Optical properties of photovoltaic materials: Organic-inorganic mixed halide perovskites CH3NH3Pb(I1-yXy)(3) (X = Cl, Br)

Recently, extensive studies have widely fabricated and demonstrated that organic-inorganic hybrid perovskite-type solar cells, CH3NH3PbI3, have the superior optoelectronic properties. We explore the structural, electronic, optical properties and stability of tetragonal phase mixed halide perovskites CH3NH3Pb(I1-yXy)(3) (X = Cl, Br; y = 0, 0.25, 0.5, 0.75), using first-principles calculations. The calculation of electronic structure reveals that the valance band maximum is governed by the halide p-orbitals and Pb 6s-orbitals while the conduction band minimum formed by the mixed contribution from the p orbitals of Pb atom and s orbitals of I atom. For the stability and optical properties of CH3NH3Pb(I1-yXy)(3), the absorption coefficients show a blueshift of the absorption onsets but their stabilities show gradually increase with the increasing of X contents. Three different doping occupation phases of MAPb(I0.5X0.5)(3) demonstrate that the impact of doping positions in linear optical property cannot be neglected but there is no change in stability. On the basis of all calculated results, we conclude that the best accouplement between absorption coefficiency and stability can be achieved at y = 0.25 in CH3NH3Pb(I1-yBry)(3) perovskites.