Lead-free perovskite quantum dot with optical limiting properties and preparation method thereof

Abstract

The present invention discloses a lead-free perovskite quantum dot with optical limiting properties and a preparation method thereof, belonging to the technical field of perovskite quantum dot material preparation. The method comprises the following steps: adding cesium bromide and antimony tribromide in a proportion to a dimethyl sulfoxide solution containing octylamine, dissolving the solution by ultrasonication, injecting the obtained precursor solution into a toluene solution containing oleic acid, centrifuging the solution, and taking the supernatant to obtain the lead-free perovskite quantum dot. The obtained Cs3Sb2Br9 quantum dot is a typical two-dimensional structure material, which can show excellent optical limiting performance under nanosecond laser irradiation, and has obvious reverse saturation absorption (RSA) characteristics, and the optical limiting threshold (F OL ) is low and is expected to be used in optical limiting materials.

Description

Technical Field

[0001] The invention belongs to the field of preparation of perovskite quantum dot materials, and in particular relates to a lead-free perovskite quantum dot with optical limiting characteristics and a preparation method thereof. Background Art

[0002] Quantum dots, also known as nanocrystals, refer to semiconductor nanocrystals with a radius less than or close to the exciton Bohr radius. Since the sizes of the three dimensions are all at the nanometer level, they are strongly affected by the quantum confinement effect, which makes quantum dots have excellent photoelectric properties. Among the many quantum dots, perovskite quantum dots are widely used in optoelectronic devices such as solar cells, photodetectors, and light-emitting diodes (LEDs) due to their large fluorescence quantum yield, narrow emission spectrum half-width, and high carrier mobility, and have attracted widespread attention. Among them, CsPbBr3 quantum dots have become a research hotspot in recent years due to their outstanding luminescence performance and adjustable fluorescence wavelength.

[0003] As the research deepened, people found that CsPbBr3 perovskite quantum dots have excellent third-order nonlinear optical properties, including large nonlinear absorption characteristics, which makes them have great application potential in optical limiting materials. Optical limiting means that when a material is irradiated by a laser, the material has high transmittance under low-intensity laser and low transmittance under high-intensity laser. The optical limiting process can be achieved through nonlinear absorption, refraction and scattering activated by the material under high-intensity laser. Compared with the input laser, the power of the output light is greatly limited, which plays a role in protecting the eyes or instruments from laser damage. The ideal optical limiting material should have a low starting threshold (F S ) and the light clipping threshold (F OL ), which has led researchers to seek materials with excellent optical limiting properties. However, for lead-based perovskite quantum dots, the toxicity of lead has severely restricted their development. At the same time, the dimension of the material's crystal structure has a significant impact on nonlinear optical properties. Therefore, people have turned their attention to low-dimensional lead-free perovskite quantum dots, which also have excellent optoelectronic properties. Summary of the invention

[0004] The purpose of the present invention is to provide a lead-free perovskite quantum dot with optical limiting properties and a preparation method thereof. The lead-free Cs3Sb2Br9 quantum dot material provided by the present invention has a typical two-dimensional structure, enhances the nonlinear optical response, and has good optical limiting performance under 532nm laser, so it has great application value in optical limiting materials and the like.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A lead-free perovskite quantum dot with optical limiting characteristics, the preparation method of which comprises the following steps:

[0007] (1) Preparation of precursor: adding cesium bromide and antimony tribromide in proportion to a dimethyl sulfoxide solution containing octylamine, and dissolving by ultrasonication to form a precursor solution;

[0008] (2) Preparation of Cs3Sb2Br9 quantum dots: The precursor solution obtained in step (1) is injected into a toluene solution containing oleic acid, and the supernatant is collected after centrifugation to obtain the lead-free perovskite quantum dots.

[0009] Furthermore, the content of octylamine in the dimethyl sulfoxide solution in step (1) is 5 μl / 3 mL.

[0010] Furthermore, the content of cesium bromide in the precursor solution obtained in step (1) is 0.3 mmol / 3 mL, and the content of antimony tribromide is 0.2 mmol / 3 mL.

[0011] Furthermore, the amount of the precursor solution used in step (2) is 0.9% of the volume of the toluene solution containing oleic acid.

[0012] Furthermore, the content of oleic acid in the toluene solution in step (2) is 100 μl / mL.

[0013] Furthermore, the centrifugal speed in step (2) is 4000 rpm.

[0014] The Cs3Sb2Br9 quantum dots prepared by the present invention have a typical two-dimensional crystal structure, which show excellent optical limiting properties under nanosecond laser (532nm, 7ns) and have obvious reverse saturation absorption (RSA) characteristics. Compared with lead-based perovskite materials, their onset threshold and optical limiting threshold are lower, and they have great application potential in the field of optical limiting.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The Cs3Sb2Br9 quantum dots prepared by the present invention have excellent optical limiting performance, low normalized transmittance, and a starting threshold (F S ) and the light clipping threshold (F OL ) low (0.25J / cm 2 , 2J / cm 2 ), which has good application prospects.

[0017] (2) The Cs3Sb2Br9 quantum dots prepared by the present invention have obvious reverse saturation absorption (RSA) characteristics under nanosecond laser.

[0018] (3) The preparation method of the present invention is environmentally friendly, has a simple process and is easy to prepare. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the crystal structure of Cs3Sb2Br9 quantum dots prepared in Example;

[0020] Figure 2 TEM image of Cs3Sb2Br9 quantum dots prepared in Example;

[0021] Figure 3 This is a Z-scan graph of Cs3Sb2Br9 quantum dots prepared in Example;

[0022] Figure 4 This is a graph showing the optical limiting curve of the Cs3Sb2Br9 quantum dots prepared in the example. DETAILED DESCRIPTION

[0023] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto. Example

[0024] First, 5 μl of octylamine was injected into 3 ml of dimethyl sulfoxide to prepare a dimethyl sulfoxide solution containing octylamine; 63.84 mg (0.3 mmol) of cesium bromide and 72.29 mg (0.2 mmol) of antimony tribromide were weighed, added to the above dimethyl sulfoxide solution containing octylamine, and ultrasonically treated at room temperature for 5 minutes to obtain a clear and transparent precursor solution.

[0025] Subsequently, 500 μl of oleic acid was injected into 5 ml of toluene as an anti-solvent, and 50 μl of the prepared precursor solution was quickly injected at room temperature. The mixture was slightly shaken to obtain an orange-yellow colloidal quantum dot solution. The resulting solution was then centrifuged at 4000 rpm, and the resulting supernatant was the Cs3Sb2Br9 quantum dot solution.

[0026] Figure 1 The schematic diagram of the crystal structure of the obtained Cs3Sb2Br9 quantum dots. It can be seen from the figure that two (SbBr6) octahedra are connected by corner contacts and surrounded by ten Cs ions. In order to balance the charge, Sb ions are removed every three layers along the (111) crystal plane, and a two-dimensional layered structure is formed as the octahedral grid extends.

[0027] Figure 2 The TEM image of the obtained Cs3Sb2Br9 quantum dots. It can be seen from the figure that the prepared Cs3Sb2Br9 quantum dots are spherical nanoparticles, which are evenly distributed and have consistent shapes. Clear lattice fringes can be observed from the high-resolution TEM image in the inset, and the interplanar spacing is 1.97Å, corresponding to the (211) crystal plane of the hexagonal phase Cs3Sb2Br9QDs.

[0028] The obtained Cs3Sb2Br9 quantum dot solution was placed in a 2mm quartz cuvette for an open hole Z-scan test. The laser light source used was Beamtech's Dawa-S mode-locked Q-switched Nd:YAG laser, with a pulsed laser wavelength of 532nm, a pulse width of 7ns, an excitation frequency of 10Hz, and a beam waist radius (ω0) of 20μm. All test processes were carried out at room temperature. The normalized transmittance (ratio of nonlinear transmittance to linear transmittance) obtained by the Z-scan test was used to evaluate the nonlinear optical (NLO) properties. A normalized transmittance value less than 1 near the zero Z position indicates the presence of a nonlinear absorption effect in the material. The lower the normalized transmittance value, the stronger the optical limiting effect.

[0029] Figure 3 The open hole Z-scan curve of the obtained Cs3Sb2Br9 quantum dots. It can be seen from the figure that the curves before and after passing through the focus are symmetrical. When the sample moves near the focus, the flat shoulder indicates that the linear transmittance is constant at low incident energy. As the excitation intensity gradually increases, the sample transmittance gradually decreases, showing a valley shape, which is a typical anti-saturation absorption effect. When the sample passes through the focus, the laser flux reaches the maximum, and the normalized transmittance of the Cs3Sb2Br9QDs colloidal solution reaches the minimum (0.4).

[0030] The relationship curve between the input energy density and the normalized transmittance obtained by processing the aperture Z-scan test data is the optical limiting curve of the obtained Cs3Sb2Br9 quantum dots. Figure 4 It can be seen that Cs3Sb2Br9 quantum dots exhibit typical light limiting performance: at low input energy, they show linear absorption with a transmittance of 1. As the input energy gradually increases and reaches a certain starting threshold (F S ), the nonlinear optical effect of the material is activated and the transmittance gradually decreases. After calculation, the starting threshold and optical limiting threshold of Cs3Sb2Br9 quantum dots are F S =0.25J / cm 2 , F OL =2 J / cm 2 (Light clipping threshold F OL is the energy density when the transmittance drops to 50% of the linear transmittance, F S and F OL The lower the value, the better the optical limiting performance).

[0031] In summary, the Cs3Sb2Br9 quantum dots prepared in the present invention have excellent nonlinear optical limiting performance and have great practical application potential.

[0032] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. An application of lead-free perovskite quantum dots as optical limiting materials, characterized in that: The preparation of the lead-free perovskite quantum dots comprises the following steps: (1) adding cesium bromide and antimony tribromide in proportion to a dimethyl sulfoxide solution containing octylamine, and dissolving them by ultrasonication to form a precursor solution; (2) The precursor solution obtained in step (1) is injected into a toluene solution containing oleic acid, and the supernatant is collected after centrifugation to obtain the lead-free perovskite quantum dots.

2. The use according to claim 1, characterized in that: The content of octylamine in the dimethyl sulfoxide solution in step (1) is 5 μl / 3 mL.

3. The use according to claim 1, characterized in that: The content of cesium bromide in the precursor solution obtained in step (1) is 0.3 mmol / 3 mL, and the content of antimony tribromide is 0.2 mmol / 3 mL.

4. The use according to claim 1, characterized in that: The amount of the precursor solution used in step (2) is 0.9% of the volume of the toluene solution containing oleic acid.

5. The use according to claim 1, characterized in that: The content of oleic acid in the toluene solution in step (2) is 100 μl / mL.

6. The use according to claim 1, characterized in that: The centrifugal speed in step (2) is 4000 rpm.

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