Contrary to the common belief that light-induced halide ion segregation in a mixed halide al-loy occurs within the illuminated area, we find that the Br ions released by light diffuse away from the area, which generates a counter-balancing Coulombic force between the anion deficit and surplus region, together resulting in a macro/mesoscopic size anion ring surrounding the center, showing a photoluminescence ring. Upon removing the illumination, the displaced anions return to the illuminated area, and the restoring force leads to a damped ultra-low-frequency oscillatory ion motion, which may be the first observation of an ionic plasma oscillation in solids.
@article{arxiv.2111.12627,
title = {Photo-induced Macro/Mesoscopic Scale Ion Segregation in Mixed-Halide Perovskites: Ring Structure and Ionic Plasma Oscillations},
author = {Xiaoxiao Sun and Yong Zhang and Weikun Ge},
journal= {arXiv preprint arXiv:2111.12627},
year = {2021}
}