Chalcogenide element doped perovskite nanocrystal and preparation method thereof

Abstract

The invention discloses a preparation method of chalcogenide-doped perovskite nanocrystals. The preparation method specifically comprises the following steps: respectively preparing a cesium precursor solution and a chalcogenide precursor solution for later use; injecting a cesium precursor into the prepared lead bromide precursor to generate perovskite nanocrystals, then injecting a chalcogenide precursor solution for doping, blocking a reaction by using an ice-water bath, and then performing centrifugal purification to obtain chalcogenide-doped perovskite nanocrystals; optionally, a cadmium precursor solution can be added during doping to further modify the morphology. According to the method, through the synergistic effect of chalcogenide element (sulfur or selenium) doping and cadmium modification, the absorption wave band of the perovskite nanocrystal can be expanded to 900 nm to the maximum in the long wavelength direction, controllable modification of the nanocrystal morphology from a cube to a sphere-like polyhedron is achieved, and a novel material basis is provided for application of wide-spectrum photothermal conversion, infrared detection and the like.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of novel nano-optoelectronic materials, and particularly relates to a chalcogen-doped perovskite nanocrystal and a preparation method thereof. Background Art

[0002] All-inorganic metal halide perovskite nanocrystals (such as CsPbX 3 , X = Cl, Br, I) exhibit great application potential in optoelectronic devices (such as solar cells, photodetectors) due to their excellent optoelectronic properties (such as high absorption coefficient, tunable bandgap and long carrier diffusion length). However, the absorption range of traditional perovskite nanocrystals is usually limited to the visible light region and is difficult to cover the near-infrared band, which restricts their application in the fields of broadband light trapping and infrared detection. In addition, perovskite nanocrystals prepared by traditional hot injection methods are mostly cubic in shape, and their sharp corners are prone to light scattering loss, reducing the optical homogeneity of the material.

[0003] In the prior art, the methods for broadening the absorption range of perovskite nanocrystals mainly include introducing narrow-bandgap components (such as CsPbI 3 ) or constructing heterostructures (such as CsPbBr 3 / PbS). However, these methods often face the following problems:

[0004] (1) Poor stability of narrow-bandgap components: For example, CsPbI 3 is prone to transform from the cubic phase to the non-luminescent orthorhombic phase at room temperature, resulting in performance degradation;

[0005] (2) Complex heterostructure process: For example, the core-shell structure requires precise control of interface growth and is difficult to produce on a large scale.

[0006] In terms of morphology control, traditional methods (such as surface ligand modification or ion doping) can partially passivate the cube corners, but it is difficult to achieve precise control of the morphology and often accompanied by loss of optical performance. For example, excessive surface ligands (such as oleic acid / oleylamine) are prone to cause aggregation of nanocrystals, while ion doping (such as Mn 2+ ) may introduce non-radiative recombination centers, reducing the light trapping efficiency of the material. Summary of the Invention

[0007] The first object of the present invention is to provide a preparation method of a chalcogen-doped perovskite nanocrystal, which realizes a significant red shift of the absorption band of the nanocrystal and controllable morphology modification through the synergistic effect of chalcogen (sulfur / selenium) doping and cadmium modification, and solves the problems of narrow absorption range and single morphology of traditional perovskite nanocrystals.

[0008] A preparation method of a chalcogen-doped perovskite nanocrystal includes the following steps:

[0009] Step (1): Under the protection of inert gas, a cesium precursor solution and a chalcogen precursor solution are respectively prepared. Among them, the cesium precursor solution is obtained by mixing cesium carbonate, oleic acid and octadecene and heating them for reaction, and the chalcogen precursor solution is obtained by mixing chalcogen element simple substance and ligand and heating them for reaction.

[0010] Step (2): Under the protection of inert gas, lead bromide, octadecene, oleic acid and oleylamine are mixed, stirred and heated to a first temperature for reaction until the solution becomes clear to obtain a lead bromide precursor solution.

[0011] Step (3): The lead bromide precursor solution is heated to a second temperature and then injected into the cesium precursor solution. After reacting for 5 - 10 s, doping is carried out. After the reaction is complete, the reaction is blocked by cooling, and chalcogen-doped perovskite nanocrystals are obtained by centrifugal purification. The specific doping method is: after mixing the chalcogen precursor solution and octadecene according to a volume ratio of 1:(11 - 12) to obtain a mixed solution, it is injected into the reaction system at a constant rate.

[0012] Preferably, the concentration of the cesium precursor solution is 0.05 - 0.08 mol / L, and the volume ratio of octadecene to oleic acid is 8:(1 - 1.2).

[0013] Preferably, the chalcogen simple substance is sulfur powder or selenium powder, the ligand of sulfur powder is oleylamine, and the ligand of selenium powder is trioctylphosphine; the concentration of the chalcogen precursor solution is 1 - 1.5 mol / L.

[0014] Preferably, the concentration of the lead bromide precursor solution is 0.02 - 0.04 mol / L, and the volume ratio of octadecene to oleic acid and oleylamine is 10:1:(1 - 1.2); when generating perovskite nanocrystals, the molar concentration ratio of cesium ions in the cesium precursor solution to lead ions in the lead bromide precursor solution is (1 - 1.5):3.

[0015] Preferably, the first temperature is 115 - 125 °C, and the second temperature is 145 - 155 °C.

[0016] Preferably, the method further includes the following steps:

[0017] Cadmium oxide, oleic acid and octadecene are heated and reacted under the protection of inert gas to obtain a cadmium precursor solution; during doping, after mixing the chalcogen precursor solution, cadmium precursor solution and octadecene according to a volume ratio of 0.4:(1 - 1.2):3.6 to obtain a mixed solution, it is injected into the reaction system at a constant rate.

[0018] Preferably, the concentration of the cadmium precursor solution is 0.3 - 0.4 mol / L, and the volume ratio of octadecene to oleic acid is 1:(1 - 1.2).

[0019] Preferably, the volume ratio of the total volume of the mixed solution injected during doping to the volume of the lead bromide precursor solution is 5:(6-6.5).

[0020] Preferably, the constant rate is 0.25-0.3 mL / min.

[0021] The second object of the present invention is to provide a chalcogen-doped perovskite nanocrystal prepared by the above method; the absorption range of the chalcogen-doped perovskite nanocrystal extends from visible light to the near-infrared region.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] (1) Significantly broadened absorption band: The present invention adopts the thermal injection method to accurately control the ratio of the chalcogen precursor to the cadmium precursor and the injection conditions under the protection of inert gas. By introducing deep-level defect states through chalcogen doping, the absorption range of the nanocrystals is significantly broadened; the absorption peak of the doped perovskite nanocrystals is significantly red-shifted, and the absorption range extends towards the long-wavelength direction, and can be extended to the near-infrared region at most, which is suitable for broadband light trapping devices, photodetectors, etc.

[0024] (2) Controllable morphology modification: The present invention optionally introduces cadmium ions, which have a surface adsorption effect, can passivate the edges and corners of the cube, form a spherical polyhedron morphology, and reduce the light scattering loss. Brief Description of the Drawings

[0025] Figure 1 It is the fluorescence spectrum and absorption spectrum of the perovskite nanocrystal prepared in Example 1.

[0026] Figure 2 It is the transmission electron microscope image of the perovskite nanocrystal prepared in Example 1.

[0027] Figure 3 It is the EDS element distribution map (Mapping) of the perovskite nanocrystal prepared in Example 1, where A is sulfur element, B is cadmium element, C is the medium-angle annular dark field image, and D is the composite image.

[0028] Figure 4 It is the fluorescence spectrum and absorption spectrum of the perovskite nanocrystal prepared in Example 2.

[0029] Figure 5 It is the transmission electron microscope image of the perovskite nanocrystal prepared in Example 2.

[0030] Figure 6 It is the EDS element distribution map (Mapping) of the perovskite nanocrystal prepared in Example 2, where A is sulfur element, B is cadmium element, C is the medium-angle annular dark field image, and D is the composite image.

[0031] Figure 7 The fluorescence spectrum and absorption spectrum of the perovskite nanocrystals prepared in Example 3.

[0032] Figure 8 The transmission electron microscope image of the perovskite nanocrystals prepared in Example 3.

[0033] Figure 9 The fluorescence spectrum and absorption spectrum of the perovskite nanocrystals prepared in Example 4. Detailed implementation manners

[0034] The present invention will be further explained below with reference to the accompanying drawings; based on the embodiments in the implementation manners, other embodiments obtained by those skilled in the art without creative efforts all fall within the protection scope of the present invention. The experimental methods in the following embodiments are all conventional methods unless otherwise specified, and the materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0035] As described above, the present invention provides a chalcogen-doped perovskite nanocrystal, which is prepared by the following method:

[0036] Step (1): Under the protection of an inert gas, a cesium precursor solution with a concentration of 0.05 - 0.08 mol / L and a chalcogen precursor solution with a concentration of 1 - 1.5 mol / L are respectively prepared; wherein, the cesium precursor solution is obtained by mixing cesium carbonate, oleic acid and octadecene and heating them for reaction, and the volume ratio of octadecene to oleic acid is 8:(1 - 1.2); the chalcogen precursor solution is obtained by mixing a chalcogen element simple substance and a ligand and heating them for reaction, the chalcogen element simple substance is sulfur powder or selenium powder, the ligand of sulfur powder is oleylamine, and the ligand of selenium powder is trioctylphosphine.

[0037] Optionally, cadmium oxide, oleic acid and octadecene are heated and reacted under the protection of an inert gas to obtain a cadmium precursor solution with a concentration of 0.3 - 0.4 mol / L, and the volume ratio of octadecene to oleic acid is 1:(1 - 1.2);

[0038] Step (2): Under the protection of an inert gas, lead bromide, octadecene, oleic acid and oleylamine are mixed, stirred and heated to 115 - 125 °C for reaction until the solution becomes clear, to obtain a lead bromide precursor solution with a concentration of 0.02 - 0.04 mol / L, and the volume ratio of octadecene to oleic acid and oleylamine is 10:1:(1 - 1.2);

[0039] Step (3): Heat the lead bromide precursor solution to 145 - 155 °C and then inject it into the cesium precursor solution. After reacting for 5 - 10 s, doping is carried out. After the reaction is complete, cool down to block the reaction, and centrifugally purify to obtain chalcogen - doped perovskite nanocrystals; the concentration ratio of cesium ions in the cesium precursor solution to lead ions in the lead bromide precursor solution is (1 - 1.5):3;

[0040] Among them, the doping specifically is: After mixing the chalcogen precursor solution and octadecene in a volume ratio of 1:(11 - 12) to obtain a mixed solution, inject it into the reaction system at a constant rate of 0.25 - 0.3 mL / min; if a cadmium precursor solution is prepared, the doping specifically is: After mixing the chalcogen precursor solution, cadmium precursor solution and octadecene in a volume ratio of 0.4:(1 - 1.2):3.6 to obtain a mixed solution, inject it into the reaction system at a constant rate of 0.25 - 0.3 mL / min;

[0041] The volume ratio of the total volume of the mixed solution injected during doping to the volume of the lead bromide precursor solution is 5:(6 - 6.5).

[0042] The following further illustrates the present invention with specific examples.

[0043] Example 1

[0044] A method for preparing chalcogen - doped perovskite nanocrystals specifically includes the following steps:

[0045] Step 1: Prepare the cesium precursor solution

[0046] Add 0.31 mmol of cesium carbonate, 0.5 mL of oleic acid and 4 mL of octadecene into a 50 - mL three - necked flask. Connect the flask to a vacuum pump and continuously evacuate for 10 minutes to completely volatilize the moisture. Under an argon atmosphere, heat the mixture in the flask to 120 °C and maintain for 1 hour. After the cesium carbonate completely reacts, cool down to room temperature to obtain the cesium precursor solution, where the concentration of cesium ions is 0.068 mol / L. Transfer the solution to a sample bottle and seal it for subsequent use.

[0047] Step 2: Prepare the chalcogen precursor solution

[0048] Add 6 mmol of sulfur powder and 6 mL of oleylamine into a 50-mL three-necked flask. Connect the flask to a vacuum pump and continuously evacuate for 10 minutes to completely volatilize the moisture. Stir and heat in an argon atmosphere to 100 °C until all the sulfur powder is dissolved to obtain the sulfur precursor solution, where the concentration of sulfur is 1 mol / L. Add 6 mmol of selenium powder and 6 mL of trioctylphosphine (TOP) into a 50-mL three-necked flask. Connect the flask to a vacuum pump and continuously evacuate for 10 minutes to completely volatilize the moisture. Stir and heat in an argon atmosphere to 100 °C until all the selenium powder is dissolved to obtain the selenium precursor solution, where the concentration of selenium is 1 mol / L. Transfer the sulfur precursor solution and the selenium precursor solution to sample bottles respectively and seal them for future use.

[0049] Step 3: Prepare the cadmium precursor solution

[0050] Add 3 mmol of cadmium oxide (CdO), 3.9 mL of oleic acid, and 3.9 mL of octadecene into a 50-mL three-necked flask. Connect the flask to a vacuum pump and continuously evacuate for 10 minutes to completely volatilize the moisture. Heat in an argon atmosphere to 220 °C and maintain for 1 hour. After CdO is completely dissolved, cool to room temperature to obtain the cadmium precursor solution, where the concentration of cadmium ions is 0.38 mol / L. Transfer the solution to a sample bottle and seal it for future use.

[0051] Step 4: Add 0.188 mmol of lead bromide, 5 mL of octadecene, 0.5 mL of oleic acid, and 0.5 mL of oleylamine into a 50-mL three-necked flask. Connect the flask to a vacuum pump and continuously evacuate for 10 minutes to completely volatilize the moisture. Under the conditions of argon and magnetic stirring, heat the mixture in the flask to the first temperature (120 °C) and maintain for 1 hour until the lead bromide is completely dissolved to obtain the lead bromide precursor solution. Subsequently, heat the solution to the second temperature (150 °C) and then inject it into the cesium precursor solution in Step 1 to react to form perovskite nanocrystals.

[0052] Step 5: Within 5 - 10 s after the injection of the cesium precursor, mix the sulfur precursor solution (0.4 mL) prepared in Step 2, the cadmium precursor solution (1 mL) prepared in Step 3, and octadecene (3.6 mL), and then inject the mixture into the reaction system at a constant rate of 0.25 mL / min. Continue the reaction for 20 min and then block the reaction with an ice-water bath. Centrifuge and purify to obtain chalcogen-doped perovskite nanocrystals.

[0053] The fluorescence spectrum and absorption spectrum of the perovskite nanocrystals prepared in this example are as Figure 1 shown, and the transmission electron microscope images are as Figure 2 shown, and the EDS element distribution map (Mapping) is as Figure 3As shown. It can be seen from the transmission electron microscope image that the morphology of the perovskite nanocrystals prepared in this example is a polyhedral morphology structure with passivated corners. The EDS element distribution map (Mapping) shows that sulfur elements are uniformly distributed in the perovskite nanocrystal structure, indicating good doping in the crystal, while cadmium elements show a more dispersed distribution.

[0054] Example 2

[0055] Based on Example 1, in this example, the precursor mixing method in Step 5 is adjusted as follows: Mix the sulfur precursor solution (0.4 mL) prepared in Step 2 with octadecene (4.6 mL) to obtain a mixed solution with a total injection volume of 5 mL. The fluorescence spectrum and absorption spectrum of the perovskite nanocrystals prepared in this example are as Figure 4 shown, and the transmission electron microscope image is as Figure 5 shown, and the EDS element distribution map (Mapping) is as Figure 6 shown. It can be seen from the transmission electron microscope image that the morphology of the perovskite nanocrystals prepared in this example is a cubic structure. The EDS element distribution map (Mapping) shows that sulfur elements are uniformly distributed in the perovskite nanocrystal structure, indicating good doping in the crystal, while cadmium elements also show a more dispersed distribution.

[0056] Example 3

[0057] Based on Example 1, in this example, the precursor mixing method in Step 5 is adjusted as follows: Mix the selenium precursor solution (0.4 mL) prepared in Step 2, the cadmium precursor solution (1 mL) in Step 3 with octadecene (3.6 mL) to obtain a mixed solution with a total injection volume of 5 mL. The fluorescence spectrum and absorption spectrum of the perovskite nanocrystals prepared in this example are as Figure 7 shown, and the transmission electron microscope image is as Figure 8 shown.

[0058] Example 4

[0059] Based on Example 1, in this example, the precursor mixing method in Step 5 is adjusted as follows: Mix the selenium precursor solution (0.4 mL) prepared in Step 2 with octadecene (4.6 mL) to obtain a mixed solution with a total injection volume of 5 mL. The fluorescence spectrum and absorption spectrum of the perovskite nanocrystals prepared in this example are as Figure 9 shown.

[0060] The above are only the embodiments of the present invention and should not be construed as limiting the scope of the present invention. For those skilled in the art, the content of the claims and the drawings can be modified, innovated, or applied to other technical fields. However, it should be noted that all modifications to the present invention should be included within the scope of the patent protection of the present invention.

Claims

1. A method for preparing chalcogen-doped perovskite nanocrystals, characterized in that: The following steps are involved: Step (1), under the protection of inert gas, respectively preparing a cesium precursor solution and a chalcogen element precursor solution; Step (2), under the protection of an inert gas, lead bromide, octadecene, oleic acid and oleylamine are mixed, stirred and heated to a first temperature for reaction until the solution is clear, thereby obtaining a lead bromide precursor solution; Step (3), heating the lead bromide precursor solution to a second temperature and then injecting the cesium precursor solution, reacting for 5 to 10 seconds before doping, cooling after the reaction is complete to stop the reaction, and centrifuging and purifying to obtain chalcogen-doped perovskite nanocrystals; The doping is specifically as follows: a chalcogen element precursor solution and octadecene are mixed in a volume ratio of 1:(11-12) to obtain a mixed solution, and then the mixed solution is injected into the reaction system at a constant rate.

2. The method for preparing chalcogen-doped perovskite nanocrystals according to claim 1, characterized in that: The cesium precursor solution is obtained by mixing cesium carbonate, oleic acid and octadecene and heating them for reaction; the concentration of the cesium precursor solution is 0.05-0.08 mol / L, and the volume ratio of octadecene to oleic acid is 8:(1-1.2).

3. The method for preparing chalcogen-doped perovskite nanocrystals according to claim 1, characterized in that: The chalcogen element precursor solution is obtained by mixing a chalcogen element single substance and a ligand and heating them for reaction; the chalcogen element single substance is sulfur powder or selenium powder, wherein the ligand of the sulfur powder is oleylamine and the ligand of the selenium powder is trioctylphosphine; the concentration of the chalcogen element precursor solution is 1-1.5 mol / L.

4. The method for preparing chalcogen-doped perovskite nanocrystals according to claim 1, characterized in that: The concentration of the lead bromide precursor solution is 0.02-0.04 mol / L, and the volume ratio of octadecene to oleic acid and oleylamine is 10:1:(1-1.2); when the perovskite nanocrystals are generated by reaction, the molar concentration ratio of cesium ions in the cesium precursor solution to lead ions in the lead bromide precursor solution is (1-1.5):

3.

5. The method for preparing chalcogen-doped perovskite nanocrystals according to claim 1, characterized in that: The first temperature is 115-125°C, and the second temperature is 145-155°C.

6. The method for preparing chalcogen-doped perovskite nanocrystals according to claim 1, characterized in that: The method further comprises the following steps: The cadmium oxide, oleic acid and octadecene are heated to react under the protection of an inert gas to obtain a cadmium precursor solution; During doping, a chalcogen precursor solution, a cadmium precursor solution and octadecene are mixed in a volume ratio of 0.4:(1-1.2):3.6 to obtain a mixed solution, which is then injected into the reaction system at a constant rate.

7. The method for preparing chalcogen-doped perovskite nanocrystals according to claim 6, characterized in that: The concentration of the cadmium precursor solution is 0.3-0.4 mol / L, and the volume ratio of octadecene to oleic acid is 1:(1-1.2).

8. The method for preparing chalcogen-doped perovskite nanocrystals according to claim 1 or 6, characterized in that: The volume ratio of the total volume of the mixed solution injected during doping to the lead bromide precursor solution is 5:(6-6.5).

9. A chalcogen-doped perovskite nanocrystal, characterized in that: Prepared by the method according to any one of claims 1 to 8; the absorption range of the chalcogen element-doped perovskite nanocrystal extends from the visible light region to the near-infrared region.

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