A DFT Computational Chemistry Approach of Narrow Bandgap Perovskites AgAZ ₃ (A = Ge, Sn; Z = Br, I) for Solar Energy Applications

Halide perovskites exhibit remarkable optoelectronic properties and compositional versatility, making them highly promising for next‐generation photovoltaics. This study investigates the photovoltaic potential of novel silver‐based halide perovskites AgAZ 3 (A = Ge, Sn; Z = Br, I) using the first‐principles method implemented in the WIEN2K code. Structural optimization, electronic band structure, density of states, and detailed optical spectra of these perovskite compounds were analyzed using the Tran–Blaha modified Becke–Johnson (TB‐mBJ) exchange–correlation potential. A comparative study of electronic properties was conducted with generalized gradient approximation (GGA)‐Perdew‐Burke‐Ernzerhof (PBE) and TB‐mBJ approaches. Structural integrity was validated via tolerance factor assessment and formation energy calculations. Density of states analysis (partial and total) identified atomic contributions. The optical properties of the compounds were evaluated by examining the real and imaginary components of the dielectric tensor, as well as reflectivity and refractive index spectra. The calculated direct bandgaps of AgGeBr 3 (1.07 eV), AgGeI 3 (0.97 eV), AgSnBr 3 (1.02 eV), and AgSnI 3 (0.81 eV) fall within the ideal range for photovoltaic applications, offering high theoretical efficiency potential and suitability for tandem or near‐infrared absorber cells. A diminution in bandgap is observed when substituting Br with I, and Ge with Sn, which also results in improved absorption efficacy. The outcomes demonstrate the strong potential of these perovskites for solar cell and optoelectronic applications. The outcomes theoretically demonstrate the strong potential of these perovskites for solar cell applications and provide a foundational roadmap for their experimental development.