Application of a non-chiral perovskite single crystal material in polarized fluorescence

Abstract

The application provides application of a non-chiral perovskite single crystal material in polarized fluorescence. The perovskite single crystal material has a molecular formula of (4-AMP)PbBr4, wherein 4-AMP is 4-aminomethylpiperidine. The (4-AMP)PbBr4 single crystal material is prepared by dissolving 4-AMP and lead bromide in a hydrobromic acid solution, slowly reducing to room temperature after heating to complete dissolution, and washing, centrifuging and drying the precipitate to obtain the (4-AMP)PbBr4 single crystal. The (4-AMP)PbBr4 single crystal prepared by the application is a non-chiral material, but has optical activity due to low symmetry of the crystal structure. Under the condition of linear polarized light excitation and circular polarized light detection, the maximum polarization degree of the perovskite single crystal material can reach 54%, and the polarization degree can be controlled by rotating the crystal. The preparation method has the advantages of low raw material price, mild conditions and simple operation, and the synthesized (4-AMP)PbBr4 single crystal has the characteristics of large polarization degree and easy control.

Description

TECHNICAL FIELD

[0001] The application relates to an application of an achiral perovskite single crystal material in polarized fluorescence and belongs to the field of polarized fluorescence. BACKGROUND

[0002] In recent years, the application of circularly polarized luminescence (CPL) in the fields of biological imaging, information storage, optoelectronics, spintronics, etc. has attracted widespread attention. Chiral materials with circular dichroism (CD), such as organic molecules, lanthanide complexes and liquid crystals, are widely used in the research of circularly polarized luminescence due to their differential absorption of left circularly polarized light (σ-) and right circularly polarized light (σ+). However, due to the relatively poor carrier mobility of organic molecules and the complex preparation process of inorganic semiconductor materials, the application of these materials in commercial devices is greatly limited. Therefore, it is very important to further develop low-cost, excellent optoelectronic properties and polarized fluorescence active materials to promote the development of the field of polarized fluorescence.

[0003] Organic lead halide perovskite materials (LHPs) have become star materials in the field of optoelectronic applications in recent years due to their large diffusion coefficient, long carrier lifetime and fast interface charge transfer rate. At the same time, their excellent optical properties also make them widely used in the field of polarized fluorescence. By using chiral organic molecules to replace the A-site cations, chiral perovskites can be directly synthesized. At present, a large number of low-dimensional chiral perovskite materials have been reported to realize the emission and detection of circularly polarized luminescence, such as (R- / S-MBA)2PbI4 (ACS Nano 2019, 13, 3659), (R / S)-α-(PEA)2PbI4 (ACS Nano 2019, 13, 9473), C5H 14 N2PbC l4 ·H2O (J. Mater. Chem. C 2018, 6, 6033). Among them, (S-MBA)2PbI4 can exhibit a fluorescence polarization degree of 17% at 77K, which is the highest value reported in the literature. However, the chiral ligand in chiral perovskite usually has a large band gap, and the different responses to circularly polarized light through the R- / S- configuration of the ligand also limit the further regulation of polarized fluorescence. Therefore, it is of great practical value to develop achiral perovskites with polarized fluorescence activity and easy regulation.

[0004] Currently, some achiral perovskite materials have been reported to achieve circularly polarized fluorescence emission. Among them, two-dimensional Dion-Jacobson (D-J) phase perovskite (4-AMP) PbI4 has a large Rashba splitting energy (~80 meV), and can achieve a fluorescence polarization degree of 24% under circularly polarized light excitation at room temperature (J. Am. Chem. Soc. 2019, 141, 15972). However, when linearly polarized light is used for excitation, most achiral perovskite materials will no longer have polarized fluorescence activity. According to the existing literature reports, only (BA)2PbI4 can achieve a circularly polarized fluorescence response of 4.8% under linearly polarized light excitation (Adv. Optical Mater. 2022, 10, 2101232), and there is no report on the regulation of the fluorescence polarization degree of achiral perovskite materials. Therefore, under linearly polarized light excitation at room temperature, achiral perovskite materials with large fluorescence polarization degree and easy regulation of fluorescence polarization degree have not been reported in Chinese patents. SUMMARY

[0005] One of the purposes of the present application is to provide the application of achiral perovskite (4-AMP) PbBr4 single crystal material in polarized fluorescence emission.

[0006] The second purpose of the present application is to provide a method for regulating the fluorescence polarization degree of (4-AMP) PbBr4 single crystal material.

[0007] The third purpose of the present application is to provide a preparation method of achiral perovskite (4-AMP) PbBr4 single crystal material.

[0008] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0009] An achiral perovskite single crystal material has a molecular formula of (4-AMP) PbBr4, wherein 4-AMP is 4-aminomethylpiperidine.

[0010] Preferably, the crystal structure of the achiral perovskite single crystal material belongs to the Pca21 space group and the mm2 point group, and the low structural symmetry of the achiral perovskite single crystal material leads to optical activity.

[0011] The application of the achiral perovskite (4-AMP) PbBr4 single crystal material in polarized fluorescence. The application method is to place the (4-AMP) PbBr4 single crystal on a fluorescence spectrometer, use linearly polarized light for excitation, and circularly polarized light for detection, and collect the left-handed and right-handed fluorescence spectra of the (4-AMP) PbBr4 single crystal, respectively.

[0012] Preferably, the excitation light wavelength is 375-406 nm, and the fluorescence spectrum collection range is 300-800 nm.

[0013] The fluorescence polarization degree of the achiral perovskite (4-AMP) PbBr4 single crystal material is regulated. Specifically, the (4-AMP) PbBr4 single crystal is rotated, and the left-handed and right-handed fluorescence spectra of the (4-AMP) PbBr4 single crystal at different angles are collected respectively.

[0014] Preferably, the rotation angle of the (4-AMP) PbBr4 single crystal is 45°-360°.

[0015] The preparation method of the achiral perovskite (4-AMP) PbBr4 single crystal material specifically comprises the following steps:

[0016] (1) Lead oxide and 4-AMP are added to a beaker;

[0017] (2) Hydrobromic acid is added to the beaker of step (1) and stirred until uniform;

[0018] (3) Heating to complete dissolution, then slowly reducing to room temperature, and collecting the precipitate;

[0019] (4) The precipitate of step (3) is washed with diethyl ether, suction filtered, and naturally dried at room temperature.

[0020] Preferably, the molar ratio of 4-AMP to lead oxide in step (1) is 1:1.

[0021] Preferably, the concentration of hydrobromic acid in step (2) is 48wt%.

[0022] Preferably, the heating temperature in step (3) is 130℃.

[0023] Preferably, the cooling rate in step (3) is 2℃ / h.

[0024] Under the conditions of online polarized light excitation and circularly polarized light detection, the maximum polarization degree of the perovskite single crystal material can reach 54%, and the polarization degree can be regulated by rotating the crystal. The preparation method has the advantages of low raw material price, mild conditions, simple operation, etc., and the synthesized (4-AMP) PbBr4 single crystal has the characteristics of high polarization degree and easy regulation.

[0025] The advantages of the present application are:

[0026] 1. The preparation method of the achiral perovskite (4-AMP) PbBr4 single crystal material has the advantages of mild conditions, simple operation, and low cost. The prepared (4-AMP) PbBr4 single crystal material has high crystallinity, wide fluorescence emission range, and good optical properties.

[0027] 2. The achiral perovskite (4-AMP)PbBr4 single crystal material has polarized fluorescence activity, and can exhibit a large degree of fluorescence polarization under a room temperature condition without a magnetic field.

[0028] 3. The (4-AMP)PbBr4 single crystal material can realize regulation of the degree of fluorescence polarization by rotating the crystal, and has potential application value in the fields of imaging, optoelectronics, spintronics and the like. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 XRD pattern of the (4-AMP)PbBr4 single crystal material;

[0030] Figure 2 UV-vis and PL patterns of the (4-AMP)PbBr4 single crystal material;

[0031] Figure 3 CD pattern of the (4-AMP)PbBr4 single crystal material;

[0032] Figure 4 Polarized fluorescence spectrum light path diagram;

[0033] Figure 5 Polarized fluorescence spectrum of the (4-AMP)PbBr4 single crystal material under excitation of 375 nm linearly polarized light;

[0034] Figure 6 Polarized fluorescence spectrum of the (4-AMP)PbBr4 single crystal material under excitation of 406 nm linearly polarized light;

[0035] Figure 7 Left-handed and right-handed fluorescence intensities of the (4-AMP)PbBr4 single crystal material under excitation of 375 nm linearly polarized light corresponding to rotation of different angles;

[0036] Figure 8 Degree of polarization and crystal rotation angle of the (4-AMP)PbBr4 single crystal material under excitation of 375 nm linearly polarized light. DETAILED DESCRIPTION

[0037] In order to further illustrate the present application, the following examples are given, but it does not limit the scope of the invention defined in each additional claim.

[0038] Example 1: Preparation of achiral perovskite (4-AMP)PbBr4 single crystal material

[0039] Lead oxide (11.3 mg, 0.05 mmol), 4-AMP (64.1 μl, 0.05 mmol) were weighed into a 25 ml beaker, 4 ml of 48 wt% hydrobromic acid was added, stirred until homogeneous, the beaker was moved to a hot plate and heated to 130 °C, after the solution was completely clear, the programmed cooling method was used to cool to room temperature at a rate of 2 °C / h, light yellow crystals were obtained, washed with diethyl ether, suction filtered, and naturally dried at room temperature to obtain the target material (4-AMP)PbBr4, the yield was about 85% (calculated based on 4-AMP).

[0040] The XRD results of the prepared product are shown in Figure 1 The figure shows that the measured X-ray powder diffraction curve of the (4-AMP)PbBr4 single crystal material is basically consistent with the simulated curve of the CIF file of the X-ray single crystal diffraction, indicating that the crystal has good crystallinity and high purity, and the difference in diffraction intensity is caused by the preferred orientation of the crystal.

[0041] Example 2: Optical properties of the (4-AMP)PbBr4 single crystal material prepared in Example 1

[0042] This example mainly investigates the optical properties of the (4-AMP)PbBr4 single crystal material prepared in Example 1, including optical absorption, fluorescence emission and chiral properties.

[0043] The (4-AMP)PbBr4 single crystal material was subjected to solid UV-vis spectroscopy test, and the test results are shown in Figure 2 The figure is a (4-AMP)PbBr4 single crystal material scanned by a solid ultraviolet spectrophotometer with white barium sulfate as a blank control group in the wavelength range of 300-800 nm. From Figure 2 It can be seen that the (4-AMP)PbBr4 single crystal material has good absorption in the ultraviolet region, and also has certain absorption in the visible region, and the absorption edge can reach 700 nm.

[0044] The PL emission is shown in Figure 2 The figure is a (4-AMP)PbBr4 single crystal scanned in the fluorescence spectrum collection range of 300-800 nm with an excitation light wavelength of 375 nm. The figure shows that the fluorescence emission peak center of the (4-AMP)PbBr4 single crystal is located at 550 nm, which has a larger Stocks shift compared to the absorption band edge, and the fluorescence emission range is wide, which is in the range of 400-780 nm. This feature indicates that the fluorescence of the (4-AMP)PbBr4 single crystal comes from the self-trapped exciton state (STE).

[0045] The CD spectrum of the (4-AMP)PbBr4 single crystal material is shown in Figure 3, which is the polarized fluorescence spectrum of (4-AMP)PbBr4 single crystal under the excitation wavelength of 375 nm and the scanning range of 300-600 nm. It can be seen from the figure that there is a certain difference between the absorption of left-handed and right-handed light of (4-AMP)PbBr4 single crystal, indicating that (4-AMP)PbBr4 single crystal material has a certain optical activity.

[0046] Example 3: Polarized fluorescence spectrum of (4-AMP)PbBr4 single crystal material prepared in Example 1

[0047] The (4-AMP)PbBr4 single crystal material was placed on the fluorescence spectrometer, and the left-handed and right-handed fluorescence spectra of (4-AMP)PbBr4 single crystal were collected respectively under the excitation of 375 nm linearly polarized light. The optical path diagram is shown in Figure 4 , the linearly polarized light excitation can be realized by adding a linear polarizer (2) between the laser (1) and the sample (3), and a lens group including a 1 / 4 wave plate (5) and a linear polarizer (6) is added between the sample (3) and the detector (7), and the left-handed and right-handed fluorescence can be detected respectively by rotating the linear polarizer (6).

[0048] The polarized fluorescence spectrum of (4-AMP)PbBr4 single crystal material under the excitation of 375 nm is shown in Figure 5 , which shows that there is a significant difference between the left-handed and right-handed fluorescence intensity of (4-AMP)PbBr4 single crystal material under the same excitation light intensity, and the right-handed fluorescence is stronger than the left-handed fluorescence. According to the formula P = (I R -I L ) / (I R +I L )(I R is the right-handed fluorescence intensity, and I L is the left-handed fluorescence intensity), the polarization degree is calculated to be 54%. Under the conditions of no magnetic field and room temperature, (4-AMP)PbBr4 single crystal material does not have chiral activity, but it can still achieve a polarization degree of more than 50%, which is obviously better than most chiral materials, and shows good application prospect.

[0049] Example 4: Polarized fluorescence spectrum of (4-AMP)PbBr4 single crystal material prepared in Example 1

[0050] The (4-AMP)PbBr4 single crystal material was placed on the fluorescence spectrometer, and the left-handed and right-handed fluorescence spectra of (4-AMP)PbBr4 single crystal were collected respectively under the excitation of 406 nm linearly polarized light, and the same optical path as in Example 3 was used Figure 4 .

[0051] This example mainly investigates the effect of excitation light wavelength on the polarized fluorescence spectrum of (4-AMP)PbBr4 single crystal material, and the results are shown in Figure 6shown. Under the excitation of 406 nm excitation light, the (4-AMP)PbBr4 single crystal material still has polarized fluorescence activity, and the right-handed fluorescence intensity is obviously stronger than the left-handed fluorescence. According to the formula P = (I R -I L ) / (I R +I L )(I R is the right-handed fluorescence intensity, and I L is the left-handed fluorescence intensity), the polarization degree is calculated to be 42.4%, indicating that the polarized fluorescence characteristics of the (4-AMP)PbBr4 single crystal material are universal.

[0052] Example 5: Regulation of the fluorescence polarization degree of the (4-AMP)PbBr4 single crystal material prepared in Example 1

[0053] The (4-AMP)PbBr4 single crystal material is placed on a fluorescence spectrometer, and is excited by 375 nm linearly polarized light. The crystal is rotated clockwise, and the rotation angles are 45°, 90°, 135°, 180°, 225°, 270°, 315° and 360°, respectively. The left-handed and right-handed fluorescence spectra of the (4-AMP)PbBr4 single crystal at different rotation angles are collected, respectively. According to the formula P = (I R -I L ) / (I R +I L )(I R is the right-handed fluorescence intensity, and I L is the left-handed fluorescence intensity), the fluorescence polarization degrees at different rotation angles are calculated to be 0.7%, -58.6%, -8.9%, 51.8%, -8.0%, -55.6%, 8.9% and 52.6%, respectively.

[0054] This example mainly investigates the regulation effect of rotating the (4-AMP)PbBr4 single crystal material on the fluorescence polarization degree. Figure 7 is the polar coordinate diagram of the left-handed and right-handed fluorescence intensities of the (4-AMP)PbBr4 single crystal material at different rotation angles under the excitation of 375 nm linearly polarized light. The rotation of the crystal can change the left-handed and right-handed fluorescence intensities. When the rotation angles are 90° and 270°, the relative intensities of the left-handed and right-handed fluorescence are reversed. Figure 8 is a graph of the relationship between the polarization degree of the (4-AMP)PbBr4 single crystal material and the rotation angle of the crystal. As can be seen from the graph, the polarization degree changes periodically with the rotation of the crystal, and the change range is -58.6% to 52.6%, indicating that the regulation of the fluorescence polarization degree can be realized by rotating the (4-AMP)PbBr4 crystal. This regulation method is simple, easy to operate and highly operable.

Claims

1. Use of a non-chiral perovskite single-crystal material in polarized fluorescence emission, characterized in that, The non-chiral perovskite single crystal material has a molecular formula of (4-AMP)PbBr4, wherein 4-AMP is 4-aminomethylpiperidine; the non-chiral peroviskite single crystal material adopts linear polarized light excitation and circular polarized light detection.

2. Use according to claim 1, characterized in that, The perovskite single crystal material belongs to Pca 21 space group, mm 2 point group, and the low structural symmetry leads to the optical activity of the achiral perovskite single crystal material.

3. Use according to claim 1, characterized in that, The rotation of the (4-AMP)PbBr4 single crystal material can realize the regulation of the degree of polarization.

4. Use according to claim 1, characterized in that, The preparation process of the non-chiral perovskite single crystal material is as follows: 4-AMP and lead oxide are dissolved in a hydrobromic acid solution, heated to complete dissolution, then cooled to room temperature, and the precipitate is washed, separated, and dried to obtain (4-AMP)PbBr4 crystals.

5. Use according to claim 4, characterized in that, The preparation process specifically comprises the following steps: (1) lead oxide and 4-AMP are added to a container; (2) hydrobromic acid is added to the container of step (1) and stirred until uniform; (3) heated to complete dissolution, then cooled to room temperature, and the precipitate is collected; (4) the precipitate of step (3) is washed with diethyl ether, suction filtered, and naturally dried at room temperature.

6. Use according to claim 4 or 5, characterized in that, The molar ratio of 4-AMP to lead oxide is 1:1 to 1:1.2; the concentration of the hydrobromic acid is 45 to 48 wt%; and the amount of the hydrobromic acid is 4 to 6 mL.

7. Use according to claim 4 or 5, characterized in that, The heating temperature is 125 to 140 DEG C; and the cooling rate of the cooling to room temperature is 2 to 5 DEG C / h.

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