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

Abstract

Ascending interest of the scientific community in layered hybrid halide perovskites (LHHPs) as materials for innovative photovoltaic and optoelectronic applications led to unprecedented expansion of this family of compounds, reaching now 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 automatic calculation of the LSF for such structures. We demonstrate the application of the proposed approach for an analysis of correlations between the LSF and band gap to reveal "structure-property" relationships. Our study gives a simple and useful approach to classify of either the layered perovskite-like structures or other layered compounds composed of layers of vertexconnected octahedra as a structural unit.

Structural Disorder in Layered Hybrid Halide Perovskites: Types of Stacking Faults, Influence on Optical Properties and Their Suppression by Crystallization Engineering

“…The second possible type of SFs with thickness variation within one slab (SF-B) is primarily characterized by a shift of [PbI 6 ] octahedra inside each distorted perovskite slab along the stacking direction (b-axis). The value of shift is characterized by translation vector [29] (t), which can be equal to 1 (whole [PbI 6 ] octahedron thickness, Figure 4b) or equal to 1/2 (a half of octahedron thickness, Figure 4c). Hereafter, we will denote these two kinds of stacking faults as SF-B(t1) and SF-B(t 1/2 ).…”

Structural chemistry of layered lead halide perovskites containing single octahedral layers

“…We will use 'layer shift' from now on to describe this. In fact, it has already been recognized that a range of degrees of shift of adjacent inorganic layers are observed in LHPs which span the RP-DJ regime (Tremblay et al, 2019;Marchenko et al, 2021). We therefore choose a definition of 'RP' and 'DJ' solely in terms of the degree of layer shift, rather than the original additional differences in A/ B stoichiometry.…”

Pressure Driven Rotational Isomerism in 2D Hybrid Perovskites

“…To quantitatively compare the degree of in-plane shift between n = 1 and 2 RPPs, we calculate the in-plane layer shift factor (LSF) 25 , i.e., Δ, in the low-pressure region (< ~ 3 GPa, where the lamellar contraction is dominated by BA organic layers). Refer to Fig.…”

“…S3 for the top views of layer shift of n = 1 and 2 RPPs under various pressures. Here, the LSF compares the in-plane coordinates of the vector 𝑙𝑙 1 � − 𝑙𝑙 2 � of each possible pair of Pb atoms ( 𝑙𝑙 1 , 𝑙𝑙 2 ) in the first and second layers in the √2 × √2 supercell metric 25 . The calculated Δ values are represented by the green filled circles for n = 1 in Fig.…”