Quantum dot light emitting device and method of manufacturing the same

Abstract

The application discloses a quantum dot light-emitting device and a preparation method thereof, and utilizes single halogen Br to synthesize CsPbBr3 metal halide perovskite quantum dot material, utilizes quantum confinement effect to increase the band gap of the material, fundamentally avoids the inherent problems brought by mixed halogen perovskite nanocrystal material, i.e. halogen phase separation under electric field, thereby improving the spectral stability of the material; by adding a certain amount of 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthrolin-2,7-diyl]bis(propane-1-aminium) bromide as a bidentate ligand in the first precursor and combining with the perovskite quantum dot surface, stronger surface stability is provided for the quantum dot, the quantum confinement effect of the quantum dot is enhanced, the luminescence wavelength of the CsPbBr3 perovskite quantum dot is blue-shifted to the blue light wavelength band, in addition, the Br atoms in TOPB2 can provide a halogen-rich environment for the quantum dot material, and the quantum confinement effect of the material is further enhanced.

Description

Technical Field

[0001] This invention relates to the field of quantum dot light emission technology, and in particular to a quantum dot light emission device and its fabrication method. Background Technology

[0002] Light-emitting diodes (LEDs) are transcending traditional lighting sources and profoundly transforming the lighting and display industries. Today, a variety of materials are available for commercially available LEDs, such as III-V semiconductor LEDs, organic LEDs (OLEDs), and quantum dot LEDs (QLEDs). Blue, as one of the three primary colors, is a crucial component of lighting. OLEDs have emerged as a potential alternative to LEDs due to their solution and vacuum deposition capabilities, large-area light emission, and flexibility. However, their low thermal and chemical stability under high brightness and current density conditions severely limits their application. QLEDs exhibit excellent high color rendering index (CRI), high stability, and high efficiency, while core-shell quantum dots are difficult to manufacture on a macro scale due to complex manufacturing processes and expensive raw materials. All these drawbacks hinder the progress of cost-effective multi-scenario electroluminescent applications. Finding promising electroluminescent materials is crucial for advancing 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 470 nm still lag behind green and red PeLEDs. Low color purity, moderate external efficiency, and poor device lifetime are serious obstacles to the commercialization of perovskite LEDs. Therefore, in promoting the commercialization of PeLEDs, issues such as full width at half maximum (FWHM), reducing efficiency roll-off, and extending device lifespan should be considered.

[0004] Currently, the main method for obtaining blue light using perovskite quantum dots is to dope CsPbBr3 perovskite quantum dots with a certain amount of chlorine (Cl) to prepare mixed halide perovskites. However, under the influence of an electric field, the mixed halide perovskite nanocrystals undergo halogen (Br, Cl) phase separation, leading to changes in the spectrum and affecting the wavelength stability of the light-emitting diode. Furthermore, chlorine doping may introduce more halogen defects into the nanocrystals, further degrading the performance and stability of the light-emitting device.

[0005] Therefore, it is necessary to develop a quantum dot light-emitting device and its fabrication method to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to design a quantum dot light-emitting device and its fabrication method in order to solve the above-mentioned problems.

[0007] The present invention achieves the above objectives through the following technical solutions:

[0008] A quantum dot light-emitting device includes a substrate with an ITO anode, a PEDOT:PSS hole transport layer, a PVK hole transport layer, a perovskite quantum dot light-emitting layer, a TPBi electron transport layer, a LiF electron transport layer, and an Al cathode, which are sequentially connected from one side to the other.

[0009] Methods for fabricating quantum dot light-emitting devices include:

[0010] 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.

[0011] 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.

[0012] S3. Spin coat a PEDOT:PSS film onto a clean substrate printed with an ITO anode using a spin coater, and heat it on a hot plate for 15 minutes.

[0013] S4. Place the product treated in step S3 into a glove box filled with nitrogen and spin coat it with PVK, and heat it on a hot plate for 20 minutes.

[0014] S5. After cooling down after processing in 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.

[0015] 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.

[0016] Furthermore, the synthesis and purification process of the perovskite quantum dot luminescent layer material includes the following steps:

[0017] 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.

[0018] S52. PbBr2, ZnBr2 and 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium) bromide were placed into a three-necked flask and octadecene was added as a solvent.

[0019] S53. Add Cs2CO3 and oleic acid to the No. 2 three-necked flask, and add octadecene as a solvent;

[0020] 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.

[0021] 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.

[0022] 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.

[0023] S57. Add 20 ml of ethyl acetate to the cooled crude perovskite quantum dot solution and centrifuge. Finally, redisperse the solution in n-octane for storage.

[0024] Preferably, in step S52, the concentration of PbBr2 is 13.7 mg / ml.

[0025] Preferably, in step S52, the concentration of ZnBr2 is 51.15 mg / ml.

[0026] Preferably, the chemical formula of 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium) bromide is C 20 H 22 Br2N4O4, chemical structural formula is:

[0027] .

[0028] Preferably, in step S52, the amount of 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium) bromide added ranges from 5 to 20 mg.

[0029] The beneficial effects of this invention are as follows:

[0030] (1) CsPbBr3 metal halide perovskite quantum dot materials were synthesized using a single halogen, Br, and the band gap of the material was increased by utilizing the quantum confinement effect, rather than by introducing Cl to adjust the band gap of the perovskite material. This fundamentally avoids the inherent problem of halogen phase separation under an electric field in mixed halogen perovskite nanocrystal materials, thereby improving the spectral stability of the material;

[0031] (2) By adding a certain amount of 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium) bromide (TOPB2) to the first precursor as a bidentate ligand to bind with the perovskite quantum dot surface, stronger surface stability is provided to the quantum dots, thereby enhancing their quantum confinement effect and causing the emission wavelength of CsPbBr3 quantum dots to shift to the blue light band. In addition, the Br atoms in TOPB2 can provide a halogen-rich environment for the quantum dot material, further enhancing the quantum confinement effect of the material. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the quantum dot light-emitting device in this invention.

[0033] 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

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0039] 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.

[0040] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0041] like Figure 1 As shown, the quantum dot light-emitting device includes a substrate with an ITO anode, a PEDOT:PSS hole transport layer, a PVK hole transport layer, a perovskite quantum dot light-emitting layer, a TPBi electron transport layer, a LiF electron transport layer, and an Al cathode, which are sequentially connected from one side to the other.

[0042] Methods for fabricating quantum dot light-emitting devices include:

[0043] 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.

[0044] 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.

[0045] S3. Spin coat a PEDOT:PSS film onto a clean substrate printed with an ITO anode using a spin coater, and heat it on a hot plate for 15 minutes.

[0046] S4. Place the product treated in step S2 into a glove box filled with nitrogen and spin coat it with PVK, and heat it on a hot plate for 20 minutes.

[0047] S5. After cooling down after processing in S3, 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.

[0048] S6. Place the product treated in S4 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.

[0049] In some embodiments, the synthesis and purification process of the perovskite quantum dot light-emitting layer material includes the following steps:

[0050] 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.

[0051] S52. PbBr2, ZnBr2 and 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium) bromide were placed into a three-necked flask and octadecene was added as a solvent.

[0052] S53. Add Cs2CO3 and oleic acid to the No. 2 three-necked flask, and add octadecene as a solvent;

[0053] 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.

[0054] 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.

[0055] 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.

[0056] S57. Add 20 ml of ethyl acetate to the cooled crude perovskite quantum dot solution and centrifuge. Finally, redisperse the solution in n-octane for storage.

[0057] In some embodiments, in step S52, the concentration of PbBr2 is 13.7 mg / ml.

[0058] In some embodiments, in step S52, the concentration of ZnBr2 is 51.15 mg / ml.

[0059] In some embodiments, the chemical formula of 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium)bromide is C 20 H 22 Br2N4O4, chemical structural formula is:

[0060] .

[0061] In some embodiments, in step S52, the amount of 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium) bromide added ranges from 5 to 20 mg.

[0062] Example 1 (Control Group):

[0063] (1) Synthesis and purification of quantum dot materials:

[0064] 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 0.511g 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. Afterward, heat both flasks to 120℃ and maintain vacuum, stirring for another 30 minutes. Next, 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.

[0065] (2) Fabrication of quantum dot light-emitting devices:

[0066] 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.

[0067] Example 2:

[0068] (1) Synthesis and purification of quantum dot materials:

[0069] Prepare two 100ml three-necked glass flasks, rinse them with deionized water and ethanol, dry them, and place clean magnetic stir bar inside. Add 0.137g PbBr2, 0.511g ZnBr2, and 5mg TOPB2 to flask No. 1, and add 10ml octadecene as the first precursor solution. Add 0.18g Cs2CO3 and 1ml oleic acid to flask No. 2, and add 10ml octadecene as the second precursor solution. The remaining steps are the same as in Example 1.

[0070] (2) Fabrication of quantum dot light-emitting devices:

[0071] This part is exactly the same as in Example 1.

[0072] Example 3:

[0073] (1) Synthesis and purification of quantum dot materials:

[0074] Prepare two 100ml three-necked glass flasks, rinse them with deionized water and ethanol, dry them, and place clean magnetic stir bar inside. Add 0.137g PbBr2, 0.511g ZnBr2, and 10mg TOPB2 to flask No. 1, and add 10ml octadecene as the first precursor solution. Add 0.18g Cs2CO3 and 1ml oleic acid to flask No. 2, and add 10ml octadecene as the second precursor solution. The remaining steps are the same as in Example 1.

[0075] (2) Fabrication of quantum dot light-emitting diodes:

[0076] This part is the same as in Example 1.

[0077] Example 4:

[0078] (1) Synthesis and purification of quantum dot materials:

[0079] Prepare two 100ml three-necked glass flasks, rinse them with deionized water and ethanol, dry them, and place clean magnetic stir bar inside. Add 0.137g PbBr2, 0.511g ZnBr2, and 15mg TOPB2 to flask No. 1, and add 10ml octadecene as the first precursor solution. Add 0.18g Cs2CO3 and 1ml oleic acid to flask No. 2, and add 10ml octadecene as the second precursor solution. The remaining steps are the same as in Example 1.

[0080] (2) Fabrication of quantum dot light-emitting diodes:

[0081] This part is the same as in Example 1.

[0082] Example 5:

[0083] (1) Synthesis and purification of quantum dot materials:

[0084] Prepare two 100ml three-necked glass flasks, rinse them with deionized water and ethanol, dry them, and place clean magnetic stir bar inside. Add 0.137g PbBr2, 0.511g ZnBr2, and 20mg TOPB2 to flask No. 1, and add 10ml octadecene as the first precursor solution. Add 0.18g Cs2CO3 and 1ml oleic acid to flask No. 2, and add 10ml octadecene as the second precursor solution. The remaining steps are the same as in Example 1.

[0085] (2) Fabrication of quantum dot light-emitting diodes:

[0086] This part is the same as in Example 1.

[0087] EL peak wavelength (nm) external quantum efficiency of LED devices Example 1 502 4.8% Example 2 483 7% Example 3 475 9.6% Example 4 470 12.% Example 5 466 11.2%

[0088] Table 1. EL performance of perovskite quantum dot LEDs

[0089] As shown in Table 1 and the attached figures, with the increase of TOPB2 content (Examples 1-5), the electroluminescence wavelength of the device exhibits a significant blue shift, indicating that the TOPB2 bidentate ligand effectively increases the band gap of the luminescent layer material. This is because the material size decreases under the coating of the bidentate ligand, thereby enhancing the quantum confinement effect and increasing the band gap, thus causing a blue shift in the emission wavelength. Furthermore, with the increase of TOPB2 content (Examples 1-4), the EQE of the LED device significantly improves. This is because the TOPB2 ligand phase has a stronger binding ability to the perovskite quantum dot surface compared to traditional oleic acid and oleylamine ligands, effectively reducing surface defects and thus significantly improving luminous efficiency. It is worth noting that if too much TOPB2 is added (Example 5), the EQE declines. This may be due to the introduction of excessive organic ammonium ions, resulting in an overly alkaline environment for the precursor, which in turn damages the quantum dot surface.

[0090] 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, characterized in that, The synthesis and purification process of perovskite quantum dot luminescent layer materials includes 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, ZnBr2, and 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium) bromide are placed in a three-necked flask and octadecene is added as a solvent. The amount of 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium) bromide added ranges from 5 to 20 mg. 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 the solution from step S53 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 solution of perovskite quantum dots. S57. Add 20 ml of ethyl acetate to the cooled crude perovskite quantum dot solution and centrifuge. Finally, redisperse the solution in n-octane for storage. The 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium) bromide added in step S52 has the chemical formula C 20 H 22 Br2N4O4, chemical structural formula is: 。 2. The method for fabricating a quantum dot light-emitting device according to claim 1, characterized in that, In step S52, the concentration of PbBr2 is 13.7 mg / ml.

3. The method for fabricating a quantum dot light-emitting device according to claim 1, characterized in that, In step S52, the concentration of ZnBr2 is 51.15 mg / ml.

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