Polarization tuneable optical properties in hybrid improper 3d-5d double perovskites from first principles calculations

Multiferroic materials with perovskite structure are also promising for photovoltaic devices. In particular, hybrid improper ferroelectric double perovskites, where A-site cation ordering induces microscopic polarization and also can tune the electronic structure for the composition of BB’, are promising because it opens the possibility of tuning the optical properties with electric field. By using Density functional theory calculations and WEIN2K simulations, we have studied the electronic and optical properties of RbA’MnWO₆ (A’= La, Y).Here the primary order parameters are rotation (Q_R+) and tilt (Q_T) distortions along a⁰a⁰c⁺ and a^-a^-c⁰, respectively. By using mBJ potential, the analysis of electronic properties shows the indirect semiconducting band gaps of 2.1eV and 2.4eV for RbY and RbLa which are suitable (Eg< 3.0 eV) for absorption of visible light. Further we discussed the band structure and optical transitions to analyze the optical absorption spectrum.And finally, we have performed molecular dynamics simulations at various finite temperatures to study the temperature dependent electronic and optical properties. In case of RbLaMnWO₆ at 600K, (50 picoseconds), we found the dielectric switching will enhance the optical properties in these materials.