Patterning method for in-situ crosslinking of single quantum dot surface ligand
By using the method of in situ cross-linking of quantum dot surface ligands, the problems of photoresist residue and charge transfer obstruction in traditional quantum dot patterning were solved, achieving high-resolution quantum dot patterning and performance improvement of electroluminescent devices.
Patent Information
- Application Number
- CN202510505098.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-22
- Publication Date
- 2025-09-09
AI Technical Summary
The residual photoresist in the traditional quantum dot patterning process is difficult to completely remove, resulting in a decrease in device performance, and the photosensitive molecules hinder charge transfer, affecting the application of high-resolution electroluminescent devices.
The method of in situ cross-linking of ligands on the surface of single quantum dots is adopted. By adding photocross-linking ligands such as azidoacetic acid on the surface of quantum dots, ultraviolet light is used to cross-link the ligands of the quantum dots themselves to form a pattern, avoiding the use of photosensitive molecules.
It achieves high-resolution quantum dot patterning, maintains photoluminescence quantum yield, improves charge transfer efficiency, and is suitable for high-resolution electroluminescent devices.
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Figure CN120614970A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of quantum dot patterning, and in particular relates to a patterning method for in-situ cross-linking of ligands on the surface of a single quantum dot. Background Art
[0002] New display technology has become one of the transformative technologies leading the development, and it has also put forward higher requirements for the development of display technology. Quantum dots (QD) have shown great potential in the development of new display technologies due to their unique optical properties, such as tunable emission wavelength, narrow spectral line width and nearly uniform photoluminescence quantum yield. Since Professor Alivisatos proposed the world's first QD electroluminescent device - quantum dot light-emitting diode (QLED) in 1994, the synthesis scheme of QD and the QLED device architecture have been continuously optimized, which has led to a significant improvement in the external quantum efficiency (EQE) of QLED devices (the ratio of the number of injected electrons to the number of emitted photons), from the initial 0.005% to more than 25%.
[0003] QLED devices assembled by patterning QDs into pixel matrices can achieve high-resolution, high-definition, and detailed images. This has become a cutting-edge field in display research and is in line with my country's strategic development plan for high-resolution new display technologies. Simultaneously, research into QD patterning processes is also evolving. Traditional patterning processes primarily consist of transfer printing, inkjet printing, and photolithography. However, the key challenges of preparing QD pixel matrices using transfer printing and inkjet printing are incomplete pixels and low fidelity.
[0004] Photolithography patterning is an important process technology for manufacturing microelectronic and optoelectronic devices. Its basic principle is to use photosensitive materials to undergo chemical or physical changes under the action of light, thereby realizing the exposure and development of the photoresist or photoresist layer, and ultimately obtaining the desired fine pattern. In recent years, photolithography patterning technology has become a hot topic in the field of high-resolution display research. The photolithography pixelation process for QD light-emitting films is mainly divided into traditional photoresist-assisted lithography and direct lithography of QD films. The traditional photolithography process has the problem of residual photoresist being difficult to completely remove, resulting in a significant decrease in device performance.
[0005] In domestic research, Li Fushan's team at Fuzhou University successfully created a QD pixel pattern with a minimum pixel size of 1.5 μm by mixing QD and a photocrosslinker. The resolution was as high as 10,000 PPI (pixels per inch). The prepared electroluminescent device had an EQE of 16.25% and a brightness of 146,413 cd / m 2(The applied voltage is 8V). Zhang Hao and others from Tsinghua University improved on their original work and designed a patterning strategy that can achieve almost lossless optoelectronic performance based on the surface characteristics of perovskite QD materials. A photocross-linking substance containing diazo groups at both ends was prepared. Under ultraviolet exposure with a wavelength of 365nm, the diazo double bond broke and the adjacent QDs were cross-linked through non-specific carbon-hydrogen bonding. Finally, the preparation of a 4000PPI pixel array was achieved, and the optoelectronic properties of perovskite QDs were taken into account. While retaining 90% of the photoluminescence quantum yield, the peak EQE reached 16%. At the same time, this strategy also has good photochemical effects on perovskite QDs with a variety of surface ligands.
[0006] Abroad, Dmitri V. Talapin et al. from the University of Chicago proposed a trichlorotriazine-based photoacid generator in 2023 and introduced it into an InP QD solution, achieving the preparation of QD patterns with a minimum line width of 1 micron. In 2022, Wan Ki Bae et al. from South Korea designed a dual-ligand surface passivation strategy for colloidal QDs. The dual ligands in this work consist of photocrosslinking ligands and dispersed ligands. When the surface-modified QDs are irradiated with ultraviolet light at a wavelength of 365, the carbon-oxygen double bonds of the photocrosslinking ligands break and form carbon-hydrogen covalent bonds with the alkyl chains on the surfaces of adjacent QDs. After the photocrosslinking reaction, a stable QD film can be obtained in a specific area to resist solvent cleaning and thus form the target pattern. Dispersed ligands can make the modified QDs more soluble in specific solvents. This work ultimately achieved the preparation of 15,000 PPI ultra-high-resolution multi-color pixel patterns.
[0007] Specifically, the traditional method involves adding photosensitizing molecules to a quantum dot solution. Under ultraviolet light, the photosensitive molecules and ligands on the quantum dots emit light, causing photocrosslinking that alters the solubility of the quantum dots. This method can produce a quantum dot pattern by washing away the quantum dots in the unexposed areas during solvent development, leaving behind the quantum dots in the UV-irradiated areas. However, the insulating properties of the photosensitive molecules introduced in this method hinder charge transfer between the quantum dots, hindering the application of quantum dot patterns in high-resolution electroluminescent devices. Summary of the Invention
[0008] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.
[0009] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.
[0010] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a patterning method for in-situ cross-linking of ligands on the surface of a single quantum dot.
[0011] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:
[0012] Cesium carbonate, undecylenic acid and a photocrosslinking ligand are added to toluene and stirred to obtain a cesium precursor solution;
[0013] Lead bromide and tetra-n-octylammonium bromide are dissolved in toluene and stirred to obtain a PbBr2 precursor solution;
[0014] Under vigorous stirring, the cesium precursor solution is rapidly added to the PbBr2 precursor solution to obtain a mixed solution I;
[0015] After the reaction of the mixed solution I, a toluene solution of didodecylammonium bromide (DDAB) was added thereto to obtain a mixed solution II;
[0016] After the reaction of the mixed solution II, ethyl acetate is added thereto, the mixture is stirred evenly and then centrifuged, the precipitate is collected and redispersed in n-octane or n-hexane to obtain a green luminescent quantum dot CsPbBr3 solution;
[0017] A green luminescent quantum dot CsPbBr3 solution is spin-coated onto a glass sheet to form a quantum dot film. A customized photomask is placed on the quantum dot film and exposed with a 365nm wavelength ultraviolet lamp. After exposure, the quantum dots in the unexposed area are washed away with n-hexane, leaving the quantum dots in the exposed area, thereby producing the desired pattern.
[0018] As a preferred embodiment of the patterning method of in-situ cross-linking of ligands on the surface of a single quantum dot according to the present invention, wherein: the photocross-linking ligand comprises azidohexanoic acid or 3-mercaptopropyl acrylate
[0019] As a preferred embodiment of the in situ cross-linking patterning method for single quantum dot surface ligands of the present invention, the mass volume ratio of cesium carbonate, undecylenic acid, and photocrosslinking ligand in the cesium precursor solution is 100-200 mg:1-5 ml:1-10 mg, wherein the concentration of cesium carbonate is 5-100 mg / ml.
[0020] As a preferred embodiment of the in-situ cross-linking patterning method for single quantum dot surface ligands of the present invention, the mass ratio of lead bromide to tetra-n-octylammonium bromide in the PbBr2 precursor solution is 1:1-100, wherein the concentration of lead bromide is 2-150 mg / ml.
[0021] As a preferred embodiment of the patterning method of in-situ cross-linking of ligands on the surface of a single quantum dot according to the present invention, the volume ratio of the cesium precursor solution to the PbBr2 precursor solution is 1 to 3:4.
[0022] As a preferred embodiment of the patterning method of in situ cross-linking of ligands on the surface of a single quantum dot according to the present invention, the reaction time of the mixed solution I is 4 to 6 minutes.
[0023] As a preferred embodiment of the patterning method for in situ cross-linking of ligands on the surface of a single quantum dot according to the present invention, the volume ratio of the didodecylammonium bromide DDAB toluene solution to the mixed solution I is 70-100 μL:15 ml, wherein the concentration of the didodecylammonium bromide DDAB toluene solution is 100 mg / ml.
[0024] As a preferred solution of the patterning method for in-situ cross-linking of ligands on the surface of a single quantum dot according to the present invention, the volume ratio of the ethyl acetate to the mixed solution II is 4:1-3.
[0025] As a preferred solution of the patterning method for in-situ cross-linking of ligands on the surface of a single quantum dot according to the present invention, the exposure time is 3 to 5 minutes.
[0026] As a preferred solution of the patterning method of in-situ cross-linking of ligands on the surface of a single quantum dot according to the present invention, the luminescent color of the quantum dots is adjusted by dripping a luminescent quantum dot solution into the green luminescent quantum dot CsPbBr3 solution.
[0027] Beneficial effects of the present invention:
[0028] The present invention innovatively directly utilizes the photocrosslinking between ligands on the surface of quantum dots to realize patterns, which solves the problem that the traditional method requires the use of ligand crosslinking between quantum dots to produce patterns, and effectively solves the problem of electron transmission obstruction caused by photocrosslinking. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:
[0030] Figure 1 This is a physical picture of the quantum dot solution prepared in Example 1 of the present invention.
[0031] Figure 2 This is the photolithography method of the quantum dot solution in Example 1 of the present invention.
[0032] Figure 3 This is a schematic diagram of the self-crosslinking of quantum dot surface ligands in Example 1 of the present invention.
[0033] Figure 4 This is a pixel painting pattern display using quantum dot imaging in Example 1.
[0034] Figure 5 This is a pixel painting pattern display using quantum dot imaging in Example 2.
[0035] Figure 6 Schematic diagram of ligand cross-linking and electron obstruction on traditional quantum dots in comparative example 1 of the present invention.
[0036] Figure 7 The voltage-current density curves of the devices obtained by assembling the thin films prepared in Example 1 and Comparative Example 1 are shown. DETAILED DESCRIPTION
[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.
[0038] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
[0039] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.
[0040] Unless otherwise specified, the raw materials used in the present invention are commonly available in the market.
[0041] Example 1
[0042] Reference Figures 1 to 3 This embodiment provides a patterning method for in-situ cross-linking of ligands on the surface of a single quantum dot, specifically:
[0043] 1) 163 mg (0.5 mmol) of cesium carbonate (Cs2CO3), 2 mL of undecylenic acid, and 10 mg of a photocrosslinking ligand (azidoacetic acid) were added to 18 mL of toluene and stirred at 60°C for 10 min to obtain a cesium precursor solution;
[0044] 2) 367 mg (1 mmol) of lead bromide (PbBr2) and 1094 mg (2 mmol) of tetra-n-octylammonium bromide (TOAB) were dissolved in 20 ml of toluene to obtain a PbBr2 precursor solution;
[0045] 3) Under vigorous stirring, 1 mL of the cesium precursor solution was rapidly added to 2 mL of the PbBr2 precursor solution to obtain a mixed solution I;
[0046] 4) After 15 ml of mixed solution I was reacted for 5 min, 70 μL of 100 mg / mL didodecyl ammonium bromide (DDAB) toluene solution was added to obtain mixed solution II;
[0047] 5) After the mixed solution II reacted for 2 minutes, ethyl acetate was added thereto at a volume ratio of 2:1 to the mixed solution II, stirred evenly, and then centrifuged (12000 rpm, 5 minutes). The precipitate was collected and redispersed in n-octane or n-hexane (5 ml of toluene) to obtain a green luminescent quantum dot (CsPbBr3) solution, as shown in the figure. Figure 1 shown.
[0048] 6)Reference Figure 2 The quantum dot solution is spin-coated onto a glass sheet to form a quantum dot film. A customized photomask is placed on the quantum dot film and then exposed to ultraviolet light with a wavelength of 365nm for 3 minutes. After the exposure is completed, the quantum dots in the unexposed area are washed away with n-hexane, leaving the quantum dots in the exposed area, thereby producing the required pattern.
[0049] Figure 3 This is a schematic diagram of the self-crosslinking of ligands on the surface of quantum dots. The present invention utilizes the crosslinking between the surface ligands on the quantum dots themselves to solve the problem that photosensitive substances hinder the charge transfer between quantum dots.
[0050] Example 2
[0051] This embodiment differs from embodiment 1 in that a red quantum dot material is prepared, specifically:
[0052] Steps 1 to 5) Referring to Example 1, 100 mg ZnI2 and 200 μL OAm were dissolved in 15 mL toluene, stirred at room temperature for 24 hours, and the prepared solution was added dropwise to the green luminescent quantum dot (CsPbBr3) solution to obtain red luminescent quantum dots (CsPbBr 1.5 I 1.5 ) solution, and the remaining steps and processes are all referred to Example 1 to achieve quantum dot imaging of this embodiment.
[0053] Figure 4 To display the pixel painting pattern using quantum dot imaging in Example 1, Figure 2The pixel painting pattern display using quantum dot imaging in Example 2 shows that both can achieve pixels of different patterns with high resolution.
[0054] Comparative Example 1
[0055] Reference Figure 6 , which is a schematic diagram of preparing a pattern by adding a photosensitive molecular cross-linker to quantum dot ligands to achieve cross-linking between quantum dots. Specifically:
[0056] Ethylene bis(4-azido-2,3,5,6-tetrafluorobenzoate) powder was dissolved in toluene to prepare an ethylene bis(4-azido-2,3,5,6-tetrafluorobenzoate) crosslinker solution with a concentration of 10 mg / ml;
[0057] CsPbBr3 quantum dots were dispersed in a crosslinker solution of toluene bis(4-azido-2,3,5,6-tetrafluorobenzoate) to prepare a CsPbBr3 quantum dot solution with a concentration of 20 mg / ml;
[0058] The CsPbBr3 quantum dot solution was spin-coated on a clean silicon substrate ( ) at a speed of 2000 rpm for 30 seconds. Subsequently, the coated film was irradiated with a UV lamp with a peak intensity of 254 (3 mW cm -2 ), the exposure dose at 254 nm is typically 60 mJ cm -2 , a patterned quantum dot film was obtained by irradiating the film through a quartz mask with a pre-designed pattern in a mask aligner system.
[0059] The conventional method of this comparative example will result in electrons being unable to be free and transmitted in quantum dots, thus hindering the application of quantum dots in electroluminescent devices.
[0060] Figure 7 The voltage-current density curves of the devices obtained by assembling thin films prepared using Example 1 and Comparative Example 1 show that the current density generated by in situ crosslinking between surface ligands on the quantum dots themselves in Example 1 is significantly higher than that of the sample with the additional introduction of a crosslinking agent.
[0061] Comparative Example 2
[0062] This comparative example differs from Example 1 in that the ligands are adjusted to oleic acid and oleylamine. Specifically, 163 mg (0.5 mmol) of cesium carbonate (Cs2CO3), 2 mL of undecylenic acid, 0.2 mL of oleic acid, and 0.3 mL of oleylamine are added to 18 mL of toluene and stirred at 60°C for 10 minutes to obtain a cesium precursor solution. The remaining steps and processes are the same as those in Example 1. As a result, the quantum dot solution obtained in this comparative example failed to achieve imaging effect.
[0063] By comparing the results of Example 1 and Comparative Example 2, it can be seen that the key to achieving self-crosslinking patterning in the present application is to add a photocrosslinking ligand (azidoacetic acid molecule) to the surface of the quantum dots as a ligand. Without this molecule, imaging is impossible.
[0064] In summary, the present invention discloses a patterning method for in situ cross-linking of ligands on the surface of a single quantum dot, in which a photocross-linking ligand (azidoacetic acid molecule) is added to the surface of the quantum dot as a ligand. Compared with the traditional method of adding a photosensitive molecule to the quantum dot solution and then photocross-linking the photosensitive molecule and the ligand on the quantum dot under ultraviolet light irradiation to change the solubility of the quantum dot, the present invention uses the cross-linking between the surface ligands on the quantum dot itself to solve the problem of photosensitive substances hindering charge transfer between quantum dots.
[0065] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.
Claims
1. A patterning method for in-situ cross-linking of ligands on the surface of a single quantum dot, characterized by: include, Cesium carbonate, undecylenic acid and a photocrosslinking ligand are added to toluene and stirred to obtain a cesium precursor solution; Lead bromide and tetra-n-octylammonium bromide are dissolved in toluene and stirred to obtain a PbBr2 precursor solution; Under vigorous stirring, the cesium precursor solution is rapidly added to the PbBr2 precursor solution to obtain a mixed solution I; After the reaction of the mixed solution I, a toluene solution of didodecylammonium bromide (DDAB) was added thereto to obtain a mixed solution II; After the reaction of the mixed solution II, ethyl acetate is added thereto, the mixture is stirred evenly and then centrifuged, the precipitate is collected and redispersed in n-octane or n-hexane to obtain a green luminescent quantum dot CsPbBr3 solution; A green luminescent quantum dot CsPbBr3 solution is spin-coated onto a glass sheet to form a quantum dot film. A customized photomask is placed on the quantum dot film and exposed with a 365nm wavelength ultraviolet lamp. After exposure, the quantum dots in the unexposed area are washed away with n-hexane, leaving the quantum dots in the exposed area, thereby producing the desired pattern.
2. The method for patterning in situ cross-linking of ligands on the surface of a single quantum dot according to claim 1, wherein: The photocrosslinking ligand includes azidohexanoic acid or 3-mercaptopropyl acrylate.
3. The patterning method for in-situ cross-linking of ligands on the surface of a single quantum dot according to claim 1, characterized in that: The mass volume ratio of cesium carbonate, undecylenic acid and photocrosslinking ligand in the cesium precursor solution is 100-200 mg:1-5 ml:1-10 mg, wherein the concentration of cesium carbonate is 5-100 mg / ml.
4. The method for patterning in situ cross-linking of ligands on the surface of a single quantum dot according to claim 1, wherein: The mass ratio of lead bromide to tetra-n-octylammonium bromide in the PbBr2 precursor solution is 1:1-100, wherein the concentration of lead bromide is 2-150 mg / ml.
5. The method for patterning in situ cross-linking of ligands on the surface of a single quantum dot according to claim 4, wherein: The volume ratio of the cesium precursor solution to the PbBr2 precursor solution is 1 to 3:
4.
6. The method for patterning in situ cross-linking of ligands on the surface of a single quantum dot according to claim 1, wherein: The reaction time of the mixed solution I is 4 to 6 minutes.
7. The method for patterning in situ cross-linking of ligands on the surface of a single quantum dot according to claim 6, wherein: The volume ratio of the didodecylammonium bromide DDAB toluene solution to the mixed solution I is 70-100 μL:15 ml, wherein the concentration of the didodecylammonium bromide DDAB toluene solution is 100 mg / ml.
8. The method for patterning in situ cross-linking of ligands on the surface of a single quantum dot according to claim 1, wherein: The volume ratio of the ethyl acetate to the mixed solution II is 4:1-3.
9. The method for patterning in situ cross-linking of ligands on the surface of a single quantum dot according to claim 1, wherein: The exposure time of the exposure is 3 to 5 minutes.
10. The patterning method for in-situ cross-linking of ligands on the surface of a single quantum dot according to claim 1, characterized in that: The luminescent quantum dot solution is added dropwise to the green luminescent quantum dot CsPbBr3 solution to adjust the luminescent color of the quantum dots.