A room temperature suspension preparation method of bromine lead cesium crystals

Abstract

The invention discloses a room temperature suspension preparation method of bromine lead cesium crystals, and relates to the technical field of crystal preparation. The method comprises preparing a CsPbBr3 precursor solution; suspending the precursor solution using a uniaxial acoustic suspension device to form suspended droplets; adjusting the acoustic field parameters so that the suspended droplets evaporate and crystallize, thereby realizing room temperature preparation of CsPbBr3 crystals. The invention adopts acoustic suspension technology to provide an ultra-clean container-free state for crystal growth. By changing the resonance state and acoustic field intensity of the suspended acoustic field, combined with precursor engineering, active regulation of the crystallization behavior of CsPbBr3 crystals and rapid preparation thereof at room temperature can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of crystal preparation, and in particular to a room temperature suspension preparation method of bromine-lead-cesium crystals. Background Art

[0002] Cb 3 As a new generation of all-inorganic halide perovskite materials, it has excellent photoelectric properties and good thermal stability, and has broad application prospects in solar cells, radiation detection, etc. 3 The preparation methods of single crystals generally include: Bridgman melt method, inversion crystallization method and antisolvent assisted crystallization method. The latter two methods belong to solution preparation methods, using CsPbBr 3 High solubility in organic solvents dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) enables CsPbBr 3 However, CsPbBr prepared conventionally in DMSO and DMF solution systems 3 Single crystals have problems such as macroscopic defects and impurity phase precipitation, and the high temperature of the preparation environment will induce solid-state phase transition, which makes it difficult to improve the quality of crystals. Therefore, it is urgent to develop a room temperature method for preparing high-quality CsPbBr 3 An effective method for crystal preparation at room temperature can not only avoid the damage to the crystal quality caused by the high temperature environment in the conventional method, but also further improve the application performance of the crystal and broaden its application in the field of optoelectronic device preparation.

[0003] As an important containerless processing technology and a key technology for ground simulation of space environment, acoustic levitation technology is widely used in research fields such as materials science, biomedicine, liquid physics, and chemistry and chemical engineering. Acoustic levitation uses the nonlinear acoustic effect generated by high-intensity sound fields to offset the gravity of objects and achieve stable suspension. This method has been used to achieve stable suspension from molten metals to living organisms. Effects such as acoustic cavitation and acoustic streaming under acoustic levitation conditions provide a unique way for heat and mass transfer and evaporation and crystallization of droplets, and also open up a new path for the preparation of advanced functional crystals. At the same time, the open observation environment also provides important experimental conditions for real-time monitoring of the crystal growth process.

[0004] In view of this, the present invention provides a room temperature suspension preparation method of bromine lead cesium crystals based on acoustic levitation technology. Summary of the invention

[0005] In view of the shortcomings of the above background technology, the present invention mainly solves the problem that CsPbBr is conventionally prepared in a DMSO and DMF solution system in the prior art. 3Single crystals have problems such as macroscopic defects and impurity phase precipitation, and the high temperature of the preparation environment will induce solid phase transition, which brings difficulties to the improvement of crystal quality. The present invention provides a room temperature suspension preparation method of cesium lead bromine crystals. The method adopts acoustic suspension technology to provide an ultra-clean container-free state for crystal growth. The prepared CsPbBr 3 The crystals have the advantages of container-free ultra-clean crystallization, controllable crystal nucleation and growth rate.

[0006] The first object of the present invention is to provide a room temperature suspension preparation method of bromine lead cesium crystals, comprising the following steps:

[0007] Preparation of CsPbBr 3 Precursor solution;

[0008] The precursor solution is suspended using a uniaxial acoustic levitation device to form suspended droplets;

[0009] Adjust the acoustic field parameters to make the suspended droplets evaporate and crystallize to obtain CsPbBr 3 Crystals;

[0010] Among them, the sound field parameter is the sound wave amplitude, which is adjusted by changing the output power of the ultrasonic transducer in the acoustic suspension device.

[0011] Preferably, the CsPbBr 3 The precursor solution was prepared according to the following steps:

[0012] CsBr and PbBr 2 The powder has a molar ratio of n(CsBr):n(PbBr 2 ) = 1:1.0~1.5 ratio was dissolved in dimethyl sulfoxide solvent to obtain CsPbBr 3 Precursor solution.

[0013] Preferably, the output power of the ultrasonic transducer used in the uniaxial acoustic suspension device is 600-720VA, and the sound wave frequency is 19-22kHz.

[0014] Preferably, the cross-sectional radius of the curved reflective end used in the uniaxial acoustic suspension device is 18-25 mm, and the curvature radius is 36-50 mm.

[0015] Preferably, when evaporative crystallization occurs for controlled crystallization, the suspension crystallization time of the suspension droplets is 100 to 300 minutes.

[0016] Preferably, the initial volume of the suspension droplets is 20-50 μL.

[0017] Preferably, when a uniaxial acoustic suspension device is used to suspend the precursor solution, the precursor solution is moved into the cavity between the reflection end and the emission end of the acoustic suspension device by a pipette, and the output power of the ultrasonic transducer is adjusted so that the initial aspect ratio of the suspended droplet is 3.20-5.70.

[0018] The second object of the present invention is to provide a cesium-lead-bromine crystal.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a room temperature suspension preparation method for cesium-lead-bromine crystals. The present invention adopts acoustic suspension technology to provide an ultra-clean container-free state for crystal growth. Under the action of the acoustic field, the solvent in the suspension droplets evaporates rapidly, causing the solution to reach supersaturation, further inducing CsPbBr 3 Nucleation and growth of crystals. CsPbBr 3 The nucleation rate, growth rate and growth morphology of the crystal depend on the nonlinear acoustic effect in the high-intensity sound field. By changing the resonant state and acoustic amplitude of the suspension sound field and combining precursor engineering, the crystallization behavior can be actively regulated and CsPbBr can be prepared at room temperature. 3 Crystals can avoid the damage to the crystal quality caused by the high temperature environment in conventional methods, further improve their application performance and broaden their application in the field of optoelectronic device preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The CsPbBr prepared in the suspension droplet of Example 1 3 Optical image of the crystal.

[0022] Figure 2 The CsPbBr prepared in the suspension droplet of Example 4 3 Optical image of the crystal.

[0023] Figure 3 The CsPbBr prepared in the suspension droplet of Example 6 3 Optical image of the crystal.

[0024] Figure 4 CsPbBr prepared by droplet crystallization on a glass slide in Comparative Example 1 3 Optical image of the crystal.

[0025] Figure 5 This is a graph showing the functional relationship between the droplet aspect ratio and the crystal growth rate. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0027] The purpose of the present invention is to provide a room temperature suspension preparation method for bromine lead cesium crystals, which can control the crystallization kinetic parameters of functional crystals by changing the resonance state of the suspension sound field and the amplitude of the sound wave, so as to realize the controllable preparation of functional crystals at room temperature.

[0028] In order to achieve the above object, the present invention provides a room temperature suspension preparation method of bromine lead cesium crystals, comprising the following steps:

[0029] Preparation of CsPbBr 3 Precursor solution;

[0030] The precursor solution is suspended using a uniaxial acoustic levitation device to form suspended droplets;

[0031] Adjust the acoustic field parameters to make the suspended droplets evaporate and crystallize to obtain CsPbBr 3 Crystals;

[0032] Among them, the sound field parameter is the sound wave amplitude, which is adjusted by changing the output power of the ultrasonic transducer in the acoustic suspension device.

[0033] It can be seen that by adjusting the acoustic field parameters, the suspended droplets evaporate and crystallize to achieve CsPbBr 3 Crystals are prepared at room temperature; the increase in output power directly increases the amplitude of the acoustic wave, changes the distribution of the acoustic pressure field, increases the aspect ratio of the droplets, increases the evaporation rate of the suspended droplets, and regulates the crystallization behavior.

[0034] Wherein, the CsPbBr 3 The precursor solution was prepared by mixing CsBr and PbBr 2 The powder has a molar ratio of n(CsBr):n(PbBr 2 )=1.0~1.5, preferably 1:1.3, is dissolved in dimethyl sulfoxide solvent to obtain CsPbBr 3 Precursor solution.

[0035] The output power of the ultrasonic transducer used in the uniaxial acoustic suspension device is 600-720VA, and the sound wave frequency is 19-22kHz.

[0036] The cross-sectional radius of the curved reflective end used by the uniaxial acoustic suspension device is 18-25 mm, and the curvature radius is 36-50 mm. Preferably, the cross-sectional radius of the curved reflective end used by the uniaxial acoustic suspension device is 20 mm, and the curvature radius is 40 mm.

[0037] When evaporation crystallization occurs for controlled crystallization, the suspension crystallization time of the suspended droplets is 100~300min.

[0038] The initial volume of the suspension droplets is 20-50 μL.

[0039] When the precursor solution is suspended using a uniaxial acoustic suspension device, the precursor solution is moved into the cavity between the reflection end and the emission end of the acoustic suspension device through a pipette, and the output power of the ultrasonic transducer is adjusted so that the initial aspect ratio of the suspended droplet is 3.20-5.70.

[0040] In one embodiment, a room temperature suspension preparation method of cesium-bromine lead crystals comprises the following steps:

[0041] Step 1: Suspending CsPbBr using a uniaxial acoustic levitation device 3 Precursor solution, forming suspended droplets;

[0042] Step 2: Adjust the distance between the transmitting end and the reflecting end of the acoustic suspension device to a fixed value, set the output power of the ultrasonic transducer to a specific value to change the acoustic pressure field, change the aspect ratio of the droplets, and control the evaporation rate of the solvent, that is, evaporation crystallization occurs to prepare CsPbBr 3 Crystal.

[0043] Among them, CsPbBr 3 The method for preparing the precursor solution comprises: mixing CsBr and PbBr 2 The powder has a molar ratio of n(CsBr):n(PbBr 2 ) = 1:1.3 ratio dissolved in dimethyl sulfoxide solvent to obtain CsPbBr 3 Precursor solution.

[0044] The CsPbBr 3 Precursor solution, with CsBr solute concentration c (Cs) is used as the standard, and the solution concentration is 0.25mol / L~0.50mol / L.

[0045] In the present invention, the preferred initial volume of the suspension droplet is 20-50 μL, more preferably, the initial volume is 50 μL.

[0046] In the present invention, CsPbBr 3 The suspension crystallization time of the solution droplets is 100-300 min, preferably, the suspension time is 100 min, and more preferably, the suspension time is 200 min.

[0047] In the present invention, the crystallized CsPbBr 3 The crystals were quickly picked up using a glass slide.

[0048] The main raw materials used in the present invention are purchased from MacLean reagent; preferably, the purity of CsBr powder is 99.5%, more preferably, the purity of CsBr powder is 99.9%; preferably, PbBr2 The powder purity is 99.0%, and more preferably, the PbBr powder purity is 99.9%.

[0049] The uniaxial acoustic suspension device used in the present invention suspends CsPbBr 3 Solution, evaporate and crystallize to obtain CsPbBr 3 In the present invention, the uniaxial acoustic suspension device is composed of an acoustic emission end and a reflection end. The schematic diagram of the device is shown in the paper “CL Shen, WJ Xie, and B. Wei, Parametrically excited sectorial oscillation of liquid drops floating in ultrasound[J],Physical Review E,2010, 81(4): 046305”.

[0050] The uniaxial acoustic suspension device used in the present invention preferably has an acoustic wave frequency of 19-22kHz and an acoustic wave output power of 600-720VA; preferably, the emitting plane of the emitting end is a flat disk with a cross-sectional radius of 15mm; preferably, the reflecting end is a concave spherical reflecting end with a cross-sectional radius of 18-25mm and a curvature radius of 36-50mm; the working medium of the acoustic suspension device is air, and the working temperature is room temperature. The distribution of the suspended acoustic field can be achieved by changing the resonant state of the suspended acoustic field, the distance between the emitting ends, and the acoustic wave amplitude. The acoustic field distribution and the droplet volume determine the aspect ratio (ratio of equatorial radius to polar radius) of the suspended droplet after deformation. The evaporation rate of the solution is closely related to the droplet aspect ratio, and the crystal growth rate in the solution is directly determined by the droplet evaporation rate. Therefore, by establishing a functional relationship between the crystal growth rate and the droplet aspect ratio, the present invention achieves the control of CsPbBr by adjusting the droplet aspect ratio 3 Controllable technology for crystal growth.

[0051] The suspension process provided by the present invention comprises the following steps:

[0052] (1) Setting the sound wave output power as required, using the intelligent numerically controlled ultrasonic generator to automatically search for frequency and determine the wave nodes of the standing wave sound field;

[0053] (2) Use a syringe to draw CsPbBr 3 Precursor solution, preferably, a fixed volume of CsPbBr is drawn using a high-precision pipette 3 Precursor solution;

[0054] (3) Appropriately increase the distance between the reflector and the emitter, slowly inject the solution and gradually reduce the distance to ensure that the droplets are stably suspended;

[0055] (4) Using a CMOS camera to observe in real time and adjust the droplet aspect ratio or the distance between the reflection ends to a fixed value.

[0056] The CsPbBr prepared by the present invention 3 The crystals are all mm-level single crystals. 3 The crystal grain size exceeds 2.0 mm.

[0057] CsPbBr prepared by the present invention 3 The crystal includes adjusting the growth kinetic parameters of the functional crystal by changing the resonance state of the suspension acoustic field and the amplitude of the acoustic wave, thereby realizing the controllable preparation of the functional crystal at room temperature.

[0058] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0059] Example 1

[0060] 1.5966g of cesium bromide powder and 3.5819g of lead bromide powder were dissolved in 15mL of dimethyl sulfoxide solvent, where the solute ratio was n(CsBr):n(PbBr 2 )=1:1.3, Cs ion concentration is 0.50mol / L, stir on a magnetic stirrer for 4h until the precipitate is completely dissolved. After filtering the impurities, CsPbBr 3 Precursor solution.

[0061] The acoustic wave output power is set to 600VA as required. The cross-sectional radius of the curved reflection end used by the uniaxial acoustic suspension device is 20 mm, and the curvature radius is 40 mm. The intelligent numerically controlled ultrasonic generator is used to automatically search the frequency and determine the standing wave acoustic field wave node. A high-precision pipette is used to absorb 50 μL of CsPbBr 3 Precursor solution; appropriately increase the distance between the reflector and the emitter, slowly inject the solution while gradually reducing the distance to allow the droplets to be stably suspended; and allow the suspended droplets to be stably suspended at room temperature for 200 minutes.

[0062] Cb 3 As the solvent evaporates, the concentration of the precursor solution drops increases to a supersaturated state, and orange-yellow CsPbBr 3 The nucleus of the crystal. CsPbBr 3 The crystal nucleus gradually grows with the slow evaporation of the solvent. When the droplet volume is reduced to 10% of the original volume, the suspended droplet is quickly removed using a glass slide to obtain the CsPbBr obtained by evaporation crystallization. 3 Crystal.

[0063] The preparation methods of Examples 2 to 6 are the same as those of Example 1, except that the experimental parameters are shown in Table 1.

[0064] Table 1 shows the experimental parameters in Examples 1 to 6

[0065]

[0066] Comparative Example 1

[0067] 1.5966g of cesium bromide powder and 3.5819g of lead bromide powder were dissolved in 15mL of dimethyl sulfoxide solvent, where the solute ratio was n(CsBr):n(PbBr 2 )=1:1.3, Cs ion concentration is 0.50mol / L, stir on a magnetic stirrer for 4h until the precipitate is completely dissolved. After filtering the impurities, CsPbBr 3 Precursor solution.

[0068] Use a high-precision pipette to draw 50 μL of CsPbBr 3 The precursor solution was placed on a clean glass slide and allowed to stand at room temperature for 2 h. After the evaporation and crystallization, CsPbBr was obtained. 3 Crystals. In Comparative Example 1, the average grain size of the obtained crystals was 0.92 mm; in Comparative Example 1, the obtained crystals were distributed near the solid-liquid-gas three-phase interface.

[0069] From Examples 1 to 6, it can be seen that the crystal growth rate is related to the CsPbBr 3 The initial aspect ratio of the precursor droplet is linearly correlated. Experiments have shown that the initial aspect ratio of the droplet has a decisive relationship with the evaporation rate and the crystal growth rate determined by the evaporation rate. The active regulation of the crystal growth process can be achieved by adjusting the aspect ratio of the droplet within a certain range, and the crystal growth kinetic parameters such as crystal growth rate and nucleation rate can be changed.

[0070] By comparing and analyzing Examples 1 to 6 with Comparative Example 1, under the same evaporation and crystallization time, the maximum grain size obtained by the room temperature suspension preparation method is larger than that of Comparative Example 1, the total number of grains is smaller than that of Comparative Example 1, and the average grain size is about 1.5 times that of Comparative Example 1, which proves that the acoustic suspension preparation method effectively promotes the 3 The evaporation of the precursor droplets increases the 3 The crystal growth rate and average grain size significantly reduce the total number of grains, which is more conducive to the preparation of large-sized and high-quality CsPbBr compared with conventional evaporation crystallization methods. 3 Crystal.

[0071] In order to illustrate the method provided by the present invention to prepare CsPbBr 3 The application performance of the crystal is explained in conjunction with the accompanying drawings.

[0072] Figure 1 The CsPbBr prepared in the suspension droplet of Example 1 3 Optical images of crystals;

[0073] Figure 1 The CsPbBr prepared by room temperature suspension in Example 1 is shown 3 The crystal morphology is a rectangular block crystal, and the average grain size of the obtained crystal is 1.52 mm. The acoustic flow inside the acoustic suspension solution droplet promotes the diffusion of the solute, forms an eddy field inside the droplet, and causes the growth mode of the crystal to change. The morphology of the prepared crystal is different from that of Comparative Example 1.

[0074] Figure 2 The CsPbBr prepared by room temperature suspension in Example 4 is shown 3 The crystal morphology is needle-shaped, and the average grain size of the prepared crystal is 1.46 mm.

[0075] Figure 3 The CsPbBr prepared by room temperature suspension in Example 6 is shown 3 The crystal morphology is a rectangular block crystal, and the average grain size of the prepared crystal is 1.80 mm.

[0076] Figure 4 This is an image of the precursor solution crystallized on a clean glass slide in Comparative Example 1 for 2 hours. 3 The crystal morphology is a prismatic single crystal. The crystal nucleation position is mainly distributed at the edge of the droplet. The crystal nucleus continues to grow near the liquid-gas surface, and the average grain size is 0.92 mm.

[0077] Figure 5 The figure is a functional relationship between the droplet aspect ratio and the crystal growth rate. The present invention establishes a relationship between the crystal growth rate kinetic parameters and the aspect ratio of the suspended droplet, and the increase in the aspect ratio of the droplet of the same volume is achieved by reducing the distance between the emission end and the reflection end; specifically, the increase in the aspect ratio of the droplet of the same volume is achieved by increasing the acoustic wave output power, and the aspect ratio is linearly related to the crystal growth rate.

[0078] The present invention provides a more convenient method for preparing CsPbBr at room temperature. 3 Crystal method, CsPbBr 3 The crystal growth rate can be actively controlled by acoustic field parameters.

[0079] The present invention can realize active regulation of crystallization behavior by changing the resonance state and acoustic amplitude of the suspended acoustic field in the uniaxial acoustic suspension device and combining precursor engineering to prepare CsPbBr at room temperature. 3Crystals should be prepared at high temperatures to avoid reducing crystal quality.

Claims

1. A room temperature suspension preparation method of cesium lead bromine crystals, characterized in that: The following steps are involved: Prepare CsPbBr3 precursor solution; The precursor solution is suspended using a uniaxial acoustic levitation device to form suspended droplets; The acoustic field parameters are adjusted to cause the suspended droplets to evaporate and crystallize, thereby obtaining CsPbBr3 crystals; Among them, the acoustic field parameter is the amplitude of the sound wave, which is adjusted by changing the output power of the ultrasonic transducer in the acoustic suspension device; The CsPbBr3 precursor solution is prepared according to the following steps: CsBr and PbBr2 powders are dissolved in a dimethyl sulfoxide solvent at a molar ratio of n(CsBr):n(PbBr2)=1:1.0-1.5 to obtain a CsPbBr3 precursor solution; The output power of the ultrasonic transducer used in the uniaxial acoustic suspension device is 600-720VA, and the sound wave frequency is 19-22kHz; The cross-sectional radius of the curved reflection end used in the uniaxial acoustic suspension device is 18-25 mm, and the radius of curvature is 36-50 mm; During evaporation crystallization, the suspension crystallization time of the suspended droplets is 100~300min; The initial volume of the suspension droplet is 20-50 μL; When the precursor solution is suspended using a uniaxial acoustic suspension device, the precursor solution is moved into the cavity between the reflection end and the emission end of the acoustic suspension device through a pipette, and the output power of the ultrasonic transducer is adjusted so that the initial aspect ratio of the suspended droplet is 3.20-5.

70.

2. A lead cesium bromine crystal obtained by the method according to claim 1.

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