CN116113256A - Precursor material of electron injection layer, preparation method and application thereof - Google Patents
Precursor material of electron injection layer, preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a precursor material of an electron injection layer, a preparation method and application thereof. The precursor material comprises metal oxide nanoparticles and a surface modifier modified on the surfaces of the metal oxide nanoparticles; wherein the surface modifier is capable of reacting upon exposure to light of a specific wavelength. According to the precursor material provided by the invention, the surface of the metal oxide nanoparticle is provided with the modification molecule with the photosensitive polarity conversion function, so that the polarity of the surface is changed when the metal oxide nanoparticle is irradiated, and the dissolution characteristic of the metal oxide nanoparticle is changed, so that the irradiated part is not easy to be cleaned and removed by the solvent with the original polarity, and the direct photoetching is realized; direct photo-forming of the metal oxide nanoparticles is realized, the use of photoresist is avoided, and the influence of the photoresist on the electrical properties of the metal oxide nanoparticles is reduced while the process steps are reduced.
Description
Technical Field
The invention relates to the technical field of semiconductor manufacturing, in particular to a precursor material of an electron injection layer, a preparation method and application thereof.
Background
The quantum dot light emitting diode (QLED) has the characteristics of simple structure, high luminous efficiency, wide color gamut and flexibility. The structure mainly comprises a Hole Injection Layer (HIL), a Hole Transport Layer (HTL), a quantum dot light emitting layer and an Electron Injection Layer (EIL), as shown in figure 1. Currently, the preparation of high-resolution QLED devices is a trend in the future display field.
The photoetching technology is a technology for effectively obtaining high-resolution patterns, and the direct photoetching method without photoresist derived from the technology has good effects while simplifying the technology. High resolution pixelation techniques for quantum dots have achieved some research results, but there are few reports on direct photolithographic techniques for other functional layer materials.
As shown in fig. 2, in the prior art, the conventional photolithography process is complicated in steps, it is difficult to obtain a high-precision pattern of an electron injection layer of a QLED device efficiently, and the use of photoresist has a great influence on the surface electrical properties thereof.
In a QLED device, due to the nature of the material itself, the metal oxide most commonly used as an electron injection layer is difficult to realize direct photo-forming, and even if direct photo-forming is realized, the metal oxide nanoparticle has a significant negative effect on the electrical performance due to the requirement of a higher annealing temperature, so that the metal oxide nanoparticle cannot be lost.
Therefore, the development of the electron injection layer direct lithography technology which is suitable for the QLED device and does not cause the loss of electrical property has important application value.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a precursor material of an electron injection layer, a preparation method and application thereof.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention comprises the following steps:
in a first aspect, the present invention provides a precursor material for an electron injection layer, comprising metal oxide nanoparticles and a surface modifier modified on the surface of the metal oxide nanoparticles;
wherein the polarity of the surface modifier is capable of being changed upon exposure to light.
In a second aspect, the present invention also provides a method for preparing a precursor material of an electron injection layer, including:
providing metal oxide nanoparticles;
modifying a surface modifier on the surface of the metal oxide nanoparticles by an ion exchange method;
wherein the polarity of the surface modifier is capable of being changed upon exposure to light.
In a third aspect, the present invention also provides a method for forming an electron injection layer, including:
providing a coating liquid in which the precursor material is dispersed;
coating the coating liquid into a film to obtain an electron injection layer precursor;
patterning illumination of the electron injection layer precursor;
and cleaning and removing the non-irradiated part of the electron injection layer precursor by using a cleaning agent with the same polarity as the solvent in the coating liquid to form a patterned electron injection layer.
In a fourth aspect, the present invention also provides a light emitting diode device, including a hole injection layer, a hole transport layer, a semiconductor functional layer, and an electron injection layer, which are sequentially stacked; the electron injection layer is formed by adopting the method for forming the electron injection layer.
Based on the technical scheme, compared with the prior art, the invention has the beneficial effects that:
according to the precursor material provided by the invention, the surface of the metal oxide nano-particle is provided with the modification molecule with the photosensitive polarity conversion function, so that the polarity of the surface of the metal oxide nano-particle is changed when the metal oxide nano-particle is irradiated, and the dissolution characteristic of the metal oxide nano-particle is changed, so that the irradiated part of the metal oxide nano-particle is not easy to be cleaned and removed by an original polar solvent, and the direct photoetching of an electron injection layer is realized;
the technical scheme provided by the invention realizes the direct photo-forming of the metal oxide nano particles, avoids the use of photoresist, reduces the process steps and simultaneously reduces the influence of the photoresist on the electrical properties of the metal oxide nano particles.
The invention is helpful to realize the manufacture of the high-resolution QLED display device through the research and development of the electron injection layer material pixelation technology.
The above description is only an overview of the technical solutions of the present invention, and in order to enable those skilled in the art to more clearly understand the technical means of the present application, the present invention may be implemented according to the content of the specification, the following description is given of the preferred embodiments of the present invention with reference to the accompanying drawings.
Drawings
Fig. 1 is a schematic structural diagram of a quantum dot light emitting diode device provided in the background of the invention;
FIG. 2 is a schematic diagram of a photoresist process for preparing an electron injection layer according to an exemplary comparative example of the present invention;
FIG. 3 is a schematic diagram of a process for preparing an electron injection layer by direct photolithography according to an exemplary embodiment of the present invention;
FIG. 4 is a photomicrograph of the morphology of an electron injection layer prepared by direct photolithography in accordance with an exemplary embodiment of the present invention;
fig. 5 is a schematic structural diagram of a quantum dot light emitting diode device according to another exemplary embodiment of the present invention.
Detailed Description
In the prior art, two methods for preparing an electron injection layer of a QLED (quantum dot light-emitting diode) device are mainly used, one is a photoresist method and the other is a photosensitive precursor (crosslinking method).
For photoresist processes, for example, metal oxide nanoparticles can be mixed with commercial photoresists and then subjected to uv exposure to achieve direct patterning. But this approach can lead to a significant decrease in the performance of the electron injection layer employing the metal oxide nanoparticles.
For the photosensitive precursor adding scheme, a sol-gel mode can be adopted to prepare a metal oxide nanoparticle precursor, for example, a photo-crosslinkable precursor (zinc dimethacrylate, zinc acrylate and the like) is generated, a patterning precursor substance is obtained through ultraviolet exposure, and then the metal oxide nanoparticle is obtained through high-temperature annealing. Due to the high temperatures required during annealing, this approach can have adverse effects on the substrate, other functional layers, or quantum dot layers.
The convenience of the method itself in the prior art and the performance of the hole transport layer to be produced are all to be improved.
In view of the shortcomings in the prior art, the inventor of the present invention has long studied and practiced in a large number of ways to propose the technical scheme of the present invention. The technical scheme, the implementation process, the principle and the like are further explained as follows.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced otherwise than as described herein, and therefore the scope of the present invention is not limited to the specific embodiments disclosed below.
One aspect of the embodiment of the invention provides a precursor material of an electron injection layer, which comprises metal oxide nanoparticles and a surface modifier modified on the surfaces of the metal oxide nanoparticles; wherein the polarity of the surface modifying agent as a surface ligand can be changed upon exposure to light.
According to the precursor material provided by the embodiment, the modification molecules with the photosensitive polarity conversion function are arranged on the surfaces of the metal oxide nanoparticles, so that the polarities of the surfaces of the metal oxide nanoparticles are changed when the metal oxide nanoparticles are irradiated by light, and/or adjacent nanoparticles are connected, so that the dissolution characteristics of the metal oxide nanoparticles are changed, the metal oxide nanoparticles which are irradiated by light are not easy to be cleaned and removed by solvents with original polarities, and the direct photoetching of an electron injection layer is realized.
In some embodiments, the surface modifying agent is further capable of coordinating with adjacent metal oxide nanoparticles upon exposure to light; part of the surface modifying agent has a dual photoactive functional group.
The specific actions of coordination and 'difunctional' are used as a surface ligand and a photosensitizer of the metal oxide nanoparticles, and anions and cations of part of photosensitive molecules have photosensitive properties.
In some embodiments, the surface modifier may preferably comprise any one or a combination of two or more of 1,2,3, 4-triazole-5-thioammonium salt, 2- (4-methyloxyphenyl) -4, 6-bis (trichloromethyl) -1,3, 5-triazine, 2-diazonium-1-naphthol-4-sulfonic acid, 1-diazonium-2 naphthol-4-sulfonic acid, diphenyliodonium fluoroborate, ammonium dithiocarbamate, 1, 2-naphthoquinone diazide-4-sulfonyl chloride, 2-phenyl-2- (5- ((o-oxy) imino) thiophene-2-methylene) -acetonitrile, butyldithiocarbamic acid, oxalic acid dithioammonium, N-hydroxynaphthalimide trifluoroester, (4-methylthio) triflate, triphenylthiotrifluoromethane sulfonate, diphenyliodotrifluoromethane sulfonate, and the like, but the selection ranges of the above listed compounds are only exemplary choices in some preferred embodiments, and any one of skill in the art can achieve the same functional advantages based on the same principles as those of the prior art.
In some embodiments, the metal oxide particles comprise any one or a combination of two or more of zinc oxide, magnesium zinc oxide, tin oxide, titanium oxide.
In some embodiments, the mass of the surface modifier is 1-15wt% of the mass of the metal oxide nanoparticles.
In some embodiments, the metal oxide nanoparticles have a particle size of 3-10nm.
In another aspect of the embodiment of the present invention, a method for preparing a precursor material of an electron injection layer is provided, including the following steps:
metal oxide nanoparticles are provided.
And modifying the surface modifier on the surface of the metal oxide nano particles by utilizing an ion exchange method.
Wherein the polarity of the surface modifier is capable of being changed upon exposure to light.
In some embodiments, the preparation method may specifically include the following steps:
the metal oxide nanoparticles are formulated as a precursor dispersion.
And uniformly mixing the precursor dispersion liquid and the surface modifier, and generating the precursor material of the electron injection layer by ion exchange.
The precursor material may be prepared by itself at the time of application, for example, in the following examples, before coating, the metal oxide nanoparticles may be directly modified in a dispersion to form a coating solution containing the precursor material, and the precursor material may be extracted from the coating solution, or may be used as a commodity or a semi-finished product, and may be reconfigured into a dispersion to be coated at the time of coating.
The key technical means of the invention is that the specific modification of the surface of the metal oxide nano-particles, no matter what way is adopted, no matter what way is self-made or commercial or entrusted processing, is within the protection scope of the invention as long as the principle and the key technical means are utilized.
Referring to fig. 3, in another aspect of the embodiment of the present invention, there is provided a method for forming an electron injection layer, including the steps of:
providing a coating liquid for dispersing the precursor material provided in any one of the above embodiments;
coating the coating liquid into a film to obtain an electron injection layer precursor;
patterning illumination of the electron injection layer precursor;
and cleaning and removing the non-irradiated part of the electron injection layer precursor by using a cleaning agent with the same polarity as the solvent in the coating liquid to form a patterned electron injection layer.
In some embodiments, the preparation method of the coating liquid specifically may include the following steps:
dispersing metal oxide nanoparticles in a solvent to form a dispersion;
and adding a surface modifier to the dispersion liquid to obtain the coating liquid.
In some embodiments, the surface modifier is present in the coating solution in an amount of 1 to 15wt%.
In some embodiments, the mass concentration of metal oxide nanoparticles in the coating solution is 10-60mg/mL, preferably 25-35mg/mL. Generally, a surface initial ligand mainly comprising hydroxyl (-OH) is formed in the synthesis process, so that the surface initial ligand can be well dissolved in common ethanol, DMF or NMF solution, and then subsequent ligand replacement is performed to obtain a required coordination structure.
More specifically, the exposure wavelength of the patterned light can be adaptively adjusted according to the characteristics of the surface modifier of the photosensitive molecule, preferably, the ultraviolet light with the wavelength of 172nm-405 nm.
As some typical application examples of the above technical solution, a preparation process of an electron injection layer may be as follows:
when preparing the metal oxide material precursor of the electron injection layer, an ion exchange method is adopted to introduce photosensitive modified substances, especially small molecules capable of forming difunctional groups, are used as ligands, have photosensitive properties, namely provide stability of nanoparticle colloid/solution, and can be subjected to chemical transformation under the excitation of specific photon energy. So that it can be used as surface modifier of metal oxide nano granules. Such as 1,2,3, 4-triazole-5-thioammonium salt (TTT), 2- (4-methyloxyphenyl) -4, 6-bis (trichloromethyl) -1,3, 5-triazine (MBT), 2-diazonium-1-naphthol-4-sulfonic acid (DNS), 1-diazonium-2-naphthol-4-sulfonic acid, diphenyliodonium fluoroborate, ammonium dithiocarbamate, 1, 2-naphthoquinone diazide-4-sulfonyl chloride, 2-phenyl-2- (5- ((o-oxy) imino) thiophene-2-methylene) -acetonitrile, butyldithiocarbamic acid, ammonium oxalate, N-hydroxynaphthalimide trifluoroester, (4-methylthio) methyl phenyl thio trifluoroacid salt, triphenylthio trifluoromethanesulfonate, diphenyliodotrifluoromethanesulfonate, and the like. The introduced small molecular modifier has photosensitivity, can be decomposed in a specific wave band or can generate related chemical reaction, and finally forms molecular modification opposite to the original polarity on the surface of the metal oxide nano particles to change the solubility, thereby realizing the direct photoetching formation of the metal oxide through development.
The mixed dispersion is formed into a film by spin coating, blade coating or dip coating, and then covered by a mask and exposed to ultraviolet light followed by washing with an original polar solvent and development to obtain the designed pattern.
In the above technical solution, the most critical technical means is that the preferred small molecule modifier is a small molecule with photosensitivity, and can be used as a surface ligand of the metal nanoparticle at the same time, and then the metal oxide with the designed pattern formed by the direct photolithography technique is used as an electron injection material.
Another aspect of the embodiment of the present invention further provides a light emitting diode device, including a first electrode, a hole injection layer, a hole transport layer, a semiconductor functional layer, an electron injection layer, and a second electrode that are sequentially stacked; the electron injection layer is formed by adopting the forming method provided by any one of the embodiments.
In the device, all layers except the electron injection layer can be manufactured by adopting a manufacturing method in the prior art, and the device has corresponding functions. The technical scheme provided by the invention still focuses on direct photoetching forming of the electron injection layer.
The technical scheme of the invention is further described in detail below through a plurality of embodiments and with reference to the accompanying drawings. However, the examples are chosen to illustrate the invention only and are not intended to limit the scope of the invention.
Example 1
This example illustrates a QLED device manufacturing process including a process of manufacturing an electron injection layer precursor material (a process of manufacturing a coating liquid described below, that is, including a process of forming a precursor material) and a process of forming an electron injection layer.
In the preparation of the device, the preparation process of the patterned electron injection layer is as follows:
preparation of the coating liquid: a ZnO ethanol dispersion with a mass concentration of 30mg/ml was prepared, wherein the average particle diameter of ZnO nanoparticles was about 5 nm. And then 1.5wt% of 2- (4-methyloxyphenyl) -4, 6-bis (trichloromethyl) -1,3, 5-triazine (MBT) photosensitizer was added to the above solution and mixed uniformly.
Coating and forming: and spin-coating the coating liquid and drying to form a precursor film of 30 nm.
And (3) exposure and development: exposing with 365nm ultraviolet light at a dose of 150mJ/cm 2 Finally, washing and developing by absolute ethyl alcohol to obtain corresponding patterns, and forming a patterned electron injection layer as shown in fig. 4.
The device structure manufactured in this embodiment is as shown in fig. 1, regarding the rest of the layers of the device in this embodiment, the substrate is a conductive glass substrate of indium tin oxide, and the hole injection layer is a PEDOT: PSS with thickness of 30nm; the hole transmission layer adopts poly [ (9, 9-dioctylfluorene-2, 7-diyl) -co- (4, 4' - (N- (4-sec-butylphenyl) diphenylamine) ] (TFB), the thickness is about 15nm, the thickness of the light-emitting layer is 20nm, the material is CdSe-based quantum dots, the material is 20mg/ml, the thickness of the electron injection layer is 30nm, the material is ZnO, and the top electrode adopts a silver/aluminum composite electrode.
Fig. 4 shows that the patterned electron injection layer prepared in this embodiment has a relatively regular morphology, the resolution is 2 μm, which indicates that the metal oxide nanoparticles can realize patterning/pixelation by a direct photolithography technique, and the quantum dot LED device prepared in this embodiment has an external quantum efficiency of 11%, and the external quantum efficiency can still be kept at 11% after being placed in an air environment for a week. .
Example 2
This example illustrates a QLED device fabrication process including an electron injection layer precursor material fabrication process and an electron injection layer formation process, which are substantially the same as example 1, with the main difference being the fabrication of the electron injection layer.
In the preparation of the device, the preparation process of the patterned electron injection layer is as follows:
preparation of the coating liquid: zn with mass concentration of 30mg/ml is configured 90 Mg 10 O-ethanol dispersion, wherein Zn 90 Mg 10 The average particle size of the O nanoparticles is about 5 nm. And then 2wt% of (4-methylthio) triflate photo-ligand was added to the above solution and mixed uniformly.
Coating and forming: and spin-coating the coating liquid and drying to form a precursor film with the thickness of 30 nm.
And (3) exposure and development: then the mask plate with preset pattern is passed through under the UV light with 254nm wavelength, and its exposure dose is 120mJ/cm 2 Finally, washing and developing by absolute ethyl alcohol to obtain corresponding patterns, and forming a patterned electron injection layer as shown in fig. 4.
The patterned electron injection layer prepared in this embodiment is still similar to embodiment 1, and has a relatively regular morphology, and the external quantum efficiency of the QLED device prepared in this embodiment is 15%, and the external quantum efficiency can still be kept at 15% after the QLED device is placed in an air environment for one week.
Example 3
This example illustrates a QLED device fabrication process including an electron injection layer precursor material fabrication process and an electron injection layer formation process, which are substantially the same as example 1, with the main difference being the fabrication of the electron injection layer.
In the preparation of the device, the preparation process of the patterned electron injection layer is as follows:
preparation of the coating liquid: a ZnO ethanol dispersion with a mass concentration of 25mg/ml was prepared, wherein the average particle diameter of ZnO nanoparticles was about 5 nm. And then 1.5wt% of 2-diazonium-1-naphthol-4-sulfonic acid (DNS) photosensitizer was added to the above solution and mixed well.
Coating and forming: and spin-coating the coating liquid and drying to form a precursor film with the thickness of 25 nm.
And (3) exposure and development: exposing with 365nm ultraviolet light at a dose of 100mJ/cm 2 Finally, washing and developing the mixture by absolute ethyl alcohol to obtainA corresponding pattern, as shown in fig. 4, forms a patterned electron injection layer.
The patterned electron injection layer prepared in this example is still similar to example 1, has a relatively regular morphology, and the external quantum efficiency of the QLED device prepared in this example is 10%, and the external quantum efficiency can be maintained at 8% after being placed in an air environment for one week
Example 4
This example illustrates a QLED device manufacturing process including a process of manufacturing an electron injection layer precursor material (a process of manufacturing a coating liquid described below, that is, including a process of forming a precursor material) and a process of forming an electron injection layer.
In the preparation of the device, the preparation process of the patterned electron injection layer is as follows:
preparation of the coating liquid: preparing SnO with mass concentration of 40mg/ml 2 Ethanol dispersion, wherein SnO 2 The average particle size of the nanoparticles is about 5 nm. And then 2wt% of (4-methylthio) triflate photo-ligand was added to the above solution and mixed uniformly.
Coating and forming: and spin-coating the coating liquid and drying to form a precursor film of 35 nm.
And (3) exposure and development: exposing with 254nm ultraviolet light at a dose of 120mJ/cm 2 Finally, washing and developing the substrate by absolute ethyl alcohol to obtain corresponding patterns, and forming a patterned electron injection layer as shown in figure 4
The device structure manufactured in this embodiment is as shown in fig. 1, regarding the rest of the layers of the device in this embodiment, the substrate is a conductive glass substrate of indium tin oxide, and the hole transport layer is a PEDOT: PSS with thickness of 30nm; the hole transport layer adopts poly [ (9, 9-dioctylfluorene-2, 7-diyl) -co- (4, 4' - (N- (4-sec-butylphenyl) diphenylamine)](TFB) having a thickness of about 15nm; the thickness of the luminescent layer is 20nm, and the material is CdSe-based quantum dots, 20mg/ml; the thickness of the electron injection layer is 30nm, and the material is SnO 2 The method comprises the steps of carrying out a first treatment on the surface of the The top electrode adopts a silver/aluminum composite electrode.
The patterned electron injection layer prepared in this embodiment is still similar to embodiment 1, and has a relatively regular morphology, and the external quantum efficiency of the QLED device prepared in this embodiment is 14%, and the external quantum efficiency is still kept at 14% after the QLED device is placed in an air environment for one week.
Example 5
This example illustrates a QLED device manufacturing process including a process of manufacturing a patterned electron injection layer precursor material (a process of manufacturing a coating liquid described below, that is, including a process of forming a precursor material) and a process of forming an electron injection layer.
In the preparation of the device, the preparation process of the patterned electron injection layer is as follows:
preparation of the coating liquid: preparing TiO with mass concentration of 35mg/ml 2 Toluene dispersion wherein TiO 2 The average particle size of the nanoparticles is about 5 nm. And then 2wt% of (4-methylthio) triflate photo-ligand was added to the above solution and mixed uniformly.
Coating and forming: and spin-coating the coating liquid and drying to form a precursor film of 30 nm.
And (3) exposure and development: exposing with 254nm ultraviolet light at a dose of 120mJ/cm 2 Finally, washing and developing the substrate by absolute ethyl alcohol to obtain corresponding patterns, and forming a patterned electron injection layer as shown in figure 4
The device structure manufactured in this embodiment is as shown in fig. 1, and regarding the rest layers of the device in this embodiment, the substrate is a conductive glass substrate of indium tin oxide, the hole transport layer is PEDOT: PSS, and the thickness is 30nm; the hole transport layer adopts poly [ (9, 9-dioctylfluorene-2, 7-diyl) -co- (4, 4' - (N- (4-sec-butylphenyl) diphenylamine)](TFB) having a thickness of about 15nm; the thickness of the luminescent layer is 20nm, and the material is CdSe-based quantum dots, 20mg/ml; the thickness of the electron injection layer is 30nm, and the material is TiO 2 The method comprises the steps of carrying out a first treatment on the surface of the The top electrode adopts a silver/aluminum composite electrode.
The patterned electron injection layer prepared in this embodiment is still similar to embodiment 1, and has a relatively regular morphology, and the external quantum efficiency of the QLED device prepared in this embodiment is 12%, and the external quantum efficiency is still maintained at 12% after the QLED device is placed in an air environment for one week.
Example 6
This example illustrates a process for preparing an inverted-structure QLED device, which includes a process for preparing a precursor material of a patterned electron injection layer (a process for preparing a coating liquid described below, that is, a process for forming a precursor material) and a process for forming an electron injection layer.
In the preparation of the device, the preparation process of the patterned electron injection layer is as follows:
preparation of the coating liquid: a ZnO ethanol dispersion with a mass concentration of 30mg/ml was prepared, wherein the average particle diameter of ZnO nanoparticles was about 5 nm. And then 2wt% of (4-methylthio) triflate photo-ligand was added to the above solution and mixed uniformly.
Coating and forming: and spin-coating the coating liquid and drying to form a 30nm film.
And (3) exposure and development: exposing with 365nm ultraviolet light to 150mJ/cm2, washing with anhydrous alcohol, developing to obtain corresponding pattern, and forming patterned electron injection layer as shown in figure 4
The device structure of this embodiment is shown in FIG. 5, in which the substrate is made of ITO conductive glass substrate, the thickness of the electron injection layer is 30nm, and the material is TiO 2 The method comprises the steps of carrying out a first treatment on the surface of the The thickness of the quantum dot layer is 20nm, and the material is CdSe-based, 20mg/ml; the hole transport layer adopts CBP with thickness of 40nm, and the hole injection layer adopts MoO 3 The thickness is 10nm; the top electrode adopts a silver/aluminum composite electrode.
The patterned electron injection layer prepared in this embodiment is still similar to embodiment 1, and has a relatively regular morphology, and the external quantum efficiency of the QLED device prepared in this embodiment is 13%.
Comparative example 1
This comparative example illustrates a process for preparing a quantum dot LED device, which is mainly different from that of example 1 in that an electron injection layer is prepared.
The electron injection layer in this comparative example was prepared as follows:
preparation of the coating liquid: a ZnO ethanol dispersion with a mass concentration of 30mg/ml was prepared, wherein the average particle diameter of ZnO nanoparticles was about 5 nm.
And (3) coating an electron injection layer: spin coating the coating solution by spin coating at 2000rpm for 30s to form a ZnO film of about 30 nm.
And (3) photoresist coating: commercial SU-8 series photoresist is selected, the film thickness is 1.5 mu m,
and (3) exposure and development: exposure wavelength 365nm, exposure dose 150mJ/cm 2 . After baking at 95℃for 15min, development was carried out in propylene glycol monomethyl ether acetate for 10min.
Pattern etching: the etching gas is oxygen (ions), the flow is 25sccm, the radio frequency power is 25W, the working air pressure is 40 mTorr, the self-bias voltage is 140V, and the etching time is 6min.
Removing photoresist and forming: and stripping the cured photoresist by using hot acetone ultrasonic waves, and obtaining a ZnO pattern similar to that of FIG. 4 after the stripping is completed.
Because the traditional photoresist method is adopted in the comparative example, on one hand, interface contact is easy to be deteriorated due to photoresist residues, and on the other hand, the gas etching process is easy to have adverse effect on quantum dots, the electron injection layer obtained by the scheme has lower performance, and is difficult to be used for preparing a QLED device.
Comparative example 2
This comparative example illustrates a process for preparing a quantum dot LED device, which is mainly different from that of example 1 in that an electron injection layer is prepared.
The electron injection layer in this comparative example was prepared as follows:
preparing a ZnO precursor solution: zinc dimethacrylate and ethanolamine were dissolved in a mixed solution of ethanol, methacrylic acid and hydrochloric acid at a mass concentration of about 0.45M.
Coating: spin coating the coating solution by spin coating, 2000rpm,60s, and then pre-baking to form a precursor film of about 140 nm.
And (3) exposure and development: exposing with 193nm ultraviolet light at a dose of 450mJ/cm 2 And (3) performing an annealing treatment to obtain a corresponding pattern after the development of the allyl alcohol, wherein the thickness of the final ZnO film is about 60nm, so that a ZnO pattern similar to that of FIG. 4 is formed, and the ZnO pattern can be used as an electron injection layer of a QLED device.
Because the comparative example adopts a method with more organic photosensitive cross-linking agents, the formed film can obtain corresponding metal oxide by high-temperature annealing in air or oxygen-containing atmosphere, and the high-temperature annealing can have adverse effects on other functional layers, particularly the quantum dot layer. In addition, the energy level matching degree of the ZnO nano-particles formed by annealing is not as good as that of ZnO nano-particles obtained by a solution method. Under the same test conditions, the external quantum efficiency of the QLED device provided by this comparative example was 2%, which is significantly different from that of example 1.
Comparative example 3
The pixelated electron injection layer in this comparative example was prepared as follows:
TiO 2 preparing a precursor solution: titanium tetraisopropoxide and methacrylic acid are mixed according to the mol ratio of 1:8, and after stirring for five minutes, 2ml of n-propanol is added and stirred for 10 minutes; then according to Ti and H 2 Adding deionized water into the mixture according to the molar ratio of O of 1:20; and adding proper amount of n-propanol to regulate viscosity.
Coating: spin-coating the coating solution at 3000rpm for 60s to form a precursor film of about 100nm
And (3) exposure and development: exposing with 193nm ultraviolet light at a dose of 30mJ/cm 2 After developing with cyclohexanone (cyclo-hexanone), the corresponding pattern is obtained, and TiO similar to that of FIG. 4 is formed 2 The pattern can be used as an electron injection layer of a QLED device.
Preparation of patterned TiO due to this comparative example 2 In the case of thin films, it is necessary to introduce ionized water to form the required sol, while water molecules have a great negative effect on QLED devices and TiO is formed by deep ultraviolet exposure 2 The film is amorphous and has low conductivity. Therefore, under the same test conditions, the quantum dot LED device provided by the comparative exampleThe external quantum efficiency of the piece was 1%, significantly inferior to example 1.
Based on the above embodiments and comparative examples, it is clear that, according to the precursor material and the application method thereof provided by the embodiments of the present invention, by arranging the modification molecule with the photosensitive polarity conversion function on the surface of the metal oxide nanoparticle, when the metal oxide nanoparticle is irradiated, the polarity of the surface of the metal oxide nanoparticle is changed, so as to change the dissolution characteristic thereof, so that the irradiated part of the metal oxide nanoparticle is not easily cleaned and removed by the solvent with the original polarity, and further direct lithography of the electron injection layer is realized.
The technical scheme provided by the embodiment of the invention realizes the direct photo-forming of the metal oxide nano particles, avoids the use of photoresist, reduces the process steps and simultaneously reduces the influence of the photoresist on the electrical properties of the metal oxide nano particles.
The embodiment of the invention is beneficial to the manufacture of the QLED display device with high resolution through the research and development of the electron injection layer material pixelation technology.
It should be noted that the preparation method provided by the invention is used as an electron injection layer in a QLED device, and is one of applications of the patternable metal oxide nanoparticle technology provided by the invention.
Namely, the invention also provides application of the preparation method in the fields of forming an electron injection layer, a nano grating, a metal oxide photoetching mask and the like.
It should be understood that the above embodiments are merely for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the present invention and implement the same according to the present invention without limiting the scope of the present invention. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.
Claims (10)
1. The precursor material of the electron injection layer is characterized by comprising metal oxide nano particles and a surface modifier modified on the surfaces of the metal oxide nano particles;
wherein the polarity of the surface modifier is capable of being changed upon exposure to light.
2. The precursor material of claim 1, wherein the surface modifier is further capable of coordinating with adjacent metal oxide nanoparticles upon exposure to light;
the surface modifier has dual photoactive functional groups.
3. The precursor material of claim 1 or 2, wherein the surface modifier comprises any one or a combination of two or more of 1,2,3, 4-triazole-5-thioammonium salt, 2- (4-methyl-oxyphenyl) -4, 6-bis (trichloromethyl) -1,3, 5-triazine, 2-diazonium-1-naphthol-4-sulfonic acid, 1-diazonium-2 naphthol-4-sulfonic acid, diphenyliodonium fluoroborate, ammonium dithiocarbamate, 1, 2-naphthoquinone diazide-4-sulfonyl chloride, 2-phenyl-2- (5- ((o-oxy) imino) thiophene-2-methylene) -acetonitrile, butyl dithiocarbamic acid, ammonium oxalate, N-hydroxynaphthalimide trifluoroester, (4-methylthio) trifluoromethanesulfonate;
and/or the metal oxide particles comprise any one or more than two of zinc oxide, magnesium zinc oxide, tin oxide and titanium oxide.
4. The precursor material of claim 1, wherein the mass of the surface modifier is 1-15wt% of the mass of the metal oxide nanoparticles;
and/or the particle size of the metal oxide nanoparticles is 3-10nm.
5. A method for preparing a precursor material for an electron injection layer, comprising:
providing metal oxide nanoparticles;
modifying a surface modifier on the surface of the metal oxide nanoparticles by an ion exchange method;
wherein the surface modifier is capable of changing or dissociating upon exposure to light, resulting in a change in polarity.
6. The preparation method according to claim 5, which comprises the following steps:
formulating the metal oxide nanoparticles as a precursor dispersion;
and uniformly mixing the precursor dispersion liquid and the surface modifier, and generating the precursor material of the electron injection layer by ion exchange.
7. A method for forming an electron injection layer, comprising:
providing a coating liquid in which the precursor material of any one of claims 1-4 is dispersed;
coating the coating liquid into a film to obtain an electron injection layer precursor;
patterning illumination of the electron injection layer precursor;
and cleaning and removing the non-irradiated part of the electron injection layer precursor by using a cleaning agent with the same polarity as the solvent in the coating liquid to form a patterned electron injection layer.
8. The method of forming according to claim 7, wherein the method of preparing the coating liquid includes:
dispersing metal oxide nanoparticles in a solvent to form a dispersion;
and adding a surface modifier to the dispersion liquid to obtain the coating liquid.
9. The forming method according to claim 7, wherein a mass fraction of the surface modifier in the coating liquid is 1 to 15wt%;
and/or the mass concentration of the metal oxide nano particles in the coating liquid is 10-60mg/mL, preferably 25-35mg/mL.
10. A light emitting diode device includes a hole injection layer, a hole transport layer, a semiconductor functional layer, and an electron injection layer stacked in this order;
the method for forming the electron injection layer is characterized in that the electron injection layer is formed by adopting the forming method of any one of claims 7-9.
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