A Comparative Theoretical Study of Structural, Electronic, and Optical Properties of A3PI3 (A = Ca, Ba, Mg) Compounds for Photovoltaic Applications

A comparative theoretical investigation of A3PI3 (A = Ca, Ba, Mg) has been performed using full potential linear augmented plane wave method (FP-LAPW) performed by WIEN2K code based on the density functional theory (DFT) within the generalized gradient approximation (GGA). The volume optimization is performed using the Birch–Murnaghan equation of states. The compound belongs to the space group 221. The structural, electronic and optical properties including the band structure and density of states are obtained. The band structure analysis revealed direct bandgaps of 1.465 eV (Ca3PI3), 0.842 eV (Ba3PI3), and 0.566 eV (Mg3PI3). Optical calculations showed high static dielectric constants, notable at 1 eV for Ba3PI3, and significant absorption in the visible region, with Ca3PI3 exhibiting the most suitable optical profile. Mg3PI3 displayed the highest reflectivity (~0.72), indicating potential for photonic applications. The novelty of this work lies in the first comparative study of these A3PI3 systems, identifying Ca3PI3 as the most promising candidate for lead-free solar cell applications due to its optimal bandgap and balanced optical response. Fortunately, A3PI3 compounds are used for photovoltaic purposes because of their optical and thermoelectric properties. It also contributes to the low-cost, nontoxic and earth—abundant materials.