Semiconductor liquid crystal material, method of preparation, optoelectronic element and use

Abstract

The application discloses a semiconductor liquid crystal material, a preparation method, an optoelectronic element and application, wherein the liquid crystal material is obtained by reinforcing a perovskite liquid crystal with nano magnetic particles, wherein the peroviskite liquid crystal is selected from A2PbX4 or A2Pb a M b X4 or A2PbBr c I (4‑c) , wherein the organic matter A is selected from PEA and BA, X is selected from Cl and Br, M is selected from Mn and I, a and b are both greater than 0 and a+b=1, and c<=4. The application effectively improves the instant response of the semiconductor liquid crystal material and realizes non-contact operation, and the band gap of the semiconductor liquid crystal can be adjusted.

Description

Technical Field

[0001] This invention relates to optoelectronic technology, and in particular to a semiconductor liquid crystal material, its preparation method, optoelectronic components, and their applications. Background Technology

[0002] Organic-inorganic hybrid perovskite materials are a class of novel optoelectronic materials with excellent photoelectric properties, and they have significant application value in fields such as organic light-emitting diodes (OLEDs) and photodetectors. Three-dimensional perovskite materials possess strong and broad visible light absorption energy, low exciton binding energy, and high carrier mobility; however, their poor environmental stability greatly limits their practical production applications. Compared to three-dimensional perovskite materials, two-dimensional perovskite materials exhibit higher environmental stability due to their quantum confinement effect and lower defect density, making them of significant research value in applications such as portable and flexible wearable devices. Furthermore, the structural characteristics of two-dimensional organic-inorganic perovskite materials result in a unique quantum well band structure. By changing the type of halogen and the number of inorganic octahedral layers (n), the band gap of the material can be altered, achieving band gap tunability under the influence of the quantum confinement effect.

[0003] Emitting liquid crystals (LCDs) possess both luminescence and anisotropy, making them promising candidates for applications in optoelectronic devices. Based on their structure and properties, LCDs can be categorized into fluorescent liquid crystal materials, metallic luminescent liquid crystal materials, ionic liquid luminescent liquid crystal materials, and aggregation-induced emission liquid crystal materials, among others. When light enters a liquid crystal, birefringence occurs; that is, a beam of light is refracted into two beams, both of which are polarized and vibrate perpendicularly to each other. Birefringence essentially indicates that the dielectric constant and refractive index differ in different directions within the liquid crystal.

[0004] Emitting-light liquid crystals (ELCs) combine the characteristics of liquid crystals with excellent luminescence and stimulus-response properties, making them applicable in numerous fields such as polarized light sources and polarized light detection systems. Their molecular order can be manipulated by external stimuli such as temperature changes, electric fields, and magnetic fields, enabling various technological advancements, such as electric field-driven liquid crystal displays. Among various types of stimulus-response systems, magnetically responsive structures have attracted considerable research interest because they can respond to external magnetic stimuli in a non-contact manner, thanks to the properties of magnetic interactions.

[0005] Currently, there are reports on methods for directly preparing liquid crystals using magnetic materials. Liquid crystals prepared directly using magnetic materials have good instantaneous responsiveness, and only a small magnetic field is needed to change their liquid crystal morphology.

[0006] While traditional liquid crystal materials may be sensitive to magnetic fields, their practical applications are severely hampered by the low magnetic susceptibility of their molecular types, requiring extremely strong magnetic fields to achieve efficient switching of molecular sequences. Furthermore, for many inorganic luminescent liquid crystals, it is difficult to precisely and continuously adjust their emission wavelength across the entire visible light range. Therefore, the systematic and low-cost development of semiconductor liquid crystal materials with magnetically responsive properties and tunable band gaps is crucial. In addition, the traditional preparation of two-dimensional organic-inorganic hybrid perovskite materials is time-consuming, involves complex reaction steps, and is costly.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide a semiconductor liquid crystal material, a preparation method, an optoelectronic device, and an application. By directly incorporating magnetic nanomaterials into the semiconductor liquid crystal, on the one hand, it has good instantaneous responsiveness and can be operated non-contactly, and on the other hand, the prepared semiconductor liquid crystal has an adjustable bandgap.

[0009] To achieve the above objectives, embodiments of the present invention provide a semiconductor liquid crystal material with magnetic response properties and a tunable bandgap, which is obtained by reinforcing perovskite liquid crystal with nano-magnetic microparticles, wherein the perovskite liquid crystal is selected from A2PbX4 or A2Pb. a M b X4 or A2PbBr c I (4-c) The organic compound A is selected from PEA and BA, X is selected from Cl and Br, M is selected from Mn and I, a and b are both greater than 0 and a+b=1, and c≤4. PEA is (phenyl)ethylammonium, and BA is C4H9NH3. The morphology of the magnetic nanoparticles can be magnetic rods (rod-shaped, similar to one-dimensional materials), magnetic sheets (thin sheets, including circular sheets, square sheets, or other regular or irregular sheets, similar to two-dimensional materials), or nanoparticles (such as circular particles or dot-shaped particles, similar to zero-dimensional or three-dimensional materials). Magnetic rods are preferred.

[0010] In one or more embodiments of the present invention, the nanomagnetic particles are selected from Fe3O4, γ-Fe2O3, γ-Fe4N, and α-Fe3N.

[0011] In one or more embodiments of the present invention, the size of the nanomagnetic particles satisfies the following: magnetic rod size: 10-50 nm; magnetic sheet size: 50-100 nm; particle size: 2-20 nm.

[0012] In one or more embodiments of the present invention, a method for preparing a semiconductor liquid crystal material having magnetic response properties and a tunable bandgap includes the following steps: A. preparing a perovskite crystal precursor; B. preparing a perovskite crystal reinforced with magnetic nanoparticles, or preparing a doped perovskite crystal doped with transition metal elements reinforced with magnetic nanoparticles.

[0013] In one or more embodiments of the present invention, the preparation of the perovskite crystal precursor in step A is as follows: a reaction system comprising at least lead halide and organic compound A is prepared, and after thermal reaction, it is cooled and separated.

[0014] In one or more embodiments of the present invention, the preparation of perovskite crystals in step B includes: preparing a perovskite precursor solution with perovskite crystal precursors; preparing an antisolvent for microcrystallization of the perovskite crystal precursors; preparing a colloidal solution including nano-magnetic particles; adding the colloidal solution to the antisolvent under stirring conditions, then adding the perovskite precursor solution, and continuing to stir; centrifuging, separating, and dispersing.

[0015] In one or more embodiments of the present invention, the preparation of the doped perovskite crystal in step B includes: preparing a perovskite precursor solution using a perovskite crystal precursor and a transition metal reagent; preparing an antisolvent for microcrystallization of the perovskite crystal precursor; preparing a colloidal solution comprising nano-magnetic particles; adding the colloidal solution to the antisolvent under stirring conditions, followed by adding the perovskite precursor solution and continuing stirring; and centrifuging, separating, and dispersing. Preferably, the transition metal reagent is selected from soluble salt solutions of transition metal elements.

[0016] In one or more embodiments of the present invention, the optoelectronic element is a semiconductor liquid crystal material, as described above, that has magnetic response properties and a tunable bandgap.

[0017] In one or more embodiments of the present invention, the semiconductor liquid crystal material with magnetic response properties and tunable bandgap, as described above, or the optoelectronic element as described above, is used in light emission, photoelectric detection, and display.

[0018] Compared with the prior art, the semiconductor liquid crystal material, preparation method, optoelectronic element and application according to the embodiments of the present invention are prepared by solution method to prepare two-dimensional perovskite crystals, and then two-dimensional perovskite nanosheets are prepared by antisolvent-induced microcrystallization method.

[0019] This invention provides a simple, inexpensive method for preparing a magnetically responsive semiconductor liquid crystal with a tunable bandgap, obtainable at room temperature. The resulting semiconductor liquid crystal exhibits strong optical anisotropy, instantaneous response performance, and non-contact operation. The light intensity of the liquid crystal can be controlled by the concentration of magnetic nanorods and the rotation angle of polarized light. The color of the liquid crystal phase can also be modulated by doping with manganese ions or by adjusting the concentration of added magnetic nanorods. The high controllability of the magnetically controlled semiconductor liquid crystal phase makes this method a new platform for converting magnetic stimuli into optical information, such as for fabricating novel optical devices. The optical changes in brightness caused by the rotation of the polarized light angle under the influence of an external magnetic field further demonstrate the formation of the alignment structure, providing a promising pathway for photonic devices. Attached Figure Description

[0020] Figure 1 These are sample detection spectra according to an embodiment of the present invention, wherein: 1a: morphological image of (PEA)2PbBr4 perovskite nanosheets under a scanning electron microscope (SEM); 1b: morphological image of Fe3O4@(PEA)2PbBr4 perovskite nanosheets under a scanning electron microscope (SEM); 1c: XRD spectra of (PEA)2PbBr4, 1 mg / mL Fe3O4@(PEA)2PbBr4, and 2 mg / mL Fe3O4@(PEA)2PbBr4 liquid crystal films;

[0021] Figure 2These are optical observation images of a sample according to an embodiment of the present invention, wherein: 2a: an image of a 1.5 mg / mL Fe3O4@(PEA)2PbBr4 liquid crystal after rotation by 0° under a polarizing optical microscope; 2b: an image of a 1.5 mg / mL Fe3O4@(PEA)2PbBr4 liquid crystal after rotation by 45° under a polarizing optical microscope; 2c: an image of a 1.5 mg / mL Fe3O4@(PEA)2PbBr4 liquid crystal after rotation by 90° under a polarizing optical microscope; 2d: an image of a 1.5 mg / mL Fe3O4@(PEA)2PbBr4 liquid crystal after rotation by 135° under a polarizing optical microscope; 2e: an image of a 1.5 mg / mL Fe3O4@(PEA)2PbBr4 liquid crystal after rotation by 0° with a full-wave plate added. Images of Fe3O4@(PEA)2PbBr4 liquid crystal under a polarizing optical microscope; 2f: Image of 1.5 mg / mL Fe3O4@(PEA)2PbBr4 liquid crystal after adding a full-wave plate and rotating 45° under a polarizing optical microscope; 2g: Image of 1.5 mg / mL Fe3O4@(PEA)2PbBr4 liquid crystal after adding a full-wave plate and rotating 90° under a polarizing optical microscope; 2h: Image of 1.5 mg / mL Fe3O4@(PEA)2PbBr4 liquid crystal after adding a full-wave plate and rotating 135° under a polarizing optical microscope;

[0022] Figure 3 These are emission spectra of samples according to an embodiment of the present invention, wherein 3a: (PEA)2PbBr4 liquid crystal is photographed under white visible light (left) and 365nm ultraviolet light (right); 3b: 2mg / mL Fe3O4@(PEA)2PbBr4 liquid crystal is photographed under white visible light (left) and 365nm ultraviolet light (right); 3c: (PEA)2Pb 0.9 Mn 0.1 Photographs of Br4 liquid crystals under white visible light (left) and 365nm ultraviolet light (right); 3d: 2mg / mL Fe3O4@(PEA)2Pb 0.9 Mn 0.1 Photographs of Br4 liquid crystal under white visible light (left) and 365 nm ultraviolet light (right); 3e: UV-Vis transmission spectra of magnetic nanorods dispersed in chlorobenzene at different concentrations (excitation wavelength 365 nm); 3f: Photoluminescence (PL) spectra of Fe3O4@(PEA)2PbBr4 perovskite liquid crystal at different concentrations (0 mg / mL, 2 mg / mL, 4 mg / mL), with λ... max =365nm; 3g: 1.5mg / mLFe3O4@(PEA)2PbBr4 and 1.5mg / mL Fe3O4@(PEA)2Pb 0.9 Mn 0.1The corresponding photoluminescence spectrum (PL) of Br4 perovskite liquid crystal, its λ max =365nm. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0024] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0025] The perovskite liquid crystals prepared in the examples below have a size of 0.5-4 μm, the specific size depending on the actual process. Similarly, the size of the nanomagnetic particles in each example depends on the actual process.

[0026] Example Group 1

[0027] 1. Preparation method of di[(phenyl)ethylammonium]lead tetrabromide ((PEA)2PbBr4) perovskite crystals

[0028] (1) Add lead oxide (PbO, 669.6 mg, 3 mmol) and hydrobromic acid solution (HBr, 37%, 20 mL) to a 50 mL round bottom flask and mix them together. Mix the system evenly by heating and stirring or by sonication.

[0029] (2) When the lead oxide has completely dissolved and the solution has become clear and transparent, add phenylethylamine (PEA, 754 μL, 6 mmol) to the system;

[0030] (3) Fix the round-bottom flask on the heating stirrer, place a condenser on top, heat to 100°C and stir continuously until the solution is completely clear and transparent;

[0031] (4) Turn off heating and stirring, and wait for the solution to cool and crystallize;

[0032] (5) After about 2 hours, it can be observed that a large number of flaky crystals will precipitate out of the originally transparent and clear solution after cooling to room temperature. The crystals are then separated from the solution by vacuum filtration and washed with cyclohexane 5-6 times.

[0033] (6) Finally, the obtained product is stored in a vacuum drying oven for 24 hours until it is completely dry.

[0034] 2-1. Preparation method of (PEA)₂PbBr₄ perovskite liquid crystal solution containing magnetic nanorods:

[0035] (1) Preparation of precursor solution: Dissolve 230.15 mg (0.3 mmol) (PEA)2PbBr4 perovskite crystals in 300 μL of DMF to prepare (PEA)2PbBr4 perovskite precursor solution;

[0036] (2) Preparation of antisolvent for microcrystallization of perovskite nanosheets: Chlorobenzene, oleic acid and oleylamine were mixed in a volume ratio of 1000:1:1 to form a mixed solution (solution A);

[0037] (3) First, add 10 mL of mixed solution A to the round-bottom flask, and slowly add an appropriate amount of magnetic nanorod colloidal solution while stirring at high speed (2500 rpm). The magnetic nanorod colloidal solution is prepared as follows: 1. First, mix polyethyleneimine (PEI, 0.275 mL) and FeCl3·6H2O (5.446 g, 20 mmol) in 100 mL of distilled water, and then stir at 80 °C for 2 h.

[0038] 2. After stirring, the brownish-yellow precipitate obtained from the reaction is separated by centrifugation, and then washed three times with acetone. The product obtained here does not need to be vacuum dried.

[0039] 3. The above product was mixed with oleylamine (3.3435 g, 25 mmol), and the mixture was heated at 200 °C for 4 h under a nitrogen atmosphere. During the heating process, the nanoparticles gradually turned from the initial brownish-yellow color to black.

[0040] 4. After heating is complete, separate the black product with a magnet, and then wash it three times with a mixture of cyclohexane and acetone;

[0041] 5. The washed product is redispersed in chlorobenzene for subsequent use;

[0042] (4) Slowly add 300 μL of (PEA)2PbBr4 precursor solution to the above mixed solution, stir for 1 min, and then centrifuge at 8000 rpm for 10 min.

[0043] (5) After centrifugation, discard the supernatant, redisperse the solid product in 10 mL of mixed solution A, and centrifuge at 8000 rpm for 30 min.

[0044] (6) After centrifugation, discard the supernatant and finally disperse the obtained solid product again in 1 mL of mixed solution A. Sonicate it to make it evenly dispersed to obtain perovskite liquid crystal.

[0045] 2-2. Preparation method of (PEA)2PbBr4 perovskite liquid crystal solution:

[0046] (1) Preparation of precursor solution: Dissolve 230.15 mg (0.3 mmol) (PEA)2PbBr4 perovskite crystals in 300 μL of DMF to prepare (PEA)2PbBr4 perovskite precursor solution;

[0047] (2) Preparation of antisolvent for microcrystallization of perovskite nanosheets: Chlorobenzene, oleic acid and oleylamine were mixed in a volume ratio of 1000:1:1 to form a mixed solution (solution A);

[0048] (3) First, add 10 mL of mixed solution A to the round-bottom flask and stir at high speed (2500 rpm);

[0049] (4) Slowly add 300 μL of (PEA)2PbBr4 precursor solution to the above mixed solution, stir for 1 min, and then centrifuge at 8000 rpm for 10 min.

[0050] (5) After centrifugation, discard the supernatant, redisperse the solid product in 10 mL of mixed solution A, and centrifuge at 8000 rpm for 30 min.

[0051] (6) After centrifugation, discard the supernatant and finally disperse the obtained solid product again in 1 mL of mixed solution A. Sonicate it to make it evenly dispersed to obtain perovskite liquid crystal.

[0052] 3-1. (PEA)₂Pb containing magnetic nanorods 0.9 Mn 0.1 Preparation method of Br4 perovskite liquid crystal solution:

[0053] (1) Preparation of precursor solution: 230.15 mg (0.3 mmol) (PEA)₂PbBr₄ perovskite crystal was dissolved in 300 μL of DMF to prepare (PEA)₂PbBr₄ perovskite precursor solution; 12.584 mg (0.1 mmol) MnCl₂ powder was dissolved in 100 μL of DMF to prepare MnCl₂ precursor solution; finally, 30 μL of MnCl₂ solution was added to the 300 μL (PEA)₂PbBr₄ precursor solution, and the mixture was ultrasonicated to form a manganese-doped (PEA)₂PbBr₄ precursor solution. 0.9 Mn 0.1 Br4);

[0054] (2) Preparation of antisolvent for microcrystallization of perovskite nanosheets: Chlorobenzene, oleic acid and oleylamine were mixed in a volume ratio of 1000:1:1 to form a mixed solution (solution A);

[0055] (3) First, add 10 mL of mixed solution A to the round bottom flask, and slowly add an appropriate amount of magnetic nanorod colloidal solution while stirring at high speed (2500 rpm).

[0056] (4) Add 330 μL of (PEA)2Pb 0.9 Mn 0.1 The Br4 precursor solution was slowly added to the above mixed solution, stirred for 1 min, and then centrifuged at 8000 rpm for 10 min.

[0057] (5) After centrifugation, discard the supernatant, redisperse the solid product in 10 mL of mixed solution A, and centrifuge at 8000 rpm for 30 min.

[0058] (6) After centrifugation, discard the supernatant and finally disperse the obtained solid product again in 1 mL of mixed solution A. Sonicate it to make it evenly dispersed to obtain perovskite liquid crystal.

[0059] 3-2.(PEA)2Pb 0.9 Mn 0.1 Preparation method of Br4 perovskite liquid crystal solution:

[0060] (1) Preparation of precursor solution: 230.15 mg (0.3 mmol) (PEA)₂PbBr₄ perovskite crystal was dissolved in 300 μL of DMF to prepare (PEA)₂PbBr₄ perovskite precursor solution; 12.584 mg (0.1 mmol) MnCl₂ powder was dissolved in 100 μL of DMF to prepare MnCl₂ precursor solution; finally, 30 μL of MnCl₂ solution was added to the 300 μL (PEA)₂PbBr₄ precursor solution, and the mixture was ultrasonicated to form a manganese-doped (PEA)₂PbBr₄ precursor solution. 0.9 Mn 0.1 Br4);

[0061] (2) Preparation of antisolvent for microcrystallization of perovskite nanosheets: Chlorobenzene, oleic acid and oleylamine were mixed in a volume ratio of 1000:1:1 to form a mixed solution (solution A);

[0062] (3) First, add 10 mL of mixed solution A to the round-bottom flask and stir at high speed (2500 rpm);

[0063] (4) Add 330 μL of (PEA)2Pb 0.9 Mn 0.1 The Br4 precursor solution was slowly added to the above mixed solution, stirred for 1 min, and then centrifuged at 8000 rpm for 10 min.

[0064] (5) After centrifugation, discard the supernatant, redisperse the solid product in 10 mL of mixed solution A, and centrifuge at 8000 rpm for 30 min.

[0065] (6) After centrifugation, discard the supernatant and finally disperse the obtained solid product again in 1 mL of mixed solution A. Sonicate it to make it evenly dispersed to obtain perovskite liquid crystal.

[0066] 4. Experimental Results

[0067] The microstructure of (PEA)₂PbBr₄ and Fe₃O₄@(PEA)₂PbBr₄ perovskite liquid crystal modules was observed using scanning electron microscopy (SEM). Based on the SEM images, it was found that both (PEA)₂PbBr₄ and Fe₃O₄@(PEA)₂PbBr₄ perovskite liquid crystal modules are square, plate-like nanoparticles. Figure 1 As shown in image a, the (PEA)₂PbBr₄ perovskite nanosheets exhibit clear morphology and distinct edges. Most nanosheets have a diameter of 500 nm, with a few reaching the micrometer scale. Notably, magnetic nanorods are difficult to observe in the SEM images of Fe₃O₄@(PEA)₂PbBr₄ nanosheets due to their extremely small size. Figure 1 b).

[0068] X-ray diffraction (XRD) data can be used to analyze the crystal phase and chemical composition of perovskites. For example... Figure 1 As shown in c, the experimental data of the prepared sample, compared with the data of perovskite single crystals, showed no stray peaks and agreed well with the simulated diffraction peaks. The XRD image showed a series of clear, distinct, and equally spaced 00h (h = 2, 4, 6, 8...) diffraction peaks perpendicular to the c-axis, exhibiting periodic repetition and characteristics of the 00h (h = 2, 4, 6, 8...) plane in a layered crystal structure. This indicates that (PEA)₂PbBr₄ has high crystallinity and good periodicity, and its structure shows a clear growth preference in the c-axis direction (00h plane). Furthermore, the XRD pattern did not change significantly with increasing magnetic nanorod concentration, indicating that the addition of a small amount of magnetic nanorods did not alter the crystal structure of the perovskite liquid crystal. Figure 1 As shown.

[0069] To establish a magnetic field as the driving force for optical manipulation of magnetic nanorods in perovskite liquid crystals, we conducted the following experiments. We observed that when the magnetic field direction remained constant, the orientation of the perovskite liquid crystal containing magnetic nanorods changed with the rotation angle. It is important to note that the magnetic field was controlled by six neodymium magnets (0.5 cm cubes) placed on both sides of the perovskite colloidal solution. The six magnets were joined adjacently to form a hexagonal prism structure, and the detection magnetic field region was defined within a 1-10 cm area centered on the central axis of the prism. In this embodiment, detection was performed within a range of 2-2.5 cm from the center point of the prism. The intensity of light passing through the liquid crystal sandwiched between cross polarizers can be described by the following formula:

[0070] I = I0Sin 2 (2α)Sin 2 (πΔnL / λ)

[0071] Where I0 is the light intensity through the first polarizer; α is the angle between the transmission axis of the polarizer and the long axis of the liquid crystal; Δn is the difference in refractive index of the liquid crystal arranged at a specific angle along the long and short axes; L is the thickness of the sample; and λ is the wavelength of the incident light. Figure 2 As shown in a and 2c, when the field of view is perpendicular or parallel to the polarizer, i.e., α is 0° or 90°, the field of view becomes dark, and the polarization optical microscope (POM) image appears dark. Figure 2 As shown in b and 2d, when the field of view is 45° or 135° from the polarizer, i.e., α is 45° or 135°, the intensity reaches its maximum and the field of view becomes brighter, according to the above formula. From the POM image, it can be seen that the perovskite liquid crystal containing magnetic nanorods exhibits birefringent fringes, indicating that it possesses the anisotropy of liquid crystal. Figure 2 f and 2h).

[0072] Figure 3 The images shown are of perovskite liquid crystals under white visible light and 365nm ultraviolet light, respectively. From left to right, they are (PEA)₂PbBr₄, Fe₃O₄@(PEA)₂PbBr₄, and (PEA)₂PbBr₄. 0.9 Mn 0.1 Br4, Fe3O4@(PEA)2Pb 0.9 Mn 0.1 Br4 perovskite liquid crystal. Under white visible light irradiation, (PEA)2PbBr4 and (PEA)2Pb... 0.9 Mn 0.1 The Br4 perovskite liquid crystal appears white. After the addition of magnetic nanorods, the color of the perovskite liquid crystal changed, becoming slightly darker. Under 365nm ultraviolet light irradiation, the (PEA)2PbBr4 perovskite liquid crystal emits blue light, while (PEA)2Pb... 0.9Mn 0.1 Br4 perovskite liquid crystals emit pinkish-purple light, and the above changes indicate that they can maintain their semiconductor properties. Even after adding magnetic nanorods, the perovskite liquid crystals still emit fluorescence, although the luminescence intensity decreases slightly under the same conditions, further demonstrating that adding an appropriate amount of magnetic nanorods does not alter their semiconductor luminescence properties.

[0073] The optical properties were further characterized by ultraviolet-visible (UV-Vis) transmission spectroscopy and photoluminescence (PL) spectroscopy. Figure 3 e represents the UV-Vis transmittance spectra of magnetic nanorods dispersed in chlorobenzene at different concentrations. The transmittance of the colloidal solution gradually decreases with increasing concentration. Since the directly obtained perovskite liquid crystal was too viscous, subsequent PL measurements used a colloidal solution obtained by diluting the original perovskite liquid crystal twice with chlorobenzene. Figure 3 As can be seen from f, the peak position of the colloidal solution gradually red-shifts with increasing magnetic nanorod concentration. Furthermore, we also observed peak positions in (PEA)₂PbBr₄ and (PEA)₂PbBr₄, respectively. 0.9 Mn 0.1 Magnetic nanorods of the same concentration were added to a Br4 perovskite liquid crystal solution, and their liquid crystal properties were then tested. Figure 3 As shown in the figure, the 1.5 mg / mL Fe3O4@(PEA)2PbBr4 perovskite liquid crystal exhibits an emission peak at 562 nm, with a full width at half maximum (FWHM) of approximately 122 nm; 1.5 mg / mL Fe3O4@(PEA)2Pb 0.9 Mn 0.1 The emission peak of Br4 perovskite liquid crystal is at 588 nm, and the full width at half maximum (FWHM) is approximately 131 nm. It can be observed that (PEA)₂Pb 0.9 Mn 0.1 The Br4 perovskite liquid crystal solution exhibits a blue shift relative to the (PEA)2PbBr4 perovskite liquid crystal.

[0074] The only difference between Example Group 2 and Example Group 1 is that the magnetic nanorod colloidal solution is a γ-Fe4N colloidal solution.

[0075] Preparation of γ-Fe4N colloidal solution:

[0076] 1. First, dissolve NiCl2·6H2O (0.118g) and NaCl (4g) in a mixed solution of 20mL anhydrous ethanol and 20mL deionized water, respectively;

[0077] 2. After complete dissolution, FeCl3 (1.622 g) and hexamethylenetetramine (HMTA, 3.5 g) were added at a molar ratio of 1:2.5, and the mixture was stirred at room temperature for 30 min to obtain a yellowish-brown suspension;

[0078] 3. Seal the above mixed solution in a 60 mL high-pressure reactor and react at 110 °C for 12 h;

[0079] 4. After cooling to room temperature, centrifuge to precipitate, wash the precipitate three times with deionized water, and dry it overnight at 60°C to obtain precursor powder;

[0080] 5. Take 0.4g of the precursor powder obtained from the above reaction and put it into a porcelain boat. Place the boat in the center of the tube furnace and place another porcelain boat containing 1.5mL of ethylenediamine 3cm in front of the precursor powder.

[0081] 6. The tube furnace is heated to 600°C at a heating rate of 20°C / min under nitrogen atmosphere protection, held at that temperature for 30 min, and then naturally cooled to room temperature to obtain the final product, which is then redispersed in chlorobenzene to obtain a colloidal solution.

[0082] The performance of the liquid crystal materials in this example group is as follows: Under a polarization microscope in a magnetic field, changes in brightness were observed at different angles of rotation. Adding a small amount (e.g., 0.1% by mass) does not change the semiconductor properties of the perovskite liquid crystal itself. With increasing magnetic nanorod concentration, the peak position of the colloidal solution gradually red-shifts. However, its brightness change is slightly less pronounced than that of the magnetic nanorods. Furthermore, a blue shift can be observed in the doped perovskite liquid crystal solution compared to the undoped perovskite liquid crystal.

[0083] The only difference between Example Group 3 and Example Group 1 is that the magnetic nanorod colloidal solution is replaced with the Fe3O4 nanoparticle colloidal solution.

[0084] Preparation of Fe3O4 nanoparticle colloidal solution:

[0085] 1. Dissolve 10.8g FeCl3·6H2O (40mmol) and 36.5g sodium oleate (120mmol) in a mixed solution of 80mL ethanol, 60mL deionized water and 140mL n-hexane, heat to 70℃ and keep warm for 4h;

[0086] 2. The obtained product was washed with distilled water in a separatory funnel to obtain a waxy oleic acid iron complex; 3. 36 g (40 mmol) of the oleic acid iron complex prepared above and 5.7 g (20 mmol) of oleic acid were dissolved in 200 g of 1-octadecene at room temperature;

[0087] 4. Heat the above mixture to 320°C at a heating rate of 3.3°C / min and hold for 30 min, during which the solution gradually changes from clear to black;

[0088] 5. After the above solution is cooled to room temperature, ethanol is added to the solution to precipitate the nanoparticles. Then, the nanoparticles are separated by centrifugation and redispersed in chlorobenzene.

[0089] The performance of the liquid crystal materials in this example group is as follows: Under a polarization microscope in a magnetic field, changes in brightness should be observed when rotating at different angles. Adding a small amount (e.g., 0.1% by mass) will not change the semiconductor properties of the perovskite liquid crystal itself. As the concentration of magnetic nanorods increases, the peak position of the colloidal solution gradually red-shifts. However, its brightness change is slightly less pronounced than that of the magnetic nanorods. Furthermore, a blue shift can be observed in the doped perovskite liquid crystal solution compared to the undoped perovskite liquid crystal.

[0090] The only difference between Example Group 4 and Example Group 1 is that the magnetic nanorod colloidal solution is replaced with the Fe3O4 nanomagnetic sheet colloidal solution.

[0091] Preparation of Fe3O4 nanofiber colloidal solution:

[0092] 1. Dissolve FeCl2 (1 mmol), FeCl3 (1.9 mmol), NaAc (22 mmol) and PEG (1.25 mmol) in 40 mL of diethylene glycol (DEG);

[0093] 2. Place the above-mentioned well-mixed solution in a reaction vessel and heat at 220°C for 7 hours;

[0094] 3. After cooling to room temperature, wash the reaction precipitate three times each with ethanol and deionized water;

[0095] 4. Add the wet Fe3O4 precipitate to 20 mL of NaOH (1.0 mM) solution and disperse it using ultrasound to form a suspension;

[0096] 5. Mix 20 mL of PAA solution (10.0 g / L) with 1 mL of FeCl3 (0.1 mol / L) to form an orange solution;

[0097] 6. Slowly add the magnetic suspension to the above orange mixed solution while stirring, then sonicate at 80°C for 15 minutes. After stirring is complete, collect the precipitate using a magnet.

[0098] 7. Add the obtained wet precipitate to 20 mL of NaOH (0.05 mol / L) solution, and sonicate the mixture for 10 seconds. After sonication, collect the mixture using a magnet and wash it three times with deionized water.

[0099] 8. The resulting product was then redispersed in chlorobenzene to form a colloidal solution.

[0100] The performance of the liquid crystal materials in this example group is as follows: Under a polarization microscope in a magnetic field, changes in brightness should be observed when rotating at different angles. Adding a small amount (e.g., 0.1% by mass) will not change the semiconductor properties of the perovskite liquid crystal itself. As the concentration of magnetic nanorods increases, the peak position of the colloidal solution gradually red-shifts. However, its brightness change is slightly less pronounced than that of the magnetic nanorods. Furthermore, a blue shift can be observed in the doped perovskite liquid crystal solution compared to the undoped perovskite liquid crystal.

[0101] The only difference between Example Group 5 and Example Group 1 is that the perovskite liquid crystal is (BA)2PbBr. c I(4-c).

[0102] Preparation method of di[butylammonium]lead tetrabromide ((BA)2PbBr4) perovskite crystals:

[0103] (1) Add lead oxide (PbO, 2232.0 mg, 10 mmol) and hydrobromic acid solution (HBr, 37%, 20 mL) to a 50 mL round bottom flask and mix them together by heating and stirring or by sonication.

[0104] (2) When the lead oxide is completely dissolved and the solution becomes clear and transparent, add butylamine (BA, 1976.8 μL, 20 mmol) to the system;

[0105] (3) Fix the round-bottom flask on the heating stirrer, place a condenser on top, heat to 100°C and stir continuously until the solution is completely clear and transparent;

[0106] (4) Turn off heating and stirring, and wait for the solution to cool and crystallize;

[0107] (5) After about 2 hours, it can be observed that a large number of flaky crystals will precipitate after the originally transparent and clear solution is cooled to room temperature. The crystals are then separated from the solution by vacuum filtration and the flask and crystal products are rinsed with cyclohexane 5-6 times.

[0108] (6) Finally, the obtained product is stored in a vacuum drying oven for 24 hours until it is completely dry.

[0109] Preparation method of di[butylammonium]lead tetraiodide ((BA)2PbI4) perovskite crystals:

[0110] (1) Mix n-butylamine (n-C4H9NH2, 10 mmol) and hydroiodic acid solution (HI, 55%, 38 mmol) and stir continuously in an ice bath for 4 h to obtain BAI solution;

[0111] (2) Dissolve lead oxide (PbO, 10 mmol) in a mixed solution of hydroiodic acid (HI, 55%, 76 mmol) and hypophosphorous acid (H3PO2, 50%, 15.5 mmol), and heat to boiling while stirring to obtain a bright yellow solution (solution 1).

[0112] (3) Add the BAI solution prepared in (1) to solution 1 and heat it to boiling again;

[0113] (4) Stop stirring immediately after boiling and wait for the solution to cool to room temperature;

[0114] (5) During the cooling process, orange flaky crystals gradually crystallize. The crystals are filtered and washed with ether. (6) Finally, the obtained product is stored in a vacuum drying oven for 24 hours until it is completely dry.

[0115] (BA)2PbBr c I (4-c) Preparation method of perovskite liquid crystal solution:

[0116] (1) Preparation of precursor solution: According to the molar ratio of (BA)2PbBr4:(BA)2PbI4=c:(4-c) (here C is 0.2), weigh 1 mol of (BA)2PbBr4 perovskite crystal and (BA)2PbI4 perovskite crystal and dissolve them in 300 LMF solution.

[0117] (2) Preparation of antisolvent for microcrystallization of perovskite nanosheets: Chlorobenzene, oleic acid and oleylamine were mixed in a volume ratio of 1000:1:1 to form a mixed solution (solution A);

[0118] (3) First, add 10 mL of mixed solution A to the round-bottom flask and stir at high speed (2500 rpm);

[0119] (4) Add 300L of (BA)2PbBr c I (4-c) The precursor solution was slowly added to the above mixed solution, stirred for 1 min, and then centrifuged at 8000 rpm for 10 min.

[0120] (5) After centrifugation, discard the supernatant, redisperse the solid product in 10 mL of mixed solution A, and centrifuge at 8000 rpm for 30 min.

[0121] (6) After centrifugation, discard the supernatant and finally disperse the obtained solid product again in 1 mL of mixed solution A. Sonicate it to make it evenly dispersed to obtain perovskite liquid crystal.

[0122] The performance of the liquid crystal material in this example group is as follows: Under a polarization microscope in a magnetic field, changes in brightness should be observed when rotating at different angles. Adding a small amount (e.g., 0.1% by mass) will not change the semiconductor properties of the perovskite liquid crystal itself. As the concentration of magnetic nanorods increases, the peak position of the colloidal solution gradually red-shifts. The difference in brightness changes compared to the first example group is not significant. Furthermore, it can be observed that the doped perovskite liquid crystal solution exhibits a blue shift compared to the undoped perovskite liquid crystal.

[0123] The only difference between Example Group 6 and Example Group 1 is that the doped perovskite liquid crystal is (PEA)₂Pb. 0.7 Mn 0.3 Br4.

[0124] The performance of the liquid crystal material in this example group is as follows: Under a polarization microscope in a magnetic field, changes in brightness should be observed when rotating at different angles. Adding a small amount (e.g., 0.1% by mass) will not change the semiconductor properties of the perovskite liquid crystal itself. As the concentration of magnetic nanorods increases, the peak position of the colloidal solution gradually red-shifts. The difference in brightness changes compared to the first example group is not significant. Furthermore, it can be observed that the doped perovskite liquid crystal solution exhibits a blue shift compared to the undoped perovskite liquid crystal.

[0125] The only difference between Example Group 7 and Example Group 1 is that the doped perovskite liquid crystal is (PEA)₂Pb. 0.2 Mn 0.8 Br4.

[0126] The performance of the liquid crystal material in this example group is as follows: Under a polarization microscope in a magnetic field, changes in brightness should be observed when rotating at different angles. Adding a small amount (e.g., 0.1% by mass) will not change the semiconductor properties of the perovskite liquid crystal itself. As the concentration of magnetic nanorods increases, the peak position of the colloidal solution gradually red-shifts. The difference in brightness changes compared to the first example group is not significant. Furthermore, it can be observed that the doped perovskite liquid crystal solution exhibits a blue shift compared to the undoped perovskite liquid crystal.

[0127] The only difference between Example Group 8 and Example Group 5 is that the perovskite liquid crystal is (BA)2PbBr2I2.

[0128] The performance of the liquid crystal material in this example group is as follows: Under a polarization microscope in a magnetic field, changes in brightness should be observed when rotating at different angles. Adding a small amount (e.g., 0.1% by mass) will not change the semiconductor properties of the perovskite liquid crystal itself. As the concentration of magnetic nanorods increases, the peak position of the colloidal solution gradually red-shifts. The difference in brightness changes compared to the first example group is not significant. Furthermore, it can be observed that the doped perovskite liquid crystal solution exhibits a blue shift compared to the undoped perovskite liquid crystal.

[0129] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a semiconductor liquid crystal material with magnetic response properties and adjustable band gap, comprising the following steps: A. preparing a perovskite crystal precursor, which is prepared by preparing a reaction system comprising at least lead halide and an organic substance A, and then cooling and separating after thermal reaction; B. preparing a nano-magnetic particle enhanced perovskite crystal, which is prepared by preparing a perovskite precursor solution with the perovskite crystal precursor; preparing an anti-solvent for microcrystallization of the perovskite crystal precursor, which is a mixed solution A of chlorobenzene, oleic acid and oleylamine in a volume ratio of 1000:1:1; preparing a colloidal solution comprising nano-magnetic particles; slowly adding the colloidal solution to 10 mL of the anti-solvent under high-speed stirring at 2500 rpm, and then adding 300 mL of a DMF perovskite precursor solution containing 0.3 mmol of perovskite crystals, and continuously stirring; and then centrifuging, separating and dispersing; or preparing a nano-magnetic particle enhanced transition metal element doped doped perovskite crystal, which is prepared by preparing a perovskite precursor solution with the perovskite crystal precursor and a transition metal reagent; preparing an anti-solvent for microcrystallization of the perovskite crystal precursor, which is a mixed solution A of chlorobenzene, oleic acid and oleylamine in a volume ratio of 1000:1:1; preparing a colloidal solution comprising nano-magnetic particles; slowly adding the colloidal solution to 10 mL of the anti-solvent under high-speed stirring at 2500 rpm, and then adding 300 mL of a DMF perovskite precursor solution containing 0.3 mmol of perovskite crystals, and continuously stirring; and then centrifuging, separating and dispersing; wherein the perovskite crystal is selected from A2PbX4or A2Pb a M b X4or A2PbBr c I （4-c） wherein the organic A is selected from PEA, BA, X is selected from Cl, Br, M is selected from Mn, I, a, b are both greater than 0 and a+b=1, c≤4.

2. The semiconductor liquid crystal material having magnetic response properties and a tunable band gap, prepared by the preparation method according to claim 1, wherein, to obtain a nano-magnetic particle enhanced perovskite liquid crystal.

3. The semiconductor liquid crystal material having magnetic response properties and band gap controllability according to claim 2, wherein, The nano-magnetic particles are selected from Fe3O4, γ-Fe2O3, γ-Fe4N and α-Fe3N.

4. The semiconductor liquid crystal material having magnetic response properties and band gap controllability according to claim 3, wherein, The nano-magnetic particles are selected from nano-magnetic rods, nano-magnetic sheets and nano-particles.

5. The semiconductor liquid crystal material having magnetic response properties and band gap controllability according to claim 2, wherein, The size of the nano-magnetic particles satisfies: the size of the magnetic rods is 10-50 nm; the size of the magnetic sheets is 50-100 nm; and the size of the particles is 2-20 nm.

6. An optoelectronic element comprising the semiconductor liquid crystal material with magnetic response properties and adjustable band gap as claimed in any one of claims 2-5.

7. Use of the optoelectronic element as claimed in claim 6 in light emission, photodetection and display.

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