ODADBr in-situ passivated perovskite quantum dot high-efficiency light-emitting LED and its fabrication method

Abstract

This invention discloses a high-efficiency LED made of perovskite quantum dots with in-situ passivation using ODADBr and its preparation method. ITO is used as the anode; PEDOT:PSS is used as the hole injection layer with a thickness of 40 nm; Poly-TPD is used as the hole transport layer with a thickness of 20 nm; PMMA is used as the interface modification layer with a thickness of 5 nm; ODADBr is 1,8-octanediamine hydrobromide; the original CsPbBr3 quantum dots, in situ passivated with ODADBr, form the light-emitting layer with a thickness of 15 nm; TPBi is used as the electron transport layer with a thickness of 50 nm; LiF is used as the electron injection layer with a thickness of 1 nm; and Al is used as the cathode with a thickness of 100 nm. ODADBr passivation is used to passivate the surface traps of the CsPbBr3 quantum dots synthesized by high-temperature thermal injection, reducing excess Pb on the quantum dot surface. 2+ With V Br This improves the fluorescence lifetime, luminescence intensity, and fluorescence quantum yield (PLQY) of the material, thereby enhancing its stability. When applied to LEDs, this can achieve high brightness, high purity, high external quantum efficiency, and improved device lifespan.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of all-inorganic perovskite quantum dot preparation and lighting technology, and particularly relates to an ODADBr in-situ passivated perovskite quantum dot high-efficiency light-emitting LED and a preparation method thereof. BACKGROUND

[0002] In the information age, semiconductor displays play a very important role in people's lives and gradually become one of the main media for people to obtain information in daily life. At present, with the improvement of people's living standards and the increasingly serious problem of energy shortage, people are increasingly pursuing more energy-saving, environmentally friendly, high-definition, efficient and stable, large viewing angle, short response time and other display requirements. In order to meet these higher level requirements, it is necessary to improve the luminous efficiency of the material, develop new luminescent materials, and seek new device structures. Since quantum dots (QDs) are a kind of direct band gap semiconductor luminescent material, have high fluorescence quantum efficiency, high color purity, fast carrier transport, adjustable luminescence peak position, low cost, simple preparation method, good stability and other characteristics, they are widely studied by researchers and are applied to light-emitting diodes (LEDs) as a luminescent layer, which can obtain high external quantum efficiency, and has the advantages of low energy consumption, thin device, small volume, simple preparation method and the like. These excellent characteristics are expected to become the leader of the next generation of display technology.

[0003] Perovskite quantum dots are usually synthesized by high-temperature hot injection method. The perovskite QDs material synthesized by this method has high fluorescence quantum yield and uniform particle size distribution, so this synthesis method is most popular. Cs2CO3 and PbX2 are the most popular raw materials, and PbX2 provides Pb and halide at the same time. In an ideal perovskite crystal structure, Pb 2+ coordinates with X － to form a [PbX6] 4－ octahedral structure, Pb 2+ is located in the middle of the octahedron, X － is located at the eight vertices of the octahedron, and Cs + fills the voids of the eight octahedrons to form a cubic phase crystal structure. According to the ion reaction equation of perovskite quantum dots: 2Cs + + 3PbX2 = 2CsPbX3 + Pb 2+ It can be seen that there are uncoordinated lead ions on the surface of the prepared perovskite quantum dots, which further form halogen vacancies (Vx), and the structural schematic diagram is as follows: Figure 1Therefore, there are a large number of halogen vacancies (Vx) on the surface of the quantum dots, which capture charges as non-radiative recombination centers, cause exciton quenching, increase the proportion of non-radiative recombination, reduce the photoluminescence intensity of the material, and limit the improvement of the fluorescence quantum yield (PLQY). If the quantum dots are applied to a light-emitting device, the brightness and external quantum efficiency (EQE) of the device will be greatly reduced, thereby hindering the wide application of the CsPbX3 QD light-emitting device.

[0004] It is found that excessive Pb 2+ acts as a non-radiative recombination center in the quantum dots, causes exciton quenching, reduces the photoluminescence intensity of the material, and easily produces halogen ion defects in the quantum dots, which are usually halogen ion vacancies (Vx). The defects have a certain impact on the performance of the LED device. Therefore, the content of Pb 2+ is artificially and purposefully reduced by ion doping to reduce the halogen ion vacancies in the material and improve the stability and photoelectric properties of the material. Doping is to artificially introduce a certain material or ion of a certain material into the perovskite material to improve the luminescent properties of the material. Generally, Cu + , Ag + , K + , Cu 2+ , Mn 2+ , Zn 2+ , Sn 2+ , Co 2+ , Ni 2+ , Ce 3+ , Al 3+ , Bi 3+ and lanthanide ions partially replace Pb 2+ . Since the ionic radii of these ions are smaller than that of Pb 2+ , the tolerance factor and octahedral factor of the material can be improved, thereby improving the structural stability of the material. In addition, the doping of these ions can also reduce the excessive Pb 2+ on the surface of the quantum dots, reduce halogen ion vacancies (Vx), thereby reducing the energy loss caused by non-radiative recombination, and also enhancing the color purity, working stability, brightness and external quantum efficiency of the LED.

[0005] Although ion doping can reduce the excessive Pb 2+ on the surface of the quantum dots, reduce halogen vacancies and reduce the energy loss caused by non-radiative recombination, and improve the external quantum efficiency of the LED device, the improvement in brightness and EQE of the LED device by such doping is still limited. When the ion content is improperly doped, [PbX6] 4－The octahedral structure is distorted, the process of destroying the lattice of the perovskite quantum dot is orderly, and then as a capture center of photo-generated carriers, so that the fluorescence quantum yield is reduced, and new impurity defects are introduced, and most of the doping of rare earth ions also introduces new luminescent centers and energy transfer, which emits light of multiple wavelengths, thereby reducing the color purity of the LED device. Especially in the comparative experiment, a large amount of time and chemical drugs need to be consumed in multiple batches of high-temperature synthesis, and the luminescent properties of the material are different due to uncontrollable factors (such as: heating table temperature, method, drug weighing and microcosmic difference of oleic acid and oleylamine ligand) each time.

[0006] In order to solve the problems existing in the prior art, the application provides a perovskite quantum dot light-emitting LED with ODADBr in-situ passivation. 2+ With V Br , thereby improving the fluorescence lifetime, luminescent intensity and fluorescence quantum yield (PLQY) of the material, and improving the stability of the material, and when the material is applied to an LED, high brightness, high purity, high external quantum efficiency and long service life of the device can be realized. SUMMARY

[0007] (I) Technical problems to be solved

[0008] In view of the deficiencies of the prior art, the application provides a perovskite quantum dot light-emitting LED with ODADBr in-situ passivation and a preparation method thereof, which solves the problems proposed in the background art.

[0009] (II) Technical solutions

[0010] To achieve the above object, the application is implemented by the following technical solutions: the perovskite quantum dot light-emitting LED with ODADBr in-situ passivation adopts ITO as an anode, PEDOT:PSS as a hole injection layer with a thickness of 40nm, Poly-TPD as a hole transport layer with a thickness of 20nm, PMMA as an interface modification layer with a thickness of 5nm, ODADBr as 1,8-octanediamine hydrobromide, and the original and ODADBr in-situ passivated CsPbBr3 quantum dots as a light-emitting layer with a thickness of 15nm, TPBi as an electron transport layer with a thickness of 50nm, LiF as an electron injection layer with a thickness of 1nm, and Al as a cathode with a thickness of 100nm.

[0011] Preferably, the steps are as follows:

[0012] Step one: preparation of ODADBr in-situ passivated perovskite QDs solution: first, prepare ODADBr solution with a concentration of 5mg / mL, shake the QDs solution after centrifugal purification and then evenly divide it into two test tubes, one of which does not add ODADBr solution, and the other adds 40uL of ODADBr solution, and performs magnetic stirring;

[0013] Step two: filter the PEDOT:PSS solution with a water-based filter head to remove larger particles for standby;

[0014] Step three: prepare Poly-TPD solution with chlorobenzene as solvent, and then perform magnetic stirring to dissolve it, and then remove larger particles with an organic filter head for standby;

[0015] Step four: prepare PMMA solution and perform sufficient magnetic stirring;

[0016] Step five: clean the ITO glass sheet and perform UV ozone treatment on its surface for 15min;

[0017] Step six: spin-coat the PEDOT:PSS solution prepared in step two on the ITO prepared in step five at a speed of 4000rpm for 40s, and then perform annealing at 150℃ in air for 20min to obtain a PEDOT:PSS film;

[0018] Step seven: move the film prepared in step six to a N2 atmosphere glove box, and after the film temperature drops to room temperature, spin-coat the Poly-TPD prepared in step three on the PEDOT:PSS film at a speed of 4000rpm for 60s, and then perform annealing at 150℃ in N2 atmosphere for 20min to obtain a Poly-TPD film;

[0019] Step eight: after the film temperature in step seven drops to room temperature, spin-coat the PMMA solution prepared in step four on the Poly-TPD film at a speed of 5000rpm for 60s, and then perform annealing at 150℃ in N2 atmosphere for 20min to obtain a PMMA film;

[0020] Step nine: after the film temperature in step eight drops to room temperature, spin-coat the QDs solution prepared in step one on the PMMA film at a speed of 2000rpm for 60s to obtain a raw and ODADBr in-situ passivated perovskite quantum dot light-emitting layer;

[0021] Step ten: place the device obtained in step nine into an evaporation chamber, and then sequentially deposit TPBi, LiF and Al on the raw and ODADBr in-situ passivated perovskite quantum dot light-emitting layer by thermal evaporation under vacuum conditions.

[0022] Preferably, in step one, the solvent is anhydrous ethanol, and the magnetic stirring time is 15 minutes.

[0023] Preferably, in step two, the diameter of the water filter head is 0.22 μm.

[0024] Preferably, in step three, the concentration of the Poly-TPD solution is 8 mg / mL, the magnetic stirring time is 5-10 h, and the diameter of the organic filter head is 0.22 μm.

[0025] Preferably, in step four, the concentration of the PMMA solution is 3 mg / mL, the solvent is toluene, and the magnetic stirring time is 5-10 h.

[0026] Preferably, in step ten, the vacuum degree is <5*10 -4 Pa, evaporation rate are respectively and

[0027] (III) Beneficial Effects

[0028] This invention provides a high-efficiency light-emitting LED made of ODADBr-passivated perovskite quantum dots and its fabrication method. It has the following beneficial effects:

[0029] Through Br in 1,8-octanediamine hydrobromide (ODADBr) － In-situ passivation of bromine vacancy defects on the surface of CsPbBr3 quantum dots synthesized by high-temperature thermal injection was performed, thereby reducing excess Pb on the quantum dot surface. 2+ With V Br Br in ODADBr － A bromine-rich environment can be provided, which can inhibit the agglomeration of perovskite quantum dots during storage, thereby reducing the luminescence performance of the material and ultimately improving the fluorescence lifetime, luminescence intensity, and stability of CsPbBr3 quantum dots. Attached Figure Description

[0030] Figure 1 Schematic diagram of the principle structure of ODADBr in-situ passivation of CsPbBr3 quantum dots;

[0031] Figure 2 X-ray diffraction (XRD) patterns of the original and ODADBr-passivated CsPbBr3 quantum dots;

[0032] Figure 3 : UV absorption and fluorescence spectra of original and ODADBr passivated CsPbBr3 quantum dots. The inset shows photographs of the two samples under fluorescent and ultraviolet light.

[0033] Figure 4 :Depend onFigure 3 The defect density in the original and ODADBr passivated CsPbBr3 quantum dot materials was calculated from the ultraviolet absorption spectrum, also known as the Herbart energy or Urbach energy.

[0034] Figure 5 Fourier transform infrared (FTIR) spectra of pristine and ODADBr-passivated CsPbBr3 quantum dots;

[0035] Figure 6 Fluorescence lifetime (TRPL) curves of original and ODADBr-passivated CsPbBr3 quantum dots;

[0036] Figure 7 EDX top view of Cs, Pb, and Br elements in ODADBr passivated CsPbBr3 quantum dot films;

[0037] Figure 8 Schematic diagram of LED device structure;

[0038] Figure 9 Energy level matching diagram and schematic diagram of electron and hole migration pathways in perovskite quantum dot high-efficiency light-emitting LEDs;

[0039] Figure 10 Two-dimensional atomic force microscopy (AFM) images of original and ODADBr-passivated CsPbBr3 quantum dot films;

[0040] Figure 11 Current density-voltage-luminance (JVL) curves of high-efficiency CsPbBr3 quantum dot LEDs with original and ODADBr passivated forms;

[0041] Figure 12 Current efficiency-current density-external quantum efficiency (CE-J-EQE) curves of high-efficiency LEDs with CsPbBr3 quantum dots and those with passivated ODADBr.

[0042] Figure 13 Normalized PL spectra of ODADBr passivated CsPbBr3 quantum dot solutions and electroluminescence (EL) spectra of high-efficiency LED devices;

[0043] Figure 14 The current density-voltage curves of a single-emitting-layer LED device using pristine and ODADBr-passivated CsPbBr3 quantum dots are used to calculate the defect density in the quantum dot material. The device structure is: ITO / pristine and ODADBr-passivated CsPbBr3 quantum dots / Al.

[0044] Figure 15The operating lifetime curves of high-efficiency LEDs made from raw and ODADBr-passivated CsPbBr3 quantum dots are shown. The tests were conducted at a constant voltage of 4V and an initial brightness of 100 cd / m². 2 Measured under the conditions;

[0045] Figure 16 CIE color coordinate diagram of CsPbBr3 quantum dot high-efficiency light-emitting LEDs passivated with ODADBr, used to study the color purity of light emitted by LED devices. Detailed Implementation

[0046] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1:

[0048] The ODADBr in-situ passivated perovskite quantum dot high-efficiency light-emitting LED of the present invention uses ITO as the anode, PEDOT:PSS as the hole injection layer with a thickness of 40nm; Poly-TPD as the hole transport layer with a thickness of 20nm; PMMA as the interface modification layer with a thickness of 5nm; original and ODADBr in-situ passivated CsPbBr3 quantum dots as the light-emitting layer with a thickness of 15nm; TPBi as the electron transport layer with a thickness of 50nm; LiF as the electron injection layer with a thickness of 1nm; and Al as the cathode with a thickness of 100nm.

[0049] The steps are as follows:

[0050] 1. First, synthesize the precursor solution (cesium oleate) required for the preparation of quantum dots.

[0051] Add 814 mg of cesium carbonate (Cs₂CO₃), 2.5 mL of oleic acid (OA), and 30 mL of octadecene (ODE) to a 100 mL three-necked flask. Place the flask on a magnetic stirring platform and stir continuously at 1000 rpm. Perform multiple vacuuming and nitrogen purging at room temperature to achieve an anhydrous, oxygen-free, and carbon dioxide-free environment. Then raise the temperature to 120 °C and maintain the vacuum at 120 °C for 1 hour. After that, heat to 150 °C under a nitrogen atmosphere and continue heating until the Cs₂CO₃ solid particles are completely dissolved. Finally, stop heating and immediately use a disposable pipette to dispense the cesium oleate into clean small bottles, seal them, and store them in the refrigerator for later use.

[0052] 2. Synthesis of CsPbBr3 quantum dots

[0053] 138 mg of lead bromide (PbBr2) and 10 mL of ODE were added to a 50 mL three-necked flask. The flask was then placed on a magnetic stirring platform and stirred continuously at 1000 rpm. The flask was repeatedly evacuated and purged with nitrogen at room temperature to achieve an anhydrous and oxygen-free environment. The temperature was then raised to 120 °C under vacuum and maintained at 120 °C for 1.5 h. After 1.5 h, nitrogen (N2) was purged. Then, 1 mL of oleylamine (OM) and 1 mL of oleic acid (OA) ligands were injected. After the solution became clear, the temperature was raised to 180 °C. When the temperature reached 180 °C, 1 mL of the previously prepared cesium oleate precursor was immediately injected. After reacting for 5 seconds, the three-necked flask was quickly placed in an ice-water bath and stirred rapidly to lower the temperature to room temperature to prevent the quantum dots from growing further.

[0054] 3. Preparation of ODADBr solution

[0055] Prepare a 5 mg / mL ODADBr solution using anhydrous ethanol as the solvent. Add a magnetic stir bar to the solution and stir magnetically to accelerate dissolution. Most importantly, stop stirring immediately once the ODADBr solid particles have completely dissolved and the solution has become clear.

[0056] 4. Purification and passivation of CsPbBr3 quantum dots with ODADBr

[0057] After thoroughly mixing the synthesized quantum dot solution, add equal volumes to two 10 mL centrifuge tubes. Centrifuge at 5000 rpm for 10 min to separate any unreacted mixture. Discard the supernatant after centrifugation. Add 2 mL of toluene to each tube to dissolve the quantum dot. After dissolution, add 4 mL of ethyl acetate and centrifuge again at 10000 rpm for 10 min. Discard the supernatant after centrifugation. Add 2 mL of toluene to each tube to dissolve the quantum dot. Once completely dissolved, label one tube as Pristine and the other as In-situ passivated, and place them in clean magnetic stirrers. Do not add ODADBr solution to the Pristine tube. Add 40 μL of ODADBr solution to the In-situ passivated tube and immediately place it on a magnetic stirrer at room temperature for 15 min to allow ODADBr to fully passivate the bromine vacancies (V) on the surface of the CsPbBr3 quantum dots. BrTo remove any defects, after stirring, add 4 mL of ethyl acetate to each test tube, and then centrifuge again at 10000 rpm for 10 min. After centrifugation, discard the supernatant, add 0.9 mL of toluene to each test tube to dissolve the residue, and finally store in a refrigerator for later use.

[0058] 5. Fabrication of high-efficiency LED devices

[0059] Solution preparation: PEDOT:PSS needs to be filtered through a 0.22um water filter before use. Poly-TPD is 8mg / mL, and the solvent is chlorobenzene. PMMA is 3mg / mL, and the solvent is toluene.

[0060] Cleaning ITO glass slides: First, scrub the surface of the glass slide with dish soap, then rinse it with deionized water. Next, ultrasonically clean it for 20 minutes each with deionized water, acetone, and isopropanol. Finally, pour clean isopropanol into the glass slides to store them.

[0061] Dry the cleaned glass slide with nitrogen gas, place it in a plasma cleaner for UV treatment for 20 minutes, then place the ITO glass slide in the center of the spin coater tray and spin coat PEDOT:PSS at 4000 rpm for 40 seconds in an air atmosphere. Then place the glass slide on a heating table and anneal at 150°C for 20 minutes.

[0062] After annealing, the film was moved to an N2 glove box to cool down. After the temperature dropped to room temperature, Poly-TPD was spin-coated at 4000 rpm for 60 seconds. Then the film was placed on a heating table and annealed at 150°C for 20 minutes.

[0063] After the temperature drops to room temperature, spin-coat PMMA at 5000 rpm for 60 seconds, then place the film on a heating table and anneal at 150°C for 20 minutes.

[0064] After the temperature drops to room temperature, spin-coating of the original and ODADBr-passivated CsPbBr3 quantum dot solution is carried out at 2000 rpm for 60 s to prepare the light-emitting layer film.

[0065] Place the sample into the vacuum evaporation apparatus and wait for the vacuum level to reach 5*10. -4 When Pa is below a certain value, TPBi, LiF, and Al are sequentially deposited on the light-emitting layer film, with deposition rates of [missing values]. and

[0066] After the vapor deposition is completed, the LED device prepared by this invention is taken out and awaits testing.

[0067] 6. Testing and Experimental Analysis

[0068] To verify the performance of the high-efficiency LED device with ODADBr in-situ passivated CsPbBr3 quantum dots according to the present invention, the following tests and experimental analyses were conducted:

[0069] (1) In order to investigate whether in-situ passivation of ODADBr changes the crystal structure of quantum dot materials, we dropped the supernatant of the original and passivated perovskite quantum dots onto a silicon wafer and tested the X-ray diffraction (XRD) of the two samples respectively. The XRD data showed that both the original and passivated CsPbBr3 quantum dots exhibited a pure cubic perovskite crystal structure. The two curves corresponded one-to-one with the standard PDF card (PDF#54-0752), indicating that in-situ passivation of ODADBr did not change the crystal structure of CsPbBr3 quantum dots.

[0070] (2) Both samples were measured under the same experimental parameters. After in-situ passivation with ODADBr, the photoluminescence intensity of the CsPbBr3 quantum dots increased to 2.3 times that of the original quantum dots. The quantum dots after in-situ passivation with ODADBr exhibited brighter green light emission under ultraviolet light, indicating that passivation reduced the Vo on the surface of the CsPbBr3 quantum dots. Br Defect density, thereby reducing energy loss due to nonradiative recombination.

[0071] (3) Theoretically, in-situ passivation of ODADBr can reduce the defect density on the surface of CsPbBr3 quantum dots. To prove the feasibility of the theory, the Urbach energies of the original and passivated CsPbBr3 quantum dots were calculated. Figure 4 Data shows that the Urbach energy, Eu, decreased from the original 35.2 meV to 31.4 meV, indicating that in-situ passivation with ODADBr reduced the defect density on the quantum dot surface. Eu can be calculated using this formula. Furthermore, a single-layer LED device confirmed that passivation reduced the defect density in the material from the original 1.39 × 10⁻⁶. 20 cm -3 The defect density was reduced to 3.12*10 after passivation. 19 cm -3 The single-emitting-layer device structure adopts ITO / original or ODADBr in-situ passivated CsPbBr3 quantum dots / Al, and the defect density is calculated by formula;

[0072] (4) As can be seen from a large number of documents, when V exists on the surface of quantum dots Br When there is a defect, Pb 2+ It will be exposed and stabilized by oleic acid. It can be found that the FTIR peak positions of the surface ligands corresponding to the two quantum dots are the same, and the original and passivated quantum dots show the same peak position at 1466 cm⁻¹.-1 COOH was present at the location. － The stretching vibration peak (from the oleic acid ligand) further confirms the presence of V on the quantum dot surface. Br However, it was found that the COOH of the quantum dots after passivation... － The decrease in the intensity of the stretching vibration peak indicates that passivation reduced the defect density on the CsPbBr3 quantum dot surface, thus reducing Vt. Br At the same time, at 1577cm -1 NH3 was found at the site + Vibration peak (from ODAD) + The protonated amino group (-NH3) in the CsPbBr3 quantum dot is mainly due to the strong hydrogen bond formed between the protonated amino group (-NH3) and the bromine on the surface of the CsPbBr3 quantum dot, which allows the protonated amino group (-NH3) to attach to the surface of the CsPbBr3 quantum dot.

[0073] (5) To further clarify the reason for the enhanced fluorescence performance, the fluorescence lifetime of the two samples was tested, and the average lifetime τ of PL was obtained by double exponential fitting. ave This increases the average fluorescence lifetime of CsPbBr3 quantum dots from the original 5.21 ns to 9.03 ns after passivation. This further demonstrates that in-situ passivation with ODADBr reduces the defect state density in CsPbBr3 quantum dots.

[0074] (6) Br in ODADBr material - It can passivate the V in the original quantum dot Br The passivation process provides a bromine-rich environment and inhibits ion aggregation. Scanning electron microscopy (SEM) analysis of the elemental distribution and content in the quantum dot film revealed a remarkably uniform Br element distribution in the passivated CsPbBr3 quantum dot material. Furthermore, while the original CsPbBr3 quantum dots had a Cs:Pb:Br atomic ratio of 0.89:1:2.89, the passivated CsPbBr3 quantum dots exhibited a ratio of 0.89:1:3.06. This further demonstrates that in-situ passivation provides a rich bromine environment and reduces V in the material. Br The defect was addressed to suppress the aggregation of quantum dots during storage; detailed data can be found at [link to data]. Figure 7 ;

[0075] (7) Good interfacial contact can reduce the turn-on voltage of LED devices and facilitate charge transport. Therefore, preparing a light-emitting layer film with low roughness and relatively uniform surface morphology is extremely important for the application of the device. We tested the two-dimensional atomic force microscopy (AFM) patterns of films prepared from two different quantum dot materials. After in-situ passivation with ODADBr, the surface roughness of the CsPbBr3 quantum dot film decreased from the original 8.35 nm to 5.99 nm after passivation. This further demonstrates that passivation can form a dense and uniform light-emitting layer film, reducing leakage current caused by poor interfacial contact. Therefore, the passivated CsPbBr3 quantum dot film can form better interfacial contact in LED devices, reducing the LED's turn-on voltage (when the device brightness is 1 cd / m²). 2 The voltage applied at that time (called the turn-on voltage) is reduced from the original 3.07V to the passivated 3.01V;

[0076] (8) High-efficiency LED devices were fabricated using pristine and passivated CsPbBr3 quantum dots. By testing their voltage, current density, and brightness, calculations revealed that the CsPbBr3 quantum dot LED device passivated in situ with ODADBr exhibited a higher current density and greater brightness, with the maximum brightness increasing by a full five times from the original 10624 cd / m². 2 Increased to 53872 cd / m after passivation 2 The increase in brightness and current density indicates that in-situ passivation of ODADBr reduces the defect state density of the material, thereby increasing the carrier mobility, as demonstrated by TRPL, Eu, and single-emitting-layer devices, which reduce the defect state density of quantum dot materials.

[0077] (9) The current efficiency-current density-external quantum efficiency (CE-J-EQE) of the original and ODADBr-passivated CsPbBr3 quantum dot high-efficiency light-emitting LEDs were tested. The results showed that the maximum current efficiency of the passivated LED device increased from 4.4 cd / A to 14.1 cd / A, and the maximum external quantum efficiency of the LED increased from 1.3% to 4.23%.

[0078] (10) The normalized PL spectrum of the ODADBr passivated CsPbBr3 quantum dot solution and the electroluminescence (EL) spectrum of the high-efficiency LED device were tested respectively. The results showed that both EL and PL had emission peaks at 516 nm, and the full width at half maximum (FWHM) of EL and PL almost completely overlapped. This indicates that there is no energy transfer from smaller particles to larger particles in the light-emitting layer, and also indicates that the particle size distribution in CsPbBr3 quantum dots is relatively uniform.

[0079] (11) To study the working stability of LED devices, the devices were tested at a constant 4V and 100cd / m². 2 The relationship between brightness and time under initial conditions. Experiments showed that when the brightness dropped to half of its original value, the passivated device exhibited a slower decay trend, indicating that in-situ passivation reduces the density of bromine vacancy defects and can improve the working stability of LED devices.

[0080] Tests revealed that the CIE color coordinates of the ODADBr passivated CsPbBr3 quantum dot LED device were (0.06, 0.79), indicating that a particularly pure green light-emitting LED was achieved.

[0081] After in-situ passivation with ODADBr, the defect density in CsPbBr3 quantum dots was reduced from the original 1.39*10⁻⁶. 20 cm -3 The value was significantly reduced to 3.12*10 after passivation. 19 cm -3 The photoluminescence intensity of the passivated quantum dots increased to 2.3 times that of the original quantum dots, and the quantum dots after in-situ passivation with ODADBr exhibited brighter green light emission under ultraviolet light. The average fluorescence lifetime of CsPbBr3 quantum dots increased from 5.21 ns to 9.03 ns after passivation, further demonstrating that passivation reduced the defect density in the material. The surface roughness of the CsPbBr3 quantum dot film decreased from 8.35 nm to 5.99 nm after passivation, further indicating that passivation can form a dense and uniform light-emitting layer film, which is beneficial for LED device fabrication, reduces leakage current, and thus allows for better interfacial contact in LED devices, reducing the device's turn-on voltage from 3.07 V to 3.01 V after passivation. This also reduced the Vo content in the material. Br This addresses the defect by providing a bromine-rich environment, which in turn suppresses the aggregation of quantum dots during storage; it also improves the current density and brightness of LED devices, increasing the maximum brightness by a full five times, from the original 10624 cd / m². 2 Increased to 53872 cd / m after passivation 2 Furthermore, the maximum current efficiency of LED devices has increased from the original... Improved to passivation The maximum external quantum efficiency was increased from the original 1.3% to 4.23% after passivation; the LED device has a longer operating life;

[0082] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0083] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. Perovskite quantum dot light-emitting diodes (QLEDs) passivated in situ by ODADBr, characterized in that: The ITO is used as an anode, the PEDOT:PSS is a hole injection layer, the thickness is 40 nm; the Poly-TPD is a hole transport layer, the thickness is 20 nm; the PMMA is an interface modification layer, the thickness is 5 nm; the ODADBr is 1,8-octanediamine hydrobromide, the original and ODADBr in-situ passivated CsPbBr3 quantum dots are a light-emitting layer, the thickness is 15 nm; the TPBi is an electron transport layer, the thickness is 50 nm; the LiF is an electron injection layer, the thickness is 1 nm; the Al is a cathode, the thickness is 100 nm.

2. The method of claim 1, wherein the method of preparing the ODADBr perovskite quantum dot light-emitting LED passivated in situ is characterized by, The steps are as follows: Step one: preparation of ODADBr in-situ passivated perovskite QDs solution: first, prepare the ODADBr solution with a concentration of 5 mg / mL, shake the QDs solution after centrifugal purification, and then evenly divide it into two test tubes, one of which does not add ODADBr solution, and the other adds 40 uL of ODADBr solution, and performs magnetic stirring; Step two: filter the PEDOT:PSS solution with a water-based filter head to filter out larger particles for standby; Step three: prepare the Poly-TPD solution, the solvent is chlorobenzene, and then perform magnetic stirring to dissolve it, and then use an organic filter head to remove larger particles for standby; Step four: prepare the PMMA solution and perform sufficient magnetic stirring; Step five: clean the ITO glass sheet and perform UV ozone treatment on the surface for 15 min; Step six: spin-coat the PEDOT:PSS solution prepared in step two on the ITO prepared in step five at a speed of 4000 rpm for 40 s, and then perform annealing at 150°C in air for 20 min to obtain a PEDOT:PSS thin film; Step seven: move the thin film prepared in step six into a N2 atmosphere glove box, and after the temperature of the thin film decreases to room temperature, spin-coat the Poly-TPD prepared in step three on the PEDOT:PSS thin film at a speed of 4000 rpm for 60 s, and then perform annealing at 150°C in a N2 atmosphere for 20 min to obtain a Poly-TPD thin film; Step eight: after the temperature of the thin film in step seven decreases to room temperature, spin-coat the PMMA solution prepared in step four on the Poly-TPD thin film at a speed of 5000 rpm for 60 s, and then perform annealing at 150°C in a N2 atmosphere for 20 min to obtain a PMMA thin film; Step nine: after the temperature of the thin film in step eight decreases to room temperature, spin-coat the QDs solution prepared in step one on the PMMA thin film at a speed of 2000 rpm for 60 s to obtain an original and ODADBr in-situ passivated perovskite quantum dot light-emitting layer; Step ten: place the device obtained in step nine into an evaporation chamber, and then sequentially deposit TPBi, LiF and Al on the original and ODADBr in-situ passivated perovskite quantum dot light-emitting layer by thermal evaporation under vacuum conditions.

3. The method of claim 2, wherein the method further comprises: In step one, the solvent is anhydrous ethanol, and the magnetic stirring time is 15 min.

4. The method of claim 2, wherein the method further comprises: In step two, the diameter of the water-based filter head is 0.22 um.

5. The method of claim 2, wherein the method further comprises: In the third step, the concentration of the Poly-TPD solution is 8 mg / mL, the magnetic stirring time is 5-10 h, and the diameter of the organic filter head is 0.22 um.

6. The method of claim 2, wherein the method further comprises: In the fourth step, the concentration of the PMMA solution is 3 mg / mL, the solvent is toluene, and the magnetic stirring time is 5-10 h.

7. The method for preparing an ODADBr in-situ passivated perovskite quantum dot LED according to claim 2, characterized in that: The vacuum degree in the step ten is < 5*10 -4 The evaporation rate of the Alq3, the LiF and the Pa is 0.8 Å / s, 0.1 Å / s and 1.5 Å / s respectively.

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