The solar cell properties of crystalline BaSi2 and BaGe2 p-n homojunctions are explored using density functional theory combined with a nonequilibrium Green function method. In particular, the quantitative estimates of solar cell parameters such as photocurrent, open-circuit voltage (V o c), short-circuit current (| J s c |), and efficiency (η) are obtained for LDA and GGA-1/2 functionals. The effect of temperature on solar cell parameters is included through electron-phonon coupling (EPC) using the special thermal displacements method. The magnitudes of J s c, V o c, and η for BaSi2 (BaGe2) at 300 K are found to be 27.35 mA/cm2 (26.1 mA/cm2), 0.84 V (0.78 V), and 18.0% (16.6%), respectively. Our study strongly suggests that the phonon-assisted photon absorption and thereby EPC significantly affect the photocurrent, and its inclusion is necessary for a proper description of various solar cell parameters. The computed solar cell parameters for BaSi2 (BaGe2) p-n homojunctions can be used as benchmark ab-initio quantum mechanical results and can be used in simulations based on continuum models. © 2022 Author(s).