Layer Shift Factor in Layered Hybrid Perovskites: Univocal Quantitative Descriptor of Composition–Structure–Property Relationships

The
increasing interest of the scientific community in layered
hybrid halide perovskites (LHHPs) as materials for innovative photovoltaic
and optoelectronic applications has led to an unprecedented expansion
of this family of compounds, reaching several hundred refined structures.
Despite the unique structural diversity of LHHPs, traditional approaches
of describing their structures, such as dividing into Dion–Jacobson
(DJ) or Ruddlesden–Popper (RP) phases for most structures,
are ambiguous and unquantifiable. Here, we introduced a quantitative
layer shift factor (LSF) for a univocal classification and quantitative
comparison of the structures. We also developed an algorithm for the
automatic calculation of the LSF for such structures. We demonstrate
the application of the proposed approach for an analysis of the correlations
between the LSF and the band gap to reveal the “structure–property”
relationships. Our study gives a simple and useful approach to classify
either the layered perovskite-like structures or other layered compounds
composed of layers of vertex-connected octahedra as a structural unit.