KR102222581B1 - Organic-inorganic hybrid perovskite quantum dot ink capable of inkjet patterning - Google Patents

Abstract

The present invention relates to an ink composition for inkjet printing including a perovskite crystal in the form of a colloidal nanocrystal and a method for manufacturing the same, and more particularly, to a downward direction optimized for green emission wavelength. _{A new FAPbBr 3} nanocrystal, which is a down-conversion material, is synthesized, and the new FAPbBr ₃ nanocrystal has excellent luminescence properties and aging stability, and exhibits excellent optical properties not only in an ink solution but also in a thin film state after inkjet printing. By confirming, it relates to the application of the novel FAPbBr ₃ nanocrystals to perovskite quantum dot nanocomposite ink and inkjet printing process technology capable of inkjet patterning for hybrid displays using Blue OLED and quantum dot color conversion technology.

Description

Organic-inorganic hybrid perovskite quantum dot ink capable of inkjet patterning

The present invention relates to an organic-inorganic hybrid perovskite quantum dot ink, a method of manufacturing the ink, and a use of the ink as a color conversion layer of a display.

The current OLED technology is mass-produced in a method that combines the RGB OLED method using FMM (Fine Metal Mask) in small size and WOLED and color filter (CF) in large size, but the FMM method has limitations in large area and high resolution. The CF (color filter) combination method has limitations in device efficiency and production yield.

In the case of perovskite LED, which is a promising candidate for future display devices, it is necessary to significantly improve the life of ink materials, and through the development of perovskite quantum dot nanocomposite ink manufacturing technology capable of inkjet patterning with a high color conversion rate, it is possible to drive pixels. We intend to develop next-generation display devices. Perovskite has excellent photophysical properties, e.g., high carrier mobility, high absorbance and very high color purity due to high photoluminescence quantum yield (PLQY), narrow full width at half-maximum (FWHM). There are light absorption and light emission ranges that can be easily turned by adjusting color purity and halide element ratio. In addition, since it has the advantages of manufacturing simplicity, low cost, and high solution processability, it can be the most competitive optoelectronic material if stability is improved.

Traditional CdSe/ZnS and InP/ZnS QDs have been used as down-conversion materials for QD/OLED hybrid display devices. It is good, has a narrower half-width of light emission, and can have a comparative advantage because the manufacturing method is easy and inexpensive.

Accordingly, the present inventors prepared perovskite crystals in the form of colloidal nanocrystals to be used as a color conversion layer of a hybrid display, inked, and applied to an inkjet printing process. , By mixing and optimizing an appropriate surfactant, a binder, and an additive for securing the aging stability of the ink and controlling the rheological properties, the present invention was completed.

Liang Su, Topics in Current Chemistry (Z), (2016) 374:42 Young-Hoon Kim, PNAS, (2016) 113(42):11694

An object of the present invention is to provide a colloidal nanocrystal form of FAPbBr ₃ (formamidinium lead tribromide) perovskite crystal and a method for synthesizing the same for manufacturing a color conversion layer of a hybrid display. .

Another object of the present invention is an inkjet in which a suitable surfactant, a binder, and an additive are added _{to the FAPbBr 3 (formamidinium lead tribromide) perovskite crystal in the form of colloidal nanocrystals to secure aging stability and control rheological properties.} It is to provide an ink composition for printing and a use for applying the same to an inkjet printing process.

In order to achieve the above object, the present invention provides an ink composition for inkjet printing comprising _{FAPbBr 3 (formamidinium lead tribromide) in the form of colloidal nanocrystals.}

In addition, the present invention

i) adding FABr and PbBr ₂ to a solvent and stirring;

ii) adding octadecanoic acid (OA) and octadecylamine (OAm) to the solution of step i) and stirring until a clear solution is obtained;

iii) taking part of the solution of step ii) and adding it to an anti-solvent, followed by stirring; And

iv) obtaining a supernatant by centrifuging the solution after the final reaction has been completed; it provides a method for preparing _{FAPbBr 3 in the form of colloidal nanocrystals.}

In addition, the present invention provides a method of preparing an ink composition for inkjet printing including a process of mixing _{FAPbBr 3 in the form of a colloidal nanocrystal, a solvent, and a photocurable resin.}

In addition, the present invention provides a color-converting film obtained by inkjet printing the ink composition for inkjet printing according to the present invention.

In addition, the present invention provides a display device obtained by inkjet printing the ink composition for inkjet printing according to the present invention.

In addition, the present invention provides an inkjet printer including the ink composition for inkjet printing according to the present invention.

_{The synthesis of the FAPbBr 3} perovskite crystal of the present invention is very simple and efficient with a one-pot synthesis process.

As a result of manufacturing a thin film for use as a QD/OLED hybrid display color conversion layer by inkjet printing the perovskite nano ink synthesized according to the present invention, the printed thin film was cured to a hard hardness through exposure of 395 nm wavelength. And, by receiving 450 nm of Blue OLED emission light, the color was efficiently converted into vivid green light. This showed much superior stability over time compared to _{the CsPbBr 3} @SiO ₂ perovskite ink complexed with silica, which is generally known to have excellent stability.

In particular, since the present invention is applied to the inkjet patterning method, if commercialized, the process steps can be drastically reduced and eco-friendly production facilities can be provided.

1 is a graph of the result of measuring the synthesized perovskite using FT-IR.
2 is a photograph of the result observed using TEM for the synthesized perovskite.
3 is a graph showing the result of measuring the particle size distribution of the synthesized perovskite using an HR-TEM image.
4 is a graph showing the result of measuring the synthesized perovskite CsPbBr ₃ @SiO _{2 using XRD.}
5 is a graph showing the result of measurement using XRD for the synthesized perovskite FAPbBr _3.
6 is a graph showing the PL strength as a percentage of the initial strength over time in order to see the storage stability _{of CsPbBr 3} @SiO ₂ , CsPbBr ₃ , and FAPbBr _{3 CNCs.}
7 is a graph showing the viscosity according to the temperature of the ink containing the synthesized perovskite, toluene and photocurable resin.
8 is a graph showing the PL intensity according to the wavelength of an ink including the synthesized perovskite and a thin film inkjet-printed with the ink.
9 is a graph showing the absorbance according to the wavelength of an ink including the synthesized perovskite and a thin film inkjet-printed with the ink.
10 is a diagram showing a result of measuring color coordinates of a thin film inkjet-printed with an ink containing the synthesized perovskite.
FIG. 11 is a photograph of observing a state in which a single ink drop is formed and dropped through a drop watcher when inkjet printing with an ink containing the synthesized perovskite ((a): CsPbBr ₃ @SiO ₂ , (b): FAPbBr ₃ ).
12 is a photograph of observation of wettability by dropping it on an inkjet printing device with an ink containing synthesized perovskite and dropping it on a surface plasma-generated glass substrate ((A): CsPbBr ₃ @SiO ₂ , (B)) : FAPbBr ₃ ).
FIG. 13 is a diagram showing the formation of an inkjet-printed dot pattern to have 220 µm drop spacing with the synthesized perovskite-containing ink and color-converted Green light emission by the blue LED of the printed thin film ((a): CsPbBr ₃ @SiO ₂ , (b): FAPbBr ₃ ).
14 is a result of inkjet printing line printing testing by adjusting drop spacing from 180 µm to 60 µm with ink containing synthesized perovskite and color-converted green light emission by Blue LED of the printed thin film It is a figure showing ((a): CsPbBr ₃ @SiO ₂ , (b): FAPbBr ₃ ).

Hereinafter, the present invention will be described in detail.

The present invention provides an ink composition for inkjet printing comprising _{FAPbBr 3 (formamidinium lead tribromide) in the form of colloidal nanocrystals.}

The colloidal nanocrystal form of FAPbBr ₃ is synthesized by dissolving a long chain ligand and a precursor in a solvent and then reprecipitation by a ligand introduced into an anti-solvent. I can.

The ink composition may further include any one or more of a surfactant, a binder, or an additive.

The ink composition may also contain a small amount of a surfactant, a wetting agent, and a viscosity modifier in order to control ink properties suitable for an inkjet printing process.

In the case of the humectant, it is used for the purpose of preventing the nozzle from clogging by preventing the ink from drying out in the nozzle, and helps to control the viscosity of the ink. In addition, in the case of surfactant, by controlling the surface tension of the ink, it affects the formation of meniscus and ink wetting of ink droplets, and plays an important role in controlling rheological properties.

In one embodiment of the present invention, _{a perovskite ink was prepared including the synthesized FAPbBr 3} colloidal nanocrystal, toluene, and a photocurable resin.

In addition, the present invention

i) adding FABr and PbBr ₂ to a solvent and stirring;

ii) adding octadecanoic acid (OA) and octadecylamine (OAm) to the solution of step i) and stirring until a clear solution is obtained;

iii) taking part of the solution of step ii) and adding it to an anti-solvent, followed by stirring; And

iv) obtaining a supernatant by centrifuging the solution after the final reaction has been completed; it provides a method for preparing _{FAPbBr 3 in the form of colloidal nanocrystals.}

The method is _{to dissolve the FAPbBr 3} material in a long chain ligand and a precursor in DMF, and then add it to an anti-solvent to re-electrophilize by a ligand, which is a simple synthesis method of low temperature and one-pot. It is a method of synthesizing a down-conversion material optimized for green emission wavelength by the (ligand assisted reprecipitation) method.

In addition, the present invention provides a method of preparing an ink composition for inkjet printing including a process of mixing _{FAPbBr 3 in the form of a colloidal nanocrystal, a solvent, and a photocurable resin.}

In the above manufacturing method, FAPbBr ₃ , the solvent and the photocurable resin are preferably mixed in a weight ratio of 1: 3 to 5: 3 to 5, respectively, to form ink, and to be mixed in a weight ratio of 1: 4: 4 More preferable.

In the above manufacturing method, any one or more of a surfactant, a binder, or an additive may be further added.

In the above manufacturing method, the photocurable resin is selected from isobornylacrylate or diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide [Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide]. It may include any one or more.

In the above manufacturing method, any one or more additives selected from the group consisting of IGEPAL, diethylene glycol, triethylene glycol, and glycol by-products may be further added.

In addition, the present invention provides a color-converting film obtained by inkjet printing the ink composition for inkjet printing according to the present invention.

In addition, the present invention provides a display device obtained by inkjet printing the ink composition for inkjet printing according to the present invention.

The thin film inkjet-printed with the ink composition according to the present invention was cured to a hard hardness through exposure of 395 nm wavelength, and was efficiently color converted into vivid green light by receiving 450 nm Blue OLED emission light. _{Compared to the CsPbBr 3} @SiO ₂ perovskite ink complexed with silica, which is generally known to have excellent stability, it showed much better aging stability.

In addition, the present invention provides an inkjet printer including the ink composition for inkjet printing according to the present invention.

Since the ink composition according to the present invention can be applied to the inkjet patterning method, if commercialized, the process steps can be drastically reduced and eco-friendly production facilities can be provided.

Hereinafter, the present invention will be described in detail by the following examples and experimental examples.

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the contents of the present invention are not limited by the following Examples and Experimental Examples.

< Example 1> FAPbBr ₃ Colloidal nanocrystals nanocrystal , CNC)

0.112 g of FABr and 0.367 g of PbBr ₂ were added to 10 mL of DMF and stirred for about an hour. 2 mL of OA and 400 μL of OAm were added and stirred until a clear solution was obtained. 7 mL of the solution from the previous step was collected and added to 200 mL of dry toluene under vigorous stirring (1,500 rpm). After 10 seconds, the stirring speed was reduced to 150 rpm, and then maintained for 120 minutes. The solution after the final reaction is centrifuged at 4000 rpm for 1 minute, and a supernatant solution is taken.

< Example 2> ink Formulation

To ensure that perovskite CNCs are stably dispersed in the ink and optimized for the inkjet printing process, the centrifuge was performed at low speed before ink formulation. In the case of CsPbBr3@SiO _{2 , aggregation has occurred due to SiO 2} or a centrifuge at 4,000 rpm to remove particles into which an excessive amount of silica has been introduced, and then supernatant solution). For FAPbBr ₃ , the CNC was centrifuged at low speed (4,000 rpm) to remove large undissolved aggregates. Ink was prepared so that the post-treated green CNCs solution, toluene, and photocurable resin had a ratio of 1:4:4. At this time, the photocurable resin is isobornyl acrylate, dipentaerylthritol hexaacrylate, and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (Diphenyl (2,4 ,6-trimethylbenzoyl)phosphine oxide) monomers were each composed of a ratio of 2:1:1, and a photoinitiator was included in 2 wt% of the total ink weight. In addition, IGEPAL 520: IGEPAL 630 = 8: 2 in the ratio of 5 wt% of the total resin weight was included as a supernatant (surfactant). Diethylene glycol, triethylene glycol, and glycol were included in an amount of 6 to 8 wt% of the total resin weight in order to match the rheological properties of the ink suitable for inkjet printing.

< Example 3> Production of color conversion film

Ink jet printing was performed on a Dimatix printer DMP-2800 with a 10-pl drop volume head attached at 19V and 1kHz. After pre-baking at 90° C. for 90 seconds, UV curing was performed [40 mWcm-2, 395 nm]. Post baking was performed at 200° C. for 20 minutes under N _{2 atmosphere to prepare a tightly cured film.}

< Experimental example 1> FAPbBr ₃ Structure analysis of colloidal nanocrystals

<1-1> Structure analysis using infrared spectroscopy (FT-IR)

To confirm the structure of perovskite CNCs, the structure was analyzed through FT-IR (Fourier Transform Infrared spectroscopy, Nicolet iS 10, Thermo) in the range of ^{650 ~ 4,000 cm -1.} Perovskite powder for measurement was used after the solution after the final reaction was centrifuged at 9,000 rpm for 10 minutes, and then the obtained precipitate was dried for one day.

As a result, as shown in Fig. 1, _{Silica introduced into CsPbBr 3} can be confirmed sharp peaks at ^{1084 cm -1} and 800 cm ^-1 due to the vibration of Si-O-Si and the asymmetric stretching vibration. The presence of the OA and OAm used as ligand (ligand) is 2,851 cm ^-1 at 2,920 cm ^-1, CsPbBr ₃ @SiO in ₂ of 2,923 cm ^-1 CH asymmetric stretching vibration (asymmetric stretching vibration), FAPbBr ₃ in FAPbBr _3, A symmetric stretching vibration of 2,854 cm ^-1 in CsPbBr3@SiO ₂ , 1,465 cm ^-1 _{in FAPbBr 3} , and 1,469 cm ^-1 in CsPbBr3@SiO _{2 were observed.} . NH bending vibration of OAm (bending vibration) was observed at 1,618 cm ^-1 is at 1,617 cm ^-1, CsPbBr ₃ @SiO ₂ in FAPbBr _3. The C=O stretching vibration of OA was confirmed at 1,715 cm ^-1 _{in FAPbBr 3} and 1,718 cm ^-1 in CsPbBr3@SiO _2. Based on this, it was confirmed that the complexation of perovskite CNCs with silica and the introduction of ligands.

<1-2> Transmission Electron Microscopy TEM ) analysis

Transmission electron microscopy (TEM) was performed with JEM-2100F manufactured by JEOL. The synthesized perovskite CNCs were centrifuged at 9,000 rpm for 10 minutes, and the precipitate was dried for one day and then obtained in the form of powder, and then re-dispersed in toluene for measurement.

_{As a result, CsPbBr 3} to which silica was not introduced was confirmed in FIG. 2 (a). It was confirmed that CNCs with a size of about 10 nm were well synthesized. _{Looking at CsPbBr 3} @SiO ₂ into which silica is introduced in (b) of FIG. 2, it was confirmed that silica particles and CsPbBr ₃ were formed in a core-shell structure. In particular, it was confirmed that silica was uniformly stacked on the surface of _{CsPbBr 3 to a thickness of 5 nm in high magnification observation.} In addition, it was confirmed that the size of the cores in the _{synthesized CsPbBr 3} and CsPbBr ₃ @SiO _{2 were synthesized with a size of about 10 nm.} Referring to (c) of FIG. 2, FAPbBr ₃ synthesized with a size of about 26 nm was observed. It was confirmed that the synthesis was neatly synthesized by the interaction of the precursor _{of FAPbBr 3} and the ligand without other additives.

<1-3> Analysis of particle size distribution

Particle size distribution analysis was estimated using HR-TEM image.

As a result, as shown in FIG. 3, in the case of CsPbBr ₃ , which is a pure core, in the histogram, an average of about 10 to 11 nm was indicated, and CsPbBr ₃ @SiO ₂ of the core-shell structure of the composite was 10 due to the influence of the SiO _{2 shell.} It was confirmed that the nm has a size of about 20 nm, which is increased. In _{the case of FAPbBr 3} , it was confirmed to have a size of about 26 nm as confirmed by HR-TEM.

<1-4> X-ray diffraction analysis

The solution after the final reaction is centrifuged at 9000 rpm for 10 minutes through a centrifuge, and the precipitate is dried for one day to obtain a powder form, and then X-Ray Difrraction (XRD) (PANalytical, Empyrean Alpha-1 X-Ray Diffractometer) Was measured.

As a result, as shown in FIG. 4, in the case of CsPbBr ₃ @SiO ₂ , strong peaks were observed at 2θ = 21.43°, 30.42°, and 43.53, showing an orthorhombic shape. As shown in FIG. 5, in the case of FAPbBr ₃ , strong peaks were observed at 2θ = 14.94°, 29.99°, and 33.57°, showing a cubic shape. FAPbBr ₃ was synthesized by interaction with FABr, PbBr _{2 and ligand without the involvement of NH 4} OH during the synthesis process, and there was no other interference, so it seems to show a cubic form well. In addition, unlike _{the synthesis process of CsPbBr 3} , the pre-heat process of the precursor during synthesis was not performed, so that the penetration of oxygen or moisture could be effectively prevented. The clean peaks at 2θ = 20 ~ 30° can be confirmed because there is no amorphous silica, which is the structure of the shell when compared _{to the previously synthesized CsPbBr3@SiO 2.}

< Experimental example 2> FAPbBr ₃ Stability analysis of colloidal nanocrystals

In _{order to see the storage stability of CsPbBr 3} @SiO ₂ , CsPbBr ₃ , and FAPbBr ₃ CNCs, the PL intensity over time was compared and expressed as a percentage of the initial intensity. The solution after the final reaction was measured using a solution centrifuged for 10 minutes at 4,000 rpm through a centrifuge. After measuring the 4th day and the 7th day, the measurement was performed at intervals of one week until the last 28 days.

The PL emission spectrum and the change over time of PL were measured using the FS-2 Fluorescence Spectrometer of scinco. The PL intensity of the final solution of perovskite silica CNCs and uncomplexed perovskite CNCs over time was compared. In the case of heat stability, the final synthesis solution of perovskite was heated at 100°C to measure the decrease in PL intensity over time. PL lifetime measurements were performed using an Edinburgh Instruments TRPL-FS5 equipped with a double index.

As a result, as shown in FIG. 6, in the _{case of CsPbBr 3} not complexed with Silica, the PL decreased rapidly until the lapse of 7 days, and only 0.11% of the initial PL intensity was shown on the 28th day, and the light emission almost disappeared. I did. On the other hand _{, in the case of CsPbBr 3} @SiO ₂ complexed with silica, it showed a PL increase of about 20% on the 7th day, and it was confirmed that the high PL intensity of 85% or more was maintained on the last 28 days, so the introduction of silica passivation perovskite The effect on improving the stability of CNCs was clearly shown. The initial PL increase of CsPbBr ₃ @SiO ₂ showed higher intensity at the beginning because it passed the trap states on the silica surface by moisture in the air. FAPbBr ₃ showed more than 50% increase in PL intensity on the 4th day as this effect was even more striking, and then showed 142% PL compared to the initial intensity on the last 28 days. It was found that while the organic-inorganic halide perovskite was stored in the atmosphere without special passivation, the presence of moisture improved the sample performance compared to the two paths. It favors the formation and partial passivation of large crystalline (and thus fewer surface and grain boundary defects) amorphous atoms at the surface by _{O 2} and H _{2 O molecules.} That is, the deep-lying trapping defect is passivated by a photochemical reaction containing oxygen in _{FAPbBr 3, resulting in a photoactivated process, and it is believed that PL is increased.} In addition, hydrogen bonding of FA cation and Pb-Br octahedral bromide ions and double ammonia group of FA ions _{inhibited movement in close-paking [PbBr 6} ] ₄ -cages, resulting in CsPbBr ₃ It had a higher stability at room temperature than. Based on this, it was confirmed that the introduction of silica capping of all inorganic perovskites (CsPbBr _{3) helped improve long-term stability at room temperature. In addition, it was confirmed that FAPbBr 3} , a hybrid organic-inorganic halide perovskite, exhibits higher PL stability even without silica capping.

< Experimental example 3> The physics of ink and Rheological Characterization

<3-1> Viscosity measurement

The viscosity and surface tension at 25° C. should be controlled in the range of 1 cP to 10 cP and 20 mN/m to 70 mN/m, respectively. In addition, it is necessary to manufacture an ink having a low viscosity change according to temperature for stable spraying. The viscosity of the perovskite ink was measured in a temperature range of 10-50°C. Viscosity was measured using Brookfield's Programmable Digital Viscometer DV-II + Pro LV.

_{In the case of FAPbBr 3 not} introduced with Silica, the risk of clogging of the nozzle is low because there is no aggregation of silica, so it was optimized to a viscosity higher than that of _{CsPbBr 3} @SiO _{2 to improve the flatness of the thin film surface.}

As shown in Fig. 7 and Table 1, all of the prepared perovskite inks showed a decrease in viscosity as the temperature increased. It was found that all the measured viscosity values were within the operating range of the inkjet printer ink.

Temperature(℃) Viscosity (cP) FAPbBr ₃ CsPbBr ₃ @SiO ₂ 10 10.31 8.54 20 7.96 6.11 30 5.98 4.48 40 4.65 3.35 50 4.02 2.99

<3-2> Surface tension, electrical conductivity and pH measurement

The surface tension of the ink was measured using a Kruss Digital Tensiometer K9 equipment, and the electrical conductivity was measured using a Myron L Ultrameter II equipment.

As shown in Table 2 below, the surface tension, electrical conductivity and pH values of the prepared perovskite ink are listed. The surface tension values of all prepared inks were in the appropriate range, which was within the operating range of the inkjet printing application.

In the case of the conductivity value, since perovskite is a crystalline material composed of ionic bonds, it is a somewhat higher value than that of organic dye ink, but it is a value of 800 mS/m or less so that there is no problem in inkjet printing. In the case of pH, a value of around 7 was suitable for inkjet printing, and was adjusted to an appropriate value through the ink composition formulation.

ink Surface tension
(mN/m) Electrical conductivity
(mS/m) pH FAPbBr ₃ 34.3 313 6.5 CsPbBr ₃ @SiO ₂ 38.5 396 6.6

< Experimental example 4> Analysis of optical and color characteristics of ink and film

<4-1> Ultraviolet/visible ray absorption spectrum measurement

The final synthetic solution was centrifuged at 4000 rpm, and the absorption wavelength was measured using a perovskite solution from which the precipitate was removed. In addition, the luminous wavelength and PLQY and FWHM were measured together with a sample in a thin film state by inkjet printing of _{inked CsPbBr 3} @SiO ₂ and FAPbBr _3.

Absolute PL Quantum yield spectrometer The absolute value (PLQY) and FWHM of the luminescence quantum yield of perovskite CNCs silica composite ink and inkjet-printed thin films with the Quantaurus-QY equipment were measured. Ultraviolet/visible light absorption spectrum was measured using Scinco's Mega-800 UV/Vis spectrometer.

As a result, it is shown in Figs. 8, 9, and Table 3.

PLQY
(%) Absorption
(@ 450 nm) Maximum PL Wavelength
(nm) PL Peak
FWHM
(nm) FAPbBr ₃ ink 78.9 0.317 525.09 18.66 FAPbBr ₃ film 76.9 0.412 547.51 21.25 CsPbBr ₃ @SiO ₂ ink 75.4 0.417 504.81 28.88 CsPbBr ₃ @SiO ₂ film 73.0 0.424 524.34 31.20

All of the synthesized perovskites showed strong absorbance under 500 nm, which was compared with the commercial CdSe QD solution. In particular, it showed higher absorbance than CdSe QD, which is a color conversion layer material, near 450 nm, which is the wavelength of blue OLED BLU. In particular, the _{absorbance of the FAPbBr 3} solution around 450 nm was very high, _{and the complexation of the CsPbBr 3} crystal with silica had little effect on the absorbance. Therefore, it was confirmed that when the newly developed perovskite ink thin film was used with blue OLED as a color conversion layer, it could exhibit a color closer to actual green due to high absorption in the 450 nm region. In addition, the PL wavelength peak was observed by excitation at 450 nm, which is a blue emission region. The inked solution form and the film form produced through photocuring were measured together, and the absorbance at 450 nm was also shown. The CsPbBr ₃ @SiO ₂ solution showed maximum intensity at 504.81 nm, and the CsPbBr ₃ @SiO ₂ film was _{red shifted by about 20 nm compared to the CsPbBr 3} @SiO ₂ solution, indicating that it had an appropriate green peak of 524.34 nm. FAPbBr ₃ The solution had 525.09 nm and the film had 547.51 nm. The reason for the red shift is that in the case of the PL measurement of the solution, the CNCs are well dispersed, and the measurement is performed by receiving external excitation light, whereas the film is measured in a solid film state and the CNCs are aggregated. Therefore, it can be expected to be due to the Forster resonance energy transfer (FRET) phenomenon, which absorbs the luminescence of nearby CNCs as well as the absorption of external excitation light. Therefore, in the case of the film, it can be seen that the emission short wavelength (490 nm ~ 520 nm) of the CNCs is absorbed and becomes relatively weak and shifts to the long wavelength region. The reason that CsPbBr _{3 emits light in a shorter wavelength than FAPbBr 3} is due to the size of the A site. Because Cs ⁺ is smaller than HC(NH ₂ ) ²⁺ , the lattice becomes smaller and the band gap becomes smaller. However, both are included in a suitable green light emitting area that can be used as a color conversion layer. In addition, since it has a narrow FWHM of around 30 nm and shows clear green, it can be suitably used as a color conversion layer using blue BLU. In particular, in _{the case of FAPbBr 3} , both the film and the solution have a very narrow FWHM of around 20 nm, enabling more vivid green color expression. In addition, in _{the case of CsPbBr 3} @SiO ₂ , it was confirmed that the solution and film had a PLQY of 75.4 and 73.0, respectively, _{and in the case of FAPbBr 3} , the solution and the film had excellent PLQY of 78.9 and 76.9, respectively. As a result, when applied to the color conversion layer of a hybrid display device, excellent photophysical performance can be exhibited.

<4-2> Color coordinates Measure

The color coordinates of the inkjet-printed thin films were measured with the M6100 IVL test system. To check the jettability of Perovskite ink, measurements were made using a Dimatix printer DMP-2800 under the conditions of a firing voltage of 19V and a firing frequency of 1kHz. In the case of a thin film for measuring color coordinates, there should be no blue leakage, so it was printed in a thicker thickness showing an absorption value of 1.5.

As a result, as shown in FIG. 10, in the case of CsPbBr ₃ @SiO ₂ , the coordinates of (0.15, 0.74) were shown, and in _{the case of FAPbBr 3} , due to the narrower half-width, the more vivid green color coordinates of (0.11, 0.75) were obtained. Indicated. These values showed the possibility of representing a wider color reproduction range than the green color standard (0.21, 0.72) of NTSC TV indicated in red. In addition, the existing CdSe QD marked in purple showed a bluish green with a slightly low y coordinate value due to insufficient absorption in the blue region, indicating that it was difficult to express a vivid green color without a yellow filter layer. That is, through the high optical properties of the synthetically developed perovskite green NC thin film, it was found that the color expression is superior to the previously reported CdSe QD-based LED performance. These results revealed a potential application capable of manufacturing a wide color gamut display device.

< Experimental example 5> Inkjet Printing performance analysis

<5-1> Spray stability measurement

The prepared perovskite inks were applied to a Dimatix ink-jet printing machine to observe drop formation of the ink, and the stability of jetting was evaluated. A single ink drop was formed and dropped through the drop watcher. The tail length, drop volume, drop speed, and drop formation factors were observed, and also the behavior of the ink according to voltage and Hz was observed.

Toluene used as a solvent has a low viscosity (0.590 cP), a low density (0.867 g/ml), and a relatively high vapor pressure of 2.9 kPa. Wetting agents, viscosity modifiers were added and the firing voltage and firing frequency were adjusted to optimize. Finally, it was confirmed that the perovskite inks prepared by being optimized under the conditions of 19 V and 1 kHz were stably sprayed.

As a result, as shown in FIG. 11, in _{the case of the FAPbBr 3} ink not introduced with Silica, the risk of nozzle clogging is low due to the lack of agglomeration of _{silica as described in the viscosity characteristics, so CsPbBr 3} @ to improve the flatness of the thin film surface. It was confirmed that the tail was formed a little longer because it was optimized to a higher viscosity than _{SiO 2 ink.} If the droplet discharge conditions are not optimized, unstable droplets are formed or satellite droplets are generated. These factors are the main reasons for deteriorating print quality in the inkjet process. When satellite droplets are generated, the linearity of the droplets is deteriorated, and printing cannot be performed at a desired point on the substrate. Therefore, stabilization of droplets discharged from the inkjet head is absolutely necessary. In order to secure the straightness of the ejected droplets, the head driving voltage, the driving waveform, and the physical and rheological characteristics of the ink must be controlled so that uniform ejection is maintained. In conclusion, it was confirmed that stable spraying of both inks was confirmed, and accurate printing was possible because satellite droplets were not created.

<5-2> Wetability ( wettability ) Measure

The prepared ink was applied to a Dimatix ink-jet printing machine and dropped onto a plasma-treated glass substrate to observe wettability. Like sprayability, it was measured at 19 V and 1 kHz. To measure the diameter of the printing dot, the measurement was made by magnifying it at 150 magnification with the printer's own camera. The diameters of the printed thin films were measured at intervals of 1 minute, 3 minutes, and 5 minutes from immediately after drop dropping, and corresponding data are shown in FIGS. 12 and 4.

The conventional method of printing functional materials is to adjust the surface energy of the substrate to allow complete wetting. This will reduce the Marangoni effect, resulting in a more even layer. However, in the case of nanoparticles, a higher contact angle may be better. In the case of spherical nanoparticles, the high contact angle not only provides a uniform gas pressure over the entire surface of the droplet, but also increases the drying time, which is helpful for the close packing of the nanospheres. Since this effect was also effective in QD, perovskite NC can also be applied. Table 4 shows the diameter by time.

time
(min) Diameter(㎛) CsPbBr ₃ @SiO ₂ ink FAPbBr ₃ ink 0 102 108 One 104 112 3 104 112 5 104 114

As a result, CsPbBr ₃ @SiO ₂ ink showed a diameter of 102 μm immediately after printing (0 min), and it was maintained at the same diameter until 5 minutes after reaching a diameter of 104 μm after 1 minute, indicating that it has excellent wettability characteristics. Confirmed. In the case of _{FAPbBr 3} ink, it was confirmed that droplets were formed a little wider because of the lower surface tension than _{CsPbBr 3} @SiO _2. Immediately after printing (0 min), the diameter was 108 μm, and at 1 minute and 3 minutes, the diameter was 112 μm, increasing by 4 μm compared to the initial period. Finally, it increased from 5 min to 114 μm, showing a total diameter increase of about 6 μm, but this was a very small change in diameter compared to the total, so it could be judged that it shows stable wettability.

<5-3> dot Dot pattern measurement

It was confirmed that ink-jet printed dot patterns were formed to have 220 µm drop spacing. The color-converted Green light emission by the Blue LED of the perovskite thin film was also shown.

As a result, as shown in FIG. 13, since both of the perovskite inks showed stable droplets, the linearity of the droplets was excellent, so that it could be accurately printed at the intended position on the substrate. This is because the physical and rheological properties of the perovskite ink are well controlled. In addition, the optimized surface tension influenced the inkjet stability. If these characteristics are not well controlled, the straightness of the droplets fall is not maintained and printing is not performed at the intended position, so that the spacing of the dot patterns is not constant, or the dot patterns overlap, making printing application difficult. As can be seen from the jetting properties, both perovskite inks have high straightness so that they could be printed at the intended position, and the overlap of dot patterns could not be found, but the shape of the stolen droplet was more stable _{in FAPbBr 3 ink.} I did.

Line printing testing was performed by adjusting the dot spacing to 60 μm.

As a result, as shown in FIG. 14, overlapping between dots did not occur up to 150 μm in both inks, but overlapping occurred from 120 μm. From 90 μm, it can be seen that the dots were not formed and all of them were printed in an overlapping form. As the dot spacing became smaller, the spacing between single drops became narrower, and the overlapping part was widened when forming the thin film, so it was found that the thickness of the thin film became thick, and it was confirmed that the proper dot spacing should be adjusted when forming the thin film. .

The present invention can develop a perovskite quantum dot nanocomposite ink capable of inkjet patterning for a hybrid display using blue OLED and quantum dot color conversion technology, and can be applied to inkjet printing process technology.

When the quantum dot nano-ink manufacturing technology according to the present invention is applied to a QD/OLED hybrid display, the structure is simplified to 50% or less compared to the existing WOLED, and at the same time, when a high color conversion efficiency and uniform pixel patterning technology are developed, perovskite You can take advantage of its excellent color realization characteristics.

Claims (9)

delete delete delete i) adding FABr and PbBr ₂ to a solvent and stirring;
ii) adding octadecanoic acid (OA) and octadecylamine (OAm) to the solution of step i) and stirring until a clear solution is obtained;
iii) taking part of the solution of step ii) and adding it to an anti-solvent, followed by stirring; And
iv) centrifuging the final reaction solution to obtain a supernatant (supernatant); including, a method for producing _{FAPbBr 3 in the form of colloidal nanocrystals.
a) preparing FAPbBr 3} in the form of colloidal nanocrystals by the method of claim 4; And
b) mixing a solvent and a photocurable resin with _{FAPbBr 3} in the form of colloidal nanocrystals prepared in step a).
The method of claim 5,
FAPbBr ₃ , a solvent and a photocurable resin are each 1: 3 to 5: 3 to 5, characterized in that ink by mixing in a weight ratio of 3 to 5, characterized in that the method for producing an ink composition for inkjet printing ink.
The method of claim 5,
A method for producing an ink composition for inkjet printing, characterized in that further mixing any one or more of a surfactant, a binder, or an additive.



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