One-dimensional perovskite lattice tilts & stretches to stabilize excitons

Quantum and dielectric confinement of excitons in low dimension organic-inorganic layered structures has been suggested to be a powerful design paradigm for applications in photocatalysis, white light emitters (self-trapped excitons), optical quantum devices etc. The key to controlling the properties of excitons in low-dimensional materials lies in tuning the electron-phonon coupling and the associated coherences. Researchers at the Tata Institute of Fundamental Research, Mumbai in collaboration with the Tata Institute of fundamental research, Hyderabad and Harish Chandra Research Institute have now demonstrated for the first time the existence of a novel transient quasiparticle termed Exciton-Polaron within a quasi-one-dimensional hybrid perovskitoid with long-coherence lifetimes. This study has recently been published in the Journal of Physical Chemistry Letters.¹

What is the advance?  

Recent work by Letian Dou and co-workers had demonstrated that one can obtain coherent lasing from 1D nanowire of perovskites (Science 2024). However  the nature of exciton mobility and coherence preservation in 1D-confined perovskite-like structures  have been missing in the literature which inhibits the rational design principles for new architectures of optoelectronic devices. Here the scientists use femtosecond impulsive Raman spectroscopy to capture real-time snapshots of exciton dynamics as it is coherently dressed with the phonon modes to form “exciton-polaron” in the quasi-1D-perovskite lattice. The uncovering of polaronic effects upon exciton formation is usually rare and significant as it suggests that optical and electronic excitations are influenced by the softness of the lattice. Scientists also ascertained that the formation of the “exciton-polaron” arises from large electron-phonon coupling to octahedra stretching and tilting modes in the 1D-chain. The direct quantification of the elctron-phonon coupling suggested that the one-dimensional lattice is soft and is almost one order of magnitude more susceptible to reorganization compared to the two-dimensional perovskite variants. The excitement of probing exciton-polaron arises from its immense potential in providing a tunable framework for new class of quasi 1D materials for optoelectronic applications eg. coherent lasing. The work therefore highlights the significance of synthesizing the such one-dimensional architectures of perovskite-like materials for multitude of exciting quantum technologies.

1. Exciton-Polaron in a Quasi-One-Dimensional Chain of Hexyl-Diammonium-BiI5  Octahedra

           Dipin K. Tomar,* Swapnil Deshpande, Shubham Gupta, Amogh K. Ravi, Sudip

           Chakraborty,* Pabitra K Nayak,* Jyotishman Dasgupta*