It is compulsory to develop technologies able to generate energy at negligible cost to the environment. Therefore, in present work, lead free vacancy ordered double perovskites Rb/Cs2TeBr6 were reported as green energy materials on basis of full potential linearized augmented plane wave method calculations. The study has been carried out in terms of structural, electronic, optical and thermoelectric properties. It was noted from values of tolerance factor and formation energy that both Rb/Cs2TeBr6 compounds are stable in perovskite structure. The band gaps were calculated in close resemblance with experiments. These values (2.09 eV Rb2TeBr6 and 2.10 eV for Cs2TeBr6 with EV-GGA) were examined in visible range of electromagnetic spectrum. The optical properties such as real and imaginary parts of dielectric function, optical conductivity and reflectivity ensured the use of Rb/Cs2TeBr6 compounds for solar cell applications. Also, the reasonable values of Seebeck coefficients and figure of merit proposed the studied compounds for thermoelectric power generation.