Closed film coating system based on surface acoustic waves, chiral perovskite thin film and preparation method of chiral perovskite thin film

Abstract

The invention relates to the technical field of microfluidics, in particular to a closed film coating system based on surface acoustic waves, a chiral perovskite thin film and a preparation method of the chiral perovskite thin film, and the system comprises a piezoelectric substrate, and a first interdigital transducer, a second interdigital transducer and a reaction tank which are arranged on the piezoelectric substrate; the first interdigital transducer and the second interdigital transducer are oppositely arranged in a staggered manner, and the reaction tank is arranged between the first interdigital transducer and the second interdigital transducer. Electric signals on a first interdigital transducer and a second interdigital transducer which are oppositely arranged in a staggered manner are converted into deformation under the action of a piezoelectric substrate, and the periodic deformation forms surface acoustic waves which are spread along the surface of the piezoelectric substrate and act on a precursor solution in a reaction tank to push the precursor solution to rotate; a film coating process on the lower surface of the target substrate is completed; the closed film coating system based on the surface acoustic waves is simple in structure, the film coating process on the target substrate is simple, convenient and rapid, the cost is effectively reduced, and an inert gas environment is not needed.

Description

Technical Field

[0001] The present invention relates to the field of microfluidics technology, and in particular to a closed film coating system based on surface acoustic waves, a chiral perovskite film and a preparation method thereof. Background Art

[0002] Chiral organic / inorganic hybrid perovskites (OIHPs) are optical semiconductor materials characterized by an asymmetric structure that cannot be superimposed on its mirror image. The chiral lattice structure induced by organic molecules or directly involved in the formation of chiral perovskites gives chiral perovskites unique optical properties, including circular dichroism caused by the difference in absorption of left-handed and right-handed circularly polarized light. OIHPs combine chirality with the excellent optoelectronic properties of perovskites, so they have a wide range of applications in solar cells, optoelectronic sensors, biodetection, spin electronics and other fields.

[0003] There are many techniques available for depositing chiral OIHPs films. The most traditional and simplest method is spin coating, which was first reported by Kojima et al. in 2009. This method requires rapid rotation of the substrate to evenly distribute the precursor solution, remove excess solution, and promote film growth by annealing. With the development of OIHPs film synthesis technology, more complex techniques have emerged, for example: Kim et al. reported scraping in 2015, which scrapes off excess solution by adjusting the distance between the blade and the substrate; similarly, Vak et al. proposed slit coating in the same year, which improves solution efficiency by flowing out of the slit. Other methods include meniscus-assisted solution coating and inkjet coating. Each of them has its own characteristics, however, these technologies rely on precision mechanical devices or pumping systems, which greatly increases the cost of preparing OIHPs films.

[0004] Moreover, most OIHPs materials have different degrees of stability problems, especially when exposed to high humidity and oxygen-rich environments, which will accelerate their decomposition. Therefore, the preparation of OIHPs films requires strict environmental conditions, which further limits the preparation and research of OIHPs films.

[0005] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a closed coating system based on surface acoustic waves, a chiral perovskite film and a preparation method thereof, aiming to solve the problems of the existing coating process being complex, costly, and requiring an inert gas environment.

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

[0008] A closed film coating system based on surface acoustic waves comprises a piezoelectric substrate, and a first interdigital transducer, a second interdigital transducer and a reaction pool arranged on the piezoelectric substrate;

[0009] The first IDT and the second IDT are arranged opposite to each other in a staggered manner, and the reaction pool is arranged between the first IDT and the second IDT.

[0010] In the closed film coating system based on surface acoustic waves, the misalignment degree between the first interdigital transducer and the second interdigital transducer is 40%-60%.

[0011] The closed coating system based on surface acoustic waves, wherein the wavelength of the first interdigital transducer is 200 microns-300 microns; the wavelength of the second interdigital transducer is 200 microns-300 microns.

[0012] In the closed coating system based on surface acoustic waves, a transition layer is provided between the piezoelectric substrate and the first interdigital transducer, and between the piezoelectric substrate and the second interdigital transducer; the thickness of the transition layer is 8nm-15nm.

[0013] In the closed coating system based on surface acoustic waves, the reaction pool is composed of a pool wall and a pool bottom attached to the pool wall on one side close to the piezoelectric substrate.

[0014] The closed film coating system based on surface acoustic waves, wherein the depth of the reaction pool is 3nm-6nm, and the inner diameter of the reaction pool is 8mm-14mm.

[0015] A method for preparing a chiral perovskite film comprises the following steps:

[0016] Provides a closed coating system based on surface acoustic waves;

[0017] Injecting a perovskite precursor solution into a reaction cell, and placing a substrate on a side of the reaction cell away from the piezoelectric substrate;

[0018] Using the first interdigital transducer and the second interdigital transducer to emit Rayleigh waves and act on the perovskite precursor solution in the reaction tank to obtain a substrate coated with the perovskite precursor solution;

[0019] The substrate coated with the perovskite precursor solution is annealed to obtain a chiral perovskite film.

[0020] The method for preparing a chiral perovskite film, wherein the solute in the perovskite precursor solution is selected from (S / R-MBA)2PbI4, PbBr2-CsBr-S- / R-NEABr, (S- / R-NEA)2PbI4(1-γ) Br 4γ , (S- / R-NEA)2PbI4, (S- / R-NEA)PbI3, (S-MBA)2PbI 4(1-x) Br 4x , (R- / S-MBA)2CuCl4 or more; the solvent in the perovskite precursor solution is selected from one or more of N,N-dimethyl sulfoxide and dimethyl sulfoxide.

[0021] The method for preparing the chiral perovskite film, wherein the temperature of the annealing treatment is 90° C.-110° C., and the time of the annealing treatment is 7 min-10 min.

[0022] A chiral perovskite film is prepared by using a method for preparing a chiral perovskite film.

[0023] Beneficial effects: The present invention provides a closed film coating system based on surface acoustic wave, a chiral perovskite film and a preparation method thereof. The closed film coating system based on surface acoustic wave includes a piezoelectric substrate, and a first interdigital transducer, a second interdigital transducer and a reaction pool arranged on the piezoelectric substrate; the first interdigital transducer and the second interdigital transducer are arranged relative to each other in a staggered manner, and the reaction pool is arranged between the first interdigital transducer and the second interdigital transducer. The present invention utilizes the electrical signals on the first interdigital transducer and the second interdigital transducer arranged relative to each other to be converted into deformation under the action of the piezoelectric substrate, and the periodic deformation constitutes a surface acoustic wave and propagates along the surface of the piezoelectric substrate, and then acts on the precursor solution in the reaction pool, pushing the precursor solution to rotate, and completing the film coating process on the lower surface of the target substrate covered on the top of the reaction pool; and the reaction pool and the target substrate covered on the top of the reaction pool can form a closed environment, isolating the air while constraining the precursor solution in the pool to form a vortex, so as to achieve film coating on the target substrate. The closed coating system based on surface acoustic waves has a simple structure, is simple and quick in the process of coating the target substrate, effectively reduces costs, and does not require an inert gas environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of a closed film coating system based on surface acoustic waves of the present invention;

[0025] Figure 2 is a schematic diagram of the layout of the first interdigital transducer and the second interdigital transducer;

[0026] Figure 3 is a reflection coefficient curve diagram of a single IDT in Example 1;

[0027] Figure 4 This is a graph showing the surface displacement test result of the IDT tested by the laser vibrometer in Example 1;

[0028] Figure 5 is a SEM image of the SAW film in Example 1;

[0029] Figure 6 is a SEM image of the spin-coated film in Example 1;

[0030] Figure 7 XRD diffraction patterns of the SAW film in Example 1 after being placed in a laboratory environment for 1, 3, 5, and 12 days;

[0031] Figure 8 is the absorption spectrum of the SAW film and the spin-coated film in Example 1;

[0032] Fig. 9 is a direct band gap diagram of the SAW film and the spin-coated film in Example 1;

[0033] Fig.10 Circular dichroism spectra of the SAW film and the spin-coated film in Example 1;

[0034] Fig.11 is the asymmetry factor g of the SAW film in Example 1 CD Data graph;

[0035] Fig.12 Graph showing the relationship between the absorbance of the SAW film and the wavelength in Example 1. DETAILED DESCRIPTION

[0036] The present invention provides a closed coating system based on surface acoustic wave, a chiral perovskite film and a preparation method thereof. In order to make the purpose, technical scheme and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as herein.

[0038] like Figure 1 and Figure 2 As shown, the present invention provides a closed coating system based on surface acoustic waves, comprising a piezoelectric substrate 10, and a first interdigital transducer 20, a second interdigital transducer 30 and a reaction pool 40 disposed on the piezoelectric substrate 10;

[0039] The first IDT 20 and the second IDT 30 are disposed opposite to each other in a staggered manner, and the reaction pool 40 is disposed between the first IDT 20 and the second IDT 30 .

[0040] In this embodiment, the electrical signals on the first interdigital transducer and the second interdigital transducer, which are arranged in a staggered manner, are converted into deformation under the action of the piezoelectric substrate. The periodic deformation constitutes a surface acoustic wave (SAW) and propagates along the surface of the piezoelectric substrate, and then acts on the precursor solution in the reaction pool, pushing the precursor solution to rotate, and completing the coating process on the lower surface of the target substrate covered on the top of the reaction pool; and the reaction pool and the target substrate covered on the top of the reaction pool can form a closed environment, isolating the air while constraining the precursor solution in the pool to form a vortex, so as to achieve coating on the target substrate. The closed film coating system (SAWM) based on surface acoustic waves has a simple structure, is simple and fast in the process of coating the target substrate, effectively reduces costs, and does not require an inert gas environment.

[0041] Specifically, the electrical signals on the first interdigital transducer and the second interdigital transducer arranged at staggered relative positions are converted into deformation under the action of the piezoelectric substrate, and the periodic deformation constitutes a surface acoustic wave and propagates along the surface of the piezoelectric substrate, thereby generating a shear force on the precursor solution in the reaction pool. The precursor solution forms a vortex under the constraint of the reaction pool, and the precursor solution rotates and is coated on the lower surface of the target substrate covered on the top of the reaction pool. Since the target substrate is covered on the top of the reaction pool, it forms a closed space with the reaction pool, which can isolate the air while constraining the precursor solution in the pool to form a vortex, thereby finally completing the coating. Furthermore, due to the characteristics of surface acoustic waves, after the two waves formed by the first interdigital transducer and the second interdigital transducer contact the precursor solution in the reaction tank, their energy is quickly coupled to the precursor solution and drives the precursor solution to move. The misalignment between the first interdigital transducer and the second interdigital transducer causes the two waves to form a shear force to generate a vortex. The precursor solution begins to rotate and keeps in contact with the lower surface of the target substrate. At the same time, adsorption and nucleation begin to complete the coating of the target substrate. Finally, annealing treatment is performed to promote crystal growth, so that the crystal gradually covers the target substrate to form a perovskite film. In addition, the closed coating system based on surface acoustic waves can be used for chiral perovskite coatings under conventional conditions, and it has been found through testing that the film prepared based on the SAWM system has higher crystallinity and narrower band gap than the traditional spin-coated film.

[0042] In some embodiments, Figure 2As shown, the misalignment degree (denoted by α) between the first IDT and the second IDT is 40%-60%. When the electrical signals on the first IDT and the second IDT are converted into deformation under the action of the piezoelectric substrate, under the condition that the periodic deformation constitutes a surface acoustic wave and propagates along the surface of the piezoelectric substrate, the first IDT and the second IDT with a misalignment degree controlled between 40% and 60% can produce a driving effect on the precursor solution in the reaction pool, so that the precursor solution rotates to form a vortex, and the coating is completed on the lower surface of the target substrate at the top of the reaction pool.

[0043] In a preferred embodiment, the misalignment between the first IDT and the second IDT is 50%, that is, the relative width of the fingers of the first IDT and the second IDT in the working range accounts for half of the total width, so that the two trains of surface acoustic waves generated by the first IDT and the second IDT shear the precursor solution in the reaction tank and form a vortex to complete the coating on the target substrate.

[0044] In some embodiments, Figure 2 As shown, the wavelength (expressed by λ) of the first IDT is 200-300 μm; the wavelength (expressed by λ) of the second IDT is 200-300 μm. By adjusting the wavelengths of the first IDT and the second IDT, the output wave mode and energy (Rayleigh wave) can be changed, thereby adjusting the morphology and quality of the film.

[0045] In a preferred embodiment, the wavelength of the first IDT and the second IDT are both 200 micrometers, and the wavelength of the SAW generated by them is similar to the wavelength of the first IDT and the second IDT.

[0046] In some embodiments, the finger width (denoted by β) of the first IDT and the second IDT is 50 μm.

[0047] In some embodiments, a transition layer is further provided between the piezoelectric substrate and the first IDT, and between the piezoelectric substrate and the second IDT; the thickness of the transition layer is 8nm-15nm. By providing the transition layer between the piezoelectric substrate and the first IDT, and between the piezoelectric substrate and the second IDT, the adhesion of the first IDT and the second IDT on the piezoelectric substrate can be increased.

[0048] In a preferred embodiment, the transition layer is a chromium layer, and the thickness of the chromium layer is 10 nm.

[0049] In some embodiments, the first IDT and the second IDT are made of gold or aluminum.

[0050] In some embodiments, the piezoelectric substrate is one of lithium niobate, lithium tantalate, zinc oxide, and aluminum nitride piezoelectric substrates.

[0051] In some embodiments, the angle between the lithium niobate wafer in the lithium niobate piezoelectric substrate and the Y-axis of the lithium niobate crystal coordinate system is 128° (Y-128°), and the thickness of the lithium niobate piezoelectric substrate is 500±10μm. This is to ensure that the output wave of the designed closed coating system is a Rayleigh wave, and the thickness of the Rayleigh wave penetrating into the lithium niobate piezoelectric substrate is 1.8-2.0 times the wavelength. If the thickness of the piezoelectric substrate is too thick, it will also affect the wave mode.

[0052] In a preferred embodiment, the thickness of the lithium niobate piezoelectric substrate is 0.5 mm, and the thickness of the Rayleigh wave penetrating into the lithium niobate piezoelectric substrate is 1.9 times the wavelength.

[0053] In some embodiments, the reaction pool is composed of a pool wall and a pool bottom attached to one side of the pool wall near the piezoelectric substrate. The reaction pool is formed by the pool wall and the pool bottom, and when coating, the target substrate is covered on the top of the reaction pool to form a closed environment that can isolate the air, and then the first interdigital transducer and the second interdigital transducer are arranged relative to each other in a staggered manner to generate a shear force on the precursor solution, so that the precursor solution forms a vortex under the constraint of the reaction pool, and the precursor solution rotates and coats the lower surface of the upper target substrate.

[0054] In some embodiments, the depth of the reaction pool is 3 nm-6 nm, and the inner diameter of the reaction pool is 8 mm-14 mm.

[0055] Specifically, the reaction pool is formed by bonding an acrylic pool wall and a glass sheet through PDMS, wherein the depth of the reaction pool is 3 nm and the inner diameter is 10 mm, so that the precursor solution generating the vortex can be more easily adsorbed and nucleated on the lower surface of the target substrate covered on the top of the reaction pool.

[0056] In some embodiments, the reaction cell is cylindrical.

[0057] In some embodiments, the first IDT and the second IDT are driven by an RF signal; that is, an RF signal is generated by a radio frequency signal generator and a power amplifier to drive the first IDT and the second IDT at a resonant frequency.

[0058] In some embodiments, the closed coating system based on surface acoustic wave is produced by a two-stage manufacturing process of photolithography and evaporation; first, the photolithography is performed by ultraviolet exposure photolithography equipment (Medas-MDA400M, South Korea), and a photoresist (SUN-lift 1303, Startech, China) is evenly coated on a lithium niobate substrate using a homogenizer; the lithium niobate substrate is heated at 65-70°C for 30-40 seconds, and then further heated at 90-100°C for 80-90 seconds, and then exposed to ultraviolet light for about 2 seconds to achieve heating and drying of the spin-coated photoresist, while relieving the internal stress caused by spin coating and improving adhesion; then, the ultraviolet-exposed lithium niobate substrate is heated at 65-70°C for 20-30 seconds, 95-100°C for 20-30 seconds, and 100-105°C for 20 seconds, and then ...100°C for 20-30 seconds Heat for 100-110 seconds to achieve a stable exposure reaction effect, and use segmentation to prevent the cracking of the glue; after heating, wait for it to cool to room temperature, then develop in a developer (SUN-238D, Startech, China) for 15 seconds, and rinse the residual developer with deionized water; then use a high vacuum evaporator (Pengcheng-pczf500, China) for evaporation to complete the preparation of the first interdigital transducer and the second interdigital transducer; finally, immerse the plated lithium niobate wafer in acetone for stripping to complete the preparation of the surface acoustic wave closed coating system. Among them, the part of the photoresist covered by the mask can be removed by development, and the part not covered by the photoresist is the device pattern. The metal is directly plated on the part not covered by the photoresist to form a device. After the part plated on the covered photoresist is stripped by soaking in acetone, the photoresist falls off with the coating, leaving only the part directly plated on the substrate to form a device.

[0059] In addition, the present invention also provides a method for preparing a chiral perovskite film, comprising the steps of:

[0060] Step S10: providing a closed coating system based on surface acoustic waves;

[0061] Step S20: injecting a perovskite precursor solution into the reaction cell, and placing a substrate on a side of the reaction cell away from the piezoelectric substrate;

[0062] Step S30: using the first IDT and the second IDT to emit Rayleigh waves and act on the perovskite precursor solution in the reaction tank to obtain a substrate coated with the perovskite precursor solution;

[0063] Step S40: performing annealing treatment on the substrate coated with the perovskite precursor solution to obtain a chiral perovskite film.

[0064] In this embodiment, the closed film coating system based on surface acoustic wave is used. Since the electrical signals on the first interdigital transducer and the second interdigital transducer arranged at the offset relative position are converted into deformation under the action of the piezoelectric substrate, the periodic deformation constitutes the surface acoustic wave and propagates along the surface of the piezoelectric substrate, forming a shear force on the perovskite precursor solution in the reaction tank. The perovskite precursor solution forms a vortex under the constraint of the reaction tank, and the perovskite precursor solution begins to rotate and keeps in contact with the lower surface of the substrate, and begins to adsorb and nucleate at the same time, completing the coating on the substrate, and finally promoting the growth of crystals through annealing treatment. The crystals gradually cover the substrate to form a chiral perovskite film. The preparation method of the chiral perovskite film can be coated in a laboratory environment, and can prepare a film with higher crystallinity and narrower band gap. At the same time, the system can also regulate the film, and has scalability.

[0065] In some embodiments, the solute in the perovskite precursor solution is selected from organic / inorganic hybrid perovskite (S / R-MBA)2PbI4, PbBr2-CsBr-S- / R-NEABr, (S- / R-NEA)2PbI 4(1-γ) Br 4γ , (S- / R-NEA)2PbI4, (S- / R-NEA)PbI3, (S-MBA)2PbI 4(1-x) Br 4x , (R- / S-MBA)2CuCl4; the solvent in the perovskite precursor solution is an organic solvent, including one or more of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Preferably, the solute in the perovskite precursor solution is (S / R-MBA)2PbI4, and the organic solvent is N,N-dimethylformamide. The above perovskite precursor solution can be used to prepare a chiral perovskite film. Among them, MBA is methylbenzylamine, NEA is ethylamine, and the S and R in front refer to the chirality of the two organic compounds, which are S chirality and R chirality, respectively.

[0066] In some embodiments, in step S20, the substrate is cleaned and activated before coating, including the steps of: ultrasonically cleaning the substrate with alcohol and water for 10 minutes respectively, and then treating the substrate with PLASMA for one minute to activate its surface. The activation treatment can enhance its hydrophilicity and promote the adsorption and nucleation process of the perovskite precursor solution.

[0067] In some embodiments, the substrate includes, but is not limited to, a glass sheet.

[0068] In some embodiments, the annealing temperature is 90° C.-110° C., and the annealing time is 7 min-10 min. The annealing promotes the growth of crystals, and the crystals gradually cover the substrate to form a chiral perovskite film.

[0069] In a preferred embodiment, the temperature of the annealing treatment is 100° C., and the time of the annealing treatment is 8 minutes.

[0070] In some embodiments, in step S20, before injecting the perovskite precursor solution into the reaction pool, 2 μl of coupling liquid (composed of a mixture of equal masses of glycerol and water) is first dropped on the bottom of the reaction pool so that the reaction pool and the piezoelectric substrate are fully fitted to promote the propagation of surface acoustic waves.

[0071] Specifically, step S20 and step S30 specifically include: mixing the prepared (S / R-MBA)2PbI4 powder with the solvent DMF according to mass ratio, and shaking until it is completely dissolved to obtain a perovskite precursor solution with a mass fraction of 30wt%; filling the reaction tank with the perovskite precursor solution, covering it with a treated substrate glass sheet, connecting an RF signal of a corresponding frequency, amplifying the RF signal through a power amplifier, and then dividing it equally into two interdigital transducers through a power divider, and converting it into Rayleigh waves that propagate along the piezoelectric substrate and act on the perovskite precursor solution in the reaction tank.

[0072] In this embodiment, in order to avoid damage to the device due to excessive power, 4W input power (2W for a single interdigital transducer) is used for coating for 10 minutes.

[0073] In addition, the present invention also provides a chiral perovskite film, which is prepared by using the preparation method of the chiral perovskite film.

[0074] In this embodiment, the chiral perovskite film prepared by the chiral perovskite film preparation method has higher crystallinity and narrower band gap, and the method can improve the crystallinity of the film and reduce the band gap, and at the same time can change the parameters to control the film, and has certain scalability.

[0075] The following examples are further given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention.

[0076] Example 1

[0077] This embodiment provides a closed film coating system based on surface acoustic waves, and uses the system to complete the preparation of chiral perovskite films, as follows:

[0078] The closed coating system (SAWM) based on surface acoustic wave provided in this embodiment is mainly composed of a lithium niobate piezoelectric substrate, an interdigital transducer (IDT) and a reaction pool; through a thermal evaporation process, a 10nm thick chromium layer is first evaporated on the lithium niobate piezoelectric substrate as a transition layer, and then a 100nm thick gold is plated as an electrode of the IDT, and a 0.5 misalignment degree is introduced between the two interdigital transducers, that is, the relative width of the interdigital transducers of the two opposite interdigital transducers in the working interval accounts for half of the total length; and the reaction pool is formed by bonding the pool wall of acrylic material and a glass sheet through PDMS, wherein the depth of the reaction pool is 3mm and the inner diameter is 10mm.

[0079] The closed film coating system based on surface acoustic wave of this embodiment is characterized as follows:

[0080] Reflection coefficient curve during testing using a network vector analyzer, Figure 3 This is a reflection coefficient curve of a single IDT, which shows that the operating frequency of the IDT is around 18.2. Secondly, its curve shape conforms to the Rayleigh wave mode; specifically, its excitation resonance frequency is 18.181MHz. The surface displacement of the IDT is tested using a laser vibrometer, and the test results are as follows: Figure 4 As shown, at an input power of 4 W (2 W for a single IDT), the vibration amplitude of the IDT is 628 nm, and the amplitude increases with increasing power, indicating that the power is directly related to the amplitude of the IDT.

[0081] The following uses this system to prepare chiral perovskite films, including:

[0082] Before coating, the substrate glass sheet was ultrasonically cleaned with alcohol and water for 10 minutes respectively, and then treated with PLASMA for one minute to activate its surface. The prepared (S / R-MBA)2PbI4 powder was mixed with the solvent DMF according to mass ratio, and shaken until completely dissolved to obtain a perovskite precursor solution with a mass fraction of 30wt%. First, 2 microliters of coupling liquid (a mixture of glycerol and water of equal mass) was dropped at the bottom of the reaction tank, and then the perovskite precursor solution was filled with the reaction tank and covered with the treated substrate glass sheet, and the RF signal of the corresponding frequency was connected. After the RF signal was amplified by the power amplifier, it was equally divided into two interdigital transducers through a power divider, and converted into Rayleigh waves to propagate along the piezoelectric substrate and act on the perovskite precursor solution in the reaction tank. Among them, 4W input power (single IDT 2W) was used for coating, and the time was 10min. After the coating was completed, it was annealed at 100℃ for 8 minutes to evaporate the solvent and promote the growth of the film to obtain a chiral perovskite film (hereinafter referred to as SAW film).

[0083] As a comparative example, spin coating was used for comparison, first at a rotation speed of 2000 rpm for 18 seconds, and then at a rotation speed of 4000 rpm for 30 seconds; after the coating was completed, annealing was performed at 100°C for 8 minutes to evaporate the solvent and promote film growth, thereby obtaining a perovskite film (hereinafter referred to as the spin-coated film).

[0084] The films were characterized, and the diffraction patterns of OIHPs were obtained using a high-resolution X-ray diffractometer (XRD) (X'pertpro, the Netherlands) and a Cu-Kα radiation source (λ = 0.15406 nm). The microstructure of the chiral perovskite films was observed using a field emission scanning electron microscope (SEM) system (ZEISS-GeminiSEM 560, Germany). The scattering transmittance circular dichroism data were collected using a circular dichroism spectrometer (JASCO-J1500, Japan). The absorption spectra were obtained using a UV-visible spectrophotometer equipped with an integrating sphere (shimadzuu-uv 3600Plus, Japan).

[0085] The morphology of the film prepared by SAWM system with 30wt% (S / R-MBA)2PbI4 solution was characterized by SEM and TEM. Figure 5 The SEM image of the SAW film is shown. The film is composed of stacked needle-shaped crystals. The spin-coated film prepared by spin coating of the solution with the same concentration is shown in Figure 2. Figure 6 As shown in the dispersed flocculent arrangement, it can be found that the membrane prepared by the SAWM system has larger crystals.

[0086] Comparing the XRD diffraction patterns of the two films, it can be found that the positions of the diffraction peaks of the two are consistent, but the XRD diffraction peak of the SAW film has a higher intensity, which further verifies the high crystallinity of the SAW film.

[0087] The film thickness was tested using a profilometer, and a line was scratched on the film with tweezers as a control. The average thickness of the film obtained by driving the precursor solution with a concentration of 30wt% at 4W input for 10 minutes was about 1.5μm, which is 2 to 3 times the thickness of the spin-coated film. In addition, we used XRD diffraction to test the stability of the SAW film. It was placed in a laboratory environment (25℃, relative humidity 40%) for 1, 3, 5, and 12 days. Figure 7 As shown, the intensity and position of its XRD diffraction peak did not change significantly, which indicates that the SAW film has a certain chemical stability.

[0088] The UV absorption of SAW film and spin-coated film was tested and the energy band gap of both was calculated to study the effect of SAW method on the optical properties of the film. Figure 8As shown in the figure, the absorption peaks of the SAW film and the spin-coated film are located at 486 nanometers. However, the absorption intensity of the SAW film is greater than that of the spin-coated film, partly due to the thickness difference between the two films. There is also a clear difference in the cutoff end of the absorption curves of the two films. The direct band gap is calculated using the Tauc plot, as shown in Fig. 9 As shown in Figure 2, the results show that the energy band gap of the SAW film is slightly lower than that of the spin-coated film. This decrease means that the conductivity of the SAW film increases. In addition, the circular dichroism spectrum is shown in Figure 2. Fig.10 As shown, the SAW film has an obvious CD signal; Fig.11 As shown, the asymmetry factor g of the SAW film is obtained by using circular dichroism and absorption calculation. CD Close to 10 -3 In addition, this embodiment changes the parameters of the system to prepare the film, and finds that the input power has a modulation effect on the film absorption, such as Fig.12 As shown, the absorption of the film decreases as the power increases.

[0089] Experimentally, the CD size of chiral materials can be determined by the absorption asymmetry factor (g CD ) to quantify:

[0090]

[0091] Where △A is the difference in absorption of left-handed and right-handed circularly polarized light by the chiral sample, A is the total absorption of unpolarized light, and θ is the ellipticity. For the first perovskite, its g CD The range is usually 10 -3 -10 -4 Magnitude.

[0092] In summary, the present invention provides a closed coating system based on surface acoustic wave, a chiral perovskite film and a preparation method thereof. The closed coating system based on surface acoustic wave includes a piezoelectric substrate, and a first interdigital transducer, a second interdigital transducer and a reaction pool arranged on the piezoelectric substrate; the first interdigital transducer and the second interdigital transducer are arranged relative to each other in a staggered manner, and the reaction pool is arranged between the first interdigital transducer and the second interdigital transducer. The present invention utilizes the electrical signals on the first interdigital transducer and the second interdigital transducer arranged relative to each other to be converted into deformation under the action of the piezoelectric substrate, and the periodic deformation constitutes a surface acoustic wave and propagates along the surface of the piezoelectric substrate, and then acts on the precursor solution in the reaction pool, pushing the precursor solution to rotate, and completing the coating process on the lower surface of the target substrate covered on the top of the reaction pool; and the reaction pool and the target substrate covered on the top of the reaction pool can form a closed environment, isolating the air while constraining the precursor solution in the pool to form a vortex, so as to achieve coating on the target substrate. The closed coating system based on surface acoustic waves has a simple structure, is simple and quick in the process of coating the target substrate, effectively reduces costs, and does not require an inert gas environment.

[0093] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A closed film coating system based on surface acoustic wave, characterized in that: It comprises a piezoelectric substrate, and a first interdigital transducer, a second interdigital transducer and a reaction cell arranged on the piezoelectric substrate; The first IDT and the second IDT are arranged opposite to each other in a staggered manner, and the reaction pool is arranged between the first IDT and the second IDT.

2. The closed film coating system based on surface acoustic wave according to claim 1, characterized in that: The misalignment degree between the first IDT and the second IDT is 40%-60%.

3. The closed film coating system based on surface acoustic wave according to claim 1, characterized in that: The wavelength of the first interdigital transducer is 200 micrometers to 300 micrometers; the wavelength of the second interdigital transducer is 200 micrometers to 300 micrometers.

4. The closed film coating system based on surface acoustic wave according to claim 1, characterized in that: A transition layer is further provided between the piezoelectric substrate and the first interdigital transducer, and between the piezoelectric substrate and the second interdigital transducer; the thickness of the transition layer is 8nm-15nm.

5. The closed film coating system based on surface acoustic wave according to claim 1, characterized in that: The reaction pool is composed of a pool wall and a pool bottom attached to one side of the pool wall close to the piezoelectric substrate.

6. The closed film coating system based on surface acoustic wave according to claim 1, characterized in that: The depth of the reaction pool is 3nm-6nm, and the inner diameter of the reaction pool is 8mm-14mm.

7. A method for preparing a chiral perovskite film, characterized in that: Includes steps: Providing a closed coating system based on surface acoustic waves as described in any one of claims 1 to 6; Injecting a perovskite precursor solution into a reaction cell, and placing a substrate on a side of the reaction cell away from the piezoelectric substrate; Using the first interdigital transducer and the second interdigital transducer to emit Rayleigh waves and act on the perovskite precursor solution in the reaction tank to obtain a substrate coated with the perovskite precursor solution; The substrate coated with the perovskite precursor solution is annealed to obtain a chiral perovskite film.

8. The method for preparing a chiral perovskite thin film according to claim 7, characterized in that: The solute in the perovskite precursor solution is selected from (S / R-MBA)2PbI4, PbBr2-CsBr-S- / R-NEABr, (S- / R-NEA)2PbI 4(1-γ) Br 4γ , (S- / R-NEA)2PbI4, (S- / R-NEA)PbI3, (S-MBA)2PbI 4(1-x) Br 4x , (R- / S-MBA)2CuCl4; the solvent in the perovskite precursor solution is selected from one or more of N,N-dimethylformamide and dimethyl sulfoxide.

9. The method for preparing a chiral perovskite thin film according to claim 7, characterized in that: The temperature of the annealing treatment is 90° C.-110° C., and the time of the annealing treatment is 7 min-10 min.

10. A chiral perovskite film, characterized in that: The chiral perovskite film is prepared by the method for preparing the chiral perovskite film as described in any one of claims 7 to 9.

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