CN111525048B - Composite material, preparation method thereof and light-emitting diode - Google Patents

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

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CN111525048B
CN111525048B CN202010370132.9A CN202010370132A CN111525048B CN 111525048 B CN111525048 B CN 111525048B CN 202010370132 A CN202010370132 A CN 202010370132A CN 111525048 B CN111525048 B CN 111525048B
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CN111525048A (en
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玉福星
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Guangdong Juhua Printing Display Technology 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
    • H10K50/15—Hole transporting layers
    • H10K50/155—Hole transporting layers comprising dopants
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    • 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
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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
    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • 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
    • H10K71/15—Deposition of organic active material using liquid deposition, e.g. spin coating characterised by the solvent used
    • H—ELECTRICITY
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    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/10—Organic polymers or oligomers
    • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
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    • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
    • H10K85/114—Poly-phenylenevinylene; Derivatives thereof
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Abstract

The invention discloses a composite material and a preparation method thereof, and a light-emitting diode, wherein the preparation method of the composite material comprises the following steps: providing a perovskite solution, providing a conductive polymer solution, and mixing the perovskite solution and the conductive polymer solution to obtain a mixed solution; and curing and molding the mixed solution to obtain the composite material. It can be understood that when the composite material prepared by the method is used as a carrier transport layer, the technical scheme of the invention can reduce surface pinholes of the carrier transport layer, avoid the generation of leakage current and improve the luminous efficiency of a light-emitting device.

Description

Composite material, preparation method thereof and light-emitting diode
Technical Field
The invention relates to the technical field of photoelectric functional materials, in particular to a composite material, a preparation method thereof and a light-emitting diode.
Background
The perovskite has the advantages of rich raw materials, low cost, high carrier mobility, capability of forming a film by a solution method at normal temperature and the like, and is widely applied to the manufacture of light emitting diodes (OLEDs) as a carrier transmission layer. In 2016, yu Tian et al prepared MAPbCl by spin coating 3 And the film is used as a hole transport layer of the OLED. In 2019, toshinori Matsushima et al prepared MAPbCl with different thicknesses by vacuum evaporation method 3 The film is used as a current carrier transmission layer of an OLED, and the hole mobility of the current carrier transmission layer with the thickness of 1000-3000nm is 0.9-1.3cm 2 V -1 s -1 Electron mobility of 2.1-2.9cm 2 V -1 s -1 The carrier mobility is about 1000 times that of the conventional carrier material. And MAPbCl is driven by high current density within 1000 hours 3 The carrier transport capability of the film is basically not weakened, and the film has good stability. It follows that perovskites have great potential as a component of carrier transport layers for application in OLEDs. In order to obtain a carrier transport layer with uniformly deposited perovskite, a perovskite organic solution is generally adopted for wet preparation, and the specific process is as follows: depositing the organic solution of perovskite on the receiving substrate, and drying the organic solution deposited on the receiving substrate to volatilize the solvent in the organic solution to obtain the carrier transport layer. However, as the solvent in the organic solution is volatilized, a large number of pinholes are formed on the surface of the formed carrier transport layer, and when the carrier transport layer is applied to the manufacturing of a light emitting device, the existence of the pinholes causes a serious leakage current of the light emitting device, thereby reducing the light emitting efficiency of the light emitting device.
Disclosure of Invention
The invention mainly aims to provide a preparation method of a composite material, which aims to reduce surface pinholes of a carrier transmission layer, avoid the generation of leakage current and improve the luminous efficiency of a light-emitting device.
In order to achieve the above purpose, the preparation method of the composite material provided by the invention comprises the following steps: providing a perovskite solution, providing a conductive polymer solution, and mixing the perovskite solution and the conductive polymer solution to obtain a mixed solution; and curing and molding the mixed solution to obtain the composite material.
Optionally, the conductive polymer in the conductive polymer solution is selected from one of a p-type conductive polymer and an n-type conductive polymer.
Optionally, the p-type conductive polymer is selected from at least one of polyethylene oxide, polyvinylcarbazole, and poly [ bis (4-phenyl) (4-butylphenyl) amine ].
Alternatively, the n-type conductive polymer is at least one selected from the group consisting of a rylimide-based polymer and a poly p-phenylenevinylene-based conjugated polymer.
Optionally, the perovskite in the perovskite solution has the general molecular formula ABX 3 Wherein A is selected from at least one of formamidine group, methylamine group and cesium ion, B is selected from at least one of lead ion and tin ion, and X is selected from at least one of chloride ion, bromide ion and iodide ion.
The invention also provides a composite material, which is prepared by the preparation method of the composite material.
The invention also provides a composite material comprising a perovskite and a conductive polymer.
The invention also provides a light-emitting diode which comprises an anode, a light-emitting layer and a cathode, wherein the light-emitting layer is arranged between the anode and the cathode;
the light-emitting diode also comprises at least one layer of a hole transport layer and an electron transport layer, wherein the hole transport layer is arranged between the anode and the light-emitting layer, and the electron transport layer is arranged between the light-emitting layer and the cathode;
the hole transport layer adopts the composite material; and/or the electron transport layer is made of the composite material.
Optionally, the thickness of the electron transport layer is 10 to 100nm;
and/or the thickness of the hole transport layer is 10-50 nm.
The invention also provides a preparation method of the light-emitting diode, which comprises the following steps:
preparing a hole transport layer between the anode and the light emitting layer;
and/or, preparing an electron transport layer between the light emitting layer and the cathode;
the preparation process of at least one of the hole transport layer and the electron transport layer includes: depositing a mixed solution of the perovskite solution and the conducting polymer solution, and solidifying and molding the mixed solution.
The invention provides a preparation method of a composite material, which comprises the following steps: providing a perovskite solution, providing a conductive polymer solution, and mixing the perovskite solution and the conductive polymer solution to obtain a mixed solution; and curing and molding the mixed solution to obtain the composite material. The conductive polymer solution is introduced and mixed with the perovskite solution to form a mixed solution, so that after the solvent in the mixed solution is volatilized, the conductive polymer is filled among crystal grains of the perovskite and forms a continuous film layer, and the pinholes formed by volatilization of the solvent are reduced in the formed composite material. And the conductive polymer has conductivity, so that the transmission of current carriers is ensured, and the generation of leakage current is avoided. It can be understood that when the composite material prepared by the method is used as a carrier transport layer, the technical scheme of the invention can reduce surface pinholes of the carrier transport layer, avoid the generation of leakage current and improve the luminous efficiency of the light-emitting device.
Drawings
Fig. 1 is a schematic structural diagram of a light emitting diode according to an embodiment of the invention;
the reference numbers illustrate:
reference numerals Name (R) Reference numerals Name (R)
1 Light emitting diode 400 Luminescent layer
100 Anode 500 Electron transport layer
200 Hole injection layer 600 Electron injection layer
300 Hole transport layer 700 Cathode electrode
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The invention provides a preparation method of a composite material, aiming at reducing surface pinholes of a carrier transmission layer, avoiding the generation of leakage current and improving the luminous efficiency of a luminous device.
In an embodiment of the present invention, a method for preparing a composite material includes the following steps: providing a perovskite solution, providing a conductive polymer solution, and mixing the perovskite solution and the conductive polymer solution to obtain a mixed solution; and curing and molding the mixed solution to obtain the composite material.
The invention provides a preparation method of a composite material, which comprises the following steps: providing a perovskite solution, providing a conductive polymer solution, and mixing the perovskite solution and the conductive polymer solution to obtain a mixed solution; and curing and molding the mixed solution to obtain the composite material. The conductive polymer solution is introduced and mixed with the perovskite solution to form a mixed solution, so that after the solvent in the mixed solution is volatilized, the conductive polymer is filled among crystal grains of the perovskite and forms a continuous film layer, and the pinholes formed by volatilization of the solvent are reduced in the formed composite material. And the conductive polymer has conductivity, so that the transmission of current carriers is ensured, and the generation of leakage current is avoided. It can be understood that when the composite material prepared by the method is used as a carrier transport layer, the technical scheme of the invention can reduce surface pinholes of the carrier transport layer, avoid the generation of leakage current and improve the luminous efficiency of the light-emitting device.
The transport process of the carriers includes a transport process inside the perovskite crystal grains and a transport process at the interface of the perovskite crystal grains. For the transmission process inside the perovskite crystal grain, because the defect state inside the perovskite crystal grain is very few, the current carrier is basically not captured by the defect when being transmitted inside the perovskite crystal grain, that is, the migration of the current carrier inside the current carrier crystal grain is not influenced. For the transmission process of the perovskite interface, as the perovskite crystal grain interfaces and the material surfaces have more defects, current carriers can be captured by the defects during the transmission between the perovskite interfaces, and the perovskite on the surface of the prepared material is easy to degrade, so that the transmission of the current carriers on the perovskite interfaces is very unstable. In order to improve the stability of carrier transmission at a perovskite interface, a conductive polymer solution and a perovskite solution are mixed to prepare a composite material, firstly, the conductive polymer is introduced into the composite material prepared by the invention, and S, N and F in the conductive polymer are coordinated with metal atoms in the perovskite, so that the defects of the prepared perovskite are reduced, and the perovskite with good shape and crystallinity is obtained; secondly, the addition of the conductive polymer can effectively inhibit the crystallization speed of perovskite, thereby obtaining large-size perovskite crystal grains, reducing the crystal boundary between the perovskite crystal grains, further reducing the capture of current carriers by defects when the current carriers are transmitted between perovskite interfaces, and further improving the luminous efficiency of the light-emitting device; and finally, the conductive polymer has a long-chain structure, is filled among the crystal grains of the perovskite and is interwoven with each other through the long-chain structure to form a continuous coating, so that moisture and oxygen in the air are isolated, the stability of the carrier transport layer is improved, and the service life of the light-emitting device is prolonged. In the invention, the perovskite is preferably a metal halide perovskite, and the hole transmission rate and the electron transmission rate of the metal halide perovskite are high, so that when the perovskite is applied to the preparation of a current carrier transmission layer, the perovskite further ensures the effective transmission of holes and electrons. In addition, the mixed solution is prepared into the carrier transport layer by adopting a wet curing forming method, the forming method of the carrier transport layer comprises a spin coating method, a vacuum evaporation method and an ink-jet printing method, and the carrier transport layer with a film structure can be obtained by the methods.
In one embodiment of the present invention, the step of providing the conductive polymer solution includes: adding the conductive polymer into an organic solvent, and dissolving the conductive polymer in the organic solvent under the condition of heating and stirring to obtain a conductive polymer solution. In order to obtain the perovskite with high crystallinity and high stability, the invention dissolves the conductive polymer in the organic solvent with high polarity to obtain the conductive polymer solution, then the conductive polymer solution is added into the perovskite solution to form the mixed solution of the conductive polymer solution and the perovskite solution, and the mixed solution is cured and formed by a wet method to obtain the composite material. Of course, the highly polar organic solvent may be selected from one of dimethylformamide and dimethylsulfoxide, and other polar solvents may be used as long as they can dissolve the conductive polymer.
In an embodiment of the present invention, the conductive polymer in the conductive polymer solution is selected from one of a p-type conductive polymer and an n-type conductive polymer. The composite material is used as a carrier transport layer, and the carrier transport layer comprises a hole transport layer and an electron transport layer. The p-type conducting polymer is also called a hole-type conducting polymer, wherein holes are majority electrons, electrons are minority electrons and are mainly conducted by the holes, the holes are mainly provided by impurity atoms, the more impurity atoms are doped, the higher the hole concentration is, and the stronger the conducting performance is. The n-type conductive polymer is also called as an electronic conductive polymer, wherein electrons are majority electrons, holes are minority electrons, the electron conduction is mainly realized by depending on electrons, the electrons are mainly provided by impurity atoms, the more impurity atoms are doped, the higher the electron concentration is, and the stronger the conductivity is. When the conductive polymer is applied to the hole transport layer, the conductive polymer is selected from p-type conductive polymers, and the p-type conductive polymer is added into the mixed solution of the perovskite, so that the preparation of the hole transport layer is realized, and the effective transmission of holes is ensured. When the conductive polymer is applied to the electron transport layer, the conductive polymer is selected from n-type conductive polymers, and the n-type conductive polymer is added into the mixed solution of perovskite, so that the preparation of the electron transport layer is realized, and the effective transmission of electrons is ensured.
In one embodiment of the present invention, the p-type conductive polymer is at least one selected from the group consisting of polyethylene oxide, polyvinylcarbazole, and poly [ bis (4-phenyl) (4-butylphenyl) amine ]. When the hole transport layer is prepared, the p-type conducting polymer is added into the mixed solution of the perovskite, so that the hole transport layer with good morphology and crystallinity is obtained, the number of crystal grain interfaces of the perovskite is effectively reduced, and the stability of hole transport is improved. Moreover, long-chain structures of the p-type conducting polymer are mutually interwoven to form a net structure, so that moisture and oxygen in the air are isolated, and the service life of the light-emitting device is prolonged.
In one embodiment of the present invention, the n-type conductive polymer is at least one selected from the group consisting of a ryleneimide-based polymer and a poly-p-phenylenevinylene-based conjugated polymer. When the electron transport layer is prepared, the n-type conducting polymer is added into the mixed solution of the perovskite, so that the electron transport layer with good form and crystallinity is obtained, the number of crystal grain interfaces is effectively reduced, and the stability of electron transport is improved. Moreover, long-chain structures of the n-type conducting polymer are mutually interwoven to form a net structure, so that moisture and oxygen in the air are isolated, and the service life of the light-emitting device is prolonged.
In one embodiment of the present invention, the perovskite in the perovskite solution has the general molecular formula ABX 3 Wherein A is selected from the formamidine group (FA) + ) Methylamino group (MA) + ) And cesium ion (Cs) + ) B is selected from at least one of lead ions and tin ions, and X is selected from at least one of chloride ions, bromide ions and iodide ions. Note that the formamidine group (FA) + ) Methylamino group (MA) + ) And cesium ion (Cs) + ) Respectively has an ionic radius of
Figure BDA0002477190430000061
And
Figure BDA0002477190430000062
the invention introduces cations with smaller radius on the A site, thereby leading the crystal lattice to shrink, enhancing the interaction between the A site cations and the metal halide in the cubo-octahedron framework and ensuring the formed ABX 3 Perovskite type has high crystallinity and high stability. Because the radiuses of the formamidine group, the formamidine group and the cesium ion are different, A can be selected from two of the formamidine group, the formamidine group and the cesium ion, and the A position substitution is carried out through the groups with two different radiuses, so that the interaction between the A position cation and the metal halide is enhanced, and the ABX is improved 3 The crystallinity of the perovskite reduces the crystal defects of the perovskite, promotes the transmission of current carriers,thereby ensuring the photoelectric property of the composite material and improving the working stability of the prepared luminescent device.
In addition, in the perovskite, the molecular formula of A is M 1-y Z y M is selected from formamidine group or methylamine group, Z is selected from cesium ion or methylamine group, M and Z are not selected from the same group, and the value range of y is 0.1to 0.5. The invention can further reduce the crystal defects of the prepared composite material by adjusting the ratio of M to Z, thereby further preventing the structural phase change, ensuring the migration of current carriers and improving the working stability of the prepared luminescent device.
In an embodiment of the present invention, the step of "providing a perovskite solution" comprises: mixing AX and BX 2 Dissolving in polar solvent to make AX and BX 2 Reacting to obtain the perovskite solution. The polar solvent is one selected from dimethylformamide and dimethylsulfoxide, but other organic solvents may be used as long as AX and BX can be dissolved simultaneously 2 And (4) finishing. Meanwhile, the polar solvent has volatility, so that when the prepared mixed solution is deposited on the surface of a base material, the organic solvent can be volatilized by low-pressure air extraction or heating, and the carrier transport layer with a thin-layer structure is obtained. In order to inhibit halogen ions in the perovskite from migrating under the action of an electric field to generate vacancies and reduce metal quenching centers in the perovskite, the invention controls AX and BX 2 So that BX is sufficiently encapsulated by AX in a molar ratio of (1) to (2): 1 2 Thereby effectively inhibiting the carrier offset and promoting the carrier migration. Of course, to ensure AX and BX 2 The invention can control the reaction temperature to be 60 ℃. Still further, the step of "providing a perovskite solution" comprises: weighing FAX and SnX with the molar ratio of 2 2 And adding into dimethyl sulfoxide, controlling reaction temperature at 60 deg.C to make FAX and SnX 2 Reacting to obtain the perovskite solution. In addition, when the mass concentration of the perovskite is too low or too high, pinholes exist on the surface of the prepared composite material, so that a light-emitting device generates large leakage current to damage the light-emitting deviceThe mass fraction is 5-20%, and the luminescent performance of the luminescent device is improved while the film forming quality of the composite material is ensured.
Specifically, the preparation method of the composite material comprises the following steps: mixing AX and BX 2 Adding into dimethyl sulfoxide, and heating at 60 deg.C to dissolve to obtain AX and BX 2 Fully reacting to obtain a perovskite solution; adding a p-type conducting polymer or an n-type conducting polymer into a glass bottle, adding dimethyl sulfoxide into the glass bottle, putting a stirring magneton into the glass bottle, putting the glass bottle into magnetic stirring equipment with a heating function, adjusting the rotating speed of the magnetic stirring equipment, and stirring at 60 ℃ to completely dissolve the conducting polymer to obtain a conducting polymerization solution; adding the conductive polymerization solution into the perovskite solution, and heating and stirring at 60 ℃ to fully mix the conductive polymerization solution with the perovskite solution to obtain a mixed solution of the conductive polymerization solution and the perovskite solution; and curing and molding the mixed solution to obtain the composite material.
In an embodiment of the present invention, the step of "solidifying and molding the mixed solution" includes: adding the mixed solution into an ink box of an ink-jet printer, setting ink-jet printing conditions, depositing the mixed solution on a bearing substrate by using an ink-jet printing mode, and drying the bearing substrate. In the spin coating method, the carrier transport layer is prepared by dropping the mixture on the receiving substrate and then forming a film from the mixture by spin centrifugation. Therefore, in the process, most of the mixed liquid is thrown out of the bearing substrate under the action of rotation and centrifugation, so that the waste of the mixed liquid is caused; on the other hand, the spin film formation cannot prepare a patterned carrier transport layer as required, and thus the patterned display of the display screen cannot be realized. However, in the vacuum deposition method, first, vacuum deposition has a high requirement for a vacuum degree, and in order to realize a high vacuum degree of vacuum deposition, a chamber sealing property and a vacuum pump are required to be high, and it is very difficult to manufacture a set of deposition lines having excellent performance; secondly, the waste of the mixed liquid is caused by vacuum evaporation, most of the active ingredients in the mixed liquid are sputtered to the periphery of the chamber or the pattern drawing baffle plate during vacuum evaporation, and only a small part of the active ingredients are sputtered to the designated pixel area, so that the waste of the mixed liquid is caused; third, the vacuum evaporation technique is also restricted by the pattern-drawing baffle, and it is difficult to realize a large-sized display screen. Compared with a spin coating method and a vacuum sputtering method, the ink-jet printing method directly prints the mixed liquid in a specific pixel area of the carrying substrate through the nozzle, avoids the waste of the mixed liquid and improves the utilization rate of the mixed liquid. In addition, the process does not need a high vacuum environment, and can be carried out in an inert atmosphere, so that the equipment requirement is reduced, and the mass production preparation is favorably realized. Meanwhile, the mixed liquid is directly sprayed to the designated area through the spray head, so that the mixed liquid is not limited by the pattern drawing baffle, and the preparation of a large-size display screen is facilitated. According to the invention, the preparation of the carrier transmission layer is realized through ink-jet printing, so that the development of the field of small-size display screens is promoted, the mass production problem of large-size display screens is solved, the cost is reduced, and the film quality of the prepared carrier transmission layer is ensured.
In an embodiment of the present invention, the step of "setting the ink jet printing condition" includes: the distance between a nozzle of the ink-jet printer and the bearing substrate is adjusted to be 0.1 mm-1 mm, the temperature of the bearing substrate is controlled to be 25-60 ℃, and the ink-jet speed of the nozzle is adjusted to be 2 m/s-10 m/s. The mixed liquid is used as ink to be added into an ink box of an ink-jet printer, the ink-jet speed is set to be 2-10 m/s, the ink adding volume is adjusted according to the size of a pixel area needing ink-jet printing, the ink adding volume is 2-50 pl, and in order to ensure that the jetted ink cannot splash or generate scattered points and other defects, the distance between a nozzle and a bearing substrate is 0.1-1 mm, preferably 0.5mm. The temperature for carrying the substrate is 25-60 ℃, and the ink-jet printing can be carried out at normal temperature. And depositing the mixed liquid after ink-jet printing in a pixel area of the bearing substrate, and drying the mixed liquid deposited on the bearing substrate to remove the solvent in the mixed liquid to obtain the composite material with the film structure. In order to realize the solidification of the composite material, the solvent is pumped out under low pressure, the range of the low pressure is 0.1-100 torr, the duration is 1-60 min, and the composite material with a film structure is obtained after the solvent is pumped out. Of course, the receiving substrate may be heat treated to ensure complete removal of the solvent, allowing the composite material to further cure, wherein the heating temperature is 50 ℃ to 150 ℃, preferably 80 ℃. In addition, the ink box for ink-jet printing can be provided with an ultrasonic device and the like, so that the mixed liquid is uniformly dispersed in the ink box through the ultrasonic device, the dispersity and the stability of the mixed liquid are ensured, and meanwhile, after the mixed liquid is added into the ink box, automatic ink-jet is started to avoid blocking a spray head.
The invention also provides a composite material, which is prepared by the preparation method of the composite material, and the composite material is obtained by solidifying and molding the mixed solution of the perovskite solution and the conductive polymer solution, so that the conductive polymer is filled among crystal grains of the perovskite and forms a continuous film layer after the solvent in the mixed solution is volatilized, and pinholes formed by volatilization of the solvent in the formed composite material are reduced. And the conductive polymer has conductivity, so that the transmission of current carriers is ensured, and the generation of leakage current is avoided. It can be understood that when the composite material is used as a carrier transport layer, the technical scheme of the invention can reduce surface pinholes of the carrier transport layer, avoid the generation of leakage current and improve the luminous efficiency of the light-emitting device.
The invention also provides a composite material, which comprises perovskite and a conductive polymer. Preferably, the mass of the conductive polymer is 0.01% to 1% of the mass of the perovskite. The conductive polymer has little addition amount, so the influence of the conductive polymer on the overall mobility of the prepared carrier transmission layer can be ignored. According to the invention, a small amount of conductive polymer is introduced into the perovskite solution, on one hand, the addition of the conductive polymer slows down the crystallization speed of the perovskite and improves the crystallinity and the film coverage rate of the perovskite, so that the defects between crystal grain interfaces are effectively reduced, and the transmission capability of current carriers is improved.
The invention also provides a light emitting diode 1, which comprises an anode 100, a light emitting layer 400 and a cathode 700, wherein the light emitting layer 400 is arranged between the anode 100 and the cathode 700; the light emitting diode 1 further includes at least one of a hole transport layer 300 and an electron transport layer 500, the hole transport layer 300 being disposed between the anode 100 and the light emitting layer 400, the electron transport layer 500 being disposed between the light emitting layer 400 and the cathode 700; the hole transport layer 300 is made of a composite material; and/or, the electron transport layer 500 is made of a composite material. Specifically, the light emitting diode 1 includes three structures, and the light emitting diode includes an anode 100, a hole transport layer 300, a light emitting layer 400, and a cathode 700, which are sequentially stacked; alternatively, the light emitting diode includes an anode 100, a light emitting layer 400, an electron transport layer 500, and a cathode 700, which are sequentially stacked; alternatively, the light emitting diode includes an anode 100, a hole transport layer 300, a light emitting layer 400, an electron transport layer 500, and a cathode 700, which are sequentially stacked. Preferably, the light emitting diode includes an anode 100, a hole transport layer 300, a light emitting layer 400, an electron transport layer 500, and a cathode 700, which are sequentially stacked, and the hole transport layer 300 and the electron transport layer 500 are both made of a composite material. The anode 100 is disposed on the substrate, the anode 100 may be deposited on the substrate after the substrate is cleaned, and the hole transport layer 300, the light emitting layer 400, the electron transport layer 500 and the cathode 700 are sequentially deposited on the surface of the anode 100 after the anode 100 is deposited, so as to implement the fabrication of the light emitting diode. Of course, the hole transport layer 300, the light emitting layer 400, and the electron transport layer 500 may be prepared by inkjet printing.
It should be noted that the material of the anode 100 is selected according to the light emitting direction of the light emitting diode 1. When the light emitting diode 1 is a bottom emission type, the material of the anode 100 is a light-transmissive material, wherein the light-transmissive material of the anode 100 includes, but is not limited to, conductive metal oxide (ITO), graphene, carbon nanotubes, and conductive polymers. When the light emitting diode 1 is of a top emission type, the anode 100 is made of an oxide/metal/oxide interlayer electrode, and the oxide includes, but is not limited to, conductive metal oxide (ITO), indium Zinc Oxide (IZO), tungsten oxide (WO) 3 ) And molybdenum oxide (MoO) 3 ) Metal including but not limited toNot limited to at least one of gold (Au) and silver (Ag). Specifically, the anode 100 of the embodiment of the invention is made of ITO/Ag/ITO, ITO/Ag/IZO, moO 3 /Ag/MoO 3 At least one of (1). Preferably, the thickness of the anode 100 is 20 to 200nm.
A hole injection layer 200 is further disposed between the anode 100 and the hole transport layer 300, the arrangement of the hole injection layer 200 reduces the energy barrier between the anode 100 and the hole transport layer 300, and improves the hole injection capability, and the material selected for the hole injection layer 200 includes, but is not limited to, organic molecules and inorganic materials of a high conductivity system. Preferably, the hole injection layer 200 is made of one of HAT-CN material and PEDOT PSS material, and the thickness of the hole injection layer 200 is 10-100 nm.
The composition of the hole transport layer 300 includes a composite material containing a p-type conductive polymer, and the hole transport layer 300 is a structure prepared by ink-jet printing. Specifically, a mixed solution of a perovskite solution and a p-type conductive polymer solution is added to an ink jet printer as ink for ink jet printing, ink jet printing conditions are set, the mixed solution is jetted to the surface of the hole injection layer 200 by an ink jet printing method, and the mixed solution jetted to the surface of the hole injection layer 200 is dried to obtain the hole transport layer 300 having a thickness of 10 to 50nm. Preferably, the thickness of the hole transport layer 300 is 30nm. The invention ensures the film quality of the prepared hole transport layer 300 through ink-jet printing, is beneficial to realizing the preparation of a large-size display screen, and simultaneously reduces the preparation cost of the hole transport layer 300.
The composition of the light emitting layer 400 includes at least one of light emitting material selected from organic light emitting material, inorganic quantum dot light emitting material and polymer light emitting material, wherein the organic light emitting material is mainly small molecule organic light emitting material, and includes phosphorescent material and thermal activation delayed fluorescent material, the phosphorescent material is mainly heavy metal complex series, and the phosphorescent material includes but is not limited to green phosphorescent material (Ir (ppy) 3 And Ir (ppy) 2 (acac)), a red phosphorescent material (PtOEP), a blue phosphorescent material (FIrpic), an iridium complex, and the like; the heat activated delayed fluorescence material consists of two parts of an electron donor and an electron acceptor, wherein the electron donorIncluding but not limited to electron donors with strong electron donating ability such as acridine group, carbazole triphenylamine group and derivatives thereof, electron acceptors including but not limited to electron acceptors with strong electron donating ability such as triazine group, 4-benzoylpyridine group and diphenylsulfone group, and thermally activated delayed fluorescence materials including but not limited to at least one of 2CzPN, 4CzPIN and TXO-TPA. The inorganic quantum dot luminescent material is at least one semiconductor nano material selected from CdSe, znS, cdS, pbS, pbSe, inP, inAs and GaAs. The polymer luminescent material is selected from PPV and derivatives thereof, polyfluorene and iridium (Ir) complex contained on a branched chain, including but not limited to one of PPV, MEH-PPV, DP-PPV, PFCZIrtbt and the like. Preferably, the thickness of the light-emitting layer is 10 to 100nm. The invention ensures the luminescent performance of the prepared luminescent layer 400 through ink-jet printing and improves the luminescent efficiency of the luminescent layer.
The electron transport layer 500 is composed of a composite material containing an n-type conductive polymer, and the electron transport layer 500 is a structure prepared by ink-jet printing. Specifically, a mixed solution of a perovskite solution and an n-type conductive polymer solution is added to an ink jet printer as an ink for ink jet printing, the ink jet printing conditions are set, the mixed solution is jetted to the surface of the light emitting layer 400 by an ink jet printing method, and the mixed solution on the surface of the light emitting layer 400 is dried to obtain the electron transporting layer 500 having a thickness of 10 to 100nm. Preferably, the thickness of the electron transport layer 500 is 50nm. The invention ensures the film quality of the prepared electronic transmission layer 500 through ink-jet printing, is beneficial to realizing the preparation of a large-size display screen, and simultaneously reduces the preparation cost of the electronic transmission layer 500.
In order to facilitate electron injection from cathode 700 into electron transport layer 500, an electron injection layer 600 is disposed between electron transport layer 500 and cathode 700, and the constituent materials of electron injection layer 600 include, but are not limited to, alkali metal compounds and alkali metal fluorides, such as CsCO 3 And at least one of Liq, liF, csF, naF, KF, or RbF, and the thickness of the electron injection layer 600 is 0.5 to 8nm.
The cathode 700 is deposited on the surface of the electron injection layer 600 by vacuum evaporation or other processes, and the material of the cathode 700 is selected according to the light emitting direction of the light emitting diode 1. When the light emitting diode 1 is a bottom emission type, the cathode 700 may be made of a metal including, but not limited to, at least one of aluminum (Al), silver (Ag), and gold (Au), and the thickness of the cathode 700 is 80 to 150nm. When the light emitting diode 1 is of a top emission type, the cathode 700 is made of a light-transmitting material including, but not limited to, at least one of a conductive metal oxide (ITO), a metal complex (Mg/Ag), and a high work function metal (Ag), and the thickness of the cathode 700 is 10 to 20nm.
The invention also provides a preparation method of the light-emitting diode, which comprises the following steps: preparing a hole transport layer 300 between the anode 100 and the light emitting layer 400; and/or, an electron transport layer 500 is prepared between the light emitting layer 400 and the cathode 700; the process of preparing at least one of the hole transport layer 300 and the electron transport layer 500 includes: depositing a mixed solution of the perovskite solution and the conducting polymer solution, and solidifying and molding the mixed solution.
Illustratively, case one: when the light-emitting diode comprises an anode, a hole transport layer, a light-emitting layer and a cathode which are sequentially stacked, the preparation method of the light-emitting diode comprises the following steps: depositing a mixed solution of a perovskite solution and a conductive polymer solution on the surface of the anode, and solidifying and molding the mixed solution to obtain a hole transport layer; depositing a light-emitting layer and a cathode on the surface of the hole transport layer in sequence to obtain a light-emitting diode;
the second situation: when the light-emitting diode comprises an anode, a light-emitting layer, an electron transport layer and a cathode which are sequentially stacked, the preparation method of the light-emitting diode comprises the following steps: depositing a light-emitting layer on the surface of the anode, depositing a mixed solution of a perovskite solution and a conductive polymer solution on the surface of the light-emitting layer, and curing and molding the mixed solution to obtain an electron transport layer; depositing a cathode on the surface of the electron transport layer to obtain a light emitting diode;
case three: when the light-emitting diode comprises an anode, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode which are sequentially stacked, the preparation method of the light-emitting diode comprises the following steps: depositing a mixed solution of a perovskite solution and a conductive polymer solution on the surface of the anode, and solidifying and molding the mixed solution to obtain a hole transport layer; depositing a light-emitting layer on the surface of the hole transport layer, depositing a mixed solution of a perovskite solution and a conductive polymer solution on the surface of the light-emitting layer, and curing and molding the mixed solution to obtain an electron transport layer; and depositing a cathode on the surface of the electron transport layer to obtain the light-emitting diode.
In the third case, of course, the method for preparing the electron transport layer may not adopt the method of "depositing the mixed solution of the perovskite solution and the conductive polymer solution, and solidifying and molding the mixed solution" mentioned in the embodiments of the present invention, but use the conventional method for depositing the ZnO electron transport film in the prior art, etc., or the method for preparing the hole transport layer may not adopt the method of "depositing the mixed solution of the perovskite solution and the conductive polymer solution, and solidifying and molding the mixed solution" mentioned in the embodiments of the present invention, but use the conventional method for depositing the hole transport layer film in the prior art, so that the device of the present application may be prepared according to the actual needs of the inventor.
According to the invention, the mixed solution of the perovskite solution and the conductive polymer solution is deposited, so that after the solvent in the mixed solution is volatilized, the conductive polymer is filled among crystal grains of the perovskite and forms a continuous film layer, and thus, pinholes formed due to volatilization of the solvent are reduced in the formed hole transport layer and/or electron transport layer. And the conductive polymer has conductivity, so that the transmission of current carriers is ensured, and the generation of leakage current is avoided. It can be understood that the technical scheme of the invention avoids the generation of leakage current and improves the luminous efficiency of the light-emitting diode.
The invention also provides a preparation method of the light-emitting diode, which comprises the following steps: depositing a mixed solution of a perovskite solution and a conductive polymer solution on the surface of the anode 100, and solidifying and molding the mixed solution to obtain a hole transport layer 300; the light emitting layer 400 and the cathode 700 are sequentially deposited on the surface of the hole transport layer 300 to obtain the light emitting diode. According to the invention, the mixed solution of the perovskite solution and the conductive polymer solution is deposited on the anode 100, so that surface pinholes of the prepared hole transport layer 300 are reduced, the generation of leakage current is avoided, and the luminous efficiency of the light-emitting device is improved.
The invention also provides a preparation method of the light-emitting diode 1, which comprises the following steps: depositing a light-emitting layer 400 on the surface of the anode 100, depositing a mixed solution of a perovskite solution and a conductive polymer solution on the surface of the light-emitting layer 400, and curing and molding the mixed solution to obtain an electron transport layer 500; a cathode 700 is deposited on the surface of the electron transport layer 500 to obtain a light emitting diode. According to the invention, the mixed solution of the perovskite solution and the conductive polymer solution is deposited on the light-emitting layer 400, so that surface pinholes of the prepared electron transport layer 500 are reduced, the generation of leakage current is avoided, and the light-emitting efficiency of the light-emitting device is improved.
The invention also provides a preparation method of the light-emitting diode, which comprises the following steps: depositing a mixed solution of a perovskite solution and a conductive polymer solution on the surface of the anode 100, and solidifying and molding the mixed solution to obtain a hole transport layer 300; depositing a light-emitting layer 400 on the surface of the hole transport layer 300, depositing a mixed solution of a perovskite solution and a conductive polymer solution on the surface of the light-emitting layer 400, and curing and molding the mixed solution to obtain an electron transport layer 500; a cathode 700 is deposited on the surface of the electron transport layer 500 to obtain a light emitting diode. Of course, the light emitting layer 400 can be obtained by depositing a mixed solution of a light emitting material, a perovskite solution and a conductive polymer solution on the surface of the hole transport layer 300 and then curing and molding, and the hole transport layer 300, the light emitting layer 400 and the electron transport layer 500 are deposited by ink jet printing. The invention ensures the film quality of the prepared light-emitting diode through ink-jet printing, is beneficial to realizing the preparation of a large-size display screen, and simultaneously reduces the preparation cost of the empty light-emitting diode.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the present specification and directly/indirectly applied to other related technical fields within the spirit of the present invention are included in the scope of the present invention.

Claims (6)

1. A preparation method of a composite material is characterized by comprising the following steps: providing a perovskite solution, providing a conductive polymer solution, and mixing the perovskite solution and the conductive polymer solution to obtain a mixed solution; solidifying and molding the mixed solution to obtain the composite material;
the conducting polymer in the conducting polymer solution is selected from one of a p-type conducting polymer and an n-type conducting polymer;
the p-type conductive polymer is at least one selected from polyethylene oxide, polyvinyl carbazole and poly [ bis (4-phenyl) (4-butylphenyl) amine ]; the n-type conductive polymer is selected from rylimide polymers.
2. The method of preparing a composite material according to claim 1, wherein the perovskite in the perovskite solution has the general molecular formula ABX 3 Wherein A is selected from at least one of formamidine group, methylamine group and cesium ion, B is selected from at least one of lead ion and tin ion, and X is selected from at least one of chloride ion, bromide ion and iodide ion.
3. A composite material produced by the method for producing a composite material according to any one of claims 1to 2.
4. A light-emitting diode is characterized by comprising an anode, a light-emitting layer and a cathode, wherein the light-emitting layer is arranged between the anode and the cathode;
the light-emitting diode also comprises at least one layer of a hole transport layer and an electron transport layer, wherein the hole transport layer is arranged between the anode and the light-emitting layer, and the electron transport layer is arranged between the light-emitting layer and the cathode;
the hole transport layer adopts the composite material of claim 3; and/or the electron transport layer adopts the composite material of claim 3.
5. The light-emitting diode according to claim 4, wherein the thickness of the electron transport layer is 10 to 100nm;
and/or the thickness of the hole transport layer is 10 to 50nm.
6. A preparation method of a light-emitting diode is characterized by comprising the following steps:
preparing a hole transport layer between the anode and the light emitting layer;
and/or, preparing an electron transport layer between the light emitting layer and the cathode;
the preparation process of at least one of the hole transport layer and the electron transport layer includes: depositing a mixed solution of a perovskite solution and a conductive polymer solution, and solidifying and molding the mixed solution;
the conductive polymer in the conductive polymer solution is selected from one of a p-type conductive polymer and an n-type conductive polymer;
the p-type conductive polymer is at least one selected from polyethylene oxide, polyvinyl carbazole and poly [ bis (4-phenyl) (4-butylphenyl) amine ]; the n-type conductive polymer is at least one selected from the group consisting of a rylimide polymer and a poly (p-phenylenevinylene) conjugated polymer.
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