Tungsten-doped double perovskite and preparation method and application thereof

Abstract

The invention relates to the technical field of luminescent materials, in particular to tungsten-doped double perovskite and a preparation method and application thereof. The first aspect of the invention is to provide tungsten-doped double perovskite, the chemical formula of the tungsten-doped double perovskite is Cs2Sn1-xCl6: xW < 4 + >, and x is greater than or equal to 0.1% and less than or equal to 5%. The invention further provides a preparation method of the tungsten-doped double perovskite, which comprises the following steps: mixing a Cs-containing compound, a Sn-containing compound, a W-containing compound and concentrated hydrochloric acid, heating, cooling, separating, washing and drying to obtain the tungsten-doped double perovskite. The third aspect of the invention is to provide application of the tungsten-doped double perovskite in the fields of near-infrared LEDs, night vision, safety monitoring or nondestructive analysis. The fourth aspect of the invention is to provide an optoelectronic device, and the luminescent material of the optoelectronic device adopts the tungsten-doped double perovskite.

Description

Technical Field

[0001] The present invention relates to the technical field of luminescent materials, and more specifically, to a tungsten-doped double perovskite and a preparation method and application thereof. Background Art

[0002] Near-infrared light (700-900nm) exhibits tremendous potential for application in numerous cutting-edge fields, including but not limited to near-infrared LED light sources, bioimaging, night vision technology, security monitoring, food composition analysis, and industrial nondestructive testing, due to its deeper penetration into biological tissues compared to visible light, minimal damage to organisms, and resistance to interference from background light. High-performance near-infrared fluorescence conversion materials are key components in building these devices.

[0003] At present, the phosphors that achieve efficient near-infrared emission mainly rely on the doping of specific activation ions, such as trivalent chromium ions (Cr³⁺), some rare earth ions (such as Nd³⁺, Er³⁺, Yb³⁺) and some transition metal ions (such as Ni²⁺, Mn²⁺ / 4 ⁺), etc. However, the existing technology system generally has the following key challenges: 1) Limited excitation band and excitation efficiency issues: Many high-efficiency near-infrared phosphors (especially Cr³⁺-doped systems) usually require ultraviolet (UV) or blue light excitation of a specific wavelength to achieve optimal efficiency, resulting in a narrow range of applications.

[0004] 2) Constraints on emission wavelength and intensity: Although some materials (such as Cr³⁺-doped garnet and gallates) can emit near-infrared light in the 700-800nm ​​range, it remains challenging to obtain phosphors with an emission peak in the 800-900nm range and sufficient intensity and stability.

[0005] 3) Selection and limitations of matrix materials: Existing research focuses on visible light emission (such as Sb³⁺, Bi³⁺, Mn 4 Research on using tungsten ions as activators to achieve efficient, near-infrared emission in double perovskites, such as Cr⁺⁺ doping (e.g., Cr³⁺⁺ doping) or specific near-infrared emission (e.g., Cr³⁺⁺ doping), is relatively rare. The specific chemical structure design, luminescence mechanism, and performance potential remain unclear. Furthermore, some reported near-infrared double perovskite materials may contain toxic or scarce elements (e.g., Pb, Tl), or face challenges such as harsh synthesis conditions (high-temperature solid-phase reaction), difficult morphology control, and difficulty in large-scale production. Summary of the Invention

[0006] The present invention aims to overcome at least one of the above-mentioned defects of the prior art and provide a tungsten-doped double perovskite and a preparation method and application thereof.

[0007] The first aspect of the present invention is to provide a tungsten-doped double perovskite, wherein the chemical formula of the tungsten-doped double perovskite is Cs2Sn 1-x Cl6:xW 4+ , among which 0.1%≤x≤5%, preferably, 0.4%≤x≤1.4%.

[0008] The tungsten-doped double perovskite of the present invention uses Cs2SnCl6 as a matrix, wherein x is the doping ion W 4+ The molar percentage of Sn relative to the matrix ion. Tests show that the tungsten-doped double perovskite of the present invention has a Cs2SnCl6 type crystal structure, in which some Sn 4+ The site is W 4+ ions occupy the ions, thus forming luminescent centers.

[0009] Furthermore, the fluorescence emission spectrum of the tungsten-doped double perovskite is 800-900 nm.

[0010] Furthermore, the absorption spectrum of the tungsten-doped double perovskite covers 200-500nm and 500-800nm.

[0011] The second aspect of the present invention is to provide a method for preparing the tungsten-doped double perovskite, comprising: mixing a Cs-containing compound, a Sn-containing compound, a W-containing compound with concentrated hydrochloric acid, heating, cooling, separating, washing, and drying to obtain the tungsten-doped double perovskite.

[0012] Furthermore, the Cs-containing compound is CsCl.

[0013] Furthermore, the Sn-containing compound is Sn chloride.

[0014] Furthermore, the W-containing compound is W chloride.

[0015] Furthermore, the chloride of Sn is SnCl4.5H2O or SnCl2.

[0016] Furthermore, the chloride of W is WCl4.

[0017] Furthermore, the ratio of the molar amount of Cs ions in the Cs-containing compound, the molar amount of Sn ions in the Sn-containing compound, and the molar amount of W ions in the W-containing compound is 2:1:(0.001-0.05), preferably 2:1:(0.004-0.014).

[0018] Furthermore, the molar ratio of Sn ions in the Sn-containing compound to the concentrated hydrochloric acid is 1 mmol:(1-10) mL.

[0019] Furthermore, the heating temperature is 140-230o C.

[0020] Furthermore, the heating time is 5 to 30 hours.

[0021] Furthermore, the heating rate is 1 to 10 o C / min.

[0022] Furthermore, the cooling end point temperature is room temperature.

[0023] Furthermore, the cooling rate is 10 to 30 o C / hour.

[0024] Furthermore, the washing uses ethanol as a washing solvent.

[0025] The purpose of washing with ethanol is to remove impurities adsorbed on the surface of the product and residual reaction mother liquor. Preferably, the number of washings is usually 2 to 5 times.

[0026] Furthermore, the drying temperature is 40 o C~80 o C.

[0027] The third aspect of the present invention is to provide an application of the tungsten-doped double perovskite in the fields of near-infrared LED, night vision, security monitoring or non-destructive analysis.

[0028] A fourth aspect of the present invention is to provide a photoelectric device, wherein the light-emitting material of the photoelectric device adopts the tungsten-doped double perovskite.

[0029] Compared with the prior art, the present invention has the following beneficial effects: 1) The tungsten-doped double perovskite of the present invention has unique dual-emission characteristics: the prepared phosphor can emit light in the near-infrared region covering 800-900nm under single wavelength excitation.

[0030] 2) The tungsten-doped double perovskite of the present invention is prepared by a hydrothermal synthesis method, which has a relatively simple process and is easy to operate and scale up.

[0031] 3) The tungsten-doped double perovskite of the present invention has a wide range of potential applications: Based on its unique luminescence properties, the material has potential application value in fields such as near-infrared LEDs, night vision, security monitoring or non-destructive analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The tungsten-doped double perovskite (Cs2Sn 1-x Cl6:xW 4+ ,0.4%≤x≤1.4%) X-ray diffraction (XRD) pattern.

[0033] Figure 2 The tungsten-doped double perovskite (Cs2Sn 0.996 Cl6:0.4%W 4+ )’s absorption spectrum.

[0034] Figure 3 The tungsten-doped double perovskite (Cs2Sn 0.99 Cl6:1.0%W 4+ ) scanning electron microscope (SEM) photograph.

[0035] Figure 4 The tungsten-doped double perovskite (Cs2Sn 0.996 Cl6:0.4%W 4+ ) fluorescence emission spectrum.

[0036] Figure 5 The tungsten-doped double perovskite (Cs2Sn 0.996 Cl6:0.4%W 4+ ) fluorescence emission spectrum. DETAILED DESCRIPTION

[0037] The first object of the present invention is to provide a tungsten-doped double perovskite, wherein the chemical formula of the tungsten-doped double perovskite is Cs2Sn 1-x Cl6:xW 4+ , where 0.1%≤x≤5%.

[0038] Preferably, 0.4%≤x≤1.4%.

[0039] A second objective of the present invention is to provide a method for preparing the tungsten-doped double perovskite, comprising: placing cesium chloride (CsCl), tin chloride, and tungsten tetrachloride (WCl4) in a polytetrafluoroethylene-lined container, adding concentrated hydrochloric acid, and mixing the mixture. The mixture is then placed in a hydrothermal reactor. The reactor is heated and maintained for a period of time, then slowly cooled to room temperature. After the crystals are separated from the acid solution, they are washed with a small amount of ethanol and finally dried in an oven to produce the doped double perovskite.

[0040] Optionally, the tin chloride may be SnCl4.5H2O or SnCl2, preferably, SnCl4.5H2O.

[0041] In a specific implementation, the molar ratio of cesium chloride to tin tetrachloride hydrate is controlled at about 2:1, and the molar doping amount of tungsten tetrachloride relative to tin tetrachloride hydrate can be controlled in the range of 0.1% to 5%, preferably 0.4% to 1.4%. In a specific implementation, for example, 0.4%, 1.0%, and 1.4%.

[0042] Preferably, the concentration of concentrated hydrochloric acid is generally that of commercially available concentrated hydrochloric acid, for example, approximately 36%-38% (mass percentage). Furthermore, the amount of concentrated hydrochloric acid used also affects the morphology and crystallinity of the reaction product. Specifically, the amount of concentrated hydrochloric acid used can be between 1 mL and 10 mL, for example, approximately 2 mL, 3 mL, 5 mL, 6 mL, 8 mL, or 10 mL, relative to 1 mmol of tin tetrachloride hydrate.

[0043] Preferably, the heating temperature range of the hydrothermal reaction is 140 o C to 230 o C, in specific implementation, for example, 140°C, 160 o C. 180 o C. 200 o C, 230° C. The holding time ranges from 5 hours to 30 hours, and in specific implementations, for example, 5 hours, 10 hours, 12 hours, 15 hours, 20 hours, 25 hours, or 30 hours.

[0044] Preferably, the heating temperature rise rate of the hydrothermal reaction is controlled at 1 o C / min to 10 o C / min, when implemented, for example, about 3 o C / min or 5 o C minutes.

[0045] Preferably, the cooling rate of the process of cooling to room temperature after the hydrothermal reaction is completed can be controlled. In specific implementation, the cooling rate is 10 o C / hour to 30 o C / hour, in practice, the cooling rate can be controlled to 10 o C / hour, 15 o C / hour, 20 o C / hour, 25 o C / hour, 30 o C / hour.

[0046] Preferably, the drying temperature is usually 40 o C to 80 o C. In specific implementation, the drying temperature can be set to 40°C, 50°C, 60°C, 70°C, 80°C, etc. The drying time is sufficient to completely dry the product.

[0047] The purpose of ethanol washing is to remove impurities adsorbed on the surface of the product and residual reaction mother liquor. In specific implementation, the number of washing times is usually 2 to 5 times.

[0048] The tungsten-doped double perovskite of the present invention uses Cs2SnCl6 as a matrix, wherein x is the doping ion W 4+The molar percentage of Sn relative to the matrix ion. Tests show that the tungsten-doped double perovskite of the present invention has a Cs2SnCl6 type crystal structure, in which some Sn 4+ The site is W 4+ ions occupy the ions, forming luminescent centers. X-ray diffraction (XRD) patterns show that the primary phase matches the standard Cs2SnCl6 card (PDF#75-0376). Scanning electron microscopy (SEM) observations reveal that the tungsten-doped double perovskite exhibits polygonal micron-sized particles ranging in size from a few to tens of microns. The surface is relatively smooth, and some particles exhibit well-defined crystal properties.

[0049] The tungsten-doped double perovskite of the present invention can effectively absorb light energy in a wide band of 200-500nm and 500-800nm, and can emit near-infrared light with a wavelength of 800-900nm. That is, it can efficiently "down-convert" widely available ultraviolet / visible light energy into near-infrared light in a specific wavelength range (800-900nm). This near-infrared emission band is penetrating and invisible, and can be efficiently detected by mature silicon detectors. Combined with the light source flexibility brought by its wide excitation spectrum, it becomes an ideal material for constructing compact, efficient, and concealed near-infrared light sources. Therefore, the tungsten-doped double perovskite of the present invention has broad application prospects in high-tech fields such as near-infrared LED lighting, concealed lighting night vision, anti-counterfeiting security monitoring, and penetrating non-destructive analysis.

[0050] The present invention also provides an optoelectronic device using the aforementioned tungsten-doped double perovskite as its luminescent material. The tungsten-doped double perovskite of the present invention exhibits the following characteristics: it acts as an efficient wavelength conversion medium between "electricity → light" (LEDs) and "light → electricity" (sensors), expanding the application band of semiconductor light sources; its material properties are highly compatible with existing optoelectronic devices (LED packaging processes, silicon-based detectors), eliminating the need for disruptive technological innovation; and its near-infrared emission combined with a wide excitation spectrum directly improves key device indicators such as concealment, penetration, and signal-to-noise ratio. In other words, the tungsten-doped double perovskite of the present invention can efficiently convert readily available "electrical energy / visible light" into "invisible near-infrared light," which is then seamlessly converted into "electrical signals" via silicon detectors, ultimately serving core optoelectronic functions such as imaging, identification, and analysis. Its application as a luminescent material in optoelectronic devices holds enormous potential.

[0051] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0052] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0053] Example 1 2mmol of cesium chloride (CsCl, analytical grade), 1mmol of tin tetrachloride hydrate (SnCl4.5H2O, analytical grade), and 0.004mmol, 0.006mmol, 0.008mmol, 0.01mmol, 0.012mmol, and 0.014mmol of tungsten tetrachloride (WCl4, analytical grade, corresponding to 0.4% doping of Sn) were placed together in a 25mL polytetrafluoroethylene liner. 10mL of concentrated hydrochloric acid (37%, mass fraction) was added to the liner and stirred to mix evenly. The polytetrafluoroethylene liner was placed in a 25mL stainless steel hydrothermal reactor and sealed. The hydrothermal reactor was placed in an oven at 3 o C / min heating rate to 200 o C, and at 200 o C for 8 hours. After the reaction is completed, o The reactor was slowly cooled to room temperature at a rate of 100 °C / hour. The product in the lining was separated from the reaction mother liquor. The obtained crystals were washed three times with a small amount of anhydrous ethanol to remove impurities adsorbed on the surface. Finally, the washed product was placed in a 60 o C in an oven to dry to constant weight to obtain the target product. The obtained product was subjected to X-ray diffraction analysis, and the results were as follows Figure 1 As shown. Figure 1 As can be seen, the main diffraction peak positions of the double perovskites of the present invention with different tungsten doping concentrations correspond well to the diffraction peaks of the cubic phase Cs2SnCl6 standard card PDF#75-0376, indicating that the products have the crystal structure of Cs2SnCl6 and are pure phases with no obvious impurity peaks. The incorporation of tungsten does not significantly change the crystal structure of the matrix.

[0054] Example 2 This embodiment provides a tungsten-doped double perovskite, whose chemical formula is the same as that of Example 1: Cs2Sn 0.996 Cl6:0.4%W 4+ The preparation method is as follows: Place 1 mmol of CsCl, 0.5 mmol of SnCl4.5H2O, and 0.002 mmol of WCl4 (corresponding to 0.4 mol% Sn doping) in a 15 mL polytetrafluoroethylene liner. Add 3 mL of concentrated hydrochloric acid (37%) and mix thoroughly. Place the liner in a 15 mL hydrothermal reactor and seal it. oHeat at a rate of 180°C / min o C and maintain for 12 hours, then o The product was slowly cooled to room temperature at a rate of C / hour. The subsequent treatment was the same as in Example 1. The absorption spectrum test was performed on the obtained product, and the results were as follows: Figure 2 As shown, the absorption range of the tungsten-doped double perovskite of the present invention covers 200-500nm and 500-800nm.

[0055] Example 3 This embodiment provides a tungsten-doped double perovskite, whose chemical formula is Cs2Sn 0.99 Cl6:1.0%W 4+ The preparation method is as follows: 2mmol CsCl, 1mmol SnCl4.5H2O and 0.010mmol WCl4 (corresponding to 1.0mol% Sn doping) were placed in a 25mL polytetrafluoroethylene liner. 6mL concentrated hydrochloric acid (37%) was added and mixed. The reactor was heated to 3 o C / min to 160 o C and kept for 15 hours. o The reaction mixture was slowly cooled to room temperature at a rate of C / hour. The subsequent treatment was the same as in Example 1 to obtain tungsten ion-doped Cs2SnCl6:1.0%W 4+ Double perovskite. The obtained product was observed by scanning electron microscopy (SEM), as shown in Figure 3 As shown, the tungsten-doped double perovskite of the present invention is mainly composed of polygonal micron-sized particles with particle sizes ranging from a few microns to tens of microns. The surface is relatively smooth, and some particles show good crystal properties.

[0056] Example 4 This embodiment provides a tungsten-doped double perovskite, whose chemical formula is the same as that of Example 1: Cs2Sn 0.996 Cl6:0.4%W 4+ The preparation method is as follows: 2mmol CsCl, 1mmol SnCl4.5H2O and 0.004mmol WCl4 (corresponding to 0.4mol% Sn doping) were placed in a polytetrafluoroethylene liner, 6mL concentrated hydrochloric acid was added and mixed, and then placed in a 25mL hydrothermal reactor. The reactor was heated to 5 o Heat at a rate of 180°C / min o C and maintain for 12 hours, then o C / hour rate and then slowly cooled to room temperature. The subsequent treatment was the same as in Example 1 to obtain tungsten ion-doped Cs2Sn 0.996 Cl6:0.4%W 4+ Double perovskite. Figure 4 The fluorescence emission spectrum of the tungsten-doped double perovskite in this embodiment is shown in FIG. 1 , where the excitation light wavelength is 350 nm. Figure 4 The emission spectrum of the tungsten-doped double perovskite of the present invention covers the range of 800-900 nm, and the strongest emission intensity is about 3.0×10 7 .

[0057] Example 5 This comparative example provides a tungsten-doped double perovskite, whose chemical formula is the same as that of Example 1: Cs2Sn 0.996 Cl6:0.4%W 4+ The preparation method is as follows: 2mmol CsCl, 1mmol tin dichloride (SnCl2) and 0.004mmol WCl4 (corresponding to 0.4mol% doping of Sn) were placed in a polytetrafluoroethylene liner, 6mL concentrated hydrochloric acid was added and mixed, and then loaded into a 25mL hydrothermal reactor. The reactor was heated at 5 o Heat at a rate of 180°C / min o C and maintain for 12 hours, then o C / hour rate and then slowly cooled to room temperature. The subsequent treatment was the same as in Example 1 to obtain tungsten ion-doped Cs2Sn 0.996 Cl6:0.4%Mo 4+ Double perovskite. Figure 5 This is the fluorescence emission spectrum of the tungsten-doped double perovskite of this embodiment, using an excitation light wavelength of 350 nm. Figure 5 The emission spectrum of this embodiment also covers the range of 800-900 nm, and the strongest emission intensity is about 2.5×10 7 .

[0058] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A tungsten-doped double perovskite, characterized in that: The chemical formula of the tungsten-doped double perovskite is Cs2Sn 1-x Cl6:xW 4 + , where 0.1%≤x≤5%.

2. The tungsten-doped double perovskite according to claim 1, characterized in that The fluorescence emission spectrum of the tungsten-doped double perovskite is 800-900 nm; and / or, The absorption spectrum of the tungsten-doped double perovskite covers 200-500 nm and 500-800 nm.

3. A method for preparing the tungsten-doped double perovskite according to claim 1 or 2, characterized in that: The tungsten-doped double perovskite is obtained by mixing a Cs-containing compound, a Sn-containing compound, and a W-containing compound, adding concentrated hydrochloric acid and mixing evenly, and performing heating, cooling, separation, washing, and drying.

4. The method according to claim 3, characterized in that The Cs-containing compound is CsCl; and / or, The Sn-containing compound is Sn chloride; and / or, The W-containing compound is W chloride.

5. The method according to claim 4, characterized in that The Sn chloride is SnCl4.5H2O or SnCl2; and / or, The W chloride is WCl4.

6. The method according to any one of claims 3 to 5, characterized in that: The ratio of the molar amount of Cs ions in the Cs-containing compound, the molar amount of Sn ions in the Sn-containing compound, and the molar amount of W ions in the W-containing compound is 2:1:(0.001-0.05).

7. The method according to any one of claims 3 to 5, characterized in that The molar ratio of Sn ions in the Sn-containing compound to the concentrated hydrochloric acid is 1 mmol:(1-10) mL.

8. The method according to any one of claims 3 to 5, characterized in that: The heating temperature is 140~230 o C; and / or, The heating time is 5 to 30 hours; and / or, The heating rate is 1 to 10 o C / minute; and / or, The cooling end point temperature is room temperature; and / or, The cooling rate is 10 to 30 o C / hour; and / or, The washing adopts ethanol as the washing solvent.

9. Use of the tungsten-doped double perovskite according to claim 1 or 2 or the tungsten-doped double perovskite prepared by the method according to any one of claims 3 to 8 in the fields of near-infrared LEDs, night vision, security monitoring, or non-destructive analysis.

10. A photoelectric device, characterized in that: The light-emitting material of the optoelectronic device is the tungsten-doped double perovskite according to claim 1 or 2 or the tungsten-doped double perovskite prepared by the method according to any one of claims 3 to 8.

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