Core-shell quantum dot and preparation method therefor, and quantum dot device
Patent Information
- Application Number
- PCT/CN2025/078793
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-02-24
- Publication Date
- 2026-08-27
Smart Images
Figure CN2025078793_27082026_PF_FP_ABST
Abstract
Description
A core-shell quantum dot, its preparation method and quantum dot device Technical Field
[0001] This disclosure relates to the field of display technology, and in particular to a core-shell quantum dot, its preparation method, and quantum dot devices. Background Technology
[0002] Quantum dots (QDs), also known as nanocrystals, are nanoparticles composed of group II-VI or III-V elements. The particle size of quantum dots typically ranges from 1 to 20 nm. Due to the quantum confinement of electrons and holes, the continuous band structure becomes a discrete energy level structure, allowing them to emit fluorescence when stimulated. With the advancement of quantum dot fabrication technology, the stability and luminous efficiency of quantum dots are continuously improving, and their application prospects in the display field are becoming increasingly promising.
[0003] Quantum dot light-emitting diodes (QLEDs) have shown great promise in the display and lighting fields due to their unique characteristics such as narrow emission peaks, high color purity, strong fluorescence lifetime, high fluorescence quantum yield, and continuously tunable fluorescence spectrum. Summary of the Invention
[0004] This disclosure provides a core-shell quantum dot, its preparation method, and a quantum dot device, as detailed below:
[0005] This disclosure provides a core-shell quantum dot, comprising a quantum dot core and a first shell structure covering the outer surface of the quantum dot core. The first shell structure is a 0-dimensional perovskite with the chemical formula A4BX6, wherein A includes at least one of an amine organic group and an inorganic metal, B is a group carbon element, and X is a group halogen element.
[0006] In one possible implementation, in the core-shell quantum dot provided in the embodiments of this disclosure, A includes CH3NH 3+ NH2CH=NH2, Cs + B includes at least one of Pb, Sn, and Ge, and X includes at least one of Cl, Br, and I.
[0007] In one possible implementation, in the core-shell quantum dot provided in the embodiments of this disclosure, the thickness of the first shell structure is greater than 5 nm, and the distance between adjacent outer surfaces of adjacent quantum dot cores is greater than 10 nm.
[0008] In one possible implementation, the core-shell quantum dots provided in the embodiments of this disclosure have a fluorescence emission spectrum with an emission peak range of 460 nm to 700 nm.
[0009] In one possible implementation, the core-shell quantum dot provided in the embodiments of this disclosure further includes a second shell structure located between the quantum dot core and the first shell structure, wherein the second shell structure includes at least one of ZnS, ZnSe, ZnTe, CdS, and CdSe.
[0010] In one possible implementation, in the core-shell quantum dot provided in the embodiments of this disclosure, the thickness of the second shell structure is less than 3 nm.
[0011] In one possible implementation, in the core-shell quantum dot provided in the embodiments of this disclosure, the elemental types of the quantum dot core are different from those of the 0-dimensional perovskite.
[0012] In one possible implementation, in the core-shell quantum dots provided in the embodiments of this disclosure, the quantum dot core is selected from compounds of groups II-VI, III-V, IV-VI, elements of group IV, compounds of group IV, and combinations thereof.
[0013] Accordingly, this disclosure also provides a method for preparing core-shell quantum dots, used to prepare the core-shell quantum dots provided in this disclosure, the preparation method comprising:
[0014] Preparation of quantum dot cores;
[0015] A first shell structure is formed on the outer surface of the quantum dot core to obtain a core-shell quantum dot.
[0016] In one possible implementation, in the preparation method provided in the embodiments of this disclosure, a first shell structure is formed on the outer surface of the quantum dot core to obtain a core-shell quantum dot, specifically including:
[0017] Preparation of precursor solution of A and preparation of precursor solution of BX2;
[0018] ZnX2, fatty acid, and noncoordinate solvent are added to the solution of the quantum dot core, and the temperature is raised to 60-80°C. Then, the precursor solution of A and the precursor solution of BX2 are added to the solution of the quantum dot core. After a preset reaction time, the core-shell quantum dots are obtained.
[0019] In one possible implementation, in the preparation method provided in the embodiments of this disclosure, a first shell structure is formed on the outer surface of the quantum dot core to obtain a core-shell quantum dot, specifically including:
[0020] Prepare a precursor solution of A;
[0021] BX2, fatty acid, coordinating solvent, and non-coordinating solvent are added to the solution of the quantum dot core, and the solution is heated to dissolve it. Then, the precursor solution of A is added, and the reaction is carried out for a preset time to obtain the core-shell quantum dot.
[0022] In one possible implementation, the preparation method provided in the embodiments of this disclosure, after the preparation of the quantum dot core and before the preparation of the precursor solution of A, further includes:
[0023] The quantum dot core is purified by washing away the coordination solvent and fatty acid ligand used in the synthesis, and the purified quantum dot core is dissolved in a non-coordination solvent.
[0024] In one possible implementation, the preparation method provided in the embodiments of this disclosure, after the preparation of the quantum dot core and before the preparation of the precursor solution of A, further includes:
[0025] A non-coordinate solvent of zinc stearate is injected into the solution of the quantum dot core, followed by the addition of a mixed solution of Se-TOP and S-TOP. The temperature is then raised to 290–310 °C, and the reaction is stopped and cooled after a preset time to obtain quantum dots with a quantum dot core / second shell structure.
[0026] In one possible implementation, the preparation method provided in the embodiments of this disclosure further includes: purifying the quantum dots with the quantum dot core / second shell structure, washing away the coordination solvent and fatty acid ligand used in the synthesis, and dissolving the purified quantum dots in a non-coordination solvent.
[0027] In one possible implementation, the preparation method provided in the embodiments of this disclosure further includes:
[0028] The core-shell quantum dots were purified.
[0029] Accordingly, this disclosure also provides a quantum dot device, including a quantum dot layer, wherein the material of the quantum dot layer includes the core-shell quantum dots described in any of the above embodiments of this disclosure. Attached Figure Description
[0030] Figure 1 is a schematic diagram of the structure of a core-shell quantum dot provided in an embodiment of this disclosure;
[0031] Figure 2 is a schematic diagram of another core-shell quantum dot provided in an embodiment of this disclosure;
[0032] Figure 3 is a schematic flowchart of a method for preparing core-shell quantum dots according to an embodiment of this disclosure;
[0033] Figure 4 is a schematic flowchart of another method for preparing core-shell quantum dots provided in this embodiment of the present disclosure;
[0034] Figure 5 is a schematic flowchart of another method for preparing core-shell quantum dots provided in this embodiment of the present disclosure;
[0035] Figure 6 is a schematic flowchart of another method for preparing core-shell quantum dots provided in an embodiment of this disclosure;
[0036] Figure 7 is a schematic flowchart of another method for preparing core-shell quantum dots provided in an embodiment of this disclosure;
[0037] Figure 8 is a schematic flowchart of another method for preparing core-shell quantum dots provided in an embodiment of this disclosure;
[0038] Figure 9 is a schematic flowchart of another method for preparing core-shell quantum dots provided in an embodiment of this disclosure;
[0039] Figure 10 is a schematic diagram of the PL spectra of Example 1 and Comparative Example 1;
[0040] Figure 11 is a schematic diagram of the structure of a display device provided in an embodiment of this disclosure. Detailed Implementation
[0041] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Furthermore, the embodiments and features in the embodiments of this disclosure can be combined with each other without conflict. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.
[0042] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "comprising" or "including," and similar terms as used in this disclosure, mean that an element or object preceding the term encompasses the elements or objects listed following the term and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "inner," "outer," "upper," and "lower" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described objects changes.
[0043] It should be noted that the dimensions and shapes of the figures in the accompanying drawings do not reflect actual proportions and are intended only to illustrate the content of this disclosure. Furthermore, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.
[0044] In the synthesis and application of quantum dots, the quantum dot shell is one of the key factors affecting the application of quantum dot materials. During the quantum dot coating process, a thin shell layer leads to a strong fluorescence resonance energy transfer (FRET) effect, causing a significant decrease in the fluorescence quantum efficiency of the quantum dot film compared to the fluorescence quantum efficiency of the quantum dot solution. The FRET effect is based on energy transfer between neighboring quantum dot nuclei, and the typical FRET effect occurs because the distance between the quantum dot nuclei is less than 7-10 nm. In QLED devices, the FRET effect causes a decrease in QLED device efficiency. Therefore, it is necessary to grow a thicker quantum dot shell layer to mitigate the FRET effect, such as a ZnS or ZnSe shell. However, stable growth of a thick shell often requires long-term growth at high temperatures and can introduce defects. Furthermore, Zn and S in the shell layer may undergo ion exchange with elements such as cadmium or selenium in the quantum dot nucleus, leading to a shift in the emission peak position.
[0045] This disclosure provides a core-shell quantum dot, as shown in FIG1, comprising a quantum dot core 10 and a first shell structure 20 covering the outer surface of the quantum dot core 10. The first shell structure 20 is a zero-dimensional perovskite, and the chemical formula of the first shell structure 20 is A4BX6, wherein A includes at least one of amine organic groups and inorganic metals, B is a carbon group element, and X is a halogen element.
[0046] The core-shell quantum dots provided in this disclosure have the advantage of having a direct band gap of approximately 3.4 eV for the A4BX6 structure of 0-dimensional perovskite, which is similar to that of ZnS. Therefore, the A4BX6 structure of 0-dimensional perovskite can serve as the shell material for quantum dots. Furthermore, quantum dots based on perovskite shells offer more ligand development strategies, allowing the application of perovskite shells in traditional quantum dots. Additionally, since the band gap of 0-dimensional perovskite is a direct band gap and is higher than that of typical quantum dot cores, using the Type I core-shell quantum dots of this disclosure can significantly improve the fluorescence quantum efficiency and stability of quantum dots. Moreover, because perovskite… The material exhibits high activity and rapid shell thickness growth. Therefore, the thickness of the first shell structure of the 0-dimensional perovskite generally exceeds 5 nm. With the addition of ligands on the quantum dot surface and gaps between quantum dots, the distance between quantum dot nuclei generally exceeds 10 nm. Thus, the first shell structure (0-dimensional perovskite) in this disclosure will effectively reduce the FRET effect, improve the stability of the quantum dot film, and enhance the fluorescence quantum efficiency of the quantum dot film. Moreover, the ionic radii and valence states of each element in the 0-dimensional perovskite are not similar to those of each element in the general quantum dot nucleus, which can reduce ion exchange, avoid the shift of emission peak position caused by ion exchange, and improve device performance.
[0047] In some embodiments, in the core-shell quantum dots provided in the present disclosure, the chemical formula A4BX6 of the first shell structure 20 may include, but is not limited to, CH3NH. 3+ NH2CH=NH2, Cs + At least one of the following, B may include, but is not limited to, at least one of Pb, Sn, and Ge, and X may include, but is not limited to, at least one of Cl, Br, and I. For example, the material of the quantum dot core 10 is CdZnSe, and the chemical formula of the first shell structure 20 is Cs4PbBr6, that is, the structure of the core-shell quantum dot provided in this embodiment is CdZnSe / Cs4PbBr6. The ionic radius and valence state of Cs / Pb / Br are not similar to those of the elements Cd / Zn / Se used in the quantum dot core, which can reduce ion exchange between the shell and the quantum dot core.
[0048] In some embodiments, as shown in FIG1, in the core-shell quantum dots provided in this disclosure, the thickness of the first shell structure 20 is greater than 5 nm, and the distance between adjacent outer surfaces of adjacent quantum dot cores 10 is greater than 10 nm. This can reduce the FRET effect, improve the stability of the quantum dot film, and increase the fluorescence quantum efficiency of the quantum dot film.
[0049] In some embodiments, the emission peak range of the fluorescence emission spectrum of the core-shell quantum dots provided in the present disclosure is adjustable between 460 nm and 700 nm.
[0050] In some embodiments, as shown in FIG2, the core-shell quantum dot provided in this disclosure may further include a second shell structure 30 located between the quantum dot core 10 and the first shell structure 20. The second shell structure 30 includes at least one of ZnS, ZnSe, ZnTe, CdS, and CdSe. Specifically, the thickness of the second shell structure 30 is less than 3 nm, that is, the core-shell quantum dot of this disclosure may be a 0-dimensional perovskite layer coated around a conventional thin-shell quantum dot. This avoids the need for long-term high-temperature growth of the second shell structure 30, reduces the FRET effect, improves the stability of the quantum dot thin film, and increases the fluorescence quantum efficiency of the quantum dot thin film.
[0051] In some embodiments, as shown in Figures 1 and 2, the elemental composition of the quantum dot core 10 differs from that of the 0-dimensional perovskite (i.e., the first shell structure 20). Specifically, the ionic radii and valence states of each element in the 0-dimensional perovskite are not similar to those of each element in the quantum dot core 10. This reduces ion exchange, avoids ion exchange-induced shifts in emission peak positions, and improves device performance.
[0052] In some embodiments, as shown in Figures 1 and 2, the quantum dot core 10 in the core-shell quantum dots provided in this disclosure can be selected from compounds of groups II-VI, III-V, IV-VI, elements of group IV, compounds of group IV, and combinations thereof. Specifically, the compounds of group II-VI can be selected from: binary compounds, wherein the binary compounds are selected from CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, and mixtures thereof; and ternary compounds, wherein the ternary compounds are selected from AgInS, CuInS, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZn S, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS and mixtures thereof; and quaternary compounds selected from HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe and mixtures thereof. Group III-V compounds may be selected from: binary compounds selected from GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb and mixtures thereof; ternary compounds selected from GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP, InNP, InNAs, InNSb, InPAs, InPSb and mixtures thereof; and quaternary compounds selected from GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb and mixtures thereof. Compounds of family IV-VI may be selected from: binary compounds selected from SnS, SnSe, SnTe, PbS, PbSe, PbTe and mixtures thereof; ternary compounds selected from SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe and mixtures thereof; and quaternary compounds selected from SnPbSSe, SnPbSeTe, SnPbSTe and mixtures thereof.Elements in Group IV can be selected from Si, Ge, and mixtures thereof. Compounds in Group IV can be binary compounds selected from SiC, SiGe, and mixtures thereof.
[0053] In one or more embodiments, the aforementioned binary, ternary, and / or quaternary compounds may exist in the particles at a uniform concentration, or may exist in the same particles with partially different concentration distributions.
[0054] Based on the same inventive concept, this disclosure also provides a method for preparing core-shell quantum dots. Since the principle of this preparation method in solving the problem is similar to that of the core-shell quantum dots described above, the implementation of the preparation method provided in this disclosure can refer to the implementation of the core-shell quantum dots described above in this disclosure, and the repeated parts will not be described again.
[0055] In some embodiments, the method for preparing core-shell quantum dots provided in this disclosure is used to prepare the core-shell quantum dots shown in Figures 1 and 2 of this disclosure. As shown in Figure 3, the preparation method may include the following steps:
[0056] S301, Preparation of quantum dot cores;
[0057] S302. A first shell structure is formed on the outer surface of the quantum dot core to obtain a core-shell quantum dot.
[0058] In some embodiments, as shown in FIG4 and FIG5, after performing step S302, the preparation method provided in this disclosure further includes:
[0059] S303. Purify the core-shell quantum dots.
[0060] Specifically, ethyl acetate can be used as an antisolvent to purify the core-shell quantum dots obtained above, and finally dissolved in toluene, n-hexane or other nonpolar solvents for later use.
[0061] In some embodiments, as shown in FIG4, in the preparation method provided in this disclosure, step S302 forms a first shell structure on the outer surface of the quantum dot core to obtain a core-shell quantum dot, which may specifically include the following steps:
[0062] S401, Prepare the precursor solution of A and prepare the precursor solution of BX2;
[0063] S402, ZnX2, fatty acid, and non-coordinate solvent are added to the solution of quantum dot cores, and the temperature is raised to 60-80℃. Then, precursor solutions of A and BX2 are added to the solution of quantum dot cores. After the reaction is carried out for a preset time, core-shell quantum dots are obtained.
[0064] Specifically, A, B, and X are A, B, and X in the aforementioned A4BX6.
[0065] In some embodiments, as shown in FIG5, in the preparation method provided in this disclosure, step S302 forms a first shell structure on the outer surface of the quantum dot core to obtain a core-shell quantum dot, which may specifically include the following steps:
[0066] S501. Prepare the precursor solution of A;
[0067] S502, BX2, fatty acid, coordinating solvent, and non-coordinating solvent are added to the solution of the quantum dot core, heated to dissolve, and then a precursor solution of A is added. After a preset reaction time, core-shell quantum dots are obtained.
[0068] Specifically, A, B, and X are A, B, and X in the aforementioned A4BX6.
[0069] In some embodiments, the fatty acids in the preparation methods provided in the present disclosure may include one or more of dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid (oleic acid, OA), octadecenoic acid, and icosanoic acid.
[0070] In some embodiments, in the preparation method provided in the present disclosure, the non-coordination solvent may include one or more of 1-octadecene, hexadecane, octadecane, eicosane, trioctylamine, and paraffin.
[0071] In some embodiments, in the preparation method provided in the present disclosure, the coordination solvent may include one or more of oleylamine (OAm), trioctylphosphine (TOP), diphenylphosphine, and tributylphosphine.
[0072] In some embodiments, as shown in FIG6 and FIG7, in the preparation method provided in the present disclosure, after performing step S301 to prepare the quantum dot core, and before performing steps S401 and S501 to prepare the precursor solution of A, the method may further include:
[0073] S601. Purify the quantum dot nuclei by washing away the coordination solvent and fatty acid ligands used in the synthesis, and dissolve the purified quantum dot nuclei in a non-coordination solvent.
[0074] In some embodiments, as shown in Figures 8 and 9, the preparation method provided in this disclosure, after performing step S301 to prepare the quantum dot core and before performing steps S401 and S501 to prepare the precursor solution of A, may further include:
[0075] In step S801, a non-coordinate solvent of zinc stearate is injected into the quantum dot core solution, followed by the addition of a mixed solution of Se-TOP and S-TOP. The temperature is then raised to 290–310 °C, and the reaction is stopped and cooled after a preset time to obtain quantum dots with a core / second shell structure. At this point, step S402 in Figure 8 becomes “ZnX2, fatty acid, and non-coordinate solvent are added to the quantum dot core / second shell structure solution, and the temperature is raised to 60–80 °C. Then, precursor solutions of A and BX2 are added, and the reaction is carried out for a preset time to obtain core-shell quantum dots.” Step S502 in Figure 9 becomes “BX2, fatty acid, coordinating solvent, and non-coordinate solvent are added to the quantum dot core / second shell structure solution, and the solution is heated to dissolve. Then, precursor solution of A is added, and the reaction is carried out for a preset time to obtain core-shell quantum dots.”
[0076] In some embodiments, the preparation method provided in this disclosure includes, after performing step S801 and before performing steps S401 and S501 to prepare the precursor solution of A, further comprising: purifying the quantum dots with a core / second shell structure, washing away the coordination solvent and fatty acid ligand used in the synthesis, and dissolving the purified quantum dots in a non-coordination solvent.
[0077] To better understand the technical solution of the preparation method provided in the embodiments of this disclosure, the preparation process of the core-shell quantum dots in the embodiments of this disclosure will be described in detail.
[0078] Example 1: Preparation of red CdZnSe / Cs4PbBr6 core-shell quantum dots.
[0079] (1) Synthesis of red CdZnSe quantum dot nuclei: 90 mg of cadmium oxide, 165 mg of zinc acetate, 5 ml of oleic acid (OA), and 10 ml of 1-octadecene (ODE) were mixed in a three-necked flask and reacted under vacuum at 120 °C for 30 min. After complete dissolution, the atmosphere was changed to nitrogen and the temperature was raised to 300 °C. Then, 3 ml of a solution of 0.5 mol selenium dissolved in trioctylphosphine (TOP) was added. The reaction was carried out for one hour to prepare the stock solution of red CdZnSe quantum dot nuclei. The stock solution of CdZnSe quantum dot nuclei was purified by using hexane and ethanol to wash away the TOP and OA ligands used in the synthesis. The purified CdZnSe quantum dot nuclei were then dissolved in 20 ml of ODE to obtain the purified CdZnSe quantum dot nuclei solution.
[0080] (2) Preparation of CsOA precursor solution: 0.488 g of cesium carbonate, 25 ml of 1-octadecene, and 3 ml of oleic acid were mixed and reacted under vacuum at 100 °C for 30 minutes until completely dissolved to obtain the CsOA precursor. Preparation of PbBr2 precursor solution: 0.073 g of lead bromide, 8 ml of 1-octadecene, 2 ml of oleylamine, and 0.4 ml of oleic acid were mixed and reacted under vacuum at 100 °C for 30 minutes until completely dissolved to obtain the PbBr2 precursor.
[0081] (3) Take 5 ml of the purified CdZnSe quantum dot core solution from step (1), and add 0.045 g of zinc bromide, 2 ml of OA, and 5 ml of ODE. Heat to 70 °C, and then slowly add 2 ml of CsOA precursor solution and 1 ml of PbBr2 precursor solution through a syringe pump. After reacting for a period of time, a red CdZnSe / Cs4PbBr6 solution is obtained. Then, the red CdZnSe / Cs4PbBr6 solution is purified by using ethyl acetate as the antisolvent, and finally dissolved in toluene, n-hexane, or other nonpolar solvents to obtain the purified red CdZnSe / Cs4PbBr6 solution.
[0082] Comparative Example 1: The red CdZnSe quantum dot core prepared in step (1) above was used as Comparative Example 1.
[0083] The inventors of this disclosure coated the CdZnSe / Cs4PbBr6 solution obtained in Example 1 and the CdZnSe solution of Comparative Example 1 into films, and tested the PL spectra of Example 1 and Comparative Example 1 (the horizontal axis is wavelength and the vertical axis is intensity), as shown in Figure 10. The fluorescence quantum efficiency (PLQY), emission peak position of the fluorescence emission spectrum and the full width at half maximum (FWHM) of the fluorescence emission spectrum of Example 1 and Comparative Example 1 are shown in Table 1 below.
[0084] Table 1
[0085] As can be seen from Figure 10 and Table 1, Embodiment 1 of this disclosure uses 0-dimensional perovskite material as the shell structure of the quantum dot core, which can greatly improve the fluorescence quantum efficiency of the quantum dot film.
[0086] Example 2: Preparation of red CdZnSe / Cs4PbBr6 core-shell quantum dots.
[0087] (1) Synthesis of red CdZnSe quantum dot nuclei: 90 mg of cadmium oxide, 165 mg of zinc acetate, 5 ml of oleic acid (OA), and 10 ml of 1-octadecene (ODE) were mixed in a three-necked flask and reacted under vacuum at 120 °C for 30 min. After complete dissolution, the atmosphere was changed to nitrogen and the temperature was raised to 300 °C. Then, 3 ml of a solution of 0.5 mol selenium dissolved in trioctylphosphine (TOP) was added. The reaction was allowed to proceed for one hour to obtain the stock solution of red CdZnSe quantum dot nuclei.
[0088] (2) Preparation of CsOA precursor solution: 0.488 g of cesium carbonate, 25 ml of 1-octadecene, and 3 ml of oleic acid were mixed and reacted under vacuum at 100 °C for 30 minutes until completely dissolved to obtain the CsOA precursor. Preparation of PbBr2 precursor solution: 0.073 g of lead bromide, 8 ml of 1-octadecene, 2 ml of oleylamine, and 0.4 ml of oleic acid were mixed and reacted under vacuum at 100 °C for 30 minutes until completely dissolved to obtain the PbBr2 precursor.
[0089] (3) Take 5 ml of the original solution of CdZnSe quantum dot cores from step (1), and add 0.045 g of zinc bromide, 1 ml of OA, and 5 ml of ODE. Heat to 70 °C, and then slowly add 2 ml of CsOA precursor solution and 1 ml of PbBr2 precursor solution through a syringe pump. After reacting for a period of time, a red CdZnSe / Cs4PbBr6 solution is obtained. Then, the red CdZnSe / Cs4PbBr6 solution is purified by using ethyl acetate as the antisolvent. Finally, it is dissolved in toluene, n-hexane, or other nonpolar solvents to obtain the purified red CdZnSe / Cs4PbBr6 solution.
[0090] Specifically, the difference between Example 2 and Example 1 is that the red CdZnSe quantum dot cores are synthesized without purification, which reduces the complexity of the process. However, since the original solution of the red CdZnSe quantum dot cores contains OA and TOP, the proportion of OA in step (3) of Example 2 should be reduced compared to step (3) of Example 1.
[0091] The CdZnSe / Cs4PbBr6 core-shell quantum dots prepared in Example 2 of this disclosure can effectively reduce the FRET effect, improve the stability of the quantum dot film, and enhance the fluorescence quantum efficiency of the quantum dot film.
[0092] Example 3: Preparation of green CdZnSe / Cs4PbBr6 core-shell quantum dots.
[0093] (1) Synthesis of green CdZnSe quantum dot cores: Cd precursor preparation: 4 mmol CdO was placed in a 100 ml three-necked flask, oleic acid and octadecene were added, and the mixture was reacted under vacuum for 10 min, then converted to nitrogen gas to prepare a 0.15 mol Cd precursor solution. Zn precursor preparation: 20 mmol ZnO was placed in a 100 ml three-necked flask, oleic acid and octadecene were added, and the mixture was reacted under vacuum for 10 min, then converted to nitrogen gas to prepare a 0.5 mol Zn precursor solution. Then, in a flask, 2 ml of Cd precursor solution, 8 ml of Zn precursor solution and 10 ml of ODE were added, the temperature was raised to 300 degrees, and 3 ml of 0.5 mol Se-TOP was added. After reacting for a period of time, the stock solution of green CdZnSe quantum dot cores was prepared. The original solution of CdZnSe quantum dot nuclei was purified by using hexane and ethanol to wash away the TOP and OA ligands used in the synthesis. The purified CdZnSe quantum dot nuclei were then dissolved in 20 ml of ODE to obtain the purified CdZnSe quantum dot nuclei solution.
[0094] (2) Preparation of CsOA precursor solution: 0.488 g of cesium carbonate, 25 ml of 1-octadecene, and 3 ml of oleic acid were mixed and reacted under vacuum at 100 °C for 30 minutes until completely dissolved to obtain the CsOA precursor. Preparation of PbBr2 precursor solution: 0.073 g of lead bromide, 8 ml of 1-octadecene, 2 ml of oleylamine, and 0.4 ml of oleic acid were mixed and reacted under vacuum at 100 °C for 30 minutes until completely dissolved to obtain the PbBr2 precursor.
[0095] (3) Take 5 ml of the purified CdZnSe quantum dot core solution from step (1), and add 0.045 g of zinc bromide, 2 ml of OA, and 5 ml of ODE. Heat to 70 °C, and then slowly add 2 ml of CsOA precursor solution and 1 ml of PbBr2 precursor solution through a syringe pump. After reacting for a period of time, a green CdZnSe / Cs4PbBr6 solution is obtained. Then, the green CdZnSe / Cs4PbBr6 solution is purified by using ethyl acetate as the antisolvent, and finally dissolved in toluene, n-hexane, or other nonpolar solvents to obtain the purified green CdZnSe / Cs4PbBr6 solution.
[0096] Specifically, the difference between Example 3 and Example 1 is that green CdZnSe / Cs4PbBr6 quantum dots are prepared, and the preparation methods of the green CdZnSe quantum dot cores are different.
[0097] The CdZnSe / Cs4PbBr6 core-shell quantum dots prepared in Example 3 of this disclosure can effectively reduce the FRET effect, improve the stability of the quantum dot film, and enhance the fluorescence quantum efficiency of the quantum dot film.
[0098] Example 4: Preparation of red CdZnSe / Cs4PbBr6 core-shell quantum dots.
[0099] (1) Synthesis of red CdZnSe quantum dot nuclei: 90 mg of cadmium oxide, 165 mg of zinc acetate, 5 ml of oleic acid (OA), and 10 ml of 1-octadecene (ODE) were mixed in a three-necked flask and reacted under vacuum at 120 °C for 30 min. After complete dissolution, the atmosphere was changed to nitrogen and the temperature was raised to 300 °C. Then, 3 ml of a solution of 0.5 mol selenium dissolved in trioctylphosphine (TOP) was added. The reaction was carried out for one hour to prepare the stock solution of red CdZnSe quantum dot nuclei. The stock solution of CdZnSe quantum dot nuclei was purified by using hexane and ethanol to wash away the TOP and OA ligands used in the synthesis. The purified CdZnSe quantum dot nuclei were then dissolved in 20 ml of ODE to obtain the purified CdZnSe quantum dot nuclei solution.
[0100] (2) Preparation of CsOA precursor solution: 0.488 g of cesium carbonate, 25 ml of 1-octadecene and 3 ml of oleic acid were mixed and reacted under vacuum at 100 °C for 30 minutes until completely dissolved to prepare CsOA precursor.
[0101] (3) Take 10 ml of the purified CdZnSe quantum dot core solution from step (1), and add 147 mg of PbBr2, 0.2 ml of OA, and 4 ml of OAM (coordination solvent). Heat and dissolve, then add 3 ml of CsOA precursor. After the reaction has been carried out for a preset time, a red CdZnSe / Cs4PbBr6 quantum dot solution is obtained.
[0102] Specifically, the red CdZnSe / Cs4PbBr6 quantum dot solution obtained by the preparation method in Example 4 contains a large amount of lead ions, which need to be separated by direct centrifugation to obtain purified red CdZnSe / Cs4PbBr6 quantum dots.
[0103] The CdZnSe / Cs4PbBr6 core-shell quantum dots prepared in Example 4 of this disclosure can effectively reduce the FRET effect, improve the stability of the quantum dot film, and enhance the fluorescence quantum efficiency of the quantum dot film.
[0104] Example 5: Preparation of InP / ZnSe / ZnS / Cs4PbBr6 core-shell quantum dots.
[0105] (1) Synthesis of InP quantum dot cores: 0.4 mmol of indium chloride, 1 mmol of zinc chloride, and 1 mmol of zinc iodide were dissolved in 5 ml of oleylamine and reacted under vacuum at 120°C for 30 min. Then, nitrogen gas was introduced and the temperature was raised to 170°C. 0.4 ml of tris(diethylamino)phosphine was injected and reacted for 20 min to obtain InP quantum dot cores. Then, 3.16 g of zinc stearate was injected into 10 ml of 1-octadecene and ultrasonically shaken. 1.5 ml of a 2 mol Se-TOP and S-TOP mixed solution was added and the temperature was raised to 300°C. After reacting for 1 hour, the reaction was stopped to obtain InP / ZnSe / ZnS quantum dots. After cooling, the solution was purified and the TOP and OA ligands used in the synthesis were washed away. The solution was then dissolved in 20 ml of ODE solution to obtain the purified InP / ZnSe / ZnS quantum dot solution.
[0106] (2) Preparation of CsOA precursor solution: 0.488 g of cesium carbonate, 25 ml of 1-octadecene, and 3 ml of oleic acid were mixed and reacted under vacuum at 100 °C for 30 minutes until completely dissolved to obtain the CsOA precursor. Preparation of PbBr2 precursor solution: 0.073 g of lead bromide, 8 ml of 1-octadecene, 2 ml of oleylamine, and 0.4 ml of oleic acid were mixed and reacted under vacuum at 100 °C for 30 minutes until completely dissolved to obtain the PbBr2 precursor.
[0107] (3) Add 0.045 g zinc bromide, 2 ml OA and 5 ml ODE to the purified InP / ZnSe / ZnS quantum dot solution in step (1), heat to 70 °C, and then slowly add 2 ml CsOA precursor and 1 ml PbBr2 precursor through a syringe pump. After the reaction, purify with ethyl acetate as the antisolvent, and finally dissolve in toluene, n-hexane or other non-polar solvents.
[0108] The InP / ZnSe / ZnS / Cs4PbBr6 core-shell quantum dots prepared in Example 5 of this disclosure can effectively reduce the FRET effect, improve the stability of the quantum dot film, and enhance the fluorescence quantum efficiency of the quantum dot film.
[0109] Based on the same inventive concept, this disclosure also provides a quantum dot device, including a quantum dot layer, wherein the material of the quantum dot layer includes the core-shell quantum dots provided in this disclosure. When the quantum dot layer is fabricated using the core-shell quantum dots provided in this disclosure, this quantum dot device effectively reduces the FRET effect, improves the stability of the quantum dot thin film, and increases the fluorescence quantum efficiency of the quantum dot thin film, thereby improving the luminescence efficiency of the quantum dot device.
[0110] In some embodiments, the quantum dot device provided in this disclosure can be a quantum dot light-emitting diode (LED), which can be either a forward-facing structure or an inverted structure. The difference between the forward-facing and inverted structures lies in the order in which the film layers are fabricated. Specifically, in the forward-facing structure, an anode, a hole injection layer, a hole transport layer, a quantum dot layer, an electron transport layer, and a cathode are sequentially formed on the substrate; in the inverted structure, a cathode, an electron transport layer, a quantum dot layer, a hole transport layer, a hole injection layer, and an anode are sequentially formed on the substrate.
[0111] In some embodiments, the light emission mode of a quantum dot light-emitting diode can be bottom emission, top emission, or double-sided emission.
[0112] In some embodiments, the quantum dot devices provided in this disclosure may also be photodetectors, photovoltaic solar cells, etc., but are not limited thereto.
[0113] Based on the same inventive concept, this disclosure also provides a display device, including the quantum dot device described above. The principle by which this display device solves the problem is similar to that of the aforementioned quantum dot device; therefore, the implementation of this display device can refer to the implementation of the aforementioned quantum dot device, and the repetitions will not be repeated here.
[0114] In specific implementation, the display device provided in the embodiments of this disclosure is an organic light-emitting display device.
[0115] In specific implementation, the display device provided in the embodiments of this disclosure may be a full-screen display device or a flexible display device, etc., and is not limited thereto.
[0116] In specific implementations, the display device provided in this disclosure can be a full-screen mobile phone as shown in Figure 11. The display device can also be any product or component with display functionality, such as a tablet computer, television, monitor, laptop computer, digital photo frame, or navigator. Other essential components of this display device are understood by those skilled in the art and will not be described in detail here, nor should they be construed as limiting this disclosure. Implementation of this display device can refer to the embodiments of the quantum dot light-emitting device described above; repeated details will not be elaborated upon.
[0117] In specific implementations, the display device provided in the embodiments of this disclosure may also include other functional film layers well known to those skilled in the art, which will not be described in detail here.
[0118] This disclosure provides a core-shell quantum dot, its fabrication method, and a quantum dot device. Since the direct band gap of the A4BX6 structured 0D perovskite is approximately 3.4 eV, similar to that of ZnS, the A4BX6 structured 0D perovskite can serve as the shell material for quantum dots. Furthermore, quantum dots based on perovskite shells offer more ligand development strategies, thus allowing the application of perovskite shells in traditional quantum dots. Additionally, because the band gap of 0D perovskite is a direct band gap and is higher than that of typical quantum dot cores, using the Type I core-shell quantum dots of this disclosure can significantly improve the fluorescence quantum efficiency and stability of quantum dots. Because perovskite materials have high activity and grow rapidly in shell thickness, the thickness of the first shell structure of 0-dimensional perovskite generally exceeds 5 nm. With the addition of ligands on the quantum dot surface and gaps between quantum dots, the distance between quantum dot nuclei generally exceeds 10 nm. Therefore, the first shell structure (0-dimensional perovskite) in this disclosure will effectively reduce the FRET effect, improve the stability of quantum dot films, and increase the fluorescence quantum efficiency of quantum dot films. Moreover, the ionic radii and valence states of each element in 0-dimensional perovskite are not similar to those of each element in general quantum dots, which can reduce ion exchange, avoid the shift of emission peak position caused by ion exchange, and improve device performance.
[0119] Although preferred embodiments of this disclosure have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this disclosure.
[0120] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this disclosure without departing from the spirit and scope of the embodiments of this disclosure. Therefore, if these modifications and variations to the embodiments of this disclosure fall within the scope of the claims of this disclosure and their equivalents, this disclosure is also intended to include these modifications and variations.
Claims
1. A core-shell quantum dot, wherein, It includes a quantum dot core and a first shell structure covering the outer surface of the quantum dot core. The first shell structure is a 0-dimensional perovskite with the chemical formula A4BX6, wherein A includes at least one of an amine organic group and an inorganic metal, B is a carbon group element, and X is a halogen element.
2. The core-shell quantum dot as described in claim 1, wherein, A includes CH3NH 3+ NH2CH=NH2, Cs + At least one of the following, B includes at least one of Pb, Sn, and Ge, and X includes at least one of Cl, Br, and I.
3. The core-shell quantum dot as described in claim 1, wherein, The thickness of the first shell structure is greater than 5 nm, and the distance between adjacent outer surfaces of adjacent quantum dot cores is greater than 10 nm.
4. The core-shell quantum dot as described in claim 1, wherein, The fluorescence emission spectrum of the core-shell quantum dots has an emission peak range of 460 nm to 700 nm.
5. The core-shell quantum dot according to any one of claims 1-4, wherein, It also includes a second shell structure located between the quantum dot core and the first shell structure, the second shell structure including at least one of ZnS, ZnSe, ZnTe, CdS, and CdSe.
6. The core-shell quantum dot as described in claim 5, wherein, The thickness of the second shell structure is less than 3 nm.
7. The core-shell quantum dot according to any one of claims 1-6, wherein, The quantum dot core has a different elemental composition than the 0-dimensional perovskite.
8. The core-shell quantum dot as described in claim 7, wherein, The quantum dot core is selected from compounds of groups II-VI, III-V, IV-VI, elements of group IV, compounds of group IV, and combinations thereof.
9. A method for preparing core-shell quantum dots, used to prepare core-shell quantum dots as described in any one of claims 1-8, wherein, The preparation method includes: Preparation of quantum dot cores; A first shell structure is formed on the outer surface of the quantum dot core to obtain a core-shell quantum dot.
10. The preparation method according to claim 9, wherein, A first shell structure is formed on the outer surface of the quantum dot core to obtain a core-shell quantum dot, specifically including: Preparation of precursor solution of A and preparation of precursor solution of BX2; ZnX2, fatty acid, and noncoordinate solvent are added to the solution of the quantum dot core, and the temperature is raised to 60-80°C. Then, the precursor solution of A and the precursor solution of BX2 are added to the solution of the quantum dot core. After a preset reaction time, the core-shell quantum dots are obtained.
11. The preparation method according to claim 9, wherein, A first shell structure is formed on the outer surface of the quantum dot core to obtain a core-shell quantum dot, specifically including: Prepare a precursor solution of A; BX2, fatty acid, coordinating solvent, and non-coordinating solvent are added to the solution of the quantum dot core, and the solution is heated to dissolve it. Then, the precursor solution of A is added, and the reaction is carried out for a preset time to obtain the core-shell quantum dot.
12. The preparation method according to claim 10 or 11, wherein, After the preparation of the quantum dot core and before the preparation of the precursor solution of A, the method further includes: The quantum dot core is purified by washing away the coordination solvent and fatty acid ligand used in the synthesis, and the purified quantum dot core is dissolved in a non-coordination solvent.
13. The preparation method according to claim 10 or 11, wherein, After the preparation of the quantum dot core and before the preparation of the precursor solution of A, the method further includes: A non-coordinate solvent of zinc stearate is injected into the solution of the quantum dot core, followed by the addition of a mixed solution of Se-TOP and S-TOP. The temperature is then raised to 290–310 °C, and the reaction is stopped and cooled after a preset time to obtain quantum dots with a quantum dot core / second shell structure.
14. The preparation method according to claim 13, wherein, It also includes: purifying the quantum dots with the core / second shell structure, washing away the coordination solvent and fatty acid ligands used in the synthesis, and dissolving the purified quantum dots in a non-coordination solvent.
15. The preparation method according to any one of claims 9-14, wherein, Also includes: The core-shell quantum dots were purified.
16. A quantum dot device, wherein, It includes a quantum dot layer, wherein the material of the quantum dot layer includes core-shell quantum dots as described in any one of claims 1-8.