Ferroelasticity in Two-Dimensional Hybrid Ruddlesden$-$Popper Perovskites Mediated by Cross-Plane Intermolecular Coupling and Metastable Funnel-Like Phases
Devesh R. Kripalani, Qiye Guan, Hejin Yan, Yongqing Cai, Kun Zhou
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引用次数: 0
Abstract
Ferroelasticity describes a phenomenon in which a material exhibits two or
more equally stable orientation variants and can be switched from one form to
another under an applied stress. Recent works have demonstrated that
two-dimensional layered organic$-$inorganic hybrid Ruddlesden$-$Popper
perovskites can serve as ideal platforms for realizing ferroelasticity,
however, the ferroelastic (FE) behavior of structures with a single octahedra
layer such as (BA)$_2$PbI$_4$ (BA = CH$_3$(CH$_2$)$_3$NH$_3$$^+$) has remained
elusive. Herein, by using a combined first-principles and metadynamics
approach, the FE behavior of (BA)$_2$PbI$_4$ under mechanical and thermal
stresses is uncovered. FE switching is mediated by cross-plane intermolecular
coupling, which could occur through multiple rotational modes, rendering the
formation of FE domains and several metastable paraelastic (PE) phases. Such
metastable phases are akin to wrinkled structures in other layered materials
and can act as a "funnel" of hole carriers. Thermal excitation tends to flatten
the kinetic barriers of the transition pathways between orientation variants,
suggesting an enhanced concentration of metastable PE states at high
temperatures, while halogen mixing with Br raises these barriers and conversely
lowers the concentration of PE states. These findings reveal the rich
structural diversity of (BA)$_2$PbI$_4$ domains, which can play a vital role in
enhancing the optoelectronic properties of the perovskite and raise exciting
prospects for mechanical switching, shape memory, and information processing.