A method for fabricating Nano-QLED devices based on two-photon lithography

Abstract

This invention discloses a method for fabricating a Nano-QLED device based on two-photon lithography. The Nano-QLED device includes a quantum dot emitting layer. The method for fabricating the quantum dot emitting layer comprises: splitting a femtosecond laser beam into multiple sub-beams using a multi-focus parallel two-photon lithography method; the multiple sub-beams acting on a carrier transport layer to form a nanoscale patterned insulating structure; the insulating structure being made of a material with two-photon response characteristics; and filling the gaps between the insulating structure with nanoscale emitting quantum dots to form the quantum dot emitting layer. This fabrication method can meet the requirements for large-area and high-precision processing.

Description

Technical Field

[0001] This application relates to the field of quantum dot light-emitting display technology, specifically to a method for fabricating Nano-QLED devices based on two-photon lithography. Background Technology

[0002] With the development of high-resolution display technologies such as near-eye displays (AR, VR), the size requirements for LED pixel units have further increased to the sub-micron level. While traditional ultraviolet lithography is mature, it is limited by exposure wavelength and process conditions, making it difficult to achieve nanoscale high-resolution patterns. Furthermore, in QLED ultraviolet lithography fabrication, it is often necessary to incorporate photoresist and other materials into the quantum dots, a complex process that may affect the photoelectric properties of the quantum dots. Direct printing technologies such as inkjet printing are simple to operate, but their resolution is typically at the micron level (low pixel density), and the difficulty in stacking and positioning makes them unsuitable for manufacturing large-area, high-density display arrays. Recent quantum dot direct lithography technologies achieve QD patterning by introducing photosensitive ligands or crosslinking agents; however, these methods require special ligands, which often reduce the luminous efficiency of the quantum dots and damage the quantum dot surface during photolithography exposure and development.

[0003] Patent application CN107446577A discloses a method for preparing a photoresist-graphene quantum dot luminescent composite system, comprising: 1) providing a mixture containing graphene quantum dots and photoresist; 2) exposing the mixture obtained in step 1) using a mask pattern; and 3) treating the exposed material obtained in step 2) with a developer to remove uncrosslinked portions, thereby obtaining the photoresist-graphene quantum dot luminescent composite system. The preparation method disclosed in this patent is inefficient and cannot meet the requirements for large-area etching.

[0004] In contrast, femtosecond laser beam two-photon lithography (TPP) technology, with its nonlinear absorption characteristics, can overcome the diffraction limit and achieve the construction of 3D patterns at the tens of nanometer scale. Patent application CN113960891A discloses a method and apparatus for parallel interleaving super-resolution high-speed laser direct-write lithography. This method uses a parallel interleaving algorithm. First, a multi-beam solid spot for writing is generated based on a spatial light modulator for writing light; a multi-beam hollow spot for suppression is generated based on a spatial light modulator for suppression light; then, the multi-beam solid spot and the multi-beam hollow spot are combined to generate a modulated multi-beam spot; next, a writing waveform is output based on a multi-channel acousto-optic modulator, and the stage moves at a constant speed until a whole column of areas is written. The optical switch is then turned off, and the stage performs a step movement; this process continues until all patterns are written. This invention, based on a parallel interleaving scanning strategy, effectively solves the problem of low writing efficiency in existing parallel rotating mirror laser direct-write lithography systems due to overly simple scanning strategies. Meanwhile, the super-resolution effect achieved based on the edge light suppression principle improves the writing accuracy of existing two-photon laser direct-write lithography. However, many multi-beam processing solutions based on spatial light modulators are insufficient to meet the processing requirements of large areas and high precision.

[0005] Therefore, there is an urgent need for a processing method that can simultaneously meet the requirements of high throughput and high precision, as well as a corresponding device technology to realize the fabrication of Nano-QLEDs. Summary of the Invention

[0006] This invention provides a method for fabricating Nano-QLED devices based on two-photon lithography, which can meet the requirements of large-area and high-precision processing.

[0007] This invention provides a method for fabricating a Nano-QLED device based on two-photon lithography, wherein the Nano-QLED device includes a quantum dot light-emitting layer, characterized in that the method for fabricating the quantum dot light-emitting layer includes:

[0008] Step (1) A femtosecond laser beam is split into multiple sub-beams using a multi-focus parallel two-photon lithography method. The multiple sub-beams act on the carrier transport layer to form a nanoscale patterned insulating structure. The material of the insulating structure has two-photon response characteristics.

[0009] Step (2) Fill the gaps in the insulating structure with nanoscale luminescent quantum dots to form the quantum dot luminescent layer.

[0010] Preferably, the specific process of step (1) includes:

[0011] The provided femtosecond laser beam is amplified by single-pulse energy.

[0012] The amplified femtosecond laser beam is sequentially collimated and split to obtain a spot array, which includes multiple independent and controllable output sub-beams, each of which has a corresponding sub-focal point.

[0013] A holographic light field image code corresponding to a preset exposure pattern is provided. Multiple output sub-beams and their corresponding sub-foci are adjusted according to the holographic light field image code to obtain the target holographic light field.

[0014] The target holographic light field is projected onto the target processing plane, and femtosecond laser beam two-photon exposure is performed to obtain a nanoscale patterned insulating structure.

[0015] The present invention controls multiple output sub-beams and their corresponding sub-focuses according to a preset holographic light field image encoding, thereby enabling parallel two-photon lithography with thousands of focus points while maintaining good lithography accuracy.

[0016] Preferably, the specific process of step (1) further includes:

[0017] When performing femtosecond laser beam two-photon exposure, a two-dimensional imaging signal is obtained using CMOS to obtain a real-time holographic projection image. At the same time, the transmitted / scattered light after the processing plane is obtained to obtain a reversed image of the real-time holographic projection image. The real-time holographic projection image and the corresponding reversed image are superimposed and compared in real time to obtain the first comparison information.

[0018] The preset holographic projection pattern is compared with the real-time ODT image to obtain the second comparison information. The ODT image is obtained by integrated optical diffraction tomography based on the transmitted / scattered light. Based on the first and second comparison information, the morphological features of the light spot array are extracted by a convolutional neural network. Then, based on the morphological features, the Transformer model is used to fit and predict the optical path drift and refractive index change in the time series, thereby constructing a dynamic correction model. The dynamic first and second comparison information are input into the dynamic correction model to obtain compensation instructions. The light intensity and focal position of multiple output sub-beams are adjusted by the compensation instructions.

[0019] The present invention constructs a dynamic correction model by using first comparison information and second comparison information, which is equivalent to two corrections. This enables the obtained dynamic correction model to output supplementary instructions more accurately, so as to reduce the error between the preset projection image and the actual processing structure.

[0020] Preferably, a multi-focus parallel two-photon lithography system is used to form nanoscale patterned insulating structures on a substrate. The multi-focus parallel two-photon lithography system includes:

[0021] A light source module is used to provide a femtosecond laser beam and amplify the energy of the femtosecond laser beam in single pulses.

[0022] A parallel beam splitting control module includes multiple mirrors and a first digital micromirror device. The multiple mirrors are used to transmit the collimated and amplified femtosecond laser beam to the first digital micromirror device. The first digital micromirror device includes multiple micromirrors, which are used to split the femtosecond laser beam to obtain a beam array. The beam array includes multiple independently controllable output sub-beams, each of which has a corresponding sub-focal point. The multiple micromirrors are also used to receive control information to adjust the multiple output sub-beams and the corresponding sub-focal points to obtain a target holographic light field.

[0023] A projection processing module is used to project the target holographic light field onto the target processing plane and perform femtosecond laser beam two-photon exposure to obtain a nanoscale patterned insulating structure.

[0024] The PC terminal is connected to the parallel beam splitting control module and is used to provide holographic light field image encoding corresponding to the preset exposure pattern, and to use the holographic light field image encoding information as control information.

[0025] Preferably, the multi-focus parallel two-photon lithography system further includes a dynamic correction module, which includes a CMOS, a second digital micromirror device, and an ODT;

[0026] The CMOS is used to obtain two-dimensional imaging signals during femtosecond laser beam two-photon exposure, thereby obtaining a real-time holographic projection image. It is also used to obtain a reversed image of the real-time holographic projection image based on the transmitted / scattered light after the processing plane.

[0027] The second digital micromirror device is used to collect the transmitted / scattered light after the surface is processed. A portion of the transmitted / scattered light after the surface is processed is transmitted to the CMOS, and another portion is transmitted to the ODT through a beam splitter.

[0028] The ODT is used to obtain an ODT image based on the transmitted / scattered light through integrated optical diffraction tomography.

[0029] The PC is also connected to CMOS and ODT, and is used to compare the received real-time holographic projection image and the corresponding inverted image in real time to obtain the first comparison information. The preset holographic projection pattern is compared with the received real-time ODT image to obtain the second comparison information. Based on the first and second comparison information, the morphological features of the light spot array are extracted by a convolutional neural network. Then, based on the morphological features, the Transformer model is used to fit and predict the optical path drift and refractive index change in the time series, thereby constructing a dynamic correction model. The real-time first and second comparison information are input into the dynamic correction model to obtain compensation instructions. The compensation instructions are input to the first digital micromirror device to adjust the light intensity and focal position of multiple output sub-beams.

[0030] Preferably, the material of the insulating structure is at least one of acrylate derivatives, polyethylene derivatives, Al2O3, SiO2, SU-8, IP-DIP, and Mr-DWL photoresist.

[0031] The insulating structure materials provided by this invention all have two-photon response characteristics, and can be used for two-photon lithography with femtosecond lasers in the visible-near-infrared range, thereby achieving linewidth processing beyond the diffraction limit while avoiding degradation by high-energy ultraviolet rays such as DUV and EUV.

[0032] Preferably, the nanoscale luminescent quantum dots are at least one of CdSe luminescent quantum dots, InP luminescent quantum dots, and halide perovskite luminescent quantum dots.

[0033] Preferably, the Nano-QLED device further includes an electron transport layer and a hole transport layer, which are formed on the upper and lower surfaces of the quantum dot light-emitting layer, respectively.

[0034] The electron transport layer is made of zinc oxide nanoparticles, zinc oxide nanoparticles doped with metal cations, a mixture of zinc oxide nanoparticles and polymers, or 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi).

[0035] The hole transport layer is made of poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine)] (TFB), TFB-X, Poly-TPD, poly(9,9-n-dioctyl-2,7-fluorene-alt-9-isooctyl-3,6-carbazole) (PF8Cz), or cross-linked PF8Cz (PF8Cz-X).

[0036] Preferably, the Nano-QLED device further includes a hole injection layer formed between the anode and the hole transport layer, wherein the hole injection layer material is at least one of polymer PEDOT:PSS, molybdenum oxide, or nickel oxide.

[0037] Preferably, the Nano-QLED devices include: positive devices, inverted devices, top-emitting devices, and stacked devices.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] This invention utilizes a multi-focus parallel two-photon lithography method to focus and split a femtosecond laser beam, simultaneously applying multiple sub-beams to the substrate. This enables parallel processing of a large number of focal points. Compared to ultraviolet lithography, laser direct writing, and electron beam direct writing, its wavelength energy is less likely to damage the functional layer material in QLEDs, and it can achieve large-area, high-precision nanoscale processing. This process is applicable to Nano-QLEDs of various device types and various light-emitting quantum dot materials, demonstrating its versatility. Attached Figure Description

[0040] Figure 1 A schematic diagram of a multi-focus parallel two-photon lithography system provided in a specific embodiment of the present invention;

[0041] Figure 2 A schematic diagram showing the speed comparison of parallel two-photon lithography provided for a specific embodiment of the present invention;

[0042] Figure 3 A flowchart of the dynamic correction module processing provided in a specific embodiment of the present invention;

[0043] Figure 4 This is a process flow diagram of the fabrication of the Nano-QLED device provided in Embodiment 1 of the present invention;

[0044] Figure 5 The present invention provides a positive Nano-QLED device and an inverse Nano-QLED device in Embodiment 1, wherein, Figure 5 (a) in the image represents a positive Nano-QLED device. Figure 5 (b) in the diagram represents an inverted Nano-QLED device;

[0045] Figure 6 An electroluminescence microscope image of the Nano-QLED device prepared in Example 1 of this invention;

[0046] Figure 7 The diagram shows the structure of the Nano-QLED device prepared in Example 2 of this invention, along with an electroluminescence microscope image. Figure 7(a) is a structural diagram of the Nano-QLED device prepared in Example 2. Figure 7 (b) is an electroluminescence microscope image of the Nano-QLED device prepared in Example 2;

[0047] Figure 8 This is a structural diagram of the Nano-QLED device prepared in Embodiment 3 of the present invention;

[0048] Figure 9 This is a structural diagram of the Nano-QLED device prepared in Example 4 of the present invention. Detailed Implementation

[0049] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0050] This invention provides a method for fabricating Nano-QLED devices based on two-photon lithography. This method enables high-throughput and high-precision fabrication of quantum dot emitting layers, thereby meeting the requirements for large-area and high-precision processing. The method for fabricating the quantum dot emitting layer provided in this invention includes:

[0051] Step (1) A femtosecond laser beam is split into multiple sub-beams using a multi-focus parallel two-photon lithography method. The multiple sub-beams act on the substrate to form a nanoscale patterned insulating structure. The material of the insulating structure has two-photon response characteristics.

[0052] Step (2) Fill the gaps in the insulating structure with nanoscale luminescent quantum dots to form the quantum dot luminescent layer.

[0053] Specifically, the specific steps for forming a nanoscale patterned insulating structure provided in the specific embodiments of the present invention include:

[0054] In this embodiment, a femtosecond laser beam is provided by a femtosecond laser, and the femtosecond laser beam is amplified by a laser amplifier using a single pulse energy amplification.

[0055] In this embodiment, the amplified femtosecond laser beam is collimated and dispersed to output a beam array. This beam array includes multiple independently controllable output sub-beams, each of which has a corresponding sub-focal point. In one embodiment, thousands of sub-focal points can be achieved, thus providing conditions for achieving high throughput and large-area lithography.

[0056] This embodiment provides a holographic light field image encoding corresponding to a preset exposure pattern. Multiple output sub-beams and corresponding sub-foci are adjusted according to the holographic light field image encoding to obtain the target holographic light field, thereby limiting the position of the sub-foci and ensuring relatively accurate photolithography.

[0057] In this embodiment, the target holographic light field is projected onto the target processing plane, and a femtosecond laser beam two-photon exposure is performed to obtain a nanoscale patterned insulating structure.

[0058] In one specific embodiment, the fabrication method of Nano-QLED device based on two-photon lithography provided in this embodiment further includes:

[0059] During femtosecond laser beam two-photon exposure, a two-dimensional imaging signal is obtained using CMOS to acquire a real-time holographic projection image. Simultaneously, transmitted / scattered light from the processed surface is acquired to obtain a reversed image of the real-time holographic projection image. The real-time holographic projection image and the corresponding reversed image are then superimposed and compared in real-time to obtain the first comparison information. Since some light is absorbed after multiple beams of light illuminate the processed surface, the light intensity changes. This invention collects the reversed image obtained from the transmitted / scattered light after the intensity change; this image is equivalent to the back side image. Comparing the reversed image with the real-time holographic projection image allows for real-time determination of the deviation.

[0060] In femtosecond laser processing, the inhomogeneity of photoresist / substrate materials often leads to inhomogeneity of refractive index and transmittance. The irradiated surface is prone to optical power and peak position drift. Therefore, by reversing the image, these potentially fluctuating points can be observed and recorded in real time at an extremely small (nanometer level) scale, thereby obtaining higher precision deviation (because the processing precision has reached the nanometer level).

[0061] In a specific embodiment of this invention, a preset holographic projection pattern is compared with a real-time ODT image to obtain second comparison information. The ODT image is obtained based on the transmitted / scattered light through integrated optical diffraction tomography. Based on the first and second comparison information, a convolutional neural network is used to extract the morphological features of the light spot array. Because the obtained information contains capture and transmission errors, a convolutional neural network is needed to denoise the information (similar to the imaging mode of some microscopes on a PC). The output is the first comparison information. In conjunction with the following text, two models process the first and second comparison information respectively, where the convolutional neural network is used to denoise the information and improve accuracy, and the Transformer is used to fit, analyze, and predict the obtained information.

[0062] This invention utilizes the Transformer model to fit and predict the optical path drift and refractive index changes in the time series of the first and second contrast information based on the morphological features, thereby constructing a dynamic correction model. In application, the real-time first and second contrast information are input into the dynamic correction model to obtain error compensation instructions, which are then used to adjust the light intensity and focal position of multiple output sub-beams.

[0063] In one specific embodiment, this embodiment realizes the formation of nanoscale patterned insulating structures on a substrate using a multifocal parallel two-photon lithography system. The multifocal parallel two-photon lithography system includes a light source module, a parallel beam splitting control module, a projection processing module, and a PC terminal.

[0064] The light source module provided in this embodiment is used to provide a femtosecond laser beam and to amplify the energy of the femtosecond laser beam using a single pulse.

[0065] Specifically, the light source module provided in this embodiment uses a Ti:sapphire femtosecond laser beam (center wavelength 780 nm, pulse width ≤ 100 fs, repetition frequency 1 kHz), and the single pulse energy is amplified by a multi-stage chirped pulse amplifier (CPA). Compared to mercury lamps (365 nm, photon energy 3.4 eV) or deep ultraviolet light sources (193 nm, photon energy 6.4 eV) used in ultraviolet lithography, the femtosecond laser beam has a lower two-photon absorption threshold (wavelength approximately 800 nm, photon energy approximately 1.55 eV), and its nonlinear effect compresses the effective processing linewidth to below the diffraction limit. This characteristic can prevent high-energy ultraviolet photons from damaging the functional layer material in QLEDs, while reducing thermal diffusion effects.

[0066] The parallel beam splitting control module provided in this embodiment includes multiple mirrors and a first digital micromirror device. The multiple mirrors are used to transmit the collimated and amplified femtosecond laser beam to the first digital micromirror device. The first digital micromirror device includes multiple micromirrors, which are used to split the femtosecond laser beam to obtain a beam array. The beam array includes multiple independently controllable output sub-beams, each of which has a corresponding sub-focal point. The multiple micromirrors are also used to receive control information to adjust the multiple output sub-beams and the corresponding sub-focal points to obtain a target holographic light field.

[0067] Specifically, the parallel beam splitting control module provided in this embodiment includes reflectors 1 and 2 guiding the light to the first digital micromirror device (DMD-1) and the liquid crystal phase plate. In one embodiment, through a self-developed "holographic-iterative" algorithm (Matlab platform), each micromirror can be independently deflected by ±12°, dispersing the single beam of light into thousands of independent and controllable sub-foci. Figure 1The DMD-1 output spot array ensures the uniformity of focal intensity due to spatial incoherence, and the phase is controlled by a liquid crystal phase plate. Compared with the serial scanning modes of electron beam writing (EBL) and laser direct writing (DWL), the overall fabrication rate can be increased by three orders of magnitude, realizing wafer-level high-throughput nanopattern construction (such as...). Figure 2 The diagram shown is a speed comparison diagram.

[0068] The projection processing module provided in this embodiment is used to project the target holographic light field onto the target processing plane and perform femtosecond laser beam two-photon exposure to obtain a nanoscale patterned insulating structure.

[0069] Specifically, the projection processing module provided in this embodiment includes a semi-transparent mirror and an objective lens. After the femtosecond laser beam is modulated by spatial light and the semi-transparent mirror, the holographically formed laser beam will generate a 3D light field designed on demand near the hologram plane (HP). The hologram plane is conjugate with the focal plane of the objective lens (such as a 40× high numerical aperture oil immersion objective lens). Then, it is projected onto the processing plane for femtosecond laser beam exposure.

[0070] The PC provided in this embodiment is connected to the parallel beam splitting control module to provide holographic light field image encoding corresponding to the preset exposure pattern, and uses the holographic light field image encoding information as control information.

[0071] In one specific embodiment, the multifocal parallel two-photon lithography system provided in this embodiment further includes a dynamic correction module comprising a CMOS, a second digital micromirror device, and an ODT.

[0072] The CMOS provided in this embodiment is used to obtain two-dimensional imaging signals during femtosecond laser beam two-photon exposure, thereby obtaining real-time holographic projection images. It is also used to obtain inverted images of real-time holographic projection images based on the transmitted / scattered light after processing the plane.

[0073] The second digital micromirror device provided in this embodiment is used to collect the transmitted / scattered light after the surface is processed. A portion of the transmitted / scattered light after the surface is processed is transmitted to the CMOS, and another portion is transmitted to the ODT through a beam splitter.

[0074] The ODT provided in this embodiment is used to obtain ODT images based on the transmitted / scattered light through integrated optical diffraction tomography.

[0075] The PC provided in this embodiment is also connected to CMOS and ODT, and is used to compare the received real-time holographic projection image and the corresponding inverted image in real time to obtain the first comparison information. The preset holographic projection pattern, i.e. the target graphic, is compared with the received real-time ODT image to obtain the second comparison information. Based on the first and second comparison information, the morphological features of the light spot array are extracted by a convolutional neural network. Then, based on the morphological features, the Transformer model is used to perform parameter fitting and prediction on the optical path drift and refractive index change in the time series, thereby constructing a dynamic correction model. The real-time first and second comparison information are input into the dynamic correction model to obtain compensation instructions. The compensation instructions are input to the first digital micromirror device to adjust the light intensity and focal position of multiple output sub-beams.

[0076] Specifically, in this embodiment, an in-situ monitoring and feedback loop is embedded in the main optical path of the high-speed parallel two-photon lithography system. An in-situ monitoring optical path is split from the processing optical path by a first digital micromirror device (DMD-1) and a semi-transparent mirror, and connected to different detection modules. The multi-focal array from DMD-1 is projected onto the processing plane through a liquid crystal phase plate. Simultaneously, a high-speed two-dimensional imaging signal is acquired by a CMOS camera through a semi-transparent mirror, a lens, and a PBS beam splitter. In addition, transmitted / scattered light is generated by an objective lens and a second digital micromirror device (DMD-2). Then, a portion of the transmitted / scattered light from the processing focal plane is guided to an integrated optical diffraction tomography (ODT) camera for three-dimensional diffraction tomography to obtain an ODT image through multiple lenses and a beam splitter. Another portion of the transmitted / scattered light is input to the CMOS through a lens and an optical fiber to realize the three-dimensional tomography of micro-nano patterns and real-time monitoring of refractive index changes. The CMOS obtains a real-time inverted image of the holographic projection image based on the transmitted / scattered light after the processing plane.

[0077] At the data processing end, the PC is used to superimpose and compare the received real-time holographic projection image with the corresponding inverted image in real time to obtain the first comparison information. The PC then compares the preset holographic projection pattern, i.e., the target graphic, with the real-time ODT image to obtain the second comparison information. A convolutional neural network (CNN) is used to extract the morphological features of the light spot array. Based on these features, a Transformer model is used to fit and predict the optical path drift and refractive index changes in the time series, constructing a dynamic correction model. The compensation commands output by this model can adjust the deflection angle and phase map of the DMD-1 micromirror, drive the liquid crystal phase plate and the nanoscale stepping platform, and achieve dynamic control of the focal position and light intensity. With this closed-loop control that integrates multimodal monitoring and deep learning, the system can capture the refractive index changes during the light aggregation process in real time and correct beam drift, thereby maintaining nanoscale pattern size and graphic accuracy while processing large areas at high speed. Its main processing flow is as follows: Figure 3 As shown.

[0078] In summary, this multi-focus parallel two-photon lithography system can ensure high-speed, high-precision, and large-area fabrication of patterned insulating layers in the Nano-QLED device fabrication technology route.

[0079] The insulating structure provided in the specific embodiments of the present invention is made of at least one of acrylate derivatives, polyethylene derivatives, Al2O3, SiO2, SU-8, IP-DIP, and Mr-DWL photoresist. In the organic system, after high-speed parallel two-photon exposure, the two-photon responsive components release active free radicals, causing the organic / metal oxide aggregates and cross-links within the material system, forming a steeply oriented microporous structure through PGMEA development; the inorganic system is shaped by resin mask transfer etching.

[0080] The nanoscale luminescent quantum dots provided in the specific embodiments of the present invention are at least one of CdSe luminescent quantum dots, InP luminescent quantum dots, and halide perovskite luminescent quantum dots. These quantum dots have the advantages of mature processing and easy acquisition.

[0081] The method for fabricating Nano-QLED devices based on two-photon lithography according to embodiments of the present invention is applicable to the fabrication of Nano-QLED devices of the following types: positive devices, inverted devices, top-emitting devices, and stacked devices. The Nano-QLED device further includes an electron transport layer and a hole transport layer located on opposite sides of the quantum dot emitting layer. The material of the electron transport layer can be: zinc oxide nanoparticles, zinc oxide nanoparticles doped with metal cations, a mixture of zinc oxide nanoparticles and a polymer, or 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi). The hole transport layer can be made of poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine)] (TFB), TFB-X, Poly-TPD, poly(9,9-n-dioctyl-2,7-fluorene-alt-9-isooctyl-3,6-carbazole) (PF8Cz), or PF8Cz-X. The Nano-QLED device may also include a hole injection layer located at a specific position (e.g., between layers xx), wherein the hole injection layer material is at least one of polymer PEDOT:PSS, molybdenum oxide, or nickel oxide.

[0082] Example 1

[0083] The method for fabricating Nano-QLED devices provided in this embodiment, such as Figure 4 As shown, it includes:

[0084] (1) Spin coating to prepare carrier transport layer / insulating material layer: deposit hole transport layer (HTL) or electron transport layer (ETL) on bottom electrode to obtain corresponding substrate, that is, form a carrier transport layer on the substrate.

[0085] (2) Parallel two-photon lithography exposure / development to prepare patterned insulating layer: Provide an insulating material layer with charge blocking effect, and remove it by femtosecond laser two-photon lithography process to form a patterned thin film with pixel pit array.

[0086] (3) Filling with luminescent material: Fill the pixel pit array with nanoscale luminescent quantum dots to obtain a quantum dot luminescent layer.

[0087] (4) A corresponding carrier transport layer and a top electrode are formed sequentially on the quantum dot light-emitting layer.

[0088] like Figure 5 As shown in (a), when a hole transport layer (HTL) is deposited on the bottom electrode and an electron transport layer (ETL) is formed on the quantum dot emitting layer, it is a positive electron transport layer (ETL); as Figure 5 As shown in (b), when the bottom electrode deposits an electron transport layer (ETL) and a hole transport layer (HTL) is formed on the quantum dot light-emitting layer, it is an inverted electron transport layer (ETL).

[0089] The process flow of the present invention will be described in more detail below through examples.

[0090] (1) The transparent conductive substrate (i.e., “substrate”) was cleaned in water, acetone, water and ethanol in sequence, and then dried with nitrogen gas flow.

[0091] (2) Place the transparent conductive substrate in an O2 plasma cleaner for 10 minutes to perform surface hydrophilic treatment on the substrate.

[0092] (3) PEDOT:PDD hole transport layer and cross-linked PF8Cz-X hole transport layer were deposited on the substrate by spin coating and annealed at 230°C for 30 minutes.

[0093] (4) Spin-coating insulating SU-8 / IP-DIP / Mr-DWL photoresist onto PF8Cz-X HTL substrate, then placing it in a high-speed parallel two-photon lithography machine for two-photon exposure, followed by development in PGMEA developer for 30 seconds to obtain a patterned insulating layer.

[0094] (5) A patterned light-emitting layer is prepared by spin-coating a quantum dot solution with an absorbance (OD value) of 30 on the patterned insulating layer obtained in step (4) at 2000 rpm and 30s. Then, a ZnMgO electron transport layer is spin-coated at 2000 rpm and 30s and a 100 nm aluminum electrode is deposited by vacuum coating machine to prepare a Nano-QLED array device.

[0095] (6) Applying a voltage to the device obtained in step (5) using a portable power supply yields an electroluminescent diode device with a unit light-emitting pixel size of approximately 500 nm, such as Figure 6 As shown.

[0096] The Nano-QLED device described in this embodiment has a color sub-pixel size that can be designed at the hundred-nanometer level, which is far superior to the resolution of traditional inkjet technology; and the entire processing does not require multiple doping steps or modification of the quantum dot surface, simplifying the process while ensuring the photoelectric performance of the quantum dots.

[0097] Example 2

[0098] The difference from Example 1 lies in the luminescent material. Specifically, it uses perovskite quantum dot luminescent material, such as CsPbI quantum dots emitting red light at a wavelength of 690 nm. The electron transport layer is a ZnO ETL, the hole transport layer is a TFB HTL, and MoOx is placed between the top electrode and the TFB HTL. Figure 7 (a) and Figure 7 Image (b) shows the structure and electroluminescence microscope image of the nanoscale perovskite quantum dot light-emitting diode device prepared in Example 2.

[0099] Example 3

[0100] The difference from Example 1 lies in the device structure: the bottom electrode is a total internal reflection metal electrode, and the top electrode is a semi-transparent light-emitting electrode. The specific structure is as follows: Figure 8 As shown, the Nano-QLED device provided in Example 3 includes, from bottom to top, a glass substrate, a silver reflective layer, a bottom electrode, a functional layer material 2, a quantum dot light-emitting layer, a functional layer material 1, and a top transparent electrode.

[0101] Example 4

[0102] The difference from Example 1 lies in the device structure. Specifically, a full-color Nano-QLED array device with red, green, and blue pixels is fabricated through the stacking of multi-color pixel layers.

[0103] The red Nano-QLED layer was completed according to Example 1, except that an electrode spacer layer was formed on the functional layer material 1, which can serve as both the top electrode of the red Nano-QLED layer and the bottom electrode of the green Nano-QLED layer.

[0104] A layer of transparent insulating polymer (such as SU-8 or silicone polymer) is spin-coated onto the surface of its electrode spacer layer. After curing, a flat surface is formed, creating a thin insulating layer that protects the red unit structure.

[0105] Green light-emitting device units were fabricated on the transparent polymer layer using the high-speed parallel two-photon lithography process described above.

[0106] Finally, a layer of transparent polymer was spin-coated onto the electrode spacer layer of the green Nano-QLED layer, and the above process was repeated to construct the blue emitting layer. The transparent polymer layer between the layers not only serves as an adhesive but also isolates the charge transport units of the different layers. The final structure is as follows. Figure 9 The stacked device shown has a bottom layer of red units, a middle layer of green units, and a top layer of blue units. From bottom to top, it includes a bottom electrode, a functional layer material 2, a red quantum dot light-emitting layer, a functional layer material 1, an electrode spacer layer, an insulating thin layer, a functional layer material 2, a green quantum dot light-emitting layer, a functional layer material 1, an electrode spacer layer, an insulating thin layer, a functional layer material 2, a blue quantum dot light-emitting layer, a functional layer material 1, and a top electrode.

[0107] In this embodiment, the stacked structure allows the three light-emitting units (red, green, and blue) to work independently in the vertical direction, and full-color light can be emitted at a single vertical pixel position through precise pixel alignment.

[0108] This invention provides a method for fabricating Nano-QLED devices based on two-photon lithography. It employs an ultrafast (femtosecond-level) multi-point parallel (nearly a thousand channels can be processed simultaneously) two-photon lithography fabrication system. This method is simple, easy to operate, and enables rapid fabrication of large-area, ultra-high-resolution Nano-QLED arrays. Two-photon lithography (TPL) utilizes nonlinear absorption to overcome the diffraction limit, achieving processing precision at the hundred-nanometer level. Simultaneously, the two-photon absorption characteristics broaden the processing light source wavelength to 780 nm and above, with lower processing wavelength energy, resulting in virtually no damage to the QLED device structure. This overcomes the technical shortcomings of traditional TPL technology, such as low point-by-point scanning efficiency, which makes it difficult to meet the requirements for large-area fabrication.

[0109] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for fabricating a Nano-QLED device based on two-photon lithography, wherein the Nano-QLED device comprises a quantum dot light-emitting layer, characterized in that, The method for preparing the quantum dot light-emitting layer includes: Step (1) A femtosecond laser beam is split into multiple sub-beams using a multi-focus parallel two-photon lithography method. The multiple sub-beams act on the insulating layer on the carrier transport layer to form a nanoscale patterned insulating structure. The material of the insulating structure has two-photon response characteristics. Step (2) Fill the gaps in the insulating structure with nanoscale luminescent quantum dots to form the quantum dot luminescent layer; Step (1) also includes a dynamic correction process, including: When performing femtosecond laser beam two-photon exposure, a two-dimensional imaging signal is obtained using CMOS to obtain a real-time holographic projection image. At the same time, the transmitted / scattered light after the processing plane is obtained to obtain a reversed image of the real-time holographic projection image. The real-time holographic projection image and the corresponding reversed image are superimposed and compared in real time to obtain the first comparison information. The preset holographic projection pattern is compared with the real-time ODT image to obtain the second comparison information. The ODT image is obtained by integrated optical diffraction tomography based on the transmitted / scattered light. Based on the first and second comparison information, the morphological features of the light spot array are extracted by a convolutional neural network. Then, based on the morphological features, the Transformer model is used to fit and predict the parameters of optical path drift and refractive index change in the time series, thereby constructing a dynamic correction model. The real-time first and second comparison information are input into the dynamic correction model to obtain error compensation instructions. The light intensity and focal position of multiple output sub-beams are adjusted by the error compensation instructions.

2. The method for fabricating a Nano-QLED device based on two-photon lithography according to claim 1, characterized in that, The specific process of step (1) includes: The provided femtosecond laser beam is amplified by single-pulse energy. The amplified femtosecond laser beam is sequentially collimated and split to obtain a spot array, which includes multiple independent and controllable output sub-beams, each of which has a corresponding sub-focal point. A holographic light field image code corresponding to a preset exposure pattern is provided. Multiple output sub-beams and their corresponding sub-foci are adjusted according to the holographic light field image code to obtain the target holographic light field. The target holographic light field is projected onto the target processing plane, and femtosecond laser beam two-photon exposure is performed to obtain a nanoscale patterned insulating structure.

3. The method for fabricating a Nano-QLED device based on two-photon lithography according to claim 1, characterized in that, A multi-focus parallel two-photon lithography system is used to form nanoscale patterned insulating structures on a substrate. The multi-focus parallel two-photon lithography system includes: A light source module is used to provide a femtosecond laser beam and amplify the energy of the femtosecond laser beam in single pulses. A parallel beam splitting control module includes multiple mirrors and a first digital micromirror device. The multiple mirrors are used to transmit the collimated and amplified femtosecond laser beam to the first digital micromirror device. The first digital micromirror device includes multiple micromirrors, which are used to split the femtosecond laser beam to obtain a beam array. The beam array includes multiple independently controllable output sub-beams, each of which has a corresponding sub-focal point. The multiple micromirrors are also used to receive control information to adjust the multiple output sub-beams and the corresponding sub-focal points to obtain a target holographic light field. A projection processing module is used to project the target holographic light field onto the target processing plane and perform femtosecond laser beam two-photon exposure to obtain a nanoscale patterned insulating structure. The PC terminal is connected to the parallel beam splitting control module and is used to provide holographic light field image encoding corresponding to the preset exposure pattern, and to use the holographic light field image encoding information as control information.

4. The method for fabricating a Nano-QLED device based on two-photon lithography according to claim 3, characterized in that, The multi-focus parallel two-photon lithography system also includes a dynamic correction module, which includes a CMOS, a second digital micromirror device, and an ODT. The CMOS is used to obtain two-dimensional imaging signals during femtosecond laser beam two-photon exposure, thereby obtaining a real-time holographic projection image. It is also used to obtain a reversed image of the real-time holographic projection image based on the transmitted / scattered light after the processing plane. The second digital micromirror device is used to collect the transmitted / scattered light after the surface is processed. A portion of the transmitted / scattered light after the surface is processed is transmitted to the CMOS, and another portion is transmitted to the ODT through a beam splitter. The ODT is used to obtain an ODT image based on the transmitted / scattered light through integrated optical diffraction tomography. The PC is also connected to CMOS and ODT, and is used to compare the received real-time holographic projection image and the corresponding inverted image in real time to obtain the first comparison information. The preset holographic projection pattern is compared with the received real-time ODT image to obtain the second comparison information. Based on the first and second comparison information, the morphological features of the light spot array are extracted by a convolutional neural network. Then, based on the morphological features, the Transformer model is used to perform parameter fitting and prediction on the optical path drift and refractive index change in the time series, thereby constructing a dynamic correction model. The real-time first comparison information and the second comparison information are input into the dynamic correction model to obtain the error compensation command. The error compensation command is input to the first digital micromirror device to adjust the light intensity and focal position of multiple output sub-beams.

5. The method for fabricating a Nano-QLED device based on two-photon lithography according to claim 1, characterized in that, The insulating structure is made of at least one of the following materials: acrylate derivatives, polyethylene derivatives, Al2O3, SiO2, SU-8, IP-DIP, and Mr-DWL photoresist.

6. The method for fabricating a Nano-QLED device based on two-photon lithography according to claim 1, characterized in that, The nanoscale luminescent quantum dots are at least one of CdSe luminescent quantum dots, InP luminescent quantum dots, and halide perovskite luminescent quantum dots.

7. The method for fabricating a Nano-QLED device based on two-photon lithography according to claim 1, characterized in that, The Nano-QLED device further includes an electron transport layer and a hole transport layer, which are formed on the upper and lower surfaces of the quantum dot light-emitting layer, respectively. The electron transport layer is made of zinc oxide nanoparticles, zinc oxide nanoparticles doped with metal cations, a mixture of zinc oxide nanoparticles and polymers, or 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene. The hole transport layer is made of poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine)], Poly-TPD, poly(9,9-n-dioctyl-2,7-fluorene-alt-9-isooctyl-3,6-carbazole), or cross-linked PF8Cz.

8. The method for fabricating a Nano-QLED device based on two-photon lithography according to claim 7, characterized in that, The Nano-QLED device further includes a hole injection layer formed between the anode and the hole transport layer, wherein the hole injection layer material is at least one of the polymer PEDOT:PSS, molybdenum oxide, or nickel oxide.

9. The method for fabricating a Nano-QLED device based on two-photon lithography according to claim 1, characterized in that, The types of Nano-QLED devices include: positive devices, inverted devices, top-emitting devices, and stacked devices.

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