Full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots and preparation method thereof

Abstract

The invention discloses a full-color Micro-LED (Light Emitting Diode) chip based on bimolecular passivated perovskite quantum dots and a preparation method of the full-color Micro-LED chip. The chip comprises a blue light Micro-LED array substrate and a perovskite quantum dot color conversion layer arranged on the light emitting side of the blue light Micro-LED array substrate. The color conversion layer comprises green light and red light perovskite quantum dot pixels which are subjected to organic large cation and short-chain ammonium bromide double-ligand synergistic passivation and are in patterned distribution corresponding to blue light pixels. The preparation method is characterized in that a layered micropore filling and atomic layer deposition in-situ packaging process is adopted. According to the scheme, the luminous efficiency and stability of the quantum dots are synergistically improved through bimolecular passivation, and the full-color Micro-LED chip with high performance and long service life is finally prepared by combining an inverted structure, pixel-level microcavity filling and multi-layer packaging, so that the full-color Micro-LED chip has a wide application prospect in the field of novel display.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to a full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots and its fabrication method. Background Technology

[0002] Micro-LED display technology is widely recognized as the core direction of next-generation display technology due to its superior performance in brightness, efficiency, response speed, contrast ratio, and lifespan, and it has broad prospects in fields such as augmented reality (AR), virtual reality (VR), and ultra-high-definition displays. However, achieving full-color display is a key technical challenge that must be overcome for Micro-LED to become industrialized. The traditional direct bonding scheme of RGB three-color chips faces severe challenges due to the need for three "mass transfers" of red, green, and blue micron-sized chips, resulting in extremely complex processes, extremely high alignment accuracy requirements, high costs, and low yields.

[0003] Against this backdrop, the "blue Micro-LED array + quantum dot color conversion layer" technology has emerged and is widely considered one of the optimal solutions for achieving full-color Micro-LED displays. This approach only requires the fabrication and transfer of a single blue Micro-LED array. Through a precisely patterned quantum dot layer on top, a portion of the blue light is efficiently converted into red and green light via photoluminescence, thus achieving full-color display. This method cleverly avoids the challenges of mass transfer of multiple colors and boasts significant advantages such as low cost, simple process, and high integration.

[0004] Among numerous quantum dot materials, perovskite quantum dots (QDs) are considered ideal candidates for color conversion layers due to their high emission purity (half-maximum width at half maximum), precisely tunable emission color (tunable bandgap), and relatively low fabrication cost. However, the inherent ionic crystal properties and low formation enthalpy of this material make it extremely sensitive to water vapor, oxygen, heat, and light in the environment, resulting in severely insufficient stability. This bottleneck not only causes rapid aging and luminous efficiency (PLQY) decay during storage and operation, but also makes it difficult to withstand the processing conditions of subsequent device fabrication (such as photolithography and coating). Therefore, it is crucial to find a simple and efficient synthesis method and improve the stability of perovskite quantum dots. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots and its fabrication method, thereby solving the technical problems of low luminous efficiency and poor environmental stability of perovskite quantum dots in Micro-LED color conversion applications.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots, comprising:

[0008] A blue Micro-LED array substrate, and a perovskite quantum dot color conversion layer disposed on the light-emitting side of the blue Micro-LED array substrate;

[0009] The perovskite quantum dot color conversion layer includes green perovskite quantum dot pixels and red perovskite quantum dot pixels corresponding to the blue Micro-LED array pixels, and the perovskite quantum dots therein are synergistically passivated using organic large cations and short-chain ammonium bromide as dual ligands.

[0010] Furthermore, the blue Micro-LED array substrate is a flip-chip structure, comprising, from bottom to top, a sapphire substrate, a u-GaN buffer layer, an electron injection layer, a multi-quantum well active region, and a hole injection layer; and is bonded to the driving circuit substrate through a metal bump array, the gaps of which are filled with an insulating material with a transmittance greater than 70% in the 450nm-470nm wavelength band.

[0011] Furthermore, the large organic cation is one of 2-phenylethylammonium bromide, 4-fluorophenylethylammonium bromide, 3-fluorophenylethylammonium bromide, and 2-fluorophenylethylammonium bromide; the short-chain ammonium bromide is one of ethylammonium bromide, propylammonium bromide, and butylammonium bromide.

[0012] Furthermore, the surface of the perovskite quantum dots is synergistically bound with the organic macrocation and the short-chain ammonium bromide ligand. Based on the quantum dot synthesis precursor, the lead ion concentration is 0.1 mol / L to 0.2 mol / L, the amount of organic macrocation added is between 0.03 mol / L and 0.18 mol / L, and the amount of short-chain ammonium bromide added is between 0.03 mol / L and 0.18 mol / L.

[0013] Furthermore, the pixel size of the perovskite quantum dot color conversion layer is 2μm to 50μm, which corresponds one-to-one with the pixels of the blue Micro-LED array below.

[0014] Furthermore, the blue light emission peak wavelength of the blue light Micro-LED array substrate is 450nm to 470nm, and its emission spectrum overlaps with the absorption spectrum of the perovskite quantum dots by more than 70%.

[0015] Furthermore, the green perovskite quantum dot pixel emits light at a wavelength of 520nm-540nm, and the red perovskite quantum dot pixel emits light at a wavelength of 620nm-640nm.

[0016] The present invention also provides a method for fabricating the full-color Micro-LED chip, comprising the following steps: S1, providing a blue Micro-LED array substrate and fabricating a pixel isolation structure on its light-emitting surface: spin-coating negative photoresist on the substrate and forming patterned pixel isolation walls by photolithography, thereby defining mutually isolated green pixel microcavities and red pixel microcavities;

[0017] S2. Preparation of dual-color quantum dot functional materials: Green and red perovskite quantum dots were synthesized separately and passivated by organic large cations and short-chain ammonium bromide dual ligands. The purified quantum dots were then mixed with optical adhesive in a certain proportion and stirred to form homogeneous green quantum dot gel and red quantum dot gel.

[0018] S3, Layered Fill and In-situ Encapsulation Color Conversion Layer:

[0019] S31. The green quantum dot gel is filled into the green pixel microcavity defined in step S1. After the surface is flattened by scraping and polishing, an atomic layer deposition process is used to deposit a first layer of aluminum oxide encapsulation film on the surface of the green quantum dot layer.

[0020] S32. On the green pixel area that has been packaged, spin-coat negative photoresist again and perform photolithography to define the red pixel microcavity.

[0021] S33. The red quantum dot gel is filled into the red pixel microcavity defined in step S32. After the surface is flattened by scraping and polishing, an atomic layer deposition process is used to deposit a second aluminum oxide encapsulation film on the surface of the red quantum dot layer, thereby forming a complete dual-color perovskite quantum dot color conversion unit.

[0022] S4. Overall surface encapsulation: A silicon nitride encapsulation layer is deposited on the surface of the color conversion unit prepared in step S3 by chemical vapor deposition.

[0023] S5. Drive circuit integration: Using flip-chip bonding, the blue Micro-LED array substrate integrating the color conversion unit is bonded to the drive circuit substrate through a metal bump array, and the gaps between the bonding bumps are filled with high light transmittance insulating material to complete the chip fabrication.

[0024] Preferably, the negative photoresist mentioned in steps S1 and S32 is SU8 series photoresist, and the size of the pixel microcavity formed is 2μm to 50μm.

[0025] Preferably, in step S2, the mass ratio of the quantum dots to the optical adhesive is (4-6):1.

[0026] The beneficial effects of this invention are mainly reflected in the following aspects:

[0027] 1. Optimized device structure design: The flip-chip structure, combined with a precision-fabricated metal bump array, achieves excellent current spreading performance and heat dissipation capability.

[0028] 2. Innovative material system: A dense protective layer is formed on the surface of perovskite quantum dots through a bimolecular synergistic passivation strategy of organic large cations and short-chain ammonium bromide, which solves the dual challenges of defect passivation and environmental stability improvement.

[0029] 3. Advanced fabrication process: Combining standard semiconductor processes with micropore filling technology, precise patterning of the quantum dot color conversion layer was achieved. In-situ encapsulation using atomic layer deposition technology provides an effective protective barrier for the quantum dots.

[0030] 4. Superior display performance: By precisely controlling the matching degree between the emission spectrum of blue Micro-LED and the absorption spectrum of perovskite quantum dots, efficient color conversion is ensured. Optimized pixel isolation wall design effectively suppresses inter-pixel crosstalk.

[0031] 5. Good process compatibility: The preparation process used in this invention is fully compatible with existing semiconductor manufacturing processes. In particular, the GaN epitaxial wafer processing technology and photolithography process used are mature processes, which are conducive to realizing large-scale industrial production.

[0032] In summary, this invention, through innovative device structure design, material system, and fabrication process, successfully solves the efficiency and stability bottlenecks faced by perovskite quantum dots in Micro-LED applications, providing a complete and feasible technical solution for achieving high-performance, long-life full-color Micro-LED displays. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A cross-sectional view of a flip-chip Micro-LED;

[0035] Figure 2 A schematic diagram of the perovskite quantum dot color conversion layer structure;

[0036] Among them, 1-TFT driving circuit, 2-bonding / filling layer, 3-hole injection layer (p-GaN), 4-multiple quantum well active region (MQWs), 5-electron injection layer (n-GaN), 6-buffer layer (u-GaN), 7-sapphire substrate, 8-blue LED, 9-sapphire substrate, 10-green perovskite quantum dot pixel layer, 11-Al2O3 encapsulation layer, 12-red perovskite quantum dot pixel layer, 13-Al2O3 encapsulation layer. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Combined with appendix Figure 1 and 2 The device structure of the present invention will be further described below:

[0039] like Figure 1 The diagram shows a cross-sectional view (from bottom to top) of the flip-chip Micro-LED chip used in this invention. The bottom layer is the TFT driving circuit 1, which provides pixel-level driving signals. Above it is the bonding / filling layer 2, which includes a metal bump array (for electrical connection and mechanical fixation) and a high-transmittance insulating material filling the gaps between the bumps (for optical coupling and planarization). Above the bonding / filling layer 2 are, in sequence, the functional layers of the blue Micro-LED array: hole injection layer (p-GaN, 3), multiple quantum well active regions (MQWs, 4), electron injection layer (n-GaN, 5), buffer layer (u-GaN, 6), and the topmost sapphire substrate 7. Blue light is emitted from this chip structure and propagates upwards.

[0040] like Figure 2 The diagram shows a perovskite quantum dot color conversion layer structure mounted on a blue Micro-LED chip. The sapphire substrate 9 is actually... Figure 1 The sapphire substrate 7 in the image is the same component, on which the active light-emitting area of ​​the blue LED 8 is located (corresponding to...). Figure 1(MQWs and other layers). In the blue light emission direction, a green perovskite quantum dot pixel layer 10 is first set, which converts part of the incident blue light into green light. A first Al2O3 encapsulation layer 11 covers this green quantum dot layer, providing in-situ passivation and protection. In the area where red light pixels are needed, a red perovskite quantum dot pixel layer 12 is further set above the first encapsulation layer, converting part of the blue light (or the transmitted light) into red light. This red quantum dot layer is also covered and protected by a second Al2O3 encapsulation layer 13. This layered structure achieves precise patterning, independent encapsulation, and optical isolation of red and green dual-color quantum dot pixels.

[0041] Example 1

[0042] This embodiment discloses a method for fabricating a bimolecular passivated perovskite quantum dot color conversion layer, which specifically includes the following steps:

[0043] S1: Green CsPbBr3 and red CsPbI3 quantum dots were prepared by in-situ synthesis of two ligands.

[0044] S11: Green quantum dots: Weigh 0.041 g of cesium carbonate, 0.095 g of lead acetate trihydrate, 0.1055 g of 2-phenylethylammonium bromide (PEABr), and 0.045 g of butylammonium bromide (BABr) according to the molar ratio of Cs:Pb:Br=1:1:4. Mix with 2 mL of oleic acid, 2 mL of oleylamine, and 10 mL of octadecene. Stir and evacuate at 120 °C for 40 minutes. Then inject 0.12 mL of benzoyl bromide under argon protection at 170 °C. After reacting for 3 seconds, cool in an ice bath to obtain the original solution of green quantum dots.

[0045] S12: Red quantum dots: First, a cesium oleate precursor was prepared. Then, 0.2777 g of lead iodide, 0.1055 g of 2-phenylethylammonium bromide (PEABr), and 0.045 g of butylammonium bromide (BABr) were mixed with oleic acid, oleylamine, and octadecene. After dehydration, the mixture was injected into a cesium oleate solution at 170°C. After reaction, the mixture was cooled in an ice bath to obtain the original red quantum dot solution. S13: The two original solutions were treated with ultraviolet light, and then purified by centrifugation, washing, and filtration to obtain a dual-color quantum dot stock solution. S2: The green and red quantum dot stock solutions were mixed with optical adhesive at mass ratios of 5:1 and 4:1, respectively, and stirred to form a homogeneous quantum dot gel. S3: SU8-2015 photoresist was spin-coated onto a blue Micro-LED array substrate, and 40 μm green and 30 μm red pixel microcavities were fabricated using photolithography. Quantum dot gels of corresponding colors were filled, and after being coated and polished, a 30nm Al2O3 film was deposited by atomic layer deposition for encapsulation. S4: A 200nm silicon nitride encapsulation layer was deposited on the surface of the color conversion layer to complete the preparation of the perovskite quantum dot color conversion layer.

[0046] Example 2

[0047] In this embodiment, a method for fabricating a color conversion layer based on bimolecular passivated perovskite quantum dots is disclosed, which specifically includes the following steps: S1: Green CsPbBr3 and red CsPbI3 quantum dots are prepared by in-situ synthesis of dual ligands.

[0048] S11: Green quantum dots: Weigh 0.043 g of cesium carbonate, 0.097 g of lead acetate trihydrate, 0.223 g of 4-fluorophenylethyl ammonium bromide (pF-PEABr), and 0.032 g of ethyl ammonium bromide (EABr) according to the molar ratio of Cs:Pb:Br=1:1:4. Mix with 2 mL of oleic acid, 2 mL of oleylamine, and 10 mL of octadecene. Stir and evacuate at 125 °C for 35 minutes. Then inject 0.13 mL of benzoyl bromide under argon protection at 165 °C. After reacting for 4 seconds, cool in an ice bath to obtain the original solution of green quantum dots.

[0049] S12: Red quantum dots: First, a cesium oleate precursor was prepared. Then, 0.280 g of lead iodide, 0.107 g of 4-fluorophenylethyl ammonium bromide (pF-PEABr), and 0.048 g of ethyl ammonium bromide (EABr) were mixed with oleic acid, oleylamine, and octadecene. After dehydration, the mixture was injected into a cesium oleate solution at 165°C. After the reaction, the mixture was cooled in an ice bath to obtain the original red quantum dot solution. S13: The two original solutions were treated with ultraviolet light, and then purified by centrifugation, washing, and filtration to obtain a two-color quantum dot stock solution.

[0050] S2: Mix the green and red quantum dot stock solutions with the optical adhesive at mass ratios of 5.5:1 and 4.2:1, respectively, and stir to form a homogeneous quantum dot gel.

[0051] S3: SU8-2015 photoresist was spin-coated onto a blue Micro-LED array substrate, and 35μm green and 25μm red pixel microcavities were simultaneously fabricated using a one-step photolithography process. Quantum dot gels of the corresponding colors were then precisely filled into the microcavities using a selective filling process. After scraping and polishing, a 25nm Al2O3 thin film was deposited by atomic layer deposition for overall encapsulation. S4: A 180nm silicon nitride encapsulation layer was fabricated on the surface of the color conversion layer using chemical vapor deposition, completing the fabrication of the perovskite quantum dot color conversion layer.

[0052] Comparative Example 1

[0053] In this comparative example, a conventional method for preparing Micro-LEDs as described in Example 1 is compared, which specifically includes the following steps:

[0054] S1: Red and green bicolor quantum dots were prepared using the traditional single-ligand synthesis method.

[0055] S11: Green quantum dots: Weigh 0.041 g of cesium carbonate and 0.095 g of lead acetate trihydrate according to the molar ratio of Cs:Pb:Br=1:1:3, mix with 2 mL of oleic acid, 2 mL of oleylamine and 10 mL of octadecene, stir and vacuum at 120 °C for 40 minutes, then inject 0.12 mL of benzoyl bromide under argon protection at 170 °C, react for 5 seconds and cool in an ice bath to obtain the original solution of green quantum dots.

[0056] S12: Red quantum dots: First, a cesium oleate precursor was prepared. Then, 0.2777 g of lead iodide was mixed with oleic acid, oleylamine, and octadecene. After dehydration, the mixture was injected into a cesium oleate solution at 170°C. After the reaction, the mixture was cooled in an ice bath to obtain the original red quantum dot solution. S13: The two original solutions were purified by centrifugation, washing, and filtration to obtain quantum dot stock solutions with stable conventional ligands. S2: The dual-color quantum dot stock solutions were mixed with optical adhesives at mass ratios of 5:1 and 4:1, respectively, and stirred to form quantum dot gels. S3: SU8-2015 photoresist was spin-coated onto a blue Micro-LED array substrate. 40 μm green and 30 μm red pixel microcavities were prepared using photolithography. The corresponding colored quantum dot gels were filled, and after scraping and polishing, a 30 nm Al2O3 film was deposited by atomic layer deposition for encapsulation. S4: A 200 nm silicon nitride encapsulation layer was deposited on the surface of the color conversion layer to complete the preparation of the perovskite quantum dot color conversion layer.

[0057] Experimental Test

[0058] Stability tests were conducted on the Micro-LEDs prepared in Comparative Example 1 and Examples 1 and 2, respectively. The basic steps were as follows: the tests were conducted under blue light irradiation at a relative humidity of 50%, a temperature of 25°C, an ultra-high power density of 2000mW cm-2, and a wavelength of 450nm. The results showed that the Micro-LEDs prepared using the methods of Examples 1 and 2 had increased lifetime and significantly improved stability.

[0059] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0060] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots, characterized in that, include: A blue Micro-LED array substrate, and a perovskite quantum dot color conversion layer disposed on the light-emitting side of the blue Micro-LED array substrate; The perovskite quantum dot color conversion layer includes green perovskite quantum dot pixels and red perovskite quantum dot pixels corresponding to the blue Micro-LED array pixels, and the perovskite quantum dots therein are synergistically passivated using organic large cations and short-chain ammonium bromide as dual ligands.

2. The full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots according to claim 1, characterized in that, The blue Micro-LED array substrate has a flip-chip structure and includes, from bottom to top, a sapphire substrate, a u-GaN buffer layer, an electron injection layer, a multi-quantum well active region, and a hole injection layer; and is bonded to the driving circuit substrate through a metal bump array, the gaps of which are filled with an insulating material with a transmittance of more than 70% in the 450nm-470nm wavelength band.

3. A full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots according to claim 1, characterized in that, The large organic cation is one of 2-phenylethylammonium bromide, 4-fluorophenylethylammonium bromide, 3-fluorophenylethylammonium bromide, and 2-fluorophenylethylammonium bromide; the short-chain ammonium bromide is one of ethylammonium bromide, propylammonium bromide, and butylammonium bromide.

4. A full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots according to claim 3, characterized in that, The surface of the perovskite quantum dots is synergistically bound with the organic macrocation and the short-chain ammonium bromide ligand. Based on the quantum dot synthesis precursor, the lead ion concentration is 0.1 mol / L to 0.2 mol / L, the amount of organic macrocation added is between 0.03 mol / L and 0.18 mol / L, and the amount of short-chain ammonium bromide added is between 0.03 mol / L and 0.18 mol / L.

5. A full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots according to claim 1, characterized in that, The pixel size of the perovskite quantum dot color conversion layer ranges from 2μm to 50μm, and there is a one-to-one correspondence between the pixels of the blue Micro-LED array below.

6. A full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots according to claim 1, characterized in that, The blue light emission peak wavelength of the blue light Micro-LED array substrate is 450nm to 470nm, and its emission spectrum overlaps with the absorption spectrum of the perovskite quantum dots by more than 70%.

7. A full-color Micro-LED chip based on bimolecular passivated perovskite quantum dots according to claim 1, characterized in that, The green perovskite quantum dot pixels emit wavelengths of 520nm-540nm, and the red perovskite quantum dot pixels emit wavelengths of 620nm-640nm.

8. A method for fabricating a full-color Micro-LED chip according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Provide a blue Micro-LED array substrate and prepare a pixel isolation structure on its light-emitting surface: spin-coat negative photoresist on the substrate and form patterned pixel isolation walls through photolithography, thereby defining mutually isolated green pixel microcavities and red pixel microcavities. S2. Preparation of dual-color quantum dot functional materials: Green and red perovskite quantum dots were synthesized separately and passivated by organic large cations and short-chain ammonium bromide dual ligands. The purified quantum dots were then mixed with optical adhesive in a certain proportion and stirred to form homogeneous green quantum dot gel and red quantum dot gel. S3, Layered Fill and In-situ Encapsulation Color Conversion Layer: S31. The green quantum dot gel is filled into the green pixel microcavity defined in step S1. After the surface is flattened by scraping and polishing, an atomic layer deposition process is used to deposit a first layer of aluminum oxide encapsulation film on the surface of the green quantum dot layer. S32. On the green pixel area that has been packaged, spin-coat negative photoresist again and perform photolithography to define the red pixel microcavity. S33. The red quantum dot gel is filled into the red pixel microcavity defined in step S32. After the surface is flattened by scraping and polishing, an atomic layer deposition process is used to deposit a second aluminum oxide encapsulation film on the surface of the red quantum dot layer, thereby forming a complete dual-color perovskite quantum dot color conversion unit. S4. Overall surface encapsulation: A silicon nitride encapsulation layer is deposited on the surface of the color conversion unit prepared in step S3 by chemical vapor deposition. S5. Drive circuit integration: Using flip-chip bonding, the blue Micro-LED array substrate integrating the color conversion unit is bonded to the drive circuit substrate through a metal bump array, and the gaps between the bonding bumps are filled with high light transmittance insulating material to complete the chip fabrication.

9. The preparation method according to claim 8, characterized in that, The negative photoresist mentioned in steps S1 and S32 is SU8 series photoresist, and the size of the pixel microcavity formed is 2μm to 50μm.

10. The method according to claim 8, characterized in that, In step S2, the mass ratio of the quantum dots to the optical adhesive is (4-6):1.

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