Two-dimensional ferroelectric material spectrum regulation and control method based on first principle calculation

Abstract

The invention discloses a two-dimensional ferroelectric material spectrum regulation and control method based on first principle calculation, belongs to the field of photoelectric property regulation and control of two-dimensional materials, and aims to realize accurate regulation and control of spectral characteristics such as band gaps and light absorption of two-dimensional ferroelectric materials through theoretical calculation. The method comprises the following steps: selecting a two-dimensional material with ferroelectric characteristics as a research object, calculating by adopting a first principle, and regulating and controlling the electronic structure and optical properties of the two-dimensional ferroelectric material by applying-8%-8% biaxial strain to the two-dimensional ferroelectric material. Under compressive strain, the light absorption edge of the two-dimensional ferroelectric material shows a red shift phenomenon, and absorption of visible light is enhanced; under tensile strain, a light absorption edge shows a blue shift phenomenon, and absorption of ultraviolet light is enhanced; by optimizing the strain, the band gap of the two-dimensional ferroelectric material is close to an ideal value, and the photoelectric conversion efficiency is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photoelectric performance regulation of two-dimensional materials, and particularly relates to a two-dimensional ferroelectric material spectrum regulation method based on first-principle calculation. BACKGROUND

[0002] In recent years, two-dimensional materials have attracted extensive attention due to their unique physical, chemical and photoelectric properties. These materials usually have single-layer or few-layer atomic thickness, and exhibit excellent mechanical, electrical and optical properties, making them have great application potential in the fields of nano-electronics, optoelectronics and energy conversion. However, traditional two-dimensional materials still face some challenges in photoelectric applications, such as limited light absorption range, insufficient carrier mobility and low photoelectric conversion efficiency. Therefore, developing new two-dimensional materials and optimizing their photoelectric performance has become a hot research topic.

[0003] Among many two-dimensional materials, two-dimensional ferroelectric materials have attracted much attention due to their unique ferroelectric properties. Ferroelectric materials have a spontaneous polarization property, that is, a polarization electric field is generated inside the material even without an external electric field. This spontaneous polarization can effectively separate photo-generated carriers, thereby improving the photoelectric conversion efficiency. In addition, two-dimensional ferroelectric materials also have tunable band gap structure and excellent light absorption performance, making them have broad application prospects in the fields of solar cells, photodetectors and photocatalysis. However, the methods for regulating the photoelectric performance of two-dimensional ferroelectric materials are still limited, especially the coordinated optimization of band gap, light absorption and ferroelectricity has not been fully solved.

[0004] Spectrum regulation is one of the key means to optimize the photoelectric performance of two-dimensional ferroelectric materials. By regulating the band gap and light absorption properties of the material, it can absorb photons in a wider spectral range, thereby improving the photoelectric conversion efficiency. Traditional spectrum regulation methods mainly rely on experimental means, such as doping, strain engineering and heterostructure construction. However, these methods often have high cost, low efficiency and difficulty in accurate prediction. SUMMARY

[0005] The present application aims to provide a two-dimensional ferroelectric material spectrum regulation method based on first-principle calculation, which can accurately predict the electronic structure and optical properties of the material at the atomic level, thereby providing theoretical guidance for experimental preparation. By applying biaxial strain to two-dimensional ferroelectric materials, the electronic structure and optical properties of two-dimensional ferroelectric materials can be regulated to achieve spectrum regulation.

[0006] The present application provides a two-dimensional ferroelectric material spectrum regulation method based on first-principle calculation, which comprises: selecting a two-dimensional material with ferroelectric properties as the research object, and applying in-plane biaxial strain to the research object.

[0007] Further, the method further comprises: performing first-principle calculation on the two-dimensional material to obtain an electronic structure of the two-dimensional material.

[0008] Further, the in-plane biaxial strain ranges from -8% to 8%.

[0009] Further, the in-plane biaxial strain comprises compressive strain and tensile strain.

[0010] Advantages: Compared with the prior art, the present application has the following advantages:

[0011] 1. The present application realizes precise regulation of the band gap of two-dimensional ferroelectric materials by regulating the in-plane biaxial strain of the two-dimensional materials, so that it can cover multiple wave bands of ultraviolet, visible light and near-infrared; under compressive strain, the light absorption edge of the two-dimensional material shows red shift phenomenon, enhancing the absorption of visible light; under tensile strain, the light absorption edge shows blue shift phenomenon, enhancing the absorption of ultraviolet light.

[0012] 2. The optimized two-dimensional ferroelectric material exhibits excellent light absorption performance in the visible light and ultraviolet light regions, widening the spectral response range and improving the utilization rate of sunlight.

[0013] 3. The present application is based on first-principle calculation, which can quickly predict and optimize the spectral characteristics of two-dimensional ferroelectric materials, providing theoretical support for experimental preparation, reducing experimental cost and time.

[0014] 4. The two-dimensional ferroelectric material regulated by the method of the present application can be used to prepare photoelectric conversion devices, so that it has higher photoelectric conversion efficiency and performance stability, showing broad application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a structure diagram of ZrSCl2 monolayer in Example 1;

[0016] Figure 2 is the density of states diagram of ZrSCl2 under different strains;

[0017] Figure 3 is the light absorption coefficient diagram of ZrSCl2 under different strains. DETAILED DESCRIPTION

[0018] In the following description, specific details are set forth such as target system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.

[0019] It should be understood that the term "comprising" as used in the specification and in the claims indicates the presence of the recited features, integers, steps, operations, elements, and / or components but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0020] It should also be understood that the term "and / or" as used in the specification and in the claims, indicates any combination of the associated listed items, as well as all possible combinations of the items.

[0021] In addition, in the description of the specification and the appended claims, the terms "first", "second", and the like are used only to distinguish descriptions, and cannot be understood as indicating or implying relative importance.

[0022] In the present specification, the phrase "one embodiment" or "some embodiments" or the like means that the target feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in other some embodiments", "in yet some embodiments", etc. appearing in various places in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically stated.

[0023] The method for spectrum regulation of a two-dimensional ferroelectric material based on first-principle calculation, according to the embodiment, comprises: selecting a two-dimensional material with ferroelectric properties as a research object, and applying in-plane biaxial strain to the research object.

[0024] In one example, a two-dimensional material with ferroelectric properties is selected as a research object, for example, ZrSCl2, which has an orthorhombic structure, a space group of Pmm2, and a ferroelectric polarization direction of b direction. This material is widely studied due to its unique ferroelectricity and good photoelectric performance.

[0025] Further, the method further comprises: performing first-principle calculation on the two-dimensional material to obtain the electronic structure of the two-dimensional material.

[0026] First-principles calculation as a theoretical calculation method provides a new way for the regulation of the photoelectric properties of materials. Through first-principles calculation, the electronic structure and optical properties of materials can be accurately predicted at the atomic level, providing theoretical guidance for experimental preparation and reducing experimental cost and time. In this example, the Vienna ab initio simulation package (VASP) is used for calculation, including the projected augmented wave (PAW) potential and the Perdew-Burke-Ernzerhof (PBE) energy functional. The band structure, density of states, optical absorption coefficient, and spectral limit maximum efficiency of a two-dimensional ferroelectric material monolayer under different degrees of strain are calculated, and the two-dimensional ferroelectric material before and after applying strain is compared.

[0027] In one example, the.cif file of the ZrSCl2 material is extracted from the database, and the structure of ZrSCl2 is designed using the visualization structure drawing software VESTA, and the structure data file type is converted to the.vasp file format.

[0028] In an embodiment, the ZrSCl2 material extracted from the database is a material thin film, and the vacuum layer is set to The initial structure, lattice parameters, and atomic arrangement positions are obtained. The structure data file type is converted from.cif to.vasp file format using VASTA software, and renamed as POSCAR for preliminary structure relaxation.

[0029] In an embodiment, the VASP software program is used to perform structure relaxation on the preliminarily constructed ZrSCl2 material monolayer using the conjugate gradient algorithm, and after obtaining the stable structure and convergence, the data structure after structure optimization is used for static self-consistent calculation.

[0030] In an embodiment, the conjugate gradient algorithm is used to optimize the lattice parameters and atomic coordinates of the ZrSCl2 material. The INCAR setting parameters are ISIF=3, IBRION=2, and the K points in the KPOINTS file are set to 6x6x1. The optimized structure is converged to the standard for static calculation. Then, the INCAR parameters are set to ISIF=2, IBRION=-1, and NSW=0. The K points in the KPOINTS file are set to 12x12x1. The ISIF parameter is used to control which degrees of freedom are optimized during the structure optimization process. ISIF=3: indicates that both lattice parameters and atomic coordinates are optimized, which is the most commonly used setting and is suitable for situations where both lattice volume and atomic positions need to be adjusted. The IBRION parameter is used to select the algorithm for ion relaxation, i.e., the method for optimizing atomic positions. IBRION=2: indicates the use of the conjugate gradient algorithm (CG). The conjugate gradient algorithm is an efficient optimization method suitable for most structure optimization problems, especially in situations where fast convergence is required. It optimizes atomic positions through iteration to minimize the energy of the system. The KPOINTS file is used to define the sampling points (k points) of the Brillouin zone. The selection of k points has an important influence on the accuracy and cost of the calculation. 6x6x1: indicates that 6, 6, and 1 k points are set in the three directions of the Brillouin zone, respectively. For two-dimensional materials such as ZrSCl2, since it is a layered structure in the out-of-plane direction, only 1 k point is set in the vertical direction (z direction). More k points are set in the in-plane direction (x and y directions) to ensure more accurate sampling of the electronic structure of the two-dimensional plane.

[0031] After the static self-consistent calculation is completed, the INCAR parameters are modified based on the static self-consistent calculation, with ISTART=1, ICHARG=11, LORBIT=11, and LWAVE=FALSE. The Perdew-Burke-Ernzerhof (PBE) method is used to calculate the photoelectric properties.

[0032] Further, the in-plane biaxial strain ranges from -8% to 8%.

[0033] Further, the biaxial strain includes compression strain and tensile strain.

[0034] In this example, in-plane biaxial strain is applied to the a-axis and b-axis of ZrSCl2, and the strain degree can be -8%, -6%, -4%, -2%, 2%, 4%, 6%, and 8%. The structure optimization, static self-consistent calculation, band structure, density of states, optical absorption coefficient, and spectral limit maximum efficiency of ZrSCl2 after strain calculation are calculated. Among them, ISIF=2.

[0035] As shown in Figure 1 is the structure of ZrSCl2 single-layer crystal under different perspectives, wherein, Figure 1 (a) is a top view, Figure 1 (b) is a side view, the space group structure of ZrSCl2 is Pmm2, and the ferroelectric polarization direction is b direction, and from the side view, it can be seen that from top to bottom, there are S atoms, Zr atoms and Cl atoms.

[0036] As shown in Figure 2 is the density of states of ZrSCl2 under different strains, the vertical axis is strain, and the horizontal axis is band gap energy, and it can be seen that the band gap of ZrSCl2 decreases with the increase of strain under compression strain, and the opposite is true under tensile strain. Figure 2 As shown in Figure 3 is the optical absorption coefficient of ZrSCl2 under different strains, and it can be seen that under compression strain, the overall optical absorption curve of ZrSCl2 shows a red shift trend, especially in the infrared region, the optical absorption is significantly enhanced, and the optical absorption enhancement phenomenon is observed in the energy range of 1.5eV~2eV and close to 3eV; at the same time, the absorption peak intensity of the purple light region is significantly improved with the increase of strain value. Under tensile strain, the optical absorption curve shows a blue shift characteristic in the visible light region, and the absorption peak position gradually shifts from the purple light region to the ultraviolet light region. The change trend of the absorption peak is consistent with the change trend of the density of states, and overall, it moves to the high energy direction with the increase of strain.

[0037] Figure 3 As shown in Figure 3 is the optical absorption coefficient of ZrSCl2 under different strains, and it can be seen that under compression strain, the overall optical absorption curve of ZrSCl2 shows a red shift trend, especially in the infrared region, the optical absorption is significantly enhanced, and the optical absorption enhancement phenomenon is observed in the energy range of 1.5eV~2eV and close to 3eV; at the same time, the absorption peak intensity of the purple light region is significantly improved with the increase of strain value. Under tensile strain, the optical absorption curve shows a blue shift characteristic in the visible light region, and the absorption peak position gradually shifts from the purple light region to the ultraviolet light region. The change trend of the absorption peak is consistent with the change trend of the density of states, and overall, it moves to the high energy direction with the increase of strain.

[0038] In the present application, by applying a biaxial strain of-8% to 8% to the two-dimensional ferroelectric material, the purpose of regulating the electronic structure and optical properties of the two-dimensional material is achieved. Under compression strain, the optical absorption edge of the material shows a red shift phenomenon, and the absorption of visible light is enhanced; under tensile strain, the optical absorption edge shows a blue shift phenomenon, and the absorption of ultraviolet light is enhanced. By optimizing the strain, the band gap of the material is close to the ideal value (about 1.5eV), and the photoelectric conversion efficiency is significantly improved.

[0039] The two-dimensional ferroelectric material subjected to spectral regulation based on the method of the present application can be used to prepare photoelectric conversion devices, such as solar cells, photodetectors or other photoelectric conversion devices, and provides theoretical support for the design of new high-efficiency photoelectric devices, which has important scientific significance and application value.​

Claims

1. A method for spectral modulation of two-dimensional ferroelectric materials based on first-principles calculations, characterized in that, include: Two-dimensional materials with ferroelectric properties are selected as the research object, and in-plane biaxial strain is applied to the research object.

2. The method for spectral modulation of two-dimensional ferroelectric materials based on first-principles calculations according to claim 1, characterized in that, Also includes: The electronic structure of the two-dimensional material is obtained by performing first-principles calculations.

3. The method for spectral modulation of two-dimensional ferroelectric materials based on first-principles calculations according to claim 1, characterized in that, The range of the in-plane biaxial strain is -8% to 8%.

4. The method for spectral modulation of two-dimensional ferroelectric materials based on first-principles calculations according to any one of claims 1 to 3, characterized in that, The in-plane biaxial strain includes compressive strain and tensile strain.

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