| The third-generation broadband semiconductor GaN and the halide chalcogenide semiconductor MAPbX3(X=I,Br,Cl)have attracted many researchers to explore the utility of their combination because of their excellent optical and absorption properties,such as piezoelectric optics,photovoltaics,and nanostructured laser diodes.However,most of the above attempts have embarked on the combination of pure materials at room temperature,ignoring the challenges posed to devise performance by the complexity of the actual environment.The study of electromagnetic radiation properties plays an important role in understanding the absorption properties of materials,as well as in assessing energy losses.Therefore,considering the effects of variables such as temperature,doping,and angle on the electromagnetic radiation properties of composite structures is important to promote the practical applications of the devices.In this paper,the dielectric functions of GaN and MAPbX3 composite structures and their spectral radiation properties are systematically investigated using ellipsometric measurements,multi-scale simulations such as atomic-scale first principles,and computational electromagnetics.The main conclusions of the work are as follows:This thesis investigates the dielectric function of GaN crystals in the ultraviolet-visible range systematically,including the origin of absorption peaks,temperature effects,and doping effects,with the help of spectroscopic ellipsometry and first-principles calculations.The ellipsometric measurements identify two absorption peaks E0(exciton)and E0(CP)in the dielectric function,which originate from the exciton effect and phonon-assisted indirect absorption,respectively.This is verified with the help of the first-principles calculations such as model Bethe-Salpeter equation,and the phonon-assisted optical absorption.As the temperature increases,a weakening and red-shifting of the absorption peak are observed,which is due to the enhanced phonon scattering electron effect,thus reducing the electron leap.When GaN is doped with Fe and Si elements,the introduced carriers will adjust its’ dielectric function;moreover,the temperature variation of the dielectric function of GaN crystals containing doping is stronger than that of non-doped GaN.This thesis constructs a composite structure of "chalcogenide MAPbX3-nanoporous GaNGaN" and selected variables such as pore size d,incidence angle,temperature,and doping.After that,this paper calculates the electromagnetic radiation properties in the UV-Vis band including reflection,electric field,and absorption energy with the help of the finite difference in time-domain method.It is found that the pore size d of nanoporous GaN has an important effect on its radiation properties,and small pore size d can ensure the uniformity of distribution based on the enhanced field strength and absorbed energy.Comparing the absorption energy of MAPbI3 and MAPbBr3 composite structures,it is found that the absorption energy of the former in the near-UV band(λ=350 nm)is higher than that of the latter,while the absorption energy in the visible band(λ=600 nm)is lower than that of the latter,which is determined by the absorption characteristics(the dielectric function characterize)of both.The excitation electric field of the MAPbCl3 structure at short-wave visible light has a lower skinning depth than that of UV light,which is different from the other two types of chalcogenide materials.The composite structure where MAPbI3 is located is used as an example to calculate the radiation performance variation under complex conditions.The large oblique incident angle will reduce the absorption amplititude and cause the absorption peak displacement in visible range,and the azimuth phase does not affect the absorption of composite structure.GaN doping elements do not have a significant effect on the radiation properties of the composite structure,but pervoskite doping elements cause stronger changes.Taking Zn doping as an example,it has a nagitive effects. |
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