KR102138074B1 - Method of manufacturing light-emitting nanocrystal-metal oxide composite thin film, optical film manufactured by the method, and backlight unit having the optical film - Google Patents

Abstract

Disclosed is a method of manufacturing a light emitting nanocrystal-metal oxide composite thin film. The disclosed manufacturing method includes the steps of preparing a composite powder of luminescent nanocrystals and metal oxides and spraying the composite powder onto a substrate through an aerosol deposition process to form a composite thin film, thereby being prepared The composite thin film has a matrix made of a metal oxide and the luminescent nanocrystals dispersed in the matrix.

Description

METHOD OF MANUFACTURING LIGHT-EMITTING NANOCRYSTAL-METAL OXIDE COMPOSITE THIN FILM, OPTICAL FILM MANUFACTURED BY THE METHOD, AND BACKLIGHT UNIT HAVING THE OPTICAL FILM}

The present invention relates to a method for manufacturing a composite thin film in which luminescent nanocrystals such as quantum dots and the like are dispersed in a metal oxide matrix, and an optical film produced thereby and a backlight unit including the optical film.

Over the past few years, metal halide perovskite materials have been spotlighted as optoelectronic materials for solar cells, light emitting diodes, and photoconversion devices for white light. In particular, inorganic CsPbX3 (X=Cl, Br, I) materials have a full widths at half maximum (FWHM), high photoluminescence quantum yield, and relative thermal stability compared to organometal halide perovskites. It is known to have excellent optical properties. As a result, inorganic metal halide perovskite materials are considered to be potential candidates for full color display development with very wide color gamut coverage.

Recently, perovskite nanocrystals have been encapsulated with various polymer materials such as polystyrene, poly-methyl methacrylate, and polyhedral oligomeric silsesquioxane. It has been demonstrated that it can be applied as a light emitting material in commercial LED devices. In addition, it was confirmed that the film in which the perovskite nanocrystals are embedded in the polymer matrix can improve the color reproducibility in the backlight of the display, and overcomes the problem of adjusting the interface between the perovskite nanocrystals and the polymer matrix. However, the insulating polymer used as a matrix still has a problem inherently vulnerable to thermal stress. In particular, long-term thermal stress can cause softening deformation or damage of thermoplastic polymers such as polystyrene, polymethylmethacrylate, cycloolefin copolymer, and the like.

On the other hand, inorganic perovskite nanocrystalline film that does not use a polymer as a matrix was formed on a substrate by a conventional spin-coating, centrifugal casting, or the like, which is a large area coating and film There is a problem in that the workability of the type is significantly reduced.

An object of the present invention is to provide a method for manufacturing a composite thin film in which light emitting nanocrystals such as quantum dots are dispersed in a metal oxide matrix.

Another object of the present invention is to provide an optical film produced by the above manufacturing method.

Another object of the present invention is to provide a backlight unit having the optical film.

A method of manufacturing a light emitting nanocrystal-metal oxide composite thin film according to an embodiment of the present invention includes a first step of preparing a composite powder of a light emitting nanocrystal and a metal oxide; And a second step of spraying the composite powder on a substrate through an aerosol deposition process to form a composite thin film, wherein the composite thin film is a matrix made of the metal oxide and the light emission dispersed inside the matrix. Nanocrystals.

In one embodiment, the luminescent nanocrystal may include quantum dots that absorb incident light and then emit light having a different wavelength.

In one embodiment, the light-emitting nanocrystals may include a metal halide-based quantum dot having a perovskite crystal structure.

In one embodiment, the first step comprises mixing the precursor material of the luminescent nanocrystals and the powder of the metal oxide in a solvent and growing the luminescent nanocrystals from the precursor material on the surface of the metal oxide powder. It may include a step.

In one embodiment, the first step is a step of mixing the synthesized luminescent nanocrystals and a metal oxide powder in a solvent, and evaporating the solvent to adsorb or bond the luminescent nanocrystals to the surface of the metal oxide powder. It may include.

In one embodiment, the luminescent nanocrystals may be included 0.5 to 20% by weight of the weight of the metal oxide powder.

In one embodiment, the aerosol deposition process may use helium (He) or nitrogen (N2) as a carrier gas.

In one embodiment, the method of manufacturing a light emitting nanocrystal-metal oxide composite thin film according to an embodiment of the present invention may further include a step of mixing the composite powder and the buffer polymer powder performed after the first step, In this case, in the second step, a mixed powder of the composite powder and the buffer polymer powder is sprayed on the substrate through the aerosol deposition process to form the composite thin film.

In one embodiment, the buffer polymer powder may be formed of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene (PE) or polypropylene (PP).

In one embodiment, the buffer polymer powder may be mixed in a ratio of 0.1 wt% or more and 2.5 wt% or less based on the total weight of the composite powder and the buffer polymer powder.

An optical film according to an embodiment of the present invention includes a substrate; A first photoconversion layer disposed on the substrate and having a first metal oxide matrix and red light emitting nanocrystals dispersed therein to absorb blue light to generate red light; And a second photo-conversion layer disposed on the first photo-conversion layer and having a second metal oxide matrix and green light-emitting nanocrystals dispersed inside and absorbing blue light to generate green light.

In one embodiment, the first metal oxide matrix may include aluminum oxide, and the red light emitting nanocrystals may include cadmium-based or non-cadmium-based quantum dots.

In one embodiment, the second metal oxide matrix includes aluminum oxide, and the green light-emitting nanocrystals may include a metal halide-based quantum dot having a perovskite crystal structure.

The backlight unit according to an embodiment of the present invention includes a light source unit that generates blue light; And an optical film absorbing a part of the blue light generated from the light source unit to generate red light and green light, the optical film comprising: a substrate disposed on the light source unit; A first photoconversion layer disposed on the substrate and having a first metal oxide matrix and red light emitting nanocrystals dispersed therein to absorb blue light to generate red light; And a second photo-conversion layer disposed on the first photo-conversion layer, and having a second metal oxide matrix and green light-emitting nanocrystals dispersed inside and absorbing blue light to generate green light.

According to the manufacturing method of the light-emitting nanocrystal-metal oxide composite thin film of the present invention and the composite thin film produced thereby, since the light-emitting nanocrystal is disposed inside the metal oxide matrix, it is remarkably compared to the light-emitting nanocrystalline thin film using a conventional polymer matrix. It can have improved thermal stability and long-term durability. In addition, since a thin film containing luminescent nanocrystals is formed using an aerosol deposition process that does not use a solvent, it is eco-friendly and can reduce process cost.

1 is a flow chart for explaining a method of manufacturing a light emitting nanocrystal-metal oxide composite thin film according to an embodiment of the present invention.
2 is a view for explaining an aerosol deposition apparatus.
3 is a cross-sectional view for describing a backlight unit according to an embodiment of the present invention.
Figure 4 shows the XRD pattern before and after the heat treatment of the CsPbBr ₃ -Al ₂ O ₃ nanocomposite powder.
Figure 5 shows the measurement results of differential scanning calorimetry (DSC) for CsPbBr ₃ -Al ₂ O ₃ .
6 and 7 are respectively a SEM image of the raw α-Al ₂ O ₃ nanoparticles _{(pristine α-Al 2 O 3} nanoparticles) and CsPbBr ₃ -Al ₂ O ₃ nanocomposite powder.
8 shows low magnification STEM images and EDS maps (energy-dispersive X-ray spectroscopy maps) for CsPbBr ₃ -Al ₂ O ₃ nanocomposite powder after heat treatment.
9 shows PL images under ultraviolet irradiation for composite thin films prepared according to Comparative Example (He), Example 1 (N ₂ ), and Example 2 (N ₂ &PTFE).
10 shows the PL intensity and absorption spectrum measured for the composite thin films prepared according to Comparative Example (He), Example 1 (N ₂ ), and Example 2 (N ₂ &PTFE).
11 to 13 show XRD patterns and cross-sectional SEM images of composite thin films prepared according to Comparative Example (He), Example 1 (N ₂ ), and Example 2 (N ₂ &PTFE).
Figure 14 is a CsPbBr ₃ -Al ₂ O ₃ -PTFE composite thin film ('1wt%) prepared using powders of 1wt% PTFE mixed with CsPbBr ₃ -Al ₂ O ₃ nanocomposite powders on a PET substrate and a glass substrate. PTFE'), CsPbBr ₃ -Al ₂ O ₃ -PTFE composite thin film ('2wt% PTFE') and 3wt% prepared using powders of 2wt% PTFE mixed with CsPbBr ₃ -Al ₂ O ₃ nanocomposite powders Images of CsPbBr ₃ -Al ₂ O ₃ -PTFE composite thin films ('3wt% PTFE') prepared using powders of PTFE mixed with CsPbBr ₃ -Al ₂ O ₃ nanocomposite powders.
15 shows PLQY and PL wavelengths measured at 150° C. for 20 days for the composite thin film prepared according to Example 2.
FIG. 16 shows the measured PL intensity and color reproducibility after placing the optical film having the light-changing layer on which the composite thin film prepared according to Example 3 and the composite thin film prepared according to Example 2 were stacked on a blue light source. .
17 is a view for explaining various processability and excellent performance of the ceramic composite layers formed by the aerosol deposition method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may be variously modified and may have various forms, and specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to specific disclosure forms, and it should be understood that all modifications, equivalents, and substitutes included in the spirit and scope of the present invention are included.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components. For example, the first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may be referred to as a first component.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "include" or "have" are intended to indicate that a feature, step, operation, component, part, or combination thereof described in the specification exists, one or more other features or steps. It should be understood that it does not preclude the existence or addition possibility of the operation, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. Terms, such as those defined in a commonly used dictionary, should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Does not.

1 is a flowchart illustrating a method of manufacturing a light emitting nanocrystal-metal oxide composite thin film according to an embodiment of the present invention, and FIG. 2 is a view for explaining an aerosol deposition apparatus.

1 and 2, a method of manufacturing a light emitting nanocrystal-metal oxide composite thin film according to an embodiment of the present invention comprises a first step of preparing a composite powder of a light emitting nanocrystal and a metal oxide (S110); And a second step (S120) of forming a thin film by spraying the composite powder on a substrate through an aerosol deposition process.

In the first step (S110), the luminescent nanocrystals may be nanoscale-sized inorganic particles having a characteristic of absorbing incident light and emitting light having a different wavelength. In one embodiment, the luminescent nanocrystals may include quantum dots or the like. For example, the luminescent nanocrystals may include metal halide-based quantum dots, metal selenide-based quantum dots, graphene-based quantum dots, etc., and these quantum dots may have a single core structure, a core shell structure, or the like. For example, the metal halide-based quantum dot may include a quantum dot having a perovskite crystal structure.

The metal oxide is not particularly limited as long as it is an oxide having insulating properties. For example, the metal oxide may include aluminum oxide.

In one embodiment, the composite powder of the luminescent nanocrystal and the metal oxide may have a size of about 100 nm or more and about 2000 nm or less in order to be sprayed in an aerosol form.

In one embodiment, the composite powder of the luminescent nanocrystal and the metal oxide is mixed with the precursor material of the luminescent nanocrystal and the metal oxide powder in a solvent, and then the luminescent nanocrystal is grown on the surface of the metal oxide powder and pulverized. Can be produced. In another embodiment, the composite powder of the luminescent nanocrystal and the metal oxide is mixed with the synthesized luminescent nanocrystal and the metal oxide powder in a solvent, and then the solvent is evaporated to adsorb the luminescent nanocrystal on the surface of the metal oxide powder. Or by combining and crushing it.

At this time, the luminescent nanocrystal precursor material or the metal oxide powder mixed with the luminescent nanocrystal may have a larger size than the luminescent nanocrystal. For example, the metal oxide powder may have a size of about 300 nm or more and 2000 nm or less. Meanwhile, in mixing the luminescent nanocrystals and the metal oxide powder, the luminescent nanocrystals may mix about 0.5 to 20 wt% of the weight of the metal oxide powder.

In the second step (S120), the aerosol deposition process may be performed using an aerosol deposition apparatus.

As shown in FIG. 2, the aerosol deposition apparatus comprises an aerosol chamber, a deposition chamber, a carrier gas supply means, a rotary pump, a booster pump, and a nozzle. It can contain. The composite powder may be accommodated in the aerosol chamber, and may be disposed on a substrate in the deposition chamber. The carrier gas supply means may supply a carrier gas to the aerosol chamber, and the vacuum pump may make the deposition chamber vacuum. The nozzle may be arranged to be spaced a predetermined distance from the substrate in the deposition chamber and may be connected to the aerosol chamber through a connection pipe. Meanwhile, the aerosol chamber may include a vibrator so that the nozzle can spray the composite powder in a uniform aerosol form.

In the aerosol deposition process, when the carrier gas is injected into the aerosol chamber through the carrier gas supply means while receiving the composite powder in the aerosol chamber and placing a substrate in the deposition chamber, the deposition chamber and the aerosol in a vacuum state The composite powders may be sprayed to the substrate through the nozzle in the form of an aerosol by a pressure difference between chambers to form a thin film of the composite on the substrate.

In one embodiment, nitrogen (N ₂ ) may be used as a carrier gas in the aerosol deposition process.

Helium (He) is used as a carrier gas in a typical aerosol deposition process. However, since helium has a small molecular weight, when helium gas is used as a carrier gas, the composite powders collide with the substrate and other composite powders at a relatively high rate during aerosol deposition. When the composite powders collide with the substrate or other composite powders at a relatively high speed by the helium gas, when the composite powders receive a high impact force, plasma discharged electrically by the helium gas is formed, and the plasma is a composite powder. In particular, it can cause serious damage to luminescent nanocrystals. In the actual aerosol deposition process, when CsPbBr ₃ -Al ₂ O ₃ composite powder was sprayed onto the substrate using helium gas as the carrier gas, strong light emission in the local area was observed, and occurred in the thin film formed through the aerosol deposition process It was confirmed that the wavelength of light to be made is blue shifted and the emission intensity is lower than the wavelength of light generated from the composite powder itself.

However, when using nitrogen (N ₂ ) as the carrier gas of the aerosol deposition process as in the present invention, nitrogen does not form a discharge plasma, thereby solving the problem of complex powder damage that occurs when helium gas is used as the carrier gas. Can. However, even when nitrogen gas is used as a carrier gas, there is a possibility that the luminescent nanocrystals may be damaged by high impact force due to collision between the composite powder and the substrate and the composite powders due to the high kinetic energy of the nitrogen gas. do.

In order to solve the above problems, the method of manufacturing a light emitting nanocrystal-metal oxide composite thin film according to an embodiment of the present invention may further include mixing the composite powder and the buffer polymer powder after the first step, In this case, the mixed powder of the composite powder and the buffer polymer powder in the second step may be sprayed onto the substrate through an aerosol deposition process to form the thin film.

In one embodiment, the buffer polymer powder may be formed of a polymer material such as polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), the total weight of the composite powder and the buffer polymer powder It can be mixed to about 0.1 to 2.5 wt% of the contrast. When the proportion of the buffer polymer powder is less than 0.5 wt%, the impact amount applied to the composite powder cannot be sufficiently reduced, which may cause a problem that the luminous intensity is lowered, and when it exceeds 2.5 wt%, mechanical properties or optical properties of the thin film Problems that degrade the characteristics may occur.

The composite thin film of light-emitting nanocrystals and metal oxides prepared according to the present invention may have a structure in which light-emitting nanocrystals are uniformly dispersed in a metal oxide matrix, and may have a thickness of about 1 to 50 μm.

Since the composite thin film has light-emitting nanocrystals disposed inside a metal oxide matrix, it can have significantly improved thermal stability and long-term durability compared to a light-emitting nanocrystal thin film using a conventional polymer matrix. On the other hand, in the case of manufacturing a composite thin film according to the present invention, since a thin film containing luminescent nanocrystals is formed using an aerosol deposition process that does not use a solvent, it is eco-friendly and can reduce process cost.

3 is a cross-sectional view for describing a backlight unit according to an embodiment of the present invention.

Referring to FIG. 3, the backlight unit 100 according to an embodiment of the present invention may include a light source unit 110 generating blue light and an optical film 120 absorbing blue light to generate red light and green light.

The light source unit 110 may include a light emitting diode that generates blue light. In one embodiment, the light source unit 110 is a direct light source unit including a diffuser plate and blue light emitting diodes disposed under the diffuser plate, or an edge including a light guide plate and blue light emitting diodes disposed on a side surface of the light guide plate. Type light source unit.

The optical film 120 may be disposed on the light source unit 110 to absorb a portion of the blue light generated by the light source unit 110 and convert it to red light and green light.

In one embodiment, the optical film 120 may include a substrate 121, a first light conversion layer 122 and a second light conversion layer 123.

The substrate 121 may be formed of a transparent polymer material, and a known optical film substrate can be applied without limitation.

The first light conversion layer 122 is formed on the substrate 121, absorbs blue light, and converts it to red light. In one embodiment, the first light conversion layer 122 may have a structure in which red light emitting nanocrystals are dispersed inside the first metal oxide matrix. The first metal oxide matrix may be formed of aluminum oxide, for example, alumina on α. The red light-emitting nanocrystals may include quantum dots, for example, cadmium-based quantum dots.

The second photo-conversion layer 123 is formed on the first photo-conversion layer 122 and absorbs blue light and converts it into green light. In one embodiment, the second light conversion layer 123 may have a structure in which green light emitting nanocrystals are dispersed in a second metal oxide matrix. The second metal oxide matrix may also be formed of aluminum oxide, for example, alumina on α. The green light-emitting nanocrystals may include quantum dots, for example, metal halide-based quantum dots having a perovskite crystal structure.

In one embodiment, the optical film 120 is manufactured by sequentially forming the first light conversion layer 122 and the second light conversion layer 123 on the substrate 121 through an aerosol deposition method Can be.

The first photo-conversion layer 122 prepares a first composite powder of red light-emitting nanocrystals and a first metal oxide, and then mixes it with a first buffer polymer powder to produce a first mixed powder, and nitrogen as a carrier gas. The first light conversion layer 122 may be formed on the substrate 121 using the first mixed powder through an aerosol deposition method.

The second light conversion layer 123 prepares a second composite powder of green light-emitting nanocrystals and a second metal oxide, and then mixes it with a second buffer polymer powder to prepare a second mixed powder, and nitrogen as a carrier gas. The second light conversion layer 123 may be formed on the first light conversion layer 122 using the second mixed powder through an aerosol deposition method.

Since the optical film applied to the backlight unit according to the present invention has a structure including luminescent nanocrystals dispersed inside a metal oxide matrix, long-term stability to external heat, moisture, and stress is excellent.

Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are only some embodiments of the present invention, and the scope of the present invention is not limited to the following examples.

<Preparation of CsPbBr ₃ -Al ₂ O ₃ nanocomposite powder>

After adding CsBr (6.7g, 22.1mmol) and PbBr ₂ (8.1g, 22.1mmol) in 200ml of DMSO, the mixture was stirred vigorously at 100°C for several minutes to dissolve completely, and the solution was completely dissolved in a planetary mixer. Moved to. The α-Al ₂ O ₃ powder (D50=520 nm, 150 g) was added to the planetary mixer in operation to form a slurry. The slurry was heated at 160°C to evaporate DMSO until it became a paste, and the paste was further dried in a drying oven at 160°C for 24 hours. CsPbBr ₃ -Al ₂ O ₃ nanocomposite powders were prepared by finely grinding the solidified powders obtained through this process using a mortar for about 10 minutes and then heat treatment at 500° C. for 1 hour.

<Preparation of CdSe/CdS/ZnS-Al ₂ O ₃ nanocomposite powder>

CdSe/CdS/ZnS red light-emitting quantum dots (R-QDs) (700 mg) having a core shell structure sequentially coated with a CdS shell and a ZnS shell on a CdSe core were dispersed in 350 ml N-hexane. While stirring through ultrasonic treatment, α-Al ₂ O ₃ powder (D50=520 nm, 100 g) was added to the R-QD solution solution, and after 5 minutes, it was dried in an oven at 80° C. for 8 hours, and Al ₂ O. The R-QD nanocomposite powder supported on ₃ was obtained.

[Example 1 and Comparative Example]

The CsPbBr ₃ -Al ₂ O ₃ nanocomposite powders were dried in an oven at 100° C., separated from each other for 1 minute through a high-speed powder mixer, and finely sliced particles were screened using a sieve net (ASTM mesh No. 120) After that, it was placed in an aerosol chamber equipped with a vibrator operating at 900 rpm.

Aerosolized composite powders were injected into the substrate using a slit nozzle having an orifice of 10.0*?*mm ² in a deposition chamber by injecting a carrier gas at room temperature. At this time, the deposition chamber was evacuated using a rotary pump and a booster pump, and the substrate holder automatically moved the substrate in the XY axis direction at a scanning speed of 3 mm/s, and the substrate was removed from the nozzle. They were placed 5 mm apart. Helium gas (comparative example) and nitrogen gas (example) were used as the carrier gas, respectively. The flow rate of the carrier gas was fixed at 4 L/min through a mass flow controller.

The CsPbBr ₃ -Al ₂ O ₃ composite thin film was formed on the substrate with an area of 20×20 mm ² .

[Example 2]

The PTFE of 1wt% using a powder mixer before being introduced into the aerosol chamber CsPbBr ₃ -Al ₂ O ₃ was mixed with the nano-composite powder, in Example 1, CsPbBr ₃ on a substrate in the same manner by using this -Al ₂ O _{A 3-} PTFE composite thin film was formed.

[Example 3]

Before injection into the aerosol chamber, 1 wt% of PTFE was mixed with CdSe/CdS/ZnS-Al ₂ O ₃ nanocomposite powders using a powder mixer, and the carrier gas flow rate was fixed at 12 L/min using the aerosol chamber CdSe/CdS/ZnS-Al ₂ O ₃ -PTFE composite thin film was formed on the substrate in the same manner as in Example 1, except that was vibrated at 300 rpm.

[Experimental Example]

Figure 4 shows the XRD pattern before and after the heat treatment of the CsPbBr ₃ -Al ₂ O ₃ nanocomposite powder, Figure 5 shows the measurement results of differential scanning calorimetry (DSC) for CsPbBr ₃ -Al ₂ O ₃ .

Referring to Figure 4, CsPbBr3-Al2O3 nanocomposite powder was found to be composed of α-alumina and monoclinic (monoclinic) CsPbBr3 phase, which was the same before and after heat treatment. However, the CsPbBr3-Al2O3 nanocomposite powder before heat treatment did not show any light emission with respect to ultraviolet irradiation, but the CsPbBr3-Al2O3 nanocomposite powder after heat treatment emitted green light by ultraviolet irradiation.

5, endothermic DSC records were observed at 142°C and 551°C, respectively. Since the bulk CsPbBr3 crystal melts at 567°C and crystallizes at 514°C, the endothermic peak at 551°C is for the melting of monoclinic CsPbBr3 crystals, and the endothermic peak at 142°C evaporates residual DMSO adsorbed on the nanocomposite powder surface. I think it is about things. Since residual DMSO is an obstacle to crystallization and luminescence properties, it is determined that heat treatment to remove it is necessary.

6 and 7 are respectively a raw α-Al ₂ O ₃ nanoparticles _{(pristine α-Al 2 O 3} nanoparticles) and CsPbBr ₃ -Al ₂ O ₃ SEM not for the nanocomposite powder.

6 and 7, it can be confirmed that CsPbBr ₃ nanocrystals in the CsPbBr ₃ -Al ₂ O ₃ nanocomposite powder are adsorbed on the submicron-sized Al ₂ O ₃ surface.

8 shows low magnification STEM images and EDS maps (energy-dispersive X-ray spectroscopy maps) for CsPbBr ₃ -Al ₂ O ₃ nanocomposite powder after heat treatment.

Referring to FIG. 8, it can be confirmed that all components of the CsPbBr ₃ nanocrystals are uniformly distributed in the same region, and the CsPbBr ₃ nanocrystals and Al ₂ O ₃ exist in a complex form.

9 shows PL images under ultraviolet irradiation for the composite thin films prepared according to Comparative Example (He), Example 1 (N ₂ ), and Example 2 (N ₂ &PTFE), and FIG. 10 shows Comparative Example (He) , PL intensity and absorption spectrum measured for the composite thin films prepared according to Example 1 (N ₂ ) and Example 2 (N ₂ &PTFE). The deposition thickness of the composite thin films measured using a surface profile meter was 6±1 μm.

9 and 10, the composite thin films prepared according to Comparative Example (He), Example 1 (N ₂ ), and Example 2 (N ₂ &PTFE) emit green light with respect to ultraviolet irradiation. Specifically, the composite thin film prepared according to Comparative Example (He) exhibited a peak wavelength of 517 nm and full widths at half maximum of 21 nm, and the composite thin film prepared according to Example 1 had a peak of 519 nm. The wavelength and full widths at half of 21 nm were shown, and the composite thin film prepared according to Example 2 exhibited a peak wavelength of 522 nm and a full widths at half maximum of 17 nm. On the other hand, the emission peak intensity of the composite thin film prepared according to Example 2 was measured significantly, and the composite thin film prepared according to Comparative Example (He) was measured to be the lowest.

Considering the peak wavelengths and half-widths measured for the CsPbBr3-Al2O3 nanocomposite powder itself are 522 nm and 17 nm, respectively, and the intensity of the peak wavelengths, the composite thin film prepared according to Example 2 has little damage to the composite powder during the aerosol deposition process. It can be seen that it was not.

11 to 13 show XRD patterns and cross-sectional SEM images of composite thin films prepared according to Comparative Example (He), Example 1 (N ₂ ), and Example 2 (N ₂ &PTFE). On the other hand, the insets of FIGS. 11 to 13 indicate PL intensity for ultraviolet irradiation.

11 to 13, the degree of peak shift and the half-width are the largest in the composite thin film prepared according to the comparative example, 0.208° and 0.718, and the smallest in the composite thin film prepared according to Example 2, 0.142° and 0.188. Appeared. The composite thin film prepared according to Example 2, in that the degree of peak shift and the half-width value generally include important criteria of physical residual stress arising from collision between particles and substrate and collision between particles in aerosol deposition process It is judged that the residual stress is the lowest and the residual stress in the composite thin film prepared according to the comparative example is the highest.

On the other hand, when helium gas is used as the carrier gas, when the substrate and the first thin film portion are subjected to a high impact force by collision of CsPbBr3-Al2O3 particles, the helium gas may form an electrically discharged plasma (EDP). . In contrast, nitrogen has a high molecular weight and does not cause discharged plasma in an aerosol deposition system. Since electrical discharge plasma generation for helium gas will cause serious damage to CsPbBr3 nanocrystals, compared to the composite thin film prepared according to Example 1, the thin film prepared according to the comparative example has a greater blue shift and lower PL strength. It is judged to have been measured.

In the case of the density of the composite thin films, the composite thin film prepared according to the comparative example was found to be higher than the composite thin film prepared according to the example 1, which is CsPbBr3-Al2O3 by helium carrier gas having a lower molecular weight than nitrogen gas having a high molecular weight. It is believed that this is because the powder transport speed is larger.

On the other hand, the crystal sizes of the composite thin films produced according to the'Scherrer formula' were 13 nm and 12 nm, respectively, for the composite thin films prepared according to the Comparative Example and Example 1, respectively. , The calculated crystal size for the composite thin film prepared according to Example 2 was 57 nm.

It was determined that the composite thin film prepared according to Example 2 exhibited a larger crystal size, a smaller degree of peak shift, and a half-width than the composite thin film prepared according to Example 1, due to the added PTFE, particle-substrate and particle-particle It is believed that this is because the impact force at the interface between them was reduced.

Figure 14 is a CsPbBr ₃ -Al ₂ O ₃ -PTFE composite thin film ('1wt%) prepared using powders of 1wt% PTFE mixed with CsPbBr ₃ -Al ₂ O ₃ nanocomposite powders on a PET substrate and a glass substrate. PTFE'), CsPbBr ₃ -Al ₂ O ₃ -PTFE composite thin film ('2wt% PTFE') and 3wt% prepared using powders of 2wt% PTFE mixed with CsPbBr ₃ -Al ₂ O ₃ nanocomposite powders Images of CsPbBr ₃ -Al ₂ O ₃ -PTFE composite thin films ('3wt% PTFE') prepared using powders of PTFE mixed with CsPbBr ₃ -Al ₂ O ₃ nanocomposite powders.

Referring to FIG. 14, a CsPbBr ₃ -Al ₂ O ₃ -PTFE composite thin film prepared using powders mixed with ₃ wt% of PTFE and CsPbBr ₃ -Al ₂ O ₃ nanocomposite powders is used on both a PET substrate and a glass substrate. It showed bad moldability. Therefore, the buffer polymer powder is preferably mixed to less than 3 wt%, preferably about 2.5 wt% or less, based on the total weight of the composite powder and the buffer polymer powder.

15 shows PLQY and PL wavelengths measured at 150° C. for 20 days for the composite thin film prepared according to Example 2.

Referring to FIG. 15, the composite thin film prepared according to Example 2 showed a blue shift smaller than 1 nm for 20 days under severe conditions of 150° C., and it was found that PLQY increased rather than decreased. From this, it can be seen that the composite thin film prepared according to Example 2 has excellent long-term thermal stability.

On the other hand, the composite thin film prepared according to Example 2 did not show any change in PL wavelength and PLQY over 4 months under atmospheric conditions.

FIG. 16 shows the measured PL intensity and color reproducibility after placing an optical film having a light-changing layer on which a composite thin film prepared according to Example 3 and a composite thin film prepared according to Example 2 were stacked on a blue light source. . In the optical film, the composite thin film prepared according to Example 3 converts blue light into red light, and the composite thin film prepared according to Example 2 converts blue light into green light.

Referring to FIG. 16, a blue LED driven at a current of 20 mA, green light emission in a CsPbBr3/Al2O3-PTFE layer of 15 μ (peak wavelength of 522 nm and half width of 17 nm) and red in an R-QD/Al2O3-PTFE layer of 12 μ The electroluminescence spectrum of luminescence (peak wavelength at 625 nm and half width at 25 nm) was shown, and a wide color gamut of 120% of NTSC standard (89% of Rec. 2020 color reproduction), luminance of about 3500 nit and (0.307, 0.312) It appeared to have a white point.

17 is a view for explaining various processability and excellent performance of the ceramic composite layers formed by the aerosol deposition method.

Referring to a and b of FIG. 17, it can be confirmed that a green light conversion pattern and a red light conversion pattern can be formed with the CsPbBr3-Al2O3-PTFE complex and the R-QD-Al2O3-PTFE complex through an aerosol deposition process using a mask. . The rectangular green and red light conversion patterns were formed to have a size of 150×500 μm ² and a thickness of 6 to 7 μ.

Referring to c of FIG. 17, it can be confirmed that successive multi-layer depositions were successfully performed according to the present invention. The thicknesses of the first layer, the second layer, and the third pattern are 12 μm, 8 μm, and 11 μm, respectively.

Referring to d of FIG. 17, it can be confirmed that the ceramic composite film deposited on the flexible PET substrate has flexibility and mechanical durability to withstand even if it is rolled with a radius of 7 mm. As a result of the automatic bending test, the CsPbBr3-Al2O3-PTFE thin film survived 100,000 repeated bending cycles without any cracking or surface damage.

Referring to e of FIG. 17, unlike a conventional method such as spin coating and centrifugal casting, CsPbBr3-Al2O3-PTFE nanocomposite powder and R-QD-Al2O3 nanocomposite powder are also used on a curved surface when an aerosol deposition technique is used. It can be confirmed that a thin film can be formed.

Although described above with reference to the preferred embodiments of the present invention, those skilled in the art may variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that you can.

100: backlight unit 110: light source unit
120: optical film 121: substrate
122: first light conversion layer 123: second light conversion layer

Claims (14)

A first step of preparing a composite powder of a luminescent nanocrystal and a metal oxide; And
A second step of forming a composite thin film by spraying the composite powder on a substrate through an aerosol deposition (Aerosol Deposition) process,
The composite powder includes an insulating metal oxide powder and a plurality of the light emitting nanocrystals directly adsorbed or bonded to the surface thereof,
The composite thin film is characterized in that it comprises a matrix made of the metal oxide and the light-emitting nanocrystals dispersed in the matrix, the method of manufacturing a light-emitting nanocrystal-metal oxide composite thin film. According to claim 1,
The light-emitting nanocrystals, characterized in that it comprises a quantum dot that emits light having a different wavelength after absorbing incident light, the method of manufacturing a light-emitting nanocrystal-metal oxide composite thin film. According to claim 2,
The light-emitting nanocrystals, characterized in that it comprises a metal halide-based quantum dot having a perovskite crystal structure, a method of manufacturing a light-emitting nanocrystal-metal oxide composite thin film. According to claim 1,
The first step includes mixing the precursor material of the luminescent nanocrystal and the powder of the metal oxide in a solvent and growing the luminescent nanocrystal from the precursor material on the surface of the metal oxide powder. Characterized in that, the method of manufacturing a light-emitting nanocrystalline-metal oxide composite thin film. According to claim 1,
The first step comprises mixing the synthesized luminescent nanocrystal and metal oxide powder in a solvent, and evaporating the solvent to adsorb or bond the luminescent nanocrystal to the surface of the metal oxide powder. A method of manufacturing a thin film of a light emitting nanocrystal-metal oxide composite. The method of claim 4 or 5,
The light-emitting nanocrystals, characterized in that contained in 0.5 to 20% by weight of the weight of the metal oxide powder, a method for producing a light-emitting nanocrystal-metal oxide composite thin film. According to claim 1,
The aerosol deposition (Aerosol Deposition) process is characterized in that using nitrogen (N2) as a carrier gas, a method of manufacturing a light emitting nanocrystalline-metal oxide composite thin film. According to claim 1,
Further comprising the step of mixing the composite powder and the buffer polymer powder is performed after the first step,
In the second step, characterized in that the mixed powder of the composite powder and the buffer polymer powder is sprayed on the substrate through the aerosol deposition process to form the composite thin film, a method of manufacturing a light emitting nanocrystal-metal oxide composite thin film . The method of claim 8,
The buffer polymer powder is polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene (PE) or polypropylene (PP), characterized in that formed of a light emitting nanocrystalline-metal oxide composite thin film production Way. The method of claim 8,
The buffer polymer powder is characterized in that it is mixed in a proportion of 0.1 wt% or more and 2.5 wt% or less of the total weight of the composite powder and the buffer polymer powder, a method of manufacturing a light-emitting nanocrystal-metal oxide composite thin film. Board;
A first photoconversion layer disposed on the substrate and having a first metal oxide matrix and red light emitting nanocrystals dispersed therein to absorb blue light to generate red light; And
An optical film comprising a second light conversion layer disposed on the first light conversion layer and having a second metal oxide matrix and green light emitting nanocrystals dispersed therein to absorb blue light to generate green light. The method of claim 11,
The first metal oxide matrix includes aluminum oxide,
The red light-emitting nanocrystals, characterized in that it comprises a quantum dot to absorb the blue light to generate red light, the optical film. The method of claim 11,
The second metal oxide matrix includes aluminum oxide,
The green light-emitting nanocrystals, characterized in that it comprises a metal halide-based quantum dot having a perovskite crystal structure, an optical film. A light source unit generating blue light; And
And an optical film that absorbs a part of the blue light generated from the light source unit to generate red light and green light,
The optical film may include a substrate disposed on the light source unit; A first photoconversion layer disposed on the substrate and having a first metal oxide matrix and red light emitting nanocrystals dispersed therein to absorb blue light to generate red light; And a second photo-conversion layer disposed on the first photo-conversion layer and having a second metal oxide matrix and green light-emitting nanocrystals dispersed inside and absorbing blue light to generate green light. , Backlight unit.

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