This paper reviews some of the recent theoretical investigations on the Rashba Dresselhaus spin effects and dielectric properties of CH3NH3PbI3 hybrid perovskites and CsPbI3 all-inorganic perovskites using Density functional theory. The spin vectors rotate in the non-centrosymmetric P4mm tetragonal phase, respectively clockwise and counterclockwise, in a manner that is characteristic of a pure Rashba effect. The high frequency dielectric constants ε∞ of MAPbI3 and CsPbI3 are similar as anticipated, since large differences are only expected at very low frequency where additional contributions from molecular reorientations show off for the hybrid compounds. A first simulation of a perovskite on silicon tandem cell, including a tunnel junction, is also investigated. Effect of halogen substitution (I/Br) is inspected, revealing limitations for short-circuit current and open-circuit voltage electrical characteristics.