| The emergence of silicon-based semiconductors has made electronic technology products more miniature and integrated.Nowadays,the exploration and research of graphene and related two-dimensional materials has rapidly promoted its application and development in various industries,and has become the most potential functional materials in the next-generation information industry.Various two-dimensional materials have been successfully synthesized and applied experimentally,and theoretically,more novel two-dimensional functional materials have been analyzed and predicted through high-performance calculations and simulations.The two-dimensional graphene-like material based on graphene single layer has ultra-high carrier mobility,Fermi velocity and quantum Hall effect,promoting the development of integrated circuits.In addition to looking for graphene-like two-dimensional materials to enrich its development in optoelectronics,mechanics,and thermodynamics,low-dimensional nanotubes can be obtained by reducing their dimensions and hydrogenation can further promoting their use in electrochemical and energy storage.In addition,the new type of physical properties that appear after the horizontal or vertical layered structure composed of semi-conductive transition metal chalcogenides has further expanded the application of two-dimensional materials.More interestingly,two-dimensional materials have also played a rare role in improving the utilization of solar energy through photoelectric conversion in photoelectronic,photovoltaic,and photocatalytic systems.Therefore,investigating the photoelectric properties of photoexcitation in two-dimensional materials has become crucial to their internal mechanism analysis and functional regulation of optoelectronic devices.However,there are still more challenges in the synthesis of graphene-like two-dimensional materials,and further exploration of the electronic properties and mechanism analysis after synthesis is needed.At the same time,it is instructive to consider the interaction between electrons,phonons,and photons and the coupling between excitons and excitons in the practical application of two-dimensional materials.The consideration of the photo-matter interaction in the excited state can provide a more valuable theoretical basis for the research and design of new types of optoelectronic,photocatalytic,and photovoltaic devices.In this dissertation,We have simulated and analyzed a variety of graphene-like materials through first-principles calculations based on density functional theory and engineering their electronic structures and interface properties;explored interlayer excitons using stacked bilayer multilayer materials to investigate the physical valley polarization mechanism;and further explore the ground state and temperature-dependent electro-phonon coupling effects by combining many body perturbation theory to reveal the excited photoelectric properties.The thesis is mainly divided into six chapters.The first chapter briefly discusses the research status and development background of two-dimensional materials.The second chapter gives the theoretical calculation methods and related calculation software used in this paper.The third chapter introduces the investigation of the electronic properties of the interface effects of graphene-like material growth condition,and tunable electronic properties and energy storage application of one-dimensional nanotubes.Chapter 4 explores the optoelectronic properties of the van der Waals layered material formed by polar MoSSe.In Chapter 5 give and insight into the photoelectric properties of monolayer and bilayer materials considering temperature dependence.The main research contents and conclusions of this paper are as follows:(1)We study two-dimensional germanene supported on Au(111)to determine the structural,electronic and interface interaction properties on the basis of first-principles electronic calculations.The simulated configuration consistent with the experiment,The germanene on Au(111)loses its linear band dispersion relationship and demonstrates intense hybridization effects with Au(111).In addition,the structural and electronic properties of the recently synthesized monolayer and bilayer germanene on Cu(111)though first-principles calculations are studied.For bilayer germanene on Cu(111),interactions with Cu(111)are reduced due to germanene inter-layer interactions,which is beneficial for the transfer of germanene.In comparison with the bottom germanene layer,the Dirac cone character of the upper germanene layer can be maintained near the Fermi level.In summary,Since the linear band dispersion is at the heart of the novel quantum phenomenon,our results will facilitate research into the synthesis,extraordinary quantum properties,and optoelectric applications based on the two-dimensional graphene-like materials.(2)Three novel types of boron nanotubes were constructed and predicted,and their electronic properties were discussed by adjusting the chirality and diameters.By means of hydrogenating the nanotubes,stable nanotubes can be obtained.Moreover,applying stress in the axial direction of the tube can achieve the transition from metal to semiconductor.Among them,two special pore boron nanotubes have studied the hydrogen storage performance,and found that they have good hydrogen storage capacity,and the interaction between hydrogen and hydrogen or between hydrogen and boron nanotubes predict that it has better hydrogen storage capacity.Therefore,it can effectively regulate the electronic properties and explore its potential for hydrogen storage by lowering dimensional of the graphene-like borophene.(3)The optical and electrical properties of a vdW layered material consisting of a single layer of polar MoSSe are discussed.The quasi-particle band structure of polar MoSSe and WSSe monolayers is given by considering the GW approximation including electron-electron self-energy correlation,and its excited state has important research value for light response.By studying the electrical properties of the horizontal or vertical heterojunction composed of polar MoSSe and WSSe,it is found that the generation of its built-in electric field improves the polarization intensity of Rashba,and the response improved significantly compared to the monolayer.In addition,the horizontal or vertical heterojunctions form the type ?band alignment,which is beneficial to the formation of interlayer excitons and the generation of long valley polarization excitons.For lateral MoSSe/WSSe,one-dimensional metal boundaries can be obtained on the basis of constructing different grain boundaries,which also indicates the occurrence of one-dimensional electron gas in this heterogeneous configuration.The above structure control of the polar MoSSe can make it commendable used in optoelectronics and spintronics devices.(4)The electronic properties of the Zeeman and Rashba splitting generated by in-plane and out-of-plane dipole moments in the homogeneous vdW bilayer and trilayers composed of MoSSe were explored.Results show that there are large band offsets in the vdW layered structure composed of MoSSe monolayers with intrinsic vertical dipole moments,which will also cause type-? band alignment features.In this case,interlayer excitons with longer valley polarization lifetimes will appear,which provides better conditions for the practical application of photovoltaic devices.In addition,the strength of Rashba splitting due to the vertical dipole moment can be adjusted by applying stress and adjusting the interlayer distance,and we also give an explanation of the internal mechanism of this regulation.The study of the electronic properties of the homogeneous vdW layered structure composed of MoSSe will have potential application value for the future use of valley-related physics and spintronics devices.(5)The photoelectric properties of excited states in polar MoSSe monolayers were investigated.Based on the many body perturbation theory,it is demonstrated that the strong excited state properties will have an important effect on the optical absorption properties of MoSSe,and it has a large exciton binding energy at low energy positions.Considering the temperature effect in practical applications,that is,including the influence of electron-phonon coupling,the band gap is reduced by 40 meV at 0 K.And as the temperature rises,the position,intensity,and width of the excitons are also affected.The theoretically calculated temperature-dependent optical band gap can correspond well with the experimental photoluminescence spectrum at room temperature.Furthermore,for polar MoSSe,the behavior of excitons under the consideration of time-dependent dynamics was also investigated,and the results show that the intralayer exciton can be rapidly combined within a certain time scale.In addition,by considering the theory of excited states of the many body Green function,the dependent angle of light incidence on the light absorption of anisotropic single-layer black phosphorus was explored,and quasi-particle band gap show an increase tendency as temperature increase by considering the temperature-dependent quasiparticle state exciton lifetime and broadening.Our research on the photoelectric properties of the excited state for polar MoSSe,anisotropy black phosphorus and the dynamics of excitons provides a favorable theoretical guidance theoretical for the light-matter interaction in two-dimensional materials.(6)The interlayer excitons in vdW layered materials composed of different TMDCs was investigated.Combining first-principles calculations with many body Green's function theory and time-dependent non-adiabatic molecular dynamics simulation,the interlayer excitons composed of three TMDCs vdW bilayers with different built-in electric fields were theoretical performed.Interlayer exciton generation can be explained by the quantum confined Stark effect.Moreover,the results of comparative analysis show that MoSSe/WSSe heterojunctions with large built-in electric fields have relatively higher exciton binding energy,larger band offset,and longer electron-hole recombination time,which means that it has high photoelectric conversion efficiency and strong valley polariton.Our results for 2D TMDCs vdW bilayers in particular show the great possibility of structural tunability to manipulate the interlayer excitonic properties and advance the excitonic devices,thus would drive more interesting studies on the excited-state properties and light-matter interactions of other 2D vdW materials. |
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