Study On Optical Properties Of ZnO Based Materials

In recent years,the use of solar energy visible light in semiconductor photocatalytic technology has aroused wide public concern in many areas.At room temperature,semiconductor material ZnO has excellent physical properties,such as high saturation mobility,high exciton binding energy,excellent photoelectric properties and so on.Therefore,it has potential application value in the field of photocatalysis.The band gap of ZnO is 3.37 eV,and the required light excitation wavelength is in the UV light region.Therefore,the intrinsic ZnO cannot realize photocatalytic activity under visible light.The study shows that the photocatalytic efficiency of visible light can be improved effectively by doping or forming a composite structure.In this paper,the electronic structure and optical properties of N-ZnO,V_Zn-ZnO,V_Zn-N-ZnO and AlN/ZnO heterostructures are studied by Castep based on the first principle method.The main results are shown below:1.The electronic structure and optical properties of ZnO,N-ZnO,V_Zn-ZnO and V_Zn-N-ZnO are studied.The results show that,ZnO is a direct band gap semiconductor material.When doped or defective,the valence bands of the three systems all pass the Fermi level,and the materials exhibit metal properties.By analyzing the absorption spectrum,it is found that ZnO has no absorption spectrum in the visible region,and the other three systems show visible light absorption,and the visible light absorption is obviously enhanced when N-V_Zn coexists,which enhances the visible light photocatalytic efficiency of ZnO.Through the analysis of density of states,the main reason is the intra-band transition of electrons in the vicinity of Fermi level.2.The AlN/ZnO heterostructure is constructed.The band structure analysis s hows that AlN is a direct band gap semiconductor material,and it displays metal properties after forming heterostructure.The absorption spectrum analysis shows that the intrinsic ZnO and AlN have no absorption spectrum in the visible light region,and the visible light absorption is obviously enhanced after the formation of the heterostructure.The main reason is also due to the intra-band transition of electrons near the Fermi level.Besides,by comparing with doping and defective systems,the visible absorption strength of AlN/ZnO is distinctly stronger than that of N-V_Zn-ZnO.Therefore,the formation of heterogeneous structure is more beneficial to the application of ZnO photocatalysis.