Preparation method and application of perovskite quantum dot ink

Abstract

The application provides a preparation method of a perovskite quantum dot ink, comprising the following steps: blending decahydronaphthalene, n-octane and white oil to obtain a ternary mixed solvent through stirring; and adding a solute into the ternary mixed solvent to obtain a mixed solution, wherein the solute is perovskite quantum dots and organic ligands arranged on surfaces of the perovskite quantum dots, so that the solute is uniformly dispersed in the ternary mixed solvent to obtain the perovskite quantum dot ink. The application forms a self-outer-to-inner Marangoni flow through a three-solvent system, and balances a self-inner-to-outer capillary flow of a coffee ring effect, so that the coffee ring is eliminated.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum dot ink, and in particular relates to a preparation method and application of perovskite quantum dot ink. Background Art

[0002] Color conversion display applications leverage the photoluminescent properties of quantum dot materials. Using a blue OLED or blue LED backplane as the excitation source, a color conversion layer composed of green and red quantum dots is integrated into the display panel. This color conversion method produces the desired green and red light emissions, which are then combined with the native blue light to achieve full-color display. Compared to traditional inorganic quantum dots (e.g., CdSe), perovskite quantum dots offer superior color purity, luminescent color, and fluorescence quantum yield, as well as a higher absorption coefficient, making them more suitable for use in color conversion layers.

[0003] During the inkjet printing process of perovskite quantum dot inks to fabricate pixelated color-conversion films, solvent evaporation significantly affects the uniformity of solute distribution within individual ink droplets, and thus the luminescence uniformity of the entire color-conversion film. The coffee ring effect is typically the primary cause of this uneven solute distribution. During solvent evaporation within the ink droplet, the three-phase pinning effect formed by the contact between the droplet and the substrate pins the droplet's edge to the original contact line, preventing it from shrinking. The droplet's diameter remains unchanged, the contact angle decreases, and the solvent evaporation rate at the edge exceeds that at the center. To compensate for the more rapid solvent loss at the droplet's edges, capillary flow is generated from the inside out. This capillary flow simultaneously drives the solute in the droplet's center to migrate and deposit toward the droplet's edges, resulting in the coffee ring phenomenon, which is thin in the middle and thick at the edges. This uneven solute distribution significantly affects the optical and electrical properties of perovskite quantum dots.

[0004] At present, binary solvent systems are mostly used in inkjet printing processes. It is difficult to achieve long-term stable printing while overcoming the "coffee ring" effect through solvent regulation methods, which increases the difficulty of preparing high-resolution perovskite quantum dot color conversion films, and therefore needs to be improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and application of perovskite quantum dot ink. To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A method for preparing perovskite quantum dot ink comprises the following steps:

[0007] Decalin, n-octane and white oil are mixed and stirred to obtain a ternary mixed solvent; a solute is added to the ternary mixed solvent to obtain a mixed solution, wherein the solute is perovskite quantum dots and an organic ligand arranged on the surface of the perovskite quantum dots, so that the solute is uniformly dispersed in the ternary mixed solvent to obtain perovskite quantum dot ink.

[0008] Furthermore, the mixed solution was filtered through a 0.22 μm filter membrane to obtain a perovskite quantum dot ink with uniformly dispersed solutes and no agglomeration.

[0009] Furthermore, the volume ratio of decahydronaphthalene, n-octane and white oil in the ternary mixed solvent is 7:2:2.

[0010] Furthermore, the concentration of the solute is represented by OD (Optical Density) at 400 nm, and the OD value is 35-100.

[0011] Furthermore, the organic ligand includes one or more of oleic acid, oleylamine, dodecylbenzenesulfonic acid, poly(isobutylene-alt-maleic anhydride) and dibromocyanoacetamide.

[0012] Furthermore, the perovskite quantum dots include at least one of CsPbBr3 and CsPbI3.

[0013] An inkjet printing method uses perovskite quantum dot ink as inkjet printing ink, and the inkjet printing method selects piezoelectric inkjet printing.

[0014] Exemplarily, the inkjet printing method includes drop-on-demand (DoD). In the DoD technology, the generation and ejection of ink droplets are controlled by pulse signals, and the ink is ejected drop by drop through the print head only when the printing point is actually set. The DoD technology significantly improves the utilization rate of ink, and the printing resolution is high, so it has gradually replaced continuous inkjet. Above the printing head is a chamber full of ink, and by reducing the volume of the chamber, the ink is ejected through the print head. Most DoD printers currently use heat-driven or piezoelectric-driven print heads. Thermal inkjet uses resistance to heat the ink to 350-400℃, which evaporates to generate a bubble, and due to the expansion of the bubble, the ink is squeezed out of the nozzle. When the ink droplet is ejected, the bubble will collapse, thereby generating a force to fill the ink. The working principle of piezoelectric inkjet is to generate mechanical movement by applying an electric pulse on a piezoelectric ceramic sheet, inducing a pressure wave in the cavity, so that the ink is pushed out of the nozzle to form an ink droplet. After the electric pulse is removed, the piezoelectric ceramic sheet returns to its original shape, and the chamber is refilled, ready to start a new ejection cycle. Therefore, piezoelectric inkjet does not require high operating temperature and has little side effect on the ink. This inkjet technology is currently used in most laboratories and industrial production. The pattern of inkjet printing adopts a dot matrix pattern, so that the display panel produced has rich color and tone changes and has good display effect. The printed substrate can be an ITO (indium tin oxide) glass substrate on which ZnO is spin-coated, so that the printed substrate can transmit charges well. The printed substrate can also use other substrates with good electronic transmission performance, and the present disclosure does not limit this.

[0015] A perovskite quantum dot pixelated color conversion film is prepared by inkjet printing using the above-mentioned quantum dot ink. Exemplarily, after the inkjet printing is completed, the substrate is placed in a vacuum annealing box for vacuum annealing, the annealing temperature is 60℃, and the annealing time is 30 min. The dried perovskite quantum dot ink droplets are the pixelated color conversion film. Vacuum annealing can reduce the drying time and is beneficial to the light emission uniformity of the film.

[0016] A display device includes a backlight and the above-mentioned quantum dot film.

[0017] The beneficial effects of the present invention are mainly reflected in the following: during the solvent volatilization process of inkjet printing, the perovskite quantum dot ink constructed using the ternary mixed solvent system forms a gradient volatilization due to decalin (high boiling point) and n-octane (low boiling point), causing an outside-to-inside Marangoni flow to balance the inside-to-outside capillary flow, thereby suppressing the "coffee ring" effect; in addition, the addition of white oil can enhance the inhibitory effect of the ternary mixed solvent system on capillary flow, hindering the migration of solutes; the synergistic effect of the two can completely eliminate the "coffee ring" effect, ensuring that the solute distribution within the ink droplets formed by the perovskite quantum dot ink is uniform and the luminescence is uniform. During the inkjet printing process using the perovskite quantum dot ink, the perovskite quantum dot ink system is stable, which is conducive to achieving long-term and stable inkjet printing. The formed perovskite quantum dot pixelated film has excellent luminescence uniformity and high resolution, and is suitable for color conversion layers in color conversion display applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 2. Schematic diagram of two-dimensional fluorescence intensity imaging of a single perovskite quantum dot ink droplet obtained by inkjet printing of the perovskite quantum dot ink prepared in Example 1;

[0019] Figure 2 3D fluorescence intensity imaging diagram of a single perovskite quantum dot ink droplet obtained by inkjet printing of the perovskite quantum dot ink prepared in Example 1;

[0020] Figure 3 is a fluorescence micrograph of a high-resolution pixelated film obtained by inkjet printing of the perovskite quantum dot ink prepared in Example 1;

[0021] Figure 4 is a fluorescence micrograph of a high-resolution pixelated color conversion film obtained by inkjet printing of the perovskite quantum dot ink prepared in Example 2;

[0022] Figure 5 2. Schematic diagram of two-dimensional fluorescence intensity imaging of a single perovskite quantum dot ink droplet obtained by inkjet printing of the perovskite quantum dot ink prepared in Comparative Example 1;

[0023] Figure 6 3D fluorescence intensity imaging diagram of a single perovskite quantum dot ink droplet obtained by inkjet printing of the perovskite quantum dot ink prepared in Comparative Example 1;

[0024] Figure 7 This is a fluorescence micrograph of a red light pixelated film obtained by inkjet printing of the perovskite quantum dot ink prepared in Comparative Example 2. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0026] In the present application, the concentration of the solute is represented by OD (Optical Density) at 400 nm, which is fixed at 100 in different embodiments.

[0027] Example 1:

[0028] In the reactor, decalin, n-octane and white oil were added and mixed by magnetic stirring to obtain a ternary mixed solvent. The solute was added to the mixed solvent to obtain a mixed solution, and then the mixed solution was filtered through a 0.22 μm filter membrane to obtain a perovskite quantum dot ink. The volume ratio of the solvent was decalin:n-octane:white oil = 7:2:2, and the concentration of the solute was OD = 100. The solute included red light CsPbI3 perovskite quantum dots and oleic acid, oleylamine and poly(isobutylene-alt-maleic anhydride) ligands arranged on the surface of the quantum dots, so that the solute was uniformly dispersed in the ternary mixed solvent.

[0029] The perovskite quantum dot ink in the present embodiment was used for piezoelectric inkjet printing, and the printing dot spacing was set to 50 μm. The ink droplets were stably and smoothly ejected from the nozzle, and there was no nozzle clogging phenomenon. By vacuum annealing the ink droplets on the printing substrate, a red light pixelated film was obtained. Figure 1 and Figure 2 is a fluorescence intensity imaging diagram of the ink droplets obtained by inkjet printing of the perovskite quantum dot ink prepared in Example 1. From Figure 1 and Figure 2 It can be seen that, due to the use of a ternary mixed solvent system, the luminescence uniformity of the ink droplets is very good, and the coffee ring effect is successfully eliminated. Figure 3 is a fluorescence micrograph of a red light pixelated film obtained by inkjet printing of the perovskite quantum dot ink prepared in Example 1. From Figure 3 It can be seen that the prepared film has a very high resolution (508 dpi), the ink dot spacing is 50 μm, and the ink dots are arranged in an orderly manner, with excellent luminescence uniformity, meeting the requirements of color conversion display applications.

[0030] Example 2:

[0031] Decalin, n-octane, and white oil were added to a reactor and mixed under magnetic stirring to obtain a ternary mixed solvent. A solute was added to the mixed solvent to obtain a mixed solution, which was then filtered through a 0.22 μm filter membrane to obtain a perovskite quantum dot ink. The solvent ratio was decalin: n-octane: white oil = 7:2:2, and the solute concentration was OD = 100. The solute included red-emitting CsPbI3 perovskite quantum dots and oleic acid, oleylamine, and poly(isobutylene-alt-maleic anhydride) ligands disposed on the quantum dot surfaces, ensuring that the solute was uniformly dispersed in the ternary mixed solvent.

[0032] The perovskite quantum dot ink used in this example was used for piezoelectric inkjet printing, with a dot pitch of 100 μm. The ink droplets ejected smoothly and stably from the nozzles, without any clogging of the printhead nozzles. By vacuum annealing the ink droplets on the printed substrate, a pixelated film with red light was obtained.

[0033] Furthermore, decahydronaphthalene, n-octane and white oil were added to the reactor, and the mixture was stirred magnetically to obtain a ternary mixed solvent. The solute was added to the mixed solvent to obtain a mixed solution, and the mixed solution was filtered through a 0.22 μm filter membrane to obtain perovskite quantum dot ink. The ratio of the solvent is decahydronaphthalene: n-octane: white oil = 7:2:2, and the concentration of the solute is OD = 100. The solute includes green light CsPbBr3 perovskite quantum dots and oleic acid, oleylamine and poly (isobutylene-alt-maleic anhydride) ligands arranged on the surface of the quantum dots, so that the solute is uniformly dispersed in the ternary mixed solvent. On the basis of the red light pixelated film obtained above, the printing point spacing is set to 100 μm, and the positioning program on the printer software is used to set the printing point to fall in the middle of the red light ink dot. The ink droplets are ejected stably and smoothly from the nozzle, and there is no clogging of the print head nozzle. By vacuum annealing the ink droplets on the printed substrate, a high-resolution perovskite quantum dot color conversion film is obtained. As Figure 4 As shown, the red and green perovskite quantum dot ink droplets are arranged alternately and regularly, and the light is uniform, meeting the requirements of color conversion display applications.

[0034] Comparative Example 1:

[0035] Decalin and n-octane were added to a reactor and mixed under magnetic stirring to form a binary mixed solvent. A solute was added to the mixed solvent to form a mixed solution. The mixed solution was then filtered through a 0.22 μm filter membrane to produce a perovskite quantum dot ink. The solvent ratio was 7:2 decalin:n-octane, and the solute concentration was OD = 100. The solute consisted of red-emitting CsPbI3 perovskite quantum dots and oleic acid, oleylamine, and poly(isobutylene-alt-maleic anhydride) ligands disposed on the quantum dot surfaces, ensuring a uniform dispersion of the solute in the binary mixed solvent. Figure 5 and Figure 6This is a schematic diagram of fluorescence intensity imaging of ink droplets obtained by inkjet printing of the perovskite quantum dot ink prepared in Comparative Example 1. Figure 5 and Figure 6 It can be seen that due to the use of binary mixed solvents and the lack of white oil, the central luminescence intensity of the ink droplets formed by perovskite quantum dot ink is significantly lower than the edge luminescence intensity, and an obvious coffee ring phenomenon occurs.

[0036] Comparative Example 2:

[0037] Decalin, n-octane, and ricinoleic acid are added to the reactor, magnetically stirred and mixed to obtain a ternary mixed solvent, the solute is added to the mixed solvent to obtain a mixed solution, and the mixed solution is filtered through a 0.22 μm filter membrane to obtain a perovskite quantum dot ink. Wherein, the ratio of the solvent is decalin: n-octane: ricinoleic acid = 7:2:2, and the concentration of the solute is OD = 100. The solute includes red light CsPbI3 perovskite quantum dots and oleic acid, oleylamine, and poly (isobutylene-alt-maleic anhydride) ligands arranged on the surface of the quantum dots, so that the solute is uniformly dispersed in the ternary mixed solvent. The perovskite quantum dot ink in this comparative example 2 is used for piezoelectric inkjet printing, and the printing dot spacing is set to 50 μm. The corresponding red light pixelated film is obtained by vacuum annealing the ink droplets on the printed substrate. Figure 7 This is a fluorescence micrograph of a red light pixelated film obtained by inkjet printing of the perovskite quantum dot ink prepared in Comparative Example 2. Figure 7 As shown, the addition of ricinoleic acid destroyed the surface ligands of the perovskite quantum dots, causing the prepared pixelated film to quickly quench when exposed to air.

[0038] Comparative Example 3:

[0039] The difference from Example 1 is that the white oil is replaced by butyl benzoate.

[0040] Comparative Example 4:

[0041] The difference from Example 1 is that white oil is replaced by chlorobenzene.

[0042] The PLQY (Photoluminescence Quantum Yield) of Example 1, Comparative Example 1, and Comparative Examples 3-4 were tested respectively, as shown in Table 1.

[0043] Specific examples or comparative examples PLQY (fluorescence quantum yield) Example 1 (adding white oil) 97％ Comparative Example 1 (without adding white oil) 97％ Comparative Example 3 (white oil replaced with butyl benzoate) 88％ Comparative Example 4 (replacing white oil with chlorobenzene) 83％

[0044] Table 1

[0045] It should be noted that: since the ligands on the surface of perovskite quantum dots are very sensitive to polar solvents, the ligands on the surface of perovskite will fall off, thereby exposing the surface defects of quantum dots and reducing the luminous efficiency. Butyl benzoate in Comparative Example 3 and chlorobenzene in Comparative Example 4 are both low-polarity solutions and are not suitable for the present invention. In addition, commonly used low-polarity solutions also include: ether solvents such as tetrahydrofuran, dioxane, anisole, 4-methoxytoluene, 3-phenoxytoluene, dibenzyl ether, diethylene glycol dimethyl ether, diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, and triethylene glycol butyl methyl ether; ester solvents such as methyl benzoate, ethyl benzoate, butyl benzoate, isoamyl benzoate, di(2-ethylhexyl) phthalate, dibutyl maleate, dibutyl oxalate, hexyl acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

[0046] The white oil in the ternary mixed solvent system constructed in the present application is suitable for the perovskite quantum dot ink formula system. The addition of white oil does not reduce the PLQY of the perovskite quantum dot ink, but can also suppress capillary flow and hinder the migration of solutes. It can be seen from the above embodiments and comparative examples that the perovskite quantum dot ink provided by the present disclosure forms a Marangoni flow from the outside to the inside to balance the capillary flow from the inside to the outside by constructing a ternary mixed solvent system. At the same time, due to the synergistic effect of white oil in suppressing capillary flow, the coffee ring phenomenon is successfully eliminated. In the process of inkjet printing using the perovskite quantum dot ink, there will be no nozzle clogging phenomenon, and long-term stable inkjet printing can be formed, and the formed perovskite quantum dot pixelated color conversion film has a very high resolution and good luminous uniformity.

[0047] The above-described embodiments provide a detailed description of the preparation scheme of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing perovskite quantum dot ink, characterized in that: The steps include: Decalin, n-octane and white oil are mixed and stirred to obtain a ternary mixed solvent; a solute is added to the ternary mixed solvent to obtain a mixed solution, wherein the solute is perovskite quantum dots and an organic ligand arranged on the surface of the perovskite quantum dots, so that the solute is uniformly dispersed in the ternary mixed solvent to obtain perovskite quantum dot ink.

2. The method for preparing perovskite quantum dot ink according to claim 1, wherein: The mixed solution is filtered through a 0.22 μm filter membrane to obtain a perovskite quantum dot ink with uniformly dispersed solutes and no agglomeration.

3. The method for preparing perovskite quantum dot ink according to claim 2, wherein: The volume ratio of decahydronaphthalene, n-octane and white oil in the ternary mixed solvent is 7:2:

2.

4. The method for preparing perovskite quantum dot ink according to claim 3, wherein: The concentration of the solute is expressed by OD (Optical Density) at 400 nm, and the OD value is 35-100.

5. The method for preparing perovskite quantum dot ink according to claim 4, wherein: The organic ligand includes one or more of oleic acid, oleylamine, dodecylbenzenesulfonic acid, poly(isobutylene-alt-maleic anhydride) and dibromocyanoacetamide.

6. The method for preparing perovskite quantum dot ink according to claim 1, wherein: The perovskite quantum dots include at least one of CsPbBr3 and CsPbI3.

7. An inkjet printing method, characterized in that: The quantum dot ink according to any one of claims 1 to 6 is used as inkjet printing ink, and the inkjet printing method is piezoelectric inkjet printing.

8. A perovskite quantum dot pixelated color conversion film, characterized in that: The film is made of the quantum dot ink according to any one of claims 1 to 6 by inkjet printing.

9. A display device, characterized in that: The display device includes a backlight source and the quantum dot film according to claim 8.

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