Comprehensive property study of new green halide perovskites Cs2YAgX6 via simulations

Abstract

People now pay increasing attention to the green high-performanced perovskites owing to their leadlessness and thus environmental-friendliness. Double perovskites materials emerge as promising candidates. In this study, the structural, elastic, optical, and electronic properties of Cs₂YAgX₆ (X = Cl, Br, I) are simulated using the density functional theory. The calculated octahedral factor, tolerance factor, negative formation energy, and elastic constants confirm the structural stability of these materials according to the Born stability criterion. The electronic properties reveal indirect bandgaps of 3.68 eV, 3.11 eV, and 2.41 eV for the Cl, Br, and I substitutions, respectively. The calculated dielectric function, refractive index, reflectivity, optical absorption, conductivity, and energy loss, indicate intense absorption in the blue and ultraviolet regions (5–13 eV and 20–30 eV), suggesting potential application in blue and ultraviolet detectors. Notably, in the energy region of ~ 14-18 eV, Cs₂YAgX₆ exhibit metallic nature. Moreover, the real refractive index is less than 1 in the 15–35 eV range, implying superluminal phase velocity and potential use as a photon accelerator in a broad spectral region. These findings indicate the potential of Cs₂YAgX₆ as green, high-performance materials for optoelectronic applications.