CN116814112A

CN116814112A - Nanocomposite, preparation method of nanocomposite, ink, preparation method of ink and light-emitting device

Info

Publication number: CN116814112A
Application number: CN202210258257.1A
Authority: CN
Inventors: 许冰
Original assignee: Guangdong Juhua Printing Display Technology Co Ltd
Current assignee: Guangdong Juhua Printing Display Technology Co Ltd
Priority date: 2022-03-16
Filing date: 2022-03-16
Publication date: 2023-09-29

Abstract

The application discloses a nanocomposite material, a preparation method, ink, a preparation method and a luminescent device, wherein the preparation method of the nanocomposite material is to coat a polymer on the surface of metal oxide nanoparticles, and then carry out freeze-drying treatment to obtain the nanocomposite material, the freeze-drying treatment can better remove residual solvent in the front-end preparation process, and the polymer can prevent irreversible agglomeration of the metal oxide nanoparticles after the freeze-drying treatment, thereby being beneficial to the subsequent redispersion to form the ink.

Description

Nanocomposite, preparation method of nanocomposite, ink, preparation method of ink and light-emitting device

Technical Field

The application relates to the field of materials, in particular to a nanocomposite, a preparation method thereof, ink, a preparation method thereof and a light-emitting device.

Background

The Light Emitting device includes, but is not limited to, an Organic Light-Emitting Diode (OLED) and a quantum dot Light-Emitting Diode (Quantum Dot Light Emitting Diodes, QLED), and is of a "sandwich" structure, i.e., includes an anode, a cathode, and a Light Emitting layer, wherein the anode and the cathode are disposed opposite to each other, and the Light Emitting layer is disposed between the anode and the cathode. The light emitting principle of the light emitting device is: electrons are injected into the light-emitting area from the cathode of the device, holes are injected into the light-emitting area from the anode of the device, the electrons and the holes are combined in the light-emitting area to form excitons, and photons are released by the combined excitons in a radiation transition mode so as to emit light.

There are various methods for preparing an electron transport layer of a light emitting device, in which a solution method is to generate metal oxide nanoparticles by chemical reaction in a solution, then remove a solvent (containing reaction byproducts and impurities) in a front-end preparation process through a precipitation centrifugation redispersion process to obtain ink, and finally coat the ink to form a thin film. The preparation method is compatible with the printing electronic technology, can meet the production requirements of large size, flexibility, low cost, high efficiency, green environmental protection and the like, and has incomparable advantages.

At present, the light emitting device still has a plurality of problems in the preparation process, such as incomplete solvent removal in the front-end preparation process, poor redispersibility of metal oxide nanoparticles, and the like.

Disclosure of Invention

The application provides a nanocomposite, a preparation method, ink, a preparation method and a light-emitting device, and aims to improve the problem that solvent is not thoroughly removed in the front-end preparation process and improve the redispersibility of metal oxide nanoparticles.

In a first aspect, an embodiment of the present application provides a method for preparing a nanocomposite, including the steps of:

providing a first dispersion comprising metal oxide nanoparticles;

adding a polymer containing polar groups into the first dispersion liquid to obtain a second dispersion liquid containing a nanocomposite, wherein the nanocomposite comprises metal oxide nanoparticles and a polymer coating the metal oxide nanoparticles; and

and performing freeze drying treatment on the second dispersion liquid to obtain the nanocomposite.

Optionally, the providing a first dispersion comprising metal oxide nanoparticles comprises:

providing a third dispersion comprising metal oxide nanoparticles;

adding a precipitant into the third dispersion liquid, and then centrifuging to obtain a precipitate containing the metal oxide nanoparticles; and

and adding a first organic solvent into the precipitate, and performing dispersion treatment to obtain the first dispersion liquid containing the metal oxide nanoparticles.

Optionally, the solvent in the third dispersion is selected from at least one of ethanol, methanol or n-butanol; and/or

The solid content in the third dispersion liquid is 3% -30%; and/or

The precipitant is selected from at least one of alkanes, aromatic hydrocarbons, esters or ethers; and/or

The volume ratio of the precipitant to the third dispersion liquid is 1.5-10 times; and/or

The first organic solvent is selected from tertiary butanol; and/or

The time of the dispersion treatment is 2-20 min; and/or

The temperature of the dispersion treatment is 35-50 ℃.

Optionally, the addition amount of the polymer is 0.1% -30% of the solid content of the metal oxide nano particles.

Optionally, the freeze drying treatment comprises a prefreezing process and a vacuum drying process, wherein the temperature of the prefreezing process is lower than-10 ℃, and the prefreezing process time is longer than 24 hours; and/or the temperature of the vacuum drying process is lower than 10 ℃, the air pressure is lower than 1torr, and the vacuum drying time is 24-72 h.

Optionally, the polymer is selected from at least one of polyvinylpyrrolidone, polyacetylimine, polyethylene glycol, polypropylene glycol, polyvinyl methyl ether or polyvinyl ethyl ether.

Optionally, the metal oxide nanoparticles are selected from zinc oxide nanoparticles undoped or doped with a metal element selected from at least one of magnesium, aluminum or lithium.

In a second aspect, the present application also provides a nanocomposite material, the nanocomposite material comprising metal oxide nanoparticles, and a polymer coating the metal oxide nanoparticles, the polymer containing polar groups, the nanocomposite material being subjected to a freeze-drying process.

Alternatively, the nanocomposite is made by the method of making the nanocomposite of the first aspect.

Optionally, in the nanocomposite, the mass ratio of the polymer to the metal oxide nanoparticles is (0.1 to 30): 100.

in a third aspect, the present application also provides a method for preparing ink, including: preparing the nanocomposite according to the method of the second aspect;

and mixing the nanocomposite with a second organic solvent to obtain the ink.

Optionally, the second organic solvent is selected from alcohol or ether alcohol solvents with boiling point between 100 ℃ and 350 ℃.

Optionally, the second organic solvent is selected from at least one of n-heptanol, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether or dipropylene glycol monoethyl ether.

In a fourth aspect, the present application also provides an ink prepared by the preparation method of the third aspect.

In a fifth aspect, the present application further provides a light emitting device, including an anode, a light emitting layer, an electron transport layer, and a cathode, which are sequentially stacked; wherein the electron transport layer is made of the nanocomposite material obtained by the preparation method of the first aspect, or the nanocomposite material of the second aspect, or the ink of the fourth aspect.

Optionally, the material of the anode is at least one of indium doped tin oxide, fluorine doped tin oxide, tin doped zinc oxide or indium doped zinc oxide; and/or the number of the groups of groups,

the material of the light-emitting layer comprises quantum dots, the quantum dotsThe point is selected from at least one of group II-VI compound, group III-V compound and group I-III-VI compound, the group II-VI compound is selected from CdSe, cdS, cdTe, znSe, znS, cdTe, znTe, cdZnS, cdZnSe, cdZnTe, znSeS, znSeTe, znTeS, cdSeS, cdSeTe, cdTeS; cdZnSeS, cdZnSeTe or CdZnSTe; the III-V compound is at least one selected from InP, inAs, gaP, gaAs, gaSb, alN, alP, inAsP, inNP, inNSb, gaAlNP or InAlNP; the I-III-VI compound is selected from CuInS ₂ 、CuInSe ₂ Or AgInS ₂ At least one of (a) and (b); and/or the number of the groups of groups,

the material of the cathode is selected from Al, cu, mo, au, ag or MoO ₃ At least one of them.

According to the application, the polymer is coated on the surface of the metal oxide nano-particles, and then freeze-drying treatment is carried out to obtain the nano-composite material, the freeze-drying treatment can better remove residual solvent in the front-end preparation process, and the polar groups of the polymer are connected with the surface of the metal oxide nano-particles in a coordination manner, so that irreversible agglomeration of the metal oxide nano-particles after the freeze-drying treatment can be prevented, and subsequent redispersion to form ink is facilitated; thus, not only the residual solvent in the front-end preparation process can be removed, but also the redispersibility of the metal oxide nanoparticles can be considered.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the description of the embodiments will be briefly described below.

Fig. 1 is a schematic flow chart of a method for preparing a nanocomposite according to an embodiment of the present application.

Fig. 2 is a schematic diagram of a light emitting device with a positive structure according to an embodiment of the present application.

Fig. 3 is a schematic view of a light emitting device with an inversion structure according to an embodiment of the present application.

Fig. 4 is a schematic diagram of the results of detection of luminous efficiency in examples of the present application and comparative example 2.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to fall within the scope of the application.

The embodiment of the application provides a nanocomposite, a preparation method thereof, ink, a preparation method thereof and a light-emitting device. The following will describe in detail. The following description of the embodiments is not intended to limit the preferred embodiments. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third and the like are used merely as labels, and do not impose numerical requirements or on the order of construction. Various embodiments of the application may exist in a range of forms; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the application; it is therefore to be understood that the range description has specifically disclosed all possible sub-ranges and individual values within that range. Whenever a numerical range is referred to herein, it is meant to include any reference number (fractional or integer) within the range referred to.

Because metal oxide nanoparticles are easy to agglomerate, the solid cannot be completely dried in the ink preparation process, and a certain wetting state needs to be maintained, otherwise, the dried metal oxide nanoparticles are agglomerated and cannot be dispersed again. Thus, the usual procedure for formulating ink is: adding a precipitator and centrifuging to deposit metal oxide nano particles at the bottom of a centrifugal bottle, pouring supernatant to remove most of the precipitator and original dispersion solvent, adding a new solvent in a state that the metal oxide nano particles are wet, and dispersing to obtain the ink. The ink thus prepared often contains a portion of the residual solvents from the front-end preparation process, including pre-reaction byproducts and impurities, etc. However, the inventors have found through studies that these residual solvents will necessarily have an effect on the consistency and stability of the ink, etc., and ultimately affect the device performance, such as the efficiency, lifetime, emission uniformity, etc., of the light emitting device.

In view of this, as shown in fig. 1, an embodiment of the present application firstly provides a method for preparing a nanocomposite, including the steps of:

s10, providing a first dispersion liquid containing metal oxide nano particles;

s20, adding a polymer containing a polar group into the first dispersion liquid to obtain a second dispersion liquid containing a nanocomposite, wherein the nanocomposite comprises metal oxide nanoparticles and a polymer coating the metal oxide nanoparticles; and

s30, performing freeze drying treatment on the second dispersion liquid to obtain the nanocomposite.

According to the embodiment of the application, the polymer is coated on the surface of the metal oxide nano-particles, and then the freeze-drying treatment is carried out to obtain the solid nano-composite material with the network structure, the freeze-drying treatment can better remove the residual solvent in the front-end preparation process, the polar groups of the polymer are connected with the surface of the metal oxide nano-particles through coordination, the irreversible agglomeration of the metal oxide nano-particles after the freeze-drying treatment can be prevented, and the subsequent redispersion of the metal oxide nano-particles into ink is facilitated.

In some embodiments, the first dispersion liquid includes metal oxide nanoparticles and a first organic solvent, and in the step S10, the providing a first dispersion liquid including metal oxide nanoparticles includes the steps of:

s11, providing a third dispersion liquid containing metal oxide nano particles;

s12, adding a precipitator into the third dispersion liquid, and then, carrying out centrifugal treatment to obtain a precipitate containing metal oxide nano particles; and

s13, adding a first organic solvent into the precipitate, and performing dispersion treatment to obtain the first dispersion liquid containing the metal oxide nano particles.

In some embodiments, in step S11, the third dispersion comprises metal oxide nanoparticles and a solvent having a boiling point of 60 ℃ -150 ℃ (celsius), for example: at least one selected from ethanol, methanol or n-butanol. The metal oxide nanoparticles are selected from zinc oxide nanoparticles undoped or doped with a metal element. Specifically, the metal element may be selected from at least one of magnesium, aluminum, or lithium.

In some embodiments, in step S11, the solids content in the third dispersion is 3% to 30%, in particular 5% to 20%. In this solid content range, the dispersing effect is good. It will be appreciated that the solids content of the third dispersion may be any value from 3% to 30%, for example: 3%, 5%, 7%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 27%, 30%, etc., or other unlisted values in the range of 3% to 30%.

In some embodiments, in step S12, the precipitant has a boiling point between 60 ℃ and 150 ℃, and may be selected from at least one of alkanes, aromatics, esters or ethers, and in particular, may be selected from at least one of cyclohexane, n-heptane, n-octane, and ethyl acetate.

In some embodiments, in step S12, the volume ratio of the precipitant to the third dispersion is 1.5 to 10 times, particularly, 2 to 5 times, and in this volume ratio range, the precipitant has a better precipitation effect. It will be appreciated that the volume ratio of the precipitant to the third dispersion is any value from 1.5 to 10 times, for example: 1.5 times, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, etc., or other non-listed values in the range of 1.5 times to 10 times.

In some embodiments, in step S12, the rotational speed of the centrifugation is 3000 rpm-6000 rpm (revolutions per minute), the time of the centrifugation is 5 min-10 min (minutes), and in this rotational speed and centrifugation time range, the centrifugation is more effective, and it is understood that the rotational speed of the centrifugation may be any value in the range of 3000 rpm-6000 rpm, for example, 3000rpm, 3500rpm, 4000rpm, 4500rpm, 5000rpm, 5500rpm, 6000rpm, etc., or other unlisted values in the range of 3000 rpm-6000 rpm. The centrifugation time may be any value in the range of 5min to 10min, for example, 5min, 6min, 7min, 8min, 9min, 10min, etc., or other non-listed values in the range of 5min to 10 min.

In some embodiments, in step S13, the first organic solvent is selected from tert-butanol, which has the characteristics of higher freezing point, higher vapor pressure and easier sublimation drying, so that when the organic solvent is selected from tert-butanol, the subsequent freeze-drying treatment is more favored, and the effect of improving the device performance is better.

In some embodiments, in step S13, the solids content in the first dispersion is 3% -30%, in particular between 5% -20%, if the solids content is too low, the subsequent freeze-drying phase needs to take longer, if the solids content is too high, it is not advantageous for adequate dispersion. It is understood that the solids content may be any value in the range of 3% to 30%, for example 3%, 5%, 7%, 10%, 13%, 15%, 17%, 20%, 23%, 25%, 27%, 30%, etc., or other unlisted values in the range of 3% to 30%.

In some embodiments, in step S13, the dispersing process may be specifically selected from at least one of stirring, shaking, and ultrasonic dispersion. Specifically, in the dispersing process, the dispersing time is 2-20 min until no macroscopic solid exists, and in the time range, the dispersing effect is better. It is understood that the time of the dispersing treatment may be any value in the range of 2min to 20min, for example, 2min, 5min, 8min, 10min, 12min, 15min, 18min, 20min, etc., or other non-listed values in the range of 2min to 20 min. In order to prevent the first organic solvent from solidifying during the dispersion treatment, the dispersion treatment may be performed at a temperature of 35 ℃ to 50 ℃, if the temperature is too high, irreversible agglomeration of the metal oxide nanoparticles may easily occur, if the temperature is too low, the first organic solvent may be easily solidified, and if the temperature is too high or too low, the dispersion effect may be easily affected, it is understood that the temperature of the dispersion treatment may be any value in the range of 35 ℃ to 50 ℃, for example 35 ℃, 38 ℃,40 ℃, 42 ℃, 45 ℃, 48 ℃,50 ℃, etc., or other unlisted values in the range of 35 ℃ to 50 ℃.

In some embodiments, in step S20, the polymer is added in an amount of 0.1% to 30%, particularly 1% to 10% of the solid content of the metal oxide nanoparticles. Wherein the solid content measurement is indicated by the weight residual percentage at 500 ℃, and the weight loss below 500 ℃ comprises dispersing solvent tertiary butanol, residual precipitator and other solvents, organic ligand on the surface of the metal oxide nano-particles and the like. The addition amount range can ensure that the polymer has better coating effect on the metal oxide nano particles when the nano composite material is formed after freeze drying treatment, so that irreversible agglomeration is prevented, and the performance of the ink is not obviously influenced. It is understood that the polymer is added in any amount ranging from 0.1% to 30% of the metal oxide nanoparticle solids content, such as 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, etc., or other unlisted values ranging from 0.1% to 30%.

In some embodiments, the freeze-drying process in step S30 includes: a prefreezing process and a vacuum drying process. In some embodiments, the temperature of the pre-freezing process is less than-10 ℃, and the pre-freezing process time is greater than 24 hours, in order to achieve a substantially frozen state; in some embodiments, the vacuum drying process is performed at a temperature of less than 10 ℃ and at a pressure of less than 1torr, and the vacuum drying time is between 24 hours and 72 hours to better dry the sample.

In some embodiments, the polymer may be selected from a polymer containing polar groups, such as at least one of polyvinylpyrrolidone (PVP), polyacetylimine, polyethylene glycol, polypropylene glycol, polyvinyl methyl ether, or polyvinyl ethyl ether, which can coordinate the polar groups of the polymer to the surface of the metal oxide nanoparticles, preventing irreversible agglomeration of the metal oxide nanoparticles after the freeze-drying process; on the other hand, it may also help to better disperse the nanocomposite.

Correspondingly, the embodiment of the application also provides a nanocomposite, which comprises metal oxide nano particles and a polymer coating the metal oxide nano particles, wherein the polymer contains polar groups, and the nanocomposite is subjected to freeze drying treatment.

In some embodiments, the nanocomposite is made by the nanocomposite preparation method described above.

In some embodiments, the mass ratio of the polymer to the metal oxide nanoparticles in the nanocomposite is (0.1-30): 100, in particular (0.1 to 30): 100. the mass ratio can enable the polymer to form better coating effect on the metal oxide nano particles, prevent irreversible agglomeration, and simultaneously can not obviously influence the performance of the ink. It is understood that the mass ratio of the polymer to the metal oxide nanoparticles may be (0.1 to 30): any value within the range of 100, for example: 0.1: 100. 1: 100. 5: 100. 10: 100. 15: 100. 20: 100. 25: 100. 30:100, etc., or (0.1 to 30): other values within the 100 range are not listed.

Correspondingly, the embodiment of the application also provides a preparation method of the ink, which comprises the following steps:

s100, preparing the nanocomposite according to the preparation method of the nanocomposite;

s200, mixing the nanocomposite with a second organic solvent to obtain the ink.

The ink provided by the embodiment of the application is prepared by mixing the nanocomposite and the second organic solvent, and the nanocomposite is subjected to freeze drying treatment, so that the residual solvent in the front-end preparation process can be better removed, and the polymer in the nanocomposite can prevent agglomeration phenomenon caused by freeze drying treatment, so that the consistency and stability of the ink can be improved, the preparation of a subsequent electron transport layer is facilitated, and the efficiency, the service life, the light emitting uniformity and other performances of the light emitting device are improved.

In some embodiments, the ink may be prepared by dispersing the nanocomposite and the second organic solvent in at least one selected from stirring, shaking, and ultrasonic dispersion. The dispersing process lasts for about 2-20 min, and the dispersing effect is better in the time range. It is understood that the dispersing time may be any value within the range of 2min to 20min, for example, 2min, 5min, 8min, 10min, 12min, 15min, 18min, 20min, etc., or other non-listed values within the range of 2min to 20min, and the dispersing process may also take some degree of temperature control based on the consideration of better dispersing effect.

In the dispersion process, the added volume of the second organic solvent is determined by the mass of the metal oxide nano particles in the nano composite material obtained by freeze drying, the solid content of the metal oxide in the final ink is kept at 1% -20%, the special solid content is kept at 2% -10%, and the solid content range is favorable for the full dispersion and stability of the metal oxide nano particles. It is understood that the solids content may be maintained at any value in the range of 1% to 20%, for example 1%, 3%, 5%, 7%, 10%, 13%, 15%, 17%, 20%, etc., or other unlisted values in the range of 1% to 20%.

In some embodiments, the ink has a viscosity of 2.5cP to 10cP (centipoise), a surface tension of 28mN/m to 42mN/m, and in particular a viscosity of 3cP to 8cP, and a surface tension of 30mN/m to 35mN/m. In this viscosity and tension range, it is further advantageous for the preparation of the electron transport layer, it is understood that the viscosity of the ink may be any value in the range of 2.5cP to 10cP (centipoise), such as 2.5cP, 3cP, 4cP, 5cP, 6cP, 7cP, 8cP, 9cP, 10cP, or other unlisted values in the range of 2.5cP to 10cP (centipoise), and the surface tension is 28mN/m to 42mN/m, and the ink provided in the embodiments of the present application has a clear and uniform characteristic, and may be removed through a polytetrafluoroethylene filter having a pore size of 0.2 μm or 0.45 μm (micrometers) prior to the preparation of the electron transport layer.

In some embodiments, the second organic solvent is an alcohol or ether alcohol solvent having a boiling point between 100 ℃ and 350 ℃ selected from, but not limited to, at least one of n-heptanol, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, or dipropylene glycol monoethyl ether.

Correspondingly, the application also provides ink, which is prepared by the preparation method of the ink. The ink prepared by the preparation method has the characteristics of less residual solvent and high consistency and stability.

In some embodiments, the ink contains not only metal oxide nanoparticles, a polymer coating the metal oxide nanoparticles, and a second organic solvent, but also uncoated metal oxide nanoparticles and polymer free in the second solvent.

For a better understanding of the present application, the following are specific examples of the preparation method of the ink when the metal oxide nanoparticles and the polymer are zinc oxide nanoparticles and PVP polymer, respectively:

(1) A large amount of precipitant is added into the original dispersion liquid (namely third dispersion liquid) containing zinc oxide nano particles, and the mixture is centrifuged, so that zinc oxide forms solid precipitate and is deposited at the bottom of a centrifuge bottle.

(2) Pouring the centrifuged supernatant and immediately adding t-butanol to the wet precipitated solid to disperse to give a clear dispersion (i.e., a first dispersion) to remove most of the precipitant and original dispersion solvent, and replacing the dispersion solvent with t-butanol to facilitate lyophilization under milder conditions.

(3) And measuring the solid content of zinc oxide in the dispersion liquid by a thermogravimetry method, and adding PVP polymer with a certain proportion of relative solid content into the dispersion liquid to ensure the content of PVP polymer in the ink to be stable, so as to obtain mixed dispersion liquid (namely second dispersion liquid).

(4) And (3) freeze-drying the mixed dispersion liquid to remove all solvents including tertiary butanol in the front-end process, so as to obtain the nanocomposite without residual solvents.

(5) And adding a solvent into the nano composite material obtained by freeze drying, and dispersing to obtain clear ink, wherein the ink can be used for preparing an electron transport layer.

The embodiment of the application also provides a light-emitting device, as shown in fig. 2 and 3, which comprises an anode 2, a light-emitting layer 5, an electron transport layer 6 and a cathode 7 which are sequentially stacked; wherein the electron transport layer 6 is made of the above ink.

The electron transport layer 6 in the light emitting device provided by the embodiment of the application is made of the nanocomposite material prepared by the preparation method, or made of the nanocomposite material, or made of the ink, in particular, the ink is prepared by dispersing the nanocomposite material subjected to freeze-drying treatment and a second organic solvent, and as the nanocomposite material comprises metal oxide nanoparticles and a polymer coating the metal oxide nanoparticles, the polar group of the polymer is connected with the surfaces of the metal oxide nanoparticles through coordination, so that irreversible agglomeration of the metal oxide nanoparticles after freeze-drying treatment can be prevented, and subsequent redispersion is facilitated; and the freeze drying treatment can better remove the residual solvent in the front-end preparation process. Therefore, the ink has the characteristics of less residual solvent and good dispersibility, has better consistency and stability, and can improve the performances of the light-emitting device, such as efficiency, service life, light-emitting uniformity and the like.

In the embodiment of the present application, the method of depositing the electron transport layer 6 on the optoelectronic device may be implemented by a solution method, wherein the solution method includes a spin coating method, a printing method, an inkjet printing method, a doctor blading method, a printing method, a dip-coating method, a dipping method, a spraying method, a roll coating method, a casting method, a slit coating method, and a bar coating method.

For example: in one embodiment of the present application, the electron transport layer 6 is prepared by an inkjet printing method in a solution method, and the inkjet printing method mainly uses an inkjet printing apparatus to prepare the electron transport layer. The ink is filtered and is put into an ink box of the ink-jet printing equipment, after parameters such as printing voltage, air pressure, waveform and the like are regulated, the alignment mark drops the ink into a preset area, and an electron transmission layer is formed. In the application, the electron transport layer 6 is prepared by an ink-jet printing method, and the method can greatly reduce the production cost and is used for mass production.

For another example: in another embodiment of the present application, the electron transport layer 6 is prepared by spin coating in a solution method, in the present application, the preparation of the electron transport layer by spin coating requires preparing ink, placing the wafer to be spin coated on a spin coater, dripping the prepared ink onto the spin coater, spin coating at a preset rotation speed, and completing the preparation of the electron transport layer after heat treatment. The spin coating method has the characteristics of mild process conditions, simple operation, energy conservation, environmental protection and the like.

In some specific embodiments, the light emitting device is a quantum dot light emitting device (QLED).

The light emitting device according to the embodiment of the application may have a positive type structure or an inverse type structure. In the light emitting device, the cathode 7 or the anode 2 side remote from the light emitting layer 5 further comprises a substrate 1, the anode 2 being arranged on the substrate 1 in a positive configuration and the cathode 7 being arranged on the substrate 1 in an negative configuration. Hole-transporting layers 4, hole-injecting layers 3, and other hole-functional layers may be further provided between the anode 2 and the light-emitting layer 5. For example:

fig. 2 shows a schematic diagram of a positive structure of the light emitting device according to the embodiment of the present application, as shown in fig. 2, where the device of the positive structure includes a substrate 1, an anode 2 disposed on a surface of the substrate 1, a hole injection layer 3 disposed on a surface of the anode 2, a hole transport layer 4 disposed on a surface of the hole injection layer 3, a light emitting layer 5 disposed on a surface of the hole transport layer 4, an electron transport layer 6 disposed on a surface of the light emitting layer 5, and a cathode 7 disposed on a surface of the electron transport layer 6, and the material of the electron transport layer 6 is made of the ink.

Fig. 3 shows a schematic diagram of an inversion structure of a light emitting device according to an embodiment of the present application, as shown in fig. 3, the inversion structure light emitting device includes a substrate 1, a cathode 7 disposed on a surface of the substrate 1, an electron transport layer 6 disposed on a surface of the cathode 7, a light emitting layer 5 disposed on a surface of the electron transport layer 6, a hole transport layer 4 disposed on a surface of the light emitting layer 5, a hole injection layer 3 disposed on a surface of the hole transport layer 4, and an anode 2, wherein the electron transport layer 6 is made of the above ink.

In embodiments of the present application, the materials of the functional layers may be the following materials, for example:

the substrate 1 may be a rigid substrate or a flexible substrate. Specific materials may include at least one of glass, silicon wafer, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyethersulfone.

The anode 2 is selected from, but not limited to, at least one of indium doped tin oxide, fluorine doped tin oxide, tin doped zinc oxide, or indium doped zinc oxide.

The material of the hole injection layer 3 is selected from PEDOT: PSS, but also other materials with good hole injection properties, such as NiO, moO ₃ 、WO ₃ Or V ₂ O ₅ At least one of them.

The hole transport layer 4 material is selected from, but not limited to, at least one of Poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine) (TFB), polyvinylcarbazole (PVK), poly (N, N '-bis (4-butylphenyl) -N, N' -bis (phenyl) benzidine) (Poly-TPD), poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-Phenylenediamine) (PFB), 4',4 "-tris (carbazole-9-yl) triphenylamine (TCTA), 4' -bis (9-Carbazole) Biphenyl (CBP), N '-diphenyl-N, N' -bis (3-methylphenyl) -1,1 '-biphenyl-4, 4' -diamine (TPD), N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine (NPB), or other high performance hole transport materials.

The material of the light emitting layer 5 includes quantum dots selected from, but not limited to, at least one of group II-VI compounds, group III-V compounds, and group I-III-VI compounds, the group II-VI compounds being selected from CdSe, cdS, cdTe, znSe, znS, cdTe, znTe, cdZnS, cdZnSe, cdZnTe, znSeS, znSeTe, znTeS, cdSeS, cdSeTe, cdTeS; cdZnSeS, cdZnSeTe or CdZnSTe; the III-V compound is at least one selected from InP, inAs, gaP, gaAs, gaSb, alN, alP, inAsP, inNP, inNSb, gaAlNP or InAlNP; the I-III-VI compound is selected from CuInS ₂ 、CuInSe ₂ Or AgInS ₂ At least one of them.

The material of the cathode 7 is selected from, but not limited to Al, cu, mo, au, ag or MoO ₃ At least one of them.

The application is illustrated in detail by the following examples.

Examples

The configuration method of the ink provided in this embodiment is as follows:

first, a raw dispersion containing zinc oxide, specifically, an ethanol dispersion having a solid content of 10%, was provided, 40mL of ethyl acetate was added to 10mL of the raw dispersion to precipitate, and the mixture was centrifuged at 4000rpm for 5 minutes. The supernatant was poured and 10mL of t-butanol preheated to 40 ℃ was immediately added to the precipitated solid in the wet state, and the solid was completely dispersed by sonication for 3min at a temperature between 35 and 45 ℃ to give a clear dispersion. The zinc oxide solids content of the above dispersion was measured by thermogravimetry. To 4mL of the above dispersion was added a PVP polymer having a relative solid content ratio of 5% (PVP polymer molecular weight 10k, PVP polymer was pre-dissolved in t-butanol to form a solution having a solid content of 5%, and this was mixed with the above zinc oxide dispersion at a predetermined ratio). Storing the mixed dispersion liquid for 24 hours at the temperature of minus 20 ℃ for prefreezing, transferring to a vacuum drying oven at the temperature of minus 10 ℃ for vacuumizing to 0.1torr, and gradually heating to 10 ℃ within 48 hours to obtain the nanocomposite without residual solvent. And adding a preset volume of diethylene glycol monomethyl ether as an ink solvent into the nano composite material obtained by freeze drying, and oscillating for 5min at room temperature to disperse the material so as to obtain clear ink with zinc oxide solid content of about 3%.

Five batches of zinc oxide INK were prepared according to the above procedure, numbered INK1, INK2, INK3, INK4, INK5, respectively.

Comparative example 1

The ink provided in this comparative example was prepared as follows:

first, a raw dispersion containing zinc oxide, specifically, an ethanol dispersion having a solid content of 10%, was provided, 40mL of ethyl acetate was added to 10mL of the raw dispersion to precipitate, and the mixture was centrifuged at 4000rpm for 5 minutes. The supernatant was poured and 10mL of t-butanol preheated to 40 ℃ was immediately added to the precipitated solid in the wet state, and the solid was completely dispersed by sonication for 3min at a temperature between 35 and 45 ℃ to give a clear dispersion. The zinc oxide solids content of the above dispersion was measured by thermogravimetry. 4mL of the mixed dispersion is stored for 24 hours at the temperature of minus 20 ℃ for prefreezing, then is transferred into a vacuum drying oven at the temperature of minus 10 ℃ for vacuumizing to 0.1torr, and is gradually heated to 10 ℃ within 48 hours, so that the zinc oxide nanoparticle solid without residual solvent is obtained after complete drying. And adding a preset volume of diethylene glycol monomethyl ether as an ink solvent into the zinc oxide solid obtained by freeze drying, vibrating for 20min at room temperature, and only partially dispersing the solid, so that white turbidity can be observed.

The difference between this comparative example and the above examples is mainly that the step of adding PVP polymer was omitted, and the lyophilized zinc oxide solid could not be sufficiently dispersed to obtain clear ink, thus demonstrating that the addition of PVP polymer to Xiang Shu butanol dispersion is a key to ensure that clear ink can be obtained finally.

Comparative example 2

The ink provided in this comparative example was prepared as follows:

first, a raw dispersion containing zinc oxide, specifically, an ethanol dispersion having a solid content of 10%, was provided, and 20mL of ethyl acetate was added to 5mL of the raw dispersion to precipitate, and the mixture was centrifuged at 4000rpm for 5 minutes. The supernatant was poured and immediately added to the precipitated solid in the wet state with 5mL of ink solvent and shaken for 5min to disperse it to give clear ink. And measuring the solid content of zinc oxide in the ink by a thermogravimetry method, and adding diethylene glycol monomethyl ether with a preset volume again to serve as an ink solvent for dilution to obtain the final ink with the solid content of about 3%.

The comparative example uses a conventional zinc oxide ink formulation method, and differs from the above examples mainly in that the steps of adding PVP polymer and freeze-drying are omitted, and the ink contains a part of other solvents remained in the front-end flow, including the pre-dispersion solvent ethanol, the precipitant ethyl acetate, etc. Five batches of zinc oxide ink were prepared according to the above procedure, numbered REF1, REF2, REF3, REF4, REF5, respectively.

Verification example 1

The inks in the above examples and comparative example 2 were subjected to DLS particle size test and repeated several times over several days to observe the particle size change. The results are shown in Table 1:

TABLE 1

From the above data, it can be seen that the ink DLS particle size and viscosity in the examples achieve good reproducibility from batch to batch and during ink storage. For example: particle diameters of INK 1to INK5 are in the range of 7.4-8.2 and viscosity is in the range of 3.4-3.5 in the first day; the fifth day particle size is in the range of 7.5-8.3 and the viscosity is in the range of 3.4-3.5, which benefits from the full removal of the influence of residual precipitants and other solvents, resulting in better ink stability. Whereas the ink in comparative example 2 was more fluctuating between batches and had a tendency to gradually increase in particle size and viscosity as the ink was stored. For example: particle diameters of REF 1to REF5 are in the range of 7.7-14.0 and viscosities are in the range of 2.2-2.6 on the first day; the fifth day particle size was in the range of 10.2 to 19.3 and the viscosity was in the range of 2.3 to 2.8, indicating that comparative example 2 had a problem in storage stability.

Verification example 2

After storing each of the inks in the above examples and comparative example 2 for one month, QLED light emitting devices were separately prepared, and the light emitting efficiency differences thereof were compared. The QLED device structure comprises an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer and a cathode which are sequentially stacked, wherein the anode is made of ITO (indium tin oxide) and has the thickness of 50nm; the hole injection layer is made of PEDOT PSS with the thickness of 70nm; the hole transport layer is made of TFB and has a thickness of 35nm; the luminescent layer is made of CdSe quantum dots with the thickness of 20nm; the electron transport layer was made of ZnO and had a thickness of 55nm, and was prepared from the inks of the above examples and comparative example 2; the cathode material is Ag, and the thickness is 100nm. The device results are shown in fig. 4:

as can be seen from fig. 4, the QLED device prepared using the ink of the example was significantly more efficient than the ink of the comparative example, with better result reproducibility. For example, the efficiency of the devices made of INK 1to INK5 in the examples was 8% or more, whereas the efficiency of the devices made of REF 1to REF5 in the comparative examples was only 6% at the most, thereby indicating that the INK in the examples prevented the influence of the residual solvent on the properties and storage stability of the INK, and had an effect of improving the device performance.

The above description is provided for the details of a nanocomposite, a preparation method, ink, a preparation method and a light-emitting device, and specific examples are applied to illustrate the principles and embodiments of the present application, and the above description is only for aiding in understanding the method and core idea of the present application; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in light of the ideas of the present application, the present description should not be construed as limiting the present application.

Claims

1. A method of preparing a nanocomposite comprising the steps of:

providing a first dispersion comprising metal oxide nanoparticles;

2. The method of preparing according to claim 1, wherein providing the first dispersion comprising metal oxide nanoparticles comprises:

providing a third dispersion comprising metal oxide nanoparticles;

3. The method according to claim 2, wherein,

the solvent in the third dispersion liquid is at least one selected from ethanol, methanol or n-butanol; and/or

The solid content in the third dispersion liquid is 3% -30%; and/or

The first organic solvent is selected from tertiary butanol; and/or

The time of the dispersion treatment is 2-20 min; and/or

The temperature of the dispersion treatment is 35-50 ℃.

4. The method of claim 1, wherein the polymer is added in an amount of 0.1% to 30% of the solid content of the metal oxide nanoparticles.

5. The method according to claim 1, wherein the freeze-drying process comprises a prefreezing process and a vacuum drying process, the prefreezing process being carried out at a temperature of less than-10 ℃ for a period of more than 24 hours; and/or the temperature of the vacuum drying process is lower than 10 ℃, the air pressure is lower than 1torr, and the vacuum drying time is 24-72 h.

6. The method according to claim 1, wherein the polymer is at least one selected from polyvinylpyrrolidone, polyacetyl imine, polyethylene glycol, polypropylene glycol, polyvinyl methyl ether and polyvinyl ethyl ether.

7. The method of claim 1, wherein the metal oxide nanoparticles are selected from zinc oxide nanoparticles undoped or doped with a metal element selected from at least one of magnesium, aluminum, or lithium.

8. A nanocomposite material, characterized in that the nanocomposite material comprises metal oxide nanoparticles, and a polymer coating the metal oxide nanoparticles, the polymer containing polar groups, the nanocomposite material being subjected to a freeze-drying treatment.

9. Nanocomposite according to claim 8, characterized in that it is produced by the production method according to any one of claims 1to 7.

10. A method of preparing ink, comprising: preparing the nanocomposite according to the preparation method of any one of claims 1to 7;

and mixing the nanocomposite with a second organic solvent to obtain the ink.

11. The method according to claim 10, wherein the second organic solvent is selected from alcohol or ether alcohol solvents having a boiling point between 100 ℃ and 350 ℃.

12. The method according to claim 10, wherein the second organic solvent is at least one selected from n-heptanol, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, and dipropylene glycol monoethyl ether.

13. An ink, characterized in that the ink is produced by the production method according to any one of claims 10 to 12.

14. A light-emitting device is characterized by comprising an anode, a light-emitting layer, an electron transport layer and a cathode which are sequentially stacked; wherein the electron transport layer is made of the nanocomposite material produced by the production method according to any one of claims 1to 7, or of the nanocomposite material according to any one of claims 8 to 9, or of the ink according to claim 13.

15. The light-emitting device according to claim 14, wherein a material of the anode is selected from at least one of indium-doped tin oxide, fluorine-doped tin oxide, tin-doped zinc oxide, or indium-doped zinc oxide; and/or the number of the groups of groups,

the material of the light emitting layer comprises quantum dots, wherein the quantum dots are selected from at least one of II-VI compounds, III-V compounds and I-III-VI compounds, and the II-VI compounds are selected from CdSe, cdS, cdTe, znSe, znS, cdTe, znTe, cdZnS, cdZnSe, cdZnTe, znSeS, znSeTe, znTeS, cdSeS, cdSeTe, cdTeS; cdZnSeS, cdZnSeTe or CdZnSTe; the III-V compound is at least one selected from InP, inAs, gaP, gaAs, gaSb, alN, alP, inAsP, inNP, inNSb, gaAlNP or InAlNP; the I-III-VI compound is selected from CuInS ₂ 、CuInSe ₂ Or AgInS ₂ At least one of (a) and (b); and/or the number of the groups of groups,