Speaker
Description
Mixed-halide perovskites offer exceptional bandgap tunability but suffer
from light-induced halide migration that degrades optical and electronic perfor-
mance. While this phenomenon has been extensively studied in bulk films and
I–Br systems, far less is known about halide migration in nanoscale structures
and Br-Cl systems. We investigate photoinduced halide migration in FAPbBr3-
based core–shell perovskite nanoparticles synthesized via reverse micelle tem-
plating, a method that enables precise control over nanoparticle size, spacing,
and interfacial chemistry.
Using a triple-loading process, the nanoparticles were fabricated with Cl
introduced through shell precursors (HCl, NiCl2, ZnCl2, and LaCl3). PL reveals
a reproducible, excitation-driven spectral shift from a mixed phase to a Br-rich
phase above a threshold excitation density. This behaviour is consistent with
light-induced halide segregation, driven by hole trapping at the lower bandgap
halide sites. Notably, the characteristic time constant of the transition increases
with excitation power and does not exhibit the saturation behaviour commonly
reported in thin-film systems. Additionally, expulsion of the lower bandgap
halide is not observed after long exposure times.
Despite differing shell chemistries, all core–shell nanoparticles exhibit simi-
lar migration kinetics, indicating that the rate of halide redistribution is gov-
erned primarily by confined carrier diffusion and nanoparticle geometry rather
than shell composition. Atomic force microscopy confirms that morphological
parameters remain constant across samples, isolating halide composition and
interfacial effects as the dominant variables. These results suggest that halide
migration in nanoparticle arrays proceeds through localized ionic rearrangement
within individual particles, rather than long-range domain growth characteristic
of bulk perovskite films.
This work demonstrates that nanoscale confinement fundamentally alters the
dynamics of light-induced halide migration and challenges existing kinetic mod-
els developed for continuous thin films. Reverse micelle–templated perovskite
nanoparticles therefore provide a powerful platform for probing ion–carrier cou-
pling, phase stability, and non-equilibrium processes in halide perovskites, with
implications for the design of optoelectronic devices based on nanostructured
perovskite materials.
| Keyword-1 | Perovskite |
|---|---|
| Keyword-2 | Nanoparticle |
| Keyword-3 | Polymer |