Exploring X 2 KBiO 6 (X = Hf, Ti, Zr) Double Perovskites as Potential Absorbers for Visible-Light Applications

The current research work aims to systematically study the X 2 KBiO 6 (X = Hf, Ti, Zr) using a combined approach of density functional theory (DFT) and finite-difference time-domain (FDTD) computations. The computed results from the DFT computations, which considered the effect of spin-orbit coupling (SOC) and employed the hybrid HSE06 methods, showed that Hf 2 KBiO 6 , Zr 2 KBiO 6 , and Ti 2 KBiO 6 possess energy bandgaps of 1.622, 1.126, and 1.807 eV, respectively. From the energy bandgap values obtained, all three materials possess the most ideal bandgap with optimal position in the visible region, thus making it more favorable for potential optical applications. Moreover, the results from the optical computation indicate that Ti 2 KBiO 6 possesses the largest absorption coefficient greater than 1.74 × 10 5 cm -1 in visible range of light spectrum. The FDTD simulation results of metal-dielectric bilayer device with a gold layer reveal that the percentage of absorption for Hf 2 KBiO 6 at 660 nm is 100%, Ti 2 KBiO 6 at 661 nm is 98%, and for Zr 2 KBiO 6 at 691 nm is 95%. This exceptional absorption arises from non-linear plasmonic field enhancement at the metal-perovskite interface. Despite the fact that these three materials have very high absorption properties and can be considered as efficient absorbers for the visible light region, Hf 2 KBiO 6 proves to be the potential material for optical applications as compared to other studied materials.