Structural, optical and electronic properties of ZnAg2GeTe4 and ZnAg2Ge0.93Fe0.07Te4 photocatalyst: a first principle approach

Abstract

By executing the Generalised Gradient Approximation (GGA) based on the Pethew Burke Emzerhof (PBE), the structural geometry, electronic band structures, total density of states (DOS), partial density of states (PDOS) and optical properties for both of undoped and doped ZnAg₂GeTe₄ were investigated. The calculated band gap of ZnAg₂GeTe is 1.06 eV, indicating strong photocatalyst for organic pollutants. To explain the photocatalytic effect owing to hybridisation of orbitals, the DOS were simulated to assess the characteristics of 4s, 3d for Zn, 5s, 4d for Ag, 4s, 3d, 4p for Ge and 4s, 5s 4d 5p for Te orbitals travelling from the highest occupied valance bands to the lowest occupied conduction bands. The optical properties, for instance absorption, reflectivity, dielectric function and loss function may be indicated the increased absorption of visible light, as well as corresponds to electronic structure. For better photocatalytic activity, Fe metal was doped by replacing Ge at 7%. After doping, the band gap was decreased from 1.06 eV to 0.09 eV, and DOS was also increased. Nevertheless, optical properties, especially absorption, were also increased which indicates higher photocatalytic activity. It can be concluded that ZnAg₂Ge_0.93Fe_0.07Te₄ shows more photocatalytic activity than ZnAg₂GeTe₄ with the evidences from the band gap and optical properties.