Preparation method of perovskite thin film electroluminescent Mini / Micro-LED

Abstract

The invention discloses a preparation method of a perovskite thin film electroluminescent Mini / Micro-LED, which comprises the following steps: in a spin coater, spin-coating a polyvinylcarbazole solution on an ITO glass substrate as a hole transport layer, and carrying out annealing treatment; spin-coating the hole transport layer with a perovskite solution, and carrying out annealing treatment to form a perovskite thin film; performing laser processing on the perovskite thin film to form an array area; and an electron transport layer and an electrode are sequentially deposited on the arrayed film by adopting a vacuum coating method. According to the invention, high-resolution electrically induced Mini / Micro-LED display is realized. According to the method, the requirements of different resolutions can be met without huge transfer and templates, and the steps of color conversion are not needed, so that the conversion efficiency is higher, large-area preparation can be performed in the later period, the potential of preparing an array with higher resolution is achieved, the operation is simple, and the cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of perovskite materials, and specifically relates to a method for preparing a perovskite thin film electroluminescent Mini / Micro-LED. Background Art

[0002] In recent years, with the increasing demand for display accuracy, Mini / Micro-LED display technology has emerged and has become one of the hottest research projects. It arrays and miniaturizes the traditional LED structure to form an ultra-small pitch LED array, and miniaturizes the size of a single pixel to less than 200μm. The drive circuit is made through the COMS integrated circuit process to control and drive each pixel array separately to achieve ultra-high resolution display. Compared with several display technologies currently on the market (TFT-LCD, OLED, QLED), in addition to the advantages of ultra-high resolution and addressable light emission, its performance is also superior in terms of brightness, luminous efficiency, response time and life. Especially after the emergence of AR / VR devices, its application prospects are more promising. Although Micro-LED display is still in the research stage, its performance advantages are more significant and it will definitely become a new generation of innovative display technology. At present, the technology for preparing Mini / Micro-LED is mainly based on mass transfer. As people's requirements for resolution become higher and higher, mass transfer technology is insufficient in cost and yield. Therefore, many research groups have begun to study color conversion Micro-LED technology. Although this method solves the problem of mass transfer, it will have problems such as low conversion efficiency and light leakage that need to be solved. In recent years, due to its unique properties, perovskite materials have good applicability in solar cells, LEDs and lasers. With advantages such as size-dependent emission wavelength, high carrier mobility, and high photoinduced quantum yield, it is currently developing rapidly in display and is regarded as a new generation of promising lighting and display materials. Therefore, more and more research groups have begun to use perovskite materials for the research of future practical perovskite light-emitting diodes. Today, the external quantum efficiency of perovskite light-emitting diodes has exceeded 20%, which is comparable to classic OLEDs, further illustrating the huge potential of perovskite materials in new light-emitting LEDs. However, the current application is mainly in large-area, low-cost display and lighting, and there is still little research on combining with high-resolution display Mini / Micro-LED. Therefore, it is necessary to develop new Mini / Micro-LED processing technologies. Summary of the invention

[0003] In view of the existing perovskite materials and electroluminescent LED device structures, the present invention combines the existing laser processing technology to provide a method for preparing perovskite thin film electroluminescent Mini / Micro-LED, which realizes high-resolution electroluminescent Mini / Micro-LED display. This method changes the film structure morphology by laser processing the perovskite film, arrays the film, and finally realizes high-resolution display after completing the LED device structure.

[0004] A method for preparing a perovskite thin film electroluminescent Mini / Micro-LED comprises the following steps:

[0005] Step 1: In a coating machine in a glove box, spin-coat a polyvinyl carbazole (PVK) solution onto an ITO glass substrate as a hole transport layer and perform annealing treatment;

[0006] Step 2: In a coating machine, spin-coat the perovskite solution onto the hole transport layer and perform annealing to form a perovskite film;

[0007] Step 3: laser treatment of the perovskite film to form an arrayed area;

[0008] Step 4: Deposit the electron transport layer and the electrode in sequence on the arrayed film by vacuum coating.

[0009] Preferably, in step 1, 80 μL of polyvinyl carbazole solution is spin-coated on a clean ITO glass substrate as a hole transport layer, and annealed, wherein the hole transport layer thickness is 30 nm ± 2 nm, the spin coating speed is 3000 rpm, and the spin coating time is 30 seconds; the annealing is performed in a nitrogen environment, the annealing temperature is 120 ° C, and the annealing time is 20 minutes.

[0010] Preferably, the polyvinyl carbazole solution refers to a chlorobenzene solution of polyvinyl carbazole with a concentration of 5 mg / mL.

[0011] Preferably, in step 2, the perovskite solution is spin-coated on the hole transport layer and annealed to form a perovskite film, wherein the spin coating speed is 5000 rpm and the spin coating time is 30 seconds; the annealing temperature is 60° C. and the annealing time is 15 minutes.

[0012] Preferably, the perovskite in the perovskite solution is [(PEA) 0.75 (GA) 0.25 ]2CsPbCl 1.6 Br 5.4 , the solvent was dimethyl sulfoxide (DMSO), and the concentration of the perovskite solution was 0.2 mmol / ml.

[0013] Preferably, in step 3, the perovskite film is treated with laser to form an arrayed area. The specific process is as follows: the ITO glass substrate on which the perovskite film is formed is placed on a three-dimensional electric translation stage; according to the required array size and spacing, the three-dimensional translation stage is programmed to control the laser movement path; wherein the laser is a 405nm continuous laser with an energy of 50mW, and the moving speed of the three-dimensional electric translation stage is 1mm / s.

[0014] Preferably, in step 4, the electron transport layer and the electrode are sequentially deposited on the arrayed film by vacuum coating, wherein the electron transport layer is a TPBi film with a thickness of 30 nm; and the electrode is a LiF / Al electrode with a thickness of 0.6 nm / 100 nm.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention is carried out in a general laboratory environment, the operation is simple, and the cost of experimental equipment is low.

[0017] 2. The experimental optical path constructed by the present invention is simple and easy to understand, and other optical elements can be added or changed according to different materials.

[0018] 3. The present invention can meet the requirements of different resolutions without templates. By setting different laser parameters and writing path programs, arrays of different intervals and sizes can be realized on the perovskite film to meet the requirements of resolution.

[0019] 4. The present invention can realize Mini / Micro-LED display without the step of mass transfer, and the process is simple and the yield rate is high.

[0020] 5. The present invention has certain expansibility in terms of materials. In addition to the perovskite materials used in the present invention, the present invention also has certain applicability to other traditional quantum dot materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the LED device processing flow chart.

[0022] Figure 2 Schematic diagram of the LED device structure.

[0023] Figure 3 (a) is the perovskite [(PEA) in Example 1 0.75 (GA) 0.25 ]2CsPbCl 1.6 Br 5.4 (b) is a detailed picture of the perovskite array of Example 1 under a fluorescence microscope.

[0024] Figure 4 (a) is the perovskite PEA2Cs2Pb3Br in Example 2 10 (b) is a physical picture of the thin film after laser processing and the LED device structure is powered on. (b) is a physical picture of the perovskite CsPbI3 thin film after laser processing and the LED device structure is powered on in Example 3. DETAILED DESCRIPTION

[0025] The present invention is further explained below in conjunction with specific test examples. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0026] The present invention proposes a perovskite thin film electroluminescent Mini / Micro-LED based on laser processing technology. The perovskite thin film on the hole transport layer in the LED device structure is processed by laser, and the thin film is formed into a high-resolution array by changing the tissue morphology of the thin film. Then, the electron transport layer and the electrode are evaporated on the film to complete the LED device to achieve high-resolution array display. This method does not require steps such as mass transfer and color conversion, so that the conversion efficiency is higher, large-area preparation can be carried out in the later stage, and the operation is simple and the cost is low. The luminescent boundary is obvious under the microscope, indicating that it has the potential to prepare higher-resolution arrays. The design of complex patterns can also be achieved through programming design, thereby further enhancing the application of perovskite materials in Mini / Micro-LED displays.

[0027] Test Example 1

[0028] According to the preparation process and equipment, laser processing of perovskite film and completion of LED device structure are carried out. The specific process is mainly divided into five steps, and its main experimental equipment and operation process are as follows: Figure 1 and Figure 2 As shown. The laser is a 405nm continuous laser, the focusing lens has a magnification of ×50, NA0.5, and the perovskite is [(PEA) 0.75 (GA) 0.25 ]2CsPbCl 1.6 Br 5.4 , the ultrasonic cleaning solvents are acetone solution, ethanol solution, and deionized water.

[0029] The specific test steps are as follows:

[0030] Step 1: In a glove box, spin coat the polyvinyl carbazole (PVK) solution onto an ITO glass substrate as a hole transport layer (e.g. Figure 1 ). The steps are as follows:

[0031] Step 1.1: Place the ITO glass substrate in a beaker, add a certain amount of acetone solution to the beaker, submerge the substrate to be cleaned, turn on the ultrasonic cleaning machine, set the power, and perform ultrasonic cleaning on the ITO glass substrate for 15 minutes. Replace the cleaning solvent with ethanol solution and deionized water in turn, and repeat the above process to remove impurities on the surface of the ITO glass substrate.

[0032] Step 1.2: Dry the ITO glass substrate cleaned in step 1.1, and then place it in a UV O3 cleaning machine for further cleaning for 15 minutes.

[0033] Step 1.3: Transfer the ITO glass substrate cleaned in step 1.2 to a glove box filled with nitrogen, and then place the ITO glass substrate in a coater in the glove box to prepare the LED device structure.

[0034] Step 1.4: Set the parameters of the coating machine, speed 3000 rpm, time 30 seconds. Use a pipette to quickly drop 80 μL of the prepared PVK solution on the ITO glass substrate as a hole transport layer.

[0035] Step 1.5: After spin coating, annealing is performed on a heating table in a nitrogen environment at a temperature of 120°C for 20 minutes.

[0036] Step 2: In a coating machine, spin-coat the perovskite solution onto the hole transport layer to form a perovskite film. The steps are as follows:

[0037] Step 2.1: Transfer the sample to a spin coater and prepare the perovskite film. Set the spin coater parameters to 5000 rpm and 30 seconds. Use a pipette to quickly drop 100 μL of the prepared perovskite solution on the hole transport layer and turn on the spin coating button to form a film.

[0038] Step 2.2: Perform annealing treatment on a heating table at a temperature of 60°C for 15 minutes to form the light-emitting layer of the device.

[0039] Step 3: Use the constructed platform to treat the perovskite film with laser (e.g. Figure 1 ), forming an arrayed area. The steps are as follows:

[0040] Step 3.1: Use the 3D electric translation stage control software in the computer to write a 3D electric translation stage movement program according to the size of the sample and the preset array size and spacing, and set its path and speed.

[0041] Step 3.1.1: Set the starting position and the translation stage moving speed to 1 mm / s.

[0042] Step 3.1.2: Open the optical path shutter, move the 3D electric translation stage once in the horizontal direction, set the moving distance to L, and close the optical path shutter.

[0043] Step 3.1.3: The 3D motorized translation stage moves once in the vertical direction, sets the distance to S, and opens the optical path shutter.

[0044] Step 3.1.4: Move the 3D electric translation stage once in the opposite direction of step 3.1.2, set the moving distance to L, and close the optical path shutter.

[0045] Step 3.1.5: The three-dimensional motorized translation stage moves once in the vertical direction, sets the distance to S, and opens the optical path shutter.

[0046] Step 3.1.6: Repeat 3.1.2 to 3.1.5 N times and close the light path shutter.

[0047] Step 3.1.7: The three-dimensional electric translation stage moves once in the vertical direction, and the distance is set to P.

[0048] Step 3.1.8: Repeat 3.1.2 to 3.1.7, M times.

[0049] Step 3.1.9: Set the 3D motorized translation stage to move to the starting position.

[0050] Step 3.1.10: Open the optical path shutter, move the 3D electric translation stage once in the vertical direction, set the moving distance to L, and close the optical path shutter.

[0051] Step 3.1.11: The three-dimensional motorized translation stage moves once in the horizontal direction, sets the distance to S, and opens the optical path shutter.

[0052] Step 3.1.12: Move the 3D electric translation stage once in the opposite direction of step 3.1.10, set the moving distance to L, and close the optical path shutter.

[0053] Step 3.1.13: The three-dimensional motorized translation stage moves once in the horizontal direction, sets the distance to S, and opens the optical path shutter.

[0054] Step 3.1.14: Repeat 3.1.10 to 3.1.13, repeat N times, and close the light path shutter.

[0055] Step 3.1.15: The three-dimensional motorized translation stage moves once in the horizontal direction, and the distance is set to P.

[0056] Step 3.1.16: Repeat 3.1.10 to 3.1.15, repeat M times. At this time, the laser treatment process of the film is completed. At this time, the L*L area is (M-1) 2 An array of pixels.

[0057] Step 3.2: Place the sample prepared in step 2 on the three-dimensional electric translation stage.

[0058] Step 3.3: Control the three-dimensional electric translation stage through the computer to move the sample to the preset starting position.

[0059] Step 3.4: Set the laser parameters and adjust its energy. The laser light is reflected by a reflector and introduced into the focusing lens to focus on the perovskite surface.

[0060] Step 3.5: The moving path and speed of the three-dimensional electric translation stage are controlled by a computer program so that the laser completes the laser processing process on the perovskite film to form an arrayed area (such as Figure 2 ).

[0061] Step 4: Deposit the electron transport layer and the electrode (such as Figure 1 ), further complete the LED device structure. The steps are as follows:

[0062] Step 4.1: Place the target materials TPBi, LiF, and Al to be used for evaporation into the crucible of the deposition chamber of the vacuum coating machine in advance, and then place the sample prepared in step 3 into the deposition chamber.

[0063] Step 4.2: Turn on the water pump, air pump, and then turn on the power to perform vacuum treatment. Set the TPBi evaporation parameters, select the appropriate deposition speed by adjusting the voltage, and the deposition thickness is 30nm.

[0064] Step 4.3: When the sensor reading is close to the predetermined thickness, the deposition speed is reduced by lowering the voltage to ensure the accuracy of the deposition thickness. After the TPBi deposition is completed, the LiF parameters are set, and the appropriate deposition speed is selected. The deposition thickness is 0.6nm.

[0065] Step 4.4: After LiF deposition is completed, set the Al parameters, select an appropriate deposition rate, and the deposition thickness is 100nm. After Al deposition is completed, evaporation is completed.

[0066] Step 4.5: Turn off the vacuum coater and take out the sample.

[0067] Step 5: Encapsulate the sample with glass and UV-curing adhesive and power on the encapsulated sample for testing. The steps are as follows:

[0068] Step 5.1: Encapsulate the prepared sample with a glass slide and UV-curable adhesive. Use a glass slide for encapsulation to improve its stability.

[0069] Step 5.2: Power on the sample and perform a test, wherein the test voltage is 1.6-6.2V.

[0070] Figure 3 (a) is the electroluminescence image of the array, and (b) is a detailed image of the perovskite array under a fluorescence microscope.

[0071] Example 2

[0072] The specific process is the same as that in Example 1, and the perovskite material used is PEA2Cs2Pb3Br 10 The solvent used was dimethyl sulfoxide (DMSO), and the concentration of the perovskite solution was 0.2 mmol / ml. Figure 4 (a) in the figure is the electroluminescent image of the array.

[0073] Example 3

[0074] The specific process is the same as that of Example 1, the perovskite material used is CsPbI3, the solvent is n-octane, and the concentration of the perovskite solution is 0.55 mmol / ml. Figure 4 (b) is the electroluminescent image of the array.

Claims

1. A method for preparing a perovskite thin film electroluminescent Mini / Micro-LED, characterized in that: The following steps are involved: Step 1: In a coating machine in a glove box, spin-coat a polyvinyl carbazole solution onto an ITO glass substrate as a hole transport layer and perform annealing treatment; Step 2: In a coating machine, spin-coat the perovskite solution onto the hole transport layer and perform annealing to form a perovskite film; Step 3: laser treatment of the perovskite film to form an arrayed area; Step 4: Deposit the electron transport layer and the electrode in sequence on the arrayed film by vacuum coating.

2. The method according to claim 1, characterized in that In step 1, 80 μL of polyvinyl carbazole solution is spin-coated on a clean ITO glass substrate as a hole transport layer, and annealed, wherein the hole transport layer thickness is 30 nm ± 2 nm, the spin coating speed is 3000 rpm, and the spin coating time is 30 seconds; annealing is performed in a nitrogen environment, the annealing temperature is 120 ° C, and the annealing time is 20 minutes.

3. The method according to claim 1, characterized in that The polyvinylcarbazole solution refers to a chlorobenzene solution of polyvinylcarbazole with a concentration of 5 mg / mL.

4. The method according to claim 1, wherein: In step 2, the perovskite solution is spin-coated on the hole transport layer and annealed to form a perovskite film, wherein the spin coating speed is 5000 rpm and the spin coating time is 30 seconds; the annealing temperature is 60° C. and the annealing time is 15 minutes.

5. The method according to claim 1, wherein The perovskite in the perovskite solution is [(PEA) 0.75 (GA) 0.25 ]2CsPbCl 1.6 Br 5.4 , the solvent was dimethyl sulfoxide, and the concentration of the perovskite solution was 0.2 mmol / ml.

6. The method according to claim 1, characterized in that In step 3, the perovskite film is treated with laser to form an arrayed area. The specific process is as follows: the ITO glass substrate on which the perovskite film is formed is placed on a three-dimensional electric translation stage; the three-dimensional translation stage is programmed according to the required array size and spacing to control the laser movement path; the laser is a 405nm continuous laser with an energy of 50mW, and the moving speed of the three-dimensional electric translation stage is 1mm / s.

7. The method according to claim 1, characterized in that In step 4, an electron transport layer and an electrode are sequentially deposited on the arrayed film by a vacuum coating method, wherein the electron transport layer is a TPBi film with a thickness of 30 nm; and the electrode is a LiF / Al electrode with a thickness of 0.6 nm / 100 nm.

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