Role of Cations on the Electronic Transport and Optical Properties of Lead-Iodide Perovskites

Using density functional theory in combination with the nonequilibrium Green's function formalism we study the role of organic (methylammonium, MA) and inorganic (cesium, Cs) cations on the electronic transport and optical properties of single crystal lead-iodide perovskite. Both dispersive interactions (i.e., van der Waals interactions) and spin-orbit coupling are taken into account in describing the properties of the considered systems. Despite sizable difference in the lattice parameters and the electric polarization of the system, both MAPbI₃ and CsPbI₃ show similar electronic transport properties. A small difference in the transmission originates from the variations of the electrostatic potential along the electronic transport direction. These two samples also exhibit similar optical and dielectric properties when they are in the same crystalline phase. Our finite temperature first-principles molecular dynamics simulations in combination with static density functional theory calculations also reveal similar electronic/optical features for the considered systems. These findings are in line with recent experimental studies where similar photovoltaic performance of hybrid organic-inorganic and all-inorganic perovskite solar cells has been reported.