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

TL;DR

This study explores how the dimensionality of organic-inorganic tin halides influences their electronic and vibrational dynamics, revealing that 1D systems exhibit strong exciton-phonon coupling leading to self-trapped excitons, unlike 2D systems.

Contribution

It provides the first direct comparison of exciton-phonon interactions in 1D and 2D tin halides, highlighting the role of dimensionality in exciton self-trapping and vibrational dynamics.

Findings

1D systems show strong exciton-phonon coupling and self-trapped exciton emission.

2D systems exhibit weaker coupling and free exciton emission.

Room-temperature vibrational wavepackets are observed in 1D but not in 2D systems.

Abstract

Photo-induced dynamics of electronic processes in materials are driven by the coupling between electronic and nuclear degrees of freedom. Here we construct 1D and 2D organic-inorganic tin halides to investigate the functional role of dimensionality to exciton-phonon coupling (EPC) and exciton self-trapping. The results show that the 1D system has strong EPC leading to excitation-independent self-trapped exciton (STE) emission, while the 2D system exhibits over ten times weaker EPC resulting in free exciton emission. By performing femtosecond transient absorption experiments, we directly resolve the room-temperature vibrational wavepackets in the 1D system, some of which propagate along the STE 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 the 2D system. These findings uncover the interplay between the dimensionality-dependent EPC and electronic/nuclear dynamics, offering constructive guidance to develop multifunctional organic-inorganic metal halides.