Blue-light halide perovskite quantum dot light-emitting device and preparation method thereof

Abstract

The invention discloses a blue halide perovskite quantum dot light-emitting device and a preparation method thereof, and belongs to the field of quantum dot light-emitting materials and devices.The light-emitting device comprises a substrate printed 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 face to the other face, and the substrate, the PEDOT: PSS hole transport layer, the PVK hole transport layer, the perovskite quantum dot light-emitting layer, the TPBi electron transport layer, the LiF electron transport layer and the Al cathode are sequentially connected from one face to the other face. The light-emitting layer is a CsPbBr3 perovskite quantum dot material which is creatively synthesized in the invention, the CsPbBr3 perovskite quantum dot material provided by the invention is synthesized by using a thermal injection method, organic halide ammonium salt is introduced into the synthesized quantum dot as a bidentate ligand, the binding force between the new ligand and the surface of perovskite is stronger, and the perovskite quantum dot material is more stable in performance. The stability of the perovskite quantum dot material can be further improved, the size of the material is reduced by the ligand, the quantum confinement effect is enhanced, the light-emitting wavelength of the device is blue-shifted, and the wavelength of the perovskite light-emitting device is blue-shifted to the blue light band.

Description

Technical Field

[0001] The present invention belongs to the field of quantum dot luminescent materials and devices, and in particular relates to a blue light halide perovskite quantum dot luminescent device and a preparation method thereof. Background Art

[0002] Light-emitting diodes (LEDs) have surpassed traditional lighting sources and are profoundly changing the lighting and display industries. Today, a variety of materials are available for commercialized LEDs, such as III-V semiconductor LEDs, organic LEDs (OLEDs), and quantum dot LEDs (QLEDs). Blue, as one of the three primary colors, is an important component in lighting. OLEDs have become an alternative in the field of LEDs due to their solution and vacuum deposition capabilities, large-area light emission, and flexibility. However, low thermal and chemical stability under high brightness and high current density conditions severely limit the application of OLEDs. QLEDs exhibit excellent high color rendering index (CRI), high stability, and high efficiency, while core-shell quantum dots are difficult to achieve macroscopic manufacturing due to cumbersome manufacturing processes and expensive raw materials. All of these shortcomings hinder the progress of cost-effective multi-scenario electroluminescent applications. Finding promising electroluminescent materials is very important to promote the development of the lighting and display industries.

[0003] Metal halide perovskites (MHPs) are a promising new type of semiconductor material with the characteristics of low cost, spectral tunability and high photoluminescence quantum yields (PLQYs), which have broadened optoelectronic application scenarios. At present, the highest external quantum efficiency (EQE) of green perovskite LEDs (PeLEDs) and red PeLEDs exceeds 28%, which is comparable to traditional OLEDs and QLEDs. However, LEDs emitting in the blue band at around 470nm 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 light-emitting diodes. Therefore, when promoting the commercial development of PeLEDs, issues such as full width at half maximum (FWHM), reducing efficiency roll-off and extending the service life of devices should be considered.

[0004] At present, the main method of obtaining blue light using perovskite quantum dots is to add a certain amount of Cl element to CsPbBr3 perovskite quantum dots to prepare mixed halogen perovskite. However, the mixed halogen perovskite nanocrystalline material will undergo halogen element (Br, Cl) phase separation under the action of an electric field, resulting in a change in the spectrum, which in turn affects the wavelength stability of the light-emitting diode. In addition, the doping of Cl elements may also introduce more halogen defects into the nanocrystals, which in turn leads to a decrease in the performance and stability of the light-emitting device. Summary of the invention

[0005] The problem to be solved by the present invention is: how to provide a method for preparing a single halogen metal halide perovskite quantum dot material and device so that its electroluminescence (EL) spectrum band is within the blue light range while having better wavelength stability.

[0006] To solve the above problems, the present invention provides the following technical solutions: A blue light halide perovskite quantum dot light-emitting device comprises a substrate printed 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 connected in sequence from one side to the other.

[0007] A method for preparing a blue light halide perovskite quantum dot light emitting device comprises the following steps: S1: Place the substrate printed with ITO anode into a mixed solution of anhydrous ethanol and deionized water, and ultrasonicate it for 20 minutes, then blow dry the liquid on its surface with nitrogen; S2: Place the substrate printed with ITO anode into UV cleaning agent and clean it with UV ozone for 15 minutes; S3: Spin-coat a PEDOT:PSS film on a substrate printed with an ITO anode using a coater and heat it on a hot plate for 15 minutes to generate a PEDOT:PSS hole transport layer on the substrate with the ITO anode; S4: Place the substrate printed with the ITO anode in a nitrogen-filled glove box, spin-coat the PVK film, and heat it on a hot plate for 20 minutes to generate a PVK hole transport layer on the PEDOT:PSS hole transport layer; S5: After the PVK film is cooled, the perovskite quantum dot material is spin-coated on the PVK hole transport layer at a rotation speed of 4000 rpm, and heated at 60° C. for 5 minutes to generate a perovskite quantum dot light-emitting layer on the PVK hole transport layer; S6: Finally, the substrate printed with ITO anode is placed in the evaporation equipment and vacuumed. When the pressure is less than 5×10 -4 TPBi, LiF and AL thin films were sequentially evaporated at pa with thicknesses of 80nm, 1nm and 100nm respectively.

[0008] Preferably, in S5, the preparation method of the perovskite quantum dot material is: S5.1: Prepare a No. 1 three-necked flask and a No. 2 three-necked flask, both with a volume of 100 ml and a stirring bar; S5.2: a certain amount of PbBr2, ZnBr2, and TOPB2 are placed in a No. 1 three-necked flask and octadecene is added as a solvent; S5.3: Add a certain amount of Cs2CO3 and oleic acid into a No. 2 three-necked flask and add octadecene as a solvent; S5.4: Heat both flasks of solution to a specific temperature and evacuate them, and keep stirring under this condition for a period of time, then fill the No. 1 three-necked flask and the No. 2 three-necked flask with nitrogen and continue stirring; S5.5: Add a certain amount of oleic acid and oleylamine to the stirred three-necked flask No. 1, and after the solid in the solution is completely dissolved, evacuate the flask again, and switch back to the nitrogen environment after a few minutes; S5.6: Heat the No. 1 three-necked flask to a certain temperature, then take a certain amount of Cs-OA solution from the No. 2 three-necked flask and quickly inject it into the No. 1 three-necked flask, react for 5 seconds, then cool the No. 1 three-necked flask in an ice bath to obtain a crude perovskite quantum dot solution; S5.7: Add a certain amount of ethyl acetate to the cooled crude perovskite quantum dot solution and centrifuge it. Finally, redisperse it into an n-octane solution for storage to obtain a perovskite quantum dot material.

[0009] Preferably, the concentration of PbBr2 in the perovskite precursor solution is 13.7 mg / ml.

[0010] Preferably, the concentration of ZnBr2 in the perovskite precursor solution is 0-42.56 mg / ml.

[0011] Preferably, TOPB2 is an organic halide diammonium salt, specifically 3,3'-[1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl]bis(propane-1-ammonium) bromide, having the chemical formula: 20 H 22 Br2N4O4, the addition amount range is 5-20mg, the chemical structure is: .

[0012] Compared with the existing material synthesis method, the present invention has the following advantages: 1. This application uses a single halogen Br to synthesize CsPbBr3 metal halide perovskite quantum dot material, and uses the quantum confinement effect to increase the band gap of the material, rather than introducing the Cl element to adjust the band gap of the perovskite material. This fundamentally avoids the inherent problem brought about by mixed halogen perovskite nanocrystalline materials: halogen phase separation under an electric field. Thereby improving the spectral stability of the material; 2. This application adds 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) as a bidentate ligand to bind to the surface of perovskite quantum dots, providing stronger surface stability for quantum dots, enhancing their quantum confinement effect, and blue-shifting the emission wavelength of CsPbBr3 mineral quantum dots to the blue light band. In addition, the Br atoms in TOPB2 can provide a halogen-rich environment for quantum dot materials, further enhancing the quantum confinement effect of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic structural diagram of the light emitting diode device involved in the present invention; The markings in the figure are: 1-substrate printed with ITO anode; 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 DESCRIPTION

[0014] In order to facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific examples. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0015] The concentration unit mM used in this application is an abbreviation for millimole per liter.

[0016] Example 1 (control group) (1) Synthesis and purification of perovskite quantum dot materials: Prepare three-necked flask No. 1 and three-necked flask No. 2, both with a capacity of 100 ml and a stirring bar. Wash them with deionized water and ethanol and blow dry them. Put 0.137g PbBr2 and 0.511g ZnBr2 into three-necked flask No. 1 and add 10ml octadecene as precursor solution No. 1. Add 0.18g Cs2CO3 and 1ml oleic acid and add 10ml octadecene into three-necked flask No. 2 as precursor solution No. 2. Heat the above two bottles of solution to 60°C and evacuate them. Keep stirring under this condition for 30 minutes. Then fill the two flasks with nitrogen and evacuate immediately. After three cycles, heat them to 120°C and keep them in a vacuum state for 30 minutes. Then adjust the heating temperature of the two flasks to 100°C and fill the flasks with nitrogen. When the temperature of the No. 1 three-necked flask reaches 100°C, add 2ml oleic acid and 3.5ml oleylamine to the No. 1 precursor solution with a syringe and stir for 1 minute. After the solid is completely dissolved, evacuate the transparent solution in the bottle for 2 minutes, and then heat the solution to 150°C under nitrogen. At this time, extract 1ml Cs-OA solution from the No. 2 precursor solution and quickly inject it into the No. 1 three-necked flask. After reacting for 5 seconds, place the No. 1 three-necked flask in ice water prepared in advance to cool it. Transfer the cooled perovskite quantum dot crude solution into a centrifuge tube and add 40ml ethyl acetate, centrifuge at 11000rpm for 1 minute. Subsequently, the supernatant was discarded and the precipitate obtained after centrifugation was redispersed in 4 ml of n-octane solvent. 8 ml of ethyl acetate was added to the above solution and centrifuged again at the same speed for 1 min. 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 mins to remove large particles. Finally, the supernatant obtained by low-speed centrifugation was filtered through a 0.22 micron filter head and placed in a clean glass bottle and sealed for storage.

[0017] (2) Preparation of quantum dot light-emitting diodes: The substrate 1 printed with ITO anode was ultrasonically cleaned with deionized water and anhydrous ethanol for 15 minutes, and treated with ultraviolet ozone for 15 minutes. The filtered PEDOT:PSS was then spin-coated on the substrate 1 printed with ITO anode (rotation speed was 4000 rpm for 40 seconds) as the PEDOT:PSS hole transport layer 2, and annealed at 150 degrees Celsius for 15 minutes. Then, PVK was dissolved in chlorobenzene at a concentration of 4 mg / ml, and spin-coated on PEDOT:PSS at a rotation speed of 1000 rpm for 40 seconds as the PVK hole transport layer 3, and annealed at 160 degrees Celsius for 30 minutes. The perovskite quantum dot material was spin-coated on the PVK film at a rotation speed of 4000 rpm as the perovskite quantum dot light-emitting layer 4, and annealed at 60 degrees Celsius for 5 minutes. Finally, the spin-coated substrate is transferred to an evaporator, and TPBi, LiF and Al are sequentially evaporated as TPBi electron transport layer 5, LiF electron transport layer 6 and Al cathode 7, with thicknesses of 80 nm, 1 nm and 100 nm respectively, to finally complete the structure as shown in FIG. Figure 1 shown.

[0018] Example 2 (1) Synthesis and purification of perovskite quantum dot materials: Prepare a No. 1 three-necked flask and a No. 2 three-necked flask, each with a stirring bar and a volume of 100 ml, wash with deionized water and ethanol, blow dry, and put a clean magnet. Put 0.137g PbBr2, 0.511g ZnBr2 and 5mg TOPB2 into the No. 1 three-necked flask and add 10ml octadecene as the No. 1 precursor solution, add 0.18g Cs2CO3 and 1ml oleic acid into the No. 2 three-necked flask and add 10ml octadecene as the No. 2 precursor solution. The rest is the same as Example 1.

[0019] (2) Preparation of quantum dot light-emitting diodes: This part is exactly the same as Example 1.

[0020] Example 3 (1) Synthesis and purification of perovskite quantum dot materials: Prepare a No. 1 three-necked flask and a No. 2 three-necked flask, both with a stirring bar and a volume of 100 ml, wash with deionized water and ethanol and blow dry, put 0.137g PbBr2, 0.511g ZnBr2 and 10mg TOPB2 into the No. 1 three-necked flask and add 10ml octadecene as the No. 1 precursor solution, add 0.18g Cs2CO3 and 1ml oleic acid into the No. 2 three-necked flask and add 10ml octadecene as the No. 2 precursor solution. The rest is the same as Example 1.

[0021] (2) Preparation of quantum dot light-emitting diodes: This part is exactly the same as Example 1.

[0022] Example 4 (1) Synthesis and purification of perovskite quantum dot materials: Prepare a No. 1 three-necked flask and a No. 2 three-necked flask, both with a stirring bar and a volume of 100 ml, wash with deionized water and ethanol and blow dry, put 0.137g PbBr2, 0.511g ZnBr2 and 15mg TOPB2 into the No. 1 three-necked flask and add 10ml octadecene as the No. 1 precursor solution, add 0.18g Cs2CO3 and 1ml oleic acid into the No. 2 three-necked flask and add 10ml octadecene as the No. 2 precursor solution. The rest is the same as Example 1.

[0023] (2) Preparation of quantum dot light-emitting diodes: This part is exactly the same as Example 1.

[0024] Example 5 (1) Synthesis and purification of perovskite quantum dot materials: Prepare a No. 1 three-necked flask and a No. 2 three-necked flask, both with a stirring bar and a volume of 100 ml, wash with deionized water and ethanol and blow dry, put 0.137g PbBr2, 0.511g ZnBr2 and 20mg TOPB2 into the No. 1 three-necked flask and add 10ml octadecene as the No. 1 precursor solution, add 0.18g Cs2CO3 and 1ml oleic acid into the No. 2 three-necked flask and add 10ml octadecene as the No. 2 precursor solution. The rest is the same as Example 1.

[0025] (2) Preparation of quantum dot light-emitting diodes: This part is exactly the same as Example 1.

[0026]

[0027] Table 1 EL performance of perovskite quantum dot LEDs It can be seen from Table 1 that as the amount of TOPB2 added increases (Examples 1-5), the electroluminescence wavelength of the device undergoes a significant blue shift, which indicates that the TOPB2 bidentate ligand effectively increases the band gap of the light-emitting layer material. This is because the size of the material is reduced under the encapsulation of the bidentate ligand, which in turn enhances the quantum confinement effect of the material and increases the band gap of the material, thereby causing a blue shift in the emission wavelength. In addition, as the TOPB2 content increases (Examples 1-4), the EQE of the LED device is significantly improved. This is because the TOPB2 ligand has a stronger binding ability with the surface of the perovskite quantum dots than the traditional oleic acid and oleylamine ligands, which effectively reduces the defects on the surface of the material, thereby significantly improving the luminous efficiency. It is worth noting that if the amount of TOPB2 added is too much (Example 5), the EQE will decline. This may be due to the introduction of too many organic ammonium ions, which causes the precursor to be in an overly strong alkaline environment, thereby causing the surface of the quantum dots to be damaged by the alkaline environment.

[0028] The present invention has been described by the above embodiments, but it should be understood that the above embodiments are only for the purpose of example and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, it can be understood by those skilled in the art that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of the protection claimed by the present invention. The protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A blue light halide perovskite quantum dot light emitting device, characterized in that: The invention comprises a substrate (1) printed with an ITO anode, 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 connected in sequence from one side to the other side.

2. The method for preparing a blue light halide perovskite quantum dot light emitting device according to claim 1, characterized in that: The following steps are involved: S1: Place the substrate (1) printed with the ITO anode in a mixed solution of anhydrous ethanol and deionized water, and ultrasonicate it for 20 minutes using an ultrasonic machine, and then blow dry the liquid on its surface with nitrogen; S2: placing the substrate (1) printed with the ITO anode in a UV cleaning agent and cleaning it with UV ozone for 15 minutes; S3: Spin-coating a PEDOT:PSS film on a substrate (1) printed with an ITO anode using a coater and heating it on a hot plate for 15 minutes to form a PEDOT:PSS hole transport layer (2) on the substrate with the ITO anode; S4: Place the substrate (1) printed with the ITO anode in a glove box filled with nitrogen, spin-coat the PVK film, and heat it on a hot plate for 20 minutes to generate a PVK hole transport layer (3) on the PEDOT:PSS hole transport layer (2); S5: After the PVK film is cooled, the perovskite quantum dot material is spin-coated on the PVK hole transport layer (3) at a rotation speed of 4000 rpm, and heated at 60° C. for 5 minutes to generate a perovskite quantum dot light-emitting layer (4) on the PVK hole transport layer (3); S6: Finally, the substrate (1) printed with the ITO anode is placed in a vacuum deposition device. When the pressure is less than 5×10 -4 TPBi, LiF and AL thin films were sequentially evaporated at pa with thicknesses of 80nm, 1nm and 100nm respectively.

3. The method for preparing a blue light halide perovskite quantum dot light emitting device according to claim 2, characterized in that: In S5, the preparation method of the perovskite quantum dot material is: S5.1: Prepare a No. 1 three-necked flask and a No. 2 three-necked flask, both with a volume of 100 ml and a stirring bar; S5.2: a certain amount of PbBr2, ZnBr2, and TOPB2 are placed in a No. 1 three-necked flask and octadecene is added as a solvent; S5.3: Add a certain amount of Cs2CO3 and oleic acid into a No. 2 three-necked flask and add octadecene as a solvent; S5.4: Heat both flasks of solution to a specific temperature and evacuate them, and keep stirring under this condition for a period of time, then fill the No. 1 three-necked flask and the No. 2 three-necked flask with nitrogen and continue stirring; S5.5: Add a certain amount of oleic acid and oleylamine to the stirred three-necked flask No. 1, and after the solid in the solution is completely dissolved, evacuate the flask again, and switch back to the nitrogen environment after a few minutes; S5.6: Heat the No. 1 three-necked flask to a certain temperature, then take a certain amount of Cs-OA solution from the No. 2 three-necked flask and quickly inject it into the No. 1 three-necked flask, react for 5 seconds, then cool the No. 1 three-necked flask in an ice bath to obtain a crude perovskite quantum dot solution; S5.7: Add a certain amount of ethyl acetate to the cooled crude perovskite quantum dot solution and centrifuge it. Finally, redisperse it into an n-octane solution for storage to obtain a perovskite quantum dot material.

4. The method for preparing a blue light emitting halide perovskite quantum dot light emitting device according to claim 3, characterized in that: The concentration of PbBr2 in the perovskite precursor solution was 13.7 mg / ml.

5. The method for preparing a blue light emitting halide perovskite quantum dot light emitting device according to claim 3, characterized in that: The concentration of ZnBr2 in the perovskite precursor solution was 0-42.56 mg / ml.

6. The method for preparing a blue light emitting halide perovskite quantum dot light emitting device according to claim 3, characterized in that: The chemical formula of TOPB2 is: 20 H 22 Br2N4O4, the addition amount range is 5-20mg, the chemical structure is: 。

Images