi level is moved to the conduction band, so that CeO 2 The forbidden band width of the quantum dot light-emitting diode is narrowed, electrons can enter a conduction band from the transition of an impurity energy level easily, and therefore the electron transmission capacity is improved.

Description

Composite material, preparation method and application thereof, light-emitting diode and preparation method thereof
Technical Field
The invention belongs to the technical field of nano materials, and particularly relates to a composite material, a preparation method and application thereof, a light-emitting diode and a preparation method thereof.
Background
The Quantum Dots (QDs) of the semiconductor have Quantum size effect, people can realize the Light emission with required specific wavelength by regulating the size of the Quantum dots, the tuning range of the Light emission wavelength of the CdSe QDs can be from blue Light to red Light, and the Quantum dots have good application prospect in Quantum Dot Light Emitting devices such as Quantum Dot Light Emitting Diodes (QLEDs). 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 wide bandgap semiconductors can be accelerated at high electric fields to gain sufficiently high energy and injected into QDs to cause them to emit light.
Cerium oxide (CeO) 2 ) Is a direct band gap wide band gap semiconductor material with a band gap width of 2.6eV, is a cheap light rare earth oxide, CeO 2 The size and the shape of the nano particles have great influence on the physical and chemical properties of the material, and the CeO has the advantages of energy level matching, good conductivity and high transmittance 2 The nano-particles have good application prospect, but the electron transmission performance of the nano-particles still needs to be improved.
Accordingly, there is a need for improvements and developments in the art.
Disclosure of Invention
The invention aims to provide a composite material, a preparation method and application thereof, and aims to solve the technical problem that the n-type doping effect of cerium dioxide is not ideal. In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a preparation method of a composite material, which comprises the following steps:
providing a nitrogen-containing precursor salt, a niobium salt and a cerium salt;
dissolving the nitrogen-containing precursor salt, the niobium salt and the cerium salt in an organic solvent, and heating under an alkaline condition to obtain a precursor solution;
carrying out solid-liquid separation on the precursor solution to obtain a composite material;
wherein the composite material comprises cerium dioxide nano-particles and nitrogen element and niobium element doped in the cerium dioxide nano-particles.
Dissolving a nitrogen-containing precursor salt, a niobium salt and a cerium salt in an organic solvent, heating under an alkaline condition, and then carrying out solid-liquid separation to obtain the composite material, wherein the composite material comprises cerium dioxide nano particles, and a nitrogen element and a niobium element which are doped in the cerium dioxide nano particles; the doped niobium element is Nb 5+ Form of solid solution of Nb 5+ Occupy Ce in the crystal lattice 4+ The position of (1) is that 4 of 5 valence electrons of Nb are combined with O to form saturated bonds, the 5 th electron is separated from impurity atoms to form 1 redundant valence electron, the energy level of the electron is positioned in an energy gap slightly lower than the bottom of a conduction band, so that enough energy can be easily obtained to jump to the conduction band to form free electrons, and the free electrons can be directionally moved under the action of an external electric field to conduct electricity, therefore, the Nb element is doped to increase the net electrons, so that CeO is formed 2 The resistance of the nanoparticles is reduced, increasing the conductivity; the doped N replaces O, and the CeO can be effectively reduced 2 Thereby making the donor level shallow and further reducing the ionization energy of the donor element. Therefore, by the acceptor (N) -donor (Nb), the donor ionization energy is remarkably reduced due to the strong coupling effect between energy levels, and interstitial acceptor defects are not easily formed during doping due to the strong affinity between N-Nb, and the doping of N-Nb can enable CeO 2 Medium electronic feeThe meter level is shifted to the conduction band so that CeO 2 The forbidden band width of the band is narrowed, electrons can jump from the impurity energy level to the conduction band easily, and therefore the electron transmission capability is improved; the composite material has good electron transport performance, so that the composite material can be used as an electron transport material for an electron transport layer of a quantum dot light-emitting diode, and the luminous efficiency of a device can be effectively improved.
In another aspect, the present invention provides a composite material including cerium oxide nanoparticles, and nitrogen and niobium doped in the cerium oxide nanoparticles.
The composite material provided by the invention comprises cerium dioxide nano particles, and nitrogen element and niobium element doped in the cerium dioxide nano particles; the doped niobium element is Nb 5+ Form of solid solution of Nb 5+ Occupy Ce in the crystal lattice 4+ The position of (1) is that 4 of 5 valence electrons of Nb are combined with O to form saturated bonds, the 5 th electron is separated from impurity atoms to form 1 redundant valence electron, the energy level of the electron is positioned in an energy gap slightly lower than the bottom of a conduction band, so that enough energy can be easily obtained to jump to the conduction band to form free electrons, and the free electrons can be directionally moved under the action of an external electric field to conduct electricity, therefore, the Nb element is doped to increase the net electrons, so that CeO is formed 2 The resistance of the nanoparticles is reduced, increasing the conductivity; the doped N replaces O, and the CeO can be effectively reduced 2 Thereby making the donor level shallow, and further reducing the ionization energy of the donor element. Therefore, by the acceptor (N) -donor (Nb), the donor ionization energy is remarkably reduced due to the strong coupling effect between energy levels, and interstitial acceptor defects are not easily formed during doping due to the strong affinity between N-Nb, and the doping of N-Nb can enable CeO 2 The medium electron fermi level is moved to the conduction band, so that CeO 2 The forbidden band width of the composite material is narrowed, electrons can jump from an impurity energy level to enter a conduction band easily, so that the electron transmission capacity is improved, and the composite material is used as an electron transmission material for a quantum dot light-emitting diode, so that the light-emitting efficiency of a device can be effectively improved.
The invention also provides the application of the composite material or the composite material obtained by the preparation method as an electron transport material. The composite material has good electron transport performance, so that the composite material can be used as an electron transport material for an electron transport layer of a quantum dot light-emitting diode, and the luminous efficiency of a device can be effectively improved.
Another object of the present invention is to provide a light emitting diode and a method for manufacturing the same, which aims to solve the technical problem that the electron transport performance of the light emitting diode is not ideal. In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a light-emitting diode which comprises an anode, a cathode and a quantum dot light-emitting layer positioned between the anode and the cathode, wherein an electron transmission layer is arranged between the cathode and the quantum dot light-emitting layer, and the electron transmission layer is composed of a composite material obtained by the preparation method or the composite material.
Correspondingly, the preparation method of the light-emitting diode comprises the following steps:
providing a substrate;
and depositing the composite material or the composite material obtained by the preparation method on the substrate to obtain the electron transport layer.
In the light-emitting diode and the light-emitting diode prepared by the preparation method provided by the invention, the electron transport layer is composed of the special composite material or the special composite material prepared by the preparation method provided by the invention, and the composite material has good electron transport performance, can promote the effective recombination of electrons and holes in the quantum dot light-emitting layer, and reduces the influence of exciton accumulation on the device performance, thereby improving the light-emitting efficiency and the display performance of the device.
Drawings
FIG. 1 is a schematic flow chart of a method for preparing a composite material provided by the present invention;
FIG. 2 is a schematic structural diagram of a quantum dot light-emitting diode provided in the present invention;
FIG. 3 is a schematic flow chart of a method for manufacturing a quantum dot light-emitting diode according to the present invention;
FIG. 4 is a schematic structural diagram of an LED with positive quantum dots according to the present invention;
fig. 5 is a schematic structural diagram of an inverted quantum dot light emitting diode provided by the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In one aspect, an embodiment of the present invention provides a method for preparing a composite material, as shown in fig. 1, the method includes the following steps:
s01: providing a nitrogen-containing precursor salt, a niobium salt and a cerium salt;
s02: dissolving the nitrogen-containing precursor salt, the niobium salt and the cerium salt in an organic solvent, and heating under an alkaline condition to obtain a precursor solution;
s03: carrying out solid-liquid separation on the precursor solution to obtain a composite material;
wherein the composite material comprises cerium dioxide nano-particles and nitrogen element and niobium element doped in the cerium dioxide nano-particles.
The preparation method of the composite material is a preparation method of N-Nb codoped cerium dioxide nano-particles, nitrogen-containing precursor salt, niobium salt and cerium salt are dissolved in an organic solvent, heating treatment is carried out under an alkaline condition, and then solid-liquid separation is carried out to obtain the composite material, wherein the composite material comprises cerium dioxide nano-particles, and nitrogen element and niobium element doped in the cerium dioxide nano-particles; the doped niobium element is Nb 5+ Form of solid solution of Nb 5+ Occupy Ce in the crystal lattice 4+ The position (2) of (1) is that 4 of the 5 valence electrons of Nb are combined with O to form a saturated bond, the 5 th electron is separated from the impurity atom to form 1 excess valence electron, and the energy level of the electron is slightly lower than the bottom of the conduction band in the energy gap, so that enough valence electrons can be easily obtained (at normal temperature)The energy of the CeO is transferred to a conductive tape to become free electrons, and the free electrons directionally move under the action of an external electric field to conduct electricity, so that the net electrons are increased by doping Nb elements, and the CeO is enabled 2 The resistance of the nanoparticles is reduced, increasing the conductivity; the doped N replaces O, and the CeO can be effectively reduced 2 Thereby making the donor level shallow and further reducing the ionization energy of the donor element. Therefore, by the acceptor (N) -donor (Nb), the donor ionization energy is remarkably reduced due to the strong coupling effect between energy levels, and interstitial acceptor defects are not easily formed during doping due to the strong affinity between N-Nb, and the doping of N-Nb can enable CeO 2 The medium electron fermi level is moved to the conduction band, so that CeO 2 The forbidden band width of the composite material is narrowed, electrons can jump from an impurity energy level to enter a conduction band easily, so that the electron transmission capacity is improved, and the composite material is used as an electron transmission material for a quantum dot light-emitting diode, so that the light-emitting efficiency of a device can be effectively improved.
Cerium oxide easily loses cerium element in the preparation process to form Ce vacancy, so that the cerium oxide forms a natural n-type semiconductor and has certain electron transport capacity, but the electron transport performance of the cerium oxide is not ideal, and the cerium oxide cannot be well applied to QLED devices. The preparation method of the composite material provided by the embodiment of the invention is a sol-gel method, and CeO is prepared by a method of codoping an acceptor (N) -donor (Nb) 2 The energy level of the middle donor becomes shallow, and the CeO is effectively reduced 2 Thereby preparing n-type doped CeO with better electron transport performance 2 。
In step S01, the nitrogen element-containing precursor salt is a soluble nitrogen source material, specifically at least one selected from urea, ammonium sulfate, ammonium nitrate and ammonium chloride; the niobium salt is soluble niobium salt, and is specifically selected from at least one of niobium nitrate, niobium chloride and niobium bromide; the cerium salt is soluble inorganic cerium salt or organic cerium salt, and is selected from at least one of cerium acetate, cerium nitrate, cerium chloride and cerium sulfate.
In the step S02, in the step of dissolving the nitrogen-containing precursor salt, the niobium salt, and the cerium salt in the organic solvent, the ratio of the total molar amount of the nitrogen element in the nitrogen-containing precursor salt and the niobium element in the niobium salt to the molar amount of the cerium element in the cerium salt is (0.05 to 0.1): 1. wherein the organic solvent is at least one of methanol, ethanol, propanol and butanol.
Cerium ion and dopant ion (N) 3- +Nb 5+ ) The mole ratio of (A) has a larger influence on the performance of the subsequently prepared composite material; when the total doping amount of N and Nb is too much, N and Nb are in CeO 2 When the solid solubility reaches saturation and the doping amount continues to increase, N and Nb are concentrated in CeO 2 The surface of the crystal grains forms a new phase, so that the nano CeO is reduced 2 Effective specific surface area of, and N 3- And Nb 5+ Into CeO 2 The crystal lattice inside of (2) causes expansion of the crystal lattice, and generates large crystal lattice distortion and strain energy, that is, an increase in doping amount causes mutation of the crystal lattice, formation of a new crystal lattice and impurity generation. If the total doping amount of N and Nb is too low, CeO is used 2 The n-type doping modification effect is lower. Therefore, the ratio of the total doping amount of N and Nb to the cerium element is (0.05-0.1): the doping effect in the range of 1 is the best. Wherein Nb is added to the adjusted CeO 2 The doping amount of the band gap is more than that of N, specifically, N: the molar ratio of Nb is controlled to be 1: 2 to 3.
Further, in the step of performing the heat treatment under an alkaline condition, the alkaline condition is pH 12 to 13. Specifically, the alkali solution can be added, and the alkali solution is a solution of organic alkali and/or inorganic alkali such as ammonia water, potassium hydroxide, sodium hydroxide, lithium hydroxide, ethanolamine, ethylene glycol, diethanolamine, triethanolamine, ethylenediamine, etc. According to the ratio of the molar weight of hydroxide ions of the alkali liquor to the sum of the molar weight of cerium ions and doping ions of (3.8-4.5): 1, adding alkali liquor to form a solution with the pH value of 12-13. When the ratio of base to the sum of the molar amounts of cerium ions and dopant ions is less than 3.8: 1, excessive metal salt, and the added N + Nb cannot be completely doped; greater than 4.5: 1, too high a pH results in a slower polycondensation rate in the system. Optimally, the ratio of the molar amount of base to the sum of the molar amounts of cerium ions and doping ions is maintained at (3.8-4.5): when the pH value of the solution is 12-13 at 1, the N-Nb codoped CeO with uniform dispersion can be obtained 2 A nanoparticle material.
Further, the method comprises the following steps of; the temperature for heating treatment under alkaline condition is 60-80 deg.C, and the time is 2-4 h. Under the condition, N-Nb codoped CeO can be well formed 2 A nanoparticle material. The temperature of the heating treatment is generally lower than the boiling point temperature of the alkali liquor and the organic solvent, and the specific temperature is set according to the boiling point of the selected alkali liquor.
In the step S03, the step of solid-liquid separation includes a sedimentation treatment or an annealing treatment. For the sedimentation treatment, the solution after the heating reaction is firstly cooled to room temperature (the room temperature of the embodiment of the invention is 20-35 ℃), then the sedimentation treatment is carried out to separate out the sediment in the solution, and the sediment is collected, washed and dried to obtain the composite material. The sedimentation treatment is achieved by adding a precipitant. For the annealing treatment, the solution after the heating treatment can be directly subjected to the annealing treatment at the temperature of 150-250 ℃ to obtain the powder composite material. In a specific embodiment, in order to obtain the composite material film, the solution subjected to the heating treatment under the alkaline condition is deposited on a substrate and subjected to an annealing treatment, so that the composite material film is obtained; specifically, the temperature of the annealing treatment is 150-250 ℃; the time of the annealing treatment is 10-20 min. The annealing condition can better remove the solvent and form a compact and dense composite material film with uniformly distributed particles.
In another aspect, embodiments of the present invention also provide a composite material, where the composite material includes ceria nanoparticles, and nitrogen and niobium doped in the ceria nanoparticles.
The composite material provided by the embodiment of the invention comprises cerium dioxide nano particles and nitrogen and niobium which are doped in the cerium dioxide nano particles; the doped niobium element is Nb 5+ Form of solid solution of Nb 5+ Occupy Ce in the crystal lattice 4+ 4 of 5 valence electrons of Nb are combined with O to form a saturated bond, the 5 th electron is separated from the impurity atom to form 1 excess valence electron, the energy level of the electron is slightly lower than the bottom of the conduction band in the energy gap, so that enough energy is easily obtained to jump to the conduction band to form a free electron, and the free electron is outside the conduction bandThe electric field is applied to make directional movement and electric conduction, so that the Nb element is doped to increase net electrons, so that CeO 2 The resistance of the nanoparticles is reduced, increasing the conductivity; the doped N replaces O, and the CeO can be effectively reduced 2 Thereby making the donor level shallow and further reducing the ionization energy of the donor element. Therefore, by the acceptor (N) -donor (Nb), the donor ionization energy is remarkably reduced due to the strong coupling effect between energy levels, and interstitial acceptor defects are not easily formed during doping due to the strong affinity between N-Nb, and the doping of N-Nb can enable CeO 2 The medium electron fermi level is moved to the conduction band so that CeO 2 The forbidden band width of the composite material is narrowed, electrons can jump from an impurity energy level to enter a conduction band easily, so that the electron transmission capacity is improved, and the composite material is used as an electron transmission material for a quantum dot light-emitting diode, so that the light-emitting efficiency of a device can be effectively improved.
In one embodiment, the ratio of the total molar amount of the nitrogen element and the niobium element to the molar amount of the cerium element in the composite material is (0.05-0.1): 1. wherein the molar ratio of the nitrogen element to the niobium element is 1: (2-3). If the total doping amount of N and Nb is too much, N and Nb are in CeO 2 The solid solubility of the intermediate alloy reaches saturation, and when the doping amount continues to increase, N and Nb are concentrated on CeO 2 The surface of the crystal grains forms a new phase, so that the nano CeO is reduced 2 Effective specific surface area of, and N 3- And Nb 5+ Into CeO 2 The crystal lattice inside of (2) causes expansion of the crystal lattice, and generates large crystal lattice distortion and strain energy, that is, an increase in doping amount causes mutation of the crystal lattice, formation of a new crystal lattice and impurity generation. If the total doping amount of N and Nb is too low, CeO is used 2 The n-type doping modification effect is lower. Therefore, the ratio of the total doping amount of N and Nb to the cerium element is (0.05-0.1): the doping effect in the range of 1 is the best. Wherein Nb is added to the adjusted CeO 2 The doping amount of the band gap is more than that of N, specifically, N: the molar ratio of Nb is controlled to be 1: 2 to 3.
The composite material disclosed by the embodiment of the invention has good electronic transmission performance, and can be used as an electronic transmission material. Therefore, the embodiment of the invention also provides an application of the composite material or the composite material obtained by the preparation method as an electron transport material. Particularly, the composite material can be used as an electron transport material for an electron transport layer of a quantum dot light-emitting diode, and the luminous efficiency of a device can be effectively improved.
Finally, an embodiment of the present invention provides a light emitting diode, which is a quantum dot light emitting diode, and as shown in fig. 2, the light emitting diode includes an anode 2, a cathode 6, and a quantum dot light emitting layer 4 located between the anode 2 and the cathode 6, an electron transport layer 5 is disposed between the cathode 6 and the quantum dot light emitting layer 4, and the electron transport layer 5 is made of a composite material obtained by the preparation method according to the embodiment of the present invention or the composite material according to the embodiment of the present invention.
The electron transport layer in the quantum dot light-emitting diode provided by the embodiment of the invention is composed of the special composite material in the embodiment of the invention or the special composite material prepared by the preparation method in the embodiment of the invention, and the composite material has good electron transport performance, can promote the effective recombination of electron-hole in the quantum dot light-emitting layer, and reduces the influence of exciton accumulation on the device performance, thereby improving the light-emitting efficiency and the display performance of the device.
In one embodiment, an electron injection layer is further disposed between the electron transport layer and the cathode. In another embodiment, a hole function layer, such as a hole transport layer, or a stacked hole injection layer and hole transport layer, is disposed between the quantum dot light emitting layer and the anode, wherein the hole injection layer is adjacent to the anode.
The quantum dot light-emitting diode provided by the embodiment of the invention comprises an upright structure and an inverted structure.
In one embodiment, the front-mounted 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, and an electron transport layer arranged between the cathode and the quantum dot light emitting layer, wherein the anode is arranged on a substrate. Furthermore, an electron injection layer can be arranged between the cathode and the electron transport layer, and an electron functional layer such as a hole blocking layer can be arranged between the cathode and the quantum dot light-emitting layer; and a hole functional layer such as a hole transport layer, a hole injection layer and an electron blocking layer can be arranged between the anode and the quantum dot light-emitting layer. In some embodiments of the front structure device, the quantum dot light emitting diode includes a substrate, an anode disposed on the surface of the substrate, the hole injection layer disposed on the surface of the anode, a hole transport layer disposed on the surface of the hole injection layer, a quantum dot light emitting layer disposed on the surface of the hole transport layer, an electron transport layer disposed on the surface of the quantum dot light emitting layer, and a cathode disposed on the surface of the electron transport layer.
In one embodiment, an inverted structure quantum dot light emitting diode includes a stacked structure of an anode and a cathode disposed opposite each other, a quantum dot light emitting layer disposed between the anode and the cathode, an electron transport layer disposed between the cathode and the quantum dot light emitting layer, and the cathode is disposed on a substrate. Furthermore, an electron injection layer can be arranged between the cathode and the electron transport layer, and an electron functional layer such as a hole blocking layer can be arranged between the cathode and the quantum dot light-emitting layer; and a hole functional layer such as a hole transport layer, a hole injection layer and an electron blocking layer can be arranged between the anode and the quantum dot light-emitting layer. In some embodiments of the device with the inverted structure, the quantum dot light emitting diode includes a substrate, a cathode disposed on the surface of the substrate, an electron transport layer disposed on the surface of the cathode, a quantum dot light emitting layer disposed on the surface of the electron transport layer, a hole transport layer disposed on the surface of the quantum dot light emitting layer, a hole injection layer disposed on the surface of the hole transport layer, and an anode disposed on the surface of the hole injection layer.
Accordingly, as shown in fig. 3, a method for manufacturing a quantum dot light emitting diode includes the following steps:
e01: providing a substrate;
e02: the composite material or the composite material obtained by the preparation method provided by the embodiment of the invention is deposited on the substrate to obtain the electron transport layer.
According to the preparation method of the quantum dot light-emitting diode, the specific composite material provided by the embodiment of the invention is prepared into the electron transmission layer of the device, and the composite material has good electron transmission performance, so that the composite material can be used as the electron transmission layer to promote the effective recombination of electrons and holes in the quantum dot light-emitting layer, the influence of exciton accumulation on the performance of the device is reduced, and the light-emitting efficiency and the display performance of the device are improved.
Specifically, the preparation of the electron transport layer comprises: the substrate is placed on a spin coater, the prepared composite material solution with a certain concentration is subjected to spin coating to form a film, the thickness of the electron transport layer is controlled by adjusting the concentration of the solution, the spin coating speed and the spin coating time, and then the film is formed by annealing at the temperature of 150-250 ℃.
In one embodiment, a quantum dot light emitting diode is prepared, comprising the following steps:
a: obtaining a cathode substrate;
b: depositing an electron transport layer on the cathode substrate;
depositing quantum dot luminescent layer on the electron transport layer;
d: the evaporation anode is arranged on the quantum dot luminescent layer to obtain the quantum dot light-emitting diode,
the material of the electron transport layer is the composite material provided by the embodiment of the invention.
In one embodiment, a method for manufacturing a quantum dot light emitting diode comprises the following steps:
a: obtaining an anode substrate;
b: depositing a quantum dot light emitting layer on an anode substrate;
c: depositing an electron transport layer on the quantum dot light emitting layer;
d: evaporating cathode on the electron transmission layer to obtain quantum dot light-emitting diode,
the material of the electron transport layer is the composite material provided by the embodiment of the invention.
In one embodiment, a method for manufacturing a QLED device includes the steps of:
a: obtaining an ITO substrate;
b: growing a hole transport layer on the ITO substrate;
c: depositing a quantum dot light-emitting layer on the hole transport layer;
d: depositing an electron transport layer on the quantum dot light emitting layer;
e: and evaporating a cathode on the electron transmission layer to obtain the quantum dot light-emitting diode.
The material of the electron transport layer is the composite material provided by the embodiment of the invention.
In order to obtain a high-quality electron transport layer, the ITO substrate needs to be subjected to a pretreatment process. The specific processing steps of the substrate include: cleaning the whole piece of ITO conductive glass with a cleaning agent, preliminarily removing stains on the surface, then sequentially carrying out ultrasonic cleaning in deionized water, acetone, absolute ethyl alcohol and deionized water for 20min respectively to remove impurities on the surface, and finally blowing dry with high-purity nitrogen to obtain the ITO positive electrode substrate.
The hole transport layer may be made of a hole transport material conventional in the art, including but not limited to TFB, PVK, Poly-TPD, TCTA, PEDOT: PSS, CBP, NiO, MoO 3 、WoO 3 Or a mixture of any combination thereof, and can also be other high-performance hole transport materials. The preparation of the hole transport layer comprises: placing the ITO substrate on a spin coater, and spin-coating 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 a thermal annealing process is performed at an appropriate temperature.
The quantum dots in the quantum dot light-emitting layer are oil-soluble quantum dots and comprise binary phase, ternary phase and quaternary phase quantum dots; wherein the binary phase quantum dots include CdS, CdSe, CdTe, InP, AgS, PbS, PbSe, HgS, etc., but are not limited thereto, and the ternary phase quantum dots include Zn X Cd 1-X S、Cu X In 1-X S、Zn X Cd 1-X Se、Zn X Se 1-X S、Zn X Cd 1-X Te、PbSe X S 1-X Etc. are not limited thereto, and the quaternary phase quantum dots include, Zn X Cd 1-X S/ZnSe、Cu X In 1-X S/ZnS、Zn X Cd 1-X Se/ZnS、CuInSeS、Zn X Cd 1-X Te/ZnS、PbSe X S 1-X the/ZnS and the like are not limited thereto. Then the quantum dots can be any one of the common red, green and blue quantum dots or other yellow light, and the quantum dots can be cadmium-containing or cadmium-free. The quantum dot light-emitting layer of the material has the characteristics of wide excitation spectrum, continuous distribution, high stability of emission spectrum and the like. Preparing a quantum dot light-emitting layer: spin-coating the prepared luminescent material solution with a certain concentration on a spin coater of a substrate with a spin-coated hole transport layer to form a film, controlling the thickness of the luminescent layer to be about 20-60nm by adjusting the concentration of the solution, the spin-coating speed and the spin-coating time, and drying at a proper temperature.
The electron transport layer is a composite material (composed of cerium dioxide nanoparticles and nitrogen and niobium doped in the cerium dioxide nanoparticles) film of the embodiment of the invention: the substrate which is coated with the quantum dot light emitting layer by spin coating is placed on a spin coater, the prepared composite material solution with a certain concentration is coated by spin coating to form a film, the thickness of the electron transmission layer is controlled by adjusting the concentration of the solution, the spin coating speed (preferably, the rotation speed is between 2000 and 6000 rpm) and the spin coating time, the thickness is about 20-60nm, and then the film is formed by annealing at the temperature of 150 and 250 ℃. The step can be annealing in air or in nitrogen atmosphere, and the annealing atmosphere is selected according to actual needs.
And then, the substrate deposited with the functional layers is placed in an evaporation bin, and a layer of 15-30nm metal silver or aluminum is thermally evaporated through a mask plate to serve as a cathode, or a nano Ag wire or a Cu wire is used, so that a carrier can be smoothly injected due to the small resistance.
Further, the obtained QLED is subjected to a packaging process, and the packaging process may be performed by a common machine or by a manual method. 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.
The invention is described in further detail with reference to a part of the test results, which are described in detail below with reference to specific examples.
Example 1
The preparation of composite material film is described in detail by using cerium sulfate, niobium bromide, urea, ethanol and potassium hydroxide as raw materials.
1) First, an appropriate amount of cerium sulfate, niobium bromide and urea was added to 50ml of ethanol, and dissolved by stirring at 70 ℃ to form a salt solution having a total concentration of 0.5M (wherein, cerium: the molar ratio of nitrogen to niobium is 1: 0.05; nitrogen: the molar ratio of niobium is 1: 3) (ii) a Weighing potassium hydroxide, dissolving potassium hydroxide in 10ml ethanol to obtain alkaline solution, and adding OH according to molar ratio - ：M x+ 4: 1(M is cerium ion and doped ion), adding alkaline solution into the above salt solution to make the solution pH 12, and stirring at 70 deg.C for 4 hr to obtain a uniform solution (formed with N-Nb codoped CeO) 2 Nano-materials).
2) And after the solution is cooled, spin-coating the treated ITO by using a spin coater and annealing at 250 ℃ to obtain the composite material film.
Example 2
The preparation of composite material film is described in detail by using cerous nitrate, ammonium nitrate, niobium nitrate, methanol and ethanolamine as raw material.
1) Firstly, adding proper amounts of cerium nitrate, niobium nitrate and ammonium nitrate into 50ml of methanol, and stirring and dissolving at 60 ℃ to form a salt solution with the total concentration of 0.8M (wherein, cerium: the molar ratio of nitrogen to niobium is 1: 0.08; nitrogen: the molar ratio of niobium is 1: 2.5). Weighing ethanolamine, dissolving the ethanolamine in 10ml of methanol to obtain alkali liquor, wherein the molar ratio of the ethanolamine to the alkali liquor is as follows: m x+ 4.5: 1(M is cerium ion and dopant ion), adding alkaline solution into the above salt solution to make the solution pH 13, and stirring at 60 deg.C for 4 hr to obtain a uniform solution (formed with N-Nb codoped CeO 2 A nanomaterial).
2) And after the solution is cooled, spin-coating the treated ITO by using a spin coater and annealing at 200 ℃ to obtain the composite material film.
Example 3
The preparation of the composite material film is described in detail by using cerium chloride, niobium chloride, ammonium chloride, propanol and sodium hydroxide as raw materials.
1) Firstly, adding proper amounts of cerium chloride, niobium chloride and ammonium chloride into 50ml of propanol, and stirring and dissolving at 80 ℃ to form a salt solution with the total concentration of 1M (wherein, cerium: the molar ratio of nitrogen to niobium is 1: 0.1; nitrogen: the molar ratio of niobium is 1: 2). Weighing sodium hydroxide, dissolving sodium hydroxide in 10ml propanol to obtain alkaline solution, and adding OH to the alkaline solution according to molar ratio - ：M x+ 3.5: 1(M is cerium ion and doped ion), adding alkaline solution into the above salt solution to make the solution pH 12, and stirring at 80 deg.C for 4 hr to obtain a uniform solution (formed with N-Nb codoped CeO) 2 Nano-materials).
2) And after the solution is cooled, spin-coating the treated ITO by using a spin coater and annealing at 150 ℃ to obtain the composite material film.
Example 4
A QLED device, the preparation method comprises the following steps:
a: firstly, growing a hole transport layer on a substrate;
b: then depositing a quantum dot light-emitting layer on the hole transport layer;
c: then depositing an electron transport layer over the quantum dot light emitting layer, the electron transport layer prepared as described in example 1;
d: and finally, evaporating a cathode on the electron transmission layer to obtain the quantum dot light-emitting diode.
The QLED device of the present embodiment is in a positive configuration, wherein fig. 4 is a schematic structural diagram of the QLED device, and the QLED device sequentially includes, from bottom to top, 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. The substrate 1 is made of a glass sheet, the anode 2 is made of an ITO substrate, the hole transport layer 3 is made of TFB, the electron transport layer 5 is made of the composite material prepared in example 1, and the cathode 6 is made of Al.
Example 5
A QLED device and a preparation method thereof comprise the following steps:
a: firstly, growing a hole transport layer on a substrate;
b: then depositing a quantum dot light-emitting layer on the hole transport layer;
c: then depositing an electron transport layer over the quantum dot light emitting layer, the electron transport layer prepared as described in example 2;
d: and finally, evaporating a cathode on the electron transmission layer to obtain the quantum dot light-emitting diode.
The QLED device of the present embodiment is in a positive configuration, wherein fig. 4 is a schematic structural diagram of the QLED device, and the QLED device sequentially includes, from bottom to top, 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. The substrate 1 is made of a glass sheet, the anode 2 is made of an ITO substrate, the hole transport layer 3 is made of TFB, the electron transport layer 5 is made of the composite material prepared in example 2, and the cathode 6 is made of Al.
Example 6
A QLED device, the preparation method comprises the following steps:
a: firstly, growing a hole transport layer on a substrate;
b: then depositing a quantum dot light-emitting layer on the hole transport layer;
c: then depositing an electron transport layer on the quantum dot light emitting layer, the electron transport layer being prepared as described in example 3;
d: and finally, evaporating a cathode on the electron transmission layer to obtain the quantum dot light-emitting diode.
The QLED device of the present embodiment is in a positive configuration, wherein fig. 4 is a schematic structural diagram of the QLED device, and the QLED device sequentially includes, from bottom to top, 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. The substrate 1 is made of a glass sheet, the anode 2 is made of an ITO substrate, the hole transport layer 3 is made of TFB, the electron transport layer 5 is made of the composite material prepared in example 3, and the cathode 6 is made of Al.
Example 7
A QLED device, the preparation method comprises the following steps:
a: firstly, growing an electron transport layer on a substrate, wherein the electron transport layer is prepared according to the method of embodiment 1;
b: depositing a quantum dot light-emitting layer on the electron transport layer;
c: depositing a hole transport layer on the quantum dot light emitting layer;
d: and finally, evaporating an anode on the hole transport layer to obtain the quantum dot light-emitting diode.
The QLED device of the present embodiment is in an inverted configuration, wherein fig. 5 is a schematic structural diagram of the QLED device, and the QLED device sequentially includes, from bottom to top, a substrate 1, a cathode 6, an electron transport layer 5, a quantum dot light-emitting layer 4, a hole transport layer 3, and an anode 2. The substrate 1 is made of a glass sheet, the cathode 6 is made of an ITO substrate, the hole transport layer 3 is made of TFB, the electron transport layer 5 is made of the composite material prepared in example 1, and the anode 2 is made of Al.
Example 8
A QLED device, the preparation method comprises the following steps:
a: firstly, growing an electron transport layer on a substrate, wherein the electron transport layer is prepared according to the method of the embodiment 2;
b: then depositing a quantum dot light-emitting layer on the electron transport layer;
c: depositing a hole transport layer on the quantum dot light emitting layer;
d: and finally, evaporating an anode on the hole transport layer to obtain the quantum dot light-emitting diode.
The QLED device of the present embodiment is in an inverted configuration, wherein fig. 5 is a schematic structural diagram of the QLED device, and the QLED device sequentially includes, from bottom to top, a substrate 1, a cathode 6, an electron transport layer 5, a quantum dot light-emitting layer 4, a hole transport layer 3, and an anode 2. The substrate 1 is made of a glass sheet, the cathode 6 is made of an ITO substrate, the hole transport layer 3 is made of TFB, the electron transport layer 5 is made of the composite material prepared in example 2, and the anode 2 is made of Al.
Example 9
A QLED device, the preparation method comprises the following steps:
a: firstly, growing an electron transport layer on a substrate, wherein the electron transport layer is prepared according to the method of embodiment 3;
b: depositing a quantum dot light-emitting layer on the electron transport layer;
c: depositing a hole transport layer on the quantum dot light emitting layer;
d: and finally, evaporating an anode on the hole transport layer to obtain the quantum dot light-emitting diode.
The QLED device of the present embodiment is in an inverted configuration, wherein fig. 5 is a schematic structural diagram of the QLED device, and the QLED device sequentially includes, from bottom to top, a substrate 1, a cathode 6, an electron transport layer 5, a quantum dot light-emitting layer 4, a hole transport layer 3, and an anode 2. The substrate 1 is made of a glass sheet, the cathode 6 is made of an ITO substrate, the hole transport layer 3 is made of TFB, the electron transport layer 5 is made of the composite material prepared in example 3, and the anode 2 is made of Al.
Comparative example 1
A quantum dot light-emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the cathode is arranged on a substrate. Wherein the substrate is made of glass sheet, the anode is made of ITO substrate, the hole transport layer is made of TFB, and the electron transport layer is made of commercial CeO 2 The material (available from sigma) and the cathode material was Al.
And (3) performance testing:
the composite material films prepared in examples 1 to 3, the electron transport layer film in comparative example 1, the quantum dot light emitting diodes prepared in examples 4 to 9 and comparative examples 1 to 3 were subjected to performance tests, and the test indexes and the test methods were as follows:
(1) electron mobility: testing the current density (J) -voltage (V) of the quantum dot light-emitting diode, drawing a curve relation diagram, fitting a Space Charge Limited Current (SCLC) region in the relation diagram, and then calculating the electron 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 the electron 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: the resistivity of the electron transport film is measured by the same resistivity measuring instrument.
(3) External Quantum Efficiency (EQE): measured using an EQE optical test instrument.
Note: the electron mobility and resistivity were tested as single layer thin film structure devices, namely: cathode/electron transport film/anode. The external quantum efficiency test is the QLED device, namely: anode/hole transport layer film/quantum dot light emitting layer/electron transport layer film/cathode, or cathode/electron transport layer film/quantum dot light emitting layer/hole transport layer film/anode.
The test results are shown in table 1 below:
TABLE 1
Figure BDA0002342939470000171
As can be seen from table 1 above, the composite films provided in examples 1 to 3 of the present invention have a resistivity significantly lower than that of the electron transport layer film in comparative example 1, and an electron mobility significantly higher than that of the electron transport layer film in comparative example 1.
The quantum dot light-emitting diodes provided in embodiments 4 to 9 of the present invention (the electron transport layer material is N-Nb co-doped CeO) 2 Nano material) has an external quantum efficiency significantly higher than that of the electron transport layer material of CeO in comparative example 1 2 The external quantum efficiency of the quantum dot light-emitting diode made of the material shows that the quantum dot light-emitting diode obtained by the embodiment has 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 as the material of the luminescent layer isThe blue light emitting system is a system which is used more (because the high efficiency of the light emitting diode of the blue light quantum dot is difficult to achieve, the blue light emitting system has more reference value), and does not represent that the invention is only used for the blue light emitting system.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (8)

1. The preparation method of the composite material is characterized by comprising the following steps:
providing a nitrogen-containing precursor salt, a niobium salt and a cerium salt;
dissolving the nitrogen-containing precursor salt, the niobium salt and the cerium salt in an organic solvent, and heating under an alkaline condition to obtain a precursor solution;
carrying out solid-liquid separation on the precursor solution to obtain a composite material;
wherein the composite material comprises cerium dioxide nano-particles and nitrogen element and niobium element doped in the cerium dioxide nano-particles.
2. The method according to claim 1, wherein in the step of dissolving the nitrogen-containing precursor salt, the niobium salt, and the cerium salt in the organic solvent, the molar ratio of the nitrogen element in the nitrogen-containing precursor salt to the niobium element in the niobium salt is 1: (2-3); and/or the presence of a gas in the gas,
the ratio of the total molar amount of nitrogen in the nitrogen-containing precursor salt and niobium in the niobium salt to the molar amount of cerium in the cerium salt is (0.05-0.1): 1.
3. the method for producing a composite material according to claim 1, wherein the step of performing the heat treatment under an alkaline condition is a step of performing the heat treatment under an alkaline condition of pH 12 to 13; and/or the presence of a gas in the atmosphere,
in the step of performing heat treatment under an alkaline condition, the temperature of the heat treatment is 60-80 ℃; and/or the presence of a gas in the gas,
in the step of carrying out heating treatment under an alkaline condition, the heating treatment time is 2-4 h; and/or the presence of a gas in the gas,
the step of solid-liquid separation comprises annealing treatment at the temperature of 150-250 ℃.
4. A method for preparing a composite material according to any one of claims 1 to 3, wherein the nitrogen-containing precursor salt is selected from at least one of urea, ammonium sulfate, ammonium nitrate and ammonium chloride; and/or the presence of a gas in the gas,
the niobium salt is at least one selected from niobium nitrate, niobium chloride and niobium bromide; and/or the presence of a gas in the gas,
the cerium salt is at least one selected from cerium acetate, cerium nitrate, cerium chloride and cerium sulfate; and/or the presence of a gas in the gas,
the organic solvent is at least one of methanol, ethanol, propanol and butanol.
5. A composite material, which is characterized by comprising cerium dioxide nanoparticles and nitrogen and niobium doped in the cerium dioxide nanoparticles, wherein the molar ratio of the nitrogen to the niobium is 1: (2-3), a ratio of a total molar amount of the nitrogen element and the niobium element to a molar amount of the cerium element in the cerium oxide nanoparticles is (0.05-0.1): 1.
6. use of a composite material obtained by the production method according to any one of claims 1 to 4 or the composite material according to claim 5 as an electron transport material.
7. A light-emitting diode comprising an anode, a cathode and a quantum dot light-emitting layer arranged between the anode and the cathode, wherein an electron transport layer is arranged between the cathode and the quantum dot light-emitting layer, and the electron transport layer is composed of the composite material obtained by the preparation method of any one of claims 1 to 4 or the composite material of claim 5.
8. A method for manufacturing a light emitting diode, comprising:
providing a substrate;
depositing a composite material obtained by the production method according to any one of claims 1 to 4 or the composite material according to claim 5 on the substrate to obtain an electron transport layer.
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