Lead‐free inorganic halides are promising semiconductors candidates for next‐generation renewable energy and optoelectronic applications. Here, we present a comprehensive first‐principles density functional theory study of silver double perovskites Rb 2 AgXBr 6 (X = Bi and Sb) using the full‐potential linearized augmented plane wave method as implemented in the Wien2k package. Structural optimization, tolerance factor analysis, and formation energy calculations confirm the thermodynamically stability in the cubic Fm‐3 m (#225) phase. Elastic parameters verify the mechanical stability and indicate ductile behavior. Electronic structure calculations using GGA–PBE and GGA–mBJ reveal indirect narrow bandgap semiconductors with smaller bandgaps than most reported halide double perovskites. Optical analysis shows high absorption and conductivity, with low reflectivity and loss energy across the visible and ultraviolet regions. Thermoelectronic transport properties, including Seebeck coefficient, power factor, figure of merit (), electrical and lattice thermal conductivity, and heat capacity, demonstrate favorable performance, practically at room temperature. These results highlight Rb 2 AgXBr 6 halide perovskites as promising candidates for advanced optoelectronic and thermoelectronic applications.
H.‐E. et al. (Sun,) studied this question.