KR20220117817A - Multimaterial printing method for nanocrystal assemblies via uniform surface via evaporation kinetics and surface energy control - Google Patents

Abstract

The present invention relates to a method for printing multi-nanoparticles of uniform surfaces by using evaporation kinetics and surface energy control and, more specifically, to a multi-image contrast medium composition and a manufacturing method thereof. The multi-nanoparticle printing method includes the following steps of: (S1) forming a pattern on the surface of a substrate by radiating ultraviolet rays to a part of the surface through a photomask; (S2) coating a solution including nanoparticles, on the substrate; and (S3) lowering the surface energy of the coated nanoparticles. In accordance with the present invention, the substrate, on which nanoparticles having uniform surfaces are nondestructively printed, can be provided, and the substrate can be used as a material for an optical element.

Description

{Multimaterial printing method for nanocrystal assemblies via uniform surface via evaporation kinetics and surface energy control}

The present invention relates to a method for printing multiple nanoparticles on a uniform surface using evaporation dynamics and surface energy control.

High-performance next-generation nano devices such as next-generation sensors, memories, and lasers have high potential due to their excellent performance and utilization. In these next-generation nanodevices, nanoparticles that show different physical properties from existing bulk materials and show high functionality are a key component. Therefore, in addition to research on synthesizing nanoparticles, a technology for implementing nanoparticles in a solution phase in a specific arrangement beyond a simple aggregated form or a complex form mixed with other materials is essential for the fabrication of next-generation nanodevices.

However, the nanoparticle array technologies that have been developed so far have been limited in forming high-efficiency devices because they cannot form an array of various materials without forming a uniform surface or damaging the printed nanoparticles and the underlying substrate. Inkjet-based printing technology has limitations in pattern formation control, making it difficult to form a pattern with a uniform surface. It is known to leave a residue or cause optical and electrical damage.

Most recently reported optical lithography techniques use radical-based chemical reactions, and thus exhibit low device performance due to physical and chemical damage to nanoparticles.

Domestic Registered Patent No. 1846741

The technical problem to be achieved by the present invention is to provide a method for non-destructively printing multiple nanoparticles with a uniform surface by controlling evaporation dynamics and the surface energy of the nanoparticle array.

Another object of the present invention is to provide a device comprising a substrate printed by the above method.

However, the technical problem to be achieved by the present invention is not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to solve the above problems, the present invention comprises the steps of forming a pattern by irradiating a portion of the surface of the substrate with ultraviolet light through a photomask (S1);

coating a solution containing nanoparticles on the substrate (S2); and

It provides a multi-nanoparticle printing method comprising the step (S3) of lowering the surface energy of the coated nanoparticles.

In one embodiment of the present invention, in step S2, a solution may be coated on a portion of the surface of the substrate irradiated with ultraviolet rays in step S1.

In another embodiment of the present invention, steps S1 to S3 may be repeatedly performed a plurality of times.

As another embodiment of the present invention, the pattern of step S1 may have a diameter of 3 um to 100 cm, and ultraviolet rays may be irradiated with a wavelength of 100 to 500 nm for 10 seconds to 10 minutes.

As another embodiment of the present invention, the substrate may be made of one or more materials selected from the group consisting of metals, metal oxides, semiconductors, and polymers.

In another embodiment of the present invention, the substrate may include polyvinylcarbazole (PVK).

As another embodiment of the present invention, step S2 may be performed by spin coating at 1,000 to 10,000 rpm.

As another embodiment of the present invention, the nanoparticles may be quantum dots.

In another embodiment of the present invention, the quantum dots are selected from the group consisting of GaN, GaAs, GaP, InP, InAs, ZnS, CdS, CdSe, ZnO, MgO, SiO2, CdO, SiC, B4C, Si3N and In2O3. may be more than one species.

As another embodiment of the present invention, in step S3, a solution containing a ligand having a surface energy of 20 mN/m or less may be applied to the nanoparticles.

In another embodiment of the present invention, the solution containing the ligand is perfluorodecanediol, 2-(perfluoroexyl)ethanediol, perfluorooctanediol, perfluorodecanesulfonic acid, and perfluorooctane. It may include at least one selected from the group consisting of sulfonic acids.

The present invention also provides a nanoparticle pattern by the above-described non-destructive uniform surface formation multi-nanoparticle printing method, comprising: a nanoparticle thin film; and a material layer formed on the edge of the nanoparticle thin film, wherein the material layer has a thickness greater than that of the nanoparticle thin film.

In another embodiment of the present invention, the thickness of the material layer is determined according to the concentration of nanoparticles in the solution.

In addition, the present invention provides a substrate printed by the above method.

In addition, the present invention provides a device including the substrate.

The uniform surface nanoparticle printing method of the present invention can be applied without restrictions on the size and constituent materials of nanoparticles because it utilizes simple evaporation acceleration without addition of organic matter or internal liquid flow. In addition, the chemically programmed substrate to be utilized has the advantage of being able to form particle arrays in various shapes because various methods such as masked UV-Ozone can be used.

The multi-nanoparticle printing method of the present invention has the advantage that it can be used for various layered solution process-based devices because it can manufacture solution-based nanoparticles into a film having a uniform surface by controlling the evaporation role. In addition, evaporation dynamics control can be applied to other solution processing techniques such as inkjet printing to produce a uniform surface pattern universally.

Since the manufacturing process of the multi-nanoparticle array of the present invention does not require both the polymer transfer medium used in transfer printing and the radicals used in optical patterning, it does not cause optical and electrical damage to the particles used and the target substrate, so that an organic material thin film is fabricated. There is an advantage that can be applied to cases such as QLED (Quantum dot light emitting diode) used as a configuration.

The technology presented in the present invention is a low-cost, large-area nanoparticle array configuration and a technology for non-destructively printing it on various substrates. It can also bring economic effects by minimizing the production cost.

1 is a schematic diagram of the nanoparticle array fabrication principle used in the present invention.
2 is a schematic diagram showing each nanoparticle array manufacturing process used in the present invention.
3 shows the results of confirming the change in UV exposure time according to the concentration of IPA.
Figure 4 shows the result of checking the presence or absence of electrical damage after the pattern formation of the present invention.
5 shows an SEM image after pattern formation of the present invention.
6 is a schematic diagram of the formation of an array of nanoparticles on a uniform surface formed by controlling the evaporation rate used in the present invention.
7 is a graph showing the evaporation rate according to RPM and the degree of film formation.
8 shows an SEM image (a), AFM analysis (b) and TEM image (c) of a substrate on which a quantum dot pattern is formed.
9 is a schematic diagram illustrating a rim forming process according to the present invention.
10 is an atomic force microscopy (AFM) analysis result for the thickness of the ring thin film according to an embodiment of the present invention.
11 shows the principle of the fluorocarbon treatment process of the present invention.
12 is a view showing the change in surface tension due to the fluorocarbon treatment.
13 is a view showing the degree of contamination by fluorocarbon treatment.
Figure 14 shows the XPS analysis results of the QD film prepared by the method of the present invention.
15 shows the results of confirming by comparing the IV curve of an electron only device including a QD film prepared by the manufacturing method of the present invention.
16 shows a confocal image of the RGB array of the present invention.
17 is a schematic diagram of a QD-LED manufactured by the method of the present invention, a light emitting image, and a result of confirming the LED performance.

The present invention accelerates the evaporation of the solvent during nanoparticle printing to form a uniform surface arrangement, and then lowers the surface energy of the patterned nanoparticle arrangement due to repeated wetting of the patterned nanoparticle arrangement below when printing other nanoparticles. It is to provide a technology that can non-destructively print various nanoparticles while having a uniform surface by using the phenomenon of preventing contamination.

The present invention comprises the steps of forming a pattern by irradiating a portion of the surface with ultraviolet light through a photomask on the surface of the substrate (S1);

coating a solution containing nanoparticles on the substrate (S2); and

It provides a multi-nanoparticle printing method comprising the step (S3) of lowering the surface energy of the coated nanoparticles.

Figure 1 is a schematic diagram showing a multi-nanoparticle printing method according to an embodiment of the present invention, Figure 2 is a schematic diagram showing the nanoparticle printing method of the present invention for each process. Hereinafter, each step will be described with reference to FIG. 2 .

Step S1 of the present invention is a step of forming a pattern through UV irradiation, and UV is irradiated to a part of the surface of the substrate through a photomask in order to program the target substrate. The surface energy of the UV-irradiated part is increased, so that selective wetting occurs only in the UV-irradiated part when the nanoparticles are in contact, so that a pattern can be formed.

However, if the UV irradiation is excessive, the target substrate is destroyed, and if the UV irradiation is too insufficient, the surface energy of the substrate is not sufficiently high, so that the wetting of the nanoparticle solution does not occur. Therefore, while preserving the properties of the target substrate, UV is irradiated with an intensity that can pattern the nanoparticles by utilizing the selective wetting phenomenon.

The substrate may be a metal, metal oxide, semiconductor, or polymer material, and specifically, a flexible substrate including a plastic substrate, a glass substrate, a silicon wafer, a ceramic substrate, a metal substrate, and the like. As an embodiment of the present invention, when UV irradiation is performed using polyvinylcarbazole (PVK) as a substrate, when UV is irradiated for 10 minutes, there is a lot of damage to electrical properties such as conductivity of PVK. It was confirmed that there was no significant change in electrical properties such as conductivity of PVK when UV was irradiated for 5 seconds, but it was confirmed that selective wetting of the nanoparticle solution did not occur. Accordingly, it was confirmed that the optimization was carried out for 40 seconds at a wavelength of 184 nm to 253 nm. The nanoparticle solution used was a solution containing QD at a concentration of 25 mg/mg (in QD ink), and the spin coating rpm was 3000 rpm.

The quantum dots may be at least one selected from the group consisting of GaN, GaAs, GaP, InP, InAs, ZnS, CdS, CdSe, ZnO, MgO, SiO2, CdO, SiC, B4C, Si3N and In2O3, but is limited thereto not. The solution containing the quantum dots may contain IPA (isopropyl alcohol) having a low surface tension as a solvent, and the QD ink can be selectively wetted to the organic hole transport layer with only the shortest possible UV exposure including the IPA. . As shown in FIG. 3 , it can be seen that the UV irradiation time becomes shorter as the concentration of IPA increases. When IPA was added to QD ink, the UV time required for QD patterning was reduced, and it could be reduced to 40s. In other words, it can be seen that QD patterning is possible with less UV time by adding IPA to QD ink. The IPA may be included in an amount of 20% by volume or more, preferably 30 to 60% by volume. In addition to the IPA, water may be included.

As such, the ultraviolet rays may be irradiated with an intensity of 100 to 500 nm for 10 seconds to 10 minutes, but the time to be destroyed by UV may vary depending on the substrate used. In addition, since the solvent of the nanoparticle solution used in addition to the substrate may be different, when a material different from the conditions described in the present invention is used, the UV irradiation time, the concentration of nanoparticles, and the spin coating rpm may be embodied in different forms. According to the nanoparticle solution and substrate conditions of the present invention, the time of UV irradiation can be shortened. As can be seen from the IV curve result of FIG. 4 , it can be seen that the organic transport layer is not electrically damaged by a short UV exposure.

In addition, the pattern may be a circular pattern having a diameter of 3 um to 100 cm. However, in addition to the original pattern, as shown in FIG. 5 , various patterns can be made according to the shape of the mask, and a target substrate programming method such as photolithography can be applied in addition to the UV irradiation used in the present invention.

The step S2 is a step of coating a solution containing nanoparticles on a substrate on which a pattern is formed by irradiating ultraviolet rays, and the spin coating rpm is adjusted to form an array of nanoparticles having a uniform surface on a substrate programmed through a photomask. Thus, evaporation acceleration was applied to the selective wetting process. The principle is as shown in FIG. 6 . When the speed of spin coating increases, the solvent increase rate increases. In this case, when the solvent increase rate becomes faster than the movement speed of the particles inside the solution, the inner particles are caught on the surface of the solution, and the alignment occurs due to thermodynamics and becomes even. This process continues until all of the solvent in the solution is evaporated, and finally, a pattern having an even surface is formed.

7 shows the results of confirming the evaporation rate and the degree of film formation according to RPM. As the RGB deviation value decreased, it means that the pattern shape was more uniform. At high rpm, the evaporation rate increased and a uniform QD pattern was obtained.

Tilt SEM analysis results (plan view) are shown in FIG. 8 .

Referring to FIG. 8 , the characteristic of the pattern manufactured according to the present invention is that a film having a uniform surface is formed therein, and a material layer containing particles is formed on the upper part of the uniform thin film with a thick thickness at the edge of the thin film. that a layer can be formed (see Fig. 8A)

That is, the present invention increases the evaporation rate to induce particles to be trapped in the solvent, thereby manufacturing a thin film having a uniform surface. However, in this case, no matter how fast the evaporation rate is, all the particles of the solvent cannot be initially trapped on the surface of the water droplet. Therefore, the particles that are not trapped in this way move to both extremes of the water droplet, forming a layer having a thicker thickness at the edge of the thin film pattern having a uniform thickness.

Therefore, the pattern according to the present invention is formed on a substrate by solvent evaporation and a uniform thin film pattern made of nanoparticles, and a nanoparticle material having a thicker thickness than the thin film pattern due to non-trapped nanoparticles formed outside the pattern include layers. Also, the width and thickness of the material layer vary from 10 nm to 1000 μm depending on the pattern size and particle concentration.

9 is a schematic diagram illustrating a rim forming process according to the present invention.

Referring to FIG. 9, as described above, in the present invention, a thin film having a uniform surface is manufactured by inducing particles to be trapped in a solvent by increasing the evaporation rate. At this time, the particles outside the droplet close to the substrate have a slow moving speed compared to the fast evaporation rate, and thus are not trapped on the droplet surface. Therefore, after the final evaporation, the outer edge of the pattern in FIG. 9 has a thicker thickness than the inner uniform thin film pattern (B), and forms the edges (A, rim) of the nanoparticle material layer.

10 is an atomic force microscopy (AFM) analysis result of the width of a material layer constituting a rim according to an embodiment of the present invention.

Referring to FIG. 10 , it can be seen that different material layer widths and thicknesses appear according to particle concentrations. As the particle concentration increases, it can be seen that a thicker particle material layer is formed at the edge. That is, the graph peaks indicating the thickness of both material layers in FIG. 9 are a ring of 400 nm at a concentration of 50 mg ml ^-1 , a material layer of a thickness of 70 nm at a concentration of 25 mg ml ^-1 , and a material layer of a thickness of 40 nm at a concentration of 15 mg ml ^-1 formation can be seen. Therefore, in the present invention, the thickness and width of the material layer formed during initial evaporation can be controlled through solution concentration, etc., and the thickness (the cross-sectional width of the thin film itself) can be up to 10 nm - 1000 μm.

In one embodiment of the present invention, in the coating process, as can be seen in FIG. 7 , when the speed of spin coating is very slow, about 500 rpm, the evaporation rate is not sufficiently fast, so that most of the nanoparticles are accumulated only at the edge of the pattern, and spin If the evaporation rate of the solvent is increased by increasing the coating rate (rpm), the film starts to form, and when a specific rpm is reached, a nanoparticle pattern having a uniform surface can be manufactured. Accordingly, the spin coating of step S2 may be performed at 1,000 to 10,000 rpm, but is not limited thereto.

For example, when using a 25 mg/mL green quantum dot solution using a PVK substrate as in the present invention, it was performed at 3000 rpm. However, since the solvent evaporation rate is different depending on the target substrate and the nanoparticle solution used, the spin coating rpm may be specified in a different form when a material different from the conditions described in the present invention is used.

Step S3 is a step of lowering the surface energy of the nanoparticles, and the surface energy of the printed nanoparticle array was controlled in order to variously and continuously print the nanoparticles with a uniform surface manufactured by the above-described process. In the present invention, the steps S1 to S3 are repeatedly performed a plurality of times, so that multiple nanoparticles can be printed. Preferably, it may be repeated 1 to 20 times.

If, unlike the present invention, multiple nanoparticles are printed using selective wetting without surface energy control, repeated wetting may occur even in the nanoparticles printed below, resulting in contamination. Accordingly, the present inventors tried to solve this by lowering the surface energy of nanoparticles. The principle is shown in FIG. 11 .

In the present invention, when using the above-described substrate and nanoparticle solution, perfluorodecanethiol was used as a fluorocarbon having a low surface energy to control the surface energy of the nanoparticle arrangement. The perfluorodecanethiol was dissolved in perfluorodecalin and dropped on the nanoparticle array on the target substrate, and then washed with perfluorodecalin. During this process, perfluorodecanethiol is thermodynamically exchanged with the existing ligand of the printed nanoparticles.

It was confirmed through the contact angle that the surface energy of the nanoparticle array with ligand exchange decreased from 70 mN/m to 25 mN/m due to perfluorodecanethiol (FIG. 12). Then, when another nanoparticle solution was printed, the patterned nanoparticle array was It was confirmed that repeated wetting did not occur (FIG. 13). Figure 14 shows the XPS analysis results of the QD film and PVK substrate prepared by the method of the present invention. From the above results, it can be seen that the process of attaching fluorocarbon thiol by ligand exchange is selective only to the QD film without affecting the underlying hole transport layer.

15 shows that the fluorocarbon thiol treatment does not significantly affect the charge transport of the QD film by manufacturing an electron only device and comparing the IV curve. It can be seen that the fluorine treatment does not interfere with the charge transport of the QD film either. have.

As a result, patterning of multi-colored QDs could be continuously performed by treatment with fluorocarbon thiol, and as shown in the confocal image, a QD RGB array could be made on the hole transport layer (FIG. 16).

The substrate manufactured by the printing method of the present invention may be manufactured as a patterned QD-LED as shown in FIG. 16 . In addition, as shown in FIG. 16, the electrical performance is also excellent, and it can be seen that the actual LED performance is shown.

The substrate of the present invention may be utilized as a device. The device is particularly an optical device, and may include, but is not limited to, a sensor, a resistive memory, a phase change memory, a heating electrode, a sensing electrode, or a catalyst.

The present invention can apply various transformations and can have various embodiments. Hereinafter, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

[Example]

In this example, an RGB QD array was fabricated through Step1 to Step4. Each Step was described in more detail below.

Step1. UV irradiation through a photomask on the organic hole transport layer

In Step 1, UV was treated through a photomask on the surface of the organic hole transport layer to be QD patterned. As experimental conditions, UV wavelength is 184nm, 253nm, UV irradiation time 40 seconds, QD concentration in QD ink is QD 25mg/mg, solvent composition in QD ink is water:IPA=60:40, organic hole transport layer is HTL: PVK was done with

When UV is irradiated under the same conditions as above, the surface energy of the UV-irradiated portion is lowered, and then only the portion exposed to QD ink UV in step2. is wetted to form a pattern.

With the existing technology, if UV is irradiated until the QD ink is wetted, the organic hole transport layer is destroyed. On the contrary, in this embodiment, a liquid (IPA) having a low surface tension is added to the QD ink to cause wetting of the QD ink only by short UV irradiation and to prevent the destruction of the hole transport layer.

Step2. Patterning through selective wetting of QD ink on the UV-treated hole-receiving layer

In Step2., QD ink was dropped and spin coated on the organic hole transport layer irradiated with UV. The spin coating speed was set to 3000rpm. As a result, it was confirmed that the pattern was formed by wetting only on the portion where the QD ink was irradiated with UV.

The QD pattern made using the existing selective wetting technology does not satisfy the conditions required for use as a light emitting layer, but in contrast to this, in this embodiment, a fast solvent of QD ink droplets wetting on the UV-irradiated portion through spin coating adjustment By inducing evaporation, a QD pattern that satisfies the light emitting layer condition was formed.

Step3. RGB array production through fluorocarbon treatment

In this Step3., after dropping the fluorocarbon on the QD patterned organic hole transport layer, it was washed immediately. Fluorocarbon was dropped perfluorodecane thiol, and the solvent for washing was hexane. The fluorocarbon is attached to the patterned QD surface, thereby lowering the QD pattern surface energy.

In the existing selective wetting technique, when QDs of different colors are subsequently printed, the QDs of different colors are contaminated on the surface of the previously patterned QDs. In contrast, this embodiment solves the problem of contamination of QDs of different colors on the patterned QD surface through a new approach called fluorocarbon attachment.

Step4. repeat the previous process

This Step4 repeats Steps 1 to 3 above, and as a result, an RGB QD array is created on the organic HTL.

As described above in detail a specific part of the content of the present invention, for those of ordinary skill in the art, it is clear that this specific description is only a preferred embodiment, and the scope of the present invention is not limited thereby. something to do. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (15)

Forming a pattern by irradiating a portion of the surface of the substrate with ultraviolet light through a photomask (S1);
coating a solution containing nanoparticles on the substrate (S2); and
Including the step (S3) of lowering the surface energy of the coated nanoparticles, multi-nanoparticle printing method.
According to claim 1,
In step S2,
Multi-nanoparticle printing method, characterized in that the solution is coated on a portion of the surface of the substrate irradiated with ultraviolet rays in step S1.
According to claim 1,
Steps S1 to S3 are multi-nanoparticle printing method, characterized in that it is repeatedly performed a plurality of times.
According to claim 1,
The pattern of step S1 is to have a diameter of 3 um to 100 cm, and ultraviolet rays are irradiated with a wavelength of 100 to 500 nm for 10 seconds to 10 minutes, the multi-nanoparticle printing method.
According to claim 1,
The substrate is made of one or more materials selected from the group consisting of metals, metal oxides, semiconductors and polymers, multi-nanoparticle printing method.
6. The method of claim 5,
Wherein the substrate comprises polyvinylcarbazole (PVK). According to claim 1,
The step S2 is, the multi-nanoparticle printing method is performed by spin coating at 1,000 to 10,000 rpm.
According to claim 1,
The nanoparticles are quantum dots, characterized in that the multi-nanoparticle printing method.
9. The method of claim 8,
The quantum dots are non-destructive, characterized in that at least one selected from the group consisting of GaN, GaAs, GaP, InP, InAs, ZnS, CdS, CdSe, ZnO, MgO, SiO2, CdO, SiC, B4C, Si3N and In2O3 A multi-nanoparticle printing method with uniform surface formation.
According to claim 1,
In the step S3, a solution containing a ligand having a surface energy of 20 mN/m or less is applied to the nanoparticles, a multi-nanoparticle printing method.
10. The method of claim 9,
The solution containing the ligand is at least one selected from the group consisting of perfluorodecanediol, 2-(perfluoroexyl)ethanediol, perfluorooctanediol, perfluorodecanesulfonic acid, and perfluorooctanesulfonic acid. A non-destructive, uniform surface-forming multi-nanoparticle printing method comprising the above. A nanoparticle pattern by the non-destructive uniform surface formation multi-nanoparticle printing method according to any one of claims 1 to 11,
nanoparticle thin film; and
and a material layer formed on the edge of the nanoparticle thin film, wherein the material layer has a thickness greater than that of the nanoparticle thin film. 13. The method of claim 12,
The thickness of the material layer is a nanoparticle pattern, characterized in that determined according to the concentration of nanoparticles in the solution. Section 1 A substrate printed by the method of any one of claims 11 to 11. A device comprising the substrate of claim 14 .

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