InP-based quantum dot and preparation method and application thereof

Abstract

The invention provides an InP-based quantum dot and a preparation method and application thereof, and the preparation method comprises the following steps: (1) mixing an indium precursor, a fatty acid ligand and a non-coordination solvent, carrying out first dehydration and deoxidation treatment to obtain a precursor solution, heating, injecting a phosphorus precursor, and carrying out a reaction to obtain an InP crystal nucleus; (2) mixing a zinc precursor and a non-coordination solvent, adding an organic amine ligand after second dehydration and deoxidation treatment, adding the InP crystal nucleus obtained in the step (1) after heating, adding DPP-Se and the zinc precursor after further heating, and carrying out first epitaxial growth to obtain InP-coated ZnSe; and (3) mixing the InP-coated ZnSe obtained in the step (2), a zinc precursor and a sulfur precursor, and carrying out second epitaxial growth to obtain the InP-coated ZnSe-coated ZnS. According to the quantum dot prepared by the method, the shell layer grows isotropically, and the quantum dot has strong electron confinement capability.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal-free quantum dots and quantum dot light-emitting diodes (QLEDs), and relates to an InP-based quantum dot, its preparation method, and its application. Background Technology

[0002] QLED has become a key candidate for next-generation display technology due to its advantages such as high color purity, wide color gamut, and low power consumption. For a long time, the best-performing quantum dots have been based on cadmium (Cd)-containing II-VI group materials. However, the high toxicity of Cd severely limits its large-scale commercial application. In recent years, heavy metal-free InP-based quantum dots have gradually become an important alternative to CdSe.

[0003] Although the external quantum efficiency (EQE) of green InP-based QLEDs has been significantly improved, their performance still lags significantly behind that of CdSe-based devices. The main reasons are: (1) InP has a small effective electron mass, requiring a more uniform and isotropic shell coating to achieve effective electron confinement; (2) Currently, the epitaxial growth of ZnSe shells on the InP core surface exhibits significant crystal plane selectivity, and it grows rapidly on the InP(111) crystal plane, resulting in a pod-like structure of quantum dots and a weak electron confinement morphology; (3) Electrons are prone to shell leakage, leading to low charge recombination efficiency, enhanced parasitic luminescence, and accelerated hole transport layer degradation, thereby significantly reducing device efficiency and lifetime.

[0004] Current mainstream methods for addressing this problem mainly include optimizing growth through shell composition control, elemental doping, and organic ligand engineering. For example, doping the ZnSe shell with metal ions aims to alter the shell band structure to enhance electronic confinement; or constructing ZnSe... x S 1-x Gradient alloy shells are used to alleviate lattice mismatch. At the same time, carboxylic acid ligands (such as oleic acid) are often used to regulate the chemical reactivity of different crystal planes through their competitive adsorption on the InP core surface, thereby inhibiting the excessively rapid growth of the (111) crystal plane.

[0005] However, doping methods struggle to precisely control the uniform distribution of ions, easily introducing defects into the crystal lattice. Furthermore, carboxylic acid ligands exhibit insufficient thermal stability during high-temperature shell growth, potentially detaching from the InP surface, leading to incomplete passivation and the introduction of new non-radiative recombination centers. These strategies fail to fundamentally achieve uniform, isotropic shell coating of the InP core, thus failing to completely resolve the problems of weakened electron confinement and leakage.

[0006] Therefore, developing a fabrication strategy that can suppress crystal plane selective growth, achieve uniform coating of InP@ZnSe shell, and thus obtain a strongly electron-confined structure is of great significance for improving the performance of InP-based QLEDs. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an InP-based quantum dot, its preparation method, and its applications. The method provided by this invention can prepare green InP@ZnSe@ZnS quantum dots with isotropic shell growth, strong electron confinement capability, and highly symmetrical morphology. This solves the problem of insufficient electron confinement caused by selective growth of the ZnSe shell crystal plane in existing InP-based quantum dots, significantly improving the efficiency, color purity, and lifespan of QLEDs.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing InP-based quantum dots, the method comprising:

[0010] (1) The indium precursor, fatty acid ligand and non-coordination solvent are mixed and subjected to a first dehydration and deoxygenation treatment to obtain a precursor solution. After heating, the phosphorus precursor is injected to react and InP crystal nuclei are obtained.

[0011] (2) The zinc precursor and non-coordination solvent are mixed, and after the second dehydration and deoxygenation treatment, an organic amine ligand is added. After heating, the InP crystal nucleus described in step (1) is added. After further heating, DPP-Se and the zinc precursor are added to carry out the first epitaxial growth to obtain InP@ZnSe.

[0012] (3) Mix the InP@ZnSe, zinc precursor and sulfur precursor obtained in step (2) and perform a second epitaxial growth to obtain InP@ZnSe@ZnS.

[0013] It can be understood that "@" in this invention refers to coating. For example, the above InP@ZnSe@ZnS means that InP is the core, and ZnSe and ZnS shells are coated in sequence.

[0014] This invention is based on a surface energy homogenization strategy, using organic amine ligands and DPP-Se (diphenylphosphine selenide solution) as synergistic ligands to selectively passivate In in the high-energy (111) crystal plane on the InP core surface. 3+ The high activity sites make the surface energies of the three crystal planes (111), (100), and (110) tend to be uniform. By increasing the ligand adsorption energy of the (111) plane, the rapid epitaxial growth rate of ZnSe on this crystal plane is weakened, achieving a uniform and isotropic coating of the ZnSe shell on the InP core surface. Furthermore, a ZnS shell is introduced on the basis of the uniform ZnSe shell to enhance the band ladder structure, improve the carrier binding ability, and enhance stability.

[0015] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0016] Preferably, the indium precursor in step (1) includes any one or a combination of at least two of indium acetate, indium chloride, indium iodide or indium acetylacetonate, and more preferably indium acetate.

[0017] Preferably, the fatty acid ligand in step (1) includes any one or a combination of at least two of myristic acid, lauric acid, palmitic acid or oleic acid, and more preferably myristic acid.

[0018] Preferably, zinc undecenoate is added during the mixing process in step (1).

[0019] In this invention, the addition of zinc undecenoate can regulate the reactivity of the P precursor, stabilize the nucleation process, improve the surface defects of the crystal nucleus, and enhance the PL (photoluminescence) performance of the obtained quantum dots.

[0020] Preferably, the noncoordinating solvents in steps (1) and (2) each independently comprise any one or a combination of at least two of octadecene, hexadecene, liquid paraffin, or octyl ether, and more preferably octadecene.

[0021] Preferably, the molar ratio of the indium precursor and the fatty acid ligand in step (1) is 1:(2~4), such as 1:2, 1:2.5, 1:3, 1:3.5 or 1:4.

[0022] Preferably, the molar ratio of indium precursor and zinc undecenoate in step (1) is 1:(2~3), such as 1:2, 1:2.25, 1:2.5, 1:2.8 or 1:3, etc.

[0023] Preferably, step (1) the first dehydration and deoxygenation treatment includes sequential nitrogen replacement and vacuum degassing.

[0024] Preferably, the vacuum degassing temperature is 120℃~140℃, such as 120℃, 125℃, 130℃, 135℃ or 140℃, and the time is 1h~3h, such as 1h, 1.5h, 2h, 2.5h or 3h.

[0025] Preferably, the temperature rise in step (1) is 270℃~300℃, for example, 270℃, 275℃, 280℃, 285℃, 290℃, 295℃ or 300℃.

[0026] Preferably, the phosphorus precursor in step (1) comprises a solution of (TMS)3P (tris(trimethylsilyl)phosphine) diluted with TOP (tri-n-octylphosphine).

[0027] Preferably, the reaction time in step (1) is 5 min to 7 min, for example, 5 min, 5.5 min, 6 min, 6.5 min or 7 min.

[0028] Preferably, the product is cooled immediately after the reaction in step (1) is completed, and the product is purified to obtain the InP crystal nuclei.

[0029] Preferably, the purification method includes: dispersing the product in toluene, and then adding ethanol for precipitation.

[0030] Preferably, the zinc precursors in steps (2) and (3) each independently comprise any one or a combination of at least two of zinc oleate, zinc carboxylate, or zinc halide, and more preferably zinc oleate.

[0031] Preferably, the second dehydration and deoxygenation treatment in step (2) includes vacuum degassing.

[0032] Preferably, the temperature of the second dehydration and deoxygenation treatment in step (2) is 120℃~140℃, for example 120℃, 125℃, 130℃, 135℃ or 140℃, and the time is 20min~40min, for example 20min, 25min, 30min, 35min or 40min.

[0033] Preferably, the organic amine ligand in step (2) includes n-octylamine and / or trioctylamine, more preferably n-octylamine.

[0034] In this invention, compared with trioctylamine, n-octylamine has stronger coordination ability and higher chemical activity; in addition, compared with other types of organic amine ligands, such as oleylamine, n-octylamine has a shorter alkyl chain length and lower steric hindrance, which is conducive to forming a tighter intermolecular interaction with DPP-Se, thereby exhibiting a better synergistic regulatory effect.

[0035] Preferably, the temperature rise in step (2) is 150℃~170℃, for example 150℃, 155℃, 160℃, 165℃ or 170℃.

[0036] Preferably, after adding the InP crystal nuclei, an HF solution is immediately added for surface treatment.

[0037] In this invention, InP crystal nuclei are highly sensitive to oxygen and are prone to surface oxidation during purification. Therefore, HF solution is added immediately after the InP crystal nuclei are introduced to remove the oxide layer formed on their surface, thereby obtaining a cleaner core-shell interface, effectively suppressing the generation of interface defects during the epitaxial growth of the ZnSe shell, and reducing non-radiative recombination channels.

[0038] Preferably, the mass concentration of the HF solution is 6wt% to 8wt%, for example, 6wt%, 6.5wt%, 7wt%, 7.5wt%, or 8wt%.

[0039] Preferably, in step (2), the temperature is further increased to 210℃~230℃, for example, 200℃, 205℃, 210℃, 215℃, 220℃, 225℃ or 230℃.

[0040] Preferably, step (2) of the first epitaxial growth process includes segmented growth under gradient heating.

[0041] Preferably, the segmented growth under gradient heating includes: after adding the selenium precursor and zinc precursor, growing for 0.5h~1.5h, for example 0.5h, 0.8h, 1h, 1.2h or 1.5h, etc., adding the same amount of selenium precursor and zinc precursor again, heating to 230℃~250℃ and continuing to grow for 0.5h~1.5h, for example growing at 230℃, 235℃, 240℃, 245℃ or 300℃ for 0.5h, 0.8h, 1h, 1.2h or 1.5h, etc., to obtain the InP@ZnSe.

[0042] Preferably, the mixing temperature in step (3) is 260℃~310℃, such as 260℃, 270℃, 280℃, 290℃, 300℃ or 310℃.

[0043] Preferably, the mixing method in step (3) includes: adding the zinc precursor and sulfur precursor dropwise to a dispersion containing the InP@ZnSe from step (2).

[0044] It is understandable that the dispersion here can be the solution after the first epitaxial growth in step (2) is completed.

[0045] Preferably, the sulfur precursor in step (3) includes any one or a combination of at least two of TOP-S (tri-n-octylphosphine sulfide), TBP-S (tributylphosphine sulfide), or dodecanethiol, and more preferably TOP-S.

[0046] Preferably, the second epitaxial growth time in step (3) is 0.5h to 1.5h, for example, 0.5h, 0.8h, 1h, 1.2h or 1.5h.

[0047] In a second aspect, the present invention provides an InP-based quantum dot prepared by the preparation method described in the first aspect, wherein the InP-based quantum dot has an InP core and is sequentially coated with a ZnSe first shell and a ZnS second shell.

[0048] Preferably, the InP-based quantum has at least one of the following characteristics:

[0049] (1) Photoluminescence quantum yield ≥ 92%, such as 92%, 93%, 94% or 95%;

[0050] (2) Narrow emission half-width is 35nm~45nm, such as 35nm, 37nm, 40nm, 42nm or 45nm, etc.;

[0051] (3) The exciton lifetime is 45.6ns~87.2ns, for example 45.6ns, 50.0ns, 55.0ns, 60.0ns, 65.0ns, 70.0ns, 80.0ns or 87.2ns, etc.;

[0052] (4) The emission peak position is stable at 530nm~545nm, such as 530nm, 532nm, 535nm, 538nm, 540nm, 542nm or 545nm, etc.;

[0053] (5) The standard deviation of particle size distribution is ≤0.3nm.

[0054] Thirdly, the present invention provides a quantum dot light-emitting diode device, the quantum dot light-emitting diode device comprising InP-based quantum dots as described in the second aspect.

[0055] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] (1) Achieving isotropic growth of ZnSe shell: By using the surface energy homogenization strategy, the rapid epitaxy of the shell on the InP(111) crystal plane is effectively suppressed, avoiding the formation of weakly electron-confined pod-like structures, and obtaining highly symmetrical and uniform strongly electron-confined quantum dots.

[0058] (2) Significantly improves electron confinement capability: The uniform shell structure effectively confines the electron wave function inside the InP core, greatly reducing surface traps and leakage, and enhancing charge recombination efficiency.

[0059] (3) Significantly improve the optical performance of QD (quantum dot): achieve high PLQY (photoluminescence quantum yield) (≥92%), narrow linewidth (35nm~45nm) and better thermal and optical stability.

[0060] (4) Significantly improves the performance and lifespan of QLEDs: QLEDs prepared using the quantum dots of this invention have a peak EQE ≥ 23.5%; peak luminance > 1.4 × 10⁻⁶. 5 cd / m2 Device lifetime (T) 50 @100cd / m 2 The operating time is over 59,000 hours, more than 100 times that of the comparative application device. There is no parasitic luminescence, and electron leakage is significantly suppressed. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the preparation process of InP-based quantum dots provided in Example 1.

[0062] Figure 2 This is a schematic diagram comparing the surface energies of different crystal planes of InP nuclei modified with different ligand combinations, calculated by DFT.

[0063] Figure 3 These are full-range STEM-EDS scans of InP@ZnSe with spherical aberration correction in Example 1 and Comparative Example 1.

[0064] Figure 4 These are TEM images and particle size distribution diagrams of the InP-based quantum dots prepared in Example 1.

[0065] Figure 5 This is a comparison diagram of the changes in the PL spectra of the InP-based quantum dots prepared in Example 1 and Comparative Example 1.

[0066] Figure 6 This is a comparison graph of the transient fluorescence lifetimes of InP-based quantum dots prepared in Example 1 and Comparative Example 1.

[0067] Figure 7 This is a comparison graph showing the change in quantum yield of InP-based quantum dots prepared in Example 1 and Comparative Example 1 as a function of photoexcitation time.

[0068] Figure 8 This is a comparison graph showing the emission peak position of the InP-based quantum dots prepared in Example 1 and Comparative Example 1 as a function of temperature.

[0069] Figure 9 This is a schematic diagram of the structure of an InP-based quantum dot QLED device provided in the application example.

[0070] Figure 10 This is a comparison chart of leakage current of InP-based quantum dot QLED devices provided in the application examples and comparative application examples.

[0071] Figure 11 This is a comparison chart of the external quantum efficiency and brightness of InP-based quantum dot QLED devices provided in the application examples and comparative application examples.

[0072] Figure 12This is a comparison graph showing the surface temperature of an InP-based quantum dot QLED device as a function of time after continuous operation at room temperature (20.0°C), provided in the application example and comparative application example.

[0073] Figure 13 This is a comparison chart of the lifetime of InP-based quantum dot QLED devices provided in the application examples and comparative application examples. Detailed Implementation

[0074] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0076] Example 1

[0077] This embodiment provides a method for fabricating highly symmetric, strongly electron-confined InP@ZnSe@ZnS multi-shell quantum dots through a crystal plane energy homogenization strategy. The fabrication method is as follows: Figure 1 As shown, the specific steps include the following:

[0078] Step 1: Preparation of InP crystal nuclei

[0079] 0.2 mmol indium acetate, 0.6 mmol myristic acid, and 0.45 mmol zinc undecenoate were added to a three-necked flask, along with 10 mL of octadecene as a solvent. After purging with nitrogen, the system was degassed under vacuum at 130°C for 2 h to ensure complete dissolution of the precursor. The mixture was heated to 280°C under nitrogen protection, and a 0.15 mmol (TMS)3P solution diluted with TOP was rapidly injected. The mixture was then held at 280°C for 6 min. After the reaction, the mixture was rapidly cooled, and the product was first dispersed in toluene, then precipitated with ethanol to obtain InP crystal nuclei, which were finally dispersed in 2 mL of toluene for later use.

[0080] Step 2: Preparation of InP@ZnSe core-shell quantum dots

[0081] 1 mmol of zinc oleate was mixed with octadecene and degassed at 120°C for 30 min. Then, 10 mL of n-octylamine was added and the temperature was raised to 160°C. The InP core solution obtained in step one was added dropwise, followed immediately by 0.12 mL of 7 wt% HF solution to remove the surface oxide layer. The mixture was then heated to 220°C, and 2 mL each of 0.4 M DPP-Se and 0.4 M zinc oleate were added dropwise for 1 h of growth. The temperature was further raised to 240°C, and the same amount of precursor was added dropwise for another 1 h of growth, yielding InP@ZnSe quantum dots with a uniform ZnSe shell.

[0082] Step 3: Preparation of InP@ZnSe@ZnS multi-shell quantum dots

[0083] The system was heated to 280°C, and 2 mL of 0.4 M Zn(OA)₂ and 0.5 mL of 1.0 M TOP-S were added dropwise. The reaction was allowed to proceed for 1 h to grow the ZnS shell. After cooling, the mixture was washed three times with ethanol / n-hexane and finally dispersed in n-octane for later use.

[0084] Example 2

[0085] This embodiment provides a method for preparing highly symmetric, strongly electron-confined InP@ZnSe@ZnS multi-shell quantum dots through a crystal plane energy homogenization strategy. The method includes the following steps:

[0086] Step 1: Preparation of InP crystal nuclei

[0087] 0.2 mmol indium acetate, 0.4 mmol myristic acid, and 0.4 mmol zinc undecenoate were added to a three-necked flask, along with 10 mL of octadecene as a solvent. After purging with nitrogen, the system was degassed under vacuum at 120°C for 3 h to ensure complete dissolution of the precursor. The mixture was heated to 270°C under nitrogen protection, and a 0.15 mmol (TMS)3P solution diluted with TOP was rapidly injected. The mixture was then held at 270°C for 7 min. After the reaction, the mixture was rapidly cooled, and the product was first dispersed in toluene, then precipitated with ethanol to obtain InP crystals, which were finally dispersed in 2 mL of toluene for later use.

[0088] Step 2: Preparation of InP@ZnSe core-shell quantum dots

[0089] 1 mmol of zinc oleate was mixed with octadecene and degassed at 130°C for 40 min. Then, 10 mL of n-octylamine was added and the temperature was raised to 150°C. The InP core solution obtained in step one was added dropwise, followed immediately by 0.12 mL of 6 wt% HF solution to remove the surface oxide layer. The mixture was then heated to 210°C, and 2 mL each of 0.4 M DPP-Se and 0.4 M zinc oleate were added dropwise for 0.5 h of growth. The temperature was further raised to 230°C, and the same amount of precursor was added dropwise for another 1.5 h of growth, yielding InP@ZnSe quantum dots with a uniform ZnSe shell.

[0090] Step 3: Preparation of InP@ZnSe@ZnS multi-shell quantum dots

[0091] The system was heated to 260°C, and 2 mL of 0.4 M Zn(OA)₂ and 0.5 mL of 1.0 M TOP-S were added dropwise. The reaction was allowed to proceed for 0.5 h to grow the ZnS shell. After cooling, the mixture was washed three times with ethanol / n-hexane and finally dispersed in n-octane for later use.

[0092] Example 3

[0093] This embodiment provides a method for preparing highly symmetric, strongly electron-confined InP@ZnSe@ZnS multi-shell quantum dots through a crystal plane energy homogenization strategy. The method includes the following steps:

[0094] Step 1: Preparation of InP crystal nuclei

[0095] 0.2 mmol indium acetate, 0.8 mmol myristic acid, and 0.6 mmol zinc undecenoate were added to a three-necked flask, along with 10 mL of octadecene as a solvent. After purging with nitrogen, the system was degassed under vacuum at 140°C for 1 h to ensure complete dissolution of the precursor. The mixture was heated to 300°C under nitrogen protection, and a 0.15 mmol (TMS)3P solution diluted with TOP was rapidly injected. The mixture was then held at 300°C for 5 min. After the reaction, the mixture was rapidly cooled, and the product was first dispersed in toluene, then precipitated with ethanol to obtain InP crystal nuclei, which were finally dispersed in 2 mL of toluene for later use.

[0096] Step 2: Preparation of InP@ZnSe core-shell quantum dots

[0097] 1 mmol of zinc oleate was mixed with octadecene and heated to 140°C for 20 min to degas. Then, 10 mL of n-octylamine was added and the temperature was raised to 170°C. The InP core solution obtained in step one was added dropwise, followed immediately by 0.12 mL of 8 wt% HF solution to remove the surface oxide layer. The mixture was then heated to 230°C, and 2 mL each of 0.4 M DPP-Se and 0.4 M zinc oleate were added dropwise for 1.5 h of growth. The temperature was further raised to 250°C, and the same amount of precursor was added again for 0.5 h of growth, yielding InP@ZnSe quantum dots with a uniform ZnSe shell.

[0098] Step 3: Preparation of InP@ZnSe@ZnS multi-shell quantum dots

[0099] The system was heated to 310°C, and 2 mL of 0.4 M Zn(OA)₂ and 0.5 mL of 1.0 M TOP-S were added dropwise. The reaction was allowed to proceed for 1.5 h to grow the ZnS shell. After cooling, the mixture was washed three times with ethanol / n-hexane and finally dispersed in n-octane for later use.

[0100] Example 4

[0101] The difference between this embodiment and Embodiment 1 is that in step two, n-octylamine is replaced with oleylamine;

[0102] The remaining preparation methods and parameters are consistent with those in Example 1.

[0103] Example 5

[0104] The difference between this embodiment and Embodiment 1 is that zinc undecenoate is not added in step one;

[0105] The remaining preparation methods and parameters are consistent with those in Example 1.

[0106] Example 6

[0107] The difference between this embodiment and Embodiment 1 is that HF ​​solution is not added in step two;

[0108] The remaining preparation methods and parameters are consistent with those in Example 1.

[0109] Example 7

[0110] The difference between this embodiment and Embodiment 1 is that in step two, the temperature is heated to 230°C, and 4 mL each of 0.4 M DPP-Se and 0.4 M zinc oleate are added dropwise for 2 hours of growth, without gradient temperature increase for segmented growth;

[0111] The remaining preparation methods and parameters are consistent with those in Example 1.

[0112] Comparative Example 1

[0113] The difference between this embodiment and Embodiment 1 is that in step two, DPP-Se is replaced with TOP-Se, and n-octylamine is replaced with oleic acid;

[0114] The remaining preparation methods and parameters are consistent with those in Example 1.

[0115] Comparative Example 2

[0116] The difference between this embodiment and Embodiment 1 is that in step two, DPP-Se is replaced with TOP-Se;

[0117] The remaining preparation methods and parameters are consistent with those in Example 1.

[0118] Comparative Example 3

[0119] The difference between this embodiment and Embodiment 1 is that in step two, n-octylamine is replaced with oleic acid;

[0120] The remaining preparation methods and parameters are consistent with those in Example 1.

[0121] Application Example 1

[0122] This application example provides a QLED device, and the schematic diagram and magnified TEM image of the device are shown below. Figure 9 As shown, from bottom to top, they are: ITO / PEDOT:PSS / PF8Cz / quantum dots prepared in Example 1 / ZnMgO / Al.

[0123] The preparation steps are as follows:

[0124] Substrate cleaning and treatment: The ITO glass is ultrasonically cleaned in sequence with detergent, deionized water, acetone, and isopropanol, and then subjected to plasma treatment.

[0125] Hole injection layer and hole transport layer spin coating: PEDOT:PSS (4000rpm, 40s, 150℃ baking for 30min): PF8Cz (8mg / mL, 3000rpm, 120℃ baking for 30min).

[0126] Quantum dot spin coating: Quantum dots prepared in Example 1 (20 mg / mL, 2000 rpm, 80 °C for 3 min).

[0127] Electron transport layer and cathode evaporation spin coating: ZnMgO (30 mg / mL, 3000 rpm, 60 °C baking for 30 min), followed by vacuum evaporation of Al cathode (100 nm).

[0128] Device packaging: UV-cured epoxy resin encapsulation.

[0129] Comparative Application Example 1

[0130] The difference between this comparative application example and application example 1 is that the quantum dots are replaced with the quantum dots prepared in comparative example 1;

[0131] The remaining preparation methods and parameters are consistent with those in Application Example 1.

[0132] Structural characterization and performance testing

[0133] The InP-based quantum dots prepared in Examples 1-7 and Comparative Examples 1-3 were physically characterized and their optical properties were tested. The test results are as follows: Figures 3-8 And as shown in Table 1.

[0134] The photoelectric performance and long-term stability of InP-based quantum dot QLED devices fabricated in corresponding use cases and comparative application examples were tested, and the test results are as follows: Figures 10-13 As shown.

[0135] Table 1

[0136]

[0137] Figure 2 This is a schematic diagram comparing the surface energies of different crystal planes of InP nuclei modified by different ligand combinations calculated by DFT. As can be seen from the figure, when using the combination of n-octylamine and DPP-Se, the surface energies of different crystal planes of InP nuclei are closest. Therefore, it can effectively suppress the rapid epitaxy of the shell on the InP(111) crystal plane. Combined with the data of Example 1 and Comparative Examples 1-3 in Table 1, it can be seen that the method provided by the present invention is more conducive to the isotropic growth of the shell.

[0138] The elemental distribution map, transmission electron microscope (TEM) image, and quantum dot size distribution map of the quantum dots obtained in Example 1 are shown below. Figure 3 a and Figure 4 As shown, the fluorescence emission spectrum is as follows: Figure 5 As shown (the vertical axis PL intensity has been normalized), the InP@ZnSe@ZnS quantum dots obtained in Example 1 have a regular crystal shape, are nearly perfectly spherical, and have a narrow emission peak (FWHM≈35nm), proving that the shell coating is highly isotropic. The elemental distribution map and TEM image of the quantum dots obtained in Comparative Example 1 are shown below. Figure 3 As shown in b, the fluorescence emission spectrum is as follows: Figure 5 As shown, it can be observed that the quantum dots obtained in Comparative Example 1 have irregular morphology, large emission peaks, and wide half-maximum widths (FWHM≈45nm), indicating that their shell coating height is significantly anisotropic.

[0139] Figures 6-8The figures show a comparison of the transient fluorescence lifetime, quantum yield, and emission peak position of the InP-based quantum dots prepared in Example 1 and Comparative Example 1, respectively, as a function of photoexcitation time and temperature. As can be seen from the figures, the InP-based quantum dots obtained in Example 1 have a higher transient fluorescence lifetime and a higher quantum yield.

[0140] Figures 10-13 The figures show a comparison of leakage current, external quantum efficiency, brightness, surface temperature change over time after continuous operation at room temperature (20.0℃), and device lifetime for the InP-based quantum dot QLED devices provided in the application example and the comparative application example. As can be seen from the figures, the application example device achieves higher external quantum efficiency and brightness while maintaining lower leakage current, and exhibits a slower temperature rise and significantly longer operating lifetime under continuous operation conditions. Overall, the device performance and operational stability are superior to the comparative application example.

[0141] Furthermore, a comparison of the data from Example 1 and Examples 4-7 in Table 1 shows that in this invention, whether zinc undecenoate is added in step one, the type of organic amine ligand in step two, whether HF solution is used for surface treatment after adding InP crystal nuclei, and whether step heating and segmented growth are used all affect the structure of the obtained InP-based quantum dots. By adopting the preferred method provided by this invention, InP-based quantum dots with superior structure and performance can be prepared.

[0142] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing InP-based quantum dots, characterized in that, The preparation method includes: (1) The indium precursor, fatty acid ligand and non-coordination solvent are mixed and subjected to a first dehydration and deoxygenation treatment to obtain a precursor solution. After heating, the phosphorus precursor is injected to react and InP crystal nuclei are obtained. (2) The zinc precursor and non-coordination solvent are mixed, and after the second dehydration and deoxygenation treatment, an organic amine ligand is added. After heating, the InP crystal nucleus described in step (1) is added. After further heating, DPP-Se and the zinc precursor are added to carry out the first epitaxial growth to obtain InP@ZnSe. (3) Mix the InP@ZnSe, zinc precursor and sulfur precursor obtained in step (2) and perform a second epitaxial growth to obtain InP@ZnSe@ZnS.

2. The preparation method according to claim 1, characterized in that, The fatty acid ligand in step (1) includes myristic acid; Preferably, zinc undecenoate is added during the mixing process in step (1); Preferably, the molar ratio of the indium precursor and the fatty acid ligand in step (1) is 1:(2~4); Preferably, the molar ratio of the indium precursor and zinc undecenoate in step (1) is 1:(2~3).

3. The preparation method according to claim 1 or 2, characterized in that, Step (1) The first dehydration and deoxygenation treatment includes sequential nitrogen replacement and vacuum degassing; Preferably, the vacuum degassing temperature is 120℃~140℃ and the time is 1h~3h.

4. The preparation method according to any one of claims 1-3, characterized in that, Step (1) involves raising the temperature to 270℃~300℃; Preferably, the phosphorus precursor in step (1) comprises a TOP-diluted (TMS)3P solution; Preferably, the reaction time in step (1) is 5 min to 7 min; Preferably, the product is cooled immediately after the reaction in step (1) is completed, and the product is purified to obtain the InP crystal nuclei; Preferably, the purification method includes: dispersing the product in toluene, and then adding ethanol for precipitation.

5. The preparation method according to any one of claims 1-4, characterized in that, Step (2) The second dehydration and deoxygenation treatment includes vacuum degassing; Preferably, the temperature of the second dehydration and deoxygenation treatment in step (2) is 120℃~140℃, and the time is 20min~40min; Preferably, the organic amine ligand in step (2) includes n-octylamine and / or trioctylamine, more preferably n-octylamine; Preferably, the temperature in step (2) is raised to 150°C~170°C; Preferably, after adding the InP crystal nuclei, an HF solution is immediately added for surface treatment; Preferably, the HF solution has a mass concentration of 6wt% to 8wt%.

6. The preparation method according to any one of claims 1-5, characterized in that, Step (2) involves further heating to 210℃~230℃; Preferably, step (2) of the first epitaxial growth process includes segmented growth under gradient heating; Preferably, the segmented growth under gradient heating includes: after adding the selenium precursor and zinc precursor, growing for 0.5h~1.5h, adding the same amount of selenium precursor and zinc precursor again, heating to 230℃~250℃ and continuing to grow for 0.5h~1.5h to obtain the InP@ZnSe.

7. The preparation method according to any one of claims 1-6, characterized in that, The mixing temperature in step (3) is 260℃~310℃; Preferably, the mixing method in step (3) includes: adding the zinc precursor and sulfur precursor dropwise to a dispersion containing the InP@ZnSe from step (2); Preferably, the second epitaxial growth time in step (3) is 0.5h to 1.5h.

8. An InP-based quantum dot prepared by the preparation method according to any one of claims 1-7, characterized in that, The InP-based quantum dot has an InP core, which is sequentially coated with a ZnSe first shell and a ZnS second shell.

9. The InP-based quantum dot according to claim 8, characterized in that, The InP-based quantum dot has at least one of the following characteristics: (1) Photoluminescence quantum yield ≥ 92%; (2) Narrow emission half-width is 35nm~45nm; (3) The exciton lifetime is 45.6 ns to 87.2 ns; (4) The emission peak position is stable at 530nm~545nm; (5) The standard deviation of particle size distribution is ≤0.3nm.

10. A quantum dot light-emitting diode device, characterized in that, The quantum dot light-emitting diode device includes InP-based quantum dots as described in claim 8 or 9.

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