Comparison of the effects of Sr2+ and Ca2+ substitution on the structural and electronic properties of the perovskites CH3NH3Pb1-xYxI3 (Y[dbnd]Sr, Ca) by using the Density Functional Theory

Abstract

The Vienna ab-initio simulation package (VASP) and Density Functional Theory (DFT) calculation method are used to study the structural and detailed electronic properties through atomic substitution in the CH3NH3Pb(1-x)Y(x)I3 (Y[dbnd]Sr, Ca x = 0.125, 0.25, 0.50, 0.75, and 1.0) perovskites. We determined that the non-stoichiometric crystal structures were calculated as a distorted orthorhombic phase as predicted by the tolerance factor range 0.7 < t < 0.9. The bandgaps of the stoichiometric CH3NH3SrI3 and CH3NH3CaI3 compounds are calculated 3.261 eV (Q → Γ indirect) and 3.144 eV (Q → Γ indirect), respectively and they are very high for ideal photo absorbers. We were determined that the bandgap (Γ → Γ direct) of the CH3NH3Pb0.875Ca0.125I3, CH3NH3Pb0.750Ca0.250I3, and CH3NH3Pb0.875Sr0.125I3 compounds are calculated 1.44 eV, 1.54 eV, and 1.525 eV respectively and are more suitable for ideal photo absorbers. It was seen that Ca2+ substitution was more successful than Sr2+ substitution. © 2020 Elsevier B.V.