Method for preparing QD pattern based on micromolecule room temperature crosslinking and QLED photoetching device prepared by same

Abstract

The invention discloses a method for preparing a QD pattern based on micromolecule room temperature crosslinking and a QLED photoetching device prepared by the method, and belongs to the technical field of quantum dot (QD) nanotechnology patterning display. The preparation method comprises the following steps: introducing a small molecular material 4, 4 '-bis (3-vinyl-9H-carbazole-9-yl)-1, 1'-biphenyl (CBP-V) and a photoinitiator 2, 2-dimethoxy-2-phenylacetophenone (DMPA) into a QD solution, so that the QD mixed solution has a photosensitive characteristic; under the condition of room temperature, CBP-V is promoted to generate cross-linking reaction through selective exposure of a handheld ultraviolet lamp, so that a cross-linking network is directly formed in a QD layer, the QD is firmly fixed in a grid, the solubility of the QD in an original solution is further changed, direct photoetching patterning of the QD is realized through development, and a high-resolution and high-precision QD pattern is obtained. And a QLED photoetching device with high performance is prepared.

Description

Technical Field

[0001] This invention belongs to the field of quantum dot (QD) nanotechnology patterned display, specifically relating to a method for preparing QD patterns based on room temperature crosslinking of small molecules and the QLED photolithography device obtained therefrom. Background Technology

[0002] Colloidal quantum dots (QDs) are nanocrystalline semiconductors with high luminescent quantum yield (PLQY), high color purity, and narrow emission bandwidth based on the quantum confinement effect. Due to their superior photophysical properties, QDs have inspired researchers to apply them as luminescent materials for displays, leading to significant advancements in quantum dot display technology, which holds promise as the next-generation display technology after organic light-emitting diodes (OLEDs).

[0003] Currently, the most advanced application of quantum dot displays is full-color display achieved using a color conversion layer (CCL), which primarily utilizes the superior photoluminescence (PL) performance of quantum dot (QD). However, due to the involvement of multiple color conversion layers, the brightness of the device inevitably decreases. Therefore, researchers have focused on the field of quantum dot electroluminescence (EL), following a similar working principle to OLEDs, where charges (electrons and holes) are directly injected into each pixelated R, G, and B sub-pixel quantum dot to electrically excite QD emission. Compared to PL quantum dot display devices with CCL, it exhibits better luminescence performance.

[0004] Regardless of the device form used, the manufacturing process requires mature patterning technology, especially for small-screen displays such as Micro-LEDs and VR / AR glasses, which have high requirements for pattern resolution and precision. Currently, there are three main mature patterning technologies: inkjet printing, transfer printing, and photolithography. Inkjet printing faces challenges such as the coffee ring effect and pixel resolution limitations, making it difficult to achieve uniform patterns below a few micrometers. Transfer printing has been proven to produce ultra-high-resolution patterns, but during drooping and peeling, elastic printing can damage the pattern film, and precise alignment for full-color displays remains a challenge. Photolithography, with continuous research and development, has become a very mature patterning technology, capable of simultaneously producing large-area and high-resolution patterns. Direct photolithography, in particular, can minimize the impact of the photolithography process on the QD luminescence performance, producing high-performance, high-resolution patterned QLED devices. While direct photolithography is excellent, designing suitable photosensitive QD solution formulations to impart photosensitive properties to the QD solution is a key focus of our research.

[0005] In 2019, Su et al. (XIE, Liming, XIONG, Xueying, CHANG, Qiaowen, et al. Inkjet-printed high-efficiency multilayer QLEDs based on a novel crosslinkable small-molecule hole transport material. Small, 2019, vol. 15, no16, p. 1900111.) addressed the challenges of fabricating multilayer high-performance QLEDs due to the patterned "coffee ring" effect and poor solvent resistance of the underlying polymer film in QD inkjet printing. They synthesized a novel small-molecule CBP-V using small-molecule CBP as the core through a two-step reaction (Vilsmeier–Haack formylation and Wittig reaction). This CBP-V can be thermosetting without an initiator after heating at 230℃ for 30 minutes, exhibiting excellent solvent resistance. This effectively solves the solvent resistance and carrier balance problems of inkjet-printed multilayer QLEDs, making inkjet printing comparable to spin coating technology in QLED fabrication. While CBP-V effectively solves the solvent resistance problem in inkjet printing, its thermal crosslinking temperature is still too high for conventional QLED devices. This can damage the underlying PEDOT:PSS (conductive polymer) and affect the stability of the flexible plastic substrate. Therefore, in 2024, Du et al. (LI, Chenguang, et al. Low-Temperature Cross-Linked Hole TransportLayer for High-Performance BlueQuantum-Dot Light-Emitting Diodes. NanoLetters, 2024, 24.19: 5729-5736.) synthesized DV-CBP by introducing vinyl-containing flexible styrene side chains into CBP as the core. This reduced the reaction temperature required for thermal crosslinking, requiring only 150℃ heating for 30 minutes to achieve good thermal curing.

[0006] Furthermore, in 2025, Wu et al. (Fang, Ke, Wu, Yuchen, et al. Ultra-High-Resolution Full-Color Quantum Dot Light-Emitting Diodes through Cross-Linking-Assisted Hierarchical Confined Assembly. Nano Letters, 2025, 5052-5059.) introduced the crosslinkable material CBP-V into the QD solution. Under the combined conditions of UV irradiation and annealing at 100℃, CBP-V formed a crosslinked network to encapsulate the QD, giving the QD film excellent solvent resistance, avoiding interlayer dissolution during subsequent deposition, and eliminating color crosstalk problems. Although the annealing temperature and time required for CBP-V crosslinking are reduced through photothermal hybrid crosslinking, how to achieve good crosslinking of CBP-V at room temperature and reduce temperature damage to the QD is a question worthy of further consideration.

[0007] The cross-linked networks formed by CBP-V or related derivatives all require prolonged annealing at high temperatures (not lower than 100°C) for more than 30 minutes to achieve thermal cross-linking. However, in direct photolithography of quantum dots, such an operation can cause irreversible damage to the luminescent properties of the quantum dots, especially for indium phosphide quantum dots. Therefore, this thermal cross-linking method is not the optimal solution for direct photolithography of quantum dots. Furthermore, existing technologies utilize self-assembly to prepare patterned quantum dot films. This method has low production efficiency (production speed) and is prone to individual pixel loss during large-area production, making it difficult to guarantee the yield of the light-emitting panel. Therefore, this application explores achieving effective cross-linking of CBP-V through direct photolithography at room temperature, thereby obtaining high-quality quantum dot patterns and pixelated device arrays. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing QD patterns based on room-temperature crosslinking of small molecules and the resulting QLED patterned devices. Using direct photolithography, the small molecule material 4,4'-bis(3-vinyl-9H-carbazole-9-yl)-1,1'-biphenyl (CBP-V) and the photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA) are introduced into the QD solution to impart photosensitive properties. At room temperature, selective exposure with a handheld UV lamp induces crosslinking of CBP-V, directly forming a crosslinked network within the QD layer. This firmly fixes the QD within the network, altering the solubility of the QD in the original solution. Further development achieves direct photolithographic patterning of the QD, resulting in high-resolution and high-precision QD patterns and the fabrication of high-performance QLED photolithographic devices. Figure 2 As shown, the main reaction mechanism is that under the photoinitiation of DMPA, the vinyl groups in the small molecule material CBP-V can undergo cross-linking reaction at room temperature to form a "mesh" structure, which confines the QD in the exposure area, resulting in a high-yield QD pattern that can be produced quickly and on a large scale. Based on this photolithography strategy, QLED photolithography devices with an EQE of up to 18.47% can be achieved.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing QD patterns based on room temperature crosslinking of small molecules, the process is as follows: By adding the small molecule material 4,4'-bis(3-vinyl-9H-carbazole-9-yl)-1,1'-biphenyl (CBP-V) and the photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA) to the quantum dot solution, selective exposure is performed using a mask and UV, followed by development, thereby achieving direct photolithography patterning of quantum dots (QD) and obtaining high-resolution and high-precision QD patterns. The amount of 4,4'-bis(3-vinyl-9H-carbazole-9-yl)-1,1'-biphenyl added is 0.5~3% of the quantum dot mass, and the amount of 2,2-dimethoxy-2-phenylacetophenone added is 15~20% of the quantum dot mass.

[0010] Furthermore, the quantum dots are CdZnSe quantum dots, and the quantum dot solution is prepared by dissolving CdZnSe quantum dots in n-octane, wherein the concentration of CdZnSe quantum dots in n-octane is 10 mg / mL to 30 mg / mL.

[0011] Further, the 4,4'-bis(3-vinyl-9H-carbazole-9-yl)-1,1'-biphenyl and 2,2-dimethoxy-2-phenylacetophenone are dissolved in chlorobenzene and then added to the QD solution. The concentration of 4,4'-bis(3-vinyl-9H-carbazole-9-yl)-1,1'-biphenyl in chlorobenzene is 1~3 mg / mL, and the concentration of 2,2-dimethoxy-2-phenylacetophenone in chlorobenzene is 20~40 mg / mL.

[0012] Furthermore, the wavelength of UV is 350~400 nm, and the power density range is 30 mW / cm². 2 ~300 mW / cm 2 The exposure time is 1 second to 100 hours.

[0013] Furthermore, n-octane is used as the developing agent during development, and the amount of developing agent used is 0.1~0.2 mL / cm³. 2 .

[0014] A QLED lithography device comprises, from bottom to top, an ITO substrate, a PEDOT:PSS hole injection layer, a TFB hole transport layer, a patterned QD light-emitting layer, a ZnMgO electron transport layer, and a cathode electrode. The patterned QD light-emitting layer is obtained by annealing the QD pattern fabricated using the method described above.

[0015] Furthermore, the thickness of the PEDOT:PSS hole injection layer is 30~60 nm, the thickness of the TFB hole transport layer is 20~50 nm, the thickness of the patterned QD light-emitting layer is 10~40 nm, the thickness of the ZnMgO electron transport layer is 20~50 nm, and the cathode electrode is aluminum with a thickness of 80~120 nm.

[0016] Furthermore, the annealing treatment refers to annealing at 70~90℃ for 5~15 minutes.

[0017] This invention introduces small-molecule materials and photoinitiators into a QD solution, endowing the QD solution with photosensitive properties. Based on the cross-linking reaction between the small-molecule materials and the photoinitiator under UV exposure, a unique "mesh" structure is formed, within which the QD is solidified. This alters the solubility of the QD in the original solution, successfully developing a novel direct photolithography method for QD patterning. This method can then be used to further fabricate QLED patterned devices and QLED photolithography devices. This opens up possibilities for QD applications in small-screen displays such as Micro-LEDs and VR / AR glasses, demonstrating significant innovation and practical value. Furthermore, the small-molecule material CBP-V requires high-temperature heating to undergo a cross-linking reaction, which can significantly damage the QD's luminescent performance. This invention effectively solves the temperature problem by adding the photoinitiator DMPA; at room temperature, CBP-V can undergo a cross-linking reaction simply through UV exposure.

[0018] This application designs a photosensitive QD mixed solution formulation suitable for direct photolithography and fabricates quantum dot patterns and pixel device arrays based on this photosensitive QD solution. Specifically, after UV exposure using the small molecule material CBP-V and the photoinitiator DMPA, a cross-linking reaction occurs at room temperature, thereby changing the solubility of QD in the original solution. Subsequently, using photomask technology, the desired high-resolution patterned QD thin film and high-performance QLED photolithography device are obtained. Attached Figure Description

[0019] Figure 1 This is a detailed photolithography flowchart of the photosensitive QD solution prepared in Example 1 and the QD pattern prepared in Example 2 of the present invention; Figure 2 This is a schematic diagram of the crosslinking of DMPA and CBP-V in Example 2 of the present invention; Figure 3 These are QD patterns of different sizes prepared using masks with minimum widths of 50 μm, 5 μm, 2 μm, and 1 μm in Embodiment 2 of the present invention. Figure 4 Photographs of the QLED patterned device and QLED pixel array prepared in Embodiment 3 of the present invention; Figure 5 This is a structural diagram of the QLED photolithography device prepared in Example 3 of the present invention; Figure 6 The current density-voltage-luminance (JVL) curve of the QLED photolithography device prepared in Example 3 of this invention; Figure 7 The current efficiency (CE)-brightness-EQE curve of the QLED lithography device prepared in Example 3 of this invention; Figure 8This is the EL emission spectrum of the QLED lithography device prepared in Example 3 of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0021] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0022] Example 1, a photosensitizing CdZnSe QD mixed solution In this embodiment, as Figure 1 As shown, the specific preparation method of the photosensitizing QD mixed solution is as follows: First, 100 mg of green CdZnSe quantum dots are dissolved in 5 mL of n-octane solution, 8 mg of CBP-V is dissolved in 4 mL of chlorobenzene solution, and 150 mg of DMPA is dissolved in 5 mL of chlorobenzene solution. The solutions are ultrasonicated and stirred until homogeneous to prepare the original QD solution, CBP-V solution, and DMPA solution. Next, 1 mL of the QD solution is taken, and 100 μL of CBP-V solution and 125 μL of DMPA solution are added sequentially, mixed, and stirred until homogeneous. Finally, the desired photosensitizing QD mixed solution is obtained.

[0023] Example 2: Fabrication of patterned QD thin films like Figure 1 As shown, the photosensitive QD mixed solution prepared in Example 1 was uniformly spin-coated onto the surface of a glass substrate with dimensions of 2.54 cm × 2.54 cm to form a transparent film of uniform thickness. Then, a photomask was tightly attached to the glass substrate, and a handheld UV lamp with a wavelength of 365 nm was used at a power density of 45 mW / cm². 2 UV exposure was performed under the condition of total power density of all LEDs and an exposure time of 3 minutes. Finally, the exposed glass substrate was developed using n-octane (1 mL each time) as the developer to obtain the desired patterned QD film. Figure 2 This is a schematic diagram of the crosslinking of DMPA and CBP-V in Example 2 of the present invention. Figure 2 It can be seen that selective exposure with a handheld UV lamp induces cross-linking of CBP-V, thereby directly forming a cross-linked network in the QD layer and firmly fixing the QD in the grid.

[0024] Figure 3These are QD patterns of different sizes prepared using a mask with a 50 μm × 150 μm rectangular pixel array, 5 μm lines, 2 μm lines, and a 1 μm × 1 μm square pixel array in Embodiment 2 of the present invention.

[0025] Example 3: Fabrication of QLED photolithography devices First, the 2.54 cm × 2.54 cm ITO glass substrate was ultrasonically washed for 15 minutes each with a washing solution, ultrapure water, acetone and isopropanol to make its surface clean and free of impurities. Then, the washed ITO glass substrate was subjected to ozone treatment for 15 minutes, followed by spin-coating of a 40 nm thick PEDOT:PSS layer and annealing at 130°C for 15 minutes. Afterward, it was transferred to a glove box under a nitrogen atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), cooled, and then spin-coated with a 30 nm thick TFB layer, annealing at 150°C for 30 minutes. After cooling, the photosensitive QD mixed solution prepared in Example 1 was spin-coated, and selective exposure was performed using the method of Example 2 through a mask and a handheld UV lamp. After exposure, development was performed with n-octane to obtain the desired QD patterned luminescent layer, which was annealed at 80°C for 10 minutes, resulting in a patterned QD film thickness of 15 nm. Then, a 30 nm thick ZnMgO layer was spin-coated and annealed at 60°C for 30 minutes. The substrate was then transferred into a vacuum chamber, where a 100 nm thick aluminum electrode was deposited. After completion, the substrate was removed from the vacuum chamber and encapsulated in a glove box to obtain the QLED photolithography device. After fabricating the QLED lithography device, various performance parameters (external quantum efficiency (EQE), luminance, current density, current efficiency (CE), etc.) and its EL emission spectrum were obtained using a marine optical spectrometer (USB2000, relative irradiation mode) and a Keithley 2400 source meter. The maximum EQE was 18.47%, the maximum CE was 87.32 cd / A, and the maximum luminance reached 1,167,822 cd / m². 2 .

[0026] Figure 4 This is a photograph of the patterned QLED device and QLED pixel array prepared in Embodiment 3 of the present invention.

[0027] Figure 5 This is a device structure diagram of the QLED lithography device prepared in Example 3 of the present invention.

[0028] Figure 6 The current density-voltage-luminance (JVL) curve of the QLED photolithography device prepared in Example 3 of this invention is shown below. Figure 6 As can be seen, the JVL characteristic curve exhibits typical diode characteristics, turning on at 2.1 V and reaching maximum brightness of 1167822 cd / m² at 9 V.2 .

[0029] Figure 7 The EQE-luminance-current efficiency (CE) curve of the QLED photolithography device prepared in Example 3 of this invention is shown below. Figure 7 It can be seen that at a brightness of 60886 cd / m² 2 At that time, the device reached its maximum EQE and CE, which were 18.47% and 87.32 cd / A, respectively.

[0030] Figure 8 The EL emission spectrum of the QLED lithography device prepared in Example 3 of this invention is shown below. Figure 8 It can be seen that the peak wavelength is 557.36 nm, the half-width is about 39.36 nm, and the shape and peak position of the EL spectrum of the device do not change when the applied voltage increases from 3 V to 8 V.

[0031] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing QD patterns based on small molecule room temperature crosslinking, characterized in that, The process is as follows: The small molecule material 4,4'-bis(3-vinyl-9H-carbazole-9-yl)-1,1'-biphenyl (CBP-V) and the photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA) are added to the QD solution, spin-coated onto a substrate, selectively exposed using a mask and UV, and then developed, thereby achieving direct photolithography patterning of QD to obtain high-resolution and high-precision QD patterns. The amount of 4,4'-bis(3-vinyl-9H-carbazole-9-yl)-1,1'-biphenyl added is 0.5~3% of the mass of the quantum dots, and the amount of 2,2-dimethoxy-2-phenylacetophenone added is 15~20% of the mass of the quantum dots.

2. The method for preparing QD patterns based on small molecule room temperature crosslinking according to claim 1, characterized in that, The quantum dots are CdZnSe quantum dots, and the quantum dot solution is prepared by dissolving CdZnSe quantum dots in n-octane. The concentration of CdZnSe quantum dots in n-octane is 10 mg / mL to 30 mg / mL.

3. The method for preparing QD patterns based on small molecule room temperature crosslinking according to claim 1, characterized in that, The 4,4'-bis(3-vinyl-9H-carbazole-9-yl)-1,1'-biphenyl and 2,2-dimethoxy-2-phenylacetophenone were dissolved in chlorobenzene and then added to the QD solution. The concentration of 4,4'-bis(3-vinyl-9H-carbazole-9-yl)-1,1'-biphenyl in chlorobenzene was 1~3 mg / mL, and the concentration of 2,2-dimethoxy-2-phenylacetophenone in chlorobenzene was 20~40 mg / mL.

4. The method for preparing QD patterns based on small molecule room temperature crosslinking according to claim 1, characterized in that, The UV wavelength is 350~400 nm, and the power density range is 30 mW / cm². 2 ~300 mW / cm 2 The exposure time is 1 second to 100 hours.

5. The method for preparing QD patterns based on small molecule room temperature crosslinking according to claim 1, characterized in that, The developing process uses n-octane as the developing agent.

6. A QLED lithography device, comprising, from bottom to top, an ITO substrate, a PEDOT:PSS hole injection layer, a TFB hole transport layer, a patterned QD light-emitting layer, a ZnMgO electron transport layer, and a cathode electrode, characterized in that, The patterned QD emitting layer is obtained by annealing the QD pattern prepared by the method described in any one of claims 1 to 5.

7. The QLED lithography device according to claim 6, characterized in that, PEDOT: The thickness of the PSS hole injection layer is 30~60 nm, the thickness of the TFB hole transport layer is 20~50 nm, the thickness of the patterned QD light-emitting layer is 10~40 nm, the thickness of the ZnMgO electron transport layer is 20~50 nm, and the cathode electrode is aluminum with a thickness of 80~120 nm.

8. The QLED lithography device according to claim 6, characterized in that, The annealing process refers to annealing at 70~90℃ for 5~15 minutes.

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