Mixed formamidinium–methylammonium lead iodide perovskite from first-principles: hydrogen-bonding impact on the electronic properties

Abstract

, is preserved in the cation mixed perovskites. It is found that MA-I bonds remain stronger than FA-I bonds throughout the composition range regardless of the unit-cell expansion as the FA content increases. Finally, from the analysis of electronic structures we unravel how the hydrogen bonds stabilize the non-bonding I-5p orbitals, spatially perpendicular to the Pb-I-Pb bond axis, lowering their energy when the H-I interaction occurs, which would explain the well-known role of hydrogen bonding in the structural stabilization of hybrid perovskites. These results contribute to the understanding of the role played by cation mixing at A sites in the physics of lead halide perovskites.

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