"DFT-Based Exploration of Structural Stability and Electronic Behavior in Lead-Free Double Perovskites Cs₂GeSnBr₆ and K₂AgSbCl₆"

In this study, density functional theory (DFT) was employed to explore the structural, electronic, and stability characteristics of two double perovskite semiconductors, Cs₂GeSnBr₆ and K₂AgSbCl₆. The computations were performed within the generalized gradient approximation (GGA) using the Perdew–Burke–Ernzerhof (PBE) functional. Both compounds were found to be structurally stable, as confirmed by negative formation energies and optimized lattice parameters showing minimal distortion. The electronic band structure analysis revealed indirect semiconducting behavior with calculated band gaps of 0.922 eV for Cs₂GeSnBr₆ and 0.377 eV for K₂AgSbCl₆. These values fall within the optimal range for visible to near-infrared optoelectronic applications, suggesting potential use in solar cells and photodetectors. Moreover, the high thermodynamic stability and environmental friendliness of these lead-free halide perovskites highlight their promise as next-generation semiconducting materials. The results provide valuable insight into the design of stable, efficient, and sustainable perovskite-based devices.