Antiperovskite derivatives have recently emerged as promising lead-free alternatives to halide perovskites for optoelectronic applications. Here, using a comprehensive first-principles calculations including density functional perturbation theory and many-body perturbation theory (involving GW and Bethe-Salpeter equation (BSE)), we investigate the stability, excitonic, polaronic, and optoelectronic properties of cubic Ba₃MA₃ (M = P, As, Sb, Bi; A = Cl, Br, I). These compounds are found to be dynamically and thermodynamically stable direct-gap semiconductors with G₀W₀@PBE+SOC band gaps spanning 1.23-2.17 eV. BSE calculations reveal moderate exciton binding energies (0.254-0.352 eV) and intermediate-radius excitons, while Fröhlich polaron analysis indicates intermediate carrier-phonon coupling and mobilities up to ∼ 75 cm²V⁻¹s⁻¹. The resulting spectroscopic limited maximum efficiencies reach ∼ 19-32%, surpassing several lead-based perovskites. Our results establish Ba-based antiperovskite derivatives as a robust, eco-friendly platform for next-generation optoelectronic devices.