A method for preparing a quantum dot light emitting device based on an amount of ion additives

Abstract

The application discloses a preparation method of a quantum dot light-emitting device based on an ion additive, utilizes single halogen Br to synthesize CsPbBr3 metal halide perovskite quantum dot material, and fundamentally avoids inherent problems caused by mixed halogen perovskite nanocrystal material, i.e. halogen phase separation under an electric field. By adding an ion additive, i.e. (2-bromoethyl)diphenyl sulfonium trifluoromethane sulfonate, into the quantum dot, as a kind of anion and cation ligand, the ion additive is strongly combined with the perovskite quantum dot surface and fills the lattice defects on the perovskite quantum dot surface, so that the quantum dot is provided with a more perfect lattice structure and stronger surface stability, defect-induced non-radiation recombination and spectrum shift caused by ripening are effectively inhibited, and the LED device prepared based on the perovskite quantum dot has higher light-emitting efficiency and operation life.

Description

Technical Field

[0001] This invention relates to the field of quantum dot light emission technology, and in particular to a method for preparing a quantum dot light emission device based on ionic additives. Background Technology

[0002] Light-emitting diodes (LEDs) have transcended traditional lighting sources and are profoundly reshaping the lighting and display industries. Currently, various types of LED materials are commercially available, including III-V semiconductor LEDs, organic light-emitting diodes (OLEDs), and quantum dot light-emitting diodes (QLEDs). As one of the three primary colors, blue light plays a crucial role in lighting technology. OLEDs, with their advantages of being able to be fabricated through solution processing or vacuum deposition, supporting large-area uniform light emission, and possessing flexibility, are considered an important alternative to LEDs; however, their insufficient thermal and chemical stability at high brightness and high current densities severely restricts their practical application. In contrast, QLEDs exhibit high color rendering index (CRI), excellent stability, and high luminous efficiency, but their core core-shell quantum dot structure is difficult to mass-produce due to complex fabrication processes and high raw material costs. These limitations hinder the widespread application of low-cost, multi-scenario electroluminescent technology. Therefore, developing promising new electroluminescent materials is crucial for driving the continued progress of the lighting and display industries.

[0003] Metal halide perovskites (MHPs) are promising new semiconductor materials with advantages such as low cost, spectral tunability, and high photoluminescence quantum yield (PLQYs), offering broad application prospects in optoelectronics. Currently, the highest external quantum efficiency (EQE) of green and red perovskite LEDs exceeds 28%, comparable to traditional OLEDs and QLEDs. However, blue-band LEDs emitting at around 480nm still lag behind green and red PeLEDs. Low color purity, poor external quantum efficiency, and device lifetime are serious obstacles to the commercialization of perovskite LEDs. Therefore, in promoting the commercialization of PeLEDs, issues such as reducing efficiency roll-off and extending device lifespan should be considered.

[0004] Due to the weak bonding between traditional ligands and the surface of CsPbBr3 perovskite quantum dots, they are prone to ripening during purification, leading to increased size and spectral shift. Therefore, the main method for achieving blue light emission from perovskite quantum dots is to dope CsPbBr3 quantum dots with a certain amount of Cl to prepare mixed halide perovskites. However, mixed halide perovskite nanocrystals undergo halogen (Br, Cl) phase separation under an electric field, resulting in spectral changes. Simultaneously, this phase separation generates more ionic defects, further reducing the luminous efficiency and lifetime of the light-emitting device.

[0005] Here, we have developed a method for fabricating quantum dot light-emitting devices based on ionic additives to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to design a method for preparing quantum dot light-emitting devices based on ionic additives in order to solve the above problems.

[0007] The present invention achieves the above objectives through the following technical solutions: A method for fabricating a quantum dot light-emitting device based on ionic additives includes the following steps: S1. Place the substrate with the ITO anode printed on it into a mixed solution of anhydrous ethanol and deionized water, and sonicate it for 20 minutes with an ultrasonic machine. Then, blow the liquid on its surface with nitrogen. S2. Place the dried substrate with the ITO anode printed on it into the UV cleaning agent and clean it with UV ozone for 15 minutes. S3. Spin coat a PEDOT:PSS film onto the clean substrate with ITO anode printed on it after the previous step using a spin coater, and heat it on a hot plate for 15 minutes. S4. Place the product treated in step S3 into a glove box filled with nitrogen to spin coat a PVK film, and heat it on a hot table for 20 minutes. S5. After cooling down after step S4, spin-coat a perovskite quantum dot light-emitting layer onto the PVK film at a speed of 4000 rpm and heat at 60°C for 5 minutes. S6. Place the product treated in S5 into the vapor deposition equipment and apply a vacuum. When the air pressure is less than 5 × 10⁻⁶, -4 TPBi, LiF and AL thin films were deposited at Pa with thicknesses of 80 nm, 1 nm and 100 nm, respectively.

[0008] Furthermore, step S5 also includes the preparation of the perovskite quantum dot luminescent layer, including: S51. Prepare two three-necked flasks, No. 1 and No. 2, each with a volume of 100ml, and place a stir bar in each of the two flasks. S52. PbBr2 and ZnBr2 are placed into a three-necked flask and octadecene is added as a solvent. S53. Add Cs2CO3 and oleic acid to the No. 2 three-necked flask, and add octadecene as a solvent; S54. Heat the solutions in the No. 1 and No. 2 three-necked flasks to 120°C and evacuate them. Maintain this condition and stir for one hour. Then fill the two three-necked flasks with nitrogen and continue stirring. S55. Reduce the temperature of the two flasks to 100°C and add oleic acid and oleylamine to the stirring three-necked flask No. 1. After the solid in the solution is completely dissolved, evacuate the vacuum again and switch back to the nitrogen environment after 1 minute. S56. Heat the No. 1 three-necked flask to a temperature of 150°C. At this time, take 1 ml of Cs-OA solution from the No. 2 three-necked flask and quickly inject it into the No. 1 three-necked flask. After reacting for 5 seconds, cool the No. 1 three-necked flask in an ice bath to obtain a crude perovskite quantum dot solution. S57. Add 40 ml of ethyl acetate to the cooled crude perovskite quantum dot solution and centrifuge. Redisperse the precipitate in n-octane solution, add another 8 ml of ethyl acetate, centrifuge again, and redisperse the precipitate in n-octane. S58. Centrifuge the perovskite quantum dot solution obtained in step S57 at a low speed of 5500 rpm and filter to remove large particles. S59. Add (2-bromoethyl)diphenylsulfonate trifluoromethane sulfonate solution to the perovskite quantum dot solution obtained in step S58 at a volume ratio of one-tenth, stir evenly and seal for storage.

[0009] Preferably, the chemical formula of (2-bromoethyl)diphenylsulfonate trifluoromethane sulfonate added in step S59 is C 15 H 14 BrF3O3S2, chemical structural formula is: .

[0010] Preferably, in step S59, the concentration range of the (2-bromoethyl)diphenylsulfonium trifluoromethane sulfonate solution is 10-25 mg / ml, and the solvent is chloroform.

[0011] Preferably, in step S52, the concentration of PbBr2 is 13.7 mg / ml.

[0012] Preferably, in step S52, the concentration of ZnBr2 is 102.3 mg / ml.

[0013] The beneficial effects of this invention are as follows: (1) The synthesis of CsPbBr3 blue light perovskite quantum dot materials using a single halogen Br fundamentally avoids the inherent problem of halogen phase separation under an electric field in mixed halogen perovskite nanocrystal materials. At the same time, the strong bonding force between (2-bromoethyl)diphenylsulfonium trifluoromethane sulfonate and the surface of perovskite quantum dots firmly fixes the surface of perovskite nanocrystals, making them less prone to ripening that leads to spectral shift, thereby improving the spectral stability of the material; (2) By adding a certain amount of ionic additive (2-bromoethyl)diphenylsulfonate trifluoromethane sulfonate to the perovskite solution as an anionic and cationic ligand, it combines with the surface of the perovskite quantum dots and fills the lattice defects on the surface of the perovskite quantum dots, providing the quantum dots with a more perfect lattice structure and stronger surface stability, effectively suppressing defect-induced nonradiative recombination, and enabling the LED devices prepared based on the perovskite quantum dots to obtain higher luminous efficiency and operating life. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the quantum dot light-emitting device prepared by the present invention.

[0015] The following are labeled in the figure: 1. Substrate with ITO anode printed on it; 2. PEDOT:PSS hole transport layer; 3. PVK hole transport layer; 4. Perovskite quantum dot light-emitting layer; 5. TPBi electron transport layer; 6. LiF electron transport layer; 7. Al cathode. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0017] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0018] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0019] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figure, or the orientation or positional relationship that the product of this invention is usually placed in when in use, or the orientation or positional relationship that is commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0021] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0023] A method for fabricating a quantum dot light-emitting device based on ionic additives, comprising: S1. Place the substrate with the ITO anode printed on it into a mixed solution of anhydrous ethanol and deionized water, and sonicate it for 20 minutes with an ultrasonic machine. Then, blow the liquid on its surface with nitrogen. S2. Place the dried substrate with the ITO anode printed on it into the UV cleaning agent and clean it with UV ozone for 15 minutes. S3. Spin coat a PEDOT:PSS film onto the clean substrate with ITO anode printed on it after the previous step using a spin coater, and heat it on a hot plate for 15 minutes. S4. Place the product treated in step S3 into a glove box filled with nitrogen to spin coat a PVK film, and heat it on a hot table for 20 minutes. S5. After cooling down after step S4, spin-coat a perovskite quantum dot light-emitting layer onto the PVK film at a speed of 4000 rpm and heat at 60°C for 5 minutes. S6. Place the product treated in S5 into the vapor deposition equipment and apply a vacuum. When the air pressure is less than 5 × 10⁻⁶, -4 TPBi, LiF and AL thin films were deposited at Pa with thicknesses of 80 nm, 1 nm and 100 nm, respectively.

[0024] In some embodiments, step S5 further includes the preparation of a perovskite quantum dot light-emitting layer, the preparation of which includes synthesis and purification processes, specifically including the following steps: S51. Prepare two three-necked flasks, No. 1 and No. 2, each with a volume of 100ml, and place a stir bar in each of the two flasks. S52. PbBr2 and ZnBr2 are placed into a three-necked flask and octadecene is added as a solvent. S53. Add Cs2CO3 and oleic acid to the No. 2 three-necked flask, and add octadecene as a solvent; S54. Heat the solutions in the No. 1 and No. 2 three-necked flasks to 120°C and evacuate them. Maintain this condition and stir for one hour. Then fill the two three-necked flasks with nitrogen and continue stirring. S55. Reduce the temperature of the two flasks to 100°C and add oleic acid and oleylamine to the stirring three-necked flask No. 1. After the solid in the solution is completely dissolved, evacuate the vacuum again and switch back to the nitrogen environment after 1 minute. S56. Heat the No. 1 three-necked flask to a temperature of 150°C. At this time, take 1 ml of Cs-OA solution from the No. 2 three-necked flask and quickly inject it into the No. 1 three-necked flask. After reacting for 5 seconds, cool the No. 1 three-necked flask in an ice bath to obtain a crude perovskite quantum dot solution. S57. Add 40 ml of ethyl acetate to the cooled crude perovskite quantum dot solution and centrifuge. Redisperse the precipitate in n-octane solution, add another 8 ml of ethyl acetate, centrifuge again, and redisperse the precipitate in n-octane. S58. Centrifuge the perovskite quantum dot solution obtained in step S57 at a low speed of 5500 rpm and filter to remove large particles. S59. Add (2-bromoethyl)diphenylsulfonate trifluoromethane sulfonate solution to the perovskite quantum dot solution obtained in step S58 at a volume ratio of one-tenth, stir evenly and seal for storage.

[0025] In some embodiments, in step S52, the concentration of PbBr2 is 13.7 mg / ml.

[0026] In some embodiments, in step S52, the concentration of ZnBr2 is 102.3 mg / ml.

[0027] In some embodiments, the chemical formula of (2-bromoethyl)diphenylsulfonate trifluoromethane sulfonate added in step S59 is C 15 H 14 BrF3O3S2, chemical structural formula is: .

[0028] In some embodiments, in step S59, the concentration of the (2-bromoethyl)diphenylsulfonium trifluoromethane sulfonate solution ranges from 10 to 25 mg / ml, and the solvent is chloroform.

[0029] like Figure 1 As shown, a quantum dot light-emitting device prepared by the method of this application includes a substrate 1 with an ITO anode printed on it, a PEDOT:PSS hole transport layer 2, a PVK hole transport layer 3, a perovskite quantum dot light-emitting layer 4, a TPBi electron transport layer 5, a LiF electron transport layer 6, and an Al cathode 7, which are sequentially connected from one side to the other.

[0030] Example 1 (Control Group): (1) Synthesis and purification of quantum dot materials: Prepare two 100ml three-necked glass flasks, clean them with deionized water and ethanol, dry them, and place clean magnetic stir bar inside. Add 0.137g PbBr2 and 1.023g ZnBr2 to flask No. 1, along with 10ml octadecene as the first precursor solution. Add 0.18g Cs2CO3 and 1ml oleic acid to flask No. 2, along with 10ml octadecene as the second precursor solution. Heat both solutions to 60℃ and evacuate them under vacuum, stirring for 30 minutes. Then, fill both flasks with nitrogen and immediately evacuate them under vacuum. Repeat this cycle three times, then heat to 120℃ and maintain vacuum while stirring for 30 minutes. Afterward, adjust the heating temperature of both flasks to 100℃ and fill them with nitrogen. When flask No. 1 reaches 100℃, add 2ml oleic acid and 3.5ml oleylamine dropwise to the first precursor solution using a syringe and stir for 1 minute. After the solid in the solution was completely dissolved, the transparent solution in the flask was evacuated for 2 minutes, and then heated to 150°C under nitrogen. At this time, 1 ml of Cs-OA solution was drawn from the second precursor solution and quickly injected into the first flask. After reacting for 5 seconds, the first flask was placed in a pre-prepared ice water to cool. The cooled crude perovskite quantum dot solution was transferred to a centrifuge tube and 40 ml of ethyl acetate was added. The mixture was centrifuged at 11000 rpm for 1 minute. The supernatant was then discarded, and the precipitate obtained after centrifugation was redispersed in 4 ml of n-octane. 8 ml of ethyl acetate was added to the above solution, and the mixture was centrifuged again at the same speed for 1 minute. The supernatant was discarded, and the precipitate was dissolved in 1.5 ml of n-octane. After the precipitate was completely dispersed, it was centrifuged at a low speed of 5500 rpm for 5 minutes to remove large particles. Finally, the supernatant obtained from the low-speed centrifugation was filtered through a 0.22-micron filter and placed in a clean glass bottle for sealing and storage.

[0031] (2) Fabrication of quantum dot light-emitting devices: The ITO-printed glass substrate was ultrasonically cleaned with deionized water and anhydrous ethanol for 15 min each, and then treated with ultraviolet ozone for 15 min. Filtered PEDOT:PSS was then spin-coated onto the ITO substrate at 4000 rpm for 40 s as a hole transport layer and annealed at 150°C for 15 min. Next, PVK was dissolved in chlorobenzene at a concentration of 4 mg / ml and spin-coated onto the PEDOT:PSS at 1000 rpm for 40 s as a hole injection layer, and annealed at 160°C for 30 min. Perovskite quantum dots were then spin-coated onto the PVK film at 4000 rpm as a light-emitting layer and annealed at 60°C for 5 min. Finally, the spin-coated substrate was transferred to an evaporator, where TPBi, LiF, and Al were sequentially deposited as electron transport layers and metal electrodes, with thicknesses of 80 nm, 1 nm, and 100 nm, respectively.

[0032] Example 2: (1) Synthesis and purification of quantum dot materials: After filtration, 0.15 ml of (2-bromoethyl)diphenylsulfonium trifluoromethane sulfonate solution with a concentration of 10 mg / ml and chloroform as the solvent was added to the purified quantum dot solution. The remainder was the same as in Example 1.

[0033] (2) Fabrication of quantum dot light-emitting devices: This part is exactly the same as in Example 1.

[0034] Example 3: (1) Synthesis and purification of quantum dot materials: After filtration, 0.15 ml of (2-bromoethyl)diphenylsulfonium trifluoromethane sulfonate solution with a concentration of 15 mg / ml was added to the purified quantum dot solution in chloroform. The remainder was the same as in Example 1.

[0035] (2) Fabrication of quantum dot light-emitting diodes: This part is the same as in Example 1.

[0036] Example 4: (1) Synthesis and purification of quantum dot materials: After filtration, 0.15 ml of (2-bromoethyl)diphenylsulfonium trifluoromethane sulfonate solution with a concentration of 20 mg / ml was added to the purified quantum dot solution in chloroform. The remainder was the same as in Example 1.

[0037] (2) Fabrication of quantum dot light-emitting diodes: This part is the same as in Example 1.

[0038] Example 5: (1) Synthesis and purification of quantum dot materials: After filtration, 0.15 ml of (2-bromoethyl)diphenylsulfonium trifluoromethane sulfonate solution with a concentration of 25 mg / ml was added to the purified quantum dot solution in chloroform. The remainder was the same as in Example 1.

[0039] (2) Fabrication of quantum dot light-emitting diodes: This part is the same as in Example 1.

[0040]

[0041] Table 1. Luminescent performance of CsPbBr3 perovskite quantum dot light-emitting devices As shown in Table 1, with the increase of the concentration of (2-bromoethyl)diphenylsulfonate trifluoromethane sulfonate solution (Examples 1-5), the operating life T of the LED increases. 50 The time required for the brightness to decrease to 50% of the initial brightness under constant current when the initial brightness is 100 nits is significantly increased. This is because the added (2-bromoethyl)diphenylsulfonate trifluoromethanesulfonate strongly binds to the halogens on the surface of the perovskite quantum dots, suppressing halogen defects generated in the LED device under continuous voltage stimulation, thereby extending its operating life. In addition, as the concentration of the added (2-bromoethyl)diphenylsulfonate trifluoromethanesulfonate solution increases (Examples 1-5), the external quantum efficiency of the LED device is significantly improved. This is because the sulfonate and Br atoms in (2-bromoethyl)diphenylsulfonate trifluoromethanesulfonate modify the surface lattice of the perovskite quantum dots, effectively passivating defects on the surface of the quantum dot material and suppressing defect-induced nonradiative recombination, thereby significantly improving its luminous efficiency. However, if the concentration of the (2-bromoethyl)diphenylsulfonium trifluoromethane sulfonate solution is too high (Example 5), it will not increase the external quantum efficiency indefinitely, and may even decline to some extent. This may be because too much organic material with poor conductivity is introduced, making current injection more difficult, and the inability to effectively inject charge carriers negatively affects its electroluminescence performance.

[0042] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a quantum dot light-emitting device based on ionic additives, characterized in that, Includes the following steps: S1. Place the substrate with the ITO anode printed on it into a mixed solution of anhydrous ethanol and deionized water, and sonicate it for 20 minutes with an ultrasonic machine. Then, blow the liquid on its surface with nitrogen. S2. Place the dried substrate with the ITO anode printed on it into the UV cleaning agent and clean it with UV ozone for 15 minutes. S3. Spin coat a PEDOT:PSS film onto the clean substrate with ITO anode printed on it after the previous step using a spin coater, and heat it on a hot plate for 15 minutes. S4. Place the product treated in step S3 into a glove box filled with nitrogen to spin coat a PVK film, and heat it on a hot table for 20 minutes. S5. After cooling down after step S4, spin-coat a perovskite quantum dot light-emitting layer onto the PVK film at a speed of 4000 rpm and heat at 60°C for 5 minutes. S6. Place the product treated in S5 into the vapor deposition equipment and apply a vacuum. When the air pressure is less than 5 × 10⁻⁶, -4 TPBi, LiF and AL thin films were deposited at Pa with thicknesses of 80 nm, 1 nm and 100 nm, respectively.

2. The method for fabricating a quantum dot light-emitting device based on ionic additives according to claim 1, characterized in that, Step S5 also includes the fabrication of the perovskite quantum dot luminescent layer, including: S51. Prepare two three-necked flasks, No. 1 and No. 2, each with a volume of 100ml, and place a stir bar in each of the two flasks. S52. PbBr2 and ZnBr2 are placed into a three-necked flask and octadecene is added as a solvent. S53. Add Cs2CO3 and oleic acid to the No. 2 three-necked flask, and add octadecene as a solvent; S54. Heat the solutions in the No. 1 and No. 2 three-necked flasks to 120°C and evacuate them. Maintain this condition and stir for one hour. Then fill the two three-necked flasks with nitrogen and continue stirring. S55. Reduce the temperature of the two flasks to 100°C and add oleic acid and oleylamine to the stirring three-necked flask No.

1. After the solid in the solution is completely dissolved, evacuate the vacuum again and switch back to the nitrogen environment after 1 minute. S56. Heat the No. 1 three-necked flask to a temperature of 150°C. At this time, take 1 ml of Cs-OA solution from the No. 2 three-necked flask and quickly inject it into the No. 1 three-necked flask. After reacting for 5 seconds, cool the No. 1 three-necked flask in an ice bath to obtain a crude perovskite quantum dot solution. S57. Add 40 ml of ethyl acetate to the cooled crude perovskite quantum dot solution and centrifuge. Redisperse the precipitate in n-octane solution, add another 8 ml of ethyl acetate, centrifuge again, and redisperse the precipitate in n-octane. S58. Centrifuge the perovskite quantum dot solution obtained in step S57 at a low speed of 5500 rpm and filter to remove large particles. S59. Add (2-bromoethyl)diphenylsulfonate trifluoromethane sulfonate solution to the perovskite quantum dot solution obtained in step S58 at a volume ratio of one-tenth, stir evenly and seal for storage.

3. The method for fabricating a quantum dot light-emitting device based on ionic additives according to claim 2, characterized in that, The chemical formula of (2-bromoethyl)diphenylsulfonate trifluoromethane sulfonate added in step S59 is C 15 H 14 BrF3O3S2, chemical structural formula is: 。 4. In the method for preparing a quantum dot light-emitting device based on ionic additives according to claim 2, in step S59, the concentration range of the (2-bromoethyl)diphenylsulfonium trifluoromethane sulfonate solution is 10-25 mg / ml, and the solvent is chloroform.

5. In the method for preparing a quantum dot light-emitting device based on ionic additives according to claim 2, in step S52, the concentration of PbBr2 is 13.7 mg / ml.

6. In the method for preparing a quantum dot light-emitting device based on ionic additives according to claim 2, in step S52, the concentration of ZnBr2 is 102.3 mg / ml.

Images