Ultrahigh-resolution quantum dot light-emitting diode and preparation method thereof

Abstract

The invention belongs to the technical field of light-emitting diodes, and particularly discloses an ultrahigh-resolution quantum dot light-emitting diode and a preparation method thereof. The device sequentially comprises a hole injection layer, a hole transmission layer, a quantum dot light-emitting layer, an electron transmission layer and an evaporation electrode. The preparation method is characterized in that the quantum dot light-emitting layer is prepared by the following steps: dropwise adding a quantum dot solution on the hole transport layer, impressing by using a Hard-PDMS hole seal, driving the solution to fill seal micropores by virtue of capillary force, drying, and uncovering the seal, so as to obtain the fine quantum dot array. According to the method, one-step patterning of the quantum dots is achieved by enhancing capillary force guidance, and precise assembly from the micron scale to the nanometer scale is completed. According to the method, professional operators are not needed, the process is simple, a simple, convenient, effective and universal preparation way is provided, low-cost and large-area manufacturing and device integration of the ultra-high-resolution quantum dot light-emitting diode can be achieved, and a new technical path is provided for ultra-high-resolution display.

Description

Technical Field

[0001] This invention belongs to the field of light-emitting diode technology, and specifically discloses an ultra-high resolution quantum dot light-emitting diode and its preparation method. Background Technology

[0002] Light-emitting diodes (LEDs), as a new generation of light-emitting display technology, have been widely used in displays, lighting, and other fields due to their advantages such as high brightness, high energy efficiency, wide color gamut, and fast response. In particular, quantum dot LEDs have become a hot topic in next-generation display technology due to their finely tunable spectral characteristics (high color purity) and high fluorescence quantum yield.

[0003] As users' demands for visual experience continue to increase, light-emitting devices are developing towards higher resolution and finer pixel structures. Especially for applications such as virtual reality (VR), augmented reality (AR), microdisplays, and high-density integrated light sources, there is a need to achieve pixel sizes and densities at the micrometer or even sub-micrometer level (i.e., ultra-high resolution). However, existing mainstream light-emitting device manufacturing technologies, such as vacuum evaporation or inkjet printing in organic light-emitting diodes (OLEDs), and photolithography, inkjet printing, and transfer printing in microLEDs, still suffer from insufficient pixelation precision and complex, high-cost processes when achieving such high resolutions.

[0004] Existing technologies disclose methods for preparing high-resolution quantum dot light-emitting diodes, which involve forming trenches by thermal nanoimprinting of polymers, followed by solution deposition of quantum dots guided by capillary effects, and then transferring the dots to a substrate and removing the polymer. However, this method is complex and cannot be mass-produced.

[0005] Therefore, realizing ultra-high resolution quantum dot light-emitting diodes, which can efficiently, accurately and cost-effectively form micron to nanometer-scale quantum dot arrays on substrates, is a key problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] This invention provides a method for fabricating ultra-high resolution quantum dot light-emitting diodes by one-step patterning of quantum dots guided by enhanced capillary force. The aim is to efficiently, accurately, and cost-effectively fabricate quantum dot arrays at the micrometer to nanometer scale, significantly improving the resolution of display devices and achieving ultra-high resolution displays.

[0007] To achieve the above objectives, the present invention employs the following technical solution: a method for fabricating an ultra-high resolution quantum dot light-emitting diode, wherein the device structure of the quantum dot light-emitting diode is, in sequence, a substrate, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer, and a vapor-deposited electrode; characterized in that the method for fabricating the quantum dot light-emitting layer is as follows: a quantum dot solution with a concentration of 1~3 mg / mL is dropped onto the surface of the hole transport layer, and then the quantum dot solution is imprinted using a Hard-PDMS pore stamp. The quantum dot solution enters the Hard-PDMS pores under the drive of capillary force. After drying, the stamp is removed, and the layer is annealed to obtain the ultra-high resolution quantum dot light-emitting layer.

[0008] Further improvements to the fabrication method of ultra-high resolution quantum dot light-emitting diodes: Preferably, the Hard-PDMS hole stamp is a surface-hardened modified polydimethylsiloxane hole stamp with a Young's modulus of 1-10 MPa.

[0009] Preferably, the Hard-PDMS perforated stamp has a micron- or nanon-sized array of recesses, wherein the micron-sized pores have a diameter of 1~10 μm and a period of 5~20 μm; and the nano-sized pores have a diameter of 20~999 nm and a period of 50~999 nm.

[0010] Preferably, the annealing temperature is 70-90 ℃ and the time is 10-20 min.

[0011] Preferably, the preparation method of the Hard-PDMS perforated stamp is as follows: S11. A silicon wafer with a raised columnar array on its surface is used as the master template, and the surface is treated with trichlorosilane. S12. Spin-coat a layer of thermosetting organic material onto the surface of a silicon master plate treated with trichlorosilane, wherein the thermosetting organic material is an oleophilic material; heat-cur the thermosetting organic material to form a hard organic material layer; S13. A layer of PDMS prepolymer is coated on the surface of the rigid organic material layer, and the PDMS prepolymer is heated and cured to form a PDMS support layer. S14. The cured hard organic material layer and the PDMS support layer are peeled off from the silicon master plate together to obtain a Hard-PDMS hole stamp composed of the hard organic material layer and the PDMS support layer.

[0012] Preferably, the quantum dot solution is one of cadmium-based quantum dot solution, indium phosphide quantum dot solution, and perovskite quantum dot solution.

[0013] The preferred method for fabricating ultra-high resolution quantum dot light-emitting diodes is as follows: S1. Pre-treat the substrate to obtain a clean and dry surface; S2. Spin-coat the hole injection layer solution onto the upper surface of the substrate and anneal it to obtain the hole injection layer. S3. Spin-coat the hole transport layer solution onto the hole injection layer and anneal it to obtain the hole transport layer. S4. Prepare a quantum dot light-emitting layer on the hole transport layer; S5. Spin-coat a charge blocking layer solution onto the quantum dot luminescent layer to obtain a charge blocking layer; S6. Spin-coat an electron transport layer solution onto the charge blocking layer and anneal it to obtain the electron transport layer. S7. Deposit metal electrodes on the electron transport layer to obtain an ultra-high resolution quantum dot light-emitting diode.

[0014] Preferably, the substrate is a rigid substrate or a flexible substrate. The rigid substrate is glass with an ITO conductive layer deposited on it, and the flexible substrate is one of polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), polystyrene (PS), and flexible glass.

[0015] Preferably, the entire fabrication of the quantum dot light-emitting layer is carried out in a glove box.

[0016] A second objective of this invention is to provide an ultra-high resolution quantum dot light-emitting diode prepared by any of the above-described methods.

[0017] The advantages of this invention compared to the prior art are as follows: (1) This invention provides a method for one-step patterning of quantum dots to prepare ultra-high resolution quantum dot light-emitting diodes using enhanced capillary force. The method involves using a device structure with a substrate, a hole injection layer, and a hole transport layer. After adding a quantum dot solution to the hole transport layer, a Hard-PDMS nano-stamp is used to imprint the solution onto the micropores of the stamp. Capillary force drives the solution to fill the micropores of the stamp. After drying, the stamp is peeled off, yielding the ultra-high resolution quantum dot light-emitting layer. The nano-stamp is a surface-hardened modified polydimethylsiloxane nano-stamp (Hard-PDMS). The surface hardening modification of the Hard-PDMS nano-stamp is to enhance the capillary interaction of the pores, thereby achieving precise assembly of ultra-high resolution quantum dots. This method can directly prepare an ultra-high resolution quantum dot light-emitting layer array on the functional layer TFB without substrate transfer or additional polymer removal steps, achieving direct assembly of the quantum dot array on the functional layer.

[0018] (2) The process of this invention is simplified and efficient, enabling low-cost, large-scale production of ultra-high resolution quantum dot emitting layer arrays using only a very small amount of quantum dot solution. The arraying of the quantum dot emitting layer is driven by capillary interactions, eliminating the need for heating, pressurization, substrate transfer, and other operations, effectively preventing damage to the quantum dots. This method can be fabricated using a glove box throughout the process, effectively isolating the effects of water, oxygen, and temperature on device performance. This invention solves the problems of insufficient pixelation accuracy and complex, high-cost processes when achieving ultra-high resolution (micrometer and nanometer scale) quantum dot emitting layers. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating a method for fabricating ultra-high resolution quantum dot light-emitting diodes using enhanced capillary force-guided one-step patterning of quantum dots, as provided in an embodiment of the present invention. Figure 2 This is a structural diagram of the ultra-high resolution quantum dot light-emitting diode obtained by the present invention; Figure 3 This is a pixel density diagram of the quantum dot emitting layer obtained in Embodiment 1 of the present invention; Figure 4 This is a performance test of the light-emitting diode prepared in Embodiment 1 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0022] It should be understood that all parameter ranges in the embodiments of the present invention are within the protection scope of the present invention.

[0023] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0024] Preparation Example This preparation example provides a method for preparing a Hard-PDMS perforated stamp, which specifically includes the following steps: S1. A silicon wafer with a raised columnar array on its surface is provided as a master template. The column is cylindrical with a diameter of 150 nm and a height of 200 nm. The center-to-center distance between adjacent columns is 600 nm. The surface of the silicon master template is treated with trichlorosilane. The specific treatment steps are as follows: the silicon master template and an open glass bottle containing trichlorosilane are placed together in a desiccator and kept under vacuum for 6 h. S2. On the trichlorosilane-treated surface containing the aforementioned columnar array, a layer of oleophilic thermosetting organic material (specifically a mixture of (7-8% vinylsiloxane)-dimethylsiloxane copolymer, toluene, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane, platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane and trimethylsiloxane-terminated (25-35% methylhydrosiloxane)-dimethylsiloxane copolymer (25-35% methane)) is spin-coated to a thickness of 400 nm; the thermosetting organic material is then heated and cured at 80 °C, and cooled to form a hard organic material layer; S3. Cover the surface of the rigid organic material layer with a layer of PDMS prepolymer with a thickness of 7 mm; heat and cure the PDMS prepolymer at 80 ℃, and cool to form a PDMS support layer; S4. The cured hard organic material layer and the PDMS support layer are peeled off from the silicon master plate together to obtain a Hard-PDMS hole stamp composed of the hard organic material layer and the PDMS support layer, with a Young's modulus of about 80 MPa.

[0025] Example 1 This embodiment provides a method for fabricating an ultra-high resolution quantum dot light-emitting diode, the structure of which is as follows: Figure 2 As shown, the specific steps include the following: S1. Take glass with an ITO conductive layer deposited on it as a substrate, pre-treat the substrate to obtain a clean and dry surface; S2. Spin-coat the hole injection layer solution (concentration 1.3wt%, composition PEDOT:PSS, spin-coating thickness 40nm) onto the upper surface of the substrate, anneal at 130 ℃ for 20 min, and cool to obtain the hole injection layer; S3. Spin-coat the hole transport layer solution (concentration 8 mg / mL, composition TFB, spin-coating thickness 30 nm) onto the hole injection layer, anneal at 120 ℃ for 20 min, and cool to obtain the hole transport layer. S4, Reference Figure 1The process flow diagram for preparing the quantum dot luminescent layer is as follows: The product of step S3 is placed in a glove box, and 1 μL of quantum dot solution (red cadmium-based quantum dot solution) with a concentration of 3 mg / mL is dropped onto the surface of the hole transport layer. Then, the quantum dot solution is imprinted with the Hard-PDMS pore stamp obtained in the preparation example. The quantum dot solution enters the Hard-PDMS pores under the drive of capillary interaction. After drying, the stamp is removed, and the layer is annealed at 70 ℃ for 20 min to obtain the ultra-high resolution quantum dot luminescent layer. S5. Spin-coat a charge blocking layer solution (concentration 1 mg / mL, composition PMMA, spin-coating thickness 40 nm) onto the quantum dot light-emitting layer to obtain the charge blocking layer. S6. Spin-coat an electron transport layer solution (concentration 25 mg / mL, composition ZnO, spin-coating thickness 50 nm) onto the charge blocking layer, anneal at 70 ℃ for 10 min, and cool to obtain the electron transport layer. S7. An Ag metal electrode with a thickness of 100 nm is deposited on the electron transport layer, and the device is encapsulated with a transparent material to obtain an ultra-high resolution quantum dot light-emitting diode.

[0026] Figure 3 The fabrication process of this invention can achieve pixel density maps. This application utilizes a method for one-step patterning of quantum dots to prepare ultra-high resolution quantum dot light-emitting diodes by enhancing capillary force, which can achieve high uniformity quantum dot array assembly with a maximum of 169333 PPI.

[0027] Figure 4 This is a performance test of the light-emitting diode prepared in Example 1, by... Figure 4 It can be seen that the red light-emitting diode prepared above has an external quantum efficiency of >15% and a brightness of 100,000 cd / m². 2 Its excellent performance.

[0028] Example 2 This embodiment provides a method for fabricating an ultra-high resolution quantum dot light-emitting diode, the structure of which is as follows: Figure 2 As shown, the specific steps include the following: S1. Take glass with an ITO conductive layer deposited on it as a substrate, pre-treat the substrate to obtain a clean and dry surface; S2. Spin-coat the hole injection layer solution (concentration 1.7wt%, composition PEDOT:PSS, spin-coating thickness 40nm) onto the upper surface of the substrate, anneal at 120 ℃ for 20 min, and cool to obtain the hole injection layer; S3. Spin-coat the hole transport layer solution (concentration 12 mg / mL, composition PF8Cz, spin-coating thickness 25 nm) onto the hole injection layer, anneal at 130 ℃ for 20 min, and cool to obtain the hole transport layer. S4, Reference Figure 1 The process flow diagram for preparing the quantum dot luminescent layer is as follows: The product of step S3 is placed in a glove box, and 5 μL of quantum dot solution (green cadmium-based quantum dot solution) with a concentration of 1 mg / mL is dropped onto the surface of the hole transport layer. Then, the quantum dot solution is imprinted with the Hard-PDMS pore stamp obtained in the preparation example. The quantum dot solution enters the Hard-PDMS pores under the drive of capillary interaction. After drying, the stamp is removed, and the layer is annealed at 90 °C for 10 min to obtain the ultra-high resolution quantum dot luminescent layer. S5. Spin-coat a charge blocking layer solution (concentration 2 mg / mL, composition PMMA, spin-coating thickness 40 nm) onto the quantum dot light-emitting layer to obtain the charge blocking layer. S6. Spin-coat an electron transport layer solution (concentration 30 mg / mL, composition ZnMgO, spin-coating thickness 55 nm) onto the charge blocking layer, anneal at 80 ℃ for 10 min, and cool to obtain the electron transport layer. S7. An Ag metal electrode with a thickness of 100 nm is deposited on the electron transport layer, and the device is encapsulated with a transparent material to obtain an ultra-high resolution quantum dot light-emitting diode.

[0029] After testing, the green light-emitting diode prepared above has an external quantum efficiency of >10% and a brightness of 80,000 cd / m². 2 Its excellent performance.

[0030] Example 3 This embodiment provides a method for fabricating an ultra-high resolution quantum dot light-emitting diode, the structure of which is as follows: Figure 2 As shown, the specific steps include the following: S1. Take glass with an ITO conductive layer deposited on it as a substrate, pre-treat the substrate to obtain a clean and dry surface; S2. Spin-coat the hole injection layer solution (concentration 1.4wt%, composition PEDOT:PSS, spin-coating thickness 35nm) onto the upper surface of the substrate, anneal at 125 ℃ for 20 min, and cool to obtain the hole injection layer; S3. Spin-coat the hole transport layer solution (concentration 12 mg / mL, composition PVK, spin-coating thickness 35 nm) onto the hole injection layer, anneal at 125 ℃ for 20 min, and cool to obtain the hole transport layer. S4, Reference Figure 1The process flow diagram for preparing the quantum dot luminescent layer is as follows: The product of step S3 is placed in a glove box, and 3 μL of quantum dot solution (blue cadmium-based quantum dot solution) with a concentration of 2 mg / mL is dropped onto the surface of the hole transport layer. Then, the quantum dot solution is imprinted with the Hard-PDMS pore stamp obtained in the preparation example. The quantum dot solution enters the Hard-PDMS pores under the drive of capillary interaction. After drying, the stamp is removed, and the layer is annealed at 80 ℃ for 15 min to obtain the ultra-high resolution quantum dot luminescent layer. S5. Spin-coat a charge blocking layer solution (concentration 1.5 mg / mL, composition PMMA, spin-coating thickness 35 nm) onto the quantum dot emitting layer to obtain the charge blocking layer; S6. Spin-coat an electron transport layer solution (concentration 20 mg / mL, composition ZnMgO, spin-coating thickness 45 nm) onto the charge blocking layer, anneal at 75 ℃ for 15 min, and cool to obtain the electron transport layer. S7. An Ag metal electrode with a thickness of 100 nm is deposited on the electron transport layer, and the device is encapsulated with a transparent material to obtain an ultra-high resolution quantum dot light-emitting diode.

[0031] After testing, the green light-emitting diode prepared above has an external quantum efficiency of >8% and a brightness of 10000 cd / m². 2 Its excellent performance.

[0032] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for fabricating an ultra-high resolution quantum dot light-emitting diode, wherein the device structure of the quantum dot light-emitting diode comprises, in sequence, a substrate, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer, and a vapor-deposited electrode; characterized in that, The quantum dot luminescent layer is prepared as follows: a quantum dot solution with a concentration of 1~3 mg / mL is dropped onto the surface of the hole transport layer, and then the quantum dot solution is imprinted with a Hard-PDMS pore stamp. The quantum dot solution enters the Hard-PDMS pores under the drive of capillary force. After drying, the stamp is removed and annealed to obtain the ultra-high resolution quantum dot luminescent layer.

2. The method for fabricating an ultra-high resolution quantum dot light-emitting diode according to claim 1, characterized in that, The Hard-PDMS hole stamp is a surface-hardened modified polydimethylsiloxane hole stamp with a Young's modulus of 1-10 MPa.

3. The method for fabricating an ultra-high resolution quantum dot light-emitting diode according to claim 1, characterized in that, The Hard-PDMS perforated stamp has a micron- or nanon-sized array of recesses, wherein the micron-sized pores have a diameter of 1~10 μm and a period of 5~20 μm; and the nano-sized pores have a diameter of 20~999 nm and a period of 50~999 nm.

4. The method for fabricating an ultra-high resolution quantum dot light-emitting diode according to claim 1, characterized in that, The annealing temperature is 70-90 ℃ and the time is 10-20 min.

5. The method for fabricating an ultra-high resolution quantum dot light-emitting diode according to claim 1, characterized in that, The quantum dot solution is one of cadmium-based quantum dot solution, indium phosphide quantum dot solution, and perovskite quantum dot solution.

6. The method for fabricating an ultra-high resolution quantum dot light-emitting diode according to claim 1, characterized in that, The preparation method of the Hard-PDMS perforated stamp is as follows: S11. A silicon wafer with a raised columnar array on its surface is used as the master template, and the surface is treated with trichlorosilane. S12. Spin-coat a layer of thermosetting organic material onto the surface of a silicon master plate treated with trichlorosilane, wherein the thermosetting organic material is an oleophilic material; heat-cur the thermosetting organic material to form a hard organic material layer; S13. A layer of PDMS prepolymer is coated on the surface of the rigid organic material layer, and the PDMS prepolymer is heated and cured to form a PDMS support layer. S14. The cured hard organic material layer and the PDMS support layer are peeled off from the silicon master plate together to obtain a Hard-PDMS hole stamp composed of the hard organic material layer and the PDMS support layer.

7. The method for fabricating an ultra-high resolution quantum dot light-emitting diode according to claim 1, characterized in that, Includes the following steps: S1. Pre-treat the substrate to obtain a clean and dry surface; S2. Spin-coat the hole injection layer solution onto the upper surface of the substrate and anneal it to obtain the hole injection layer. S3. Spin-coat the hole transport layer solution onto the hole injection layer and anneal it to obtain the hole transport layer. S4. Prepare a quantum dot light-emitting layer on the hole transport layer; S5. Spin-coat a charge blocking layer solution onto the quantum dot luminescent layer to obtain a charge blocking layer; S6. Spin-coat an electron transport layer solution onto the charge blocking layer and anneal it to obtain the electron transport layer. S7. Deposit metal electrodes on the electron transport layer to obtain an ultra-high resolution quantum dot light-emitting diode.

8. A method for fabricating an ultra-high resolution quantum dot light-emitting diode according to claim 1 or 7, characterized in that, The substrate can be a rigid substrate or a flexible substrate. The rigid substrate is glass with an ITO conductive layer deposited on it, and the flexible substrate is one of polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), polystyrene (PS), and flexible glass.

9. A method for fabricating an ultra-high resolution quantum dot light-emitting diode according to claim 1 or 7, characterized in that, The entire fabrication of the quantum dot luminescent layer was carried out in a glove box.

10. An ultra-high resolution quantum dot light-emitting diode prepared by the method of any one of claims 1-9.

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