A method for preparing an all-inorganic CsPbBr3 / layered double hydroxide superlattice

Abstract

The present application relates to a method for preparing a full inorganic CsPbBr3 / layered double hydroxide (CsPbBr3 / LDH) superlattice. However, at present, the perovskite quantum well material is mainly based on the organic-inorganic hybrid system of long-chain organic amine ions, and the structural stability is poor. Therefore, it is of great significance to develop full inorganic two-dimensional perovskite superlattice with inorganic quantum barrier for artificial lighting application. Here, we design an ion exchange strategy to prepare a full inorganic CsPbBr3 / layered double hydroxide (CsPbBr3 / LDH) superlattice. The prepared CsPbBr3 / LDH superlattice emits blue light, and the FWHM and PLQY are 20 nm and 55%, respectively. The research results provide a general strategy for preparing full inorganic superlattice, and provide a platform for synthesizing ordered and designable perovskite superlattice.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials and relates to a method for preparing an all-inorganic CsPbBr3 / layered double hydroxide (CsPbBr3 / LDH) superlattice. Background Technology

[0002] Metal halide perovskites, with their diverse chemical structures, tunable band gaps, bright exciton emission, and high defect tolerance, have found wide application in optoelectronic devices. Since chemical composition, nanoscale order, microstructure, and macroscopic form significantly influence the physical properties of these materials, multi-scale structural control is highly desirable. In recent years, two-dimensional (2D) perovskite multiple quantum wells (MQWs), or superlattices, have attracted considerable research interest, with their promising optoelectronic properties enriching fundamental research in areas such as photovoltaics, light-emitting diodes, and superfluorescence. Compared to 3D perovskites, 2D perovskite superlattices are typically constructed by inserting organic molecules between 2D inorganic perovskite plates. The strong dielectric sieving effect of organic molecules positions electrons within the inorganic octahedral layers. The controlled quantum barrier (dielectric properties of the organic molecules) and periodicity (thickness of the inorganic octahedral layers) of the perovskite superlattice can tune its electrical and optical properties. Organic-inorganic two-dimensional perovskite superlattices (B2A) are commonly synthesized and studied. n- 1M n X 3n+1 B = R-NH3 + A = Cs + , HC(NH2) + CH3NH3 + M = Pb 2+ Sn 2+ X = Cl - , Br - I - (n = 1, 2, 3...). However, synthesizing fully inorganic two-dimensional perovskite superlattices with inorganic quantum barriers remains a significant challenge. Summary of the Invention

[0003] This invention modulates the divalent / trivalent metal ions (Mg) 2+ / Al 3+ By adjusting the ratio of PbBr6, Mg-Al-LDH materials with large interlayer spacing were prepared, which is crucial for the diffusion of large perovskite ions into the LDH interlayer. 4- Anions can replace NO3 between LDH layers at room temperature. -Anions self-assemble into highly ordered, densely packed perovskite layers. Metal halide perovskites are soft-lattice crystals, and PbBr6 octahedra can adapt to the LDH lattice through lattice distortion. Simultaneously, CsPbBr3 / LDH superlattices (LDH2Cs) with different periodicities (n=1, 2...) are formed. n-1 Pb n Br 3n+1 The synthesized CsPbBr3 / LDH superlattice exhibits blue emission with a main PL peak at 463 nm, a narrow FWHM of 20 nm, and a PLQY as high as 55%. Compared with organic-inorganic perovskite superlattices, the all-inorganic perovskite superlattice shows a weaker dielectric shielding effect and a smaller band gap.

[0004] The structure of the product obtained by this invention is as follows:

[0005] 1. Figure 1 Structure of Mg-Al-LDH materials: (a) XRD pattern of Mg-Al-LDH. HRTEM images of Mg-Al-LDH (x = 0.3) (b) and Mg-Al-LDH (x = 0.45) (c). HAADF and EDS mapping images of Mg-Al-LDH (x = 0.3) (d) and Mg-Al-LDH (x = 0.45) (e).

[0006] 2. Figure 2 PL spectra of CsPbBr3 / Mg-Al-LDH: (a) Fluorescence images of CsPbBr3 / Mg-Al-LDH (x = 0.2, 0.3, 0.4, 0.43, 0.45, 0.47). (b) PL spectra of CsPbBr3 / Mg-Al-LDH (x = 0.2, 0.3, 0.4, 0.43, 0.45, 0.47).

[0007] 3. Figure 3 Structure of CsPbBr3 / Mg-Al-LDH: (a, b) TEM images of CsPbBr3 / Mg-Al-LDH (x = 0.3). Figure b is a stitch-together image of two consecutively taken images. (c) HAADF and EDS mapping images of CsPbBr3 / Mg-Al-LDH (x = 0.3). (d, e) TEM images of CsPbBr3 / Mg-Al-LDH (x = 0.45). (c) HAADF and EDS mapping images of CsPbBr3 / Mg-Al-LDH (x = 0.45). Attached Figure Description

[0008] Figure 1 The structure of Mg-Al-LDH material.

[0009] Figure 2The PL spectrum of CsPbBr3 / Mg-Al-LDH.

[0010] Figure 3 The structure is CsPbBr3 / Mg-Al-LDH.

[0011] Advantages and Positive Effects of the Invention: This invention develops an ion exchange strategy for synthesizing all-inorganic CsPbBr3 / LDH superlattices. The CsPbBr3 / LDH superlattice synthesized by this invention exhibits blue emission and a PLQY as high as 55%. Compared with organic-inorganic perovskite superlattices, the all-inorganic perovskite superlattice exhibits a weaker dielectric shielding effect and a smaller band gap. This invention opens a new avenue for synthesizing novel, ordered, and functional perovskite superlattices. It should be understood that various changes and modifications can be made within the scope of the claims of this invention. Detailed Implementation

[0012] The following synthetic examples are used to further illustrate the present invention, but are not intended to limit the invention.

[0013] (1) Synthesis of layered bimetallic hydroxides (LDHs):

[0014] LDH was synthesized via a hydrothermal method. 0.008 mol Mg(NO3)2·6H2O and 0.0062 mol Al(NO3)3·9H2O were dissolved in 10 mL of deionized water. Then, 0.0032 mol NaOH was dissolved in 15 mL of deionized water to form a clear solution, which was then added to the above salt solution. The suspension was stirred for 1 minute and transferred to a 50 mL PTFE-lined stainless steel autoclave, and maintained at 110 °C for 24 hours. After centrifugation, the mixture was washed several times with deionized water and ethanol. The white precipitate (LDH) was dried at 70 °C for 12 h to obtain a solid product. After drying, it was washed once more with deionized water to remove residual NaNO3. The white precipitate (LDH) was dried at 70 °C for 10 h to obtain a solid product. LDH in all proportions was synthesized using the above method.

[0015] (2) Preparation of CsPbBr3 / LDH:

[0016] CsBr (0.2 mmol), PbBr2 (0.2 mmol), OA (0.5 mL), and OM (0.25 mL) were dissolved in DMF (5 mL) at room temperature to form a precursor solution. Then, 0.05 g of LDH was dispersed in 5 mL of toluene and stirred for 20 min. Next, 1.5 mL of the precursor solution was rapidly added to the LDH / toluene suspension and stirred at room temperature for 60 min. The composite material was centrifuged and washed with hexane. Finally, the target product was dried at room temperature.

[0017] (3) Characterization of layered bimetallic hydroxides (LDHs):

[0018] The X-ray diffraction (XRD) pattern of LDH was determined using an X'Pert-PRO MPD diffractometer (PANalytical BV, Holland) under CuKα radiation at 40 kV and 40 mA. The surface morphology of the material was analyzed by transmission electron microscopy (TEM) using a JEM-F200 microscope (JEOL, Japan).

[0019] (4) Characterization of CsPbBr3 / LDH:

[0020] PL spectra at different excitation wavelengths and power densities were measured using a QEPro spectrometer (OceanOptics, America). Time-resolved PL (TR-PL) spectra were measured using an FLS1000 fluorescence spectrometer (Edinburgh Instruments, UK) and a 375 nm picosecond pulsed laser.

Claims

1. A method for preparing an all-inorganic CsPbBr3 / layered bimetallic hydroxide superlattice, characterized in that: First, MgAl-LDH was synthesized, and then CsPbBr3 / layered bimetallic hydroxide superlattice was prepared using an ion exchange strategy. The CsPbBr3 / layered bimetallic hydroxides prepared by the method described above form CsPbBr3 / LDH superlattices with different periodicities, denoted as LDH2Cs. n−1 Pb n Br 3n+1 Where n = 1, 2, ...; the CsPbBr3 / LDH superlattice synthesized by the method exhibits blue emission, with a main PL peak at 463 nm, a narrow FWHM of 20 nm, and a PLQY as high as 55%; The method for preparing the all-inorganic CsPbBr3 / layered bimetallic hydroxide superlattice includes the following specific steps: First, MgAl-LDH was synthesized: 0.008 mol Mg(NO3)2⋅6H2O and 0.0062 mol Al(NO3)3⋅9H2O were dissolved in 10 mL of deionized water; then, 0.0032 mol NaOH was dissolved in 15 mL of deionized water to form a clear solution, which was then added to the salt solution; the mixture suspension was stirred for 1 minute, transferred to a 50 mL PTFE-lined stainless steel autoclave, and kept at 110°C for 24 hours; after centrifugation, it was washed several times with deionized water and ethanol; the white precipitate was dried at 70°C for 12 h to obtain solid product 1; after drying, it was washed once more with deionized water to remove the remaining NaNO3, and dried at 70°C for 10 h to obtain solid product 2; the MgAl-LDH was synthesized using the above method. The CsPbBr3 / layered bimetallic hydroxide superlattice was then prepared using an ion exchange strategy: 0.2 mmol CsBr, 0.2 mmol PbBr2, 0.5 mL OA and 0.25 mL OM were dissolved in 5 mL DMF at room temperature to form a precursor solution; then, 0.05 g LDH was dispersed in 5 mL toluene and stirred for 20 min; then, 1.5 mL of the precursor solution was rapidly added to the LDH / toluene suspension and stirred for 60 min at room temperature. After centrifugation and washing with hexane, the product CsPbBr3 / layered bimetallic hydroxide superlattice was obtained after drying at room temperature.

Images