Theoretial Study On Structural Design And Optical Absorption Properties Of ZnO/Fe₃O₄ And Graphene Composites

Light-absorbing materials are functionalized by absorbing light of different wavelengths,which have been widely used in civil technology and defense technology fields such as photodetectors,solar cells,aircraft stealth and so on.However,many currently known light-absorbing materials have shortcomings such as narrow use of the spectral range,cannot achieve multi-functionality and so on.Therefore,the development of new functional materials with high absorption properties has become a popular topic in current scientific research.In this work,the electronic structures and optical absorption properties of composites which are composed by metal oxides and graphene are studied by employing the first-principles density functional theory with the VASP package.Through the comparison of the absorption coefficients and reflectivity,the influence of charge transfer in the interface area and resulting interfacial polarization on the light absorption capacity of the composites is revealed.It is found that ZnO(0001)/graphene and ZnO(000(?))/graphene composites make up for the lack of infrared absorption properties of graphene,enhance the absorption intensity of ultraviolet light,and expand the light absorption range from 0 to 1.03 eV and 6.82 to 9.7 eV.ZnO(10(?)0)/graphene composites also can absorb infrared and ultraviolet,which absorption peak in the ultraviolet band is higher than that of the monomer material.In the ultraviolet band,the light reflection ability of ZnO/graphene composits are generally lower than monomer materials,which improve the light absorption and transmission capabilities of the materials.Among them,ZnO(000(?))/G-CZ has the best absorption performance and the strongest absorption capacity for ultraviolet light.There is a red shift phenomenon in the ultraviolet band with stronger absorption for Fe₃O₄/graphene composites.Compared with graphene,the absorption edge of the composite has different degrees of red shift,indicating that the band gap of the composite is smaller than graphene.In contrast,it is more conducive to promoting the occurrence of electronic transition behavior between bands to improve its light absorption performance.Compared with graphene,the red shift of Fe₃O₄(001)-O/G' is 1.54 eV,and the absorption coefficient is 1.28×106 cm-1 in the ultraviolet band.The ability of Fe₃O₄/graphene composites to reflect ultraviolet light is generally lower than that of monomer materials.It also means that in comparison with the monoer materials,the light absorption and light transmission capabilities in the ultraviolet band of the composites are improved.Both composite systems can absorb infrared,visible and ultraviolet light.The ability of ZnO/graphene composites to absorb ultraviolet light is stronger than Fe₃O₄/graphene composites,in the visible band,the light absorption capacity and reflectivity of the Fe₃O₄/graphene composites are higher than ZnO/graphene composites.It is also found that there are obvious differences in the performance of light absorption and light reflection for these composites with metal oxide crystal different planes and graphene,which shows that the interface structure strongly correlates with the optical properties of the material.It is found that the interfaicial van der Waals interaction is more favorable to improve the light absorption properties of composites than the bonding interaction.Bader charge analysis shows that the interface polarization caused by the charge transfer between the interfaces plays a key role in enhancing the light absorption capacity of the metal oxide/graphene composites.This work provides theoretical guidance for the development of composite materials with high light absorption properties.