Discovery of enhanced lattice dynamics in a single-layered hybrid perovskite

Abstract

Layered hybrid perovskites exhibit emergent physical properties and exceptional functional performances, but the coexistence of lattice order and structural disorder severely hinders our understanding of these materials. One unsolved problem regards how the lattice dynamics are affected by the dimensional engineering of the inorganic frameworks and their interaction with the molecular moieties. Here, we address this question by using a combination of spontaneous Raman scattering, terahertz spectroscopy, and molecular dynamics simulations. This approach reveals the structural dynamics in and out of equilibrium and provides unexpected observables that differentiate single- and double-layered perovskites. While no distinct vibrational coherence is observed in double-layered perovskites, an off-resonant terahertz pulse can drive a long-lived coherent phonon mode in the single-layered system. This difference highlights the dramatic change in the lattice environment as the dimension is reduced, and the findings pave the way for ultrafast structural engineering and high-speed optical modulators based on layered perovskites.

Dielectric Engineering of 2D Organic–Inorganic Hybrid Perovskites

“…As n gradually diminishes from ∞ to 1, a solitary atomic layer of [PbX 6 ] 4– is isolated by the voluminous organic spacers, thus transforming the dimensionality from 3D to 2D accordingly. Owing to the soft nature, the perovskite lattices always undergo significant lattice dynamics, giving rise to octahedral tilting in and out of the perovskite planes. , For example, by measuring the mean octahedral elongation and angle variance of [PbX 6 ] 4– , Petrozza’s and Karunadasa’s groups have shown that the inorganic lattice geometries of 2D OIHPs could be deviated largely from an ideal octahedron due to the deformation of the Pb–X bond length and X–Pb–X bond angles.…”

Time-Resolved Dynamics of Metal Halide Perovskite under High Pressure: Recent Progress and Challenges

“…Despite its promising trajectory, this field faces many challenges. One of these is the development of sophisticated, sensitive measurement techniques capable of accurately capturing ultrafast processes under extreme conditions. − Moreover, the intrinsic instability of perovskites under high-pressure conditions presents a major obstacle, complicating experimental methodologies and the interpretation of the resultant data. Ensuring structural integrity during the pressure application and dynamic measurements is imperative for reliable data acquisition and analysis.…”