First principle study of lead‐free double perovskites halides Rb2Pd(Cl/Br)6 for solar cells and renewable energy devices: A quantum DFT

Summary Lead‐free double perovskites are promising materials for environmental friendly photovoltaics and other optoelectronics. In this article, optical, thermoelectric, and thermodynamic properties of Rb2Pd(Cl/Br)6 are explored by modified Becke and Johnson potential. The Goldschmidt tolerance factor (0.90‐1.04) ensures the cubic phase is structurally stable. The negative formation energy and positive phonon dispersion authenticate the thermodynamic stability. The band gap of Rb2PdCl6 is 1.88 eV, which reduces to 1.21 eV by replacing Cl with Br anion. The first absorption regions (620‐413)nm for Rb2PdCl6 and (826‐496)nm for Rb2PdBr6 increase their solar cells' implication. The transport properties are investigated by Boltzmann transport theory through the BoltzTraP code. Finally, the high values 0.76 and 0.75 of the figure of merit at room temperature also ensure their importance for thermoelectric generators. This work is the study of alternative materials of lead and organic perovskites to avoid toxicity and instability. Here, we found that the inorganic lead‐free double perovskites Rb2PdBr6 and Rb2PdCl6 have an excellent and suitable range of bandgap for solar cells and other optoelectronic applications. The bandgap‐dependent thermoelectric figure of merit and maximum energy absorption in the visible region increases the potential for renewable energy. The band gaps 1.31 and 1.98 eV falls the absorption bands in the wavelength range 708 to 496 nm, and 551 to 413 nm. The bandgap 1.31 eV is considered more suitable for solar cells.