Quantum dot material, preparation method thereof, and quantum dot film and backlight module using the same

Abstract

A quantum dot material, a method for preparing it, and a quantum dot film and a backlight module using the same are disclosed. The quantum dot material comprises a core layer, a ligand layer, and a coating layer. The ligand layer forms and covers at least a portion of the surface of the core layer and is bonded to the core layer. The coating layer forms and covers at least a portion of the surface of the ligand layer and is bonded to the ligand layer. The ligand layer is formed of at least three ligand compounds, comprising a first type of ligand compound and a second type of ligand compound; the first type of ligand compound has a first coordinating group for bonding with the core layer, and the second type of ligand compound has a second coordinating group for bonding with the coating layer. The core layer has an ABX3 crystal structure, wherein the A-site is occupied by a formamidinium ion, the B-site by a lead ion, and the X-site by one of a chloride ion, a bromide ion, and an iodide ion. When the incident light wavelength is 450 nm, the quantum dot material has a maximum emission wavelength between 450 nm and 760 nm in response to the incident light.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to quantum dot materials, preparation methods, and quantum dot films and backlight modules using the same. Prior Technology

[0002] Quantum dot films have a wide range of applications in displays. Their properties, when used in backlight modules, can improve the brightness, color saturation, and contrast of displays. The quantum dot material that makes up the quantum dot film is a nanoscale crystalline material. Due to its size, the electron-hole pairs present in the quantum dot material exhibit energy level quantization within the quantum dot, creating a band gap, as the size of the quantum dot is close to the wavelength of the material's matter waves. Therefore, by changing the size of the quantum dot, the band gap of the material can be altered, thereby creating optical properties such as adjustable emission wavelengths.

[0003] Among existing quantum dot materials, metal halide perovskite materials have become an important research direction in related fields due to their excellent photoelectric properties. Metal halide perovskite materials have various crystal structures, such as ABX3, (AA')BX4, A2BX4, and other perovskite structures. Due to the quantum confinement effect and the change of halogen sites, perovskite quantum dots can emit light of different wavelengths, and have the advantages of narrow emission spectrum half-width at half-maximum and high photoluminescence quantum yield (PLQY).

[0004] However, quantum dot materials have a relatively large surface area, so their surface activity is high and they are prone to dangling bonds or defects, which can lead to the formation of trap states. This results in a decrease in PLQY and poor environmental stability. They are easily degraded or fail due to environmental factors such as water, oxygen, light, and heat, which can cause their highly active surface reactions.

[0005] More specifically, traditional perovskite synthesis methods primarily use oleic acid (OA) and oleylamine (OLA) as ligands for quantum dot capping. However, perovskite quantum dot materials prepared by traditional methods typically exhibit high dynamic binding on their surface (generally composed of anions OA- and cations OLA+, and surface ions with opposite charges). Due to the mutual balance between ligands, the protective ligand layer on the perovskite quantum dot surface is prone to rapid decomposition during purification, leading to a rapid decrease in stability and luminescence efficiency, ultimately resulting in agglomeration. Therefore, relying solely on these two ligands for capping will cause ligand detachment due to the dynamic balance between the ligands and the quantum dot surface, leading to quantum dot agglomeration or degradation. Furthermore, ligands may lose their coordination ability due to electron or proton exchange, resulting in ligand detachment and causing surface instability in the quantum dot material, making it difficult for quantum dot materials to be practically applied and commercialized.

[0006] Besides these methods, the most common existing methods for preparing metal halide perovskite materials (especially FAPbBr3) are ligand-assisted reprecipitation (LARP) and hot injection (HI). However, these two methods are not only costly, but also difficult to control the quality of the final product, making mass production challenging.

[0007] In the LARP synthesis method, the use of expensive formamidine bromide (FABr) and lead bromide (PbBr₂) as precursors makes it difficult to reduce production costs. Furthermore, the need for dimethylformamide (DMF) or dimethylamine as a polar solvent in the reaction system, which interacts with the precursors and corrodes the structure of the perovskite nanocrystals during synthesis, thus reducing both yield and luminescence efficiency. In the HI synthesis method, formamidine acetate (FAAc) combined with PbBr₂ is typically used as a dual precursor. This method requires a high-temperature, anhydrous, and oxygen-free environment, and the reaction must be terminated by rapid ice bath cooling after precursor injection. These difficult-to-control environmental conditions and processes result in poor quality control of the final product and hinder large-scale production.

[0008] Furthermore, since both of the above preparation methods require the use of PbBr2 as a precursor, but the ratio of cations and anions used in the synthesis is related to the ratio of the selected inorganic salt, it is difficult to precisely adjust the composition of the final product.

[0009] All of the above-mentioned problems have made it difficult to mass-produce perovskite quantum dot materials that have good and stable quality and meet the light emission requirements of the International Telecommunication Union Radiocommunication Sector (ITU-R) specifications for high-definition imaging (Rec. 2020, BT. 2020). Summary of the Invention

[0010] The purpose of this application is to provide a quantum dot material and a backlight module using the quantum dot material to solve the above-mentioned problems.

[0011] This application provides a quantum dot material, characterized by comprising a core layer, a ligand layer, and a coating layer. The ligand layer forms and covers at least a portion of the surface of the core layer and is bonded to the core layer. The coating layer forms and covers at least a portion of the surface of the ligand layer and is bonded to the ligand layer. The ligand layer is formed of at least three ligand compounds, and the at least three ligand compounds include a first type of ligand compound and a second type of ligand compound; the first type of ligand compound has a first coordinating group for bonding with the core layer, and the second type of ligand compound has a second coordinating group for bonding with the coating layer.

[0012] This application proposes a quantum dot material, characterized in that: the organic-inorganic perovskite material has an ABX 3 crystal structure, wherein the A site is occupied by formamidinium ions, the B site is occupied by lead ions, and the X site is occupied by bromide ions, wherein the organic perovskite material, when the wavelength of incident light is 450 nm, has a maximum emission wavelength in response to the incident light that is between 450 nm and 760 nm, preferably between 525 nm and 535 nm.

[0013] This application proposes a quantum dot material, characterized in that: the organic-inorganic perovskite material has an ABX3 crystal structure, wherein the A site is occupied by formamidinium ions, the B site is occupied by lead ions, and the X site is occupied by bromide ions, wherein the infrared absorption spectrum of the organic-inorganic perovskite material has a relative peak of stretching vibration in the wavenumber range of 750 cm⁻¹ to 1250 cm⁻¹.

[0014] In some embodiments of this application, the highest emission wavelength is between 528 nm and 532 nm.

[0015] In some embodiments of this application, the full width at half maximum (FWHM) of the organic-inorganic perovskite material is less than 23 nm.

[0016] In some embodiments of this application, the quantum efficiency of the organic-inorganic perovskite material is greater than 60%.

[0017] In some embodiments of this application, the quantum efficiency of the organic-inorganic perovskite material is greater than 90%.

[0018] In some embodiments of this application, the average fluorescence lifetime of the organic-inorganic perovskite material is between 18.3 ns and 30.5 ns.

[0019] In some embodiments of this application, the infrared absorption spectrum of the organic-inorganic perovskite material has a relative peak of stretching vibration in the wavenumber range of 750 cm⁻¹ to 1250 cm⁻¹.

[0020] In some embodiments of this application, the organic-inorganic perovskite material is synthesized from at least three precursors.

[0021] In some embodiments of this application, the at least three precursors include a formamidinium ion precursor, a lead ion precursor, and a bromide ion precursor, wherein the formamidinium ion precursor includes a salt for generating a formamidinium free base, the lead ion precursor includes a lead compound, and the bromide ion precursor includes an organic bromide.

[0022] In some embodiments of this application, the salt used to generate formamidine free base includes formamidine acetate, the lead compound includes at least one of lead acetate and lead monoxide, and the organic bromide includes benzoyl bromide.

[0023] In some embodiments of this application, the ligands involved in the reaction during the preparation of the organic-inorganic perovskite material include sulfobetaine and oleic acid.

[0024] In some embodiments of this application, the sulfobetaine comprises 3-(N,N-dimethyloctylammonio)-propanesulfonate.

[0025] In some embodiments of this application, the temperature during the preparation of the organic-inorganic perovskite material does not exceed 120°C.

[0026] In some embodiments of this application, the chemical formula of the first type of ligand compound is: , where Z is the first coordinating group; and n is the first alkane, and n1 is the chain number of the first alkane, which is greater than 0.

[0027] In some embodiments of this application, the first type of ligand compound further comprises: a first functional group, such that the chemical formula of the first type of ligand compound is: , where W m1 is the first functional base, m1 is the number of the first functional bases, which is a positive integer.

[0028] In some embodiments of this application, the first functional group is selected from any of the following: methyl (-CH 3), ethyl (-C 2H 6), propyl (-C 3H 7), butyl (-C 4H 9), pentyl (-C 5H 11), hydroxyl (-OH), amino (-NH 3), and pyridyl (-C 5H 5N).

[0029] In some embodiments of this application, the chemical formula of the second type of ligand compound is: ,in n is the second alkane, and n2 is the chain number of the second alkane, which is greater than or equal to 0; and KX is the second coordinating group.

[0030] In some embodiments of this application, the second coordinating group is selected from any of the following: siloxane compounds, titanoxane compounds, zirconoxane compounds, aluminumoxane compounds, zincoxane compounds, and sulfuroxane compounds.

[0031] In some embodiments of this application, the second type of ligand compound further comprises: a second functional group, such that the chemical formula of the second type of ligand compound is: , where W m2 is the second functional group, and m2 is the number of the second functional groups, which is a positive integer.

[0032] In some embodiments of this application, the second functional group is selected from any of the following: methyl (-CH 3), ethyl (-C 2H 6), propyl (-C 3H 7), butyl (-C 4H 9), pentyl (-C 5H 11), hydroxyl (-OH), amino (-NH 3), and pyridyl (-C 5H 5N).

[0033] In some embodiments of this application, the infrared absorption spectrum of the quantum dot material has relative peaks of stretching vibrations in the wavenumber ranges of 750 cm⁻¹ to 850 cm⁻¹, 900 cm⁻¹ to 1000 cm⁻¹, 1050 cm⁻¹ to 1150 cm⁻¹, and 3400 cm⁻¹ to 3500 cm⁻¹.

[0034] In some embodiments of this application, at least one of the materials in the coating layer has a melting point greater than 60 degrees.

[0035] In some embodiments of this application, the average fluorescence lifetime of the quantum dot material is less than 120 ns.

[0036] In some embodiments of this application, the A site of the crystal structure of the core layer is occupied by formamidinium ions, the B site is occupied by lead ions, and the X site is occupied by one of chloride ions, bromide ions, and iodide ions. The quantum dot material has a maximum emission wavelength between 450 nm and 760 nm when the incident light wavelength is 450 nm.

[0037] In some embodiments of this application, the coating layer is formed based on any of the following materials: silicon oxide, titanium oxide, aluminum oxide, boron oxide, zinc sulfide, and lead sulfide.

[0038] In some embodiments of this application, the coating layer comprises at least one of tetraethoxysilane (TEOS; CAS NO: 78-10-4), tetramethyl orthosilicate (TMS; CAS NO: 681-84-5), 3-methcryloxypropyltrimethoxysilane (CAS NO: 2530-85-0), sulfur powder (CAS NO: 7704-34-9), selenium powder (CAS NO: 07782-49-2), and lead(II) oxide (CAS NO: 1317-36-8).

[0039] In some embodiments of this application, the thickness of the coating layer is between 5 nm and 100 μm.

[0040] In some embodiments of this application, the first coordinating group is selected from any of the following: carboxylic acid group (-COOH), sulfonic acid group (-SO 3H), sulfinic acid group (-SOOH), thiosulfonic acid group (-COSH), nitrate group (-ONO 2), nitrite group (-ONO), cyanate group (-OCN), isocyanate group (-NCO), phosphate group (-OPO(OH) 2), phosphite group (-PO(OH) 2), thiol group (-SH), primary amino group (-NH 2), secondary amino group (-NH), and tertiary amino group (-NR 2).

[0041] In some embodiments of this application, the first type of ligand compound comprises at least two of the following: oleic acid (CAS NO: 112-80-1), stearic acid (CAS NO: 57-11-4), 4-dodecylbenzenesulfonic acid (CAS NO: 121-65-3), 1-octadecanethiol (CAS NO: 2885-00-9), 2,2'-iminodiethanol (CAS NO: 111-42-2), methylammonium acetate (CAS NO: 6998-30-7), and pyridinium propanesulfonate (CAS NO: 15471-17-7).

[0042] In some embodiments of this application, the second type of ligand compounds include (3-Aminopropyl)triethoxysilane (APTES; CAS NO: 919-30-2), (3-Aminopropyl)trimethoxysilane (APTMS; CAS NO: 13822-56-5), (3-Mercaptopropyl)triethoxysilane (MPTES; CAS NO: 14814-09-6), (3-Mercaptopropyl)trimethoxysilane (MPTMS; CAS No. 4420-74-0), cysteine ​​(Cysteine; CAS No. 52-90-4), and 3-mercaptopropylpropanoic acid (3-Sulfanylpropanoic acid; CAS No. 13822-56-5). The following substances are listed: 107-96-0), ethanolate (titanium(4+); CAS No: 3087-36-3), titanium isopropoxide (Titanium isopropoxide; CAS No: 546-68-9), titanium tetrachloride (Titanium tetrachloride; CAS No: 7550-45-0), trimethylalane (Trimethylalane; CAS No: 75-24-1), and zirconyl nitrate (Zirconyl nitrate; CAS No: 13826-66-9).

[0043] In some embodiments of this application, the main chain length of the first type of ligand compound has a carbon number greater than or equal to 10.

[0044] This application provides a method for preparing quantum dot materials, characterized by comprising the following steps: mixing a formamidinium ion precursor, a lead ion precursor, and a ligand in a solvent to form a mixed solution; drying the mixed solution at a first temperature; cooling the dried mixed solution to a second temperature below the first temperature under an inert gas environment; and injecting a bromide ion precursor into the mixed solution at the second temperature to generate a solution containing the organic-inorganic perovskite material, wherein the generated quantum dot material has an ABX3 crystal structure, with the A-site occupied by a formamidinium ion, the B-site occupied by a lead ion, and the X-site occupied by a bromide ion.

[0045] This application provides a method for preparing quantum dot materials, characterized by comprising the following steps: providing at least three compounds as precursors for FA ions, Pb ions, and Br ions, respectively; and treating the at least three compounds at an environment not exceeding 120°C to generate the quantum dot materials.

[0046] This application provides a method for preparing quantum dot materials, characterized by comprising the following steps: providing a variety of compounds as precursors for FA ions, Pb ions, and Br ions; and providing oleic acid and 3-(N,N-dimethyloctadecylammonium)-propanesulfonate as ligands to react with the precursors to generate the quantum dot materials.

[0047] In some embodiments of this application, the formamidine ion precursor comprises formamidine acetate.

[0048] In some embodiments of this application, the lead ion precursor comprises at least one of lead acetate and lead monoxide.

[0049] In some embodiments of this application, the bromide precursor comprises benzoyl bromide.

[0050] In some embodiments of this application, the ligand comprises oleic acid and sulfobetaine.

[0051] In some embodiments of this application, the sulfobetaine comprises 3-(N,N-dimethyloctadecylammonium)-propanesulfonate.

[0052] In some embodiments of this application, the first temperature does not exceed 120°C.

[0053] In some embodiments of this application, the first temperature is greater than or equal to 100°C, and the second temperature is between 40°C and 75°C.

[0054] In some embodiments of this application, the inert gas is nitrogen.

[0055] In some embodiments of this application, the method for preparing the quantum dot material further includes the following steps: performing a first centrifugation on a solution containing the organic-inorganic perovskite material to obtain a precipitate; adding an organic solvent to the precipitate and performing a second centrifugation; and filtering the quantum dot material based on the supernatant after the second centrifugation.

[0056] This application provides a quantum dot film suitable for backlight modules, characterized in that it comprises a quantum dot material as described in any of the preceding embodiments. The quantum dot material is, for example, an organic-inorganic perovskite material, and the organic-inorganic perovskite material comprises FAPbBr3.

[0057] This application provides a backlight module, characterized in that it includes a quantum dot film made of quantum dot material as described above.

[0058] The quantum dot materials proposed in this application possess excellent and stable material properties, particularly in thermal stability, and can produce green light that meets the requirements of the Rec. 2020 standard. Furthermore, the quantum dot materials proposed in this application exhibit a shorter average fluorescence lifetime, reducing fluorescence defects and increasing the proportion of fast electron-hole recombination, resulting in better emission efficiency. The preparation method of the quantum dot materials proposed in this application can synthesize high-performance and high-quality organic perovskite materials at low temperatures using cost-effective three precursors. Compared to existing methods, this method offers higher reproducibility and is suitable for mass production. Simple Explanation of the Diagram

[0059] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort. Figure 1 is a schematic diagram of a display device according to some embodiments of this application; Figure 2 is a schematic diagram of a backlight module according to some embodiments of this application; Figures 3A to 3C are schematic diagrams of the structure of quantum dot materials according to some embodiments of this application; Figures 4A and 4B are schematic diagrams of transmission electron microscopy analysis of quantum dot materials according to some embodiments of this application; Figures 5A to 5G are schematic diagrams of the absorption and emission spectra of quantum dot materials in some experimental examples and comparative examples of this application; Figures 6A and 6B show the time-resolved fluorescence spectra of quantum dot materials used in this application, including some experimental examples and comparative examples. Figures 7A and 7B show the fluorescence spectra of the quantum dot materials of the comparative example and experimental example 5 of this application at different temperatures; Figure 8 shows the X-ray diffraction spectra of quantum dot materials from some embodiments of this application; Figures 9A and 9B show the infrared absorption spectra of quantum dot materials according to some embodiments of this application; and Figure 10 is a flowchart of the steps of a method for manufacturing quantum dot materials according to some embodiments of this application. Implementation

[0060] To make the aforementioned objectives, features, and advantages of this technical solution more apparent and understandable, the specific embodiments of the proposed technical solution are described in detail below with reference to the accompanying drawings. The following descriptions of various embodiments of the technical solution of this invention are for illustrative purposes only and do not represent all embodiments of the invention or limit the invention to specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort should fall within the scope of protection of this disclosure.

[0061] It should be noted that when an element is described as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," "up," "down," and similar expressions used herein are only to indicate relative positional relationships based on diagrams and are not intended to limit the elements using these terms to only the representational form. When the absolute position of the described object changes, the description of the relative position may also change accordingly.

[0062] In all descriptions relating to specific numerical values ​​in this application, even if not explicitly stated, the terms "approximately" or "substantially" are included, meaning that these specific numerical values ​​encompass a possible range of numerical error to account for potential unintended effects and deviations in the process or material selection. This range of numerical error may include numerical changes that do not significantly alter the material's structure, properties, or effects, such as a deviation of 0% to 10%, which is clear to those skilled in the art.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0064] Figure 1 is a schematic diagram of a display device according to some embodiments of this application. Referring to Figure 1, the display device 10 includes a backlight module 100 and a display panel 200, wherein the backlight module 100 and the display panel 200 are disposed on the xy plane, and the display panel 200 is disposed on the backlight module 100 along the z-axis. The backlight module 100 is used to provide sufficient brightness and uniformly distributed light source toward the display panel 200. The display panel 200 is used to control and adjust the light passing through it, so as to display a corresponding image thereon. In this embodiment, the display device 10 can be any electronic device with display function, such as a television, a screen, a laptop computer, or a mobile phone, and this application is not limited thereto.

[0065] The backlight module 100 includes a light-emitting layer 110, a quantum dot film 120, and an optical adjustment layer 130 arranged sequentially along the z-axis. The quantum dot film 120 is disposed on the light-emitting layer 110, and the optical adjustment layer 130 is disposed on the quantum dot film 120. That is, the quantum dot film 120 is disposed between the light-emitting layer 110 and the optical adjustment layer 130.

[0066] The light-emitting layer 110 includes a plurality of light-emitting elements (LEDs) arranged in an array, which can be used to emit light towards the display panel 200. In some embodiments, the light-emitting elements (LEDs) may be blue light-emitting diodes (or light-emitting diodes with emission wavelengths in the blue light range). In some embodiments, the light-emitting elements (LEDs) may be mini-LEDs or micro-LEDs, but this application is not limited thereto. In other embodiments, the light-emitting elements (LEDs) may also be of other sizes and / or types.

[0067] A quantum dot film 120 is disposed on the light transmission path of the light-emitting layer 110 and is used to adjust the wavelength of some of the light emitted by the light-emitting elements LEDs, while allowing another portion of the light emitted by the LEDs to pass through directly without adjustment. For example, when the light-emitting elements LEDs emit light in the blue light wavelength range (e.g., 400nm-520nm), the quantum dot film 120 can adjust the wavelength of the first portion of the received light to the red light wavelength range (e.g., 610nm-720nm), adjust the wavelength of the second portion of the received light to the green light wavelength range (e.g., 520nm-610nm), and maintain the third portion of the received light in the blue light wavelength range for direct output without adjustment. In this way, the first to third portions of light emitted by the light-emitting layer 110 can mix to form white light after passing through the quantum dot film 120.

[0068] The optical adjustment layer 130 is also located on the light transmission path of the light-emitting layer 110 and is used to adjust the direction of the received light so as to make the transmitted light source more uniform. In some embodiments, the optical adjustment layer 130 includes a plurality of optical microstructures (not shown) and / or optical films (not shown) for adjusting the direction of light, but this application is not limited thereto.

[0069] The display panel 200 includes, for example, a pixel array substrate, a counter substrate, and a non-self-emissive display medium, wherein the pixel array substrate and the counter substrate are disposed opposite to each other, and the non-self-emissive display medium is disposed between the pixel array substrate and the counter substrate. In some embodiments, the non-self-emissive display medium may be, for example, liquid crystal, but this application is not limited thereto.

[0070] More specifically, the configuration of the backlight module 100 in this embodiment is shown in FIG2, which is a schematic diagram of a backlight module according to an embodiment of this application. Referring to FIG2, in this embodiment, the light-emitting layer 110 includes light-emitting elements LEDs, a substrate 111, and a protective layer 112. The light-emitting elements LEDs are disposed on the substrate 111 and emit light in the direction of the quantum dot film 120. The protective layer 112 covers the light-emitting elements LEDs.

[0071] The quantum dot film 120 includes an active layer 121, a support layer 122, a bonding layer 123, and a water-blocking layer 124. The active layer 121 may include a substrate (not shown) and quantum dot material (not shown) doped in the substrate. The substrate may be, for example, a light-transmitting polymer material (such as a resin material), and the quantum dot material may be, for example, semiconductor quantum dots synthesized from nanocrystalline semiconductor materials (such as group II-VI semiconductor materials, group III-V semiconductor materials, or other combinations thereof), but this application is not limited thereto. When the quantum dot material is irradiated with light, it emits light of a different wavelength than the irradiated light. For example, when the quantum dots are irradiated with blue light, they can emit green and red light.

[0072] A support layer 122 is disposed on the light-emitting surface S1 of the light-emitting layer 110 and serves to support / fix the functional layer 121, allowing the material of the functional layer 121 to be adhered to / coated onto the support layer 122. The support layer 122 may be formed, for example, of an organic polymer and / or inorganic material having light transmittance and a certain degree of support. The organic polymer may be, for example, polyvinylidene chloride (PVdC), cyclic olefin polymer (COC), high-density polyethylene (HDPE), polyethylene terephthalate (PET), polyimide (PI), polyethersulfone (PES), polyethylene naphthalate (PEN), polycarbonate (PC), or a combination of the foregoing. The inorganic material may be, for example, a metal oxide (such as SiOx, SixNy, etc.).

[0073] In some embodiments, the support layer 122 may be a polymer barrier film formed using PVdC and COC materials, which can provide a certain degree of water and oxygen barrier properties.

[0074] The bonding layer 123 is used to provide a bonding force so that the active layer 121 and the support layer 122 can be effectively and reliably bonded / fixed, wherein the bonding layer 123 may be formed, for example, by optical clear adhesive (OCA) or a primer.

[0075] The water-blocking layer 124 is directly or indirectly applied to at least a portion of the surface of the functional layer 121 to prevent the functional layer 121 from being affected by moisture and thus extending its service life. Specifically, the water-blocking layer 124 can be implemented using a protective polymer film. For example, the water-blocking layer 124 can be implemented using poly-para-xylene (Parylene). Parylene possesses properties such as high and low temperature resistance, corrosion resistance, acid and alkali resistance, water and moisture resistance, transparency, and high insulation strength. Therefore, when used as the water-blocking layer 124 to cover the functional layer 121, it can effectively isolate the functional layer 121 from the influence of moisture.

[0076] In this embodiment, the quantum dots in the active layer 121 can be implemented using various quantum dot materials with novel structures (e.g., organic-inorganic perovskite materials). In some embodiments, the quantum dot material can be used to excite light that conforms to the definition of green light in the specifications (Rec. 2020, BT. 2020) for high-definition images formulated by the International Telecommunication Union Radiocommunication Sector (ITU-R), that is, light with CIE-1931 color space coordinates (0.170, 0.797) and a wavelength between 530 nm and 535 nm. By utilizing the quantum dot material as the main material in the quantum dot film 120 / active layer 121, a good green light emission effect can be achieved, and the problems mentioned in the background art can be solved.

[0077] In addition, the quantum dot materials proposed in this application can also be used as substrates for most light-emitting elements in the optoelectronic field. For example, the organic-inorganic perovskite materials can also be used in the design of lasers, solar cells, and photosensors, but this application is not limited thereto.

[0078] Figures 3A to 3C are schematic diagrams of the structure of quantum dot materials according to some embodiments of this application, wherein Figure 3A is a schematic diagram of the cross-sectional structure of quantum dot materials according to some embodiments of this application, and Figures 3B and 3C are enlarged schematic diagrams of local areas of Figure 3A in different embodiments.

[0079] Referring first to Figure 3A, the quantum dot material 200' of this embodiment includes a core layer 210 and a ligand layer 220. The ligand layer 220 forms and covers at least a portion of the surface of the core layer 210 and is bonded to the core layer 210. In some embodiments, the quantum dot material 200' may further include a coating layer 230, which forms and covers at least a portion of the surface of the ligand layer 220 and is bonded to the ligand layer 220.

[0080] Specifically, in this embodiment, the core layer 210 can be, for example, composed of any nanomaterial with a size less than 100 nm. In some embodiments, the material constituting the core layer 210 can be an organic-inorganic perovskite material having an ABX3 crystal structure, wherein the A site can be cations such as Cs+, FA+ (formamidinium), or MA+ (methylammonium), the B site can be divalent metal ions such as Pb2+ or Sn, and X is a halogen, but this application is not limited to this. In other embodiments, the material of the core layer 210 can also be formed of nanomaterials with structures such as a sphalerite structure and / or a wurtzite structure.

[0081] In some embodiments, the core layer 210 can be made of FAPbBr3, meaning that in the crystal structure of the core layer 210, the A-site is occupied by formamidinium ions, the B-site by lead ions, and the X-site by bromide ions. In this embodiment, the quantum dot material 200' can be used to excite light that conforms to the definition of green light in the specifications (Rec. 2020, BT. 2020) for high-definition imaging developed by the International Telecommunication Union Radiocommunication Sector (ITU-R), that is, light with CIE-1931 color space coordinates (0.170, 0.797) and a wavelength between 525 nm and 535 nm (when the incident light wavelength is 450 nm). By using the quantum dot material as the main material in the quantum dot film 120 / active layer 121, a good green light emission effect can be achieved. In some embodiments, when the wavelength of the incident light is 450 nm, the highest emission wavelength of the quantum dot material 200' in response to the incident light may also be between 450 nm and 760 nm, that is, between the wavelengths of blue light and red light, but this application is not limited thereto.

[0082] The ligand layer 220 may be formed, for example, by a variety of ligand compounds. Its main function is to enable the quantum dots to be well dispersed in various nonpolar organic solvents and to improve the overall surface properties of the quantum dot material, such as temperature resistance and compatibility of the quantum dots with other materials, thereby further enhancing the optical performance of the quantum dot material.

[0083] More specifically, Figure 3B illustrates a partial cross-sectional structural embodiment of a quantum dot material 200a. The quantum dot material 200a of this embodiment includes a core layer 210 and a ligand layer 220a, wherein the ligand layer 220a may contain a variety of first-class ligand compounds LT1. The general chemical formula of the first-class ligand compound LT1 may be, for example, […]. Z is the first coordinating group; n1 is the first alkane, and n1 is the chain number of the first alkane, which is greater than 0; and m1 is the first functional group, m1 is the number of the first functional groups, which is a positive integer or zero.

[0084] In some embodiments, the first coordinating group Z in the first type of ligand compound LT1 may be, for example, an organic functional group capable of coordinating with the core layer 210 material. In some embodiments, the first coordinating group Z may be selected from any of the following functional groups: carboxylic acid group (-COOH), sulfonic acid group (-SO3H), sulfinic acid group (-SOOH), thiosulfonic acid group (-COSH), nitrate group (-ONO2), nitrite group (-ONO), cyanate group (-OCN), isocyanate group (-NCO), phosphate group (-OPO(OH)2), phosphite group (-PO(OH)2), thiol group (-SH), primary amino group (-NH2), secondary amino group (-NH), and tertiary amino group (-NR2), but this application is not limited to these.

[0085] In some embodiments, the main chain length of the first type of ligand compound LT1 (the chain with the largest number of carbons) is greater than or equal to 10, and the number of π bonds and σ bonds in its molecular structure can be arbitrary and exist in any possible position.

[0086] In some embodiments, the first functional group Wm1 is an optional structure in the first type of coordination compound LT1, where m1 is the number of functional groups, which can be a positive integer or zero. In other words, in some embodiments, the general chemical formula of the first type of coordination compound LT1 can also be expressed as: The primary functions of the first functional group Wm1 are (1) to modify surface defects, (2) to block water and oxygen, (3) to reduce reflection and increase refractive index, (4) to adjust surface polarity and / or (5) to enhance conductivity or insulation.

[0087] In some embodiments, the first functional group W m1 may be selected from any of the following functional groups: methyl (-CH 3), ethyl (-C 2H 6), propyl (-C 3H 7), butyl (-C 4H 9), pentyl (-C 5H 11), hydroxyl (-OH), amino (-NH 3), and pyridyl (-C 5H 5N), but this application is not limited thereto.

[0088] In some embodiments, the first class of ligand compound LT1 conforming to the above general chemical formula may be, for example, one or more of oleic acid (CAS NO: 112-80-1), stearic acid (CAS NO: 57-11-4), 4-dodecylbenzenesulfonic acid (CAS NO: 121-65-3), 1-octadecanethiol (CAS NO: 2885-00-9), 2,2'-iminodiethanol (CAS NO: 111-42-2), methylammonium acetate (CAS NO: 6998-30-7), pyridinium propanesulfonate (CAS NO: 15471-17-7), and sulfobetaine.

[0089] In some embodiments, the sulfobetaine may, for example, comprise 3-(N,N-dimethyloctylammonio)-propanesulfonate (SBE-18) or other compounds with similar properties, and this application is not limited thereto.

[0090] Figure 3C illustrates a partial cross-sectional structural embodiment of another quantum dot material 200b. The quantum dot material 200b of this embodiment includes a core layer 210, a ligand layer 220b, and a coating layer 230. The ligand layer 220b may be formed from at least three types of ligand compounds (a process referred to as "hybridization"). These three ligand compounds may include at least a first type of ligand compound LT1 and a second type of ligand compound LT2. The ligand layer 220b is bonded to the core layer 210 through a first coordinating group in the first type of ligand compound LT1, and to the coating layer 230 through a second coordinating group in the second type of ligand compound LT2.

[0091] Specifically, the basis for forming the ligand layer 220b through hybridization is the addition of N or more ligand compounds (N ≥ 3) during the synthesis of the quantum dot material 200. In some embodiments, the N ligand compounds may include at least two first-class ligand compounds LT1 and one second-class ligand compound LT2. Through ligand hybridization, a product meeting the desired conditions can be prepared according to the target conditions, achieving optimal performance. The description of the first-class ligand compound LT1 can be found in the above embodiments and will not be repeated here. The characteristics of the second-class ligand compound LT2 are further described below.

[0092] The general chemical formula of the second-class ligand compound LT2 is: Z is the first coordinating group; n is the second alkane, and n2 is the chain number of the second alkane, which is greater than or equal to 0; KX is the second coordinating group; and Wm2 is the second functional group, where m2 is the number of the second functional groups, which is a positive integer or zero.

[0093] Specifically, the second type of ligand compound LT2 can be a coupling agent that conforms to the general definition in the chemical system. At least one end of its molecule is a compound that can coordinate with the coating layer 230 and stack, and the other end is an organic functional group that can coordinate with the core layer 210, serving as a binding layer connecting organic materials and inorganic materials.

[0094] The first coordinating group Z in the second type of ligand compound LT2 is the same as that described above. It is an organic functional group that can coordinate with the core layer 210 material. Similar parts will not be repeated.

[0095] Dialkane The chain number is greater than or equal to 0, and the number of π bonds and σ bonds in its molecular structure can be arbitrary and exist in any possible position.

[0096] The second coordinating group KX can be any group grafted through chemical and physical bonding. The second coordinating group KX is located at the end not coordinated with the core layer 210 and contains at least X groups, where X is a positive integer. In some embodiments, the second coordinating group KX can be selected from any of the following compounds: siloxane compounds, titanoxane compounds, zirconoxane compounds, aluminumoxane compounds, zincoxane compounds, and sulfuroxane compounds, but this application is not limited to these.

[0097] The second functional group Wm2 is an optional structure in the second-class coordination compound LT2, where m2 is the number of functional groups, which can be a positive integer or zero. In other words, in some embodiments, the general chemical formula of the second-class coordination compound LT2 can also be represented as: [Second functional group]. Wm2 functions similarly to the first functional group Wm1, and its structure and implementation examples can be referred to the above embodiments, which will not be repeated here.

[0098] In some embodiments, the second-class ligand compound LT2 conforming to the above general chemical formula may be, for example, 3-aminopropyltriethoxysilane ((3-Aminopropyl)triethoxysilane, APTES; CAS NO: 919-30-2), 3-aminopropyltrimethoxysilane ((3-Aminopropyl)trimethoxysilane, APTMS; CAS NO: 13822-56-5), 3-mercaptopropyltrimethoxysilane ((3-Mercaptopropyl)triethoxysilane, MPTES; CAS NO: 14814-09-6), 3-mercaptopropyltrimethoxysilane ((3-Mercaptopropyl)trimethoxysilane, MPTMS; CAS No. 4420-74-0), cysteine ​​(Cysteine; CAS No. 52-90-4), or 3-mercaptopropionic acid (3-Sulfanylpropanoic acid). The invention application contains at least one of the following: acid; CAS No. 107-96-0), ethanolate; titanium(4+); CAS No: 3087-36-3, titanium isopropoxide; CAS No: 546-68-9, titanium tetrachloride; CAS No: 7550-45-0, trimethylalane; CAS No: 75-24-1, and zirconyl nitrate; CAS No: 13826-66-9, but is not limited thereto.

[0099] The coating layer 230 can be made of any material capable of coordinating with the second type of ligand compound LT2 and crosslinking with homologous substances to stack and thicken the shell structure via covalent, ionic, or metallic bonds. In some embodiments, the material of the coating layer 230 can be, for example, silicon oxide, titanium oxide, aluminum oxide, boron oxide, zinc sulfide, lead sulfide, etc., but this application is not limited to these.

[0100] In some specific embodiments, the coating layer 230 may comprise at least one or more of the following: tetraethoxysilane (TEOS; CAS NO: 78-10-4), tetramethyl orthosilicate (TMS; CAS NO: 681-84-5), 3-methcryloxypropyltrimethoxysilane (CAS NO: 2530-85-0), sulfur powder (CAS NO: 7704-34-9), selenium powder (CAS NO: 07782-49-2), and lead(II) oxide (CAS NO: 1317-36-8), but this application is not limited thereto. Furthermore, in some embodiments, the thickness of the coating layer 230 may be, for example, between 5 nm and 100 μm.

[0101] In summary, the quantum dot material 200a of the embodiment in Figure 3B of this application is a quantum dot structure synthesized using a first-class ligand compound LT1 and a core layer material 210. The quantum dot material 200b of the embodiment in Figure 3C of this application involves hybridization of specific ligands followed by a coating process to alter the physical properties of the quantum dot luminescent material through a composite method. Hybridizing the ligands in the quantum dot material means introducing dissimilar composite elements or compounds into the structure. This process will alter the optical properties, electronic properties, and environmental stability of the quantum dots, including resistance to light, heat, water, oxygen, and other chemical reactions.

[0102] The type, ratio, and amount of ligands can be used as important parameters to adjust the core layer during the synthesis process. Furthermore, by selecting appropriate ligands, they can be stacked outwards to graft the coating layer, thereby reducing the difficulty of synthesis.

[0103] It should be noted that although the quantum dot material 200' shown in Figures 3A to 3C is composed of a single core layer 210, a ligand layer 220, and a coating layer 230 arranged in sequence, this application is not limited to this. In other embodiments, the quantum dot material 200' may also include multiple units of core layer 210 and ligand layer 220 arranged in an overlapping manner, and then the multiple units of core layer 210 and ligand layer 220 are covered by coating layer 230, and this application is not limited thereto.

[0104] In some embodiments, the core layer 210 of the quantum dot material 200a / 200b can be synthesized from at least three precursors. The at least three precursors include a formamidinium ion precursor, a lead ion precursor, and a bromide ion precursor, wherein the formamidinium ion precursor contains a salt for generating a formamidinium free base, the lead ion precursor contains a lead compound, and the bromide ion precursor contains an organic bromide. Furthermore, in some embodiments, the salt for generating the formamidinium free base contains formamidinium acetate, the lead compound contains at least one of lead acetate and lead monoxide, and the organic bromide contains benzoyl bromide.

[0105] In some embodiments, the compound used to form the ligand layer 220a / 220b of the quantum dot materials 200a / 200b may comprise oleic acid (OA) and sulfobetaine. The sulfobetaine may be, for example, 3-(N,N-dimethyloctylammonio)-propanesulfonate.

[0106] In some embodiments, the quantum dot material 200b can be formed into a ligand layer 220b by using a mixture of oleic acid (OA) and hard fatty acid (SA) combined with a mixture of oleylamine (OAm) and stearylamine (SAm).

[0107] In some embodiments, at least one of the materials used to form the coating layer 230 has a melting point greater than 60 degrees Celsius. Specifically, the various novel quantum dot materials proposed in this application include (1) using sulfobetaine as a ligand to replace the traditional synthesis method / structure using OLA as a ligand (as shown in Figure 3B or Figure 3C); and (2) using a hybrid synthesis method containing at least two first-class ligand compounds LT1 and one second-class ligand compound LT2 as ligands to form a quantum dot material 200b structure as shown in Figure 3C. In the above-mentioned embodiment (1), sulfobetaine is used as a ligand to replace the traditional synthesis method using OLA as a ligand. Replacing OLA with sulfobetaine allows the preparation process to be carried out at an environment below 120°C, thus making the overall synthesis reaction less violent, and thus allowing for more precise control of the particle size of the material during the preparation process, which is suitable for large-scale production.

[0108] In the above-mentioned second type of embodiment, specific different types of ligand compounds LT1 and LT2 were used to prepare quantum dot materials, which can make quantum dot materials 200b have a ligand layer 220b structure that can be grafted with coating layer 230, thereby making the physical and chemical properties of quantum dot materials 200b more stable.

[0109] Figures 4A and 4B are schematic diagrams of transmission electron microscopy analysis of quantum dot materials according to different embodiments of this application. Referring first to Figure 4A, the dark nanocrystals visible in Figure 4A represent the core layer 210 of the quantum dot material 200' in this embodiment, with the lighter-colored outer portion being the coating layer 230. As shown in Figure 4A, the shape of the quantum dot material 200' can be arbitrary and is not limited to whether the core layer 210 shares the coating layer 230.

[0110] Please refer to Figure 4B again, which shows an experimental example of quantum dot material composed of FAPbBr3. In Figure 4B, it can be observed that the quantum dot material of this embodiment exhibits a well-distributed and uniformly arranged cubic structure, wherein the particle size of FAPbBr3 is approximately 30 nm. In some embodiments, the particle size of the cubic crystal structure of FAPbBr3 can be between 10 nm and 35 nm, and this application is not limited thereto.

[0111] The following figures 5A to 9B further illustrate the comparison of the characteristics of the quantum dot materials of the present application in several different specific experimental examples. Figures 5A to 5G are schematic diagrams of the absorption and emission spectra of quantum dot materials of some experimental examples and comparative examples of the present application. Figures 6A and 6B are time-resolved fluorescence spectra of quantum dot materials of some experimental examples and comparative examples of the present application. Figures 7A and 7B are fluorescence spectra of quantum dot materials of comparative example and experimental example 5 of the present application at different temperatures. Figure 8 is an X-ray diffraction analysis spectrum of quantum dot materials of some embodiments of the present application. Figures 9A and 9B are infrared absorption spectra of quantum dot materials of some embodiments of the present application. Ligand 1 (OA) Ligand 2 (SA) Ligand 3 (OAm) Ligand 4 (SAm) Ligand 5 (SBE-18) Comparative Example 0.0025 0 0.0016 0 0 Experimental Example 1 0.00235 0.00015 0.0016 0 0 Experimental Example 2 0.0022 0.0003 0.0016 0 0 Experimental Example 3 0.0025 0 0.0014 0.00015 0 Experiment Example 4 0.0025 0 0.0012 0.0003 0 Experimental Example 5 0.0022 0.0003 0.0012 0.0003 0 Experimental Example 6 0.0025 0 0 0 0.084 Table 1

[0112] As shown in Table 1, the comparative examples are perovskite quantum dot materials formed using only ligand 1 (OA) and ligand 2 (SA). Examples 1 to 5 correspond to the quantum dot materials of the above-described (2) type of embodiments, wherein Examples 1 and 2 are perovskite quantum dot materials formed by mixing ligand 1, ligand 2, and ligand 3 (OAm); Examples 3 and 4 are perovskite quantum dot materials formed by mixing ligand 1, ligand 3, and ligand 4 (SAm); and Example 5 is a perovskite quantum dot material formed by mixing ligands 1 to ligand 4. Example 6 corresponds to the quantum dot materials of the above-described (1) type of embodiments, wherein Example 6 is a FAPbBr3 perovskite quantum dot material formed by mixing ligand 1 and ligand 5 (SBE-18) (hereinafter, the quantum dot material of Example 6 will be referred to as FAPbBr3).

[0113] Please refer to Figures 5A to 5F. From the absorption spectra and emission parameters of this embodiment, it can be seen that although the comparative examples and experimental examples 1 to 5 have different ligand hybridization methods and ratios, the spectral characteristics they exhibit basically match the target spectral positions of the quantum dot material. In other words, the quantum dot material formed by ligand hybridization treatment in this application embodiment will not experience optical property instability due to changes in the ligand addition ratio.

[0114] Referring to Figure 5G, in this experimental example, the FAPbBr3 responds to the incident light at a wavelength of 450 nm, with a maximum emission wavelength between 525 nm and 535 nm, and a full width at half maximum (FWHM) of less than 23 nm.

[0115] In some experimental examples, using hexane as the background solvent and with an absorbance defined as 0.1, the highest emission wavelength of the FAPbBr3 material in this application embodiment was 530 ± 2 nm (i.e., between 528 nm and 532 nm), and the FWHM was 22 ± 1 nm. Furthermore, under the above test conditions, the quantum efficiency was calculated to be greater than 90%.

[0116] The quantum efficiency range can be measured using a fluorescence spectrometer (e.g., a FluoroMax R4 Fluorometer) paired with an integrating sphere apparatus (e.g., a Quanta-φ). The measurement method can be, for example, placing the sample and the integrating sphere apparatus in a sample chamber, exciting the sample by introducing incident excitation light into the integrating sphere, causing the sample to emit light which is then reflected within the sphere. The quantum efficiency is then calculated by collecting the light rays exiting the chamber at a specific location. However, this application is not limited to this method.

[0117] Please refer to Figure 6A, which shows the time-resolved fluorescence spectra of the comparative example and Experiments 1 to 5. The calculation results of the quadratic nonlinear fitting parameters based on the time-resolved fluorescence spectra in Figure 6 reveal that, compared to the comparative example using only ligands 1 and 3, the average fluorescence lifetimes of Experiments 1 and 2, which added ligand 2 (SA) to ligand 1, both show a decreasing trend. For example, the average fluorescence lifetime calculated for the comparative example is approximately 60.029 ns, while the average fluorescence lifetimes calculated based on Experiments 1 and 2 are approximately 49.694 ns and 52.445 ns, respectively.

[0118] On the other hand, in Examples 3 and 4, where ligand 4 was mixed with ligand 3, the amount of ligand 4 added increased, and Examples 3 and 4 showed a significant decreasing trend compared to the comparative example. For example, the average fluorescence lifetimes calculated based on Examples 3 and 4 were approximately 48.133 ns and 43.881 ns, respectively. In Example 5, where ligands 2 and 4 were mixed with ligands 1 and 3, respectively, the average fluorescence lifetime was reduced to 35.529 ns.

[0119] In other words, in some embodiments, the average fluorescence lifetime of the quantum dot material 200b with ligand layer 220b formed after hybridization can be reduced to less than 55 ns. Therefore, Figure 6A and the related calculation results demonstrate that by selecting appropriate ligands for hybridization to form ligand layer 220b, the fluorescence defects of the quantum dot material can be reduced, and the proportion of fast electron-hole recombination can be increased, resulting in better emission efficiency.

[0120] Referring to Figure 6B, in this embodiment, two complex factors can be obtained by performing a quadratic nonlinear fitting operation on the TRPL spectral data. One of these complex factors can be defined as relating to the photon capture rate caused by defects in the material itself, and the other can be defined as relating to the photon recombination rate constant and the photon capture rate constant. Then, the average fluorescence lifetime of FAPbBr3 can be calculated using these two complex factors, ranging from 21.9 ns to 26.6 ns. In some experimental examples, the calculated average fluorescence lifetime is 24.4 ns.

[0121] Figure 7A shows the fluorescence spectra of comparative quantum dot materials at 20°C, 40°C, 50°C, 60°C, 80°C, and 100°C, from top left to bottom right. The experimental results in Figure 7A clearly show that when perovskite quantum dots are synthesized using only oleic acid and oleylamine as ligands, the fluorescence intensity begins to decrease with increasing temperature at 40°C. Furthermore, the blue shift in the emission wavelength indicates that perovskite quantum dots decompose due to high heat.

[0122] Similarly, Figure 7B shows the fluorescence spectra of the quantum dot material of Experimental Example 5 at 20°C, 40°C, 50°C, 60°C, 80°C, and 100°C, sequentially from top left to bottom right. The experimental results in Figure 7B show that the thermal stability of the perovskite quantum dot material synthesized through the hybridization treatment of the embodiments of this application is significantly improved. As shown in Figure 7B, the fluorescence intensity of the perovskite quantum dot material of Experimental Example 5 slightly increases at 40°C, but only after 50°C does the light intensity of the perovskite quantum dot material decrease and undergo a blue shift due to the high temperature.

[0123] Figure 8 shows the X-ray diffraction analysis spectrum of FAPbBr3 in some embodiments of this application. Referring to Figure 8, in this embodiment, it can be observed that the three main peaks of FAPbBr3 occur on the crystal planes corresponding to (001), (002) and (003) respectively, that is, FAPbBr3 has a good Pm3m cubic structure.

[0124] Figures 9A and 9B show the infrared absorption spectra of quantum dot materials according to some embodiments of this application. In Figure 9A, the core layer of the quantum dot material is exemplified by a perovskite material, and the second type of ligand compound LT2 in the ligand layer is exemplified by a siloxane compound. That is, the ligand layer of the quantum dot material in this embodiment will form a coordination reaction between the siloxane compound and the coating layer, but this application is not limited to this. Figure 9B compares the infrared absorption spectra of FAPbBr3 from Experimental Example 6 with those of other common perovskite quantum dots.

[0125] Please refer to Figure 9A. Characteristic curve CV1 is the transmittance characteristic curve of the siloxane compound used to form the second type of ligand compound LT2. Characteristic curve CV2 is the transmittance characteristic curve of the material mixed with the first type of ligand compound LT1 and the second type of ligand compound LT2. Characteristic curve CV3 is the transmittance characteristic curve of the perovskite quantum dot material formed based on the aforementioned first type of ligand compound LT1 and the second type of ligand compound LT2.

[0126] In Fig. 9A , it can be found that upon addition of the second class of ligand compound LT2, the quantum dot material has a relative peak of the stretching shock within the corresponding wavenumber interval. In this embodiment, whether it is a material mixed with a first-class ligand compound LT1 and a second-class ligand compound LT2 or a quantum dot material formed based on the above-mentioned ligand compounds, its at wavenumbers are 3422 cm-1 (representing the characteristic peak of the Si–OH bond), 1094 cm-1 (representing the characteristic peak of the Si–O–Si bond), Relative peaks of stretching shocks are present in the intervals of -1 (representing the characteristic peak of the Si–O bond).

[0127] Therefore, if it is possible from the infrared absorption spectrum of the quantum dot material, at wavenumbers from 750 cm-1 to 850 cm-1, 900 cm-1 to 1000 cm-1, 1050 cm-1 to 1150 cm-1, and 3400 cm-1 to 3500 cm When relative peaks with stretching shocks are observed within the intervals of -1, it means that the quantum dot material is formed by a complexation treatment of the embodiments of the present application to form a ligand layer comprising the first class of ligand compound LT1 and the second class of ligand compound LT2.

[0128] Referring next to FIG.

[0129] In some experimental examples, FAPbBr 3 has a peak of S=O stretching shock at a wavenumber of 1035 cm -1, the main cause of which lies in the adoption of sulfobetaine as the ligand during synthesis by FAPbBr 3 in the embodiment of the present application (this section is further described in the embodiment of the subsequent preparation method).

[0130] Through the above measurement results, it can be found that FAPbBr 3 in Experimental Example 6 has good and stable material characteristics and can produce green light that satisfies the requirements of Rec.

[0131] Further below illustrates the preparation method of quantum dot material of the embodiments of the present application, wherein FIG.

[0132] In step S110, the formamidine ion precursor comprises, for example, formamidine acetate (FAAc), and the lead ion precursor comprises, for example, lead acetate (PbAc) and lead monoxide (PbO), at least one of them. The ligand may comprise, for example, oleic acid (OA) and sulfobetaine, wherein the sulfobetaine comprises, for example, 3-(N,N-dimethyloctylammonio)-propanesulfonate (SBE-18).

[0133] In some experimental examples, step S110 involves mixing FAAc, PbO, SBE-18, and OA in a certain ratio using 1-octadecene (ODE) as a solvent to form the mixed solution. The ratio may be, for example, 105:66:42:5:1.25 (FAAc:PbO:SBE-18:ODE:OA), but this application is not limited to this.

[0134] Next, the mixed solution formed in step S110 is dried at a first temperature (step S120).

[0135] In step S120, the first temperature is, for example, a temperature not exceeding 120°C, such as 100°C.

[0136] In some experimental examples, step S120 involves heating the mixed solution in a vacuum at 100°C for 30 minutes, but this application is not limited to this.

[0137] Next, the dried mixed solution is cooled to a second temperature below the first temperature under an inert gas environment (step S130), and a bromide ion precursor is injected into the mixed solution at the second temperature to generate a solution containing the organic-inorganic perovskite material (step S140).

[0138] In step S130, the inert gas may be, for example, nitrogen, and the second temperature may be, for example, between 40°C and 75°C.

[0139] In some experimental examples, step S130 involves cooling the mixed solution to 60°C in a nitrogen atmosphere before proceeding to step S140.

[0140] In step S140, the bromide precursor includes, for example, benzoyl bromide.

[0141] In some experimental examples, when benzyl bromide is injected into the mixed solution in step S140, the benzyl bromide reacts with OA to release hydrobromic acid (HBr), which is then used to synthesize the final FAPbBr3.

[0142] By following steps S110-S140 above, FAPbBr3 with an ABX3 crystal structure and the material properties described in Experimental Example 6 can be generated. The FAPbBr3 synthesized in the above experimental example, under test conditions of an excitation wavelength of 450 nm and an absorbance defined as 0.1, exhibits an emission wavelength of approximately 530 nm, an FWHM of approximately 21.6 nm, and a calculated quantum efficiency of approximately 95.7%.

[0143] Following step S140, the generated FAPbBr3 can be purified (step S150) to fabricate a quantum dot membrane using the treated FAPbBr3 material. In some embodiments, the purification process may include, for example, the following steps: performing a first centrifugation on a solution containing FAPbBr3 to obtain a precipitate; adding an organic solvent to the precipitate and performing a second centrifugation; and filtering out the FAPbBr3 material based on the supernatant after the second centrifugation.

[0144] In the above-mentioned purification process, the first centrifugation can be performed by adding toluene to a solution containing FAPbBr 3 and centrifuging at 15,000 rpm for 5 minutes; then, the precipitate is mixed with hexane and centrifuged again at 15,000 rpm for 5 minutes, and the resulting supernatant is the final product.

[0145] Compared to existing methods for preparing FAPbBr3, the method described in this application synthesizes FAPbBr3 using at least three precursors. Since it eliminates the need for costly FABr and PbBr2, production costs are effectively reduced. Furthermore, because the method in this application does not require DMF or DMSO as a polar solvent, the problem of crystal structure corrosion during synthesis, which could lead to decreased yield and luminescence efficiency, is avoided. The final produced material has also been verified to possess a good and complete structure.

[0146] Furthermore, since the preparation method of this application embodiment can be carried out at low temperature (about 40°C-75°C) for bromine precursor injection, it is less susceptible to the influence of temperature factors that may cause FAPbBr 3 to undergo quality changes and decomposition.

[0147] In summary, the quantum dot material preparation method described in the embodiment of Figure 10 has higher reproducibility, lower cost, and can be carried out at low temperature compared with existing methods. The produced quantum dot material also has good material properties and can emit highly saturated green light.

[0148] Incidentally, the quantum dot materials proposed in this application can also be used as substrates for most light-emitting elements in the optoelectronic field. For example, the quantum dot materials can also be used in the design of lasers, solar cells, and photosensors, but this application is not limited thereto.

[0149] It should also be noted that the above description of various embodiments is provided to clearly illustrate the various inventive features of this application. However, this does not mean that each embodiment can only be implemented alone. Those skilled in the art can design feasible implementation examples by combining them together as needed, or replace / combine the synthetic parts in different embodiments according to their needs. In other words, the implementation methods taught in this application are not limited to the states described in the following embodiments, but also include substitutions, combinations, and arrangements between various embodiments / structures / processes where feasible, which will be described in advance. For example, although Experimental Example 6 is a quantum dot material not generated by hybridization, in some embodiments it can be combined with the hybridization treatment of Experimental Examples 1-5 to further form the ligand layer 220b structure shown in Figure 3C, so that the overall material properties can be further improved. This application does not limit individual embodiments / experiments to be implemented alone.

[0150] Although this application has disclosed the above embodiments, it is not intended to limit this application. Any modifications and alterations made by those skilled in the art to the above embodiments without departing from the spirit and scope of this application shall still fall within the technical scope protected by this application. Therefore, the scope of protection of this application shall be determined by the claims.

[0151] 10: Display device 100: Backlight Module 110: Emissive layer 111:Substrate 112: Protective layer 120:Quantum dot film 121: Activation Layer 122: Support layer 123: Bonding layer 124: Water-blocking layer 130: Optical Adjustment Layer 200', 200a, 200b: Quantum dot materials 210: Core Layer 220, 220a, 220b: Ligand layers 230: Covering layer LEDs: Light-emitting elements LT1: Class I ligand compounds LT2: Class II ligand compounds

Claims

1. A quantum dot material comprising: a core layer; a ligand layer forming and covering at least a portion of the surface of the core layer and bonded to the core layer; and a coating layer forming and covering at least a portion of the surface of the ligand layer and bonded to the ligand layer, wherein, The ligand layer is formed of at least three ligand compounds, including a first type of ligand compound and a second type of ligand compound. The first type of ligand compound has a first coordinating group for bonding with the core layer, and the second type of ligand compound has a second coordinating group for bonding with the coating layer. The core layer has an ABX3 crystal structure, with formamidinium ions occupying the A-site, lead ions occupying the B-site, and chloride, bromide, and iodide ions occupying the X-site. The quantum dot material has a maximum emission wavelength between 450 nm and 760 nm when the incident light wavelength is 450 nm. The at least three ligand compounds include sulfobetaine and oleic acid.

2. The quantum dot material as claimed in claim 1, wherein the chemical formula of the first type of ligand compound is: wherein Z is the first coordinating group; and is a first alkane, and n1 is the chain number of the first alkane, which is greater than 0.

3. The quantum dot material as claimed in claim 2, wherein the first type of ligand compound further comprises: a first functional group such that the chemical formula of the first type of ligand compound is: , where Wm1 is the first functional group, m1 is the number of the first functional groups, which is a positive integer.

4. The quantum dot material as claimed in claim 3, wherein the first functional group is selected from any of the following: methyl (-CH3), ethyl (-C2H6), propyl (-C3H7), butyl (-C4H9), pentyl (-C5H11), hydroxyl (-OH), amino (-NH3), and pyridyl (-C5H5N).

5. The quantum dot material as claimed in claim 2, wherein the chemical formula of the second type of ligand compound is: , where n is a second alkane, and n2 is the chain number of the second alkane, which is greater than or equal to 0; and KX is the second coordinating group.

6. The quantum dot material as claimed in claim 5, wherein the second coordinating group is selected from any of the following: siloxane compounds, titanoxane compounds, zirconoxane compounds, aluminoxane compounds, zincoxane compounds, and sulfoxane compounds.

7. The quantum dot material as claimed in claim 5, wherein the second type of ligand compound further comprises: a second functional group such that the chemical formula of the second type of ligand compound is: , where Wm2 is the second functional group, and m2 is the number of the second functional groups, which is a positive integer.

8. The quantum dot material as claimed in claim 7, wherein the second functional group is selected from any of the following: methyl (-CH3), ethyl (-C2H6), propyl (-C3H7), butyl (-C4H9), pentyl (-C5H11), hydroxyl (-OH), amino (-NH3), and pyridyl (-C5H5N).

9. The quantum dot material as claimed in claim 1, wherein the infrared absorption spectrum of the quantum dot material has relative peaks of stretching vibrations in the wavenumber ranges of 750 cm⁻¹ to 850 cm⁻¹, 900 cm⁻¹ to 1000 cm⁻¹, 1050 cm⁻¹ to 1150 cm⁻¹ and 3400 cm⁻¹ to 3500 cm⁻¹.

10. The quantum dot material as claimed in claim 1, wherein at least one of the materials of the coating layer has a melting point greater than 60 degrees.

11. The quantum dot material as claimed in claim 1, wherein the average fluorescence lifetime of the quantum dot material is less than 120 ns.

12. The quantum dot material as claimed in claim 1, wherein the sulfobetaine comprises 3-(N,N-dimethyloctylammonio)-propanesulfonate.

13. The quantum dot material as claimed in claim 1, wherein the coating layer is formed based on any of the following materials: silicon oxide, titanium oxide, aluminum oxide, boron oxide, zinc sulfide, and lead sulfide.

14. The quantum dot material as claimed in claim 1, wherein the coating layer comprises at least one of tetraethoxysilane (TEOS; CAS NO: 78-10-4), tetramethyl orthosilicate (TMOS; CAS NO: 681-84-5), 3-methcryloxypropyltrimethoxysilane (CAS NO: 2530-85-0), sulfur powder (CAS NO: 7704-34-9), selenium powder (CAS NO: 07782-49-2), and lead(II) oxide (CAS NO: 1317-36-8).

15. The quantum dot material as claimed in claim 1, wherein the thickness of the coating layer is between 5 nm and 100 μm.

16. The quantum dot material as claimed in claim 1, wherein the highest emission wavelength is between 525 nm and 535 nm, and the full width at half maximum (FWHM) of the quantum dot material is between 15 nm and 30 nm.

17. The quantum dot material as claimed in claim 1, wherein the quantum dot material has a quantum efficiency range greater than 90%.

18. The quantum dot material as claimed in claim 1, wherein the average fluorescence lifetime of the quantum dot material is between 18.3 ns and 30.5 ns.

19. The quantum dot material as claimed in claim 1, wherein the infrared absorption spectrum of the quantum dot material has a relative peak of stretching vibration in the wavenumber range of 750 cm⁻¹ to 1250 cm⁻¹.

20. The quantum dot material as claimed in any one of claims 1 to 19, wherein the first coordinating group is selected from any one of the following: carboxylic acid group (-COOH), sulfonic acid group (-SO3H), sulfinic acid group (-SOOH), thiosulfonic acid group (-COSH), nitrate group (-ONO2), nitrite group (-ONO), cyanate group (-OCN), isocyanate group (-NCO), phosphate group (-OPO(OH)2), phosphite group (-PO(OH)2), thiol group (-SH), primary amino group (-NH2), secondary amino group (-NH), and tertiary amino group (-NR2).

21. The quantum dot material as claimed in any one of claims 1 to 19, wherein the first class of ligand compounds comprises at least two of the following: oleic acid (CAS NO: 112-80-1), stearic acid (CAS NO: 57-11-4), 4-dodecylbenzenesulfonic acid (CAS NO: 121-65-3), 1-octadecanethiol (CAS NO: 2885-00-9), 2,2'-iminodiethanol (CAS NO: 111-42-2), methylammonium acetate (CAS NO: 6998-30-7), and pyridinium propanesulfonate (CAS NO: 15471-17-7).

22. The quantum dot material as claimed in claim 7 or 8, wherein the second type of ligand compound comprises (3-Aminopropyl)triethoxysilane (APTES; CAS NO: 919-30-2), (3-Aminopropyl)trimethoxysilane (APTMS; CAS NO: 13822-56-5), (3-Mercaptopropyl)triethoxysilane (MPTES; CAS NO: 14814-09-6), (3-Mercaptopropyl)trimethoxysilane (MPTMS; CAS No. 4420-74-0), cysteine ​​(CAS No. 52-90-4), and 3-sulfanylpropanoic acid (CAS No. 4420-74-0). The following are listed as at least one of the following: No. 107-96-0, ethanolate (titanium(4+); CAS No: 3087-36-3), titanium isopropoxide (Titanium isopropoxide; CAS No: 546-68-9), titanium tetrachloride (Titanium tetrachloride; CAS No: 7550-45-0), trimethylalane (Trimethylalane; CAS No: 75-24-1), and zirconyl nitrate (Zirconyl nitrate; CAS No: 13826-66-9).

23. The quantum dot material as claimed in any one of claims 1 to 19, wherein the main chain length of the first type of ligand compound has a carbon number greater than or equal to 10.

24. A method for preparing a quantum dot material, comprising: mixing a formamidinium ion precursor, a lead ion precursor, and a ligand in a solvent to form a mixed solution; drying the mixed solution at a first temperature; cooling the dried mixed solution to a second temperature below the first temperature under an inert gas environment; and injecting a bromide ion precursor into the mixed solution at the second temperature to generate a solution containing the quantum dot material, wherein the second temperature is between 40°C and 75°C. The generated quantum dot material has an ABX3 crystal structure, with formamidinium ions occupying the A site, lead ions occupying the B site, and bromide ions occupying the X site. The generated quantum dot material has a maximum emission wavelength between 525 nm and 535 nm when the incident light wavelength is 450 nm.

25. The method for preparing a quantum dot material as claimed in claim 24, wherein the ligand comprises oleic acid and sulfobetaine.

26. The method for preparing a quantum dot material as claimed in claim 25, wherein the sulfobetaine comprises 3-(N,N-dimethyloctadecylammonium)-propanesulfonate.

27. The method for preparing a quantum dot material as claimed in claim 24, wherein the first temperature does not exceed 120°C.

28. The method for preparing a quantum dot material as claimed in claim 27, wherein the first temperature is greater than or equal to 100°C.

29. The method for preparing quantum dot material as claimed in claim 24 further comprises: performing a first centrifugation on a solution containing the quantum dot material to obtain a precipitate; adding an organic solvent to the precipitate and performing a second centrifugation; and filtering the quantum dot material based on the supernatant after the second centrifugation.

30. A method for preparing a quantum dot material as claimed in claim 24, wherein the ligand comprises two first-class ligand compounds and a second-class ligand compound, wherein: The solution containing the quantum dot material is subjected to a first centrifugation treatment to obtain a precipitate; the chemical formula of the first type of ligand compound is: , where Z is the first coordinating group; And n1 is the first alkane, and n1 is the chain number of the first alkane, which is greater than 0; and the chemical formula of the second type of ligand compound is: , n2 is the chain number of the second alkane, which is greater than or equal to 0, and KX is the second coordinating group.

31. The method for preparing a quantum dot material as claimed in claim 30, wherein the second type of ligand compound further comprises: a second functional group, such that the chemical formula of the second type of ligand compound is: , where Wm2 is the second functional group, m2 is the number of the second functional groups, which is a positive integer.

32. The method for preparing quantum dot materials as claimed in claim 31, further comprising: performing a first centrifugation treatment on a solution containing the quantum dot materials to obtain a precipitate; the first type of ligand compound having the chemical formula: , where Z is the first coordinating group; and is a first alkane, and n1 is the chain number of the first alkane, which is greater than 0; and the second type of ligand compound having the chemical formula: , where is a second alkane, n2 is the chain number of the second alkane, which is greater than or equal to 0, and KX is a second coordinating group.

33. A quantum dot film suitable for a backlight module, comprising a quantum dot material as described in any one of claims 1-19 or a quantum dot material prepared by any one of claims 24-32.

34. A backlight module comprising a quantum dot film as described in claim 33.

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