Blue-light quantum dot material, preparation method, and use in optoelectronic device
By designing a multi-layered blue quantum dot material, the shortcomings of existing blue quantum dot materials in terms of luminous efficiency, stability, and cadmium content have been overcome, achieving efficient and stable blue light emission that is suitable for full-color displays and meets environmental protection requirements.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2024-10-28
- Publication Date
- 2026-05-07
AI Technical Summary
Existing blue quantum dot materials have shortcomings in terms of luminous efficiency, stability, and cadmium content, making it difficult to meet the commercial application requirements of full-color displays. Furthermore, the environmental issues associated with the heavy metal cadmium limit its widespread application.
A multi-layered blue quantum dot material was formed by using ZnSex0Sy0Te1-x0-y0 as the quantum dot core, coating it with Cdx1Zn1-x1Sey1 as the first shell layer, and then sequentially coating it with N outer shell layers Cdx2Zn1-x2Sey2. Its photoluminescence performance and stability were optimized by controlling the chemical composition and thickness.
It improves the luminous efficiency and stability of blue quantum dots, reduces cadmium content, meets the application requirements of full-color displays, and complies with environmental protection standards.
Smart Images
Figure CN2024127728_07052026_PF_FP_ABST
Abstract
Description
A blue quantum dot material, its preparation method, and its application in optoelectronic devices. Technical Field
[0001] This application relates to a blue quantum dot material, its preparation method, and its application in optoelectronic devices, belonging to the field of blue quantum dot materials and devices. Background Technology
[0002] Quantum dots are a novel class of semiconductor nanomaterials. Due to their easily tunable spectra, high fluorescence quantum yield, narrow emission peaks, and solution-processability, they are potential application materials for display technology. Currently, cadmium-based quantum dot materials based on core-shell or gradient alloy structures have achieved photoluminescence quantum yields exceeding 80% across the entire display band (blue, green, and red), and the corresponding external quantum efficiencies of electroluminescent devices have exceeded 20%, approaching the theoretical upper limit. However, the operating lifetime of blue electroluminescent devices is significantly shorter than that of red and green devices, and has not yet met the requirements for commercial applications. The time T taken for the device brightness to decay to 95% of its initial brightness of 1,000 nits in constant current mode is also considered. 95 As an evaluation indicator of device lifespan, cadmium-based red and green light devices have lifespan records of 45,000 hours and 7,200 hours, respectively, while blue light devices only reach 227 hours.
[0003] The quantum dot materials used to display high-efficiency electroluminescence in the blue light (450-480nm) band mainly have CdSe, CdZnSe, CdZnS, CdZnSeS and CdSeS as their cores. Besides the systems mentioned above, quantum dots with InP cores can also achieve blue light emission; however, they have a wide half-width at half-maximum (WHM) (approximately 45 nm) and low efficiency (less than 5%) in electroluminescent devices. Quantum dots with ZnSe cores typically exhibit deep blue light emission (390–445 nm), which does not meet the pure blue light band required for display applications. Quantum dots with tellurium-doped ZnSeTe cores can achieve pure blue light emission and have high fluorescence quantum yield (100%) and high efficiency (over 20%) in electroluminescent devices; however, the resulting emission spectrum broadening (approximately 35 nm) is not conducive to meeting the high color purity required for wide color gamut displays, and the device lifetime has not yet met application requirements. Quantum dots constructed with ZnS cores and CdZnSe or ZnSeTe as quantum wells can also achieve blue light emission; however, the device efficiency and stability are both low.
[0004] Besides the shortage of high-performance blue light materials, the environmental impact of the heavy metal cadmium is also a significant challenge hindering the application of quantum dot displays. The European Union has issued RoHS (Royal Harmful Materials Directive), which limits the cadmium content to no more than 100 ppm. However, the performance gap between cadmium-free quantum dot materials and devices and cadmium-based materials and devices remains substantial.
[0005] In summary, developing blue light materials and devices with high efficiency, high stability, and low cadmium content is a key challenge for realizing quantum dot full-color display applications.
[0006] Summary of the Invention
[0007] The blue light quantum dot material provided by this application is a blue light material with high efficiency, high stability, and low cadmium content for electroluminescence.
[0008] According to the first aspect of this application, a blue light quantum dot material is provided.
[0009] A blue light quantum dot material includes a quantum dot core, a first shell layer coated outside the quantum dot core, and N outer shell layers coated in sequence outside the first shell layer,
[0010] where 1 ≤ N ≤ 5;
[0011] The chemical composition of the quantum dot core is ZnSe x0 S y0 Te 1-x0-y0 ,
[0012] where 0 < x0 ≤ 1, 0 ≤ y0 < 1, and 0.8 ≤ x0 + y0 ≤ 1;
[0013] The chemical composition of the first shell layer of the quantum dot is Cd x1 Zn 1-x1 Se y1 S 1-y1 ,
[0014] where 0 < x1 ≤ 1, 0 < y1 ≤ 1, and x1 and y1 are not both 1 at the same time;
[0015] The chemical composition of the N outer shell layers of the quantum dot is independently Cd x2 Zn 1-x2 Se y2 S 1-y2 ,
[0016] where 0 ≤ x2 ≤ 1, 0 ≤ y2 ≤ 1, and when x2 = x1, y2 ≠ y1.
[0017] Optionally, 0.1 ≤ x0 ≤ 1, 0.1 ≤ y1 ≤ 1.
[0018] Optionally, the core, the first shell layer, and the N outer shell layers of the quantum dot are all homogeneous.
[0019] Optionally, the core of the quantum dot contains Se element and is selected from one of ZnSe, ZnSeS, ZnSeTe, ZnSeSTe.
[0020] Optionally, the first shell of the quantum dot contains both Cd and Se elements, selected from one of CdZnSe, CdZnSeS, and CdSeS.
[0021] Optionally, the outermost N-layer of the quantum dot is independently selected from one of ZnSe, ZnS, CdSe, CdS, CdZnSe, CdZnS, CdSeS, ZnSeS, and CdZnSeS.
[0022] Optionally, the core thickness of the quantum dot is 2–20 nm, the thickness of the first shell of the quantum dot is 0.3–10 nm, and the total thickness of the N-layer outermost shell of the quantum dot is 0.3–20 nm.
[0023] Optionally, the center wavelength of the photoexcited fluorescence spectrum of the quantum dot is greater than or equal to 440 nm and less than or equal to 490 nm, and the full width at half maximum (FWHM) of the spectrum is greater than or equal to 8 nm and less than or equal to 40 nm.
[0024] According to a second aspect of this application, a method for preparing the blue quantum dot material described above is provided.
[0025] The preparation method of the aforementioned blue quantum dot material includes the following steps:
[0026] S1. Prepare Cd precursor, Zn precursor, Se precursor, S precursor and Te precursor solutions respectively;
[0027] S2. Preparation of ZnSeSTe nuclear quantum dot solution;
[0028] S3. Inject Cd precursor, Se precursor, Zn precursor, and S precursor solution into the ZnSeSTe nuclear quantum dot solution obtained in S2. After the reaction, a ZnSeSTe / CdZnSeS quantum dot solution is obtained.
[0029] S4. Inject Cd precursor, Zn precursor, Se precursor, and S precursor solution into the ZnSeSTe / CdZnSeS quantum dot solution obtained in S3. Perform this operation independently N times to coat the ZnSeSTe / CdZnSeS quantum dots with N layers of CdZnSeS outer shell.
[0030] In the above preparation method, the preparation method can be adaptively matched according to the different blue quantum dot materials to be prepared. That is, the specific composition of the elements determines the matching and use of the method. For example, when the first shell of the quantum dot is CdZnSe, it is not necessary to inject the S precursor solution in step S3.
[0031] The preparation methods for Cd precursor, Zn precursor, Se precursor, S precursor, and Te precursor solutions are all conventional techniques in this field and are not limited here. They can be used according to the actual situation.
[0032] According to a third aspect of this application, an application of the aforementioned blue quantum dot material in optoelectronic devices is provided.
[0033] The applications of the aforementioned blue quantum dot materials in optoelectronic devices include any one of photoluminescent devices, electroluminescent devices, photodetectors, and nonlinear optical devices.
[0034] It should be noted that in this application, the chemical formulas representing the quantum dot structure only represent the presence of each element and do not represent the specific proportion of each element.
[0035] The beneficial effects that this application may produce include, but are not limited to:
[0036] (1) The electrons and holes of the blue quantum dots provided in this application are in a state of partial or complete delocalization in the core due to the energy band matching between the core and the first shell, which is beneficial to charge injection and the improvement of luminescence efficiency and quantum dot stability.
[0037] (2) The ZnSeSTe core of the blue quantum dot provided in this application can effectively alleviate the lattice mismatch of the first shell CdZnSeS, which is beneficial to the improvement of luminous efficiency and quantum dot stability;
[0038] (3) The core of the blue quantum dots provided in this application does not contain cadmium, which leads to a further reduction in the cadmium content of the quantum dot material compared with the prior art, making it more compatible with the application requirements of low cadmium. Attached Figure Description
[0039] Figure 1 is a schematic diagram of the core-shell structure of the blue quantum dot material of the present invention.
[0040] Figure 2 is a transmission electron microscope image of the blue quantum dots in Embodiment 2 of the present invention. Detailed Implementation
[0041] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0042] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0043] Unless otherwise specified, the blue quantum dots and devices in the embodiments of this application are tested using conventional methods and manufacturer-recommended settings.
[0044] The emission wavelength and full width at half maximum (FWHM) of the blue quantum dots were obtained by steady-state fluorescence spectroscopy. The testing equipment was a Tianjin Gangdong F-380 fluorescence spectrometer, the excitation source was a xenon lamp, and the excitation wavelength was 370 nm.
[0045] The quantum yield of blue quantum dots was obtained by absolute fluorescence quantum yield testing. The testing equipment was a Hamamatsu C9920-02 absolute PLQY testing system (including a PMA-12 photon multichannel analyzer and an integrating sphere), with an excitation wavelength of 370 nm.
[0046] The size of the blue quantum dots was obtained by transmission electron microscopy. The testing equipment was a FEI Tecnai G2 F30 high-resolution transmission electron microscope with an accelerating voltage of 300kV.
[0047] The blue quantum dot electroluminescent device was fabricated using an ITO / PEDOT:PSS / TFB / blue quantum dot / ZnMgO / Al structure. The external quantum efficiency of the device was measured in a glove box using a test system combining a Keithley 2400 digital source meter and a SpectraScan PR-788 wide dynamic range spectrophotometer, and was calculated using a method reported in the literature.
[0048] Figure 1 is a schematic diagram of the core-shell structure of the blue quantum dot material of the present invention, wherein the quantum dot core is composed of binary or higher ZnSeSTe containing Se but not Cd, the first shell of the quantum dot is composed of ternary or higher CdZnSeS containing Se, and the outermost N-layer of the quantum dot is composed of binary or higher CdZnSeS.
[0049] Example 1
[0050] Preparation of ZnSe / CdZnSe / ZnS quantum dots:
[0051] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0052] (2) Mix 5 mmol of zinc acetate, 10 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1.
[0053] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 9.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0054] (4) Weigh 0.2 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Inject it into the solution obtained in step (3), and then heat it to 300℃ and react for 10 min to obtain ZnSe quantum dot solution.
[0055] (5) Dissolve 2 mmol of selenium powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0056] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor 1 obtained in step (2) and 0.2 mL of selenium precursor obtained in step (5) into the reaction solution at a rate of 0.6 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.3 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0057] (7) Inject 2 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6), and add octyl mercaptan dropwise after the temperature stabilizes. The dropwise addition rate is 0.6 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0058] (8) Purify ZnSe / CdZnSe / ZnS from the solution in step (7), and then redisperse the resulting solid powder in n-hexane.
[0059] Example 2
[0060] Preparation of ZnSe / CdZnSe / ZnSe / ZnS quantum dots:
[0061] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0062] (2) Mix 5 mmol of zinc acetate, 10 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1.
[0063] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 9.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0064] (4) Weigh 0.2 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Inject it into the solution obtained in step (3), and then heat it to 300℃ and react for 10 min to obtain ZnSe quantum dot solution.
[0065] (5) Dissolve 2 mmol of selenium powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0066] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor 1 obtained in step (2) and 0.2 mL of selenium precursor obtained in step (5) into the reaction solution at a rate of 0.6 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.4 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0067] (7) Inject 2 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6). After the temperature stabilizes, add selenium precursor obtained in step (6) dropwise at a rate of 0.6 mL / h. After the addition is complete, react for 10 min.
[0068] (8) Inject 5 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (7), and add octyl mercaptan dropwise after the temperature stabilizes. The dropwise addition rate is 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0069] (9) Purify ZnSe / CdZnSe / ZnSe / ZnS from the solution in step (8), and then redisperse the resulting solid powder in n-hexane.
[0070] Figure 2 shows a transmission electron microscope image of the blue quantum dot. The quantum dot has a uniform size distribution and an average size of about 12.4 nm.
[0071] Example 3
[0072] Preparation of ZnSe / CdZnSe / CdZnSeS / ZnSeS / ZnS quantum dots:
[0073] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0074] (2) Mix 10 mmol zinc acetate, 20 mmol fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1;
[0075] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 9.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0076] (4) Weigh 0.2 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Inject it into the solution obtained in step (3), and then heat it to 300℃ and react for 10 min to obtain ZnSe quantum dot solution.
[0077] (5) Dissolve 10 mmol of selenium powder in 5 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0078] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor 1 obtained in step (2) and 0.2 mL of selenium precursor 2 obtained in step (5) to the reaction solution at a rate of 0.6 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.4 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0079] (7) Dissolve 10 mmol of sulfur powder in 5 mL of trioctylphosphine under an inert gas atmosphere to obtain sulfur precursor;
[0080] (8) Inject 3 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6). After the temperature stabilizes, mix selenium precursor 2 obtained in step (5) and sulfur precursor obtained in step (7) in a 1:1 ratio. Then add the mixed precursor to the solution dropwise at a rate of 0.6 mL / h. After the reaction is complete for 10 min, inject 0.3 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0081] (9) Inject 4 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (8). After the temperature stabilizes, mix selenium precursor 2 obtained in step (5) and sulfur precursor obtained in step (7) in a 1:1 ratio. Then add the mixed precursor to the solution dropwise at a rate of 0.3 mL / h. After the addition is complete, react for 10 min.
[0082] (10) Inject 6 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (9). After the temperature stabilizes, add sulfur precursor obtained in step (7) dropwise at a rate of 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0083] (11) Purify ZnSe / CdZnSe / CdZnSeS / ZnSeS / ZnS from the solution in step (10), and then redisperse the resulting solid powder in n-hexane.
[0084] Example 4
[0085] Preparation of ZnSe / CdZnSe / CdZnS / ZnSe / ZnSeS / ZnS quantum dots:
[0086] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0087] (2) Mix 10 mmol zinc acetate, 20 mmol fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1;
[0088] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 10.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0089] (4) Weigh 0.2 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Inject it into the solution obtained in step (3), and then heat it to 300℃ and react for 10 min to obtain ZnSe quantum dot solution.
[0090] (5) Dissolve 10 mmol of selenium powder in 5 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0091] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor 1 obtained in step (2) and 0.2 mL of selenium precursor 2 obtained in step (5) to the reaction solution at a rate of 0.6 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.5 mL of cadmium precursor obtained in step (1).
[0092] (7) Dissolve 10 mmol of sulfur powder in 5 mL of trioctylphosphine under an inert gas atmosphere to obtain sulfur precursor;
[0093] (8) Inject 2 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6). After the temperature stabilizes, add sulfur precursor obtained in step (7) at a rate of 0.3 mL / h. After the reaction is completed and 10 min has elapsed, inject 0.3 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0094] (9) Inject 3 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (8). After the temperature stabilizes, add selenium precursor 2 obtained in step (5) at a rate of 0.3 mL / h. After the addition is complete, react for 10 min.
[0095] (10) Inject 4 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (9). After the temperature stabilizes, mix selenium precursor 2 obtained in step (5) and sulfur precursor obtained in step (7) in a 1:1 ratio. Then add the mixed precursor to the solution dropwise at a rate of 0.3 mL / h. After the addition is complete, react for 10 min.
[0096] (11) Inject 5 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (10). After the temperature stabilizes, add sulfur precursor obtained in step (7) dropwise at a rate of 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0097] (12) Purify ZnSe / CdZnSe / CdZnS / ZnSe / ZnSeS / ZnS from the solution in step (11), and then redisperse the resulting solid powder in n-hexane.
[0098] Example 5
[0099] Preparation of ZnSe / CdZnSe / CdZnSeS / ZnSe / ZnSeS / CdZnS / ZnS quantum dots:
[0100] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0101] (2) Mix 10 mmol zinc acetate, 20 mmol fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1;
[0102] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 10.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0103] (4) Weigh 0.2 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Inject it into the solution obtained in step (3), and then heat it to 300℃ and react for 10 min to obtain ZnSe quantum dot solution.
[0104] (5) Dissolve 10 mmol of selenium powder in 5 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0105] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor 1 obtained in step (2) and 0.2 mL of selenium precursor 2 obtained in step (5) to the reaction solution at a rate of 0.6 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.5 mL of cadmium precursor obtained in step (1).
[0106] (7) Dissolve 10 mmol of sulfur powder in 5 mL of trioctylphosphine under an inert gas atmosphere to obtain sulfur precursor;
[0107] (8) Inject 3 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6). After the temperature stabilizes, mix selenium precursor 2 obtained in step (5) and sulfur precursor obtained in step (7) in a 1:1 ratio. Then add the mixed precursor to the solution dropwise at a rate of 0.6 mL / h. After the reaction is complete for 10 min, inject 0.3 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0108] (9) Inject 3 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (8). After the temperature stabilizes, add selenium precursor 2 obtained in step (5) at a rate of 0.3 mL / h. After the addition is complete, react for 10 min.
[0109] (10) Inject 4 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (9). After the temperature stabilizes, mix selenium precursor 2 obtained in step (5) and sulfur precursor obtained in step (7) in a 1:1 ratio. Then add the mixed precursor to the solution dropwise at a rate of 0.3 mL / h. After the addition is complete, react for 10 min.
[0110] (11) Inject 2 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (10). After the temperature stabilizes, add sulfur precursor obtained in step (7) at a rate of 0.3 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.3 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0111] (12) Inject 5 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (11). After the temperature stabilizes, add sulfur precursor obtained in step (7) dropwise at a rate of 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0112] (13) Purify ZnSe / CdZnSe / CdZnSeS / ZnSe / ZnSeS / CdZnS / ZnS from the solution in step (12), and then redisperse the resulting solid powder in n-hexane.
[0113] Example 6
[0114] Preparation of ZnSeS / CdZnSe / ZnS quantum dots:
[0115] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0116] (2) Mix 5 mmol of zinc acetate, 10 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1.
[0117] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 9.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0118] (4) Weigh 0.1 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Weigh 0.1 mmol of sulfur powder and dissolve it in 0.1 mL of trioctylphosphine to obtain sulfur precursor 1. Mix selenium precursor 1 and sulfur precursor 1 to obtain mixed precursor. Inject it into the solution obtained in step (3). Then heat it to 300℃ and react for 10 min to obtain ZnSeS quantum dot solution.
[0119] (5) Dissolve 2 mmol of selenium powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0120] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor 1 obtained in step (2) and 0.2 mL of selenium precursor obtained in step (5) into the reaction solution at a rate of 0.6 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.3 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0121] (7) Inject 2 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6), and add octyl mercaptan dropwise after the temperature stabilizes. The dropwise addition rate is 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0122] (8) Purify ZnSeS / CdZnSe / ZnS from the solution in step (7), and then redisperse the resulting solid powder in n-hexane.
[0123] Example 7
[0124] Preparation of ZnSeTe / CdZnSe / ZnS quantum dots:
[0125] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0126] (2) Mix 5 mmol of zinc acetate, 10 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1.
[0127] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 9.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0128] (4) Weigh 0.2 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Weigh 0.005 mmol of tellurium powder and dissolve it in 0.05 mL of trioctylphosphine to obtain tellurium precursor. Mix selenium precursor 1 and tellurium precursor to obtain mixed precursor. Inject it into the solution obtained in step (3). Then heat it to 300℃ and react for 1 h to obtain ZnSeTe quantum dot solution.
[0129] (5) Dissolve 2 mmol of selenium powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0130] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor 1 obtained in step (2) and 0.2 mL of selenium precursor obtained in step (5) into the reaction solution at a rate of 0.6 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.3 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0131] (7) Inject 2 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6), and add octyl mercaptan dropwise after the temperature stabilizes. The dropwise addition rate is 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0132] (8) Purify ZnSeTe / CdZnSe / ZnS from the solution in step (7), and then redisperse the resulting solid powder in n-hexane.
[0133] Example 8
[0134] Preparation of ZnSeTeS / CdZnSe / ZnS quantum dots:
[0135] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0136] (2) Mix 5 mmol of zinc acetate, 10 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1.
[0137] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 9.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0138] (4) Weigh 0.1 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Weigh 0.1 mmol of sulfur powder and dissolve it in 0.1 mL of trioctylphosphine to obtain sulfur precursor 1. Weigh 0.005 mmol of tellurium powder and dissolve it in 0.05 mL of trioctylphosphine to obtain tellurium precursor. Mix selenium precursor 1, sulfur precursor 1 and tellurium precursor to obtain mixed precursor. Inject it into the solution obtained in step (3). Then heat it to 300℃ and react for 1 h to obtain ZnSeTeS quantum dot solution.
[0139] (5) Dissolve 2 mmol of selenium powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0140] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor 1 obtained in step (2) and 0.2 mL of selenium precursor obtained in step (5) into the reaction solution at a rate of 0.6 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.3 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0141] (7) Inject 2 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6), and add octyl mercaptan dropwise after the temperature stabilizes. The dropwise addition rate is 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0142] (8) Purify ZnSeTeS / CdZnSe / ZnS from the solution in step (7), and then redisperse the resulting solid powder in n-hexane.
[0143] Example 9
[0144] Preparation of ZnSe / CdZnSeS / ZnS quantum dots:
[0145] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0146] (2) Mix 5 mmol of zinc acetate, 10 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1.
[0147] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 9.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0148] (4) Weigh 0.2 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Inject it into the solution obtained in step (3), and then heat it to 300℃ and react for 10 min to obtain ZnSe quantum dot solution.
[0149] (5) Dissolve 2 mmol of selenium powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0150] (6) Dissolve 2 mmol of sulfur powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain sulfur precursor 1;
[0151] (7) Inject 2 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (4). After the temperature stabilizes, mix selenium precursor 2 obtained in step (5) and sulfur precursor 1 obtained in step (6) in a 1:1 ratio. Then add the mixed precursor to the solution dropwise at a rate of 0.5 mL / h. After the reaction is complete for 10 min, inject 0.2 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0152] (8) Inject 2 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (7), and add octyl mercaptan dropwise after the temperature stabilizes. The dropwise addition rate is 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0153] (9) Purify ZnSe / CdZnSeS / ZnS from the solution in step (8), and then redisperse the resulting solid powder in n-hexane.
[0154] Example 10
[0155] Preparation of ZnSe / CdSeS / ZnS quantum dots:
[0156] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0157] (2) Mix 5 mmol of zinc acetate, 10 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1.
[0158] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 9.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0159] (4) Weigh 0.2 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Inject it into the solution obtained in step (3), and then heat it to 300℃ and react for 10 min to obtain ZnSe quantum dot solution.
[0160] (5) Dissolve 2 mmol of selenium powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0161] (6) Dissolve 2 mmol of sulfur powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain sulfur precursor 1;
[0162] (7) Cool the solution obtained in step (4) to 240°C, mix the selenium precursor 2 obtained in step (5) and the sulfur precursor 1 obtained in step (6) in a 1:1 ratio to obtain a mixed precursor, and then add 4 mL of the cadmium precursor obtained in step (1) and 0.5 mL of the mixed precursor alternately to the reaction solution. After the addition is complete, react for 10 min.
[0163] (8) Inject 4 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (7), and add octyl mercaptan dropwise after the temperature stabilizes. The dropwise addition rate is 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0164] (9) Purify ZnSe / CdSeS / ZnS from the solution in step (8), and then redisperse the resulting solid powder in n-hexane.
[0165] Comparative Example 1
[0166] Preparation of ZnS / CdZnSe / ZnS quantum dots:
[0167] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0168] (2) Mix 5 mmol of zinc acetate, 10 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1.
[0169] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 9.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0170] (4) Weigh 0.2 mmol of sulfur powder and dissolve it in 0.5 mL of trioctylphosphine to obtain sulfur precursor 1. Inject it into the solution obtained in step (3), and then heat it to 300 °C and react for 10 min to obtain ZnS quantum dot solution.
[0171] (5) Dissolve 2 mmol of selenium powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0172] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor 1 obtained in step (2) and 0.2 mL of selenium precursor obtained in step (5) into the reaction solution at a rate of 0.6 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.3 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0173] (7) Inject 2 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6), and add octyl mercaptan dropwise after the temperature stabilizes. The dropwise addition rate is 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0174] (8) Purify ZnS / CdZnSe / ZnS from the solution in step (7), and then redisperse the resulting solid powder in n-hexane.
[0175] Comparative Example 2
[0176] Preparation of ZnSe / CdZnS / ZnS quantum dots:
[0177] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0178] (2) Mix 5 mmol of zinc acetate, 10 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor 1.
[0179] (3) Mix 0.8 mL of the zinc precursor obtained in step (2) with 9.2 mL of octadecene and heat under an inert gas atmosphere to obtain zinc precursor 2;
[0180] (4) Weigh 0.2 mmol of selenium powder and dissolve it in 0.5 mL of diphenylphosphine to obtain selenium precursor 1. Inject it into the solution obtained in step (3), and then heat it to 300℃ and react for 10 min to obtain ZnSe quantum dot solution.
[0181] (5) Dissolve 2 mmol of sulfur powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain sulfur precursor 1;
[0182] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor 1 obtained in step (2) and 0.2 mL of sulfur precursor obtained in step (5) into the reaction solution at a rate of 0.6 mL / h. After the addition is complete and the reaction is completed for 10 min, inject 0.4 mL of cadmium precursor obtained in step (1) and react for 30 min.
[0183] (7) Inject 4 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6), and add octyl mercaptan dropwise after the temperature stabilizes. The dropwise addition rate is 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0184] (8) Purify ZnSe / CdZnS / ZnS from the solution in step (7), and then redisperse the resulting solid powder in n-hexane.
[0185] Comparative Example 3
[0186] Preparation of CdZnSe / ZnSe / ZnS quantum dots:
[0187] (1) Mix 5 mmol of cadmium oxide, 20 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain cadmium precursor.
[0188] (2) Mix 5 mmol of zinc acetate, 10 mmol of fatty acid and octadecene, heat under an inert gas atmosphere to remove acetic acid, and cool to obtain zinc precursor;
[0189] (3) Mix 0.02 mL of the cadmium precursor obtained in step (1), 0.8 mL of the zinc precursor obtained in step (2) with 10 mL of octadecene, and heat under an inert gas atmosphere to obtain a cadmium / zinc mixed precursor.
[0190] (4) Weigh 0.4 mmol of selenium powder and dissolve it in 1 mL of trioctylphosphine to obtain selenium precursor 1. Inject it into the solution obtained in step (3), and then heat it to 300℃ and react for 30 min to obtain CdZnSe quantum dot solution.
[0191] (5) Dissolve 2 mmol of selenium powder in 1 mL of trioctylphosphine under an inert gas atmosphere to obtain selenium precursor 2;
[0192] (6) Heat the solution obtained in step (4) to 300℃, and add 2 mL of zinc precursor obtained in step (2) and 0.2 mL of selenium precursor obtained in step (5) into the reaction solution at a rate of 0.6 mL / h. After the addition is complete, react for 10 min.
[0193] (7) Inject 3 mL of zinc precursor 1 obtained in step (2) into the solution obtained in step (6), and add octyl mercaptan dropwise after the temperature stabilizes. The dropwise addition rate is 0.3 mL / h. After the addition is complete, react for 10 min and then cool to room temperature.
[0194] (8) Purify CdZnSe / ZnSe / ZnS from the solution in step (7), and then redisperse the resulting solid powder in n-hexane.
[0195] Table 1 lists the properties and performance of the blue quantum dot materials in the above embodiments and comparative examples, as well as the specific chemical element composition ratios in the quantum dot structure.
[0196] Table 1
[0197] Examples 1-5 show quantum dot structures with different numbers of outermost shell layers N (N = 1, 2, 3, 4, 5), using ZnSe as the quantum dot core and CdZnSe as the first shell, respectively. Examples 6-8 show quantum dot structures using ZnSeS, ZnSeTe, and ZnSeTeS as the quantum dot core, CdZnSe as the first shell, and ZnS as the outermost shell, respectively. Examples 9-10 show quantum dot structures using ZnSe as the quantum dot core, CdZnSeS, CdSeS as the first shell, and ZnS as the outermost shell, respectively. All of these structures exhibit pure blue light emission between 460 and 475 nm, a narrow spectral half-width of less than 25 nm, a high fluorescence quantum yield exceeding 85%, and an external quantum efficiency exceeding 10%.
[0198] Compared with Comparative Example 1, the quantum dot of Example 1 has a ZnSe core containing Se, while the quantum dot of Comparative Example 1 has a ZnS core that does not contain Se. Example 1 has a narrower spectral half-width, higher fluorescence quantum yield and higher external quantum efficiency.
[0199] Compared with Comparative Example 2, the quantum dot of Example 9 has CdZnSeS containing Se as the first shell, while the quantum dot of Comparative Example 2 has CdZnS without Se as the first shell. Example 9 has a narrower spectral half-width, higher fluorescence quantum yield and higher external quantum efficiency.
[0200] Compared with Comparative Example 3, Example 2 has a ZnSe quantum dot core, while Comparative Example 2 does not have a ZnSe quantum dot core. Example 2 has a narrower spectral half-width, higher fluorescence quantum yield and higher external quantum efficiency.
[0201] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any modifications or alterations made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A blue quantum dot material, characterized in that, It includes a quantum dot core, a first shell layer coated outside the quantum dot core, and N outer shell layers coated outside the first shell layer in sequence, where 1 ≤ N ≤ 5; The chemical composition of the quantum dot core is ZnSe. x0 S y0 Te 1-x0-y0 , where 0 < x0 ≤ 1, 0 ≤ y0 < 1, and 0.8 ≤ x0 + y0 ≤ 1; The chemical composition of the first shell of the quantum dot is Cd. x1 Zn 1-x1 Se y1 S 1-y1 , where 0 < x1 ≤ 1, 0 < y1 ≤ 1, and x1 and y1 are not both 1 at the same time; The chemical composition of the N-layer outer shell of the quantum dot is independently Cd. x2 Zn 1-x2 Se y2 S 1-y2 , where 0 ≤ x2 ≤ 1, 0 ≤ y2 ≤ 1, and when x2 = x1, y2 ≠ y1.
2. The blue quantum dot material according to claim 1, characterized in that, 0.1 ≤ x0 ≤ 1, 0.1 ≤ y1 ≤ 1.
3. The blue quantum dot material according to any one of claims 1-2, characterized in that, The core, the first shell layer and the N outer shell layers of the quantum dots are all homogeneous.
4. The blue quantum dot material according to any one of claims 1-3, characterized in that, The core of the quantum dots contains Se element and is selected from one of ZnSe, ZnSeS, ZnSeTe, ZnSeSTe.
5. The blue quantum dot material according to any one of claims 1-4, characterized in that, The first shell layer of the quantum dots contains both Cd and Se elements and is selected from one of CdZnSe, CdZnSeS, CdSeS.
6. The blue quantum dot material according to any one of claims 1-5, characterized in that, The N outermost shell layers of the quantum dots are independently selected from one of ZnSe, ZnS, CdSe, CdS, CdZnSe, CdZnS, CdSeS, ZnSeS, CdZnSeS.
7. The blue quantum dot material according to any one of claims 1-6, characterized in that, The thickness of the core of the quantum dots is 2 - 20 nm, the thickness of the first shell layer of the quantum dots is 0.3 - 10 nm, and the total thickness of the N outermost shell layers of the quantum dots is 0.3 - 20 nm.
8. The blue quantum dot material according to any one of claims 1-7, characterized in that, The central wavelength of the photoluminescence excitation fluorescence spectrum of the quantum dots is greater than or equal to 440 nm and less than or equal to 490 nm, and the full width at half maximum of the spectrum is greater than or equal to 8 nm and less than or equal to 40 nm.
9. The method for preparing the blue quantum dot material according to any one of claims 1 to 8, characterized in that, It includes the following steps: S1. Prepare Cd precursor, Zn precursor, Se precursor, S precursor, Te precursor solutions respectively; S2. Prepare ZnSeSTe core quantum dot solution; S3. Inject Cd precursor, Se precursor, Zn precursor, S precursor solutions into the ZnSeSTe core quantum dot solution obtained in S2, and obtain ZnSeSTe / CdZnSeS quantum dot solution after reaction; S4. Inject Cd precursor, Zn precursor, Se precursor, S precursor solutions into the ZnSeSTe / CdZnSeS quantum dot solution obtained in S3, and operate independently for N times to coat N layers of CdZnSeS outer shell layers outside the ZnSeSTe / CdZnSeS quantum dots.
10. The application of the blue quantum dot material according to any one of claims 1 to 8 in optoelectronic devices, characterized in that, The optoelectronic device includes any one of a photoluminescence device, an electroluminescence device, a photodetector device, and a nonlinear optical device.