Layered hybrid perovskites have gained significant attention in the field of materials science due to their diverse physical properties and exceptional functionality. However, understanding these materials can be challenging due to the co-existence of lattice order and structural disorder. In a recent study published in Science Advances, a team of scientists from the University of Pennsylvania, University of Texas, Austin, and the Massachusetts Institute of Technology used a combination of experimental techniques and molecular dynamics simulations to unravel the structural dynamics of two-dimensional hybrid perovskites.
The researchers focused on two prototypical two-dimensional hybrid perovskites with different configurations. By using spontaneous Raman scattering, they were able to monitor the collective responses and structural disorder in these materials. The Raman spectra revealed a sizably reduced structural disorder in the thermal equilibrium state of the hybrid perovskites. Interestingly, the behavior of bromide hybrid perovskites differed significantly from iodide hybrid perovskites, providing a benchmark for comparing the octahedral dynamics in the double-layered and single-layered structures.
To gain deeper insights into the structural dynamics, the team employed ultrafast experimental techniques. Using optical Kerr effect spectroscopy, they studied the lattice and molecular reorientation dynamics in hybrid perovskites. The signals obtained were affected by the nonlinear effect of light propagation. The researchers then utilized terahertz field induced Kerr-effect spectroscopy to monitor the lattice behavior in real-time. This approach allowed them to perturb the lattice degrees of freedom and investigate the low-energy vibrations of the inorganic frameworks.
To further understand the nature of both thermal and coherent dynamics, the scientists performed ab initio molecular dynamics simulations. These simulations provided insights into the equilibrium states of the hybrid perovskites and allowed the calculation of spontaneous Raman responses. By combining the spectroscopic measurements with molecular dynamics simulations, the researchers were able to distinguish the lattice response of single-layered hybrid perovskites from their double-layered counterparts.
The study outcomes highlighted the potential of using tailored terahertz light excitation to study complex structural materials. The researchers demonstrated that hybrid lattices can display a complex interplay of molecular and ionic dynamics when exposed to specific terahertz frequencies. This approach opens up possibilities for exploring other structurally complex materials, including artificially engineered heterostructures, and harnessing emergent properties and unique functionalities with light.
The findings of this study shed light on the structural complexity of layered hybrid perovskites and provide valuable insights into the understanding and design of these materials. The ability to manipulate and control the lattice dynamics in these materials opens up new avenues for developing advanced optical methods and optoelectronic devices. Additionally, the combination of experimental techniques and molecular dynamics simulations offers a powerful approach to investigate the structural dynamics of other complex materials systems.
The research conducted by Zhuquan Zhang and his colleagues revealed the intricate lattice dynamics of layered hybrid perovskites. Through a comprehensive experimental and theoretical study, the team unraveled the structural complexity of two-dimensional hybrid perovskites and highlighted the importance of dimensional engineering and interactions with molecular moieties. The insights gained from this study contribute to the advancement of materials science and pave the way for the development of novel optoelectronic devices and advanced optical methods.