Study on Electronic, Mechanical and Optical Properties of Perovskite Cs₂AgGaX₆ (X = Cl, Br)

Recently, halide double perovskite materials have attracted more and more attention due to their structural stability and excellent photoelectric properties. In this work, the electronic, mechanical and optical properties of halide double perovskite Cs2AgGaX6 (X = Cl, Br) have been studied by first-principle calculations. The results show that the Goldschmidt’s tolerance factor t of these compounds is close to 1, which is the ideal value of structurally stable cubic perovskite. Moreover, their thermodynamic stability is also ensured by the calculated negative formation energy. The Cs2AgGaX6 (X = Cl, Br) is a direct band-gap semiconductor with values of 2.038 eV and 0.967 eV, respectively. Compared with many halide double perovskites, both Cs2AgGaX6 (X = Cl, Br) compounds exhibit the advantage of low effective carrier mass. Finally, their reflectance, absorption coefficient and dielectric function in the range of 0~30 eV were studied. The results show that these compounds have certain application value in optoelectronic devices.