FIRST PRINCIPLE STUDY: OPTICAL PROPERTIES OF CH3NH3PBI3 AND CH3NH3SNI3 FOR PEROVSKITE PHOTOVOLTAICS

Tetragonal perovskite structure of methyl-ammonium metal iodide CH 3 NH 3 MI 3 (M=Sn, Pb) was investigated, with space group of #99 with P4mm, lattice parameter of a = b = 6.6718A, c = 6.4101A, bond angle of α = β = γ = 90˚.  The electronic structure, parital density of states (DOS) and optical calculations were performed, with generalized gradient approximations (GGA). These investigations were carried out using ab initio density functional theory (DFT) calculations. To conclude, the direct bandgap was opened up to 1.9eV (Sn=0.2). We obtained a comprehensive data set, not to mention the optical absorption, with the peak value reported to be 358.2eV (Sn=302.9), but also the conductivity, reflectivity, refractive index and the electron loss function. This will be useful to experimentalist, in fabrication of an enhanced solar cell.