A computational insight of the lead-free double perovskites Rb2AgSbCl6 and Rb2AgSbBr6 for optoelectronic and thermoelectric applications

Based on first-principles calculations, we have computed the optoelectronics and thermoelectric properties of double Perovskite halides Rb2AgSbX6 (X = Cl, Br). Our calculation suggested the favorable nature of Rb2AgSbX6 (X = Cl, Br) due to lower formation energy. Additionally, we have explored the electronic properties in terms of band structure and density of states. We find that both Rb2AgSbCl6, and Rb2AgSbBr6 possess an indirect band gap of 2.19 and 1.56 eV, respectively. Furthermore, the Rb2AgSbX6 (X = Cl, Br) absorbs the light well in the visible region with a sharp peaks confirming the transition of electron from valence band to the conduction band. We find that Rb2AgSbX6 (X = Cl, Br) absorbed light below 4.0 eV, which suggested its prominent application in the solar cells. At room temperature, the zT value is 0.73 and 0.76 for Rb2AgSbCl6 and Rb2AgSbBr6, respectively. Thus, our findings could be useful for future (experimental) studies to investigate Rb2AgSbX6 (X = Cl, Br) for applications relevant to renewable power devices.