Bromine-based two-dimensional chiral perovskite monocrystal nanosheet, and preparation method and application thereof

Abstract

The present application relates to a kind of bromine-based two-dimensional chiral perovskite monocrystal nanosheet and its preparation method and application, belong to the technical field of optoelectronic materials and devices.The bromine-based two-dimensional chiral perovskite monocrystal nanosheet is prepared by chiral organic ligand ((R)‑(+)‑1‑(2‑naphthyl)ethylamine or (S)‑(‑)‑1‑(2‑naphthyl)ethylamine), PbO and HBr in turn through natural cooling, vacuum filtration, toluene washing and purification after oil bath heating.Experimental results show that its morphology is monocrystal nanosheet, has good two-dimensional semiconductor photoelectric property, strong light absorption capacity, and has strong chiral characteristics simultaneously, can produce short-wavelength circularly polarized light, so it has great application prospect in circularly polarized laser and heterojunction photodetector.In addition, the preparation method of the bromine-based two-dimensional chiral perovskite monocrystal nanosheet is simple and easy to operate, the kind of raw material is less and the price is low, and the operation process does not need to be carried out in vacuum or nitrogen atmosphere.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic materials and devices, and relates to a bromine-based two-dimensional chiral perovskite single crystal nanosheet, a preparation method thereof, and an application thereof. Background Art

[0002] Organic-inorganic hybrid metal halide perovskite is a semiconductor material with excellent optoelectronic properties, and is widely used in photovoltaics, luminescence, and detection. Introducing chiral organic ligands into the inorganic metal halide perovskite skeleton can form chiral organic-inorganic hybrid metal halide perovskite (referred to as chiral perovskite). The chiral perovskite has chiral optical characteristics such as circular dichroism (CD) and circularly polarized luminescence (CPL), and thus has potential application prospects in nonlinear optical fields such as circularly polarized luminescence and detection. Compared with chiral perovskites, non-chiral perovskites generally do not have chiral optical properties, that is, they do not produce circular polarization. For example, the common three-dimensional MAPbI3 and quasi-two-dimensional (PEA)2(MA)3Pb4I 13 Non-chiral perovskite materials do not produce circularly polarized light and cannot be used in circularly polarized light detection. Although there are literature reports that these materials can produce circular polarization and emit circularly polarized light when placed in an external strong magnetic field with a magnetic intensity of approximately 17.5T. However, it is worth noting that the places with such strong magnetic field equipment are very limited, and because these strong magnetic fields are all pulsed magnetic fields, the magnetic field intensity is maintained for a short time and cannot be maintained permanently. It can be seen that it is relatively difficult to experimentally produce circular polarization in non-chiral perovskite materials. Therefore, chiral perovskite materials have a natural advantage. They do not require any external field and have circular polarization themselves. This provides opportunities for the development of nonlinear optical applications such as circularly polarized luminescence and detection.

[0003] Currently, the main methods for preparing chiral perovskite materials include in situ synthesis and ex situ synthesis. The in situ synthesis method involves first preparing an achiral inorganic metal halide perovskite system, then adding a chiral organic ligand to the system, and finally forming the chiral perovskite through a chemical reaction. For example, when preparing the chiral lead iodide perovskite (R / S-α-methylbenzylamine)2PbI4, lead oxide and hydroiodic acid are directly mixed. After the yellow lead oxide powder completely dissolves in the hydroiodic acid to form a yellow transparent solution, the chiral organic ligand is added. A large amount of orange-yellow precipitate quickly forms in the yellow transparent solution. The solution is then heated in an oil bath until the precipitate completely disappears, and then naturally cooled to obtain a needle-like orange-yellow (R / S-α-methylbenzylamine)2PbI4 single crystal. The specific preparation process of the heterositu synthesis method is: adding the prepared achiral metal halide inorganic perovskite to oleic acid or oleylamine, so that they wrap the surface of the inorganic perovskite, thereby forming a layer of stabilizer on the surface of the inorganic perovskite crystal, avoiding the destruction of the achiral inorganic perovskite crystal structure by the chiral organic ligands with higher polarity, thereby better making the chemical bond matching and hybridization between the chiral organic ligand and the inorganic perovskite, and finally growing a complete chiral perovskite single crystal.

[0004] However, both the in-situ synthesis method and the ex-situ synthesis method have the following shortcomings: (1) There are strict requirements on the experimental steps and experimental sequence; (2) The entire preparation process must be carried out in a vacuum or inert gas environment, which has strict requirements on experimental conditions and experimental equipment and is costly; (3) It takes a long time to obtain a single crystal, generally 2 to 3 days; (4) Surface stabilizers need to be introduced during the ex-situ synthesis process, which increases the cost of experimental raw materials; (5) It takes a lot of time to find the appropriate stirring time and heating temperature to prepare the chiral perovskite precursor solution, otherwise it will affect the formation of chiral perovskite single crystals or the chiral photocatalysis. (6) The chiral perovskite single crystals prepared are mainly iodine-based chiral perovskite single crystals, while pure bromine-based two-dimensional chiral perovskite single crystals have not been reported; (7) The color and shape of the prepared chiral perovskite single crystals are uncontrollable; (8) The circularly polarized luminescence wavelength of the prepared chiral perovskite is mainly concentrated in the long wavelength range of 450-800nm, and most of them show green circularly polarized light emission; (9) The polarization and circular dichroism of the prepared chiral perovskite are generally weak, and there are more asymmetric peaks in the circular dichroism spectrum and the wavelength range is wide, which is not conducive to the application and development of monochromatic circularly polarized light technology.

[0005] The current preparation process for chiral perovskites is complex and time-consuming, and the process requires high environmental requirements for moisture and oxygen, making it unsuitable for large-scale commercial production. Preparation can only be performed in laboratory glove boxes or vacuum chambers. Furthermore, reported circularly polarized luminescence (CPL) emission and detection of chiral perovskites lacks CPL in the short wavelength range of 200-400nm. This necessitates the development of chiral perovskite materials with simple preparation processes and methods, short CPL wavelengths, and promising applications in CPL emission and detection devices. Summary of the Invention

[0006] In view of this, one of the objects of the present invention is to provide a method for preparing bromine-based two-dimensional chiral perovskite single crystal nanosheets; a second object of the present invention is to provide a bromine-based two-dimensional chiral perovskite single crystal nanosheet; a third object of the present invention is to provide the application of bromine-based two-dimensional chiral perovskite single crystal nanosheets in the preparation of circularly polarized lasers or heterojunction photodetectors.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] 1. A method for preparing bromine-based two-dimensional chiral perovskite single crystal nanosheets, the preparation method being as follows:

[0009] (1) mixing a chiral organic ligand, lead monoxide, and hydrobromic acid to obtain a precursor solution;

[0010] The chiral organic ligand is any one of (R)-(+)-1-(2-naphthyl)ethylamine or (S)-(-)-1-(2-naphthyl)ethylamine;

[0011] (2) The precursor solution in step (1) is transferred to an oil bath for heating, heated to 150°C at a heating rate of 20°C / min, and then maintained for 20 minutes to obtain a colorless transparent solution. The colorless transparent solution is naturally cooled to room temperature to obtain a white snowflake-like solid, which is then vacuum filtered, washed with toluene, and purified to obtain bromine-based two-dimensional chiral perovskite single crystal nanosheets ((R / S-NEA)2PbBr4).

[0012] Preferably, the molar ratio of the chiral organic ligand, lead monoxide and hydrobromic acid in step (1) is 2:1:1.

[0013] Preferably, the specific operation process of the purification in step (2) is: first vacuuming and then heating and drying.

[0014] Preferably, the vacuuming time is 5 minutes; the heating and drying temperature is 100° C. and the time is 24 hours.

[0015] 2. Bromine-based two-dimensional chiral perovskite single crystal nanosheets prepared by the preparation method.

[0016] 3. Application of the bromine-based two-dimensional chiral perovskite single crystal nanosheets in the preparation of circularly polarized lasers or heterojunction photodetectors.

[0017] The present invention provides a bromine-based two-dimensional chiral perovskite single crystal nanosheet. The chiral perovskite single crystal nanosheet ((R / S-NEA)2PbBr4) is prepared by heating (R / S)-1-(2-naphthyl)ethylamine ((R / S)-NEA) as a chiral organic ligand with lead monoxide and hydrobromic acid in an oil bath, followed by natural cooling, vacuum filtration, washing with toluene, and purification. The prepared (R / S-NEA)2PbBr4 is a single crystal in the form of a white flake, exhibiting strong chiral characteristics and excellent two-dimensional semiconductor optoelectronic properties, crystallization properties, and crystal orientation. Furthermore, it exhibits strong circular dichroism intensity and can emit circularly polarized light with a wavelength less than 450nm, making it promising for use in circularly polarized lasers.

[0018] The present invention also provides a method for preparing bromine-based two-dimensional chiral perovskite single crystal nanosheets. The preparation method is simple, time-saving, has low chemical reagent loss, high single crystal formation rate, and large single crystal nanosheet size. Specifically, the following aspects are shown: (1) There is no requirement for the order of adding the chiral organic ligand, lead monoxide, and hydrobromic acid during the preparation process; (2) The entire preparation process can be carried out in an air environment; (3) When preparing the precursor solution, no stirring or heating is required, which reduces time costs; (4) The colorless and transparent solution can be directly washed with the single crystal after being cooled to room temperature, and the speed of obtaining the single crystal is very fast; (5) The chiral perovskite single crystals prepared have a high yield, have a flake morphology, are large in size, about 5 mm, and are easy to peel off from each other; (6) No surface stabilizer (oleylamine or oleic acid) is required, which reduces the complexity and time of the experiment.

[0019] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0021] Figure 1 Schematic diagram of the preparation process of bromine-based two-dimensional chiral perovskite single crystal nanosheets ((R / S-NEA)2PbBr4) in Example 1 and Example 2;

[0022] Figure 2 The crystalline form of the white snowflake-shaped solid with a right-handed configuration prepared in step (2) of Example 1 in a colorless transparent solution;

[0023] Figure 3 The appearance of the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((R-NEA)2PbBr4) with a right-handed configuration prepared in step (2) of Example 1;

[0024] Figure 4 This is a microscopic morphology of the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((R-NEA)2PbBr4) with a right-handed configuration prepared in step (2) of Example 1;

[0025] Figure 5 Circular dichroism spectra of the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((R-NEA)2PbBr4) with a right-handed configuration prepared in step (2) of Example 1 and the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((S-NEA)2PbBr4) with a left-handed configuration prepared in step (2) of Example 2;

[0026] Figure 6 The UV-visible absorption spectra of the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((R-NEA)2PbBr4) with a right-handed configuration prepared in step (2) of Example 1 and the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((S-NEA)2PbBr4) with a left-handed configuration prepared in step (2) of Example 2;

[0027] Figure 7 X-ray powder diffraction patterns of the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((R-NEA)2PbBr4) with a right-handed configuration prepared in step (2) of Example 1 and the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((S-NEA)2PbBr4) with a left-handed configuration prepared in step (2) of Example 2;

[0028] Figure 8 Schematic diagram of the application of bromine-based two-dimensional chiral perovskite single crystal nanosheets ((R / S-NEA)2PbBr4) prepared in Example 1 and Example 2 in circularly polarized lasers. DETAILED DESCRIPTION

[0029] Following, the embodiments of the present application will be described in detail by specific examples, and other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure of this specification. The present application can also be implemented or applied by other different specific embodiments, and various modifications or changes can be made to the details in this specification based on different views and applications without departing from the spirit of the present application. It should be noted that the drawings provided in the following examples only illustrate the basic concept of the present application in a schematic manner, and the following examples and features in the examples can be combined with each other without conflict.

[0030] Example 1

[0031] A bromine-based two-dimensional chiral perovskite monocrystal nanosheet ((R-NEA)2PbBr4) is prepared as follows:

[0032] (1) 306.432 mg of white organic ligand solid powder (R)-(+)-1-(2-naphthyl)ethylamine and 200 mg of yellow powder lead monoxide are weighed separately using an electronic balance, 12 mL of colorless transparent hydrobromic acid is sucked using a pipette, and then mixed and transferred into a previously prepared 20 mL clean glass bottle to obtain a precursor solution;

[0033] (2) The precursor solution in step (1) is transferred into an oil bath pot for heating, the heating temperature gradient is set by adjusting the temperature controller, the temperature is slowly heated to 150°C at a heating rate of 20°C / min, and then maintained for 20 min to obtain a colorless transparent solution, the colorless transparent solution is placed in a room temperature environment for natural cooling, a white snowflake-shaped solid is obtained, the solid is taken out from the glass bottle and placed in a vacuum filter, after vacuum filtration for 5 min, 10 mL of toluene is sucked using a dropper to wash the surface of the solid (a total of 3 times, each washing time is 5 min, a new filter paper is needed for each washing, and the vacuum pump is always turned on during the washing process to ensure that the residual chiral perovskite solvent is removed with toluene in time after washing), then the washed solid is placed in a 20 mL clean brown bottle, the brown bottle is placed in a vacuum chamber, vacuumed for 5 min, and then transferred to a 100°C oven for drying for 24 h, the residual solvent between the layers of monocrystal nanosheets is evaporated again by vacuumizing and heating, and finally a bromine-based two-dimensional chiral perovskite monocrystal nanosheet ((R-NEA)2PbBr4) is obtained.

[0034] Example 2

[0035] A bromine-based two-dimensional chiral perovskite monocrystal nanosheet ((S-NEA)2PbBr4) is prepared as follows:

[0036] The difference from Example 1 is that the (R)-(+)-1-(2-naphthyl)ethylamine in step (1) is replaced by (S)-(-)-1-(2-naphthyl)ethylamine.

[0037] The chemical reagents required for preparing the bromine-based two-dimensional chiral perovskite single crystal nanosheets in Examples 1 and 2 are all commercially available. The specifications, manufacturers, and proportions of the chemical reagents are shown in Table 1 below:

[0038] Table 1 Experimental reagents, specifications, manufacturers and proportions

[0039]

[0040] Figure 1 The figure shows the preparation process of the bromine-based two-dimensional chiral perovskite single crystal nanosheets ((R / S-NEA)2PbBr4) in Examples 1 and 2. During the oil bath heating process, as the temperature gradually increased to 80°C, the white chiral organic ligand solid powder and yellow lead oxide powder gradually dissolved in the hydroiodic acid, causing the glass bottle to become increasingly turbid and produce a white precipitate. As the oil bath temperature slowly approached the target temperature of 150°C, the white precipitate in the glass bottle gradually dissolved. After reaching the target oil bath temperature, the white precipitate in the glass bottle continued to dissolve for another 20 minutes, forming a colorless, transparent solution.

[0041] Figure 2 The crystal form of the white snowflake-like solid with right-handed configuration prepared in step (2) of Example 1 in a colorless transparent solution is shown. Figure 2 It can be clearly seen that a large amount of crystals are generated in the transparent glass bottle, which shows that a large amount of chiral perovskite crystals can be synthesized using the preparation method and proportion in this application.

[0042] Figure 3 The appearance of the cleaned and purified bromine-based two-dimensional chiral perovskite single crystal nanosheet ((R-NEA)2PbBr4) with right-handedness is shown. Figure 3 The (R-NEA)2PbBr4 single crystals appear as white, snowflake-like flakes, separated from each other and easily peeled off from each other. Furthermore, these single-crystal nanosheets are large, approximately 5 mm in size.

[0043] Figure 4 The surface morphology of the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((R-NEA)2PbBr4) with a right-handed configuration prepared in step (2) of Example 1 is shown under a microscope. Figure 4 It can be seen that the (R-NEA)2PbBr4 single crystal presents a clear flake shape, is very thin, and has strong transmittance.

[0044] Similarly, the white snowflake-like bromide two-dimensional chiral perovskite monocrystal nanosheets with left-handed configuration prepared in Example 2 were also subjected to the same morphology test as Example 1, and similar experimental results were obtained, again proving that the chiral perovskite monocrystal nanosheets with snowflake-like morphology and thin thickness can be prepared by the method of the present application.

[0045] Figure 5 Circular dichroism spectra of the bromide two-dimensional chiral perovskite monocrystal nanosheets ((R-NEA)2PbBr4) with right-handed configuration prepared in step (2) of Example 1 and the bromide two-dimensional chiral perovskite monocrystal nanosheets ((S-NEA)2PbBr4) with left-handed configuration prepared in step (2) of Example 2. It can be seen from Figure 5 that the circular dichroism spectra of (R-NEA)2PbBr4and (S-NEA)2PbBr4are mutually symmetrical about the 0 axis. This indicates that the bromide two-dimensional chiral perovskite monocrystal nanosheets prepared by the experimental method in the present application have chiral characteristics, and also verifies that the chiral organic ligand (R)-(+)-1-(2-naphthyl)ethylamine or (S)-(-)-1-(2-naphthyl)ethylamine can transfer its chiral properties to the inorganic perovskite framework [PbBr4] 2- in the present application, so that the organic ligand and the inorganic perovskite hybridize to form a chiral perovskite, and finally the (R / S-NEA)2PbBr4has chiral natural optical activity and can produce circularly polarized light. In addition, four obvious signal peaks appear in the circular dichroism spectra of (R-NEA)2PbBr4and (S-NEA)2PbBr4, respectively at 322 nm, 339 nm, 379 nm and 389 nm. The circular dichroism signal peak at 389 nm is derived from the exciton state transition process of the chiral perovskite. Obviously, these circular dichroism signal peaks are all in the short wavelength range (<400 nm). This indicates that the bromide two-dimensional chiral perovskite (R / S-NEA)2PbBr4monocrystal nanosheets prepared by the present application can be applied to a monochromatic circularly polarized laser source.

[0046] Figure 6 UV-Vis absorption spectra of the bromide two-dimensional chiral perovskite monocrystal nanosheets ((R-NEA)2PbBr4) with right-handed configuration prepared in step (2) of Example 1 and the bromide two-dimensional chiral perovskite monocrystal nanosheets ((S-NEA)2PbBr4) with left-handed configuration prepared in step (2) of Example 2. In order to more clearly and intuitively compare the light absorption properties of (R-NEA)2PbBr4and (S-NEA)2PbBr4, the corresponding light absorption spectra were subjected to normalization processing. It can be seen from Figure 6The absorption spectra of the two chiral perovskite single crystal nanosheets are similar, with both exhibiting strong light absorption at a wavelength of 384 nm. The absorption band edges of (R-NEA)2PbBr4 are 404 nm, while those of (S-NEA)2PbBr4 are 400 nm. The similar absorption band edges of (R-NEA)2PbBr4 and (S-NEA)2PbBr4 single crystal nanosheets indicate that both can generate steady-state circularly polarized light (CPL) of similar wavelengths, suggesting similar chiral photophysical properties.

[0047] Figure 7 The X-ray powder diffraction patterns of the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((R-NEA)2PbBr4) with a right-handed configuration prepared in step (2) of Example 1 and the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((S-NEA)2PbBr4) with a left-handed configuration prepared in step (2) of Example 2 are shown. Similarly, in order to more clearly and intuitively compare the crystallization characteristics of (R-NEA)2PbBr4 and (S-NEA)2PbBr4, the X-ray diffraction spectra were normalized. Figure 7 The results show that the two chiral perovskite single crystal nanosheets exhibit identical X-ray diffraction signals, with both producing eight diffraction peaks, appearing in multiples of (001I, I=1, 2, 3, 4, ...). These diffraction peaks indicate that the chiral perovskite (R / S-NEA)2PbBr4 single crystal not only possesses good crystallization properties and a distinct crystal orientation, but also exhibits two-dimensional semiconductor characteristics. Clearly, these experimental results are consistent with the physical properties of the (R / S-NEA)2PbBr4 single crystal nanosheets, further confirming that the (R / S-NEA)2PbBr4 prepared in this application is a two-dimensional bromine-based perovskite.

[0048] Figure 8 The following is a schematic diagram of the application of the bromine-based two-dimensional chiral perovskite single crystal nanosheet ((R / S-NEA)2PbBr4) prepared in Example 1 and Example 2 in a circularly polarized laser. The structure of the circularly polarized laser is, from bottom to top, a glass substrate, a UV-curable adhesive, and a chiral perovskite single crystal nanosheet ((R / S-NEA)2PbBr4). The function of the UV-curable adhesive is to adhere the chiral perovskite single crystal nanosheet to the glass substrate. By using a short-wavelength femtosecond pump laser (such as a 355nm pump light) to excite the chiral perovskite single crystal nanosheet, monochromatic left-handed or right-handed circularly polarized laser can be directly generated. Obviously, this laser not only has a simple structure and preparation process, but also can output circularly polarized laser light with high efficiency.

[0049] In summary, the present invention provides a bromine-based two-dimensional chiral perovskite single crystal nanosheet. This bromine-based two-dimensional chiral perovskite single crystal nanosheet possesses the physical properties of two-dimensional sheet semiconductors while also exhibiting strong chirality. It can generate circularly polarized light with a wavelength within the short wavelength range and possesses high exciton transition energy, making it highly suitable for use in circularly polarized lasers and heterojunction photodetectors.

[0050] The present invention also provides a method for preparing bromine-based two-dimensional chiral perovskite single crystal nanosheets. This method does not require vacuum or nitrogen atmosphere, has no requirements for the order in which the raw materials are added, is simple and easy to operate, and has low raw material and time costs.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing bromine-based two-dimensional chiral perovskite single crystal nanosheets, characterized by: The preparation method is as follows: (1) mixing a chiral organic ligand, lead monoxide, and hydrobromic acid to obtain a precursor solution; The chiral organic ligand is any one of (R)-(+)-1-(2-naphthyl)ethylamine or (S)-(-)-1-(2-naphthyl)ethylamine; The molar ratio of the chiral organic ligand, lead monoxide and hydrobromic acid in step (1) is 2:1:1; (2) The precursor solution in step (1) is transferred to an oil bath for heating, heated to 150°C at a heating rate of 20°C / min, and then maintained for 20 minutes to obtain a colorless transparent solution. The colorless transparent solution is naturally cooled to room temperature to obtain a white snowflake-like solid, which is then vacuum filtered, washed with toluene, and purified to obtain bromine-based two-dimensional chiral perovskite single crystal nanosheets.

2. The preparation method according to claim 1, wherein: The specific operation process of the purification in step (2) is: first vacuuming and then heating and drying.

3. The preparation method according to claim 2, wherein: The vacuuming time is 5 minutes; the heating and drying temperature is 100° C. and the time is 24 hours.

4. Bromine-based two-dimensional chiral perovskite single crystal nanosheets prepared according to the preparation method according to any one of claims 1 to 3.

5. Use of the bromine-based two-dimensional chiral perovskite single crystal nanosheet according to claim 4 in the preparation of ultraviolet short-wavelength circularly polarized lasers or heterojunction photodetectors.

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