Indium phosphide quantum dot ink and preparation method and application thereof

Abstract

The invention belongs to the technical field of nano material preparation and printing, and particularly relates to indium phosphide quantum dot ink as well as a preparation method and application thereof. According to the preparation method disclosed by the invention, the indium phosphide quantum dot core is firstly synthesized, and then the acrylic acid / polyacrylic acid / acrylate derivative ligand is used for carrying out surface treatment on the indium phosphide quantum dot, so that the surface passivation and stability improvement of the indium phosphide quantum dot and the optimization of the rheological property of the ink are synchronously realized, and the quantum efficiency is improved; the photoluminescence quantum yield is increased by 80% to 100% compared with that of similar InP / ZnSe quantum dots which are not treated by acrylic acid and the like. Indium phosphide / zinc selenide quantum dots treated by acrylic acid and the like are dispersed in an organic solvent to adjust the adaptive concentration to obtain the quantum dot ink, the ink does not need to be added with an additional rheology modifier or a film-forming polymer, the coffee ring effect can be effectively inhibited during drying, and preparation of high-resolution micro-patterns is achieved. The material can be directly used as a color conversion layer to be integrated with a blue micron light-emitting diode chip to form a display device.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation and printing technology, specifically relating to an indium phosphide quantum dot ink, its preparation method, and its application. Background Technology

[0002] Quantum dot inks have attracted widespread attention as functional materials in high-resolution patterning technologies due to their advantages such as size-tunable luminescence properties, narrow emission linewidth, and high quantum yield. They are ideal candidate materials for color conversion layers in advanced photonic devices such as next-generation micron-sized LED displays. Among various patterning techniques, electrofluid printing has become an important processing method due to its high spatial resolution, precise droplet control, and good compatibility with solution-processed materials. However, achieving defect-free, high-resolution quantum dot micropatterns requires inks with excellent colloidal stability, tunable rheological properties, and robust luminescence performance, which remains a current technological challenge.

[0003] Among various quantum dots, indium phosphide (IP) quantum dots have attracted widespread attention as an environmentally friendly, cadmium-free alternative. Despite significant progress in core / shell structure engineering and surface passivation, the practical application of IPT quantum dots remains limited by their inherent surface trapped states, leading to nonradiative recombination and low photoluminescence quantum yield. Furthermore, their relatively unstable surface chemistry and sensitivity to environmental conditions also reduce the long-term stability of the material. Besides optical properties, the poor printability of traditional IPT quantum dot dispersions is another key obstacle, particularly insufficient ink viscosity and uneven drying processes, which easily lead to the coffee ring effect and irregular deposition, hindering their application in electrofluid printing. In the prior art, various strategies have been explored to address these challenges, such as using surface ligand exchange and shell growth to passivate trapped states and improve photoluminescence performance. However, such modifications often sacrifice colloidal stability or require the use of toxic fluorinated reagents. Similarly, polymer encapsulation and hybrid matrix embedding can enhance stability, but usually at the expense of ink homogeneity or luminescence efficiency.

[0004] To date, there is a lack of a comprehensive solution that can simultaneously improve optical performance, ensure ink stability, and provide rheological control capabilities suitable for electrohydraulic printing. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide an indium phosphide quantum dot ink, its preparation method and application. The invention utilizes acrylic acid / polyacrylic acid / acrylate derivative ligands to simultaneously treat aminophosphine-based indium phosphide / zinc selenide core-shell quantum dots, thereby simultaneously achieving surface passivation, stability improvement, and ink rheological property optimization of the indium phosphide quantum dots. The InP-AA / ZnSe quantum dots are dispersed in an organic solvent at an adjusted concentration to obtain the quantum dot ink. This ink does not require the addition of additional rheology modifiers or film-forming polymers and can effectively suppress the coffee ring effect during drying.

[0006] The technical solution adopted is as follows: A method for preparing indium phosphide quantum dot ink includes the following steps: (1) Synthesis of indium phosphide (InP) quantum dot cores: Indium chloride and zinc chloride were used as metal sources and co-solvented in oleylamine to obtain mixture A. Tris(dimethylamino)phosphide was used as the phosphorus source and added to mixture A by hot injection, followed by the addition of oleylamine to carry out the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, and the reaction solution was centrifuged to separate the unreacted metal salts and collect the supernatant. The supernatant was added to anhydrous acetone to precipitate the mixture, and after centrifugation again, the supernatant was discarded. Finally, the obtained indium phosphide quantum dot nuclei were dispersed in an organic solvent for later use. (2) Preparation of indium phosphide / zinc selenide core-shell quantum dots by surface treatment of acrylic acid / polyacrylic acid / acrylate derivatives: The prepared indium phosphide quantum dot core, organic solvent, and acrylic acid / polyacrylic acid / acrylate derivative are mixed to obtain mixture B, which is then subjected to the first treatment, namely, heating and continuous stirring under a nitrogen atmosphere to etch and passivate the surface of the quantum dot core. Subsequently, 1-octadecene was added to the system as a solvent, heated, degassed, and the system was cooled. A second treatment was performed by adding acrylic acid / polyacrylic acid / acrylate derivatives. Then, selenium precursor solution and zinc precursor solution were injected into the reaction system to react, thereby growing a zinc selenide shell on the core. After the reaction was completed, the mixture was cooled to room temperature, acetone was added to precipitate the quantum dots, and after centrifugation, the core-shell quantum dots of the final product were dispersed in an organic solvent for storage. (3) Preparation of quantum dot ink: By adjusting the concentration of the prepared quantum dots dispersed in an organic solvent, quantum dot ink can be obtained.

[0007] Preferably, in step (1), the mass ratio of indium chloride, zinc chloride and oleylamine is 20mg:60mg:1ml; mixture A is stirred and degassed at 100-120°C for 0.5-1 hour to remove moisture and oxygen.

[0008] Preferably, the volume ratio of phosphorus source to oleylamine added again is 0.45:2; under nitrogen protection, the temperature is raised to 180-200°C, tris(dimethylamino)phosphorus is injected as phosphorus source, and oleylamine is added; the temperature is maintained at 180-200°C for 15-20 minutes.

[0009] Preferably, after the reaction is completed, the mixture is allowed to cool naturally to room temperature, and the reaction solution is centrifuged at 5000 rpm for 10 minutes; the organic solvent is toluene or n-hexane, and the concentration of indium phosphide quantum dot nuclei dispersed in the organic solvent is 50 μM.

[0010] Preferably, in step (2), during the first treatment, the volume ratio of indium phosphide quantum dot cores to acrylic acid / polyacrylic acid / acrylate derivatives is 5000:4. Mixture B is heated to 80°C under a nitrogen atmosphere and stirred continuously for 20 to 30 minutes to complete the first surface treatment.

[0011] Preferably, during the secondary treatment, 1-octadecene is added to the system as a solvent, and the system is heated to 100-110°C for degassing for 60 minutes; then, the system is cooled to 75°C, and the volume of the acrylic acid / polyacrylic acid / acrylate derivative added a second time is the same as that of the first time, the reaction time is 20-30 minutes, and the volume ratio of the acrylic acid / polyacrylic acid / acrylate derivative added a second time to 1-octadecene is 10:1; the acrylate derivative is any one of methyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, butyl acrylate, and acrylamide.

[0012] Preferably, a 2.0 M selenium precursor solution is injected using a syringe pump while the reaction temperature is raised to 250°C. At this temperature, a 2.0 M zinc precursor solution is pumped in at a rate of 1.0 mL / h to perform epitaxial growth of the zinc selenide shell, and the reaction lasts for 60 minutes. Toluene or n-hexane is also used as the organic solvent.

[0013] Preferably, the selenium precursor solution is a TOP-Se (trioctylphosphine selenide) solution, the zinc precursor solution is a zinc acetate solution, and the volume ratio of the selenium precursor solution to the zinc precursor solution is 1:1.

[0014] The present invention discloses a method for preparing indium phosphide quantum dot ink. The InP-AA / ZnSe quantum dot concentration is adjusted to 20 mg / mL, allowing for direct use as a printing ink. The ink's viscosity is suitable for electrohydraulic printing, and no additional rheology modifiers or film-forming polymers are required. Furthermore, the ink effectively suppresses the coffee ring effect during drying.

[0015] The application of quantum dot ink provided by this invention involves loading quantum dot ink into a metal nozzle of a printing device, with a nozzle-to-substrate distance of 200 micrometers, applying voltage, and achieving an ink propulsion flow rate of 50 nanoliters / minute; by performing programmed control printing on a moving glass substrate (as a printing material, using electrofluid printing technology), the printed quantum dot pattern can be used as a color conversion layer for micron-sized light-emitting diode displays.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The core of this invention lies in surface treatment of indium phosphide quantum dot cores using acrylic acid or acrylate derivatives, causing in-situ polymerization to form a polyacrylic acid coating layer while etching and passivating surface trapped states. This coating layer not only significantly improves the photoluminescence quantum yield and photostability of the quantum dots, but also endows the quantum dot dispersion with suitable rheological properties, allowing it to be used directly as an electrofluid printing ink without any additives, effectively suppressing the coffee ring effect, and achieving the fabrication of high-resolution micropatterns.

[0017] The quantum dots obtained in this invention have a core-shell structure, with an indium phosphide core treated with acrylic acid / polyacrylic acid / acrylate derivatives and a zinc selenide shell. The acrylic acid / polyacrylic acid coating layer forms a conformal protective layer with the quantum dot core surface through chemical bonding. This structure effectively reduces surface defects, improves quantum efficiency, and increases the photoluminescence quantum yield by 80% to 100% compared to similar InP / ZnSe quantum dots without acrylic acid treatment. It also enhances their stability during solvent dispersion and film formation.

[0018] The indium phosphide / zinc selenide quantum dots treated with acrylic acid / polyacrylic acid / acrylate derivatives obtained by the method of this invention can be directly dispersed in organic solvents such as toluene and n-hexane to form a uniform and stable quantum dot ink. This ink can be precisely deposited on a substrate using electrohydraulic printing technology under preset parameters such as voltage, flow rate, and substrate movement speed to form pixelated or linear micropatterns. After drying, these patterns can be directly integrated as a color conversion layer with a blue micron-sized light-emitting diode chip to form a display device. Attached Figure Description

[0019] Figure 1 This is a schematic diagram and chemical mechanism of the acrylic surface treatment process for indium phosphide quantum dot cores according to the present invention.

[0020] Figure 2 (a) is a transmission electron microscope comparison image of the indium phosphide quantum dot core before (a) and after (b) acrylic acid treatment in Example 1. (c) is the normalized optical absorption and photoluminescence spectrum of the indium phosphide quantum dot core before and after acrylic acid treatment.

[0021] Figure 3The images show transmission electron microscopy (TEM) images of indium phosphide / zinc selenide core-shell quantum dots before (a) and after (b) acrylic acid treatment in Example 1, and the normalized optical absorption and photoluminescence spectra of emission quantum dots with a size distribution of approximately 8 nm (c) and approximately 5 nm (d), respectively.

[0022] Figure 4 The absorption (solid line) and photoluminescence (dashed line) spectra of indium phosphide quantum dot cores before and after treatment with different acrylic homologues (a) and acrylate derivatives (b): From top to bottom, the monomers in (a) are tigrinic acid, succinic anhydride, polyacrylic acid, senglitinic acid, and acrylic acid; the derivatives in (b) are methyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, butyl acrylate, and acrylamide; the photoluminescence quantum yield values ​​after surface treatment are also marked in the figure.

[0023] Figure 5 (a) is a schematic diagram of the quantum dot ink printing process in electrohydrodynamics; (b) is a schematic diagram of the suppression mechanism of the coffee ring effect by acrylic acid-treated indium phosphide / zinc selenide quantum dots and the optical image of the printed micro-dot array; (c) is a chemical image of the pattern printed by quantum dot ink, showing a smooth and uniform pattern morphology. Detailed Implementation

[0024] The accompanying drawings are for illustrative purposes only. To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and do not limit the invention in any way. Unless otherwise specified, the methods, reagents, and equipment used in this invention are all conventional methods, reagents, and equipment in this technical field, and all such reagents and equipment are commercially available.

[0025] Example 1 A method for preparing indium phosphide quantum dot ink includes the following steps: (1) Indium phosphide (InP) quantum dot cores were synthesized by thermal injection method.

[0026] The specific steps are as follows: Weigh 100 mg of indium chloride and 300 mg of zinc chloride, dissolve them together in 5 mL of oleylamine, and place the solution in a 50 mL three-necked flask. Stir the mixture at 120 °C and degas for 1 hour to remove moisture and oxygen. Then, raise the temperature to 200 °C under nitrogen protection. Quickly inject 0.45 mL of tris(dimethylamino)phosphide as a phosphorus source and add 2 mL of oleylamine. Maintain the reaction at this temperature for 20 minutes. After the reaction is complete, allow it to cool naturally to room temperature, centrifuge the reaction solution at 5000 rpm for 10 minutes to separate the unreacted metal salt. Collect the supernatant, add anhydrous acetone to precipitate, centrifuge again and discard the supernatant. Finally, redisperse the obtained indium phosphide quantum dot cores in anhydrous toluene at a concentration of 50 μM for later use.

[0027] (2) Preparation of InP-AA / ZnSe (acrylic acid treated indium phosphide / zinc selenide) core-shell quantum dots by acrylic acid surface treatment.

[0028] like Figure 1 As shown, 1.25 mL of the indium phosphide quantum dot core toluene solution obtained in step (1) was placed in a 50 mL reaction flask, and 40 μL of acrylic acid was added. The mixture was heated to 80 °C under a nitrogen atmosphere and stirred continuously for 30 minutes to complete the surface treatment. The indium phosphide quantum dot core was surface treated with acrylic acid, which caused it to undergo in-situ polymerization to form a polyacrylic acid coating layer while etching and passivating the surface trap states.

[0029] Subsequently, 4 mL of 1-octadecene was added to the system as a solvent, and the mixture was degassed at 110 °C for 60 min. The system was then cooled to 75 °C, and 40 μL of acrylic acid was added again for secondary stabilization, with the reaction proceeding for 30 min. Next, 1.0 mL of a 2.0 M TOP-Se (trioctylphosphine selenide) solution was slowly injected using a syringe pump, while the reaction temperature was rapidly programmed to 250 °C. At this temperature, 1.0 mL of a 2.0 M zinc acetate solution was slowly pumped in at a rate of 1.0 mL / h to perform epitaxial growth of the zinc selenide shell, with the reaction lasting 60 min. After the reaction was complete, the mixture was cooled to room temperature, and acetone was added to precipitate the quantum dots. After centrifugation, the final product, InP-AA / ZnSe quantum dots, was dispersed in toluene for storage.

[0030] like Figure 4 As shown, the photoluminescence quantum yield (PLQY) of InP-AA / ZnSe quantum dots was tested to be 30.4%.

[0031] (3) Preparation of quantum dot ink and electrofluid printing.

[0032] like Figure 5As shown, the concentration of the InP-AA / ZnSe quantum dot toluene solution obtained in step (2) was adjusted to 20 mg / mL and used directly as printing ink. This ink was loaded into the metal nozzle of the printing device, and the printing parameters were set as follows: nozzle-to-substrate distance of 200 μm, applied voltage of 2.0 kV, and ink flow rate of 50 nanoliters / minute. Through programming control on a moving glass substrate, a regular array of red fluorescent lines with a linewidth of 5 μm was successfully printed. The printed pattern was uniform, without any brown ring phenomenon, and exhibited bright red light emission under blue light excitation, making it suitable for use as a color conversion layer in micron-sized LED displays.

[0033] like Figure 2 As shown in the figure, (a) the surface of the indium phosphide quantum dot core is unetched and passivated before acrylic treatment, (b) the surface of the indium phosphide quantum dot core is etched and passivated after acrylic treatment, and (c) the normalized optical absorption spectrum and photoluminescence spectrum. The fluorescence intensity of the indium phosphide quantum dot core is low before acrylic treatment, and the fluorescence intensity is significantly improved after treatment. The fluorescence intensity of the indium phosphide quantum dots increased by more than three times, and the quantum yield increased from <10% to 30%.

[0034] The InP-AA / ZnSe quantum dots prepared in this invention have a size of 5–8 nm.

[0035] like Figure 3 As shown, the quantum dots are more uniform and densely distributed after acrylic acid treatment. Before acrylic acid treatment, the fluorescence intensity of indium phosphide / zinc selenide core-shell quantum dots of different sizes is not high. After treatment, the fluorescence intensity of quantum dots with a size distribution of about 8 nm (c) and about 5 nm (d) is significantly improved, and the fluorescence color is different. The fluorescence intensity of the quantum dots increased by more than two times, and the quantum yield increased by one time.

[0036] Example 2 A method for preparing indium phosphide quantum dot ink, which differs from Example 1 in that indium phosphide / zinc selenide core-shell quantum dots are prepared by surface treatment with senglitin.

[0037] The photoluminescence quantum yield was tested to be 25.6%.

[0038] Example 3 A method for preparing indium phosphide quantum dot ink, which differs from Example 1 in that indium phosphide / zinc selenide core-shell quantum dots are prepared by surface treatment with polyacrylic acid.

[0039] The photoluminescence quantum yield was tested to be 21.6%.

[0040] Example 4 A method for preparing indium phosphide quantum dot ink, which differs from Example 1 in that indium phosphide / zinc selenide core-shell quantum dots are prepared by surface treatment with succinic anhydride.

[0041] The photoluminescence quantum yield was tested to be 27.3%.

[0042] Example 5 A method for preparing indium phosphide quantum dot ink, which differs from Example 1 in that it uses tiger acid surface treatment to prepare indium phosphide / zinc selenide core-shell quantum dots.

[0043] The photoluminescence quantum yield was tested to be 29.4%.

[0044] Example 6 A method for preparing indium phosphide quantum dot ink, which differs from Example 1 in that indium phosphide / zinc selenide core-shell quantum dots are prepared using methyl methacrylate.

[0045] The photoluminescence quantum yield was tested to be 23.6%.

[0046] Example 7 A method for preparing indium phosphide quantum dot ink, which differs from Example 1 in that indium phosphide / zinc selenide core-shell quantum dots are prepared by surface treatment with diethylaminoethyl methacrylate.

[0047] The photoluminescence quantum yield was tested to be 25.8%.

[0048] Example 8 A method for preparing indium phosphide quantum dot ink, which differs from Example 1 in that indium phosphide / zinc selenide core-shell quantum dots are prepared by surface treatment with dimethylaminoethyl methacrylate.

[0049] The photoluminescence quantum yield was tested to be 24.3%.

[0050] Example 9 A method for preparing indium phosphide quantum dot ink, which differs from Example 1 in that indium phosphide / zinc selenide core-shell quantum dots are prepared by surface treatment with butyl acrylate.

[0051] The photoluminescence quantum yield was tested to be 21.7%.

[0052] Example 10 A method for preparing indium phosphide quantum dot ink, which differs from Example 1 in that indium phosphide / zinc selenide core-shell quantum dots are prepared by surface treatment with acrylamide.

[0053] The photoluminescence quantum yield was tested to be 25.4%.

[0054] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing indium phosphide quantum dot ink, characterized in that, Includes the following steps: (1) Synthesis of indium phosphide quantum dot cores: Indium chloride and zinc chloride were used as metal sources and co-solvented in oleylamine to obtain mixture A. Tris(dimethylamino)phosphide was used as the phosphorus source and added to mixture A by hot injection, followed by the addition of oleylamine to carry out the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, and the reaction solution was centrifuged to separate the unreacted metal salts and collect the supernatant. The supernatant was added to anhydrous acetone to precipitate the mixture, and after centrifugation again, the supernatant was discarded. Finally, the obtained indium phosphide quantum dot nuclei were dispersed in an organic solvent for later use. (2) Preparation of indium phosphide / zinc selenide core-shell quantum dots by surface treatment of acrylic acid / polyacrylic acid / acrylate derivatives: The prepared indium phosphide quantum dot core, organic solvent, and acrylic acid / polyacrylic acid / acrylate derivative are mixed to obtain mixture B, which is then subjected to the first treatment, namely, heating and continuous stirring under a nitrogen atmosphere to etch and passivate the surface of the quantum dot core. Subsequently, 1-octadecene was added to the system as a solvent, heated, degassed, and the system was cooled. A second treatment was performed by adding acrylic acid / polyacrylic acid / acrylate derivatives. Then, selenium precursor solution and zinc precursor solution were injected into the reaction system to react, thereby growing a zinc selenide shell on the core. After the reaction was completed, the mixture was cooled to room temperature, acetone was added to precipitate the quantum dots, and after centrifugation, the quantum dots of the final product were dispersed in an organic solvent for storage. (3) Preparation of quantum dot ink: By adjusting the concentration of the prepared quantum dots dispersed in an organic solvent, quantum dot ink can be obtained.

2. The method for preparing indium phosphide quantum dot ink according to claim 1, characterized in that, In step (1), the mass ratio of indium chloride, zinc chloride and oleylamine is 20mg:60mg:1ml; mixture A is stirred and degassed at 100-120°C for 0.5-1 hour to remove moisture and oxygen.

3. The method for preparing indium phosphide quantum dot ink according to claim 2, characterized in that, The volume ratio of phosphorus source to oleylamine added again is 0.45:2; under nitrogen protection, the temperature is raised to 180-200℃, tris(dimethylamino)phosphorus is injected as phosphorus source, and oleylamine is added; the temperature is maintained at 180-200℃ for 15-20 minutes.

4. The method for preparing indium phosphide quantum dot ink according to claim 3, characterized in that, After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The reaction solution was then centrifuged at 5000 rpm for 10 minutes. The organic solvent was toluene or n-hexane, and the concentration of indium phosphide quantum dot nuclei dispersed in the organic solvent was 50 μM.

5. The method for preparing indium phosphide quantum dot ink according to claim 1, characterized in that, In step (2), during the first treatment, the volume ratio of indium phosphide quantum dot cores to acrylic acid / polyacrylic acid / acrylate derivatives is 5000:

4. Mixture B is heated to 80°C under a nitrogen atmosphere and stirred continuously for 20 to 30 minutes to complete the first surface treatment.

6. The method for preparing indium phosphide quantum dot ink according to claim 5, characterized in that, In the secondary treatment, 1-octadecene is added to the system as a solvent, and the system is heated to 100-110°C for degassing for 60 minutes. After that, the system is cooled to 75°C. The volume of the acrylic acid / polyacrylic acid / acrylate derivative added a second time is the same as that added a first time, and the reaction time is 20-30 minutes. The volume ratio of the acrylic acid / polyacrylic acid / acrylate derivative added a second time to 1-octadecene is 10:

1. The acrylate derivative is any one of methyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, butyl acrylate, or acrylamide.

7. The method for preparing indium phosphide quantum dot ink according to claim 6, characterized in that, A 2.0 M selenium precursor solution was injected using a syringe pump while the reaction temperature was raised to 250°C. At this temperature, a 2.0 M zinc precursor solution was pumped in at a rate of 1.0 mL / h to carry out epitaxial growth of the zinc selenide shell. The reaction lasted for 60 minutes.

8. The method for preparing indium phosphide quantum dot ink according to claim 7, characterized in that, The selenium precursor solution is a TOP-Se solution, and the zinc precursor solution is a zinc acetate solution, with a volume ratio of 1:1 between the selenium precursor solution and the zinc precursor solution.

9. The quantum dot ink prepared by the method for preparing indium phosphide quantum dot ink according to any one of claims 1-8, characterized in that, The quantum dot concentration was adjusted to 20 mg / mL for direct use as printing ink; the organic solvent used was toluene or n-hexane.

10. The application of the quantum dot ink prepared by the method for preparing indium phosphide quantum dot ink according to any one of claims 1-8, characterized in that, Quantum dot ink is loaded into the metal nozzle of the printing device, with a nozzle-to-substrate distance of 200 μm. Voltage is applied, and the ink propulsion flow rate is 50 nanoliters per minute. By programming and controlling the printing on a moving glass substrate, the printed quantum dot pattern can be used as a color conversion layer for micron-sized light-emitting diode displays.

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