Photoresistless photopatterning method of colloidal nanocrystals in green solvents

Abstract

The present invention belongs to the technical fields of nanomaterials and photoetching, and in particular, relates to a method for photoresist-free photopatterning of colloidal nanocrystals in a green solvent. By introducing a photosensitive ligand with a structure similar to that of the green solvent, the nanocrystals can be successfully dispersed in the green solvent, allowing direct photolithography of the nanocrystals. After ligand exchange, the resulting photosensitive nanocrystals can be effectively dispersed in the green solvent, maintaining their absorption / emission spectra, morphology, and dimensions unchanged, while maintaining a fluorescence quantum yield (PLQY) of approximately 90%. This invention solves the problem of nanocrystals being unable to be directly photolithographed in a green solvent and is expected to be applied to the commercialization of nanocrystals in the fields of electroluminescence and photoluminescence quantum dot displays.

Description

[Technical Field]

[0001] The present invention belongs to the technical field of nanomaterials and photoetching, and in particular to a method for photoresist-less photopatterning of colloidal nanocrystals in a green solvent. [Background technology]

[0002] Currently, photopatterning methods for nanocrystals (NCs) are primarily based on two approaches. (1) Photoresist-based photolithography techniques mainly utilize commercially available photoresists with mature development. These techniques can be subdivided into two distinct approaches: (i) direct photolithography of commercial photoresists, followed by partial removal of the photoresist using a developer, followed by filling the photoresist template with nanocrystals, and finally removing the photoresist to obtain patterned nanocrystals (Figure 1a); (ii) direct mixing of nanocrystals with commercial photoresists, followed by direct photolithography of the mixture, followed by embedding the nanocrystals in the photoresist, followed by partial removal of the photoresist and nanocrystals in a developer (Figure 1b); (2) photoresist-less direct photolithography techniques, which involve introducing photoacid generators (PAGs) or bifunctional surface ligands into colloidal nanocrystal systems (as shown in Figure 2). At specific wavelengths, the introduced photosensitizer decomposes, causing changes in the surface environment of the nanocrystals, thereby affecting their stability in some solvents. The unexposed areas can be removed by rinsing the nanocrystals with a suitable solvent (Figure 1c). Such ligands have a wide photosensitivity range, from deep ultraviolet (DUV, 254 nm) to visible light (450 nm), allowing photolithography of nanocrystals containing specific photosensitive groups.

[0003] The photoresist-based nanocrystal patterning method inevitably involves the use of photoresist, but commercially available photoresists cannot be completely removed effectively during the development process. The residual photoresist significantly affects the charge transport, heat conduction, and other properties of the nanocrystals, and the high cost of the photoresist itself increases the cost of the nanocrystal patterning process.

[0004] Although photoresist-less photolithography technology avoids the problems associated with the introduction of commercially available photoresists, nanocrystals cannot be directly dispersed in green solvents such as propylene glycol methyl ether acetate (PGMEA), diethylene glycol ethyl ether acetate (DGMEA), and octane. The patterning process can only be carried out in industrially unacceptable solvents such as toluene and N,N-dimethylformamide (DMF). This significantly limits the practical application of current nanocrystal patterning technology in industrial production. Furthermore, the introduced functional ligands not only change the nanocrystal surface composition but also damage the nanocrystal surface, affecting its optical performance. Therefore, after patterning is complete, further post-treatment is required to repair the nanocrystal surface and partially restore its performance. Summary of the Invention

[0005] The present invention solves the above-mentioned technical problems in the prior art by proposing a photoinduced crosslink lithography (PICL) technique and designing a series of bifunctional ligands. On the one hand, these ligands all share partial structural similarities with green solvents, and after binding to the nanocrystal surface via carboxylate, amino, or mercapto groups, they serve to disperse nanocrystals in green solvents such as PGMEA, DGMEA, and octane according to the principle of "like dissolves like." On the other hand, these ligands all contain photosensitive methacryloyl or benzophenone groups, which allow for coupling polymerization under irradiation with light of a specific wavelength, thereby enabling direct photolithographic patterning of nanocrystals. This method retains the easy-to-operate advantages of photoresistless photolithography, while completing patterning without damaging the nanocrystal surface, preserving the fluorescent properties of the nanocrystals, shortening the distance between nanocrystals, and effectively improving the efficiency of charge transport between nanocrystals.

[0006] The technical means of the present invention are as follows:

[0007] A green photosensitive nanocrystal coating comprising nanocrystals and a photosensitive ligand, wherein the selected photosensitive ligand comprises a group that coordinates with the nanocrystal, such as a carboxylate group, an amino group, or a mercapto group, and a methacryloyl group or a benzophenone photosensitive group.

[0008] Preferably, the photosensitive ligand is 2-(3-mercaptopropionyloxy)ethyl methacrylate, 5-[3-methoxy-4-(2-methylprop-2-enoyloxy)phenyl]pent-4-enoic acid, (2E)-3-(3-methoxy-4-{2-[(2-methylprop-2-enoyl)oxy]ethoxy}phenyl)prop-2-enoic acid, 4-(4-(methacryloyloxy)phenoxy)-4-oxobutyric acid, mono-2-(methacryloyloxy)ethyl succinate, (E)-6-(4-(methacryloyloxy)phenyl)-4-oxohex-5-enoic acid, (E)- The compound is any one of 6-(4-(methacryloyloxy)-3-methoxyphenyl)-4-oxohex-5-enoic acid, (E)-6-(4-(methacryloyloxy)-3,5-dimethoxyphenyl)-4-oxohex-5-enoic acid, 2-(6-(2-(methacryloyloxy)ethoxy)-2-oxo-2H-chromen-3-yl)acetic acid, phenyl-[4-(10-mercaptodecyloxy)phenyl]methanone, phenyl-[4-(10-mercaptodecylthio)phenyl]methanone, and 4-pyrrolidinyl-phenyl-[4-(10-mercaptodecylthio)phenyl]methanone.

[0009] Preferably, the nanocrystals contain original organic ligands that are any one or more of a carboxylic acid, a phosphinic acid, and an amine, each having an aliphatic chain with more than 8 carbon atoms. More preferably, the original organic ligands are any one or more of a combination of oleic acid, stearic acid, palmitic acid, oleylamine, octadecylamine, and octadecylphosphonic acid.

[0010] Preferably, the nanocrystals include, but are not limited to, inorganic nanocrystals such as CdS, CdSe, CdSe / ZnS, CdSeS / ZnS, CdSe / CdZnSeS / ZnS, CdZnS / ZnS, CdZnSe / ZnS, ZnSe / ZnS, CdSe / CdS, CdSeS / CdS, InP, InP / ZnS, InP / ZnSe / ZnS, InGaP / ZnSe / ZnS, CdTe, PbS, PbSe, PbS / CdS, Fe2O3, Fe3O4, TiO2, ITO, In2O3, CsPbBr3, and MAPbBr3.

[0011] The green photosensitive nanocrystal coating is produced by ligand exchange between nanocrystals bearing organic ligands on their surfaces and photosensitive ligands. Specifically, the photosensitive ligands are added to a solution of nanocrystals bearing organic ligands on their surfaces, and the resulting mixture is vigorously stirred or shaken to obtain a precipitate, i.e., a product.

[0012] Preferably, the nanocrystal solution having the organic ligand on its surface and the photosensitive ligand are mixed in a mass ratio of 10:1, and the resulting mixture is vigorously stirred or shaken until a precipitate, i.e., a product, is formed. Preferably, the concentration of the photosensitive ligand is 50 mg / mL or more.

[0013] Preferably, the ligand exchange is carried out under an inert atmosphere.

[0014] In the method for producing the green photosensitive nanocrystal ink, the green photosensitive nanocrystal coating is dispersed in a green solvent, which is propylene glycol methyl ether acetate (PGMEA), ethylene glycol methyl ether acetate (EGMEA), diethylene glycol ethyl ether acetate (DGMEA), or propylene glycol methyl ether (PGME), octane.

[0015] Preferably, the green photosensitive nanocrystal paint is dispersed in a green solvent to form a stable colloidal solution, and the concentration of the green photosensitive nanocrystal paint is 10-25 mg / mL.

[0016] A method for photoresistless photopatterning of colloidal nanocrystals in a green solvent, comprising the steps of: using the green photosensitive nanocrystal ink to fabricate a continuous, dense, and thickness-controllable nanocrystal thin film on a substrate; pressing a mask engraved with a specific pattern onto the thin film; exposing it to an ultraviolet light source; and developing it in a developer.

[0017] Preferably, the substrate is a silicon wafer, a quartz wafer or a glass wafer.

[0018] Preferably, the developer is propylene glycol methyl ether acetate (PGMEA), ethylene glycol methyl ether acetate (EGMEA), diethylene glycol ethyl ether acetate (DGMEA) or propylene glycol methyl ether (PGME), octane.

[0019] The advantages of the present invention over the prior art are as follows: The present invention successfully disperses nanocrystals in green solvents by introducing photosensitive ligands whose structure is similar to that of the green solvent, and enables direct photolithography of the nanocrystals.

[0020] The present invention found that the photosensitive nanocrystals obtained after ligand exchange could be effectively dispersed in green solvents, with no changes in their absorption / emission spectra or morphology, and with a fluorescence quantum yield (PLQY) of approximately 90%. Mechanism studies revealed that this process involves radical polymerization of the acryloyl in the photosensitive ligand structure under ultraviolet light, shortening the distance between nanocrystals and significantly reducing their solubility in solvents such as toluene and propylene glycol methyl ether acetate.

[0021] The present invention solves the problem that nanocrystals cannot be directly photolithographed in green solvents, and this technology has potential applications for the commercialization of nanocrystals in the fields of electroluminescent and photoluminescent quantum dot displays. [Brief explanation of the drawings]

[0022] [Figure 1] Figure 1 shows a schematic diagram of several methods for photopatterning nanocrystals. Figure 1a shows a photoresist-based photoetching technique 1. Figure 1b shows a photoresist-based photoetching technique 2. Figure 1c shows a photoresist-less photolithography technique. Figure 1d shows a photopatterning method of the present invention that does not impair fluorescent performance. [Figure 2] FIG. 2 illustrates the introduction of photoacid generators (PAGs) or bifunctional surface ligands into colloidal nanocrystal systems to achieve photoresistless photolithography. [Figure 3] FIG. 3 is a schematic diagram of the nanocrystal surface treatment method of the present invention. [Figure 4] FIG. 4 is a schematic diagram of a photolithography process according to the present invention. [Figure 5] Figure 5 shows a comparison of transmission electron micrographs of nanocrystals before (left) and after (right) ligand exchange. [Figure 6] Figure 6 compares the luminescence performance of nanocrystals before (black line) and after (gray line) treatment with a photosensitive ligand. [Figure 7] FIG. 7 shows a photolithography pattern using 2-(3-mercaptopropionyloxy)ethyl methacrylate as a ligand. [Figure 8] FIG. 8 shows a photolithography pattern using 5-[3-methoxy-4-(2-methylprop-2-enoyloxy)phenyl]pent-4-enoic acid as a ligand. [Figure 9] FIG. 9 shows a photolithography pattern using 2-(6-(2-(methacryloyloxy)ethoxy)-2-oxo-2H-chromen-3-yl)acetic acid as a ligand. DETAILED DESCRIPTION OF THE INVENTION

[0023] Example 1: Direct photolithography of nanocrystals (quantum dots) with 2-(3-mercaptopropionyloxy)ethyl methacrylate as a ligand in green solvents using deep ultraviolet light as a light source All ligand exchanges were carried out in a nitrogen-filled glove box (O2 and H2O less than 0.01 ppm) using anhydrous solvents. The photolabile ligand used was 2-(3-mercaptopropionyloxy)ethyl methacrylate.

[0024] Red fluorescent nanocrystalline CdSe / ZnS quantum dots bearing oleic acid on their surfaces were dispersed in n-hexane. 2-(3-mercaptopropionyloxy)ethyl methacrylate was used as a pure substance. First, a ligand exchange process was performed: 200 μL of NC solution (25 mg / mL) was added with 20 μL of 2-(3-mercaptopropionyloxy)ethyl methacrylate, and the resulting mixture was vigorously stirred or shaken until NC precipitation was observed. After centrifugation, the precipitate was redispersed in 200 μL of PGMEA and precipitated with 1 mL of n-hexane to remove excess 2-(3-mercaptopropionyloxy)ethyl methacrylate ligand. After centrifugation, the precipitate was further dispersed in PGMEA to form a stable colloidal solution (10–25 mg / mL). A transmission electron microscope (TEM) image of the material is shown in Figure 5. A 10 μL drop of the NCs in PGMEA solution was placed on the surface of a silicon wafer and spin-coated into a uniform thin film on a spin coater. A mask with a specific pattern was pressed onto the thin film, which was then exposed to a 254 nm UV light source and developed in PGMEA developer. The resulting pattern is shown in Figure 7.

[0025] Example 2: Direct photolithography of nanocrystals (quantum dots) with 5-[3-methoxy-4-(2-methylprop-2-enoyloxy)phenyl]pent-4-enoic acid as a ligand in green solvents using a 365 nm light source All ligand exchanges were carried out in a nitrogen-filled glove box (O2 and HO less than 0.01 ppm) using anhydrous solvents. The photolabile ligand used was 5-[3-methoxy-4-(2-methylprop-2-enoyloxy)phenyl]pent-4-enoic acid.

[0026] Green fluorescent nanocrystalline CdSe / CdZnSeS quantum dots with oleic acid as the surface ligand were dispersed in n-hexane and 5-[3-methoxy-4-(2-methylprop-2-enoyloxy)phenyl]pent-4-enoic acid was prepared as an n-hexane solution. First, a ligand exchange process was performed: 200 μL of NCs solution (25 mg / mL) was added to 20 μL of 5-[3-methoxy-4-(2-methylprop-2-enoyloxy)phenyl]pent-4-enoic acid n-hexane solution (50 mg / mL). The resulting mixture was vigorously stirred or shaken until NCs precipitated. After centrifugation, the precipitate was redispersed in 200 μL of PGMEA and precipitated with 1 mL of n-hexane to remove excess 5-[3-methoxy-4-(2-methylprop-2-enoyloxy)phenyl]pent-4-enoic acid ligand. After centrifugation, the precipitate was further dispersed in PGMEA to form a stable colloidal solution (10–25 mg / mL). Figure 6 shows a comparison of the absorption and fluorescence spectra before and after the treatment. A 10 μL PGMEA solution of NCs was dropped onto the surface of a silicon wafer and spin-coated into a uniform thin film on a spin coater. A mask with a specific pattern was pressed onto the thin film, exposed to a 365 nm UV light source, and developed in PGMEA developer. The resulting pattern is shown in Figure 8. To fully demonstrate the generality of this method, we photolithographed red-fluorescent CdSeS / ZnS quantum dots and blue-fluorescent CdZnS / ZnS quantum dots, obtaining nanocrystal patterns that retained their fluorescence.

[0027] Example 3: Direct photolithography of nanocrystals (quantum dots) with 2-(6-(2-(methacryloyloxy)ethoxy)-2-oxo-2H-chromen-3-yl)acetic acid as a ligand in green solvents using a 405 nm light source All ligand exchanges were carried out in a nitrogen-filled glove box (O2 and HO less than 0.01 ppm) using anhydrous solvents. The photolabile ligand used was 2-(6-(2-(methacryloyloxy)ethoxy)-2-oxo-2H-chromen-3-yl)acetic acid.

[0028] Green fluorescent nanocrystalline CdSe / CdZnSeS quantum dots bearing oleic acid on their surfaces were dispersed in n-hexane and 2-(6-(2-(methacryloyloxy)ethoxy)-2-oxo-2H-chromen-3-yl)acetic acid was prepared as an n-hexane solution. First, a ligand exchange process was performed: 20 μL of NCs solution (25 mg / mL) was added to 200 μL of NCs solution (25 mg / mL) with 20 μL of 2-(6-(2-(methacryloyloxy)ethoxy)-2-oxo-2H-chromen-3-yl)acetic acid in n-hexane (50 mg / mL). The resulting mixture was vigorously stirred or shaken until NCs precipitation was observed. After centrifugation, the precipitate was redispersed in 200 μL of PGMEA and precipitated with 1 mL of n-hexane to remove excess 2-(6-(2-(methacryloyloxy)ethoxy)-2-oxo-2H-chromen-3-yl)acetic acid ligand. After centrifugation, the precipitate was further dispersed in PGMEA to form a stable colloidal solution (10–25 mg / mL). A 10 μL PGMEA solution of NCs was dropped onto the surface of a silicon wafer and spin-coated into a uniform thin film on a spin coater. A mask engraved with a specific pattern was pressed onto the thin film, which was then exposed to a 365 nm UV light source and developed in PGMEA developer. The resulting pattern is shown in Figure 9.

[0029] Example 4: Similar to the experimental method of Example 3, the same technical effect can be obtained by using the following photosensitive ligands instead of 2-(6-(2-(methacryloyloxy)ethoxy)-2-oxo-2H-chromen-3-yl)acetic acid. (2E)-3-(3-methoxy-4-{2-[(2-methylprop-2-enoyl)oxy]ethoxy}phenyl)prop-2-enoic acid 4-(4-(methacryloyloxy)phenoxy)-4-oxobutyric acid Mono-2-(methacryloyloxy)ethyl succinate (E)-6-(4-(methacryloyloxy)phenyl)-4-oxohex-5-enoic acid (E)-6-(4-(methacryloyloxy)-3-methoxyphenyl)-4-oxohex-5-enoic acid (E)-6-(4-(methacryloyloxy)-3,5-dimethoxyphenyl)-4-oxohex-5-enoic acid Phenyl-[4-(10-mercaptodecyloxy)phenyl]methanone, Phenyl-[4-(10-mercaptodecylthio)phenyl]methanone 4-Pyrrolidinyl-phenyl-[4-(10-mercaptodecylthio)phenyl]methanone

[0030] Example 5: Similar to the experimental method of Example 3, instead of CdSe / CdZnSeS quantum dots, CdS, CdSe, CdSe / ZnS, CdSeS / ZnS, CdSe / CdZnSeS / ZnS, CdZnS / ZnS, CdZnSe / ZnS, ZnSe / ZnS, CdSe / CdS, CdSeS / CdS, InP, InP / ZnS, InP / ZnSe / ZnS, InGaP / ZnSe / ZnS, CdTe, PbS, PbSe, PbS / CdS, Fe2O3, Fe3O4, TiO2, ITO, In2O3, CsPbBr3, and MAPbBr3 nanocrystals can be used, respectively, to achieve the same technical effects.

[0031] Example 6: Similar to the experimental method of Example 3, octane, ethylene glycol methyl ether acetate (EGMEA), diethylene glycol ethyl ether acetate (DGMEA) or propylene glycol methyl ether (PGME) can be used instead of propylene glycol methyl ether acetate (PGMEA), and the same technical effect can be obtained.

[0032] It should be noted that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent replacements or substitutions made based on the above also fall within the scope of protection of the present invention.

Claims

1. A green photosensitive nanocrystal paint comprising nanocrystals and a photosensitive ligand, the nanocrystals being dispersed in a green solvent to form a green photosensitive nanocrystal ink, the photosensitive ligand comprising a group that coordinates with the nanocrystals and a methacryloyl group or a benzophenone photosensitive group; The photosensitive ligand may be 2-(3-mercaptopropionyloxy)ethyl methacrylate, 5-[3-methoxy-4-(2-methylprop-2-enoyloxy)phenyl]pent-4-enoic acid, (2E)-3-(3-methoxy-4-{2-[(2-methylprop-2-enoyl)oxy]ethoxy}phenyl)prop-2-enoic acid, 4-(4-(methacryloyloxy)phenoxy)-4-oxobutyric acid, mono-2-(methacryloyloxy)ethyl succinate, (E)-6-(4-(methacryloyloxy)phenyl)-4-oxohex-5-enoic acid, (E)-6-(4-(methacryloyloxy)phenyl)-4-oxohex-5-enoic acid, 2-(6-(2-(methacryloyloxy)ethoxy)-2-oxo-2H-chromen-3-yl)acetic acid, phenyl-[4-(10-mercaptodecyl)oxy)phenyl]methanone, phenyl-[4-(10-mercaptodecylthio)phenyl]methanone, or 4-pyrrolidinyl-phenyl-[4-(10-mercaptodecylthio)phenyl]methanone.

2. 2. The green photosensitive nanocrystal paint according to claim 1, wherein the groups coordinated to the nanocrystals are one or more of a carboxylate group, an amino group, and a mercapto group.

3. The nanocrystals include CdS, CdSe, CdSe / ZnS, CdSeS / ZnS, CdSe / CdZnSeS, CdSe / CdZnSeS / ZnS, CdZnS / ZnS, and CdZnSe. / ZnS, ZnSe / ZnS, CdSe / CdS, CdSeS / CdS, InP, InP / ZnS, InP / ZnSe / ZnS, InGaP / ZnSe / ZnS, CdTe, PbS, P 2. The green photosensitive nanocrystal paint of claim 1, wherein the nanocrystal is one of the following: bSe, PbS / CdS, Fe2O3, Fe3O4, TiO2, ITO, In2O3, CsPbBr3, and MAPbBr3, and the nanocrystals contain original organic ligands, which are one or more combinations of carboxylic acids, phosphinic acids, and amines with an aliphatic chain carbon number greater than 8.

4. A method for producing the green photosensitive nanocrystal paint according to any one of claims 1 to 3, characterized in that it comprises the steps of adding a photosensitive ligand to a solution of nanocrystals having organic ligands on their surfaces, and vigorously stirring or shaking the resulting mixture to obtain a precipitate, i.e., a product.

5. The method of claim 4, characterized in that a nanocrystal solution having organic ligands on its surface at 25 mg / mL and a photosensitive ligand are mixed in a volume ratio of 10:1 under an inert atmosphere, and the resulting mixture is vigorously stirred or shaken until a precipitate, i.e., a product, is produced.

6. A method for producing a green photosensitive nanocrystal ink, comprising dispersing the green photosensitive nanocrystal paint according to any one of claims 1 to 3 in a green solvent selected from propylene glycol methyl ether acetate, ethylene glycol methyl ether acetate, octane, diethylene glycol ethyl ether acetate, and propylene glycol methyl ether.

7. The method of claim 6, wherein the green photosensitive nanocrystal paint is dispersed in a green solvent to form a stable colloidal solution, and the concentration of the green photosensitive nanocrystal paint is 10-25 mg / mL.

8. 10. A method for photoresistless photopatterning of colloidal nanocrystals in a green solvent, comprising the steps of: fabricating a continuous, dense, and thickness-controllable nanocrystal thin film on a substrate using the green photosensitive nanocrystal ink of claim 6; pressing a mask engraved with a specific pattern onto the thin film; exposing it to an ultraviolet light source; and developing it in a developer.

9. 9. The method of claim 8, wherein the substrate is a silicon wafer, a quartz wafer, or a glass wafer, and the developer is propylene glycol methyl ether acetate, ethylene glycol methyl ether acetate, octane, diethylene glycol ethyl ether acetate, or propylene glycol methyl ether.

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