A rare earth-containing high-entropy all-inorganic perovskite nanomaterial and its synthesis method

Abstract

The present invention relates to a rare-earth-containing high-entropy all-inorganic perovskite nanomaterial and a synthesis method thereof. The chemical formula of the rare-earth-containing high-entropy all-inorganic perovskite nanomaterial is CsBCl3, where B is composed of at least five metal ions selected from 2+ Mg 2+ Cu 2+ Fe 2+ Zn 2+ Mn 2+ Ni 2+ Sn 3+ Yb 3+ Eu 3+ The molar numbers of various metal ions constituting B are equal, and at least one metal ion is selected from Yb 3+ and Eu. The present invention synthesizes a rare-earth element-containing high-entropy all-inorganic perovskite material with good luminescence performance by a two-step method, which not only refines the process but also enhances the stability.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic perovskite nanomaterials, and specifically to a rare-earth-containing high-entropy all-inorganic perovskite nanomaterial and a synthesis method thereof. Background Art

[0002] As a rising star in the field of new materials in recent years, all-inorganic perovskite CsPbX3 (X = Cl / Br / I) nanocrystals (Nanocrystals, hereinafter referred to as NCs) have excellent optoelectronic properties such as high fluorescence quantum yield, tunable emission spectrum, and narrow emission peak. In terms of process, the synthesis of perovskite materials is divided into solid-phase method and liquid-phase method, that is, all raw materials are weighed and stirred and mixed, and then subsequent operations are carried out. Although it is simple and fast, there are many and complex factors in the synthesis process, the material properties are unstable, it is easy to cause the synthesized powder to be impure, and the luminescence performance is poor, making it difficult to achieve the repeatable and batch preparation of high-quality nanocrystals.

[0003] The luminescence performance of perovskite materials can be improved by ion doping. Most of the existing doping of perovskite materials is to use one or two kinds of ions to replace Cs + and Pb 2+ in CsPbCl3, so as to improve its optical properties, but the effect is limited. Introducing rare-earth ions will change the symmetry of the local crystal field, increase the mixing ability of their f states with higher electron configurations, and ultimately lead to enhanced luminescence. For example, Patent CN115851273A discloses a synthesis method of rare-earth-doped perovskite nanocrystals, and this method improves the luminescence performance of the material through rare-earth doping.

[0004] However, in the above methods, due to the possible oxidation of the doped ions or uneven dispersion during doping, a single phase cannot be formed, so there are still problems with unstable performance.

[0005] At present, the newly developed high-entropy materials have excellent properties, but rare-earth-doped high-entropy perovskite materials have not been reported yet. Summary of the Invention

[0006] An object of the present invention is to obtain a rare-earth-containing inorganic perovskite material with good stability. The main technical idea is to introduce the concept of high entropy into perovskite materials. First, the multi-component cations have high dispersibility (occupying the lattice with the same probability), and due to the difference in cation sizes, lattice distortion and stress field disorder are caused, thereby slowing down the diffusion of ions in the lattice of the high-entropy material, which can, to a certain extent, limit the penetration of O2 and H2O, and is expected to enhance the stability of the material in a humid and O2-rich environment. Second, according to the Gibbs free energy formula G = U - TS + PV = H - TS, it can be judged that the larger the entropy value of the system and the smaller the enthalpy change, the more likely a single phase is formed and the more stable the system is. Moreover, the increase in entropy will cause some interesting effects in the material, including the high-entropy effect in thermodynamics, the sluggish diffusion effect in kinetics, and the "cocktail" effect in performance, etc.

[0007] The specific solution of the present invention is as follows:

[0008] A rare-earth-containing high-entropy all-inorganic perovskite nanomaterial, with the chemical formula CsBCl3, where B is composed of at least five metal ions selected from 2+ Mg 2+ Cu 2+ Fe 2+ Zn 2+ Mn 2+ Ni 2+ Sn 3+ Yb 3+ Eu 3+ The molar numbers of various metal ions constituting B are equal, and at least one metal ion is selected from Yb 3+ and Eu

[0009] With the diversification of doping ions and the increase in entropy value in high-entropy materials, interactions will occur between multiple atoms in the system, causing energy differences in energy levels of the same quantum state and generating multiple energy levels (i.e., energy level splitting).

[0010] The present invention simulates and calculates the structure and properties of high-entropy perovskite, thereby determining the raw materials for synthesizing high-entropy perovskite. Considering various factors such as the octahedral factor, the difference in lattice constants, the similar ionic radii of substitution sites, the same crystal structure, similar electronegativity, the same valence state, entropy formation ability, Goldschmid tolerance factor, size disorder factor, and valence electron concentration, etc., metal ions suitable for replacing Pb 2+ are calculated and selected. The calculation results show that Pb 2+ can be replaced by Mg 2+ Cu 2+ Fe 2+ Zn 2+ Mn 2+ Ni 2+ Sn 2+, Yb 3+ , Eu 3+ etc. This project intends to select PbCl2, MgCl2, CuCl2, FeCl2, MnCl2·4H2O, NiCl2, ZnCl2, SnCl2, YbCl3·6H2O, EuCl3, etc. as raw materials for preparing high-entropy all-inorganic perovskites.

[0011] Preferably, the chemical formula is Cs(Pb 1 / 5 Mn 1 / 5 Ni 1 / 5 Zn 1 / 5 Yb 1 / 5 )Cl3. Experimental verification shows that this kind of perovskite nanomaterial has excellent luminescent properties.

[0012] Another object of the present invention is to synthesize a high-entropy all-inorganic halide material with good luminescent properties and high stability by refining the synthesis process and adding raw materials step by step.

[0013] The specific scheme is a synthesis method of a rare-earth-containing high-entropy all-inorganic perovskite nanomaterial, which includes the following steps:

[0014] 1) Raw material selection: Select CsCl, and at least four of PbCl2, MgCl2, CuCl2, FeCl2, MnCl2·4H2O, NiCl2, ZnCl2, SnCl2, and at least one of YbCl3·6H2O and EuCl3 as raw materials for preparing high-entropy all-inorganic perovskites, where the molar ratio of CsCl to the sum of the remaining raw materials is 1:1;

[0015] 2) Weigh various raw materials in proportion. At least one of the raw materials selected from MgCl2, CuCl2, FeCl2, MnCl2·4H2O, NiCl2, ZnCl2, SnCl2 is a secondary additive. Mix the remaining raw materials and conduct primary ball milling, and add oleylamine during primary ball milling;

[0016] 3) After the primary ball milling is completed, add the secondary additive for secondary ball milling;

[0017] 4) After the secondary ball milling is completed, add a solvent to dissolve the sample, conduct solid-liquid separation, and dry;

[0018] 5) Crush and grind the dried product to obtain a rare-earth-containing high-entropy all-inorganic perovskite nanomaterial.

[0019] A highly-entropic all-inorganic halide material with good luminescence performance and high stability was synthesized by adding raw materials step by step. Also, because the raw materials contain rare earth elements, the luminescence range was extended from the visible light region to the near-infrared region, and the highly-entropic all-inorganic perovskite material containing rare earth elements was also prepared for the first time. Although there are applications of perovskite materials in photovoltaics and color (visible light and white) luminescence, highly-entropic perovskite materials can still be used in many emerging fields, which are impossible for undoped all-inorganic perovskite materials, especially in the fields of NIR emission, optical coding, luminescence-based sensing, and nonlinear emission processes, etc.

[0020] Preferably, the solvent used in step 4) is cyclohexane.

[0021] Preferably, both the first ball milling and the second ball milling are carried out by high-energy ball milling method. The high-energy ball milling method, also known as mechanochemical synthesis method, is a method that combines physical method and chemical method. Through the high-speed rotation and vibration of the ball mill, the grinding tank is driven to do periodic motion, so that the hard balls strongly impact, grind and stir the raw materials. It can significantly reduce the reaction activation energy, refine the grains, enhance the activity of nanocrystals and induce chemical reactions, and finally synthesize new compounds and crush them into nanoscale particles.

[0022] Preferably, in step 4), after adding the solvent to dissolve the sample and separating the solid and liquid twice, drying is carried out.

[0023] Preferably, the solid-liquid separation is carried out by centrifugation.

[0024] Preferably, in step 1), at least one raw material is ZnCl2, and ZnCl2 is a secondary additive.

[0025] The advantages of the present invention are as follows: (1) A highly-entropic all-inorganic perovskite material containing rare earth elements with good luminescence performance was synthesized by a two-step method, which not only refined the process but also enhanced the stability; (2) For the selection of raw materials for synthesizing highly-entropic perovskite materials, various factors such as the perovskite tolerance factor, similar ionic radii, entropy value, electronegativity, atomic size mismatch, and lattice constant difference were considered, and suitable B-site doping ions were selected. By selecting different raw materials, highly-entropic all-inorganic perovskite materials were synthesized; (3) In the present invention, the raw materials were not directly ground after being weighed and mixed, but by a two-step method, one of the raw materials was left to be added at the end. The experimental results showed that the final luminescence intensity was significantly improved compared with direct all mixing. (4) The advantage of equimolar doping compared with other non-equimolar doping is that with the diversification of doping ions, the increase in entropy value is beneficial to improving the luminescence intensity of the sample, and the final experimental results also verified this point. (5) At the same time, rare earth ion doping improved the optical properties and stability of the highly-entropic perovskite materials. It not only reduced the proportion of lead, increased the entropy value, but also extended the luminescence range of perovskite to the near-infrared region. Description of the Drawings

[0026] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0027] Figure 1 Schematic diagram of the preparation process of the rare earth element-containing high-entropy all-inorganic perovskite luminescent material by the two-step method in Example 1.

[0028] Figure 2 XRD patterns of the luminescent materials synthesized in Example 1, Comparative Example 2 and Comparative Example 3.

[0029] Figure 3 Absorption spectra and band gap spectra of the luminescent materials synthesized in Example 1 and Comparative Example 2.

[0030] Figure 4 PL spectra of the luminescent materials synthesized in Example 1, Comparative Example 2 and Comparative Example 3 and the actual luminescence diagram of the luminescent material synthesized in Example 1.

[0031] Figure 5 For the rare earth element-containing high-entropy Cs(Pb 1 / 5 Mn 1 / 5 Ni 1 / 5 Zn 1 / 5 Yb 1 / 5 )Cl3 fluorescence intensity versus temperature graph.

[0032] Figure 6 PL comparison graph between directly mixing and ball milling all raw materials in one step in Comparative Example 1 and the luminescent material synthesized by the two-step method in Example 1.

[0033] Figure 7 PL comparison graph of the luminescent materials synthesized in Example 1 and Comparative Examples 4 - 7. Specific Embodiments

[0034] The present invention will be clearly described below in conjunction with specific embodiments of the present invention. The description here is only used to explain the present invention, but not to limit the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative efforts, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

[0035] Example 1

[0036] (1) Simulate and calculate the structure and properties of high-entropy perovskite to determine the raw materials for synthesizing high-entropy perovskite. Considering various factors such as the octahedral factor, lattice constant difference, similar ionic radii of substitution sites, the same crystal structure, similar electronegativity, the same valence state, entropy formation ability, Goldschmid tolerance factor, size disorder factor, and valence electron concentration, calculate and select suitable ions to replace Pb2+ For metal ions, the calculation results show that Pb 2+ Mg can be selected 2+ , Cu 2+ , Fe 2+ , Zn 2+ , Mn 2+ , Ni 2+ , Sn 2+ , Yb 3+ , Eu 3+ etc. In this project, PbCl2, MgCl2, CuCl2, FeCl2, MnCl2·4H2O, NiCl2, ZnCl2, SnCl2, YbCl3·6H2O, EuCl3, etc. are proposed to be used as raw materials for preparing high-entropy all-inorganic perovskites.

[0037] (2) The chemical formula of the all-inorganic halide perovskite material is CsPbCl3. At least five of the ten chlorides of PbCl2, MgCl2, CuCl2, FeCl2, MnCl2·4H2O, NiCl2, ZnCl2, SnCl2, YbCl3·6H2O, and EuCl3 are weighed.

[0038] In this example, five raw materials of PbCl2, MnCl2·4H2O, NiCl2, YbCl3·6H2O, and ZnCl2, as well as the CsCl raw material, are weighed. Among them, the molar amounts of the five raw materials of PbCl2, MnCl2·4H2O, NiCl2, YbCl3·6H2O, and ZnCl2 are equal, and the total molar amount of these five raw materials is equal to the molar amount of CsCl. The above raw materials are used to synthesize Cs(Pb 1 / 5 Mn 1 / 5 Ni 1 / 5 Zn 1 / 5Yb 1 / 5 )Cl3 nanocrystal luminescent materials.

[0039] In some other examples, in addition to CsCl, five other types of raw materials can also be selected, but at least one is selected from YbCl3·6H2O and EuCl3.

[0040] Such as PbCl2, MnCl2·4H2O, CuCl2, YbCl3·6H2O, SnCl2, which are used to synthesize Cs(Pb 1 / 5 Mn 1 / 5 Fe 1 / 5 Sn 1 / 5Yb 1 / 5 )Cl3 nanocrystal luminescent materials, where SnCl2 is used as a secondary additive;

[0041] Or PbCl2, MnCl2·4H2O, FeCl2, YbCl3·6H2O, SnCl2, used for synthesizing Cs(Pb 1 / 5 Mn 1 / 5 Cu 1 / 5Sn 1 / 5 Yb 1 / 5 )Cl3 nanocrystal luminescent material, where SnCl2 is used as a secondary additive;

[0042] It is also possible to select more than five raw materials, such as PbCl2, MnCl2·4H2O, FeCl2, NiCl2, ZnCl2, EuCl3, for synthesizing Cs(Pb 1 / 6 Mn 1 / 5 Fe 1 / 6 Zn 1 / 6 Ni 1 / 6 Eu 1 / 6 )Cl3 nanocrystal luminescent material, where ZnCl2 is used as a secondary additive.

[0043] Such as Figure 1 As shown in the process flow, in this embodiment, first, the raw materials CsCl, PbCl2, MnCl2·4H2O, NiCl2, YbCl3·6H2O are placed in a zirconia ceramic ball mill pot (inner diameter 37.5 mm) equipped with two zirconia ceramic grinding balls (diameter 12.7 mm, total weight 11.2 g). A rubber ring is placed on the sealing part of the ball mill pot, and the ball mill cover is covered and sealed well;

[0044] (3) Place the ball mill pot in a high-energy ball mill for pre-ball milling. Through the high-speed rotation and vibration of the ball mill, drive the grinding pot to perform periodic motion. The ball milling time is 5 min and the rotation speed is 1000 rpm;

[0045] (4) After the first pre-ball milling is completed, take out the ball mill pot and transfer it to the fume hood. Open the ball mill pot, and use a pipette to add 0.075 mL of oleylamine (OAm) into the ball mill pot. Seal the ball mill pot well;

[0046] (5) Continue to use the high-energy ball mill to ball mill for 15 min;

[0047] (6) After 15 min of ball milling, take out the ball mill pot and transfer it to the fume hood. Open the ball mill pot, add the last weighed raw material ZnCl2, and then ball mill for 5 min;

[0048] (7) After the ball milling is completed, transfer the ball milling jar to the fume hood. Open the ball milling jar, add cyclohexane to dissolve the sample, transfer the raw materials in the ball milling jar to a centrifuge tube. After centrifuging the sample for 10 min (at a rotation speed of 8000 rpm), discard the supernatant. Then add a certain amount of cyclohexane solution to the centrifuge tube again, and ultrasonically disperse (for 10 min) to disperse the precipitate, and then centrifuge for 10 min (at a rotation speed of 10000 rpm);

[0049] (8) Then place the centrifuge tube in an oven, set the drying temperature at 50 - 80 °C, and set the drying time to 6 - 8 h;

[0050] (9) After drying, take out the raw materials and place them in a household crusher, use the crusher to grind them into powdery particles, and then put the particles into a mortar and grind them more finely into powder;

[0051] (10) Analyze and characterize the milled sample to determine its phase composition and luminescence properties.

[0052] Comparative Example 1

[0053] The raw material composition is the same as that in Example 1. In the preparation steps, all raw materials are added during the first pre - ball milling, and the remaining processes are the same as those in Example 1.

[0054] Comparative Example 2

[0055] The raw materials are PbCl2 and CsCl, which are used to synthesize CsPbCl3, and the preparation process is the same as that in Comparative Example 1.

[0056] Comparative Example 3

[0057] The raw materials are PbCl2, CsCl, and MnCl2·4H2O, which are used to synthesize Cs(Pb 1 / 2 Mn 1 / 2 )Cl3, and the preparation process is the same as that in Example 1. MnCl2·4H2O is an additive added in the second step.

[0058] Figure 2 For the comparison of the XRD diffraction patterns of the luminescent materials synthesized in Example 1, Comparative Example 2, and Comparative Example 3, it can be seen from the comparison that the diffraction peak intensity corresponding to the CsPbCl3 crystal in the material obtained in Example 2 is significantly stronger than that in Comparative Example 1 and 2. By using the two - step synthesis method, when there are more types of doped elements, a high - entropy inorganic perovskite material can be obtained, and the purity of the nanocrystals is improved.

[0059] Figure 3 For the comparison of the absorption spectra and band - gap width spectra of the luminescent materials obtained in Example 1 and Comparative Example 2, it can be seen that Cs(Pb 1 / 5 Mn 1 / 5 Ni 1 / 5 Zn 1 / 5 Yb1 / 5 ) The Cs(Pb

[0060] Figure 4 The PL spectra comparison of the luminescent materials synthesized in Example 1, Comparative Example 2 and Comparative Example 3, and the actual luminescence picture of the luminescent material synthesized in Example 1. It can be seen that Cs(Pb 1 / 5 Mn 1 / 5 Ni 1 / 5 Zn 1 / 5 Yb 1 / 5 )Cl3 has good luminescence intensity.

[0061] Figure 5 The graph shows the change of the fluorescence intensity of the luminescent material synthesized in Example 1 with temperature. It can be seen that Cs(Pb 1 / 5 Mn 1 / 5 Ni 1 / 5 Zn 1 / 5 Yb 1 / 5 )Cl3 has good stability when the temperature changes.

[0062] Figure 6 The PL comparison of the luminescent materials synthesized in Example 1 and Comparative Example 1 shows that, under the condition of the same raw material composition, the luminescence intensity of the luminescent material synthesized by the two-step method is significantly better than that of the luminescent material synthesized by the one-step method.

[0063] Comparative Example 4

[0064] The raw materials are PbCl2, CsCl, MnCl2·4H2O, NiCl2, ZnCl2, YbCl3·6H2O, used for non-equimolar synthesis of Cs(Pb 1 / 5 Mn 1 / 5 Ni 3 / 10 Zn 1 / 10 Yb 1 / 5 )Cl3, and the preparation process is the same as that of Example 1, with ZnCl2 as the secondary additive.

[0065] Comparative Example 5

[0066] The raw materials are PbCl2, CsCl, MnCl2·4H2O, YbCl3·6H2O, used for non-equimolar synthesis of Cs(Pb 9 / 20 Mn 9 / 20 Yb 1 / 10 )Cl3, and the preparation process is the same as that of Example 1, with YbCl3·6H2O as the secondary additive.

[0067] Comparative Example 6

[0068] The raw materials are PbCl2, CsCl, MnCl2·4H2O, and YbCl3·6H2O, which are used for non-equimolar synthesis of Cs(Pb 2 / 5 Mn 2 / 5Yb 1 / 5 )Cl3. The preparation process is the same as that of Example 1, and YbCl3·6H2O is a secondary additive.

[0069] Comparative Example 7

[0070] The raw materials are PbCl2, CsCl, MnCl2·4H2O, and YbCl3·6H2O, which are used for synthesizing Cs(Pb 7 / 20 Mn 7 / 20 Yb 3 / 10 )Cl3. The preparation process is the same as that of Example 1, and YbCl3·6H2O is a secondary additive.

[0071] Figure 7 For the PL comparison of the luminescent materials synthesized in Example 1 and Comparative Examples 4-7, it can be seen from the figure that the broadband peak generated at 600 nm is a new emission position due to the energy transfer between the host energy level and the doped ion energy level, which is attributed to the 2+ of 4 T1- 6 A1 transition. Therefore, when the Pb / Mn ratio remains unchanged, the technical effect of unequal molar amounts is not as good as that of the high-entropy sample. It can also prove that the synthesis method of the high-entropy sample is innovative.

[0072] Compared with all other perovskite materials doped with divalent and trivalent ions, the difference between the present invention and the above-mentioned scheme is that the present invention synthesizes a rare-earth element-containing high-entropy perovskite luminescent material by a two-step method by selecting different doping raw materials, not only enhancing the luminescence performance and stability, but also overall refining the synthesis process, and not using a large amount of organic solvents during the synthesis process, thereby reducing environmental pollution. The synthesis of rare-earth element-containing high-entropy perovskite by multi-element doping expands the application range of high-entropy perovskite and provides a scientific basis for the subsequent research and development of high-entropy perovskite.

Claims

1. A synthesis method of a rare earth-containing high-entropy all-inorganic perovskite nanomaterial, characterized in that, The chemical formula is Cs(Pb 1 / 5Mn 1 / 5 Ni 1 / 5 Zn 1 / 5 Yb 1 / 5 )Cl3, and the synthesis method comprises the following steps: 1) Raw material selection: Select CsCl, PbCl2, MnCl2·4H2O, NiCl2, ZnCl2, and YbCl3·6H2O as raw materials for preparing high-entropy all-inorganic perovskite, where the molar ratio of CsCl to the sum of the remaining raw materials is 1:1; 2) Weigh various raw materials proportionally. ZnCl2 is used as a secondary additive for raw materials. Mix the remaining raw materials and conduct primary ball milling, adding oleylamine during primary ball milling; 3) After the primary ball milling is completed, add the secondary additive for secondary ball milling; 4) After the secondary ball milling is completed, add a solvent to dissolve the sample, conduct solid-liquid separation, and dry; 5) Crush and grind the dried product to obtain a rare-earth-containing high-entropy all-inorganic perovskite nanomaterial.

2. The synthesis method of the rare earth-containing high-entropy all-inorganic perovskite nanomaterial according to claim 1, characterized in that: The solvent used in step 4) is cyclohexane.

3. The synthesis method of the rare earth-containing high-entropy all-inorganic perovskite nanomaterial according to claim 1, wherein: Both the primary ball milling and the secondary ball milling are carried out by high-energy ball milling method.

4. The synthesis method of the rare earth-containing high-entropy all-inorganic perovskite nanomaterial according to claim 1, characterized in that: In step 4), add a solvent to dissolve the sample and conduct solid-liquid separation twice before drying.

5. The synthesis method of the rare earth-containing high-entropy all-inorganic perovskite nanomaterial according to claim 1, characterized in that: The solid-liquid separation is carried out by centrifugation.

6. A rare-earth-containing high-entropy all-inorganic perovskite nanomaterial, characterized in that: The chemical formula is Cs(Pb 1 / 5 Mn 1 / 5 Ni 1 / 5Zn 1 / 5 Yb 1 / 5 )Cl3, and the preparation method is as described in Claim 1.

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