Preparation method of quantum dot color conversion array based on dielectric electro-wetting technology

Abstract

The preparation method of quantum dot color conversion array based on medium electric infiltration technology relates to the field of photoelectric materials and devices, and solves the problem that the pixel size and conversion rate cannot be met in the prior art. The electrode array is made on the substrate, the accurate arrangement of quantum dot droplets can be realized, the method is mature in technology and convenient to operate, and the multicolor quantum dot color conversion layer of the pixel with extremely small size (microliter to picoliter level droplets) can be realized.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials and devices, specifically to a method for fabricating a quantum dot color conversion array based on dielectric electrowetting technology. Background Technology

[0002] Using blue LEDs as the excitation source and quantum dot color conversion layer to achieve full-color Micro LED displays is an effective technical approach. Currently, there are two main methods for fabricating high-density, micro-pixel-sized quantum dot color conversion arrays: inkjet printing and photoresist doping patterning. Inkjet printing technology can currently achieve a minimum quantum dot color conversion pixel size of around 30μm. However, as the pixel size shrinks further, inkjet printing technology cannot meet the requirements. While photoresist doping patterning can achieve the fabrication of color conversion layers with a size of less than 10μm, the doping process can easily degrade the quantum dots, reducing their conversion efficiency. In addition, this method results in a significant waste of quantum dots. Summary of the Invention

[0003] To address the shortcomings of quantum dot color conversion layer technology, this invention proposes a method for fabricating quantum dot color conversion arrays based on dielectric electrowetting technology, which solves the problems of insufficient pixel size and reduced conversion rate in existing technologies.

[0004] The technical solution adopted by this invention to solve the technical problem is as follows:

[0005] A method for fabricating quantum dot color conversion arrays based on dielectric electrowetting technology, comprising the following steps:

[0006] Step 1: Prepare the sacrificial layer, the first sealing layer, and the transparent conductive layer sequentially from bottom to top on the substrate;

[0007] Step 2: Fabricate an electrode array structure on the transparent conductive layer;

[0008] Step 3: Fabricate annular metal electrodes on the side surface and part of the upper surface of the electrode array structure;

[0009] Step 4: Sequentially prepare a dielectric layer and a hydrophobic layer on the upper surface of the annular metal electrode, the electrode array structure, and part of the first sealing layer;

[0010] Step 5: On the hydrophobic layer, quantum droplets are placed on the electrode array structure corresponding to the electrode array structure; the temporal change of the electrode array potential is controlled to drive the quantum dot droplets to move, thus preparing a red quantum dot array and a green quantum dot array, and then heating and solidifying them;

[0011] Step 6: Prepare a protective layer on the surface of the quantum droplet and the partial hydrophobic layer;

[0012] Step 7: Prepare a groove on the protective layer, wherein the bottom surface of the groove is a hydrophobic layer, and the protrusion of the groove contains the quantum droplet;

[0013] Step 8: Prepare an optically insulating layer on the protective layer and part of the hydrophobic layer; the optically insulating layer fills the groove described in Step 7;

[0014] Step 9: Remove the substrate and sacrificial layer to realize the preparation method of quantum dot color conversion array based on dielectric electrowetting technology.

[0015] Preferably, in step one: the substrate is a rigid transparent material, such as glass, acrylic sheet, or quartz; the sacrificial layer is SiO2, hydrosol, UV adhesive, or photoresist; the first sealing layer is polyimide, PDMS, or PET; and the transparent conductive layer is an indium tin oxide conductive film.

[0016] Preferably, in step three, the metal electrode material is Au / Cr (Au / Ti) or Al / Cr (Al / Ti).

[0017] Preferably, in step four: the thickness of the dielectric layer is greater than that of the hydrophobic layer, wherein the material of the dielectric layer is PDMS, SU8, or Parylene-C; and the material of the hydrophobic layer is Teflon AF1600, PET, PTFE, CYTOP, or PDMS.

[0018] Preferably, the protective layer material in step six is ​​Parylene.

[0019] Preferably, the photoisolator material in step eight is SU8 and photoresist.

[0020] The method for fabricating quantum dot color conversion arrays based on dielectric electrowetting technology, with the following replacement steps:

[0021] Step A: Deposit a metal layer on the substrate and prepare a groove structure, wherein the bottom surface of the groove structure is the upper surface of the substrate;

[0022] Step B: A dielectric layer, a PET film, and a hydrophobic layer are sequentially prepared on the metal layer and part of the substrate from bottom to top;

[0023] Step C: On the hydrophobic layer, quantum droplets are placed on the electrode array structure corresponding to the electrode array structure; the temporal change of the electrode array potential is controlled to drive the quantum dot droplets to move, thus preparing a red quantum dot array and a green quantum dot array, and then heating and solidifying them;

[0024] Step D: Prepare a protective layer on the surface of the quantum droplet and the partial hydrophobic layer;

[0025] Step E: A groove is prepared on the protective layer, the bottom surface of the groove is a hydrophobic layer, and the protrusion of the groove contains the quantum droplet;

[0026] Step F: Prepare an optically insulating layer on the protective layer and part of the hydrophobic layer; the optically insulating layer fills the groove described in step seven;

[0027] Step G: Remove the substrate, metal layer, and dielectric layer to realize the preparation method of quantum dot color conversion array based on dielectric electrowetting technology.

[0028] Preferably, the metal layer material in step A is Au / Cr (Au / Ti) or Al / Cr (Al / Ti).

[0029] Preferably, in step B, the dielectric layer, PET film, and hydrophobic layer are immersed in a solution to form a self-assembled monolayer.

[0030] The beneficial effects of this invention are: the present invention fabricates an electrode array on a substrate, which can achieve precise arrangement of quantum dot droplets. This method is technically mature, easy to operate, and can realize a multicolor quantum dot color conversion layer with extremely small size pixels (manipulating droplets at the microliter to picoliter level). Attached Figure Description

[0031] Figure 1 A schematic diagram of the principle of driving quantum dot droplets based on the dielectric electrowetting effect (EWOD).

[0032] Figure 2 Flowchart of Example 1 of the preparation method of quantum dot color conversion array based on dielectric electrowetting technology of the present invention.

[0033] Figure 3 Flowchart of Example 2 of the preparation method of quantum dot color conversion array based on dielectric electrowetting technology of the present invention.

[0034] In the figure: 1. Droplet, 2. Hydrophobic layer, 3. Dielectric layer, 4. First electrode, 5. Second electrode, 6. Substrate, 7. Sacrificial layer, 8. First sealing layer, 9. Transparent conductive layer, 10. Electrode array structure, 11. Metal electrode, 12. Red fluorescent quantum dot, 13. Green fluorescent quantum dot, 14. Blank, 15. Protective layer, 16. Groove structure, 17. Optical isolation layer, 18. Metal layer, 19. Second groove structure, 20. PET film. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0036] The principle of driving quantum dot droplets based on the dielectric electrowetting effect (EWOD) is as follows: Figure 1As shown, when no voltage is applied to the first electrode 4 and the second electrode 5 below the dielectric layer 3, due to the presence of the hydrophobic layer 2, there is a large contact angle between the droplet and the contact surface, such as... Figure 1 As shown in (a), when a potential is applied to the second electrode 5 below the dielectric layer 3, the surface tension between the droplet and the dielectric layer 6 is changed, thereby altering the contact angle between the solid and liquid surfaces, as shown in (a). Figure 1 As shown in (b). The change in contact angle is given by the Lipmann equation:

[0037]

[0038] Where γ g-l Let C be the surface tension between the droplet and the air, C be the capacitance per unit area of ​​the dielectric layer 3, and V be the potential applied to the second electrode 5. Since the potential on the first electrode 4 is 0, the contact angle does not change, resulting in asymmetric deformation on the left and right sides of the droplet, generating a pressure difference that causes the quantum dot droplet to move towards the charged second electrode 5.

[0039] A method for fabricating quantum dot color conversion arrays based on dielectric electrowetting technology, comprising the following steps:

[0040] Step 1: A sacrificial layer 7, a first sealing layer 8, and a transparent conductive layer 9 are sequentially fabricated from bottom to top on a substrate 6. The substrate 6 is a rigid transparent material, such as glass, acrylic sheet, or quartz. The sacrificial layer 7 can be SiO2, hydrosol, UV adhesive, or photoresist. The first sealing layer 8 is a flexible, transparent material, such as polyimide, PDMS, or PET. The transparent electrode layer 9 is a layer of indium tin oxide (ITO) conductive film deposited by sputtering, evaporation, or other methods.

[0041] Step 2: Fabricate an electrode array structure 10 on the transparent conductive layer 9; the fabrication steps include photolithography, development, etching, etc.

[0042] Step 3: Prepare annular metal electrodes 11 on the side surface and part of the upper surface of the electrode array structure 10 to increase the conductivity of the electrodes; the material of the metal electrode 11 can be Au / Cr (Au / Ti) or Al / Cr (Al / Ti), and the preparation process includes sputtering, photolithography, etching, etc.

[0043] Step 4: A dielectric layer 3 and a hydrophobic layer 2 are sequentially prepared on the upper surfaces of the annular metal electrode 11, the electrode array structure 10, and part of the first sealing layer 8. The dielectric layer 3 is a transparent and flexible material, such as PDMS, SU8, Parylene-C, etc. The hydrophobic layer 2 is relatively thin compared to the dielectric layer, and Teflon AF1600 is usually selected, but PET, PTFE, CYTOP, PDMS, etc. can also be selected.

[0044] Step 5: On the hydrophobic layer 2, quantum droplets are placed on the electrode array structure 10; the temporal change of the potential of the electrode array structure 10 is controlled to drive the quantum dot droplets to move, thus preparing the red quantum dot array 12, the green quantum dot array 13 and the blank 14, and then heating and solidifying them;

[0045] Step 6: Prepare a protective layer 15 on the surface of the quantum droplet and the partial hydrophobic layer 2; the material is parylene.

[0046] Step 7: Prepare a groove structure 16 on the protective layer. The bottom surface of the groove structure 16 is a hydrophobic layer 2, and the protrusion of the groove structure 16 contains the quantum droplet. The preparation process includes chemical vapor deposition, photolithography, development, reactive ion etching, etc.

[0047] Step 8: Prepare an optical isolation layer 17 on the protective layer 15 and part of the hydrophobic layer 2; fill the groove structure 16 described in step 7 with the optical isolation layer 17; the optical isolation layer 17 is an opaque material, such as SU8, photoresist, etc.; and remove the excess optical isolation layer to form the structure. The methods used include photolithography and etching, laser processing, mechanical drilling, hot pressing, electrical discharge machining, etc.

[0048] Step 9: Remove the substrate 6 and the sacrificial layer 7. The removal method can be solution etching, thermal melting, light irradiation, etc.; realize the preparation method of quantum dot color conversion array based on dielectric electrowetting technology.

[0049] The method for fabricating quantum dot color conversion arrays based on dielectric electrowetting technology, with the following replacement steps:

[0050] Step A: Deposit a metal layer 18 on the substrate 6 and prepare a second groove structure 19, wherein the bottom surface of the second groove structure 19 is the upper surface of the substrate 6; the material of the metal layer 18 can be Au / Cr (Au / Ti) or Al / Cr (Al / Ti), and the preparation process of the second groove structure includes sputtering, photolithography, development, etching, etc.

[0051] Step B: A dielectric layer 20, a PET film 21, and a hydrophobic layer 2 are sequentially prepared on the metal layer 18 and part of the substrate from bottom to top; the dielectric layer 20 is made of PDMS and is coated on the metal layer 18 and the substrate 6 by dilution, ultra-high speed spin coating, and curing; a PET film 21 is coated on the dielectric layer 20, and a hydrophobic layer trichlorooctadecylsilane is coated on the PET film 21. The main preparation process is to immerse the PET film 21 in a solution for five minutes to form a very thin self-assembled monolayer.

[0052] Step C: On the hydrophobic layer 2, quantum droplets are placed on the second groove structure 19; the temporal change of the potential of the electrode array is controlled to drive the quantum dot droplets to move, and a red quantum dot array 12, a green quantum dot array 13 and a blank 14 are prepared, and then heated and solidified.

[0053] Step D: Prepare a protective layer 15 on the surface of the quantum droplet and the partial hydrophobic layer 2; the material is parylene.

[0054] Step E: A third groove is prepared on the protective layer 15. The bottom surface of the third groove is a hydrophobic layer 2, and the protrusion of the third groove contains the quantum droplet. The preparation process includes chemical vapor deposition, photolithography, development, reactive ion etching, etc.

[0055] Step F: Prepare a photoisolation layer 17 on the protective layer 15 and part of the hydrophobic layer 2; the photoisolation layer 17 fills the third groove; the photoisolation layer 17 is an opaque material, such as SU8, photoresist, etc.; and remove the excess photoisolation layer to form a structure. The methods used include photolithography and etching, laser processing, mechanical drilling, hot pressing, electrical discharge machining, etc.

[0056] Step G: Separate the film from the dielectric layer 3 and the hydrophobic layer 2. The separation method is as follows: Since PET and PDMS are separated by van der Waals forces, they can be gently and slowly peeled off by hand with the assistance of tools such as tweezers, thereby realizing the preparation method of quantum dot color conversion array based on dielectric electrowetting technology.

Claims

1. A method for fabricating quantum dot color conversion arrays based on dielectric electrowetting technology, characterized in that, The method includes the following steps: Step 1: Prepare a sacrificial layer, a first sealing layer, and a transparent conductive layer sequentially from bottom to top on a substrate; the substrate is a rigid transparent material, such as glass, acrylic sheet, or quartz; the sacrificial layer is SiO2, hydrosol, UV adhesive, or photoresist; the first sealing layer is polyimide, PDMS, or PET; and the transparent conductive layer is an indium tin oxide conductive film. Step 2: Fabricate an electrode array structure on the transparent conductive layer; Step 3: Fabricate annular metal electrodes on the side surface and part of the upper surface of the electrode array structure; Step 4: Sequentially prepare a dielectric layer and a hydrophobic layer on the upper surface of the annular metal electrode, the electrode array structure, and part of the first sealing layer; Step 5: On the hydrophobic layer, quantum droplets are placed on the electrode array structure corresponding to the electrode array structure; the temporal change of the electrode array potential is controlled to drive the quantum dot droplets to move, thus preparing a red quantum dot array and a green quantum dot array, and then heating and solidifying them; Step 6: Prepare a protective layer on the surface of the quantum droplet and the partial hydrophobic layer; Step 7: Prepare a groove on the protective layer, wherein the bottom surface of the groove is a hydrophobic layer, and the protrusion of the groove contains the quantum droplet; Step 8: Prepare an optically insulating layer on the protective layer and part of the hydrophobic layer; the optically insulating layer fills the groove described in Step 7; Step 9: Remove the substrate and sacrificial layer to realize the preparation method of quantum dot color conversion array based on dielectric electrowetting technology.

2. The method for fabricating a quantum dot color conversion array based on dielectric electrowetting technology according to claim 1, characterized in that, In step three: the metal electrode material is Au / Cr (Au / Ti) or Al / Cr (Al / Ti).

3. The method for fabricating a quantum dot color conversion array based on dielectric electrowetting technology according to claim 1, characterized in that, In step four: the thickness of the dielectric layer is greater than that of the hydrophobic layer, wherein the material of the dielectric layer is PDMS, SU8, or Parylene-C; and the material of the hydrophobic layer is Teflon AF1600, PET, PTFE, CYTOP, or PDMS.

4. The method for fabricating a quantum dot color conversion array based on dielectric electrowetting technology according to claim 1, characterized in that, The protective layer material in step six is ​​Parylene.

5. The method for fabricating a quantum dot color conversion array based on dielectric electrowetting technology according to claim 1, characterized in that, The photoisolator material in step eight is SU8 and photoresist.

6. The method for fabricating a quantum dot color conversion array based on dielectric electrowetting technology according to claim 1, characterized in that, The replacement steps of this method are as follows: Step A: Deposit a metal layer on the substrate and prepare a groove structure, wherein the bottom surface of the groove structure is the upper surface of the substrate; Step B: A dielectric layer, a PET film, and a hydrophobic layer are sequentially prepared on the metal layer and part of the substrate from bottom to top; in Step B, the dielectric layer, the PET film, and the hydrophobic layer are immersed in a solution to form a self-assembled monolayer; Step C: On the hydrophobic layer, quantum droplets are placed on the electrode array structure corresponding to the electrode array structure; the temporal change of the electrode array potential is controlled to drive the quantum dot droplets to move, thus preparing a red quantum dot array and a green quantum dot array, and then heating and solidifying them; Step D: Prepare a protective layer on the surface of the quantum droplet and the partial hydrophobic layer; Step E: A groove is prepared on the protective layer, the bottom surface of the groove is a hydrophobic layer, and the protrusion of the groove contains the quantum droplet; Step F: Prepare an optically insulating layer on the protective layer and part of the hydrophobic layer; the optically insulating layer fills the groove described in step seven; Step G: Remove the substrate, metal layer, and dielectric layer to realize the preparation method of quantum dot color conversion array based on dielectric electrowetting technology.

7. The method for fabricating a quantum dot color conversion array based on dielectric electrowetting technology according to claim 6, characterized in that, The metal layer material in step A is Au / Cr (Au / Ti) or Al / Cr (Al / Ti).

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