A method for manufacturing a quantum dot micro-led color conversion layer based on a three-dimensional microcavity array

Abstract

The application discloses a kind of quantum dot Micro-LED color conversion layer based on three-dimensional microcavity array manufacturing method, recess array is formed on transparent substrate, and when microfluidic cover is bonded thereon, so that microfluidic channel and recess array are staggered certain proportion alignment bonding realizes the construction of three-dimensional microcavity array, controllable quantum dot microdroplet array is realized by microfluid behavior control, further manufacture the independent array deposition of different quantum dots to form quantum dot color conversion layer, finally prepare Micro-LED full-color display device.The application utilizes three-dimensional microcavity in microchannel to capture quantum dot solution, so that it can more stably retain larger volume microdroplet than open microstructure when being blown out with non-miscible fluid, and quantum dot color conversion layer array pattern can be formed in three-dimensional microcavity array structure after quantum dot solvent volatilization.The method of the application can be suitable for the deposition of various different types of quantum dots, with the characteristics of low cost, high throughput and universality.

Description

Technical Field

[0001] This invention relates to the field of semiconductor display technology, and in particular to a method for fabricating a quantum dot color conversion layer based on a three-dimensional microcavity array and a Micro-LED full-color display device. Background Technology

[0002] Compared to LCD and OLED displays, Micro-LED technology is superior in almost every aspect, including brightness, contrast, viewing angle, energy consumption, response speed, resolution, lifespan, and color reproduction. It also features self-illumination without the need for a backlight, and is smaller and thinner. It has broad application prospects in augmented / virtual reality technology, optical communication / optical interconnection, flexible transparent displays, medical detection, and smart car lights, and is considered the "ultimate display technology".

[0003] The realization of Micro-LED full-color display is mainly achieved through the following two methods: (1) Three-primary-color chip scheme, which requires the use of "mass transfer technology" to integrate red, green and blue Micro-LED chips in an array on the display back panel. (2) Quantum dot color conversion scheme, which realizes red, green and blue full-color display by utilizing the mechanism that quantum dot materials can perform color conversion under the excitation of short-wavelength Micro-LED chips. Quantum dot color conversion can usually be made into different patterns using inkjet printing, photolithography, microfluidics and other technologies to meet various needs. Among them, the quantum dot color conversion layer design scheme of Micro-LED full-color display based on microfluidics technology has a series of advantages such as simple process, fast preparation and material saving, providing a new idea for the design and preparation of Micro-LED color conversion layer.

[0004] However, in existing microfluidic-based color conversion layer fabrication methods, the continuous deposition of quantum dot materials on transparent substrates cannot effectively avoid optical crosstalk between pixels, thus affecting the display performance of the device. In the past two years, methods for fabricating color conversion layers by introducing hydrophilic or hydrophobic surfaces or open microstructures into microfluidic devices have been reported. However, when blowing out quantum dot solutions with immiscible liquids, less quantum dot solution is deposited in the grooves of the transparent substrate's morphology pattern under shear force. Therefore, the color conversion layer thickness is low, requiring numerous repeated depositions to meet the thickness requirements of Micro-LED color conversion layers, greatly increasing the time and workload, and affecting the deposition quality. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of insufficient single-deposition thickness caused by the small volume of quantum dot solution remaining in the array under the fluid shearing action in the open patterned array when preparing quantum dot color conversion layers based on microfluidic technology. The invention provides a design method for quantum dot Micro-LED color conversion layers based on a three-dimensional microcavity array. By misaligning and bonding the microfluidic channel with the morphologically patterned glass substrate, the quantum dot particles can be effectively deposited in the morphological pattern after the quantum dot solution is introduced.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for fabricating a quantum dot Micro-LED color conversion layer based on a three-dimensional microcavity array includes the following steps:

[0008] 1) Pattern the substrate surface by etching to form a groove array;

[0009] 2) Provide a microfluidic cover plate, the microfluidic cover plate having a plurality of channels, the microfluidic cover plate being bonded to a substrate so that the channels and the substrate surface enclose to form a microchannel, the microchannel having an inlet and an outlet at both ends; wherein each channel corresponds to a plurality of grooves for conduction, and the opening of the channel and the opening of the groove are staggered, so that the groove forms a three-dimensional microcavity.

[0010] 3) The quantum dot solution is introduced into the microchannel through the inlet, so that the quantum dot solution fills the microchannel and the three-dimensional microcavity;

[0011] 4) Ineligible fluid is introduced into the microchannel through the inlet, allowing the immiscible fluid to flow from the inlet to the outlet to discharge the quantum dot solution in the microchannel, while retaining the quantum dot microdroplets located in the three-dimensional microcavity;

[0012] 5) After the solvent in the quantum dot microdroplets evaporates, the deposited quantum dot units are obtained. The microfluidic cap is peeled off to obtain the quantum dot color conversion layer located in the substrate.

[0013] Optionally, the plurality of channels are parallel, spaced-apart strip channels, with each channel corresponding to a column of grooves in the groove array.

[0014] Optionally, the area where the opening of the groove overlaps and connects with the opening of the channel accounts for 10% to 70% of the area of ​​the opening of the groove.

[0015] Optionally, the depth of the groove ranges from 3 to 8 μm, and the width ranges from 10 to 80 μm.

[0016] Optionally, the substrate includes a glass substrate and a chromium layer disposed on the glass substrate, and the etch depth of the groove extends to a portion of the depth of the glass substrate.

[0017] Optionally, step 1) includes:

[0018] 1.1) A photoresist layer is formed on a substrate, and the photoresist layer is photolithographically etched using a mask to obtain a patterned photoresist layer, wherein a chromium layer is exposed at the morphological pattern.

[0019] 1.2) Etch away the chromium layer at the topographic pattern to expose the glass substrate surface at the topographic pattern.

[0020] 1.3) Strip the photoresist;

[0021] 1.4) A groove array is formed on the glass substrate surface at the etched topographic pattern.

[0022] Optionally, the photoresist layer can be a positive photoresist, such as BP218-37s, BP218-45s, AZ5214, AZ4620, EPG516, etc. The developer can be NaOH solution, KOH solution, tetramethylammonium hydroxide TMAH, etc., and it is rinsed with deionized water after development.

[0023] Optionally, the chromium layer can be etched using a cerium ammonium nitrate solution, wherein the cerium ammonium nitrate solution consists of cerium ammonium nitrate, acetic acid, and deionized water.

[0024] Optionally, the etching methods for the glass substrate include: plasma etching, which uses CHF3, C2H6, C3F8, SF6, etc. as process gases mixed with inert gases to etch the glass substrate; and wet etching, which uses aqueous solutions of HF, HNO3, and NH4F.

[0025] Optionally, the photoresist can be stripped by immersing it in an organic solvent (ethanol, acetone, etc.) and placing it in an ultrasonic cleaner until the photoresist is completely dissolved.

[0026] Optionally, between steps 1) and 2), a partial surface modification treatment is also included to hydrophilic or hydrophobicate the surface of the substrate.

[0027] Optionally, the material of the microfluidic cover plate includes quartz, glass, polydimethylsiloxane, polymethacrylate, polystyrene, and polycarbonate; the width of the channel is less than the sum of the spacing width between adjacent grooves in the groove array and the width of the groove.

[0028] Optionally, the depositable quantum dots can be any of ZnS, CdTe, CdSe, CdS, ZnSe, ZnO, ZnCdS, ZnSeS, CdZnS, InP, perovskite quantum dots, etc., or a core-shell structure composed of several materials.

[0029] Optionally, the quantum dot solution is a red or green quantum dot solution, and the corresponding water-soluble or oil-soluble quantum dots can be selected according to the hydrophilic or hydrophobic modification type of the glass substrate.

[0030] Optionally, the immiscible fluid is a gas, and in step 4), the air velocity in the microchannel ranges from 10 to 300 μm / s.

[0031] A Micro-LED full-color display device includes a Micro-LED chip array, a DBR layer, and a quantum dot color conversion layer fabricated by the above method. The Micro-LED chip array is bonded to the side of the substrate away from the quantum dot color conversion layer, the DBR layer is disposed on the quantum dot color conversion layer, and the Micro-LED chips and quantum dot units correspond one-to-one.

[0032] The Micro-LED chip includes a driving substrate located below the chip, comprising a P-type substrate, an N-type electrode, a driving circuit, multiple quantum wells, metal electrodes, and a buffer insulating layer, which are respectively connected to a plurality of unit electrodes of the Micro-LED chip array.

[0033] Optionally, the DBR layer is an RGB filter array corresponding to the quantum dot color conversion layer.

[0034] The beneficial effects of this invention are as follows:

[0035] (1) A three-dimensional microcavity structure is used to design the quantum dot color conversion layer. When the quantum dot solution is blown out using an immiscible fluid, a large volume of quantum dot solution can be stably retained in the three-dimensional microcavity. This solves the problem of continuous deposition of color conversion arrays based on microfluidic technology or the problem of fewer quantum dots per deposition caused by the small volume of quantum dot solution retained in the open microarray after blowing out. This reduces the number of depositions required to prepare quantum dots of the same thickness, thereby reducing time and material costs.

[0036] (2) This preparation method can precisely control the misalignment and alignment of microstructures and microchannels to prepare three-dimensional microcavity arrays of different volumes. Therefore, it can prepare three-dimensional microcavities of various sizes based on microstructures of the same scale, and then prepare color conversion arrays of different sub-pixels. Therefore, it is not necessary to design multiple photomasks for the preparation of pixels of different sizes, which has strong design flexibility and reduces the manufacturing cost. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a chrome plate photolithography method for a specific embodiment.

[0038] Figure 2 This is a schematic diagram of the structure after photolithography of the chrome plate in step 1 of the embodiment.

[0039] Figure 3 This is a schematic diagram of chromium layer etching on a homogenized chromium plate as shown in the embodiment.

[0040] Figure 4 This is a schematic diagram of the structure after etching the chromium layer and removing the photoresist in step 2 of the embodiment.

[0041] Figure 5 This is a schematic diagram of the structure of the glass after dry etching in step 4 of the embodiment.

[0042] Figure 6 This is a schematic diagram of step 6 of the embodiment, which involves constructing microchannels on a glass substrate.

[0043] Figure 7 This is a schematic diagram illustrating the steps of introducing a quantum dot solution into a microchannel, as shown in the embodiment.

[0044] Figure 8 This is a schematic diagram illustrating the steps of the embodiment, where air is blown at a constant pressure to align the quantum dot solution with the microchannel and the morphology pattern.

[0045] Figure 9 This is a schematic diagram of the quantum dot pattern obtained after peeling off the microchannel in the embodiment.

[0046] Figure 10 A schematic diagram of the structure of the Micro-LED full-color display device prepared for the example. Detailed Implementation

[0047] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. The accompanying drawings are merely illustrative to facilitate understanding of the invention, and their specific proportions can be adjusted according to design requirements. The vertical relationships of relative elements and the definitions of front / back in the graphics described herein should be understood by those skilled in the art to refer to the relative positions of the components; therefore, they can all be flipped to present the same component, and all of this should fall within the scope disclosed in this specification.

[0048] The structure and fabrication method of the Micro-LED full-color display device based on microfluidic and patterning technologies in this embodiment are as follows:

[0049] 1. Photolithography of the chrome-plated substrate. (Reference) Figure 1 The substrate 1 is a spin-coated positive photoresist chromium plate, comprising a glass substrate 11 and a chromium layer 12 with a thickness of 120 nm. The photoresist layer 2 is spin-coated onto the chromium layer 12 and exposed to 365 nm ultraviolet light for approximately 15 seconds. The photolithographically patterned sample is then developed in a 0.5% NaOH solution to obtain a patterned photoresist layer, exposing the chromium layer 12 at the patterned areas. The resulting image after development is shown below. Figure 2 As shown.

[0050] 2. Etch the chromium layer and remove the photoresist. Place the developed homogenized chromium plate into a cerium ammonium nitrate solution to etch the chromium layer in the morphology pattern, exposing the glass substrate 11 at the morphology pattern area, such as... Figure 3 As shown. Afterwards, the photoresist plate was cleaned in ethanol and then sonicated for 1 minute to remove the positive photoresist layer 2 from the sample surface. Following ultrasonic cleaning, it was rinsed with deionized water for 30 seconds and then dried to obtain... Figure 4 The schematic diagram shown illustrates that the chromium layer serves as a protective layer for the array pattern.

[0051] 3. Dry etching of the glass layer. In this embodiment, a dry etching method is used. The arrayed glass pattern obtained in step 2, with chromium layer 12 as the protective layer, is etched using CHF3 / Ar plasma for 20 minutes. The CHF3 gas flow rate is 30 sccm, the Ar gas flow rate is 15 sccm, and the etching power RF is 250W. Afterwards, the surface is rinsed with water and dried with nitrogen to obtain a patterned glass substrate with an etching depth of 3 μm. Figure 5 As shown, this results in an array of grooves 1a, which is preferably arranged in a matrix. The grooves 1a are, for example, rectangular, with a width ranging from 10 to 80 μm.

[0052] 4. Misaligned bonding of microchannels to patterned glass substrate. In this embodiment, PDMS is used to fabricate the microfluidic capping plate 3. The microfluidic capping plate 3 has several parallel and spaced strip channels 31. The microfluidic capping plate 3 is bonded to the substrate 1, so that the channels 31 and the substrate surface enclose to form a microchannel. The microchannel has an inlet and an outlet at both ends. Each channel 31 corresponds to a row of grooves 1a for conduction, and the opening of the channel is misaligned with the opening of the groove 1a, so that the groove 1a forms a three-dimensional microcavity. In this embodiment, the area of ​​overlap between the groove 1a and the channel 31 accounts for 10% to 70% of the area of ​​the groove opening. Thus, the groove openings in the non-overlapping areas are shielded by the surface of the microfluidic capping plate. Figure 6 As shown. The exposed surface of the glass substrate 11 (i.e., the surface of the groove) can be pre-modified with hydroxyl groups to improve its hydrophilicity. The resulting microchannels contain red and green quantum dot channels.

[0053] 5. Injecting and Ejecting Quantum Dot Solutions. Using a pressure injection pump, inject the red CdSe / ZnS water-soluble quantum dot solution R and the green CdSe / ZnS water-soluble quantum dot solution G into their respective microchannels. The pressure injection pump can provide a constant injection pressure. Figure 7 As shown. Once the quantum dot solution fills the channels, the three-dimensional microcavity is now filled with the solution. Using a pressure injection pump, air is injected into both the red and green microchannels at the same injection pressure, with a flow rate of approximately 20 μm / s. This causes the quantum dot solution at the points where the microchannels and the grooves of the morphological pattern are perfectly aligned to be expelled, while the solution at the points where the grooves are misaligned remains. This maximizes the retention of the quantum dot solution within the three-dimensional microcavity. Figure 8 As shown.

[0054] 6. Allow the solvent to evaporate and quantum dot particles to deposit, thus obtaining quantum dot units R / G. Remove the PDMS microfluidic cover plate 3, as shown. Figure 9 As shown, a quantum dot color conversion layer 4 was obtained in the substrate 1, which includes a red quantum dot unit R, a green quantum dot unit G and an empty groove region as a blue light transmission region.

[0055] 7. Bonding to the DBR layer and the ultraviolet Micro-LED chip. The prepared quantum dot color conversion layer is bonded to the corresponding DBR reflective layer 5 and the blue Micro-LED chip array 6, and then encapsulated through the encapsulation cover plate 7 to obtain a Micro-LED full-color display device, such as... Figure 10 As shown.

[0056] refer to Figure 10 A Micro-LED full-color display device is obtained, including a package cover plate 7, a DBR reflective layer 5, a quantum dot color conversion layer 4 located in the substrate 1, and a blue Micro-LED chip array 6. The quantum dot color conversion layer includes red and green quantum dot pixel arrays, which correspond one-to-one with the blue Micro-LED chip array 61 located at the bottom. Full-color display is achieved through the DER array located above the color conversion layer.

[0057] The above method overcomes the problem of insufficient single deposition thickness caused by the small volume of quantum dot solution remaining in the array under the fluid shearing action in the open patterned array when preparing quantum dot color conversion layers based on microfluidic technology. By misaligning the microfluidic channel with the morphologically patterned glass substrate, the quantum dot particles can be effectively deposited in the morphological pattern after the quantum dot solution is introduced.

[0058] The above embodiments are only used to further illustrate a method for fabricating a quantum dot Micro-LED color conversion layer based on a three-dimensional microcavity array according to the present invention. However, the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for fabricating a quantum dot Micro-LED color conversion layer based on a three-dimensional microcavity array, characterized in that, Includes the following steps: 1) Pattern the substrate surface by etching to form a groove array; 2) Provide a microfluidic cover plate, the microfluidic cover plate having a plurality of channels, the microfluidic cover plate being bonded to a substrate so that the channels and the substrate surface enclose to form a microchannel, the microchannel having an inlet and an outlet at both ends; the plurality of channels are parallel spaced strip channels, each channel being connected to a column of grooves in the groove array, and the opening of the channel being staggered from the opening of the groove, so that the groove forms a three-dimensional microcavity; 3) The quantum dot solution is introduced into the microchannel through the inlet, so that the quantum dot solution fills the microchannel and the three-dimensional microcavity; 4) Ineligible fluid is introduced into the microchannel through the inlet, allowing the immiscible fluid to flow from the inlet to the outlet to discharge the quantum dot solution in the microchannel, while retaining the quantum dot microdroplets located in the three-dimensional microcavity; 5) After the solvent in the quantum dot microdroplets evaporates, the deposited quantum dot units are obtained. The microfluidic cap is peeled off to obtain the quantum dot color conversion layer located in the substrate.

2. The method for fabricating a quantum dot Micro-LED color conversion layer based on a three-dimensional microcavity array according to claim 1, characterized in that: The area where the opening of the groove overlaps with the opening of the channel accounts for 10% to 70% of the area of ​​the opening of the groove.

3. The method for fabricating a quantum dot Micro-LED color conversion layer based on a three-dimensional microcavity array according to claim 1, characterized in that: The groove has a depth range of 3~8 μm and a width range of 10~80 μm.

4. The method for fabricating a quantum dot Micro-LED color conversion layer based on a three-dimensional microcavity array according to claim 1, characterized in that: The substrate includes a glass substrate and a chromium layer disposed on the glass substrate, and the groove is etched to a portion of the depth of the glass substrate.

5. The method for fabricating a quantum dot Micro-LED color conversion layer based on a three-dimensional microcavity array according to claim 4, characterized in that: Step 1) includes: 1.1) A photoresist layer is formed on a substrate, and the photoresist layer is photolithographically etched using a mask to obtain a patterned photoresist layer, wherein a chromium layer is exposed at the morphological pattern. 1.2) Etching removes the chromium layer at the topographic pattern, exposing the glass substrate surface at the topographic pattern. 1.3) Strip the photoresist; 1.4) A groove array is formed on the glass substrate surface at the etched topographic pattern.

6. The method for fabricating a quantum dot Micro-LED color conversion layer based on a three-dimensional microcavity array according to claim 1, characterized in that: Between step 1) and step 2), there is also a partial surface modification treatment to modify the surface of the substrate by making it hydrophilic or hydrophobic.

7. The method for fabricating a quantum dot Micro-LED color conversion layer based on a three-dimensional microcavity array according to claim 1, characterized in that: The microfluidic cover plate is made of materials including quartz, glass, polydimethylsiloxane, polymethacrylate, polystyrene, and polycarbonate; the width of the channel is less than the sum of the spacing width between adjacent grooves in the groove array and the width of the groove.

8. The method for fabricating a quantum dot Micro-LED color conversion layer based on a three-dimensional microcavity array according to claim 1, characterized in that: The immiscible fluid is a gas, and in step 4), the flow rate of the gas in the microchannel is in the range of 10~300 μm / s.

9. A Micro-LED full-color display device, characterized in that: The invention includes a Micro-LED chip array, a DBR layer, and a quantum dot color conversion layer fabricated by the fabrication method of any one of claims 1 to 8. The Micro-LED chip array is bonded to the side of the substrate opposite to the quantum dot color conversion layer, the DBR layer is disposed on the quantum dot color conversion layer, and the Micro-LED chip corresponds one-to-one with the quantum dot unit.

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