Title: Lead-free double perovskites for thermoelectric and optoelectronic applications: Ab initio study

Abstract

Energy consumption is increasing day by day in today’s world so it is the matter of concern for the scientific community to find the alternative power generation mechanisms by minimizing the whole world’s reliance on traditional power generation methods. Thermoelectricity and optoelectronics have emerged as an attractive area of research for finding efficient non-traditional power generation mechanisms. In this scenario, it is a matter of immense potential to find more efficient materials for optoelectronic and thermoelectric power generation. Currently, the structural, electronic, optical, phononic and thermoelectric properties of double perovskites A2NaBCl6 (A=Cs,Rb,K and B=Bi,Sb) have been studied in details using density functional theory (DFT) within the frame work of generalized gradient approximation(GGA). The results of Cs2NaBiCl6and Cs2NaSbCl6are consistent with already reported data whereas Rb2NaBiCl6, K2NaBiCl6, Rb2NaSbCl6 and K2NaSbCl6have been reported for the first time. The structural stability, thermal stability, large Seebeck coefficients and figure of merit (close to unity) of these lead-free double perovskites suggest various thermoelectric device applications. High absorption coefficient, high optical conductivity and low reflection coefficient suggests the applications of these compounds in solar cells as a source of low cost eco-friendly power generation schemes.