Direct visualization of ultrafast lattice ordering triggered by an electron-hole plasma in 2D perovskites

TL;DR

This study visualizes how ultrafast electron-hole plasma interactions induce lattice ordering in 2D perovskites, revealing a new light-driven structural dynamic crucial for optoelectronic applications.

Contribution

It provides the first direct visualization of ultrafast lattice dynamics triggered by hot-carrier interactions in 2D perovskites, highlighting the role of organic spacer layers.

Findings

Ultrafast electron diffraction shows light-induced in-plane octahedra rotation.

Hot-carrier plasma creation triggers lattice ordering within femtoseconds.

Lattice interaction can be tuned by modifying the organic spacer layer.

Abstract

Direct visualization of ultrafast coupling between charge carriers and lattice degrees of freedom in photo-excited semiconductors has remained a long-standing challenge and is critical for understanding the light-induced physical behavior of materials under extreme non-equilibrium conditions. Here, by monitoring the evolution of the wave-vector resolved ultrafast electron diffraction intensity following above-bandgap photo-excitation, we obtain a direct visual of the structural dynamics in monocrystalline 2D perovskites. Analysis reveals a surprising, light-induced ultrafast lattice ordering resulting from a strong interaction between hot-carriers and the perovskite lattice, which induces an in-plane octahedra rotation, towards a more symmetric phase. Correlated ultrafast spectroscopy performed at the same carrier density as ultrafast electron diffraction reveals that the creation of a hot and dense electron-hole plasma triggers lattice ordering at short timescales by modulating the crystal cohesive energy. Finally, we show that the interaction between the carrier gas and the lattice can be altered by tailoring the rigidity of the 2D perovskite by choosing the appropriate organic spacer layer.