<p>In this paper, we present density functional theory calculations on lead-free Rb₂MoXO₆ (X= Si, Ge, and Sn) double perovskites for photovoltaic and optoelectronic applications. The structure of all the examined perovskites are optimized and found to be semiconductors with a cubic space group. The observed band gaps are 1.69 eV for Rb₂MoSiO₆, 1.53 eV for Rb₂MoGeO₆, and 1.28 eV for Rb₂MoSnO₆; these all fall in the visible energy range, demonstrating their potential applications for solar cell technology. All compounds exhibit structural and thermodynamic stability due to their tolerance factors and negative formation energies. Ab initio molecular dynamics simulation and phonon calculation validated the thermal and dynamic stability of our predicted compounds. All three compounds satisfy the Born-Huang criteria, confirming their mechanical stability. Moreover, all compounds are brittle and exhibit anisotropic nature. The investigation of optical properties disclosed strong absorption and optical conductivity over a wide range of visible light, signifying their potential use in solar cell technology.</p> Graphical Abstract <p></p>