Janus transition metal chalcogenide material photovoltaic effect regulation and control method, device and medium

Abstract

The invention belongs to the technical field of photovoltaic material regulation and control, and relates to a Janus transition metal chalcogenide material photovoltaic effect regulation and control method and device and a computer readable storage medium, periodic cells of a Janus transition metal chalcogenide material are constructed, lattice constants of the periodic cells are changed to simulate the application of tensile strains with different strain coefficients to the periodic cells, and the photovoltaic effect of the Janus transition metal chalcogenide material is regulated and controlled. Obtaining periodic cells corresponding to the tensile strain of different strain coefficients; simulating the electronic state change of each periodic cell in a preset laser electric field, and calculating the dynamic polarization current of each periodic cell; calculating the displacement light current density of each periodic cell based on the order expansion function of the dynamic polarization current of each periodic cell relative to the electric field; based on the lattice constants and the displacement photocurrent density of all the periodic cells, fitting to obtain a relation equation of the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material with respect to a tensile strain coefficient, so as to regulate and control the photovoltaic effect of the Janus transition metal chalcogenide material.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic material regulation, and in particular to a method, device, and computer-readable storage medium for regulating the photovoltaic effect of Janus transition metal chalcogenide materials. Background Art

[0002] In recent years, with the rapid development of renewable energy technologies, photovoltaics (PV) have garnered widespread attention as a core area of clean energy conversion. Current mainstream PV materials include silicon-based solar cells, organic photovoltaics (OPVs), perovskite solar cells (PSCs), and emerging two-dimensional semiconductor PV materials such as transition metal dichalcogenides (TMDs), black phosphorus, and Janus transition metal chalcogenides.

[0003] Silicon-based solar cells are the mainstream photovoltaic material in the current market, but their manufacturing costs are high and the processing process is complex. Furthermore, because silicon is an indirect bandgap semiconductor with a bandgap of approximately 1.1 eV, its absorption of near-infrared light is limited, and it faces a physical light absorption efficiency limit, thus failing to fully utilize the low-energy photons in sunlight. OPVs offer advantages such as lightweight, solution-processable, and large-area fabrication capabilities. However, due to the inherent characteristics of organic materials, their photoelectric conversion efficiency and long-term stability are low, hindering large-scale commercial application. PSCs have seen rapid development in recent years due to their high photovoltaic absorption coefficient and tunable bandgap. However, perovskite materials are susceptible to environmental factors (visibility, temperature, and light intensity), resulting in poor environmental stability. Furthermore, some high-performance perovskite materials contain lead, posing potential environmental pollution risks in their applications. Emerging two-dimensional semiconductor materials have strong absorption coefficients, tunable band gaps, flexibility and low-dimensional properties, and can therefore bring about novel photovoltaic effects, such as displacement photocurrent and photoinduced spin current. These effects can be used to manufacture high-speed light detectors, high-performance terahertz detectors and other devices. Therefore, emerging two-dimensional semiconductor materials have gradually attracted attention and become the photovoltaic materials currently under research focus.

[0004] Among the emerging two-dimensional semiconductor materials, Janus transition metal chalcogenides have a non-centrosymmetric structure (i.e., broken out-of-plane symmetry). This structure gives them a natural out-of-plane electric dipole moment, built-in electric field, and intramolecular stress, all of which enable them to generate displacement photocurrent and photogenerated spin current. Moreover, by varying the type of transition metal, the combination of chalcogen atoms, and the interlayer stacking method, the energy band structure of Janus transition metal chalcogenides can be effectively manipulated, thereby achieving a continuous change from a narrow band gap to a wide band gap. Therefore, Janus transition metal chalcogenides are currently emerging two-dimensional semiconductor materials with great application prospects as photovoltaic materials. However, the displacement photocurrent intensity currently generated by Janus transition metal chalcogenides still cannot meet the needs of some light detection applications. For example, scenarios such as long-distance detection, fine light intensity resolution, and clear imaging in low-light environments all require devices to generate extremely strong displacement photocurrents to increase sensitivity to weak light signals. However, there is no relevant research in the existing technology on the enhanced regulation of the photovoltaic effect of Janus transition metal chalcogenides, and therefore it is impossible to provide theoretical guidance for the regulation of the displacement photocurrent of Janus transition metal chalcogenides.

[0005] In summary, the displacement photocurrent intensity that can be generated by existing Janus transition metal chalcogenides is relatively low. How to improve the photovoltaic effect of Janus transition metal chalcogenides so that they can generate higher displacement photocurrent is a problem that needs to be solved at present. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is how to improve the photovoltaic effect of Janus transition metal chalcogenides so that they can generate higher displacement photocurrent.

[0007] To solve the above technical problems, the present invention provides a method for regulating the photovoltaic effect of a Janus transition metal chalcogenide material, comprising: Construct a periodic cell of Janus transition metal chalcogenide material and change the lattice constant of the periodic cell multiple times to simulate the tensile strain with different gauge coefficients applied to the periodic cell, and obtain the periodic cell corresponding to the tensile strain with different gauge coefficients; The ground state wave function, eigenvalue, quasiparticle self-energy and light absorption spectrum of each periodic cell are used as the initial conditions of the time-dependent evolution to simulate the electronic state changes of each periodic cell in the preset laser electric field, and obtain the dynamic polarization current of each periodic cell in the preset laser electric field; Based on the order expansion function of the dynamic polarization current of each periodic cell in the preset laser electric field with respect to the electric field, the displacement photocurrent density of each periodic cell is calculated; Based on the lattice constants and displacement photocurrent densities of all periodic cells, the relationship equation between the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material and the tensile gauge coefficient was fitted, so that the photovoltaic effect of the Janus transition metal chalcogenide material can be regulated by changing the tensile gauge coefficient applied to the Janus transition metal chalcogenide material.

[0008] Preferably, the relationship equation between the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material and the tensile gauge coefficient is expressed as: , in, The applied gauge factor is The conductivity of the displacement photocurrent of Janus transition metal chalcogenides under tensile strain; represents the conductivity of the initial displacement photocurrent of the Janus transition metal chalcogenide material when no tensile strain is applied; represents the tensile strain coefficient; , in, represents the lattice constant of Janus transition metal chalcogenide material after tensile strain is applied; represents the lattice constant of the Janus transition metal chalcogenide material when no tensile strain is applied.

[0009] Preferably, density functional theory is used to calculate the ground state wave function and eigenvalue of each periodic cell, which specifically includes: Input the periodic cell into Quantum Espresso software, and adjust the position of each atom in the periodic cell to perform structural relaxation on the periodic cell until the total force of the periodic cell reaches a preset total force value and the total energy of the periodic cell converges to a preset total energy value; A vacuum layer of preset thickness is set in the out-of-plane direction of the periodic cell, and a dipole correction is added to the vacuum layer to obtain the target periodic cell; The Perdew-Burke-Ernzerhof generalized gradient approximation function and the conservative gauge pseudopotential are selected as the exchange-correlation functional. Based on the preset plane wave cutoff energy and k-point grid, a self-consistent iterative calculation is performed on the target periodic cell, and the ground state wave function and eigenvalue of the target periodic cell are output.

[0010] Preferably, the quasiparticle self-energy and light absorption spectrum of each periodic cell are calculated using the multi-body perturbation theory, which specifically includes: The periodic cells are input into the Yambo software, and the Dyson equation is solved based on the preset K grid, dielectric matrix cutoff energy, number of energy bands, and Coulomb cutoff to obtain the quasiparticle self-energy of the periodic cells. The valence band and conduction band of the periodic cell are set with the goal of covering the solar spectrum. The Bethe-Salprter equation is solved based on the valence band and conduction band to obtain the light absorption spectrum of the periodic cell.

[0011] Preferably, the ground state wave function, eigenvalue, quasiparticle self-energy and light absorption spectrum of each periodic cell are used as initial conditions for time-dependent evolution, and the electronic state changes of each periodic cell in a preset laser electric field are simulated to obtain the dynamic polarization current of each periodic cell in the preset laser electric field, including: Based on the modified Hamiltonian without external field perturbation and the external field perturbation term, the electron motion equation of the periodic cell in the preset laser electric field is constructed; Based on modern polarization theory and the periodicity of Bloch waves, the polarization current equation of the periodic cell in the preset laser electric field is constructed; A single-frequency external electric field is applied to the periodic cell in a preset laser electric field. An imaginary term is introduced into the modified Hamiltonian without external field perturbation to simulate the decoherence process. Time-dependent simulation is performed based on the ground state wave function, eigenvalue, quasiparticle self-energy and optical absorption spectrum of the periodic cell. Based on the time-dependent simulation process, the electron motion equation is integrated to obtain the Bloch state term that evolves with time. The Bloch term that evolves with time is substituted into the polarization current equation to obtain the dynamic polarization current of the periodic cell in the preset laser electric field.

[0012] Preferably, the electron motion equation is expressed as: , in, represents the effective Hamiltonian, , represents the modified Hamiltonian without external field disturbance, , represents the Kohn-Sham Hamiltonian under the independent particle approximation, represents the quasiparticle correction considering electron-electron interaction, represents the time-dependent Hartree correction, represents the time-dependent screened Hartree-Fock correction; represents the external field perturbation term, , represents the electron-external field coupling operator; Indicates time The partial derivative of Represents a unit imaginary number; represents the Bloch state term with momentum k and energy band number n; , in, Indicates the outfield; ; represents the next k-point in the grid in the Cartesian direction; , Represents the distance between two adjacent k points; represents the projection operator; , in, represents the total number of occupied energy bands, express The dual state of represents the Bloch state term with momentum k and energy band number x; , in, express The inverse matrix of the overlap matrix formed with its dual state; The polarization current equation is expressed as: , Among them, among them, represents the polarization current equation; represents the charge of an electron; represents the reduced Planck constant; represents the Fermi velocity; represents the energy band index; represents the wave vector; Indicates that the periodic cell is The number of lattices along each crystal axis; represents the Berry connection term; Indicates that the periodic cell is The original lattice vectors in the directions of the crystal axes; The imaginary part term introduced in the modified Hamiltonian without external field perturbation is expressed as: , in, represents the imaginary part term introduced in the modified Hamiltonian without external field perturbation; represents the decoherence rate; represents the sequence number of the Bloch state; represents the Bloch state term with momentum k and energy band number l; Represents the valence band when there is no external field perturbation.

[0013] Preferably, the order expansion function of the dynamic polarization current with respect to the electric field is expressed as: , in, The first Order coefficient, , represents the dynamic polarization current; , represents the energy of the incident field; Represents a unit imaginary number.

[0014] Preferably, the displacement photocurrent density of the periodic cell is expressed as: , in, represents the displacement photocurrent density of the periodic cell; represents the displacement current conductivity; Indicates energy; represents the electric field polarized along the b direction; represents the electric field polarized along the c direction.

[0015] The present invention also provides a Janus transition metal chalcogenide material photovoltaic effect control device, comprising: The strain simulation module is used to construct periodic cells of Janus transition metal chalcogenides and repeatedly change the lattice constants of the periodic cells to simulate the tensile strain of different gauge coefficients applied to the periodic cells, thereby obtaining the periodic cells corresponding to the tensile strain of different gauge coefficients. The electronic state evolution module is used to use the ground state wave function, eigenvalue, quasiparticle self-energy and light absorption spectrum of each periodic cell as the initial conditions of time-dependent evolution, simulate the electronic state changes of each periodic cell in a preset laser electric field, and obtain the dynamic polarization current of each periodic cell in the preset laser electric field; A displacement photocurrent density calculation module is used to calculate the displacement photocurrent density of each periodic cell based on the order expansion function of the dynamic polarization current of each periodic cell in a preset laser electric field with respect to the electric field; The control relationship acquisition module is used to fit the relationship equation of the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material with respect to the tensile gauge coefficient based on the lattice constant and displacement photocurrent density of all periodic cells, so as to control the photovoltaic effect of the Janus transition metal chalcogenide material by changing the tensile gauge coefficient applied to the Janus transition metal chalcogenide material.

[0016] The present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the above-mentioned method for regulating the photovoltaic effect of Janus transition metal chalcogenide materials are implemented.

[0017] The Janus transition metal chalcogenide material photovoltaic effect control method provided in this application has the following beneficial effects: Through experimental simulation, the present application found that when tensile strain is applied to the Janus transition metal chalcogenide material, the electronic structure and photoconductivity tensor of the Janus transition metal chalcogenide material change, causing its nonlinear photovoltaic effect to change accordingly, and the density of the displacement photocurrent that can be generated also changes. At the same time, as the tensile gauge coefficient increases, the displacement photocurrent density that can be generated by the Janus transition metal chalcogenide material gradually increases, thereby increasing the photogenerated carrier separation efficiency of the material under sunlight and gradually widening the spectral response range to the solar spectrum. That is, by changing the tensile gauge coefficient applied to the Janus transition metal chalcogenide material, the displacement photocurrent generated by it can be affected, thereby affecting its photoelectric conversion performance and light utilization efficiency. Based on this discovery, the present application changes the lattice constant of the periodic cells of the Janus transition metal chalcogenide material and uses the lattice constant to simulate the tensile strain with different gauge coefficients applied to the material; by performing time-dependent evolution of the periodic cells under different gauge coefficients in a preset laser electric field, the dynamic polarization current and displacement photocurrent density of each periodic cell are obtained; finally, by fitting the displacement photocurrent density of the periodic cells under multiple tensile gauge coefficients, the relationship equation of the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material with respect to the tensile gauge coefficient is obtained. Based on this relationship equation, the displacement photocurrent of the Janus transition metal chalcogenide material under different tensile strain degrees can be obtained, thereby providing theoretical guidance for the regulation of its displacement photocurrent, so as to achieve the regulation of the photovoltaic effect of the Janus transition metal chalcogenide material by applying tensile strain with different gauge coefficients to the Janus transition metal chalcogenide material. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 Flowchart of the method for regulating the photovoltaic effect of Janus transition metal chalcogenide materials provided in this application; Figure 2 A schematic diagram of the lattice structure of a periodic unit cell of a Janus transition metal chalcogenide material provided in an embodiment of the present application; Figure 3 for Figure 2 Schematic diagram of photovoltaic effect with and without tensile strain in the lattice structure shown; Figure 3 (a) is a schematic diagram of the linear optical absorption spectrum with and without tensile strain. Figure 3 (b) is a schematic diagram of the displacement photocurrent with and without tensile strain. Figure 3 (c) is a schematic diagram of the exciton spectrum with and without tensile strain; Figure 4For Figure 2 Schematic diagram of the photovoltaic effect after applying tensile strain with a gauge factor of 1% to 4% on the lattice structure shown in FIG. Figure 4 (a) is a schematic diagram of the quasiparticle band structure and PBE band structure of the lattice structure. Figure 4 (b) is a schematic diagram of the linear light absorption spectrum of the lattice structure. Figure 4 (c) is a schematic diagram of the displacement photocurrent of the lattice structure; Figure 5 Schematic diagram of the structure of the Janus transition metal chalcogenide material photovoltaic effect control device provided in this application. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0020] See also Figure 1 , Figure 1 The figure shows a flow chart of the method for regulating the optical effects of Janus transition metal chalcogenide materials provided by this application, which specifically includes: S10: Construct a periodic cell of Janus transition metal chalcogenide material and change the lattice constant of the periodic cell multiple times to simulate the tensile strain with different gauge coefficients applied to the periodic cell, and obtain the periodic cell corresponding to the tensile strain with different gauge coefficients.

[0021] Specifically, the present application constructs a periodic cell of Janus transition metal chalcogenide materials in VESTA software.

[0022] As a specific example of the present application, the lattice constant of the periodic cell is continuously changed in the range of 3.25 Å to 3.38 Å, thereby simulating the tensile strain with a gauge factor of 1% to 4% applied to the periodic cell.

[0023] S20: Taking the ground state wave function, eigenvalue, quasiparticle self-energy and light absorption spectrum of each periodic cell as the initial conditions of time-dependent evolution, simulate the electronic state changes of each periodic cell in the preset laser electric field to obtain the dynamic polarization current of each periodic cell in the preset laser electric field.

[0024] S30: Based on the order expansion function of the dynamic polarization current of each periodic cell in the preset laser electric field with respect to the electric field, the displacement photocurrent density of each periodic cell is calculated.

[0025] S40: Based on the lattice constants and displacement photocurrent densities of all periodic cells, the relationship equation between the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material and the tensile gauge factor is fitted, so that the photovoltaic effect of the Janus transition metal chalcogenide material can be regulated by changing the tensile gauge factor applied to the Janus transition metal chalcogenide material.

[0026] Specifically, the conductivity of the displacement photocurrent can be obtained by performing Fourier transform on the displacement photocurrent density, thereby obtaining its relationship with the tensile gauge factor.

[0027] Specifically, the relationship equation between the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material and the tensile gauge coefficient obtained by fitting in this application is expressed as: , in, The applied gauge factor is The conductivity of the displacement photocurrent of Janus transition metal chalcogenides under tensile strain; represents the conductivity of the initial displacement photocurrent of the Janus transition metal chalcogenide material when no tensile strain is applied; represents the tensile strain coefficient; , in, represents the lattice constant of Janus transition metal chalcogenide material after tensile strain is applied; represents the lattice constant of the Janus transition metal chalcogenide material when no tensile strain is applied.

[0028] The present application discovers for the first time that applying tensile strain to Janus transition metal chalcogenide materials changes the electronic structure and photoconductivity tensor of the Janus transition metal chalcogenide materials, thereby changing their nonlinear photovoltaic effect, causing the displacement photocurrent that the Janus transition metal chalcogenide materials can generate under the solar spectrum to change; and, through a large number of experimental simulations, it is found that as the coefficient of the tensile strain applied to the Janus transition metal chalcogenide materials increases or decreases, the displacement photocurrent density that the Janus transition metal chalcogenide materials can generate also shows a trend of gradually increasing or decreasing, thereby causing the photogenerated carrier separation efficiency of the material under sunlight to increase or decrease, and the spectral response range to the solar spectrum to gradually widen or narrow. Therefore, the following conclusions are drawn: 1. Applying tensile strain to Janus transition metal chalcogenide materials can change the photovoltaic effect of the material; 2. By changing the gauge coefficient of the tensile strain applied to the material, the size of the displacement photocurrent generated by the material can be controlled, thereby achieving regulation of the material's photovoltaic effect.

[0029] Based on the above conclusions, this application changes the lattice constant of the periodic cells of the Janus transition metal chalcogenide material, and uses the lattice constant to simulate the tensile strain with different gauge coefficients applied to the material; by performing time-dependent evolution of the periodic cells under different gauge coefficients in a preset laser electric field, the dynamic polarization current and displacement photocurrent density of the periodic cells under different gauge coefficients are obtained; finally, by fitting the displacement photocurrent density of the periodic cells under multiple tensile gauge coefficients, the relationship equation of the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material with respect to the tensile gauge coefficient is obtained. Based on this relationship equation, the displacement photocurrent of the Janus transition metal chalcogenide material under different tensile strain degrees can be obtained, thereby providing theoretical guidance for the regulation of its displacement photocurrent, so as to achieve the regulation of the photovoltaic effect of the Janus transition metal chalcogenide material by applying tensile strain with different gauge coefficients to the Janus transition metal chalcogenide material.

[0030] It's worth noting that in practical applications, there are multiple ways to apply tensile strain to Janus transition metal chalcogenides, including substrate stretching, atomic force microscopy (AFM) tip methods, and microelectromechanical system (MEMS) fixture methods. Specifically, the substrate stretching method transfers the Janus transition metal chalcogenide onto a stretchable substrate, such as polydimethylsiloxane (PDMS). Mechanically stretching the substrate causes strain to be applied to the attached Janus transition metal chalcogenide. The atomic force microscopy (AFM) tip method gently presses the AFM tip against the material surface. By controlling the tip's position and pressure on the material surface, local strain is induced in the material beneath the tip. The MEMS fixture method secures the Janus transition metal chalcogenide to a fixture and applies an external force, such as an electric field, magnetic field, or mechanical force, to the MEMS fixture, causing the fixture to deform and thus induce strain in the material.

[0031] Specifically, this application uses Quantum Espresso software based on density functional theory to calculate the ground state wave function and eigenvalue of the periodic cell. The specific calculation process is as follows: The periodic cells are input into the Quantum Espresso software, and the positions of the atoms in the periodic cells are adjusted to perform structural relaxation on the periodic cells until the total force of the periodic cells reaches a preset total force value and the total energy converges to a preset total energy value.

[0032] A vacuum layer of preset thickness is set in the out-of-plane direction of the periodic cell, and a dipole correction is added to the vacuum layer to obtain the target periodic cell.

[0033] The Perdew-Burke-Ernzerhof generalized gradient approximation function and the conservative gauge pseudopotential are selected as the exchange-correlation functional. Based on the preset plane wave cutoff energy and k-point grid, a self-consistent iterative calculation is performed on the target periodic cell, and the ground state wave function and eigenvalue of the target periodic cell are output.

[0034] Specifically, the equations for solving the ground state wave function and eigenvalue are expressed as: , in, represents the ground state wave function; represents the eigenvalue.

[0035] Specifically, by placing a vacuum layer in the out-of-plane direction of the periodic cells, it is possible to prevent spurious interactions between the periodic cell layers from affecting the ground state wave function and eigenvalue calculation results. Furthermore, adding a dipole correction to the vacuum layer prevents the out-of-plane electric dipole moment from damaging the periodic cells.

[0036] As a specific example of this application, the preset total force value is 10 -4 eV / Å, the default total energy value is 10 -7 eV; the preset plane wave cutoff energy is 80Ry, the preset k-point grid is a 21*21*1 k-grid; the thickness of the vacuum layer is 15 Å.

[0037] Furthermore, the present application uses Yambo software to calculate the quasiparticle band structure and optical absorption spectrum of each periodic cell based on the multi-body perturbation theory GW-BSE. The specific calculation process includes: The periodic cells are input into the Yambo software, and the Dyson equation is solved based on the preset K grid, dielectric matrix cutoff energy, number of energy bands and Coulomb cutoff to obtain the quasiparticle self-energy of the periodic cells.

[0038] Specifically, the Dyson equation is expressed as: , in, represents the self-energy operator under the GW approximation; represents the energy of the quasiparticle with momentum k and conduction band number n; represents the wave function.

[0039] The valence band and conduction band of the periodic cell are set with the goal of covering the solar spectrum. The Bethe-Salprter equation is solved based on the valence band and conduction band to obtain the light absorption spectrum of the periodic cell.

[0040] Specifically, the Bethe-Salprter equation is expressed as: , in, represents the energy of the quasiparticle with momentum k and conduction band number c; represents the energy of the quasiparticle with momentum k and valence band number v; represents the exciton wave function; denote the overlap matrices of the Bloch state terms corresponding to momentum k, conduction band number c, and valence band number v, respectively; The nucleus represents the Coulomb interaction of electron and hole; Represent the corresponding momentum , Conductor band number , valence band number The overlap matrix of the Bloch state terms; represents the exciton energy.

[0041] The optical absorption spectrum is expressed as: , in, represents the exciton state; represents the velocity operator along the polarization direction e of the incident light.

[0042] As a specific example of the present application, when calculating the GW of the quasiparticle band structure, the preset K grid is a 21*21*1 grid, the preset dielectric matrix cutoff energy is 10Ry, and the preset number of energy bands is 30 times the number of valence bands; when calculating the BSE of the optical absorption spectrum, the valence band and conduction band of the periodic cell are both set to 6.

[0043] Furthermore, the present application uses Yambo software to simulate the electronic state changes of each periodic cell in a preset laser electric field. In a specific simulation embodiment, in order to ensure the simulation accuracy and stability, the propagation time of each laser frequency is set to 140fs, the time step is 5as, and the laser intensity I=1000kW / cm 2 In addition, in order to consider the finite broadening effect of the spectral line, a decoherence term of 0.05 eV is introduced in the simulation to simulate the smoothing effect in the linear response.

[0044] Specifically, the ground state wave function, eigenvalue, quasiparticle self-energy and light absorption spectrum of each periodic cell are used as the initial conditions of the time-dependent evolution, and the electronic state changes of each periodic cell in the preset laser electric field are simulated. The dynamic polarization current of each periodic cell in the preset laser electric field is obtained, including: Based on the modified Hamiltonian without external field perturbation and the external field perturbation term, the electron motion equation of the periodic cell in the preset laser electric field is constructed.

[0045] Based on modern polarization theory and the periodicity of Bloch waves, the polarization current equation of the periodic cell in the preset laser electric field is constructed.

[0046] A single-frequency external electric field is applied to the periodic cell in a preset laser electric field, and an imaginary part term is introduced into the modified Hamiltonian without external field perturbation to simulate the decoherence process. Time-dependent simulation is performed based on the ground state wave function, eigenvalue, quasiparticle self-energy and light absorption spectrum of the periodic cell.

[0047] Based on the time-dependent simulation process, the electron motion equation is integrated to obtain the Bloch state term that evolves with time. The Bloch term that evolves with time is substituted into the polarization current equation to obtain the dynamic polarization current of the periodic cell in the preset laser electric field.

[0048] Specifically, the electron motion equation is expressed as: , in, represents the effective Hamiltonian, , represents the modified Hamiltonian without external field disturbance, , represents the Kohn-Sham Hamiltonian under the independent particle approximation, represents the quasiparticle correction considering electron-electron interaction, represents the time-dependent Hartree correction, represents the time-dependent screened Hartree-Fock correction; represents the external field perturbation term, , represents the electron-external field coupling operator; Indicates time The partial derivative of Represents a unit imaginary number; represents the Bloch state term with momentum k and energy band number n; , in, Indicates the outfield; ; represents the next k-point in the grid in the Cartesian direction; , Represents the distance between two adjacent k points; represents the projection operator; , in, represents the total number of occupied energy bands, express The dual state of represents the Bloch state term with momentum k and energy band number x; , in, express The inverse matrix of the overlap matrix formed with its dual state; The polarization current equation is expressed as: , in, represents the polarization current equation; represents the charge of an electron; represents the reduced Planck constant; represents the Fermi velocity; represents the energy band index; represents the wave vector; Indicates that the periodic cell is The number of lattices along each crystal axis; represents the Berry connection term; Indicates that the periodic cell is The original lattice vectors in the directions of the crystal axes; The imaginary part term introduced in the modified Hamiltonian without external field perturbation is expressed as: , in, represents the imaginary part term introduced in the modified Hamiltonian without external field perturbation; represents the decoherence rate; represents the sequence number of the Bloch state; represents the Bloch state term with momentum k and energy band number l; Represents the valence band when there is no external field perturbation.

[0049] It is worth noting that once all eigenfrequencies are eliminated, the remaining current is one cycle A periodic function of .

[0050] In a specific example of this application, the introduction After the external electric field is applied, the formula for iterative solution of the electron motion equation is: , in, express The Bloch state term with moment momentum k and energy band number n; represents the modified Hamiltonian without external field disturbance by introducing the imaginary part; express The Bloch state term with moment momentum k and energy band number n.

[0051] The order expansion function of the dynamic polarization current with respect to the electric field is expressed as: , in, The first Order coefficient, , represents the dynamic polarization current; , represents the energy of the incident field; Represents a unit imaginary number.

[0052] Specifically, due to The integration of requires a very small time step to obtain the converged value, which is significantly smaller than the time iterative integration of the electron motion equation. Perform Fourier expansion and truncate the expanded order S to be slightly larger than the required nonlinear optical order. Internal sampling 2S+1 value, The Fourier expansion of can be expressed as a series of linear equations , which can be achieved by Fourier matrix of order Find the inverse to get along Directional component and through Obtain the conductivity of the target order. For the conductivity of the displacement photocurrent calculated in this application, S=4 is required to ensure the convergence of the results.

[0053] Furthermore, the displacement photocurrent density of the periodic cell is expressed as: , in, represents the displacement photocurrent density of the periodic cell; represents the displacement current conductivity; Indicates energy; represents the electric field polarized along the b direction; represents the electric field polarized along the c direction.

[0054] The above-mentioned method for regulating the photovoltaic effect of Janus transition metal chalcogenide materials is further explained below through a specific embodiment.

[0055] In this embodiment, Janus MoSSe single layer material is taken as an example. Figure 2 The figure shows a schematic diagram of the periodic unit cell lattice structure of the Janus MoSSe single-layer material constructed in the VESTA software. Specifically, the lattice structure contains one Mo atom, one S atom, and one Se atom, respectively. The S atom is located on the upper surface and the Se atom is located on the lower surface, thus destroying the radial symmetry of the unit cell.

[0056] Figure 3The figure shows the photovoltaic effect of the Janus MoSSe single layer material with and without tensile strain, where: Figure 3 (a) is a schematic diagram of the linear optical absorption spectrum with and without tensile strain. Figure 3 (b) is a schematic diagram of the displacement photocurrent with and without tensile strain. Figure 3 (c) is a schematic diagram of the exciton spectrum with and without tensile strain.

[0057] From the figure, we can see that for The Janus MoSSe single layer material of the point group has 21 non-zero components in its second-order nonlinear optical response tensor, satisfying: , , . Refer to experimental measurements, only considering the in-plane component Similar to the linear spectral response, the displacement photocurrent spectrum also shows a strong exciton effect, resulting in a large displacement photocurrent response within the quasiparticle band gap range. As shown by the vertical arrows, resonance peaks and enhancement peaks that are consistent with the experiment can be observed.

[0058] exist Figure 3 As can be seen in (a), compared with the case without exciton effect, the maximum value of the displacement photocurrent increases by several orders of magnitude, which indicates that the exciton effect significantly enhances the displacement photocurrent. This enhancement effect is much stronger than the enhancement in the linear optical spectrum: in the linear optical spectrum, after considering the exciton effect, the light absorption of the Janus MoSSe monolayer is enhanced by about 2 times; in the displacement photocurrent spectrum, the maximum photocurrent response in the solar spectrum range is enhanced by about 7 times, far exceeding the non-interaction case.

[0059] Furthermore, by continuously changing the lattice constant of the periodic cells in the range of 3.25 Å to 3.38 Å, the tensile strain with a gauge factor of 1% to 4% applied to the periodic cells was simulated.

[0060] like Figure 4 The figure shows the photovoltaic effect after applying a tensile strain with a gauge factor of 1% to 4% to the lattice structure of the Janus MoSSe single layer material; Figure 4 (a) is a schematic diagram of the quasiparticle band structure and PBE band structure of the lattice structure. Figure 4 (b) is a schematic diagram of the linear light absorption spectrum of the lattice structure. Figure 4 (c) is a schematic diagram of the displacement photocurrent of the lattice structure.

[0061] By comparison Figure 4The band structures calculated by GW (red solid line) and PBE (blue dashed line) in (a) show the regulation effect of tensile strain on the electronic energy band of the material: as the strain increases from +1% to +4%, the energy band shrinks as a whole, indicating that the band gap decreases, which is consistent with the subsequent optical absorption calculation results. Figure 4 As can be seen from (b) in the figure, when there is no tensile strain, the first light absorption peak of the material appears at 1.9 eV, while under +4% strain, the absorption peak shifts to 1.5 eV, indicating that tensile strain can effectively reduce the optical band gap, thereby broadening the light absorption range and improving the utilization rate of low-energy photons. Figure 4 As can be seen in (c), in the range of 1.4 eV to 2.0 eV, with the increase of tensile strain, a displacement photocurrent peak that has not been observed in the unstrained system appears, and the peak value increases with the increase of strain. At the same time, the position of the peak red-shifts, which indicates that tensile strain can not only optimize the light absorption characteristics, but also effectively regulate the displacement photocurrent response.

[0062] Based on the above examples, it can be seen that when Janus MoSSe is subjected to tensile strain, the energy of its first main displacement current peak gradually decreases from 1.9 eV (visible light) in the 0% system to 1.5 eV (near infrared) in the 4% system, with a linear change rate of 0.1 eV / %. The peak value of the displacement photocurrent gradually increases with the degree of tensile strain, from 31 μV / A in the 0% system to 1.5 eV (near infrared). 2 Regulated to 49μV / A at 4% 2 , increases linearly and its rate of change is 4.5μV / A 2 %.

[0063] Based on the Janus transition metal chalcogenide material photovoltaic effect control method provided in the above embodiment, the present application embodiment also provides a Janus transition metal chalcogenide material photovoltaic effect control device, such as Figure 5 As shown, the device specifically includes: The strain simulation module 10 is used to construct a periodic cell of the Janus transition metal chalcogenide material and change the lattice constant of the periodic cell multiple times to simulate applying tensile strains with different gauge coefficients to the periodic cell, thereby obtaining periodic cells corresponding to the tensile strains with different gauge coefficients.

[0064] The electronic state evolution module 20 is used to use the ground state wave function, eigenvalue, quasiparticle self-energy and light absorption spectrum of each periodic cell as the initial conditions of time-dependent evolution, simulate the electronic state changes of each periodic cell in the preset laser electric field, and obtain the dynamic polarization current of each periodic cell in the preset laser electric field.

[0065] The displacement photocurrent density calculation module 30 is used to calculate the displacement photocurrent density of each periodic cell based on the order expansion function of the dynamic polarization current of each periodic cell in the preset laser electric field with respect to the electric field.

[0066] The control relationship acquisition module 40 is used to fit the relationship equation of the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material with respect to the tensile gauge factor based on the lattice constant and displacement photocurrent density of all periodic cells, thereby regulating the photovoltaic effect of the Janus transition metal chalcogenide material by changing the tensile gauge factor applied to the Janus transition metal chalcogenide material.

[0067] The embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the above-mentioned method for regulating the photovoltaic effect of Janus transition metal chalcogenide materials are implemented.

[0068] In summary, the control method provided by this application enables the device to more widely utilize low-energy photons in the solar spectrum, improve the photoelectric conversion efficiency, and thus be suitable for high-efficiency photovoltaic cells and infrared light detectors; and the generation of displacement photocurrent no longer depends on an external bias voltage, and can be used for self-powered photovoltaic devices, reducing external circuit requirements and improving energy conversion efficiency; in addition, this application can regulate photoelectric performance on a flexible substrate, making it suitable for emerging application fields such as flexible solar cells, wearable sensors, and transparent photovoltaic devices.

[0069] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0070] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1A device that provides the functions specified in a block or multiple blocks.

[0071] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0072] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0073] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for regulating the photovoltaic effect of a Janus transition metal chalcogenide material, characterized in that: include: Construct a periodic cell of Janus transition metal chalcogenide material and change the lattice constant of the periodic cell multiple times to simulate the tensile strain with different gauge coefficients applied to the periodic cell, and obtain the periodic cell corresponding to the tensile strain with different gauge coefficients; The ground state wave function, eigenvalue, quasiparticle self-energy and light absorption spectrum of each periodic cell are used as the initial conditions of the time-dependent evolution to simulate the electronic state changes of each periodic cell in the preset laser electric field, and obtain the dynamic polarization current of each periodic cell in the preset laser electric field; Based on the order expansion function of the dynamic polarization current of each periodic cell in the preset laser electric field with respect to the electric field, the displacement photocurrent density of each periodic cell is calculated; Based on the lattice constants and displacement photocurrent densities of all periodic cells, the relationship equation between the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material and the tensile gauge coefficient was fitted, so that the photovoltaic effect of the Janus transition metal chalcogenide material can be regulated by changing the tensile gauge coefficient applied to the Janus transition metal chalcogenide material.

2. The method for controlling the photovoltaic effect of Janus transition metal chalcogenide materials according to claim 1, characterized in that: The relationship between the conductivity of the displacement photocurrent of Janus transition metal chalcogenides and the tensile gauge coefficient is expressed as: ， in, The applied gauge factor is The conductivity of the displacement photocurrent of Janus transition metal chalcogenides under tensile strain; represents the conductivity of the initial displacement photocurrent of the Janus transition metal chalcogenide material when no tensile strain is applied; represents the tensile strain coefficient; ， in, represents the lattice constant of the Janus transition metal chalcogenide material after tensile strain is applied; represents the lattice constant of the Janus transition metal chalcogenide material when no tensile strain is applied.

3. The method for controlling the photovoltaic effect of Janus transition metal chalcogenide materials according to claim 1, wherein: Density functional theory is used to calculate the ground state wave function and eigenvalue of each periodic cell, which specifically includes: Input the periodic cell into Quantum Espresso software, and adjust the position of each atom in the periodic cell to perform structural relaxation on the periodic cell until the total force of the periodic cell reaches a preset total force value and the total energy of the periodic cell converges to a preset total energy value; A vacuum layer of preset thickness is set in the out-of-plane direction of the periodic cell, and a dipole correction is added to the vacuum layer to obtain the target periodic cell; The Perdew-Burke-Ernzerhof generalized gradient approximation function and the conservative gauge pseudopotential are selected as the exchange-correlation functional. Based on the preset plane wave cutoff energy and k-point grid, a self-consistent iterative calculation is performed on the target periodic cell, and the ground state wave function and eigenvalue of the target periodic cell are output.

4. The method for controlling the photovoltaic effect of Janus transition metal chalcogenide materials according to claim 1, wherein: The quasiparticle self-energy and light absorption spectrum of each periodic cell are calculated using the many-body perturbation theory, which specifically includes: The periodic cells are input into the Yambo software, and the Dyson equation is solved based on the preset K grid, dielectric matrix cutoff energy, number of energy bands, and Coulomb cutoff to obtain the quasiparticle self-energy of the periodic cells. The valence band and conduction band of the periodic cell are set with the goal of covering the solar spectrum. The Bethe-Salprter equation is solved based on the valence band and conduction band to obtain the light absorption spectrum of the periodic cell.

5. The method for controlling the photovoltaic effect of Janus transition metal chalcogenide materials according to claim 1, wherein: The ground state wave function, eigenvalue, quasiparticle self-energy and light absorption spectrum of each periodic cell are used as the initial conditions of the time-dependent evolution. The electronic state changes of each periodic cell in the preset laser electric field are simulated, and the dynamic polarization current of each periodic cell in the preset laser electric field is obtained, including: Based on the modified Hamiltonian without external field perturbation and the external field perturbation term, the electron motion equation of the periodic cell in the preset laser electric field is constructed; Based on modern polarization theory and the periodicity of Bloch waves, the polarization current equation of the periodic cell in the preset laser electric field is constructed; A single-frequency external electric field is applied to the periodic cell in a preset laser electric field. An imaginary term is introduced into the modified Hamiltonian without external field perturbation to simulate the decoherence process. Time-dependent simulation is performed based on the ground state wave function, eigenvalue, quasiparticle self-energy and optical absorption spectrum of the periodic cell. Based on the time-dependent simulation process, the electron motion equation is integrated to obtain the Bloch state term that evolves with time. The Bloch term that evolves with time is substituted into the polarization current equation to obtain the dynamic polarization current of the periodic cell in the preset laser electric field.

6. The method for controlling the photovoltaic effect of Janus transition metal chalcogenide materials according to claim 5, characterized in that: The electron motion equation is expressed as: ， in, represents the effective Hamiltonian, , represents the modified Hamiltonian without external field disturbance, , represents the Kohn-Sham Hamiltonian under the independent particle approximation, represents the quasiparticle correction considering electron-electron interaction, represents the time-dependent Hartree correction, represents the time-dependent screened Hartree-Fock correction; represents the external field perturbation term, , represents the electron-external field coupling operator; Indicates time The partial derivative of Represents a unit imaginary number; represents the Bloch state term with momentum k and energy band number n; ， in, Indicates the outfield; ; represents the next k-point in the grid in the Cartesian direction; , Represents the distance between two adjacent k points; represents the projection operator; ， in, represents the total number of occupied energy bands, express The dual state of represents the Bloch state term with momentum k and energy band number x; ， in, express The inverse matrix of the overlap matrix formed with its dual state; The polarization current equation is expressed as: ， in, represents the polarization current equation; represents the charge of an electron; represents the reduced Planck constant; represents the Fermi velocity; represents the energy band index; represents the wave vector; Indicates that the periodic cell is The number of lattices along each crystal axis; represents the Berry connection term; Indicates that the periodic cell is The original lattice vectors in the directions of the crystal axes; The imaginary part term introduced in the modified Hamiltonian without external field perturbation is expressed as: ， in, represents the imaginary part term introduced in the modified Hamiltonian without external field perturbation; represents the decoherence rate; represents the sequence number of the Bloch state; represents the Bloch state term with momentum k and energy band number l; Represents the valence band when there is no external field perturbation.

7. The method for controlling the photovoltaic effect of Janus transition metal chalcogenide materials according to claim 1, wherein: The order expansion function of the dynamic polarization current with respect to the electric field is expressed as: ， in, The first Order coefficient, , represents the dynamic polarization current; , represents the energy of the incident field; Represents a unit imaginary number.

8. The method for controlling the photovoltaic effect of Janus transition metal chalcogenide materials according to claim 1, wherein: The displacement photocurrent density of the periodic cell is expressed as: ， in, represents the displacement photocurrent density of the periodic cell; represents the displacement current conductivity; Indicates energy; represents the electric field polarized along the b direction; represents the electric field polarized along the c direction.

9. A Janus transition metal chalcogenide photovoltaic effect control device, characterized in that: include: The strain simulation module is used to construct periodic cells of Janus transition metal chalcogenides and repeatedly change the lattice constants of the periodic cells to simulate the tensile strain of different gauge coefficients applied to the periodic cells, thereby obtaining the periodic cells corresponding to the tensile strain of different gauge coefficients. The electronic state evolution module is used to use the ground state wave function, eigenvalue, quasiparticle self-energy and light absorption spectrum of each periodic cell as the initial conditions of time-dependent evolution, simulate the electronic state changes of each periodic cell in a preset laser electric field, and obtain the dynamic polarization current of each periodic cell in the preset laser electric field; A displacement photocurrent density calculation module is used to calculate the displacement photocurrent density of each periodic cell based on the order expansion function of the dynamic polarization current of each periodic cell in a preset laser electric field with respect to the electric field; The control relationship acquisition module is used to fit the relationship equation of the conductivity of the displacement photocurrent of the Janus transition metal chalcogenide material with respect to the tensile gauge coefficient based on the lattice constant and displacement photocurrent density of all periodic cells, so as to control the photovoltaic effect of the Janus transition metal chalcogenide material by changing the tensile gauge coefficient applied to the Janus transition metal chalcogenide material.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the Janus transition metal chalcogenide material photovoltaic effect control method according to any one of claims 1 to 8 are implemented.

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