# Dimensionality-dependent electronic and vibrational dynamics in low-dimensional organic-inorganic tin halides

## TL;DR

This paper shows how changing the dimensionality of tin halide materials affects their electronic and vibrational behavior, switching emission types through exciton-phonon coupling.

## Contribution

The study reveals how dimensionality controls exciton-phonon coupling and self-trapping in organic-inorganic tin halides.

## Key findings

- One-dimensional systems show strong exciton-phonon coupling leading to self-trapped exciton emission.
- Two-dimensional systems exhibit much weaker coupling and free exciton emission.
- Vibrational wavepackets in one-dimensional systems propagate along the self-trapped-exciton potential energy surface.

## Abstract

Photo-induced dynamics of electronic processes are driven by the coupling between electronic and nuclear degrees of freedom. Here, we construct one- and two-dimensional organic-inorganic tin halides to investigate how dimensionality controls exciton-phonon coupling and exciton self-trapping. The results show that a one-dimensional system has strong exciton-phonon coupling leading to excitation-independent self-trapped exciton emission, whereas a two-dimensional system exhibits over ten times weaker coupling resulting in free exciton emission. The difference originates from enhanced Anderson localization in a one-dimensional system. Femtosecond transient absorption experiments directly resolve room-temperature vibrational wavepackets in a one-dimensional system, some of which propagate along the self-trapped-exciton potential energy surface. A combination of wagging and asymmetric stretching motions (~106 cm-1) in tin iodide is identified as such a mode, inducing exciton self-trapping. While no room-temperature wavepackets are observed in a two-dimensional system. These findings uncover the interplay between dimensionality-dependent exciton-phonon coupling and electronic/nuclear dynamics, offering constructive guidance to develop multifunctional organic-inorganic metal halides.

The study shows that tuning organic–inorganic tin halides from 2D to 1D significantly enhances coupling between excitons and lattice vibrations, thereby switching emission from free excitons to self-trapped states. Ultrafast spectroscopy identifies the key electronic and vibrational dynamics.