Method for controlling chiral optical properties of organic-inorganic hybrid metal halide

Abstract

The application discloses a method for regulating chiral optical properties of organic-inorganic hybrid metal halide. The method of the application regulates the strain level of the R-NEAPbI3 film by changing the content of PbI2 phase in the film, so as to improve the regulation level of the chiral optical properties of the film, CD and g CD The experimentally highest reaches 5350 mdeg and 0.20.

Description

Technical Field

[0001] This application relates to the technical field of chiral optical materials, and in particular to methods for controlling the chiral optical properties of organic-inorganic hybrid metal halides. Background Technology

[0002] Chirality, the mirror asymmetry of matter, is a fundamental geometric property permeating all aspects of nature, from amino acids to spiral galaxies. Chiral materials often possess chiral optical properties, including circular dichroism (CD), i.e., preferential absorption of left / right circularly polarized light, which has wide applications in asymmetric catalysis, biomedicine, information encryption, and quantum communication. However, most natural substances exhibit weak chiral optical properties (CD asymmetry factor g) due to their weak coupling with electromagnetic waves. CD In 10 -3 (on the order of magnitude). For chiral organic material systems, exciton coupling achieved through supramolecular assembly has successfully enhanced their chiral optical properties, with the highest g... CD In 10 -1 On the order of magnitude. In chiral inorganic material systems, current research has utilized the dielectric resonance effect to amplify chiral optical properties through the design of chiral superstructures, achieving a maximum g... CD In 10 0 The order of magnitude is significant. However, the disordered supramolecular orientation and complex metasurface preparation processes limit the practical applications of chiral organic and inorganic systems.

[0003] Recently, chiral organic-inorganic hybrid metal halides (CMHs) have exhibited tunable band gaps, long spin relaxation times, and highly ordered directional crystallization, leading to their widespread integration into numerous spin- and polarization-selective optoelectronic devices, ranging from circularly polarized photodetectors to spin-emitting diodes. However, the low exciton chirality of CMHs remains a major limitation to their device performance. Recent research suggests that the chirality of CMHs originates from the chiral transfer from chiral organic molecules to the metal halide framework, a process largely dependent on the strength of the organic-inorganic electronic interactions, determined by factors such as the composition and relative positions of the organic and inorganic components. Therefore, most experimental attempts to modulate the exciton chirality of CMHs focus on compositional and structural modifications, such as chiral organic molecule modulation, halogen mixing, metal alloying, and structural dimensional control. Among these, the structure and arrangement of chiral organic molecules have the most significant impact on chiral optics. However, due to a lack of understanding of the relationship between molecular chirality and chiral optical properties, most of these experiments have yielded limited improvements in exciton chirality, with reported gi values ​​for CMHs... CD Usually in 10 -4 Up to 10 -2 Magnitude. Summary of the Invention

[0004] This application aims to at least address one of the technical problems existing in the prior art. To this end, one objective of this application is to provide a method for controlling the chiral optical properties of organic-inorganic hybrid metal halides, so as to improve the control level of chiral optical properties.

[0005] This application provides a method for controlling the chiral optical properties of organic-inorganic hybrid metal halides by changing the PbI2 phase content in the R-NEAPbI3 thin film to regulate the strain level of the film, thereby achieving controllable adjustment of the chiral optical properties of the film.

[0006] In any implementation, the controllable adjustment is achieved through the following formula:

[0007]

[0008] L d = (B + C × ε) 3 )L a ;

[0009] In the above formula, ε b Given the background dielectric constant, To reduce Planck's constant, c is the speed of light, Γ is the exciton broadening, ω0 is the exciton resonance frequency, D is the exciton dipole moment, and L is the exciton dipole moment. a L represents the molecular size of the chiral organic ammonium ion, γ is the angle between the organic ammonium ion and the c-axis, and L... d For organic ammonium ions, there are helical dislocations along the b-axis, with B being 5.8 × 10⁻⁶. -4 C is 7.6 × 10 -4 ε is strain, g CD It is the circular dichroism asymmetry factor.

[0010] In any implementation, the L a L d Follow the following relationship,

[0011]

[0012] In the above formula, R is the helical radius of the molecular assembly.

[0013] In any implementation, the L a γ follows the following relationship:

[0014] H≈L a cosγ / π;

[0015] In the above formula, H is the helical spacing of the molecular assembly.

[0016] In any embodiment, when the PbI2 phase content is below 40.7 wt%, the strain level of the film varies in the range of 0.45% to 1.5%.

[0017] In any implementation, the PbI2 phase is added in the following manner:

[0018] PbI2 is dispersed in the R-NEAI solution to form a precursor solution;

[0019] The precursor solution is used to form the R-NEAPbI3 film after spin coating and curing.

[0020] In any embodiment, the solvent is a polar solvent.

[0021] In any embodiment, the precursor solution is heated and aged at 70-80°C for 0.5-2 hours prior to spin coating.

[0022] In any embodiment, the spin coating includes a first stage spin coating at a rotation speed of 500-1500 rpm for a duration of 2-15 s and a second stage spin coating at a rotation speed of 4500-5500 rpm for a duration of 40-90 s.

[0023] In any embodiment, the curing conditions are annealing at 90-110°C for 2-8 minutes.

[0024] The method described in this application modulates the strain level of the R-NEAPbI3 thin film by changing the PbI2 phase content, thereby improving the tuning level of the film's chiral optical properties, CD, and g. CD The highest values ​​achieved in the experiment were 5350 mdeg and 0.20. Attached Figure Description

[0025] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0026] Figure 1 A schematic diagram of the crystal structure of the one-dimensional chiral metal halide R-NEAPbI3 provided for embodiments of this application;

[0027] Figure 2 The embodiments of this application are based on theoretical models CD and g. CD With γ and L d Changes in CD and g CD (already normalized);

[0028] Figure 3 The DFT-based structural optimization provided for the embodiments of this application, γ and L d The changing trend of strain;

[0029] Figure 4 The data fitting of the theoretical model (curve) and experimental data (points) provided in the embodiments of this application;

[0030] Figure 5 The CD and g implemented by the method of this application are provided for embodiments of this application. CD Comparison with methods in related technologies;

[0031] Figure 6 SEM images of multiphase thin films provided in embodiments of this application;

[0032] Figure 7 XRD patterns of multiphase thin films provided in embodiments of this application;

[0033] Figure 8 The tensile strain distribution of the multiphase thin film provided in the embodiments of this application varies with the PbI2 content;

[0034] Figure 9 CD and g of the multiphase thin films provided in the embodiments of this application CD The spectrum changes with PbI2 content. Detailed Implementation

[0035] The embodiments of this application are disclosed in detail below with appropriate reference to the accompanying drawings. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims. The "scope" disclosed in this application is defined in the form of a lower limit and an upper limit, whereby a given scope is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular scope. Scopes defined in this way may include or exclude end values ​​and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a scope. For example, if a scope of 60-120 and 80-110 is listed for a specific parameter, it is expected that the scopes of 60-110 and 80-120 are also included. Furthermore, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4, and 5 are listed, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range “ab” represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range “0-5” means that all real numbers between “0-5” have been listed herein, and “0-5” is merely a shortened representation of these numerical combinations. Additionally, when a parameter is stated as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0037] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0038] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0040] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0041] [Background of Establishment]

[0042] Currently, most experimental attempts to modulate the exciton chirality of CMHs focus on compositional and structural modifications, such as chiral organic molecule modulation, halogen mixing, metal alloying, and structural dimensional control. Among these, the structure and arrangement of chiral organic molecules have the most significant impact on chiral optics. However, due to a lack of understanding of the relationship between molecular chirality and chiral optical properties, most of these experiments have limited effectiveness in improving exciton chirality, with reported g-values ​​for CMHs showing limited improvement. CD Usually in 10 -4 Up to 10 -2 Magnitude.

[0043] Through arduous exploration, the inventors discovered that by altering the content of achiral PbI2 in R-NEAPbI3 multiphase thin films with chiral optical properties, thermal and lattice mismatches between the two phases can be induced, thereby changing the strain. More importantly, the inventors found that strain variation significantly enhances chiral optical properties compared to other methods. Furthermore, the degree of strain change and the resulting change in chiral optical properties exhibit a clear and customizable trend, thus enabling controllable adjustment of the chiral optical properties of the thin film.

[0044] Methods for controlling chiral optical properties

[0045] The strain level of the R-NEAPbI3 film was controlled by changing the PbI2 phase content, thereby achieving controllable adjustment of the chiral optical properties of the film.

[0046] [How to add the PbI2 phase]

[0047] Please refer to Figure 1 , Figure 1 The crystal structure of pure R-NEAPbI3 without the PbI2 phase was simulated using well-known computer software.

[0048] The preparation of R-NEAPbI3 thin films is not the primary objective of this application, and can be obtained by those skilled in the art through known techniques. A non-limiting, referable preparation method is as follows:

[0049] Step 1: Preparation of precursor solution: Lead iodide (PbI2) and chiral organic ammonium iodate ethylamine [R-NEA, i.e., 1-(1-naphthyl)] are mixed and dissolved in a polar solvent (e.g., N,N-dimethylformamide) to obtain the precursor solution;

[0050] Step 2: Preparation of chiral metal halide and PbI2 nanoparticle mixed-phase thin film: The precursor solution is spin-coated onto the substrate and cured (by annealing process) to obtain a two-phase homogeneous mixed-phase thin film.

[0051] Here, the precursor solution is heated and aged at 70-80°C (e.g., 70°C, 72°C, 75°C, 78°C or 80°C) for 0.5-2 hours (e.g., 0.5h, 0.75h, 1h, 1.5h, 2h, etc.) before spin coating.

[0052] Here, the above spin coating includes a first stage spin coating at a speed of 500-1500 rpm (e.g., 500 rpm, 600 rpm, 800 rpm, 1000 rpm, 1200 rpm or 1500 rpm) for a duration of 2-15 s (e.g., 2 s, 5 s, 8 s, 10 s, 12 s or 15 s) and a second stage spin coating at a speed of 4500-5500 rpm (4500 rpm, 4800 rpm, 5000 rpm, 5200 rpm, 5500 rpm, etc.) for a duration of 40-90 s (e.g., 40 s, 45 s, 50 s, 55 s, 60 s, 80 s, 90 s).

[0053] Here, the curing conditions described above are annealing at 90-110℃ (e.g., 90℃, 92℃, 95℃, 100℃, 105℃, 108℃ or 110℃) for 2-8 minutes (2 minutes, 3 minutes, 5 minutes, 6 minutes, 8 minutes).

[0054] [Controllable and Adjustable Model Formula]

[0055] Please refer to Figure 2 and Figure 3 This controllable adjustment is achieved through the following formula:

[0056]

[0057] L d = (B + C × ε) 3 )L a (2);

[0058] In the above formula, ε b Given the background dielectric constant, To reduce Planck's constant, c is the speed of light, Γ is the exciton broadening, ω0 is the exciton resonance frequency, D is the exciton dipole moment, and L is the exciton dipole moment. a L represents the molecular size of the chiral organic ammonium ion, γ is the angle between the organic ammonium ion and the c-axis, and L... d For organic ammonium ions, there are helical dislocations along the b-axis, with B being 5.8 × 10⁻⁶. -4 C is 7.6 × 10 -4 ε is strain, g CD It is the circular dichroism asymmetry factor.

[0059] In some typical implementations, the L a L d Follow the following relationship,

[0060]

[0061] In the above formula, R is the helical radius of the molecular assembly.

[0062] The La γ follows the following relationship:

[0063] H≈L a cosγ / π (4);

[0064] In the above formula, H is the helical spacing of the molecular assembly.

[0065] Based on formulas (3) and (4), it can be seen that increasing the helical radius and decreasing the helical spacing contribute to higher CD and g. CD This indicates that the spatial helical assembly of chiral organic molecules determines the chiral transfer process and controls the strength of chiral optical properties.

[0066] at the same time Figure 2 It can be seen that when other parameters remain constant, larger γ and L d It is beneficial to obtain higher CD and g CD value.

[0067]

Example

[0068] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0069] R-NEAPbI3 films were prepared according to the following method, and the evaluation of these films is described below. 0.0403 g of R-NEAI (R-1-(1-naphthyl)ethylamine iodate) and an appropriate amount of PbI2 were added to 200 μL of DMF solution. The precursor solution was first aged at 75 °C for 1 hour on a hot plate, and then spin-coated onto a soda-lime glass substrate. A first stage spin-coating was performed at 1000 rpm for 10 s, followed by a second stage spin-coating at 5000 rpm for 60 s. After spin-coating, 200 μL of chlorobenzene was added as an antisolvent, and the substrate was annealed at 100 °C for 5 min on a hot plate to complete the curing process and obtain the film.

[0070] In the above preparation method, the following examples and comparative examples were formed with the number of moles of PbI2 added to the DMF solution as the variable value (all other preparation conditions are the same). The PbI2 phase content of the prepared films was tested using a known energy dispersive spectroscopy method, as shown in the table below.

[0071]

[0072] Note: Pure perovskite films are prepared when the molar amount of PbI2 added is 1, meaning the mass content of the PbI2 phase in the film is 0.

[0073]

evaluate

[0074] The R-NEAPbI3 films corresponding to some or all of the above embodiments and comparative examples were evaluated as follows. The test procedures described below are all well-known techniques and are omitted here.

[0075] 1. [Verification of this control method]

[0076] Please refer to Figure 4 This figure compares the measured chiral optical properties of the R-NEAPbI3 thin films corresponding to Examples 1-4 and Comparative Example 1 with the theoretical simulation calculation results. As shown in the figure, in the mixed system of R-NEAPbI3 and PbI2 nanoparticles, with strain ranging from 0.45% to 1.5%, the absorption spectra of R-NEAPbI3 and PbI2 are separated. This indicates that the exciton properties of R-NEAPbI3 are essentially unchanged with strain. Therefore, we consider that strain has a small impact on the exciton properties of R-NEAPbI3, and thus D and Γ are constants. Furthermore, considering... Figure 3 The DFT structural optimization presented shows that, theoretically, R-NEAPbI3 under different strain magnitudes has different γ and L values. d The magnitude of the change, L, as the strain increases from 0% to 2%. d L increases significantly, while γ increases slightly. Within the strain range of 1% to 2%, L... d The main increase indicates that tensile strain effectively separates molecules along the planar direction, enhancing dislocation. At higher strains (>3%), L... d And γ decreases. Therefore, within the strain range of 0.45% to 1.5%, assuming that the γ parameter remains essentially unchanged with strain, it is 30.13°, while L... d The relationship with strain (ε) is L d = (B + C × ε) 3 )L a L a The molecular size of R-NEA is Further data fitting between the theoretical model and the experimental structure revealed that B is 5.8 × 10⁻⁶. -4 C is 7.6 × 10 -4 The fitted R 2 The value is 0.95, indicating good agreement between the experimental data and the theoretical model. Based on this, we can predict that when the strain is further increased to the point before structural fracture, i.e., 2% tensile strain, R-NEAPbI3 can achieve the highest possible CD and g values. CD The values ​​can reach 9850 mdeg and 0.35.

[0077] Please refer to Figure 5This figure refers to the R-NEAPbI3 film corresponding to Example 3. (From...) Figure 5 It can be seen that strain engineering effectively amplifies the chiral optical properties of R-NEAPbI3 and achieves the highest CD value among chiral hybrid semiconductors. CD This is higher than all previously reported chiral organic-inorganic hybrid semiconductor materials, including chiral organic molecular coordination quantum dots (CQDs), chiral metal-organic frameworks (CMOSs), and CMHs.

[0078] 2. [Morphology of R-NEAPbI3 thin film]

[0079] Please refer to Figure 6 This figure refers to the R-NEAPbI3 film corresponding to Example 3. (From...) Figure 6 It can be seen that the precipitated PbI2 phase is uniformly distributed on the surface and inside of the film in the form of nanoparticles (i.e., the area circled in red).

[0080] 3. [The effect of PbI2 phase mass content in thin films on chiral optical properties]

[0081] The evaluation of the R-NEAPbI3 films corresponding to all the above embodiments and Comparative Example 1 is carried out in this section. The test procedures involved are all well-known techniques and are briefly described here.

[0082] Please refer to Figure 7 , Figure 7 The XRD pattern of the thin film indicates the presence of 1D CMH and PbI2 phases. Figure 7 It can be seen that Examples 1-4 and Comparative Example 1 show diffraction peaks at essentially the same diffraction angle, which also indicates that the content of PbI2 phase in the film cannot change the characteristics of the XRD diffraction peaks.

[0083] Please refer to Figure 8 As shown in the figure, by utilizing the mismatch between the lattice constant and thermal expansion coefficient at the interface between the 1D CMH and PbI2 phases, and by adjusting the content of the PbI2 phase, the tensile residual strain distributed in the film can be changed from 0.45% to 1.50%. The magnitude and direction of the residual strain are determined by grazing incidence X-ray diffraction (GIXRD) and classical X-ray diffraction. The method has been determined.

[0084] Please refer to Figure 9 As shown in the figure, with the PbI2 phase mass content in the film being 0 wt%, 17.9 wt%, 27.8 wt%, 40.8 wt%, and 47.7%, the CD of the film reaches 5350 mdeg / g. CD Up to 0.20.

[0085] The above embodiments are merely illustrative of the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for controlling the chiral optical properties of organic-inorganic hybrid metal halides, characterized in that, To change R The strain level of the NEAPbI3 thin film can be controlled by adjusting the PbI2 phase content, thereby achieving controllable adjustment of the chiral optical properties of the film.

2. The method for controlling the chiral optical properties of organic-inorganic hybrid metal halides according to claim 1, characterized in that, The controllable adjustment is achieved through the following formula. ； ； In the above formula, Given the background dielectric constant, To reduce Planck's constant, At the speed of light, To broaden the exciton, The exciton resonance frequency, For the exciton dipole moment, The molecular size of the chiral organic ammonium ion. The angle between the organic ammonium ion and the c-axis is denoted as . For organic ammonium ions, there are helical dislocations along the b-axis, with B being 5.8 × 10⁻⁶. -4 C is 7.6 × 10 -4 , In response to the change, g CD It is the circular dichroism asymmetry factor.

3. The method for controlling the chiral optical properties of organic-inorganic hybrid metal halides according to claim 2, characterized in that, The , Follow the following relationship, ； In the above formula, R denoted as the helical radius of the molecular assembly.

4. The method for controlling the chiral optical properties of organic-inorganic hybrid metal halides according to claim 1, characterized in that, The , Follow the following relationship, ； In the above formula, H The helical spacing of the molecular assembly.

5. The method for controlling the chiral optical properties of organic-inorganic hybrid metal halides according to claim 1, characterized in that, When the PbI2 phase content is below 40.7 wt%, the strain level of the film varies in the range of 0.45%-1.5%.

6. The method for controlling the chiral optical properties of organic-inorganic hybrid metal halides according to claim 1, characterized in that, The PbI2 phase is added in the following way: Disperse PbI2 in R In the NEAI solution, a precursor solution is formed; The precursor solution is used to form the [structure / method] after spin coating and curing. R -NEAPbI3 film.

7. The method for controlling the chiral optical properties of organic-inorganic hybrid metal halides according to claim 6, characterized in that, The R The solvent for NEAI solutions is a polar solvent.

8. The method for controlling the chiral optical properties of organic-inorganic hybrid metal halides according to claim 6, characterized in that, Before spin coating, the precursor solution is heated and aged at 70-80°C for 0.5-2 hours.

9. The method for controlling the chiral optical properties of organic-inorganic hybrid metal halides according to claim 6, characterized in that, The spin coating includes a first stage spin coating at a rotation speed of 500-1500 rpm for a duration of 2-15 s and a second stage spin coating at a rotation speed of 4500-5500 rpm for a duration of 40-90 s.

10. The method for controlling the chiral optical properties of organic-inorganic hybrid metal halides according to claim 6, characterized in that, The curing conditions are annealing at 90-110℃ for 2-8 minutes.

Images