A DJ-type two-dimensional perovskite LPbI4 single crystal based on organic ligands of different chain lengths, its preparation method and luminescence modulation method

Abstract

This invention discloses a D-J type two-dimensional perovskite LPbI4 single crystal based on organic ligands of different chain lengths, its preparation method, and its luminescence control method, belonging to the technical field of lead halide perovskite materials. The growth process of the two-dimensional perovskite LPbI4 single crystal is controlled by adjusting the raw material ratio, reaction heating temperature, and annealing temperature and time, ultimately producing a two-dimensional D-J type perovskite LPbI4 single crystal with n=1. This preparation method introduces defects, achieving bicolor emission even without doping. Furthermore, the emission color can be controlled by pulsed excitation light with different power densities or pulse frequencies. The emission color continuously changes from blue to red with increasing excitation pulse power or frequency, and the emission color is reversible. The synthesis process is simple, environmentally friendly, and produces little pollution. It yields high crystal quality, more regular single crystal shape, and a convenient method for controlling the emission color.

Description

Technical Field

[0001] This invention relates to the field of lead halide perovskite materials technology, and in particular to a DJ-type two-dimensional perovskite LPbI4 single crystal based on organic ligands with different chain lengths, its preparation method, and its luminescence regulation method. Background Technology

[0002] Organic-inorganic hybrid perovskites, as novel "star" semiconductors, have become one of the hottest research materials in recent years due to their excellent photophysical properties. Their outstanding luminescence efficiency and wavelength tunability make them promising for applications in LEDs, X-ray scintillators, fluorescent sensors, and thermometers. Currently, the color and efficiency of their luminescence are mainly controlled by altering the morphology, chemical composition, and ion doping of perovskites. Regarding morphology control, it is often difficult to precisely control each stage of crystal growth, resulting in products with poor crystal quality, poor reproducibility, size inhomogeneity, and poor stability. Regarding chemical composition control, although changing the halogen ratio at the X-site can adjust the band gap and luminescence intensity, photo-induced phase separation limits its application range. As for ion doping, doped metal ion luminescence is a type of impurity energy level recombination luminescence distinct from defect luminescence, typically exhibiting broadband emission and a long fluorescence lifetime. Commonly used luminescent ions include Mn. 2+ Bi 3+ Sb 3+ Cd 2+ Cu 2+ Te 4+ Rare earth ions, etc. With Mn 2+ Taking doping as an example, when electrons transition to the excited state under photoexcitation, their radiative recombination mainly occurs through two pathways: one is direct recombination between excited-state electrons and holes, resulting in a radiative transition back to the ground state; the other is through excitons via Mn. 2+ The d→d* radiative transition produces luminescence, thereby introducing Mn into the emission spectrum. 2+ It exhibits a broad orange-red emission, with a fluorescence lifetime typically on the order of μs to ms. However, among all three-dimensional metal halide perovskites, CsPbCl3 has the most suitable band gap for free excitons to migrate towards Mn. 2 + The d-state energy level transition occurs, therefore Mn 2+ Doped CsPbCl3 exhibits narrow band-edge emission and broad orange light emission.

[0003] Lead halide perovskite materials possess excellent photophysical properties, such as long carrier lifetime, long diffusion length, and high photoluminescence quantum yield (PLQY), showing great promise for applications in solar cells, light-emitting diodes (LEDs), and other optoelectronic devices. In perovskite semiconductor materials, doping with heteroatoms is a common method for controlling their optical properties. Compared to semiconductors such as CdS or CdSe, lead halide perovskites have a more flexible lattice structure and higher ion mobility, making it easier for homovalent or heterovalent ions to be doped into their crystal structure. For example, perovskites with mixed halide compositions can be prepared through simple ion exchange, thereby enabling the control of their bandgap energy and emission spectrum throughout the visible light region; furthermore, the metal cation Pb in lead halide perovskites... 2+ It can also be reacted with divalent metal cations (such as Sn). 2+ Cu 2+ and Mn 2+ Pb may be partially or completely replaced. 2+ The replacement of heavy metals not only reduces the use of heavy metals, but also introduces a wealth of optical, magnetic, and electrical properties into the main material; in Mn 2+ In doped CsPbCl3 nanocrystals (NCs), some photogenerated excitons from the perovskite host can be transferred to Mn. 2+ Regarding dopants, Mn 2+ Ions pass through d→d * The transition enables downconversion emission, therefore Mn 2+ Doped perovskites exhibit bicolor emission, including high-energy bandgap emission and low-energy Mn emission. 2+ Emission, this characteristic makes Mn 2+ Doped perovskites have become candidate materials for light-emitting sources with tunable emission colors.

[0004] Cadmium-based halide perovskites are also considered materials with application potential, due to the presence of cadmium. 2+ and Pb 2+ With similar ionic radii, they exhibit excellent properties in enhancing the luminescence properties and stability of lead-based perovskites. For example, Boukheddaden et al. synthesized 1D (C6H)-based perovskites. 11 NH3)2CdBr4, its [CdBr6] 4- The broad peak (2.94 eV) of the octahedron mixed with the broad peak (2.53 eV) of the organic component forms a single-component white light emitting material. Furthermore, self-trapped excitons and intrinsic defects can also produce broadband emission; Michael Worku et al. reported broadband emission of one-dimensional C4N2H. 14PbBr4 perovskite exhibits a PLQY (Power, Quality, and Energy) of 20% for white light emission at room temperature, attributed to self-trapped exciton emission generated by its 1D structure. Currently, reported broadband-emission perovskite materials cover the entire visible light spectrum; however, research on highly efficient luminescent perovskite materials still faces numerous challenges. Therefore, understanding the regulation of luminescence properties, the exploration of luminescence mechanisms, and their physical property relationships is crucial.

[0005] Therefore, developing novel lead-free halide perovskites, controlling their optical properties such as luminescence color and luminescence efficiency, and studying their luminescence mechanism are of great significance for expanding their application fields. Summary of the Invention

[0006] The purpose of this invention is to provide a DJ-type two-dimensional perovskite LPbI4 single crystal based on organic ligands of different chain lengths, along with its preparation method and luminescence modulation method. Using alkyl diamine ligands of different chain lengths, a two-dimensional DJ-type perovskite LPbI4 single crystal with n=1 is prepared. This preparation method introduces defects, achieving dual-color emission even without doping, and the emission color can be modulated by changing the excitation power and frequency.

[0007] To achieve the above objectives, this invention provides a method for controlling the luminescence of DJ-type two-dimensional perovskite LPbI4 single crystals based on organic ligands of different chain lengths. The luminescence color of the two-dimensional perovskite LPbI4 single crystal is controlled by excitation with pulsed excitation light of different power densities or pulse frequencies. The luminescence color changes continuously from blue to red as the excitation light power density or pulse frequency increases, and changes continuously from red to blue as the excitation light power density or pulse frequency decreases.

[0008] Preferably, the pulse frequency of the pulsed excitation light is: the excitation light repetition frequency range is 0.01–41 MHz, the laser single pulse energy is consistent for different repetition frequencies, and the laser single pulse energy is 3.5 μJ / cm² during fluorescence spectroscopy testing. -2 The laser single-pulse energy during bright-field imaging is 7 μJ / cm². -2 and 10.5 μJcm -2 .

[0009] Preferably, the power density of the pulsed excitation light is as follows: during fluorescence spectroscopy testing, the excitation light repetition frequency is 2MHz, and the range of the changed laser power is 0.001–10uw; during bright-field imaging, the laser repetition frequency is 5MHz, and the range of the changed laser power is 0.001–20uw; it is divided into wide-field and fixed-point excitation, and the excitation wavelength is 405nm.

[0010] The present invention also provides a two-dimensional perovskite LPbI4 single crystal whose emission color is controlled by the above-mentioned emission control method, wherein the two-dimensional perovskite LPbI4 single crystal is a two-dimensional DJ-type perovskite single crystal.

[0011] The above-mentioned method for preparing DJ-type two-dimensional perovskite LPbI4 single crystals based on organic ligands of different chain lengths is as follows: The two-dimensional perovskite LPbI4 single crystals are obtained by the ion exchange reaction between solid PbI2 and organic ligands in HI solution. The growth process of the two-dimensional perovskite LPbI4 single crystals is controlled by adjusting the proportion of ions in the solution, the reaction heating temperature, and the annealing temperature and time. The basic principle of its synthesis is:

[0012] PbI2(s)+L(s)+2I - →LPbI4(s)

[0013] Preferably, the organic ligand is an alkyl diamine, the two-dimensional perovskite LPbI4 single crystal has a regular morphology and a geometric shape, and the geometric shape of the two-dimensional perovskite LPbI4 single crystal is related to the chain length of the alkyl diamine.

[0014] Preferably, the specific preparation includes the following steps:

[0015] (1) Mix solid PbI2 with organic ligands and place them in a reaction flask. Add hydroiodic acid dropwise into the reaction flask in small amounts several times. Heat and stir until the solid reactants are just completely dissolved.

[0016] (2) The solution in step (1) is gradually and uniformly cooled until the concentration reaches saturation and perovskite solid is precipitated to obtain the mother liquor.

[0017] (3) Place the coverslip, which has been cleaned by ultrasonication with ethanol and plasma cleaning machine, on the heating stage. Use a cotton swab to apply a small amount of the mother liquor from step (2) onto the coverslip for annealing. Let it stand for 5–30 seconds until it is completely dry to obtain a regular two-dimensional perovskite LPbI4 single crystal.

[0018] Preferably, in step (1), the molar ratio of solid PbI2 to organic ligand is (0.5-4):1.

[0019] Preferably, the heating and stirring temperature in step (1) is 80-180℃.

[0020] Preferably, the annealing temperature of the coverslip in step (3) is 50–120°C.

[0021] Therefore, the present invention employs the above-mentioned DJ-type two-dimensional perovskite LPbI4 single crystal based on organic ligands of different chain lengths, its preparation method, and its luminescence modulation method, which have the following beneficial effects:

[0022] (1) The two-dimensional DJ-type perovskite LPbI4 single crystal material based on alkyl diamines of different chain lengths as organic ligands described in this invention employs a simple one-step method to synthesize a saturated solution and rapidly anneal to precipitate single crystals. The synthesis process is simple, environmentally friendly, and produces minimal pollution, enabling the rapid, economical, and green synthesis of two-dimensional perovskite LPbI4 single crystals with alkyl diamines of different chain lengths as organic ligands. The micron-sized DJ-type two-dimensional perovskite LPbI4 single crystals synthesized by this method exhibit high crystal quality and more regular single crystal shapes.

[0023] (2) This invention prepares two-dimensional DJ-type perovskite LPbI4 single crystals with different n=1 by changing the chain length of the organic ligands in the two-dimensional perovskite; introduces defects through a synthesis method of rapid annealing of single crystals on a coverslip with a saturated solution to achieve bicolor emission of the perovskite; and effectively controls the emission color of the micron-sized DJ-type two-dimensional perovskite LPbI4 single crystals by simply changing the excitation pulse power and frequency, which is beneficial for its design and application in photovoltaic devices. This invention has the advantages of simple operation, low equipment requirements, no need for expensive reaction devices, and ease of large-scale synthesis, and is expected to generate good social and economic benefits.

[0024] (3) Unlike the more common RP-type two-dimensional perovskite L2PbI4 single crystals supported by van der Waals forces, the two-dimensional perovskite LPbI4 single crystals prepared in this invention are DJ-type. The organic ligands, acting as bifunctional divalent cations, give the DJ-type two-dimensional perovskite LPbI4 single crystals of this invention a more stable structure. Furthermore, current research on the photophysical properties and carrier dynamics of DJ-type two-dimensional perovskites is not yet in-depth. Previous synthesized samples were mostly powdered single crystals or polycrystalline thin films, inevitably influenced by grain size and grain boundaries. The LPbI4 single crystals prepared in this invention have a very regular shape and excellent single crystal quality, making them an excellent substrate for studying the intrinsic photophysical properties of DJ-type two-dimensional perovskites.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 This is a microscope image of the two-dimensional perovskite LPbI4 single crystal in Example 1;

[0027] Figure 2 This is a microscope image of the two-dimensional perovskite LPbI4 single crystal in Example 2;

[0028] Figure 3 This is a SEM image of a two-dimensional perovskite LPbI4 single crystal from Example 1;

[0029] Figure 4 This is a SEM image of a two-dimensional perovskite LPbI4 single crystal from Example 2;

[0030] Figure 5 The UV-Vis absorption spectrum and steady-state fluorescence spectrum of the two-dimensional perovskite LPbI4 single crystal in Example 1 are shown.

[0031] Figure 6 The UV-Vis absorption spectrum and steady-state fluorescence spectrum of the two-dimensional perovskite LPbI4 single crystal in Example 2 are shown.

[0032] Figure 7 The power-dependent normalized fluorescence emission spectrum of the two-dimensional perovskite LPbI4 single crystal in Example 3;

[0033] Figure 8 The power-dependent normalized fluorescence emission spectrum of the two-dimensional perovskite LPbI4 single crystal in Example 4;

[0034] Figure 9 The two-dimensional perovskite LPb in Example 5 I4 Frequency-dependent normalized fluorescence emission spectrum of a single crystal;

[0035] Figure 10 The frequency-dependent normalized fluorescence emission spectrum of the two-dimensional perovskite LPbI4 single crystal in Example 6;

[0036] Figure 11 These are photographs showing the change in emission color of the two-dimensional perovskite LPbI4 single crystal after changing the excitation light power density in Example 3.

[0037] Figure 12 This is a photograph showing the change in emission color of the two-dimensional perovskite LPbI4 single crystal after changing the excitation light power density in Example 4.

[0038] Figure 13 This is a photograph showing the change in the emission color of the two-dimensional perovskite LPbI4 single crystal after changing the laser pulse frequency in Example 5.

[0039] Figure 14 This is a photograph showing the change in the emission color of the two-dimensional perovskite LPbI4 single crystal after changing the laser pulse frequency in Example 6. Detailed Implementation

[0040] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0041] This invention provides a method for controlling the luminescence of DJ-type two-dimensional perovskite LPbI4 single crystals based on organic ligands of different chain lengths. The two-dimensional perovskite LPbI4 single crystal is a two-dimensional DJ-type perovskite single crystal. The emission color is controlled by excitation with pulsed light of different power densities or pulse frequencies. The emission color changes continuously from blue to red as the excitation light pulse power or frequency increases; the emission color changes continuously from red to blue as the excitation light power density or pulse frequency decreases.

[0042] The pulse frequency of the pulsed excitation light is as follows: the repetition frequency range of the excitation light is 0.01–41 MHz, and the energy of the single laser pulse remains consistent for different repetition frequencies. The energy of the single laser pulse during fluorescence spectroscopy testing is 3.5 μJ / cm². -2 The laser single-pulse energy during bright-field imaging is 7 μJ / cm². -2 and 10.5 μJcm -2 .

[0043] The power density of the pulsed excitation light is as follows: during fluorescence spectroscopy testing, the excitation light repetition frequency is 2MHz, and the laser power range is 0.001–10uw; during bright-field imaging, the laser repetition frequency is 5MHz, and the laser power range is 0.001–20uw; it is divided into wide-field and fixed-point excitation, and the excitation wavelength is 405nm.

[0044] The method for preparing two-dimensional perovskite LPbI4 single crystals based on organic ligands with different chain lengths involves a chemical reaction between solid PbI2 and organic ligands in HI solution. The growth process of the two-dimensional perovskite LPbI4 single crystals is controlled by adjusting the proportion of ions in the solution, the reaction heating temperature, and the annealing temperature and time, and the final result is obtained.

[0045] The organic ligand is an alkyl diamine. The two-dimensional perovskite LPbI4 single crystal has a regular morphology and a geometric shape. The geometric shape of the two-dimensional perovskite LPbI4 single crystal is related to the chain length of the alkyl diamine.

[0046] The specific preparation includes the following steps:

[0047] (1) Mix solid PbI2 with organic ligands in a molar ratio of (0.5-4):1 and place it in a reaction flask. Add hydroiodic acid dropwise to the reaction flask in small amounts several times. Heat and stir at 80-180℃ until the solid reactants are just completely dissolved.

[0048] (2) The solution in step (1) is gradually and uniformly cooled until the concentration reaches saturation and perovskite solid is precipitated to obtain the mother liquor.

[0049] (3) Place the coverslip, which has been cleaned by ultrasonication with ethanol and plasma cleaning machine, on the heating stage. Use a cotton swab to apply a small amount of the mother liquor from step (2) onto the coverslip. Anneal at 50–120°C and let stand for 5–30 seconds until completely dry to obtain a regular two-dimensional perovskite LPbI4 single crystal.

[0050] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered within the scope of protection of this invention.

[0051] In this embodiment, a UV-Vis absorption spectrometer (UV-6000PC, Shanghai Yuanxi Instrument Co., Ltd.) was used to measure the UV-Vis absorption spectrum; a 405nm laser (PIXEA-405, Aurea Technology, France) was used as the excitation source, and a spectrometer (SpectraPro-2300i, Acton Research Co., USA) was used to collect the fluorescence spectrum. X-ray diffraction (XRD) spectroscopy was used to analyze the crystal structure of the material, field emission scanning electron microscopy (FESEM) and dark-field optical microscopy were used to observe the morphology and size of the material, and transmission electron microscopy (TEM) was used to analyze the microcrystalline structure.

[0052] Example 1

[0053] This embodiment provides a two-dimensional perovskite LPbI4 single crystal, prepared as follows: Solid PbI2 and 1,4-butanediamine in a molar ratio of 2:1 are placed in a reaction flask. HI is added in small amounts several times, accompanied by heating and stirring at 160°C until the solid reactants are just completely dissolved. The solution is then gradually and uniformly cooled until the concentration is saturated, and perovskite solid precipitates. A coverslip that has been ultrasonically cleaned with ethanol and then cleaned with a plasma cleaner is placed on an 80°C heating stage. A small amount of the mother liquor is applied to the coverslip with a cotton swab, and the solution is left to stand for 30 seconds until completely dry, thus producing a two-dimensional perovskite LPbI4 single crystal.

[0054] The crystal appears as shown in microscope and SEM images, respectively. Figure 1 as well as Figure 3 As shown in the image, the crystal has a regular hexagonal morphology. The UV-Vis absorption spectrum and steady-state fluorescence spectrum of the crystal are shown below. Figure 5 As shown, its exciton resonance absorption peak is 496 nm, and the center wavelength of the exciton emission peak is 506 nm. In addition to the exciton emission peak, a broadband emission with a center wavelength of 663 nm appears in the long-wavelength band, which belongs to defect state emission.

[0055] Example 2

[0056] This embodiment provides a two-dimensional perovskite LPbI4 single crystal, prepared as follows: Solid PbI2 and 1,6-hexanediamine in a molar ratio of 2:1 are placed in a reaction flask. HI is added in small amounts several times, accompanied by heating and stirring at 150°C until the solid reactants are just completely dissolved. The solution is then gradually and uniformly cooled until the concentration is saturated, and perovskite solid precipitates. A coverslip that has been ultrasonically cleaned with ethanol and then cleaned with a plasma cleaner is placed on an 80°C heating stage. A small amount of the mother liquor is applied to the coverslip with a cotton swab, and the solution is left to stand for 30 seconds until completely dry, thus producing a two-dimensional perovskite LPbI4 single crystal.

[0057] The crystal appears as shown in microscope and SEM images, respectively. Figure 2 as well as Figure 4 As shown in the image, the crystal has a regular, quadrilateral morphology. The UV-Vis absorption spectrum and steady-state fluorescence spectrum of the crystal are shown below. Figure 6 As shown (normalized to the exciton peak), its exciton resonance absorption peak is 486 nm, and the center wavelength of the exciton emission peak is 496 nm. In addition to the exciton emission peak, a broadband emission with a center wavelength of 666 nm appears in the long-wavelength band, which belongs to defect state emission.

[0058] Example 3

[0059] This embodiment uses the two-dimensional perovskite LPbI4 single crystal prepared in Example 1. The emission color is modulated by changing the power density of the excitation light. For fluorescence spectroscopy testing, the repetition frequency is 2 MHz, and the laser power range is 0.001–10 μW. For bright-field imaging, the repetition frequency is 5 MHz, and the laser power range is 0.001–20 μW. Both wide-field and fixed-point excitation methods are used, with an excitation wavelength of 405 nm. The power-dependent normalized fluorescence emission spectrum of this crystal is as follows: Figure 7 As shown in the figure (normalized to exciton peaks), it can be seen that with the increase of excitation power, the proportion of defect luminescence first increases, reaching 3.57 mJ / cm². -2 The emission color reaches its maximum at a certain point, after which the proportion of defect-state emission gradually decreases with increasing or decreasing excitation power. Images showing the color change after changing the excitation power density are shown below. Figure 11 As shown in the image, the color of the crystal's emission changes continuously from blue to red as the power density increases.

[0060] Example 4

[0061] In this embodiment, the emission color of the two-dimensional perovskite LPbI4 single crystal prepared in Example 2 was modulated by changing the power density of the excitation light. During fluorescence spectroscopy testing, the repetition frequency was 2 MHz, and the laser power range was 0.001–10 μW. For bright-field imaging, the repetition frequency was 5 MHz, and the laser power range was 0.001–20 μW. Both wide-field and fixed-point excitation methods were used, with an excitation wavelength of 405 nm. The power-dependent normalized fluorescence emission spectrum of this crystal is shown below. Figure 8 As shown in the figure (normalized to exciton peaks), it can be seen that with the increase of excitation power, the proportion of defect luminescence first increases, reaching 3.18 mJ / cm². -2 The emission color reaches its maximum at a certain point, after which the proportion of defect-state emission gradually decreases with increasing or decreasing excitation power. Images showing the color change after changing the excitation power density are shown below. Figure 12 As shown in the image, the color of the crystal's emission changes continuously from blue to red as the power density increases.

[0062] Example 5

[0063] This embodiment uses the two-dimensional perovskite LPbI4 single crystal prepared in Example 1. The emission color is modulated by changing the excitation light pulse frequency. The excitation light repetition frequency range is 0.01-41 MHz, and the laser single pulse energy remains consistent across different repetition frequencies. During fluorescence spectroscopy testing, the laser single pulse energy is consistently 3.5 μJ / cm². -2 During bright-field imaging, the laser single-pulse energy is 7 and 10.5 μJ / cm². -2 The frequency-dependent normalized fluorescence emission spectrum of this crystal is as follows: Figure 9 As shown (normalized to exciton peaks), the proportion of broadband spectrum caused by defect states gradually increases with the increase of excitation power.

[0064] The image shows the change in the emitted color of the crystal after the laser pulse frequency is changed. Figure 13 As shown, the color of the crystal's emission changes continuously from blue to red as the pulse frequency increases.

[0065] Example 6

[0066] This embodiment uses the two-dimensional perovskite LPbI4 single crystal prepared in Example 2. The emission color is modulated by changing the excitation light pulse frequency. The excitation light repetition frequency range is 0.01-41 MHz, and the laser single pulse energy remains consistent across different repetition frequencies. During fluorescence spectroscopy testing, the laser single pulse energy is consistently 3.5 μJ / cm². -2 During bright-field imaging, the laser single-pulse energy is 7 and 10.5 μJ / cm². -2 The frequency-dependent normalized fluorescence emission spectrum of this crystal is as follows: Figure 10 As shown (normalized to exciton peaks), the proportion of broadband spectrum caused by defect states gradually increases with the increase of excitation power.

[0067] The image shows the change in the emitted color of the crystal after the laser pulse frequency is changed. Figure 14 As shown, the color of the crystal's emission changes continuously from blue to red as the pulse frequency increases.

[0068] Therefore, this invention provides a DJ-type two-dimensional perovskite LPbI4 single crystal based on organic ligands with different chain lengths, as well as its preparation method and luminescence regulation method. Using alkyl diamine ligands with different chain lengths, a two-dimensional DJ-type perovskite LPbI4 single crystal with n=1 is prepared. This preparation method introduces defects, enabling the generation of dual-color emission even without doping, and the emission color can be regulated by changing the excitation light power and frequency.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for controlling the luminescence of DJ-type two-dimensional perovskite LPbI4 single crystals based on organic ligands of different chain lengths, characterized in that, The two-dimensional perovskite LPbI4 single crystal is excited and its emission color is controlled by pulsed excitation light with different power densities or pulse frequencies. The emission color changes continuously from blue to red as the excitation light pulse power or frequency increases, and the emission color is reversible. The two-dimensional perovskite LPbI4 single crystal is a two-dimensional DJ-type perovskite single crystal. The two-dimensional perovskite LPbI4 single crystal was prepared by an ion exchange reaction between solid PbI2 and organic ligands in HI solution. The growth process of the two-dimensional perovskite LPbI4 single crystal was controlled by adjusting the proportion of ions in the solution, the reaction heating temperature, and the annealing temperature and time. The organic ligand is an alkyl diamine, which is 1,4-butanediamine or 1,6-hexanediamine; the two-dimensional perovskite LPbI4 single crystal has a regular morphology and a geometric shape, and the geometric shape of the two-dimensional perovskite LPbI4 single crystal is related to the chain length of the alkyl diamine. The specific preparation of the two-dimensional perovskite LPbI4 single crystal includes the following steps: (1) Mix solid PbI2 with organic ligands in a reaction flask, add hydroiodic acid dropwise to the reaction flask in small amounts, and heat and stir until the solid reactants are just completely dissolved; (2) The solution in step (1) is gradually and uniformly cooled until the concentration reaches saturation and perovskite solid is precipitated to obtain the mother liquor; (3) Place the coverslip that has been cleaned by ultrasonication with ethanol and plasma cleaning machine on the heating stage, dip a small amount of the mother liquor in step (2) into a cotton swab, apply it to the coverslip and anneal, let stand for 5–30 seconds until it is completely dry, and obtain a two-dimensional perovskite LPbI4 single crystal with regular morphology. In step (1), the molar ratio of solid PbI2 to organic ligand is (0.5-4):1; The heating and stirring temperature in step (1) is 80-180℃; In step (3), the annealing temperature of the coverslip is 50–120℃.

2. The method for controlling the luminescence of DJ-type two-dimensional perovskite LPbI4 single crystals based on organic ligands of different chain lengths according to claim 1, characterized in that, The pulse frequency of the pulsed excitation light is: the repetition frequency range of the excitation light is 0.01–41 MHz, and the energy of the single laser pulse remains consistent for different repetition frequencies. The energy of the single laser pulse during fluorescence spectroscopy testing is 3.5 μJ / cm². -2 The laser single-pulse energy during bright-field imaging is 7 μJ / cm². -2 and 10.5 μJcm -2 .

3. The method for controlling the luminescence of DJ-type two-dimensional perovskite LPbI4 single crystals based on organic ligands of different chain lengths according to claim 1, characterized in that, The power density of the pulsed excitation light is as follows: during fluorescence spectroscopy testing, the excitation light repetition frequency is 2MHz, and the laser power range is 0.001–10uw; during bright-field imaging, the laser repetition frequency is 5MHz, and the laser power range is 0.001–20uw; it is divided into wide-field and fixed-point excitation, and the excitation wavelength is 405nm.

Images