Photo-crosslinkable perovskite nanocrystalline ink and preparation method and patterning application thereof

Abstract

The invention discloses photo-crosslinkable perovskite nanocrystal ink which comprises perovskite nanocrystals dispersed in a solvent, the surfaces of the perovskite nanocrystals are coated with protective layers, the surfaces of the protective layers of part of the perovskite nanocrystals are modified with first photosensitive molecules, and the first photosensitive molecules are modified with second photosensitive molecules. The surface of the protective layer of the other part of the perovskite nanocrystals is modified with second photosensitive molecules, the first photosensitive molecules carry C = C groups, the second photosensitive molecules carry C = O groups, and the first photosensitive molecules and the second photosensitive molecules can be subjected to a photo-crosslinking reaction. The invention further discloses a preparation method and patterning application of the quantum dot, photoresist and a special developing solution thereof do not need to be used in the patterning process, and the luminescence performance and stability of the quantum dot are effectively protected.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor microdisplay, and in particular relates to a photo-crosslinkable perovskite nanocrystal ink and a preparation method and patterned application thereof. Background Art

[0002] The quantum dot color conversion scheme provides a low-cost and fast design solution for the full-colorization of the emerging micro-light-emitting diode Micro-LED display technology. At present, the quantum dots used in Micro-LED display technology mainly include II-VI quantum dots, III-V quantum dots and perovskite quantum dots. Among them, perovskite quantum dots are considered to be ideal fluorescent materials for achieving high color purity, high light efficiency and high color gamut micro-display due to their highly adjustable band gap, wide emission spectrum range, adjustable luminescent color and nearly uniform photoluminescence quantum yield characteristics. The main methods for patterning quantum dots include inkjet printing, photolithography, laser processing, microfluidics, micro-transfer printing, selective electrophoresis deposition, etc. Among them, photolithography technology provides a fast and large-scale preparation solution for the preparation of high-resolution, high-density and high-uniformity quantum dot patterns, and is considered by the industry to be the quantum dot patterning method with the greatest potential for industrial application. In summary, the reliable patterning of perovskite quantum dots through photolithography technology is an ideal solution for the construction of high-quality micro-display devices.

[0003] The currently developed perovskite quantum dot lithography patterning technology can be divided into photoresist-assisted lithography and perovskite quantum dot direct lithography. Perovskite quantum dots are an ionic crystal that is prone to the problem of reduced quantum dot luminescence performance under conditions such as water, oxygen, heating, and light, causing a decrease in device stability and quality. In the photoresist-assisted perovskite quantum dot patterning method, chemical substances such as photoresist and its special developer are required. The use of these substances, especially when multiple lithography processes are used to achieve the construction of perovskite quantum dot patterns of various colors, will significantly reduce the luminescence intensity and stability of the quantum dots. The direct perovskite quantum dot lithography method changes the solubility of quantum dots in the mother liquor through the photochemical reaction of quantum dot ligands under conditions such as ultraviolet light, thereby achieving patterning. Direct lithography does not need to rely on the use of photoresist and developer, but the photochemical reaction of the ligand will cause the ligand to protect the surface of the perovskite quantum dot, increase the surface defect density, and lead to reduced luminescence performance. In summary, both of these lithography schemes have the problem that the lithography process has a significant impact on the luminescence performance and stability of perovskite quantum dots. Therefore, it is very necessary to develop high-stability perovskite quantum dot inks suitable for lithography technology. Summary of the invention

[0004] The present invention aims at the problems existing in the existing photolithography patterning technology of perovskite quantum dots, provides a design scheme of photo-crosslinkable perovskite nanocrystal ink, and realizes the photolithography patterning of perovskite quantum dots. The formulated perovskite nanocrystal ink has high fluorescence quantum yield and good stability, and the quantum dot array film maintains high luminescence efficiency and stability after the direct photolithography process, which effectively solves the problem of decreased luminescence performance and stability of traditional perovskite quantum dot ink during the photolithography process.

[0005] In order to achieve the above purpose, the technical solution of the present invention is:

[0006] A photo-crosslinkable perovskite nanocrystal ink comprises perovskite nanocrystals dispersed in a solvent, wherein the chemical formula of the perovskite nanocrystals is ABX3, wherein A is an organic cation or a metal cation, B is a metal cation, and X is a halogen anion; the surface of the perovskite nanocrystal is coated with a protective layer, wherein the surface of the protective layer of some perovskite nanocrystals is modified with a first photosensitive molecule, and the surface of the protective layer of other perovskite nanocrystals is modified with a second photosensitive molecule, the first photosensitive molecule has a C=C group, and the second photosensitive molecule has a C=O group, and the first photosensitive molecule and the second photosensitive molecule can undergo a photo-crosslinking reaction.

[0007] Optionally, the material of the protective layer may be inorganic substances such as SiO2, Al2O3, ZnO, ZnS, SnO2, TiO2, CdS, or polymers such as polyimide, polystyrene, polyvinyl pyrrolidone, polyacrylic acid, with a thickness of 1 to 20 nm.

[0008] Optionally, the solvent includes at least one of methane, toluene, ethane, acetone, chloroform, chlorobenzene, isopropanol, N,N-dimethylformamide, and N-methylformamide.

[0009] Optionally, the first photosensitive molecule and the second photosensitive molecule are small organic molecules, and at least one end of the first photosensitive molecule and / or the second photosensitive molecule has a functional group that binds to the protective layer, and the functional group includes a thiol, a methoxyl, an ethoxyl, -Cl or -SH. The second photosensitive molecule with a C=O group is, for example, a photosensitive molecule with a thio group of a benzophenone derivative at one end.

[0010] Optionally, the size of the perovskite nanocrystals is 5 to 30 nm, and the content of the perovskite nanocrystals in the solvent is 1 to 100 mg / mL.

[0011] A method for preparing the above-mentioned photocrosslinkable perovskite nanocrystal ink comprises the following steps:

[0012] 1) Preparation of perovskite nanocrystals;

[0013] 2) Coating a protective layer on the surface of the perovskite nanocrystal;

[0014] 3) modifying the surface of the protective layer of a portion of the perovskite nanocrystals with a first photosensitive molecule, and modifying the surface of the protective layer of another portion of the perovskite nanocrystals with a second photosensitive molecule;

[0015] 4) Mixing and dispersing the differently modified perovskite nanocrystals in a solvent to obtain the photo-crosslinkable perovskite nanocrystal ink.

[0016] Optionally, the ratio of the perovskite nanocrystals modified with the first photosensitive molecule to the perovskite nanocrystals modified with the second photosensitive molecule ranges from 10:1 to 1:10.

[0017] A method for making a quantum dot pattern, comprising:

[0018] 1) coating the above-mentioned photo-crosslinkable perovskite nanocrystal ink on the surface of a substrate, and forming a photo-crosslinkable perovskite nanocrystal film after the solvent evaporates;

[0019] 2) selectively exposing the photo-crosslinkable perovskite nanocrystal film using a photolithography plate, so that the first photosensitive molecules and the second photosensitive molecules in the exposed area undergo a photo-crosslinking reaction;

[0020] 3) Using a developer to develop, remove the photo-crosslinkable perovskite nanocrystal film in the unexposed area, and obtain a quantum dot pattern.

[0021] Optionally, the developer is the same as the solvent of the photo-crosslinkable perovskite nanocrystal ink, and the solubility of the perovskite nanocrystal in the solvent is reduced through a photo-crosslinking reaction between the first photosensitive molecule and the second photosensitive molecule.

[0022] Optionally, the substrate includes glass, ITO, or a polymer substrate.

[0023] Optionally, the coating method includes spin coating, blade coating, slit coating, etc., and the film thickness is set according to actual needs.

[0024] Optionally, the light used for the exposure may be ultraviolet light, X-rays, etc.

[0025] A method for making a quantum dot color conversion layer comprises: preparing light-crosslinkable perovskite nanocrystal inks of different colors, respectively using the above-mentioned method for making quantum dot patterns, sequentially forming quantum dot patterns of different colors on a substrate to form a sub-pixel unit array.

[0026] Optionally, in the ABX3, A is a methylamine ion (CH3NH3 + , referred to as MA + ), formamidinium ion (CH(NH2) 2+ , referred to as FA + ), cesium ion (Cs+ ) etc., B is lead ion (Pb 2+ ), tin ions (Sn 2+ ), Germanium ions (Ge 2+ ), etc., X is a halogen anion: Cl, Br or I or a combination thereof. By changing the composition and ratio of X, photo-crosslinkable perovskite nanocrystal inks of different colors in the visible light region from blue to red can be obtained.

[0027] Optionally, the above method is used to construct a sub-pixel unit array of red and green perovskite color conversion layers, and is aligned and bonded with a blue light Micro-LED chip and a driving substrate to construct a Micro-LED full-color display device.

[0028] Optionally, the blue light Micro-LED chip is a GaN-based Micro-LED chip, and the driving substrate adopts complementary metal oxide semiconductor driving technology, thin film transistor driving technology, flip chip bonding technology, etc.

[0029] Optionally, the above method is used to construct a perovskite color conversion layer sub-pixel unit array of three colors of red, green and blue, and is aligned and bonded with an ultraviolet light Micro-LED chip and a driving substrate to construct a Micro-LED full-color display device.

[0030] The beneficial effects of the present invention are:

[0031] The photo-crosslinkable perovskite nanocrystal has a three-layer structure: the inner part is responsible for the light emission of the nanocrystal; the middle protective layer plays a role in passivating the nanocrystal to enhance its light emission performance and improve the stability of the nanocrystal, while providing reaction sites for the grafting of the photosensitive molecules in the outer layer; the two photosensitive molecules with C=C and C=O groups in the outer layer are mainly responsible for photo-crosslinking. In this quantum dot ink design, the three-layer structure has a clear division of labor. The photosensitive molecules grafted outside the protective layer undergo photochemical reactions to achieve cross-linking of the quantum dots, reduce their solubility in the mother solution (developer), and then achieve patterning through the development process; the patterning process does not require the use of photoresist and its special developer, effectively protecting the light emission performance and stability of the quantum dots; the ligands that are weakly bound to the surface of the perovskite quantum dots do not need to participate in the photo-crosslinking reaction, thus effectively maintaining the light emission characteristics and stability of the quantum dots. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structure of the perovskite nanocrystal coated with a protective layer in Example 1;

[0033] Figure 2 is a schematic diagram of a perovskite nanocrystal modified with a first photosensitive molecule according to Example 1;

[0034] Figure 3is a schematic diagram of the perovskite nanocrystal modified with a second photosensitive molecule according to Example 1;

[0035] Figure 4 Schematic diagram of selective exposure of the photo-crosslinkable green light perovskite nanocrystal film of Example 3;

[0036] Figure 5 This is a schematic diagram of the first photosensitive molecule and the second photosensitive molecule in Example 3 realizing a photo-crosslinking reaction under ultraviolet light;

[0037] Figure 6 This is a schematic diagram of developing the photo-crosslinkable green light perovskite nanocrystal film of Example 3;

[0038] Figure 7 is a schematic diagram of a green light quantum dot pattern of Example 3;

[0039] Figure 8 is a schematic diagram of a red and green quantum dot color conversion layer of Example 3;

[0040] Fig. 9 Schematic diagram of bonding the red and green quantum dot color conversion layer to the blue light Micro-LED chip array of Example 3. DETAILED DESCRIPTION

[0041] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. The various drawings of the present invention are only for illustration to make it easier to understand the present invention, and the specific proportions can be adjusted according to design requirements. The upper and lower relationships of the relative elements and the definitions of the front / back in the figures described in the text should be understood by those skilled in the art to refer to the relative positions of the components, so they can all be flipped to present the same components, which should all fall within the scope disclosed in this specification.

[0042] Example 1

[0043] The following describes a method for preparing photo-crosslinkable green light perovskite nanocrystal ink.

[0044] Synthesis of green light perovskite nanocrystals. This embodiment adopts the hot injection method to synthesize CsPbBr3 green light perovskite nanocrystals. Cs2CO3, oleic acid (OA), and octadecene (ODE) are mixed, kept at 120°C in a vacuum for one hour, and then heated to 150°C in nitrogen to obtain a cesium precursor. Lead bromide, OA, and oleylamine (OAM) are dissolved in ODE, kept at 120°C in a vacuum for half an hour, and then heated to 160°C in nitrogen to obtain a bromine precursor. Rapidly inject the cesium precursor solution just obtained under high-speed stirring, and ice bath after 5s to obtain a green light perovskite nanocrystal solution. The size range of the perovskite nanocrystals is about 5 to 30nm.

[0045] The perovskite nanocrystal is coated with a protective layer. In this embodiment, silicon dioxide is used as the protective layer. 0.1 mL of 3-aminopropyltriethoxysilane (APTES) is added to the green light perovskite nanocrystal solution, and then 10 μL of water is added and stirred for 30 minutes. A 2 nm thick SiO2 protective layer 2 is coated on the surface of the perovskite nanocrystal 1. The structure is as follows: Figure 1 shown.

[0046] The protective layer is modified with organic small molecules. This embodiment uses photosensitive molecules containing unsaturated C=C and C=O groups. The perovskite nanocrystal solution coated with the SiO2 protective layer is divided into two equal parts. The first part is added with the first photosensitive molecule containing C=C, such as acrylate oxypropyl dimethyl methoxy silane; the other part is added with the second photosensitive molecule containing C=O group, such as 4-(N-phenyl-N-methylamino) benzoic acid thiobenzoylmethyl ester. The reaction is stirred for 5 minutes to obtain the following. Figure 2 The perovskite nanocrystal modified with the first photosensitive molecule as shown, and Figure 3 The perovskite nanocrystal modified with the second photosensitive molecule is shown. The perovskite nanocrystal solution modified with the organic small molecule is then centrifuged, the supernatant is removed, and the solution is dispersed in xylene. The perovskite nanocrystal solutions modified with the two photosensitive molecules are mixed to prepare a photo-crosslinkable green light perovskite nanocrystal ink.

[0047] Example 2

[0048] The method for preparing photo-crosslinkable red light perovskite nanocrystal ink is different from that of Example 1 in that the lead bromide used to generate the bromine precursor is replaced with lead iodide, and the photo-crosslinkable red light perovskite nanocrystal ink is obtained by repeating the above steps.

[0049] Example 3

[0050] The following describes a method for making a red and green quantum dot color conversion layer.

[0051] like Figure 4 As shown, a layer of photo-crosslinkable green light perovskite nanocrystal ink of Example 1 is spin-coated on a glass substrate 10, and after the solvent evaporates, a uniform photo-crosslinkable green light perovskite nanocrystal film 20 is formed on the substrate 10, and its thickness is, for example, 100 nm. It is exposed to 365 nm ultraviolet light through a photomask 30 for about 20 seconds, so that the exposed area has photosensitive molecules with unsaturated C=C, C=O and other groups, which undergo photochemical reactions under the action of light and become single bonds, and crosslinking occurs between the photosensitive molecules of different perovskite nanocrystals, such as Figure 5 As shown, the solubility of green light quantum dots (perovskite nanocrystals) in the original solvent is reduced. Figure 6As shown, in this example, the original solvent xylene is used as the developer to realize the quantum dot patterning process. By rotating and washing in xylene, the photo-crosslinkable green light perovskite nanocrystalline film 20 in the unexposed area is dissolved by xylene, and the film crosslinked in the exposed area becomes insoluble in the non-polar organic solvent xylene and remains unchanged, thereby realizing the following Figure 7 The preparation of the green light quantum dot pattern shown has a plurality of green light quantum dot units G arranged in an array.

[0052] A layer of photo-crosslinkable red light perovskite nanocrystal ink of Example 2 is spin-coated on the substrate 10 having the green light quantum dot unit G, and a uniform photo-crosslinkable red light perovskite nanocrystal film is formed on the substrate after the solvent evaporates. Referring to the preparation process of the green light quantum dot pattern mentioned above, it is exposed to 365nm ultraviolet light and selectively exposed through a photolithography plate for about 20s, so that the exposed area has photosensitive functional molecules with unsaturated C=C, C=O and other groups, which undergo photochemical reactions under the action of light and become single bonds, and cross-linking occurs between the photosensitive molecules of different perovskite nanocrystals, reducing the solubility of the red light quantum dots in the original solvent. By rotating and washing in xylene, the photo-crosslinkable red light perovskite nanocrystal film in the unexposed area is dissolved by xylene, and the film that is cross-linked in the exposed area becomes insoluble in the non-polar organic solvent xylene and remains unchanged, thereby realizing the preparation of a red light quantum dot pattern, which has a plurality of red light quantum dot units R arranged in an array, such as Figure 8 As shown, the quantum dot color conversion layer of the sub-pixel unit array is formed together with the green light quantum dot pattern and the blank blue light transmission area B.

[0053] like Fig. 9 As shown, the obtained pattern arrayed quantum dot color conversion layer is aligned and bonded with the corresponding blue light Micro-LED chip array 40 that has been bonded to the driving substrate, and the pixel points (red light quantum dot unit R / green light quantum dot unit G / blue light transmission area B) correspond to the light-emitting unit 41 to prepare the perovskite nanocrystal color conversion Micro-LED full-color display device. Turn on the driving circuit, light up the blue light Micro-LED chip array, and excite the upper red and green light perovskite nanocrystal color conversion layer to form red, green and blue pixel units.

[0054] In other embodiments, a similar manufacturing method can also be used to manufacture a three-color color conversion layer of a red light quantum dot unit / a green light quantum dot unit / a blue light quantum dot unit, and full-color display can be achieved through excitation of an ultraviolet light Micro-LED chip array.

[0055] The above embodiments are only used to further illustrate a photo-crosslinkable perovskite nanocrystal ink and its preparation method and patterned application of the present invention, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the technical solution of the present invention.

Claims

1. A photo-crosslinkable perovskite nanocrystal ink, characterized in that: It includes perovskite nanocrystals dispersed in a solvent, wherein the chemical formula of the perovskite nanocrystals is ABX3, wherein A is an organic cation or a metal cation, B is a metal cation, and X is a halogen anion; the surface of the perovskite nanocrystal is coated with a protective layer, wherein the surface of the protective layer of some perovskite nanocrystals is modified with a first photosensitive molecule, and the surface of the protective layer of other perovskite nanocrystals is modified with a second photosensitive molecule, the first photosensitive molecule has a C=C group, and the second photosensitive molecule has a C=O group, and the first photosensitive molecule and the second photosensitive molecule can undergo a photocrosslinking reaction.

2. The photo-crosslinkable perovskite nanocrystal ink according to claim 1, characterized in that: The material of the protective layer includes SiO2, Al2O3, ZnO, ZnS, SnO2, TiO2, CdS, polyimide, polystyrene, polyvinyl pyrrolidone or polyacrylic acid, and the thickness is 1 to 20 nm.

3. The photo-crosslinkable perovskite nanocrystal ink according to claim 1, characterized in that: The solvent includes at least one of methane, toluene, ethane, acetone, chloroform, chlorobenzene, isopropanol, N,N-dimethylformamide, and N-methylformamide.

4. The photo-crosslinkable perovskite nanocrystal ink according to claim 1, characterized in that: At least one end of the first photosensitive molecule and / or the second photosensitive molecule has a functional group that binds to the protective layer, and the functional group includes a thiol group, a methoxy group, an ethoxy group, -Cl or -SH.

5. The photo-crosslinkable perovskite nanocrystal ink according to claim 1, characterized in that: The size of the perovskite nanocrystal is 5 to 30 nm, and the content of the perovskite nanocrystal in the solvent is 1 to 100 mg / mL.

6. A method for preparing the photo-crosslinkable perovskite nanocrystal ink according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) Preparation of perovskite nanocrystals; 2) Coating a protective layer on the surface of the perovskite nanocrystal; 3) modifying the surface of the protective layer of a portion of the perovskite nanocrystals with a first photosensitive molecule, and modifying the surface of the protective layer of another portion of the perovskite nanocrystals with a second photosensitive molecule; 4) The differently modified perovskite nanocrystals are mixed and dispersed in a solvent to obtain the photo-crosslinkable perovskite nanocrystal ink.

7. A method for making a quantum dot pattern, characterized in that: include: 1) applying the photo-crosslinkable perovskite nanocrystal ink according to any one of claims 1 to 5 to a substrate surface, After the solvent evaporates, a photo-crosslinkable perovskite nanocrystalline film is formed; 2) selectively exposing the photo-crosslinkable perovskite nanocrystal film using a photolithography plate to cause a photo-crosslinking reaction between the first photosensitive molecules and the second photosensitive molecules in the exposed area; 3) Using a developer to develop, remove the photo-crosslinkable perovskite nanocrystal film in the unexposed area, and obtain a quantum dot pattern.

8. The method for making a quantum dot pattern according to claim 7, characterized in that: The developer is the same as the solvent of the photo-crosslinkable perovskite nanocrystal ink, and the solubility of the perovskite nanocrystal in the solvent is reduced through the photo-crosslinking reaction between the first photosensitive molecule and the second photosensitive molecule.

9. A method for manufacturing a quantum dot color conversion layer, characterized in that: include: Photo-crosslinkable perovskite nanocrystal inks of different colors are prepared, and the method for making quantum dot patterns according to claim 7 or 8 is respectively used to sequentially form quantum dot patterns of different colors on a substrate to form a sub-pixel unit array.

10. The method for manufacturing a quantum dot color conversion layer according to claim 9, characterized in that: In the ABX3, A is methylamine ion, formamidine ion or cesium ion, B is lead ion, tin ion or germanium ion, and X is Cl ion, Br ion, I ion or a combination thereof; by changing the composition and ratio of X, photo-crosslinkable perovskite nanocrystal inks of different colors can be obtained.

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