A DFT investigation of mechanical, optical and thermoelectric properties of double perovskites K2AgAsX6 (X = Cl, Br) halides

Focusing on renewable energy device applications, we explored double perovskites K2AgAsX6 (X = Cl, Br) halides for the first time. We used WIEN2k (all-electron method) and BoltzTrap code to investigate optoelectronic and thermoelectric properties for renewable energy device applications. For structural and elastic calculations, we employed PBEsol generalized gradient approximations and found that both halides in the cubic phase are structurally stable. Further, Pugh's and Poisson's predicted values indicate that both halides are ductile. Furthermore, we also calculate the formation energy to check the thermodynamical stability of both halides. For accurate calculations of optoelectronic properties, we applied Tran-Bhala modified Becke and Johnson potential (TB-mBJ). Electronic band structure calculations indicate both halides are indirect bandgap nature having values of 2.1 eV and 1.6 eV, respectively, and might be potential candidates for solar cell applications. We also discussed the optical parameters within the incident photon energy range of 0-12 eV. We found strong absorption in the visible region for K2AgAsX6 (X = Cl, Br) halides indicating both halides are appropriate solar cell devices. Lastly, we calculate thermoelectric parameters against temperature and chemical potential. A probing figure of merit shows halides is also potential candidates for thermoelectric device applications.